instrument on Nimbus 4 involved the employment of a system for the on-board subtraction of dark ... Georgia Institute of Technology ... University of Florida.
I NA RP 109 ,'
NASA Reference Publication 1095
(2.1
June 1982
User’s Guide for the Solar Backscattered Ultraviolet (SBUV) Instrument First-Year Ozone-S Data Set A. J. Fleig, K. F. Klenk, P. K. Bhartia, D. Gordon, and W. H. Schneider
TECH LIBRARY KAFB, NM
Illllll 1111 lllll IIIH lllll lllll Ill11 Ill1 Ill1
NASA Reference Publication 1095
DlJb3249
1982
User’s Guide for the ~Solar Backscattered ’ Ultraviolet (SBUV) Instrument First-Year ~Ozone-S Data Set A. J. Fleig Goddard Space Flight ~ Greenbelt, Maryland
Center
K. F. Klenk, P. K. Bhartia, D. Gordon, and W. H. Schneider Systems and Applied Sciences Corporation Bladensburg, Maryland
Natlonal Aeronautics and Space Administration
Scientific and Technical Information Branch
PREFACE NIMBUS EXPERIMENT TEAM (NET) VALIDATION STATEMENT FOR FIRST YEAR SBUV/TOMS OZONE DATA SET Total ozone and ozone vertical profile results for Solar Backscattered Ultraviolet/Total Ozone Mapping Spectrometer (SBUV/TOMS) operation from November 1978 to November 1979 are available. The algorithms used have been thoroughly tested; the instrument performance-examined in detail; and the ozone results have been compared with Dobson, Umkehr, balloon, and rocket observations. The accuracy and precision of the satellite ozone data is good to at least within the ability of the ground truth to check and is self consistent to within the specifications of the instrument. The primary input to the ozone retrieval algorithms is the ratio of the backscattered radiance to the incident solar radiance. Both radiance and irradiance are measured seAccuracy in the determination of this parately by the SBUV and TOMS instruments. ratio depends upon the calibration accuracy of a diffuse reflector used to measure the solar irradiance. Precision in the measurement of this ratio is better than 0.5% for SBUV and 1.0% for TOMS. Prelaunch calibration uncertainties affect the absolute accuracy of these measurements. We are continuing to assess the magnitude of these uncertainties. During the first year of instrument operation inflight diffuser degradation is less than 1.5% at 339.8 nm and less than 3.0% at 273.5 nm. No correction for this has been applied to the data. This inflight degradation can introduce an apparent long term drift in an analysis of the data. One of the major design improvements of the Nimbus 7 SBUV instrument over the BUV instrument on Nimbus 4 involved the employment of a system for the on-board subtraction of dark current. This has improved the instrument’s performance to a point where no radiation induced signal has been observed in the South Atlantic anomaly to date. Total ozone has been derived from both the SBUV and TOMS instruments. Analysis of the variance of comparisons between colocated TOMS and AD pair direct sun (00 code) Dobson observations shows that total ozone retrieval precision is better than 2% to within 10 degrees of the solar terminator. There are biases of -6.5% and -8.3% for TOMS These biases are and SBUV respectively when compared to the Dobson network. primarily due to inconsistancies in the ozone absorption coefficients used by the space and ground systems. If absorption coefficients available on a preliminary basis from the National Bureau of Standards were used for both SBUV/TOMS and the Dobson measurements, the biases would be less than 3%. Vertical profiles of ozone have been derived from the SBUV step scan radiances at 273.5 nm and longer wavelengths using an optimum statistical inversion algorithm. Comparison with Umkehr measurements at Boulder and Arosa indicate that the precision of the derived layer ozone amounts is on the order of 5%. The altitude range, for which the inferred SBUV profiles is determined primarily by the radiance measurements, depends on several factors including the solar zenith angle, the total ozone amount, and the shape of the ozone profile. This altitude range typically extends from 0.7 mbar (50 km) down to the peak of the ozone density profile (20-40 mb) or 22-26 km.The derived layer ozone amounts below this region as produced by the optimum statistical inversion algorithm depend on the a priori statistical information about the correlation between these layers and the observed total ozone and upper level profile amounts. iii
Variations of UV solar flux associated with the rotation of -active regions on the sun (27day solar rotation period) have been observed with the continuous scan solar observations (160-400 nm). However, no significant solar flux variation was observed at the wavelengths used for the total ozone and vertical profile retrievals. Therefore, a long term smoothed solar flux was used in the processing with no 27 day period component. To the extent that there may have actually been a small 27 day period in the real solar flux this would introduce a small (less than l/2%) artifact in the data. Ground truth for the SBUV ozone profile consists of Umkehr profiles, ozone balloon sondes, several optical ozone rocket sondes, and a chemiluminescent rocket sonde. This set of data was not sufficient to precisely determine the accuracy and validity range of the satellite retrievals or to evaluate possible latitudinal or temporal trends in the data. However, there are indications that the SBUV values may be slightly ( 5%) lower than the balloon and Umkehr measurements below the mixing ratio peak (5-7 mb). At upper levels the agreement with the optical ozonesonde rockets flown in November of 1979 for the International Ozone Rocket Intercomparison is within + 5%.
Chairman, SBUV/TO MS NET
Arthur D. Belmont Pawan K. Bhartia’ Derek M. Cunnold Albert J. Fleiglp2 Alex E.S. Green Donald F. Heath William L. Imhof V.G. Kaveeshwar’ Kenneth F. Klenk’ Arlin J. Krueger Carlton L. Mateer Alvin J. Miller Hongwoo W. Park’
Control Data Corporation Systems and Applied Sciences Corporation Georgia Institute of Technology NASA/Goddard Space Flight Center University of Florida NASA/Goddard Space Flight Center Lockheed Space Science Laboratory Systems and Applied Sciences Corporation . Systems and Applied Sciences Corporation NASA/Goddard Space Flight Center Atmospheric Environment Service, Canada National Meteorological Center/NOAA Systems and Applied Sciences Corporation
‘Associate Member of NET ‘Nimbus Project Scientist iv
CONTENTS Section 1.
Page SOLAR BACKSCATTERED Introduction Instrument Theoretical
1.1 1.2 1.3 2.
2.2
.
.
.
TAPE
FORMATS
3.1 3.2
Physical Logical .
...........................
Algorithm
..............
.
.
.
.
.
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.
.
(I/F;
:
.
.
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6 7 10 10 12 14 15 18
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.
of Ozone-S Tape of Tape ............ .
1
6
................
Structure Structure .
.
1 2 3
18
Inversion to Obtain Profile ........ Calculation of Multiple-Scattering Component ................. A Priori Profile and Covariance Matrix Measurement Covariance Matrix ....... Validity Checks ..............
2.2.3 2.2.4 2.2.5
.
6
Algorithm
2.2.1 2.2.2
.
.
Computation of Theoretical Radiances Computation of Normalized Radiances Calculation of Reflectivity ........ Calculation of Total Ozone ........ Calculation of IFOV Pressure ....... Calculation of Best Ozone ......... Validity Checks ..............
Profile
REFERENCES
EXPERIMENT
......................
Total-Ozone 2.1.1 2.1.2 2.1.3 2.1.4 2.1.5 2.1.6 2.1.7
3.
................... Overview FoundatioAs
THE ALGORITHM 2.1
ULTRAVIOLET
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19 20 24 24 26 26 28
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52
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APPENDIX
A--F;
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.
55
APPENDIX
B-- SAMPLE FORTRAN PROGRAM AND JCL FOR THE OZONE-S TAPE . . . . . . . . . . . . . . . . . . . . .
.
59
APPENDIX
C-- DATA AVAILABILITY
AND COST
APPENDIX
D-- SBUV OZONE-S
CATALOG
CORRECTION
FUNCTION
TAPE
V
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63
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65
_ ..-..-_.-.--.- -.--
,.
ILLUSTRATIONS Figure
Page
1
Quality
2
Block
Flags
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Identifier
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16
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28
TABLES Table
Page
1
External
Inputs
....................
2
& Priori
Profile
Coefficients
3
-A Priori
Profile
Error
4
Format
First
Record
5
Data
Record
6
-Format
of
Last
7
Format
of
Trailer
of
Format
for
Record File
8 .............
Covariance on
Files
OZONE-S
Tape
Data
Record
vi
.......
Matrix
Data
on
22
Files .............
.........
23 30
..........
33
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45 48
USER'S GUIDE FOR THE SOLAR BACKSCATTERED ULTRAVIOLET (SBUV) INSTRUMENT FIRST-YEAR OZONE-S DATA SET
1. 1.1
SCLAR BACKSCATTERED ULTRAVIOLET EXPERIMENT ---INTRODUCTION
The solar backscattered ultraviolet (SBUV) instrument was proposed by D, F. Heath for Nimbus-G (7), and it represents an improved version of the backscattered ultraviolet (BUV) instrument that was proposed by D. F. Heath and J. V. Dave and flown on Nimbus 4. The instrument design is described by Heath --et al. 1 The principal improvements incorporated into the Nimbus 7 SBUV instrument were: (1) mechanical chopping of the electromagnetic radiation entering the entrance slit of the double monochromator, which eliminated all (2) stowinterference from high-energy trapped-particle radiation; ing the solar-viewing diffuser plate except when observing the Sun in order to reduce the effects of spacecraft outgassing contaminants: and (3) the incorporation of a continuous scan (0.2-nm intervals) mode for observing either the Sun or the Earth in the 160- to 400-nm wavelength regions. The combined SBUV/TOMS instrument has been supported by an experiment team consisting of D. F. Heath, Chairman, A. J. Krueger, C. L. Mateer, A. J. Miller, D. Cunnold, A. E. Green, A. Belmont, and W. L. Imhof. The SBUV/TOMS instrument was built by Beckman Instruments, of Anaheim, California. Algorithm development, evaluation of Inc., instrument performance, ground-truth validation, and data production efforts were carried out by A. J. Fleig, K. F. Klenk, P. K. Bhartia, H. W. Park, K. D. Lee, and V. G. Kaveeshwar of the Ozone Processing Team (OPT). The OPT is managed by A. J. Fleig and is supported by individuals from Systems and Applied Sciences Corporation and Goddard Space Flight Center.
This
guide
is
total-ozone
intended
and
ozone
SBUV instrument ment. ozone to
and
Section and
the
profile
retrieval and
--et formats.
obtaining and
job
ozone Appendix 1.2
the sets
at
account
of
the
of
theory
therein.
A contains Appendix
that
C contains a catalog
the
see the
functions
used on
available
scattering
algorithm,
a sample
be
totalpertinent
3 describes
correction
can
experi-
the
and
behind
information of
produce
the
SBUV wavelengths).
Section the
the
information the
B contains
(JCL)
to
absorption
each
describes
behind
external the
7 SBUV first-year
section
used
lists
flux
D contains
INSTRUMENT
and
solar
Appendix
This
algorithm
references
Nimbus
foundations
the
language
the
set.
(namely,
albedos.
control
data
of
theoretical
Appendix
the tape.
the
users
algorithm
detailed 2 al. and
tape
profile
data
a mOre
Klenk
the
2 presents
coefficients For
for
for
used
Fortran reading
ordering
ozone for
program an SBUV
tapes.
tapes.
OVERVIEW
is on board the Nimbus 7 satellite is designed to measure the total ozone and its distribution with height in the atmosphere in a vertical column beneath the satellite. The SBUV contains a double monochromator and a filter photometer designed to measure ultraviolet (UV) spectral intensities. In its the monochromator measures solar radiprimary mode of operation, ation backscattered by the atmosphere in 12 wavelength bands in the ranging from 255.5 to 339.8 nm, each with a bandpass of 1.0 near-UV, algorithm uses the four longest wavelength nm. The total-ozone 317.5, 331.2, and 339.8 nm), whereas the profiling bands (312.5, algorithm uses the shorter wavelengths. The photometer operates at 343 nm with a 3.0-nm bandpass and was designed to measure the reflectivity of the surface in the instantaneous field of view (IFOV). The SBUV also makes periodic measurements of the solar flux by deploying a diffuser plate into the field of view (FOV) to reflect sunlight into the instrument. The
SBUV instrument
The
rronochromator
in
the
degrees.
nadir As
that
and
direction the
satellite
the with
photometer
are
coincident moves
in
2
mounted
FOV's
of
so
that
11.3
by
a Sun-synchronous
they 11.3
retrograde
look
orbit, the FOV traces 200-km wide paths on the ground separated by The satellite footprint moves at a 26-degree longitude intervals. and the interval between consecutive SBW speed of about 6 km/set, The order of measurements is 339.8 to 255.5 nm scans is 32 seconds. For each and the integration time is 1 second per measurement. monochromater measurement there is a photometer measurement. 1.3
THEORETICAL FOUNDATIONS
The UV radiance received at the satellite in the total-ozone bands consists mainly of solar radiation that has penetrated through the stratosphere and has been reflected back by the dense tropospheric air and the surface. Ozone, being concentrated in the stratosphere above the region in which most of the radiation is scattered, acts By determining the amount of as an attenuator of this radiation. attenuation in the ozone absorption band, the amount of ozone above More than 90 the reflecting surface can be accurately estimated. percent of the ozone is located above the tropopause, and all clouds, most of the aerosols, and approximately 80 percent of the This almost complete separation atmosphere are located beneath it. of the ozone from the scatterers and reflectors minimizes errors caused by vertical profile shape, clouds, aerosols, and other tropospheric variables. Several important variables are necessary for computing the theoretultraviolet (BUV) light at ical intensity, I, of the backscattered The pressure, PO, and the reflectivity, R, the 13 SBUV wavelengths. The solar of the reflecting surface in the IFOV must be determined. the optical slant path, zenith angle, eo, is needed for calculating down through the atmosphere and S(= 1 + set eo), of the UV light back to the satellite.
The total backscattered radiance, I, flux at wavelength h can be expressed Dave3 as follows:
I(A,
eO,R,Po&f)
for 7r units of incident solar as the sum of two terms after
= Io(h~Oo~Po&f)
+
T (be,rP,&d) (1)
1 - RSb(bPo,%d,
Sb is the atmosphere where T is the atmospheric transmission, to and a is the total ozone. surface backscatter fraction, The arguments specify the independent variables in the computation. The the dependence on ozone profile shape. symbol, d, signifies The first term of equation 1, IO, is the purely atmospheric backscattered radiation intensity-the intensity at zero surface reThe second term accounts for the direct and diffuse flectivity. The ratio, radiation reflected by the surface. I/F (sometimes where F is the incident solar flux, called the geometric albedo), used to determine total-ozone and ozone profiles.
is
Because they are more sensitive to ozone absorption, the shorter wavelengths are used to determine the vertical ozone profile. The intensity of the BUV light at the satellite is affected by the ozone Thus, the ozone distribution and the distribution of air molecules. distribution is most easily determined in terms of the distribution as a function of pressure, p). of air molecules (i.e., The BUV h can be expressed by: intensity, IA, at wavelength
P(COS e,)
PO
FA
4n
/
0
-S(ah
e
’
+P,p)
dp
+ I
(2)
where =
Rayleigh
=
Rayleigh scattering phase function for solar Using a depolarization factor zenith angle 8,. this can be written as 0.7629 (1 + of 0.035, 0.932 cos2 eo'
=
incident
solar
PO
=
pressure
at the bottom
S
=
optical slant path for a plane atmosphere (= 1 + set eo)
=
ozone
=
ozone overburden
PA P(cos
eoj
FA
5
X
scattering
coefficient
flux
absorption
at wavelengthh
at wavelength
h
of the atmosphere parallel
coefficient
at wavelength
at pressure
p
h
the multiple scattered and reflected The term, IMsh, represents The integral term gives the single scattered intensity. intensity. is defined as: If a Q-value
then
by using
a similar
IA
47T
QA =
ph
. P(COSe,)
definition
for
(
G
(3)
>
QMs , equation h
2 becomes:
r0
QA -QMS,=
s
Oe
-S(CQ
The right-hand side of this equation and the left-hand scattered Q-value,
5
x + PAp)
dp
is referred to as the single side as the measured Q-value
(4)
corrected for multiple scattered and reflected radiation. The inversion of equation 4, using the measured Q-values for each profile wavelength, yields the ozone profile. 2.
THE ALGORITHM
The SBUV algorithm consists of and an ozone-profile algorithm. from an RUT-S tape (raw units RUT-S has had terrain pressures, radiometer (THIR) cloud data, it. The THIR is an instrument 2.1
two parts, a total-ozone algorithm The data are input to the program tape). In addition to SBUV data, the temperature/humidity infrared and snow/ice thicknesses merged onto that is on board Nimbus 7.
TOTAL-OZONE ALGORITHM
The algorithm for deriving total ozone from backscattered radiances is fundamentally very simple. Given the solar zenith angle, e,, the surface reflectivity, R, and the surface pressure, PO, the columnar amount of total-ozone, fi, is obtained by a lookup and interpolation using a table of precomputed radiances. procedure, The following paragraphs outline the various steps of the algorithm. 2.1.1
Computation
of Theoretical
Radiances
The radiance tables were created by using a set of 21 climatological 4 ozone vertical profiles. These profiles were determined for three latitude bands using balloon ozonesondes. There are three profiles for low latitudes (n = 0.2 to 0.3 atm-cm in 0.05-atm-cm steps), eight for midlatitudes (0.2 to 0.55 atm-cm), and ten for high latitudes (0.2 to 0.65 atm-cm). The precomputed radiance tables (called standard tables) were calculated by using the auxiliary equation solution to the radiative 3 transfer equation. The ozone absorption coefficients are based on 5 6 the measurements of Inn and Tanaka, using Vigroux's temperature
6
coefficients. The computation of the band-average coefficients is 7 described by Klenk. These absorption coefficients are listed in Table 1. The reflecting surface is assumed to be Lambertian. For each of the 21 standard profiles, radiances are computed for reflecting surface pressures of 1.0 and 0.4 atm. The tables have an upper limit on the solar zenith angle of 85.7 degrees. 2.1.2
Computation
of Normalized
Radiances,(I/F)
The algorithm calculates a nominal the prelaunch irradiance calibration soon after launch, as follows:
F?L= Kh . Ch (do)
value of the solar flux, F, using constants and measurements made
l
Fl
(a,P)
R2(do)
(5)
where
FA
= solar
KA
= irradiance
CA(do)
= measured counts at wavelength measurement of the solar flux
F1bP)
= angular
R2 (do)
= Sun/Earth = l-0.0167
A nominal
value
flux
at wavelength
h normalized
calibration
response
constant
function
distance
to 1 AU
at h h on day do, after launch
of the diffuser
the
first
plate
on day do in AU
cos (27r(do-4)/365.25)
of the backscattered =A = Kh
l
C'
intensity (d)
is
also
calculated: (6)
Table 1 External Inputs
Wavelength (nm)
Effective Ozone Absorption Coefficient (atm-cm -1 )
Rayleigh Scattering Coefficient
Solar
(watt/cm3/AU)
(atm -3
255.652
297.3
2.4526
273.608
162.6
1.8198
Flux
76.09
Prelaunch Calibration
Radiance
Constant
(watt/cm3/ster/count) (gain range 2) 5.102
x 1O-5
186.6
5.506
x 1O-5
283.099
76.50
1.5688
315.4
5.978
287.702
45.32
1.4628
323.2
6.157
x 1O-5 x 10 -5
292.289
26.32
1.3663
528.7
6.274
x 1O-5
297.586
13.18
1.2650
508.9
6.352
x 1O-5 x 10 -5
301.972
7.300
1.1881
439.9
6.366
305.872
4.455
1.1245
567.1
6.347
312.565
1.750
1.0250
670.8
6.268
x 1O-5 x 10 -5
317.561
0.9209
0.9580
773.2
6.188
x 1o-5
331.261
0.1675
0.8005
987.7
5.203
x 10-5
339.892
0.0406
0.7183
1043.6
4.463
x 1O-5
343.3 (photometer)
0.0191
0.688
972.0
1.853
x 1O-3
( I
where C;(d)
= measured
BW counts
kA
= prelaunch
radiance
A corrected
value
of
I/F
at wavelength calibration
is obtained
=
R2(d)
l
constant
from
and F by multiplying by a time-varying given in Appendix A.
A on day d
the nominal
correction
l
values
function,
F;(t)
of I F;'
(7)
corrected accounts for any changes in the The correction function, F;(t), solar output with time and for any changes in the instrument throughput with time. For the calculation of the albedos (I/F), instrumental and solar-flux changes need not be known separately. functions were obtained by assuming Note, however, that the F2(t) that the optical characteristics of the diffuse solar reflector did not change since the prelaunch calibrations. Stability of this reflector is important because it is the only optical component that is used for solar-flux measurements but not for radiance measureOn the basis of studies of equatorial radiances, it is bements. lieved that the diffuser plate reflectance was stable within 2 percent at 339.8 nm during the first year of satellite operation. It is convenient to convert called an N-value, defined
NA = -100
the as:
albedos
loglo
into
an attenuation
number,
(8)
9
IlIllllllIIlIl IIlllIlllIIlllllI I I III
2.1.3
Calculation
of Reflectivity
For wavelengths in which no ozone absorption occurs, the measured the reflectivity of the IFOV. radiance, I M' can be used to infer Removing the ozone dependence from equation 1 and solving for the reflectivity, R,
R=
2~ T(W,,
rM-ro(h,eo,Po) PO) + Sb(h,Po).
IM -
(9)
1
=O(beOrpO)
tables. where I , T, and Sb are computed from the standard The two 1ongest'SBUV wavelengths --the 343-nm photometer and the 339.8-nm inside the ozone absorption monochrometer channel-- are slightly at these wavelengths, Fortunately, the amount of ozone needs band. to be known only approximately (50.05 atm-cm) for the error in the reflectivity attributable to ozone contamination to be less than 1 percent. The 343-nm filter photometer has experienced continued degradation It is anticipated that it will evenduring the first year of data. tually not be sensitive enough to accurately determine the reflecIt has therefore been decided to exclusively use the tivity. 339.8-nm monochromator channel for determining reflectivity to avoid a discontinuity in the data when the photometer becomes unusable. is still used to account for scene changes However, the photometer between different wavelength steps of the monochromator, which, in per step. extreme cases, could be as large as 5 percent 2.1.4
Calculation
A-pair defined
and B-pair as:
of Total N-values
NA = N312.5
Ozone used in the
- N331,2
10
total-ozone
algorithm
are
(loa)
*B = *317.5
(lob)
- *339.8
The algorithm calculates the total ozone by a simple linear polation between adjacent N-values in the standard tables. done for each of the two pressure levels of the tables--l.0 according to the IFOV pressure. atm-- to be combined later Page. 1 An important ical standard zenith angle made entirely Latitude 0 -+20 -+30 +60 -270
interThis is and 0.4 (See next
step is the selection of the proper set of climatologWhen the solar tables from the three sets available. is less than 78.5 degrees (S c 6.0), this decision is on the basis of the latitude of the IFOV as follows: Use
(deqrees) to to to to to
220 230 260 -+70 290
Abrupt discontinuities mixture by latitude regions.
Low-latitude Mix low- and Mid-latitude Mix mid- and High-latitude
tables mid-latitude tables high-latitude tables
tables tables
in total ozone are avoided by using a linear of two of the tables in the latitude mixing
A different table selection scheme is used when the solar zenith angle is 78.5 degrees or greater (S 2 6.0) because of the increased This selection is sensitivity of total ozone to the profile. shape. made between the mid- and high-latitude tables on the basis of the A Nmeas' Theoretical A-pair N-values are measured A-pair N-value, interpolated from the tables, using the B-pair mid- and highOEid and G?:igh ), giving Ntid and NEigh. latitude ozone values
11
The weight used in mixing obtained as follows:
the mid-
WEIGHT i
This
weight
is
then
tables
A NA meas - *mid A NA high - *mid
used to combine
aB = sphigh
and high-latitude
the
. WEIGHT + &a
l
is
then
(11)
two ozone
values
(1 - WEIGHT)
as follows: (12)
WEIGHT + 2.0) is calculated to indicate how the A "table index"(= To avoid a discontinuity, tables were mixed. mid- and high-latitude total-ozone values calculated from the low and the high zenith angle (ZA) methods are combined linearly by slant path between S = 6.0 and (S = 8.0) is the new ZA = 81.8 degrees Thus, not until S = 8.0. in the high ZA method, A-pair Note that, method in full force. ozone is not calculated. 2.1.5
Calculation
of IFOV Pressure
The average pressure of the reflecting surface in the IFOV must be -determined in order to properly combine the l.O- and 0.4-atm ozone Two methods are used in the algorithm to find this presvalues. (1) using the reflectivity and (2) using data from the THIR sure: instrument. method, the terrain pressure is com2.1.5.1 Method l-- In the first bined with the cloud-top pressure according to the reflectivity and A latitude-dependent climatologithe presence or absence of snow. cal average cloud-top pressure obtained from THIR studies is calculated according to: Pcloud
= 0.3 + 0.15
- cos
12
(2 l lat)
1
atm
(13)
The average
IFOV pressure, PO = f
.
PO, is obtained
Pcloud
+
(1
-
f)
as follows:
f, is obtained by usinq information as follows:
where the estimated fractional cloudiness, R, and snow/ice the measured reflectivity, With .-
No Snow
Snow (>0.5
f ZR
0.2 < Rx0.6
inches
thick)
f = 0 f = 0.5 - 0.2 f 2 0.8
f = 0 f = 1
Rr0.2 Rs0.6
(14)
’ Pterrain
- 0.2 0.4
2.1.5.2 Method 2--The second method uses THIR cloud data when THIR 11.5-pm radiances are used to determine the cloudavailable. and the fractional cloudiness, f, in the SBUV top pressure, Pcloudt These quantities are contained on the RUT-S tape. The equaIFOV. tion for the THIR-derived pressure is identical to equation 14. Because the ozone retrieval is very sensitive to the IFOV pressure at low reflectivities, limits are set on the use of THIR. For Rr0.2, terrain pressure is used regardless of THIR. To prevent una latitude-dependent minimum allowreasonably low THIR pressures, able cloud-top pressure is defined, as follows: pmin cloud This
+ 0.15
is used to compute
cloudiness and snow/ice
l
lat)
a minimum acceptable
pmin = f . pmin THIR cloud The fractional reflectivity
1 - cos (2
+ (l
- f,
. 'terrain
1
atm
THIR pressure
(15) given
by: (16)
in equation 16 is determined from the thickness as in method 1. The actual THIR
13
IFOV
pmin THIR'
pressure is reported on the ozone tape, but, if it is less min the total-ozone calculations are made, using PTHIR.
than
When IFOV pressures are determined, both a reflectivity-derived and a THIR-derived ozone are calculated for each pair (or for B-pair only at ZA 2 78.5 degrees) by a linear interpolation of the ozone values derived by using the l.O- and. the 0.4-atm tables. The ozone values calculated represent the total ozone down to the terrain height. In the presence of clouds, the reported ozone implicity includes a climatologically determined amount of ozone below the cloud. 2.1.6
Calculation
of Best
Ozone
After adjusting for the IFOV pressure, the A-pair and B-pair ozone values are combined to get a single "best" ozone estimate. The weighting of the A- and B-pair ozone is done on the basis of the (S I 2.5), the A-pair ozone is preslant path, S. At small values ferable because algorithmic errors are usually larger for the B-pair At large values (S L 5.0), the B-pair ozone is preferable ozone. because the A-pair becomes more sensitive to the shape of the ozone values of the slant path, the ABecause, at intermediate profile. and B-pair sensitivities to the ozo'ne profile and to algorithmic errors are comparable, a weighted mean is taken as the best ozone. is computed as: Thus, best ozone, Best' aBest
= 'A
QBest =
'Best
'A
(5.0 - S) + 'B 2.5
(S - 2.5) 2.5
(S 5 2.5)
(17a)
(2.5~
(17b)
Sc5.0)
(S 25.0)
= 52B
14
(17c)
2.1.7
Validity
Checks
The algorithm contains several validity checks for maintaining data In processing before the ozone determination, several quality. checks are made on the solar zenith angle, satellite attitude, and instrument status to ensure the quality of the radiances and other This section describes the quality checks pergeophysical input. formed on the derived reflectivity and ozone to identify bad scans caused by either bad input that passed preprocessing checks or limitations of the ozone algorithm. A flow chart of the quality checks is shown in Figure 1. The computed total ozone for each pair must be within the dynamic For low, mid, and high latitudes, range of the radiance tables. the ranges are 0.18 to 0.35, 0.18 to 0.60, and 0.18 to 0.65 atm-cm, respectively. If A- or B-pair ozone exceeds the range, it is set to -999, best ozone is set to -999, and quality flag = 9 is assigned. The reflectivity Next, a check is made on the best reflectivity. than +1.05. If this range must be no less than -0.05 and no greater is exceeded, the best ozone is set to -999, and quality flag = 8 is assigned. A second check is made on the reflectivity. Even though the 343-nm photometer reflectivity is not used in the total-ozone computation, it is used as a check on the 339.8-nm monochromator reflectivity. If these two differ by more than 0.15, the best ozone is set to Significant differences in -999, and quality flag = 7 is assigned. the two‘reflectivities could result from instrument calibration errors or significant departure of the real atmosphere and surface from the algorithmic model. If the data pass flags 9, 8, and 7, the slant-path length (1 + set Two additional checks are made on low solar zenith 0,) is checked. and three are made on high solar zenith angle angle data (S < 6.0), data (S 2 6.0). 15
PATH > 6.6
I FLA R BEST
SENSITIVITY TOO SMALL
DESCENDING
FLAG=2
I
NO
4
X'
[
I
(18)
the multiple where SS implies the single scattering term, MS implies and the scattering term, Xk is the ozone amount in the kth layer, prime denotes the result of the previous iteration. A priori information in the form of a predicted climatological profile and an associated covariance matrix (paragraph 2.2.3) are The standard deviations and correlaprovided for the inversion. tions between the Q-values (the measurement covariance matrix) are The solution is obtained by minimizing the weighted sum also input. of the squares of the differences between the logarithms of the observed and calculated Q-values and the difference between observed and calculated total-ozone values under the constraint that the solution profile differs minimally from the 2 priori profile. The constraints are imposed in a statistically optimum manner by including the full covariance matrix of the radiance errors and Two to three iterations errors in estimating the 2 priori profile. In addition to the solution profile (the 12 layer normally suffice. a solution profile error covariance matrix (the standard amounts), deviations) is also obtained. 2.2.2
Calculation
of Multiple-Scattering
Component
which occurs in the troposphere, is important Multiple scattering, only at wavelengths longer than 290 nm. The multiple-scattering terms for the longer wavelengths are computed before the solution process and are kept fixed. Multiple scattering is weakly dependent
19
dependon the profile shape (see Taylor -et al. lo) but are strongly angle, the surface present on the total ozone, the solar zenith Although the reflectivity is reflectivity. sure, and the surface obtained by using the 339.8-nm band of the monochromator, the photometer is used to account for scene changes between the 339.8-nm measurement and those at the profile wavelengths. Multiple-scattering Q-values are tabulated for three latitude bands Low- and midin terms of total ozone and optical path length. Mid- and latitude values are used from +45 to -45 degrees latitude. Interhigh-latitude values are used from 245 degrees to the poles. polation between latitude bands is done linearly by comparing the If the Q is outside the observed Q with the two calculated Q's. band whose Q is nearest range of the calculated Q's, the latitude The amount of interpolation in latitude the observed Q is used. between the multiple-scattered Q-values is specified for each wavelength by the multiple-scattering mixing fraction, in which values the low-, mid-, and high-latitude of 1.0, 2.0, and 3.0 indicate bands, respectively. As part of scattering Q-value to lengths. scattering culate the scattering 2.2.3
the interpolation process for determining the multiplethe sensitivity of the multiple-scattering Q-value, total ozone is calculated for each of the longer waveThe sensitivity is the partial derivative of the multipleQ-value with respect to total ozone and is used to calvariances and covariances associated with the multiplecomponent of Q for the measurement covariance matrix.
A Priori
Profile
and Covariance
Matrix
matrix represent The d priori profile and its covariance titative knowledge of the amount of ozone in each layer
20
the quanof the
atmosphere as a function of latitude in each kth layer is given by: X.
k
= Ak -I- 1-cos
(2*lat)
and time.
Bk + Ck
l
The amount
cos
of ozone
(19)
A (+'i',) 365
where Ak
= ozone
in layer
k at the
Equator
Bk
= change in yearly average ozone in layer k in going from the Equator to 45 degrees latitude
'k
= amplitude of the annual 45 degrees latitude
@ k
= day of the peak of the annual variation Northern Hemisphere (+,' = I$, + 182.5 Southern Hemisphere)
lat
= latitude
d
= day of the year
wave in the
kth
layer
at
in the days in the
Table 2 lists the coefficients for each layer, and Table 3 gives the a priori profile error covariance matrix assumed by the retrieval algorithm. This matrix gives the covariances of the fractional difference between the measured layer ozone amounts from those preThis covariance matrix is used for all meadicted by equation 19. Nimbus 4 BUV data from 1971 were employed to obtain the surements. coefficients and covariance matrix elements for the layers above 16 matm. For the lower layers, the ozonesonde data set compiled by the Atmospheric Environment Service, Canada, was used.
21
-A Priori
Table Profile
Layer*
Coefficients
No.
Pressure
(k)
(matm)
1
2 Coefficients
O-0.24
Ak (DU)** 0.110
Bk
'k
'k
(DU)
(DU)
(day)
-0.010
0.004
0
2
0.24-0.49
0.250
0.010
0.040
-10
3
0.49-0.98
0.850
0.130
0.250
-11
4
0.98-1.95
3.00
0.600
1.00
5
1.95-3.9
11.5
-0.400
0.700
6
3.9
-7.8
33.0
-7.400
1.90
164
7
7.8
-15.6
62.0
2.40
154
8
15.6
-31
75.0
-6.00
44.0
38.0
13.0
59
9
31-62
-19.0
-9 4
0.00
10
62 -125
5.00
49.0
16.0
62
11
125 -250
3.00
25.0
12.0
91
12
250 -1000
10.0
8.0
182
15.0
*Although the pressure range of the layers defined here are identical to those used for Umkehr retrievals, the numbering scheme is the reverse of that for Umkehr, for which the numbers increase with height. **DU
=
Dobson
units.
22
A Priori Layer Number 1
1' 22.50
2 3
2
3
12.60
4.29
14.40
Profile
7
8
9
10
11
12
0
0
0
0
0
0
0
0
0
9.24
2.28
0
0
0
0
0
0
0
0
12.10
7.70
0.97
0
0
0
0
0
0
0
10.00
4.16
-0.72
0
0
0
0
0
0
6.40
2.18
-1.04
0
0
0
0
0
6.40
4.00
0
0
0
0
0
10.00
5.76
0
0
0
0
14.40
10.08
-0.36
0
0
22.50
17.55
7.35
0
90.00
89.67
6.30
6 7 8
MATRIX SYMMETRICAL ABOUT DIAGONAL
9
Matrix*
6
5 E
3 Covariance
5
4
4
Table Error
10 11
240.1
12 *All
53.17 122.5
elements
must be multiplied
by 10 -3 .
Layer
numbers are identical
to those
in Table
2.
2.2.4
Measurement
Covariance
Matrix
The measurement covariance matrix specifies uncertainties in the measured and calculated Q-values and any correlations that might exist between these errors. Diaqonal elements of the covariance matrix contain a sum of the square of three errors: a 0.5-percent error in radiances due to an assumed l-percent instrument error, error in ozone absorption coefficients, and error in multiple scattering corrections due to a 2-percent error in total ozone (applies only to wavelengths longer than 292.3 nm). These errors are computed for each SBUV scan because they vary with solar zenith angle The combined rms errors vary from -0.7 and surface reflectivity. percent for the shortest wavelengths to as much as 10 percent for Off-diagonal the longest wavelengths for scenes containing clouds. terms of the covariance matrix are caused by total-ozone errors that cause correlated errors in multiply-scattered wavelengths. (For see Section 3 of Schneider et al. 8, more details, -2.2.5
Validity
Checks
Several checks are made to identify abnormal values. If the scan fails file error code is assigned.
scans with missing or grossly any one of these checks, a pro-
If any profile wavelength measurements are missing, a profile error code of 1 is assigned. If a best-ozone value has not been computed then a profile error code of 2 is in the total-ozone algorithm, assigned. If the monochromator reflectivity for any wavelength is changes by outside the range -0.05 to +1.05, or if the reflectivity more than 0.05 from wavelength to wavelength, then a profile error code of 3 is assigned.
24
The algorithm uses the 274- and 283-nm Q-values to calculate values ozone at 1 mbar, and u, the ratio of the atfor C, the cumulative mospheric scale height to the ozone scale height, assuming that the cumulative ozone, X, is a function of the pressure, p:
x = c pi/u
(20)
If cr is outside the range from 0.3 to 0.8, a profile error code of 4 If C is greater than 3.0 matm-cm or less than 0.5 is assigned. error code of 5 is assigned. matm-cm, a profile If the observed Q-value differs by more than 60 percent from the Q-value calculated from the 2 priori profile and the tabulated multiple-scattering Q'S, a profile error code of 6 is assigned. solution is terminated For error codes 1 through 6, the profile soon as the error code is assigned. The function of error codes 5, and 6 is to prevent grossly abnormal Q-values from being used input to the algorithm. These may result from momentary lapses the instrument performance or the data transmission and storage process. Profile error code 7 is not currently used.
as 4, as in
If the scan passes checks 1 through 6, the ozone profile is computed, and two additional checks are made. If the atmospheric pressure at which the cumulative ozone is one half of the total is considered ozone is not between 10 and 100 mbar, the profile If the ozone suspicious, and a profile error code of 8 is assigned. mixing ratio between 0.3 and 40 mbars exceeds 23 pgm/gm, the profile and a profile error code of 9 is is also considered suspicious, assigned. If the profile passes these checks, it is considered a and a profile code of 0 is assigned. good profile,
25
3.
TAPE FORMATS
The
SBUVALL
This
tape
and/or
program
can
in
be
The block
(FB)
followed
of
its
in
tape
is
of
on
OF OZONE-S
an
files
for
IBM
each
called
its
the
physical
OZONE-S
tape.
structures
structure. TAPE
a multiple-file
format by
tape
terms
logical
STRUCTURE
OZONE-S
an output
described
terms
PHYSICAL
3.1
creates
binary
360
tape It
machine.
orbit
of
data
written
in
fixed-
contains
a header
finally,
a trailer
and,
file,
file. The is
first
file
written
the
is
in
a special
a format
tical
Operational blocks of 630
sists
of
Lines
1 and
the
Nimbus
five
2 are
the
0
System
(NOPS).
characters
written
archivable This
written
according
in
to
Record.
NOPS tape of
header,
tapes file
which
produced
contains Each
EBCDIC.
a standardized
The
by
two
iden-
block
con-
standard
format
header
script
"b"
indicates
Tape
sequence
number
identifying
the
sequence
number tape
format
called
records
For
con-
all
OZONE-S
nuniber tapes,
tape unique
con-
the The
charsub-
a blank. consisting (for
of
OZONE-S
to
specifying is
specification
bNIMBUS-7bNOPSbSPECbNObT634041.
is
number
product
30 characters.
string
OZONE-S
standard
lines.
acter
digit
all
the
information:
Nimbus-7 sisting
0
to
Header
following
called
common
126-character
NOPS Standard
tain
file
each
the
copy
FE83231-2.
26
a two-character this
tape,
is
FE)
a hyphen,
number.
code a 5-character and
An example
a onefor
an
0
0
Subsystem identification preceded and followed bSBUVb.
code consisting of 4-characters by blanks. For OZONE-S, this is
Generation and destination facilities consisting of four An example is SACCbTObIPDb. characters each are given. this example SACC is the computer facility that generated OZONE-S tape and IPD in the destination of the tape.
In the
a
The beginning and ending dates of data coverage are given as bSTARTb19YYbDDDbHHMMSSbTOb19YYbDDDbHHMMSSbwhere YY is the day of the year, HHMMSSare the hour, year, DDD is the Julian minute, and second of the day. For the OZONE-S tape, the ending date is not the true ending date of the data on the In order to tape but a fill date (i.e., 1999b365bO02400). avoid unnecessary processing complications, the true ending date does not appear in the header record.
0
The tape generation date is given GENb19YYbDDDbHHMMSSb. above:
The following record:
character
string
in a similiar
is an example
format
as
of an OZONE-S header
NIMBUS-7 NOPS SPEC NO T634041 SQ NO FE83231-2 SBUV SACC TO IPD START 1978 328 090427 TO 1999 365 002400 GEN 1981 106 115029 Lines 3, 4, and 5 are used by the subsystem analyst for further identification of the data tape. Line 3 of the header file is usually left blank. Lines 4 and 5 contain information about the processing software such as program name, version number, and version date. The remaining files on the tape each contain a variable blocks, each of which is 16,560 bytes long. The first block contains a 32-bit block identifier (Figure 2). 27
number of word of each
BITS:
1-12
13-16
BLOCK NUMBER ON TAPE Spare
17
18
1
1
Fbr
For
Last Block On File
Last File
25-32
19-24
Record ID's: decimal) 03-First
(in
block
on data files 18-Intermediate blocks
on
Spare
data
files
53-Last data
58-All
block files
blocks
trailer
Figure 3.2
2.
Block
on
file
Identifier
LOGICAL STRUCTURE OF TAPE
The IPD header file is followed by the data files, one for each For most users of the tapes, it will be orbit of data on the tape. more convenient to treat the data files as a collection of logical each 828 bytes long. (Note that 20 of these records are records, blocked together before writing on the tape.) The first record of each file contains processing information about Its format is described in Table 4. Each the data that follows. of the following records contain total-ozone and profile information from a single 32-second scan of the SBW instrument. The format for these data records is given in Table 5. Typically, the SBW takes 90 to 100 scans during the daylight half of each orbit; under normal operating conditions, one file on the tape therefore, should contain as many data records. The last record Table 6. This
of useful information on each file record follows the last data record
28
is described of the file
in and
contains a processing summary of the preceding orbit of data. record will be dummy records to fill the last Following this "last" These dummy records keep all blocks the same length and block. should be ignored. The record type can be identified by word 2 of each record. It contains the logical sequence number of records within the file. It begins at 1 for the first record of the file and is incremented by 1 for each successive record. For the last record, which contains the file processing summary (and dummy records following), the negative of the logical sequence number is written. It contains The last file on the tape is called the trailer file. 20 identical copies of a trailer record (to fill one block), which It contains a processing summary of the is described in Table 7. entire tape, similar to that of the last record of each data file. The trailer-file records can be identified by their logical sequence number of -1.
29
Table Format
of
First
4
Record
on
Data
Files*
Description
4-Byte Words 1
Block
2
Logical
3
Orbit
4-7
Date
8
Day
of
first
good
scan
9
GMT of
first
good
scan
10
Year
11
Subsatellite
latitude
12
Subsatellite
longitude
for
13
GMT of
ascending
node
14-17
Processing
18-30
13 solar
31-67
37 radiance
68-80
13 instrument
31-93
Ozone
34-106
Rayleigh
107-126
20 processing
127-207
Spare
identifier sequence
(Figure
2)
number
(1)
number of
job
of
run
first
(MON DEC 10,
good
right
1978)
(seconds)
scan for
first
scan
first
scan
of
(degrees) (degrees)
orbit
parameters irradiance
values
conversion
(1
for
each
wavelength)
factors
wavelengths
absorption
coefficient
scattering
for
coefficients
instrument -1 (atm
wavelengths
)
options
(-77) (Continued)
*Word and
1 contains the
remaining
hexadecimal words
words
data, contain
data
(R*4).
30
in
4 to
7 contain
IBM
floating-point
EBCDIC
data,
format
Table Detailed
4
Description
(Continued)
of
First
Record
on
Data
Files
Comments
Word 11
12
14-17
Latitudes
range
from
-90
latitudes
being
negative.
Longitudes
range
from
longitudes
being
negative.
The
following
to
-180
processing
+90
to
degrees,
+180
options
southern
degrees,
are
western
currently
imple-
mented: Maximum
solar
Minimum
latitude
(word
15)
Maximum
latitude
(word
16)
solar
irradiance
The
18-30
units . . .. 31-67
The units
of
angle
counts
nm, to
(word
for
the
current
in
the
order
watts/cm3/AU
29:339.8
of
zenith
30:
radiance
monochromator
gain
ranges
64-66:339.8
in nm,
word
day
is
words:
given
conversion
factors
are
and
given
order
for
words:
67 has
each value
given
in
an
nm).
are of
the
in
the for
three . . ..
31-33:255.5,
the
in
18:255.5,
(343
wavelength the
14)
photometer
watt/cm3/steradian/count
each
a
for
the
photome-
nm in
the
same
ter. 68-80
Instrument order .~-
as
wavelengths the
solar
are
flux. (Continued)
31
Table
4
(Continued) ..
Detailed
Description.of --
First
Record
on
Data
-1
Files
..--..~-.-
Comments
Word
~... 81-93
The
ozone
going
absorption
wavelengths
coefficients are
in
for
units
of
each
of -1
(atm-cm)
the
fore-
with
base
e. 107-126
There
are
20 possible
which
are
currently
processing
options,
implemented
(0
-
only,
disabled,
6 of 1 -
enabled): Word
107 --THIR
yORD
108 --Check
and
processing remaining
input/ouput
Word
112 --Profile
Word
113 --Do
central
processing
unit
time processing not
use
301.9-nm
channel
in
profile
not
use
255.5-nm
channel
in
profile
not
use
312.5-nm
channel
in
profile
processing Word
114--Do
processing Word
115 --Do
processing
32
Table Data
Record
5
Format
for
OZONE-S
Tape
4-Byte Description
Words 1
Block
2
Logical
identifier
(ZXO
sequence
800);
number
X = block
(N+l):
number
N = number
of
data
records 3
Orbit
number
4
Julian
day
5
GMT (seconds)
6
Subsatellite
of
year
at
the
latitude
start
at
the
of
scan
beginning
of
scan
(degrees) 7
Subsatellite
longitude
at
the
beginning
of
scan
(degrees) Total-Ozone 8
View
latitude
9
View
longitude--
10
Solar
11-14
Four
photometer
15-18
Four
monochromator
Output
--Average
ZA --Average
for
Average for
total
for total
N-values
(Continued) 33
ozone
ozone
(degrees)
(339.8,
nm)
:
(degrees)
total
(339.8,
N-values
ozone
331.2, 331.2,
(degrees)
317.5, 317.5,
312.5
nm)
312.5
Table
(Continued)
5
Description Gain
selection
Surface
flags
category
for
best
ozone
THIR
A-pair
THIR
pressure
(atm)
THIR
average
reflectivity
THIR
percent
cloudiness
THIR
error
flag
A-pair
sensitivity
A-pair
average
Spare Repeat Best A-pair
(Dobson
units)
minus
B-pair
ozone
ozone
of
four
X's
code
THIR
A-pair
each
for
total
(Dobson
ozone
(Dobson
ozone
units) (dN/dQ)
reflectivity
(-77) 27 through ozone ozone
30
for
(Dobson
units)
minus
B-pair
(Continued) 34
B-pair
ozone
(Dobson
units)
units)
Table
5 (Continued)
4-Byte Description
Words 37
Pressure
of
reflecting
38
Average
39
Spare
(-77)
40
Error
flag
41
Table
selection
42
Snow
43
Photometer/monochromator
44
Terrain
45-47
Spare
for
total
View
longitude--
50
Solar
contains
units
(DU);
block
size
may
contain
Profile
Output*
--Average
for
Average
ZA-- Average
IBM
for
for
atm-cm.
indicating
(degrees)
(degrees)
format
1 DU = 0.001 bytes
(degrees)
profile
profile
floating-point data.
= 16,560
profile
(Continued)
hexadecimal
-77,
difference
(atm)
.-
which
reflectivity
(-77)
49
in
index
(inches)
pressure
latitude
are
ozone
scheme
thickness
View
words
(estimated)
reflectivity
48
*All
surface
(20 fill
All
ozone
Logical
LRECL/BLOCK). data. 35
(R*4) values record Any
except are
word in
1,
dobson
size
= 828
word
in
the
bytes: record
._.._---...--
Table
5 (Continued)
4-Byte Description
Words 51-58
Eight
photometer 283,
273.5, 59-66
Eight
67-68
Gain
69-80
A priori
N-values
monochromator
N-values
flags
profile
for
layers
81
Total
(matm-cm)
82-91
Q-values
ozone
corrected
reflectivity
(255.5
92-101
Initial
102-106
Multiple-scattering for
residuals
five
317.5 107-111
Monochromator
Sensitivity correction channels
117-121
of
through
X's. (matm-cm)
scattering
(255.5
through
and
reflectivity
in
profile
317.5
wavelength
wavelengths)
amounts
2 priori
multiple
and
eight
ozone
255.5, 305.8 nm)
and
surface
nm) 317.5
nm) correction
channels
(297.5
to
Q
through
nm)
channels 112-116
longer
each
for
for
301.9,
(profile
individual
12 pressure
wavelengths
297.5,
292.2,
287.6,
selection
(profile
reflectivities
(297.5 of
through
for 317.5
and
total ozone for (297.5 through 317.5
Multiple-scattering wavelength channels
mixing (297.5
(Continued) 36
longer
wavelength
nm)
multiple-scattering
tc
five
five nm)
fraction through
longer
for 317.5
reflectivity wavelength
five nm)
longer
Table
5 (Continued)
4-Byte Words
Description
122-131
Final
132-143
Solution
residues profile
12 pressure 144-155
Standard
individual
deviations amounts
156
Total
ozone
157
Pressure
solution
(matm-cm) (matm-cm)
mbar
nm) amounts
(matm-cm)
in for
profile
12 pressure solution
at
which
cumulative
in
C and
sigma
(~1
individual layers
profile ozone
is
one
half
ozone
Parameters
160-175
Solution
176
Error
flag
177
Solar
zenith
angle
178
Solar
zenith
angle
179-190
Standard
191-200
317.5 ozone
for
158-159
ozone
through
layers
ozone
total
(255.5
mixing
ratio
for
profile
deviations amounts
(pgm/gm)
at
at
start
scan
at
end
for
(matm-cm)
Standard
deviations
scattering
and
for
reflectivity (Continued)
37
of of
scan
16 pressure
(rad (rad
profile -a priori in 12 pressure Q-values (255.5
levels
x 104) x 104) individual layers
corrected through
for 317.5
multiple nm)
of
Table
5 (Continued) ____-~____
-. _ ^
..
4-Byte Description
Words 201
Number
of
interations
202-207
Spares
(-77)
Detailed
Word 11-18
for
~__...-.-.-.
profile
Description
of
-.. ~__~ .._-=_--_.
solution
Data
Record
Comment
I N-value
is
N=
-100
where
I
computed
from
loglo
I
each
measurement
as:
(I/F)
= measured
radiance
and
F = measured
solar
irradiance. 19
Gain the
selection
flags
339.8-nm
gain
are
being
packed the
in
most
powers
of
significant
ten
with
decimal
digit.
20
Surface
21-26
Final
28,32
output
of
code
(not
total-ozone
by
the
processing
using
Sensitivity
of
a pair
is
defined
as
AN~/AR,
difference
in
the
N-value
of
pair
and Final
is
the output
information
total of
THIR
algorithm).
from
the
the
used
information
is
35-40
category
the
cloud
instrument. where
N
wavelengths
P
ozone. total-ozone
as provided
reflectivity. (Continued)
38
..-
processing indirectly
using from
the
the
cloud
measured
Table
5 (Continued)
Comment
Word 26,40
Error
flags
0 -
Low
l-
High
2 -
Low of
3 -
High
4-
Low
are
defined
as
path
length,
good
path path orbit path path
estimates
5 -
8 -
(sunlit
polar
length,
High
than path has
by
length, 1.8
or
length,
orbit
and
more
part
data
B-pair
than
total-ozone
10 percent
low
index
greater table
of
the
is
than
out
of
range
3.5).
selection
scheme
total
sensitivity.
flectivity
differ reflectivity
greater
descending
night)
table
reflectivity
or
in
estimate.
Photometer
Best
taken
A-pair
differ
path
scan
descending
length,
High
ozone 7 -
data
total-ozone
scan
good
length,
best
(less 6-
length,
follows:
than
by
more
out
of
1.05)
(Continued)
39
and
monochromator
than
0.15.
range
(less
than
re-
-0.05
Table
5 (Continued)
Comment
Word 9 - A-pair
or
range
59-66
67-68
N-values
69-80
of
Latitude
25"
Latitude
>55"
Packed
as
in
19,
ozone
are
in
order
the
top
of
the
from of
each
2 and
are
0.49,
125,
250
matm.
from
250
to
that
amount
in
series and
1000
the
dynamic
ranges
are:
180
to
350
DU
180
to
600
DU
180
to
650
DU
word
order:
0.24
day
59:
68.
each
layer
is
(Continued)
3.9, layer
The
is 12
pressure
layer
layers from
word
69
pressures
at
the
7.8,
by 15.6,
word
80
a factor 31,
by
a
for
increase for
obtained
that
year.
The
layer
matm.
40
word
The
1.95,
significant
of
of
matm.
final
most
atmospheric
succeeding 0.98,
the
expression
atmosphere.
The
the
being
increasing
0 to
bottom
in
2922
latitude of
dynamic
55"
2555
a harmonic of
to
exceeds
nm.
67 and
The
extends
305.8
word
word
function
The
8 wavelengths
. . . . 66:
-a priori evaluating
ozone
tables. 1308, (n)
=
- 1.67
Fi
1.024
F;
(n)
- 7.93
1.0 by:
x 1O-4 n + 1.628
is given
is given
x 10 -7 n2
by:
x 1o-5
n + 6.18
x 10 -8 n2
by:
= 1027.3
=
F'2 is given
1.029
600~ n(1308, F;
For orbits
(n)
For orbits
by: F;
For orbits
the photometer.
- 5.516
974.3 x 10 -2 n - 9.72
5-7
x 1o-7
n2
APPENDIX
B
SAMPLE FORTRAN PROGRAM AND JCL FOR THE OZONE-S TAPE C SAMPLE FORTRAN PROGRAM FOR READING THE OZONE-S TAPE ON THE GSFC C 360/91 OR 360/75 C TAPEIN REAL*8 DIMENSION BUFFER(207) DIMENSION OZ(12), STDV(12) NAMELIST/LIST/ TAPEIN,IFILIN,IFILEN C C**** READ THE NAMELIST VARIABLES FROM UNIT 5. TAPEIN = TAPE NAME, IFILIN = FIRST FILE NUMBER DESIRED, IFILEN = LAST FILE DESIRED C 5 READ(5,LIST,END=999) C**** MOUNT THE TAPE ON UNIT 10 CALL MOUNT(l,lO,TAPEIN,l) C C**** READ FROM FILE IFILIN TO IFILEN DO 100 IFILE=IFILIN,IFILEN IF(IFILE.GE.2) CALL POSN(l,lO,IFILE) C 10 CONTINUE C**** READ ONE LOGICAL RECORD FROM UNIT 10 CALL FREAD(BUFFER,lO,LEN,&900,&900) C C**** CHECK LOGICAL SEQUENCE NUMBER HEADER RECORD (FIRST RECORD 0~ DATA FILE) FOUND, C **** FIND THE ORBIT NUMBER (ORBN) AND THE YEAR, THEN C READ TIIE NEXT LOGICAL RECORD. C IF(BUFFER(2) .NE. 1.) GO TO 20 ORBN=BUFFER(3) YEAR=BUFFER(lO) GO TO 10 TRAILER RECORD (LAST RECORD ON DATA FILE) FOUND, GO C **** TO NEXT FILE. C 20 IF(BUFFER(2) .LT. -1.) GO TO 100 TRAILER FILE RECORD FOUND, READ NEXT NAMELIST STEP, STOP C **** IF NO MORE NAMELIST STEPS. C IF(BUFFER(2) .EQ. -1.) GO TO 200 C DATA RECORDS **+***+**+**++**++*++* C ***************e C C**** CHECK ERROR FLAG IF(BUFFER(40).LT.O.O) GO TO 10 C LONGITUDE AND SOLAR ZENITH ANGLE IN DEGREES C **** LATITUDE, XLAT=BUFFER(8) XLONG=BUFFER(g) ZA=BUFFER(lO) C **?* JULIAN DAY NUMBER IDAY=BUFFER(4) c*********************************************************************** 59
C C
NON THIR DATA (DETERMINED USING REFL. PRESSURE) **** BEST TOTAL OZONE (DOBSON UNITS) OZONE=BUFFER(35) C **** A-PAIR, R-PAIR OZONE (DOBSON UNITS) OZONEA = BUFFER(27) OZONEB = BUFFER(31) BEST REFLECTIVITY (PER CENT) C **** REFL=BUFFER(38)*100.0 PRESSURE DETERMINED FROM REFLECTIVITY (ATM) C **** PRES=BUFFER(37) C **** ERROR FLAG IERR=BUFFER(40) C*********************************************************************** C THIR DERIVED DATA C **** BEST TIIIR OZONE (DOBSON UNITS) OZTNIR=BUFFER(21) C **** THIR PRESSURE (ATM) PTHIR=BUFFER(23) C **** THIR REFLECTIVITY (PER CENT) RTHIR=BUFFER(24)*100.O C **** THIR PERCENT CLOUDINESS PRCNT=EUFFER(25) C **** THIR TOTAL OZONE ERROR FLAG IRTHIR=BUFFER(26) C*********************************************************************** PROFILE DATA C OZONE AMOUNTS AND STANDARD DEVIATIONS (D.U.) C **** DO 40 1=1,12 OZ(I)=BUFFER(I+131) 40 STDV(I)=BUFFER(I+l43) PROFILE ERROR FLAG C **** IPFLAG=BUFFER(176) C*********************************************************************** C GO TO 10 C 900 CONTINUE 100 CONTINUE 200 CONTINUE C GO TO 5 999 STOP END
60
IN 12 LAYERS
//ZMDGGSBU JOB (F12345678D,T,L00001,HOOHOO) //*OZONE-S JCL // EXEC FORTRANG //SYSIN DD DISP=SHR,DSN=ZMDGG.PROGRAM.FORT // EXEC LINKGO,REGION.G0=200K //GO,FT06FOOl DD SYSOUT=A //GO.FTlOFOOl DD DISP=(OLD,PASS),UNIT=(6%5O,,DEFER), // LABEL=(,NL),VOL=SER=WONG, // DCB=(RECFM=FB,LRECL=828,BLKSIZE=l656O,BUFNO=l) //GO.DATAS DD *,DCB=BLKSIZE=3200 &LIST TAPEIN='SBUV54',IFILIN=2,IFILEN=3OO, &END &LIST TAPEIN='SBUV55',IFILIN=2,IFILEN=5OO, &END // EXEC NOTIFYTS /* //
61
I:
APPENDIX C Data Availability
and Cost
SBUV Ozone-S data tapes are archived and available from the National Space Sciende Data Center (NSSDC). The NSSDC will furnish limited quantities of data to qualified users without charge. The NSSDC may establish a nominal charge for production and dissemination if a large volume of data is requested. Whenever a charge is required, a cost estimate will be provided to the user prior to filling the data request. Domestic requests for data should be addressed to: National Space Science Data Center Code 601 NASA/Goddard Space Flight Center Greenbelt, MD 20771 All requests from foreign researchers must be specifically
addressed to:
Director, World Data Center A for Rockets and Satellites Code 601 NASA/Goddard Space Flight Center Greenbelt, MD 20771 USA When ordering data from either NSSDC or the World Data Center, a user should specify why the data are needed, the subject of his work, the name of the organization with which he is connected, and any government contracts he may have for performing his study. Each request should specify the experiment data desired, the time period of interest, plus any other information that would facilitate the handling of the data
request. A user requesting data on magnetic tapes should provide additional information concerning the plans for using the data, i.e. what computers and operating systems will be used. In this context, the NSSDC is compiling a library of routines that can unpack or transform the contents of many of the data sets into formats that are appropriate for the user’s computer. NSSDC will provide, upon request, information concerning its services. When requesting data on magnetic tape, the user must specify whether he will supply new tapes prior to the processing, or return the original NSSDC tapes after the data have been copied. Data product order forms may be obtained from NSSDC/World Data Center A.
63
APPENDIX D SBUV Ozone-S Tape Catalog First Year Week Number 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Orbit Range(‘)
Day Rangeta) 304-308 309-315 316-322 323-329 330-336 338-343 344-350 351-356 358-364 365-006 007-013 014-020 021-027 028-034 035-041 042-048 049-055 056-062 063-069 070-075 077-083 084-090 091-097
102-162 163-258 259-355 356-452 453-549 564-645 647-742 743-825 841-936 950-1032 1034-1130 1131-1213 1228-1323 1324-1420 1421-1517 1518-1614 1617-1710 1711-1807 1808-1904 1905-1986 2003-2097 2101-2194 2196-2291
Number of Files(‘) 62 94 80 85 85 70 71 85 82 71 86 66 88 99 85 70 80 92 67 81 77 85 96
(1)
See the data inventory in the “User% Guide for the SBUV and TOMS First Year RUT-S and RUT-T Data Sets” for orbit availability for each day.
(2)
The data set begins on 10/31/78 (day 304) and ends on 11/3/79 (day 307). Data on the tapes is grouped into days based on the starting time of the orbits. Therefore, minor variations in day ranges may be noted as compared to the data inventory (see the llUserls Guide for the SBUV and TOMS First Year RUT-S and RUT-T Data Sets) which groups orbits into days based on the ending time of the orbits.
(3)
Number of files includes the header and trailer present. 65
files plus one file for each orbit
SBUV Ozone-S Tape Catalog First Year (continued) Week Number
Orbit Range
Day Range
24 25
2292-2374
098-103
2389-2484 2500-2580
105-111 113-118
85 97 61
2582-2678 2679-2775
119-125 126-132
74 81
30
2776-2871 2886-2968
133-139 141-146
82 84
31
2969-3065
147-153
32 33
3066-3148 3163-3258
154-i59 161-167
61 68 82
34 35
3273-3355
169-174
50
3357-3452
175-181
63
36 37
3453-3535 3550-3645
38 39
3646-3742 3743-3839
182-187 189-195 196-202
70 81 74
203-209
40 41
3840-3922 3937-4032
42
4047-4129
210-215 217-223 225-230
56 72
43
4131-4226
231-237
44 45
4227-4322 4324-4419
46 47
4455-45 14
238-244 245-251 254-258
78 47
4520-4584
259-263
52
48 49
4614-4710 4711-4805
83
50 51
4821-4902
266-272 273-279 281-286
73 69
4904-4997 5001-5096 5097-5193
287-293 294-300 301-307*
53 82 97
26 27 28 29
52 53
*Last orbit ends on day 308, 11/4/79. 66
Number of Files
78 57 69 74
-..
FOR THE SOLAR BACKSCATTE Goddard Space Flight Greenbelt, Maryland
National Aeronautics Washington, D.C. 15. Supplementary
Center 20771
and Space
Reference
Administration
Publication
20546
Notes
16. Abstract
Total-ozone and ozone vertical profile results for Solar Backscattered Ultraviolet/Total Ozone Mapping Spectrometer (SBUV/TOMS) Nimbus 7 operation The algorithms used have from November 1978 to November 1979 are available. the instrument performance has been examined in debeen thoroughly tested, and the ozone results have been compared with Dobson, Umkehr, balloon, tail, The accuracy and precision of the satellite ozone and rocket,observations. data are good to at least within the ability of the ground truth to check and are self-consistent to within the specifications of the instrument. The "SBUV User's It also provides including how to
describes the Guide" detailed information order tapes from the
17. Key Words (Selected by Author(s))
Ozone, profile, violet 19. Security
sale by the National
20. Security
Technical
Information
Service,
Statement
STAR Category 47 Unclassified--Unlimited
Classif. (of this page)
Unclassified
Unclassified ‘For
18. Distribution
Ozone Vertical Total ozone, Nimbus 7 SBUV/TOMS, UltraAtmospheric ozone radiation, Classif. (of this report)
SBUV experiment and algorithms used. on the data available on computer tape, National Space Science Data Center.
SpringfAd,
21. No. of Pages 72
Virginia
22161.
A04
22. Price’
NASA-Langley,
1982
