May 5, 1986 - Brown and Ms. Gail P. Anderson of the Optical Environment Division. They provided .... H-unime), J.R., Sheitle, L. ,and Loni-in, 1). R. H 1988) -A ...
GL-TR-90-0349
AD-A237 675 Effects of Solar Heating by Aerosols and Trace Gases on the Temperature Structure Constant
J.R. Hummel E.P. Shettle
SPARTA, Inc. 24 Hartwell Avenue Lexington, MA 02173
DTIC
SUS
^ELECTE ML JUL 0 81991,w 9 August 1990
Scientific Report No. 6
I
Approved for Public Release; Distribution Unlimited
GEOPHYSICS LABORATORY AIR FORCE SYSTEMS COMMAND UNITED STATES AIR FORCE HANSCOM AIR FORCE BASE, MASSACHUSETIS 01731-5000
91-03945
B i~iIlI 11111111,
"This technical report has been reviewed and approved for publication"
Robert R. Beland Contract Manager
Donald E. Bedd, Chief Electro-Optical Measurement Branch
FOR THE COMMANDER
R. Earl Good, SES, Director Optical Environment Division This document has been reviewed by the ESD Public Affairs Office (PA) and is releasable to the National Technical Information Service (NTIS).
Qualified requestors may obtain additional copies from the Defense Technical Information Center. All others should apply to the National Technical Information Service.
If your address has changed, or if you wish to be removed from the mailing list, or if the addressee is no longer employed by your organization, please notify PL/IMA, Hanscom AFB, MA 01731-5000. This will assist us in maintaining a current mailing list.
Do not return copies of this report unless contractual obligations or notices on a specific document requires that it .. e 4 eturileu.
UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE
REPORT DOCUMENTATION PAGE ia. REPORT SECURITY CLASSIFICATION
lb. RESTRICTIVE MARKINGS
UNCLASSIFIED 2a. SECURITY CLASSIFICATION AUTHORITY
3. ISRIBUTION /AVAILABILITY OF REPORT
APPROVED FOR PUBLIC RELEASE:
2b. DECLASSIFICATION i DOWNGRADING SCHEDULE
DISTRIBUTION UNLIMITED 4 PERFORMING ORGANIZATION REPORT NUMBER(S)
5. MONITORING ORGANIZATION REPORT NUMBER(S)
LTR90-009
CL-TR-90-0349
6s. NAME OF PERFORMING ORGANIZATION
6b.OFFICE SYMBOL (If apspilcable)
7s. NAME OF MONITORING ORGANIZATION
SPARTA, INC.
GEOPHYSICS LABORATORY
6c. ADDRESS (Cay, State, and Zip Code)
7b. ADDRESS (City, State, and Zip Code)
24 HARTWELL AVENUE LEXINGTON, MA 02173 3a. NAME OF FUNDING iSPONSORING ORGANIZATION
HANSCOM AFB, MA 01731-5000 8b. OFFICE SYMBOL (If applicable)
9. PROCUREMENT INSTRUMENT IDENTIFICATION NUMBER
F19628-88-C-0038 3c. ADDRESS (Cty, State, and Zip Code)
10. SOURCE OF FUNDING NUMBERS PROGRAM ELEMENT NO.
PROJECT NO.
62101 F
WORK UNIT ACCESSION NO.
TASK NO.
15
7670
AP
11. TITLE (Include SeCunty Classification)
EFFECTS OF SOLAR HEATING --V AEROSOLS AND TRACE GASES ON THE TEMPERATURE STRUCTURE CONSTANT 12. PERSONAL AUTHOR(S)
J. R. Hummel and E. P. Shettle" 13. TYPE OF REPORT
13b. TIME COVERED
SCIENTIFIC REPORT #6
FROM
07/01/88
14. DATE OF REPORT (yeer. Month, Day) TO
12/31/90
1S. PAGECOUNT
1990 AUGUST 9
24
le. SUPPLEMENTARY NOTATION
.Naval Research Laboratory, Code 65221 Washington DC 20375 fCOATI LO D
18 SUBJECT TERMS (Continue -n reverse it necessary end idenidy by block number
CODES GROUP GU
SUB GROUP/ UOptical
Turbulence, Solar Heating, Ozone, Aerosols, Index of Refraction,
Structure Function '.
ABSTRACT (Continue on reverse it necessary end identify by block number)
-hermosonde measurements made inthe stratosphere indicate an increase in the temperature structure constant, T during daylight hours. Simplified calculations indicate that temperature perturbations resulting from solar heating by
thi1 iayers of areosols and ozone could provide the mechanism for the observed day-night differences in C 2 T Estimates of the vertical variations in ozone and aerosol abundances on spatial scales between a few tens of meters to about a kilometer have been used with mean ozone and aerosol profiles to make detailed calculations of the solar 'heating rates by ozone and aerosols. The calculations have utilized the temperature dependent ozone absorption cross secions and the aerosol properties from the AFGL model atmospheres. Perturbations of various amounts and at fferent altitudes have been applied to the mean ozone and aerosol profiles to study the impact on the healing rates with ,oal of tryng to understand the stratospheric thermosonde measurements. 121. ABSTRACT SECURITY CLASSIFICATION
3. [) ,TRBUTiONi AVAILABILITY OF ABSTRACT
E-]
UNCLASSIFIEDIUNUMITED
22ij. NAME OF PF PONSIBL
"
N
.SAMEAS RPT.
"!NI',IUAL
ROBERT BEI AND W)'3 FORM 1473, 84 MAR
UNCLASSIFIED
OTIC USERS
22b. TELEPHONE (Include Area Coder
(617) 377-4604 83 APR edition mvay hi useod until oxhaiwlsd All other edriuns are obsole'.E"
r2.2
t.FICE SYMBOL
GL/OPA 'ECUerty CiASSI1CATON OF THIS PACE
UNCLASSIFIED
Accession For
NTTS
(~~44,
DTi,
CPA&I TAB
Unawwmunced
por
5
E
Just Ift.ation By Distribution/
Avellabl.lity Codes jAvail and/or
Dist
fSpecial
1 I
1.
2.
3. 4.
Contents 1 INTRODUCTION 1 1.1 Background and Purpose of the Study 1 1.2 Organization of Report 2 BACKGROUND AND RELEVANT OBSERVATIONS 2 2.1 Background 3 2.2 Relevant Observations 3 2.2.1 Ozone Measurements 4 2.2.2 Aerosol Measurments 6 2.3 Related Studies 6 DETAILS OF CALCULATIONS 8 RESULTS 8 4.1 Unperturbed Conditions 8 4.2 Perturbed Conditions 4.3 Determining the Solar Heating Rates Required to Initiate Turbulence 10 11 4.4 Sensitivity of Results to Model Calculations 11 4.4.1 Impact of Local Time 11 4.4.2 Impact of Latitude 13 4.4.3 Impact of Height of Perturbation 13 4.4.4 Impact of Choice of Stratospheric Aerosol
iii
5. SUMMARY AND CONCLUSIONS 5.1 Summary 5.2 Conclusions 5.2.1 Role of Perturbations in Ozone 5.2.2 Role of Perturbations in Stratospheric Aerosols References
iv
14 14 14 14 14 16
Figures 1. An Example of the Daytime Enhancement in C2 as Measured With an AFGL Thermosonde 2. Balloon Measurements of Ozone Mixing Ratio Over (a.) 15 to 30 km and (b.) 24 - 26 km From March 1984 3. Dustsonde Measurements of Aerosol Concentration as a Function of Altitude 4. Calculated Solar Heating Rates for the Background, Unperturbed Model Atmosphere 5. Heating Rate as a Function of Altitude Assuming a 50 % Change in (a.) the Aerosol and (b.) Ozone Concentrations 6. Values of the Critical Temperature Gradient as a Function of Wind Shear for Three Representative Stratospheric Temperatures 7. An Example of Vertical Wind Shears Measured During the AFGL - Penn State Measurement Program 8. Heating Rate Gradient as a Function of Local Time for Two Different Solar Albedo Conditions
V
3 5 6 8 9 10 12 12
Acknowledgement
The authors would like to acknowledge the contributions of Mr. James H. Brown and Ms. Gail P. Anderson of the Optical Environment Division. They provided significant suggestions and insight to the research and their contributions and time are greatly appreciated.
vi
EFFECTS OF SOLAR HEATING BY AEROSOLS AND TRACE GASES ON THE TEMPERATURE STRUCTURE CONSTANT
1. INTRODUCTION 1.1 Background and Purpose of the Study The propagation of radiation through the atmosphere can be affected by variations in the index of refraction. These variations can be studied by measuring the index of refraction structure constant, C 2 . The index of refraction structure constant is a measure of the variations in the atmospheric index of refraction as a function of altitude and, in turn, is a measure of the amount of optical turbulence present in the atmosphere. Thermosonde measurements of C" made during daylight conditions indicate an enhancement in the temperature structure constant relative to measurements made at night. Simplified calculations indicate that temperature perturbations resulting from solar heating by aerosols and ozone could provide the mechanism for the observed day-night differences in C2. The purpose of this study is to perform detailed calculations of the solar heating rates of ozone and aerosols on spatial and temporal scales appropriate to the observed "ariations in the temperature structure constant. 1.2 Organization of Report Chapter 2 sets the background for the phenomenon, presents some relevant observations, and discusses related stwuies from tle scintifc litermture. Chapter 3
describes the methodology used to perform the calculations and Chapter 4 discusses the results from the calculations. Finally, Chapter 5 provides the conclusions and recommendations for additional work. 2. BACKGROUND AND RELEVANT OBSERVATIONS 2.1 Background The Air Force Geophysics Laboratory (AFGL) has undertaken an extensive measurement program of C 2 over the years utilizing balloon-borne thernosondes. Thermosondes measure the temperature difference over a one meter horizontal path. 1 The mean square temperature fluctuation is evaluated and over the one
meter distance equals the temperature structure constant, C2. The temperature structure constant is then related to the index of refraction structure constant via the relationship, neglecting the small contribution from H 2 0, C2(z) 2 ,~ -oZ - [79.9P(z)xlO T2(z) 16-1 "JTk where z is the altitude in km, P is the atmospheric pressure in mb, and T is the
atmospheric temperature in K. The thermosonde unit is carried piggyback fashion with a conventional radiosonde which measures the pressure, temperature, relative humidity, and wind speed and direction. The AFGL program has measured C 2 at different latitudes and under day and night conditions. The thermosonde measurements of C '2 have indicated a dramatic difference between the averaged day and night conditions. Between about 15 and 30 kin, mere is an enhancement uf daUyimc C 2 "alues that is not seen in the nighttime values. Figure 1 demonstrates the daytime enhancement in C2 by comparing two thermosonde flights taken during a measurement program conducted at Penn State in 1986. The two thermosonde missions were taken on the same day and under the same syncptic weather conditions. This enhancement is believed to be real and not due to any instrumental effects. One possible explanation for the daytime enhancement is from solar heating by atmospheric gases, such as ozone, and/or aerosols. A detailed examination of possible instrumental sources of error has not indicated an instrumental source for the observed phenomenon. 2 GL is continuing to study the possibility of balloon thermal wake effects on the turbulence measurements. A series of dropsonde tests Brown, J. H., Good, R. E., Bench, P. M., and Faucher, G., (1982) "Sonde Experiments for Comparative Measurements of Optical Turbulence", AFGL-TR-82-0079, ADA 118740, 24 February 1982. 2 Brown, J. H., Dewan, E., Thomas, P., and Murphy, E., (1989) "Study of Possible Solar Heating Effects on Thermosonde Probes - Error Analysis", Geophysics Laboratory, Hanscom AFB, MA, GL-TR-89-0178, 10 July 1989, ADA 218116.
•
mnumllnnmlunllllllllII a m um
II~i llllllinIm
HI•2~
are planned for late 1990 to study if balloon wake effects could be contributing to the enhancement. The fact that this phenomenon is observed independently of location supports the belief of a solar heating-driven mechanism.
3
0
I
Averaged Thermosonde
11-11;
I
I
lr
I
.
1 111,r1
1 1 l f~r
1 1 1 r- lr1r
AFGL -
~Program
25E 20
1 1 m i,,,
N.
1 1
al
Penn State
5/5/86
.~,.
11:28 pm
_
------
---
10
1 r1 |
w
-10
5[
Data
5
"=110 -
---..
10 " " 10
" j0 - 1
C. (m
2:03 pm
,-Z r
/
)-" 10
" 10 -4 10
1
Figure I. An Example of the Daytime Enhancement in C2 as Measured With an AFGL Thermosonde
2.2 Relevant Onservations Two pieces of observational evidence support the hypothesis that solar heating is the driving force. One, the ozone mixing ratio and solar heating rates are increasing in this altitude range. Also, stratospheric aerosols peak in this altitude range. Second, measurements have shown that the profiles of ozone and stratospheric aerosols exhibit structure on spatial scales small enough to possibly give rise to the thermal variation that ultimately gives rise to the variation in the temperature structure constant.
2.2.1 Ozone Measurements The vertical profile of ozone is routinely measured using ba!loon-borpe elecuii, ,i ium :aviolet *bsaotion );.-tometers, trochemical ozoriesondes.
aind saTlil>
'e, e tectlniqtues inidicate that structure exists in the vertical
o:nen
h'>.:
