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measurements with the earth near telemetrical measuring system ZIMEN in Germany show, ... Telemetrical Measuring Network ZIMEN of Rheinland-Pfalz.
STRATOSPHERIC O3-INTRUSIONS CAUSE TROPOSPHERIC O3-BACKGROUND IN MIDDLE EUROPE

by

Dr. Horst Borchert Lecturer at Johannes-Gutenberg University, Mainz, Geogr. Institute, Fa. UMAD GmbH, D-13053 Berlin, Germany, Wartenberger Str. 24 Address: Westring 159, D 55120 Mainz

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1.

Summery

Simultaneous measurements of air pollutants and meteorological components with telemetrical measuring systems have shown, that cold weather frontiers of cyclones, coming from western directions, are nearly always accompanied with increasing Ozone concentrations in middle Europe. This Ozone is a contamination of stratospheric cold and dry air masses, which are transported by jet streams into the biosphere during tropospheric air folding. It comes from lower stratospheric regions and forms mainly the tropospheric O3background. Therefor the biosphere was already in pre industrial times exposed by O3. This known O3-production seems to be underestimated. In the following paper some examples of measurements with the earth near telemetrical measuring system ZIMEN in Germany show, that these natural O3-Intrusion is producing monthly averages of at least 20 to 40 µg/m3. Short time fluctuations of this intruded stratospheric Ozone have concentrations which are lying within the range of the lower limiting values to protect plants. Therefor this phenomenon should be considered by a new definition of Ozone limiting values to protect the human beings and the nature. 2.

Telemetrical Measuring Network ZIMEN of Rheinland-Pfalz.

To control the development of air pollution, in all sixteen federal countries of Germany telemetric networks had been installed. In the country Rheinland-Pfalz are located 32 measuring stations. Control centre of this system, called ZIMEN, is located in the capital Mainz. It gives information about expansion, transportation and sources of air pollution. In the industrialised towns the measurements had been started in 1977 to get information about the development of air pollution in urban areas. To study the causes of forest decline, measurements of air pollution had been started 1984 at five places in the forested highlands of Rheinland-Pfalz. Long time results of ZIMEN are published 1998 at 11.th Clean Air Congress in Durban /1/. Short time data are published in monthly reports since 1978 /2/. Actual data from all 17 German air pollution networks one can get by internet calling "http://www.umad.de". 3.

Long-time Measurement Results of Ozone (O3)

Since about 1982 Ozone as an air pollutant becomes important. O3 is one of the strongest gaseous oxidiser. It attacks the needles of conifers and reduces the assimilation of CO2. Therefore the first measurements of O3 had been started to study the cause of forest decline in Germany. Fig. 1 shows monthly averages of O3, averaged about five forested places and six urban stations. Seasonal alternations of O3 correspond with the curves of global rays and air temperature. Mechanism of the photochemical production and transportation of O3 are very good known: Tropospherical O3 mainly origins by photolysis of NO2 in the presence of peroxides produced from mainly anthropogeneous hydrocarbons. These precursors NO and hydrocarbons are mainly produced by traffic, gas power plants and households. O3 is a harmful respiration gas and attacks the lungs. Therefore the measurements of O3 had been started in towns too. Sliding annual concentrations of O3 in forests are nearly twofold of these in urban regions (Fig. 1).

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It is remarkable, that in winter-times with relative small photochemical production of tropospherical O3 because of low global rays and at places far away from sources of anthropogenic precursors, the monthly averages are relative high (between 30 and 50 µg/m3). Mon th ly and Yearly Averag e of Oz on e and Tem perature in F orests and U rb an R egio ns in R h ein lan d-P falz - Germany - fro m 1984 b is 2000 Te m p. [° C]

O3 [µ g/m 3 ] 140

14

Fo rests H un srück, E ifel, H o ch w esterw ald, P fälz erw ald

S lidin g Yearly Averag e of Tem peratu re 12 S lidin g Yearly Averag es of O3 10

120

100

80

8

60

6

40

4

20

2

U rb an R egio ns Main z and Lu dw ig shafen

0

1984 Bc ht00

1985

1986

1987

1988

1989

1990

1991

(Y ear-Number at the Beginning of the Y ear)

1992

1993

1994

1995

1996

Fig. 1

1997

0

1998

1999

2000

Data:ZIMEN-LfUG -

Fig. 1: Monthly and Annual Averages of O3- Concentrations in Towns and Forests Therefore it is of interest, to look for the cause of this phenomena. It was found, that during every intrusion of cold and dry western winds, beginning with increasing pressure after its minimum, relative high Ozone-concentrations occur. As an example Fig.2 shows the course of half hour averages of O3, pressure, absolute humidity and wind-direction in the month November 1991, measured in a suburb of Mainz. O 3 -C o n c e n tra tio n s in D e z e m b e r 1 9 9 1 in M a in z O 3 -Co n c e n tr a tio n [µ g /m 3 ], (P r e s s u r e -9 9 0 ) [m b a r ]

Ab s . Hu m id ity [m b a r ], W in d -Dir . [S e c t.]

80

16

W in d -D ire c tio n (3 0 ° S e c to rs )

O z o n -C o n c e n tra tio n [µ g /m 3 ]

70

14

(A ir-P re s s u re -9 9 0 ) [m b a r]

60

12

50

10

40

W

8

A b s o lu t H u m id ity [m b a r]

S

30

6

5

4

20

4

1

10

O

2

3

2

N

0

0 0

B c h t9 9

2

4

6

8

10

12

14

16

F ig . 2

18

20

22

24

26

28

da y

30

Fig. 2: Half-hour Averages of Ozone, NO2, air-pressure, humidity and Wind-direction.

A “family” of 5 cyclones occurs with intrusions of dry and cold western winds. Each cyclone is signified by a minimum of pressure. Generally at this points the O3-concentrations increase. Such O3 - Intrusions are observed as well in urban regions as in forests: Cold dry air, which comes during the cold-front of the cyclone by the yet stream from stratospheric regions, is contaminated with Ozon /3/. Such frontal-cyclones are often shown in the daily weather forecast at the Television. Cyclones occur, when cold air masses are coming from the north-western region into eastern directions and are meeting warm air masses, which are coming from south west directions to Europe /4/.

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4.

O3-Intrusion during Frontal-Cyclones in Detail

In the following Fig. 3 and 4 a typical example of intrusions of stratospheric Ozone during two frontal-cyclones (No. 1 and 2 in Fig. 2) is shown together with simultaneously measured meteorological parameters at urban and forested measuring places. O 3 - C o n c e n t r a t io n a n d m e te o r o lo g ic a l C o m p o n e n t s f r o m 1 8 . t o 2 0 . 1 2 . 1 9 9 1 in a n u r b a n A r e a ( M a in z ) O 3 , N O 2 [µ g /m 3 ]

Te m p e r a tu r e [°C ], ( Pr e s s u r e - 9 9 5 ) *0 ,5 [m b a r ], a b s .H u m . [m b a r ], W in d d .[S e k to r } , W iv e l. [m /s e c ]

P r e s s u re

90

B

W in d -d ir e c tio n

75

B

12

In tru s io n o f d ry a n d c o ld A ir O z o n -C o n c e n tr a tio n

A b s o l. H u m id ity

D ry a n d c o ld A ir

C

A

10W

C

60

8

A

45

S

(O 3 + N O 2 )

NO2

6

1

30

4

15

2

2

G lo b a l R a y s

O

N

0

0 0

1 8 .1 2 .

24

48

1 9 .1 2 .

B c h t9 9

72

2 0 .1 2 .

F ig . 3

hours

D a ta : L f U G - Z IM EN -

Fig. 3: O3-Intrusion during two frontal-cyclones, measured at the suburb station Mainz Frontal-cyclones start with slow increasing temperature and absolute humidity of the air, which comes mainly from south-western directions (sector 8) into the country, accompanied with some precipitation (Warm-front at Point A). Normally follows a region with nearly constant warm and humid air masses (Warm-region B). This region ends again with precipitation. Than follows with increasing and changing winds from more western directions (sector 9 to 12) the intrusion of cold air masses, which are accompanied with increasing O3Concentrations (Point C). Temperature and absolute humidity are decreasing very strong (about 2 °C/h resp. 2 mbar/h). Air-pressure has at this moment its minimum and starts to O 3 -C o n c e n tra tio n u n d m e te o ro lo g ic a l C o m p o n e n ts fro m 1 8 . b is 2 0 . 1 2 . 1 9 9 1 in E ife l F o r e s ts - 6 8 0 m a b o v e NN O3 , N O2 , (O3 + N O2 ) [µg /m 3 ]

90

Ab s .H u m ., (Pre s s .-9 9 6 )/2 [m b a r],W in ve l [m /s e c],W in d d r.[S e kt.], Te m p .[°C ]

O 3 +NO 2

75

B

60

Ab s. H u m id ity

B

O3 [µg /m 3]

C

10 W

C

8

O3

A

45

4

NO 2

W in d vel.[m /sec]

15

2

0 0 Bc ht00

S 6

T em p er. [°C ]

1

30

12

W in d d irect.

(P ressu re-996)/2 in T rier

18.12.

24

19.12.

F ig . 4

48

NO 2

O

2

N 0

20.12.

72

hours

Data: Lf UG - Z IMEN -

Fig. 4: O3-Intrusion during two frontal-cyclones, measured at the Forests Eifel increase with about 2 mbar per hour. This cold and dry air is the outcome of a tropospheric air folding and originates mainly from stratospheric cold regions, transported by a jet stream /5/. Fig. 4. shows in comparison to the urban station in Fig. 3 the same frontal-cyclones in the forest region of the Eifel-mountains. -4-

The comparison shows that the averaged concentrations of O3 in the forests are about double of this in urban regions. This fact is the consequence of the oxidation between the intruded O3 and mainly anthropogenic NO in the lower troposphere. In forest regions, this influence of NO is relatively small. In urban regions this influence is high: Concentrations of the intruded stratospheric O3 are reduced by this relative quick oxidation with the velocity of about v = 27 [1/(ppm*min)]. That means, the real O3-concentration intruded into the lower troposphere is given by the sum (O3 + NO2). This is guilty, so long the measured NO2 is not produced direct within the source (ca 5% of the NOx-Emission of the motor car) or the production of NO2 is not possible by the quicker oxidation of NO with Peroxides (RO2) (v =.2300 [1/(ppm*min)]), which are produced by anthropogeneous hydrocarbons. So far there is no other relevant NO2-Production, the real intruded stratospheric O3-concentration by yet streams is given by the sum (O3+NO2). Using the units [µg/m3], the failure is lower than the statistical failure of the measurements of both components. NO2-production by the very slow oxidation of NO with O2 is not very relevant. 5.

O3-Flux into the Lower Troposphere.

To estimate the quantity of O3-molecules transported by such events into the lower biosphere, one can made the assumption, that the O3-concentrations of the air masses at the measuring high of wind velocity at 10 m above ground (measuring point of wind components) have within 10 percent the same O3-concentration like at measuring high of 3.5 m above ground (sucking point of the station). Multiplying the half hour average of O3 with the averaged wind velocity, one gets the current of O3 through a vertical square meter per second in units [g/(m2*sec)] at the high of 10 m. Fig. 5 shows that there is no relevant difference of the accumulated O3-Flux between forests and towns with the assumption, anthropogenic NO is changing a part of the intruded O3 into NO2. Only the relative high situated forest station in the Eifel shows some higher values. At this place the intruded O3 first appears with air masses from western directions. (O3+NO2)-current and accumulated (O3+NO2)-Flux into the Forests and into urban regions from 18. to 20.12.1991 x10^11[Molec/(cm2*sec)] 100

4x(Pressure-995)[mbar], acc.O3-Flux[g/m2] 100

Forest Hunsrück (650 m ab. NN)

Eifel-Forest (680 m ab. NN)

Town Mainz (120 ab. NN)

80

80

Town Neuwied (68 m ab. NN) 60

60

40

40

1

20

Pressure in Mainz

0 0 Bcht01

20

2

18.12.91

24

19.12.91

Fig.5

48

20.12.91

0 72 [h]

Data: LfUG - ZIMEN -

Fig. 5: O3-Flux, caused by two frontal-cyclones into forest and urban region. With the assumption, these O3 contaminated air masses will reach the soil, the down load of O3 lies between 4 and 40 g/m2 per frontal-cyclone in middle Europe. Stratospheric O3currents reach in this example values till 80x10^11 [molec./(cm2*sec)] with in the jet stream in the biosphere. That lies small above ranges of earlier published estimations /6/.

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6.

The Monthly Concentration of Stratospheric Ozone-Background .

To estimate the toxic relevance of this intruded O3 the caused monthly background is to calculate. Smallest possible monthly O3-background concentrations are given by these measuring values of O3 and NO2, which are correlated with decreasing absolute humidity and which are coming from western directions (wind sector 8 to 12 of the 30 degree wind-scale between 1 (North) and 12, marked by bigger points in Fig. 6). O3-Intrusion in Forest Region Hunsrück in Germany (480 m beyond NN)

µg/m3, g/m2, w /m2*sec 120

mbar, °C, sector

Wind-Dir. Absol. Hum idity [m bar]

(O3+NO2) [µg/m 3]

100

12

10 W

Pressure - 1000 m bar

80

8

60

6

S 1

(O3+NO2) Flux acc. (O3) [µg/m 3] Tem perature

40

West-Dir.

(NO2) [µg/m 3]

Global Rays

20

17.12.91

18.12.91

N

19.12.91

20.12.91

Fig. 6

Bcht01

O

Dry, Cold, West. 2

2

0

4

0 Data: LfUG - ZIMEN -

Fig. 6: O3-Intrusion in Forest Region Hunsrück in Germany Result is, that intrusions of stratospheric Ozon by frontal cyclones into the troposphere produces a natural O3-background with monthly averages of at least 10 to 30 µg/m3 countrywide (Fig. 7). Surely the natural O3-background is higher, fore the stratospheric air masses of the jet stream become mixed partly with air masses of the next upcoming western warm-front, which is on this way transporting rests of stratospheric O3 into the biosphere. µ g /m 3 70

M o n th ly A v e ra g e s o f S tra to s p h e ric O 3 -B a c k g ro u n d in F o re s ts a n d U rb a n R e g io n s in W e s te rn G e rm a n y 1 9 9 2

60

F ore s t H u c d w F ore s t H u w

P o s s ib le h ig h e s t s tra to s p h e ric O 3 -B a c k g ro u n d (w e s te rn a ir)

U rb s Trir c d w U rb s Trier w

50

F ore s t E if c dw 40

F ore s t E if w F or.W es t.c dw

30

F or W es t W U rb s B d-K .c dw

20

U rb s B d-K .w 10

A ver.M in.

lo w e s t s tra to s p h e ric O 3 -B a c k g ro u n d (c o ld d ry w e s te rn a ir)

A ver.M ax .

0 0 Bc h t0 1

1

2

3

4

5

6

7

8

F ig . 7

9

10

11

Mo n th

12 Da ta : L f UG - Z IMEN -

Fig. 7: Monthly averages of O3, produced by frontal cyclones in towns and forests. This condition leads to an estimation of the possibly highest values of the O3-concentration produced by western frontal cyclones. This argumentation is supported by the fact, that both, the lowest and the possibly highest values of these O3 are respectively nearly equal in forests and towns (Fig. 7). The Quantity of the monthly stratospheric O3-background depends on the intensity and on the number of frontal cyclones per month. Fig. 8 shows a correlation between the Number of frontal-cyclones and lowest resp. possible highest stratospheric O3-background countrywide. -6-

µg/m3

Average lowest and highest monthly - NO2 corrigated stratospheric O3-Back-Ground Concentration in Rheinland-Pfalz 1992 in correlation with the number of Frontal-Cyclones

60 50

Western Winds (sect. 8 to sect. 12)

40 30 20

Western dry Winds

10

Number of Frontal Cyclones per Month

0

0

Bcht01

1

2

3

4

Fig. 8

5

6

7

8

Fig. 8: Correlation between Number of frontal cyclones and stratospheric O3-background It seems, the more frontal cyclones occur per month, the lower is the intensity of intruded stratospheric O3 per frontal cyclone till a certain saturation. 7.

Conclusion

Studying the concentrations of O3 and NO2 together with the meteorological components at several different points in the lower troposphere (3,5 to 10 m above ground) one can find, that there is a natural background of O3 with a monthly average between 20 to 50 µg/m3, produced by cold and dry western air masses, which are contaminated with stratospheric O3. and which are transported by jet streams, caused by tropospheric folding into the biosphere. In the lower troposphere the O3-concentrations are reduced by anthropogenic NO, which is to consider by estimating the quantity of intruded stratospheric Ozone. Examples show, that stratospheric O3 produces such background concentrations all over the year. The magnitude depends on the frequency of frontal cyclones per month. This phenomenon already existed before industrial times and surely every where in the world caused by frontal cyclones. This Ozone is coming from the lower region of the stratosphere. It should be of interest to prove these results by correlation with cosmogenic radio nuclides /7/. 8.

Literature

/1/ Borchert, H.: ”The Trend of Air Pollution in Western Germany in the past twenty Years as a Result of Clean Air Management” in: Proceedings of 11th World Clean Air Congressn, South Africa, IUAPPA ,Vol.3, pp 8A-9, ISBN 0-620-23064-9 (1998). /2/ Borchert, H and Kampe, U.: Monthly Reviews of Measuring Results of ZIMEN, Editor: Landesamt für Umweltschutz, Rheinallee 97 – 101, D –5118 Mainz, ISSN 0720-3934. /3/ Borchert, H.: “Ozone Episodes 1988/1989 During Special Meteorological Conditions in Rheinland-Pfalz“ in Report 25 of the E. C., Brüssel, ISBN 2-87263-045-7, (1990) /4/ Borchert, H., Hinner, H.: „Ozone Intrusion During Cold Air Invasion in Middle Europe" in: Proc. of 10th World Clean Air Congress, Espoo, Finland, ISBN 952-90-6473-X,(1995) /5/ Danielsen, E.F., Mohnen, V.A.,: „Ozone Transport, in situ Measurements and Meteorological Analyses of Tropopause Folding“,J.Geophys. Res., 82, 5867-5877 (1977) /6/ Oberreuter, A. : „,Intrusion stratosphärischen Ozons in die Troposphäre durch Tropopausenfaltungen und Kaltlufttropfen“ in „Mitteilungen aus dem Institut für Geophysik und Meteorologie der Universität zu Köln“, Heft 87, ISSN 0069-5882 (1992) /7/ Reiter R., Munzert K., Kanther H.-J., Pöttl K.: „Cosmogenic Radionuclides and Ozone at a Mountain Station at 3.0 km “ in Arch.Met.Geoph. Biocl., Ser. B, 32, pp 131-160, (1983).

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