Investigations of long and short term changes in Total Ozone at the Sonnblick Observatory (3106 m, Austria)

S. Simic, P. Weihs and G. Rengarajan and W. Laube Institute of Meteorology and Physics, Universität für Bodenkultur,

Vienna, Austria (E-mail: stana.simic@mail.boku.ac.at)

Figure 4 shows the deviations of winter (left Fig.4), spring, autumn and summer (rigth Fig.4) monthly means 1994 to 2001 from years-long mean in percent. Largest decrease rates occurred in winter/spring. The winter of 1994/1995 proved to be particularly striking with decrease rates of as much as 15 %. This was attributed to the influence of polar vortex over Austria. Very low temperature levels enabled the formation of polar stratospheric clouds in which very strong ozone dissociations could occur. Overall, the mean yearly ozone averages over the years 1994-2001 are for winter 9 %, for spring 8%, for summer 5 % and for autumn 3 % lower than the long term average.

-Correlation between total ozone and meteorological parameters

Short term variations are compared with analysis maps of the ECMWF weather forecast model and with radiosonde measurements. A negative correlation between relative topography and ozone was found. The quality of the correlation was found to be dependent on the season. Using the relative topography, 20 to 56 % of the ozone variability may be explained. Total ozone has also a very strong anticorrelation with tropopause height that means total ozone increases with increasing tropopause pressure and with decreasing tropopause temperatures. Strong correlation was found between 300 hPa geopotential and total ozone. 50% of the variability may be explained by changes in the 300 hPa level.

There is currently one Brewer Spectrophotometer being operated in Austria. The instrument, No.093, is located at the mountain observatory Hoher Sonnblick (latitude 47°03´, longitude 12°57´) at 3106 m above sea level. After eight years of continuous ozone measurements, first climatological research can be carried out and conclusions drawn. The results of numerous individual measurements of total ozone carried out over the day, as well as those of the continuous eight-year measurement series permit some first studies concerning a possible trend and statements about seasonal ozone distribution as well as about day-to-day and time of day variations. In this presentation we first show the yearly and seasonal changes in total ozone measured at Sonnblick from 1993 to 2001. Second, an analysis of the short term variations at Sonnblick Observatory is presented. Short term variations are compared with analysis maps of the ECMWF weather forecast model and with radiosonde measurements.

Sonnblick (47°03´N, 12°57´E, 3106 m) Brewer Spectrophotometer

The results of numerous individual measurements of total ozone carried out over the day, as well as those of the continuous eight-year measurement series permit statements about seasonal ozone distribution as well as about day-to-day and time of day variations (Fig.1).

Changes in stratospheric temperatures and tropospheric weather conditions may also result in very large daily fluctuations of ozone concentrations. Daily fluctuations as high as 100 DU have been observed. Low pressure zones in the troposphere are connected with high stratospheric ozone concentrations and vice versa. Low stratospheric temperatures and an area of high pressure in the troposphere will for example lead to very low stratospheric ozone concentrations. These minima are however short-lived because of quick changes in the tropospheric weather system.

25 50 75 100 125 150 175 200 225 250 275 300 325 350200

250

300

350

400

450

500

19941995199619971998199920002001

tota

l ozone (

DU

)

Julian day

-40

-30

-20

-10

0

10

20

30

40

%

1996 1997 1998 1999 2000 2001

Jan. Feb. Mrz. Apr. Mai. Jun. Jul. Aug. Sept. Okt. Nov. Dez.

Fig.1 Fig.1 Daily means of total ozone at Sonnblick in the course of a year from 1994 to 2001.

Fig.2 Fig.2 Deviation of daily means of total ozone at Sonnblick from years-long mean,(1927-1978) measured at Arosa

winter94/95

winter95/96

winter96/97

winter97/98 winter

98/99 winter99/00 winter

00/01

S1

-16

-14

-12

-10

-8

-6

-4

-2

0

(%)

-14

-12

-10

-8

-6

-4

-2

0

2

4

(%)

1994 1995 1996 1997 1998 1999 2000 2001

spring summer autumn

Jan Feb Mar Apr Mai Jun Jul Aug Sep Oct Nov Dez200

220

240

260

280

300

320

340

360

380

400

420

440

460

480

500 Monthly min Monthly max Monthly mean (1994-2001)

tota

l ozo

ne

(D

ob

so

n u

nits)

Month

Fig.3 Fig.3 Observed monthly mean, minimum and maximum column ozone values at Sonnblick for 1994-2001

Fig.4 Fig.4 Deviation of monthly means of total ozone at Sonnblick from years-long mean (1928-78), measured at Arosa

CORRELATION COEFFICIENT

0.4

0.45

0.5

0.55

0.6

0.65

0.7

0.75

0.8

Jan Feb Mär Apr Mai Jun Jul Aug Sep Okt Nov Dez

neg.

cor

r. c

oeff

.

total ozone/ thickness pattern (250/700 hPa)

total ozone/temperature 700 hPa, 500 hPa, 300 hPa

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Jan Feb Mar Apr Mai Jun Jul Aug Sep Oct Nov Dez

neg.

cor

r. c

oeff

.

T700 hPa T500 hPa T300 hPa

total ozone/tropopause height

0.3

0.35

0.4

0.45

0.5

0.55

0.6

Jan Feb Mär Apr Mai Jun Jul Aug Sep Okt Nov Dez

pos.

cor

r.co

eff.

total ozone/500, 300, 150 hPa geopotential

0.4

0.45

0.5

0.55

0.6

0.65

0.7

0.75

0.8

Jan Feb Mar Apr Mai Jun Jul Aug Sep Okt Nov Dez

neg.

cor

r. c

oeff

.

H500 H300 H150

Fig 5. Relation between ozone and tropopause height (1994-2000)

Fig 6. Relation between ozone and thickness 250/700 hPa (1994-2000)

Fig 7. Relation between ozone and geopotential 500,300 and 150 hPa (1994-2000)

Fig 8. Relation between ozone and temperature (1994-2000)

Acknowledgments: This work has been funded by the Austrian Ministry for Environment