Ozone loss in the Arctic stratosphere over Kiruna,Sweden, during winter 2005/06

Ozone loss in the Arctic stratosphere over Kiruna,Sweden, during winter 2005/06

1 2 2 3 1U. Raffalski , G. Hochschild , G. Kopp , J. Urban , P. Voelger

Swedish Institute of Space Physics, Kiruna, Sweden, E-mail: Uwe.Raffalski@irf.se2Institute of Meteorology and Climate Research, Forschungszentrum und Universität Karlsruhe,

3 Chalmers University of Technology, Gothenburg, Sweden

Forschungszentrum Karlsruhe In der Helmholtz-Gemeinschaft

CHALMERSwww.irf.se

Introduction

IRF Kiruna is located above the polar circle (67.8° N/20.4° E). With the millimetre wave radiometer KIMRA we investigate the ozone layer within the polar vortex during Arctic winter. The ground-based observations of stratospheric trace-gases cover the altitude range from 15 up to 55 km. Here we present continuous observations of stratospheric ozone covering the winter 2005/2006. From the mea-surements we calculated ozone profiles and partial column densities. For the estimated ozone loss we considered only measurements well within the polar vortex defined by the 'Equivalent Latitude' method described by Nash et al. [1996]*. In order to discriminate dynamic effects we deploy N O data from the Odin satellite.2

* Nash, E. R., P. A. Newmann, J. E. Rosenfield, and M. R. Schoeberl, An objective determination of

the polar vortex using Ertel's potential vorticity, J. Geophys. Res., 101, 9471 - 9478, 1996.

Acknowledgements

We would like to thank the ECMWF for the PV and temperature data and NCEP for providing temperature and pressure data used for the retrievals via the Goddard automailer system. KIMRA was partly funded by the Swedish Knut and Alice Wallenberg foundation, the former Swedish Natural Research Council (NFR) the Swedish National Space Board and the Swedish Kempe foundation.

Figure 1: Evolution of the polar vortex in terms of equivalent latitudes. The white lines describe the inner and outer edge of the vortex, respectively, while the black line describes the mean vortex edge, i.e. the strongest gradient in PV for the particular day. The colour coding shows the strength of the vortex in PVU. The open circles depict the PV over Kiruna on the particular measurement days and refer to the underlying PV colour coding, showing how far away from or how deep inside the vortex a measurement has been taken at IRF.

Results

The Arctic winter 2005/06 has started with moderately low temperatures in November and December. In late December and early January a period of very low temperatures as far down as 186 K at 475 K isentropic level (as shown in fig. 2) with observation of persistent polar stratospheric clouds appeared (see fig 5). However, unlike other winters the polar vortex was neither very large nor stable and at the end of January it has virtually disappeared again in the middle stratosphere (550 K and upward). Certainly Kiruna was not located under the vortex after day 30 as can be seen from the equivalent latitude calculations in fig 1. In order to estimate the winter ozone loss we identified 6 periods with measurements well inside the vortex between November 13 (day -46) and January 24 (day 23) (see profiles in fig. 3). Part of the total ozone loss is covered by the diabatic subsidence inside the vortex. In order to correct for the diabatic subsidence Odin vortex mean values of N O are used (see fig. 4).2

The calculated ozone loss between 20-30% with a maximum around 23 km. With respect to the weak and warm polar vortex during February and March we expect no further substantial ozone loss during this period.

early December and late January was

Figure 4: N O isopleths as measured by Odin 2

(upper panel) indicating the subsidence of air masses. In the lower panel the vmr data as shown in figure 3 are calculated on N O isopleths 2

provided by Odin data in order to eliminate effects of diabatic subsidence. The systematic error for the ozone vmr data between 17 and 27 km is of the order of 20% or 0.2 - 1.1 ppmv respectively.

Measurements

Observations of stratospheric ozone at 195 GHz provide an almost uninterrupted time series of ozone data. The data in figure 2 present the period October 2005 to February 2006.Deploying the FWHM of the averaging kernels we can obtain a verti-cal resolution of the ozone profiles of at best 6 km (at 25 km altitude). Contributions from the measurements to the retrieved profiles are typ-ically larger than 75% in the altitude range between 15 and 55 km. However the partial column densities are calculated for 10 to 80 km.

-80 -60 -40 -20 0 20 40405060708090

Equ

ivale

ntl

atit

ude

[°]

Day of year 2006

27.00 -- 28.00 26.00 -- 27.00 25.00 -- 26.00 24.00 -- 25.00 23.00 -- 24.00 22.00 -- 23.00 21.00 -- 22.00 20.00 -- 21.00 19.00 -- 20.00 18.00 -- 19.00 17.00 -- 18.00 16.00 -- 17.00 15.00 -- 16.00 14.00 -- 15.00 13.00 -- 14.00 12.00 -- 13.00

405060708090 50.00 -- 52.00

48.00 -- 50.00 46.00 -- 48.00 44.00 -- 46.00 42.00 -- 44.00 40.00 -- 42.00 38.00 -- 40.00 36.00 -- 38.00 34.00 -- 36.00 32.00 -- 34.00 30.00 -- 32.00 28.00 -- 30.00 26.00 -- 28.00 24.00 -- 26.00 22.00 -- 24.00 20.00 -- 22.00

130.0 -- 136.0 124.0 -- 130.0 118.0 -- 124.0 112.0 -- 118.0 106.0 -- 112.0 100.0 -- 106.0 94.00 -- 100.0 88.00 -- 94.00 82.00 -- 88.00 76.00 -- 82.00 70.00 -- 76.00 64.00 -- 70.00 58.00 -- 64.00 52.00 -- 58.00 46.00 -- 52.00 40.00 -- 46.00

405060708090

405060708090

360.0 -- 380.0 340.0 -- 360.0 320.0 -- 340.0 300.0 -- 320.0 280.0 -- 300.0 260.0 -- 280.0 240.0 -- 260.0 220.0 -- 240.0 200.0 -- 220.0 180.0 -- 200.0 160.0 -- 180.0 140.0 -- 160.0 120.0 -- 140.0 100.0 -- 120.0 80.00 -- 100.0 60.00 -- 80.00

405060708090

-80 -60 -40 -20 0 20 40 1696 -- 1792 1600 -- 1696 1504 -- 1600 1408 -- 1504 1312 -- 1408 1216 -- 1312 1120 -- 1216 1024 -- 1120 928.0 -- 1024 832.0 -- 928.0 736.0 -- 832.0 640.0 -- 736.0 544.0 -- 640.0 448.0 -- 544.0 352.0 -- 448.0 256.0 -- 352.0

-80 -60 -40 -20 0 20 40

200

250

300

350

400

450

170

180

190

200

210

10

20

30

40

50

60

O3 vmr

[ppmv]

20062005

februaryjanuarydecembernovemberoctober

Alti

tude

[km

]

7.5 -- 8.0 7.0 -- 7.5 6.5 -- 7.0 6.0 -- 6.5 5.5 -- 6.0 5.0 -- 5.5 4.5 -- 5.0 4.0 -- 4.5 3.5 -- 4.0 3.0 -- 3.5 2.5 -- 3.0 2.0 -- 2.5 1.5 -- 2.0 1.0 -- 1.5 0.5 -- 1.0 0.0 -- 0.5

Tem

perature@

475K

[K]

Day of year 2006

Par

tialc

olum

n[D

U]

Figure 2: Time series of O during winter 2005/06 (upper 3

panel). The contour plot shows the volume mixing ratio in ppmv. The lower panel presents the partial O column 3

density from 10 to 80 km. The blue line indicates the temperature at 475 K isentropic level over Kiruna.

10

15

20

25

30

35

40

45

50

55

60

0 1 2 3 4 5 6 7

Ozone mixing ratio [ppmv]

Alti

tude

[km

]

051113-051117 051127-051202 051225-051226 060107-060108 060118-060124

Figure 3: Ozone profiles for periods with inside-vortex measurements of KIMRA.

Figure 5: Observations of the new IRF lidar system from Jan 6-9. The layer at around 10 km depicts high cirrus clouds. The layer at 25 km indicates PSC (type II) with moderate depolarization on Jan 7. PSC with low depolarization (type I) were observed Jan 8-9.

PSC

435 K

475 K

550 K

675 K

950 K

-40 -30 -20 -10 0 10 20 3016

17

18

19

20

21

22

23

24

25

26

27

28

29

N2O 25 ppbv

N2O 50 ppbv

N2O 75 ppbv

N2O 100 ppbv

N2O 125 ppbv

N2O 150 ppbv

N2O 175 ppbv

N2O 200 ppbv

Alti

tude

[km

]

Day of year 2006

-40 -30 -20 -10 0 10 20 30

1,5

2,0

2,5

3,0

3,5

4,0

4,5

5,0

5,5

Ozo

nevo

lum

em

ixin

gra

tio[p

pmv]

Day of year 2006

N2O 25 ppbv

N2O 50 ppbv

N2O 75 ppbv

N2O 100 ppbv

N2O 125 ppbv

N2O 150 ppbv

N2O 175 ppbv

N2O 200 ppbv