Sudden stratospheric warming and O3 depletion

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Eleanore Bridges
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1 Sudden Stratospheric Warming (SSW) and O3 T. Flury, K. Hocke, N. Kämpfer, A. Haefele Institute of Applied Physics, University of Bern ISSI workshop

2 Outline 1) GROMOS measures O3 depletion during SSW 2) Temperatures during the SSW 3) Wind shear 4) Trajectory analysis 5) Explanations

3 Facts about the SSW in Bern > Observations: Stratospheric warming above 35 km Stratospheric cooling between km Ozone depletion between km Strong wind shear at 35 km > Data sources: GROMOS ozone radiometer ECMWF temperatures and winds Payerne radiosonde temperatures MIAWARA and Aura/MLS water vapor

4 Overview of measurements in Bern

5 Ozone depletion 4.3 hpa 3.3 hpa 1.8 hpa > Depletion propagates downward > Lasts for more than 1 week. > Different signature in lower stratosphere 2.4 hpa

6 Northern Hemisphere Temperatures > Opposite temperature distribution at 20 km than at 40 km > Upper stratospheric warming, lower stratospheric cooling

7 Temperatures at Bern > Cooling in layer km > Warming above 35 km > Since 1994 only 4 times T<190 K in the lower stratosphere measured at Payerne > T<190 K during SSW 1.Jan 04, 19. Jan 06 and 19 Feb 08

8 Payerne Radiosonde (46.8 N, 6.95 E) > T below PSC threshold > Strange behavior of ascent speed

9 Polar Stratospheric Clouds > Calipso satellite Lidar detects clouds > PSC can form for T<195 K in the lower stratosphere > Heterogeneous chemistry on PSC ice crystal surfaces reduces ozone > Air with reduced ozone values to find down stream of the PSC

10 Strong Wind Shear

11 TomTom: Tom's Trajectory Model Question: Where does the air come from? Method: Air parcel trajectories > No mesospheric trajectories available on Internet > Selfmade Simple Trajectory Model TomTom > Isentropic trajectories > Validation with Goddard Automailer and Hysplit for z<40 km Flow Chart of TomTom Model ECMWF wind data on 1.1 spaced grid and 60 height levels Trajectory Calculation + Visualisation MySQL database Matlab Output: Map + Trajectory Datafile

12 40 hour backward trajectories > Air from polar regions below 40 km > Air from tropical regions above 40 km > Cold air from polar vortex, further cooling through upward motion > Descent motion and adiabatic heating for the tropical air

13 Detailed Trajectories lower stratosphere

14 Detailed trajectories upper stratosphere

15 Water vapor enhancement Miawara and Aura/MLS H2O 30 8 hpa Aura/MLS 17 Feb 10 hpa (850 K,32 km) > Trajectories show that H2O rich air was brought to Switzerland from the polar vortex (yellow on MLS)

16 H2O as tracer 40 h backward trajectory. Start 19 Feb Feb Feb Feb 08

17 Explanations for O3 depletion above 35 km Ralph Lehmann, AWI Potsdam, priv. comm. > Temperature dependent chemistry responsible > Box model shows decrease of the same amount due to warming at 1650 K (40 km)?

18 Explanations for O3 depletion around 20 km > In the lower stratosphere [O3] proportional to Temperature > Cold air from the pole transported to Switzerland

19 Summary > Sudden warming for z>35 km, cooling for z<35 km. > O3 depletion for z<35 km due to transport of polar air with low ozone values. Depletion in vortex due to PSC. > O3 depletion for z>35 km due to downward transport from tropical regions and enhanced chemical destruction due to temperature increase. > A SSW leads to O3 depletion at mid latitudes.

What is a Sudden Stratospheric Warming?

What is a Sudden Stratospheric Warming? rapid increase of T at h~32 km from Evelyn De Wachter (PhD thesis, IAP-Bern):!"#$%&'()*+,-*../0** DA /%:,'$,&?/.%0.$ 34$ N3&%8$ 9.%&$ 1.9:./%1/.$ 34$ 93/.$ 17%&$