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:./%1O/.$ 34$ 93/.$ 17%&$ HK$ <.8-,&$ P,17,&$ %$ 4.P$ '%20$ ;%1$ :QDE$ 7#%R$:38.P%/'$34$MEE$8%S1O'.A$$ HA$ $,1$ $,0$ $%$9%1,-*../*,4$DA$,0$4O8T88.'$ %&'$ ,4$ 17.$ N3&%8$ 9.%&$ N3&%8$ P,&'$ /.-./0.0$ 4/39$ .%01P%/'$ 13$ P.01P%/'$ ',/.?S3&$ 43/$ 0.-./%8$ '%20$ %1$ DE$ 7#%R$ :38.P%/'$ 34$ MEE$ 8%S1O'.=$$ !"#$%&'$())*$$$$$$$$$$$$$$$$$$$$$$$$$$$ +&,-./0,12$34$5./&$ reversal to westward wind -> major SSW on 19 Feb. 2008 DIE$ Qualitative Explanation of Sudden Stratospheric Warming: ①  planetary wave (from troposphere at mid-latitudes) propagates into stratosphere at high latitudes and „collapses“ at about 40-50 km ②  sudden deposition of westward wave momentum reverses the zonal mean eastward wind (wave – mean flow interaction) ③  rapid increases of poleward wind, pressure, and temperature are forcing the polar vortex (-> shifting or splitting of polar vortex) upwelling of isentrope -> adiabatic cooling in the mesosphere Flury et al., JGR, 2009: SSW at Bern downwelling of isentrope -> adiabatic heating 67.$*.018.00$"1930:7./.$;<=$>[email protected]$B$C%-.$ upwelling and cooling DID$ How is the response of ozone to the SSW? Stratospheric ozone profiles are measured at University of Bern since 1994 (http://www.iapmw.unibe.ch/research/projects/GROMOS) Reasons: - detection of long-term trends of the ozone layer - cross-validation of satellite experiments - ozone as tracer of middle atmosphere dynamics - atmospheric research NO + O3 "NO2 + O2 NO2 + O "NO + O2 ############ O3 + O " 2O2 strong ozone depletion caused by the major stratospheric warming (19 Feb. 2008): Chemical box model provides explanation for observations at!Bern. Catalytic ozone destruction (due to the NO cycle) is accelerated if the temperature increases during the SSW (Flury et al., 2009) => it was a combined effect of dynamics and chemistry DIH$ Open questions in research on sudden stratospheric warmings !  Meridional and vertical exchange and mixing of air masses by SSWs. Is the Brewer-Dobson circulation decelerated or accelerated by SSWs? !  Why is there upwelling in the upper troposphere and lower stratosphere? !  Role of gravity waves during SSW !  Large ionospheric disturbances occur in the equatorial ionosphere during SSWs. Is it due to interaction between tides and planetary waves? !  Why have there been no SSWs in the 90s? !  Are there resonance periods of polar vortex oscillations ? Average winter and summer spectrum (1994-2010) of ozone fluctuations above Bern derived by bandpass filter-periodogram using ozone profiles of GROMOS radiometer: •  ozone fluctuations at Bern possibly •  reflect perturbations of the vortex •  20 days could be a resonance period •  winter spectrum has stronger peaks than the summer spectrum DII$ reservoirs of Cl chemical reaction takes place on the surface of the ice particle ClONO2 HCl n=1,2,3,... ice particle: NAT (nitric acid trihydrate) T < -77 oC 3 H2O (is reached in the dark, cold winter stratosphere + cooling in updrafts) n (HNO3 . 3 H2O) Activation of Cl + Cl2 (n+1) (HNO3 . 3 H2O) by mountain waves) sunlight produces atomic Cl Polar lower stratosphere: (ozone hole) ClO + ClO + M Cl2O2 + hv ClO2 + M then: 2 x (Cl + O3) Catalytic cycles: 2 Cl and Cl2 + h!" ice particle is now a bit larger and Cl2 is now in the dangerous gas phase! Upper/middle stratosphere: net: Cl + O3 ==> ClO + O2 ClO + O ==> Cl + O2 -----------------net result: O3 + O ===> 2O2 Cl PSC: polar stratospheric cloud (usually induced O3 O3 O3 2 O3 -> -> -> -> Cl2O2 + M Cl + ClO2 Cl + O2 + M 2 x (ClO + O2) -> 3 O2 O O O O + O3 ClO + O2 Harmful UV flux at surface increases with depletion of ozone: ClO + Cl O + O2 Catalytic destruction of O3 and O by only one chlorine atom Cl Cl is now ready for the next cycle PV (white lines) make sense! http://mls.jpl.nasa.gov !"#$%&'$())*$$$$$$$$$$$$$$$$$$$$$$$$$$$ +&,-./0,12$34$5./&$ 67.$*.018.00$"1930:7./.$;<=$>[email protected]$B$C%-.$ DIM$ Atmospheric waves from troposphere Change of the polar vortex in the stratosphere Tides + Seasons CFCs PSC Variability of time series of O3 and H2O observed by radiometers at Bern Change of composition and circulation of mesosphere and stratosphere Solar activity and geomagnetic storms Climate Change Volcano + ... QBO (2.4 years) SAO (0.5 years) (11 years, 27 days) .2334-5*467*82)&,,%* !  Observations can sometimes reveal relationships (e.g., wave-mean flow interaction, polar ozone chemistry) !  Description of the restless atmosphere rapidly increases with advances in computer technology and remote sensing. However understanding remains difficult! !  IAP-Bern has a lot of instruments and data waiting for experimental investigations, analysis and simulations !  Future of high-resolution Earth system models is described in a recent issue of a meteorological journal: http://journals.ametsoc.org/toc/bams/91/10 Literature recommendation: Newman, P. A., Oman, L. D., Douglass, A. R., Fleming, E. L., Frith, S. M., Hurwitz, M. M., Kawa, S. R., Jackman, C. H., Krotkov, N. A., Nash, E. R., Nielsen, J. E., Pawson, S., Stolarski, R. S., and Velders, G. J. M.: What would have happened to the ozone layer if chlorofluorocarbons (CFCs) had not been regulated? Atmos. Chem. Phys., 9, 2113-2128, doi:10.5194/acp-9-2113-2009, 2009 (open access) !"#$%&'$())*$$$$$$$$$$$$$$$$$$$$$$$$$$$ +&,-./0,12$34$5./&$ 67.$*.018.00$"1930:7./.$;<=$>[email protected]$B$(O1833@$ DIF$ .2334-5*467*82)&,,%* $ UV3$ 17.$ W%?@X/3O&'$ 9%2$ W.$ 3/',&%/2$ :720,?0Y?8%00,?%8$ 9.?7%&,?0$ %&'$ 17./93'2&%9,?0$ %::8,.'$ 13$ %$ ZO,'$ 3&$ %$ /31%S&XR$ ',[./.&S%882B7.%1.'$ 0:7./.YWO1$ 17.$ 01O'2$ 34$ 17.$ P738.$ :/3?.00$ 7%0$ ,10$ 3P&$ O&,\O.$ Z%-3O/=$ 67.$ %::/3%?7$ ,0$ >(]!V6!)$ /%17./$ 17%&$ /.'O?S3&,01R$ W.?%O0.$ 17./.$ ,0$ &.-./$ %$ 0,&X8.$?%O0.=^$$$ $ $ ;_=$ `%/07%88R$ *=$ "=$ #8O9Wa$ "1930:7./.R$ (?.%&$ %&'$ )8,9%1.$ b2&%9,?0R$ "?%'.9,?$#/.00R$HEEFA$$ *9"46%*5,2*+,-*5,2-*4:#6746$#*467*5,2-** ****** ***;4<#6$#*=')"*3#>**?,;#+2&&5*5,2*()45*** **********'6)#-#()#7*'6*4)3,(;"#-'$*($'#6$#(>* *@#--5*!"-'()34(*467*4*?4;;5*A#=*B#4-*** !"#$%&'$())*$$$$$$$$$$$$$$$$$$$$$$$$$$$ +&,-./0,12$34$5./&$ 67.$*.018.00$"1930:7./.$;<=$>[email protected]$B$(O1833@$ NASA