EPP contribution to (stratospheric and) tropospheric variations. Annika Seppälä Finnish Meteorological Institute Academy of Finland

Transcription

1 EPP contribution to (stratospheric and) tropospheric variations Annika Seppälä Finnish Meteorological Institute Academy of Finland A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 0

2 So far... Energetic Particle Precipitation (EPP) initial effects on middle atmosphere chemistry relatively well known. We have also learned more about indirect effects on stratospheric chemistry, thanks to satellite observations. EPP effects on dynamics and lower altitudes less clear. Mesospheric dynamical changes from SPE. Jackman et al., 007. What about the stratosphere and troposphere? A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 0

3 EPP and tropospheric temperatures (Surface Air Temperature) >0 years of re-analysis data NH: High EPP - Low EPP SH: High EPP - Low EPP!"#!!" ("( Local polar effect during winter season, not a global effect. Links to Northern Annular Mode in NH?!0 ) *+) *,+), -+) -.+). /+) /!/+)!.!.+)!-!-+)!,!,+)!*!*+)!) A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 0 Seppälä et al., 009.

4 So far... Energetic Particle Precipitation (EPP) initial effects on middle atmosphere chemistry relatively well known. We have also learned more about indirect effects on stratospheric chemistry, thanks to satellite observations. EPP effects on dynamics and lower altitudes less clear. Mesospheric dynamical changes from SPE. Jackman et al., 007. What about the stratosphere and troposphere? Connection between solar wind/geomagnetic activity/epp and the NAM/NAO/AO? Boberg and Lundstedt, 00, Thejll et al., 00, Lu et al., 00, Seppälä et al., 009, Baumgaertner et al., 0. How does the signal propagate from ~mesospheric altitudes to the troposphere? What happens in the stratosphere? I will try to put some of these pieces together. A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 0

5 EPP and chemistry Long lived changes during winter and progressing into spring. Chemical changes limited to the mesosphere and stratosphere, above about km. How is the troposphere influenced? O NOx itude itude Oct Nov Dec Jan Feb Oct NovDec Jan Feb Oct Nov Dec Jan Feb OctNovDecJanFeb Oct Nov Dec Jan Feb Oct NovDec Jan Feb Oct Nov Dec Jan Feb OctNovDecJanFeb NO Mixing ratio [ppbv] O Mixing ratio [ppmv] Randall et al., 00. If the NOx reaches the stratosphere before spring, effects on stratospheric ozone significant. Possibility for effects until summer? Is this the pathway to influencing troposphere? Seppälä et al., 007. A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 0

6 Middle atmosphere dynamics Active dynamics and atmospheric coupling taking place in the winter pole. Poles - access regions for EPP. Location of chemical changes. Strong winds acting as a transport barrier. Isolates polar air forming the Polar vortex. Maintains NOx in the polar region, transport downward. A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 0

7 SPRING EPP and dynamics Assumption: EPP leads to reduction on stratospheric ozone in the SPRING. From chemistry: Less O, less long wave heating from O Cooling. Statistical study by Lu et al: Opposite. Lu et al., 00. Similar spring time zonal mean zonal wind results from WACCM presented by Kvissel et al., 0. London, 90. A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 0

8 SPRING EPP and dynamics Assumption: EPP leads to reduction on stratospheric ozone in the SPRING. From chemistry: Less O, less long wave heating from O Cooling. Statistical study by Lu et al.: Opposite seen. EPP influence on stratosphere and troposphere dynamics, probably not from an in situ chemical effect. Back to the drawing board! Lu et al., 00. Similar spring time zonal mean zonal wind results from WACCM presented by Kvissel et al., 0. London, 90. A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 0

9 EPP and dynamics WINTER What have we learned from models? EPP impact on chemistry understood. Model experiments: Chemistry-General Circulation Models forced with EPP-NOx source. (Rozanov et al., 00, Baumgaertner et al., 0) Mean DJF Change Less ozone Both show similar surface temperature results to re-analysis data during WINTER. Baumgaertner et al. (0): Ozone loss Reduction in long wave radiative cooling in WINTER polar upper stratosphere-mesosphere Positive WINTER temperature anomaly. Decreased mean meridional circulation Cooling the polar stratosphere. Chemistry coupling to dynamics already during winter? What is the pathway? What about HOx? Less cooling from O = heating Decreased circulation = cooling A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 0 Baumgaertner et al., 0

10 Recap EPP can reduce polar O in mesosphere and stratosphere. O heating effects: Heating in short wave (UV from Sun). SPRING Cooling in long wave (Terrestrial outgoing radiation). WINTER LESS O would lead to a warm anomaly if less long wave cooling, and cold anomaly if less short wave heating. WINTER SPRING Springtime dynamical effect NOT directly from ozone. A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 0

11 EPP and dynamics: A closer look 0 NOV 00 U HAp T HAp 0km 0 years of ERA re-analysis data DEC 00 # 0km Monthly means of zonal mean zonal wind, temperature and Eliassen-Palm flux. All data divided into High EPP and low EPP based on the Ap index. Looking at deviations from the dataset mean JAN FEB # #7 #7 0 MAR # A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct L Seppälä et al., in review, 0.

12 0 NOV U HAp # T HAp 0km 0km The results agree fairly well with previous studies for the polar region. 0 DEC 00 DJF mean change JAN # #7 7 # FEB #7 # Baumgaertner et al., MAR 00 Seppälä et al., in review, 0. #7 # A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 0 Lu et al.,

13 EPP and dynamics Wave forcing 0 NOV 00 U HAp T HAp EP HAp 0km Eliassen-Palm flux (EP flux), a measure of wave activity (energy transfer). Arrows: Direction of wave propagation Contours: Zonal flow acceleration or deceleration from wave breaking DEC JAN FEB # # #7 #7 0 m s 0km 0 MAR 00 # A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 0 Seppälä et al., in review, 0.

14 EPP and dynamics U, T, EP 0 NOV 00 U HAp T HAp EP HAp 0km Dec-Feb: More waves are reflected towards the equator and away from the polar region under high EPP. Less waves disturbing the polar vortex stronger vortex, until Mar. Winds and temperatures show downward movement with time. Waves play a significant role in transferring the EPP signal from the stratosphere to the troposphere. Coupling through wave-mean flow interaction important just like for solar irradiance influences DEC JAN FEB MAR 00 7 # # #7 #7 0 m s # A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 0 Seppälä et al., in review, 0. 0km

15 How are the surface level temperatures modulated? From Here To Here? 0 NOV 00 U HAp T HAp EP HAp DEC 00 # 0 m s JAN # #7 7 # # FEB #7 # MAR 00 # # A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 0

16 How are the surface level temperatures modulated? Stronger Polar Vortex 0 NOV 00 U HAp T HAp EP HAp Northern Annular Mode (NAM/NAO/AO)!"# DEC 00 # 0 m s JAN # #7 7 # FEB MAR 00 #7 # # The Northern Annular Mode 0 0 (NAM) is an internal mode of variability in the atmosphere, which reflects the strength of the polar vortex. Stronger polar vortex drives positive NAM anomalies. The high EPP temperature pattern is typical to # positive NAM. A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 0

17 Interhemispheric differences. NH vs. SH Focus on the NH. What about the SH?!!" More stable polar vortex in SH. Better conditions for descent from mesosphere. Dynamics more difficult to influence? Shorter timeseries of observations, only since 979. Nevertheless, SH tropospheric temperatures show variations, both in model simulations and re-analysis! Effects show up earlier than in NH. Same mechanism or different mechanism? A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 0

18 Conclusions EPP effects middle atmosphere chemistry during winter (both HOx and NOx). Transition from chemical control to dynamical control in the stratosphere. From December to March anomalously strong polar vortex and more planetary wave reflection towards the equator. Also, for those interested: EPP effect on wave propagation more likely during high solar irradiance periods or westerly QBO. More details in the paper. Strong polar vortex leads to positive NAM anomalies, reflecting on surface temperatures. We are still working towards fully understanding the EPP coupling to dynamics, there are lots of connections to SOLARIS work. Thank you for your attention pre-ice breaker! A. Seppälä, HEPPA-SOLARIS Workshop, Boulder, Oct 0