38th annual European Meeting on Atmospheric Studies by Optical Methods , Siuntio, Finland, 22-26 August 2011

1. Study on the impact of sudden stratosphericwarmings in mid-latitude MLT region according to ground-based and satellite temperature measurementsMedvedeva I.V.(1), Semenov A.I.(2)Chernigovskaya M.A.(1), Perminov V.I.(2)1 - Institute of Solar-Terrestrial Physics (ISTP), Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia;2- Obukhov Institute of Atmospheric Physics (IAP), Russian Academy of Sciences, Moscow, Russiae-mail:ivmed@iszf.irk.ru 38th annual European Meeting on Atmospheric Studies by Optical Methods, Siuntio, Finland, 22-26 August 2011

2. Sudden stratospheric warmings (SSW) are an important manifestation of vertical dynamical coupling in the atmosphere. During strong SSW variations of dynamic and temperature regime in the middle atmosphere are observed, the disturbances during SSW cover large atmospheric range from troposphere to MLT heights. • MajorSSW occur when the westerly winds at 60N and 10hPa (geopotential height) reverse, i.e. become easterly (westwards). A complete disruption of the polar vortex is observed. • Minor SSW are similar to major warmings however they are less dramatic, the westerly (eastward) winds are slowed, however do not reverse. Therefore a breakdown of the vortex is never observed.

3. Background It is known that mesospheric coolings are associated with SSWs. The key mechanism by Matsuno (1971) is now widely accepted: the growth of upward propagating planetary waves from the troposphere and their interaction with the mean flow. Liu and Roble (2002) predicted mesospheric cooling extending up to the heights of ~ 110 km with a secondary warming between 110-170 km. Experimental results confirmed impact of SSW on MLT region were presented in (Myrabo et. al., 1984; Matveeva & Semenov, 1985; Walterscheid, 2000; Sigernes et al., 2003). Using the data of OH rotational temperature the authors revealed the mesopause temperature decrease.

4. Background However, association between SSW events and the MLT region is not fully understood. • Questions about the timing of stratosphericand mesospheric disturbances remain. Myraboet al. (1984) report a 1–2 day delay in the mesosphericresponse to a stratospheric event, and Hernandez (2004) suggests the mesosphere cooling is a 1–2 month leading indicatorof stratospheric warmings, while the model result of Liuand Roble (2002) indicates little, if any, phase lag or leadbetween the temperature anomalies in the mesosphere andstratosphere. • The height distribution of mesosphere cooling associated with SSW events is also not yet well established. Thus, (Siskind, et.al., 2005) using the SABER temperature data revealedthat mesospheric temperaturesbetween 0.7 hPa and 0.01 hPa (~52-80 km) show a significantanticorrelation with stratospheric temperatures during SSW. However, forpressures <0.01 hPa, this anticorrelation breaks down and near 0.002 hPa (~88 km), which is thepressure associated with the peak of the OH* emission, thecorrelation coefficient is close to zero or slightly positive, indisagreement with calculations of Liuand Roble (2002).

5. Objective The study is based on measurements of the atmospheric temperature, obtained in different longitudinal zones – Irkutsk (52N, 103E) and Zvenigorod (56N, 37E) • Study of variations in atmospheric temperature at the MLT heights during the winter stratospheric warming in 2008-2011 using ground-based and satellite measurements data; - Comparison of satellite and ground-based measurements data on temperature at MLT height

6. Analyzed Data: • data about the variations of mesopause temperature (~87 km) obtained from ground-based spectrographic measurements of the OH emission (834.0 nm, band (6-2)) at ISTP and IAP observatories near Irkutsk (52N, 103E) and Zvenigorod (56N, 37E) respectively; • satellite data on vertical temperature distribution in the atmosphere from MLS (Microwave Limb Sounder) aboard the spacecraft EOS Aura[http://disc.sci.gsfc.nasa.gov/Aura/MLS/index.shtm]; • ECMWF stratosphere temperature data presented by Stratospheric Research Group of FU Berlin [http://strat-www.met.fu-berlin.de/cgi-bin/winterdiagnostics]; • data on zonal temperature and wind ofNCEP GDAS and CPC [http://www.cpc.noaa.gov/products/stratosphere/strat-trop]; • annual NCEP data for the Northern Hemisphere [http://acdb-ext.gsfc.nasa.gov/Data_services/met/ann_data.html]

7. Analyzed Data Mesopause temperature in Irkutsk and Zvenigorod was determined using the emission spectrum of OH(6-2). Measurements and data handling at both observatories were carried out by the same method. High-aperture diffraction spectrographs with receivers on the CCD matrix allowing to register the emission spectrum of the night sky in the near infrared region with high spectral (~ 2-3 A) and temporal (~ 2 min) resolutions were used. To determine the rotational temperature we used the first 3 lines of P-branch of the vibration-rotation band of OH(6-2). The temperature is determined with 1-2 K accuracy. An example of the emission spectrum of the night airglow in the area of 780-1030 nm. Top side – OH and O2 bands. High-aperture diffraction spectrograph SP-50

8. Maximum temperature of the stratosphere at 10 hPa isobaric level (~31 km) for each analyzed SSW event The mean temperature of winter stratosphere at that altitude in quite conditionsis ~ 210 К

9. NCEP Data for the Northern Hemisphere. In January-February 2008, January 2009 and January 2010, there were very intense, long time winter SSW, covering large part of the Northern Hemisphere. The SSW in January 2011 was less intense, however well-pronounced in zonal stratospheric temperatureat 50 N.SSWs in 2008-2009 are among the most intense events in the Northern Hemisphere since 1978. Especially remarkable was the SSW in January 2009, when the stratospheric temperature reached record values. This event is described in a number of publications(Labitzke, 2009, Harada et al. 2009) . Ellipse – periods of analyzed SSW events

10. Zonal Mean Temperature (60-90N) SSW 2008 - oscillatory nature during period of about a month 2010 2009 Zonal Mean Temperature (50N) 2011

11. Zonal Mean Wind50-80N 2008 2010 2009 Major SSW 2009 – 10 hPa zonal circulation reversal

12. SSW in January 2009 3 hPa (~40 km) 10 hPa (~31 km)

13. ResultsAltitude-temporal maps of the atmospheric temperature distribution according to the MLS AURA for the region of Irkutsk and Zvenigorod (search radius is 900 km) 2008 During SSW 2008-2011, stratospheric temperature disturbances of large spatial scales were observed.

14. The temperature disturbances in almost the entire middle atmosphere and significant change in the vertical distribution of temperature occured. 2009

15. 2010 The largest temperature increases were observed in the stratosphere at altitudes of 40-50 km. Registered cooling of the atmosphere at altitudes of MLT was distributed very irregularly in both altitude and time.

16. 2011

17. Т of the stratosphere averaged for 3.16-1 hPa • (39-49 km) levels, Aura data; • b) T of the mesopause region averaged for • 0.005-0.002 hPa (84-88 km) levels, Aura data; • с) Т ОН (~87 km), ground-based data Zvenigorod:During all analyzed SSW events decrease in T of the mesopause region was observed. Irkutsk: the pattern is not so well-definite. Thus, during the period of the SSW 2008, oscillations of the atmospheric temperature at altitudes both the stratosphere and mesopause with periods of about 6-8 days were observed.

18. Quantitative characteristics of the relationship of day-to-day T stratosphere (39-49 km) and T mesopause (84-88 km) values during the SSWs has been obtained by regression analysis of Aura data Irkutsk: Correlation between Tmes and Tstr for the SSW 2008 and 2010 practically absent. Probably, this is due to the longitudinal manifestation of nature of the interaction of dynamic and thermal processes during analyzed periods of SSW. In any case, this result as the result of the work (Siskind et. al., 2005), does not correspond to model calculations (Liu & Roble, 2002), predicted a steady decrease in MLT temperature of up to heights ~110 km during the SSW. For SSW 2008-2010, Zvenigorod andSSW 2009, Irkutsk, the regression dependency was revealed: Tmes= -(0.35±0.04)*Тstr + 288±12, r = -0.55, r - correlation coefficient

19. CrossCorrelationFunctions of Tstrat (39-49 km) andT mes (84-88 km). First variable: Tstrat, Lagged: Tmes. Zvenigorod 2008 r=-0.62 2009 r=-0.59 Negative correlation of T str and T mes. Maximal correlation coefficients at Lag=0 In the European longitudinal zone Tmes decreased almost simultaneously with increase of the T strat. 2010 r=-0.57

20. In the East Asian longitudinal zone - a reaction temperature of the mesopause on the SSW did not reveal a stable tendency. Manifestations of the influence of SSW on the mesopause region in the East Asian longitude zone is more complicated than in the European one. CrossCorrelationFunctions of Tstrat (39-49 km) andT mes (84-88 km).First variable: Tstrat, Lagged: Tmes. Irkutsk 2008 2009 2010

21. Altitude of the mesopause is changing as altitude of the stratopause change also. We compared the ratio of the temperatures of the stratopause and mesopause, at the altitudes where mesopause and stratopause were located each day. The value of this ratio changed from 1.1 up to 1.9 during analyzed SSWs. This ratio could be probably used as quantitative characteristic of manifestation of the complicated processes of interaction between lower and upper atmosphere during SSW events.

22. Conclusions • The analysis of the atmospheric temperature variations according ground-based and satellite data during the events of winter stratospheric warming in 2008-2011 revealed a disturbances in the middle atmosphere from the stratosphere to the mesopause. • Regression and correlation dependency of day-to-day temperatures of the stratosphere and mesopause during the SSW were obtained. It was revealed that manifestations of the influence of SSW on the mesopause region in the East Asian longitude zone is more complicated than in the European one. In the European longitudinal zone Tmes decreased almost simultaneously with rise of the T strat. In all these SSW events, when the stratospheric temperature increases by ~ 30 K, the temperature in the mesopause decreased by ~ 20 K. In East Asia - a reaction of the mesopause temperature on the SSW did not reveal a stable tendency. These results may indicate on a possible longitudinal effect of SSW on the thermal and dynamic regimes of the middle and upper atmosphere. • The ratio of the temperatures at the stratopause and mesopause, at the altitudes where mesopause and stratopause be located each day was analyzed. This ratio could be probably used as quantitative characteristic of manifestation of the complicated processes of interaction between lower and upper atmosphere during SSW events. • Comparison of satellite and ground-based data on mesopause temperature showed a pretty good agreement

23. References • Harada Y., Goto A., Hasegawa H., Fujikawa N., Naoe H., Hirooka T. (2010) A major stratospheric sudden warming event in January 2009 // J. Atmos. Sci., 2010. doi: 10.1175/2009JAS3320.1. • Hernandes G. (2004) Winter mesospheric temperatures above South Pole (90S): Mesospheric cooling during 2002 // Geophys. Res. Lett., 31, L07109, doi:10.1029/2004GL019414. 2004. • Labitzke K., Kunze M. (2009) On the remarkable Arctic winter in 2008/2009 //J. Geoph. Res., 2009. V. 114, D00I02. doi:10.1029/2009JD012273. • Liu H.-L. and Roble R.G. (2002) A study of a self-generated stratospheric sudden warming and its mesospheric–lower thermospheric impacts using the coupled TIME-GCM/CCM3 // J. Geoph. Res., 2002. V. 107, № D23, 4695, doi:10.1029/2001JD001533. • Matsuno T. (1971) A dynamical model of the Stratospheric Sudden Warming // J. Atmos. Sci., 1971. V. 28. Р. 1479-1494. • Matveeva O.A., Semenov A.I. (1985) The results of hydroxyl emission observations during MAP/WINE period; stratospheric warmings (February, 1984) // MAP/WINE Newsletters. 1985. 3, 4-5. • Myrabo H.K., Deehr C.S., and Lybekk B. (1984) Polar cap OH airglow rotational temperature at the mesospause during a stratospheric warming event // Planet. Space Sci., 1984. 32. Р. 853-856. • Sigernes F., Shumilov N., Deehr C.S., Nielsen K.P., Svenoe T. and Havnes O. Hydroxyl rotational temperature record from the auroral station in Adventdalen, Svalbard (78N, 15E. // J. Geophys. Res. 2003. V. 108. № A9. P. 1342. doi:10.1029/2001JA009023. 2003 • Siskind, D. E., L. Coy, and P. Espy Observations of stratospheric warmings and mesospheric coolings by the TIMED SABER instrument, Geophys. Res. Lett., 32, L09804, doi:10.1029/2005GL022399. 2005. • Walterscheid R.L., Sivjee G.G., Roble R.G. (2000) Mesospheric and lower thermospheric manifestations of a stratospheric warming event over Eureka, Canada (80N) // Geophys. Res. Lett., 2000. 27(18), 2897.

24. Thanks for attention!