A distinct stronger warming in the tropical tropopause layer during using GPS radio occultation: Association with minor volcanic eruptions

Transcription

1 A distinct stronger warming in the tropical tropopause layer during using GPS radio occultation: Association with minor volcanic eruptions Sanjay Kumar Mehta 1*, Masatomo Fujiwara 2, and Toshitaka Tsuda 1 1 Research Institute for Sustainable Humanosphere (RISH), Kyoto University, Japan 2 Facaulty of Environmental Earth Science, Hokkaido University, Japan ICGPSRO, May 14-16, 2013

2 Temperature Changes in the Tropical Tropopause Layer (TTL) Coupling Coupling SUN Ozone Depletion SUN Recovering ozone warming Cooling Greenhous e Gases (GHGs) Emissions Aerosol Layer Major Volcanic Eruptions Weakening B D Circulation 70 hpa TTL Aerosol Layer 150 hpa Ozone Depleting Substances (ODSs) Ocean GHGs Emissions Minor volcanic eruptions during (?) B D Circulation Change? Reduced ODSs Water Vapor Change? Ocean warming Cooling

3 Long term changes in OZONE during 21 st century :Multimodal assessment Gettelman et. al., 2008 The stratospheric ozone layer has been depleted by anthropogenic emissions of halogenated species since 1980s. Observations show that Antarctic ozone hole is expected to disappear in the first half of the 21st century as a result of the implementation of the Montreal Protocol (as CFCs are banned).

4 Long term changes in water vapor: observation Water vapor mixing ratio averaged for hpa Tropics [10N 10S] Various Observations NOAA (FPH,CFH) HALOE, MLS SOWER (CPH) Fujiwara et al., 2010 Boulder, Colorado Hurst et al., 2011 Water vapor in the stratosphere influences variability and recovery of the ozone layer through its radiative and photochemical nature [e.g., Kley et al., 2000].

5 Long term changes in the TTL during 21 st century, Couple Chemistry Model Austin and Reichler, 2008 Global warming and ozone depletion. Due to upwelling Due to changes in SST and Ozone Global warming and ozone recovery

6 Deseasonalized tropical temperature anomalies: Tropics [15N 15S] Stratospheric cooling and tropospheric warming is not continuous Several step and trend changepoints particularly associated with Volcanic eruptions and ENSO

7 Step and trend changepoints Using Lund and Reeves, 2002

8 RICH Temperature Trends:

9 Temperature Trends during

10 Temperature changes during : GPS RO Long term detection capabilities of GPS RO: Though GPS RO data length is short, it represents the long term changes. Stronger warming in the TTL is a sticking feature. Trend is estimated while considering only the QBO and ENSO Other related references e.g. Steiner et al., 2009, 2011, Schmidt et al., 2010 Lackner et al., 2011

11 Our Objectives Estimation of the temperature trend while considering the QBO, ENSO and minor Volcanic Eruptions during Validation of the temperatures in the TTL

12 Minor Volcanic Eruptions: Vernier et al., 2011 Minor Volcanic eruption Lon Lat Date of eruption Ruang Sep-02 Reventador Nov-02 Manam Jan-05 Soufriere Hills May-06 Tavurvur Oct-06 Solomon et al., 2011

13 Data Sets, Location of the selected radiosonde stations and Minor volcanic eruptions GPS Radio Occultations data ( ) CHAMP (May May 2006) and COSMIC (June 2006-Dec. 2010) Radiosonde ( ) Unadjusted data (IGRA):A set of 25 stations and subset of 5 stations Adjusted data sets (RICH and HadAT2) ERA-Interim ( ) Subset of 5 Stations Truk Rochambeau Singapore Seychelles Darwin

14 Method of Analysis Standard linear regression Multiple Regression (Method-1) Seasonal modulation in the form of Thus, Eq (1) in this form Multiple Regression (Method-2) Randel and Cobb, 1994

15 Method of Analysis (Cont. ) Before the regression analysis (from deseasonalized anomalies) we must know Is there any step and trend changepoint? Are there any time lag between temperature and Independent variables (with significant correlations)? After the regression analysis (Examine) is residual minimized?

16 The reference time series: Zonal wind at 50 hpa N3.4 SST anomalies Minor Volcanic eruptions during Solar Cycle; F10.7 cm radio flux

17 TTL Temperature anomalies :

18 Lag correlation analysis ( ): Temp and various Indices Remarkable significant correlation at zero lag between AOD and TTL temperature during

19 Regression methods: Typical examples hpa) GPSRO Standard linear regression Method-1 (QBO and ENSO) Method-2 (QBO and ENSO) Method-2 (QBO, ENSO and AOD)

20 Annual mean temperature trends:

21 Seasonal Variation of the temperature trends Standard linear regression Method-2 (QBO and ENSO removed) Method-2 (QBO, ENSO and AOD removed) 90% significance test

22 Latitudinal Variation of the temperature trends between 16 km and 19 km: GPS RO

23 Role of AOD in temperature fitting : attribution km average

24 Annual mean temperature response to the QBO, ENSO and AOD:

25 Seasonal Variation of the temperature response to the QBO, ENSO and AOD:

26 Explained variance (R 2 ) Fractional Change in the explained variance (R 2 ) due to AOD

27 Summary The deseasonalized temperature anomalies from different data show overall agreements among themselves except ERA-Interim at 100 hpa which show large difference about K between mid 2006 to mid Comparison of undadjusted data with GPS RO is better than adjusted data for the period The AOD due to minor volcanic eruptions show significant correlation of about with temperature at 0 month lag between 16 and 19 km during The distinct stronger warming trend ( K/decade) in the TTL between 16 and 19 km reported earlier and in current study using method-1 is observed to be partly due to seasaonality in the QBO and ENSO and partly due to the minor volcanic eruptions during 2000s. Removing them using method-2 results into insignificant temperature trend. Thus, there is no significant temperature change observed due to anthropogenic climate change in the TTL between 16 and 19 km during in consistent to WMO report [2010]. A positive and significant AOD temperature response about K is observed in the TTL between 16 and 19 km during explaining about 5-15% of the total variability.

28 Thank You

29 Global Warming Global warming is the continuing rise in the average temperature of Earth's atmosphere and oceans. General effect of Global Warming Sea Level rise Change in amount and precipitation pattern Expansion of deserts Extreme weather From Hansen et al., (2001) Effect of Global warming Greenhouse Gases Greenhouse Gases (GHGs) Water vapor (H2O), Carbon Dioxide (CO2), Methane (CH4), Nitrous oxide (N2O) and ozone (O3) Anthropogenic GHGs Mainly chlorofluorocarbons (CFCs) The CFCs and other halogens affected the stratospheric ozone depletion, especially in the polar stratosphere, which caused the stratospheric cooling From Trenberth, 1992

30 Interannual variations in the TTL Periodic Quasi-Periodic Episodic Semi-Annual Oscillation (SAO) Annual Oscillation (AO) Volcanic Aerosols Major Volcanic Eruptions Angung (Bali, Indonesia, 1963) El, Chichon (Maxico, 1982) Mount Pinatubo (Philippines, 1991) Volcanic Eruptions Pinatubo Quasi-Biennial Oscillation (QBO), El Nino Southern Oscillation (ENSO), Solar Cycle QBO ( ~ 2years) EL Nino (~2-7 years) Solar cycle (~11 years)

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