1. Mihir Kumar Dash*, Dhrubajyoti Samanta* and P. C. Pandey** * Indian Institute of Technology, Kharagpur * Indian Institute of Technology, Bhubaneswar

2. Outline Introduction Data and Methodology Rossby wave breaking and circulation over the West Asia Convective inhibition over the Indian subcontinent Summary Indian Institute of Technology, Kharagpur

3. Introduction Indian Institute of Technology, Kharagpur Major 200-hPa circulation anomalies accompanied with climatological zonal wind (shading >15m) from June to September. The dotted line indicates the zero zonal wind line in 200-hPa Adopted from Ding Q. 2008 Westerly Jet or wave guide High Pressure regions

4. Indian Institute of Technology, Kharagpur Krishnan et al. 2009 Low over WCI Blocking high over south eastern china

5. Ten-day back trajectories from central India. Dry spell for trajectories terminating at 850 (green) and 700 (red) hPa (from Krishnamurti et al, 2010) 18 June 2009 4 th August 2009 16 th July 2002 30 th August 2001 Indian Institute of Technology, Kharagpur Western Asia Dry Air Incursion

6. Indian Institute of Technology, Kharagpur Rossby Wave Breaking Overturning of PV event at 350-K PV (a)Anticyclonic (b) Cyclonic. contoured every 2 potential vorticity units. From Strong and Magnusdottir, 2009

7. Data and Methodology

8. Indian Institute of Technology, Kharagpur Climatology of Isentropic Potential Vorticity and horizontal wind at 350K Level

9. Indian Institute of Technology, Kharagpur Sample cases of Rossby Wave Breaking and intensification of circulation over the western India

11. Potential Vorticity and Wind Field anomalies at 350K Over Asia and Africa

12. Geopotential Height and Temperature anomalies at 500hPa Over Asia and Africa

13. Indian Institute of Technology, Kharagpur

14. Meridional Cross-section of Specific humidity over Central India

15. Thermodynamics of the upper-troposphere

17. Hadley Circulation during Breaking condition

18. Summary Rossby Wave Breaking over the Western/Western Central Asia Formation of blocking high over Western Central Asia Descending of dry air from western and central Asia forming a inversion layer over Indian sub- continent Modification of Hadley circulation over the Indian Subcontinent Suppression of convection over the Indian – subcontinent and Drought

19. THANK YOU