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

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

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 Westerly Jet or wave guide High Pressure regions

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

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 th August th July th August 2001 Indian Institute of Technology, Kharagpur Western Asia Dry Air Incursion

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

Data and Methodology

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

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

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

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

Indian Institute of Technology, Kharagpur

Meridional Cross-section of Specific humidity over Central India

Thermodynamics of the upper-troposphere

Hadley Circulation during Breaking condition

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

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