Abstract:
Intense rains on 16–17 June 2013 over Mandakini River catchment caused Kedarnath disaster in Uttarakhand State (India). Normal and departure-from-normal 3D global atmospheric thermal structure and general and monsoon circulations during the event have been compared using equatorially/globally- conditioned surface and upper air parameters (1000–100 hPa) (period: 1979–2013). Briefly, normal monsoon structure is: 1000‒850 hPa layer- cross-equatorial flows over Indian Ocean and Eurasian westerlies confluence over Indian domain, the two flows further confluence downstream with Pacific easterlies and then the accumulated airmasses blow northeastward; 700‒500 hPa layer- Eurasian westerlies after sweeping entire Indian subcontinent make exit northeastward; and 400‒100 hPa layer- upper tropospheric anticyclone well-developed over subtropical Asia and outflows are spread all around. On 16–17 June 2013, two upper tropospheric anticyclonic cells occurred, one over Tibet-China and another Mediterranean-Middle East. Troposphere (1000–250 hPa) was significantly warmer-and thicker over Tibet-China followed by Mediterranean-Middle East while cooler-and-thinner over central Asia-India sector. Departures in downward slopes of tropospheric temperature and thickness from Tibet-China outward were significantly steeper. A huge trough evolved over Indo-Pacific region from an interaction between Eurasian westerlies and Indo-Pacific easterlies, and outflows from the trough made forced exit through western Himalaya which modulated north mid-high lati tudes westerlies into a single wave structure. Combined five factors produced disastrous rains over Kedarnath: cool-low and warm-low regime contrast; squeezing of deep warm-moist flows; orographic lifting; and pumping and suction effects. Forced warm-moist outflows from Indo-Pacific region caused warmer-thicker troposphere over eastern Russia-North America. Lesser outflows from Tibet-China anticyclone were directed southward, consequently troposphere was cooler-thinner over southern mid-high latitudes.
