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Time evolution of monsoon low‐level jet observed over an Indian tropical station during the peak monsoon period from high‐resolution Doppler wind lidar measurements
Author(s) -
Ruchith R. D.,
Raj P. Ernest,
Kalapureddy M. C. R.,
Deshpande Sachin M.,
Dani K. K.
Publication year - 2014
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2013jd020752
Subject(s) - maximum sustained wind , lidar , wind speed , atmospheric sciences , climatology , altitude (triangle) , wind profiler , monsoon , daytime , wind shear , geology , african easterly jet , depth sounding , westerlies , thermal wind , environmental science , wind gradient , tropical cyclone , remote sensing , radar , tropical wave , oceanography , telecommunications , geometry , mathematics , computer science
Doppler wind lidar measurements of horizontal winds at an Indian tropical station, Mahbubnagar (16.73°N, 77.98°E, 445 m above mean sea level), were used to investigate the time evolution of the monsoon low‐level jet (MLLJ) during the southwest monsoon season. Vertical profiles of zonal wind in the altitude range of 100 to 3000 m above surface (at every 50 m height interval and 5 min time averaged) obtained during the period 25 July to 23 August 2011 are considered for the analysis. The zonal winds in the altitude up to 3000 m above ground are predominantly westerly throughout the period and on almost all the days there is a westerly wind speed maximum around 500 m above ground during nighttime. Soon after local sunrise, the core of this wind speed maximum (jet) gets lifted up and by afternoon, the westerly wind maximum is shifted to a higher altitude of 2000 m–2500 m without much change in its magnitude. Analysis of the high‐resolution lidar data strongly indicates that the same nocturnal LLJ seems to be moving up and evolving into a daytime westerly MLLJ reported in several previous studies. Wind speed and direction derived from the wind lidar agree reasonably well with simultaneously observed GPS upper air sounding wind measurements. Further analysis shows that the time‐height evolution of the jet core is closely associated with daytime convection and boundary layer growth. The presence of clouds over the region seems to inhibit this type of time evolution.