The Indian Mesosphere-Stratosphere-Troposphere (MST) radar observations of vertical distribution of mean vertical velocities w in convective regions during the wet and dry spells of the Indian summer monsoon over a tropical station at Gadanki, India (13.58N, 79.28E) are discussed. The composite w profile during the wet spell consistently shows a single peak at ;13 km whereas during the dry spell it shows two peaks, one at 5 km and another at 11-13 km. The characteristics of this altitudinal

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... ribution in w are discussed in terms of background wind and thermal structure during both spells of the monsoon. Background w obtained from NCEP-NCAR reanalysis shows subsidence throughout the depth of the troposphere during the dry spell of the monsoon over Gadanki. Analysis of background wind and thermal structure clearly reveal that wind shear and temperature inversion in the midtroposphere are different in the dry spell compared to that of the wet spell, which may be the possible reason for the observed double-peak w structure during the dry spell of the monsoon. The present analysis for the first time brought out the distinct vertical distribution in w and the background meteorological conditions during the wet and dry spells of the monsoon over Gadanki, which may have implications in understanding the monsoon convective systems during the wet and dry spells of the Indian summer monsoon.