The Daily Variation of Wind in the Lower Atmosphere over Ahmedabad

Abstract

The lower atmospheric wind structure over Ahmedabad has been studied from a detailed. analysis of one complete year's observations. It is found that the local winds introduced by the orographical peculiarities of the surrounding country are (1) the katabatic wind that comes as. a Northeasterly current extending to a depth of about 0'15 to 0,25 km in the months of October to January and (2) the sea breeze that reaches from ,the Gulf of Cambay in the hot months just prior to and after the local monsoon. A seasonal examination of the pilot balloon winds shows that the nature of the diurnal variation of wind is governed mainly by the amount of turbulence in the frictional layer. This variation is confined to about'3000 ft in winter and extends to a greater from the Gulf height in summer. It is also shown how, in the winter months, both the wind and temperature distributions help in the formation of a very stable layer just above 3000 ft limiting the upper reach of surface turbulence.