Spatial distribution of meteorological parameters around 900 hPa level over the Arabian Sea and Indian Ocean regions during the IFP-99 of the INDOEX programme as revealed from the constant altitude balloon experiments conducted from Goa

During the IFP-99 of the INDOEX programme, an Indo-French joint scientific team conducted 17 constant balloon flights from Goa mainly to study the var ious features of the continental air mass flow from the Indian subcontinent towards the ITCZ induced by the NE winter circulation and thereby to deriv e the transportation of the continental aerosols and trace gases to the Ind ian Ocean regions. Out of the 17 flights, 15 were successful. Data obtained from the Constant Altitude Balloon Experiment are analysed to study the fe atures of the wind fields and thermodynamic parameters of the marine bounda ry layer at similar to 900hPa level over the oceanic regions adjoining west -coast of Peninsular India, From the balloon co-ordinates, the instantaneou s vector wind as well as its zonal and meridional components are estimated. Also estimated are the ambient air temperature and relative humidity at 30 min interval. These data are examined for the spatial features. Mean wind showed presence of three broad flow channels, from India, Africa and West Asia, that are important in influencing the Arabian Sea environmen t and provide potential pathways for transport of continental pollutants, V ariations associated with the MJ oscillations are present in the zonal wind , close to the equator. On several occasions wind showed occurrence of eddi es with anticyclonic circulation having temporal scales of one to five days . Temperature and humidity structure showed large dry areas over the Arabia n Sea associated with the flow channels. Rather humid regions occur over co astal India and near the ITCZ.