Structural characteristics of the Inter Tropical Convergence Zone over theequatorial Indian Ocean during INDOEX-1999 field phase experiment

Inter Tropical Convergence Zone (ITCZ) is a narrow region (of about 200-300 km in width) where trade winds emanating from different hemispheres (north ern/ southern) converge. In an averaged sense around the globe, ITCZ lies t o the north of the equator during the northern summer and to the south of t he equator during the northern winter/southern summer. Typical patterns of the ITCZ are examined for the active and weak phases of its activity throug h the evaluation of meridional plane divergent circulation, temperature and moisture, etc. In an attempt to study the performance evaluation of the gl obal data assimilation and forecasting system (GDAFS) in predicting the enh anced ITCZ activity, the successive day-3 forecasts are utilized to delinea te the predictive characteristics associated with the ITCZ over the equator ial Indian Ocean. Further, the assessment of the impact of INDOEX glass son de data on the analysis circulation over the equatorial western Indian Ocea n with regard to the cyclonic circulation formed around 5 February 1999 is attempted. It is found that the operational analyses brings out the active and weak ph ases of the ITCZ activity over the equatorial Indian Ocean quite well, Furt her, the successive day-3 forecasts of the GDAFS are found to be reasonably successful in predicting the typical enhancement of the ITCZ activity. Ass imilation of the INDOEX glass sonde data for a selected period suggests a g eneral improvement in the description of the cyclonic circulation and its a ssociated characteristics.