6. Intra-seasonal variability during Indian summer Monsoon-1999

S.C. Kar, R.K. Paliwal & S.V. Singh, NCMRWF, New Delhi.

Daily anomalies of atmospheric data were constructed for monsoon season of 1999 using analysed data at NCMRWF. The data indicated that the monsoon was somewhat subdued during 1999 but during BOBMEX period, the atmospheric conditions over the Bay of Bengal was near normal.
Filtered anomalies of velocity potential indicated that Madden-Julian oscillations propagated eastward in the equatorial zone. There were few occasions of northward propagation of wind anomalies over the Bay of Bengal. The NCMRWF wind anomalies over the Bay agreed well and consistent with the GPCP rainfall data.

Temporal Variation of Thermodynamics of the marine atmosphere 17.5°N, 89.0°E during BOBMEX-1999

V.R. Mujumdar, S.G. Nagar, S.P. Ghanekar, P. Seetaramayya and U.V. Bhide, Indian Institute of Tropical Meteorology, Pune

The surface synoptic features like zonal index (pressure difference between Thiruvananthpuram and Nagpur), intensity of seasonal low, sea level pressure at stationary ship location (17.5 N, 89.0 E) and the percentage departure of rainfall showed active monsoon over India during Phase I (15 July - 10 August 99) and weaker monsoon in Phase II (11 - 30 August 99) of BOBMEX-99.
The changes in 500 hPa circulation pattern over the Bay of Bengal from strong westerlies to easterlies or weak westerlies could be attributed to suppressed atmospheric activity in Phase II.
Daily variation in the mid-tropospheric thermodynamic parameters, viz., q_v, q_e, q_es, Rh, (p*-p) over ship during stationary period 28 July - 5 August 1999 (Phase I), 14 - 22 August 1999 (Phase II) were found to be sensitive to the location of vortex and the trough line with respect to ship’s position. The overall decrease in the values of the parameters in Phase II indicated cooler mid-troposphere and lull in convective activity during the period.

8. Comparison of total precipitable water vapour derived from IRS-P4/MSMR with BOBMEX (Vaisala) data

B. Simon, M.M. Ali, Rashmi Sharma, C.A. Prabhakar and G.S. Bhat, Space Application Centre, Ahmedabad