Convective Activity Associated with Intraseasonal Variation over the Eastern Indian Ocean Observed during R/V Mirai Cruise in 2002 and 2003

摘要

Two-years onboard observations have been carried out with R/V Mirai over the eastern Indian Ocean, where we have less in situ lower tropospheric data, to examine variations of maritime convective activities including MCSs, e.g., diurnal and intraseasonal variations. OLR variation showed that cruise periods of MR02 and MR03 correspond to ISV active and inactive phases, respectively. We found different characteristics of convective activity during each period that ISV active (inactive) phase shows more (less) rainfall amount, duration, and stratiform fraction, but less (more) convective instability and amplitude of diurnal cycle. In ISV inactive phase (MR03), we have detected three robust MCSs, which were embedded in the diurnal variation (they passed over the ship 24 LT every time), and found they had the typical squall line structure of reflectivity and Doppler wind fields. Diurnal cycles of convective activity suggest a robust interaction between MCSs and the background environment The onboard cruise observation over the eastern Indian Ocean with R/V Mirai during boreal summer monsoon season in 2004 are scheduled. We are going to compare these results with those over the western Pacific and the Atlantic Oceans during TOGA-CO ARE and GATE, respectively, and clarify the unique feature of MCSs over the eastern Indian Ocean.