Satellite-Based Surface Heat Budgets and Sea Surface Temperature Tendency in the Tropical Eastern Indian and Western Pacific Oceans for the 1997/98 El Nino and 1998/99 La Nina
Shu-Hsien Chou, NASA/GSFC, Greenbelt, MD; and M. D. Chou, P. K. Chan, and P. H. Lin
The 1997/98 is a strong El Nino warm event, while the 1998/99 is a moderate La Nina cold event. We have investigated surface heat budgets and sea surface temperature (SST) tendency for these two events in the tropical western Pacific and eastern Indian Oceans using satellite-retrieved surface radiative and turbulent fluxes. The radiative fluxes are taken from the Goddard Satellite-retrieved Surface Radiation Budget (GSSRB), derived from radiance measurements of the Japanese Geostationary Meteorological Satellite 5. The GSSRB covers the domain 40oS–40oN, 90oE–170oW and a period from October 1997 to December 2000. The spatial resolution is 0.5ox0.5o lat–long and the temporal resolution is 1 day. The turbulent fluxes are taken from Version 2 of the Goddard Satellite-based Surface Turbulent Fluxes (GSSTF-2). The GSSTF-2 has a spatial resolution of 1o x 1o lat–long over global oceans and a temporal resolution of 1 day covering the period July 1987–December 2000. Daily turbulent fluxes are derived from the SSM/I (Special Sensor Microwave/Imager) surface wind and surface air humidity, and the SST and 2-m air temperature of the NCEP/NCAR reanalysis, using a stability-dependent bulk flux algorithm.
The changes of surface heat budgets, SST and tendency, cloudiness, wind speed, and zonal wind stress of the1997/98 El Nino relative to the1998/99 La Nina for the northern winter and spring seasons are analyzed. The relative changes of surface heat budgets and SST tendency of the two events are quite different between the tropical eastern Indian and western Pacific Oceans. For the tropical western Pacific, reduced solar heating (more clouds) is generally associated with decreased evaporative cooling (weaker winds), and vise versa. The changes in evaporative cooling over-compensate that of solar heating and dominate the spatial variability of the changes in net surface heating. Both solar heating and evaporative cooling offset each other to reduce interannual variability of net surface heating. In addition, the area of increased SST tendency is larger than that of increased net surface heating, due to less solar radiation penetration through the bottom of deeper ocean mixed layer (stronger winds). For the tropical eastern Indian Ocean, enhanced solar heating (less clouds) is generally associated with reduced evaporative cooling (weaker winds). Both solar heating and evaporative cooling reinforce each other to increase interannual variability of net surface heating. In addition, the area of increased SST tendency is smaller than that of increased net surface heating in the southern domain. The relative changes in wind and zonal wind stress indicate more solar radiation penetration through the ocean mixed layer and more northward heat transport by ocean current from the south to the north Indian Ocean for the El Nino than for the La Nina.
Poster Session 4, Moisture, Fluxes and Retrievals
Thursday, 13 February 2003, 10:00 AM-12:00 PM
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