Software package for estimating Heat budget from satellite data for tropical Indian ocean

INTERNATIONAL SYMPOSIUM ON INFORMATION TECHNOLOGY IN OCEANOGRAPHY (ITO-98)

GOA, INDIA 12-16 OCTOBER 1998

P. M. Muraleedharan and P. V. Sathe

Heat budget of the tropical Indian ocean and its coupling with monsoon rainfall over the Indian subcontinent has a significant impact on India's economy which is predominantly based on agriculture. Shipborne observations have been too sparse to compute air-sea of fluxes on both spatial and temporal time scales to draw meaningful conclusions on large-scale phenomena like Asian Monsoon. This needs recourse to satellite technology. With the launch of India's premier ocean satellite Oceansat-1, scheduled in the current year, India will have the capability to collect all relevant data required for addressing such outstanding problems of her economic importance.

Computation of heat budget requires information on latent heat flux, sensible heat flux and radiation transfer across ocean atmosphere interface. This paper presents a software package to process all relevant satellite and model derived data and to compute surface heat fluxes and finally the heat budget over tropical Indian ocean. It makes use of satellite data on sea surface temperature from Advanced Very High Resolution Radiometer (AVHRR), water vapour and sea surface wind data from Special Sensor Microwave Imager (SSM/1), Sea level pressure from European Center for Medium Range Weather Forecasting (ECMWF) and surface radiation budget from Geostationary Meteorological Satellite (GMS).

Surface level air temperature, not readily available from satellite observations, was derived empirically using a second order polynomial relation between in situ air-temperature and humidity from a well distributed (temporal and spatial) surface meteorological data set. This involved construction of a series of polynomials to represent a wide range of climatic conditions of the tropical Indian ocean. The package is validated with surface flux values This is computed from available insitu data over the tropical Indian Ocean. This is again compared with the flux estimates from COADS data. Finally the program satellite computes the inherent errors in flux estimates, incorporating satellite observations. Complete source code of the package in FORTRAN 77 is included in the paper.

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