Surface Freshwater Flux Estimation Using TRMM Measurements Over the Tropical Oceans

Satya Prakash,Samir Pokhrel,Rakesh Mohan Gairola,Mahesh C

doi:10.4236/acs.2011.14025

Abstract

The exchange of surface freshwater, heat and moisture fluxes across the air-sea interface strongly influences the oceanic circulation and its variability at all time scales. The goal of this paper is to estimate and examine surface freshwater flux at monthly scale exclusively from the Tropical Rainfall Measuring Mission (TRMM) measurements over the tropical oceans for the period of 1998 - 2010. The monthly mean fields of TRMM Microwave Imager (TMI) sea surface temperature (SST), wind speed (WS), and total precipitable water (W) are used to estimate the surface evaporation utilizing the bulk aerodynamics parameterization formula. The merged TRMM Multisatellite Precipitation Analysis (TMPA)-3B43 product is combined with the estimated evaporation to compute the surface freshwater flux. A preliminary comparison of the satellite derived evaporation, precipitation and freshwater flux has been carried out with the Hamburg Ocean Atmosphere Parameters and Fluxes (HOAPS-3) datasets. Also, the estimated evaporation and TMPA-3B43 precipitation are validated with in-situ observations from the moored buoys in the different oceans. The results suggest that the TRMM has great potential to estimate surface freshwater flux for climatological and oceanic hydrological applications.

Highlights

Short-term climate changes are believed to be strongly influenced by large scale ocean-atmosphere interactions through exchanges of momentum, heat and water
The surface freshwater flux is computed from the TRMM Multisatellite Precipitation Analysis (TMPA)-3B43 precipitation and the present evaporation estimates and compared with another independent satellite derived HOAPS-3 datasets
Depending on the inter-annual variations, the inter-tropical convergence zones (ITCZ) migrates throughout the year between 5 ̊ N and 20 ̊ N being farthest from equator in July and closest to the equator in January [37] which are clearly seen in both the precipitation products

Summary

Introduction

Short-term climate changes are believed to be strongly influenced by large scale ocean-atmosphere interactions through exchanges of momentum, heat and water. One of the strongest links between ocean, land and atmosphere is the freshwater fluxes due to evaporation (E) and precipitation (P) processes. Evaporation connects the energy to the hydrological cycles of ocean and atmosphere. Evaporation minus precipitation (E-P) is usually referred to as the net flux of freshwater or the total freshwater in or out of the oceans. E-P determines surface salinity of the ocean, which helps in determining the stability of the water column. Since the distribution of evaporation, precipitation, ice and continental runoff is the primary factor in the determination of surface salinity, it is essential to quantify it to adequately understand the ocean hydrological cycle [1]

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