Variability of evaporation-precipitation (E-P) and sea surface salinity (SSS) over Indonesian maritime continent seas

Abstract

The needs of global analysis for oceanic fresh water budget (evaporation–precipitation, E-P) and Sea Surface Salinity (SSS) are important to better understand the Earth’s climate system and the global water cycle. However, this analysis is often obstructed by time series data availability of both variabilities. This research used the Sea Surface Salinity (SSS) data that are derived from Aquarius satellite to describe the variability of SSS over marginal seas of Indonesian Maritime Continent (IMC), especially in Karimata Strait, Java Sea and Banda Sea. The variability of precipitation (P) and evaporation (E) can be identified from ECMWF ERA INTERIM re-analysis data. All of these monthly data were obtained from September 2011 until May 2015. The estimation showed that the evaporation in these waters is approximately -0.025 Sv to -0.059 Sv. Linear relationships between oceanic fresh water budget (E-P) and SSS is significantly different over the Indonesian ocean and expressed in the determinant coefficient (R2). The correlation between SSS and E-P was shown clearly in Indonesian waters. Almost half of SSS variation can be explained by E-P (27-53%), meanwhile the rest of SSS can be explained by other factors. From the two primary components of the fresh water budget, precipitation gave dominant influence compared to evaporation in explaining SSS variation. It was shown by the SSS when the precipitation decreased in the three waters. The correlation between the increase of E-P and SSS gradient and zonal and meridional wind speed was also shown there. The linear regression analysis was conducted to identify other variable which influence the SSS. The wind speed gave significant influence to SSS in the three waters. In Karimata Strait, the determinant coefficient (R2) between zonal and meridional wind speed explained dominantly almost half of SSS variation (38-49%), meanwhile SSS can be explained by other factors. It means that the wind can influence SSS through the evaporation process in which the increase of wind speed may cause evaporation increase. Then, the increase of evaporation will influence the degree of SSS in these waters.