Application of the AQ rain accumulation product for investigation of rain effects on AQ Sea Surface Salinity measurements

Abstract

Sea Surface Salinity (SSS) is a tracer of the ocean circulation and fresh water exchange, between ocean and atmosphere. Hence, it provides vital information to be able to understand how the Earth's hydrological cycle responds to climate change. An analysis of the Aquarius (AQ) Sea Surface Salinity retrievals reveals that the spatial patterns of reduced SSS are correlated with the spatial distribution of rainfall. Therefore, it is important to understand the SSS changes due to seawater dilution by rain, and the associated near-surface salinity stratification. This paper focuses on the effects produced by rainfall on the AQ SSS retrieval, using a macro-scale rain impact model (RIM). This model is based on the superposition of a one-dimension, empirical, transient, near-surface salinity stratification profile model that relates the surface salinity to depth, rain accumulation and time since rainfall. Also, an AQ Rain Accumulation (AQ RA) product (based on CMORPH - CPC Morphing technique - global precipitation dataset), that provides the rainfall history for 24 hours (in half hour intervals) prior to the observation time and each AQ measurement cell is presented. This AQ RA product facilitates the identification of instantaneous rain and prior rainfall accumulations, which will aid in the investigation of rainfall effects on the SSS measurements. In this paper, RIM was validated by comparing measured and simulated AQ SSS for two months of 2012 in the Pacific Ocean over the ITCZ (Inter-Tropical Convergence Zone). Results are presented showing the high cross-correlation for the comparison between simulated SSS and retrieved SSS.