Evaluation of ASCAT-Based Daily Gridded Winds in the Tropical Indian Ocean

Abstract

he quality of daily gridded Advanced Scatterometer (ASCAT; DASCAT) blended winds is examined in the tropical Indian Ocean using 3-day running mean gridded Quick Scatterometer (QuikSCAT; QSCAT) winds and in situ daily winds from the Research Moored Array for African?Asian?Australian Monsoon Analysis and Prediction (RAMA). The primary objective of this study is to examine whether DASCAT is a reliable replacement for the widely used QSCAT wind products. Spatial distributions of DASCAT and QSCAT winds show good agreement in speed and direction, except over a few localized regions. The study finds a significant spatial coherence between rainfall and the regions of discrepancy between DASCAT and QSCAT. Comparison of DASCAT and QSCAT wind products with RAMA moorings indicates that DASCAT better captures the overall wind variability compared to QSCAT, especially during rainy and low wind (<5 m s?1) conditions. The root-mean-square of the RAMA?DASCAT (RAMA?QSCAT) difference during rainfall in the zonal and meridional winds is 1.4 and 1.6 m s?1 (2.7 and 2.0 m s?1), respectively. The present study indicates that the DASCAT blended wind product is a reliable alternative to QSCAT in the tropical Indian Ocean.