Quantifying the inflation factors of observation error variance for COMS and MTSAT Atmospheric Motion Vectors considering spatial observation error correlation

Abstract

In this study, the spatial error correlations in the Atmospheric Motion Vectors (AMVs) derived from the geostationary satellite imagery over East Asia are investigated. Good characterization of systematic errors in observations is essential in order to extract the maximum amount of information from the observations during the assimilation process. The spatial structure of AMV error correlations was identified based on datasets of AMVs collocated with sonde observations for July 2015. Results of AMVs from water vapour (WV; 6.7 µm) and infrared (IR; 10.8 µm) channels of the Korean geostationary Communication, Ocean and Meteorological Satellite (COMS) and the Multifunction Transport Satellite‐2 (MTSAT) are presented. For both channels, the length scales of the spatial error correlations in the MTSAT AMVs are longer than those of the COMS AMVs. For MTSAT (COMS) AMVs, a longer (shorter) length‐scale yields more (less) inflated observation error variance, and a larger (smaller) inflation factor for the diagonal form of the observation error covariance matrix is required to obtain the best quality of analysis.