Application of Cumulative Distribution Functions to Compositing Precipitable Water with Low Earth Orbit Satellite Data

Precipitable water (PW) is a leading indicator of severe weather, such as heavy rainfall. The National Meteorological Satellite Center receives observation data directly from Low Earth Orbit (LEO) satellites, including NOAA-18, 19, MetOp-A, B, and Suomi-NPP, and generates level 2 products in near real time for the East Asia region. In this study, PW data were retrieved from the abovementioned sources and composited to determine meteorologically significant PW fields from all available data sources considering the boundary layer (BL), middle layer (ML), high layer (HL), and total column. Cumulative distribution function (CDF) matching was performed for PW retrieved from the five satellites within specific time windows in order to integrate them and minimize their differences. The PW composite data were matched to reference PW CDF data from the Unified Model (UM) Regional Data Assimilation Prediction System (RDAPS) analysis data, which are updated according to selected time windows. PW data were composited for 03:00–09:00, 09:00–15:00, 15:00–21:00, and 21:00–03:00 UTC time windows. PW data composited during the summer and winter seasons in 2015, 2016, and 2017 were then validated. The results show improvements in composite Total Precipitable Water and BL PW from Suomi-NPP of approximately 15% and 40% (RMSE), respectively.