Validating time series of a combined GPS and MERIS integrated water vapor product

Increased knowledge of atmospheric water vapor can improve weather predictions and is expected to reduce errors in products derived from GPS and (In)SAR data. At GPS ground stations Integrated Water Vapor (IWV) is estimated from the GPS signal delay with a high temporal resolution. The Envisat MERIS spectrometer obtains spatially dense IWV observations but at limited moments in time. In this research the additional value of MERIS IWV is evaluated when added to GPS IWV for the purpose of obtaining a high quality spatial-temporal water vapor product. At each of 39 stations, first GPS IWV from surrounding stations is used to produce a two months time series of IWV with a temporal resolution of one hour. Then both GPS and MERIS IWV are used together. The two resulting time series are validated against direct GPS IWV as measured at the station.