Is There Really a Closure Gap Between 183.31-GHz Satellite Passive Microwave and <italic>In Situ</italic> Radiosonde Water Vapor Measurements?

Abstract

We present a new closure study between radiosonde and microwave satellite humidity measurements. The radiosonde data are from the Global Climate Observing System Reference Upper-Air Network. The satellite data are from the radiometers: MHS, Advanced Technology Microwave Sounder, and Sondeur Atmospherique du Profil d’Humidite Intertropicale par Radiometrie. Like previous studies, we find the satellite data to be “colder” than simulated radiosonde data. But the mean bias value (0.4 K) is smaller than previously reported and, according to our analysis, not significant. The error budget suggests an uncertainty of 0.52–1.06 K. We also show that the improvement in closure can be attributed to improvements in the intercomparison methodology.