First extended validation of satellite microwave liquid water path with ship‐based observations of marine low clouds

Abstract We present the first extended validation of satellite microwave (MW) liquid water path (LWP) for low nonprecipitating clouds, from four operational sensors, against ship‐borne observations from a three‐channel MW radiometer collected along ship transects over the northeast Pacific during May–August 2013. Satellite MW retrievals have an overall correlation of 0.84 with ship observations and a bias of 9.3 g/m 2 . The bias for broken cloud scenes increases linearly with water vapor path and remains below 17.7 g/m 2 . In contrast, satellite MW LWP is unbiased in overcast scenes with correlations up to 0.91, demonstrating that the retrievals are accurate and reliable under these conditions. Satellite MW retrievals produce a diurnal cycle amplitude consistent with ship‐based observations (33 g/m 2 ). Observations taken aboard extended ship cruises to evaluate not only satellite MW LWP but also LWP derived from visible/infrared sensors offer a new way to validate this important property over vast oceanic regions.