Entrainment Rate Diurnal Cycle in Marine Stratiform Clouds Estimated from Geostationary Satellite Retrievals and a Meteorological Forecast Model

Abstract

The mean diurnal cycle of cloud entrainment rate (w(sub e)) over the northeast Pacific region is for the first time computed by combining, in a mixedlayer model framework, the hourly composited GOES15 satellitebased cloud top height (H(sub T)) tendency, advection, and largescale vertical velocity (w) during May to September 2013, with horizontal winds and w taken from the European Centre for MediumRange Weather Forecasts (ECMWF) model. The tendency term dominates the magnitude and phase of the w(sub e) diurnal cycle, with a secondary role of w, and a modest advective contribution. The peak and minimum in we occur between 20:0022:00 LT and 9:0011:00 LT, respectively, in close agreement with the diurnal cycle of turbulence driven by cloud top longwave cooling. Uncertainties in H(sub T) and ECMWF fields are assessed with in situ observations and three meteorological reanalysis data sets. This study provides the basis for constructing nearly global climatologies of w(sub e) by combining a suite of wellcalibrated geostationary satellites