Comparison of cirrus cloud coverage calculated from reanalysis meteorological data with satellite data

Abstract

An offline cirrus cloud coverage calculation was conducted using a parameterisation similar to that adopted in ECHAM (Chen et al., 1997), as part of a preliminary analysis from ongoing work on estimating the uncertainties from contrail radiative forcing. The resulting cirrus cloud coverage, calculated from ECMWF ERA-40 reanalysis specific humidity and temperature data, was compared with ISCCP cirrus cloud data. Monthly mean results showed that computed coverage statistics between 45° South and 45° North were comparable with those from satellite observations. Similar spatial coverage structures, i.e. the high and low coverage values, were captured by both the parameterised calculation and the ISCCP dataset. A sensitivity analysis on the critical value of relative humidity over ice (Uci) necessary for clouds to form highlights the importance