Bias Characteristics of COSMIC RO Data within Clouds Based on Different Background Fields

Abstract

The Global Constellation Observing System for Meteorology， Ionosphere， and Climate （COSMIC） radio occultation （RO） from 2007 to 2009 were collocated with the CloudSat nadir-pointing cloud profiling radar （CPR） in time and space in this study.We investigated the characteristics of fractional refractivity differences between COSMIC RO and the analysis of the European Centre for Medium-Range Weather Forecasts （ECMWF） and the National Centers for Environmental Prediction （NCEP） within the different clouds.NbiasECMWF and NbiasNCEP indicate the fractional differences of refractivity between COSMIC RO and ECMWF， and COSMIC RO and NCEP analysis， respectively.The maximum values of NbiasECMWF within cumulus， stratocumulus， altocumulus and altostratus are 1.2%， 0.2%， 0.5%， and 0.2%.The highest values of NbiasNCEP are 1.8%， 0.5%， 0.5% and 0.4%， respectively.In the lower troposphere， the value of NbiasECMWF is positive and increases with the liquid water content， whereas the value of NbiasNCEP is negative.From the perspective of global distribution， large positive refractivity differences for both ECMWF and NCEP analyses are shown in the equatorial convergence zone， which is highly correlated with the positive bias of water vapor and the negative bias of temperature in space.

Keywords

• cosmic ro
• cloudsat
• refractivity n-bias
• lwc