Evaluation of tropical cirrus cloud properties derived from ECMWF model output and ground based measurements over Nauru Island

Abstract

Cirrus clouds play an important role both radiatively and dynamically in the tropics. Understanding the mechanisms responsible for the formation and persistence of tropical cirrus is an important step in accurately predicting cirrus in forecast and climate models. In this study, we compare ground-based measurements of cloud properties with those predicted by the ECMWF model at a location in the tropical western Pacific. Our comparisons of cloud height and optical depth over an 8 month time period indicate that the model and measurements agree well. The ECMWF model predicts cirrus anvils associated with deep convection during convectively active periods, and also isolated cirrus events that are influenced by large-scale vertical ascent. We also show through examination of an upper tropospheric cirrus case that the model produces tropospheric waves that appear to influence the morphology and maintenance of the cirrus layer. Copyright 2004 by the American Geophysical Union.