Evaluation of the hydrological cycle of MATCH driven by NCEP reanalysis data: comparison with GOME water vapor measurements

[摘要] This study examines two key parameters of the hydrological cycle, water vapor(WV) and precipitation rates (PR), as modelled by the chemistry transportmodel MATCH (Model of Atmospheric Transport and Chemistry) driven by NationalCenters for Environmental Prediction (NCEP) reanalysis data (NRA). For modeloutput evaluation we primarily employ WV total column data from the GlobalOzone Monitoring Experiment (GOME) on ERS-2, which is the only instrumentcapable measuring WV on a global scale and over all surface types with asubstantial data record from 1995 to the present. We find that MATCH and NRAWV and PR distributions are closely related, but that significant regionaldifferences in both parameters exist in magnitude and distribution patternswhen compared to the observations. We also find that WV residual patternsbetween model and observations show remarkable similarities to residualsobserved in the PR when comparing MATCH and NRA output to observationscomprised by the Global Precipitation Climatology Project (GPCP). We concludethat deficiencies in model parameters shared by MATCH and NRA, like in thesurface evaporation rates and regional transport patterns, are likely to leadto the observed differences. Monthly average regional differences betweenMATCH modelled WV columns and the observations can be as large as 2 cm,based on the analysis of three years. Differences in the global mean WVvalues are, however, below 0.1 cm. Regional differences in the PR betweenMATCH and GPCP can be above 0.5 cm per day and MATCH computes on average ahigher PR than what has been observed. The lower water vapor content of MATCHis related to shorter model WV residence times by up to 1 day as compared tothe observations. We find that MATCH has problems in modelling the WV contentin regions of strong upward convection like, for example, along the InterTropical Convergence Zone, where it appears to be generally too dry ascompared to the observations. We discuss possible causes for this bias anddemonstrate the value of the GOME WV record for model evaluation.

[学科分类] 大气科学