Precipitation and Moisture in Four Leading CMIP5 Models: Biases across Large-Scale Circulation Regimes and Their Attribution to Dynamic and Thermodynamic Factors
Autor: | Guang J. Zhang, Mengmiao Yang, De-Zheng Sun |
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Rok vydání: | 2018 |
Předmět: |
Atmospheric Science
Coupled model intercomparison project 010504 meteorology & atmospheric sciences Moisture Scale (ratio) Humidity 010502 geochemistry & geophysics 01 natural sciences Physics::Geophysics Circulation (fluid dynamics) General Circulation Model Climatology Environmental science Precipitation Vertical velocity Physics::Atmospheric and Oceanic Physics 0105 earth and related environmental sciences |
Zdroj: | Journal of Climate. 31:5089-5106 |
ISSN: | 1520-0442 0894-8755 |
Popis: | As key variables in general circulation models, precipitation and moisture in four leading models from CMIP5 (phase 5 of the Coupled Model Intercomparison Project) are analyzed, with a focus on four tropical oceanic regions. It is found that precipitation in these models is overestimated in most areas. However, moisture bias has large intermodel differences. The model biases in precipitation and moisture are further examined in conjunction with large-scale circulation by regime-sorting analysis. Results show that all models consistently overestimate the frequency of occurrence of strong upward motion regimes and peak descending regimes of 500-hPa vertical velocity [Formula: see text]. In a given [Formula: see text] regime, models produce too much precipitation compared to observation and reanalysis. But for moisture, their biases differ from model to model and also from level to level. Furthermore, error causes are revealed through decomposing contribution biases into dynamic and thermodynamic components. For precipitation, the contribution errors in strong upward motion regimes are attributed to the overly frequent [Formula: see text]. In the weak upward motion regime, the biases in the dependence of precipitation on [Formula: see text] and the [Formula: see text] probability density function (PDF) make comparable contributions, but often of opposite signs. On the other hand, the biases in column-integrated water vapor contribution are mainly due to errors in the frequency of occurrence of [Formula: see text], while thermodynamic components contribute little. These findings suggest that errors in the frequency of [Formula: see text] occurrence are a significant cause of biases in the precipitation and moisture simulation. |
Databáze: | OpenAIRE |
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