RegCM4: Model description and preliminary tests over multiple CORDEX domains

Climate Research (Impact Factor: 2.71). 01/2011; 936:577X. DOI: 10.3354/cr01018

ABSTRACT A new version of the RegCM regional climate modeling system, RegCM4, has been recently developed and made available for public use. Compared to previous versions, RegCM4 includes new land surface, planetary boundary layer, and air-sea flux schemes, a mixed convection and tropical band configuration, modifications to the pre-existing radiative transfer and boundary layer schemes, and a full upgrade of the model code towards improved flexibility, portability, and user friendliness. The model can be interactively coupled to a 1D lake model, a simplified aerosol scheme (including organic carbon, black carbon, SO4, dust, and sea spray), and a gas phase chemistry module (CBM-Z). After a general description of the model, a series of test experiments are presented over 4 domains prescribed under the CORDEX framework (Africa, South America, East Asia, and Europe) to provide illustrative examples of the model behavior and sensitivities under different climatic regimes. These experiments indicate that, overall, RegCM4 shows an improved performance in several respects compared to previous versions, although further testing by the user community is needed to fully explore its sensitivities and range of applications.

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    ABSTRACT: A regional climate model, RegCM has been utilized to examine the dynamic impacts of large aerosol radiative forcing on the atmospheric temperature and circulation in India during the monsoon (Jun-Sep) seasons of 2009 and 2010. Surface shortwave radiative forcing at the aerosol hot spots is in the range −25 to −60 W m−2 with the larger values observed during the summer monsoon season of 2010 (due to larger dust load) relative to that in 2009. It is important to note that the summer monsoon rainfall in 2010 was declared to be a normal monsoon as against the deficit rain in 2009. Changes in near surface air temperature show a spatial dipole pattern with the aerosol effect dampening out above 500 hPa with a larger change observed for natural aerosols relative to anthropogenic aerosols. The dipole pattern is characteristics of aerosol-induced change. Aerosols tend to strengthen the summer monsoon zonal mean wind at 850 hPa over the hotspots (larger effect in 2009 than in 2010) whereas there is negligible impact on the corresponding mean meridional wind component. This has resulted in a southward shift of the monsoon circulation during 2010 summer, leading to an increase in upward motion over the core monsoon region and thereby increasing the cloud fraction. This may also be facilitated by the aerosol induced heating in the lower troposphere. In 2009, the upward motion is enhanced to the south of the core monsoon region. The dynamic effects imply a positive feedback of the aerosol direct radiative forcing on the summer monsoon circulation over India.
    Climate Dynamics 03/2014; 44(5-6):1685-1697. DOI:10.1007/s00382-014-2284-4 · 4.62 Impact Factor
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    ABSTRACT: The effect of different cumulus parameterization schemes (CPSs) on precipitation over China is investigated by using the International Centre for Theoretical Physics (ICTP) Regional Climate Model version 4.3 (RegCM-4.3) coupled with the land surface model BATS1e (Biosphere-Atmosphere Transfer Scheme version 1e). The ERA-interim data are utilized to drive a group of simulations over a 31-yr period from September 1982 to December 2012. Two typically sensitive regions, i.e., the eastern Tibetan Plateau (TP; 29°-38°N, 90°-100°E) and eastern China (EC; 26°-32°N, 110°-120°E), are focused on. The results show that all the CPSs have well reproduced the spatial distribution of annual precipitation in China. The simulation with the Emanuel scheme shows an overall overestimation of precipitation in China, different from the other three CPSs which only overestimate over northern and northwestern China but underestimate over southern China. Seasonally, the Tiedtke scheme shows the smallest overestimation in winter and summer, and the best simulation of the annual variance of precipitation. Interannual variations of precipitation among the four CPSs are generally simulated better in summer than in winter, and better for entire China than in the subregions of TP and EC. The precipitation trend is simulated better over EC than over TP, and better in summer than in winter. An overestimate (underestimate) of the East Asian summer monsoon index (EASMI) exists in the simulations with the Grell and the Emanuel (the Kuo and the Tiedtke) schemes. The smallest EASMI bias in the Tiedtke simulation could explain its small precipitation bias. A negative correlation between the EASMI and summer precipitation over the middle and lower reaches of Yangtze River is found in the Grell and the Emanuel simulations, but was missed by the simulations using the Kuo and the Tiedtke schemes.
    02/2015; 29(1):119-131. DOI:10.1007/s13351-014-4042-2


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