Cloud Parameterizations in SUNYA Regional Climate Model for the East Asia Summer Monsoon Simulations

Cheng, Chao‐Tzuen; Wang, Wei‐Chyung

doi:10.3319/tao.2005.16.5.959(rcs)

Cited by 2 publications

(3 citation statements)

References 30 publications

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“…The scheme, suitable for application to grid size of several tens of kilometers, is found to provide the best simulation among several convective schemes (Ferretti et al 2000). The cloud cover is diagnosed based on relative humidity, atmosphere layer stability, and convective precipitation (Liang and Wang 1995), while the cloud water uses a hybrid scheme which, as indicated in Cheng and Wang (2005), simulates the least biases in shortwave (SW) cloud radiative forcing (CRF) and subsequently yields a surface temperature in better agreement with observation. For the radiation calculation, CCM3 radiation scheme (Kiehl et al 1996), in which cloud random overlapping is assumed, is used.…”

Section: Modelmentioning

confidence: 99%

“…This macroscopic parameter has taken into account contributions from cloud cover, cloud optical depth, and cloud emissivity, providing direct and useful information about the cloud-climate interaction (see Cheng and Wang 2005 for a more detailed definition). Wang et al (2004a), the net CRF consists of two components, a dominant cooling by SW CRF due to low clouds and a warming by LW CRF attributed to high clouds.…”

Section: Toa Cloud Radiative Forcingmentioning

confidence: 99%

“…The SUNYA RCM, evolved from National Center for Atmospheric Research (NCAR) Mesoscale Model version 5, has been used to study the 1991 severe flood event over the Yangtze-Huai River valley (YHRV) focusing on the ability to simulate the spatial and temporal precipitation patterns Wang et al 2000) and the sensitivity of rainfall to cloud parameterization (Cheng and Wang 2005). The present study is based on the latest version, although we switched to the Kain-Fritsch convective scheme to provide sufficient removal of the convective available potential energy (Kuo et al 1996).…”

Section: Modelmentioning

confidence: 99%

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SUNYA Regional Climate Model Simulations of East Asia Summer Monsoon: Effects of Cloud Vertical Structure on the Surface Energy Balance

Gong¹,

Wang²

2007

Terr. Atmos. Ocean. Sci.

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We used the State University of New York at Albany (SUNYA) regional climate model to study the effect of cloud vertical distribution in affecting the surface energy balance of the East Asia summer monsoon (EASM). Simulations were conducted for the summers of 1988 and 1989, during which large contrast in the intra-seasonal cloud radiative forcing (CRF) was observed at the top of the atmosphere.The model results indicate that both the high and low clouds are persistent throughout the summer months in both years. Because of large cloud water, low clouds significantly reduce the solar radiation flux reaching the surface, which nevertheless still dominate the surface energy balance, accounting for more than 50% of the surface heating. The low clouds also contribute significantly the downward longwave radiation to the surface with values strongly dependent on the cloud base temperature. The presence of low clouds effectively decreases the temperature and moisture gradients near surface, resulting in a substantial decrease in the sensible and latent heat fluxes from surface, which partially compensate the decrease of the net radiative cooling of the surface. For example, in the two days, May 8 and July 11 of 1988, the total cloud cover of 80% is simulated, but the respective low cloud cover (water) was 63% (114 gm -2 ) and 22% (21 gm -2 ). As a result, the downward solar radiation is smaller by 161 Wm -2 in May 8. On the other hand, the cloud temperature was 10°C lower, yielding 56 Wm -2 smaller downward longwave radiation. The near surface temperature and Terr. Atmos. Ocean. Sci., Vol. 18, No. 3, August 2007 494 gradient is more than 1°C smaller (and moisture gradient), leading to 21 and 81 Wm -2 smaller sensible heat and latent heat fluxes. It is also demonstrated that the model is capable to reproduce the intra-seasonal variation of shortwave CRF, and catches the relationship between total cloud cover and SW CRF. The model results show the dominance of high cloud on the regional mean longwave CRF and low cloud on the intra-seasonal variation of shortwave CRF, indicating the importance of cloud vertical structure.The strong negative feedbacks from the responses of latent and sensible heat flux tend to limit the effects of low clouds on the surface temperature simulations, as evidently the surface air temperatures bias of only 0.34°C in the EASM simulations while the variances of the surface radiative fluxes and heat fluxes are, respectively, in the ranges of 100 -200 and 60 -110 Wm -2 when total cloud cover are all near 80%. Therefore, it is also concluded that surface air temperature, precipitation, and total cloud cover, which are three frequently examined variables for climate models, are not sufficient for model evaluation, but instead the cloud vertical structure needs to be examined.(Key words: Cloud radiative forcing, East Asia summer monsoon, Regional climate model)

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Section: Modelmentioning

confidence: 99%

Section: Toa Cloud Radiative Forcingmentioning

confidence: 99%