海-陆-气全球耦合模式能量收支的误差

通过分析GOALS模式两个版本GOALS 1.1和GOALS 2的能量收支 ,并与观测对比 ,结果表明 :模式模拟的地表净短波辐射通量在高纬地区偏低 ,而净长波辐射通量又偏高 ,导致极地表面温度偏低 ,感热通量在高纬地区为很高的负值。而在陆地上感热加热作用显著偏强 ,使地表有较大的向上净能量给大气 ,引起陆地上有些暖中心也偏强 ,这也解释了模式模拟地表面空气温度场的误差原因。海洋上潜热通量偏低 ,特别是在副热带洋面上偏少更明显。陆地上的欧亚和北美大陆大部分地区潜热通量仍偏低。这也是模式降水在大部分地区偏少的重要原因。两模式大气顶OLR偏低的模拟主要是在中低纬度 ,大气顶净短波辐射通量的模拟在中低纬度虽然与NCEP结果接近 ,但与地球辐射收支试验ERBE资料比较仍偏小较多 ,说明改进中低纬度云 辐射参数化方案对改进全球能量收支的模拟有重要意义。GOALS 2模式中诊断云方案模拟的云量除赤道地区外普遍偏小 ,尤以中纬度为甚 ,造成那里能量收支出现大的误差 。

Intercomparison of different physics schemes in the WRF model over the Asian summer monsoon region

Enhancing the ability of the WRF model in simulating a large area covering the West Pacific Ocean, China's Mainland, and the East Indian Ocean is very important to improve prediction of the East Asian monsoon climate. The objective of this study is to identify a reasonable configuration of physical parameterization schemes to simulate the precipitation and temperature in this large area. The Mellor-Yamada-Janjic （MYJ） and Yonsei University （YSU） PBL schemes, the WSM3 and WSM5 microphysics schemes, and the Betts-Miller-Janjic （BMJ） and Tiedtke cumulus schemes are compared through simulation of the regional climate of summer 2008. All cases exhibit a similar spatial distribution of temperature as observed, and the spatial correlation coefficients are all higher than 0.95. The cases combining MY J, WSM3/WSM5, and BMJ have the smallest biases of temperature. The choice of PBL scheme has a significant effect on precipitation in such a large area. The cases with MYJ reproduce a better distribution of rain belts, while YSU strongly overestimates the precipitation intensity. The precipitation simulated using WSM3 is similar to that using WSM5. The BMJ cumulus scheme combined with the MYJ PBL scheme has a smaller bias of precipitation. However, the Tiedtke scheme reproduces the precipitation pattern better, especially over the ITCZ.

Validation for a tropical belt version of WRF: sensitivity tests on radiation and cumulus convection parameterizations

Version 3.9 of WRF-ARW is run with a tropical belt configuration for a period from 2012 to 2016 in this study. The domain covers the entire tropics between 45°S and 45°N with a spatial resolution of about 45 km. In order to verify two radiation schemes and four cumulus convection schemes, eight experiments are performed with different combinations of physics parameterization schemes. The results show that eight experiments present reasonable spatial patterns of surface air temperature and precipitation in boreal summer, with the spatial correlation coefficient (COR) between simulated and observed temperature exceeding 0.95, and that between simulated and observed precipitation ranges from 0.65 to 0.82. The four experiments with the RRTMG radiation scheme show a better performance than the other four experiments with the CAM radiation scheme. In the four experiments with the RRTMG radiation scheme, the COR between simulated and observed surface air temperature is about 0.98, and that between simulated and observed precipitation ranges from 0.76 to 0.82. Comparatively, the two experiments using the new Tiedtke cumulus parameterization scheme can simulate better diurnal variation of precipitation in boreal summer than the other six experiments. In particular, for the diurnal cycle of precipitation over land and ocean, the experiment using the RRTMG radiation scheme and the new Tiedtke cumulus convection scheme shows that the peaks of precipitation rate appear at 0400 LST and 1600 LST, in agreement with observation.

IMPACTS OF CUMULUS PARAMETERIZATION AND RESOLUTION ON THE MJO SIMULATION

Madden-Julian Oscillations (MJO) in six integrations using an AGCM with different cumulus parameterization schemes and resolutions are examined to investigate their impacts on the MJO simulation. Results suggest that the MJO simulation can be affected by both resolution and cumulus parameterization, though the latter, which determines the fundamental ability of the AGCM in simulating the MJO and the characteristics of the simulated MJO, is more crucial than the former. Model resolution can substantially affect the simulated MJO in certain aspects. Increasing resolution cannot improve the simulated MJO substantially, but can significantly modulate the detailed character of the simulated MJO; meanwhile, the impacts of resolution are dependent on the cumulus parameterization, determining the basic features of the MJO. Changes in the resolution do not alter the nature of the simulated MJO but rather regulate the simulation itself, which is constrained by cumulus parameterization schemes. Therefore, the vertical resolution needs to be increased simultaneously. The vertical profile of diabatic heating may be a crucial factor that is responsible for these different modeling results. To a large extent, it is determined by the cumulus parameterization scheme used.

Sensitivity of simulated tropical intraseasonal oscillations to cumulus schemes

The sensitivity of simulated tropical intraseasonal oscillations (ISO) to different cumulus parameterization schemes was analyzed using an atmospheric general circulation model (latest version-SAMIL2.2.3) developed at the Laboratory for Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG) at the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences.Results show that the basic features of tropical climatological intraseasonal oscillations (CISO) can be captured using all three cumulus schemes.The CISO simulated by the Tiedtke scheme was found to be more realistic than that of the Manabe and Zhang-McFarlane schemes.The results of simulated transient intraseasonal oscillations (TISO) indicate that although the Tiedtke and the Zhang-McFarlane schemes in the new version SAMIL2.2.3 have been adjusted according to different problems,only the latter can simulate the eastward propagation of the 27-50-day TISO mode.It may be associated with the more realistic diabatic heating profile simulated by the Zhang-McFarlane scheme.In addition,the Manabe scheme in SAMIL2.2.3 is the same as that in the prior version SAMIL2.08.However,some aspects of the physical process,such as the radiation scheme and aerosol condition,have been changed.Conversely the eastward propagation from 100°E to the west of the tropical 27-50-day TISO mode only can be simulated using the Manabe scheme of SAMIL 2.08.Consequently,not all the improvements of physical parameterization schemes work well in every respect.The coordinated developments between dynamic frame and physical processes,and among different physical processes,are important methods that may be used to improve the model.

Features of rainfall and latent heating structure simulated by two convective parameterization schemes

Using the latest version of SAMIL (Spectral Atmosphere Model of IAP LASG) developed by LASG/IAP,we evaluate the model performance by analyzing rainfall,latent heating structure and other basic fields with two different convective parameterization schemes:Manabe Scheme and Tiedtke Scheme.Results show that convective precipitation is excessively overestimated while stratiform precipitation is underestimated by Tiedtke scheme,thus causing less stratiform rainfall proportion compared with TRMM observation.In contrast,for Manabe scheme stratiform rainfall belt is well simulated,although precipitation center near Bay of Bengal (BOB) spreads eastward and northward associated with unrealistic strong rainfall downstream of the Tibet Plateau.The simulated latent heating structure indicates that Tiedtke scheme has an advantage over Manabe scheme,as the maximum convective latent heating near middle of troposphere is well reproduced.Moreover,the stratiform latent heating structure is also well simulated by Tiedtke scheme with warming above freezing level and cooling beneath freezing level.As for Manabe scheme,the simulated maximum convective latent heating lies near 700 hPa,lower than the observation.Additionally,the warming due to stratiform latent heating extends to the whole vertical levels,which is unreasonable compared with observation.Taylor diagram further indicates that Tiedtke scheme is superior to Manabe scheme as higher correlation between model output and observation data is achieved when Tiedtke scheme is employed,especially for the temperature near 200 hPa.Finally,a possible explanation is addressed for the unrealistic stratiform rainfall by Tiedtke scheme,which is due to the neglect of detrained cloud water and cloud ice during convective process.The speculation is verified through an established sensitivity experiment.