摘要
1997/98年强ElNio背景下西太平洋暖池区云辐射强迫的变化,表现出诸多不同于以往的特征,已经成为检验气候模式性能的一个重要标准。本文基于卫星资料,分析了大气环流模式GAMIL1.0和2.0版对上述现象的模拟能力。结果表明,GAMIL1.0模式对热带地区云辐射特征分布,尤其对西太平洋暖池区的长(短)波云辐射强迫及其异常的模拟结果均和观测接近,但其模拟的长(短)波云辐射以及净云辐射冷却作用的强度均偏强,且模拟的1998年异常亦不如观测明显。GAMIL2.0对热带云辐射强迫空间分布的模拟较GAMIL1.0存在一定改进,但其未能模拟出1998年暖池地区云辐射强迫异常。对比观测发现,暖池区云辐射强迫的模拟偏差主要源自模式对该处云量、云水路径及云垂直结构的模拟偏差。在GAMIL1.0中,它们共同造成模拟的短波云辐射明显偏强,而其相互补偿使长波云辐射模拟略好于前者,导致模拟净云辐射冷却作用过强。在GAMIL2.0中,高估的云水路径致使短波云辐射过强,而其模拟云量、平均云顶高度偏低则导致长波云辐射强迫偏弱。模式的晴空短(长)波辐射通量过高(低),亦对模拟短波云辐射强迫以及净云辐射冷却作用偏强有影响。
Abstract The authors evaluated the performance of two versions of the Grid-point Atmospheric General Circulation Model of IAP/LASG （GAMIL1.0 and 2.0）, by comparing the climatological patterns of the cloud-radiative forcings （CRFs）, i.e., shortwave cloud radiative forcing （SF）, longwave cloud radiative forcing （LF）, and their ratio N = - SF/LF, as well as their contrasts between the 1997/98 E1 Nifio years and the normal years over the tropical Pacific region in both the observations and simulations. The result shows that the spatial distributions of multi-year averaged cloud radiative forcing （CRF） and the anomalies of the strong 1997/98 E1 Niflo over the tropical Pacific region is well produced by GAMIL1.0, especially over the western Pacific warm pool region. However, the magnitudes of climatological SF, LF, and their ratio N are all overestimated, and the differences between the strong 1997/98 El Nino years and the normal years are underestimated. Although GAMIL2.0 has better spatial patterns than GAMIL1.0, it loses the anomalies of strong 1997/98 El Nino in the warm pool. Analysis shows that the discrepancies in CRFs are caused by unrealistic cloud vertical structure （i.e. overestimates in deep convective clouds and middle clouds while underestimate in cirrus）, in-cloud water path, and high cloud fraction. It is found that the simulation of LF is better than that of SF in GAMIL1.0. The better simulation of LF results from the opposite effect of biases in cloud vertical structure and high could fraction to LF and the joint effect of biases to SE In GAMIL2.0, the overestimated in-cloud water path compensates the contributions of underestimated cloud cover and then leads to stronger SE However, it has fewer effects on LF that mainly reflect the impact from the underestimated cloud cover. As a result, the value of N is overestimated by these two versions. In addition, the large discrepancies in the clear-sky fluxes at the top of atmosphere in GAMIL also lead to the overestimation of N value
出处
《大气科学》
CSCD
北大核心
2012年第5期863-878,共16页
Chinese Journal of Atmospheric Sciences
基金
国家高技术研究发展计划(863计划)项目2010AA012304
全球变化国家重大科学研究计划项目2010CB951904
关键词
云辐射强迫
模式评估
EL
Nio
西太平洋暖池
cloud-radiation forcing, model evaluation, E1 Nifio, westem Pacific warm pool
