海气耦合模式FGOALS_gl模拟的水汽和云辐射反馈过程

摘要

The characteristics of greenhouse effect of water vapor (Ga) and cloud radiative forcings (CRFs) over the low-latitude Pacific simulated by a coupled model developed by the State Key Laboratory of Numerical Modeling forAtmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics (IAP), ChineseAcademy of Sciences (CAS), namely FGOALS_gl, are analyzed in this paper. The reasons for model discrepancies are discussed. While the spatial distributions of climatological Ga and CRFs are generally well reproduced by the FGOALS_gl, some discrepancies are also evident. The model underestimates the intensities of Ga over the cold tongue and the northwestern Pacific, due to the biases in the simulated Sea Surface Temperature (SST) and the water vapor amount especially in the middle troposphere The model generally overestimates the amplitudes of both C1and Cs. The minimum center of C1 in the northern subtropical Pacific and the maximum center of Cs over the southeast Pacific are not evident in the model. The discrepancies in C1 (C8) are mainly due to the biases in the simulated high (total) cloud amount. The biases in the cloud vertical structure and optical thickness also have contributions.The spatial distributions of the responses of Ga, C1, and Cs to El Ni(n)o warming are well reproduced by the FGOALS_gl,even though the model overestimates the westward extent of maximum centers compared to the observations. The biases in Ga responses are caused by the discrepancies in magnitude and spatial pattern of SST anomalies associated with ENSO events, and the water vapor response to ENSO forcing. The responses of C1 (Cs) to ENSO forcing are closely related to the high (total) cloud amount anomalies, while biases in the cloud top altitude and optical thickness also have impacts.%本文分析了中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室(LASG)发展的快速耦合模式FGOALS_gl对低纬太平洋区域水汽温室效应(Ga)和云辐射强迫特征的模拟能力,讨论了模拟偏差的成因.结果表明,FGOALS_gl能合理再现Ga、云辐射强迫的气候态空间分布特征,但也存在明显的偏差.模式低估了冷舌区和西北太平洋Ga的强度,原因在于表层海温(ssT)和对流层(特别是中层)水汽的模拟偏差.模式总体上高估了云长波辐射强迫(Cl)和云短波辐射强迫(Cs)的强度,未能合理再现副热带北太平洋的Cl低值中心和东南太平洋的Gs大值中心.模式对Cl(Cs)的模拟偏差主要来自高云量(总云量)的偏差,云辐射强迫的模拟偏差还与云垂直结构和光学厚度的模拟偏差有关.从对El Nino型海温强迫的反馈来看,模式能基本再现低纬太平洋区域Ga正反馈、Cl正反馈和Cs负反馈的空间分布,但较之观测,反馈大值区过于西伸.Ga正反馈的偏差主要源自低纬太平洋SST年际异常的强度和空间型,及水汽对ENSO响应的偏差.高云量(总云量)对ENSO响应的偏差是导致Gl正反馈(Ga负反馈)的主要原因,同时,在部分区域云顶高度和云光学厚度对云辐射反馈的模拟偏差亦有影响.