IAP近期际气候预测系统海洋初始化试验中海表温度和层积云的关系

doi:10.11867/j. issn. 1001-8166.2017.04.0373

地球科学进展 ›› 2017, Vol. 32 ›› Issue (4): 373 -381. doi: 10.11867/j. issn. 1001-8166.2017.04.0373

郭准 ^1, ²(

), 周天军 ^1, ³

1.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,北京 100029
2.中国科学院气候变化研究中心,北京 100029
3.中国科学院大学,北京 100049

收稿日期:2016-11-07 修回日期:2017-02-28 出版日期:2017-04-20
基金资助:
公益性行业(气象)科研专项项目“基于FGOALS-s、CMA和CESM气候系统模式的年代际集合预测系统的建立与研究”(编号:GYHY201506012);国家自然科学基金青年科学基金项目“云辐射反馈过程对东亚—西北太平洋地区海气相互作用的影响及其气候模式模拟的不确定性”(编号:41405103)资助

The Simulation of Stratocumulus and Its Impacts on SST:Based on the IAP Near-Term Climate Prediction System

Zhun Guo ^1, ²( ), Tianjun Zhou ^1, ³

1.LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
2.Climate Change Research center, Chinese Academy of Sciences, Beijing 100029, China
3.University of Chinese Academy of Sciences, Beijing 100029, China

Received:2016-11-07 Revised:2017-02-28 Online:2017-04-20 Published:2017-04-20
About author:
First author:Zhun Guo(1983-),male,Yiyang City,Henan Province,Associate Professor. Research areas include cloud physics, cloud-climate interaction.E-mail:guozhun@lasg.iap.ac.cn
Supported by:
Foundation item:Project supported by the R&D Special Fund for Public Welfare Industry (Meteorology) “Development and research of ensemble decadal climate prediction system based on global climate models FGOALS-s, CAMS and CESM”;The National Natural Science Foundation of China“The role of cloud feedback in Air-Sea interaction over east asian-northwestern pacific ocean region and its simulating uncertainties”(No.41405103)

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气候预测系统的海洋初始化积分试验考虑了海气相互作用,可以视为一种弱耦合同化试验。海温(SST)和层积云的关系是检验海气相互作用过程模拟效果的重要参考。分析了基于耦合气候系统模式FGOALS-s2的中国科学院大气物理研究所近期气候预测系统IAP DecPreS的海洋初始化模拟实验(简称EnOI-IAU试验)所模拟的海温—云关系。结果表明,EnOI-IAU试验较好地模拟出了SST和低云的气候态空间分布,但在主要层积云区低估了低云云量和云水,SST模拟偏高,特别在副热带东大洋沿岸和南大洋。部分原因是这些地区实际影响海表温度模拟的是模式的内部过程,而低云模拟不足导致了海表入射更多的短波辐射(强度约偏强20 W/m²),迫使局地SST模拟过高。分析显示,低云模拟不足主要是由于EnOI-IAU试验不能再现合理的边界层逆温结构,表现为大气垂直速度、温度和湿度过于集中在近地层,使得边界层垂直热输送较弱、边界层无法充分混合,进而无法有效模拟出层积云。这些结果表明,未来引入大气观测数据同化,特别是改善边界层结构的模拟,对形成完整的耦合同化系统具有必要性。

关键词: 初始化试验, 耦合气候系统模式, 海表温度, 层积云, 大气边界层

The near-term climate prediction system (DecPreS) is built on the initialization of the ocean state, which can be regarded as a full-coupled system with “adjusted” air-sea interactions. The relationship between stratocumulus and Sea Surface Temperature (SST ) is an essential part of air-sea interactions. In this study, we investigated such a relationship in DecPreS of the Institute of Atmospheric Physics, in which the merge of the Ensemble Optimal Interpolation (EnOI) and Incremental Analysis Update (IAU) scheme was employed. EnOI-IAU generally reproduces the spatial pattern of SST and low-clouds. However, the simulated cloud fraction/liquid water path are underestimated while the SST is overestimated in stratocumulus regimes, especially in the subtropical East Pacific and South Ocean. It is partly because the unrealistic air-sea interaction dominates these regions that the underestimated stratocumulus allows more input of incoming shortwave flux (20 W/m²). The deficient stratocumulus is highly related to the unrealistic vertical structure of Atmospheric Boundary Layer (ABL), in which the moisture, temperature and vertical heat transports concentrate at the surface layer. Our results imply that stratocumulus and ABL be important in DecPreS. Clarifying the importance of ABL and stratocumulus will provide a possible way to improve the DecPreS.

Key words: near-term prediction, Coupled GCM, SST, Stratocumulus, Atmospheric boundary layer.

中图分类号:

P426.5

图1 1984—2010年平均海表温度对比(单位:K)
(a)HadISST;(b)ENOI试验样本集合(MME);(c)ENOI减去HadISST

Fig.1 Spatial pattern of surface sea temperature (K) averaged from 1984 to 2010
(a)HadISST dataset; (b)Model results; (c)Model results subtract HadISST

图2 全球年平均低云云量(单位:%)
(a)CloudSat;(b)ENOI试验样本集合(MME);(c)ENOI减去HadISST; CloudSat 资料取自2006—2011年平均

Fig.2 Spatial pattern of annual mean low-cloud fraction (unit:%)
(a) CloudSat dataset; (b) Model results and (c) Model results subtract CloudSat; CloudSat data is averaged from 2006 to 2011

图3 全球年平均云水含量(单位:g/ m ²)
(a)NVAP;(b)ENOI试验样本集合(MME);(c)ENOI减去NVAP;NVAP资料取自1989—1999年平均

Fig.3 Spatial pattern of annual mean cloud liquid water path (unit:g/ m ²)
(a) NVAP dataset;(b) Model results and (c) Model results subtract NVAP; NVAP data is averaged from 1989 to 1999

图4 全球年平均短波云辐射强迫(单位:W/ m ²)
(a)CERES;(b)ENOI试验样本集合(MME);(c)ENOI减去CERES

Fig.4 Spatial pattern of annual mean shortwave cloud radiative forcing (unit:W/m ²)
(a) CERES dataset;(b) Model results; (c)Model results subtract CERES

图5 副热带(30°S~30°N)海洋区域平均的层积云区的海表热通量收支(向下为正)
观测资料OAFLUX和模式资料取1984—2010年的时间平均

Fig.5 SST tendency budgets (down is positive)over subtropical stratocumulus regions
Both OAFLUX and model results are averaged from 1984 to 2010

图6 20°S处秋季平均云量的经度—高度剖面
(a)模拟结果,取1984—2011年的平均;(b)CloudSat卫星观测,取2006—2011年的平均

Fig.6 Vertical cross sections of averaged cloud fraction (fraction) along the 20°S transect in SON
(a)is derived from model result that is averaged from 1984 to 2011; (b) is derived from CloudSat, which is averaged from 2006 to 2011

图7 秋季平均20°S,75°W区域的边界层垂直结构
实线为观测,分别取自ERAIM和CloudSat卫星;虚线为模拟结果,取1984—2011年的平均值

Fig.7 Vertical profiles of autumn boundary layer at 20°S and 75°W
Observation/reanalysis data set is shown in dash lines: Cloud fraction is from CloudSat, while humidity, large-scale pressure vertical velocity, and potential temperature are from the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim ReAnalysis (ERA-Interim). The model results are shown in solid line, which is averaged from 1984 to 2011

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