| 副热带东太平洋低云对LASG耦合环流模式FGCM-0中"双ITCZ"的影响 |
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| 作者姓名： | DAI Fushan YU Rucong ZHANG Xuehong YU Yongqiang LI Jianglong |
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| 作者单位： | [1]BeijingInstituteofAppliedMeteorology,Beijing100029 [2]LASG,InstituteofAtmosphericPhysics,ChineseAcademyofSciences,Beijing100029 [3]NationalClimateCenter,Beijing100081 |
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| 基金项目： | the National Natu-
ral Science Foundation of China under Grant No.40023001
and No.40233031，and"Innovation Program"under Grant
ZKCX2-SW-210，and the National Key Basic Research
Project under Grant G200078502. |
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| 摘 要： | 与其他耦合环流模式一样，LASG耦合模式FGCM-0也存在虚假的“双ITCZ”。为了认识FGCM-0中“双ITCZ”，首先研究了FGCM-0的大气分量模式，剧INCAR(美国国家大气研究中心)的公用气候模式CCM3对秘鲁和加利福尼亚沿岸低云以及低层大气整体稳定度的模拟能力。发现：尽管CCM3模拟的低层大气整体稳定度与利用NCEP(美国国家环境预报中心)再分析资料分析的结果较一致，但模拟的低云量比ISCCP(国际卫星云气候计划)观测值显偏少。利用ISCCP低云量与由NCEP再分析温度场分析的低层整体稳定度之间的回归关系，修改了CCM3中低云参数化方案，并用于敏感性试验，以研究副热带东太平洋低云对FGCM-0中“双ITCZ”的影响。结果发现，修改的方案能显增强对低云量的模拟，秘鲁沿岸冷海域低云量增加能显减弱赤道以南热带东太平洋海表面温度(SST)的暖偏差，但同时也将使赤道冷舌增强、向西伸展更远；加利福尼亚沿岸低云量增加可以有效减弱赤道以北ITCZ区SST暖偏差。为了检验秘鲁沿岸SST与低云间的正反馈，又实施了一个控制秘鲁沿岸SST的敏感性试验，结果表明：控制秘鲁沿岸SST抑制其增暖，对自东南太平洋向西北至中、西赤道太平洋广大区域产生的影响，与增加秘鲁沿岸低云量产生的影响相似。
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| 关 键 词： | 耦合模式 “双ITCZ” 低云 |
| 收稿时间： | 22 April 2002 |
The impact of low-level cloud over the eastern subtropical Pacific on the “Double ITCZ” in LASG FGCM-0 |
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| DAI Fushan,YU Rucong,ZHANG Xuehong,YU Yongqiang,LI Jianglong.The impact of low-level cloud over the eastern subtropical Pacific on the “Double ITCZ” in LASG FGCM-0[J].Advances in Atmospheric Sciences,2003,20(3):461-474. |
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| Authors: | Dai Fushan Yu Rucong Zhang Xuehong Yu Yongqiang Li Jianglong |
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| Institution: | LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029;Beijing Institute of Applied Meteorology, Beijing 100029,LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029;National Climate Center, Beijing 100081 |
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| Abstract: | Like many other coupled models, the Flexible coupled General Circulation Model (FGCM-0) suffersfrom the spurious "Double ITCZ". In order to understand the "Double ITCZ" in FGCM-0, this study firstexamines the low-level cloud cover and the bulk stability of the low troposphere over the eastern subtropicalPacific simulated by the National Center for Atmospheric Research (NCAR) Community Climate Modelversion 3 (CCM3), which is the atmosphere component model of FGCM-0. It is found that the bulkstability of the low troposphere simulated by CCM3 is very consistent with the one derived from theNational Center for Environmental Prediction (NCEP) reanalysis, but the simulated low-level cloud coveris much less than that derived from the International Satellite Cloud Climatology Project (ISCCP) D2data. Based on the regression equations between the low-level cloud cover from the ISCCP data and thebulk stability of the low troposphere derived from the NCEP reanalysis, the parameterization scheme otlow-level cloud in CCM3 is modified and used in sensitivity experiments to examine the impact of low-levelcloud over the eastern subtropical Pacific on the spurious "Double ITCZ" in FGCM-0. Results show thatthe modified scheme causes the simulated low-level cloud cover to be improved locally over the cold oceans.Increasing the low-level cloud cover off Peru not only significantly alleviates the SST warm biases in thesoutheastern tropical Pacific, but also causes the equatorial cold tongue to be strengthened and to extendfurther west. Increasing the low-level cloud fraction off California effectively reduces the SST warm biasesin ITCZ north of the equator. In order to examine the feedback between the SST and low-level cloudcover off Peru, one additional sensitivity experiment is performed in which the SST over the cold ocean offPeru is restored. It shows that decreasing the SST results in similar impacts over the wide regions fromthe southeastern tropical Pacific northwestwards to the western/central equatorial Pacific as increasing thelow-level cloud cover does. |
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| Keywords: | coupled model double ITCZ low-level cloud |
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