GRIST模式夏季气候回报试验中东亚降水季节内特征的评估

Assessment of intraseasonal characteristics of precipitation over East Asia in the GRIST model summer climate hindcast

  • 摘要: 基于中国自主研发的全球-区域一体化预测系统(GRIST)模式,分析了其在夏季气候回报试验中的东亚地区夏季降水气候特征,重点关注季节内尺度的变化。通过与格点融合分析数据(CMPA)、卫星观测数据(GPM)及两个全球气候模式(CAM5和SPCAM5)结果进行比较,检验模式性能并探究模式间的差异。结果表明,GRIST模式能较好地模拟出西北太平洋及中国东部地区季节内降水变化及其演变过程,但模拟的降水变化幅度和雨量与观测相比偏高。进一步探究其内部影响,发现小时尺度视热源(Q1)、视水汽汇(Q2)和大尺度垂直速度等在垂直剖面上随时间的变化皆与模拟降水的演变对应。模式能准确地再现雨带和副热带高压脊线的位置及其向北推进过程,并能基本抓住大气季节内振荡(ISO)经向北传特征。但ISO传播强度、周期等与观测存在较大差异。这可能与纬向风移动路径较远、持续时间较长有关。

     

    Abstract: Based on the seasonal climate hindcast experiment of the Global-to-Regional Integrated forecast SysTem (GRIST) model, the simulated climate features of East Asian summer precipitation are analyzed with emphasis on the intraseasonal variation. Compared with the China Merged hourly Precipitation Analysis (CMPA) grid fusion analysis dataset, the Global Precipitation Measurement (GPM) satellite dataset and results of two global climate models, i.e., the Community Atmosphere Model version 5 (CAM5) and the SuperParameterized CAM5 (SPCAM5), this study evaluates the simulation results and explores the inter-model differences. Results show that the GRIST can better simulate seasonal variation and evolution of precipitation over the Northwest Pacific Ocean and eastern China, but the magnitude of precipitation variation and rainfall amount are higher than the observed values. It is shown that precipitation evolution closely corresponds to daily mean vertical variations of hourly apparent heat source (Q1) and apparent moisture sink (Q2) and large-scale vertical velocity. The model can accurately reproduce the location and northward progression of rain belt and the subtropical high ridge line, and overall can capture the northward propagation of the Intrasesonal Oscillation (ISO). However, the intensity and period of the ISO propagation are quite different from the observations possibly due to the long moving path and duration of zonal wind.

     

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