Regional simulation of Indian summer monsoon intraseasonal oscillations at gray-zone resolution
Regional simulation of Indian summer monsoon intraseasonal oscillations at gray-zone resolution
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DOI：
10.5194/acp-18-1003-2018
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发表时间：
2017-07
影响因子：
6.3
通讯作者：
Xingchao Chen;O. Pauluis;Fuqing Zhang
中科院分区：
文献类型：
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作者：
Xingchao Chen;O. Pauluis;Fuqing Zhang
摘要。本研究描述了利用允许云的天气研究与预报（WRF）模式在灰色区分辨率下对印度夏季风的模拟，特别强调了模式捕捉季风季节内振荡（MISOs）的能力。利用ERA-Interim再分析作为侧向边界强迫资料，模拟了2007 - 2011年的5个北方夏季。我们的实验设置依赖于9 km的水平网格间距来明确模拟深层对流，而不使用积云参数化。与更粗网格间距（27 km）和使用积云方案的模拟相比，9 km模拟减少了平均降水的偏差，并产生了与MISOs相关的更真实的低频变率。结果表明，该模式在9 km灰区分辨率下捕捉到了夏季风的显著特征。WRF模拟的季风降雨的空间分布和时间演变与热带降雨测量任务（TRMM）的观测结果在质量上得到了很好的验证，区域最大值位于西高止山脉、印度中部、喜马拉雅山麓和缅甸西海岸。该模式还真实地捕捉了每年夏季风的开始、中断和退出。模拟中季风降水、低层风和可降水量异常的miso相复合也与观测结果在质量上一致。模拟和观测结果均表明，在印度夏季风活跃期和间歇期，索马里急流在阿拉伯海上空增强和减弱，MISOs向东北方向传播。
Abstract. Simulations of the Indian summer monsoon by the cloud-permitting Weather Research and Forecasting (WRF) model at gray-zone resolution are described in this study, with a particular emphasis on the model ability to capture the monsoon intraseasonal oscillations (MISOs). Five boreal summers are simulated from 2007 to 2011 using the ERA-Interim reanalysis as the lateral boundary forcing data. Our experimental setup relies on a horizontal grid spacing of 9 km to explicitly simulate deep convection without the use of cumulus parameterizations. When compared to simulations with coarser grid spacing (27 km) and using a cumulus scheme, the 9 km simulations reduce the biases in mean precipitation and produce more realistic low-frequency variability associated with MISOs. Results show that the model at the 9 km gray-zone resolution captures the salient features of the summer monsoon. The spatial distributions and temporal evolutions of monsoon rainfall in the WRF simulations verify qualitatively well against observations from the Tropical Rainfall Measurement Mission (TRMM), with regional maxima located over Western Ghats, central India, Himalaya foothills, and the west coast of Myanmar. The onset, breaks, and withdrawal of the summer monsoon in each year are also realistically captured by the model. The MISO-phase composites of monsoon rainfall, low-level wind, and precipitable water anomalies in the simulations also agree qualitatively with the observations. Both the simulations and observations show a northeastward propagation of the MISOs, with the intensification and weakening of the Somali Jet over the Arabian Sea during the active and break phases of the Indian summer monsoon.