Pathak Amey, Ghosh Subimal, Kumar Praveen, Murtugudde Raghu
Department of Civil Engineering, Indian Institute of Technology Bombay, Mumbai, 400 076, India.
Interdisciplinary Program in Climate Studies, Indian Institute of Technology Bombay, Mumbai, 400 076, India.
Sci Rep. 2017 Oct 6;7(1):12729. doi: 10.1038/s41598-017-13115-7.
Summer Monsoon Rainfall over the Indian subcontinent displays a prominent variability at intraseasonal timescales with 10-60 day periods of high and low rainfall, known as active and break periods, respectively. Here, we study moisture transport from the oceanic and terrestrial sources to the Indian landmass at intraseasonal timescales using a dynamic recycling model, based on a Lagrangian trajectory approach applied to the ECMWF-ERA-interim reanalysis data. Intraseasonal variation of monsoon rainfall is associated with both a north-south pattern from the Indian landmass to the Indian Ocean and an east-west pattern from the Core Monsoon Zone (CMZ) to eastern India. We find that the oceanic sources of moisture, namely western and central Indian Oceans (WIO and CIO) contribute to the former, while the major terrestrial source, Ganga basin (GB) contributes to the latter. The formation of the monsoon trough over Indo-Gangetic plain during the active periods results in a high moisture transport from the Bay of Bengal and GB into the CMZ in addition to the existing southwesterly jet from WIO and CIO. Our results indicate the need for the correct representation of both oceanic and terrestrial sources of moisture in models for simulating the intraseasonal variability of the monsoon.
印度次大陆夏季季风降雨在季节内时间尺度上表现出显著的变率，有10 - 60天的高降雨期和低降雨期，分别称为活跃期和中断期。在此，我们使用一个动态再循环模型，基于应用于欧洲中期天气预报中心（ECMWF）- ERA interim再分析数据的拉格朗日轨迹方法，研究季节内时间尺度上从海洋和陆地源到印度大陆的水汽输送。季风降雨的季节内变化与从印度大陆到印度洋的南北模式以及从核心季风区（CMZ）到印度东部的东西模式都有关联。我们发现，水汽的海洋源，即印度洋西部和中部（WIO和CIO）促成了前者，而主要的陆地源，恒河盆地（GB）促成了后者。活跃期印度 - 恒河平原上季风槽的形成，除了现有的来自WIO和CIO的西南急流外，还导致了从孟加拉湾和GB向CMZ的高水汽输送。我们的结果表明需要在模型中正确表示水汽的海洋和陆地源，以模拟季风的季节内变率。
