Subseasonal extremes of precipitation and active‐break cycles of the Indian summer monsoon in a climate‐change scenario
Subseasonal extremes of precipitation and active‐break cycles of the Indian summer monsoon in a climate‐change scenario
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气候变化情景下印度夏季风的次季节极端降水和活跃中断周期
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
J. Slingo
中科院分区：
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作者：
A. Turner;J. Slingo
本研究使用Hadley中心耦合模式HadCM3的工业化前和2 × CO2积分来评估印度夏季风的亚季节降水极端和活动中断周期的变化，该模式能够合理地模拟季风季节周期。在2 × CO2时，平均夏季降雨量略有增加，特别是在印度中部和北方。季风期间的平均日降水强度增加，符合少雨天，并有增加到大雨事件超出了平均值的变化。在印度北方，暴雨达到特定阈值的可能性大约增加一倍，从而增加了季节性洪水破坏的可能性。然而，由于平均季风降雨量变化和相关的极端情况即使在最新的耦合气候模式中也有很大的差异，因此这种预测的地方分布是不确定的。印度上空测得的最强降水事件的增加与大气变暖的程度和相关的特定湿度的增加大致一致，从而为极端降雨的变化提供了一定程度的可预测性。印度夏季风的活跃中断周期，特别是由于其对农业产量的影响，在HadCM3中得到了合理的表示，特别是在一定程度上向北传播。我们注意到，活动和休息事件的加剧，特别是当衡量对年度周期，虽然没有任何变化的持续时间或季风休息的可能性的建议。版权所有© 2009皇家气象学会
Changes to the behaviour of subseasonal precipitation extremes and active‐break cycles of the Indian summer monsoon are assessed in this study using pre‐industrial and 2 × CO2 integrations of the Hadley Centre coupled model HadCM3, which is able to simulate the monsoon seasonal cycle reasonably. At 2 × CO2, mean summer rainfall increases slightly, especially over central and northern India. The mean intensity of daily precipitation during the monsoon is found to increase, consistent with fewer wet days, and there are increases to heavy rain events beyond changes in the mean alone. The chance of reaching particular thresholds of heavy rainfall is found to approximately double over northern India, increasing the likelihood of damaging floods on a seasonal basis. The local distribution of such projections is uncertain, however, given the large spread in mean monsoon rainfall change and associated extremes amongst even the most recent coupled climate models. The measured increase of the heaviest precipitation events over India is found to be broadly in line with the degree of atmospheric warming and associated increases in specific humidity, lending a degree of predictability to changes in rainfall extremes. Active‐break cycles of the Indian summer monsoon, important particularly due to their effect on agricultural output, are shown to be reasonably represented in HadCM3, in particular with some degree of northward propagation. We note an intensification of both active and break events, particularly when measured against the annual cycle, although there is no suggestion of any change to the duration or likelihood of monsoon breaks. Copyright © 2009 Royal Meteorological Society