Pradhan Maheswar, Rao A Suryachandra, Srivastava Ankur, Dakate Ashish, Salunke Kiran, Shameera K S
Monsoon Mission, Indian Institute of Tropical Meteorology, Dr Homi Bhabha Road, Pashan, Pune, 411008, Maharashtra, India.
Department of Atmospheric Sciences, Cochin University of Science and Technology, Kochi, Kerala, 682022, India.
Sci Rep. 2017 Oct 27;7(1):14229. doi: 10.1038/s41598-017-12594-y.
Monsoon onset is an inherent transient phenomenon of Indian Summer Monsoon and it was never envisaged that this transience can be predicted at long lead times. Though onset is precipitous, its variability exhibits strong teleconnections with large scale forcing such as ENSO and IOD and hence may be predictable. Despite of the tremendous skill achieved by the state-of-the-art models in predicting such large scale processes, the prediction of monsoon onset variability by the models is still limited to just 2-3 weeks in advance. Using an objective definition of onset in a global coupled ocean-atmosphere model, it is shown that the skillful prediction of onset variability is feasible under seasonal prediction framework. The better representations/simulations of not only the large scale processes but also the synoptic and intraseasonal features during the evolution of monsoon onset are the comprehensions behind skillful simulation of monsoon onset variability. The changes observed in convection, tropospheric circulation and moisture availability prior to and after the onset are evidenced in model simulations, which resulted in high hit rate of early/delay in monsoon onset in the high resolution model.
季风爆发是印度夏季风固有的瞬变现象，人们从未设想过这种瞬变能够在提前很长时间被预测。尽管季风爆发很急促，但其变率与诸如厄尔尼诺-南方涛动（ENSO）和印度洋偶极子（IOD）等大尺度强迫存在很强的遥相关，因此可能是可预测的。尽管当前最先进的模式在预测此类大尺度过程方面取得了巨大进展，但这些模式对季风爆发变率的预测仍只能提前2至3周。通过在一个全球海气耦合模式中使用一个客观的季风爆发定义，研究表明在季节预测框架下对季风爆发变率进行有技巧的预测是可行的。不仅对大尺度过程，而且对季风爆发演变期间的天气尺度和季节内特征进行更好的表示/模拟，是有技巧地模拟季风爆发变率的关键所在。模式模拟证实了季风爆发前后对流、对流层环流和水汽可用性的变化，这使得高分辨率模式中季风爆发提前/延迟的命中率很高。
