Characteristic intraseasonal oscillation of rainfall and its effect on interannual variability over Bangladesh during boreal summer
Characteristic intraseasonal oscillation of rainfall and its effect on interannual variability over Bangladesh during boreal summer
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DOI：
10.1002/joc.2146
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发表时间：
2011-06
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通讯作者：
H. Fujinami;D. Hatsuzuka;T. Yasunari;Taiichi Hayashi;T. Terao;F. Murata;Masashi Kiguchi;Y. Yamane;J. Matsumoto;Md. Nazrul Islam;A. Habib
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作者：
H. Fujinami;D. Hatsuzuka;T. Yasunari;Taiichi Hayashi;T. Terao;F. Murata;Masashi Kiguchi;Y. Yamane;J. Matsumoto;Md. Nazrul Islam;A. Habib
利用25个雨量站20年（1981 - 2000年）的逐日降雨资料，研究了夏季风季节（6 - 8月）降雨的季节内振荡（ISO）及其对孟加拉国夏季风总降雨量年际变化（IAV）的可能影响。次月季尺度（7 - 25天）的ISO是孟加拉国夏季降雨波动的主要模态。在ISO的活跃（抑制）阶段，从印度东北部到孟加拉国的对流层低层会形成气旋（反气旋）环流异常，孟加拉湾上空出现反气旋（气旋）环流异常，同时孟加拉国上空的西风/西南风（东风/东南风）水汽通量异常增强。夏季风总降雨量的年际变化与降雨方差的年际变化显著相关，主要在次月季尺度上，这表明ISO活动控制着夏季风总降雨量的年际变化。此外，与ISO和IAV相关的大气环流和对流的空间格局在季风槽周围，特别是从印度东北部到孟加拉国非常相似。在湿润季风年，与干燥季风年相比，更频繁的强次月季尺度ISO以及与活跃ISO阶段相关的雨日数量更多是很明显的。从气候学角度来看，孟加拉国是次月季尺度ISO最主要的区域之一；然而，30 - 60天的ISO并不显著。这些特征可能使得次月季尺度ISO能够调节孟加拉国及其附近的季节总降雨量以及环流和对流的空间格局。版权所有©2010英国皇家气象学会
Intraseasonal oscillation (ISO) of rainfall during the summer monsoon season (June–August) and its plausible effect on interannual variation (IAV) of total summer monsoon rainfall over Bangladesh are examined using daily rainfall data from 25 rain‐gauge stations for 20 years (1981–2000). Submonthly scale (7–25 days) ISO is a dominant mode of summer rainfall fluctuation over Bangladesh. In the active (suppressed) ISO phases, a cyclonic (anticyclonic) circulation anomaly develops at the low‐level troposphere from northeastern India to Bangladesh, and an anticyclonic (cyclonic) circulation anomaly appears over the Bay of Bengal, accompanied by the enhancement of westerly/southwesterly (easterly/southeasterly) moisture flux anomalies over Bangladesh. The IAV of total summer monsoon rainfall is significantly correlated with that of the rainfall variance, mainly in the submonthly scale, suggesting that the ISO activity controls the IAV of the total summer monsoon rainfall. Moreover, the spatial patterns of atmospheric circulation and convection associated with the ISO and the IAV are quite similar to each other around the monsoon trough, especially from northeastern India to Bangladesh. In wet monsoon years, more frequent strong submonthly scale ISOs and a larger number of rainy days related to the active ISO phase are evident compared with that of dry monsoon years. Climatologically, Bangladesh is one of the most predominant areas of submonthly scale ISO; however, 30–60‐day ISO is not prominent. These characteristic features probably allow the submonthly scale ISO to modulate the total seasonal rainfall and the spatial patterns of circulation and convection over and near Bangladesh. Copyright © 2010 Royal Meteorological Society