Characteristic intraseasonal oscillation of rainfall and its effect on interannual variability over Bangladesh during boreal summer

International Journal of Climatology - Tập 31 Số 8 - Trang 1192-1204 - 2011
Hatsuki Fujinami1, Daisuke Hatsuzuka2, Tetsuzo Yasunari1, Taiichi Hayashi3, Toru Terao4, Fumie Murata5, Masashi Kiguchi6, Yusuke Yamane7, Jun Matsumoto8, Md. Nazrul Islam9, Arjumand Habib10
1Hydrospheric Atmospheric Research Center, Nagoya University, Nagoya, Japan
2Weathernews, Chiba, Japan
3Disaster Prevention Research Institute, Kyoto University, Kyoto, Japan
4Faculty of Education, Kagawa University, Kagawa, Japan
5Faculty of Science, Kochi University, Kochi, Japan
6Institute of Industrial Science, The University of Tokyo, Tokyo, Japan
7Center for Southeast Asian Studies, Kyoto University, Kyoto, Japan
8Department of Geography, Tokyo Metropolitan University, Tokyo, Japan
9Faculty of Meteorology, King Abdulaziz University, Jeddah, Saudi Arabia
10Bangladesh Meteorological Department, Dhaka, Bangladesh

Tóm tắt

AbstractIntraseasonal 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

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