Initial Development of Tropical Precipitation Patterns in Response to a Local Warm SST Area: An Aqua-Planet Ensemble Study
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- NAKAJIMA Kensuke
- Faculty of Sciences, Kyushu University
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- TOYODA Eizi
- Numerical Prediction Division, Japan Meteorological Agency
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- ISHIWATARI Masaki
- Graduate School of Environmental Earth Science, Hokkaido University
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- TAKEHIRO Shin-ichi
- Institute of Mathematical Sciences, Kyoto University
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- HAYASHI Yoshi-Yuki
- Graduate School of Science, Hokkaido University
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For the purpose of examining the initial development of the atmospheric response to a warm SST anomaly placed at the equator, an ensemble switch-on experiment is conducted with an aqua-planet GCM. An ensemble average of the size of 128 significantly reduces the transient noises caused by both small scale convective activity and large scale intraseasonal variability.<br>In the first three days after the switch-on of the SST anomaly, a convection center develops above the warm SST area. As a barotropic response to the heating of convection center, a global increase of surface pressure occurs outside the low pressure region around the warm SST area. The response after the emergence of the high pressure anomaly is consistent with Gill (1980); a warm Kelvin wave-like anomaly is emitted to the east of the convection center, while a warm Rossby wave-like anomaly is emitted to the west.<br>The Kelvin wave-like signal propagates at a speed slower than that of free Kelvin wave expected from its vertical wavelength, suggesting that the signal is a “moist” Kelvin wave. Transient decrease of precipitation occurs at the moist Kelvin wave front; a decrease of convection associated with the downward motion at the wave front is consistent with its slow propagation. After several days, precipitation recovers and is even intensified because of the surface frictional convergence associated with the Kelvin wave-like equatorial low pressure anomaly. To the west of the warm SST area, on the other hand, precipitation decreases monotonically. The continuous reduction of precipitation is caused by the equatorial surface frictional divergence associated with the relatively high pressure anomaly at the equator of the Rossby wave structure.<br>Finally, there appears a slow zonally symmetric response within the Hadley cell characterized with surface pressure rise in the tropics and westerly wind anomaly in the troposphere. The change of eddy zonal momentum transport, together with the transport toward the lower level by the Hadley circulation and the geostrophic adjustment to the resulting low level westerly acceleration, seems to be responsible for the response.
収録刊行物
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- 気象集誌. 第2輯
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気象集誌. 第2輯 82 (6), 1483-1504, 2004
公益社団法人 日本気象学会
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詳細情報 詳細情報について
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- CRID
- 1390282681479158144
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- NII論文ID
- 110001817364
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- NII書誌ID
- AA00702524
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- ISSN
- 21869057
- 00261165
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- NDL書誌ID
- 7215918
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- 本文言語コード
- en
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- データソース種別
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- JaLC
- NDL
- Crossref
- NDL-Digital
- CiNii Articles
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- 抄録ライセンスフラグ
- 使用不可