Relative importance of tropical SST anomalies in forcing East Asian summer monsoon circulation

The relative importance of tropical SST anomalies to the dominant variability of East Asian Summer Monsoon (EASM) circulation is investigated using an atmospheric general circulation model and a linear inverse model. It is found that the cooling over the central tropical Pacific is crucial in develo...

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Bibliographic Details
Published in:	Geophysical research letters Vol. 40; no. 10; pp. 2471 - 2477
Main Authors:	Fan, Lei, Shin, Sang-Ik, Liu, Qinyu, Liu, Zhengyu
Format:	Journal Article
Language:	English
Published:	Washington Blackwell Publishing Ltd 28-05-2013 John Wiley & Sons, Inc
Subjects:	Anomalies Anticyclones Asian Atmospheric circulation Atmospheric precipitations Central-Pacific Circulation Cooling East Asian monsoon East Asian Summer Monsoon El Nino El Nino events Evolution General circulation General circulation models Geophysics Linear Inverse model Loads (forces) Marine Mathematical models Meteorology Monitoring Monsoon circulation Monsoons Ocean circulation Ocean temperature Ocean warming Ocean-atmosphere interaction Precipitation Predictions Sea surface Sea surface temperature Sea Surface Temperature Anomalies Sensitivity map Spring Spring (season) Strength Summer Summer circulation Summer monsoon Surface temperature Temperature anomalies Temperature effects Tropical climate Variability Western Pacific Anticyclone Winter Indian Ocean
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Summary:	The relative importance of tropical SST anomalies to the dominant variability of East Asian Summer Monsoon (EASM) circulation is investigated using an atmospheric general circulation model and a linear inverse model. It is found that the cooling over the central tropical Pacific is crucial in developing and maintaining the summertime northwest Pacific anticyclones, associated with the EASM precipitation. In this regard, the previously suggested El Niño event in the preceding winter and accompanying tropical Indian Ocean warming alone may not be enough to predict the strength of EASM circulation. Instead, monitoring and predicting the evolution of sea surface temperature anomalies in the central tropical Pacific, especially in spring to summer, may greatly improve the prediction of EASM circulation. Key Points Sensitivity of the summer WPAC to tropical SSTAs is estimated using ECHAM5Relative importance of SSTAs to the WPAC is investigated seasonally using LIMThe Central‐Pacific cooling is most important to the boreal summer WPAC
Bibliography:	Korea National Institute of Meteorological Research (SS) Multi-variable EOF of 850-hPa winds, sea level pressure (contour lines) and land precipitation (shading) for the period 1979-2004. (a) and (b) are the spatial pattern from ECHAM5 simulations and observational data, respectively. (c) shows the principle component for ECHAM 5 (black solid-open circle line) and observation (red solid-open circle line). The similar spatial patterns and the correlation value (0.64) between the two component indicate the ECHAM 5 performance in simulating EASM.Atmospheric anomalies as responses to cold SST anomalies over a patch (blue shading in (a)) in the central Pacific. The sea level pressure (contours in (a)), 850-hPa winds (vectors in (a)), 200-hPa geopotential high (contours in (b)), 200-hPa winds, and precipitation (shading in (b), in unit mm/day) are shown. The contour interval is 0.3 hPa in (a) and 5 geopotential meters in (b). Negative contours are denoted with blue dash while others are denoted with red solid.Positive-negative composite analysis of SSTA (shading), 850-hPa wind anomalies (vectors), and SLP anomalies (contour lines with yellow for positive, green for negative and zero lines omitted) in spring (MAM, left column) and summer (JJA, middle column) for the cases of (the 1st row) all the El Niño decays phases, (the 2nd row) El Niño decays only to neutral conditions, (the 3rd row) all the La Niña developing phases, and (the 4th row) La Niña develops only from neutral conditions. For reference, the evolution of Niño-3.4 SSTAs for each year is shown in the right column (c, f, i, and l) with the red lines for the same sign as the case defined, and the blue lines for the sign-reversed opposite ENSO phase. For instance, the red in (c) indicates that of El Niño decay while the blue indicates the sign-reversed that of La Niña decay.Similar to Figure (a) but based on Nino4 warming cases, namely, 1948, 1953, 1957, 1958, 1966, 1969, 1972, 1977, 1982, 1987, 1991, 1992, 1993, 1994, 1997, 2002, 2004, and 2009.list of years for the composite analysis of Figure .Supporting informationSupporting information Natural Science Foundation of China - No. 41176006; No. 40921004 Ministry of Science and Technology of China - No. GYHY200906016 ArticleID:GRL50494 istex:8AEEF1D94ACF7F0EADC0E6706028918C500675C5 National Basic Research Program of China - No. 2012CB955602; No. 2012CB955200 ark:/67375/WNG-J0QQ2X6B-G ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0094-8276 1944-8007
DOI:	10.1002/grl.50494