Real-time multivariate indices for the boreal summer intraseasonal oscillation over the Asian summer monsoon region

June Yi Lee; Bin Wang; Matthew C. Wheeler; Xiouhua Fu; Duane E. Waliser; In Sik Kang

doi:10.1007/s00382-012-1544-4

Real-time multivariate indices for the boreal summer intraseasonal oscillation over the Asian summer monsoon region

June Yi Lee
, Bin Wang
, Matthew C. Wheeler
, Xiouhua Fu
, Duane E. Waliser
, In Sik Kang

Research output: Contribution to journal › Article › peer-review

489 Scopus citations

Abstract

The boreal summer intraseasonal oscillation (BSISO) of the Asian summer monsoon (ASM) is one of the most prominent sources of short-term climate variability in the global monsoon system. Compared with the related Madden-Julian Oscillation (MJO) it is more complex in nature, with prominent northward propagation and variability extending much further from the equator. In order to facilitate detection, monitoring and prediction of the BSISO we suggest two real-time indices: BSISO1 and BSISO2, based on multivariate empirical orthogonal function (MV-EOF) analysis of daily anomalies of outgoing longwave radiation (OLR) and zonal wind at 850 hPa (U850) in the region 10°S-40°N, 40°-160°E, for the extended boreal summer (May-October) season over the 30-year period 1981-2010. BSISO1 is defined by the first two principal components (PCs) of the MV-EOF analysis, which together represent the canonical northward propagating variability that often occurs in conjunction with the eastward MJO with quasi-oscillating periods of 30-60 days. BSISO2 is defined by the third and fourth PCs, which together mainly capture the northward/northwestward propagating variability with periods of 10-30 days during primarily the pre-monsoon and monsoon-onset season. The BSISO1 circulation cells are more Rossby wave like with a northwest to southeast slope, whereas the circulation associated with BSISO2 is more elongated and front-like with a southwest to northeast slope. BSISO2 is shown to modulate the timing of the onset of Indian and South China Sea monsoons. Together, the two BSISO indices are capable of describing a large fraction of the total intraseasonal variability in the ASM region, and better represent the northward and northwestward propagation than the real-time multivariate MJO (RMM) index of Wheeler and Hendon.

Original language	English
Pages (from-to)	493-509
Number of pages	17
Journal	Climate Dynamics
Volume	40
Issue number	1-2
DOIs	https://doi.org/10.1007/s00382-012-1544-4
State	Published - Jan 2013
Externally published	Yes

Funding

We thank the organization and members of the WWRP/THORPEX/WCRP YOTC MJO Task Force for their insights. We also thank two anonymous reviewers for their valuable comments that helped to improve our manuscript. JYL, BW, XF, and DW acknowledge support from the NOAA/MAPP project Award number NA10OAR4310247, AMDT1. BW and XF acknowledge support from Climate Dynamics Program of the National Science Foundation under award No AGS-1005599. This study has been also supported by APEC Climate Center and International Pacific Research Center, which is in part supported by JAMSTEC, NOAA (NA09OAR4320075) and NASA (NNX07AG53G). DW’s contribution was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. ISK were supported by the National Research Foundation of Korea (NRF) Grand Funded by the Korean Government (MEST) (NRF-2009-C1AAA001-2009-0093042). This is the SEOST publication number 8744 and IPRC publication number 912.

Keywords

Asian summer monsoon
Boreal summer intraseasonal oscillation
Madden-Julian Oscillation
Monsoon onset
Northward propagation
Real-time multivariate index

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10.1007/s00382-012-1544-4

Cite this

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title = "Real-time multivariate indices for the boreal summer intraseasonal oscillation over the Asian summer monsoon region",

abstract = "The boreal summer intraseasonal oscillation (BSISO) of the Asian summer monsoon (ASM) is one of the most prominent sources of short-term climate variability in the global monsoon system. Compared with the related Madden-Julian Oscillation (MJO) it is more complex in nature, with prominent northward propagation and variability extending much further from the equator. In order to facilitate detection, monitoring and prediction of the BSISO we suggest two real-time indices: BSISO1 and BSISO2, based on multivariate empirical orthogonal function (MV-EOF) analysis of daily anomalies of outgoing longwave radiation (OLR) and zonal wind at 850 hPa (U850) in the region 10°S-40°N, 40°-160°E, for the extended boreal summer (May-October) season over the 30-year period 1981-2010. BSISO1 is defined by the first two principal components (PCs) of the MV-EOF analysis, which together represent the canonical northward propagating variability that often occurs in conjunction with the eastward MJO with quasi-oscillating periods of 30-60 days. BSISO2 is defined by the third and fourth PCs, which together mainly capture the northward/northwestward propagating variability with periods of 10-30 days during primarily the pre-monsoon and monsoon-onset season. The BSISO1 circulation cells are more Rossby wave like with a northwest to southeast slope, whereas the circulation associated with BSISO2 is more elongated and front-like with a southwest to northeast slope. BSISO2 is shown to modulate the timing of the onset of Indian and South China Sea monsoons. Together, the two BSISO indices are capable of describing a large fraction of the total intraseasonal variability in the ASM region, and better represent the northward and northwestward propagation than the real-time multivariate MJO (RMM) index of Wheeler and Hendon.",

keywords = "Asian summer monsoon, Boreal summer intraseasonal oscillation, Madden-Julian Oscillation, Monsoon onset, Northward propagation, Real-time multivariate index",

author = "Lee, \{June Yi\} and Bin Wang and Wheeler, \{Matthew C.\} and Xiouhua Fu and Waliser, \{Duane E.\} and Kang, \{In Sik\}",

year = "2013",

month = jan,

doi = "10.1007/s00382-012-1544-4",

language = "English",

volume = "40",

pages = "493--509",

journal = "Climate Dynamics",

issn = "0930-7575",

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TY - JOUR

T1 - Real-time multivariate indices for the boreal summer intraseasonal oscillation over the Asian summer monsoon region

AU - Lee, June Yi

AU - Wang, Bin

AU - Wheeler, Matthew C.

AU - Fu, Xiouhua

AU - Waliser, Duane E.

AU - Kang, In Sik

PY - 2013/1

Y1 - 2013/1

N2 - The boreal summer intraseasonal oscillation (BSISO) of the Asian summer monsoon (ASM) is one of the most prominent sources of short-term climate variability in the global monsoon system. Compared with the related Madden-Julian Oscillation (MJO) it is more complex in nature, with prominent northward propagation and variability extending much further from the equator. In order to facilitate detection, monitoring and prediction of the BSISO we suggest two real-time indices: BSISO1 and BSISO2, based on multivariate empirical orthogonal function (MV-EOF) analysis of daily anomalies of outgoing longwave radiation (OLR) and zonal wind at 850 hPa (U850) in the region 10°S-40°N, 40°-160°E, for the extended boreal summer (May-October) season over the 30-year period 1981-2010. BSISO1 is defined by the first two principal components (PCs) of the MV-EOF analysis, which together represent the canonical northward propagating variability that often occurs in conjunction with the eastward MJO with quasi-oscillating periods of 30-60 days. BSISO2 is defined by the third and fourth PCs, which together mainly capture the northward/northwestward propagating variability with periods of 10-30 days during primarily the pre-monsoon and monsoon-onset season. The BSISO1 circulation cells are more Rossby wave like with a northwest to southeast slope, whereas the circulation associated with BSISO2 is more elongated and front-like with a southwest to northeast slope. BSISO2 is shown to modulate the timing of the onset of Indian and South China Sea monsoons. Together, the two BSISO indices are capable of describing a large fraction of the total intraseasonal variability in the ASM region, and better represent the northward and northwestward propagation than the real-time multivariate MJO (RMM) index of Wheeler and Hendon.

AB - The boreal summer intraseasonal oscillation (BSISO) of the Asian summer monsoon (ASM) is one of the most prominent sources of short-term climate variability in the global monsoon system. Compared with the related Madden-Julian Oscillation (MJO) it is more complex in nature, with prominent northward propagation and variability extending much further from the equator. In order to facilitate detection, monitoring and prediction of the BSISO we suggest two real-time indices: BSISO1 and BSISO2, based on multivariate empirical orthogonal function (MV-EOF) analysis of daily anomalies of outgoing longwave radiation (OLR) and zonal wind at 850 hPa (U850) in the region 10°S-40°N, 40°-160°E, for the extended boreal summer (May-October) season over the 30-year period 1981-2010. BSISO1 is defined by the first two principal components (PCs) of the MV-EOF analysis, which together represent the canonical northward propagating variability that often occurs in conjunction with the eastward MJO with quasi-oscillating periods of 30-60 days. BSISO2 is defined by the third and fourth PCs, which together mainly capture the northward/northwestward propagating variability with periods of 10-30 days during primarily the pre-monsoon and monsoon-onset season. The BSISO1 circulation cells are more Rossby wave like with a northwest to southeast slope, whereas the circulation associated with BSISO2 is more elongated and front-like with a southwest to northeast slope. BSISO2 is shown to modulate the timing of the onset of Indian and South China Sea monsoons. Together, the two BSISO indices are capable of describing a large fraction of the total intraseasonal variability in the ASM region, and better represent the northward and northwestward propagation than the real-time multivariate MJO (RMM) index of Wheeler and Hendon.

KW - Asian summer monsoon

KW - Boreal summer intraseasonal oscillation

KW - Madden-Julian Oscillation

KW - Monsoon onset

KW - Northward propagation

KW - Real-time multivariate index

UR - https://www.scopus.com/pages/publications/84871919031

U2 - 10.1007/s00382-012-1544-4

DO - 10.1007/s00382-012-1544-4

M3 - Article

AN - SCOPUS:84871919031

SN - 0930-7575

VL - 40

SP - 493

EP - 509

JO - Climate Dynamics

JF - Climate Dynamics

IS - 1-2

ER -

Real-time multivariate indices for the boreal summer intraseasonal oscillation over the Asian summer monsoon region

Abstract

Funding

Keywords

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