TY - JOUR
T1 - Low and high frequency Madden-Julian oscillations in austral summer
T2 - Interannual variations
AU - Izumo, Takeshi
AU - Masson, Sébastien
AU - Vialard, Jérome
AU - de Boyer Montegut, Clément
AU - Behera, Swadhin K.
AU - Madec, Gurvan
AU - Takahashi, Keiko
AU - Yamagata, Toshio
N1 - Funding Information:
The authors would like to thank the three reviewers for their helpful comments and corrections, that significantly improved the readability and clarity of the manuscript. The authors would also like to thank JAMSTEC, especially FRCGC and the Earth Simulator Center, for their great hospitality and the high performance material and computer facilities they offer. Dr. Sophie Cravatte, Dr. Fabien Durand, and all the LEGOS and LOCEAN teams are greatly thanked for their support of this research project. Most of the observations data were made available mainly by NOAA/NCEP/CPC through Climate Diagnostics Center (CDC), IRI/LDEO Climate Data Library and AVISO servers. AVHRR Pathfinder SST is NODC/NOAA. QuikScat data are produced by Remote Sensing Systems and sponsored by the NASA Ocean Vector Winds Science Team. Those data were obtained from the IFREMER (CERSAT) ftp server. The authors also wish to acknowledge the use of NOAA/PMEL Ferret program for analysis and graphics in this paper. The Japan Society for the Promotion of Science (JSPS) and the French Research Agency (ANR, Project INLOES) funded this work.
PY - 2010
Y1 - 2010
N2 - The Madden-Julian oscillation (MJO) is the main component of intraseasonal variability of the tropical convection, with clear climatic impacts at an almost-global scale. Based on satellite observations, it is shown that there are two types of austral-summer MJO events (broadly defined as 30-120 days convective variability with eastward propagation of about 5 m/s). Equatorial MJO events have a period of 30-50 days and tend to be symmetric about the equator, whereas MJO events centered near 8°S tend to have a longer period of 55-100 days. The lowerfrequency variability is associated with a strong upperocean response, having a clear signature in both sea surface temperature and its diurnal cycle. These two MJO types have different interannual variations, and are modulated by the Indian Ocean Dipole (IOD). Following a negative IOD event, the lower-frequency southern MJO variability increases, while the higher-frequency equatorial MJO strongly diminishes. We propose two possible explanations for this change in properties of the MJO. One possibility is that changes in the background atmospheric circulation after an IOD favour the development of the low-frequency MJO. The other possibility is that the shallower thermocline ridge and mixed layer depth, by enhancing SST intraseasonal variability and thus ocean-atmosphere coupling in the southwest Indian Ocean (the breeding ground of southern MJO onset), favour the lower-frequency southern MJO variability.
AB - The Madden-Julian oscillation (MJO) is the main component of intraseasonal variability of the tropical convection, with clear climatic impacts at an almost-global scale. Based on satellite observations, it is shown that there are two types of austral-summer MJO events (broadly defined as 30-120 days convective variability with eastward propagation of about 5 m/s). Equatorial MJO events have a period of 30-50 days and tend to be symmetric about the equator, whereas MJO events centered near 8°S tend to have a longer period of 55-100 days. The lowerfrequency variability is associated with a strong upperocean response, having a clear signature in both sea surface temperature and its diurnal cycle. These two MJO types have different interannual variations, and are modulated by the Indian Ocean Dipole (IOD). Following a negative IOD event, the lower-frequency southern MJO variability increases, while the higher-frequency equatorial MJO strongly diminishes. We propose two possible explanations for this change in properties of the MJO. One possibility is that changes in the background atmospheric circulation after an IOD favour the development of the low-frequency MJO. The other possibility is that the shallower thermocline ridge and mixed layer depth, by enhancing SST intraseasonal variability and thus ocean-atmosphere coupling in the southwest Indian Ocean (the breeding ground of southern MJO onset), favour the lower-frequency southern MJO variability.
KW - Air-sea interactions
KW - Australian weather
KW - Diurnal cycle
KW - El Nino southern oscillation (ENSO)
KW - Indian Ocean dipole (IOD)
KW - Interannual variations
KW - Intraseasonal Madden-Julian oscillation (MJO)
KW - Mixed layer
KW - Ocean-atmosphere coupling
KW - Oceanic diurnal warm layers
KW - Seychelles-Chagos thermocline ridge/thermocline dome of the Indian Ocean
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U2 - 10.1007/s00382-009-0655-z
DO - 10.1007/s00382-009-0655-z
M3 - Article
AN - SCOPUS:77950545238
SN - 0930-7575
VL - 35
SP - 669
EP - 683
JO - Climate Dynamics
JF - Climate Dynamics
IS - 4
ER -