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Ogata T.,International Pacific Research Center | Ogata T.,University of Tsukuba | Xie S.-P.,University of Hawaii at Manoa | Xie S.-P.,University of California at San Diego | And 2 more authors.
Journal of Climate | Year: 2013

The amplitude of El Niño-Southern Oscillation (ENSO) displays pronounced interdecadal modulations in observations. The mechanisms for the amplitude modulation are investigated using a 2000-yr preindustrial control integration from the Geophysical Fluid Dynamics Laboratory Climate Model, version 2.1 (GFDL CM2.1). ENSO amplitude modulation is highly correlated with the second empirical orthogonal function (EOF) mode of tropical Pacific decadal variability (TPDV), which features equatorial zonal dipoles in sea surface temperature (SST) and subsurface temperature along the thermocline. Experiments with an ocean general circulation model indicate that both interannual and decadal-scale wind variability are required to generate decadal-scale tropical Pacific temperature anomalies at the sea surface and along the thermocline. Even a purely interannual and sinusoidal wind forcing can produce substantial decadal-scale effects in the equatorial Pacific, with SST cooling in the west, subsurface warming along the thermocline, and enhanced upper-ocean stratification in the east. A mechanism is proposed by which residual effects of ENSO could serve to alter subsequent ENSO stability, possibly contributing to long-lasting epochs of extreme ENSO behavior via a coupled feedback with TPDV. © 2013 American Meteorological Society. Source

Rhee J.,Climate Center | Cai W.,CSIRO | Plummer N.,Bureau of Meteorology | Sivakumar M.,World Meteorological Organization | And 3 more authors.
Bulletin of the American Meteorological Society | Year: 2015

The Asia-Pacific Economic Cooperation (APEC) Climate Symposium 2013 was held with the theme of regional cooperation on drought prediction science for disaster preparedness and management. Gusti Muhammad Hatta, the Indonesian minister for research and technology, opened the symposium, noting the importance of the event in strengthening drought preparedness in order to contribute to the APEC mission of sustainable economic growth and prosperity in the Asia-Pacific region. In his keynote address, Donald Wilhite, professor at the University of Nebraska-Lincoln and founder of the National Drought Mitigation Center, presented a state-of-the-art system for monitoring drought conditions in the United States. The second keynote address, by Andi Eka Sakya of the Indonesia Agency for Meteorology, Climatology, and Geophysics (BMKG), focused on a potential drought monitoring information system for Indonesia. He introduced the geographical and climatological conditions of Indonesia and explained other existing information systems produced by BMKG. The conference presentations described the extent of existing research and scientific understanding of the processes and mechanisms that control rainfall and other variables relevant to drought in different areas. Source

Ogata T.,International Pacific Research Center | Xie S.-P.,Pacific University in Oregon | Xie S.-P.,Ocean University of China | Lan J.,Ocean University of China | Zheng X.,Ocean University of China
Journal of Climate | Year: 2013

Interannual anomalies of sea surface temperature (SST), wind, and cloudiness in the southeastern tropical Indian Ocean (SE-TIO) show negative skewness. In this research, asymmetry between warm and cold episodes in the SE-TIO and the importance of ocean dynamics are investigated.Acoupled model simulation and observations show an asymmetric relationship between SST and the thermocline depth in the SE-TIO where SST is more sensitive to an anomalous shoaling than to deepening of the thermocline. This asymmetric thermocline feedback on SST is a result of a deep mean thermocline. Sensitivity experiments with an ocean general circulation model (OGCM) show that a negative SST skewness arises in response to sinusoidal zonal wind variations that are symmetric between the westerly and easterly phases. Heat budget analysis with an OGCM hindcast also supports the importance of ocean dynamics for SST skewness off Sumatra and Java. © 2013 American Meteorological Society. Source

Xu J.,Chinese Academy of Meteorological Sciences | Wang Y.,International Pacific Research Center | Wang Y.,University of Hawaii at Manoa
Weather and Forecasting | Year: 2015

The dependence of tropical cyclone (TC) intensification rate IR on storm intensity and size was statistically analyzed for North Atlantic TCs during 1988-2012. The results show that IR is positively (negatively) correlated with storm intensity (the maximum sustained near-surface wind speed Vmax) when Vmax is below (above) 70-80 knots (kt; 1 kt = 0.51 m s-1), and negatively correlated with storm size in terms of the radius of maximum wind (RMW), the average radius of gale-force wind (AR34), and the outer-core wind skirt parameter DR34 (=AR34 - RMW). The turning point for Vmax of 70-80 kt is explained as a balance between the potential intensification and the maximum potential intensity (MPI). The highest IR occurs for Vmax = 80 kt, RMW ≤ 40 km, and AR34 = DR34 = 150 km. The high frequency of occurrence of intensifying TCs occurs for Vmax ≤ 80 kt and RMW between 20 and 60 km, AR34 ≤ 200 km, and DR34 ≤ 150 km. Rapid intensification (RI) often occurs in a relatively narrow parameter space in storm intensity and both inner- and outer-core sizes. In addition, a theoretical basis for the intensity dependency has also been provided based on a previously constructed simplified dynamical system for TC intensity prediction. © 2015 American Meteorological Society. Source

Li T.,International Pacific Research Center
Geophysical Monograph Series | Year: 2010

The Asian monsoon consists of three subcomponents, Indian monsoon (IM), East Asian monsoon (EAM), and western North Pacific monsoon (WNPM). All these submonsoon systems exhibit remarkable intraseasonal and interannual variabilities. In this chapter, we will review recent progress in understanding the monsoon annual cycle and some of major issues related to the monsoon intraseasonal and interannual variabilities; describe the spatial-temporal structure of the northward propagating intraseasonal oscillation in the monsoon region; and discuss what physical processes lead to quasi-biennial and lower-frequency variabilities of the India monsoon, how El Niño (La Niña) events have a delayed impact on East Asian climate, and how the atmosphere-ocean interaction in the monsoon-warm ocean leads to the tropospheric biennial oscillation. Specific emphases are placed on the discussion of the physical processes that are responsible for the described phenomena. Copyright © 2010 by the American Geophysical Union. Source

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