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Evolution of the 2015/16 El Nio and historical perspective since 1979

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Science China Earth Sciences 2017年第9期60卷 1572-1588页

作者： Yan XUE Arun KUMAR Climate prediction center National Centers for Environmental Prediction National Weather Service National Oceanic and Atmospheric Administration College Park MD 20740 USA

The 2015/16 El Nio developed from weak warm conditions in late 2014 and NINO3.4 reached 3℃ in November 2015. We describe the characteristics of the evolution of the 2015/16 El Nio using various data sets including SST, surface winds,outgoing longwave radiation and subsurface temperature from an ensemble operational ocean reanalyses, and place this event in the context of historical ENSO events since 1979. One salient feature about the 2015/16 El Nio was a large number of westerly wind bursts and downwelling oceanic Kelvin waves(DWKVs). Four DWKVs were observed in April-November 2015 that initiated and enhanced the eastern-central Pacific warming. Eastward zonal current anomalies associated with DWKVs advected the warm pool water eastward in spring/summer. An upwelling Kelvin wave(UWKV) emerged in early November 2015 leading to a rapid decline of the event. Another outstanding feature was that NINO4 reached a historical high(1.7℃), which was 1℃(0.8℃) higher than that of the 1982/83(1997/98) El Nio . Although NINO3 was comparable to that of the 1982/83 and 1997/98 El Nio , NINO1+2 was much weaker. Consistently, enhanced convection was displaced 20 degree westward, and the maximum D20 anomaly was about 1/3.1/2 of that in 1997 and 1982 near the west coast of South America.

关键词： ENSO Sea surface temperature Westerly wind bursts ocean Kelvin waves Thermocline variability ocean reanalysis

A MODELING STUDY OF INHOMOGENEOUS COASTAL GALES ASSOCIATED WITH THE LANDFALL OF TYPHOON SOUDELOR(2015)

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Journal of Tropical Meteorology 2019年第1期25卷 1-10页

作者： ZHU Ye ZHANG Hong-lei CHEN You-li ZHAI Guo-qing LIU Rui Zhejiang center for ocean Monitoring and prediction Department of atmospheric Sciences School of Earth Sciences Zhejiang University Ningbo Weather Bureau

In this study, coastal gales and rainfall attributed to the landfall of Typhoon Soudelor(2015) are analyzed based on observational dense automatic weather stations data, advanced scatterometer-retrieved 10-m ocean surface wind data and simulations using the Weather Research and Forecast(WRF) model. This study focuses on gale bands in the right-front quadrant of the typhoon and associated coastal winds over Zhejiang and Fujian Provinces in China before the landfall of the typhoon. The results are summarized as follows.(1) 10-m surface wind data from automatic weather stations over land and islands, advanced scatterometer-retrieved 10-m ocean surface wind data, and the WRF simulation indicate similar mesoscale offshore gales.(2) The model simulation with a 333-m grid mesh indicates a gale zone over the right-front quadrant of the typhoon; the gale is "broken" over the coastal areas, and formed an inhomogeneous gale band.(3) The model-simulated winds agree well with the island observations.(4) Non-uniform gales over boundary layers result in horizontal wind-speed gradients and strong convergence that favors the development of convection and the maintenance of ocean surface gales.

关键词： ocean surface gale Typhoon Soudelor severe convection WRF model Inhomogeneous field

Projection of global mean surface air temperature changes in next 40 years: Uncertainties of climate models and an alternative approach

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Science China Earth Sciences 2011年第9期54卷 1400-1406页

作者： FU CongBin QIAN Cheng WU ZhaoHua Institute for Climate and Global Change Research School of Atmospheric Sciences Nanjing University Nanjing 210093 China Key Laboratory of Regional Climate-Environment for Temperate East Asia Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China Department of Earth Ocean and Atmospheric Science & Center for Ocean-Atmospheric Prediction Studies Florida State University Tallahassee F132308 USA

The Fourth Assessment Report (AR4) of the Intergovernmental Panel of Climate Change (IPCC) concluded that the climate projection using climate models that took account of both human and natural factors provided credible quantitative estimates of future climate change; however, the mismatches between the IPCC AR4 model ensembles and the observations, especially the multi-decadal variability (MDV), have cast shadows on the confidence of the model-based decadal projections of future cli mate. This paper reports an evaluation of many individual runs of AR4 models in the simulation of past global mean tempera ture. We find that most of the individual model runs fail to reproduce the MDV of past climate, which may have led to the overestimation of the projection of global warming for the next 40 years or so. Based on such an evaluation, we propose an al ternative approach, in which the MDV signal is taken into account, to project the global mean temperature for the next 40 years and obtain that the global warming during 2011–2050 could be much smaller than the AR4 projection.

关键词： decadal prediction global warming multi-decadal climate variability the Ensemble Empirical Mode Decomposition CMIP3 multi-model

Quantifying the Role of the Eddy Transfer Coefficient in Simulating the Response of the Southern ocean Meridional Overturning Circulation to Enhanced Westerlies in a Coarse-resolution Model

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Advances in atmospheric Sciences 2024年第9期41卷 1853-1867页

作者： Yiwen LI Hailong LIU Pengfei LIN Eric PCHASSIGNET Zipeng YU Fanghua WU School of ocean Sciences China University of GeosciencesBeijing 100083China Laoshan Laboratory Qingdao 266237China Institute of atmospheric Physics Chinese Academy of SciencesBeijing 100029China center for ocean-atmospheric prediction studies Florida State UniversityTallahassee 32306FloridaUSA China Meteorological Administration Beijing 100081China

This study assesses the capability of a coarse-resolution ocean model to replicate the response of the Southern ocean Meridional Overturning Circulation(MOC) to intensified westerlies,focusing on the role of the eddy transfer coefficient(κ).κ is a parameter commonly used to represent the velocities induced by unresolved *** findings reveal that a stratification-dependent κ,incorporating spatiotemporal variability,leads to the most robust eddy-induced MOC response,capturing 82% of the reference eddy-resolving *** the eddy-induced velocity into its vertical variation(VV) and spatial structure(SS) components unveils that the enhanced eddy compensation response primarily stems from an augmented SS term,while the introduced VV term weakens the ***,the temporal variability of the stratification-dependent κ emerges as a key factor in enhancing the eddy compensation response to intensified *** experiment with stratification-dependent κ exhibits a more potent eddy compensation response compared to the constant κ,attributed to the structure of κ and the vertical variation of the density *** results underscore the critical role of accurately representing κ in capturing the response of the Southern ocean MOC and emphasize the significance of the isopycnal slope in modulating the eddy compensation mechanism.

关键词： eddy transfer coefficient mesoscale eddy parameterization enhanced westerlies Southern ocean Meridional Overturning Circulation ocean model

Contribution of Water Vapor to the Record-Breaking Extreme Meiyu Rainfall along the Yangtze River Valley in 2020

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Journal of Meteorological Research 2021年第4期35卷 557-570页

作者： Licheng WANG Xuguang SUN Xiuqun YANG Lingfeng TAO Zhiqi ZHANG CMA-NJU Joint Laboratory for Climate prediction studies School of Atmospheric SciencesNanjing UniversityNanjing 210023

A record-breaking extreme Meiyu rainfall occurred along the Yangtze River valley(YRV)in 2020 since 1961,persisting from 11 June to 31 July with the largest amount and the highest *** the aspect of water vapor,the causes of its formation are revealed in this *** 2020 Meiyu rainfall amount is directly attributed to the greatly enhanced vertically integrated water vapor transport(IVT)convergence,which is in turn primarily determined by the mean circulation dynamic(MCD)contribution associated with anomalous East Asian summer monsoon(EASM)and the thermodynamic component(TH)contribution due to water vapor *** MCD contribution is mainly responsible for the extreme Meiyu rainfall amount and abundant water vapor convergence in the YRV,whereas the TH contribution tends to shift Meiyu rain belt northward to the Yangtze-Huaihe River valley,extending the Meiyu rainfall coverage ***,the excessive moist static energy(MSE)associated with the largest water vapor anomaly could substantially increase the atmospheric instability,favoring the extreme 2020 Meiyu rainfall *** terms of the tremendous IVT to the YRV from both the South China Sea and Bay of Bengal during the 2020 Meiyu period,the low-level anticyclone anomalies over the western North Pacific(WNP)and Bay of Bengal provide appropriate atmospheric circulation conditions,and they are generated by the super suppressed WNP convective activities as a Matsuno-Gill type response,which are further attributed to the combined warm SST anomalies in both the tropical western Indian ocean(TWIO)and tropical Atlantic ocean(TAO)eventually.

关键词： water vapor convective activity Meiyu rainfall Indian ocean Atlantic ocean

atmospheric eddy anomalies associated with the wintertime North Pacific subtropical front strength and their influences on the seasonal-mean atmosphere

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Science China Earth Sciences 2016年第10期59卷 2022-2036页

作者： WANG LiYing HU HaiBo YANG XunQun REN XueJuan CMA-NJU Joint Laboratory for Climate prediction studies Instituted for Climate and Global Change Research School of Atmospheric Science Nanjing University

This study investigates transient eddy activity anomalies in the mid-latitude upper troposphere associated with intensity variability of the wintertime North Pacific subtropical front. Our results show that the meridional gradient of air temperature and baroclinic instability in the mid-latitude atmosphere become stronger as the subtropical front intensifies, and the mid-latitude westerly jet accelerates with barotropic structure. We further divide the mid-latitude atmospheric eddy activities into high-(2–7 days) and low-frequency(10–90 days) eddy activities according to their life periods. We find that, when the oceanic subtropical front intensifies, the high-frequency atmospheric eddy activity in the mid-latitudes strengthens while the low-frequency eddy activity weakens. The stronger high-frequency eddy activity tends to moderate the air temperature gradient and baroclinicity in the mid-latitudes. High-frequency eddy anomalies accelerate the westerly jet on the northern side and downstream of the westerly jet, and enhance the jet with equivalent barotropic structure. In contrast, the weaker low-frequency eddy activity has a negative contribution to zonal wind speed tendency and attenuates the zonal homogenization of the jet. The anomalous thermodynamic forcing of the low-frequency eddy activity helps maintain the meridional gradient of air temperature in the mid-troposphere.

关键词： North Pacific subtropical front Frequency Eddy activity Mid-Latitude ocean-Atmosphere interaction

Subseasonal Zonal Oscillation of the Western Pacific Subtropical High during Early Summer

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Journal of Meteorological Research 2018年第5期32卷 768-780页

作者： Weina GUAN Xuejuan REN Wei SHANG Haibo HU China Meteorological Administration–Nanjing University Joint Laboratory for Climate prediction studies School of Atmospheric Sciences Nanjing University

This study examines the features and dynamical processes of subseasonal zonal oscillation of the western Pacific subtropical high （WPSH） during early summer, by performing a multivariate empirical orthogonal function （MV- EOF） analysis on daily winds and a diagnosis on potential vorticity （PV） at 500 hPa for the period 197%2016. The first MV-EOF mode is characterized by an anticyclonic anomaly occupying southeastern China to subtropical west-ern North Pacific regions. It has a period of 10-25 days and represents zonal shift of the WPSH. When the WPSH stretches more westward, the South Asian high （SAH） extends more eastward. Above-normal precipitation is ob- served over the Yangtze-Huaihe River （YHR） basin. Suppressed convection with anomalous descending motion is located over the subtropical western North Pacific. The relative zonal movement of the SAH and the WPSH helps to establish an anomalous local vertical circulation of ascending motion with upper-level divergence over the YHR basin and descending motion with upper-level convergence over the subtropical western Pacific. The above local ver-tical circulation provides a dynamic condition for persistent rainfall over the YHR basin. An enhanced southwest flow over the WPSH＇s western edge transports more moisture to eastem China, providing a necessary water vapor condition for the persistent rainfall over the YHR basin. A potential vorticity diagnosis reveals that anomalous diaba- tic heating is a main source for PV generation. The anomalous cooling over the subtropical western Pacific produces a local negative PV center at 500 hPa. The anomalous heating over the YHR basin generates a local positive PV cen-ter. The above south-north dipolar structure of PV anomaly along with the climatological southerly flow leads to northward advection of negative PV. These two processes are conducive to the WPSH＇s westward extension. The vertical advection process is unfavorable to the westward extension but contributes to the ea

关键词： western Pacific subtropical high subseasonal timescale diabatic heating potential vorticity

Identification Standard for ENSO Events and Its Application to Climate Monitoring and prediction in China

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Journal of Meteorological Research 2018年第6期32卷 923-936页

作者： Hong-Li REN Bo LU Jianghua WAN Ben TIAN Peiqun ZHANG Laboratory for Climate studies &China Meteorological Administration–Nanjing University Joint Laboratory for Climate prediction studies National Climate Center China Meteorological Administration Department of atmospheric Science School of Environmental Studies China University of Geoscience

The El Ni?o–Southern Oscillation(ENSO)reflects anomalous variations in the sea surface temperature(SST)and atmospheric circulation over the tropical central–eastern *** remarkably impacts on weather and climate worldwide,so monitoring and prediction of ENSO draw intensive ***,there is not yet a unique standard internationally for identifying the timing,intensity,and type of ENSO *** National Climate center of China Meteorological Administration(NCC/CMA)has led the effort to establish a national identification standard of ENSO events,which was officially endorsed by the National Standardization Administration of China and implemented operationally in NCC/CMA in *** this paper,two key aspects of this standard are ***,the Ni?o3.4 SST anomaly index,which is well-recognized in the international ENSO research community and used operationally in the US,has replaced the previous Ni?o Z index and been used to identify the start,end,and peak times,and intensity of ENSO ***,two new indices—the eastern Pacific ENSO(EP)index and the central Pacific ENSO(CP)index,based on the SST conditions in Ni?o3 and Ni?o4 region respectively,are calculated to first determine the ENSO type before monitoring and assessing the impacts of ENSO on China’s *** this standard,all historical ENSO events since 1950 are consistently re-identified;their distinct properties are diagnosed and presented;and the impacts of ENSO events under different types on China’s climate are *** standard is also employed to validate the intensity,grade,and type of the ENSO events predicted by the NCC/CMA operational ENSO prediction *** new standard and the thus derived unified set of re-analyzed historical ENSO events and associated information provide a good reference for better monitoring and prediction of future ENSO events.

关键词： El Ni?o–Southern Oscillation identification standard monitoring prediction

ENSO Features, Dynamics, and Teleconnections to East Asian Climate as Simulated in CAMS-CSM

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Journal of Meteorological Research 2019年第1期33卷 46-65页

作者： Bo LU Hong-Li REN Laboratory for Climate studies & China Meteorological Administration–Nanjing University Joint Laboratory for Climate prediction studies National Climate Center China Meteorological Administration Xinjiang Climate center Department of atmospheric Science School of Environmental Studies China University of Geoscience

This study evaluates the performance of CAMS-CSM(the climate system model of the Chinese Academy of Meteorological Sciences) in simulating the features, dynamics, and teleconnections to East Asian climate of the El Ni?o–Southern Oscillation(ENSO). In general, fundamental features of ENSO, such as its dominant patterns and phase-locking features, are reproduced well. The two types of El Ni?o are also represented, in terms of their spatial distributions and mutual independency. However, the skewed feature is missed in the model and the simulation of ENSO is extremely strong, which is found—based on Bjerknes index assessment—to be caused by underestimation of the shortwave damping effect. Besides, the modeled ENSO exhibits a regular oscillation with a period shorter than observed. By utilizing the Wyrtki index, it is suggested that this periodicity bias results from an overly quick phase transition induced by feedback from the thermocline and zonal advection. In addition to internal dynamics of ENSO,its external precursors—such as the North Pacific Oscillation with its accompanying seasonal footprinting mechanism, and the Indian ocean Dipole with its 1-yr lead correlation with ENSO—are reproduced well by the model. Furthermore, with respect to the impacts of ENSO on the East Asian summer monsoon, although the anomalous Philippine anticyclone is reproduced in the post-El Ni?o summer, it exhibits an eastward shift compared with observation;and as a consequence, the observed flooding of the Yangtze River basin is poorly represented, with unrealistic air–sea interaction over the South China Sea being the likely physical origin of this bias. The response of wintertime lowertropospheric circulation to ENSO is simulated well, in spite of an underestimation of temperature anomalies in central China. This study highlights the dynamic processes that are key for the simulation of ENSO, which could shed some light on improving this model in the future.

关键词： model evaluation ENSO dynamics teleconnection CAMS-CSM