Zonal heat advection （ZHA） plays an important role in the variability of the thermal structure in the tropical Pacific Ocean, especially in the western Pacific warm pool （WPWP）. Using the Simple Ocean Data Assimil...Zonal heat advection （ZHA） plays an important role in the variability of the thermal structure in the tropical Pacific Ocean, especially in the western Pacific warm pool （WPWP）. Using the Simple Ocean Data Assimilation （SODA） Version 2.02/4 for the period 1958-2007, this paper presents a detailed analysis of the climatological and seasonal ZHA in the tropical Pacific Ocean. Climatologically, ZHA shows a zonal- band spatial pattern associated with equatorial currents and contributes to forming the irregular eastern boundary of the WPWP （EBWP）. Seasonal variation of ZHA with a positive peak from February to July is most prominent in the Nifio3.4 region, where the EBWP is located. The physical mechanism of the seasonal cycle in this region is examined. The mean advection of anomalous temperature, anomalous advection of mean temperature and eddy advection account for 31%, 51%, and 18% of the total seasonal variations, respectively. This suggests that seasonal changes of the South Equatorial Current induced by variability of the trade winds are the dominant contributor to the anomalous advection of mean temperature and hence, the seasonality of ZHA. Heat budget analysis shows that ZHA and surface heat flux make comparable contributions to the seasonal heat variation in the Nifio3.4 region, and that ZHA cools the upper ocean throughout the calendar year except in late boreal spring. The connection between ZHA and EBWP is further explored and a statistical relationship between EBWP, ZHA and surface heat flux is established based on least squares fitting.展开更多
The authors investigate the characteristics of propagation and the influence on tropical precipitation of 9–29-day intraseasonal variation over midlatitude East Asia during boreal winter, and find that the intraseaso...The authors investigate the characteristics of propagation and the influence on tropical precipitation of 9–29-day intraseasonal variation over midlatitude East Asia during boreal winter, and find that the intraseasonal wind signal can propagate both eastward and southward. In the case of eastward propagation, the intraseasonal wind signal is mainly confined to the midlatitudes, featuring eastward migration of anomalous cyclones and anticyclones. In the case of southward propagation, intraseasonal meridional wind perturbations may extend from the mid to the low latitudes, and even the equatorial region. The accompanying wind convergence/divergence induces anomalous precipitation in the near-equatorial regions, forming a north–south dipole precipitation anomaly pattern between the southern South China Sea and the eastern China– Japan region. An anomalous meridional overturning circulation plays an important role in linking tropical and midlatitude intraseasonal wind and precipitation variations.展开更多
The E1 Nifio-Southern Oscillation （ENSO） phenomenon in the tropical Pacific has been a focus of ocean and climate studies in the last few decades. Recently, the short-term climate variability in the tropical Indian ...The E1 Nifio-Southern Oscillation （ENSO） phenomenon in the tropical Pacific has been a focus of ocean and climate studies in the last few decades. Recently, the short-term climate variability in the tropical Indian Ocean has attracted increasingly more attention, especially with the proposition of the Indian Ocean Dipole （IOD） mode. However, these phenomena are often stud- ied separately without much consideration of their interaction. Observations reveal a striking out-of-phase relationship between zonal gradients of sea surface height anomaly （SSHA） and sea surface temperature anomaly （SSTA） in the tropical Indian and Pacific Oceans. Since the two oceans share the ascending branch of the Walker cells over the warm pool, the variation within one of them will affect the other. The accompanied zonal surface wind anomalies are always opposite over the two basins, thus producing a tripole structure with opposite zonal gradients of SSHA/SSTA in the two oceans. This mode of variability has been referred to as Indo-Pacific Tripole （IPT）. Based on observational data analyses and a simple ocean-atmosphere coupled model, this study tries to identify the characteristics and physical mechanism of IPT with a particular emphasis on the rela- tionships among ENSO, IOD, and IPT. The model includes the basic oceanic and atmospheric variables and the feedbacks between them, and takes into account the inter-basin connection through an atmospheric bridge, thus providing a valuable framework for further research on the short-term tropical climate variability.展开更多
Climatological characteristics of diurnal variations in summer precipitation over the Asian monsoon region are comprehensively investigated based on the Tropical Rainfall Measuring Mission(TRMM) satellite data during ...Climatological characteristics of diurnal variations in summer precipitation over the Asian monsoon region are comprehensively investigated based on the Tropical Rainfall Measuring Mission(TRMM) satellite data during 1998-2008.The topographic influence on the diurnal variations and phase propagations of maximum precipitation are identified according to spatiotemporal distributions of the amplitude and peak time of the diurnal precipitation.The amplitude and phase of diurnal precipitation show a distinct geographical pattern.Significant diurnal variations occur over most of continental and coastal areas including the Maritime Continent,with the relative amplitude exceeding 40%,indicating that the precipitation peak is 1.4 times the 24-h mean.Over the landside coasts such as southeastern China and Indochina Peninsula,the relative amplitude is even greater than 100%.Although the diurnal variations of summer precipitation over the continental areas are characterized by an afternoon peak(1500-1800 Local Solar Time(LST)),over the central Indochina Peninsula and central and southern Indian Peninsula the diurnal phase is delayed to after 2100 LST,suggesting the diurnal behaviors over these areas different from the general continental areas.The weak diurnal variations with relative amplitudes less than 40% exist mainly over oceanic areas in the western Pacific and most of Indian Ocean,with the rainfall peak mainly occurring from midnight to early morning(0000-0600 LST),indicating a typical oceanic regime characterized by an early morning peak.However,apparent exceptions occur over the South China Sea(SCS),Bay of Bengal(BOB),and eastern Arabian Sea,with the rainfall peak occurring in daytime(0900-1500 LST).Prominent meridional propagations of the diurnal phase exist in South Asia and East Asia.Along the eastern Indian Peninsula,there is not only the southward phase propagation with the peak occurring around 25°N but also the northward phase propagation with the peak beginning with the southernmost continent,and both reach the central Indian continent to finish.Along the same longitudes where southern China and Kalimantan are located,the diurnal phase of the former propagates from the oceanic area(northern SCS) toward the inland continent,while the phase of the latter propagates from the land area toward the outside sea,showing a landward or seaward coastal diurnal regime.A distinct zonal propagation of the diurnal phase is observed over the BOB oceanic area.The maximum precipitation zone originates from the land-sea boundary of the eastern coast of the Indian peninsula at around 0300 LST,and then propagates eastward with increasing time to reach the eastern coast of the BOB on 1800 LST,finally migrates into the Indochina continent on about 2100 LST.展开更多
基金Supported by the National Basic Research Program of China(973 Program)(No.2012CB417401)the CAS Strategic Priority Research Program(No.XDA10010104)
文摘Zonal heat advection （ZHA） plays an important role in the variability of the thermal structure in the tropical Pacific Ocean, especially in the western Pacific warm pool （WPWP）. Using the Simple Ocean Data Assimilation （SODA） Version 2.02/4 for the period 1958-2007, this paper presents a detailed analysis of the climatological and seasonal ZHA in the tropical Pacific Ocean. Climatologically, ZHA shows a zonal- band spatial pattern associated with equatorial currents and contributes to forming the irregular eastern boundary of the WPWP （EBWP）. Seasonal variation of ZHA with a positive peak from February to July is most prominent in the Nifio3.4 region, where the EBWP is located. The physical mechanism of the seasonal cycle in this region is examined. The mean advection of anomalous temperature, anomalous advection of mean temperature and eddy advection account for 31%, 51%, and 18% of the total seasonal variations, respectively. This suggests that seasonal changes of the South Equatorial Current induced by variability of the trade winds are the dominant contributor to the anomalous advection of mean temperature and hence, the seasonality of ZHA. Heat budget analysis shows that ZHA and surface heat flux make comparable contributions to the seasonal heat variation in the Nifio3.4 region, and that ZHA cools the upper ocean throughout the calendar year except in late boreal spring. The connection between ZHA and EBWP is further explored and a statistical relationship between EBWP, ZHA and surface heat flux is established based on least squares fitting.
基金supported by the National Natural Science Foundation of China [grant numbers 41530425,41721004,41475081,and 41775080]
文摘The authors investigate the characteristics of propagation and the influence on tropical precipitation of 9–29-day intraseasonal variation over midlatitude East Asia during boreal winter, and find that the intraseasonal wind signal can propagate both eastward and southward. In the case of eastward propagation, the intraseasonal wind signal is mainly confined to the midlatitudes, featuring eastward migration of anomalous cyclones and anticyclones. In the case of southward propagation, intraseasonal meridional wind perturbations may extend from the mid to the low latitudes, and even the equatorial region. The accompanying wind convergence/divergence induces anomalous precipitation in the near-equatorial regions, forming a north–south dipole precipitation anomaly pattern between the southern South China Sea and the eastern China– Japan region. An anomalous meridional overturning circulation plays an important role in linking tropical and midlatitude intraseasonal wind and precipitation variations.
文摘The E1 Nifio-Southern Oscillation （ENSO） phenomenon in the tropical Pacific has been a focus of ocean and climate studies in the last few decades. Recently, the short-term climate variability in the tropical Indian Ocean has attracted increasingly more attention, especially with the proposition of the Indian Ocean Dipole （IOD） mode. However, these phenomena are often stud- ied separately without much consideration of their interaction. Observations reveal a striking out-of-phase relationship between zonal gradients of sea surface height anomaly （SSHA） and sea surface temperature anomaly （SSTA） in the tropical Indian and Pacific Oceans. Since the two oceans share the ascending branch of the Walker cells over the warm pool, the variation within one of them will affect the other. The accompanied zonal surface wind anomalies are always opposite over the two basins, thus producing a tripole structure with opposite zonal gradients of SSHA/SSTA in the two oceans. This mode of variability has been referred to as Indo-Pacific Tripole （IPT）. Based on observational data analyses and a simple ocean-atmosphere coupled model, this study tries to identify the characteristics and physical mechanism of IPT with a particular emphasis on the rela- tionships among ENSO, IOD, and IPT. The model includes the basic oceanic and atmospheric variables and the feedbacks between them, and takes into account the inter-basin connection through an atmospheric bridge, thus providing a valuable framework for further research on the short-term tropical climate variability.
基金supported by Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No.KZCX2-YW- Q11-04)National Basic Research Program of China (Grant Nos.2011CB403505 and 2010CB950402)National Natural Science Foundation of China (Grant Nos.40975052)
文摘Climatological characteristics of diurnal variations in summer precipitation over the Asian monsoon region are comprehensively investigated based on the Tropical Rainfall Measuring Mission(TRMM) satellite data during 1998-2008.The topographic influence on the diurnal variations and phase propagations of maximum precipitation are identified according to spatiotemporal distributions of the amplitude and peak time of the diurnal precipitation.The amplitude and phase of diurnal precipitation show a distinct geographical pattern.Significant diurnal variations occur over most of continental and coastal areas including the Maritime Continent,with the relative amplitude exceeding 40%,indicating that the precipitation peak is 1.4 times the 24-h mean.Over the landside coasts such as southeastern China and Indochina Peninsula,the relative amplitude is even greater than 100%.Although the diurnal variations of summer precipitation over the continental areas are characterized by an afternoon peak(1500-1800 Local Solar Time(LST)),over the central Indochina Peninsula and central and southern Indian Peninsula the diurnal phase is delayed to after 2100 LST,suggesting the diurnal behaviors over these areas different from the general continental areas.The weak diurnal variations with relative amplitudes less than 40% exist mainly over oceanic areas in the western Pacific and most of Indian Ocean,with the rainfall peak mainly occurring from midnight to early morning(0000-0600 LST),indicating a typical oceanic regime characterized by an early morning peak.However,apparent exceptions occur over the South China Sea(SCS),Bay of Bengal(BOB),and eastern Arabian Sea,with the rainfall peak occurring in daytime(0900-1500 LST).Prominent meridional propagations of the diurnal phase exist in South Asia and East Asia.Along the eastern Indian Peninsula,there is not only the southward phase propagation with the peak occurring around 25°N but also the northward phase propagation with the peak beginning with the southernmost continent,and both reach the central Indian continent to finish.Along the same longitudes where southern China and Kalimantan are located,the diurnal phase of the former propagates from the oceanic area(northern SCS) toward the inland continent,while the phase of the latter propagates from the land area toward the outside sea,showing a landward or seaward coastal diurnal regime.A distinct zonal propagation of the diurnal phase is observed over the BOB oceanic area.The maximum precipitation zone originates from the land-sea boundary of the eastern coast of the Indian peninsula at around 0300 LST,and then propagates eastward with increasing time to reach the eastern coast of the BOB on 1800 LST,finally migrates into the Indochina continent on about 2100 LST.
