The features of 30-60-day convection oscillations over the subtropical western North Pacific （WNP） were investigated, along with the degree of tropical-subtropical linkage between the oscillations over the WNP durin...The features of 30-60-day convection oscillations over the subtropical western North Pacific （WNP） were investigated, along with the degree of tropical-subtropical linkage between the oscillations over the WNP during summer 1998. It was found that 30-60-day oscillations were extremely strong in that summer over both the subtropical and tro]~ical WNP, providing a unique opportunity to study the behavior of subtropical oscillations and their relationship to tropical oscillations. Further analyses indicated that 30-60-day oscillations propagate westwards over the subtropical WNP and reach eastern China. In addition, 30-60-day oscillations in the subtropics are affected by those over the South China Sea （SCS） and tropical WNP through two mechanisms： （1） direct propagation from the tropics into the subtropics; and （2） a seesaw pattern between the tropics and subtropics, with the latter being predominant.展开更多
Two record-breaking rainfalls in late June of 2015 led to widespread flooding in Eastern China, espe- cially over the Yangtze River Delta, and this in turn led to huge economic losses. Analysis suggests that the E1 Ni...Two record-breaking rainfalls in late June of 2015 led to widespread flooding in Eastern China, espe- cially over the Yangtze River Delta, and this in turn led to huge economic losses. Analysis suggests that the E1 Nifio- like sea surface temperature pattern during that month facilitated an intensified and southwestward-shifted west- ern Pacific subtropical high and enhanced water vapor convergence along the Meiyu front, which provided a favorable environment for the occurrence of heavy rainfall over Eastern China. Meanwhile, two midlatitude troughs were successively formed over East Asia in the second half of the month as a consequence of the downstream energy dispersions of two midlatitude blockings. These configu- rations facilitated the southward intrusion of the extrat- ropical high potential vorticity toward the Meiyu front. In this way, the ascent was enhanced along the Meiyu front over Eastern China, and the occurrence of heavy rainfalls was triggered. Moreover, a tropical intraseasonal active convection propagated northward and also contributed constructively to the heavy rainfall.展开更多
A series of climate ensemble experiments using the climate model from National Centers for Environmental Prediction (NCEP) were performed to exam impact of sea surface temperature (SST) on dynamics of El-Nino/South-c... A series of climate ensemble experiments using the climate model from National Centers for Environmental Prediction (NCEP) were performed to exam impact of sea surface temperature (SST) on dynamics of El-Nino/South-crn Oscillation (ENSO).A specific question addressed in this paper is how important the mean stationary wave influences anomalous Rossby wave trains or teleconnection patterns as often observed during ENSO events.Evidences from those ensemble simulations argue that ENSO anomalies,especially over Pacific-North America (PNA) region,appear to be a result of modification for climatological mean stationary wave forced by persistent tropical SST anomalies Therefore,the role of SST forcing in maintaining climate basic state is emphasized.In this argument,the interaction between atmospheric internal dynamics and external forcing,such as SST is a key element to understand and ultimately predict ENSO.展开更多
基金supported by the National Basic Research Program of China(Grant No2010CB950403)by the National Natural Science Foundation of China(Grant No.U0933603)
文摘The features of 30-60-day convection oscillations over the subtropical western North Pacific （WNP） were investigated, along with the degree of tropical-subtropical linkage between the oscillations over the WNP during summer 1998. It was found that 30-60-day oscillations were extremely strong in that summer over both the subtropical and tro]~ical WNP, providing a unique opportunity to study the behavior of subtropical oscillations and their relationship to tropical oscillations. Further analyses indicated that 30-60-day oscillations propagate westwards over the subtropical WNP and reach eastern China. In addition, 30-60-day oscillations in the subtropics are affected by those over the South China Sea （SCS） and tropical WNP through two mechanisms： （1） direct propagation from the tropics into the subtropics; and （2） a seesaw pattern between the tropics and subtropics, with the latter being predominant.
基金supported by the National Basic Research Program of China(2013CB430203)the National Natural Science Foundation of China(4123052741422501)
文摘Two record-breaking rainfalls in late June of 2015 led to widespread flooding in Eastern China, espe- cially over the Yangtze River Delta, and this in turn led to huge economic losses. Analysis suggests that the E1 Nifio- like sea surface temperature pattern during that month facilitated an intensified and southwestward-shifted west- ern Pacific subtropical high and enhanced water vapor convergence along the Meiyu front, which provided a favorable environment for the occurrence of heavy rainfall over Eastern China. Meanwhile, two midlatitude troughs were successively formed over East Asia in the second half of the month as a consequence of the downstream energy dispersions of two midlatitude blockings. These configu- rations facilitated the southward intrusion of the extrat- ropical high potential vorticity toward the Meiyu front. In this way, the ascent was enhanced along the Meiyu front over Eastern China, and the occurrence of heavy rainfalls was triggered. Moreover, a tropical intraseasonal active convection propagated northward and also contributed constructively to the heavy rainfall.
文摘 A series of climate ensemble experiments using the climate model from National Centers for Environmental Prediction (NCEP) were performed to exam impact of sea surface temperature (SST) on dynamics of El-Nino/South-crn Oscillation (ENSO).A specific question addressed in this paper is how important the mean stationary wave influences anomalous Rossby wave trains or teleconnection patterns as often observed during ENSO events.Evidences from those ensemble simulations argue that ENSO anomalies,especially over Pacific-North America (PNA) region,appear to be a result of modification for climatological mean stationary wave forced by persistent tropical SST anomalies Therefore,the role of SST forcing in maintaining climate basic state is emphasized.In this argument,the interaction between atmospheric internal dynamics and external forcing,such as SST is a key element to understand and ultimately predict ENSO.
