A possible reason for the unreasonable simula- tion of maximum rainfall location, intensity and seasonal evolution over eastern China in CCM3 has been investigated. The analyses focus on the relationship between the s...A possible reason for the unreasonable simula- tion of maximum rainfall location, intensity and seasonal evolution over eastern China in CCM3 has been investigated. The analyses focus on the relationship between the simulated East Asian subtropical westerly jet biases and the seasonal evolution of rainbelt over eastern China. Comparisons of the simulated and observed precipitation distributions indicate that the simulated maximum rainfall location, intensity and seasonal evolution are inconsistent with reality. The simu- lated westerly jet center is located to the north of 40°N, which shifts eastward and northward and strengthens, com- pared with NCEP/NCAR reanalysis. The correlation analysis shows that there exists a significant positive correlation be- tween the maximum rainfall amount and zonal wind at 200 hPa over the Great Bend of the Huanghe River. Thus the simulated unrealistic heavy precipitation in the inland area of western China is related to the biases in the location and intensity of the East Asian subtropical westerly jet. Further analysis indicates that the temperature differences from south to north in the lower troposphere and the larger sensi- ble heating over the southeast Tibetan Plateau are responsi- ble for the westerly jet location and intensity biases. There- fore, much more attention should be paid to the accurate simulation of the surface heating near the Tibetan Plateau and the location and intensity of the East Asian subtropical westerly jet for the improvement of precipitation simulation over East Asia.展开更多
Zonal wind anomaly over the equatorial west- ern Pacific plays an important role in the occurrence of ENSO. The mechanism to produce zonal wind anomaly over the equatorial western Pacific is studied in this paper. It ...Zonal wind anomaly over the equatorial west- ern Pacific plays an important role in the occurrence of ENSO. The mechanism to produce zonal wind anomaly over the equatorial western Pacific is studied in this paper. It is shown clearly that zonal wind anomaly over the equatorial western Pacific is closely related to the anomaly of East- Asian winter monsoon. Anomalous strong (weak) East-Asian winter monsoon can excite not only the westerly (easterly) anomaly over the equatorial western Pacific but also a cyc- lonic (an anticyclonic) circulation over the east of the Philip- pines. The above anomalous circulation results from dy- namical impacts of anomalous pressure pattern due to the East-Asian winter monsoon. Because there is westward (eastward) pressure gradient over the equatorial western Pacific, i.e. there is ?? xp <0(> 0), during strong (weak) East-Asian winter monsoon.展开更多
基金supported jointly by the National Natural Science Foundation of China(Grant No.40333026)the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.ZKCX2-SW-210)
文摘A possible reason for the unreasonable simula- tion of maximum rainfall location, intensity and seasonal evolution over eastern China in CCM3 has been investigated. The analyses focus on the relationship between the simulated East Asian subtropical westerly jet biases and the seasonal evolution of rainbelt over eastern China. Comparisons of the simulated and observed precipitation distributions indicate that the simulated maximum rainfall location, intensity and seasonal evolution are inconsistent with reality. The simu- lated westerly jet center is located to the north of 40°N, which shifts eastward and northward and strengthens, com- pared with NCEP/NCAR reanalysis. The correlation analysis shows that there exists a significant positive correlation be- tween the maximum rainfall amount and zonal wind at 200 hPa over the Great Bend of the Huanghe River. Thus the simulated unrealistic heavy precipitation in the inland area of western China is related to the biases in the location and intensity of the East Asian subtropical westerly jet. Further analysis indicates that the temperature differences from south to north in the lower troposphere and the larger sensi- ble heating over the southeast Tibetan Plateau are responsi- ble for the westerly jet location and intensity biases. There- fore, much more attention should be paid to the accurate simulation of the surface heating near the Tibetan Plateau and the location and intensity of the East Asian subtropical westerly jet for the improvement of precipitation simulation over East Asia.
基金supported by the National Natural Science Foundation of China(Grant No.40233033)the Blazing New Trails Program of the Chinese Academy of Sciences(Grant No.ZKCX3-SW-226).
文摘Zonal wind anomaly over the equatorial west- ern Pacific plays an important role in the occurrence of ENSO. The mechanism to produce zonal wind anomaly over the equatorial western Pacific is studied in this paper. It is shown clearly that zonal wind anomaly over the equatorial western Pacific is closely related to the anomaly of East- Asian winter monsoon. Anomalous strong (weak) East-Asian winter monsoon can excite not only the westerly (easterly) anomaly over the equatorial western Pacific but also a cyc- lonic (an anticyclonic) circulation over the east of the Philip- pines. The above anomalous circulation results from dy- namical impacts of anomalous pressure pattern due to the East-Asian winter monsoon. Because there is westward (eastward) pressure gradient over the equatorial western Pacific, i.e. there is ?? xp <0(> 0), during strong (weak) East-Asian winter monsoon.
