利用耦合了CLM4(Community Land Model)的CAM5.1(Community Atmosphere Model)模式研究了中国东部地区城市范围扩展对东亚春季气候的可能影响.结果表明城市化改变了地面能量平衡,表现为地面净辐射通量和感热通量增加,地面潜热通量减小,造成近地面温度、日最高气温和最低气温升高,气温日较差增大,且近地面增温的幅度与城市比例密切相关,但对城市范围扩展的响应具有一定程度的不确定性.城市范围扩展所引起的近地面热力强迫可以影响到东亚地区低层大气环流,但由于近地面对不同程度城市范围扩展的热力响应具有非线性变化,导致东亚春季低空环流的变化也具有一定的不确定性,但其总体上会减弱长江中下游以南地区的西南气流.因此,中国东部地区的城市范围扩展会使得长江以北地区春季降水量偏少而长江以南地区降水量偏多,造成东亚春季雨带南移.
The eff ect of anthropogenic aerosols on the spring persistent rain （SPR） over eastern China is investigated by using a high-resolution Community Atmosphere Model version 5.1 （CAM5.1）. The results show that the SPR starts later due to anthropogenic aerosols, with a shortened duration and reduced rainfall amount. A reduction in air temperature over the low latitudes in East Asia is linked to anthropogenic aerosols;so is a weakened southwesterly on the north side of the subtropical high. Meanwhile, air temperature increases signifi cantly over the high latitudes. This north-south asymmetrical thermal eff ect acts to reduce the meridional temperature gradient, weakening the upper-level westerly jet over East Asia and the vertical motion over southeastern China. As a result, the SPR is reduced and has a much shorter duration. The indirect eff ect of anthropogenic aerosols also plays an important role in changing the SPR. Cloud droplet number concentration increases due to anthropogenic aerosols acting as cloud condensation nuclei, leading to a reduction in cloud eff ective radius over eastern China and a reduced precipitation effi ciency there.
There are two types of ENSO,namely,the eastern Pacific（EP） ENSO that is characterized by the warmest（coldest） SST anomalies in the eastern equatorial Pacific,and the central Pacific（CP） ENSO whose maximum（minimum） SST anomalies are over the central equatorial Pacific.Asymmetric features of SST anomalies for the EP and CP types of ENSO events and their possible mechanisms were analyzed by using a variety of data during the period 1961-2010.The responses of atmospheric circulation to the two types of ENSO were also discussed.The results showed asymmetric features of SST anomalies in terms of spatial and temporal distributions and intensity.Although the dominant mechanisms differed at both development and decay stages,the oceanic vertical advection played a key role in the asymmetric intensity of the two ENSO events.In addition,both local and remote atmospheric responses showed strong asymmetric signals,which were consistent with the asymmetric distribution of SST anomalies.The asymmetric atmospheric responses in EP-ENSO（CP-ENSO） were similar to those associated with EP-El Nino（CP-La Nina）.The intensity of asymmetric responses related to the EP-ENSO was much stronger than that related to the CP-ENSO.
