全球变暖情景下西北太平洋地区台风活动背景场气候变化的预估

A projection of future climate change over the western North Pacific related to typhoon activities.

中文关键词:  全球变暖， SRES A2， 耦合模式， 西北太平洋， 台风活动

英文关键词:Global warming, SRES A2, GCM, Western North Pacific, Typhoon activities

中文摘要:

      为了分析在全球变暖的情景下西北太平洋地区（WNP）可能发生的气候变化，从而为该地区 台风活动的未来变化提供必要的背景信息，文中选取了18个参加CMIP3试验的全球海气耦合 模式,考查了在SRES A2试验中21世纪末 (2080—2099年)相对于20C3M试验中20世纪末（1980—1 999年）对台风活动有重要影响的环境场包括海表面温度(SST)、纬向风的垂直切变（MWS）、海平面气压（SLP）、大气顶向外的长波辐射（OLR）和降水在WNP的变化情况。主要分析了多模式集合的结果以及环境场的变化在模式间的一致性。结果表明：到21世纪末，所有模式在西北太平洋区域SST都是一致的升高趋势，增幅在2 ℃以上，SST的变化是所有考虑的变量中在模式间一致性最好的，绝大部分区域信噪比都在4以上；降水在整个WNP区域也是一致增强的趋势，在赤道低纬度地区增幅较强，其变化在模式间的一致性较好，大部分区域18个模式中超过12个表现出降水增加的变化，在这些区域信噪比大都在0.6以上；SLP的变化特征主要表现为高低压系统的强度均为减弱的趋势，其中低压的减弱在模式间有着更好的一致性，大部分区域的信噪比都大于0.6；MWS和OLR在空间上没有一致的变化趋势，而且在不同的模式间变化的差异较大，大部分区域的信噪比都在0.3左右。但是在与台风活动有显著负相关的关键区内，大部分模式区域平均的MWS和OLR在SRES A2试验中都变小，多模式集合也是减弱的趋势。从SST、降水、关键区的MWS和OLR的分析来看，在全球变暖的情景下，环境场的变化可能是有利于台风活动的。但是目前关于环境场对于台风活动的影响和相互关系还缺乏 足够的认识，环境场的变化对于台风活动会有怎样的具体影响还有待进一步深入分析。

英文摘要:

      In order to investigate possible climate change over the western North Pacific (WNP) under global warming scenario, which is the background for the projection of future typhoon activities, outputs of 18 GCMs from the CMIP3 multi model dataset are emplo yed. The background fields considered in this paper include the sea surface temperature (SST), the magnitude of vertical zonal wind shear (MWS), the sea level pressure (SLP), the outgoing longwave radiation (OLR) and the precipitation. These fields are all closely related to typhoon activities. We compare the changes of these fields during typhoon season (June to October) between SRES A2 experiment and 20C3M experiment for the two periods of 2080-2099 and 1980-1999. The analyses of the change in the multi model ensemble (MME) and the consistency among the models are mainly presented in this paper. The results show that there is a warming in SST over the entire WNP area with increment larger than 2 ℃. And all the 18 models show the same tendency. The signal to noise ratio for SST is larger than 4 over most of the area. The precipitation in the MME also increases over the entire WNP area with larger change over the lower latitudes. More than 12 models show more precipitation over most of the WNP area, where the signal to noise ratio is mostly larger than 0.6. For the projection of SLP, both of the high and low pressure systems become weaker in SRES A2 and the change in low pressure area is more robust among the models with signal to noise ratio mainly larger than 0.6. There are no consistent changes in the MWS and the OLR over the entire WNP. And the spread of projection in the different models is larger than that in the other variables. The signal to noise ratio for both the MWS and the OLR is about 0.3 for most of the WNP area. But over the key areas where there are significant negative correlations between the MWS, the OLR and the typhoon frequency in the observations, the area averaged MWS and OLR in the MME decrease in SRES A2, and most of the 18 model shows the same tendency. Changes in the SST, precipitation, MWS and OLR over the key areas could imply that the background fields become favorable to typhoon activities in global warming secnario. But nowadays, the mechanism of the influence of large scale environmental factors on the tropical cyclone behaviours still remains to be fully understood, so it is needed to further analyse how exactly the typhoon activities react to the change in background fields.