ENSO年代际变化对全球陆地生态系统碳通量的影响

使用动态植被陆面模式AVIM2，以NCEP (National Centers for Environmental Prediction)再分析气象资料作为大气强迫场，模拟了1953-2004年全球陆地生态系统净初级生产力(NPP)和净生态系统生产力(NEP) 的空间分布及时间变化特征。结果得到，1953-2004年陆地生态系统NPP和NEP全球总量52 a的C平均值分别为65 Pg/a和1.2 Pg/a，NPP呈明显的上升趋势，而NEP的上升趋势不明显。虽然NPP和NEP的年代际增长趋势不同，但是在20世纪70年代中期，NPP和NEP的年代际变化都出现了一个明显的突变，突变点后的增长趋势都没有之前的增长趋势高。这是由于太平洋的年代际振荡(PDO)冷暖位相影响了厄尔尼诺与南方涛动（El Nin~o Southern Oscillation，ENSO)的年代际变化，对NPP和NEP的年代际变化也产生了重要的影响。1976年以前PDO处于冷位相年，增加了ENSO冷位相的强度和频率，使热带地区的气候偏凉爽湿润，从而利于NPP和NEP趋势增长，而1976年以后PDO进入暖位相年，El Nin~o发生频繁，赤道地区多为干热的气候异常，会降低NPP和NEP的增长趋势。

Influences of the decadal variation of ENSO on the carbon flux in the terrestrial ecosystems

The Atmosphere Vegetation Interaction Model version 2(AVIM2)is used to make an offline simula-tion of terrestrial carbon cycle and its response to climatic variation under the forcing of the meteorological reanalysis data from the National Center for Environmental Prediction.The spatial distribution and its tempo-ral characteristics of global net primary production(NPP)and net ecosystem production(NEP)in the terres-trial ecosystem are simulated from 1953to 2004.Results show that 52-year averaged global NPP and NEP from 1953to 2004are 65Pgc/a and 1.2Pgc/a respectively,and reveal that NPP obviously increases with time,while the trend of increase in NEP is not statistically significant.Although the trends of decadal increases in NPP and NEP are different,in the middle of the 1970stheir decadal changes all revealed an abrupt change.Their growing trends were all decreased after the abrupt point.This is because the Pacific decadal oscillation(PDO)affected the decadal change of El Nin～o-Southern Oscillation(ENSO),which also affected the decadal variation of NPP and NEP.Before 1976,when PDO was in the cool phase,the strength and frequency of the cool phase of ENSO was increased,which led to the cooler and humid climate in the tropical region so that it was beneficial to the increase in NPP and NEP.On the contrary,while the PDO was in a warm phase after 1976,El Nin～o took place frequently,so that in the equatorial region the drier and warmer climate reduced the increasing trends of NPP and NEP.