Japan suffered a M9.0 earthquake and massive tsunami on March 11, 2011, which seriously damaged the Fukushima Nuclear Power Plant and caused a nuclear crisis. The spread of nuclear radiation from the power plant through the atmosphere and ocean was predicted with a short-term climate forecasting model and an ocean circulation model under some idealized assumptions. If nuclear matter were leaked in the near-ground layer of 992 hPa, the climate model results show that the nuclear radiation would cover North America 10 days after the initial leakage, with the concentration at the forefront dramatically reduced to 10 millionths of the initial model concentration at the source. The radiation would span Europe in 15 days and cover much of the Northern Hemisphere in 30 days. If the initial leakage was assumed to occur in the layer 5000-m above the ground, the radiation would cover Europe in 10 days and cover much of the Northern Hemisphere in 15 days. Moreover, under the assumption that the nuclear matter leaked in the 10000-m layer, the radiation would affect much of China after 10 days. The ocean circulation model indicates that the nuclear material would be slowly transported northeast of Fukushima and reach 150°E in 50 days, and the nuclear debris in the ocean would be confined to a narrow band. Compared with the spread in the ocean, the area affected by leaked nuclear radiation in the atmosphere would be very large. Atmospheric monitors in North America and Europe will be helpful for estimating the effect in China of any leaked nuclear material.
QIAO FangLi WANG GuanSuo ZHAO Wei ZHAO JieChen DAI DeJun SONG YaJuan SONG ZhenYa
Numerical simulations using a version of the GFDL/NOAA Modular Ocean Model （MOM 3） are analyzed to demonstrate interdecadal pathway changes from the subtropics to the tropics in the South Pacific Ocean. After the 1976 -77 climate shift, the subtropical gyre of the South Pacific underwent significant changes, characterized by a slowing down in its circulation and a southward displacement of its center by about 5°- 10° latitude on the western side. The associated circulation altered its flow path in the northwestern part of the subtropical gyre, changing from a direct pathway connecting the subtropics to the tropics before the shift to a more zonal one after. This effectively prevented some subtropical waters from directly entering into the western equatorial Pacific. Since waters transported onto the equator around the subtropical gyre are saline and warm, such changes in the direct pathway and the associated reduction in equatorward exchange from the subtropics to the tropics affected water mass properties downstream in the western equatorial Pacific, causing persisted freshening and cooling of subsurface water as observed after the late 1970s. Previously, changes in gyre strength and advection of temperature anomalies have been invoked as mechanisms for linking the subtropics and tropics on interdecadal time scales. Here we present an additional hypothesis in which geographic shifts in the gyre structure and location （a pathway change） could play a similar role.
全球动态植被模型(CLM3.5-DGVM)是美国国家大气研究中心(NCAR)开发的陆面模式CLM3.5(CommunityLand Model Version3.5)的陆地碳循环子模块,模型本身根据当地的温度和降水等环境条件计算得出植被分布。本研究参照陆地-碳模式比较计划(C-LAMP)的模拟方案和评价标准,对CLM3.5-DGVM中的碳循环过程进行了模拟与检验。结果表明,CLM3.5-DGVM高估了陆地生态系统的叶面积指数(LAI)和净初级生产力(NPP),且在中高纬地区尤为明显;其模拟的LAI最大值与观测值相比在全球尺度上有1～6个月不等的位相偏差。CLM3.5-DGVM很好的模拟了NPP的全球分布以及总初级生产力(GPP)和感热通量(SH)的季节变化,但在北半球中高纬度地区对NPP模拟过高;对陆地碳通量的年际变率模拟较好,但高估了其振幅。
通过ICOADS(The International Comprehensive Ocean-Atmosphere Data Set)船测资料,验证了El Ni o引发的北印度洋(North Indian Ocean,NIO)海表温度(SST)的2次增暖过程。前人研究发现,第1次增暖发生在El Ni o盛期,源于El Ni o导致的大气环流变化产生了正的短波辐射及潜热通量异常;第2次增暖发生在El Ni o消亡的夏季,是由于反对称风场异常导致蒸发失热减少所造成。研究进一步发现,短波辐射和潜热通量在这两次增暖中都有着重要作用,但二者的作用在时间上并不一致。两次增暖过程都是短波辐射首先产生影响,其后才是风场导致的潜热通量的变化。两次增暖在东西两个海盆也存在差异,第1次增暖主要集中在阿拉伯海区域,第二次增暖在东西两个海盆都较明显。另外,通过El Ni o和La Ni a对比发现,ENSO对北印度洋SST的影响具有不对称性。El Ni o期间北印度洋产生2到3次增暖,而La Ni a只有第二年夏季的降温比较明显,强度也比较弱。
