白令海峡入流水影响下的楚科奇海海冰面积时空变化特征

利用美国国家冰雪中心的Bootstrap海冰密集度卫星遥感资料分析1991—2015年楚科奇海海冰覆盖面积的时空变化特征,并探讨白令海峡入流水对海冰面积变化的作用机制。楚科奇海海冰覆盖面积月距平以0.7%×a~(–1)的速度减小,从2002年开始维持负距平特征。白令海峡入流水的热通量及其在楚科奇海的环流路径显著影响楚科奇海海冰的时空变化。海冰面积变化与入流水热通量具有高相关性(R=–0.86),夏季(5—8月)两者的相关性更加显著,热通量增加对海冰面积显著减小起关键作用。楚科奇海海冰分布减小的区域与白令海峡入流水环流特征和分布关系密切, 5—7月海冰分布在入流水三条主要流动路径上(海渃德海谷、中央通道、巴罗海谷)的季节特征和年际变化最为显著。海冰面积及分布对入流水的响应均有1—2月的滞后。     

北欧海中尺度涡旋特征分析

基于Nencioli等的涡旋判定方法,借助于高分辨率卫星高度计反演的地转流异常数据和海平面异常数据,对北欧海域2012年的中尺度涡旋进行了识别和对比验证,并系统分析了该海域中尺度涡旋的空间分布、生命周期、半径范围和运移路径及速度等基本特征。结果显示,在北欧海域,选取网格间距a=3,b=2进行涡旋识别所得到的位置与海表高度的正负异常几乎一一对应,表明结果是可信、可靠的。北欧海域存在生命周期2周以上的气旋涡280个,反气旋涡316个,其中生命周期大于4周的涡旋数量约有20%。该海域中尺度涡旋主要集中分布在寒暖流交汇区和挪威沿岸海域,受大尺度环流影响,0°经线以东海域的涡旋呈向南移动的趋势,约有40%的涡旋移动速度为10cm·s-1,最大可达20cm·s-1,而沿岸海域的涡旋受地形影响,呈原地旋转的运动状态。     

基于无线电探空和无线电掩星观测的北极上层气温研究

The air temperature is one of the most important parameters used for monitoring the Arctic climate change. The constellation observing system for meteorology, ionosphere, and climate and Formosa Satellite Mission 3(COSMIC/FORMOSAT-3) radio occultation(RO) "wet" temperature product(i.e., "wet Prf") is used to analyze the Arctic air temperature profiles at 925–200 hPa in 2007–2012. The "wet" temperatures are further compared with radiosonde(RS) observations. The results from the spatially and temporally synchronized RS and COSMIC observations show that their temperatures agree well with each other, especially at 400 hPa. Comparisons of seasonal temperatures and anomalies from the COSMIC and homogenized RS observations suggest that the limited number of COSMIC observations during the spatial matchup may be insufficient to describe the smallscale spatial structure of temperature variations. Furthermore, comparisons of the seasonal temperature anomalies from the RS and 5°×5° gridded COSMIC observations at 400 hPa during the sea ice minimum(SIM) of2007 and 2012 are also made. The results reveal that similar Arctic temperature variation patterns can be obtained from both RS and COSMIC observations over the land area, while extra information can be further provided from the densely distributed COSMIC observations. Therefore, despite COSMIC observations being unsuitable to describe the Arctic temperatures in the lowest level, they provide a complementary data source to study the Arctic upper-air temperature variations and related climate change.