排序方式： 共有16条查询结果，搜索用时 15 毫秒
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利用ERA-Interim再分析资料、NOAA海温资料、CMAP格点降水资料和中国气象站降水资料,通过合成、相关和回归分析等方法研究了1979—2012年东亚夏季风强度与其先兆信号的关系,并分析了热带海温异常的可能影响。研究表明:东亚夏季风先兆指数反映了2月200 hPa纬向风距平的主要模态特征 (EOF1),前冬热带中东太平洋海温偏低 (高),2月亚洲地区西风急流位置偏北 (偏南),东亚夏季风先兆指数偏强 (弱)。前期热带海温异常对东亚夏季风强度有明显影响,前冬热带中东太平洋海温偏低 (高) 有利于东亚夏季风偏强 (弱)。2月亚洲中纬度地区纬向风异常特征在春季不能持续,先兆信号与东亚夏季风强度的联系主要源自热带海洋。 相似文献
2.
中国地质学会第40届理事会提出了将中国地质学会建设成为国内领先、世界一流学会的设想。为实现这一目标,本文将中国地质学会与美国地质学会、英国地质学会、澳大利亚地质学会、加拿大地质学会等4家地质领域世界领先学会进行了对比分析,找出了差距,明确了目标,并对如何将中国地质学会建成国内领先、世界一流学会提出了对策和建议。 相似文献
3.
<正>2017年8月20日,中国地质学会召开第16届青年地质科技奖(金、银锤奖)终评会议,评选产生了第16届青年地质科技奖(金、银锤奖)获奖者。会议决定授予10位青年地质学家"第16届青年地质科技奖——金锤奖"荣誉称号,授予40位青年地质学家"第16届青年地质科技奖——银锤奖"荣誉称号(名单见后)。 相似文献
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The extratropical transitions(ETs)of tropical cyclones(TCs)over China and the ocean east to 150°E are investigated by the use of best-track data and JRA-25 reanalysis spanning 1979-2008.The ET events occurring north of 25°N and in the warm season(from May to October)are extracted from the reanalysis to emphasize the interaction between TC and midlatitude circulation.Statistical analysis shows that 18.5%of the warm-season TCs go through land ETs north of 25°N in the western North Pacific.And 20.5%of the ET events occur over the ocean east of 150°E.Most(62.2%)ET TCs over China gradually die out after ET,but more(70.7%)ocean ET cases have post-ET reintensification.The evolutions in cyclone phase space and the composite fields for land and ocean ETs,as well as the ET cases with and without post-ET reintensification,are further analyzed.It is found that most TCs with ET over China and those without post-ET reintensification evolve along the typical ET phase path as follows:emergence of thermal asymmetry→losing upper-level warm core→losing lower-level cold core→evolving as extratropical cyclone.The TCs undergoing ETs over ocean and those with post-ET reintensification form a high-level cold core before the ET onset.The TCs with land ET have long distance between the landing TC and a high-level trough.That makes the TC maintain more tropical features and isolates the TC flow from the upstream and downstream jets of the midlatitude trough.The structure of circulation leads to weak development of baroclinicity in land ET.On the contrary,shorter distance between ocean TC and high-level trough makes the high-level trough absorb the TC absolutely.Under that baroclinicity-favorable environment,strong cold advection makes the TC lose its high-level warm core before ET onset.The composite fields confirm that the TC with ocean ET has stronger baroclinic features.Generally,the TC at land ET onset is located to the south of the ridge of the subtropical high,which tends to prevent the TCs from interacting with midlatitude circulation.But for the ocean ET,the situation is just the opposite.Similar analyses are also carried out for the TCs with and without post-ET reintensification over both land and ocean east of 150°E.The results further prove that the TC with stronger baroclinic characteristics,especially in the circumstance favorable to its interaction with high-level midlatitude systems,has more opportunity to reintensify as an extratropical cyclone after ET. 相似文献
5.
华西地区（25°N～35°N,100°E～110°E）是中国秋季降水主要地区之一。本文根据华西地区72站月平均降水资料、NCEP/NCAR再分析资料和哈德莱中心海温及海冰资料,利用相关和回归等分析方法研究了1961～2014年华西地区秋雨的年代际变率及其与大气环流和海温的关系。华西秋季降水年代际变率分解为呈现显著下降趋势的P1时段（1964～1998年）和呈现上升趋势的P2时段（1998～2014年）发现,对应P1时段降水下降趋势的华西区域大气位势高度异常场具有西正东负结构,大尺度环流场显示为从大西洋东传经北极巴伦支—喀拉海区至东亚的准纬向波列,该波列体现了上游负位相NAO（North Atlantic Oscillation）的调制作用。对于P2时段的降水上升趋势,其位势高度场配置与P1时段相反,而大尺度波列结构在欧亚大陆的部分呈西北—东南走向,且整体偏西,体现了上游正位相NAO的调制作用。这种环流结构导致华西区域西北侧形成负异常中心,有利于西南暖湿气流进入研究区域。影响华西秋雨趋势转折的海温关键区位于热带中东太平洋和热带印度洋。在P1时段,华西秋雨降水趋势与同期热带中东太平洋和印度洋海温呈显著正相关关系。而在P2时段,华西秋雨与前冬热带中东太平洋和印度洋海温存在显著负相关,前冬西北太平洋海温正异常也同时影响了华西秋雨的上升趋势。 相似文献
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A CLIMATOLOGY OF EXTRATROPICAL TRANSITION OF TROPICAL CYCLONES IN THE WESTERN NORTH PACIFIC 总被引：1，自引：1，他引：0
Based on best-track data and JRA-25 reanalysis, a climatology of western North Pacific extratropical
transition (ET) of tropical cyclone (TC) is presented in this paper. It was found that 35% (318 out of 912) of all
TCs underwent ET during 1979–2008. The warm-season (June through September) ETs account for 64% of all ET events
with the most occurrence in September. The area 120°E–150°E and 20°N–40°N is the most favorable region for ET
onsets in western North Pacific. The TCs experience ET at latitudes 30°N–40°N and have the greatest intensity in
contrast to other latitude bands. The distribution of ET onset locations shows obviously meridional migration in
different seasons. A cyclone phase space (CPS) method was used to analyze the TC evolution during ET. Except for
some cases of abnormal ET at relatively high latitudes, typical phase evolution paths—along which TC firstly
showed thermal asymmetry and an upper-level cold core and then lost its low-level warm core—can be used to
describe the main features of ET processes in western North Pacific. Some seasonal variations of ET evolution paths
in CPS were also found at low latitudes south of 15°N, which suggests different ET onset mechanisms there. Further
composite analysis concluded that warm-season ETs have generally two types of evolutions, but only one type in cold
season (October through next May). The first type of warm-season ETs has less baroclinicity due to long distance
between the TC and upper-level mid-latitude system. However, significant interactions between a mid-latitude upper
-level trough and TC, of either approaching or being absorbed into the trough, and TC’s relations with downstream
and upstream upper-level jets, are the fingerprints for both a second type of warm-season ETs and almost all the
cold-season ETs. For each type of ETs, detailed structural characteristics as well as precipitation distribution
are illustrated by latitude. 相似文献
8.
应用台站观测资料对ERA-40, NCEP/NCAR以及NCEP/DOE再分析地表气压产品在中国不同区域、不同年代和不同季节的适用性进行了评估。分析发现, 几种再分析产品虽然能在一定程度上反映出观测资料所具有的时空分布特征, 但它们之间的差异却具有明显的区域和季节变化特征, 即冬季小而夏季大、东部地区小而西部地区大; 同时还发现ERA-40和NCEP/NCAR再分析产品在20世纪70年代以前均与观测资料有相对较大的差别, 特别是NCEP/NCAR在70年代以前的夏季气压值过于偏低, 从而夸大了很多地区的年代际变化特征。相比而言, ERA-40地表气压的长期变化趋势以及时空演变规律在中国大多数地区要优于NCEP/NCAR再分析产品, 特别是在中国西部地区。分析还表明, NCEP/DOE虽与观测资料存在一定的系统性偏差, 却与另外两种再分析产品有着较为相似的年际变化特征及趋势。 相似文献
9.
中国东部地区大城市和小城镇极端温度及日较差变化对比分析 总被引：22，自引：2，他引：22
利用中国东部地区1961～2000年61个大城市站点和169个小城镇站点的逐日最高、最低温度资料,对比分析了大城市和小城镇的最高、最低温度和日较差极端值以及相对极端值变化特征.结果表明:大城市最高、最低温度的极端值均高于小城镇.二者最高温度的极端最大值在90年代后显著升高,极端最小值40年来均显著增加;二者最低温度的极端值也随时间明显升高.在所分析时段,大城市和小城镇暖日和暖夜天数均显示出增多趋势;二者冷日和冷夜天数均呈现下降趋势.就总体而言,大城市暖日、暖夜、冷日、冷夜天数均多于小城镇.大城市日较差的极端值均比小城镇小,并且二者均有显著的下降趋势;大城市和小城镇相对较长日较差(日较差超过第95个百分位数)出现的天数显著下降,但相对较短日较差(日较差低于第5个百分位数)出现的天数明显上升. 相似文献
10.
利用多通道奇异谱方法（MSSA）分析了1953~2003年亚洲和北美Palmer干旱指数（PDSI）与热带和北半球温带海洋海表面温度异常（SSTA）的主要周期振荡特征及其相互联系.结果表明：亚洲和北美PDSI以及SSTA均存在明显的3~6年的年际以及10年左右的年代尺度振荡;此外,亚洲PDSI还存在显著的6~8年的年际振荡.SSTA的年际振荡主要体现了ENSO的变化特征,而其年代尺度振荡的空间分布具有热带太平洋和北太平洋共同作用的类ENSO型.同时,MSSA的分析结果给出了亚洲和北美主要振荡信号的时间和空间演变特征.相关性分析表明,亚洲和北美PDSI的年际及年代尺度振荡均显示明显的对SSTA强迫信号的响应.对于年际振荡,亚洲PDSI对SSTA响应强于北美,但年代尺度振荡则反之.此外,亚洲和北美PDSI对于SSTA信号响应的关键区域也随时间尺度的不同而发生变化.亚洲的西西伯利亚、青藏高原东西两侧以及中西伯利亚东部在年际和年代尺度上均为受SSTA影响最显著的区域;在年际尺度上,北美中部地区的干湿变化与SSTA存在显著相关,而在年代尺度上,美国西部更易受SSTA年代尺度振荡的影响. 相似文献