南海夏季风活动激发的大气遥相关型

北半球夏季,南海地区是全球大气热状况变化最为激烈的区域之一,而南海夏季风则是该地区最为活跃的天气事件,它的演变必将导致其它地区大气环流的响应．通过相关计算、合成分析等手段,揭示与南海夏季风活动相关联的北半球大气遥相关型的存在．该波列状的遥相关型与东亚地区相连,经北太平洋延伸至北美西岸．最高的相关位于西太平洋副热带高压区域,因而它可能对我国旱涝天气产生重要影响．     

Sea surface temperature east of Australia： A predictor of tropical cyclone frequency over the western North Pacific？

The relationship between sea surface temperature (SST) east of Australia and tropical cyclone frequency over the western North Pacific (WNPTCF) is analyzed by use of observation data.The WNPTCF from June to October is correlated negatively to spring SST east of Australia.When the spring SST is in the positive phase,a cyclonic circulation anomaly in the upper troposphere and an anticyclonic circulation anomaly in the lower troposphere prevail over the western North Pacific from June to October,concurrent with an anomalous atmospheric subsidence and an enlarged vertical zonal wind shear.These conditions are unfavorable for tropical cyclone genesis,and thus WNPTCF decreases.The negative phase of the spring SST east of Australia leads to more tropical cyclones over the western North Pacific.The spring SST east of Australia may give rise to simultaneous change in tropical atmospheric circulation via the teleconnection wave train,and then subsequently affect atmospheric circulation variation over the western North Pacific.     

季节因素对气候网络影响研究

气候网络在地球科学领域研究中是一个新的热点,对于分析和揭示气候场的特征及关联结构具有较强优势.已有气候网络的构建一般选取冬季月份的样本数据,而且在研究中忽略了其他季节月份对气候网络的影响.本文研究了季节因素对气候网络的影响,研究发现:气候网络在不同季节的整体特征参数基本保持稳定,但是网络社团结构以及局部节点拓扑连接随季节变化显著.可以利用这一结论来研究不同季节全球遥相关模态变化情况以及局部地区气候特征随季节变化情况.     

Stable H and O isotope-based investigation of moisture sources and their role in river and groundwater recharge in the NE Carpathian Mountains,East-Central Europe†

The region situated between the mountain area and the lowlands in NE Romania (East-Central Europe) is experiencing increased competition for water resources triggered by a growing population, intensification of agriculture, and industrial development. To better understand hydrological cycling processes in the region, a study was conducted using stable isotopes of water and atmospheric trajectory data to characterize regional precipitation and vapour sources derived from the Atlantic Ocean, Mediterranean and Black Seas, as well as recycled continental moisture, and to assess and partition these contributions to recharge of surface and groundwater. Atmospheric moisture in the lowlands is found to be predominantly delivered along easterly trajectories, while mountainous areas appear to be dominated by North Atlantic Ocean sources, with moisture transported along mid-latitude, westerly storm tracks. Large-scale circulation patterns affect moisture delivery, the North Atlantic Oscillation being particularly influential in winter and the East Atlantic pattern in summer. Winter precipitation is the main contributor to river discharge and aquifer recharge. As winter precipitation amounts are projected to decrease over the next decades, and water abstraction is expected to steadily increase, a general reduction in water availability is projected for the region.     

南海及周边地区对流活动的时空变化及其与长江流域夏季降水的遥相关

利用美国 NCEP 1 95 8～ 1 998年高斯网格月平均再分析的向外长波辐射 ( OLR)资料和中国国家气象中心的全国 1 60站 1 95 1～ 1 998年月平均降水资料 ,分析了南海及周边地区 (以下简称南海地区 ) ( 0°N～2 0°N,1 0 0°E～ 1 2 5°E)对流活动的时空变化及和长江流域夏季降水的遥相关关系。结果表明 :南海地区对流活动具有明显的季节转换特征 ,主要呈一致性的分布形势 ,具有多时间尺度的变化特征 ,不同时间尺度振动的周期显著性和强度存在明显的年际差异。SVD分析表明 ,南海地区夏季对流活动与中国长江流域夏季降水密切相关。     

Spatial teleconnection pattern between Indian Ocean Dipole and the southern high-latitude sea level pressure field

Sea level pressure (SLP) anomalies over the southern high latitudes associated with the Indian Ocean Dipole Mode (IOD) are investigated. Partial correlation and composite analysis depict, for the first time, the seasonal spatial variability in the relationship of SLP field in Southern Ocean with IOD. Results suggest that the IOD signal exists in the southern high latitudes and it is enhanced in boreal autumn, an active season of IOD. On interannual to subdecadal timescales, the spatial teleconnection pattern exhibits a wavenumber-3 pattern around the circumpolar Southern Ocean and the lead-lag correlation analysis shows that there are about 3 months of SLP anomalies in southern high latitudes lagging IOD, which indicates that the response time is almost instantaneous.     

A dynamic view of the tropospheric teleconnection between IOD and the Pacific Ocean

The tropospheric teleconnection pattern between the Indian Ocean Dipole （IOD） and the Pacific Ocean was studied using GISST and NECP/NCAR reanalysis data. Results show that a structure of Rossby wave train extends from the tropical Indian Ocean over southern subtropical regions of Australia and Pacific Ocean to the tropical Pacific Ocean, where a strong correlation between IOD and geopotential height （GH） anomaly of Pacific Ocean exists. Energy propagating pathways of the planetary wave with wave numbers 1-3 are qualitatively in agreement with the Rossby wave train, which implies that the energy propagation of the stationary planetary wave could be responsible for the tropospheric teleconnection between IOD and tropical Pacific Ocean.     

Linkage between winter sea surface temperature east of Australia and summer precipitation in the Yangtze River valley and a possible physical mechanism

The relationship between winter sea surface temperature (SST) east of Australia and summer precipitation in the Yangtze River valley and a possibly related physical mechanism were investigated using observation data. It is found that winter SST east of Australia is correlated positively to summer precipitation in the Yangtze River valley. When the SST east of Australia becomes warmer in winter, the western Pacific subtropical high and the East Asian westerly jet tend to shift southward the following summer, concurrent with low-level southwesterly anomalies over eastern China. These conditions favor precipitation increase in the Yangtze River valley, whereas the opposite conditions favor precipitation decrease. The influence of winter SST east of Australia on East Asian summer atmospheric circulations may occur in two ways. First, by an anomalous SST signal east of Australia in winter that persists through the following summer, thus affecting East Asian atmospheric circulations via the inter-hemispheric teleconnection. Second, when the SST east of Australia is warmer in winter, higher SST appears simultaneously in the southwest Indian Ocean and subsequently develops eastward by local air-sea interaction. As a result, the SST in the Maritime Continent increases in summer, which may lead to an anomalous change in East Asian summer atmospheric circulations through its impact on convection.     

Relationship between Hadley circulation and sea ice extent in the Bering Sea

The linkage between Hadley circulation （HC） and sea ice extent in the Bering Sea during March-April is investigated through an analysis of observed data in this research. It is found that HC is negatively correlated to the sea ice extent in the Bering Sea, namely, strong （weak） HC is corresponding to less （more） sea ice in the Bering Sea. The present study also addresses the large-scale atmospheric general circulation changes underlying the relationship between HC and sea ice in the Bering Sea. It follows that a positive phase of HC corresponds to westward located Aleutian low, anomalous southerlies over the eastern North Pacific and higher temperature in the Bering Sea, providing unfavorable atmospheric and thermal conditions for the sea ice forming, and thus sea ice extent in the Bering Sea is decreased, and vice versa. In addition, it is further identified that East Asian-North Pacific-North America teleconnection may play an important role in linking HC and changes of atmospheric circulations as well as sea ice in the Bering Sea.     

末次冰盛期青藏高原冰川变化对亚洲气候的影响

以末次冰盛期(约2.6~1.9万年前)的气候为背景, 利用大气模式CAM4耦合陆面模式CLM4, 对青藏高原冰川规模扩大对气候产生的影响进行研究。结果表明, 末次冰盛期青藏高原冰川对北半球夏季的气候影响较显著, 除在冰川分布区引起显著的降温外, 通过遥相关作用, 还使得白令海峡附近显著升温。另外, 冰川产生的扰动会显著地增强南亚夏季风, 增加南亚地区降水。对比末次冰盛期与工业革命前时期不同气候态下青藏高原冰川规模扩大对气候的影响, 发现工业革命前时期的影响显著小于末次冰盛期, 说明青藏高原冰川对气候的影响与背景气候态有关。