Two Opposite Extreme Events in Seasonal Mean Winter Rainfall over East China during the Past Three Decades

In this study,the extremes of winter seasonal mean precipitation have been investigated by using daily precipitation data from 91 stations in East China,the National Centers for Environmental Prediction/the National Center for Atmospheric Research(NCEP/NCAR)monthly reanalysis,and sea surface temperature data from the Hadley Centre for 1979–2007.The largest anomalous rainfall amount was observed in regions south of the Yangtze River.In the most recent three decades,extreme events in the seasonal mean winter precipitation occurred in 1985 and 1997.Because it was influenced mainly by a La Ni a event,the precipitation in 1985 showed a deficit following a stronger winter monsoon.The rainfall amount in 1997 was influenced by El Ni o and was significantly larger than normal with a weaker winter monsoon.Both the circulation anomalies and wave energy dispersions during the winters of 1985 and 1997 differed significantly.In 1985,the North Atlantic Oscillation anomalously excited the Eurasian-Pacific teleconnection and circumglobal teleconnection phenomena.Consequently,Rossby wave energy propagated along the north and south branches of the westerlies,strengthening the East Asian trough along with a stronger winter monsoon,which facilitated the wintertime dry extreme in East China.In1997,however,Rossby wave energy propagated from low latitudes northeastward into the southern part of China,resulting in a weaker winter monsoon and the wettest winter.The results of this study will be helpful for future monitoring and prediction of extreme winter rainfall events in East China.     

热带海水温度多时间尺度变化特征分析

利用高时间分辨率热带海洋浮标站点观测资料,分析热带区域海水温度多时间尺度变化特征,研究海水温度的日变化、季节变化和季节内变化。结果表明:热带海表面温度(Sea Surface Temperature,SST)具有不对称性的日变化特征。SST日较差与天气状况关系密切。有降水日的SST日平均值和幅度均低于无降水日,其不对称性具有区域性差异。在不同ENSO位相年份下的SST日平均值和振幅变化具有区域性,太平洋西部(Western Pacific,WP)的平均值和振幅差距较小,太平洋东部(Eastern Pacific,EP)和印度洋(Indian Ocean,IO)区域在El Niňo年的日平均值和振幅均大于La Niňa年。SST随季节变化具有区域性特征,WP区域SST的日平均温度和振幅在秋季最大,冬季最小;而EP和IO区域的日平均温度和振幅在春季最大,夏季最小。且SST日变化幅度随季节变化显著,主要受太阳短波辐射、降水和风速随季节变化的调制。此外,在季节内振荡时间尺度上,海水温度在200 m深度内随时间呈周期性变化,海水温度出现最大变率的中心位于100～150 m的深度范围内。不同区域由于温跃层深度不同,最大变率位置也有所差别。对海水温度变化特征分析可以为海—气耦合模式提供观测依据,以便准确地评估模式对海水温度的模拟效果。     

A mirage at Regina

The Dirt Hills, located roughly forty miles to the southwest of the Regina Weather Office, at Regina, Saskatchewan, were clearly visible on the horizon in the early morning of the 29th day of August 1972 from the Regina Weather Office. This mirage was documented and a picture of it was taken.     

PROGRESSES AND PROSPECTS IN RESEARCH ON SEASON DIVISION AND SEASONAL CHANGES IN CHINA

Progresses in the research for season division and seasonal changes are reviewed systematically in this paper,which particularly introduces the results of a national natural science foundation project,"the nonlinear identification of seasonal changes and its responses to global warming".The project developed two objective and quantitative methods for season division:the non-linear similarity measure(NSM) method and the regional multi-element optimal dissection(RMOD) method,which differ from traditional ones for season division.Besides,the project further investigated seasonal changes and their responses to global warming,analyzed evolution characteristics of the starting date and length of seasons in history,revealed their relationships with extreme events and precipitation patterns in rainy seasons,and thereby built a research system for seasonal changes in China under the global warming background.Finally,the authors make an outlook on the research for season division and seasonal changes and put forward several issues associated with season and climate changes that need to be further explored.     

Transition of Zonal Asymmetry of the Arctic Oscillation and the Antarctic Oscillation at the End of 1970s

In this study,the interdecadal changes in the zonal symmetry of both Arctic Oscillation(AO) and Antarctic Oscillation(AAO) were analyzed.To describe the zonal asymmetry,a local index of AO and AAO was defined using the normalized sea level pressure(SLP) differences between 40° and 65°(latitudes) in both hemispheres.The zonal covariability of local AO and AAO can well represent the zonal symmetry of AO and AAO.Results show that the zonal asymmetry of both AO and AAO significantly changed in the late 1970s.AO was less asymmetric in the zonal direction in the boreal winter season during the latter period,while in the boreal summer it became more asymmetric after 1979.The zonal symmetry of AAO in both austral summer and winter has also significantly decreased since the late 1970s.These changes may imply interdecadal transition in the atmospheric circulation at middle and high latitudes,which is of vital importance to understanding climate variability and predictability across the globe,including the African-Asian-Australian monsoon regions.     

Model Evidence for Interdecadal Pathway Changes in the Subtropics and Tropics of the South Pacific Ocean

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.     

Light-Time Effect in the Eclipsing Binaries GO Cyg, GW Cep, AR Aur and V505 Sgr

Orbital period changes of the eclipsing binaries GO Cyg and GW Cep are explained by the light-time effect for the first time. New minima of the eclipsing binary AR Aur improve the predicted light-time orbit. The light-time orbit with the quadratic ephemeris of the binary matches the new observations of V505 Sgr better than the linear one. As the light-time effect fits in corresponding O − C diagrams of all four systems have been reaching extreme values, the observations of minima times in forthcoming years are highly desirable.     

PERMAFROST CHANGES AND ENVIRONMENTAL PROBLEMS ALONG THE QINGHAI－XIZANG HIGHWAY

ＰＥＲＭＡＦＲＯＳＴＣＨＡＮＧＥＳＡＮＤＥＮＶＩＲＯＮＭＥＮＴＡＬＰＲＯＢＬＥＭＳＡＬＯＮＧＴＨＥＱＩＮＧＨＡＩ－ＸＩＺＡＮＧＨＩＧＨＷＡＹ￥ＷａｎｇＳｈａｏｌｉｎｇ（王绍令）（ＬａｎｚｈｏｕＩｎｓｔｉｔｕｔｅｏｆＧｌａｃｉｏｌｏｇｙａｎｄＧｅｏｃｒ...     

Weichselian sediments at Foss‐Eikeland,Jæren (southwest Norway): sea‐level changes and glaciation history

The Jæren area in southwestern Norway has experienced great changes in sea‐levels and sedimentary environments during the Weichselian, and some of these changes are recorded at Foss‐Eikeland. Four diamictons interbedded with glaciomarine and glaciofluvial sediments are exposed in a large gravel pit situated above the post‐glacial marine limit. The interpretation of these sediments has implications for the history of both the inland ice and the Norwegian Channel Ice Stream. During a Middle Weichselian interstadial, a large glaciofluvial delta prograded into a shallow marine environment along the coast of Jæren. A minor glacial advance deposited a gravelly diamicton, and a glaciomarine diamicton was deposited during a following marine transgression. This subsequently was reworked by grounded ice, forming a well‐defined boulder pavement. The boulder pavement is followed by glaciomarine clay with a lower, laminated part and an upper part of sandy clay. The laminated clay probably was deposited under sea‐ice, whereas more open glaciomarine conditions prevailed during deposition of the upper part. The clay is intersected by clastic dykes protruding from the overlying, late Weichselian till. Preconsolidation values from the marine clay suggest an ice thickness of at least 500 m during the last glacial phase. The large variations in sea‐level probably are a combined effect of eustasy and glacio‐isostatic changes caused by an inland ice sheet and an ice stream in the Norwegian Channel. Copyright © 2002 John Wiley & Sons, Ltd.     

Studies of community structure and seasonal dynamics of planktonic copepods in saline-alkaline ponds

Abstracts Species abundance and seasonal succession of copepods in saline-alkaline ponds were studied in Zhaodian Fish Farm, Gaoqing County, Shandong Province, from 5 April 1997 to 1 September 1998. The results indicated that in the conditions of salinity ranging from 1.36 to 20 g/L, total alkalinity changing from 2.4 to 7.2 mmol/L and pH 8-9, zooplankton in saline-alkaline ponds was composed of freshwater salt-tolerated species or halophile species, some of which are halobiont species and usually occurs in freshwater. In our study, copepods were predominant in many fish-culture ponds and all control ponds without fishes in spring, late autumn and early winter. Dominant species of copepods were Sinocalanus tenellus, Cyclops vicinus, Thermocyclops taihokuensis. The biomass of copepods in the control ponds without fishes was higher than that of the fish-culture ponds.