A STUDY ON THE VARIATIONS OF CIRCULATION PATTERN IN THE NORTHERN HEMISPHERE AND CLIMATE CHANGE IN CHINA FOR THE RECENT 100 YEARS

The time series of annual frequency of the circulation patterns W,C,E in the Northern Hemisphere and annual mean temperature of Beijing (T_B),Shanghai (T_S) and the whole country (T_C) in the period 1891-1990 are expanded as a long-term tendency,a periodic function and a random function.The coherence between circulation and temperature is calculated and analyzed.The abrupt change of circulation and temperature in the last 100 years is revealed with the methods of the accumulated anomalous curves,the signal/noise ratio as well as the Mann-Kendall test.The correlations between anomalous circulation and climate are discussed with some explanations.     

Transition to two-dimensional turbulent convection in a rapidly-rotating annulus

Abstract

We study a semi-analytical model of convection in a rapidly-rotating, differentially-heated annulus with sloping top and bottom lids. Rapid rotation leads to a preservation of relatively simple, two-dimensional (2-D) structure in the experimentally-observed flow, while temporal complexity increases with the Rayleigh number. The model is, therefore, two-dimensional; it exhibits a sequence of bifurcations from steadily-drifting, azimuthally-periodic convection columns, also called thermal Rossby waves, through vacillation and a period-doubling cascade, to aperiodic, weakly-turbulent solutions.

Our semi-analytical results match to within a few percent previous numerical results with a limited-resolution 2-D model, and extend these results, due to the greater flexibility of the model presented here. Two types of vacillation are obtained, which we call, by analogy with classical nomenclature of the baroclinic annulus with moderate rotation rates, amplitude vacillation and tilted-trough vacillation. Their properties and dependence on the problem's nondimensional parameters are investigated. The period-doubling cascade for each type of vacillation is studied in some detail.     

The Sedimentary Characteristics and Environmental Significance of Saline Lake Shore in North Tibetan Plateau

正Introduction Through the study of environmental change indicators:landform,strata sedimentary characteristics,mineralogy characteristics and Grain-size,magnetic susceptibility analysis for 3101 cm height profile of Dogai Coring salt lake shore in the northern of Tibet plateau,the conclusion is roughly obtained about six major climate change process:     

非对称环流的细致结构与台风路径的摆动

应用准地转三层斜压模式数值模拟热带气旋的移动，详细分析热带气旋非对称环流的三度空间结构及其与热带气旋移动的关系。结果表明：非线性涡度平流与线性β项相结合不但可以产生大尺度β涡旋对，而且还可产生小尺度涡旋对；这两种不同尺度的非对称涡旋不断相互作用，导致热带旋移速的振荡和移向的摆动。     

气候波动对典型草原区潜在蒸散的影响

根据FAO推荐的彭曼—孟蒂斯方程,利用典型草原区1961—2008年25个地面气象站资料,分析了典型草原区潜在蒸散量的变化趋势以及与气候波动间的关系。结果表明,1）典型草原区四季与年潜在蒸散量均呈现出一致的减少趋势,且春季潜在蒸散量减少趋势最为显著,减少率为3.71mm/（10a）,其次为夏季和秋季,冬季最少。典型草原区年潜在蒸散量的80%以上集中在牧草返青、生长关键期,且此时又是潜在蒸散量变幅最大的季节,由此可能引发典型草原区干旱事件频发、地上生物量减少、草场的退化。2）对典型草原区潜在蒸散量影响最为密切的因子为：相对湿度、降水量、日照时数和平均风速,气温影响不显著。究其原因从能量平衡原理分析,典型草原区近50a平均风速减少影响了空气动力学对蒸散的影响,日照时数减少和湿度的略增是太阳辐射减少的原因,从而导致了潜在蒸散量的降低。3）21世纪典型草原区潜在蒸散量处于低的平均态和变率增大时期,极有可能引发干旱灾害,这与目前该地区气候变暖后生态耗水加大、干旱化加剧、生态退化严重等结论是一致的