Four-dimensional data assimilation method based on SVD: Theoretical aspect

Summary A new method of four-dimensional data assimilation based on Singular Value Decomposition (SVD) is proposed. In it, a set of atmospheric states is obtained by integrating a numerical weather prediction model and simulated observations are taken and calculated from the model variables. Then the SVD technique is used to create the base vectors from this coupled data set. Finally, the analysis is obtained by projecting actual observation data into a space spanned by the base vectors. Using this approach, the four-dimensional data assimilation becomes a simple linear inverse problem the linearization of the nonlinear forward model is avoided, and the developments of the adjoint and background error covariance matrix are no longer needed. Since the SVD technique is used here, the method is simply called 4DSVD.     

Climate Suitability for Stable Malaria Transmission in Zimbabwe Under Different Climate Change Scenarios

Climate is one factor that determines the potential range of malaria. As such, climate change may work with or against efforts to bring malaria under control. We developed a model of future climate suitability for stable Plasmodium falciparum malaria transmission in Zimbabwe. Current climate suitability for stable malaria transmission was based on the MARA/ARMA model of climatic constraints on the survival and development of the Anopheles vector and the Plasmodium falciparum malaria parasite. We explored potential future geographic distributions of malaria using 16 projections of climate in 2100. The results suggest that, assuming no future human-imposed constraints on malaria transmission, changes in temperature and precipitation could alter the geographic distribution of malaria in Zimbabwe, with previously unsuitable areas of dense human population becoming suitable for transmission. Among all scenarios, the highlands become more suitable for transmission, while the lowveld and areas with low precipitation show varying degrees of change, depending on climate sensitivity and greenhouse gas emission stabilization scenarios, and depending on the general circulation model used. The methods employed can be used within or across other African countries.     

天气预报的相似-动力方法

本文将预报对象分解为参考态和扰动态两部分,参考态根据与预报对象初始场相似的原则从历史观测资料中选定,其演变过程是已知的;扰动态的演变则用动力方法预报。用准地转正压模式作了若干模拟实验,结果表明,该方法能利用历史资料提供的信息部分弥补预报模式的缺陷,不要求参考态与预报对象有很高的相似性,其预报结果就明显优于现行的数值预报方法。     

甘肃“5·5"黑风暴小波分析

用小波变换理论对１９９３年春季甘肃省河西走廊地区一场特大黑风暴进行了分析。结果表明，小波分析能比较客观地将时间序列中不同时间尺度的振动分离开，使我们能清楚地看到黑风暴中的中尺度扰动。     

西北中部半干旱区兴隆山森林岛降水机理的数值模拟

通过WRF V2.1.2模式数值模拟试验并结合长期观测数据,研究了中国西北半干旱区长期存在和维持的森林山区(兴隆山区,103.84°E、35.86°N)的降水特征及其与周边地区的降水差异,并探讨了造成这种差异的主要原因。结果表明,兴隆山区与周边地区的降水差异主要表现在夏、秋季。在夏、秋季兴隆山区受东南湿润气流的影响,获得较多的水汽输入和较稳定的水汽来源,而山地地形则有利于截留东南气流携带的水汽并形成降水;兴隆山区及其周边地区局地的蒸散差异对二者之间降水差异的贡献不大。另外,兴隆山区土壤堆积覆盖的石质山构造和森林下垫面也有利于降水的截留和贮存以及植被的生长。因此,有利于水汽输入的大尺度环流形势、地形对空中水汽的截留以及特殊的地质因素是兴隆山山区孤立森林岛在半干旱区长期存在和维持的原因。     

非线性大气动力学的进展

总结了自新中国成立以来中国科学院大气物理研究所在非线性大气动力学领域的进展,其中主要介绍了在非线性适应过程、非线性稳定与不稳定、全局分析理论、可预报性、低阶谱方法与多平衡态动力学、非线性波动、波流相互作用、阻塞高压非线性动力学、中小尺度非线性动力学等几个方面的研究成果及最新进展.     

FURTHER STUDY ON THE PROPERTIES OF OPERATORS OF ATMOSPHERIC EQUATIONS AND THE EXISTENCE OF ATTRACTOR

The equivalent operator equation is derived from the full primitive nonlinear equations of theatmospheric motion and the properties and physical senses of the operators are studied.In theinfinite dimensional Hilbert space,the global asymptotic behavior of the atmosphere system withthe non-stationary external forcing is studied under the assumption of the bounded externalforcing.The existence theorems of the global absorbing set and the global attractor are obtained.Thus,the conclusions deduced from the large-scale atmosphere(Li and Chou 1996 a;1996 b)areextended to the general atmosphere.     

Complex study of characteristics of a Cb cloud developing over the Arabian Peninsula under high dew point deficit in the atmosphere. Part 1. Field observations and numerical modeling

Basing on airmass motion trajectory calculations over the Arabian Peninsula on April 10, 2008, it can be assumed that in the lower and middle troposphere, zones with increased air moisture exist due to air inflow from the Red Sea. As a result, mesoscale volumes of dry and moist air are neighboring, though large-scale field is comparatively homogeneous with low humidity. In the mesoscale zones, intense thunderstorm and hailstorm Cb clouds developed, whose characteristics and evolution are studied in the paper. Continuous radar observations of the clouds are carried out during 5 hours. Numerical simulation of the cloud evolution is performed with nonstationary 1.5-dimensional model. It is noted that under the mentioned atmospheric conditions, in the area under consideration, heavy rain and hail from the Cb clouds are observed. The main factors of their origination are high thermal instability of the atmosphere and moist air inflow from outside.     

A western North Pacific tropical cyclone intensity prediction scheme

A western North Pacific tropical cyclone (TC) intensity prediction scheme (WIPS) is developed based on TC samples from 1996 to 2002 using the stepwise regression technique, with the western North Pacific divided into three sub-regions: the region near the coast of East China (ECR), the South China Sea region (SCR), and the far oceanic region (FOR). Only the TCs with maximum sustained surface wind speed greater than 17.2 m s⁻¹ are used in the scheme. Potential predictors include the climatology and persistence factors, synoptic environmental conditions, potential intensity of a TC and proximity of a TC to land. Variances explained by the selected predictors suggest that the potential intensity of a TC and the proximity of a TC to land are significant in almost all the forecast equations. Other important predictors include vertical wind shear in ECR, 500-hPa geopotential height anomaly at the TC center, zonal component of TC translation speed in SCR, intensity change of TC 12 or 24 h prior to initial time, and the longitude of TC center in FOR.     

洱海湖滨带水生植物多样性及分布现状

湖滨带水生植物对湖泊生态系统健康的维持具有重要作用。为了解当前洱海湖滨带水生植物现状,本研究于2020—2021年间每季度对洱海湖滨带水生植物进行调查。调查结果表明:(1)洱海湖滨带现有水生植物206种,属56科156属,其中湿生植物149种,挺水植物24种,沉水植物21种,漂浮植物7种,浮叶植物5种;常见种有狗牙根(Cynodon dactylon)、菰(Zizania latifolia)、苦草(Vallisneria natans)、菱(Trapa bispinosa)等,偶见种为忍冬(Lonicera japonica)、披碱草(Elymus dahuricus)等。(2)从区系分布来看,洱海湖滨带物种主要为世界分布(83种)和热带分布(55种)两种类型,分别占总物种数比例的40.28%和26.71%。(3)在植物群落方面,洱海湖滨带共有18个主要植物群落类型,其中湿生植物群落4种,挺水植物群落3种,沉水植物群落9种,浮叶植物群落2种;以狗牙根群落、菰群落、苦草群落、菱群落为主。通过与历史文献结果的对比分析得出,近年来洱海湖滨带水生植物多样性有了显著提高,但目前存在挺水植物群落...