Discrimination and Validation of Clouds and Dust Aerosol Layers over the Sahara Desert with Combined CALIOP and IIR Measurements

This study validates a method for discriminating between daytime clouds and dust aerosol layers over the Sahara Desert that uses a combination of active CALIOP（Cloud-Aerosol Lidar with Orthogonal Polarization） and passive IIR（Infrared Imaging Radiometer） measurements;hereafter,the CLIM method.The CLIM method reduces misclassification of dense dust aerosol layers in the Sahara region relative to other techniques.When evaluated against a suite of simultaneous measurements from CALIPSO（Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations）,CloudSat,and the MODIS（Moderate-resolution Imaging Spectroradiometer）,the misclassification rate for dust using the CLIM technique is 1.16%during boreal spring 2007.This rate is lower than the misclassification rates for dust using the cloud aerosol discriminations performed for version 2（V2-CAD;16.39%） or version 3（V3-CAD;2.01%） of the CALIPSO data processing algorithm.The total identification errors for data from in spring 2007 are 13.46%for V2-CAD,3.39%for V3-CAD,and 1.99%for CLIM.These results indicate that CLIM and V3-CAD are both significantly better than V2-CAD for discriminating between clouds and dust aerosol layers.Misclassifications by CLIM in this region are mainly limited to mixed cloud-dust aerosol layers.V3-CAD sometimes misidentifies low-level aerosol layers adjacent to the surface as thin clouds,and sometimes fails to detect thin clouds entirely.The CLIM method is both simple and fast,and may be useful as a reference for testing or validating other discrimination techniques and methods.     

谈“撒哈拉以南非洲”一课的辩证关系及教学策略

正辩证关系就是指事物之间、事物内部要素之间以及事物的两重性之间的既对立又统一的关系。从世界观角度看,辩证关系是客观事物存在的状态;从方法论角度看,辩证关系是我们认识事物的普遍方法。把握辩证关系的关键在于用对立统一的方法看问题,客观、全面地揭示事物矛盾双方的相互关系。在世界众多的国家和地区中,基于"重视世界上地理问题突出的地区和国家"的区域选择原则,教材选择了在自然和人文地理方面均具有显著特色的撒哈拉以南的非洲,作为七年级下册第八章第三节学生学习世界地理的一个案例。     

冈瓦纳大陆解体的三维数值模型解开撒哈拉大西洋未形成之谜

正2014年3月1日《Geology》出版文章"赤道大西洋的斜向裂谷作用:为什么不存在撒哈拉大西洋"(Oblique rifting of the Equatorial Atlantic:Why there is no Saharan Atlantic Ocean),研究人员通过复杂的板块构造理论与三维数值模型模拟,发现1.3亿年前的冈瓦纳超级大陆解体导致形状完全不同的非洲和南美洲大陆,以及今天的撒哈拉大沙漠。研究强调,西非裂谷的走向近乎垂直于大陆延伸方向决定了该裂谷并未扩张形成撒哈拉大西洋。     

阿尔及利亚南部地区地下水与主要摄入食物（椰枣和茶）中的氟含量

在阿尔及利亚南部地区,氟斑牙病作为一种流行病在人群中的患病范围悄然扩大。本文研究的目的是确定水、椰枣和茶等日常摄入的食物的氟离子含量。结果表明,35％的饮水井中氟离子浓度超标（〉1．5mg／1）。研究区东部水中含氟量很高且地方性氟斑牙病情分布广。椰枣,茶和水为氟的主要来源之一,其一般分配比例依次为10％,20％以及超过70％。通过食用这三种食物,成年人日常摄入氟的量超过了建议的安全用量即每天0．05-0．07mg／kg。     

撒哈拉次大陆干旱研究综述

1 引言自七十年代以来,北非撒哈拉次大陆,出现了本世纪以来最严重的多年持续性干旱,曾引起全世界的极大关注,并在国际气象学界逐渐形成了一个重要的研究课题。严中伟等指出,夏季五十年代湿润多雨和七十至八十年代持续性干旱的气候跃变现象,自北非向东北伸展,波及印度、中国中部直至     

撒哈拉地区沙尘气溶胶南北空间型分布特征及其成因

本次研究利用MODIS、CALIPSO等卫星观测资料以及MERRA-2再分析资料分析了2007–2017年撒哈拉地区气溶胶光学厚度的空间分布特征。结果表明,撒哈拉地区气溶胶光学厚度的空间分布具有明显的季节变化,夏季沙尘气溶胶光学厚度高值区位于撒哈拉北部地区,高达0.6以上;而冬季沙尘气溶胶光学厚度高值区位于撒哈拉南部地区,最大值约为0.5。此外,撒哈拉地区在不同季节的主要气溶胶类型均为沙尘,但在撒哈拉南部地区沙尘气溶胶光学厚度对总气溶胶光学厚度的贡献有明显的季节性差异。基于CALIPSO体积退偏比的研究结果表明,在撒哈拉南部地区,夏季人为气溶胶占比大,气溶胶粒子趋于球形,冬季气溶胶粒子的退偏比则明显高于夏季,粒子非球形程度更高。夏季撒哈拉北部地区位于脊前槽后的位置,以南地区近地面主要为偏西风,携带了大量水汽的气流由大西洋吹向撒哈拉地区,使撒哈拉南部地区进入雨季,增强了沙尘气溶胶的沉降,因此夏季撒哈拉地区沙尘气溶胶光学厚度分布北高南低;冬季高压控制着撒哈拉北部地区,撒哈拉南部地区近地面盛行偏东风,且冬季温度偏低,容易形成逆温,不利于沙尘气溶胶和局地污染物扩散,导致沙尘气溶胶光学厚度南高北...     

Model-Simulated Atmospheric Carbon Dioxide: Comparisons with Satellite Retrievals and Ground-Based Observations

Atmospheric CO2 concentrations from January 2010 to December 2010 were simulated using the GEOS-Chem（Goddard Earth Observing System-Chemistry） model and the results were compared to satellite Gases Observing Satellite（GOSAT） and ground-based the Total Carbon Column Observing Network（TCCON） data. It was found that CO2 concentrations based on GOSAT satellite retrievals were generally higher than those simulated by GEOS-Chem. The differences over the land area in January and April ranged from 1 to 2 ppm, and there were major differences in June and August. At high latitudes in the Northern Hemisphere in June, as well as south of the Sahara, the difference was greater than 5 ppm. In the high latitudes of the Northern Hemisphere the model results were higher than the GOSAT retrievals, while in South America the satellite data were higher. The trend of the difference in the high latitudes of the Northern Hemisphere and the Saharan region in August was opposite to June. Maximum correlation coefficients were found in April, reaching 0.72, but were smaller in June and August. In January, the correlation coefficient was only 0.36. The comparisons between GEOS-Chem data and TCCON observations showed better results than the comparison between GEOS and GOSAT. The correlation coefficients ranged between 0.42（Darwin） and 0.92（Izana）. Analysis of the results indicated that the inconsistency between satellite observations and model simulations depended on inversion errors caused by data inaccuracies of the model simulation＇s inputs, as well as the mismatch of satellite retrieval model input parameters.     

明晰权属 规划空间——从非洲“土改”看全球土地治理趋势

正土地治理在经济社会发展中处于重要地位,是非洲保持和进一步提高增长率和实现发展潜力的重要途径。其中,土地管理中需要公共福利优先、权属管理和空间规划是基础、实行资源综合管理等,对我国土地管理制度改革亦有启发借鉴意义。土地管理改革势在必行非洲土地资源丰富,拥有大量可供耕作的土地,还在撒哈拉以南拥有世界上近一半可供利用的未开垦土