Changes in air pollutants during the COVID-19 lockdown in Beijing:Insights from a machine-learning technique and implications for future control policy

基于2015-2020年北京35个环境空气站和20个气象站观测资料,应用机器学习方法(随机森林算法)分离了气象条件和源排放对大气污染物浓度的影响.结果发现,为应对疫情采取的隔离措施使北京2020年春节期间大气污染物浓度降低了35.1％-51.8％;其中,背景站氮氧化物和一氧化碳浓度的降幅最大,超过了以往报道较多的交通站...     

GRAPES_GFS 2.0模式系统误差评估

通过选取2014年1月、4月、7月、10月的GRAPES_GFS 2.0预报产品和NCEP FNL分析资料进行对比分析,发现GRAPES_GFS 2.0的系统误差具有以下特性:位势高度场误差的空间分布具有纬向条带状或波列状特征,误差大值集中在中高纬度地区,低纬度地区误差较小。误差在南北半球各自的冬季最大、夏季最小,并呈现明显的季节变化特征。误差随预报时效的增速略低于线性增速且不同预报时效下误差随高度变化的曲线趋势相似。温度场误差的空间分布相对均匀,误差大值位于30°S~30°N附近地区。纬向风场误差没有十分明显的分布规律,与纬度变化、海陆分布和地形的关系均不密切,西风误差和东风误差交替出现。结果表明:模式对冬季中高纬度地区和边界层及对流层顶的模拟技巧尚需提高。明确GRAPES_GFS 2.0的系统误差分布特性,有助于有针对性地进行模式订正,改善误差大值区域的模式预报方法。     

浙江省电子沙盘气象应用系统

用高程数据建立电子沙盘表面模型,并对高程数据、矢量数据和影像数据进行三维可视化处理,在三维场景中建立了渲染过的浙江省电子沙盘模型;以Microsoft.NET为开发平台,基于ArcGIS Engine构建了浙江省电子沙盘显示平台,实现电子沙盘的集成显示、基本地图操作、自动站叠加显示、属性查询、MICAPs第4类网格资料...     

Mass Concentration and Mineralogical Characteristics of Aerosol Particles Collected at Dunhuang During ACE-Asia

Measurements were performed in spring 2001 and 2002 to determine the characteristics of soil dust in the Chinese desert region of Dunhuang, one of the ground sites of the Asia-Pacific Regional Aerosol Characterization Experiment (ACE-Asia). The mean mass concentrations of total suspended particle matter during the spring of 2001 and 2002 were 317 μg m?3 and 307 μg m?3, respectively. Eleven dust storm events were observed with a mean aerosol concentration of 1095 μg m?3, while the non-dusty days with calm or weak wind speed had a background aerosol loading of 196 μgm?3 on average in the springtime. The main minerals detected in the aerosol samples by X-ray diffraction were illite, kaolinite, chlorite, quartz, feldspar, calcite and dolomite. Gypsum, halite and amphibole were also detected in a few samples. The mineralogical data also show that Asian dust is characterized by a kaolinite to chlorite (K/C) ratio lower than 1 whereas Saharan dust exhibits a K/C ratio larger than 2. Air mass back-trajectory analysis show that three families of pathways are associated with the aerosol particle transport to Dunhuang, but these have similar K/C ratios, which further demonstrates that the mineralogical characteristics of Asian dust are different from African dust.     

Effects of current climate,paleo-climate,and habitat heterogeneity in determining biogeographical patterns of evergreen broad-leaved woody plants in China

Journal of Geographical Sciences - Understanding biogeographic patterns and the mechanisms underlying them has been a main issue in macroecology and biogeography, and has implications for...     

Stabilization of Bottom Hole Temperature With Finite Circulation Time and Fluid Flow

As an alternative to finite element or finite difference modelling, analytical solutions are derived by the method of Laplace transformation and numerical results obtained for several models of the bottom hole temperature stabilization. Included in the models are the finite circulation time, the thermal property contrast between the borehole mud and the surrounding formation, and the presence of radial or lateral fluid flow in the formation, all of which are found to have significant effects on the dissipation of the thermal disturbance induced by drilling.
The mud circulation is considered to have the effect of either maintaining the borehole mud at a constant temperature or supplying a constant amount of heat per unit length per unit time to the borehole. For small circulation times, the former reduces to the 'zero circulation' model in which the mud circulation creates an instantaneous temperature anomaly at the hole bottom; for small borehole radii, the latter reduces to the line source model and the traditional 'Homer plot'.
For typical drilling operations in which the bottom hole temperatures are measured several hours to several tens of hours after the hole is shut in, the new models generally predict higher equilibrium formation temperatures than does the Horner plot. However, predictions from the various models converge if the BHTs are taken after the hole has been shut in for a period which is greater than about five times the circulation period.     

黑龙江省与呼伦贝尔盟土地类型的划分及其分布规律

本文就土地研究的几个主要概念,即土地、土地分类、土地分级作了简要讨论,并结合黑龙江省及呼伦贝尔盟的具体条件,对为农、林、牧业服务的土地分类原则进行了初步探讨,还拟订了该区土地分级系统——土地类和土地型,及适合于大比例尺制图的土地组。在此基础上,将全区分为18个土地类、71个土地型。文章还从水平带性、垂直带性和土地结构三个方面,介绍了该区土地类型分布的一般规律。     

基于脱钩模型的煤炭城市可持续发展动态分析——以徐州市为例

促进经济与环境协调是煤炭城市可持续发展的关键和核心。采用物质流分析、脱钩分析和分解分析等方法,深入分析了1995—2007年徐州市经济增长与资源环境之间的脱钩类型、可持续状态及驱动因素。结果表明:研究期内徐州市DMI和DPO的年均增长率分别为2.74%和0.91%,而GDP年均增长率为12.62%,二者之间呈较为明显的正相关关系,而物质代谢效率的提升又使其发展方式呈现向资源节约型、环境友好型发展模式转型的趋势;资源投入、废物排放与经济增长之间均出现弱脱钩现象,表明徐州经济系统正处于显著的弱可持续发展态势;经济规模扩大和技术效应抑制作用减弱是引起煤炭城市资源环境约束性增强、可持续发展降低的主要驱动因素。     

北京零售业的空间分布及影响因素

零售业是生活性服务业的重要组成部分,传统零售业通常通过零售商业网点形式展开。零售商业网点具有数量多、分布广、差异大等特点,其区位选择不仅影响居民的生活品质,也关乎商业网点空间布局的合理性。北京中心城区的零售业整体及其各细分行业均呈现出显著的空间集聚态势,集聚中心主要沿长安街及其延长线分布。影响零售业的区位选择因素包括交通通达性、地价成本、消费市场规模、消费偏好、政策引导、城市商业发展历史等。近年来,随着零售业与互联网的深度融合,零售业区位选择的影响因素及其作用方式不断发生变化,需要更多关注“新零售时代”对零售业空间布局的影响。     

Spatial and temporal variability of stable isotopes (δ18O and δ2H) in surface waters of arid,mountainous Central Asia

Characterization of spatial and temporal variability of stable isotopes (δ¹⁸O and δ²H) of surface waters is essential to interpret hydrological processes and establish modern isotope–elevation gradients across mountainous terrains. Here, we present stable isotope data for river waters across Kyrgyzstan. River water isotopes exhibit substantial spatial heterogeneity among different watersheds in Kyrgyzstan. Higher river water isotope values were found mainly in the Issyk‐Kul Lake watershed, whereas waters in the Son‐Kul Lake watershed display lower values. Results show a close δ¹⁸O–δ²H relation between river water and the local meteoric water line, implying that river water experiences little evaporative enrichment. River water from the high‐elevation regions (e.g., Naryn and Son‐Kul Lake watershed) had the most negative isotope values, implying that river water is dominated by snowmelt. Higher deuterium excess (average d = 13.9‰) in river water probably represents the isotopic signature of combined contributions from direct precipitation and glacier melt in stream discharge across Kyrgyzstan. A significant relationship between river water δ¹⁸O and elevation was observed with a vertical lapse rate of 0.13‰/100 m. These findings provide crucial information about hydrological processes across Kyrgyzstan and contribute to a better understanding of the paleoclimate/elevation reconstruction of this region.