Predicting Potential Geographic Distribution of Tibetan Incarvillea younghusbandii Using the Maxent Model

Incarvillea younghusbandii is a well-known Tibetan medicinal plant with considerable development and research value distributed widely throughout the Tibetan plateau. It is important to study spatial distribution patterns of the plant in order to develop effective protection measures. Based on field survey work and environmental data, the potential geographic distribution of Incarvillea younghusbandii was delineated using a Maximum Entropy (Maxent) model with 28 environmental variables that screened for climate, topography, human activity and biological factors. Our results showed that the main geographic range of Incarvillea younghusbandii included the valley between the Yarlung Zangbo river and the Duoxiong Zangbo river, the valley in the middle section of the Himalaya Mountains, and the area between the north side of the east section of the Himalayas and the south bank of the middle reach of the Yarlung Zangbo river. Distribution may spread to parts of the eastern Himalayas. The Jackknife test indicated that soil types, ratio of precipitation to air temperature, extreme atmospheric pressure differences and annual precipitation were the most important predictive factors for the model, while other variables made relatively small contributions.     

2008-2014年祁连山区夏季降水的日变化特征及其影响因素

基于中国自动气象站与CMORPH降水产品融合的逐时降水量0.1°×0.1°网格数据集通过逐时降水量、降水频率和降水强度等指标研究了2008-2014年祁连山区夏季降水的日变化特征,并结合ERA-Interim再分析资料分析了气象要素对降水日变化的影响。结果表明：① 祁连山区逐时平均降水量和降水频率的时空分布特征较为一致,即东中段大于西段,且7月最大,6月次之,8月最小;降水强度的空间分布则与降水量和降水频率的存在差异,且6月的降水强度平均值最大。② 白天和夜间的降水量均表现出东中段多于西段、山区多于平原的特点,并有明显的夜雨现象;从年际差异来看,2008-2014年白天和夜间的降水量均呈增加趋势。③ 祁连山区夏季降水平均相对变率介于5%~38%之间,全区20:00平均相对变率最大;逐时降水量和降水频率普遍存在较好的相关性,尤其是在东中段。④ 对比再分析资料发现,祁连山区降水日变化与相对湿度和地面温度等气象要素有关。     

祁连山及周边降水分布聚类检验和典型流域增雨效果评价

祁连山及周边区域地形复杂,降水分布极不均匀,如何科学地分区分型,对把握研究区域降水分布特征具有极为重要的意义。利用该区域31个国家基本站1961—2020年5—9月降水量资料,采用主成分分析方法（PCA）对该区域降水量进行分析,再通过聚类分析（CAST）对该结果进行显著性检验,最后将分区分型结果应用于人工增雨作业效果评估。结果表明：（1） 祁连山及周边可分成7个区域（Z1~Z7）,累积方差贡献率超过78%。（2） 这7个区域分别以乐都、海晏、野牛沟、武威、高台、临泽、刚察为中心点,划分结果与降水量、地理地形、海拔高度显著关联。（3） 依托区域历史回归统计方法对人工增雨作业效果进行评价,发现1992—2020年石羊河流域5—9月绝对增雨量、相对增雨率分别为8.91 mm、6.51%,其中7月最高（6.30 mm、21.86%）,8月次之（5.44 mm、16.11%）。基于地面降水量的作业效果评价往往受对比区选择的影响,聚类检验方法不仅有助于复杂地形下降水量的分区研究,还为科学选择对比区提供了客观依据。     

中国高分辨率温度和降水模拟数据的验证

PRISM模型是一种基于地理特征和回归统计方法生成气候图的模型。基于中国及其周边国家地区2450多个气象台站观测数据,以PRISM模型模拟生成了中国2.5′×2.5′(≈4～5km)逐月温度和降水数据。利用独立于模拟数据的中国生态系统研究网络18个野外观测站的长年气候观测数据,检验了PRISM模型的模拟结果,表明PRISM模型较好地模拟了我国温度和降水的空间分布及季节变化,除了在高山和亚热带地区由于地表覆盖和局部地形的差异影响模拟结果,其模拟值与实测值之间的趋势线同1∶1线基本一致,具有显著相关关系,其中降水效果略差     

石羊河流域主汛期降水日变化特征

利用石羊河流域2009-2013年主汛期(6-8月)有完整资料的32个区域气象站和5个自动气象站共37个站点逐时降水资料,运用常规的气候统计方法,采用逐时降水量、逐时降水频次、逐时降水强度和不同持续时间降水4个指标对石羊河流域主汛期降水日变化特征进行了研究。结果表明:石羊河流域主汛期降水总量及日数的空间分布总体上与其地理位置、海拔、纬度以及影响系统密切相关,表现为自上游向下游呈递减趋势,降水强度空间分布较复杂。石羊河流域主汛期小时降水量、降水频次及降水强度呈三峰型分布,主要集中出现在20:00-23:00、01:00-09:00、14:00-20:00,其中强降水呈现双峰分布,基本都出现在20:00-23:00、14:00-20:00;石羊河流域主汛期持续1～3 h短时降水的降水量和降水次数大于持续10 h以上降水过程的降水量和降水次数,且持续1～6 h的短时降水多发于午后到傍晚,持续时间超过6 h的长持续性降水的最大降水量通常出现在夜晚-凌晨和午后-傍晚。     

降雨量地面观测数据空间探索与插值方法探讨

空间插值方法广泛应用于气象数据产品的制作,其精度与气象要素的空间变异特征、气象观测站分布和插值方法选择有关。选择美国得州599个地面观测站30年平均降雨量记录,设计了27个观测站样本方案,选择全年、1月和8月数据,利用空间统计、空间自相关、半变异函数等方法探索降雨量的空间变异特征,并采用5种常规方法进行空间插值,比较和解释插值结果,在此基础上讨论基于知识的气象要素空间插值方法。案例研究发现:①降雨量地面观测数据通常具有明显的空间趋势、较强的空间自相关特征和较稳定的空间变异规律,但针对不同时段或采样方案,其空间自相关强度和半变异函数模型会有一定的差异。②增加气象观测站数,空间插值误差有减小的趋势;但观测站数目达到一定数值后,增加观测站数,插值精度提高并不明显。③在观测站较少时,不同插值方法间的精度差异较大,而在观测站充足的情况下,其差异有减小的趋势。④探讨气象要素与地理环境要素之间的关系,获得定量化的先验知识,开发基于知识的空间插值模型,是高精度气象要素插值的关键;线性加权回归和地理加权回归方法的初步试验验证了这一思路的有效性。     

Regional Patterns of the Diurnal Properties of Heavy Hourly Precipitation*

Heavy precipitation is one of the most significant natural hazards in the United States today. Knowledge of the climatography, including the temporal characteristics, of this phenomenon is necessary in order to better plan, design for, and predict this hazard. In this study, cluster analysis is used to simplify and clarify the spatial patterns in the time of day heavy precipitation most frequently occurs. Regions with similar diurnal properties are delineated, and the substantial seasonal fluctuations in the regional patterns are traced. Of particular interest is the expansion during the cool season and contraction during the warm season of the nocturnal precipitation regime in the central United States.     

Assessment of diurnal variation of summer precipitation over the Qilian Mountains based on an hourly merged dataset from 2008 to 2014

To investigate the diurnal variation of summer precipitation in the Qilian Mountains in the northeast Tibetan Plateau, the hourly precipitation amount for this region during the summers of 2008–2014 are analyzed using an hourly merged precipitation product at 0.1°×0.1° resolution. The main results are as follows. (1) The spatial distribution and temporal variation of mean hourly precipitation amount and frequency are generally similar and hourly precipitations in the eastern and middle portions are larger and more frequent than that in the western portion. The high value area of precipitation intensity is obviously different from that of precipitation amount and frequency. (2) The spatial distribution of daytime precipitation is generally similar to that of nighttime precipitation, and the daytime precipitation is heavier than the nighttime precipitation. (3) The change rate of precipitation has a maximum at 20:00 Beijing time, and a minimum at 12:00. The hourly precipitation amount significantly correlated with frequency, especially for the middle and eastern portions.     

Spatial patterns of seasonal scale trends in extreme hourly precipitation in South Africa

Hourly precipitation data from 1998 to 2007 spread across 102 stations in South Africa were analyzed for trends in extreme hourly precipitation events. The analyses were conducted at the seasonal scale for summer and winter for nine different variables. The results of our analysis showed predominantly positive trends during summer, with the strongest trends concentrated in the coastal areas in the southeast. The spatial variations in the trends were reversed during the winter season, with negative trends observed in the coastal areas and positive trends occurring in the interior. The summer patterns also overlap with areas experiencing overall increasing trends in annual extreme precipitation as well as a stronger diurnal cycle identified in recently published literature.     

宁夏月、季、年降水量正态性分析

利用1951\_2004年共54 a宁夏各气象站的年、季、月降水量资料,使用偏度与峰度检验方法和x2检验方法,对降水量分布的正态性进行了分析。结果表明:宁夏大多数气象站的年降水量服从正态分布。夏季18站降水通过正态性检验,秋季12站通过,春季和冬季各有7和4站通过正态性检验。夏、秋季的计算结果普遍比冬、春季更好。不同季节通过正态性检验的气象站地理分布具有明显的区域性特征。针对宁夏月降水总体分析表明,各站均不服从正态性分布。逐月降水检验结果是,9月、8月、10月通过正态性检验的站数最多,11月通过站数最少。六盘山站通过正态性检验的月份最多,全年有10个月的月降水量服从正态分布。另有7站各月降水均不服从正态分布。未能通过正态性检验的降水样本中,偏度系数存在强烈的偏向低值的情况。偏度系数未能达到阈值标准是非正态分布的根本原因。     

黄土高原旱作区马铃薯叶片和土壤水势对垄沟微集雨的响应特征

于2011年在黄土高原半干旱地区以平地不覆膜为对照,研究了不同沟垄和覆膜方式对马铃薯叶片和土壤水势水势的影响。结果表明：不同沟垄和覆膜方式在不同土层和不同生育期对土壤和叶片水势的影响差异显著。（1）土壤水势日变化趋势：0～20 cm土层,土垄处理在开花期为先下降后上升型,土垄和覆膜垄处理在块茎膨大期为先下降后上升型,覆膜垄和全膜双垄沟播处理在成熟期为先下降后上升型,其余为逐渐下降型;20～40 cm土层,各处理土壤水势呈逐渐下降趋势。（2）叶片水势日变化趋势：开花期和块茎膨大期表现为双低谷型,双低谷分别在13：00和17：00,成熟期为“V”型,即单低谷型,低谷出现在17：00。各处理变化趋势相同,但水势存在差异。土垄处理在水分关键期（开花期和块茎膨大期）叶片水势显著高于其他处理,而全膜双垄沟播处理在成熟期最高。（3）生育期土壤水势和叶片水势均表现为先减小后增大的趋势。20～40 cm土层对叶片水势影响较大,土垄处理在该土层具有较好的水分状态,蒸腾作用较强加速了水分运移速率,是导致覆膜垄和全膜双垄沟播处理水势低于土垄的主要原因。在前期降雨较少的年份,由于较小的蒸腾作用,土垄处理可以保证马铃薯承受较小的水分胁迫;在前期降雨量较多的年份,覆膜垄和全膜双垄沟播处理则可以凭借其较大的蒸腾作用发挥较大的增产效果。     

陕西暖季降水的日变化特征及南北差异

利用2008—2015年CMORPH卫星与自动观测站的逐时降水量融合产品,分析了陕西地区5~10月降水量、降水频次、降水强度的日变化特征,以及陕西南北降水日变化上的差异。结果表明：（1）降水量和降水频次从南向北明显递减,地形作用下的纬向变化是陕西地区降水最重要的特征,但降水强度呈现出南北高、中间低的分布特征,两个高值中心分别位于陕南南部和陕北的东北部,EOF分析表明陕西南部夜雨特征明显。（2）陕西南部降水量和降水频次、降水强度日变化特征一致,均以夜晚至次日清晨为高值区, 而在中午前后达到最低值。陕西北部降水量、降水频次峰值则主要出现在上午,降水强度峰值出现在傍晚。区域对比分析表明,陕西南部降水量日变化主要来自于降水强度的贡献,而陕西北部日变化以降水频次的贡献为主。（3）陕西降水的南北分界线特征明显,34 °N以南地区降水日变化明显且降水主要集中在夜间。34~37 °N之间的中部地区降水日变化较弱,37 °N以北地区降水的日变化特征和陕西南部相反。（4）除榆林、渭南和商洛东部地区外,其他大部分地方白天的降水量都明显低于夜间的降水量,特别是陕南秦巴山区夜间降水量超过白天的一倍以上。     

1961-2010年武威市气温日较差变化趋势及影响因子分析

利用1961-2010年武威市5个气象站逐日地面最高气温、最低气温及年平均气温、日照时数、蒸发量、降水量、相对湿度、平均风速等观测资料,运用趋势系数法系统分析了该区域近50年气温日较差的时空分布及强度特征,采用多元线性回归中的标准化回归系数分析了影响气温日较差的气象因子。结果表明：受天气系统、地形地貌以及海拔等影响,武威市气温日较差低海拔地区大于高海拔地区。各地年、年代气温日较差总体呈减小趋势,民勤县、古浪县的减小趋势尤为显著,年平均气温日较差的时间序列存在着6～8年的准周期变化;各季节气温日较差变化趋势不太一致,总体上呈减小趋势;月气温日较差变化也存在差异,除天祝藏族自治县外,3月和9月为两个低谷,4-6月和10月为两个高峰。年气温日较差极大值和极小值均呈减小趋势。年最高、最低气温均呈升高趋势,年气温日较差与年最高、最低气温呈相反的变化趋势,最低气温的快速升高和最高气温的缓慢升高是气温日较差减小的直接原因,最低气温显著升高的季节气温日较差的减小趋势更大。影响武威市气温日较差的主要因子是蒸发量、平均气温、平均风速、日照时数,关联性最强的是蒸发量,其次是平均气温,其中气温日较差与日照时数、蒸发量、相对湿度以及平均风速呈正相关,与平均气温和降水量呈负相关。影响各地气温日较差的主要因子有所不同。     

Characterization of the July 2007 Swaziland fire disaster using satellite remote sensing and GIS

Data from the NASA'S MODIS (Aqua and Terra) and EUMETSAT'S MSG-SEVIRI satellite sensors is analysed to characterise the geographic and temporal (including diurnal) evolution of the July 2007 fire disaster in the Kingdom of Swaziland using a geographic information system (GIS). Significant fire activity was observed during a three-day period beginning on the 27th July 2007. A total of 1358 and 4365 active fire hotpots were detected by MODIS and MSG-SEVIRI, respectively, mainly concentrated in the Highveld (70.91% for MODIS, 89.89% for MSG) and Middleveld (11.27% for MODIS, 5.23% for MSG) with MSG/MODIS active fire count ratio ranging from a high of 3.69 in the Highveld to a low of 0.06 in the Lubombo Plateau. The results indicate complex differences in spatial fire distribution, behaviour and risk within the country and the effect of sensor differences. A pronounced fire diurnal cycle with a broad afternoon peak centred on 14:00 local time is observed, in general agreement with observations from the region. Despite their limitations, the study demonstrates the importance and usefulness of remotely sensed data and GIS technology for fire disaster and risk assessment for a developing country, where fire monitoring resources are scarce.     

DIURNAL VARIATIONS OF SUMMERTIME VERY HEAVY PRECIPITATION IN THE EASTERN AND CENTRAL UNITED STATES

This study was prompted by the apparent confusion in the meteorological and climatological literature on the time of day very heavy precipitation is most likely to occur. Harmonic analysis and cluster analysis were used to investigate the large-scale spatial variations in the diurnal cycle of very heavy precipitation in the United States east of the Rocky Mountains. Significant spatial variations in the diurnal cycle of very heavy precipitation were found to exist, and seven largely contiguous regions with unique diurnal characteristics of very heavy precipitation were identified.     

Visualizing Diurnal Population Change in Urban Areas for Emergency Management

There is an increasing need for a quick, simple method to represent diurnal population change in metropolitan areas for effective emergency management and risk analysis. Many geographic studies rely on decennial U.S. Census data that assume that urban populations are static in space and time. This has obvious limitations in the context of dynamic geographic problems. The U.S. Department of Transportation publishes population data at the transportation analysis zone level in fifteen-minute increments. This level of spatial and temporal detail allows for improved dynamic population modeling. This article presents a methodology for visualizing and analyzing diurnal population change for metropolitan areas based on this readily available data. Areal interpolation within a geographic information system is used to create twenty-four (one per hour) population surfaces for the larger metropolitan area of Salt Lake County, Utah. The resulting surfaces represent diurnal population change for an average workday and are easily combined to produce an animation that illustrates population dynamics throughout the day. A case study of using the method to visualize population distributions in an emergency management context is provided using two scenarios: a chemical release and a dirty bomb in Salt Lake County. This methodology can be used to address a wide variety of problems in emergency management.     

Spatial Distribution of Meso-Scale Precipitation in Scania, Southern Sweden

The aim of this study is to analyse the spatial variability of meso‐scale precipitation in Scania and to assess the influence of synoptic scale atmospheric circulation. The modes of spatial variation are revealed by EOF analysis of monthly precipitation totals between 1963 and 1990, which were obtained from a dense rain‐gauge network in Scania, southern Sweden. The influence of local physiography on the spatial distribution of precipitation is assessed by GIS techniques using a digital elevation model of Scania. The relation to synoptic scale atmospheric circulation is analysed using regional circulation indices and weather types. It is shown that the daily precipitation distribution in the area is significantly influenced by synoptic scale pressure patterns. Nevertheless, the covariability of the monthly precipitation within Scania is high. About 80% of the precipitation variability is connected to the passage of low‐pressure centres over or close to the region, which are likely to produce precipitation over the whole area. A wind‐direction dependency found in the distribution indicates that there might be a limit between precipitation regimes within the landscape. Topography greatly influences the spatial distribution in Scania. The distribution of land and surrounding sea is also an important factor and makes the relationship between physiography and precipitation rather complex. The physiographical effects vary over a single year. The dampening effect of the sea on the atmospheric temperature influences the local stability in coastal areas and results in seasonally dependent precipitation patterns.     

中国西南少数民族聚居区聚落分布的空间格局特征与主控因子分析——以哈尼梯田区为例

聚落格局是乡村地理学研究的基础,也是人地地域系统的重要组成部分,更是目前地理学研究的热点之一。科学分析、揭示、刻画少数民族等脆弱地区的聚落格局,对合理、高效推进该区域新型城镇化道路建设,实现民族团结和繁荣,全面建成小康社会具有重要意义。而目前,对于少数民族、尤其是多民族共生区的聚落格局研究还不足。论文以中国西南少数民族聚居的哈尼梯田区为例,从聚落分布的空间位置特征、民族格局特征、区位环境特征及其主控因子等方面,刻画了哈尼梯田区哈尼、彝、壮、汉、苗、瑶、傣等7个民族的聚落格局特征。结果表明：① 在空间位置上,哈尼梯田区68%的聚落分布在区内西中部,主要以哈尼、彝、壮为主。② 在民族格局上,形成了以哈尼—彝混居的大格局,以壮、汉、苗、瑶、傣混居的小格局。③ 在区位环境上,7个民族在海拔、坡度、气温、降水量、与河流距离、聚落规模、耕地面积、与行政中心距离和粮食单产等区位环境特征上具有显著差异。④ 在主控因子上,壮、苗、瑶聚落分布的主控因子为经济、行政、旅游中心距离,贡献率分别为86.4%和75.3%、92.8%;彝族聚落布局的主控因子为气温(贡献率为52.0%);汉、哈尼、傣聚落布局的主控因子为降水量,贡献率分别为98.7%、52.2%、97.0%。⑤ 整体而言,哈尼梯田区聚落格局在垂直向上,形成了多民族共生的立体格局,在水平向上形成了多民族互嵌格局。研究可为少数民族地区新农村建设、聚落格局优化、精准扶贫、全面建设小康社会提供科学参考。     

SYNOPTIC-SCALE VARIABILITY IN THE PROBABILITY OF PRECIPITATION FROM THUNDERSTORMS IN THE UNITED STATES

A synoptic-scale climatology of precipitation amounts from thunderstorms was developed by analysis of amounts from individual storms for 220 stations in the conterminous United States for the period 1948-1977. The probability of having a thunderstorm without rainfall was assessed for each station. For storms which did produce precipitation, the probability distribution of amounts was found to be well summarized by the incomplete gamma distribution. Sets of seasonal maps of the probability of receiving any measurable amount, less than 4 mm, and more than 20 mm of precipitation are presented. Consistent spatial patterns are found. Thunder without precipitation is most likely in the west. The greatest probability of heavy precipitation occurs along the Gulf Coast, extending in the summer throughout the mid-section of the nation. Topographic effects are apparent, with mountainous areas generally having less intense precipitation than surrounding regions. [Key World: thunderstorms, precipitation probabilities, gamma distribution.]     

基于GIS的北京山区优势林分生态位分析

应用生态位理论,以北京山区森林资源为研究对象,分析优势林分的空间分布及其资源利用和环境适应能力的差异。基于GIS方法,建立优势林分空间分布数据库以及资源梯度信息数据库,分别采用Levins公式和Smith公式,在水分、热量、光照和土壤质量4维环境因子梯度上测定了研究区8个优势林分的生态位宽度,采用Pianka公式测定生态位重叠。结果表明:Smith公式考虑资源可利用性,得到的生态位宽度更能客观地反映优势林分资源空间利用程度;研究区各优势林分重叠度普遍较大,反映了对环境要求的相似性及资源共享的趋势性。