基于DEM的江西潦河流域河网信息提取方法

介绍了GIS环境下数字高程模型（DEM）的预处理、水流方向确定、汇流累积量确定、河网生成,以及其他水文信息提取的原理和方法;基于DEM对江西潦河流域进行河网提取和流域边界的划分,并对试验结果进行了比较和分析。结果表明,利用GIS空间分析功能,基于DEM提取的潦河中上游数字河网与实际河网基本吻合;DEM精度和汇流能力阈值对提取的河网精度有着明显的影响,对于中小流域的潦河来说,1：50000精度的DEM和汇流能力为1000的阈值可满足实际应用的要求;基于DEM和ArcGIS提取的数字化河网,其水文要素（如坡度等）可直接作为流域预报模型参数,不仅大大提高了模型的效率,而且还可以方便地利用遥感等数据源,数据获取快速且成本低。从宏观效果上看,利用现有的GIS软件,基于DEM数据提取河网、流域范围等水文信息,从提取效率和结果的精度来说都是切实可行的;从微观上讲,已有的算法还无法确保计算结果与某些特殊地形区域（如平坦区域）的实际河网一致。     

基于GIS的洛清江流域洪涝致灾面雨量计算方法研究

根据气象风险预警服务业务需要,基于1:250000基础地理信息数据,利用GIS水文分析模型,划分洛清江流域范围;基于气象要素及灾情资料,分析洛清江流域暴雨洪涝气候背景、洪涝灾害特征;采用线性回归统计分析方法,建立洛清江流域雨洪关系模型,确定洛清江流域不同风险等级致灾面雨量阈值;并通过历史典型个例,对洛清江流域致灾面雨量阈值加以验证,结果表明:基于GIS的洛清江流域洪涝致灾面雨量阈值划分较为合理,可为广西精细化暴雨洪涝灾害风险普查和气象风险预警服务业务化提供基础支撑。     

北江、珠三角河网降水量级与面雨量的统计关系

文中利用北江流域和珠江三角洲河网的面雨量资料，分别对流域内出现各级降水量级(雨型)时所对应的面雨量进行统计，并将面雨量与流域内出现暴雨以上降水的范围进行比较分析，找出了区域内出现暴雨的站数与平均面雨量的关系，发现区域内有40％以上测站出现暴雨时，该区域面雨量一般接近50mm。     

基于GIS的广西电网流域面雨量计算方法与监测预警

以广西电网直调水电厂所处的西江流域为研究对象,基于GIS技术,在对西江流域面雨量监测区域基础信息处理基础上,采用比较分析方法,开展分流域面雨量计算方法研究,结果表明:(1)以1:5万数字高程模型为数据基础,针对西江流域河网、自动气象站、水电站等分布特点,结合水系、等高线特征,沿水系分水岭对西江流域干流进行精细化分区,为分流域面雨量计算提供基础参数;(2)对分流域面雨量采用算术平均法与泰森多边形法计算,结果为两种方法计算结果偏差较小,取算术平均法为流域分区面雨量计算方法;(3)逐小时处理、计算面雨量实时数据,实现西江流域面雨量的实时监测与预警服务。     

赤水河流域生态环境状况遥感监测分析

利用多源卫星遥感数据,对贵州赤水河流域2021年生态环境状况进行监测,定量评估赤水河流域的生态环境状况。结果表明：1）赤水河流域生态环境状况EI指数为68.15,生态环境状况综合评价为良;2）赤水河流域贵州段的土地利用类型主要以林地和耕地为主,流域监测区内生境质量为I级,生物多样性丰富;3）流域NDVI平均值0.42,植被覆盖度高,固土护坡、水源涵养能力较强;4）流域雨水充沛,河网密布,水网密度高达6.8;5）流域土地坡度起伏大,监测区内中度以上土地侵蚀强度的土地面积约占49%。相比,流域污染负荷指数较低,生态环境治理成效持续显现。     

气象洪级的划分方案及应用

气象洪级的划分方案与以往的洪涝等级划分不同，既要考虑流域洪涝的水文参量，又要考虑流域的面雨量等气象参量，因此气象洪级的等级大小既反映了流域中主要江河的洪涝程度，又反映了流域中大范围的强降水所引发的流域内小河流的洪涝和内涝程度。     

基于数字高程模型的河网和流域边界提取

为了获取流域河网及分水岭等数字化水文信息,以便更好地开展流域面雨量预报服务等气象工作。对通过最大坡降法(D8算法)采用ArcGIS软件基于数字高程模型,提取水文信息的方法,进行了研究实践。介绍了主要算法原理及关键技术,并就其中需要注意的细节及可能遇到的问题,给出了提醒及解决办法。提取的河网及流域边界为通用GIS文件,方便交换使用,可便捷地应用于相关气象工作。     

用雨量试作马口站洪水预报

夏季,只要西、北江流域同时出现大范围的连续性暴雨,引发江河水位暴涨,佛山市就可能出现严重的洪涝灾害。如“94．6”西、北江同时并发超五十年一遇的大洪水,仅广东省就有62个市县受灾,受灾人口达1254万,直接经济损失180多亿元。可见研究洪水,意义非常重大。珠江流域的西、北江洪水传至三水市思贤7窖后,通过自然调节汇人珠江三角洲河网区.马口水文站（以下简称马口站）位于西、北江三角洲河网区的顶端,是西江进人河网区前必经的第一关隘。掌握和预报马口站的水情是做好其下游防洪抗洪工作的关键。马口站防洪警戒水位为7．50m,1951…     

基于GIS的渠江流域暴雨洪涝灾害风险评估与区划

基于自然灾害风险四因子理论,选取1970～2021年渠江流域内16个气象观测站逐日降水资料,结合当地的基础地理信息和社会经济数据,构建由12个指标组成的渠江流域暴雨洪涝灾害风险评估体系,利用GIS技术对其进行定量评估与区划。结果表明：（1）渠江流域北部暴雨强度大、频次高,危险性总体呈“北高南低”的特征。（2）渠江流域南部地势低洼、河网密布、人口密集、经济发达,暴露性和脆弱性总体呈“南高北低”的特征。（3）南江、巴中北部、平昌西北部、渠县、广安、大竹和邻水西侧暴雨洪涝灾害综合风险最高,不同地区高风险的主导因素存在差异。     

细网格推算流域面雨量方法应用浅析

介绍了流域细网格化的划分、在不固定测站条件下通过距离权重插补网格结点的雨 量和流域面雨量计算的方法，以及利用API函数(GetPixel)统计流域内网格结点的技术。     

On condensation oscillations

Condensation oscillations in showers and thunderstorms are represented by variations in the vertical air currents that are induced by the accumulation and fallout of condensed water. A simple analytic theory of condensation oscillations and calculations on more complete numerical models indicate that their period is approximately proportional to the inverse square root of the condensation function, i.e. the amount of condensate produced per unit rise of saturated air, and that the period is independent of the magnitude of thermal buoyancy.     

On the cover

正A scientist from the NIFROCLIM (Soil nitrogen turnover and nitrous oxide emissions in permafrost landscapes of northern China in a changing climate; www.nifroclim.de) project collecting intact frozen soil cores. For more information on the NIFROCLIM project, see Ramm et al. (2020), starting on page 793, in this issue.     

On the cover

正Greenhouse gas emissions (top) in cities can be detected in remote areas (bottom).The cover art design for the bottom figure is reproduced from a photo taken by Mr.Peng LIU showing the China Global Atmosphere Watch Baseline Observatory (CGAWBO) at Mt.Waliguan,Qinghai Province.For more information,see the     

On hurricane energy

Warm seawater is the energy source for hurricanes. Interfacial sea-to-air heat transfer without spray ranges from 100?W?m^?2 in light wind to 1,000?W?m^?2 in hurricane force wind. Spray can increase sea-to-air heat transfer by two orders of magnitude and result in heat transfers of up to 100,000?W?m^?2. Drops of spray falling back in the sea can be 2–4?°C colder than the drops leaving the sea, thus transferring a large quantity of heat from sea to air. The heat of evaporation is taken from the sensible heat of the remainder of the drop; evaporating approximately 0.3?% of a drop is sufficient to reduce its temperature to the wet bulb temperature of the air. The heat required to evaporate hurricane precipitation is roughly equal to the heat removed from the sea indicating that sea cooling is due to heat removal from above and not to the mixing of cold water from below. The paper shows how case studies of ideal thermodynamic processes can help explain hurricane intensity.     

On moisture-flux parameterization

From direct measurements of vertical fluxes of moisture representing conditions in extremely different areas, parameterization according to the simple linear Dalton-formula leads to an apparent negative moisture flux. It is argued that this effect can be traced to deviations of moisture conditions at the interface from the saturation value according to the subsurface sea-temperature. The measurements presented were taken over the German Bight and the Baltic sea using a microwave-refractometer, a sonic-anemometer and a fine platinum wire thermometer. The BOMEX-and San Diego measurements (Phelps and Pond, 1971) have been added to the sample.     

On the cover

正In this issue, Brient (2020), beginning on page 1, reviews the concept of emergent constraints, which aims to find relationships between intermodel variations of some aspect of the recent observable climate and the uncertainties of particular future climate predictions. The idea is that the observations would then inform the     

论公共气象

从现代政府经济学的角度,指出了公共产品的四大特征,分析了我国不同类型气象产品的属性,概括了世界主要国家提供社会气象产品的几种类型,阐述了我国提出公共气象理论的重大现实意义;通过对中国与世界发达国家公共气象的规模和公共财务状况的比较,提出了运用公共气象理论指导我国气象部门深化改革的基本思路。     

On triangular tomography

Long range acoustic soundings with triads of transducers can determine accurately the vorticity integrated over the corresponding triangular areas of the ocean. However, for a given number n of transducers not all such observations are independent. In this note we show, first, that the number N of possible independent observations is in fact N = (n ? 1) (n ? 2)/2 Secondly, we shall show such observations are in principle able to provide estimates of the vorticity field and its derivatives up to order m = (n ? 3). Thus four transducers yield an accurate estimate of the scalar vorticity ω and its horizontal gradient δ ω, while five transducers will yieldalso the Laplacian δ²ω.