我国东部持续性暴雨水汽输送特征的比较分析

基于武汉市加密站的降水量资料和ERA5再分析资料,对2020年7月5—6日发生在武汉江夏的一次特大暴雨过程的水汽通量、水汽收支进行分析,并引入拉格朗日混合单粒子轨道模型(HYSPLIT4)定量分析暴雨过程中的水汽来源以及水汽源区对降水的贡献。结果表明：(1)天气系统的有效配置和异常稳定是本次江夏特大暴雨产生和维持的主要原因。(2)特大暴雨所需水汽主要由南边界和西边界输入暴雨区,低纬度印度夏季风环流和副高外沿的偏南气流对水汽的输送和聚集是此次特大暴雨得以发生发展的必要条件,两支环流中偏南气流带来的水汽净流入是暴雨区水汽净收支的主要贡献者。(3)定量估算结果表明,水汽源地可追踪至印度洋、孟加拉湾-南海和西太平洋,对此次特大暴雨事件的水汽贡献率分别是24%、41%和34%。(4)对流层低层的水汽通道和源地发现925 hPa以南方路径为主,其水汽来源大值区为西太平洋和南海,而850 hPa则以西南路径为主,其水汽来源大值区位于印度洋和孟加拉湾。

     

A Gill twin propeller-vane anemometer for flux measurements during moderate and strong winds

A wind velocity measuring system based on the Gill propeller anemometer is described. A method of calculating the vertical component, which allows for the non-cosine response and avoids the region of stall and nonlinear operation, is presented. A summary of the possible errors in Reynolds stress and drag coefficient estimates is given. A method of establishing the distance constant using field observations is presented. Finally, some preliminary results and some intercomparisons with other anemometers are described briefly.Now at the Institute of Ocean Sciences, Patricia Bay, B.C., Canada.     

Turbulence measurements during mistral winds with a 1-dimensional sonic anemometer

Fluctuations in the vertical wind velocity and air temperature were measured with a 1-dimensional sonic anemometer and fine thermocouple over a flat agricultural site in the Rhone Valley, France. Strong Mistral winds with speeds up to 20 m s^–1 kept atmospheric conditions very close to neutral and ensured stationarity. Friction velocities estimated both by eddy correlation (sonic plus Gill Bivane) and inertialdissipation (sonic only) methods agreed within 1 and 5 % respectively of traditional profile measurements over the measured range of 0.2 to 1.2 m s^–1. The coefficient of eddy transport for heat exceeded that of momentum by a factor of 1.38 (± 0.05), a result almost identical to that obtained in the Kansas experiment (Businger et al., 1971). For - 0.15 >= z/L >= 0.05, the ratio _w /u _* was 1.69 and 1.34 for unstable and stable conditions, respectively. For ¦z/L¦ >= 0.05, the ratio /T _* was 1.40 independent of whether neutrality was approached from either stable or unstable conditions.     

Acoustic tomography and conventional meteorological measurements over heterogeneous surfaces

Summary Conventional micro-meteorological measuring methods are not particularly suitable for the investigation of the energy exchange under heterogeneous surface conditions. To consider the influence of the different surface properties, area-covered and spatially averaged meteorological measurements in combination with highly resolved simulations are necessary. In this context, the method of acoustic travel time tomography is introduced to provide information about the horizontal temperature and wind field.To check the applicability of the tomographic method for this problem and to provide data for the model initialisation a field experiment was carried out.The tomographic system and conventional meteorological equipment were utilised inside the investigation area with an extension of several hundred meters (300×700m²), which was arranged over areas with different surface properties: grassland and bare soil.The results of the field experiment show that differences between the measuring systems (in-situ and remote sensing) exist and the heterogeneity of the underlying surface is visible in the near surface temperature and wind field at a scale, which can be resolved with highly resolved numerical models. Depending on the incoming solar radiation and the local advection regional distinctions in the air temperature and wind field as well as in the vertical sensible heat fluxes were observed.The investigations demonstrate that the sensitivity of the acoustic tomography is sufficient to verify gradients in the meteorological fields even when the horizontal differences in sensible heat flux are small.     

Coastal CCN measurements at Mace Head with enhanced concentrations in strong winds

Surface measurements of cloud condensation nuclei (CCN) number concentration (cm⁻³) are presented for unmodified marine air and for polluted air at Mace Head, for the years 1994 and 1995. The CCN number concentration active at 0.5% supersaturation is found to be approximately log-normal for marine and polluted air at the site. Values of geometric mean, median and arithmetic mean of CCN number concentration (cm⁻³) for marine air are in the range 124–135, 140–150 and 130–157 for the two years of data. Analysis of CCN number concentration for high wind speed, U, up to 20 m s⁻¹ show enhanced CCN production for U in excess of about 10–12 m s⁻¹. Approximately 7% increase in CCN per 1 m s⁻¹ increase in wind speed is found, up to 17 m s⁻¹. A relationship of the form log₁₀CCN=a+bU is obtained for the periods March 1994 and January, February 1995 for marine air yielding values a of 1.70; 1.90 and b of 0.035 for both periods.     

极轨气象卫星资料地理定位误差评估与订正方法综述

首先介绍了极轨气象卫星资料地理定位误差的来源,回顾了地理定位误差的研究状况.随后重点分析了3种可行的定位误差评估与订正的数学方法,并结合极轨卫星资料定位误差的订正实例,对不同订正方法进行了比较和讨论.最后展望了地理定位误差订正方法的研究方向.     

基于频谱补偿和数值模拟技术的江苏近海大气边界层百米高度处极端风速研究

在平均风速基本满足近海风力发电需求的前提下,近海大气边界层百米高度处极端风速的合理估算成为中国海上风电开发领域的研究热点。与低纬度海域台风极端风速的广泛研究不同,由于缺乏有效的技术手段,对于台风影响相对较少的中纬度海域,极端风速的科学认识明显不足。研究以江苏近海为例,通过频谱分析技术,定量刻画了数值模拟风速能谱在高频波段的能量衰减和截断特征;进而利用风速能谱曲线在频率域的积分及其在高频波段的补偿,实现无观测区域年最大风速的估算。与台风风场数值模拟技术相结合,综合考虑了中国中纬度海域受寒潮大风和热带气旋大风影响的复杂、特有气候特征,建立了一套可推广应用的近海大气边界层百米高度处极端风速估算的新方法。据此推算了江苏近海100 m高度处50年一遇的极端风速。结果表明:受寒潮大风影响,江苏北部海域的50年一遇风速超过40 m/s;少量北上的热带气旋则造成响水和如东附近海域40 m/s,甚至44 m/s以上的50年一遇风速;中部盐城附近海域的50年一遇风速则普遍低于35 m/s。研究成果不仅为该海域近海海洋工程的开发设计及安全运行提供重要的科学支撑,同时也有助于加深对中国极端气候事件的科学认识和大气边界层科学理论的发展。      

气象探测环境现状及保护措施的探讨

良好的气象探测环境,才能获取优质的气象探测信息。近几十年来,城市化带来的城市建筑面积猛增和城市建设用地增加,致使气象探测环境频频遭受破坏,严重影响了气象探测资料的准确性、代表性和比较性,必须引起高度重视。简述了气象探测环境保护要求的历史沿革和法律依据。以实例分析了气象探测环境保护面临的严峻形势。统计得出气象探测环境遭破坏主要由于周围建筑物超过《气象探测环境和设施保护办法》限制的高度,其原因来自于气象部门外部和内部两个方面,国家经济社会快速发展和当地政府的土地开发利益使得房地产建设迅猛发展,不可遏制;气象部门内部的办公、业务用房建设标准以及气象观测站新站址选择模式,使得选址困难和频繁被迁站。有针对性地提出保护气象探测环境也应从气象部门内部和外部两个方面入手,气象部门内部需要确立气象探测环境保护标准的科学性、严谨性,建立气象探测环境的分类保护机制;依法保护气象探测环境的同时充分应用行政干预;顺应国家经济社会的发展形势,周全应对气象探测环境保护问题;对被迫搬迁的气象观测站,选择新址时应将探测环境保护需求放在首位;同时新站址的建设布局可以采用多种模式。     

Correlation of optical propagation near the sea surface with bulk meteorological measurements

A time-dependent integrated dynamical boundary-layer model is used to study various features of the nocturnal low-level jet (LLJ). The basic concept is that of Thorpe and Guymer (1977). It is extended by entrainment processes, advection and an equation for the upper height of the turbulent layer. Applications show the role of the energy terms and how the LLJ changes considerably under synoptic forcing processes of variable geostrophic wind.     

Construction of vertical wind profile from satellite-derived winds for objective analysis of wind field

During summer Monex-79, a variety of observing systems viz. research ships, research aircrafts, constant pres-sure balloons and geostationary satellite etc. were deployed, besides the regular conventional observations The pur-pose of these additional systems was to make the best possible data for the studies on various aspects of monsoon cir-culation. The present study is aimed at the construction of vertical wind profile using cloud motion vectors obtained from GOES (I-O) satellite and to examine whether the constructed wind profiles improves the representation of the monsoon system, flow pattern etc. in the objective analysis. For this purpose, climatological normals of the wind field are considered as the initial guess and the objective analyses of the wind field are made with, first using only data from conventional observations over land areas, subsequently including the constructed winds from cloud motion vectors. These analyses are then compared with the standard analyses of wind field obtained from Quick Look Atlas by T. N. Krishnamurti et al. (1979).It is inferred that satellite estimated mean wind profiles show good agreement with the mean wind profiles of the research ships with RMS errors less than 5 mps below 500 hPa and less than 8 mps above 500 hPa. It is further infer-red that the inclusion of constructed winds shows a positive impact on the objective analysis and improvement is seen to be more marked in the data-sparse region of the Arabian sea. Analyses which include the constructed winds show better agreement with the standard analysis, than the analyses obtained using only conventional winds. Thus, results of our study suggest that the wind profiles constructed using cloud motion vectors are of potential use in objective analysis to depict the major circulation features over the Indian region.     

Metoz: Total ozone from meteorological parameters

Abstract

On the basis of two well‐known ozone‐weather relationships, an algorithm is proposed that estimates total ozone amounts using readily available meteorological information. The technique has been labelled METOZ from Meteorological Total Ozone. A rationale and derivation of the technique is presented.

METOZ total ozone amounts were generated for Toronto and Edmonton locations and compared with ground‐based Brewer spectrophotometer measures for these two stations in the Canadian ozone monitoring network for data from January to April 1989. Per cent differences between METOZ and Brewer total ozone measurements were calculated and are presented.

This mid‐latitude wînter metoz algorithm was also used to produce a hemispherical total ozone field for 16 March 1986, which was compared with the corresponding TOMS data to demonstrate other potential applications of the technique.     

The first meteorological measurements in the Iberian Peninsula: evaluating the storm of November 1724

Early instrumental series can play a key role in the study of recent climate change or assessments of specific extreme events. Unfortunately in the Iberian Peninsula few series are available relative to the 18th century. In this article we retrieved and make available the first daily instrumental series obtained in Iberia. The observations were made in Lisbon between 1 November 1724 and 11 January 1725 by Diogo Nunes Ribeiro. While pressure and temperature values were registered twice a day, the remaining variables, i.e. the state of the sky, wind direction and force, have only one value per day. Despite the relatively short period covered by this series, we were very fortunate to discover that it helps to characterize one of the strongest storms that struck Lisbon since the early 17th century. In particular, the data provide evidence for an outstanding pressure drop of 28.61 hPa from 1010.76 hPa on the 18 November to just 982.15 hPa on the 19 November. Using recently digitized pressure data for Lisbon since 1863, we can state that this 24 h decrease of surface pressure has been surpassed only once on the 28 November 1879. Moreover, the extreme winds associated with this “bomb” affected severely the entire Lisbon area as well as large sections of central and northern Portugal during the afternoon of 19 November and caused important damage in the eastern coast of Madeira the night before (18 November). This storm resembles the rare tropical storms that have reached the Iberian Peninsula as a tropical storm (Vince 2005) or the low intense hurricane that occurred in 1842.     

上海TWP3型边界层风廓线雷达探测性能评估

基于2018年7月—2019年6月上海宝山移动式风廓线雷达（mobile wind profiler radar,MWPR）资料,从获取率、水平风误差和上海6类典型天气条件下测风数据的可靠性三方面,对其探测性能进行了评估与分析。结果发现：（1）获取率受湍流强度影响最大,受大气温度、湿度影响次之。获取率具有较明显的日变化和季节变化特征,边界层内夏秋季获取率高于冬春季,且有午后获取率高、深夜和清晨低的特点;自由大气中冬春季获取率高于夏秋季。以获取率80%为其业务准入标准,边界层内MWPR的获取率达标。（2）相比L波段探空测风数据,MWPR整层的水平风速均偏小,低模态时有34.4%的数据位于偏小2.0~6.0 m·s^-1区间内;风向偏差超过±15°以上的水平风向数据占比为48.9%。（3）定性分析结果显示,MWPR探测到的垂直速度的指向性是合理的。雨强较大时,MWPR探测的垂直速度实际上是降水粒子的下降速度与大气湍流速度之和。MWPR的水平风数据在台风天、雪天等大气均一性强的时段内可靠性高。总体上,上海宝山MWPR的探测性能基本能满足日常监测服务之需,但其测风精度与业务准入标准相比尚有一定差距。

     

An inexpensive and reliable atmometer for estimating evaporation from sandy surfaces

Summary A modern modification to an inexpensive atmometer, of long-standing design, is demonstrated. In field experiments, Cantoni atmometers were observed to respond sharply to variations in solar radiation. Furthermore, this inexpensive instrument correlates well with the more expensive Livingston atmometer, and has proved to be a reliable indicator of potential evaporation from small pots of wet sand, mounted as micro-lysimeters.With 3 Figures     

Improved methods for estimating equilibrium climate sensitivity from transient warming simulations

Climate Dynamics - Equilibrium climate sensitivity (ECS) refers to the total global warming caused by an instantaneous doubling of atmospheric CO2 from the pre-industrial level in a climate system....     

Spectra and gust factors for gale force marine winds

Wind turbulence measurements obtained at a stable floating platform 10 km off the coast of Nova Scotia are unique in the range of wind speeds covered, and in freedom from influences of platform motion and flow distortion. Spectra of wind velocity components are presented according to Monin-Obukhov similarity theory. Gust factors for downwind, lateral and vertical components are reported for a range of gust durations and sampling intervals. These results are compared with published values, confirming the concept of similarity theory for spectra in gale force winds, and resolving a discrepancy among published gust factors.