辽宁中部城市群度日的变化特征

利用1951—2006年辽宁中部城市群沈阳、抚顺、本溪、鞍山4城市逐日气温资料,分析各城市热度日HDD和冷度日CDD的变化规律,并探讨度日与平均气温及城市热岛强度等的关系。结果表明:辽宁中部城市群HDD和CDD最大值分别出现在1月和7月。4城市HDD年际变化均呈下降趋势;CDD年际变化沈阳和鞍山呈微弱的上升趋势,而抚顺和本溪呈微弱的下降趋势。自1950s始至21世纪的2006年,除抚顺外,其他各城市HDD年代际变化均表现为明显的下降趋势,而CDD年代际变化均表现为降—升—降的规律。年代HDD均值与年代平均气温呈反位相,而年代CDD均值与年代平均气温呈正位相,冬季HDD与城市热岛强度呈负相关。     

Formulation and verification of a land surface parameterization for atmospheric models

The need for a well-defined lower boundary condition for atmospheric numerical models is well documented. This paper describes the formulation of a land surface parameterization, which will be used in atmospheric boundary-layer and mesoscale numerical models. The land surface model has three soil layers for the prediction of soil moisture and soil temperature. Model soil properties depend on soil texture and moisture content. A homogeneous distribution of vegetation is also included, so that transpiration may be included, as well as the interception of precipitation by vegetation elements. The simulated vegetation also affects the mean surface albedo and roughness characteristics.First ISLSCP Field Experiment (FIFE) data are used to verify the model. Three cases during the growing season were chosen, each case having different amounts of vegetation cover. Stand alone simulations, where observations of atmospheric and radiation variables are input to the land surface model, were performed. These simulations show that the model is able to reproduce observed surface energy budgets and surface temperatures reasonably well. The RMS differences between modeled and obsered turbulent fluxes of heat and moisture are quite comparable to those reported by more detailed land surface models.     

A Simple Mixing Length Formulation for the Eddy-Diffusivity Parameterization of Dry Convection

In this paper a simple mixing length formulation for the eddy-diffusivityparameterization of dry convection is suggested. The new formulation relates the mixinglength to the square root of the turbulent kinetic energy (e) and a time scale ( ):l = e. To close the parameterization the time scale is calculated as a functionof the boundary-layer height (h) and the convective velocity scale (w_*), h/w_*. Thesimpler approach of a constant time scale is also studied. The simulation of a case of dry atmosphericconvection with a one-dimensional boundary-layer model shows that the model with the new formulationreproduces quite well the main properties of the convective boundary layer. In particular,the entrainment is realistically represented by the new mixing length, which has the advantage of naturallydecreasing with the turbulent kinetic energy. Sensitivity studies to the surface flux and the lapserate, in the context of a simplified situation, show the robustness of the new formulation.     

Probabilistic Formulation of Spatio-temporal Drought Pattern

Summary Meteorological and hydrological drought occurrences along time and space take place randomly and therefore their scientific quantifications are possible by the probabilistic methods. Herein drought occurrences are assumed to have spatial and temporal stationarity with underlying independent generating mechanism. The drought stricken area is considered as composed of mutually exclusive and collectively exhaustive subareas each with different probability of drought occurrence. Two types of spatio-temporal drought formulations are presented. The first is referred to as the regional persistence model and it assumes that if any subarea is stricken by drougth it will remain to stay in this state till the whole area is covered by drought. The second alternative is multi-seasonal model and it is based on the assumption that drought stricken area might recover and have wet period during the course of time. The necessary theoretical probability distribution functions for partially drought stricken areas are derived based on the Bernoulli trials both along time and space axis. The expectation and variance parameters are derived based on the percentage of drought stricken area and the basic wet and dry spell probabilities. Necessary charts for practical purposes are prepared and interpretations are given. Received January 23, 1998 Revised June 30, 1998     

新疆降水量级标准的划分

根据新疆的气候特点和业务需求，给出了适合新疆的降水量级的24h以及12h划分标准。通过近10年降水实况资料的检验，认为该标准适合于干旱半干旱地区降水量级的划分。     

Calculations of hailstone growth in a sloping steady updraft

Abstract

Analytical solutions to the equations of growth and motion of hailstones in updrafts with cloud water contents that vary linearly with height are used to investigate hail growth in a model cloud. The model storm is steady and two‐dimensional and is constructed by compositing sections with linear variations of vertical air velocity and cloud water content so as to approximate the Fleming storm. Hail embryos are introduced at various positions in the updraft and their subsequent history calculated. A strong correlation is found between the embryo starting position and its trajectory and final size. Embryos starting in the central portions of the updraft are carried up rapidly and displaced far from the updraft. Embryos starting near the upshear edge of the updrafr have a simple arcing up and down trajectory and produce small hailstones that can be expected to melt before reaching the ground. Embryos starting near the downshear edge of the updraft give rise to the largest hailstones and have recirculating trajectories. Effects of changing some of the model parameters are investigated.     

南海月平均流的计算

本文用一个二维全流方程模式,计算了南海1—12月的逐月平均流。所得的南海逐月环流的总趋势以及一些中小尺度的涡旋现象不仅与海洋观测相一致,也与已有的一些研究结果相吻合。而且,计算所得的海洋场和海面起伏场均很好地反映出南海的季节性变化特征,特别是高海暖流的存在在计算中又进一步得到了证实。文中对南海海流的机理也作了一此初步探讨。     

南海月平均流的计算

本文用一个二维全流方程模式,计算了南海1—12月的逐月平均流。所得的南海逐月环流的总趋势以及一些中小尺度的涡旋现象不仅与海洋观测相一致,也与已有的一些研究结果相吻合。而且,计算所得的海洋场和海面起伏场均很好地反映出南海的季节性变化特征,特别是高海暖流的存在在计算中又进一步得到了证实。文中对南海海流的机理也作了一此初步探讨。     

Bulk Formulation of the Surface Heat Flux

An interpretive literature survey examines different approachesfor applying the bulk aerodynamic formulato predict the surface heat flux. The surface heat flux is often predicted in terms of the surface radiation temperature, which is also used to predict the upward longwave radiation and the heat flux into the soil. In models, the thermal roughness length based on the surface radiation temperature (radiometric roughness length) is often specified to be smaller than the roughness length for momentum for a number of distinct reasons. The definition of the radiometric roughness length depends on the way that the surface temperature is measured, the choice of stability functions and displacement height and inclusion of any additional resistances.Using airborne eddy correlation data collected over eight different sites including bare soil, crops and grassland and several types of forests, the radiometric roughness length is found to vary by orders of magnitude in a manner that is difficult to formulate. Alternatively, we evaluate the approach where the thermal roughness length is equated with the better behaved roughness length for momentum and the corresponding aerodynamic surface temperature is modelled in terms of the surface radiation temperature, solar radiation, and vegetation index. The influence of wind speed and soil moisture on the difference between the aerodynamic and surface radiation temperatures is also examined.     

Budget Calculations for Ozone and Its Precursors: Seasonal and Episodic Features Based on Model Simulations

Results from two air quality models (LOTOS, EURAD) have been used toanalyse the contribution of the different terms in the continuity equationto the budget of ozone, NO_x and PAN. Both models cover largeparts of Europe and describe the processes relevant for troposphericchemistry and dynamics. One of the models is designed to simulate episodesin the order of 1–2 weeks (EURAD), the other is focussing on theseasonal scale (LOTOS). Based on EURAD simulations it is found that theatmospheric boundary layer (ABL) in Central Europe during a summer-smogepisode in 1990 acts as a source of ozone, which is partly exported from theproduction region in Central Europe. About 40% of the ozone producedchemically in the ABL is lost from Central Europe due to net transport(large-scale and turbulent), 40% are deposited within the domain. Vertical mass exchange of ozone is dominated by the prevailing subsidenceand averaged vertical mass fluxes are directed downward. Averaged massfluxes of PAN, which has no stratospheric source, are upward in the upperpart of the ABL. The results from LOTOS are discussed for the same episodeand for a two month period (July/August 1990). The budget calculation showlarger chemical production for the LOTOS model compared to EURAD. Therelative importance of deposition and net transport, however, is in the sameorder. Differences between the two-month calculation and the one weekepisode are only important for Western Europe where the chemical production is enhanced by 30% during the summer-smog episode. The dependence ofthe results on initial and boundary values is discussed for ozone on thebasis of a simple sensitivity study with EURAD where ozone in the FT is setto 10 ppb initially. This leads to a reversal in the direction of averagedozone mass fluxes in the upper part of the ABL.     

Calculations of the transpiration rate and temperature of a leaf

Summary Sample calculations of the water-loss rate and the temperature of a leaf have been made in terms of three climatic factors (i. e. net radiation intensity, ambient temperature and ambient vapour pressure) and two diffusion resistances, respectively within and outside the leaf tissue. The results indicate the variability of the ratio of the respective water losses from a leaf and a water surface. Increasing the external diffusion resistance, e. g. by lowering the wind speed, is shown to lead to either an increase or a decrease of transpiration, depending on atmospheric humidity. The cooling of a leaf resulting from transpiration is shown to increase as the ambient air becomes more dry and calm.

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Zusammenfassung Der Wasserverlust und die Temperatur eines Blattes wurden in Abhängigkeit von drei meteorologischen Faktoren (Strahlungsbilanz, Umgebungstemperatur und Umgebungsfeuchte) und zwei Diffusionswiderständen (innerhalb und außerhalb des Blattes) berechnet. Die Ergebnisse zeigen die Veränderlichkeit des Verhältnisses zwischen dem gleichzeitigen Wasserverlust von einem Blatt und von einer Wasseroberfläche. Wird der äußere Diffusionswiderstand erhöht, z. B. durch Verminderung der Windgeschwindigkeit, so äußert sich das entweder in einer Erhöhung oder einer Verminderung der Transpiration, je nach dem Wassergehalt der Luft. Die Abkühlung des Blattes durch die Transpiration wird um so größer, je trockener und ruhiger die Umgebungsluft ist.

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Résumé On a calculé la perte d'eau et la température d'une feuille en partant de trois éléments météorologiques (bilan de radiation, température et humidité du milieu ambiant) ainsi que de deux résistances de diffusion (à l'intérieur et à l'extérieur de la feuille). Les chiffres obtenus montrent la variabilité du rapport existant entre les pertes d'eau simultanées d'une feuille et d'une surface d'eau libre. Si la résistance à la diffusion augmente à l'extérieur, par exemple par suite d'une diminution de la vitesse du vent, la transpiration augmente ou diminue selon la teneur en eau de l'air ambiant. Le refroidissement de la feuille par suite de la transpiration est d'autant plus marqué que l'air ambiant est plus sec et plus calme.

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With 3 Figures     

一次浮尘源地及其三维路径的计算

应用三维风场,借助计算气块路径的方法,对一次沙暴天气引起的浮尘飘移,进行了逆向追踪计算,得出了浮尘源地的位置和浮尘飘移的三维空间路径。经与天气实况对比,两者基本相符。这对于预测大气中污染物的飘移和确定污染源的位置,具有实际意义。     

European VOC Emission Estimates Evaluated by Measurements and Model Calculations

Observations and model calculations of the concentration of hydrocarbonsat five Scandinavian rural sites during March–June 1993are reported.Decreasing concentrations from March to June are observedat all sites. The highest concentrations of hydrocarbons were found in air massescoming in from the southwest to southeast, indicating that long rangetransport fromcontinental Europe and the U.K. is important in pollution episodes. An episode of elevated concentrations of hydrocarbons observed at three of the sites in the middle of Marchis described and discussed in relation to the synoptic situation and thepresenceof other chemical compounds (NO₂, PAN, total nitrate andozone).A Lagrangian numerical model is used to calculate the concentrations of theindividual hydrocarbons at the fivesites and comparison with observations is made.The calculated concentrations for nonmethane hydrocarbons with quite longchemicallifetimes agree well with the observations.For the sum of observed and calculated hydrocarbons the correlationcoefficientsare in the range of 0.65–0.88 for the five sitesand the ratio between calculated and measured concentrations was0.72–0.97, indicating thatthe European VOC emission inventory is quite well estimated.     

The Optimized Short-Range Ensemble Forecast Based on Singular Vector Calculations

In ensemble forecast,by summing up ensemble members,filtering the uncertainty,and retaining the common component,the ensemble mean with a better result can be achieved.However,the filtering works only when the initial perturbation develops nonlinearly.If the initial perturbation propagates in a linear space,the positive and negative members will counteract,leading to little difference between ensemble mean and control forecast and finally insignificant ensemble result.In 1 2-day ensemble forecast,based on singular vector (SV) calculations,to avoid this insignificance,the counteracting members originated from the same SV are advised not to put into the ensemble system together;the only candidate should be the one with the better forecast.Based on the ingredient analysis of initial perturbation development,a method to select ensemble members is presented in this paper,which can fulfill the above requirement.The regional model MM5V1 of NCAR/PSU (National Center for Atmosphere Research/Pennsylvania State University) and its corresponding tangent adjoint model are used.The ensemble spread and forecast errors are calculated with dry energy norm.Two mesoscale lows on the Meiyu front along the Yangtze River are examined.According to the analysis of the perturbation ingredient,among couples of counteracting members from different SVs,those members performing better always have smaller or greater spread compared with other members.Following this thinking,an optimized ensemble and an inferior ensemble are identified.The ensemble mean of the optimized ensemble is more accurate than that of the inferior ensemble,and the former also performs better than the traditional ensemble with positive and negative members simultaneously.As for growth of the initial perturbation,those initial perturbations originated from the summed SVs grow more quickly than those from the single SV,and they enlarge the range of spread of the ensemble effectively,thus leading to better performance of ensemble members.     

两类不同月平均气温空间推算方法的对比

利用全国660个常规气象站40年(1961-2000年)整编气象资料.采用逆距离权重反比法、样条函数法和普通克立格法等常用的3种插值方法,分析了直接插值法和综合余项法对气温插值的影响,提出了去除气温形成中的确定性部分后,以随机项进行插值可提高气温插值精度。并从空间上、时间上对比眲不同插值方法的误差,最后分析了气象站的空间分布密度对插值方法的敏感性。验证结果表明:除个别月份外,综合余项法的各项平均绝对误差均在1℃以内,比直接插值法减小了0.6～1.6℃,精度提高了38%～85%;且综合余项法的精度不依赖于台站密度的大小、插值方法的不同,具有较高的精确性和稳定性,这说明影响空间插值精度的关键因子并非是气象观测站点密度的提高、空问插值方法的改进。     

A Simple Theoretical Radiation Scheme for Regular Building Arrays

We propose a simple theoretical radiation scheme for regular building arrays. The essential difference of the present radiation scheme from the previous ones is the explicit consideration of the three-dimensional features of the surface geometry. The model is assumed to be an infinitely extended regular array of uniform buildings, each building composed of six faces (roof, floor, and four vertical walls). Without using time-consuming iterations or statistical approaches, we calculated the view factors of the faces, the complicated sunlit--shadow distributions, and the resulting canopy albedo for any time and location. The model was evaluated by comparing to outdoor experiments in a wide range of seasons and surface geometries. The simulated canopy albedos agreed well with measured values, and the accuracy is a significant improvement over two-dimensional-based model outputs.     

二氧化碳红外吸收带透过率的计算

本文较简单而系统地说明了大气中CO_2及类似于CO_2的线形分子的红外吸收带透过率公式及计算方法。在不伤害物理本质的前提下采用分子光谱模型处理。在计算P、R两支谱线的吸收时,采用艾尔萨斯模型并加上弱谱线吸收订正。当有Q支谱线时则在靠近Q支吸收有影响的波段计及Q支谱线的吸收,对它也采用相应的模型处理。     

Impact of Accurate Photolysis Calculations on the Simulation of Stratospheric Chemistry

The interpretation of atmospheric measurements and the forecasting of the atmospheric composition require a hierarchy of accurate chemical transport and global circulation models. Here, the results of studies using Bremens Atmospheric Photochemical Model (BRAPHO) are presented. The focus of this study is given to the calculation of the atmospheric photolysis frequencies It is shown that the spectral high resolved simulation of the O₂ Schumann–Runge bands leads to differences in the order of 10% in the calculated O₂ photolysis frequency when compared with parameterizations used in other atmospheric models. Detailed treatment of the NO absorption leads to even larger differences (in the order of 50%) compared to standard parameterizations. Refraction leads to a significant increase in the photolysis frequencies at large solar zenith angles and, under polar spring conditions, to a significant change in the nighttime mixing ratio of some trace gases, e.g., NO₃. It appears that recent changes in some important rate constants significantly alter the simulated BrO_x- and HO_x-budgets in the mid-latitude stratosphere.     

电子信息系统雷击风险评估方法及其应用

根据武汉市所辖汉口、江夏、新洲、黄陂、蔡甸等5个气象站近40年(1961-2000年)平均年雷电日数资料。采用建筑物电子信息系统雷击风险评估计算方法,对武汉市一幢通信大楼电子信息系统的雷击风险进行了评估。其结论是．该通信大楼电子信息系统雷电防护等级为A级,对其电源系统应采用4级浪涌保护器(SPD)加以保护,对其信号系统应采用3级SPD加以保护。