河北省月平均气温分布式模型应用研究

利用1971-2000年河北省及周边126个气象台站的常规观测资料,应用月平均气温分布式模型,实现了起伏地形下河北省月平均气温的分布式模拟,制作出100 m×100 m分辨率的气温空间制图。结果表明：坝上高原和河北省平原地区地势平坦,气温分布比较均匀;燕山山脉和太行山山脉地形复杂,气温受局地地形影响显著。在角度相同的坡地上,偏南坡与偏北坡的气温差异1月>10月>4月>7月。在同一时段,偏南坡与偏北坡的气温差异随坡度的增加而增加;张家口地区多盆地河谷,气温分布均匀且较周围地区高;月平均气温分布式模型在河北省具有良好的模拟精度、时间维和空间维模拟性能及山地扩展性能。     

高分辨地形对华南区域GRAPES模式地面要素预报影响的研究

华南区域GRAPES模式动力框架的更新使得高分辨地形数据能够进入模式。引入SRTM数据实现静态数据更新,结合模式内置数据,进行了批量模拟试验;通过站点检验方式,对批量试验结果进行对比,得出以下结论:对比业务使用的Topo10 m地形、Topo30 s地形、SRTM地形和基于SRTM多种插值方案得到的地形,海拔偏差的空间分布和分位数统计都有明显的改善,复杂地形区域的改善效果更显著。通过地面要素平均绝对误差(MAE)箱须图统计和模式西部站点绝对误差(AE)时间序列图对比分析,发现高分辨地形试验的2 m气温和10 m风速MAE和AE有大幅度的改善。高分辨地形对模式静态数据的改善是2 m气温和10 m风速MAE下降的主要原因,地形复杂区域对MAE改善的贡献高于模式其他区域。高分辨地形进入模式后会引起动力过程计算的虚假扰动,适当的滤波平滑能够抑制扰动,从而进一步提高预报精度。      

A new large-eddy simulation model for simulating air flow and warm clouds above highly complex terrain. Part I: The dry model

This paper presents the dry version of a new large-eddy simulation (LES) model, which is designed to simulate air flow and clouds above highly complex terrain. The model is three-dimensional and nonhydrostatic, and the governing equations are sound filtered by use of the anelastic approximation. A fractional step method is applied to solve the equations on a staggered Cartesian grid. Arbitrarily steep and complex orography can be accounted for through the method of viscous topography. The dynamical model core is validated by comparing the results for a spreading density current against a benchmark solution. The model accuracy is further assessed through the simulation of turbulent flow across a quasi two-dimensional ridge. The results are compared with wind-tunnel data. The method of viscous topography is not restricted to moderately sloped terrain. Compared to models using curvilinear grids, it allows this model to be applied to a much wider range of flows. This is illustrated through the simulation of an atmospheric boundary-layer flow over a surface mounted cube. The results show that the dry model version is able to accurately represent the complex flow in the vicinity of three-dimensional obstacles. It is concluded that the method of viscous topography was successfully implemented into a micrometeorological LES model. As will be shown in Part II, this allows the detailed study of clouds in highly complex terrain.     

一次鄂西地区暴雨过程中地形敏感性试验研究

利用WRF模式中提供的不同平滑地形方案对2007年5月30-31日发生在湖北西部地区的暴雨过程进行数值模拟。在此基础上,利用WRF模式进行地形高度敏感性试验。结果表明：地形平滑方案与降水的时空分布有很大的相关性,地形越接近实际地形,降水的时空分布越接近实况;地形高度对降水的强度及落区影响较大,随着山脉地形高度的增加,迎风坡和背风坡的2个降水中心带有远离山脉的趋势,当山脉高度达到一定高度以后,迎风坡和背风坡的两个降水中心带又有靠近山脉的趋势。     

The Numerical Simulation on Atmospheric Transport and Dispersion of the Spray Atomized from Flood Discharging by Hydropower Station over Complex Terrain

Summary  A three-dimensional, nonhydrostatic numerical model with high spatial resolution, in which a simple energy closure scheme is employed, has been developed to simulate the spray dispersion over complex terrain. The evaporation, condensation, and dispersion of the spray and moisture are taken into account in model equations. The term of latent heat due to phase transformation is considered in detail to account for its effects on the temperature field and airflow. As an application of the model, the spray concentration and air relative humidity are calculated under neutral condition. The results indicate that under the neutral condition, the spray is transported to about 0.6 km downwind from the source, and its effects on the air humidity reach a further distance of 0.9 km downwind from the source. Attention is given to the dependence of the results upon the various factors influencing the simulation, such as the intensity of the source, the atmospheric stratification, and the dynamic factor of the terrain. Some numerical tests were carried out to provide extra insight to the effects of these factors. It has been demonstrated that the simulation results such as relative humidity and temperature are sensitive to these factors, especially to the thermal stratification. Under unstable conditions, the effects of the spray source increase significantly, and the variation extent of the temperature, relative humidity and flow field is larger than that under neutral condition. The effects of dynamic and thermal factors on the air flow field are discussed through the comparison of the modeling results over complex terrain and flat terrain. Received June 8, 1998 Revised April 17, 1999     

Numerical modeling of pollutant transport and chemistry during a high‐ozone event in northern Taiwan

An air pollution prediction model system (APOPS) is developed and applied to northern Taiwan with complex terrain and local thermal circulations. It consists of a nonhydrostatic mesoscale meteoro‐logical model system (MMPMS) and a gas/aerosol transport and air quality model (GATAM). The basic processes relevant to modeling the urban air pollution problems such as meteorology, dispersion, chemistry and deposition are solved at the same time on practically the same grid. The APOPS was tested on a high‐ozone event in northern Taiwan on 16 November 1998. Comparison with observed surface winds shows able to predict local flow patterns such as sea/land breezes and mountain‐valley wind in this high air pollution episode. The predicted surface concentrations of ozone and other pollutants are compared with measured values, and a fairly good agreement with the mean normalized biases of −6%, −11%, for one‐day simulation and for daytime, respectively, is obtained for ozone. Thus, it is confirmed that the APOPS can be utilized to predict urban air quality in complex terrain area.     

山区复杂地形上区域大气质量模式的试验研究

由于复杂地形上的气流多变，所以，进行区域空气质量模拟是比较困难的。根据大气污染总量控制和环境规划的需要，发展了一种可适用于山谷城市的大气质量模式，该模式的主要特点；（１）采用目前尚少的复杂地形上的三维边界层模式作为大气扩散模式所需城三维边界层要素场；（２）用复杂地形上的三维以模式和斯扩散氏架源（包括面源）和主架源所造在的地面ＳＯ２浓度，然后将两者的模拟浓度在相应网各上叠加。验证结果表明，该混合模式     

2011年9月中国华西致灾暴雨环流特征及地形强迫效应分析

采用陕西及周边地区7213个雨量站资料,分析了2011年9月1-18日期间华西地区降水量分布特征,结果表明：该时段累计降水量是历史同期水平的2-3倍,持续时间长,致灾严重。降水主要分为4-6日、11日和16-18日3次大的过程。利用NCEP 1°×1°的资料分析3次过程的水汽和环流特征,表明暴雨区低层的主要水汽输送,除了偏南气流从川东一带向北输送外,还有偏东气流从华北平原南部一带向西输送。与3次降水过程对应,华西地区500 hPa有3次西风槽过境,700 hPa偏南风和850 hPa偏北风分别出现3个明显的控制时段;700 hPa偏南气流先期输送大量暖湿空气到华西地区,形成不稳定层结,当遇到偏北风输送的干冷空气楔入其下将其抬升时,叠加槽前的动力抬升作用和地形造成的风场辐合抬升,使得对流活动增强,不稳定能量释放,暴雨发生。稳定的环流形势（乌拉尔山阻高）导致特定地形下形成持续的不稳定层结以及动力抬升条件被不断重复满足,从而不断引发上升运动释放不稳定能量,这是2011年华西秋雨稳定持续的根本原因。     

Multi-Year Simulations and Experimental Seasonal Predictions for Rainy Seasons in China by Using a Nested Regional Climate Model (RegCM_NCC) Part Ⅱ: The Experimental Seasonal Prediction

A nested regional climate model has been experimentally used in the seasonal prediction at the China National Climate Center (NCC) since 2001. The NCC/IAP (Institute of Atmospheric Physics) T63coupled GCM (CGCM) provides the boundary and initial conditions for driving the regional climate model (RegCM_NCC). The latter has a 60-km horizontal resolution and improved physical pararneterization schemes including the mass flux cumulus parameterization scheme, the turbulent kinetic energy closure scheme (TKE) and an improved land process model (LPM). The large-scale terrain features such as the Tibetan Plateau are included in the larger domain to produce the topographic forcing on the rain-producing systems. A sensitivity study of the East Asian climate with regard to the above physical processes has been presented in the first part of the present paper. This is the second part, as a continuation of Part Ⅰ.In order to verify the performance of the nested regional climate model, a ten-year simulation driven by NCEP reanalysis datasets has been made to explore the performance of the East Asian climate simulation and to identify the model's systematic errors. At the same time, comparative simulation experiments for 5 years between the RegCM2 and RegCM_NCC have been done to further understand their differences in simulation performance. Also, a ten-year hindcast (1991-2000) for summer (June-August), the rainy season in China, has been undertaken. The preliminary results have shown that the RegCM_NCC is capable of predicting the major seasonal rain belts. The best predicted regions with high anomaly correlation coefficient (ACC) are located in the eastern part of West China, in Northeast China and in North China,where the CGCM has maximum prediction skill as well. This fact may reflect the importance of the largescale forcing. One significant improvement of the prediction derived from RegCM_NCC is the increase of ACC in the Yangtze River valley where the CGCM has a very low, even a negative, ACC. The reason behind this improvement is likely to be related to the more realistic representation of the large-scale terrain features of the Tibetan Plateau. Presumably, many rain-producing systems may be generated over or near the Tibetan Plateau and may then move eastward along the Yangtze River basin steered by upper-level westerly airflow, thus leading to enhancement of rainfalls in the mid and lower basins of the Yangtze River.The real-time experimental predictions for summer in 2001, 2002, 2003 and 2004 by using this nested RegCM_NCC were made. The results are basically reasonable compared with the observations.     

利用区域气候模式对我国南方百年气温和降水的动力降尺度模拟

本文采用NCAR的WRF3.5.1模式,以NOAA的20世纪再分析资料作为区域气候模式的初始场和侧边界场,对东亚地区进行了百年以上(1900~2010年)尺度、水平分辨率为50 km的动力降尺度数值模拟试验。通过与观测气候资料的对比,分析了驱动场(20世纪再分析资料)和区域气候模式对我国南方地区近50年(1961~2010年)气温和降水的气候平均态的模拟能力。结果表明:经过动力降尺度的区域气候模式试验结果能更好地模拟我国南方地区气温气候平均态和季节循环。WRF模式模拟的气温与观测的气温的空间相关系数均在0.97以上。年平均和夏季,WRF模式模拟的气温与观测的气温的偏差大多介于-1°C到+1°C之间。对于降水,WRF模式显著提高了我国南方降水的模拟能力。和驱动场相比,WRF模式模拟的降水与观测的偏差明显减小。夏季,WRF模式模拟的降水空间相关系数在0.5以上。由此延伸至对近百年我国南方地区三个子区域(华南地区、江淮地区和西南地区)四个时段(1914~1942年、1943~1971年、1972~2000年和2001~2010年)的分析,结果表明区域气候模式动力降尺度的结果在区域平均的气温和降水的模拟数值上与观测比较接近,夏季模拟能力有明显的提高,冬季存在气温模拟偏低的误差。对气温趋势分析表明,在20世纪40年代以后的两个时间段,区域气候模式明显提高了气温变化线性趋势的模拟性能。     

梅雨锋暴雨数值模拟中地形的作用

通过WRF模式对2003年7月9日至10日梅雨锋暴雨天气过程在有、无地形情况下数值模拟的结果的分析,探讨了地形对梅雨锋暴雨的影响。研究表明:在有地形的模拟中,模拟的结果较好地再现了梅雨锋降水过程、主要影响系统和梅雨锋的结构;而无地形的模拟中,模拟的雨带偏南,强降水范围偏大,降水系统偏南。地形对梅雨锋暴雨的作用是由于地形减弱了北方冷空气的强度。     

城市大气污染物扩散模拟系统开发

简单介绍了一个应用于复杂地形，下垫面条件下的中尺度大气污染物扩散模式的开发和利用；并为城市大气质量数值模拟和预测的实施，以兰州为例进行了初步的理想数值试验，其结果将对改进模式和城市污染源描述提供依据并积累经验，同时这也是最终形成城市大气质量预测系统的前期工作。     

逐层平滑地形的平缓地形追随坐标在高分辨率GRAPES模式中的应用研究

高分辨率GRAPES模式如3 km模式对地形的识别程度更高,模式中各高度坐标面可识别的地形坡度也更大,地形作用带来的气压梯度力计算误差和平流输送误差更突出。平缓地形追随坐标可以通过多种方式衰减坐标面上的地形影响进而减小这些计算误差。选择一种逐层平滑地形的平缓地形追随坐标,基于GRAPES-3km模式进行理想试验和批量模拟试验。试验结果显示:逐层平滑地形的平缓地形追随坐标相对其他平缓地形追随坐标对地形重力波模拟更接近解析值;24 h滚动预报月连续模拟试验中逐层平滑地形的平缓地形追随坐标一定程度上能降低高层月平均的温度场、风场的模拟误差,月平均的降水评分也有所提高。逐层平滑地形的平缓地形追随坐标应用于GRAPES-3km模式有较好的模拟效果。      

Effects of complex terrain on net surface longwave radiation in China

Net surface longwave radiation (NSLR) is one of key meteorological factors and is strongly influenced by cloud cover, surface temperature, humidity, and local micrometeorological conditions as well as terrain conditions. Realistically estimating NSLR is vitally important for understanding surface radiation balance and investigating micrometeorological factors of air pollution dispersion, especially in regions with complicated terrain. In this study, we proposed a distributed model for estimating NSLR by considering effects of complex local terrain conditions in China. Meteorological data (including mean temperature, relative humidity, and sunshine percentage) and observed NSLR data from 1993 to 2001 together with the digital elevation model data were used to parametrize the model and account for the effects of atmospheric factors and surface terrain factors according to the isotropic principle. The monthly NSLR during 1961–2000 was estimated at a spatial resolution of 1 km. Topographic analysis suggests that the distribution characteristics of NSLR with elevation or slope are consistent with those of field observations. In particular, the estimated NSLR is favorably comparable with site-level observations on the Tibetan Plateau (average relative error < 11%). Our results indicate that this model can describe microscale distribution features in mountainous areas in detail and that this improved approach can be used for NSLR spatial estimation in other regions with complicated terrain.     

“03.8”辽宁地区暴雨过程成因的诊断分析

对2003年8月5～6日辽宁地区暴雨过程的环流形势及雷达回波进行了分析。并利用中尺度MM5模式对这次暴雨过程的模拟结果进行了诊断分析，探讨了过程中主要影响系统——华北气旋在渤海西岸生成后迅速发展加强的原因。结果表明。中纬度短波槽的充分发展引导贝加尔湖冷空气的南下、副高的稳定与加强和低空急流的建立输送大量暖湿气流是华北气旋生成的重要条件。而“干侵入”则是造成此次华北气旋迅速发展加强的重要原因。     

Multi-Year Simulations and Experimental Seasonal Predictions for Rainy Seasons in China by Using a Nested Regional Climate Model （RegCM_NCC） Part Ⅱ： The Experimental Seasonal Prediction

A nested regional climate model has been experimentally used in the seasonal prediction at the China National Climate Center (NCC) since 2001. The NCC/IAP (Institute of Atmospheric Physics) T63 coupled GCM (CGCM) provides the boundary and initial conditions for driving the regional climate model (RegCM NCC). The latter has a 60-km horizontal resolution and improved physical parameterization schemes including the mass flux cumulus parameterization scheme, the turbulent kinetic energy closure scheme (TKE) and an improved land process model (LPM). The large-scale terrain features such as the Tibetan Plateau are included in the larger domain to produce the topographic forcing on the rain-producing systems. A sensitivity study of the East Asian climate with regard to the above physical processes has been presented in the first part of the present paper. This is the second part, as a continuation of Part I. In order to verify the performance of the nested regional climate model, a ten-year simulation driven by NCEP reanalysis datasets has been made to explore the performance of the East Asian climate simulation and to identify the model’s systematic errors. At the same time, comparative simulation experiments for 5 years between the RegCM2 and RegCM NCC have been done to further understand their differences in simulation performance. Also, a ten-year hindcast (1991–2000) for summer (June–August), the rainy season in China, has been undertaken. The preliminary results have shown that the RegCM NCC is capable of predicting the major seasonal rain belts. The best predicted regions with high anomaly correlation coefficient (ACC) are located in the eastern part of West China, in Northeast China and in North China, where the CGCM has maximum prediction skill as well. This fact may reflect the importance of the largescale forcing. One significant improvement of the prediction derived from RegCM NCC is the increase of ACC in the Yangtze River valley where the CGCM has a very low, even a negative, ACC. The reason behind this improvement is likely to be related to the more realistic representation of the large-scale terrain features of the Tibetan Plateau. Presumably, many rain-producing systems may be generated over or near the Tibetan Plateau and may then move eastward along the Yangtze River basin steered by upper-level westerly airflow, thus leading to enhancement of rainfalls in the mid and lower basins of the Yangtze River. The real-time experimental predictions for summer in 2001, 2002, 2003 and 2004 by using this nested RegCM NCC were made. The results are basically reasonable compared with the observations.     

中尺度地形对“98.7”鄂东特大暴雨的动力作用

用一个高分辨的 η坐标模式对 1998年 7月 2 1日鄂东沿江特大暴雨过程进行数值模拟 ,得到与实况相吻合的结果。通过敏感性试验和分析 ,研究了局地中尺度地形对这次暴雨过程的影响及其机理。结果表明 ,虽然地形对这次特大暴雨过程的基本面貌并未起到决定性的作用 ,但也有一些重要影响。大别山对边界层南风暖湿气流的阻挡使位于其迎风面上游的暴雨带有所加强。幕阜山对边界层水汽流入的拦截则使位于其背风面下游的暴雨带的初期发展减缓。到了暴雨盛期 ,由于暴雨带南侧有中尺度低空急流出现并正好位于幕阜山区 ,因地形而抬高的摩擦层内的Ekman风矢偏转直指暴雨区 ,加强了暴雨区水汽的辐合。由于强对流暴雨系统盛期近地层气流转为辐散 ,对暴雨维持起关键作用的辐合层升高 ,因此地形抬高的摩擦辐合恰好叠加其上使之增强 ,这可能是此次鄂东沿江特大暴雨过程持续时间长的一个重要原因。     

一次盆地强降雨过程的多模式结果对比分析

运用西南区域数值模式SWCWARMS、欧洲中心细网格预报模式EC以及国家气象中心中尺度区域模式GRAPES对2018年6月25日12时～26日12时发生在四川盆地内的一次强降雨过程进行预报对比分析,多模式结果表明:EC模式与GRAPES模式对盆地西北部的暴雨漏报现象较为突出,SWCWARMS模式能较好模拟整个雨带的强度与位置,对比中尺度系统西南涡的模拟,在低涡出现和发展的12小时内,EC模式对低涡的预报能力偏弱,预报降雨量偏小,低涡位置与强度预报GRAPES与实况最接近,SWCWARMS模式与GRAPES相似,但仅有SWCWARMS预报出低涡南侧与低涡西北象限的强降雨,在低涡减弱阶段,3种模式趋于相同。EC与GRAPES模式在四川盆地内的初始涡度偏弱,辐合偏小,盆地西部边坡对流层低层垂直上升运动偏小,相对湿度偏低,这导致了EC和GRAPES模式在四川盆地西部边坡降雨强度偏小,仅有SWCWARMS模式与实况最符合,尤其对复杂地形下的降雨过程有较强的预报能力。      

Frost risk mapping for landscape planning: A methodology

Summary Minimum air temperatures were measured during three winters with a network of stations in open, undulating terrain. It was observed that the change in minimum air temperature with elevation could be predicted from mean nighttime windspeed, total nighttime net radiation loss and a hill-top reference minimum temperature. It was also found that the deviation of temperatures at individual sites could be predicted from a local terrain parameter which reflects the extent of cold air accumulations. Thus a methodology for frost risk mapping has been developed which is based on regional weather dataand local terrain analysis. This paper describes the model and illustrates the regional weather and terrain effects with three-dimensional block diagrams.With 8 Figures     

Validation of the Atmospheric Infrared Sounder Retrieval Products over China and Their Application in Numerical Model

The atmospheric infrared sounder (AIRS) instrument onboard Aqua Satellite is a high spectral resolution infrared sounder. In recent years, AIRS has gradually become the primary method of atmospheric vertical observations. To examine the validation of AIRS retrieval products (V3.0) over China, the AIRS surface air temperature retrievals were compared with the ground observations obtained from 540 meteorological stations in July 2004 and January 2005, respectively. The sources of errors were considerably discussed. Based on the error analysis, the AIRS retrieved surface air temperature products were systemi-cally corrected. Moreover, the AIRS temperature and humidity profile retrievals were compared with T213 numerical forecasting products. Because T213 forecasting products are not the actual atmospheric states, to further verify the validation, the AIRS temperature and humidity profile products were assimilated into the MM5 model through the analysis nudging. In this paper, the case on February 14, 2005 in North China was simulated in detail. Then, we investigated the effects of AIRS retrievals on snowfall, humidity field, vertical velocity field, divergence field, and cloud microphysical processes. The major results are: (1) the errors of AIRS retrieved surface air temperature products are largely systematic deviations, for which the influences of terrain altitude and surface types are the major reasons; (2) the differences between the AIRS atmospheric profile retrievals and T213 numerical prediction products in temperature are generally less than 2 K, the differences in relative humidity are generally less than 25%; and (3) the AIRS temperature and humidity retrieval products can adjust the model initial field, and thus can improve the capacity of snowfall simulation to some extent.