【作者】 王秋云；

【导师】 严明良； 包云轩；

【作者基本信息】 南京信息工程大学 ， 应用气象学， 2011， 硕士

【摘要】 随着社会经济的迅猛发展,高速公路建设不断加快,通车里程不断增加。与此同时,由于不利气象条件导致的高速公路交通事故率也随之递增,给人民生命财产带来了巨大损失。为了确保公路交通的安全,对高速公路沿线高、低温胁迫的形成机制及预报技术的研究显得尤其重要。本文根据沪宁高速公路AMMS实时监测数据筛选出若干典型的高、低温个例,应用美国新一代中尺度数值预报模式WRF(Weather Research and Forecast Model for Version 3.2)结合NCEP气象再分析资料对其进行了数值模拟试验,经检验发现模拟效果较为理想。根据模式输出结果对公路环境下高、低温天气形成的物理机制进行了诊断分析,探讨了下垫面因素对高、低温胁迫形成的影响。在此基础上,提取了沪宁高速公路高低温天气的预警参数,并建立了相应的预报模型。通过对筛选出的30个高温个例的数值模拟及统计分析表明：(1)利用WRF模式对沪宁高速公路沿线的高温天气过程进行模拟是可行的；(2)对模式输出物理量进行统计分析后,提取了沪宁高速公路沿线高温天气的数值预警指标,这些指标包括：沪宁高速公路沿线前一日14时地表温度Ts≥40℃、地面潜热通量F1为正且其值≥350W·m-2、近地面相对湿度Hr≤60%、当日08时地面感热通量Fs为负且绝对值≥70 W·m-2、当日08时地面水平风速Vs≤3m·s-1；(3)以上述预警指标为预报因子建立了梅村和河阳站的高温天气预报模型,经检验发现所建模型对2010年7～8月每日14时气温的预报准确率较高,基本符合预报要求。利用2008年7月4日至6日高温个例的模式输出结果对其诊断分析后发现：(1)温度平流对此次高温天气过程中地面增温影响较小；(2)江苏的沿江和苏南地区上空大气层结稳定,有强烈下沉运动,有利于高温的形成;(3)高温时段内,该地区高、低空相对湿度低,地面水平风速小,地表长波辐射强,是贴地气层增温迅速的重要原因；(4)地形起伏对公路沿线高温天气产生的影响主要从焚风效应上反映出来,而不同土地利用类型对近地层气温变化的作用可以通过感热吸收和潜热释放的差异来体现。考虑下垫面因素的影响,本文针对WRF模式耦合不同陆面参数化方案对2009年7月19日至21日出现的高温天气过程模拟效果的影响进行了一系列敏感性试验,结果表明：(1)此次高温天气对陆面过程较为敏感,模式中耦合陆面参数化方案后的试验结果更接近实况。SLAB、NOAH、RUC三种陆面方案均较为真实地模拟出了梅村站气温变化趋势,但耦合NOAH陆面方案对气温的预报准确率最高；(2)不同陆面方案的模拟结果共同反映出,沪宁高速公路沿线感热通量大而潜热通量小这一特征,NOAH方案对感热和潜热通量的模拟效果更理想；(3)垂直运动对陆面方案的敏感性较强,基于NOAH方案模拟的垂直运动效果最好；(4)SLAB、NOAH和RUC陆面方案模拟的相对湿度间存在差异,SLAB方案较其他两个方案的模拟效果更好些；(5)三种陆面方案模拟的地面水平风速都较小,这有利于地面高温出现,地面风速模拟对陆面方案的选择较为敏感,NOAH方案对其模拟效果最佳。通过对筛选出的30个低温个例的数值模拟与统计分析表明：(1)利用WRF模式对沪宁高速公路沿线的低温天气过程进行模拟是可行的；(2)提取的沪宁高速公路沿线低温天气的预警指标有：沪宁高速公路沿线前一日05时地表温度Ts≤-3℃、前一日05时850hPa温度平流Atemp≤-1×10-3K/s、前一日05时地面长波辐射通量Fdlw≤230W·m-2、前一日23时近地面相对湿度Hr≤45%、地面向上热通量Fuh在-50W·m-2与0W·m-2之间；(3)建立了玉祁和镇江站的低温天气预报模型,经检验发现所建模型对2010年1月每日05时气温的预报准确率较高,具有一定的应用价值。对2009年1月23日至25日低温天气过程的模拟及诊断分析表明：(1)江苏处于西北气流的风场中,北方冷空气源源不断地输送至此,使江苏大幅度降温：(2)苏南大部分地区都存在较强的冷平流,沪宁高速公路沿线均被冷平流控制,温度平流为低温的形成、发展及维持提供了一个相对稳定的热力背景；(3)对流层低层几乎没有垂直运动,绝热冷却项不是造成此次低温天气的主要原因；(4)模拟区域内高低层水汽含量较低,且近地层风速较小,上下层空气热量交换不显著,此形势有利于夜间辐射降温。本研究以高速公路实测气象资料为基础,利用WRF模式,合理选择参数化方案和陆面物理过程,对高速公路高低温天气过程进行了较精细的数值模拟,取得了较好的模拟和预报效果。同时根据模式输出结果,结合不同尺度天气气候背景,在GIS技术支持下,利用DEM模型深入而客观地剖析了高速公路高低温胁迫形成的物理机制及公路周边特殊地理环境对高低温天气产生的影响。研究具有精细性、机理性、系统性,为我国高速公路现代交通气象预警预报技术的发展提供了重要的科学参考。更多还原

【Abstract】 With the rapid development of society and economy in China, the highway construction has been accelerating and the mileage has been increasing. Meanwhile, the rate of the traffic accidents caused by the unfavorable meteorological conditions on the highway has been rising rapidly and it has brought great loss to the lives and property of people. In order to reduce the loss and ensure the traffic safety on the highway, it seems very important to ascertain the formation mechanism of the high and low temperature stress along highways and develop their accurate meteorological forecasting techniques.Based on the real-time data monitored by the automatic meteorological monitoring system (AMMS) on the Shanghai-Nanjing Expressway, In this paper, some high and low temperature weather events were filtered out and simulated by using WRF 3.2 (Weather Research and Forecast for Version 3.2),a new generation of mesoscale numerical forecasting model. A set of researches was showed that the simulation results were satisfactory after the verifications from the observed values. After the analysis on the simulations and observations, the physical mechanisms of the engendering of these high and low temperature weather events were explained and the influence of the underlying factors under the special environment of the highway on the formation of high and low temperature stress were discussed. Consequently, the forewarning parameters of the high and low temperature weather on the Shanghai-Nanjing Expressway were extracted and the forecast models at some stations were established.The results of numerical simulation and statistical analysis on the filtered 30 typical high temperature weather events showed as followed:(1) The selective simulations on the high temperature weather along the Shanghai-Nanjing Expressway by using WRF model were feasible. (2)After the statistical analysis on the output physical variables from the WRF model,the numerical forewarning indices of the high temperature weathers on the Shanghai-Nanjing Expressway were extracted as follows:the surface temperature at 14:00 (BJT) on the previous day of the predicted day is above 40℃, the latent heat flux on the ground at 14:00 (BJT) on the previous day of the predicted day is above 350 W·m-2, the air relative humidity near the ground at 14:00 (BJT) on the previous day of the predicted day is below 60%, the sensible heat flux at the surface at 08:00 (BJT) on the predicted day is negative and its absolute value is above 70 W·m-2, and the horizontal wind speed on ground at 08:00 (BJT) on the predicted day is below 3m·s-1. (3)Based on the above numerical forewarning indices, the forecasting models of the high temperature weathers at Meicun Station and Heyang Station were established. The air temperature values at 14:00(BJT) per day from July to August in 2010 were predicted by the established regression equations and it was indicated that the forecast accuracy of the forecasting models was satisfactory.The diagnostic analysis on the simulation results of the high temperature weather process from Jul.4th to Jul.6th in 2008 indicated that:(1) The effect of the temperature advection on the warming at the ground was very small in this high temperature weather event. (2) When the air was stable over Jiangsu province and there was strong sinking movement in the vertical direction, it was favorable to the forming of high temperature weather. (3) In this high temperature weather process, the low relative humidity in the high and low level of the atmosphere, the small horizontal wind speed at the ground and the strong downward long-wave radiation were key factors that resulted into a rapid rising of the air temperature in the studied area. (4) The influence of topography on the high temperature weather along the Shanghai-Nanjing Expressway was mainly reflected from some foehn effects and the impact of different land-use types and the change of air temperature at the surface was displayed by the different values of the obtaining sensible heat and the releasing latent heat during the high temperature weather process occurred.Considering the impact of topographic characteristic of underlying surface, the sensitivity tests of coupling different land surface schemes (SLAB, NOAH and RUC) to the WRF model were conducted. The results were described as followed:(1) The integrated simulations coupling the land surface parameterization schemes to WRF model were closer to the reality and the sensitivity of the high temperature weather simulations to the land surface physical processes was significant. The simulated temperature values of Meicun Station based on the three different land surface schemes were close to the observed values and when the NOAH scheme was coupled into the WRF model, the prediction accuracy of the simulation on the air temperature was highest. (2) From the simulations of coupling the three different land surface schemes, it was showed that the sensible heat flux was high and the latent heat flux was low along the Shanghai-Nanjing Expressway. The integrated simulation of coupling NOAH scheme was more satisfactory. (3) The vertical movement simulated by the WRF model was sensitive to the selection of different land surface schemes and NOAH scheme gave more reasonable results than the others. (4) In the simulations on the relative humidity, there were some differences between each other for the three schemes and the SLAB scheme had more ideal effect than the NOAH scheme or the RUC scheme. (5) The horizontal wind speed at ground surface simulated by the three land surface schemes was small, which was conducive to the emergence of high temperature stress at the surface. The simulation to wind speed by WRF model was sensitive to the selection of different land surface processes. Results simulated by the NOAH scheme had a better effect than the others.The numerical simulations and statistical analysis on 30 typical low temperature weather events showed that:(1) The selective simulations on the low temperature weather along the Shanghai-Nanjing Expressway by using WRF model were feasible. (2)The numerical forewarning indices of the low temperature weathers on the Shanghai-Nanjing Expressway were extracted as follows:the surface temperature at 05:00 (BJT) on the day before the predicted day along the Shanghai-Nanjing Expressway is below -3℃, the temperature advection value on 850hPa at 05:00 (BJT) is below -1×10-3K/s, the long wave flux downward at ground surface at 05:00 (BJT) is below 230W·m-2, the relative humidity near the surface at 23:00 (BJT) on the day before the predicted day is below 45%, the upward heat flux at ground surface is above -50 W·m-2 and below 0 W·m-2 at 23:00 (BJT). (3)Under the assistance of SAS (the Statistical Analysis System), an statistical analysis software, the forecast models of the low temperature weathers at Yuqi Station and Zhenjiang Station were established with a multiple linear regression method. The air temperature values at 05:00 (BJT) per day in January of 2010 were predicted by the established regression equations and it was indicated that the forecast accuracy of the forecasting models was satisfactory.The observed data from AMWS and the numerical simulations of a low temperature weather process from Jan.23th to Jan.25th in 2008 indicated that:(1) Jiangsu Province was in the wind field of northwest airflow in the upper and lower air and the northern cold air was continuously transmitted to Jiangsu. As a result, the air temperature dropped significantly. (2) There was strong cold advection in the southern part of Jiangsu and the regions along the Shanghai-Nanjing Expressway were controlled by the cold advection.The relatively stable thermal background was provided for the formation, development and maintenance of the low temperature weather by the cold advection. (3) There was hardly vertical movement in the lower troposphere, so the adiabatic cooling was not the main reason why caused the engendering of this low temperature weather event. (4) The relative humidity was low in the high and low level of the atmosphere in the simulated area. The wind speed at ground surface was small, so the heat exchange between the upper and lower layers of the atmosphere was not significant, which was favorable to radiation cooling at night.By the reasonable selecting of the parameterization and land physical process schemes, this study was innovative to simulate the high and low temperature weather events under the complicated weather backgrounds on Shanghai-Nanjing Expressway by using WRF model combined the real-time data from AMMS with NCEP reanalyzed meteorological data. Considering the weather backgrounds of the different scales, it was objective and comprehensive to diagnose the simulated fields of different physical variables, explain the physical mechanisms of the high and low temperature weathers engendering in the special periphery environment of the Expressway and discuss the effect of underlying factors such as topography, water systems, vegetation, land use types in these processes using DEM model in ArcGIS software. Under the assistance of WRF model, a set of the sensitivity tests for terrain, land surface physical processes and land use types in the high and low temperature weather events were used to verify their effect quantitatively. This study is accurate, systematic in the method and explicit in the physical mechanism and it will provide an important scientific reference for the development of traffic meteorological forewarning and forecasting on highways in China.更多还原