南岭山地高速公路雾区能见度预报系统

在研究南岭山地浓雾的气候规律,开展了2次多学科综合野外观测,对典型个例进行了天气学分析、雾的宏观结构特征分析、雾的微物理特征分析,在利用数值试验分析了雾生成的物理机制等研究的基础上,研制开发了4种南岭山地京珠高速公路云岩雾区的能见度预报方法,包括：中尺度数值模式产品释用方法、结构预测方法、天气学指标预报方法和动态统计预报方法;并研制了相应的自动化程度高的预测预报系统,与京珠高速公路粤境北段通车同步投入准业务运行,使用雾区路段的5套自动气象站和能见度仪资料,制作的集成预报结果为高速公路行车安全提供服务,经过各种方法的独立预报检验和准业务运行服务的预报结果检验,预报准确率比较高,提供服务的集成预报准确率可达83．3％。     

南岭大瑶山高速公路浓雾的宏微观结构与能见度研究

南岭山地地处南亚热带湿润型季风气候区,每年9月至次年5月有华南准静止锋活动时均会有浓雾发生,每月浓雾日可高达15-18 d,尤其是中国目前最长的京珠高速公路通过南岭主脉大瑶山的乐昌-乳源段,路面海拔高度从200 m增至800多米,山地的抬升使雾害更加严重.在南岭大瑶山高速公路开展的两次多学科综合野外观测,内容包括目测能见度、器测能见度、雾滴谱、雾含水量、系留探空、双参数低空探空、雾层湍流扩散、气溶胶粒子谱、气溶胶成分谱、雾水样品成分、雨水样品成分.对典型个例进行了天气学分析,雾的宏观结构特征分析,雾的微物理特征分析.认识到南岭山地浓雾发生频率高,雾害十分严重,是典型的平流雾和上坡雾,实质上是出现在相对较高海拔高度上的低云,与华南锋面活动尤其是华南准静止峰的活动密切相关,局地地形的作用也非常重要.其特点是浓雾持续时间长、能见度极其恶劣、团块结构明显、雾滴尺度大、浓度不高、含水量较大、雾层内的湍流扩散能力比晴空区强,与中国过去研究较多的辐射雾差别较大.发现雾含水量与能见度呈明显的反相关关系,含水量较大时能见度较小;南岭山地雾含水量等微结构特征量的起伏变化,除与雾体本身的结构不均匀有关外,一个重要的原因是平流因素的影响,南岭山地下垫面的不均匀性,雾体随环境风的平移过程中,不规则的爬坡、翻越山坡的运动是造成雾体结构不均匀、振荡起伏变化的另一个重要原因.该地气溶胶粒子谱是呈单调下降的幂函数谱,次微米粒子浓度甚高,南岭山地气溶胶中含有高浓度的硫酸盐粒子,是优质凝结核,有利于雾的形成.雾的存在可以清除大气中的微量成分,雾滴可以包含浓度很高的污染物成分.同时,较之云滴而言,雾滴也很容易被地表物体(如植被、建筑物等)的垂直表面所截获,构成另一类清除过程.在南岭这样的大面积森林地区,这类清除过程可能是很重要的.研究本地区雾的特征变化,对建立本地区雾的预警预报系统有很大的现实意义,并为开展消雾试验提供了基本资料.     

广州市气溶胶质量谱和水溶性成分谱分析

对2006年9月—2007年1月在广州市采集的气溶胶粒子的质量谱和水溶性成分进行分析表明,广州市各测点的气溶胶质量谱基本呈双峰或三峰分布,细粒子浓度占气溶胶总浓度的四成到六成;在气溶胶水溶性离子成分中,浓度最高的阴离子是SO42-和NO3-,浓度最高的阳离子是NH4+和Na+;各离子多呈三峰或是双峰分布,但不同离子的峰值不尽相同;广州市的粉尘污染逐渐减少,而NH4+浓度迅速增大;相对土壤,只有Na+和NH4+富集度比较大,SO42-和K+有一定富集;相对海洋,F-的富集度非常大,其他离子则无明显富集;Cl-被严重耗损;致酸离子以SO42-为主,NO3-作用较弱些;SO42-和NH4+谱分布有很好的相关性,并且在细粒子和巨粒子粒径范围有共同的来源。     

广州地区春季污染雾的化学特征分析

使用2005年2～3月在广州地区采集的雾水样品资料,分析了广州地区污染雾雾水的化学组分;对3次典型污染雾过程雾水的离子浓度及其可能的来源进行了分析。广州地区的污染雾雾水中的诸离子浓度远高于雨水中的值,因而,雾不但造成视程障碍,而且是高浓度污染的液态颗粒物,对人体健康十分有害。在雾水中浓度最高的阴离子是SO4=, 其次是NO3-;在阳离子中Ca++、NH4+的浓度最高。雨水比雾水更酸,说明虽然雾水中的离子浓度较雨水高得多,但大量的离子成分中存在更多的缓冲物质,比如说NH4+和Ca++。雾水中的Ca++、SO4=、Mg++有明显的富集现象,广州地区的污染雾雾水主要受大陆环境和人类活动的影响。这期间广州地区出现严重污染雾与水汽充足和大量气溶胶污染粒子的存在直接有关。     

基于非迭代海-气通量算法的蒸发波导预测模型研究

蒸发波导易发生在海洋等水体之上.为了深入研究蒸发波导预测模型的诊断预报技术,本研究依据目前最新的非迭代海-气通量算法,建立了非迭代通量算法蒸发波导预测模型-NEW模型,进而对新模型进行了敏感性试验,且用我国近海试验数据进行了检验.最后将NEW模型与目前使用广泛、效果较好的4种蒸发波导模型(即P-J模型、Babin模型、NPS模型和伪折射率模型)进行了对比分析,得到了不同模型蒸发波导高度随气象海洋要素变化的规律,结果表明非迭代通量算法模型与传统模型对不同海洋气象要素的敏感性响应是一致的.不稳定层结条件下NEW模型对蒸发波导的诊断结果接近于Babin模型和NPS模型,而稳定条件下略高于NPS模型.试验表明NEW模型可以有效地诊断预报蒸发波导.本研究系统阐述了非迭代通量算法模型的建立和适用情况,为蒸发波导预测诊断算法的更新和模型发展提出了新的思路.     

STUDY ON THE CHEMICAL CHARACTERISTICS OF POLLUTING FOG IN GUANGZHOU AREA IN SPRING

Samples of fog water collected in the area of Guangzhou during February, March and April of 2005 are used in this work to study the chemical composition of fog water in polluting fog there. Three typical episodes of polluting fog are analyzed in terms of ionic concentration and their possible sources. It is found that the concentration of various ions in fog water is much higher than those in rainwater. Fog not only blocks visual range but contains liquid particles that result in high degree of pollution and are very harmful to human health. SO₄⁼ is the anion with the highest concentration in fog water, followed by NO₃^-.For the cation, Ca⁺⁺ and NH₄⁺ are the highest in concentration. It is then known that rainwater is more acidic than fog water, indicating that ionic concentration of fog water is much higher than that of rainwater, but there are much more buffering materials in fog water, like NH₄⁺ and Ca⁺⁺. There is significant enrichment of Ca⁺⁺, SO₄⁼, and Mg⁺⁺ in fog water. In the Guangzhou area, fog water from polluting fog is mainly influenced continental environment and human activity. The episodes of serious fog pollution during the time have immediate relationships with the presence of abundant water vapor and large amount of polluting aerosol particles.     

A COMPOSITE STUDY OF RAINFALL ASYMMETRY OF TROPICAL CYCLONES AFTER MAKING LANDFALL IN GUANGDONG PROVINCE

Based on observed rainfall data, this study makes a composite analysis of rainfall asymmetry in tropical cyclones(TCs) after making landfall in Guangdong province(GD) during 1998—2015. There are 3.0 TCs per year on average making landfall in GD and west of GD(WGD) has the most landfall TCs. Most of TCs make landfall in June,July, August, and September at the intensities of TY, STS, and TS. On average, there is more rainfall in the southwest quadrant of TC in CGD(center of GD), WGD, and GD as a whole, and the maximum rainfall is located in the southwest near the TC center. The mean TC rainfall in the east of GD(EGD) leans to the eastern side of TC. The TC rainfall distributions in June, July, August, and September all lean to the southwest quadrant and the maximum rainfall is located in the southwest near the TC center. The same features are found in the mean rainfall of TD, TS, STS, TY,and STY. The maximum rainfall is mainly in the downshear of vertical wind shear. Vertical wind shear is probably the dominate factor that determines asymmetric rainfall distribution of TCs in GD. Storm motion has little connection with TC rainfall asymmetry in GD.     

珠江三角洲城市地区MODIS气溶胶光学厚度产品的检验分析

根据2004年1—11月地面太阳光度计的气溶胶光学厚度的观测数据,对美国航空航天局(NASA)发布的中分辨率成像光谱仪气溶胶光学厚度产品(MODIS AOD C004)在珠江三角洲城市地区的准确性进行了检验,并分析了造成MODIS AOD误差的可能原因。分析结果表明:⑴MODIS AOD的误差在NASA的预期误差范围内,MODIS AOD可作为气候变化的研究和区域大气污染监测的有效手段。⑵与世界上其他地区的检验结果类似,MODIS AOD在珠江三角洲城市地区存在一定的系统性偏差:当AOD较小时,MODIS AOD值大多高估,而当AOD比较大时,MODIS AOD值偏低,这一系统性偏差大于全球平均偏差。其中广州和南海的偏差最为显著,东莞和番禺次之。⑶导致MODIS AOD在珠江三角洲城市地区出现较大系统性偏差的原因包括:珠江三角洲工业化和城市化的发展,使地表的植被覆盖率已大幅减少,MODIS AOD反演所采用的地表反照率估算值可能偏小;气溶胶模型中设定的单散射反照率值偏高,低估了珠江三角洲城市地区气溶胶的吸收性。     

兰州地区高云和气溶胶光学特性及其辐射效应

利用激光雷达探测分析了兰州上空的高云与气溶胶的光学参数,并用LOWTRAN7定量模拟出高云对气溶胶辐射特性的影响。结果表明,消光系数廓线与相对湿度廓线随高度的变化一致性较好,气溶胶层主要在2km以下,低层气溶胶和高云的消光系数和相对湿度较大。白天,高云的存在使云下气溶胶短波加热率减小。有云和无云时气溶胶加热率的差别在地表处最为明显,中午前后差别较大,最大为11:00的0.096K.h-1。夜间,高云的存在使云下气溶胶长波冷却率减小,在1000m以下有云和无云时气溶胶冷却率的差别小,在1000m以上差别大,最大差别出现在1500m处(02:00～04:00),为0.033K.h-1。     

IMPROVEMENT OF REGIONAL PREDICTION OF SEA FOG ON GUANGDONG COASTLAND USING THE FACTOR OF TEMPERATURE DIFFERENCE IN THE NEAR-SURFACE LAYER

The relationship between the factor of temperature difference of the near-surface layer(T_(1000 hPa)-T_(2m))and sea fog is analyzed using the NCEP reanalysis with a horizontal resolution of l°xl°(2000 to 2011) and the station observations(2010 to 2011).The element is treated as the prediction variable factor in the GRAPES model and used to improve the regional prediction of sea fog on Guangdong coastland.(1) The relationship between this factor and the occurrence of sea fog is explicit:When the sea fog happens,the value of this factor is always large in some specific periods,and the negative value of this factor decreases significantly or turns positive,suggesting the enhancement of warm and moist advection of air flow near the surface,which favors the development of sea fog.(2) The transportation of warm and moist advection over Guangdong coastland is featured by some stages and the jumping among these states.It also gets stronger over time.Meanwhile,the northward propagation of warm and moist advection is quite consistent with the northward advancing of sea fog from south to north along the coastland of China.(3) The GRAPES model can well simulate and realize the factor of near-surface temperature difference.Besides,the accuracy of regional prediction of marine fog,the relevant threat score and Heidke skill score are all improved when the factor is involved.