星载测雨雷达和测云雷达探测的夏季高原云和降水特征研究

发布时间：2018-01-03 09:01

本文关键词：星载测雨雷达和测云雷达探测的夏季高原云和降水特征研究　出处：《中国科学技术大学》2016年博士论文　论文类型：学位论文

【摘要】：云和降水在气候变化中具有重要意义,使用卫星多仪器多通道联合观测云和降水已经成为当前大气遥感和气候变化领域的研究热点。青藏高原通过热-动力作用,对区域气候变化具有极大影响,被称为全球气候变化的“驱动机与放大器”,研究高原云和降水具有重要意义。同时,不同类型的云和降水形成的热-动力过程和微物理过程不同,因此,针对青藏高原不同类型的云和降水特征进行研究,可以更好地理解高原云和降水形成的热-动力和微物理过程,为模式提供参考依据,提高模式预报的准确性。本文利用热带测雨卫星(TRMM)搭载的测雨雷达(PR)和可见光/红外扫描仪(VIRS) 1998-2012年的融合资料,研究了青藏高原夏季不同类型降水的水平分布、光谱信号、垂直结构和日变化特征,以及各类型降水之间的关系。同时,借助CloudSat-CALIPSO的云层分类,在气候尺度上考察不同云层类型云量的分布、垂直结构、微物理特征和云辐射等属性上的定量差异,并分析了相应的大气环境特征以及白天和夜晚云分布的不同。论文还研究了不同地形下降水的水平分布、光谱信号、垂直结构、大气环流和日变化特征,揭示了地形对降水的影响。论文主要取得的结论如下：1.深厚降水和浅薄降水的气候特征夏季高原降水主要以深厚弱对流降水为主(67.8%),浅薄降水次之(26.4%),深厚强对流降水出现最少(5.8%),相应的条件降水强度分别为1.3,1.4和9.5mm/h,对高原总降水的贡献分别达18.5%,51.2%和30.3%。不同云顶红外辐射温度的平均降水廓线表明,深厚降水从回波顶高度至近地面高度均经历先增大,后减小的过程,而浅薄降水只有增大过程。深厚强对流和深厚弱对流降水频次峰值均出现在16：00LT(当地时,下同),降水强度峰值分别出现在18：00LT和13：00LT,其中深厚强对流降水强度在00：00 LT还出现次峰值。浅薄降水的降水频次及强度峰值均出现在20：00 LT,呈现夜雨特点。深厚降水和浅薄降水云顶红外辐射温度日变化特征相似,最低值均出现在19：00 LT。研究还表明,深厚强对流和深厚弱对流降水具有明显的东移特征,其中深厚弱对流降水的东移特征更为明显,而浅薄降水无明显的东传特征。2.不同相态降水云的气候特征以云顶相态定义的青藏高原降水类型统计表明,夏季高原主体降水以冰相降水为主(43.01%),其次是冰水混合相1型降水(38.85%)和冰水混合相2型降水(17.79%),水相降水最少(0.35%)。各类型降水强度均较小,主要集中在0.5-2mm/h范围内。空间分布表明,冰相和冰水混合相降水的频次和强度均自高原西部向东部增加,而其降水回波顶高度自高原西、中部向东部降低。根据降水垂直廓线在不同高度上相对的稳定斜率,各云顶相态云的降水垂直结构均可以分为两层：第一层从回波顶高度至近地面7.25 km高度,回波强度随着高度的降低不断增强；第二层从7.25 km高度至近地面高度,回波强度随着高度的降低逐渐减弱。降水日循环曲线表明,在高原西部,冰相降水和混合相降水频次峰值均出现在16：00 LT附近,降水发展过程不显著；在高原中部和东部,冰水混合2型、冰水混合1型和冰相降水频次的位相依次向后推移2小时,表明这些地区降水的发展过程显著。且90°E以东地区,各类型降水位相自西向东依次向后推移,表明了对流系统自西向东传播的过程。3.云结构气候特征夏季高原云覆盖率高达86.79%,主要以单层云为主(56.86%),双层云次之(24.47%),随着云层数增加,云所占比例递减。单层云相对高值区集中在高原北部,多层云整体呈东南向西北递减的分布形式。云顶最大高度约为17km,云概率在7.5 km高度达到最大。单层云的厚度大于多层云,且上层云的值一般小于下层云。单层云的各微物理量特征值(粒子数密度、云水含量和粒子有效半径)大于多层云,上层云的值一般小于下层云,且各微物理量值均随雷达反射率呈指数性增长。云的短(长)波辐射为加热(冷却)效应,单层云的冷却(加热)效应大于(小于)多层云。高原降水以液态降水为主,其次为固态降水,毛毛雨降水最少,且毛毛雨主要发生在多层云降水中。大气垂直廓线表明,中低层温度越高,比湿越大,气压越高越有助于多层云的形成。云分布昼夜差异显著,单层云白天所占的比例(62.99%)高于夜晚(51.00%),而双层云和三层云白天的比例均低于夜晚,表明多层云更易发生在夜晚,这与夜晚近地面比湿大和气压高有关。液态降水白天所占比例大于夜晚,而固态降水和毛毛雨则相反。4.喜马拉雅山陡峭地形上降水特征本文利用1998-2012年5-8月的TRMM PR和VIRS融合数据研究了喜马拉雅山陡峭地形及其周边区域,包括恒河平原(flat Gangetic Plains-FGP)、喜马拉雅山山脚(foothills of Himalayas-FHH)、喜马拉雅山陡坡(steep slope of south Himalayas -SSSH)和喜马拉雅山-高原抬地(Himalayas-Tibetan Plateau tableland-HTPT)的降水特征,并结合ECMWF再分析资料,研究了相应区域的大气环流特征。研究结果表明,降水频次从FGP经FHH显著增加,在SSSH的2.5 km高度处达到最大值,然后随地形的继续增加单调减小,最小值出现在HTPT。降水强度在FGP、FHH、SSSH和HTPT的值依次为4mm/h,5.5mm/h,2～4mm/h和低于2mm/h。20dBZ回波顶高度在FGP最高,达16km,然后依次为FHH(15.5km), SSSH (14 km)和HTPT (14 km)。同时,地形对降水云的云相态特征影响也较大。在FGP、FHH和HTPT,60%以上的降水云顶是由冰粒子组成,然而在SSSH,70%以上的降水云顶是由冰水混合粒子组成。研究结果还表明在SSSH产生的强降水频次和喜马拉雅山地形抬升引起的强烈上升运动密切相关。暖湿的洋面气流在FHH被SSSH阻挡,在低层产生辐合,致使最强降水强度发生在FHH。代替地形高度,文中定义的地形指数与降水参量有显著的线性关系,表明地形指数在复杂地形降水的分布中具有很好的指示意义。降水日变化空间分布呈现显著的区域性差异,HTPT、FGP降水频次峰值位于午后,SSSH降水频次有两个峰值,分别出现在午后和傍晚,FHH降水频次峰值位于午夜至凌晨期间。大气环流具有明显的日变化特征,且与降水的分布有很好的对应关系,垂直运动向上,低层辐合,高层辐散的距平环流场有助于降水的产生。
[Abstract]:Cloud and precipitation plays an important role in climate change, the use of satellite multi instrument multichannel joint observations of clouds and precipitation has become a hotspot of current remote sensing of atmosphere and climate change. The Qinghai Tibet Plateau by thermal power, has great influence on the regional climate change, known as the "driver and amplifier" with global climate change. Significance of the research on the plateau of clouds and precipitation. Meanwhile, different types of cloud and precipitation of thermo dynamical and microphysical processes are different, therefore, to study the characteristics of different types of clouds and precipitation of the Tibetan Plateau, you can better understand the plateau cloud and precipitation thermal dynamic and microphysical processes, and provide reference for improving mode. The accuracy of model prediction. By using TRMM Precipitation Radar (TRMM) with (PR) and visible / infrared scanner (VIRS) in 1998-2012 Data fusion, horizontal distribution, on the Tibetan Plateau in summer precipitation in different types of spectrum signal, the characteristics of vertical structure and diurnal variation, and the relationship between various types of precipitation. At the same time, with the help of cloud classification CloudSat-CALIPSO, effects of different types of cloud distribution, clouds in climate scale vertical structure, micro quantitative differences in physical characteristics and cloud radiation other attributes, and analyzes the features of atmospheric environment and the corresponding day and night cloud distribution is different. The paper also studies the distribution of precipitation, the level of different terrain spectrum signal, the vertical structure of the atmospheric circulation characteristics and diurnal variation, reveals the influence of terrain on precipitation. The main conclusions are as follows: 1. deep precipitation and shallow precipitation climatic characteristics of summer precipitation mainly in the deep weak convective precipitation (67.8%), (26.4%) the precipitation of shallow, deep convective precipitation is the most Less (5.8%), the conditions of the corresponding precipitation intensity were 1.3,1.4 and 9.5mm/h, on the plateau of the total precipitation contribution reached 18.5%, the average precipitation profiles and 51.2% different 30.3%. cloud infrared radiation temperature showed that deep precipitation from the echo top height to the ground height first increased, then decreased, and shallow only increase the precipitation process. Deep convection and deep weak convection precipitation frequency peak appeared at 16:00LT (local time, the same below), the precipitation intensity peaks at 18:00LT and 13:00LT, in which deep strong convective precipitation intensity in the 00:00 LT also appeared the first peak. Shallow precipitation frequency and intensity of precipitation peak appeared at 20:00 LT. The rain has deep and shallow precipitation characteristics. Similar characteristics of infrared radiation temperature diurnal variation of precipitation in Genting, the lowest value appeared in the 19:00 LT. study also showed that deep convection and strong deep weak convection Precipitation has obvious characteristics of deep eastward, the weak eastward characteristics of convective precipitation is more obvious, and the shallow precipitation type Tibetan Plateau eastward propagation characteristics of.2. precipitation statistics without obvious different phase precipitation characteristics of cloud to cloud phase definition indicates that the main water drop to plateau summer ice phase precipitation (43.01%). Is the second phase precipitation ice water mixed type 1 (38.85%) and mixed ice water phase precipitation type 2 (17.79%), water (0.35%). The least rainfall type rainfall intensity are small, mainly concentrated in the range of 0.5-2mm/h. The spatial distribution shows that the ice and ice water mixed phase precipitation frequency and intensity from the Western to the eastern plateau increased but, the precipitation echo top height from the west to the East Central Primary and lower slope stability. The relative height according to the rainfall in different vertical profiles, the cloud phase precipitation cloud vertical structure can be divided into two layers: the first From the height of echo top layer near the ground surface to the height of 7.25 km, the echo intensity with the decrease of height increasing; second layers from 7.25 km to near ground level, the echo intensity weakened gradually with the decrease of height. The diurnal cycle of precipitation in the western plateau, curve shows that the ice phase precipitation and mixed phase precipitation frequency peak appeared at 16:00 near LT, no significant precipitation in the process of development; in the middle and East, mixed type 2, type 1 and mixed phase ice ice phase precipitation frequency in turn back over 2 hours, showed that the development of these precipitation significantly. And 90 degrees east of E, various types of precipitation phase from west to East over backwards that shows that the convective system spread from west to east of the.3. cloud structure of climatic characteristics of summer plateau cloud coverage rate up to 86.79%, mainly in the single (56.86%), mainly stratus cloud layer times (24.47%), with the increase in the number of clouds Plus, the proportion of cloud decreasing. Single cloud relatively high value area concentrated in the northern plateau, the overall distribution is cloud southeast to northwest. The maximum height of the cloud is about 17km, the probability of cloud at 7.5 km height. The maximum monolayer thickness is greater than the multi stratus cloud, and the cloud is generally less than the lower level the micro physical characteristics of single-layer clouds value (particle density, water content and particle effective radius) is greater than the clouds, cloud is generally less than the lower level, and the micro physical values with the radar reflectivity exponentially. The cloud short (long) wave radiation for heating (cooling) effect a single cloud, cooling (heating) effect is greater than (less than) multilayer clouds. Precipitation in liquid precipitation, followed by solid precipitation, precipitation and drizzle at least, drizzle occurs mainly in water drop in the cloud. The atmospheric vertical profiles show that the lower layer temperature is high, humidity The greater the higher the pressure helps to form a multi stratus cloud distribution. Significant differences between day and night, single day cloud proportion (62.99%) higher than the night (51%), and three day double clouds and clouds were lower than that at night, clouds are more likely to happen in the night, the night near the ground and the high high humidity and air pressure. The proportion of liquid precipitation during the day than at night, while the solid precipitation and drizzle in Himalaya Range.4. steep terrain characteristics of precipitation by using 1998-2012 TRMM PR and 5-8 VIRS on the steep terrain of Himalaya Range and its surrounding areas of data fusion, including Ganges RIver plain (flat Gangetic Plains-FGP), Himalaya Range (at the foot of the mountain foothills of Himalayas-FHH (steep slope), Himalaya Range of South Himalayas slope -SSSH) and Himalaya Range (Himalayas-Tibetan Plateau tableland-HTPT plateau elevation drop) Water features, combined with the ECMWF reanalysis data, the atmospheric circulation characteristics of the corresponding region. The results show that the precipitation frequency from FGP by FHH significantly increased in SSSH at the height of 2.5 km reached the maximum value, and then continue to decrease monotonically increase with the terrain, the minimum occurred in HTPT. precipitation intensity in FGP, FHH. The SSSH and HTPT value were 4mm/h, 5.5mm/h, 2 ~ 4mm/h and 2mm/h.20dBZ is lower than the height of echo top in FGP the highest, up to 16km, followed by FHH (15.5km), SSSH (14 km) and HTPT (14 km). At the same time, terrain on Precipitation Cloud cloud phase characteristics have greater influence in FGP. FHH, and HTPT, more than 60% of the precipitation cloud is composed of ice particles, but in SSSH, more than 70% of the cloud precipitation is composed of ice water mixed particles. The results also show that the strong ascending motion in SSSH caused by the generation of intense precipitation frequency and Himalaya Range terrain elevation is closely related to the warm. The ocean is blocked in the wet air SSSH FHH, produced the convergence in the lower layer, resulting in the strongest precipitation intensity instead of terrain height in FHH., in this paper the definition of the topographic index and precipitation parameters had significant linear relationship, show that the topographic index is a good indication of the distribution of precipitation in complex terrain in the spatial distribution of precipitation in a day. Showed regional differences, significant HTPT, FGP precipitation frequency peak in the afternoon, SSSH precipitation frequency has two peaks, respectively, in the afternoon and evening, during the FHH precipitation frequency peak at midnight to midnight. The atmospheric circulation has obvious diurnal variation, and have a good relationship with the distribution of rainfall, vertical motion upward, lower level convergence, upper level divergence from the bulk flow flat ring contribute to the precipitation.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P412.25

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