中国东部云-降水对应关系的分析与模式评估

为评估和改进模式中不同类型云与降水的对应关系,利用1998—2007年卫星-台站融合降水资料和国际卫星云气候计划的卫星观测云资料,采用诊断方法分析了中国东部季风区冬季层云、夏季对流云、层云与降水的水平分布及季节变化对应关系,并评估了BCC_AGCM模式的T42和T106分辨率版本对云-降水对应关系的模拟能力。观测资料分析结果表明,中国东部冬季云带和雨带都稳定少动,降水主要来自雨层云和高层云,南部沿海层云和层积云也对降水有贡献;夏季,中国东部表现为层积混合云降水特征,对流云带与降水带具有较好的对应关系,并具有一致的移动特征。对流降水主要来自深对流云和卷层云,深对流云云量和降水中心完全吻合,卷层云云带则表现出比深对流云主体和降水带偏北的现象;层云降水主要来自高层云和层积云。模式评估结果表明,中、低分辨率版本的BCC_AGCM模式均模拟出了冬季层云和稳定少动的降水带、夏季深对流云、卷层云和降水带的对应关系及随季风推进的移动特征。与T42模式版本相比,T106模式版本在夏季对流云云量的模拟及其与降水带的对应关系方面有所改善,说明改进的BCC_AGCM积云对流参数化方案与高分辨率模式网格更匹配,但冬季层云云量模拟误差变大,与降水带的对应关系变差,其原因值得进一步分析研究。     

基于星载测雨雷达探测的亚洲对流和层云降水季尺度特征分析

利用热带测雨卫星搭载的测雨雷达10年探测结果,就季尺度亚洲对流降水和层云降水的降水频次和强度及降水垂直结构的特点进行了研究.结果表明春、秋、冬三季东亚季平均降水环西太平洋副热带高压呈带状分布,雨强一般不超过10 mm/d;夏季,沿孟加拉湾、中国西南、中国东部至日本的大片雨区中出现了大于12 mm/d强降水;亚洲陆面对流和层云降水强度均弱于洋面.亚洲山地强迫不但可引起迎风坡上千公里长度的高降水频次和强降水带,而且导致其下风方向降水频次减少.季尺度降水频次分析表明,亚洲大部分地区对流降水频次小于3%;而层云降水频次一般大于3%,最高可超过10%;副热带高压南侧及西南侧的热带地区对流和层云降水频次均高于副热带高压北侧及西北侧的中纬度地区;降水频次的区域分布还表明,春季中南半岛至中国华南及南海南部对流活动多于同期的印度次大陆.季平均对流和层云降水廓线的季节变化主要表现为"雨顶"高度的季节变化,即降水云的厚度变化;两类降水平均廓线季节变化的区域性差异表明,热带外地区较热带地区显著、陆面较同纬度洋面显著、孟加拉湾比南海显著,而南海和西太平洋暖池无明显的季节变化.此外,降水结构的剖面分析还表明对流降水存在4层结构、层云降水存在3层结构.     

青藏高原及其下游地区降水厚度季、日变化的气候特征分析

利用10年的TRMM卫星降水雷达观测资料, 首次对青藏高原及其下游平原及海洋地区降水厚度的地区差异进行了对比分析, 并对青藏高原及其周边地区对流和层云降水厚度的水平分布及其日变化和季节变化进行了统计分析, 结果表明: (1) 青藏高原地区对流和层云降水厚度都要比下游平原地区更为浅薄, 东部海洋地区对流降水厚度比平原地区小, 而层云降水厚度与平原地区相当。青藏高原及其下游平原地区对流降水厚度的日变化特征非常明显, 海洋地区对流降水厚度日夜差异则不大。层云降水厚度在各地区的日变化特征都不明显。青藏高原、下游平原及海洋地区对流和层云降水厚度的季节变化都非常明显, 从冬至夏, 对流和层云降水逐渐变得深厚, 而从夏入冬, 对流和层云降水则逐渐变得浅薄。(2) 青藏高原及其周边地区对流和层云平均降水厚度的分布形式和降水量分布具有较好的对应关系, 降水量大的地区其降水厚度一般较为深厚, 降水少的地区则降水厚度比较浅薄。对流和层云降水厚度存在明显差异, 对流降水一般要比层云降水深厚。青藏高原及其周边地区降水厚度水平分布的日夜差距不大, 但季节变化非常明显, 且与气候系统的季节变化紧密相关。     

星载测雨雷达探测的夏季亚洲对流与层云降水雨顶高度气候特征

利用热带测雨卫星测雨雷达的10年探测结果,对夏季亚洲对流降水与层云降水雨顶高度分布、雨顶高度与地表降水强度的关系、雨顶高度日变化特征进行了研究。结果表明,青藏高原和中国东部平原的多数(70%以上)对流降水雨顶高度分布在8—12和5—10km,其他地区分布在5—9km;陆面对流降水雨顶平均高度高于洋面。洋面和陆面层云降水雨顶高度没有明显差异,多在5—8km。夏季亚洲浅对流降水比例少,而深厚对流主要出现在中国东部平原、西南、印度次大陆西部至伊朗高原东部地区,比例约40%。洋面和陆面的弱对流降水的雨顶平均高度在7—8km,弱层云降水相应的雨顶平均高度多小于7.5km;陆面约90%的强对流降水雨顶平均高度在9km以上,而强层云降水雨顶的平均高度通常不超过8.5km。夏季亚洲对流降水和层云降水的雨顶平均高度均随着地面平均降水率的增大而升高,两者遵从二次函数关系。对流降水及层云降水频次、强度和雨顶高度的日变化峰值分析表明,陆面这些参量的日变化强于洋面,并且三者的日变化基本同步。     

亚洲夏季风区中尺度地形降水结构及分布特征

采用高分辨率TRMM、AIRS卫星实测资料, 从气候态的降水微物理过程角度分析了亚洲夏季风期间中尺度山脉对不同性质降水垂直结构和水平分布的影响。研究表明, 中尺度山脉迎风、背风坡均以层云降水为主, 层云降水强度在迎风坡强于背风坡; 对流降水在迎风坡主要为浅对流, 背风坡主要为深对流, 对流降水强度在背风坡强于迎风坡。沿西南季风推进方向依次经过的中尺度山脉, 其两侧发生降水像素个数、 降水微物理特征等差异逐渐减小, 其中, 对流降水迎风坡向背风坡转变明显, 而层云降水背风坡向迎风坡转变明显。大气稳定度与对流降水在迎风、背风坡的分布相一致。另外, 对中尺度地形降水的研究为区域气候模式模拟高精度地形降水分布提供了实测依据。     

华北汛期降水与亚洲季风异常关系的研究

文中诊断分析了华北汛期降水与亚洲季风区环流异常以及低纬地区热源异常的关系,结果表明:在华北汛期干旱年,亚洲季风偏弱,而在华北汛期降水偏多年,亚洲季风较强,并巳存在两个明显的变化中心,一个位于印度半岛中北部地区,另一个位于菲律宾群岛附近。华北汛期干旱年上述两个地区的热源偏弱,而降水偏多年则偏强。 华北地区干旱年和降水偏多年的前期亚洲季风区热源就已存在明显的不同:华北汛期干旱年前期,亚洲季风区的热源偏弱且位置偏南,表现出季节变化推迟的趋势;华北汛期降水偏多年前期,亚洲季风区的热源偏强且位置偏北,表现出季节变化提早的趋势。 利用IAP L9R15 AGCM气候数值模式,进一步研究了亚洲季风区凝结潜热加热异常对大气环流和华北地区降水的影响,结果表明,印度半岛中北部地区和菲律宾附近地区的凝结潜热加热异常将引起青藏高压和西太平洋副高的异常变化,进而影响到华北地区的降水。     

基于飞机观测的华北积层混合云降水微物理特征的数值模拟研究

基于2009年5月1日积层混合云降水2架飞机观测数据分析,使用中尺度模式WRFV3对此次过程积云区和层云区的微物理特征和转化过程进行数值模拟比较研究。飞机观测数据分析表明,此次积层混合云中的层云区和积云区冰粒子形状和形成过程有明显差别,层云区的粒子形状组成比较复杂,包含针状、柱状和辐枝状等,而积云区主要以辐枝状粒子为主,聚并、凇附过程明显。数值模式能较好地模拟出此次积层混合云降水过程的基本特征,包括回波分布、飞行路径上降水粒子的数浓度和液态水含量等。数值模拟结果表明,云水相对丰富、上升气流强的层云区凇附过程较强,产生的雪在低层融化为雨水,为后期高层形成的雪和霰提供丰富的液态水,能发展成对流较强的积云区,存在播种—供给机制。在积云区,水成物的比例从大到小依次为雪（51.9%）、霰（31.0%）和雨水（16.0%）;雪的主要源项包括淞附增长（56.8%）和凝华增长（40.1%）,霰的主要源项包括凇附增长（46.6%）、雨水碰并雪成霰（42.6%）和凝华增长（16.1%）,雨水的主要源项是霰（77.6%）和雪（22.4%）的融化。而相对云水较少、上升气流较弱的层云区将保持层云的状态,层云区水成物的比例从大到小依次为雪（90.4%）、雨水（6.1%）、冰晶（3.5%）;高层冰晶和雪通过凝华过程增长,雪在零度层下融化为弱的降水。     

利用星载测雨雷达探测结果对夏季中国南方对流和层云降水气候特征的分析

本文利用热带测雨卫星(TRMM)上搭载的测雨雷达(PR)十年的探测结果, 对夏季中国南方对流降水和层云降水的气候特征进行了分析。研究结果表明:夏季中国南方层云降水频次较对流降水频次高出两倍以上, 而对流降水强度至少是层云降水强度的4倍; 就整个中国南方而言, 这两种类型的降水对总降水量贡献相当。日变化分析表明夏季中国南方大部分地区的对流降水主要出现在午后, 层云降水出现时间并不集中, 但这两类降水的频次日变化均显示了明显的地域性特征; 对降水廓线日变化的分析结果表明, 对流降水和层云降水廓线的日变化主要表现在“雨顶”高度的日变化, 即对流降水云的厚度有明显的日变化变化特征, 不同地区的降水廓线存在明显的差异。降水率剖面分析结果显示了对流降水的“雨顶” 高度日变化较层云降水剧烈, 降水率的日变化则相反, 且层云降水率的地域性特征更强。     

气候变化背景下陆地季风与非季风区极端降水特征对比

利用月平均地表气候要素数据集(CRU TS 4.02)的逐月降水和逐月日平均气温资料,采用线性趋势分析、滑动平均和相关分析等方法,研究了1901-2017年气候变化背景下全球陆地季风区与非季风区的极端降水特征。结果表明:我国所处的亚洲季风区的极端降水频率分布较为稳定,仅在变暖减缓时段出现大范围小值区;非季风区在急剧加速变暖时段极端降水频率分布呈现两极化,大范围的小值区与大值区共存,而季风区不易出现这种情况。季风与非季风区极端降水频率均值变化基本趋于一致,只在加速变暖时段有所不同。季风与非季风极端降水频率小值区格点数占比变化趋于一致,仅在两个加速变暖时段有所区别,而对于大值区,除去1921-1949年和1950-1972年,季风区大值区格点数占比均低于非季风区。季风与非季风区极端降水量的分布形式受气候变化影响相对较小,但无论处于哪个冷暖时段,季风区的极端降水量均远远高于非季风区。非季风区的极端降水频率与气温的相关性要好于季风区,叠加温度趋势变化时,中高纬度大部分地区呈正相关的关系,去趋势后,相关性减弱。     

黄南地区汛期云和降水特征的分析

利用黄南地区尖扎、同仁、泽库、河南4站2007-2009年汛期(5-9月份)的地面观测资料,对该地区主要降水云状和降水特征进行统计分析。结果表明:混合云的降水频率最高,其次是积云,层云较低;降水特征有明显的差异,降水强度,降水次数北部明显小于南部,大降水南部多于北部;尖扎、泽库混合性降水出现频率最高,河南阵性降水最高,同仁连续性降水多,各站降水最高频数多出现在8月份,而河南则出现在6月份;降水概率各站之间有明显的差异,降水最大值多站出现在8月份,而河南则出现在7月份。低云量进入统计后,部分站出现了双峰型变化特征。     

A STUDY ON THE PRECIPITATION CHARACTERISTICS OVER THE SOUTH CHINA SEA BEFORE AND AFTER THE MONSOON ONSET

This paper presents a study on the temporal and spatial variations of the precipitation over the area of the South China Sea (SCS) during the monsoon onset period. The data used are from the Tropical Rainfall Measuring Mission (TRMM) observations between April and June over the nine years from 1998 to 2006. This study focuses on the central and northern part of South China Sea (110-120°E, 10-20°N). Based on the observations, the 27th pentad is selected as the occurrence time of the SCS monsoon onset. The conclusions are as follows. (1) After the monsoon onset, the specific area, defined as the ratio of the number of pixels with certain type of precipitation to the number of total pixels, extends significantly for both convective and stratiform rain, with the latter having a larger magnitude. The specific rainfall, defined as the ratio of the amount of certain type of precipitation to the total amount of precipitation, decreases for convective rain and increases for stratiform rain. (2) Results also show significant increase in heavy rain and decrease in light rain after the monsoon onset. (3) Changes are also observed in the rainfall horizontal distributions over the SCS before and after the monsoon onset, manifested by the relocation of precipitation minima for both convective and stratiform rain. (4) After the monsoon onset, the variability in characteristics of precipitation vertical structure increases significantly, leading to more latent heat release and consequently deeper convection. Meanwhile, the bright-band altitude of stratiform precipitation is also elevated.     

The Relationship Between some Large-scale Atmospheric Parameters and Rainfall over Southeast Asia: A Comparison with Features over India

Summary Monthly rainfall data for 135 stations for periods varying from 25 to 125 years are utilised to investigate the rainfall climatology over the southeast Asian monsoon regime. Monthly rainfall patterns for the regions north of equator show that maximum rainfall along the west coasts occurs during the summer monsoon period, while the maximum along the east coasts is observed during the northeast monsoon period. Over the Indonesian region (south of the equator) maximum rainfall is observed west of 125 °E during northern winter and east of 125 °E during northern summer. The spatial relationships of the seasonal rainfall (June to September) with the large scale parameters – the Subtropical Ridge (STR) position over the Indian and the west Pacific regions, the Darwin Pressure Tendency (DPT) and the Northern Hemisphere Surface Temperature (NHST) – reveal that within the Asian monsoon regime, not only are there any regions which are in-phase with Indian monsoon rainfall, but there are also regions which are out-of-phase. The spatial patterns of correlation coefficients with all the parameters are similar, with in-phase relationships occurring over the Indian region, some inland regions of Thailand, central parts of Brunei and the Indonesian region lying between 120° to 140 °E. However, northwest Philippines and some southern parts of Kampuchea and Vietnam show an out-of-phase relationship. Even the first Empirical Orthogonal Function of seasonal rainfall shows similar spatial configuration, suggesting that the spatial correlation patterns depict the most dominant mode of interannual rainfall variability. The influence of STR and DPT (NHST) penetrates (does not penetrate) upto the equatorial regions. Possible dynamic causes leading to the observed correlation structure are also discussed. Received October 10, 1996 Revised February 25, 1997     

TRMM测雨雷达对1998年东亚降水季节性特征的研究

利用热带测雨计划卫星上的测雨雷达得到的降水资料,对1998年东亚降水,特别是中国大陆东部、东海和南海的降水,进行了分析研究,并对比了热带降水研究结果。年统计结果表明,东亚地区层状云降水出现概率极高(比面积达83.7％),对流云降水的比面积仅占13.6％,然而两者对总降水量的贡献相当。结果还表明,暖对流云降水出现的比例和对总降水量的贡献很小。在季节尺度,对流云和层状云降水的比与两者的面积比成比例关系。除夏季外,测雨雷达降水量与GPCP降水量可比性好。研究结果还指出:在中纬度陆地和海洋上对流云和层状云的比降水量和比面积呈相反方向作季节性南北移动,这一活动与东亚季风变化一致;该地区降水的季节性变化还表现为降水垂直廓线的变化。除冬季外,南海地区降水垂直结构呈热带特征。CRAD分析表明,对流云降水的地面雨强变化大,尤其在陆地上,而层状云多表现为地面弱降水。     

江淮地区夏季雨量与北半球500 hPa环流遥相关的不稳定性

用50年 (1951~2000年) 观测资料, 分成1951~1976年和1977~2000年两个时段, 研究了江淮地区夏季 (6~8月) 雨量与北半球500 hPa季平均环流时滞遥相关的年代际变化, 同时提出了遥相关不稳定指数, 讨论了遥相关不稳定性的空间分布和季节变化。结果表明, 这两个时段遥相关的空间分布存在显著差异, 且前一时期时滞遥相关强度明显强于后一时期, 特别是江淮地区夏季雨量与前期冬季西太平洋型 (WP) 的相关仅在1976年以前显著, 1977年以后迅速减弱消失, 而对于后一时期, 与春季欧亚遥相关型 (EU) 的相关明显加强。另外, 后一时期江淮地区夏季雨量与夏季EAP波列的相关明显强于前一时期。它反映了太平洋年代际振荡 (PDO) 对东亚季风降水和环流年际相关的影响, 这种遥相关的不稳定性与年代际和年际时间尺度振荡之间的相互作用有密切联系。     

An Analysis of Thermally-Related Surface Rainfall Budgets Associated with Convective and Stratiform Rainfall

Both water vapor and heat processes play key roles in producing surface rainfall.While the water vapor effects of sea surface temperature and cloud radiative and microphysical processes on surface rainfall have been investigated in previous studies,the thermal effects on rainfall are analyzed in this study using a series of two-dimensional equilibrium cloud-resolving model experiments forced by zonally-uniform,constant,large-scale zonal wind and zero large-scale vertical velocity.The analysis of thermally-related surface rainfall budget reveals that the model domain mean surface rain rate is primarily associated with the mean infrared cooling rate.Convective rainfall and transport of hydrometeor concentration from convective regions to raining stratiform regions corresponds to the heat divergence over convective regions,whereas stratiform rainfall corresponds to the transport of hydrometeor concentration from convective regions and heat divergence over raining stratiform regions.The heat divergence over convective regions is mainly balanced by the heat convergence over rainfall-free regions,which is,in turn,offset by the radiative cooling over rainfall-free regions.The sensitivity experiments of rainfall to the effects of sea surface temperature and cloud radiative and microphysical processes show that the sea surface temperature and cloud processes affect convective rainfall through the changes in infrared cooling rate over rainfall-free regions and transport rate of heat from convective regions to rainfall-free regions.     

Differences between Convective and Stratiform Precipitation Budgets in a Torrential Rainfall Event

Differences in rainfall budgets between convective and stratiform regions of a torrential rainfall event were investigated using high-resolution simulation data produced by the Weather Research and Forecasting(WRF) model. The convective and stratiform regions were reasonably separated by the radar-based convective–stratiform partitioning method, and the threedimensional WRF-based precipitation equation combining water vapor and hydrometeor budgets was further used to analyze the rainfall budgets. The results showed that the magnitude of precipitation budget processes in the convective region was one order larger than that in the stratiform region. In convective/stratiform updraft regions, precipitation was mainly from the contribution of moisture-related processes, with a small negative contribution from cloud-related processes. In convective/stratiform downdraft regions, cloud-related processes played positive roles in precipitation, while moisture-related processes made a negative contribution. Moisture flux convergence played a dominant role in the moisture-related processes in convective or stratiform updraft regions, which was closely related to large-scale dynamics. Differences in cloud-related processes between convective and stratiform regions were more complex compared with those in moisture-related processes.Both liquid-and ice-phase microphysical processes were strong in convective/stratiform updraft regions, and ice-phase processes were dominant in convective/stratiform downdraft regions. There was strong net latent heating within almost the whole troposphere in updraft regions, especially in the convective updraft region, while the net latent heating(cooling) mainly existed above(below) the zero-layer in convective/stratiform downdraft regions.     

A Modeling Study of Surface Rainfall Processes Associated with a Torrential Rainfall Event over Hubei, China, during July 2007

The surface rainfall processes associated with the torrential rainfall event over Hubei,China,during July 2007 were investigated using a two-dimensional cloud-resolving model.The model integrated the large-scale vertical velocity and zonal wind data from National Centers for Environmental Prediction(NCEP)/Global Data Assimilation System(GDAS) for 5 days.The time and model domain mean surface rain rate was used to identify the onset,mature,and decay periods of rainfall.During the onset period,the descending motion data imposed in the lower troposphere led to a large contribution of stratiform rainfall to the model domain mean surface rainfall.The local atmospheric drying and transport of rain from convective regions mainly contributes to the stratiform rainfall.During the mature periods,the ascending motion data integrated into the model was so strong that water vapor convergence was the dominant process for both convective and stratiform rainfall.Both convective and stratiform rainfalls made important contributions to the model domain mean surface rainfall.During the decay period,descending motion data input into the model prevailed,making stratiform rainfall dominant.Stratiform rainfall was mainly caused by the water vapor convergence over raining stratiform regions.     

中国地区降水持续性的季节变化特征

本文利用我国588个气象站1969-2008年逐12小时的降水资料,分析了中国地区降水持续性的空间分布特征及其季节演变规律。分析结果表明,35°N以南,西部和东部年平均的降水平均持续时间较长,中部略短;35°N以北,西北和内蒙西部最短,东北地区北部略长。将降水事件按持续时间分类自南向北,东南地区、江淮和黄淮地区、东北和华北北部地区短时降水（持续一个时次,12小时）的降水量和降水频率占全年总降水的比例逐渐增加,持续性降水（持续3个时次及以上）的比例减少。降水平均持续时间随季节的变化基本能反映出江南春雨、江淮梅雨、东北和华北夏季雨季、关中盆地和汉水谷地的秋雨以及青藏高原地区和西南地区夏季雨季。同时,东南地区秋冬季节、江淮和黄淮地区10月上旬和西南地区10月下旬存在降水平均持续时间的峰值,与降水量的变化不一致,是由持续性降水频率的增加和短时降水频率的减少造成的。此外,东部三个区域降水平均持续时间的夏季季节内变化对应了季风雨带的“北跳和南撤”过程。