摘要
基于2007~2012年TRMM卫星上搭载的降水雷达提供的雷达反射率因子、降水率、降水类型等产品,结合ECMWF提供的再分析数据资料,分析了全球热带海洋地区平均降水率、400 h Pa垂直速度、850 h Pa相对湿度和下对流层稳定度的时空分布特征.根据400 h Pa垂直速度的季节差异确定了4个子研究区及相应对比季节,给出了对比季节内浅对流单体、层云、对流云3种降水系统降水量、降水面积、降水强度以及垂直结构上的差异.结果表明:(1)热带海洋地区平均降水率与400 h Pa上升速度在时空分布上存在一个显著的正相关,即400 h Pa上升速度越强的地区平均降水率越大;(2)4个子研究区内层云降水对区域累积降水面积贡献率最大(年均值均超过50%),对流云降水次之(约30%),而对流云降水对区域累积降水量贡献率最大(约65%),层云降水次之(约25%);(3)400 h Pa上升速度较强时,4个子研究区中3类降水系统的累积降水面积、累积降水量都有所增加,但降水强度以及降水系统垂直结构的变化存在差异,其中对流云降水强度一致增大且其垂直结构上的发展更旺盛;(4)对流云降水系统的雨顶高度、雷达反射率重心以及30 d BZ回波顶高随着400 h Pa上升速度的增强以及850 h Pa相对湿度的增加而迅速抬升,同时随着下对流层稳定度的降低有所抬升,但变化率较小.说明影响对流降水系统垂直结构的主要气象条件是400 h Pa上升速度和850 h Pa相对湿度.
The radar reflectivity and precipitation rate from Precipitation Radar （PR） onboard Tropical Rainfall Measuring Mission （TRMM） are obtained over the global tropical regions （35°S-35°N） during the period from 2007 to 2012, combined with coincident vertical velocity at 400 hPa （ω400 hPa）, relative humidity at 850 hPa （RH850 hPa） and lower tropospheric stability （LTS） from European Centre for Medium-Range Weather Forecasts （ECMWF） reanalysis. First of all, the seasonal and spatial distribution of meteorological factors, including ω400 hPa, RH850 Wa, and LTS, together with rain rate are investigated Next, four typical Regions of Interest （ROIs） and their individual seasons （i.e., favorable and non-favorable seasons for rainfall） are identified for further analysis by determining whether there exist most pronounced seasonal differences observed in ω400 hPa. Meanwhile, rainy area, and rainfall of three precipitation types （i.e., shallow, stratus, and convection precipitation regimes） over the ROIs has been calculated. The three dimensional structures of individual precipitating system are analyzed, based on normalized contoured frequency by altitude diagram （NCFAD） and other statistical methods. Finally, with a focus on convection precipitation system, we give a quantitative description of the response of precipitation vertical structure to meteorological factors. Namely, how the rain echo top height （RTH）, echo top height with reflectivity of 30 dBZ （ZTH30 dBZ）, and reflectivity center of gravity （ZCOG） vary with ω400 hPa, RH850 hPa, and LTS. In particular, （1） high rain rate dominates over intertropical convergence zone, which is characterized by strong updraft, sufficient moisture, and low LTS, showing the average rain rate is negatively associated with ω400 hPa at both temporal and spatial scales. That is to say, lower ω400 hPa comes with more intensive rain rate. （2） The meteorological factors, along with average rain rate, exhibit appreciable seasonal variation. To be specific, negative （positive） ω400 hPa anomalies is mostly found over the northern （southern） hemisphere in summer and autumn, as opposed to the patterns found in winter and spring. （3） In terms of the area with rainfall, the stratiform precipitating system accounts for more than 50% of the total area under investigation, followed by the convective precipitating system （about 30%）, and the shallow precipitating system （less than 20%）. In contrast, convective precipitating system, among others, takes the lead （about 65%） in contributing to the accumulated rainfall amount in the ROIs studied, followed by stratiform precipitating system （about 25%）, and the shallow precipitating system （about 10%）. （4） In the season with relatively higher ω400 hPa, both rainy area and accumulated rainfall amount for all three types of precipitation show a increasing trend, irrespective of ROI. By comparison, rain rate and its vertical structures show large discrepancy, i.e., the intensity of convective precipitation system in favorable season tends to systematically increase as compared with that in non-favorable season. （5） The bulk precipitation system parameters used to describe convective precipitating system, including RTH, ZTH30 dBZ, and ZCOG, are observed to be elevated sharply with increasing ω400 hPa and RH850 hPa. The same holds for the increasing LTS but with a smaller magnitude in the elevated height. This implies that ω400 hPa and RH850 hPa most likely play a dominant role in dictating the vertical development of convection.
作者
刘欢
郭建平
陈田萌
翟盘茂
LIU Huan GUO JianPing CHEN TianMeng ZHAI PanMao(State Key Laboratory of Severe Weather ＆ Key Laboratory of Atmospheric Chemistry of China Meteorological Administration, Chinese Academy of Meteorological Sciences, Beijing 100081, China College of Earth Sciences, University of Chinese Academy of Sciences, Beijing 100049, China College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2017年第1期90-104,共15页
Chinese Science Bulletin
基金
国家自然科学基金(41471301,91544217,41171294)
中国气象科学研究院基本科研业务费(2014R18)资助
