基于不同背景场条件的雷达资料同化在登陆台风“桑美”中的应用研究

本文针对2006年登陆我国的超强台风“桑美”,分别采用美国国家环境预报中心的全球预报系统(Global Forecasting System, GFS)再分析资料和日本气象厅(Japan Meteorological Agency, JMA)区域客观再分析资料作为背景场,利用中尺度数值模式WRF(Weather Research and Forecasting Model)及其三维变分同化系统进行多普勒雷达资料同化和数值模拟试验,考察不同的背景场条件下雷达资料同化对台风初始场、内部结构及其随后确定性预报的影响。结果表明:GFS试验和JMA试验在同化了雷达资料之后分析出的台风700 hPa风场和500 hPa高度场相比其初始场均有所增强,JMA试验在3 h同化窗内的均方根误差和最小海平面气压的改进效果均比GFS试验显著,同时对台风动力和热力结构的改进效果也优于GFS试验;JMA试验对台风降水、路径、强度的预报均优于GFS试验,且能预报出台风前沿的降水,更加接近观测实况。     

FY-4A白天对流风暴和闪电产品在华北强雷暴天气分析中的应用

我国第二代静止气象卫星FY-4A观测能力较之前有明显提升,在天气特别是对流性天气监测和预测中具有较强的应用潜力。利用FY-4A气象卫星多通道扫描辐射成像仪(Advanced Geosynchronous Radiation Imager,AGRI)和闪电成像仪(Lightning Mapping Imager,LMI)数据开展研究,分析了反演产品在强雷暴天气中的应用。研究表明,扫描辐射成像仪多通道组合白天对流风暴红-绿-蓝（red-green-blue,RGB）合成产品可以突出具有强上升气流的对流性雷暴云,较单通道及多通道可见光合成产品具有监测优势;闪电成像仪产品较地面闪电探测闪电产品能够探测到更多的闪电,对新生对流和较弱对流产生的闪电监测具有优势;在华北和黄淮一次强雷暴天气过程中,白天对流风暴RGB合成产品能够监测云系发展的过程,卫星监测闪电活动频数和冰雹活动一致性较好。     

Quality Assessment of FY-4A Lightning Data in Inland China

The Lightning Mapping Imager (LMI) equipped on the FY-4A (FengYun-4A) geostationary satellite achieves lightning positioning through optical imaging and has the advantages of high temporal resolution, high stability, and continuous observation. In this study, FY-4A LMI lightning event, group and flash data from April to August 2018 are selected, and their quality are assessed through qualitative and quantitative comparison with the ground-based Advanced Time of Arrival and Direction system (ADTD) lightning observation network data and the American International Space Station (ISS) lightning imaging sensor (LIS) data. The results show that the spatial distributions of FY-4A lightning are consistent with those of the ground-based ADTD and ISS LIS. The temporal variation in FY-4A lightning group frequency is consistent with that of ADTD stroke, which reflects that FY-4A LMI can capture the lightning occurrence in inland China. Quantitative statistics show that the consistency rate of FY-4A LMI and ISS LIS events is relatively high but their consistency rate is lower in terms of lightning group and flash data. Compared with the lightning observations by the ISS LIS and the ground-based ADTD, FY-4A LMI reports fewer lightning events in the Tibetan Plateau. The application of Tibetan Plateau lightning data requires further processing and consideration.     

中国云气候特征的分析

利用1983年7月至2001年8月的ISCCP卫星总云量资料, 分析了我国总云量的空间分布特征, 并将全国用193个网格点表示, 采用聚类分析方法, 按照总云量年内变化规律相同的原则将中国分为3个区, 逐区讨论了总云量的年内变化特征;同时, 分析了18年来中国总云量的变化趋势。最后利用奇异值分解法(SVD)找到了我国青藏高原冬季总云量与全国夏季降水的高相关区, 证明青藏高原总云量与我国东北降水正相关密切。     

PRELIMINARY STUDY ON THE INFLUENCE OF FY-4 LIGHTNING DATA ASSIMILATION ON PRECIPITATION PREDICTIONS

Data from the lightning mapping imager on board the Fengyun-4 meteorological satellite (FY-4) were used to study the assimilation of lightning data and its influence on precipitation predictions. We first conducted a quality control check on the events observed by the first Fengyun-4 satellite (FY-4A) lightning mapping imager, after which the noise points were removed from the lightning distribution. The subsequent distribution was more consistent with the spatial distribution and range of ground-based observations and precipitation. We selected the radar reflectivity, which was closely related to the lightning frequency, as the parameter to assimilate the lightning data and utilized a large sample of lightning frequency and radar reflectivity data from the eastern United States provided by Vaisala. Based on statistical analysis, we found the empirical relationship between the lightning frequency and radar reflectivity and established a look-up table between them. We converted the lightning event data into radar reflectivity data and found that the converted reflectivity and composite reflectivity of ground-based radar observations showed high consistency. We further assimilated the lightning data into the model, adjusted the model cloud analysis process and adjusted the model hydrometeor field by using the lightning data. A rainstorm weather process that occurred on August 8, 2017, in south China was used for the numerical forecast experiment, and three experiments were designed for comparison and analysis: a control experiment, an experiment without the assimilation of FY-4 lightning data (NoLig), and an experiment with the assimilation of FY-4 lightning data (Lig). The results show that after assimilating the FY-4A lightning data, the accuracies of the intensity, central location and range of the precipitation predicted by the Lig experiment were obviously superior to those predicted by the control and NoLig experiments, and the effect was especially obvious in the short-term (1–2 hour) forecast. The studies in this paper highlight the application value and potential of FY-4 lightning data in precipitation predictions.     

A SPATIAL-TEMPORAL DISTRIBUTION CHARACTERISTICS STUDY ON THE ATMOSPHERIC CARBON DIOXIDE OBSERVED BY GOSAT SATELLITE REMOTE SENSING

The variation of the atmospheric Carbon Dioxide (CO2) concentration plays an important role in global climate and agriculture. We analyzed the spatial-temporal characteristics of CO2 in the China region and around the globe with the CO2 column mixing ratios observed by the Japanese GOSAT satellite (Greenhouse Gases Observing Satellite). In order to make sure that the accuracy of the CO2 data retrieved by the satellite meets the needs of the climate characteristics analyses, we ran a validation on the CO2 column mixing ratios retrieved by the satellite against the ground-based TCCON (Total Carbon Column Observing Network) observation data. The result shows that the two sets of data have a correlation coefficient of higher than 0.7, and a bias of within 2.2 ppmv. Therefore, the GOSAT CO2 data can be used for the climate characteristics analysis of global CO2. Our analysis on the spatial-temporal characteristics of the CO2 column mixing ratios observed during the period of June 2009 through January 2014 proved that, with the impact of the natural emission of near ground CO2 and human activities, the global CO2 concentration has a significant latitudinal characteristics with its highest level averaging 390 ppmv in the 0-40oN latitudinal zone in the Northern Hemisphere, and 387 ppmv in the Southern Hemisphere. China has a relatively higher CO2 concentration with the highest level exceeding 398 ppmv, and the eastern area higher than the western area. The variation of global CO2 concentration shows a seasonal pattern, i.e. the CO2 concentration reaches its highest in spring in the Northern Hemisphere averaging more than 392 ppmv, second highest in winter, and lowest in summer averaging less than 387 ppmv. It fluctuates the most in the Northern Hemisphere with an average concentration of 392.5 ppmv in April, and 385.5 ppmv in July. While in the Southern Hemisphere, the seasonal fluctuation is smaller with the highest concentration occurring in July. Over the recent years, the global CO2 concentration has shown an elevating trend with an average annual increase rate of 1.58 ppmv per year. It is a challenge that the human kind has to face to slow down the increase of the CO2 concentration.     

2011年春季北极臭氧异常低值监测和特征分析

利用中国第二代极轨气象卫星“风云三号”A星(FY-3A)搭载的紫外臭氧总量探测仪(TOU),连续监测全球臭氧总量分布的遥感数据,分析后发现,自2011年3月初开始,北极地区臭氧总量急剧下降,形成一个臭氧低值区,3月中旬低值区中心部分臭氧总量日平均值只有同期的一半左右.分析风云三号气象卫星及国外卫星1979-2011年北...     

总云量产品在中国区域的分析检验

对ISCCP、常规观测以及MODIS总云量3种目前使用较多的总云量资料进行对比分析, 重点考察时间序列较长的ISCCP和常规观测总云量, 给出定量对比结果, 为使用这3种总云量资料的用户提供参考。研究表明:ISCCP与常规观测总云量相比, 7月二者的空间分布具有很好的一致性, 但白天ISCCP总云量比常规观测总云量多, 夜间却往往比常规观测总云量少, 二者误差分布表现为东部和东南部小于西北部的特征; 而1月二者空间分布比较一致, 但是在天山和东北地区高、低值中心经常不匹配, 这两个区域总云量资料需慎用; 7月ISCCP总云量精度明显高于1月。ISCCP、常规观测以及MODIS总云量对比结果表明:1月MODIS总云量比其他两种资料大, 而7月为最小。相对常规观测, 1月ISCCP总云量精度优于MODIS, 而7月MODIS总云量略优于ISCCP。     

FY-4A白天对流风暴和闪电产品在华北强雷暴天气分析中的应用

我国第二代静止气象卫星FY-4A观测能力较之前有明显提升,在天气特别是对流性天气监测和预测中具有较强的应用潜力。利用FY-4A气象卫星多通道扫描辐射成像仪(Advanced Geosynchronous Radiation Imager,AGRI)和闪电成像仪(Lightning Mapping Imager,LMI)数据开展研究,分析了反演产品在强雷暴天气中的应用。研究表明,扫描辐射成像仪多通道组合白天对流风暴红-绿-蓝(red-green-blue,RGB)合成产品可以突出具有强上升气流的对流性雷暴云,较单通道及多通道可见光合成产品具有监测优势;闪电成像仪产品较地面闪电探测闪电产品能够探测到更多的闪电,对新生对流和较弱对流产生的闪电监测具有优势;在华北和黄淮一次强雷暴天气过程中,白天对流风暴RGB合成产品能够监测云系发展的过程,卫星监测闪电活动频数和冰雹活动一致性较好。