排序方式： 共有66条查询结果，搜索用时 23 毫秒
51.
在原模式版本TRAMS-V2.0的基础上,通过对三维静力参考大气、拉格朗日矢量投影、云降水物理和辐射等技术方案进行改进,并且针对高分辨率模式易产生强垂直运动和小尺度扰动等问题,引入水平扩散、垂直运动耗散等技术方案,同时优化模式动力物理过程各功能块的调用方式和一些技术参数,最终形成适合热带高分辨率的模式版本TRAMS-V3.0。批量测试表明,新版模式TRAMS-V3.0的预报性能明显优于TRAMS-V2.0,新版模式不仅对形势场和地面要素的预报误差较小,而且各量级降水预报的准确率也比较高,如48小时2 m温度预报RMS由原来的2.4 ℃降低为1.8 ℃,晴雨48小时预报准确率由原来的0.736提高到0.810等。基于TRAMS-V3.0建立的预报系统,实时业务应用中展现了系统在晴雨、暴雨、地面要素等方面预报的优势。并针对暴雨空漏报等问题进行了初步的分析,提出下一步技术改进的设想。 相似文献
52.
选取华南2017年5月15日两段不同系统影响的典型个例降水,基于ERA Interim分析资料和地面、雷达等观测资料,从两类降水的大尺度环境及中尺度特征方面探讨了两类降水系统的差异,并利用模式潜热廓线订正方案对两类降水个例的潜热进行反演。结果表明,季风降水主要受偏南风影响,边界层内强辐合、高温高湿,中高层（600~150 hPa）较强辐散,而锋面降水受低层锋面系统影响,对流层低层强辐合,800~300 hPa较强辐散,水汽输送深厚,斜压性结构明显,且垂直运动剧烈。除两者的辐合辐散中心、正涡度的中心以及水汽通量辐合中心和垂直运动大值中心所在的层次明显不同外,其强度也差别较明显,就垂直运动而言,锋面降水的最大值达-1.2 hPa/s,远远大于季风降水（-0.2 Pa/s）。两者的中尺度特征和加热结构也存在显著差异,季风降水中尺度雨团沿海岸线自西向东移动发展,潜热加热中心为单峰值,位于5~6 km;锋面降水中尺度雨团在一条西南-东北走向的雨带上不断向东南方向合并发展,潜热加热中心有两个,分别位于1~2 km和6~7 km。 相似文献
53.
Warm-sector torrential rainfall (WSTR) events that occur in the annually first rainy season in south China are characterized by high rainfall intensity and low radar echo centroids. To understand the synoptic characteristics related to these features, 16 WSTR events that occurred in 2013-2017 were examined with another 16 squall line (SL) events occurred during the same period as references. Composite analysis derived from ERA-Interim reanalysis data indicated the importance of the deep layer of warm and moist air for WSTR events. The most significant difference between WSTR and SL events lies in their low-level convergence and lifting; for WSTR
events, the low-level convergence and lifting is much shallower with comparable or stronger intensity. The trumpet-shaped topography to the north of the WSTR centers is favorable for the development of such shallow convergences in WSTR events. Results in this study will provide references for future studies to improve the predictability of WSTR. 相似文献
54.
利用影响南海夏季风年际变化的主要气候现象厄尔尼诺-南方涛动（El Ni?o-Southern Oscillation,ENSO）和对流层准两年振荡（Tropospheric Biennial Oscillation,TBO）相关的气候因子,提出了以过程判别函数确定物理过程的持续性,建立年际尺度的集成物理统计预测模型,而非年际尺度变率由经验统计模型预测,二者相结合,发展了集成物理-经验统计预测模型。经验模型在拟合时段的回报结果很好,但在独立样本预测时效果明显降低,其中预测评分（PS）降低了23%,距平相关系数（ACC）降低了63%;相比之下,集成物理-经验统计预测模型在独立样本预测时比经验模型有更好的预测结果（PS评分提高了9.5%,ACC提高了75%）,且预测结果相对稳定。此外,集成物理-经验统计预测模型对南海夏季风降水的空间分布也有一定预测能力。 相似文献
55.
广东前汛期锋面强降水和后汛期季风强降水特征对比分析 总被引：3，自引：7，他引：3
应用近二十年的历史观测资料和EC再分析资料,对由锋面和季风槽两种不同天气系统影响下广东发生的两组暴雨过程的天气形势、降水/短时强降水落区及其对流活动和物理量特征进行了诊断分析和对比分析。结果表明:无论是前汛期锋面降水还是后汛期季风降水,珠三角（珠江三角洲）地区都是次中心,有大到暴雨量级降水。珠三角地区也是小时雨量≥50 mm的短时强降水高发区。前汛期锋面对流活动的抬升凝结高度约在900~850 hPa,南北方向的温度梯度提供了斜压不稳定能量,0~3 km强的风垂直切变使对流易于维持和发展;对流区有较强的水汽通量辐合;风暴相对螺旋度较大,对流的旋转性和沿着旋转方向的移动特征明显。相对而言,后汛期季风强降水对流凝结高度更低,对流活动具有正压的热带对流性质,可在弱的水汽通量辐合和垂直风切变环境中维持,但对流强度不如前汛期。以上结论可为同类天气的短期和短临主客观预报提供预报思路和依据。 相似文献
56.
2012年南海夏季风活跃期与非活跃期广东电白地区海陆大气边界层特征分析 总被引：2，自引：0，他引：2
利用2012年6—9月南海夏季风期间的近海海洋气象观测平台 (海上平台站) 和电白国家气候观象台 (电白站) 的地面气象站资料,气象塔资料以及GPS探空资料对海上平台站和电白站两站在季风活跃期和非活跃期的大气边界层结构特征进行研究分析。结果表明,活跃期与非活跃期两地的大气边界层结构特征有明显差异。(1) 在活跃期两站近地层风向全天由东南风主导,风速较大,且两站均出现连续降水,受云系和降水的影响,与非活跃期相比,电白站近地层日平均气温降低约为2 ℃;非活跃期两站风向全天无规则变化,且风速值小。(2) 在活跃期大气边界层内风向均为一致的东南风,风速较大,200 m以上的风速均大于8 m/s,而在非活跃期大气边界层内风速较小,风向变化较大,同一时刻不同高度的风向差可达180 °。(3) 在季风非活跃期混合层高度最高可达937 m,而在活跃期,受降水和云系的影响混合层高度明显降低,最大高度仅为700 m左右。(4) 活跃期受连续降水影响,大部分时刻的大气边界层内相对湿度大于80%。由此可见在季风活跃期与非活跃期不仅海陆气能量交换发生变化,大气边界层结构特征也有显著变化。 相似文献
57.
Spatio-temporal distribution characteristics and variation trends of tropospheric NO_2 in Pearl River Delta(PRD) urban group and its adjacent areas were analyze from 2005 to 2013 based on remote sensing data from ozone monitoring instrument(OMI) satellite, and further explored the impact of human activities on NO_2. Compared with the ground observation data, the OMI NO_2 remote sensing data displayed high reliability. Due to active industrial production, high car ownership, great energy and power consumption, the average tropospheric NO_2concentration(7.4×1015molec/cm2) of PRD region is about 3 times of the adjacent areas. At the same time, the regional high pollution NO_2 in PRD region as a whole, the urban group effect is remarkable. Sinusoidal model can well fit the periodic variation of the NO_2 in PRD and adjacent areas. NO_2 concentration was highest in winter while lowest in summer. The concentration of NO_2 in PRD region is decreasing in recent 9 years, which has a significantly negative correlation with the second industry output and car ownership. This suggests that the nitrogen oxide emissions governance in PRD region had achieved initial results. The concentration of NO_2 increased significantly in the eastern and northern Guangdong Province, there are good positive correlations with the second industrial outputs and car ownerships, it is thus clear that industrial emissions and automobile exhausts are important sources of NO_2 in these regions. The concentration of NO_2 in western Guangdong area is stable. 相似文献
58.
The quantitative precipitation forecast (QPF) in very-short range (0-12 hours) has been investigated in this paper by using a convective-scale (3km) GRAPES_Meso model. At first, a latent heat nudging (LHN) scheme to assimilate the hourly intensified surface precipitation data was set up to enhance the initialization of GRAPES_Meso integration. And then based on the LHN scheme, a convective-scale prediction system was built up in considering the initial “triggering” uncertainties by means of multi-scale initial analysis (MSIA), such as the three-dimensional variational data assimilation (3DVAR), the traditional LHN method (VAR0LHN3), the cycling LHN method (CYCLING), the spatial filtering (SS) and the temporal filtering (DFI) LHN methods. Furthermore, the probability matching (PM) method was used to generate the QPF in very-short range by combining the precipitation forecasts of the five runs. The experiments for one month were carried out to validate the MSIA and PM method for QPF in very-short range.
The numerical simulation results showed that: (1) in comparison with the control run, the CYCLING run could generate the smaller-scale initial moist increments and was better for reducing the spin-up time and triggering the convection in a very-short time; (2) the DFI runs could generate the initial analysis fields with relatively larger-scale initial increments and trigger the weaker convections at the beginning time (0-3h) of integration, but enhance them at latter time (6-12h); (3) by combining the five runs with different convection triggering features, the PM method could significantly improve the QPF in very-short range in comparison to any single run. Therefore, the QPF with a small size of combining members proposed here is quite prospective in operation for its lower computation cost and better performance. 相似文献
59.
The linear regression and horizontally stepwise correction are conducted on the observational data from AMSU-A L1 B of NOAA polar orbit satellite to invert a 40-layers(from 1,000 h Pa to 0.1 h Pa) dataset of atmospheric temperature with a horizontal resolution of 0.5°×0.5° after the correction of satellite antenna pattern and limb adjustment. Case study shows that the inversion data of temperature can reveal the detail structure of warm core in tropical cyclone. We choose two categories of tropical depressions(TDs) over the South China Sea, including the non-developing TDs and developing TDs. Both of them are developed downward from the middle and upper level to the lower level. Comparison between the evolutions of warm core in the two categories of TDs indicates that the warm core is developed downward from the middle and upper troposphere to the sea surface in all the downward-developing TDs. The difference is that in the group of further developing TDs, the warm core in the upper troposphere is intensified suddenly when it is extending to the sea surface. The warm core in the upper and lower troposphere is strengthened in a meantime. But the similar feature is not observed in the non-developing TDs. Then it may be helpful to judge the TD development by monitoring the change in its warm-core structure. 相似文献
60.
In the previous study, the influences of introducing larger- and smaller-scale errors on the background error covariances estimated at the given scales were investigated, respectively. This study used the covariances obtained in the previous study in the data assimilation and model forecast system based on three-dimensional variational method and the Weather Research and Forecasting model. In this study, analyses and forecasts from this system with different covariances for a period of one month were compared, and the causes for differing results were presented. The variations of analysis increments with different-scale errors are consistent with those of variances and correlations of background errors that were reported in the previous paper. In particular, the introduction of smaller-scale errors leads to greater amplitudes in analysis increments for medium-scale wind at the heights of both high- and low-level jets. Temperature and humidity analysis increments are greater at the corresponding scales at the middle- and upper-levels. These analysis increments could improve the intensity of the jet-convection system that includes jets at different levels and the coupling between them that is associated with latent heat release. These changes in analyses will contribute to more accurate wind and temperature forecasts in the corresponding areas. When smaller-scale errors are included, humidity analysis increments are significantly enhanced at large scales and lower levels, to moisten southern analyses. Thus, dry bias can be corrected, which will improve humidity forecasts. Moreover, the inclusion of larger- (smaller-) scale errors will be beneficial for the accuracy of forecasts of heavy (light) precipitation at large (small) scales because of the amplification (diminution) of the intensity and area in precipitation forecasts. 相似文献