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201.
Deep convection systems (DCSs) can rapidly lift water vapor and other pollutants from the lower troposphere to the upper troposphere and lower stratosphere. The main detrainment height determines the level to which the air parcel is lifted. We analyzed the main detrainment height over the Tibetan Plateau and its southern slope based on the CloudSat Cloud Profiling Radar 2B_GEOPROF dataset and the Aura Microwave Limb Sounder Level 2 cloud ice product onboard the A-train constellation of Earth-observing satellites. It was found that the DCSs over the Tibetan Plateau and its southern slope have a higher main detrainment height (about 10?16 km) than other regions in the same latitude. The mean main detrainment heights are 12.9 and 13.3 km over the Tibetan Plateau and its southern slope, respectively. The cloud ice water path decreases by 16.8% after excluding the influences of DCSs, and the height with the maximum increase in cloud ice water content is located at 178 hPa (about 13 km). The main detrainment height and outflow horizontal range are higher and larger over the central and eastern Tibetan Plateau, the west of the southern slope, and the southeastern edge of the Tibetan Plateau than that over the northwestern Tibetan Plateau. The main detrainment height and outflow horizontal range are lower and broader at nighttime than during daytime. 相似文献
202.
利用FY-2F快速扫描资料分析对流初生阶段的云顶物理量特征 总被引:2,自引:0,他引:2
基于FY-2F静止气象卫星提供的2015年5—9月的高分辨率数据,通过温度阈值法识别出深、浅对流后,分析和比较了深、浅对流在对流初生(convective initiation,CI)至发展阶段中云顶高度、云顶快速降温率(cloud top cooling rate,CTC)以及多通道差值等云顶物理量特征的变化异同。结果表明:深、浅对流在CI阶段的云顶物理量特征具有相似变化特征,即云顶高度均在短时间内快速上升,CTC值均先减小后增大;深、浅对流差异表现为深(浅)对流云顶上升高度能(不能)超越水汽层高度;深对流CTC最低值较浅对流CTC最低值更低。基于CI阶段深、浅对流的CTC最低值的差异,通过个例验证,表明利用深、浅对流CTC最低值的差异,可以在识别出CI的基础,判断出CI是否发展成为深对流,从而能提前做出预警。 相似文献
203.
利用热带测雨卫星测雨雷达(TRMM PR)降水回波反射率因子廓线(降水率廓线)与全球探空大气温湿廓线(IGRA)的多年融合资料,研究了青藏高原拉萨站夏季降水结构及相应的大气温湿结构特征。结果表明,该站降水回波反射率因子分布在17~45 dBz,大部分小于26 dBz;回波顶高度达17 km,呈现“瘦高”外形;相应的大气低层湿润,降水云内大气并非饱和,但温度露点差比全部状态时的值小。深厚降水系统的回波外形也呈现“瘦高”,按照降水率随高度的非线性变化,其垂直结构可分为三层,而浅薄降水系统的垂直结构呈现一层,即平均降水率斜率随高度呈对数线性变化,最大平均降水率(0.7 mm·h^-1)出现在地面。深厚降水与浅薄降水云体内400 hPa高度(7.5 km)上下的露点温度递减的速率不同。降水云体内的零度层高度大约6.3 km,但PR没有探测到零度层亮带。统计结果还表明拉萨探空站及附近的大气可降水量为20.89 mm·d^-1,降水转化率为27.0%,深厚降水系统的降水转化率是浅薄降水系统的2.9倍,深厚降水系统和浅薄降水系统的CAPE值分别为1941.7 J·kg^-1和1451.8 J·kg^-1。本研究结果为模式模拟青藏高原降水云内的温湿结构提供了观测依据。 相似文献
204.
该文将循环神经网络(recurrent neural network,RNN)应用于雷达临近预报。使用预测循环神经网络(predictive RNN)架构,利用雷达历史组合反射率因子建模,给出雷达组合反射率因子未来1 h的预报结果。预测循环神经网络的核心是在长短时记忆单元(long short-term memory,LSTM)中增加时空记忆模块,能够提取雷达回波不同尺度的空间特征,配合循环神经网络架构,可以有效解决反射率因子预测问题。北京大兴雷达和广州雷达长时间序列的独立检验结果和2个强对流天气个例检验结果表明:该方法和传统的基于交叉相关法的1 h雷达外推临近预报相比,在20 dBZ和30 dBZ检验项目内,临界成功指数(CSI)可以提升0.15~0.30,命中率(POD)提高0.15~0.25,虚警率(FAR)降低0.15~0.20,该方法对反射率因子强度变化有一定预报能力。 相似文献
205.
近区瞬变场的频率效应与大深度探测能力的研究 总被引:1,自引:1,他引:0
在时域中,磁源近区瞬变场的时间特性取决于场源所含低频谱的分数幂.对于磁感应强度Bz(t)∝∑iω3/2i,对于感应电势εz(t)∝∑iω5/2i.这表明,现有的瞬变电磁探测系统只适用于浅部勘查,对于大深度的勘查,需要研制超强能量且轻便化的场源(发送系统),同时完善超导磁强计(接收系统)的实用化. 相似文献
206.
207.
Comparison of the earthquake detection abilities of PhaseNet and EQTransformer with the Yangbi and Maduo earthquakes
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PhaseNet and EQTransformer are two state-of-the-art earthquake detection methods that have been increasingly applied worldwide. To evaluate the generalization ability of the two models and provide insights for the development of new models, this study took the sequences of the Yunnan Yangbi M6.4 earthquake and Qinghai Maduo M7.4 earthquake as examples to compare the earthquake detection effects of the two abovementioned models as well as their abilities to process dense seismic sequences. It has been demonstrated from the corresponding research that due to the differences in seismic waveforms found in different geographical regions, the picking performance is reduced when the two models are applied directly to the detection of the Yangbi and Maduo earthquakes. PhaseNet has a higher recall than EQTransformer, but the recall of both models is reduced by 13%–56% when compared with the results reported in the original papers. The analysis results indicate that neural networks with deeper layers and complex structures may not necessarily enhance earthquake detection performance. In designing earthquake detection models, attention should be paid to not only the balance of depth, width, and architecture but also to the quality and quantity of the training datasets. In addition, noise datasets should be incorporated during training. According to the continuous waveforms detected 21 days before the Yangbi and Maduo earthquakes, the Yangbi earthquake exhibited foreshock, while the Maduo earthquake showed no foreshock activity, indicating that the two earthquakes’ nucleation processes were different. 相似文献
208.
209.
A systematic assessment of Planctomycetales diversity in a South China Sea, deep‐sea sediment (1657 m) was conducted using the 16S rRNA gene analysis approach. PCR amplification of the samples from seven sediment layers (0.1, 1, 3, 5, 7, 9 and 11 m below the surface sediment) using the primer set Pla‐46‐F/1392‐R showed that the Planctomycetales existed within a limited range of sediment depths (≤ 5 m), and had a decreasing trend in diversity with increasing depth. The majority of the retrieved Pla‐46‐F/1392‐R sequences belonged to Pirellula‐related Planctomycetales, and two sequences retrieved from the 0.1‐m layer (GenBank accession numbers: DQ996944 and DQ996945 ) shared the same anammox‐related signature oligonucleotides and were closely related to commonly recognized anammox organisms. To identify new anammox‐related biomarkers, three primer sets were designed for amplifying the fragments of hydroxylamine oxidoreductase and S‐adenosylmethionine radical enzyme genes, but no related sequences were found. Our multiple 16S rRNA gene primer sets (Journal of Rapid Methods and Automation in Microbiology, 2008, in press) revealed even an higher diversity of Planctomycetales in the 0.1‐m layer of the sediment, especially at genus level. Our data profiled the distribution pattern of Planctomycetales diversity along sediment depths, and provided molecular evidence for the existence of anammox‐related bacteria in a new location, which broadens our understanding of Planctomycetales diversity in deep sea sediments. 相似文献
210.