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1.
A Lagrangian advection scheme (LAS) for solving cloud drop diffusion growth was previously proposed (in 2020) and validated with simulations of cloud droplet spectra with a one-and-a-half dimensional (1.5D) cloud bin model for a deep convection case. The simulation results were improved with the new scheme over the original Eulerian scheme. In the present study, the authors simulated rain embryo formation with the LAS for a maritime shallow cumulus cloud case from the RICO (Rain in Cumulus over the Ocean) campaign. The model used to simulate the case was the same 1.5D cloud bin model coupled with the LAS. Comparing the model simulation results with aircraft observation data, the authors conclude that both the general microphysical properties and the detailed cloud droplet spectra are well captured. The LAS is robust and reliable for the simulation of rain embryo formation.摘要云滴凝结增长的拉格朗日平流方案(LAS)于2020年提出, 并通过一维半(1.5D)分档云模式模拟深对流个例得到验证. 相比原先的欧拉平流方案, 新方案的使用改进了模拟结果. 本研究中, 我们进行了海洋性浅积云雨胚形成的个例模拟研究, 个例取自RICO (Rain in Cumulus over the Ocean) 外场试验. 浅积云个例的模拟同样使用耦合了LAS的1.5D分档云模式. 对比飞机观测数据, 我们认为模拟结果较好的刻画了积云的总体微物理特征和精细的云滴谱分布, 利用LAS模拟雨胚形成是合理可信的.  相似文献   

2.
Fengyun-4 (FY-4), the latest collection of Chinese geostationary meteorological satellites, monitors the Eastern Hemisphere with high spatiotemporal resolutions. This study developed a cloud optical and microphysical property product for the Advanced Geosynchronous Radiation Imager (AGRI) onboard the FY-4 satellites. The product focuses on cloud optical thickness (COT) and cloud effective radius (CER) using a bi-spectral retrieval algorithm, and also includes cloud mask and phase using machine learning (ML) algorithms as prerequisites for COT and CER retrievals. The ML-based algorithm develops four independent models using Random Forest methods for cloud mask, liquid water, ice, and mixed-phase/multi-layer clouds, respectively. A two-habit ice and sphere water cloud model are employed to give their optical properties. Look-up tables of cloud reflectance in the COT and CER sensitive channels are built for efficient forward simulations, and the retrieval is performed by an optimal estimation algorithm. Compared with collocated active observations, the cloud mask and phase results give true positive rates of ∼95% and ∼85% and are more sensitive to mixed-phase clouds. Meanwhile, the AGRI-based COT and CER agree closely with those given by the collocated MODIS and AHI cloud products, and the correlation coefficients between MODIS and the AGRI results are 0.76 and 0.63 for COT and CER, respectively. The COT and CER retrievals will be persistently maintained and improved as the operational product for FY-4/AGRI.摘要风云四号作为中国新一代静止气象卫星, 提供了高时空分辨率的监测产品. 本文介绍风云四号搭载的先进地球同步轨道辐射成像仪AGRI的云光学和微物理特性产品. 该产品包含了基于双光谱通道反演的云光学厚度和云粒子有效半径产品, 以及基于机器学习的云识别和云相态产品. 与时空匹配的主动卫星观测结果对比显示, 该产品的云识别和云相态的准确率分别在95%和85%; 该产品提供的云光学厚度和云有效粒径与经典的MODIS产品的相关系数达到0.76和0.63. 团队将持续优化和更新该云光学和微物理特性定量产品, 服务风云四号卫星定量应用.  相似文献   

3.
Spectral relative dispersion of different hydrometeors is vital to accurately describe sedimentation. Here, the Weather Research and Forecasting model with spectral bin microphysics is used to simulate convective clouds in Shouxian of Anhui province in China to study the spectral relative dispersion of different hydrometeors. Firstly, regardless of clean or polluted conditions, the relative dispersion of ice crystal spectra and its volume-mean diameter are negatively correlated, while the relative dispersion of other hydrometeor spectra is positively related to their respective volume-mean diameter. The correlations for cloud droplets and raindrops are affected by the process of collision–coalescence; the correlations for ice crystals, graupel particles, and snow particles could be affected by the deposition, riming, and aggregation processes, respectively. Secondly, relative dispersion parameterizations are developed based on a comprehensive consideration of the relationships between the relative dispersion and volume-mean diameter under both polluted and clean conditions. Finally, the relative dispersion parameterizations are applied to terminal velocity parameterizations. The results show that for cloud droplets, ice crystals, graupel particles, and snow particles, assuming the shape parameter in the Gamma distribution is equal to 0 underestimates the shape parameter and overestimates the relative dispersion; and for raindrops, assuming the shape parameter is equal to 0 is close to the relative dispersion parameterizations. The most appropriate constant shape parameters are recommended for different hydrometeors. The relative dispersion parameterizations developed here shed new light for further optimizing the terminal velocity parameterizations in models.摘要离散度的诊断对模式中沉降过程的准确描述至关重要. 本文利用WRF模式结合谱分档方案模拟安徽寿县地区的对流云, 研究不同水成物的离散度. 首先, 无论在清洁还是污染条件下, 除冰晶谱的离散度与体积平均直径间呈现负相关关系外, 云滴, 雨滴, 霰粒子与雪粒子谱离散度与体积平均直径呈现正相关关系; 云滴和雨滴受碰并过程影响, 冰晶, 霰粒子和雪粒子分别受凝华过程, 淞附过程和聚并增长影响. 其次, 综合考虑污染与清洁条件下离散度和体积平均直径之间的相关关系, 建立了离散度的参数化方案. 最后, 把该离散度方案应用到下落末速度的参数化方案中, 结果表明, 对于云滴, 冰晶, 霰粒子和雪粒子, 在Gamma分布中假设谱形参数等于0会低估谱形参数而高估离散度. 对于雨滴而言, 假设谱形参数等于0与参数化方案结果接近. 针对不同的水成物, 给出了最合适的谱形参数定值. 本文发展的离散度方案为进一步优化模式中下落末速度参数化方案提供参考.  相似文献   

4.
In recent years, the Cloud Imaging Probe (CIP) and Precipitation Imaging Probe (PIP) produced by Droplet Measurement Technologies (DMT) have been introduced by a number of meteorological research and operation centers in China. The supporting software provided by DMT, i.e., PADS (Particle Analysis and Display System), cannot output detailed information on each individual particle, which definitely limits the in-depth utilization of cloud and precipitation particle image data in China. In this paper, particle-by-particle information was extracted by decompressing the CIP and PIP original particle image data, based on which a new definition of the dimension for nonspherical particles is proposed by using the area of the convex hull enclosing a particle to obtain the equivalent diameter of a circle with equal area. Based on the data detected during one flight in Inner Mongolia, the particle size distribution obtained using the new particle size definition and that used by the other four existing definitions are compared. The results show that the particle number concentration calculated using different particle size definitions can vary by up to an order of magnitude. The result obtained based on the new particle size definition is closest to that calculated with the area-equivalent diameter definition.摘要 国内许多气象部门已引进美国DMT公司的云粒子图像探头 (CIP) 和降水粒子图像探头 (PIP) . 由于其配套软件不能输出逐个粒子的详细信息, 在很大程度上限制了对云降水粒子图像探测数据的深入挖掘. 通过解析CIP和PIP原始数据, 提出了一种基于包围粒子凸多边形的面积求取粒子尺度的新定义. 利用在内蒙古的一次航测数据, 对比分析了基于新定义及已有的四种粒子尺度定义求取的粒子尺度谱分布.  相似文献   

5.
This study presents the simulated aerosol spatiotemporal characteristics over the Tibetan Plateau (TP) with a newly developed coupled aerosol–climate model (FGOALS-f3-L). The aerosol properties are simulated over the TP for the period 2002–11. The results indicate that soil dust, sulfate, and carbonaceous aerosols (black carbon (BC), organic carbon (OC) and BC/OC) account for 53.6%, 32.2%, and 14.2% of the total aerosol mass over the TP, respectively. The simulated aerosol surface mass concentrations and aerosol optical depths (AODs) are evaluated with ground-based and satellite observations, respectively. Underestimations of the aerosol surface mass concentration are found at the Lhasa site, especially for BC and OC. The spatial distribution and interannual variation of AOD are consistent with MODIS observations, with the RMSE of 0.081 and bias of 0.036. Due to the uncertainty of the parameterization of dust emissions, the model's performance in summer and autumn is much better than that in spring.摘要基于新耦合气溶胶气候模式FGOALS-f3-L模拟分析了2002–2011年青藏高原地区气溶胶时空分布特征.结果表明:青藏高原地区, 沙尘,硫酸盐,碳质气溶胶 (包括黑碳,有机碳和混合碳) 地表质量浓度分别占比为53.6%, 32.2%, 14.2%;在拉萨站点, 模拟的气溶胶地表质量浓度被低估, 尤其是黑碳和有机碳气溶胶;模拟的气溶胶光学厚度 (AOD) 时空分布与卫星观测结果较为一致, 均方根误差和偏差分别为0.081和0.036;由于模式中沙尘排放参数化的不确定性, 模式对AOD的模拟效果在夏季和秋季优于春季  相似文献   

6.
Aircraft observation data obtained in a mesoscale convective system are compared to Weather Research and Forecasting (WRF) model simulations using four microphysics schemes (Morrison, WSM6, P3, SBM) with different complexities. The main purpose of this paper is to assess the performance of the microphysics ensemble in terms of cloud microphysical properties. Results show that although the vertical distributions of liquid water content (LWC) and ice water content (IWC) simulated by the four members are quite different in the convective cloud region, they are relatively uniform in the stratiform cloud region. Overall, the results of the Morrison scheme are very similar to the ensemble average, and both of them are closer to the observations compared to the other schemes. Besides, the authors also note that all members still overpredict the LWC by a factor of 2–8 in some regions, resulting in large deviation between the observation and ensemble average.摘要使用 WRF 模式中的 Morrison,WSM6,SBM,P3 四种微物理方案的集合, 模拟中尺度对流系统降水过程.研究发现不同的微物理方案模拟的对流云区液态含水量,冰水含量的垂直分布各不相同, 而模拟的层状云区液态含水量, 冰水含量的垂直分布结果相似. 总的来说与其他方案相比, Morrison 方案和集合平均的结果最接近观测值.我们也注意到在一些区域, 所有成员均高估了液态含水量 2–8 倍, 这也导致了在这些区域集合平均值与观测相比仍然有很大的差距.  相似文献   

7.
The regional air quality modeling system RAMS-CMAQ was applied to simulate the aerosol concentration for the period 2045–2050 over China based on the downscaled meteorological field of three RCP scenarios from CESM (NCAR's Community Earth System Model) in CMIP5. The downscaling simulation of the meteorological field of the three RCP scenarios showed that, compared with that under RCP2.6, the difference in near-surface temperature between North and South China is weakened and the wind speed increases over North and South China and decreases over central China under RCP4.5 and RCP8.5. Under RCP2.6, from 2045 to 2050, the modeled average PM2.5 concentration is highest, with a value of 40–50 µg m−3, over the North China Plain, part of the Yangtze River Delta, and the Sichuan Basin. Meanwhile, it is 30–40 µg m−3 over central China and part of the Pearl River Delta. Compared with RCP2.6, PM2.5 increases by 4–12 µg m−3 under both RCP4.5 and RCP8.5, of which the SO42− and NH4+ concentration increases under both RCP4.5 and RCP8.5; the NO3− concentration decreases under RCP4.5 and increases under RCP8.5; and the black carbon concentration changes very slightly, and organic carbon concentration decreases, under RCP4.5 and RCP8.5, with some increase over part of Southwest and Southeast China under RCP8.5. The difference between RCP4.5 and RCP2.6 and the difference between RCP8.5 and RCP2.6 have similar annual variation for different aerosol species, indicating that the impact of climate change on different species tends to be consistent.摘要基于来自于 CMIP5 中 CESM 模式的三种 RCP 情景下的气象场的降尺度模拟, 应用区域空气质量模式系统 RAMS-CMAQ 模拟 2045-2050 年中国地区气溶胶浓度.三种 RCP 情景下气象场的降尺度模拟表明, 与 RCP2.6 相比, 在 RCP4.5 和 RCP8.5 下, 华北和华南的近地表温度差减小, 风速在华北和华南地区增加, 在中部地区下降. RCP2.6 情景下, 模拟的 2045 年到 2050 年平均的 PM 2.5浓度在华北平原, 长三角的部分地区和四川盆地最高, 约为 40-50 µg m–3, 在中国中部和珠三角的部分地区约为 30-40 µg m–3. 与 RCP2.6 相比, 在 RCP4.5 和 RCP8.5 下, PM2.5增加了 4-12 µg m–3, 其中在 RCP4.5 和 RCP8.5 下, SO42–和 NH4+的浓度增加, 在 RCP4.5 下, NO3–浓度降低, 在 RCP8.5 下, NO3–浓度升高, 在 RCP4.5 和 RCP8.5 下, BC 浓度变化很小, 而 OC 浓度下降, 其中在 RCP8.5 下, 西南和东南部分地区的 OC 有所增加.不同的气溶胶物种浓度在 RCP4.5 和 RCP2.6 之间的差异以及 RCP8.5 和 RCP2.6 之间的差异具有相似的年度变化, 这表明气候变化对不同物种的影响趋于一致.  相似文献   

8.
A 2D axisymmetric bin model is used to conduct idealized numerical experiments of cloud seeding. The simulations are performed for two clouds that differ in their initial wind shear. Results show that, although cloud seeding with an ice concentration of 1000 L?1 in a regime that has relatively high supercooled liquid water can obtain a positive effect, the rainfall enhancement seems more pronounced when the cloud develops in a wind shear environment. In no-shear environment, the change in the microphysical thermodynamic field after seeding shows that, although more graupel is produced via riming and this can increase the surface rainfall intensity, the larger drag force and cooling of melting graupel is unfavorable for the development of cloud. On the contrary, when the cloud develops in a wind shear environment, since the main downdraft is behind the direction of movement of the cloud, its negative effect on precipitation is much weaker.摘要本文采用二维轴对称分档云模式开展了人工催化数值试验, 对两种不同初始风切变的对流云进行了模拟. 结果表明, 尽管在过冷水相对较高的区域播撒 1000 L?1 的冰晶可以增加地面降水, 但当云在风切变环境中发展时, 人工播撒对降雨增强的作用似乎更加明显. 在无切变环境下, 微物理量, 热力场的变化表明播撒后大量的霰所产生的拖曳力和融化冷却有可能切断主上升气流, 从而不利于云的发展. 相反, 当云在风切变环境中发展时, 由于播撒产生的主下沉气流位于云的运动方向之后, 其对降水的负面影响要弱得多.  相似文献   

9.
China has implemented a series of emission reduction policies since 2013, and the concentration of air pollutants has consequently decreased significantly. However, PM2.5 (particulate matter with an aerodynamic diameter less than 2.5 µm) pollution still occurs in China in relation to the interannual variations in meteorological conditions. Considering that El Niño–Southern Oscillation (ENSO) is the strongest signal modulating the interannual variation in the atmosphere–ocean system, in this study the authors investigate the variations in PM2.5 concentrations in four megacity clusters of China during the winter season associated with four individual ENSO events from 2014 to 2021. Results show that the wintertime PM2.5 concentrations in the Beijing–Tianjin–Hebei and Fenwei Plain regions during El Niño years are higher than those during La Niña years, which can be explained by the anomalous southerly (northerly) winds during El Niño (La Niña) favoring PM2.5 accumulation (diffusion). In the Pearl River Delta region, PM2.5 concentrations decrease in El Niño relative to La Niña years owing to the enhanced water vapor flux and precipitation, removing more PM2.5 from the atmosphere. The comprehensive effects of wind and precipitation anomalies lead to the unpredictability of the impacts of ENSO on PM2.5 over the Yangtze River Delta region, which should be analyzed case by case.摘要2013年以来中国实施了一系列减排政策, 大气污染物浓度明显下降, 但由于气象条件的年际变化, 中国PM2.5 (空气动力学直径小于2.5 µm的颗粒物) 污染仍然存在. 厄尔尼诺–南方涛动 (ENSO) 是调节大气–海洋系统年际变化的最强信号. 本文研究了2014–2021年四次ENSO事件期间, 中国四个特大城市群冬季PM2.5浓度的变化. 结果表明, 在京津冀和汾渭平原地区, 由于厄尔尼诺 (拉尼娜) 期间的偏南风 (偏北风) 异常有利于 PM2.5 的积累 (扩散), 冬季PM2.5浓度在厄尔尼诺年高于拉尼娜年. 在珠三角地区, 由于厄尔尼诺冬季水汽通量和降水的增加有利于大气中PM2.5的湿清除, 冬季PM2.5浓度在厄尔尼诺年低于拉尼娜年. 在环流和降水异常的综合作用下, ENSO对长三角地区PM2.5浓度的影响难以预测, 应逐案分析.  相似文献   

10.
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11.
Surface irradiance measurements with high temporal resolution can be used to detect clear skies, which is a critical step for further study, such as aerosol and cloud radiative effects. Twenty-one clear-sky detection (CSD) methods are assessed based on five years of 1-min surface irradiance data at Xianghe—a heavily polluted station on the North China Plain. Total-sky imager (TSI) discrimination results corrected by manual checks are used as the benchmark for the evaluation. The performance heavily relies on the criteria adopted by the CSD methods. Those with higher cloudy-sky detection accuracy rates produce lower clear-sky accuracy rates, and vice versa. A general tendency in common among all CSD methods is the detection accuracy deteriorates when aerosol loading increases. Nearly all criteria adopted in CSD methods are too strict to detect clear skies under polluted conditions, which is more severe if clear-sky irradiance is not properly estimated. The mean true positive rate (CSD method correctly detects clear sky) decreases from 45% for aerosol optical depth (AOD) ≤ 0.2% to 6% for AOD > 0.5. The results clearly indicate that CSD methods in a highly polluted region still need further improvements.摘要根据位于华北平原的重污染站点——香河5年的分钟级别地表太阳辐射和人工订正的全天空成像仪数据, 对21种晴空识别 (CSD) 方法进行了评估:晴空识别准确率较高的方法云天识别准确率较低, 反之亦然;由于CSD 方法采用的参数阈值不适用于污染情况, 当气溶胶含量增加时, 识别准确率呈下降趋势.研究结果显示, 利用太阳辐射数据识别晴空的方法在高污染地区使用时需进行改进.  相似文献   

12.
Based on the 1%CO2 experiment of CMIP6, in response to increasing CO2, the summer-mean radiative heating (RH) over the global monsoon area (MA) generally features an increasing response in the mid-troposphere and a decreasing response in the lower and upper troposphere. The pressure level of the maximum RH increase over the Asian MA is the highest and largest in range (500–775 hPa); the maximum increases over the North African, South American, and Australian MA are at 550–600 hPa; throughout the North American MA, the maximum heating increase is at 600 hPa; and the levels of the maximum over South Africa are 600 and 775 hPa. For most of the global MA, the maximum enhancement of RH is at 500, 550, and 600 hPa. It is mainly led by the increase in cloud water at and above the maximum level and the decrease in cloud water below, which leads to similar changes in total cloud mass. Because of the longwave heating (cooling) effect at the cloud base (top), the RH enhancements peak at those levels. For the northeast part of the Asian MA and southeast part of the South African MA, RH enhancement peaks at 700 and 775 hPa, mainly attributable to the cloud water reduction below. The reduction leads to similar changes in total cloud. Due to the longwave cooling effect at the cloud top, the reduction contributes to the RH enhancement at the corresponding maximum levels.摘要大气CO2浓度增加, 大气辐射平衡调整, 将影响到大气的辐射加热, 对季风环流的产生影响.CMIP6结果显示, 大气CO2浓度增加, 可减弱季风区主雨季对流层高,低层的辐射加热, 加强对流层中层的辐射加热.各季风区加热响应的峰值层次不同:亚洲季风区平均层次最高 (500-775 hPa) , 北非,南美,澳洲季风区次之 (550-600 hPa) , 北美 (600 hPa) 和南非季风区 (600-775 hPa) 较低.各季风区水云的垂直分布及其长波辐射效应的变化是形成峰值层次差异的主因.  相似文献   

13.
The Chinese Academy of Sciences Flexible Global Ocean–Atmosphere–Land System atmospheric component model (FGOALS-f3-L) participated in Phase 6 of the Coupled Model Intercomparison Project, but its reproducibility of surface temperature (Ts) over the Tibetan Plateau (TP) as a key climatically sensitive region remains unclear. This study evaluates the capability of FGOALS-f3-L in reproducing the climatological Ts over the TP relative to the Climate Forecast System Reanalysis. The results show that FGOALS-f3-L can reasonably capture the spatial pattern of Ts but underestimates the annual mean Ts for the whole TP. The simulated Ts for the whole TP shows a cold bias in winter and spring and a warm bias in summer and autumn. Further quantitative analysis based on the surface energy budget equation shows that the surface albedo feedback (SAF) term strongly contributes to the annual, winter, and spring mean cold bias in the western TP and to the warm bias in the eastern TP. Compared with the SAF term, the surface sensible and latent heat flux terms make nearly opposite contributions to the Ts bias and considerably offset the bias due to the SAF term. The cloud radiative forcing term strongly contributes to the annual and seasonal mean weak cold bias in the eastern TP. The longwave radiation term associated with the overestimated water vapor content accounts for a large portion of the warm bias over the whole TP in summer and autumn. Improving land surface and cloud processes in FGOALS-f3-L is critical to reduce the Ts bias over the TP.摘要中国科学院全球海洋–大气–陆地耦合模式 (FGOALS-f3-L) 参加了耦合模式比较计划的第六阶段 (CMIP6) 试验,但是其对关键气候敏感地区青藏高原的地表温度的再现能力还不清楚.这项研究用再分析资料CFSR评估了FGOALS-f3-L模式对青藏高原地表温度的再现能力.结果表明, FGOALS-f3-L可以合理模拟整个高原上年平均地表温度的空间分布, 但低估了整个高原上年平均地表温度.模拟的地表温度在整个高原上冬春季表现为冷偏差, 夏秋季表现为暖偏差.基于地表能量平衡方程的进一步定量分析表明, 地表反照率反馈 (SAF) 项极大地贡献了高原西部年平均, 冬春季平均地表温度的冷偏差, 而对高原东部是暖偏差贡献.与SAF项相比, 地表感热项对地表温度偏差的贡献几乎相反, 这大大抵消了SAF项引起的偏差.云辐射强迫项对高原东部的年平均和季节平均弱冷偏差有很大贡献.与高估的水蒸气含量有关的长波辐射项造成了夏秋季整个高原上大部分的暖偏差.该研究表明, 提高FGOALS-f3-L中的陆面和云过程对降低高原上地表温度偏差至关重要.  相似文献   

14.
The global planetary boundary layer height (PBLH) estimated from 11 years (2007–17) of Integrated Global Radiosonde Archive (IGRA) data, Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) soundings, and European Center for Medium-Range Weather Forecasts (ECMWF) interim reanalysis (ERA-Interim) data, are compared in this study. In general, the spatial distribution of global PBLH derived from ERA-Interim is consistent with the one from IGRA, both at 1200 UTC and 0000 UTC. High PBLH occurs at noon local time, because of strong radiation energy and convective activity. There are larger differences between the results of COSMIC and the other two datasets. PBLHs derived from COSMIC are much higher than those from radiosonde and reanalysis data. However, PBLHs derived from the three datasets all exhibit higher values in the low latitudes and lower ones in the high latitudes. The latitudinal difference between IGRA and COSMIC ranges from −1700 m to −500 m, while it ranges from −500 m to 250 m for IGRA and ERA-Interim. It is found that the differences among the three datasets are larger in winter and smaller in summer for most studied latitudes.摘要用11年的全球无线电掩星数据 (COSMIC) , 无线电探空数据 (IGRA) 以及欧洲中心再分析资料 (ERA-Interim) 对全球大气边界层高度 (PBLH) 进行估算比较. 结果表明: (1) 在1200 UTC和0000 UTC, 由ERA-Interim和IGRA数据估算得到的全球PBLH空间分布较为一致, 相关性较好, 在白天正午时候太阳辐射能力较强, 对流活动频繁, 估算得到的大气边界层高度较高. (2) 由COSMIC掩星数据估算得到的边界层高度比探空数据和再分析数据估算结果整体偏大. (3) COSMIC掩星数据, IGRA 探空数据以及 ERA-Interim 再分析资料估算结果都表明边界层高度在低纬度地区偏大, 高纬度地区偏小. (4) 分析不同数据估算边界层高度纬向季节性差异表明, IGRA探空数据和COSMIC数据间差异为-1700m至-500m, IGRA与ERA-Interim之间的差异为-500m至250m.此外, 对于大多数纬度而言, 三个数据集之间的差异在冬季较大, 在夏季较小.  相似文献   

15.
Tropical cyclones (TCs) seriously endanger human life and the safety of property. Real-time monitoring of TCs has been one of the focal points in meteorological studies. With the development of space technology and sensor technology, satellite remote sensing has become the main means of monitoring TCs. Furthermore, with its superior data mining capability, deep learning has shown advantages over traditional physical or statistical-based algorithms in the geosciences. As a result, more deep-learning algorithms are being developed and applied to extract TC information. This paper systematically reviews the deep-learning frameworks used for TC information extraction and then gives two typical applications of deep-learning models for TC intensity and wind radius estimation. In addition, the authors present an outlook on the future perspectives of deep learning in TC information extraction.摘要热带气旋 (TC) 严重危害人类生命和财产安全, TC的实时监测一直是研究热点, 随着空间和传感器技术的发展, 卫星遥感已成为监测TC的主要手段. 此外, 深度学习具有卓越的数据挖掘能力, 在地球科学中的表现优于基于物理或统计的算法, 越来越多的深度学习算法被开发和应用于TC信息的提取, 本文系统地回顾了深度学习在TC信息提取中的应用, 并给出了深度学习模型在TC强度和风圈半径提取中的应用. 此外, 本文还展望了深度学习在TC信息提取中的应用前景.  相似文献   

16.
Using model simulated data, the distribution characteristics, genesis, and impacts on precipitation of available potential energy (APE) are analyzed for a heavy rainfall event that took place over the eastern Tibetan Plateau during 10–11 July 2018. Results show that APE was mainly distributed below 4 km and within 8–14 km. The APE distribution in the upper level had a better correspondence with precipitation. Northwestern cold advection and evaporation of falling raindrops were primary factors leading to positive anomalies of APE in the lower level, while positive anomalies of APE in the upper level were caused by a combination of thermal disturbances driven by latent heat and potential temperature perturbations resulting from the orography of the Tibetan Plateau. Budget analysis of APE indicated that APE fluxes and conversion between APE and kinetic energy (KE) were the main source and sink terms. Meridional fluxes of APE and conversion of KE to APE fed the dissipation of APE in the lower level. Vertical motion enhanced by conversion of APE to KE in the upper level was the major factor that promoted precipitation evolution. A positive feedback between APE and vertical motion in the upper level generated a powerful correlation between them. Conversion of KE to APE lasted longer in the lower level, which weakened vertical motion; whereas, northwestern cold advection brought an enhanced trend to the APE, resulting in a weak correlation between APE and vertical motion.摘要针对2018年7月10-11日青藏高原东部一次暴雨过程, 利用模式模拟资料分析了有效位能分布特征,成因及其对降水发展演变的影响.结果表明, 有效位能主要分布在对流层低层4km以下和高层8-14km, 高层有效位能和降水有更好的对应性西北冷平流和降水粒子下落的蒸发作用是低层有效位能高值中心的主要成因, 而降水过程释放潜热带来的热力扰动叠加高原大地形造成的位温扰动是导致高层有效位能高值的主要原因.有效位能收支分析表明, 有效位能的通量输送项以及与动能间的转换项是主要源汇项.低层有效位能的经向通量输送和动能向有效位能的转化补给了有效位能的耗散;高层有效位能向垂直动能转化增强垂直运动是促进降水发展演变的主要因素.高层有效位能与垂直运动之间的正反馈过程使得两者相关性较强;低层较长时间内均存在垂直动能向有效位能的转化, 削弱了垂直运动, 而西北冷平流使得低层有效位能有增强的趋势, 因此二者相关性较弱.  相似文献   

17.
To evaluate the downscaling ability with respect to tropical cyclones (TCs) near China and its sensitivity to the model physics representation, the authors performed a multi-physics ensemble simulation with the regional Climate–Weather Research and Forecasting (CWRF) model at a 30 km resolution driven by ERA-Interim reanalysis data. The ensemble consisted of 28 integrations during 1979–2016 with varying CWRF physics configurations. Both CWRF and ERA-Interim can generally capture the seasonal cycle and interannual variation of the TC number near China, but evidently underestimate them. The CWRF downscaling and its multi-physics ensemble can notably reduce the underestimation and significantly improve the simulation of the TC occurrences. The skill enhancement is especially large in terms of the interannual variation, which is most sensitive to the cumulus scheme, followed by the boundary layer, surface and radiation schemes, but weakly sensitive to the cloud and microphysics schemes. Generally, the Noah surface scheme, CAML(CAM radiation scheme as implemented by Liang together with the diagnostic cloud cover scheme of Xu and Randall(1996)) radiation scheme, prognostic cloud scheme, and Thompson microphysics scheme stand out for their better performance in simulating the interannual variation of TC number. However, the Emanuel cumulus and MYNN boundary layer schemes produce severe interannual biases. Our study provides a valuable reference for CWRF application to improve the understanding and prediction of TC activity.摘要为评估CWRF模式的降尺度能力和其热带气旋模拟对物理参数化方案的敏感性, 本文利用ERI再分析资料驱动CWRF在30km网格上对1982-2016年中国近海热带气旋开展了一次集合模拟.结果表明:CWRF与ERI均能模拟出热带气旋的季节变化和年际变化形势且均存在低估, 但相较ERI, CWRF的降尺度技术和集合模拟可以再现更多的热带气旋, 显著减少低估.年际变化结果提升最为明显, 它对积云方案最为敏感, 其次是边界层, 陆面和辐射方案, 对云和微物理方案较弱.该研究为应用CWRF理解和预报热带气旋提供了参考.  相似文献   

18.
This paper examines truncation and round-off errors in the numerical solution of the 1D advection equation with the Lax–Friedrichs scheme, and accumulation of the errors as they are propagated to high temporal layers. The authors obtain a new theoretical approximation formula for the upper bound of the total error of the numerical solution, as well as theoretical formulae for the optimal grid size and time step. The reliability of the obtained formulae is demonstrated with numerical experimental examples. Next, the ratio of the optimal time steps under two different machine precisions is found to satisfy a universal relation that depends only on the machine precision involved. Finally, theoretical verification suggests that this problem satisfies the computational uncertainty principle when the grid ratio is fixed, demonstrating the inevitable existence of an optimal time step size under a finite machine precision.摘要本文对于应用Lax- Friedrichs 格式数值求解一维平流方程, 研究数值求解过程中产生的截断误差与舍入误差, 以及两种误差逐层向高时间层传播的累积, 得到新的数值解总误差上界的理论近似公式, 以及最优格距和最优时间步长的理论公式. 通过数值算例验证了所得公式的可靠性. 然后, 发现了两种不同机器精度下最优时间步长之比满足的一个仅与机器精度有关的普适关系. 最后, 理论验证了在网格比固定的情况下, 此问题满足数值计算的不确定性原理, 以及在机器有限精度下最优时间步长的必然存在.  相似文献   

19.
Severe air pollution with visibility deterioration has long been a focus in the North China Plain (NCP). In this study, concentration and light extinction analysis of PM2.5 chemical components were carried out from 2014 to 2017 to study the pollution characteristics in Baoding, a case city of the NCP. The annual average concentration of total PM2.5 components showed a declining trend, decreasing by 11 µg m−3 (water-soluble inorganic ions), 23 µg m−3 (carbonaceous aerosols), and 1796 ng m−3 (inorganic elements). Contributing 82.9% to the concentration of total ions, the dominant components, NH4+, NO3−, and SO42− became the main pollutants in PM2.5 pollution. Based on the IMPROVE algorithm, the average reconstructed PM2.5 mass concentration was 93 ± 69 µg m−3 during the observation period. Meanwhile, the light extinction coefficients were 373.8 ± 233.6 M m−1, 405.3 ± 300.1 M m−1, 554.3 ± 378.2 M m−1 and 1005.2 ± 750.3 M m−1, in spring, summer, autumn, and winter, respectively. Ammonium sulfate, ammonium nitrate, and organic matter were the largest contributors to light extinction, accounting for a total of 55%–77% in the four seasons. The bsca (light scattering by particles and gases) reconstructed from PM2.5 components (Rbsca) and the bsca converted from visibility (Vbsca) were compared to evaluate the performance of the IMPROVE algorithm, revealing a high correlation coefficient of 0.84. The high values of Vbsca were underestimated while the low values were overestimated, as determined through comparison with the one-to-ne line. Especially, when Rbsca > 1123 M m−1 (corresponding to < 2.0 km, approximately), Vbsca was underestimated by 17.6%. PM2.5 mass concentration and relative humidity also had an impact on the estimation.摘要华北平原大气污染与低能见度状况一直是人们关切的问题.本文通过分析2014 - 2017年PM2.5化学成分的浓度和消光效果, 研究了华北平原典型城市保定市的大气污染特征.结果表明, PM2.5组分的年均浓度显示下降趋势, 水溶性无机离子,碳质气溶胶和金属元素分别减少了11 µg m−3, 23 µg m−3和1796 ng m−3.NH4+,NO3−和SO42−是PM2.5污染的主要污染物, 三者之和占总离子浓度的82.9%.基于IMPROVE方程对细颗粒物进行重构, 在观测期间PM2.5质量浓度平均为93 ± 69 µg m−3, 春季,夏季,秋季和冬季的消光系数分别为373.8 ± 233.6 M m−1,405.3 ± 300.1 M m−1,554.3 ± 378.2 M m−1和1005.2 ± 750.3 M m−1.硫酸铵,硝酸铵和有机物对消光的贡献最大, 不同季节下占比达55% ~77%.通过PM2.5组分进行重构, 利用IMPROVE算法计算得到Rbsca, 用能见度测量值转换得到Vbsca, 二者具有较高的相关性 (r2=0.84) ;但存在Vbsca的高值被低估, Vbsca的低值被高估的现象;特别是当Rbsca > 1123 M m−1 (对应能见度约小于2.0 km) 时, Vbsca的值被低估了17.6%.高浓度PM2.5和高湿度对IMPROVE算法结果有显著的影响.  相似文献   

20.
The influences of strong El Niño events (1997/98 and 2015/16) on summertime near-surface ozone (O3) concentrations over China are investigated using the GEOS-Chem model. The results show that near-surface O3 concentrations increased by a maximum of 6 ppb (parts per billion) during the summer of the developing phase of the 1997/98 El Niño in northeastern China, mainly due to the increased chemical production related to the hot and dry conditions. Besides, the O3 concentration increased by 3 ppb during the developing summer of both the 1997/98 and 2015/16 El Niño in southern China. It was linked to the weakened prevailing monsoon winds, which led to the accumulation of O3 in southern China. In contrast, in the summer of the decaying phase of the two El Niño events, O3 concentrations decreased over many regions of China when the El Niño reversed to the cooling phase. This highlights that El Niño plays an important role in modulating near-surface O3 concentrations over China.摘要利用全球大气化学三维模式 (GEOS-Chem) 模拟研究两次强厄尔尼诺事件 (1997/98和2015/16) 对中国夏季近地面臭氧 (O3) 浓度的影响. 结果表明1997/98年厄尔尼诺事件发展期夏季中国东北区域O3浓度升高, 最大值超过6ppb, 这主要归因于高温晴朗低湿等气象因素导致O3化学生成升高. 此外, 两次厄尔尼诺事件发展期夏季O3浓度在中国南部均增加了3ppb, 这与盛行季风减弱导致中国南方O3局地积累有关. 相反, 在两次强厄尔尼诺衰减期夏季, 中国大部分地区O3浓度下降伴随着海温模态转变为拉尼娜事件. 这表明厄尔尼诺在调节中国近地面O3浓度中发挥着重要作用.  相似文献   

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