Low and equatorial latitudes topside in NeQuick     

《Journal of Atmospheric and Solar》2008,70(6):901-906

The NeQuick electron density model of the ionosphere is designed for trans-ionospheric propagation applications. The model topside has been revised on the basis of ISIS 2 topside sounder profiles, producing a new formulation of its empirical shape parameter. Comparisons between experimental slant TEC data and values modelled using both versions of NeQuick topside showed that in general we have obtained a distinct improvement. However, during some months of the year and at low latitudes, the new topside formulation does not produce improvements on the slant TEC estimates. We discuss the likely reasons for this behaviour including assessment of merits and shortcomings of the ISIS 2 data in low latitudes. The topside sounder on Intercosmos 19 satellite extensively sounded the equatorial region during a period of high solar activity, which was less covered by ISIS 2. This paper presents comparisons of NeQuick and topside sounders profiles at low latitudes using Intercosmos 19 satellite data.  相似文献   

A regional monthly precipitation simulation model based on an L-moment smoothed statistical regionalization approach     

Javier González  Juan B. Valdés 《Journal of Hydrology》2008,348(1-2):27-39

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基于OMOS方法的地面气温短时预报——以重庆市为例     

王田  季焱  杜钦  朱寿鹏  智协飞 《气象科学》2023,43(5):652-661

基于重庆市气象局业务运行的风暴尺度快速同化和预报系统(Storm-Scale Rapid Assimilation and Forecast System, SSRAFS)、气象信息综合分析处理系统(Meteorological Information Comprehensive Analysis And Process System, MICAPS)地面观测和高空观测资料,进行模式输出统计(Model Output Statistics, MOS)方法和纳入超前实况因子的MOS(MOS with Prior Observation Predictors, OMOS)方法对重庆地区地面气温96 h内逐小时预报试验,并以SSRAFS地面气温预报结果作为参考进行对比分析。结果表明：MOS方法在1～96 h预报时效内的预报技巧高于SSRAFS,气温预报均方根误差(Root Mean Square Error, RMSE)平均减小1.22℃,CC和HR2分别平均增大0.006和20.4%;在1～7 h预报时效,RMSE平均减小1.70℃,CC和HR2分别平均增大0.07和34.5%;且MOS方...  相似文献   

Parameterization of the Ångström–Prescott formula based on machine learning benefit estimation of reference crop evapotranspiration with missing solar radiation data     

Shang Chen  Wenzhe Feng  Liang He  Wei Xiao  Hao Feng  Qiang Yu  Jiandong Liu  Jianqiang He 《水文研究》2024,38(2):e15091

Accurately estimated reference evapotranspiration (ET₀) is essential to regional water management. The FAO recommends coupling the Penman–Monteith (P-M) model with the Ångström–Prescott (A-P) formula as the standard method for ET₀ estimation with missing R_s measurements. However, its application is usually restricted by the two fundamental coefficients (a and b) of the A-P formula. This paper proposes a new method for estimating ET₀ with missing R_s by combining machine learning with physical-based P-M models (PM-ET₀). The benchmark values of the A-P coefficients were first determined at the daily, monthly, and yearly scales, and further evaluated in R_s and ET₀ estimates at 80 national R_s measuring stations. Then, three empirical models and four machine-learning methods were evaluated in estimating the A-P coefficients. Machine learning methods were also used to estimate ET₀ (ML-ET₀) to compare with the PM-ET₀. Finally, the optimal estimation method was used to estimate the A-P coefficients for the 839 regular weather stations for ET₀ estimation without R_s measurement for China. The results demonstrated a descending trend for coefficient a from northwest to southeast China, with larger values in cold seasons. However, coefficient b showed the opposite distribution as the coefficient a. The FAO has recommended a larger a but a smaller b for southeast China, which produced the region's largest R_s and ET₀ estimation errors. Additionally, the A-P coefficients calibrated at the daily scale obtained the best estimation accuracy for both R_s and ET₀, and slightly outperformed the monthly and yearly coefficients without significant difference in most cases. The machine learning methods outperformed the empirical methods for estimating the A-P coefficients, especially for the sites with extreme values. Further, ML-ET₀ outperformed the PM-ET₀ with yearly A-P coefficients but underperformed those with daily and monthly ones. This study indicates an exciting potential for combining machine learning with physical models for estimating ET₀. However, we found that using the A-P coefficients with finer time scales is unnecessary to deal with the missing R_s measurements.  相似文献   

Analysis of fluid inclusions using nuclear magnetic resonance     

《Geochimica et cosmochimica acta》1987,51(8):2233-2235

Nuclear magnetic resonance (NMR) spectra from ²³Na and ³⁵C1 in fluid inclusions in samples of quartz and beryl show the potential of NMR as a powerful analytical technique for the study of fluid inclusions.  相似文献   

Growth and Interactions of Multi-Source Perturbations in Convection-Allowing Ensemble Forecasts     

闵锦忠  庄潇然  王世璋  魏莉青 《热带气象学报(英文版)》2024,30(2):118-131

This study investigated the growth of forecast errors stemming from initial conditions (ICs), lateral boundary conditions (LBCs), and model (MO) perturbations, as well as their interactions, by conducting seven 36 h convection- allowing ensemble forecast (CAEF) experiments. Two cases, one with strong-forcing (SF) and the other with weak-forcing (WF), occurred over the Yangtze-Huai River basin (YHRB) in East China, were selected to examine the sources of uncertainties associated with perturbation growth under varying forcing backgrounds and the influence of these back- grounds on growth. The perturbations exhibited distinct characteristics in terms of temporal evolution, spatial propagation, and vertical distribution under different forcing backgrounds, indicating a dependence between perturbation growth and forcing background. A comparison of the perturbation growth in different precipitation areas revealed that IC and LBC perturbations were significantly influenced by the location of precipitation in the SF case, while MO perturbations were more responsive to convection triggering and dominated in the WF case. The vertical distribution of perturbations showed that the sources of uncertainties and the performance of perturbations varied between SF and WF cases, with LBC perturbations displaying notable case dependence. Furthermore, the interactions between perturbations were considered by exploring the added values of different source perturbations. For the SF case, the added values of IC, LBC, and MO perturbations were reflected in different forecast periods and different source uncertainties, suggesting that the combination of multi-source perturbations can yield positive interactions. In the WF case, MO perturbations provided a more accurate estimation of uncertainties downstream of the Dabie Mountain and need to be prioritized in the research on perturbation development.  相似文献   

南京地区一次强降水超级单体过程的双偏振雷达观测分析     

袁媛  孙康远  陈刚  董金芳  夏斌 《气象科学》2022,42(6):825-834

基于南京信息工程大学C波段双偏振雷达观测数据,结合探空和地面实况资料,对2016年7月7日发生在南京地区的一次强降水超级单体过程进行双偏振雷达变量特征分析。结果表明：(1)当后向传播和多单体合并造成02—03时出现129.2 mm·h^-1极端强降水时,最强回波Z_H约60 dBZ,差分反射率因子Z_DR达5 dB,差分相位常数K_DP超过8 (°)·km^-1。K_DP大值区与地面上小时雨强极大值中心存在较好的对应关系。反射率因子Z_H、差分反射率因子Z_DR、差分相位常数K_DP与小时雨强也有显著的正相关。(2)强降水超级单体发展旺盛阶段,垂直运动明显增强,上升气流活跃,冰雹和霰占的比例高,-20°C以上存在深厚的混合相态区,闪电的频次和强度明显增强,分钟雨强增大。相关系数小值区ρ_HV以及Z_DR弧超前于超级单体1个体扫发生,并可以指示超级单体底层上升气流区的位置...  相似文献   

A nested pre-operational model for the Egyptian shelf zone: Model configuration and validation/calibration     

《Dynamics of Atmospheres and Oceans》2017

We explored the variability of the Egyptian shelf zone circulation connected to atmospheric forcing by means of a numerical simulation of the general circulation. A high resolution model grid was used at 1/60° horizontal resolution and 25 sigma layers. The simulation was carried out using the most recent version of the Princeton Ocean Model (POM). The initialised model was run the whole year of 2006 using the analysis forcing data for the same year obtained from ECMWF and MFS (Mediterranean Forecasting System, Pinardi et al., 2003). The model skills were evaluated by means of the root mean square error (RMSE) and correlations. The Egyptian Shelf Model (EGYSHM) simulation suggests the presence of an Egyptian Shelf Slope Current (ESSC), which is flowing eastward at different depths in the domain. We found that the maximum velocity of the ESSC [0.25 m/s] is located near the continental slope during the summer time, while in winter the velocity of ESSC is weaker [0.12 m/s] in the same location. The ESSC appears to be directly affected by Mersa-Matruh gyre system. EGYSHM reproduced the main region circulation patterns, especially after adding the Nile River outflow. We found that wind stress is crucial to force the circulation of the Egyptian shelf zone. EGYSHM SST was significantly correlated to satellite SST in all months at a 95% confidence limit, with a maximum of 0.9743 which was obtained in May 2006. The RMSE between EGYSHM and Argo floats salinity data was about 0.09. We compared our results with satellite altimetry to verify the positions and shapes of mesoscale features.  相似文献   

Circulation analysis in the northwest Indian Ocean using ARGO floats and surface drifter observations,and SODA reanalysis output     

《Dynamics of Atmospheres and Oceans》2017

This study incorporates observations from Array of Real-time Geostrophic Oceanography (ARGO) floats and surface drifters to identify seasonal circulation patterns at the surface, 1000 m, 1500 m, and 2000 m in the northwest Indian Ocean, and quantify velocities associated with them. A skill comparison of the Simple Ocean Data Assimilation (SODA) reanalysis output was also performed to contribute to the understanding of the circulation dynamics in this region.Subsurface currents were quantified and validated using the ARGO float data. Surface currents were identified using surface drifter data and compared to the subsurface observations to enhance our previous understanding of surface circulations. Quantified Southwest Monsoon surface currents include the Somali Current (v_max = 179.5 cm/s), the East Arabian Current (v_max = 52.3 cm/s), and the Southwest Monsoon Current (v_max = 51.2 cm/s). Northeastward flow along the Somali coast is also observed at 1000 m (v_max = 26.1 cm/s) and 1500 m (v_max = 12.7 cm/s). Currents associated with the Great Whirl are observed at the surface (v_max = 161.4 cm/s) and at 1000 m (v_max = 16.2 cm/s). In contrast to previous studies, both ARGO and surface drifter data show the Great Whirl can form as early as the boreal Spring intermonsoon, lasting until the boreal Fall intermonsoon. The Arabian Sea exhibits eastward/southeastward flow at the surface, 1000 m, 1500 m, and 2000 m. Quantified Northeast Monsoon surface currents include the Somali Current (v_max = 97.3 cm/s), Northeast Monsoon Current (v_max = 30.0 cm/s), and the North Equatorial Current (v_max = 28.5 cm/s). Southwestward flow along the Somali coast extends as deep as 1500 m.Point-by-point vector and scalar correlations of SODA output to ARGO and surface drifter data showed that surface SODA output and surface drifter data generally produced a strong correlation attributed to surface currents strongly controlled by the monsoons, while subsurface correlations of SODA output and ARGO were mostly insignificant due to variability associated with intermonsoonal transitions. SODA output produced overall smaller velocities than both observational datasets. Assimilating ARGO velocities into the SODA reanalysis could improve subsurface velocity assimilation, especially during the boreal fall and spring when ARGO observations suggest that flow is highly variable.  相似文献   

利用卫星遥感资料分析台风“烟花”(202106)的影响过程          下载免费PDF全文

唐飞  陈凤娇  诸葛小勇  吴福浪  宇路  姚彬 《大气科学学报》2021,44(5):703-716

2021年第6号台风“烟花”于7月18日生成,7月30日变性为温带气旋,生命史长达13 d,先后对中国东部14个省市造成影响,其主要特点是移动速度慢、陆上滞留时间长和累积雨量大。基于静止气象卫星、极轨气象卫星和全球降水测量卫星的多通道观测和产品,对“烟花”的影响过程进行分析。结果表明：“烟花”空间尺度较大（最大半径约为350 km）,登陆前对流深厚、云系螺旋特征显著,登陆后云系结构遭到破坏、中等对流分布密集但没有组织性;“烟花”在洋面上时液态水和冰态水含量丰富并表现出非对称分布,登陆后液态水和冰态水主要集中在台风前进方向的右侧。基于微波成像仪的降水反演结果显示：降水主要分布在台风外围螺旋雨带位置,且在位置和形态上与实况较吻合;虽然雨量估计值与实况存在一定偏差,但对降水预报,特别是常规资料稀少区域的降水预报仍具有参考意义。  相似文献