Development of 1km-Scale Operational Model in South China     

陈子通  戴光丰  吴凯昕  钟水新  徐道生 《热带气象学报(英文版)》2021,27(4):319-329

To support short-range weather forecast, a high-resolution model (1km) is developed and technicallyupgraded in the South China Regional Center, including the improvement of the 3D reference scheme and predictor-corrector method for Semi-Implicit and Semi-Lagrangian (SISL) in model dynamical core, as well as the improvementof physical parameterization. Furthermore, the multi-process parallel I/O and parallel nudging techniques are developedand have facilitated rapid updating in the assimilation prediction system and fast-output post processing process. Theexperimental results show that the improved 3D reference scheme and upgraded physic schemes can effectively improvethe prediction accuracy and stability with a longer integration time step. The batch test shows that the precipitationforecast performance of 1-km model is significantly better than that of 3-km model. The 1-km model is in operation withrapidly updating cycle at 12-minute intervals, which can be applied to short-range forecast and nowcasting application.  相似文献   

Multi‐site evaluation of hydrology component of SWAT in the coastal plain of southwest Georgia     

Jaepil Cho  David Bosch  George Vellidis  Richard Lowrance  Timothy Strickland 《水文研究》2013,27(12):1691-1700

Simulation of watershed scale hydrologic and water quality processes is important for watershed assessments. Proper characterization of the accuracy of these simulations, particularly in cases with limited observed data, is critical. The Soil & Water Assessment Tool (SWAT) is frequently used for watershed scale simulation. The accuracy of the model was assessed by extrapolating calibration results from a well studied Coastal Plain watershed in Southwest Georgia, USA, to watersheds within the same geographic region without further calibration. SWAT was calibrated and validated on a 16.7‐km² subwatershed within the Little River Experimental Watershed by varying six model parameters. The optimized parameter set was then applied to a watershed of similar land use and soils, a smaller watershed with different land use and soils and three larger watersheds within the same drainage system without further calibration. Simulation results with percent bias (PB) ±15% ≤ PB < ±25% and Nash–Sutcliffe efficiency (NSE) 0.50 < NSE ≤ 0.65 were considered to be satisfactory, whereas those with PB < ±10% and 0.75 < NSE ≤ 1.00 were considered very good. With these criteria, simulation results for the five non‐calibration watersheds were satisfactory to very good. Differences across watersheds were attributed to differences in soils, land use, and surficial aquifer characteristics. These results indicate that SWAT can be a useful tool for predicting streamflow for ungauged watersheds with similar physical characteristics to the calibration watershed studied here and provide an indication of the accuracy of hydrologic simulations for ungauged watersheds. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

对多普勒雷达集合交叉相关外推技术的构造与实例检验   总被引：1，自引：0，他引：1  

符式红  钟青  寿绍文 《气象》2012,38(1):47-55

本文构造了集合的线性交叉相关方法,对多普勒雷达回波进行外推。因为线性交叉相关算法仅根据两个时次的回波外推下一时次的回波分布,且对于单个外推回波单元是线性变化的;而基于集合的线性交叉相关方法,考虑了多时刻回波的演变过程、回波的移向和移速以及回波在移动过程中的形变,都具有非线性特征,与实际情况更为符合。本文利用集合的线性交叉相关方法和最小二乘拟合方法分别对两次暴雨过程进行回波外推,通过比较发现,利用集合交叉相关外推方法所推得的回波分布与实况更为接近;利用Z-I关系,进一步分析了基于集合交叉相关外推方法的降水评分。与最小二乘拟合方法外推相比,集合交叉相关外推技术所得的回波移动位置与实况较为一致,且1小时累积降水预报效果也较好,因此集合交叉相关外推技术在临近预报中具有一定的应用价值。  相似文献   

A Composite Approach of Radar Echo Extrapolation Based on TREC Vectors in Combination with Model-Predicted Winds   总被引：3，自引：0，他引：3  

LIANG Qiaoqian  FENG Yerong  DENG Wenjian  HU Sheng  HUANG Yanyan  ZENG Qin  CHEN Zitong 《大气科学进展》2010,27(5):1119-1130

Extending the lead time of precipitation nowcasts is vital to improvements in heavy rainfall warning, flood mitigation, and water resource management. Because the TREC vector (tracking radar echo by correlation) represents only the instantaneous trend of precipitation echo motion, the approach using derived echo motion vectors to extrapolate radar reflectivity as a rainfall forecast is not satisfactory if the lead time is beyond 30 minutes. For longer lead times, the effect of ambient winds on echo movement should be considered. In this paper, an extrapolation algorithm that extends forecast lead times up to 3 hours was developed to blend TREC vectors with model-predicted winds. The TREC vectors were derived from radar reflectivity patterns in 3 km height CAPPI (constant altitude plan position indicator) mosaics through a cross-correlation technique. The background steering winds were provided by predictions of the rapid update assimilation model CHAF (cycle of hourly assimilation and forecast). A similarity index was designed to determine the vertical level at which model winds were applied in the extrapolation process, which occurs via a comparison between model winds and radar vectors. Based on a summer rainfall case study, it is found that the new algorithm provides a better forecast.  相似文献   

一种改进后的交叉相关法(COTREC)在降水临近预报中的应用   总被引：8，自引：0，他引：8  

陈雷  戴建华  陶岚 《热带气象学报》2009,25(1):117-122

利用多普勒雷达资料,采用一种改进后的交叉相关法(COTREC)建立了一种降水临近预报方法。COTREC法的基本原理是对传统交叉相关法(TREC)反演的风场进行水平无辐散处理,得到COTREC风场,用新的风场外推得出的回波能够保持平滑连续的形状。但是这种方法也存在缺陷,由于采用水平无辐散限制,使得外推反演得到的风场在不同程度上受到削弱,从而外推后的回波略慢于实况观测的回波。通过引入数值预报平均风场作为TREC风场背景场,较好地解决了TREC风场受到削弱的问题,并用该方法对2007年6月23—24日强雷雨天气和2007年台风“圣帕”两次降水过程进行了预报试验,试验结果表明：采用改进后的交叉相关方法的降水临近预报与雷达实际观测比较一致,可作为台风、强对流等灾害性天气的降水临近预报方法之一。  相似文献   

逐层子空间迭代法在地下水数值计算中的应用     

成建梅 《地质科技情报》1997,16(1):103-107

介绍了逐层子空间迭代法的基本原理及实现步骤，通过实例计算，与普遍迭代法对比，体现该算法的显著特点及其有于水文地质数值计算的可行性。  相似文献   

单程波算子积分解的象征表示   总被引：7，自引：5，他引：7       下载免费PDF全文

刘洪  王秀闽  曾锐  李幼铭  勾永峰 《地球物理学进展》2007,22(2):463-471

单程波波场延拓算子在地震偏移成像中有重要应用.单程波波场延拓算子按其实现方式可分为Kirchhoff积分、空间隐式有限差分和Fourier变换方法，他们代表了算子的不同表示方法，当截断使用这些方法时会得到不同的精度.象征表示对这些方法的导出和精度分析有重要作用.算子作用于正弦波函数所得函数称为算子的象征.算子的象征是褶积算子Fourier变换的推广.Fourier变换方法则直接用象征函数的可分表示求出.空间隐式有限差分则可以用象征函数的Padè近似或部分分式导出.单程波算子在深度域的积分称为单程波算子积分解.本文推导了单程波算子积分解的象征表达式，给出了算子象征的代数运算的头几阶表达式，这些表达式还未在前人文献中发现.Kirchhoff积分所需格林函数可以通过象征函数和鞍点法导出.基于积分解的象征表达式给出了非对称走时公式，对改善Kirchhoff积分的聚焦性能有重要意义.  相似文献   

Wavefield downward extrapolation for migration velocity analysis on Marmousi data-set     

Andrzej Kostecki  Anna Półchłopek 《Acta Geophysica》2007,55(2):209-221

The authors present a method for estimation of interval velocities using the downward continuation of the wavefield to perform layer-stripping migration velocity analysis. The generalized, phase-shift migration MG(F-K) in wavenumber-frequency domain was used for fulltime downward extrapolation of the wavefield. Such downward depth extrapolation accounts for strong changes of velocity in lateral and vertical directions and helps in correct positioning of the wavefield image in complex structures. Determination of velocity is the recursive process which means that the wavefield on depth level z _n−1 (n = 0, 1, ...) is an input data-set for determination of velocity on level z _n . The velocity ν [x, z _n − z _n−1] can be thus treated as interval velocity in Δz _n = z _n − z _n−1 step. This method was tested on synthetic Marmousi data-set and showed satisfactory results for complex, inhomogeneous media.  相似文献   

轴对称各向异性介质波动方程深度偏移的对称非平稳相移方法   总被引：6，自引：1，他引：6       下载免费PDF全文

刘礼农  陈小宏  张剑锋  刘洪 《地球物理学报》2007,50(1):277-284

由所建立的三维qP波相速度表示式出发，导出并解析求解各向异性介质中的频散方程，得到三维各向异性介质中的相移算子，进而将以相移算子为基础的对称非平稳相移方法推广到各向异性介质，发展了一个三维各向异性介质的深度偏移方法. 文中使用的各向异性介质的速度模型与现行的各向异性构造的速度估计方法一致，将各向同性、弱各向异性及强各向异性统一在一个模型中. 所建立的各向异性介质对称非平稳相移波场延拓算子可以同时适应速度及各向异性参数横向变化；文中给出的算例虽然是针对二维VTI介质的，但所提出的算法同样适用于三维TI介质.  相似文献   

最优可分表示法三维波场延拓     

张致付  孟小红  刘洪  陈景波  李幼铭 《应用地球物理》2006,3(4):218-225

适于复杂介质的高精度波场延拓算子是叠前深度偏移研究的重要内容。本文采用最优可分表示方法,运用正反傅立叶变换构造了三维单程波场延拓算子,算子实现了波数域变量与空间(速度)域变量分离。波数域内进行相移计算,在空间域对因介质横向变速引起的时移作修正。脉冲响应显示在区域内各速度的脉冲计算值与理论值基本一致,说明最优可分表示法叠前深度偏移可适用于强变速条件下复杂介质的成像需求。SEG／EAGE模型和实测数据的成像结果验证了本文方法对复杂构造的成像能力。  相似文献