一种新的多因子约束下的NWP反演ZTD残差改正模型

对流层延迟是GNSS定位的主要误差源之一,利用NWP模型的气象数据积分反演ZTD是当前研究热点.然而,采用两大气象预报中心(ECMWF和NCEP)的再分析资料反演ZTD的残差一般在±60 mm之间浮动,预报资料反演的ZTD的精度更差,都不能直接用于精密定位.一般是先将此反演的ZTD作为初值,设定先验方差,将残差作为未知参数求解.NWP反演的ZTD的精度,将直接影响对流层和模糊度参数在滤波过程中收敛速度.前人的研究表明,NWP反演ZTD的残差大小与测站所在纬度相关,利用纬度与残差的相关函数可提高NWP反演ZTD的精度,但效果并不明显.针对以上问题,比较ECMWF和NCEP再分析资料反演ZTD的精度,然后分析精度较高的ECMWF资料反演的ZTD的残差随温度、湿度、纬度、季节等因子变化的规律,并结合基于最小绝对残差法的多项式拟合方法拟合残差,提出一种新的多因子约束下的NWP反演ZTD的残差改正模型,从而提高NWP反演ZTD的精度.为验证模型的性能,以133个IGS站高精度ZTD为参考,拟合2015年ECMWF反演ZTD的残差,构建残差改正模型,并利用此模型改正2016年ECMWF反演的ZTD.实验结果表明：在纬度高于15°的地区,NWP反演的ZTD的平均残差和均方根误差比使用模型前分别减小了86.9%和36.3%.另外,对于较低纬度地区,此残差改正模型的效果不明显.     

A spectral model based on atmospheric self-memorization principle

Based on the atmospheric self-memorization principle, a complex memory function was introduced and the spectral form of atmospheric self-memorial equation was derived. Setting up and solving the equation constitute a new approach of the numerical weather prediction. Using the spectral model T42L9 as a dynamic kernel, a global self-memorial T42 model (SMT42) was established, with which twelve cases of 30-d integration experiments were carried out. Compared with the T42L9, the SMT42 is much better in 500 hPa forecast not only for daily circulation but also for monthly mean circulation. The anomaly correlation coefficient (ACC) of forecast for monthly mean circulation has been improved to 0.42, increased by 0.05, and the root-mean-square error (RMSE) has been reduced from 6.09 to 4.03 dagpm.     

驻马店2012年盛夏期间一次区域暴雨的成因分析

2012年8月20—21日驻马店市出现了一次区域暴雨,局部大暴雨天气过程.这次降水过程的特点是降水范围广、短时间强度大.从天气图、数值预报产品、稳定度、雷达产品等方面对这次降水过程进行成因分析,从而得出了对大暴雨预报的一些有意义的结论:暴雨的产生前要有强烈的垂直上升运动;深厚的湿云层为这次暴雨过程提供了充足的水汽条件;地面弱冷空气所致低层的偏东到东北急流为这次降水的持续提供了有利的条件.低层形成了较强的垂直切变,增强了辐合上升运动,为这次强降水提供了触发机制.新一代天气雷达监测资料分析表明,强降水天气的基本反射率强度≥45 d Bz的高度一般集中在较低的层次;暴雨要维持较长的降水时间需要一系列降水回波或多单体风暴中的不同单体连续不断经过同一个地方,或者不同移向的降水回波交叉经过同一地方,形成降水的汇集地.     

Resolving unsteady micro-scale atmospheric flows by nesting a CFD simulation into wide range numerical weather prediction models

The open boundary conditions for the CFD simulation of the micro- and meso-scale flow and temperature distribution around the Grimming mountain, Austria, are determined by an optimisation approach from interior observations. The numerical weather prediction model ALADIN–Austria provides wind speed and wind direction at those spatially arbitrarily defined observations. Furthermore, the plausibility of the resulting flow over the Grimming mountain is checked (a) by data of a ground station at the top of the Grimming mountain showing suitable correlation with the measurements. Besides, (b) the vertical turbulence profiles at the ground station are qualitatively compared to extensive studies covering the Askervein hill. In addition, (c) the wavelength of internal gravity waves obtained from the numerical CFD model is examined by analytic approximations at the Grimming mountain and by linear mountain wave theory at a mathematically idealised hill. Finally, the grid independence of the presented CFD model is shown.     

模糊神经网络方法在定点定量降水预报中的应用研究

以单站24小时降水量作为预报对象,采用模糊神经网络方法进行了新的数值预报产品释用预报方法研究.首先通过对T 213、ECMW F预报因子场以及高空气象探测资料进行处理,有效浓缩多种物理量因子场的实况及预报信息,并进一步建立了南宁、桂林、河池、百色4站的降水模糊神经网络释用预报模型.运用与实际业务相同的预报方法对2006年6—8月进行逐日的降水量预报试验,并与相同时次的T 213降水预报产品进行对比分析.结果表明,4个单站的定点、定量模糊神经网络降水预报模型,在预报性能上明显优于同期T 213数值预报模式的降水预报结果.     

河南输电线路舞动气象风险的可预报性分析

为了研究基于数值模式的河南输电线路舞动预测的可预报性,以数值预报(numerical weather prediction, NWP)数据和常规舞动气象风险预测模型为基础,通过对河南121个国家气象站的舞动高影响气象要素预报能力的评估,揭示了借助数值预报开展舞动预测的可能性,同时针对河南容易发生输电线路舞动区域进行检验评估。结果表明：河南东部平原地区输电线路舞动具有较好的可预报性,而西部山地丘陵地区舞动可预报性相对较低,4个舞动高发区可预报由高到低分别是：东部平原地区、南部山区、西北部山区、西南部盆地。河南地区温度、风速和湿度预报均表现为东部平原地区偏差小、西部山区偏差大的特点。输电线舞动的气象高影响区间的可预报性从大到小依次是风速、温度、湿度,其命中率分别为73.4%、78.4%和67.1%,温度和风速在河南东部的可预报性明显高于河南西部,而湿度在河南南部可预报性高而北部可预报性低。温度、风速和湿度的可预报性区域分布有差异,要提高输电线路舞动预测水平,需要在不同区域针对不同要素进行预报订正和调整。     

Multi-Layer Forecast Project of Rain-Induced Debris Flow

Based on four kinds of methods--numerical weather prediction model, cloud image of stationary meteorological satellite, echo image of meteorological radar and telemetric rain gauge, multi space-time scale precipitation prediction products have been achieved, and muhidayer project of debris flow forecast is established with different space-time scale to get different forecast precision. The forecast system has the advantages in combination of regions and ravines, rational compounding of time and space scale. The project, which has debris flow forecast models of Sichuan province, Liangshan district and single ravine, can forecast debris flow in 3 layers and meets the demand of hazard mitigation in corresponding layer.     

基于WRF-Chem的AOD预报在一次沙尘天气中的研究

气溶胶光学厚度(AOD)是表征大气气溶胶光学特征的最基本量;它可以用来推算大气气溶胶含量,是确定大气气溶胶辐射气候效应及大气污染程度的关键因子。利用WRF-Chem数值模式对我国北方2010年3月19~23日的一次沙尘天气过程进行了模拟分析,主要分析了模式对于AOD的预报能力。结果表明:模式对于气溶胶光学特性具有较好的模拟能力,模拟结果中AOD、PM2.5、PM10的时空分布具有很好的一致性。通过与MODIS AOD卫星资料和地基AERONET观测网站点实测数据进行对比分析,发现AOD模拟结果与卫星产品和站点实测数据较吻合,模式24 h预报能够较好地体现AOD随时间的变化特征。