GRAPES地面风场同化方案研究

随着预报准确度要求以及同化分析循环周期的缩短,具有高时空分辨率的地面观测资料在同化系统中也越来越受到重视,而且一个好的资料同化系统应该能够给出模式近地面动力、热力和湿度状况的合理分析。利用GRAPES区域同化预报系统(GRAPES——Global and Regional Assimilation and Prediction Enhanced System),在近地层Monin_Obukhov相似理论的基础上,考虑了边界层的动力和湿热力约束,建立新的地面风场观测算子。将此新方案与目前GRAPES系统使用的三次样条插值的地面同化方案进行高度场预报试验、统计试验以及降水预报的TS评分比较,结果表明,加入新方案地面风场资料同化后,预报效果和对降水的预报能力都比旧方案有所提高。     

A New Global Four-Dimensional Variational Ocean Data Assimilation System and Its Application

A four-dimensional variational data assimilation （4DVar） system of the LASG/IAP Climate Ocean Model, version 1.0 （LICOM1.0）, named LICOM-3DVM, has been developed using the three-dimensional variational data assimilation of mapped observation （3DVM）, a 4DVar method newly proposed in the past two years. Two experiments with 12-year model integrations were designed to validate it. One is the assimilation run, called ASSM, which incorporated the analyzed weekly sea surface temperature （SST） fields from Reynolds and Smith （OISST） between 1990 and 2001 once a week by the LICOM-3DVM. The other is the control run without any assimilation, named CTL. ASSM shows that the simulated temperatures of the upper ocean （above 50 meters）, especially the SST of equatorial Pacific, coincide with the Tropic Atmosphere Ocean （TAO） mooring data, the World Ocean Atlas 2001 （WOA01） data and the Met Office Hadley Centre＇s sea ice and sea surface temperature （HadISST） data. It decreased the cold bias existing in CTL in the eastern Pacific and produced a Nifio index that agrees with observation well. The validation results suggest that the LICOM-3DVM is able to effectively adjust the model results of the ocean temperature, although it＇s hard to correct the subsurface results and it even makes them worse in some areas due to the incorporation of only surface data. Future development of the LICOM-3DVM is to include subsurface in situ observations and satellite observations to further improve model simulations.     

宽甸环斑花岗岩的同化混染成因

环斑花岗岩是发育于前寒武纪的一种特殊岩石。本文从环斑花岗岩的地质学、岩石学及矿物学等方面讨论了宽甸元古宙环斑花岗岩的成因,认为环斑花岗岩是由分异出石英二长岩的富钾质残余岩浆在深部同化围岩(类似盖县组的矽线石榴黑云斜长片麻岩及黑云母变粒岩等岩石)形成的含大量围岩捕虏晶的晶粥状岩浆,经侵位结晶而成。环斑长石的斜长石外壳是来自围岩的捕虏晶,它通过流动、吸附作用附着于钾长石巨晶的周围,构成环斑结构。     

基于GRACE卫星和GLDAS系统的地下水水位估算模型——以和田地区克里雅河流域为例

地球重力场的变化是导致陆地水储量变化的重要因素之一,利用GRACE(Gravity Recovery and Climate Experiment)重力场恢复与气候实验重力卫星数据,结合GLDAS(Global Land Data Assimilation Systems)全球陆面数据同化系统和实测地下水位数据,反演和田地区克里雅河流域11年间四季和田地区的陆地水储量动态变化,模拟计算地下水等效水高变化趋势,构建了地下水水位估算模型。研究结果表明：和田地区春、夏两季的陆地水储量呈现出增加趋势,而秋、冬两季出现亏损状态;GRACE地球重力卫星所反演的陆地水储量比GLDAS同化系统所模拟的水资源变化更为剧烈,但2类数据的动态变化拟合度很高;GLDAS水资源等效水高二阶微分、GLDAS水资源变化倒数一阶微分、GRACE陆地水储量变化倒数变化、地下水储量变化一阶微分的敏感程度最高,构建的多元逐步回归模型明显优于线性函数,且水位深度越浅,该估算模型的适用性越高。     

Insights into the Microwave Instruments Onboard the Fengyun 3DSatellite: Data Quality and Assimilation in theMet Office NWP System

正1Met Office, Exeter EX1 3PB, UK2National Satellite Meteorological Center, China Meteorological Administration, Beijing 100081, China     

面向同化应用的红外高光谱探测资料局地综合通道选择方案及在FY-3D/HIRAS中的初步应用

通道选择是红外高光谱探测资料同化的关键技术。为了最大限度提取红外高光谱探测资料观测信息,减少模式在青藏高原等常规观测稀少地区的初始场的误差,不同区域需要选取不同通道进行同化。基于信号自由度的通道选择方法提出一种面向资料同化的红外高光谱资料的局地综合通道选择方案,该方案综合考虑了局地的大气温度垂直分布特征、背景误差协方差、仪器通道的雅克比函数、权重函数和其他影响红外高光谱模拟和同化的因素。针对CMA＿GFS（原GRAPES＿GFS）全球背景误差协方差,在高原和海洋两个典型区域对FY-3D/HIRAS红外高光谱资料的温度通道进行局地综合通道选择,并通过一维变分同化评估了局地综合通道选择方案对分析场的影响。结果表明,高原和海洋两个典型区域的大气温度垂直分布特征、背景误差协方差、模式垂直分层以及各通道的雅克比函数和权重函数均有明显的差异,选出的敏感通道也明显不同,相比较在其他区域选择出的通道,在对应地区选择的通道能够显著提高红外高光谱资料的同化效果。     

Variational Assimilation of GPS Precipitable Water Vapor and Hourly Rainfall Observations for a Meso-β Scale Heavy Precipitation Event During the 2002 Mei-Yu Season

Recent advances in Global Positioning System (GPS) remote sensing technology allow for a direct estimation of the precipitable water vapor (PWV) from delayed signals transmitted by GPS satellites, which can be assimilated into numerical models with four-dimensional variational (4DVAR) data assimilation. A mesoscale model and its 4DVAR system are used to access the impacts of assimilating GPS-PWV and hourly rainfall observations on the short-range prediction of a heavy rainfall event on 20 June 2002. The heavy precipitation was induced by a sequence of meso-β-scale convective systems (MCS) along the mei-yu front in China.The experiments with GPS-PWV assimilation successfully simulated the evolution of the observed MCS cluster and also eliminated the erroneous rainfall systems found in the experiment without 4DVAR assimilation. Experiments with hourly rainfall assimilation performed similarly both on the prediction of MCS initiation and the elimination of erroneous systems, however the MCS dissipated much sooner than it did in observations. It is found that the assimilation-induced moisture perturbation and mesoscale low-level jet are helpful for the MCS generation and development. It is also discovered that spurious gravity waves may post serious limitations for the current 4DVAR algorithm, which would degrade the assimilation efficiency, especially for rainfall data. Sensitivity experiments with different observations, assimilation windows and observation weightings suggest that assimilating GPS-PWV can be quite effective, even with the assimilation window as short as 1 h. On the other hand, assimilating rainfall observations requires extreme cautions on the selection of observation weightings and the control of spurious gravity waves.     

云迹风资料同化对东亚海域风场数值模拟的影响

为了揭示云迹风资料同化对于东亚海域内各层模拟风场的影响,采用由日本GMS卫星红外和水汽通道资料反演得到的1999年6月底至7月初的云迹风资料,首先对这些云迹风资料进行质量评估,评估结果表明云迹风u,v分量的均方根误差和偏差都在所容许的误差范围之内.然后针对10个个例进行5种不同的四维同化模拟试验,多种同化试验和无同化控制试验的检验对比表明:在经过初始12 h常规高空地面资料和云迹风资料同化过程以后,模拟结果质量有了比较明显的提升;各种同化试验与控制试验间的最大差异发生在12h,也即同化结束的时刻,此后随着模拟时间的增长,两者间的差异逐渐变小;但24~36h同化试验对控制试验的改进效果又开始提升,36h后效果再次下降.由于海面上缺少常规测站,因此无法实现海面部分的测站同化,而这必将影响到海面部分的模拟质量,而云迹风资料恰可以祢补这个不足.试验表明云迹风资料对u,v风场的改进则主要集中在对流层高层(300~200hPa),对中低层的影响不很明显,这与云迹风资料主要集中在高层是相一致的.另外,敏感性试验表明经过质量控制的云迹风同化模拟的性能相对不采用质量控制的同化模拟有了一定程度的提高.     

WRF-DA中地面观测资料同化方案的改进与应用

为了改善地面自动气象站观测数据在WRF-DA(the Weather Research and Forecasting Model-Data Assimilation)系统中的同化应用效果,提高数值模式的预报性能,对WRF-DA地面资料同化方案中温度和风速订正方案进行改进,形成地面资料同化更新方案.通过考虑地形高度差异...