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1.
多普勒激光雷达风场反演方法研究 总被引：3，自引：0，他引：3
采用三维变分同化反演(3DVAR)、 四维变分同化反演(4DVAR) 对多普勒激光雷达资料反演风场的方法进行了研究, 利用车载多普勒激光雷达在2008年残奥会测试赛期间外场试验取得的数据, 反演了海面10 m高度处的风场, 并将风场反演结果与浮标资料进行了对比分析, 结果表明: 3DVAR、4DVAR风场反演方法均能实现近海面风的精细化风场反演, 并能反映出风向的变化, 反演风场与浮标数据基本一致, 在风速较大的天气情况, 3DVAR与4DVAR反演风场的一致性要好于风速较小的天气情况; 4DVAR反演方法中以浮标资料作为背景场, 使得其与浮标的符合程度要好于3DVAR方法反演风场; 反演风场的风向与浮标风向具有很好的相关关系, 反演风场的风速与浮标风速具有一定的相关关系, 反演风场的风向、风速与浮标的风向、风速之间平均均方根误差和平均绝对误差表明, 这两序列之间具有一定差别, 在风速较小的天气情况下使用时需要注意。 相似文献
2.
Dynamical and Microphysical Retrieval from Simulated Doppler Radar Observations Using the 4DVAR Assimilation Technique 总被引：3，自引：0，他引：3
Based on a cloud model and the four-dimensional variational (4DVAR) data assimilation method developed by Sun and Crook (1997), simulated experiments of dynamical and microphysical retrieval from Doppler radar data were performed. The 4DVAR data assimilation technique was applied to a cloud scale model with a warm rain parameterization scheme. The 3D wind, thermodynamical, and microphysical fields were determined by minimizing a cost function, defined by the difference between both radar observed radial velocities and reflectivities and their model predictions. The adjoint of the numerical model was used to provide the gradient of the cost function with respect to the control variables. Experiments have demonstrated that the 4DVAR assimilation method is able to retrieve the detailed structure of wind, thermodynamics, and microphysics by using either dual-Doppler or single-Doppler information. The quality of retrieval depends strongly on the magnitude of constraint with respect to the variables. Retrieving the temperature field, cloud water and water vapor is more difficult than the recovery of the wind field and rainwater. Accurate thermodynamic retrieval requires a longer assimilation period. The inclusion of a background term, even mean fields from a single sounding, helped reduce the retrieval errors. Less accurate velocity fields were obtained when single-Doppler data were used. It was found that the retrieved velocity is sensitive to the location of the retrieval domain relative to the radars while the other fields have very little changes. Two radar volumetric scans are generally adequate for providing the evolution, although the use of additional volumes improves the retrieval. As the amount of the observations decreases, the performance of the retrieval is degraded. However, the missing observations can be compensated by adding a background term to the cost function. The technique is robust to random errors in radial velocity and calibration errors in reflectivity. The boundary conditions from the dual-Doppler synthesized winds are sufficient for the retrieval. When the retrieval is mainly controlled by the observations in the regions away from the boundaries, the simple boundary conditions from velocity azimuth display (VAD) analysis are also available. The microphysical retrieval is sensitive to model errors. 相似文献
3.
多普勒雷达资料4DVAR同化反演的模拟研究 总被引：21，自引：5，他引：21
利用Sun等建立的同化模式和四维变分同化方法对多普勒雷达资料反演大气风场、热力场和微物理场进行了模拟试验研究.反演的基本思路是将4DVAR同化方法应用到三维云模式,定义价值函数表征雷达资料与模式预报结果之间的差别,通过极小化价值函数得到反演场,价值函数相对模式控制变量的梯度由伴随模式求取.试验结果表明,4DVAR同化技术能够从单(双)多普勒雷达资料反演大气三维风场、热力场和微物理场.各个变量反演精度高低与同化过程中变量受约束的大小程度呈正相关.速度场和雨水场反演精度较高,温度场、云水和水汽的反演精度次之,温度场的准确反演需要较长的同化时间.价值函数中加入背景场,哪怕是单点探空给出的平均场信息也有利于提高反演精度.在采用单部多普勒雷达资料进行反演时,速度场的反演误差较大.反演区相对雷达站的位置变化对速度场反演结果有一定的影响,而对其他变量的反演影响很小.两个时次的雷达观测资料基本足够提供反演所需的时间演变信息,同化更多时次的雷达资料,反演效果改进很小.雷达观测资料的缺值会显著降低同化效果,甚至可能导致同化失败,引入背景场可以改善这一状况.4DVAR同化技术对于雷达观测资料误差不太敏感.利用双多普勒雷达合成风场提供水平风场边界条件是比较准确可靠的.在反演主体离边界较远时,VAD风场也基本可用作水平风场边界条件.微物理场的反演对模式中的微物理参数化方案较敏感. 相似文献
4.
利用三维变分方法对2014年3月30—31日华南一次强飑线过程进行风场反演,经与风廓线雷达探测结果、双多普勒天气雷达反演结果、原始径向速度数据等对比分析,得到如下结论：三维变分方法反演的中低层水平风场与风廓线雷达探测到的结果较为一致,且能很好地表现飑线过境时的风向切变;通过与双多普勒雷达风场反演结果对比发现,两种方法得到的风场空间分布十分相似,均能很好地表现2 km高度上系统内部强带状回波前缘的辐合线以及5 km高度上较弱的辐散;三维变分方法反演的水平风场与径向速度场有较好的一致性,2 km高度强回波带前缘阵风锋处的辐合线位置以及5 km和8 km高度上辐散区的位置均与径向速度场十分吻合;三维变分方法反演的垂直速度能较好地反映该飑线过程中气流的上升和下沉运动,平行于飑线方向的气流变化较小,而系统气流变化主要沿垂直于飑线的方向。三维变分方法反演的飑线系统的三维风场结构合理,反演结果可靠。 相似文献
5.
边界层流场和地形特征对青岛奥帆赛场午后海风影响的研究 总被引：4，自引：1，他引：3
奥帆赛是奥运会唯一以自然风为动力的竞赛项目,而北京奥运会期间的8月,青岛的风速是一年中最小的,因风速过小致使帆船竞赛地法进行的情况时有发生。鉴于青岛的弱风与海陆风的发展状况关系密切,文中分析8、9月青岛奥帆赛和残奥帆赛期间竞赛海域海陆风的发展条件,并用高分辨率数值模式对相关个例进行了模拟试验研究。结果发现,地面背景气流、边界层中上部径向气流和周围地形、海陆分布等边界层特征,都对竞赛海域海陆风的发展产生影响。其中晴天时,地面西风、弱的北风和东风、均压场环境以及边界层中上部弱的北风条件等,都是竞赛海域海风发展的有利条件;而地面南风(无论大小)、强的北风以及边界层中上部较强的南风和很强的北风等,则是海风发展的不利条件。此外,当地面为东北风时,位于竞赛海域上游的崂山对地面风速有阻挡减弱的作用,从而有利于海风的发展;地面为南风时,崂山和浮山等地形强迫气流在竞赛海域附近向左右分为两支,胶州湾和崂山湾侧向海风(东南风)急流发展又加大了这种分流作用,导致竞赛海域常减小为弱风,使比赛无法进行。以上结论在2008年奥帆赛和残奥帆赛气象保障预报服务中得到运用。 相似文献
6.
The present study designs experiments on the direct assimilation of
radial velocity and reflectivity data collected by an S-band Doppler weather
radar (CINRAD WSR-98D) at the Hefei Station and the reanalysis data produced by
the United States National Centers for Environmental Prediction using the Weather
Research and Forecasting (WRF) model, the WRF model with a three-dimensional
variational (3DVAR) data assimilation system and the WRF model with an ensemble
square root filter (EnSRF) data assimilation system. In addition, the present
study analyzes a Meiyu front heavy rainfall process that occurred in the Yangtze
-Huaihe River Basin from July 4 to July 5, 2003, through numerical simulation.
The results show the following. (1) The assimilation of the radar radial velocity
data can increase the perturbations in the low-altitude atmosphere over the heavy
rainfall region, enhance the convective activities and reduce excessive simulated
precipitation. (2) The 3DVAR assimilation method significantly adjusts the
horizontal wind field. The assimilation of the reflectivity data improves the
microphysical quantities and dynamic fields in the model. In addition, the
assimilation of the radial velocity and reflectivity data can better adjust the
wind fields and improve the intensity and location of the simulated radar echo
bands. (3) The EnSRF assimilation method can assimilate more small-scale wind
field information into the model. The assimilation of the reflectivity data alone
can relatively accurately forecast the rainfall centers. In addition, the
assimilation of the radial velocity and reflectivity data can improve the
location of the simulated radar echo bands. (4) The use of the 3DVAR and EnSRF
assimilation methods to assimilate the radar radial velocity and reflectivity
data can improve the forecast of precipitation, rain-band areal coverage and the
center location and intensity of precipitation. 相似文献
7.
On the cool skin of the ocean 总被引：1，自引：0，他引：1
Jin Wu 《Boundary-Layer Meteorology》1985,31(2):203-207
Previous data relating sea-surface temperature to heat flux across the air-sea interface were reanalyzed with a common formula for the wind-stress coefficient. An expression is proposed for the nondimensional thickness of the thermal sublayer: the expression increases with wind velocity at light winds and has a value of 7 when the wind velocity reaches 7 m s–1. 相似文献
8.
卫星反演海面风场资料能够弥补海上气象测风资料缺乏的不足,对近海风能资源评估具有重要意义。通过ASCAT(Advanced Scatterometer)风速数据与美国及中国近海岸浮标测风资料的对比分析,结果表明,ASCAT风速的均方根误差为1.27 m·s-1。比较利用近海岸浮标逐小时风速及与其相匹配ASCAT瞬时风速计算的各项风能参数,得出ASCAT与浮标的平均风速和风功率密度的残差分别在±0.5 m·s-1和±50 W·m-2以内,该残差占浮标计算结果的比例分别在±8%和±12%以内。使用ASCAT风速资料拟合的Weibull分布函数与浮标的结果较吻合。因此,ASCAT风速资料也能够为海上风能资源评估提供有用的风能参数信息。最后使用ASCAT瞬时风速数据分析了中国近海10 m及70 m高度处的风能资源的空间分布特征,结果表明,台湾海峡平均风速和风功率密度最大。 相似文献
9.
暴雨模拟中多普勒雷达径向速度变分同化的应用 总被引：1，自引：0，他引：1
针对2008年6月广东地区的一次强降雨过程,利用WRF中尺度数值模式及其三维变分同化系统(WRF-3DVAR),进行了多普勒雷达径向速度变分同化对暴雨过程模拟效果影响研究。结果表明:WRF-3DVAR能够有效地同化多普勒雷达径向速度,同化后的主要影响在于改进了初始动力场,使得初始场包含有更详尽的中尺度特征信息,进而显著提高模式对广东局地暴雨过程的模拟效果。在高分辨率中尺度数值模式中有效地利用多普勒天气雷达资料,是提高中尺度降雨预报的关键。 相似文献
10.
In this study, both reflectivity and radial velocity are assimilated into the Weather Research and Forecasting (WRF) model using ARPS 3DVAR technique and cloud analysis procedure for analysis and very short range forecast of cyclone ÁILA. Doppler weather radar (DWR) data from Kolkata radar are assimilated for numerical simulation of landfalling tropical cyclone. Results show that the structure of cyclone AILA has significantly improved when radar data is assimilated. Radar reflectivity data assimilation has strong influence on hydrometeor structures of the initial vortex and precipitation pattern and relatively less influence is observed on the wind fields. Divergence/convergence conditions over cyclone inner-core area in the low-to-middle troposphere (600–900 hPa) are significantly improved when wind data are assimilated. However, less impact is observed on the moisture field. Analysed minimum sea level pressure (SLP) is improved significantly when both reflectivity and wind data assimilated simultaneously (RAD-ZVr experiment), using ARPS 3DVAR technique. In this experiment, the centre of cyclone is relocated very close to the observed position and the system maintains its intensity for longer duration. As compared to other experiments track errors are much reduced and predicted track is very much closer to the best track in RAD-ZVr experiment. Rainfall pattern and amount of rainfall are better captured in this experiment. The study also reveals that cyclone structure, intensification, direction of movement, speed and location of cyclone are significantly improved and different stages of system are best captured when both radar reflectivity and wind data are assimilated using ARPS 3DVAR technique and cloud analysis procedure. Thus optimal impact of radar data is realized in RAD-ZVr experiment. The impact of DWR data reduces after 12 h forecast and it is due to the dominance of the flow from large-scale global forecast system model. Successful coupling of data assimilation package ARPS 3DVAR with WRF model for Indian DWR data is also demonstrated. 相似文献
11.
12.
Study on the Variational Assimilation Technique for the Retrieval of Wind Fields from Doppler Radar Data 总被引：2，自引：0，他引：2 
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下载免费PDF全文 This paper introduces a variational assimilation technique for the retrieval of wind fields from Doppler radar data. The assimilated information included both the radial velocity (RV) and the movement of radar echo. In this assimilation technique, the key is transforming the movement of radar echo to a new radar measuring variable- "apparent velocity" (AV). Thus, the information of wind is added, and the indeterminacy of recovering two-dimensional wind only by AV was overcome effectively by combining RV with AV. By means of CMA GRAPES-3Dvar and CINRAD data, some experiments were performed. The results show that the method of retrieval of wind fields is useful in obtaining the construction of the weather system. 相似文献
13.
从新一代天气雷达径向速度资料中反演出可靠的三维风场对提高新一代天气雷达的应用水平有重要的作用，将雷达直接观测的径向速度转换成台站预报员更为熟悉的风场结构，对识别中小尺度信息有很大帮助。为此该文对4DVAR同化技术在风场业务反演中应用的可能性进行了探讨，利用广州、济南新一代多普勒天气雷达观测资料，从是否加入云模式湿过程以及迭代次数、计算时间、背景场、初始场、分辨率和反演区域等方面对干模式的4DVAR系统进行了讨论，并从风场结构、均方根差别等方面对反演结果进行分析。多种试验表明，干模式的4DVAR系统与湿的云模式反演结果差异不大。模式的初始场和背景场对反演结果具有较高的敏感性，利用前一时次的反演结果作为背景场迭代15～20次的干模式结果可以很好地在业务上试运行，对台站预报员提高中小尺度天气预报的准确率有着很重要的作用。 相似文献
14.
散射计和下投式探空仪资料对台风模拟的影响 总被引：2，自引：1，他引：1
为了评估同化QuikSCAT海平面气压场资料和Dropsonde资料对台风"Bilis"和"Kat-rina"模拟的影响,通过WRF-3DVAR变分同化系统将QuikSCAT海平面气压场资料和Dropsonde资料同化到WRF模式中,并以未同化任何资料和同化了QuikSCAT海平面气压场以及同化了Drop-sonde资料的数据为初始场,应用WRF模式进行模拟预报,并对得到的初始分析场和模拟预报得到的结果与台风实况报文进行了对比,得到的结论是:对台风初始时刻海平面气压场分布、初始台风中心定位、台风初始暖心结构的改善、台风路径、海平面最低气压场、海面最大风速和雷达回波的模拟方面,同化QuikSCAT海平面气压场的效果比同化Dropsonde资料明显,其中二者对海平面最低气压场的改进效果比海面最大风速的要好。但是两种资料的同化对初始相对湿度和台风强度细节变化方面都没有产生明显改善作用。同化QuikSCAT海平面气压场试验虽然仅仅同化了单层海平面气压场,但是在三维变分同化系统的动力约束作用下,也可以影响到中高层的各个要素场。 相似文献
15.
The purpose of this study is to select a suitable sea wind retrieval method for FY-3B(MWRI). Based on the traditional empirical model of retrieving sea surface wind speed, and in the case of small sample size of FY-3B satellite load regression analysis, this paper analyzes the channel differences between the FY-3B satellite microwave radiation imager(MWRI) and TMI onboard the TRMM. The paper also analyzes the influence of these differences on the channel in terms of receiving temperature, including channel frequency, sensitivity and scaling precision. Then, the limited range of new model coefficient regression analysis is determined(in which the channel range settings include the information and features of channel differences), the regression methods of the finite field are proposed, and the empirical model of wind speed retrieval applicable to MWRI is obtained, which achieves robust results. Compared to the TAO buoy data, the mean deviation of the new model is 0.4 m/s, and the standard deviation is 1.2 m/s. In addition,the schematic diagram of the tropical sea surface wind speed retrieval is provided. 相似文献
16.
利用渤海观测站风场对ASCAT风场进行检验,发现其风速、风向均有较大误差,尤其在渤海中部以外的海域可信度相对较低。为提高ASCAT风场在渤海海域的精度,基于变分方法,利用渤海观测站风场对2017年9月—2018年2月的ASCAT风场进行订正,得到空间分辨率为12.5 km×12.5 km的订正风场。并对辽东湾、渤海湾、莱州湾、渤海中部和渤海海峡5个海域风场的订正误差进行检验,结果表明:ASCAT风场订正后精度提高显著,风速平均偏差从4 m·s-1减小为1 m·s-1,风向平均偏差从-30°~30°减小为-7°~4°,可见变分方法对渤海ASCAT风场有很好的订正效果,尤其对误差较大的渤海湾订正效果最为明显。对2017年12月18日的一次大风过程进行订正分析,结果表明:订正风场可以很好地反映沿岸风场信息和大风过程中的风速极值区,并能动态监测大风变化过程。变分方法解决了海面观测数据空间分辨率低、ASCAT数据精度低的问题,能够实时监测海上大风,且对大风预报有很好的指导意义,能够为海洋模式提供更精确的初始场。 相似文献
17.
基于WRF-3DVAR同化多源融合数据对近海风模拟的改进试验 总被引：1，自引：1，他引：0
本文利用WRF模式及其3DVAR同化系统,以2008年4月20日00时—23日00时的江苏近海10 m风场为研究个例,对Quik SCAT、Wind SAT、多源测风融合数据进行同化试验,通过比较WRF-3DVAR同化系统对模拟风场初始场和预报场的改进,检验了同化不同类型资料后WRF模式对研究区域内单点及区域近地层风速的预报效果。结果表明:同化试验对初始场有改进,且对预报场的改进较FNL资料明显;不同资料对风场模拟的影响不同,同化星星、星地多源融合资料效果最佳,Quik SCAT次之,Wind SAT最差。此外,在模式分辨率一定的情况下,提高观测资料的分辨率并不一定能够改善模拟效果,资料的稀疏分辨率存在最佳选择。 相似文献
18.
Abstract Airborne measurements of mean wind velocity and turbulence in the atmospheric boundary layer under wintertime conditions of cold offshore advection suggest that at a height of 50 m the mean wind speed increases with offshore distance by roughly 20% over a horizontal scale of order 10 km. Similarly, the vertical gust velocity and turbulent kinetic energy decay on scales of order 3.5 km by factors of 1.5 and 3.2, respectively. The scale of cross‐shore variations in the vertical fluxes of heat and downwind momentum is also 10 km, and the momentum flux is found to be roughly constant to 300 m, whereas the heat flux decreases with height. The stability parameter, z/L (where z = 50 m and L is the local Monin‐Obukhov length), is generally small over land but may reach order one over the warm ocean. The magnitude and horizontal length scales associated with the offshore variations in wind speed and turbulence are reasonably consistent with model results for a simple roughness change, but a more sophisticated model is required to interpret the combined effects of surface roughness and heat flux contrasts between land and sea. Comparisons between aircraft and profile‐adjusted surface measurements of wind speed indicate that Doppler biases of 1–2 m s?1 in the aircraft data caused by surface motions must be accounted for. In addition, the wind direction measurements of the Minimet anemometer buoy deployed in CASP are found to be in error by 25 ± 5°, possibly due to a misalignment of the anemometer vane. The vertical fluxes of heat and momentum show reasonably good agreement with surface estimates based on the Minimet data. 相似文献
19.
由于单雷达在探测台风临近、登陆时仍具有双部或多部雷达难以具备的优势,目前利用单多普勒雷达反演涡旋风场的方法并不多见,本文对能够反演涡旋风场的3种方法NIVAP(自然坐标系的积分VAP方法)、EVAPTC(反演热带气旋的EVAP方法)、GBVTD(地基速度追踪法)进行了比较,分别从每种方法的假设条件和数学方法以及结果精度来比较3种方法对涡旋风场的适用性。利用中尺度气旋Rankine模式模拟了纯涡旋性气旋、只有环境风场时、环境风场和辐合(辐散)同时存在时的径向速度场及风场,比较了各种情况下的反演风场和模拟风场的相似系数。在对模拟风场比较之后,选取了2014年"威马逊"台风登陆前1h、登陆时及登陆后1h的3个实测雷达资料,对比分析了3种方法反演实测资料的风场特征,3种方法中EVAPTC方法最好,GBVTD方法在应用中有一定的限制,NIVAP方法较差。 相似文献
20.
利用2019年4—9月高时空分辨率的长沙机场阵列天气雷达资料开展三维变分（three-dimensional variational data assimilation,3DVAR）风场反演研究。为验证该算法的反演效果,选取外场试验中10次降水过程,在阵列天气雷达的三维精细探测区内,采用阵列天气雷达合成风场和1部L波段边界层风廓线雷达产品作为参考值对阵列反演风场进行验证评估。结果表明:在稳定性降水条件下,阵列反演风场与阵列合成风场、风廓线雷达产品的结果较为一致;在对流性降水条件下,由于不均匀性会造成风廓线测风精度下降,风廓线雷达产品与阵列反演风场和阵列合成风场差异较大。阵列反演风场与阵列合成风场在稳定性、对流性降水条件下水平风速相对偏差分别低于19%,29%,水平风向差分别低于14.92°,26.35°,稳定性降水条件下阵列反演风场更优,误差在可接受范围内。两种算法得到的风场结构符合各类天气系统的基本特征,水平风场空间分布和风速、风向非常接近。 相似文献