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1.
为了发展云雷达与微波辐射计联合反演液态水含量的方法, 利用2019年4—9月中国气象科学研究院在广东龙门开展的综合观测试验中的双波段云雷达和微波辐射计数据, 首先检验了在降水条件下微波辐射计天顶观测和斜路径观测两种探测模式反演温度(T)、相对湿度(RH)、液态水含量(LWC)和液态水路径(LWP)的合理性, 然后分析了两种探测设备反演LWC和LWP的差别。得到以下结论: (1)微波辐射计在斜路径观测模式下反演的产品受降水影响较小, 其反演结果明显优于天顶观测模式; (2)两种探测设备反演的LWP相关性较好且随时间变化较为一致, 但云雷达反演LWP与平均回波强度有明显相关, 随着雷达回波强度的增大, 云雷达与微波辐射计反演的LWP之比越大; (3)两种探测设备反演的LWC相关性较差且存在明显偏差, 在不考虑融化层的情况下单波段云雷达反演LWC与微波辐射计随高度变化趋势相近, 双波段云雷达反演LWC与微波辐射计反演结果在1 km及其以上区间存在明显差异。   相似文献   

2.
By using the cloud echoes first successfully observed by China's indigenous 94-GHz SKY cloud radar, the macrostructure and microphysical properties of drizzling stratocumulus clouds in Anhui Province on 8 June2013 are analyzed, and the detection capability of this cloud radar is discussed. The results are as follows.(1) The cloud radar is able to observe the time-varying macroscopic and microphysical parameters of clouds,and it can reveal the microscopic structure and small-scale changes of clouds.(2) The velocity spectral width of cloud droplets is small, but the spectral width of the cloud containing both cloud droplets and drizzle is large. When the spectral width is more than 0.4 m s-1, the radar reflectivity factor is larger(over –10 dBZ).(3) The radar's sensitivity is comparatively higher because the minimum radar reflectivity factor is about–35 dBZ in this experiment, which exceeds the threshold for detecting the linear depolarized ratio(LDR) of stratocumulus(commonly –11 to –14 dBZ; decreases with increasing turbulence).(4) After distinguishing of cloud droplets from drizzle, cloud liquid water content and particle effective radius are retrieved. The liquid water content of drizzle is lower than that of cloud droplets at the same radar reflectivity factor.  相似文献   

3.
Cloud microphysical properties including liquid and ice particle number concentration (NC), liquid water content (LWC), ice water content (IWC) and effective radius (RE) were retrieved from CloudSat data for a weakly convective and a widespread stratus cloud. Within the mixed-phase cloud layers, liquid-phase fractions needed to be assumed in the data retrieval process, and one existing linear (p1) and two exponential (p2 and p3) functions, which estimate the liquid-phase fraction as a function of subfreezing temperature (from -20°C to 0°C), were tested. The retrieved NC, LWC, IWC and RE using p1 were on average larger than airplane measurements in the same cloud layer. Function p2 performed better than p1 or p3 in retrieving the NCs of cloud droplets in the convective cloud, while function p1 performed better in the stratus cloud. Function p3 performed better in LWC estimation in both convective and stratus clouds. The REs of cloud droplets calculated using the retrieved cloud droplet NC and LWC were closer to the values of in situ observations than those retrieved directly using the p1 function. The retrieved NCs of ice particles in both convective and stratus clouds, on the assumption of liquid-phase fraction during the retrieval of liquid droplet NCs, were closer to those of airplane observations than on the assumption of function p1.  相似文献   

4.
Cloud microphysical property retrievals from the active microwave instrument on a satellite require the cloud droplet size distribution obtained from aircraft observations as a priori data in the iteration procedure.The cloud lognormal size distributions derived from 12 flights over Beijing,China,in 2008-09 were characterized to evaluate and improve regional CloudSat cloud water content retrievals.We present the distribution parameters of stratiform cloud droplet (diameter <500 tm and <1500 μm) and discuss the effect of large particles on distribution parameter fitting.Based on three retrieval schemes with different lognormal size distribution parameters,the vertical distribution of cloud liquid and ice water content were derived and then compared with the aircraft observations.The results showed that the liquid water content (LWC) retrievals from large particle size distributions were more consistent with the vertical distribution of cloud water content profiles derived from in situ data on 25 September 2006.We then applied two schemes with different a priori data derived from flight data to CloudSat overpasses in northern China during April-October in 2008 and 2009.The CloudSat cloud water path (CWP) retrievals were compared with Moderate Resolution Imaging Spectroradiometer (MODIS) liquid water path (LWP) data.The results indicated that considering a priori data including large particle size information can significantly improve the consistency between the CloudSat CWP and MODIS CWP.These results strongly suggest that it is necessary to consider particles with diameters greater than 50 tm in CloudSat LWC retrievals.  相似文献   

5.
对基于雷达反射率因子观测数据的层状云降水粒子谱参数反演算法进行研究。(1)给出层状云降水粒子谱参数的反演理论和反演算法流程;(2)选取吉林省伊通县的一次降水层状云过程进行反演试验和验证分析,利用雷达反射率因子观测数据反演得到雨滴平均直径和数浓度参数,并用放置在伊通县气象局观测场中的Parsivel激光雨滴谱仪的实测数据与近地层反演结果进行对比。结果发现,通过反演算法计算得到的滴谱与实测滴谱的变化趋势基本相同,而且反演的雨滴平均直径和数浓度在量级和数值上的大小与实测数据具有良好的一致性,说明该反演方法用于从现有天气雷达回波强度数据中挖掘出降水性层状云的微物理参数是可行的。   相似文献   

6.
本文利用风廓线雷达数据反演了降水云体的大气垂直速度、雨滴下落末速度等云动力特征和云水混合比、雨水混合比等云微物理参数,并结合天气雷达、探空、自动站、雨滴谱仪和微波辐射计等数据对2020年5月7~8日发生在北京市海淀区的一次夏季降水过程进行垂直综合观测.结果表明:垂直探测仪器观测及其反演的数据可以获得降水云体的详细动力参...  相似文献   

7.
在假设冰云粒子呈球形以及粒子谱服从对数正态分布的条件下,利用离散偶极子近似法(DDA),计算出太赫兹频段(220 GHz)冰云粒子的雷达反射率因子,及其与瑞利假设下雷达反射率因子的比值。忽略衰减和多次散射的影响,根据太赫兹波段冰云的雷达反射率因子,基于最优估计理论反演冰云的微物理参数,并验证该算法的可靠性。反演结果表明,当冰云粒子大小在设定的尺度范围内时,有效粒子半径(re)的反演误差小于4%,粒子谱宽(σ)的误差小于2.5%、粒子数密度(NT)的误差小于1%,冰水含量(IWC)的误差小于5%。还分析了当NT和σ为定值时,反演结果随粒子尺寸的变化情况,当冰云粒子尺寸在模拟计算设定的范围内时,re的反演误差小于0.04%,σ的反演误差小于0.02%,NT的反演误差小于0.50%,IWC的反演误差小于0.08%,如果冰云粒子大小超出模拟计算设置的范围,反演误差随着re增加而增大。该结果证明了基于最优估计理论反演得到的冰云微物理参数与模拟设定值有良好的一致性,说明该方法可应用于太赫兹频段云雷达的冰云观测及云微物理参数的反演和研究。   相似文献   

8.
刘黎平  张扬  丁晗 《大气科学》2021,45(5):1099-1113
在Ka波段云雷达上升级改造建成的Ka/Ku(Ka和Ku波段波长分别为8.9 mm和2.2 cm)双波段云雷达2019年用于华南云降水垂直结构观测,以改进云内动力和微物理参数探测能力。为了利用该双波段云雷达研究华南降水微物理和动力结构,本文提出了基于双波段云雷达回波强度谱密度(SZ)数据和最优估计技术的云内空气垂直运动速度(Vair)、雨滴谱(DSD)、含水量(LWC)、雨强(R)的反演方法(DWSZ),雨区衰减的订正方法。利用2019年在广东龙门观测的一次降水过程数据,对比分析了云雷达反演的微物理参数与雨滴谱直接观测量,并检验了云雷达反演的低层空气垂直运动速度,利用反演结果分析了一次混合云过程的Vair与这些微物理参数的垂直结构和相互关系。结果表明:Ka/Ku双波段云雷达合理反演了微降水微物理和动力参数及其垂直分布,经过衰减订正的Ka和Ku波段回波强度偏差明显减小。该双波段云雷达数据可以用于分析0~30 dBZ回波强度的云降水垂直结构。本次过程为混合云降水,对流单体前部存在明显的上升气流,后部存在下沉气流;从平均垂直结构来看:Vair和粒子平均直径(Dm)在2 km高度层到达最大,粒子数密度(Nw)、LWC和R在2 km以下明显增强,粒子直径却减小,水汽凝结过程、雨滴碰并云滴是本次过程的主要机制。这一工作验证了Ka和Ku波段组合的双波段云雷达的可行性,为Ka/Ku波段云雷达技术的推广,单波段云雷达反演算法进一步改进,云降水精细结构分析等提供了基础。  相似文献   

9.
利用2017—2019年中国气象局大气探测试验基地Ka波段云雷达资料,结合地面自动气象站、激光云高仪资料,从强度、速度、线性退极化比以及晴空回波高度等方面,分析晴空回波垂直结构和变化特征。基于激光和微波对粒子半径和数密度散射的差异,区分云和晴空回波。结果表明:Ka波段云雷达探测到的晴空回波在边界层主要包含层状湍流回波和点状昆虫回波,且回波顶高在3000 m以内。晴空回波强度和高度具有明显的季节和日变化特征,冬季回波顶高较低,夏季回波顶高较高,与地面气温具有很好的相关性,每年的1,2,11,12月几乎没有晴空回波,而7月和8月回波顶平均高度最高。晴空回波反射率因子为-40~-15 dBZ,其中层状湍流回波反射率因子概率密度峰值处反射率因子为-35 dBZ,点状昆虫回波反射率因子概率密度峰值处反射率因子为-30 dBZ。晴空回波垂直移动速度为-1.5~+0.5 m·s-1,整体呈下沉运动。层状湍流回波线性退极化比较点状昆虫回波稍大,一般为-10~-5 dB,点状昆虫回波线性退极化比一般为-15~-8 dB。  相似文献   

10.
刘黎平  谢蕾  崔哲虎 《大气科学》2014,38(2):223-236
本文首先利用数值模拟的方法,分析了利用毫米波云雷达功率谱密度反演雨滴谱时,降水粒子米散射效应、空气湍流、空气上升速度等对雨滴谱和液态水含量等参数反演的影响;建立了功率谱密度处理及其直接反演雨滴谱、液态水含量、降水强度和空气上升速度的方法;并利用2012年7月在云南腾冲观测的二次弱降水数据,采用毫米波雷达和Ku波段微降水雷达观测的回波强度、径向速度垂直廓线以及780 m高度上的功率谱密度对比的方法,以及毫米波云雷达观测的780 m高度上功率谱密度、回波强度与地面雨滴谱计算得到的这些量的对比方法,分析了毫米波雷达数据的可靠性;并将780 m高度上毫米波雷达反演的雨滴谱与地面雨滴谱数据进行了对比,分析了毫米波雷达反演的雨滴谱的准确性;分析了毫米波雷达回波强度偏弱的原因,讨论了该高度以下降水对毫米波雷达衰减的影响。结果表明:空气湍流对弱降水微物理参数反演影响不大,而空气上升速度和米散射效应均对反演结果有一定影响;毫米波雷达观测到的径向速度和功率谱密度与微降水雷达比较一致,回波强度的垂直廓线的形状与微降水雷达也比较一致,但毫米波雷达观测的回波强度偏弱;与雨滴谱计算值相比,毫米波雷达观测的低层的回波强度也偏弱,天线上的积水是造成毫米波雷达回波强度变弱的主要原因。毫米波雷达观测的低层的功率谱密度与地面雨滴谱观测的数据形状比较一致,但有一定的位移。毫米波雷达反演的雨滴谱与地面观测的谱型和粒子大小也比较一致。这些结果初步验证了毫米波雷达观测的功率谱密度及其反演方法的可靠性。  相似文献   

11.
层析法微波辐射计遥感反演云液水含量的二维垂直分布   总被引:1,自引:1,他引:0  
周珺  雷恒池  陈洪滨 《大气科学》2010,34(5):1011-1025
通过机载双天线微波辐射计的观测数据层析反演出云液水的空间分布是一个有限角度的图像重建问题。为提高这一反问题的适定性, 本文对已有的正则化方法进行了改进: 根据云液水的分布特征选择W1,2空间范数的离散形式作为正则项; 通过数值模拟试验确定双天线仰角的最优设置方案为 (30°, 90°) 等。为避免已有方法中对目标函数进行线性化处理而产生的模型误差, 采用L-BFGS-B算法对非线性目标函数直接求解。按照侧边界内云液水分布是否已知将反演模型分为已界模型和未界模型。已界模型的反演结果表明, 反演误差在8.6%~12.3%之间, 反演图像可以反映出不同云型的结构特征。敏感性试验表明, 影响反演精度的主要因素为投影数据的角度分辨率、 辐射计观测噪声以及侧边界云液水分布的不确定性; 受云液水含量、 正则算子特性及边界因素的综合影响, 不同云型的反演精度存在差异。为使微波辐射计探测云液水分布能够独立于其它探测手段, 本文针对未界模型提出嵌套反演方法。数值模拟试验表明, 嵌套反演方法可以为目标区域的反演提供足够的侧边界信息。  相似文献   

12.
宗蓉  刘黎平  银燕 《大气科学进展》2013,30(5):1275-1286
Cloud properties were investigated based on aircraft and cloud radar co-observation conducted at Yitong, Jilin, Northeast China. The aircraft provided in situ measurements of cloud droplet size distribution, while the millimeter-wavelength cloud radar vertically scanned the same cloud that the aircraft penetrated. The reflectivity factor calculated from aircraft measurements was compared in detail with simultaneous radar observations. The results showed that the two reflectivities were comparable in warm clouds, but in ice cloud there were more differences, which were probably associated with the occurrence of liquid water. The acceptable agreement between reflectivities obtained in water cloud confirmed that it is feasible to derive cloud properties by using aircraft data, and hence for cloud radar to remotely sense cloud properties. Based on the dataset collected in warm clouds, the threshold of reflectivity to diagnose drizzle and cloud particles was studied by analyses of the probability distribution function of reflectivity from cloud particles and drizzle drops. The relationship between reflectivity factor (Z) and cloud liquid water content (LWC) was also derived from data on both cloud particles and drizzle. In comparison with cloud droplets, the relationship for drizzle was blurred by many scatter points and thus was less evident. However, these scatters could be partly removed by filtering out the drop size distribution with a large ratio of reflectivity and large extinction coefficient but small effective radius. Empirical relationships of Z-LWC for both cloud particles and drizzle could then be derived.  相似文献   

13.
毫米波测云雷达在降雪观测中的应用初步分析   总被引:2,自引:0,他引:2  
本文利用毫米波云雷达联合称重式雨量计、气球探空和S波段天气雷达在北京对2015年11月三次降雪进行了观测,以2015年11月22~23日降雪过程为例,主要从降雪系统的宏观结构特征、微物理变化以及毫米波雷达在降雪探测中电磁波衰减情况、雪粒子含水量和地面降雪量估测几方面进行初步分析。结果表明:(1)毫米波云雷达具有高时空分辨率,能对降雪系统进行精细化探测,在降雪系统发展最旺盛的阶段能够通过反射率(Z)、退极化比(LDR)和径向速度(V)初步判断出云中是否含有过冷液滴;(2)降雪回波强度最大值能反映整层云系中含水量最大的区域,当最大值Z大于20 dBZ时,最大值的大小、最大值持续时间、最大值出现的高度与地面降水量成正相关,速度最大值表示云中粒子上升最大速度(速度为正时)或者粒子下落的最小速度(速度为负时),主要分布在-0.5~2 m s?1,速度最小值表示粒子下落的最大速度,主要在-3~-1 m s?1;(3)随着高度增加反射率的垂直廓线会出现多个峰值,这是由于不同高度层风速分布不均造成的,降雪回波这种特点比降雨回波更明显;(4)对比Ka与S波段雷达反射率可知,两雷达反射率平均差值小于2.5 dBZ,Ka波段反射率略大S波段雷达反射率;(5)降雪量反演与地面降雪量仪数据对比,逐小时降雪量反演精度为20.38%,累计降雪量反演误差为6.58%,24小时累计降雪量绝对误差为1.9 mm,说明云雷达估算累计降雪量具有较高的可行性,能够很准确的反映地面实际降雪情况,当降雪系统发展旺盛时,雪粒子含水量分布在0.05~0.15 g m?3,在降雪初期或者降雪系统消散期,雪粒子含水量一般小于0.04 g m?3,能够很好地反映出整层降雪回波的雪粒子含水量。这些云雷达在降雪观测中的应用和初步分析结果可以更好的地了解降雪系统宏微观结构,为云模式的发展和人工影响天气中增雪潜力评估提供一些参考。  相似文献   

14.
任意基线雷达反射率因子垂直剖面生成算法   总被引:2,自引:1,他引:1       下载免费PDF全文
该文提出了一种基于雷达体扫资料的任意基线雷达反射率因子垂直剖面的生成算法。在计算雷达反射率因子垂直剖面上的格点在雷达极坐标中的仰角、方位和斜距位置后, 采用径向、方位上的最近邻居和垂直方向的线性内插相结合的客观分析方法得到格点上的反射率因子分析值。在垂直线性内插时分别用dBZ值和Z值 (单位: mm6/m3) 进行插值。结果表明:用该方法得到的雷达反射率因子垂直剖面从回波强度和空间位置来看都是合理的; 当采用垂直线性内插时, 用dBZ值插值比用Z值插值得到的雷达反射率因子垂直剖面在空间分布上更连续, 反射率因子分析值总体上更接近观测值; 低仰角的插值效果比高仰角的好。  相似文献   

15.
关皓  周林  王汉杰  宋帅 《气象学报》2008,66(3):342-350
利用中尺度大气模式MM5(V3)和第3代海浪模式WWATCH建立考虑大气-海浪相互作用的风浪耦合模式.在耦合模式中引入考虑波浪影响的海表粗糙度参数化方案,大气模式分量提供海面10 m风场驱动海浪模式分量运行,并利用海浪模式分量反馈的波龄参数计算海表粗糙度.利用耦合模式模拟南海的一次台风过程,通过3组对比试验,检验耦合模式对台风过程的模拟效果并研究大气-海浪相互作用对台风过程的影响.结果表明:耦合模式能够较好地模拟南海的台风过程,与非耦合大气模式相比,其模拟的台风强度略有增强,路径变化不大;耦合模式对台风过程中海表热通量及降水影响显著,在台风充分发展过程中,耦合模式模拟的海表热通量增强,台风螺旋雨带上尤其是台风路径的右侧,耦合模式模拟的降水强于非耦合模式;耦合模式较好地模拟了台风过程海浪场的分布和演变,与非耦合模式相比,其模拟的海浪场增强,与实际更为接近;考虑了海表粗糙度对波浪的依赖关系后,海浪场同时影响海表的动力过程和热力过程,从本次个例看,在台风发展初期,海浪对海表动力作用影响显著,其反馈作用使台风系统减弱,但在台风充分发展后,耦合系统中海表热通量增加,热力作用显著增强,海浪的反馈作用有利于台风系统的发展和维持.  相似文献   

16.
An X-band phased-array meteorological radar (XPAR) was developed in China and will be installed in an airplane to observe precipitation systems for research purposes.In order to examine the observational capability of the XPAR and to test the operating mode and calibration before installation in the airplane,a mobile X-band Doppler radar (XDR) and XPAR were installed at the same site to observe convective precipitation events.Nearby S-band operational radar (SA) data were also collected to examine the reflectivity bias of XPAR.An algorithm for quantitative analysis of reflectivity and velocity differences and radar sensitivity of XPAR is presented.The reflectivity and velocity biases of XPAR are examined with SA and XDR.Reflectivity sensitivities,the horizontal and vertical structures of reflectivity by the three radars are compared and analyzed.The results indicated that while the XPRA with different operating modes can capture the main characteristic of 3D structures of precipitation,and the averaged reflectivity differences between XPAR and XDR,and XDR and SA,were 0.4 dB and 6.6 dB on 13 July and-4.5 dB and 5.1 dB on 2 August 2012,respectively.The minimum observed reflectivities at a range of 50 km for XPAR,XDR and SA were about 15.4 dBZ,13.5 dBZ and-3.5 dBZ,respectively.The bias of velocity between XPAR and XDR was negligible.This study provides a possible method for the quantitative comparison of the XPAR data,as well as the sensitivity of reflectivity,calibration,gain and bias introduced by pulse compression.  相似文献   

17.
Quantitative estimates of liquid water path (LWP) in clouds using satellite measurements are critical to understanding of cloud properties and the assessment of global climate change. In this paper, the relationship between microwave brightness temperature (TB) and LWP in the nonprecipitating clouds is studied by using satellite microwave measurements from the TRMM Microwave Imager (TMI) onboard the Tropical Rainfall Measuring Mission (TRMM), together with a radiative transfer model for microwave radiance calculations. Radiative transfer modeling shows that the sensitivity is higher at both 37.0- and 85.5-GHz horizontal polarization channels for the LWP retrievals. Also, the differences between the retrieved values responding to TBs of various channels and the theoretical values are displayed by the model. Based upon above simulations, with taking into account the factor of resolution and retrieval bias for a single,channel, a nonprecipitating cloud LWP in the summer subtropical marine environment retrieval algorithm is formulated by the combination of the two TMI horizontal polarization channels, 37.0 and 85.5 GHz. Moreover,by using TMI measurements (1Bll), this algorithm is applied to retrieving respectively LWPs for clear sky, nonprecipitating clouds, and typhoon precipitating clouds. In the clear sky case, the LWP cl~anges from -1 to 1 g m-2, and its mean value is about 10^-5 g m^-2. It indicates that, using this combination retrieval algorithm, there are no obvious systemic deviations when the LWP is low enough. The LWP values varying from 0 to 1000 g m^-2 in nonprecipitating clouds are reasonable, and its distribution pattern is very similar to the detected results in the visible channel of Visible and Infrared Scanner (VIRS) on the TRMM. In typhoon precipitating clouds, there is much more proportion of high LWP in the mature phase than the early stage. When surface rainfall rate is lower than 5 mm h^-1, the LWP increases with increasing rainfall rate.  相似文献   

18.
This paper describes the retrieval procedure of liquid water content (LWC) in cloud or rainfall distri-bution by a combination of microwave radiometry and radar and its numerical simulation. The per-formance of a combined dual-wavelength (35.0& 9.375 GHz) radar-radiometer system for the remote sensing of cloud LWC and rainfall is given. During the two summers of 1980 and 1981, the preliminary obser-vations of different clouds and storms by the combined system and combined radar-radiometric cloud and rain parameter retrievals are carried out. Research results show that by the use of the combined radar-radiometric method, improvement are obtained in accuracy of rms LWC and rainfall over the pure radio-metric technique or the radar alone.  相似文献   

19.
使用中国气象局大气探测综合试验基地35 GHz毫米波云雷达和L波段风廓线雷达2016年5月1日-7月31日在降水条件下的观测数据,根据不同观测模式下两部雷达得到的数据,计算在一定高度区间内不同下落速度的降水粒子反射率因子变化量,初步分析不同下落速度的降水粒子对毫米波衰减的影响。结果表明:在持续时间较长的层状云降水且降水粒子在雷达观测范围内均匀分布条件下,毫米波衰减与降水粒子下落速度呈近似线性关系,且毫米波经过的路径长度越长,衰减越大;毫米波在经过1110~2430 m,1110~3510 m的高度区间时,下落速度处于3.5~7.5 m·s-1之间的降水粒子对毫米波的衰减作用导致毫米波云雷达所测的等效反射率因子分别减小约1~7 dB和2~11 dB。  相似文献   

20.
2015年10月29日弱降雨前后的层状云微物理参数反演和分析   总被引:4,自引:4,他引:0  
利用Ka波段毫米波云雷达和微波辐射计资料对2015年10月29日安徽寿县的一次弱降雨过程的云参数进行了反演,所采用的反演方案是单参数法和双参数法。论文先介绍了单参数和双参数反演方法,然后反演了降雨前后的云微物理参数,对比分析表明:(1)降水发生前云滴数浓度较大,典型值1 000个·cm-3左右,有效半径小于4.5 μm;(2)降雨后,云滴数浓度显著减小,典型值在500个·cm-3左右,但有效半径略增大了1~1.5 μm;(3)云中含水量的变化不明显,降雨后略增大,增加量在0.1 g·m-3以内; (4)降水发生前,云微物理参数随高度的起伏较大,降水后的廓线比较平缓,显示出降雨后的云层动力特性更稳定。  相似文献   

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