L波段雷达-电子探空仪系统的几点实用技巧

介绍新一代高空探测系统在操作过程中的一些实用技巧.     

基于地基微波辐射计资料对成都双流机场两次雷雨过程的分析

利用地基微波辐射计资料,比较了2017年7月成都双流机场的两次雷雨过程,根据天气形势分为"两高切变"和"东高西低"2类,在此基础上分析微波辐射计要素变化特征,结果表明:在垂直方向0～10 km,以相对湿度达到80%来区分干区和湿区,则两次过程前3 h,相对湿度在垂直方向均呈现"上下干、中间湿"三层结构,并早于近地层前2 h达到饱和状态;过程期间相对湿度呈现"上干、下湿"两层结构;过程结束后湿层抬高,低层变干。两次过程水汽含量充沛,保持在70 kg/m~2以上,峰值超过85 kg/m~2。每一次中阵雨发生后水汽含量都会短暂回落,但仍高于过程前的数值,不足2 h后再次发生中阵雨。由0℃线高度变化可知,降水过程中,暖区(温度≥0℃)内相对湿度≥90%;云中液态水含量主要分布于6 km以下,温度在0℃以上的液态水占比很高,故两次过程以暖云降水为主。雷雨前1 h左右有"低层气温上升,0℃层抬升,K指数、CAPE指数也明显增大"的典型特征。降水发生在相对湿度、水汽总含量、云中液态水含量和稳定度指数快速增长的波峰中。     

探测仪器特性曲线异常分析

探测仪器感应曲线发生变化,造成升速异常、等压面的温度、湿度错误、雷达〖CD*2〗气压高差偏大、时间〖CD*2〗高度线曲变化异常造成的规定高度上的风误差偏大,使部分资料或整份资料失真,影响探测准确性。本文主要从仪器的感应曲线变化后对各气象要素产生的影响进行分析,得出结论：不同的元件变性对气象要素产生的影响不同,气压变化的影响侧重于高差和升速,温度变化则侧重于规定等压面的温度绝对误差和规定等压面高度的偏差。采用绝对误差计算、加密气象要素计算等方法,结合图形、数据对比,可以确定感应曲线变化时间,从而及时、有效的对探测数据做出合适的处理,进一步提高探测数据的精准度。     

Azimuthal resistivity soundings over a steeply dipping anisotropic formation: A case history in central Tunisia

Azimuthal Resistivity Soundings (ARS), using the so-called “Arrow-type array” as proposed by Bolshakov et al. were carried out in Central Tunisia, together with azimuthal resistivity tomography, because of the known anisotropic behaviour of the nearly vertical formations.First, the developments designed by Bolshakov et al. are reviewed: they deal with the separation between the effects of anisotropy and of heterogeneities, the design of the Arrow-type array and the introduction of the azimuthal spectral analysis.Second, the main methodological results obtained near Gouazine Lake are presented: (1) the clear effect of a quasi-vertical contact and (2) the characterisation of the anisotropic substratum below a thin superficial layer in one site close to the axis of the valley: the strike direction (α = 50°N), and a rather high anisotropy coefficient (λ ≈ 4) are determined.And lastly two directions for further developments are suggested.     

Granitic coastal geomorphology: applying integrated terrestrial and bathymetric LiDAR with multibeam sonar to examine coastal landscape evolution

Coasts composed of resistant lithologies such as granite are generally highly resistant to erosion. They tend to evolve over multiple sea level cycles with highstands acting to remove subaerially weathered material. This often results in a landscape dominated by plunging cliffs with shore platforms rarely occurring. The long‐term evolution of these landforms means that throughout the Quaternary these coasts have been variably exposed to different sea level elevations which means erosion may have been concentrated at different elevations from today. Investigations of the submarine landscape of granitic coasts have however been hindered by an inability to accurately image the nearshore morphology. Only with the advent of multibeam sonar and aerial laser surveying can topographic data now be seamlessly collected from above and below sea level. This study tests the utility of these techniques and finds that very accurate measurements can be made of the nearshore thereby allowing researchers to study the submarine profile with the same accuracy as the subaerial profile. From a combination of terrestrial and marine LiDAR data with multibeam sonar data, it is found that the morphology of granite domes is virtually unaffected by erosion at sea level. It appears that evolution of these landscapes on the coast is a very slow process with modern sea level acting only to remove subaerially weathered debris. The size and orientation of the joints determines the erosional potential of the granite. Where joints are densely spaced (<2 m apart) or the bedrock is highly weathered can semi‐horizontal surfaces form. Copyright © 2014 John Wiley & Sons, Ltd.     

不同时次地基微波辐射计反演产品评估

利用北京大型活动期间探空和微波辐射计资料,采用统计方法进行评价分析,目的是了解该型微波辐射计的性能。结果表明:①总体平均:对温度,有降水时误差变化范围大,无降水时相对比较小,比较平稳;无降水时比有降水时更接近于探空观测结果。对相对湿度,误差的变化与温度比较相似,但从相对误差的变化来看,有降水时比无降水时小。无降水时反演的相对湿度与探空的比较一致。②不同时次:对温度,无降水时统计量随高度的变化规律性比较明显,趋势一致;有降水时的规律相对较差。无降水时,20:00误差比较小,比较接近探空;14:00误差比较大。有降水时,各时次误差比无降水时大,反演的20:00温度变化曲线与探空最接近。对相对湿度,无降水时统计量随高度的变化规律性比较明显,趋势较一致;有降水时的规律性相对比较差。总体来看,降水对微波辐射计影响较大,反演的20:00的资料误差小一些,5000m高度上下误差变化比较大,与云层有关。     

利用风廓线雷达研究郑州机场低空急流特征及其对飞行的影响

利用2016、2017年郑州机场高分辨率边界层风廓线雷达半小时平均观测资料, 对机场上空低空急流时空分布特征进行统计研究, 结果表明:夏末、秋季低空急流出现次数相对较少, 春季、夏初是高发时期, 冬季易出现较强的超低空急流, 只有春季风速从低层到高层呈现先增大后减小、再增大的变化过程, 8月末可能是急流的时空转换期; 夜间和凌晨是高发时段, 白天降低30%~40%, 一般情况下, 00—12时(世界时, 下同)急流较弱, 12时后明显增强向上发展, 19时开始减弱, 持续至21时; 急流中心最大风速一半以上在12~18 m/s, 高度集中在60~180 m和300~900 m, 超低空急流占大部分, 夜间出现最大风速的概率远高于白天; 低空急流发生高度大部分在飞机起飞或着陆的范围内, 使飞机复飞概率增加, 对夜间航班影响更大。      

雷雨天气预防数字探空仪突失应注意的问题

通过对数字探空仪在雷雨天气中容易发生突失的原因分析，提出相应的应对措施。     

14时探空在改进北京地区对流天气潜势预报中的作用

为了探讨增加14时探空对于对流天气短时临近潜势预报的作用。用1995—2005年北京地区22个人工观测站资料统计了夏季常见的对流天气日变化特征。结果表明,41．6％的雷阵雨、61．3％的冰雹以及58．5％的雷暴大风发生在15—-20时之间。利用探空资料计算并对比了出现在2006年7—9月14时探空释放后到20时期问11个雷暴个例的08时和14时BCAPE、DCAPE、CIN等对流参数。结果表明,对于多数个例,在判断对流是否发生时14时探空优于08时。因此,增加14时探空对于提高对流天气有无预报准确率有帮助。     

新一代雷达风廓线与探空风廓线资料相关分析

利用南昌新一代多普勒天气雷达获取的2002～2005年37次（共计614组样本）完整风廓线资料,与同期探空风廓线进行相关分析。结果表明：探空风廓线与雷达风廓线之间具有比较好的相关性。风向相关系数R≥0．6次数占总数78％,其中R≥0．8次数占总数60％。风速相关系数R≥0．6次数占总数81％,其中R≥0．8次数占总数57％。随着高度增加,探空风向与雷达风向的相关度明显降低,风速的相关变化不大。