基于双金属球三维电场探空仪的一次雷暴云内电荷结构观测研究

本文自主研制性能稳定的双金属球三维电场探空仪,并结合气象探空仪等构建了雷暴电场-气象综合探空系统,实现了雷暴云内三维电场及温度、湿度的同步测量.2019年夏季对华北平原地区雷暴开展穿云观测,并结合地面大气电场、雷达回波、变分多普勒雷达分析系统(VDRAS)反演的动力场等资料进行综合研究,首次给出该地区雷暴云内的电场和电荷结构分布特征.对2019年8月7日发生的一次中尺度对流系统电场探空发现,在雷暴减弱阶段,其弱回波区内存在5个极性交替的电荷区:4.4~5.6 km之间的上部正电荷区(0℃附近)、3.6~4.4 km之间的中部负电荷区和1.0~3.6 km之间的下部正电荷区,此外在1 km下方有一个负极性电荷区,雷暴云顶附近5.7~6.9 km之间为一个弱负极性屏蔽电荷区.其中,中部负电荷区和下部正电荷区由多个不同强度、不同厚度的电荷层构成.此外,电场探空系统在中部负电荷区高度范围内经历的上升—下沉—再次上升的往返探空数据表明,雷暴云内动力环境复杂,电荷结构分布相似但又有所差异,反映了实际雷暴云内电荷分布的时空不均匀性和复杂性.     

夏季青藏高原及其周边地区卫星MLS水汽、臭氧产品的探空检验分析

根据Aura卫星微波临边探测(MLS)2.2,3.3版水汽和臭氧廓线,采用线性内插方法,将夏季在青藏高原(西藏的那曲和拉萨)及其周边地区(云南腾冲)通过冷冻霜点仪(CFH)和电化学反应池型(ECC)探空仪分别测得的水汽和臭氧数据插值到与卫星产品规定的气压高度进行比较分析,以检验MLS水汽和臭氧廓线产品.结果表明:MLS 2.2和3.3版水汽相对误差在100 h Pa的对流层顶附近分别为(9.8±46.0)%(n=18),(23.0±45.8)%(n=17);在小于并包含82.5h Pa在内的下平流层则分别为(-2.2±15.7)%(n=74),(0.3±14.9)%(n=75);而在对流层316~121h Pa高度则分别为(21.5±90.6)%(n=104),(6.0±83.4)%(n=99).相应MLS 2.2,3.3版臭氧的误差分别为:(-3.5±54.4)%(n=27),(-8.7±41.6)%(n=38)(100 h Pa);(-11.7±16.3)%(n=135),(15.6±24.2)%(n=305)(下平流层);(18.0±79.1)%(n=47),(34.2±76.6)%(n=160)(对流层上层).MLS水汽和臭氧的误差垂直分布在对流层上层-平流层低层振荡和离散分布明显,部分误差可能由于此高度层水汽和臭氧浓度梯度大和比较用线性插值探空数据引起."臭氧低谷"期间,拉萨地区70 h Pa高度以下MLS卫星臭氧浓度误差明显增加;腾冲、那曲与拉萨三地的MLS臭氧误差的垂直分布特征较一致.卫星产品与探空测值的初步关系表明,MLS廓线的灵敏度与水汽和臭氧在大气中垂直分布有密切联系,3.3版水汽产品的灵敏度在82.5 h Pa以上高度略有提高,臭氧产品灵敏度没有明显变化.文中还讨论了导致MLS水汽和臭氧廓线产品误差的可能因素.     

西藏高原斜压对流边界层风、温、湿廓线特征

利用1998年夏季第2次青藏高原大气科学试验当雄观测站的边界层观测资料以及拉萨、改则和武汉等地探空资料,分析讨论西藏高原斜压对流边界层风、温、湿廓线的特征. 研究结果表明,高原地区白天对流边界层发展可高达2200m,显著超过中纬度平原地区和海面上对流边界层高度. 高原对流边界层中温度廓线具有较好的混合特征,湿度廓线有时在某一高度上出现湿度极大值. 高原对流边界层内热量和水汽收支分析表明,水平平流作用对边界层结构具有重要作用. 在对流边界层中平均风速垂直分布存在风切变现象. 水平温度梯度形成较强的斜压性是形成边界层风切变的主要原因.     

基于COSMIC掩星探测资料的云底高反演研究

本文基于相对湿度廓线进入云层时的突变实现云底高反演的思想,采用2008年11月至2009年1月的COSMIC掩星湿空气数据反演全球云底高度,并与探空资料反演结果进行对比分析,得出以下重要结论:(1)当温度－40 ℃相似文献   

一种基于土壤温湿资料计算地表土壤热通量的温度预报校正法

分析大气边界层观测站地表能量平衡需要估计其地表土壤热通量。发展了一种由多层土壤温度和湿度观测资料估算土壤热通量的新方法。该方法首先求解一维热扩散方程得到土壤温度的基本廓线,然后校正所求温度廓线与观测值的偏差,最后积分温度廓线得到土壤各层的热通量。与众多的方法不同,该方法不需要事先给定不易准确测量和推求的热传导（或热扩散）系数值。通过与实测资料对比、模型合成数据试验、以及敏感性分析等,表明该方法的计算结果稳定可靠,对土壤表层数厘米深度内有无观测资料也不敏感。此外,指出热流板可准确测量热通量的方向和相位,但所测通量值的误差常较大。     

山基GPS掩星折射率与探空折射率比较

本文简要阐述了山基GPS掩星数据处理过程,介绍了雾灵山(40.60.N,117.48.E,～2118 m)山基GPS掩星观测实验的基本情况,将雾灵山山基GPS掩星折射率与探空折射率进行了比较.按照山基掩星和无线电探空在空间(经纬度)上相差在2.以内、时间上相差在1.5 h以内的条件,共选出了206个山基掩星折射率廓线样本用于比较分析.山基掩星折射率与探空折射率的个例比较,表明山基掩星折射率廓线合理,且和探空折射率基本一致.统计结果显示,在2100 m 以下,山基掩星折射率与探空折射率相对偏差的平均值为-2.0%,标准偏差为7.3%.     

基于纯转动Raman激光雷达的中低空大气温度高精度探测

本文介绍了一套纯转动Raman测温激光雷达系统,通过高分辨光谱分光与滤光优化设计、收发精确匹配以及弱信号检测等技术,实现在武汉城市上空从10km至40km的中低空大气温度高精度探测.观测结果与同时段探空气球进行比对,在30km以下激光雷达探测温度与探空气球得到的温度数据吻合较好,最大偏差约为3.0K,表明了该激光雷达温度测量的可靠性.采用30min时间分辨率,在10~20km高度范围内温度统计误差约为0.3K(300m空间分辨);20~30km统计误差约为0.8K(600m空间分辨);30~40km统计误差约为3.0K(900m空间分辨).通过整晚的温度廓线反演,为研究中低层大气中的波动现象提供依据.该转动Raman激光雷达实现了至40km高度的高精度大气温度探测,进一步可与Rayleigh测温激光雷达30~80km的高度衔接,为实现中低层大气连续观测研究提供了重要手段.     

闪电VHF辐射源三维定位网络测量精度的实验研究

利用自制的探空球载闪电模拟源对青海大通地区建立的闪电VHF辐射源三维定位网络的精确度进行了实验研究,通过探空闪电模拟源携带的GPS飞行轨迹,对观测网络中心上空附近和网络外辐射源定位的误差进行了估算,并与模型理论计算作比较.对最小二乘拟合优度卡方值作计算检验,估算了拟合公式中的测时误差.结果表明,三维定位网络的几何设置,测量设置和计算方法合理,得到的定位数据和标定结果一致,在一定的误差范围内.定位误差随高度增加,网内辐射源在网络中心上空的水平定位误差范围为10~48 m(rms),整层平均误差21 m(rms).垂直定位误差范围为20~78 m(rms),整层平均误差49 m(rms),对于网络内外辐射源的定位误差分别采用不同的模型计算,其结果和误差标定结果一致.对于网内采用标准差合适,网外采用协方差,且定位误差是径向距离的函数,定位误差随距离增加.模型预测径向距离和高度误差随r2增加,径向距离误差随距离呈抛物线形状,通过协方差计算结果也证实了这一点.分析又指出,对于闪电辐射源,其拟合卡方值??应该小于5,拟合公式中的测时误差?trms在50~66 ns范围内.     

GNSS掩星中大气水汽的非线性反演

研究利用无线电掩星探测数据反演大气水汽参数,文中使用一维非线性方法,反演对流层水汽压廓线.首先,定义了一维目标函数,并以几何光学假设为前提,反演出电波弯曲角;将电波弯曲角作为掩星探测量,大气模式输出的温、湿参量作为初始场,代入目标函数,对目标函数求最优反演出水汽压廓线.文中给出了部分反演结果,经讨论分析认为:非线性方法反演水汽压对初始场的精度依赖较小,能够同时反演出大气温度\水汽压廓线及相应的误差分析,对数值天气预报的应用及数据同化研究具有重要意义.     

基于Zoeppritz偏导方程精确解的地层密度多角度反演

基于Zoeppritz方程对介质密度偏导数所建立的偏导方程的精确解,构造了多角度反演地层介质密度的反演方程,在偏导数求解过程中考虑了介质密度对波速度的影响因素,并由此实现了利用反射系数梯度精确解计算地层密度的多角度联合反演.通过数值算例考察了计算方法,结果显示:反演方法对层状地层模型不论反射波是否存在相干现象均获得了较好的反演结果,反演迭代10次后计算结果的最大相对误差能够收敛到1%之内;随着反演角度的增加地层介质密度反演的精度逐步提高,反演具有自动校正能力,有快的计算速度.本方法克服了传统AVO(Amplitude Versus Offset)基于Zoeppritz方程近似所遇到的困难,不受反演角度大小及反射界面对波反射强弱的限制,为地层介质密度的多角度包括大角度反演提供了一种新的快速有效的计算方法.     

基于毫米波雷达、无线电掩星和探空仪资料的云边界高度对比研究

为准确评估基于相对湿度廓线法反演云边界高度的有效性,以CloudSat和CALIPSO联合探测结果为基准,对2008年1月至2009年1月COSMIC无线电掩星和探空仪的云底高与云顶高反演结果进行定量对比验证,结果表明:CloudSat、掩星和探空仪检测到高云的比例差异较大,掩星和探空仪云检测效率相近,但云检测质量掩星优于探空仪,云层沿高度的发生概率同样掩星与CloudSat具有更好的一致性;陆地与海洋地区掩星和探空仪云底高反演精度大于云顶高,且反演精度与云层高度有关,二者对不同类型云的边界高度具有不同的反演优势,云底高发生概率掩星和探空仪与CloudSat都有很好的一致性,但云顶高概率掩星与CloudSat的吻合程度更好;CloudSat云边界高度随纬度升高而减小,其与掩星和探空仪的反演偏差同样是低纬大于中高纬,且具有不同的季节分布特点.此外,三者检测的底层云中低云所占比例从冬季到夏季逐渐减小,顶层云中云顶高于10 km的比例从冬季到夏季却逐渐增加.     

A model for accurately calculating hyper-spectral,middle-shortwave infrared radiative transfer for remote sensing

Although the calculation of radiative transfer in the middle-shortwave infrared band is important in the field of optical remote sensing, studies in this area of research are rare in China. Both solar reflection and atmospheric emission should be considered when calculating radiative transfer in the middle-shortwave infrared band. This paper presents a new radiative transfer model based on the doubling and adding method. The new model uses approximate calculations of direct solar reflection,multiple scattering, and thermal emissions for a finitely thin atmospheric layer and considers both the solar and thermal sources of radiation. To verify its accuracy, the calculation results produced by the model for four typical scenarios(single layer at night,multi-layer aerosols, double-layer with ice and water clouds, and multi-layer with clouds and aerosols) were compared with those of the DISORT model. With the exception of a few channels, the absolute deviation between the two models was less than2×10~(-6) K. For the same calculation, the computation speed of the new model was approximately two to three times faster than that of the DISORT model. Sensitivity studies were performed to evaluate the error resulting from using simplified calculation methods in the new model. The results obtained in this study indicated that atmospheric thermal emission made a significant contribution to the measured radiance in the strong-absorption band(2230–2400 cm~(-1)), whereas solar radiation could be neglected in this region. However, neglecting solar radiation in the window region(2400–2580 cm~(-1)) introduced error on the order of dozens of K. Employing the average-layer temperature method simplified the calculation of thermal radiation but caused a larger error in the strong-absorption band than in the window region. In the doubling and adding method, the calculation error decreased as the value used for minimum optical thickness decreased. Under the condition of satisfying the requirement of calculation precision, we can consider using the layer-average temperature radiation method and selecting a relative larger minimum optical thickness value to improve the calculation efficiency. The new radiative calculation model proposed herein can be used in the simulation, inversion, and assimilation of middle-shortwave infrared measurements by hyper-spectral satellite instruments.     

Simultaneous measurement of humidity and temperature in the lower troposphere over Chung-Li,Taiwan

A combined Raman–Rayleigh lidar has been designed at Chung-Li, Taiwan for the simultaneous measurement of water-vapor mixing ratio, temperature and extinction-to-backscatter ratio of aerosol in the lower troposphere. The technique of Raman–Rayleigh lidar can retrieve correct temperature profile in the lower troposphere where the measurements are underestimated due to the aerosol loading. Two typical cases are discussed under different humidity (dry/wet) conditions. The water vapor and temperature profile have shown a good agreement with radiosonde. Simultaneous measurement of Raman–Rayleigh lidar also illustrates the physical nature of the aerosol and is useful in understanding the effects of humidity on aerosol swelling.     

不同发展阶段雷暴云中电荷的静电力散度分布及其动力作用

太阳活动与地球天气气候间关系的相关及其机理研究是当前日-地关系研究中的一个活跃领域。目前认为太阳活动影响天气最可能的途径之一是通过调制大气电状态来实现的。太阳活动可以影响大气电状态不仅已被大量观测结果的统计分析所证实,而且通过高空气球对气-地电流密度的实地观测表明,太阳耀斑暴发前后的气-地电流     

Impact of wind on the spatial distribution of rain over micro‐scale topography: numerical modelling and experimental verification

The wind‐driven‐rain effect refers to the redistribution of rainfall over micro‐scale topography due to the existence of local perturbed wind‐flow patterns. Rainfall measurements reported in the literature point to the fact that the wind‐driven‐rain distribution can show large variations over micro‐scale topography. These variations should be taken into account in hillslope hydrology, in runoff and erosion studies and in the design of rainfall monitoring networks. In practice, measurements are often not suitable for determining the wind‐driven‐rain distribution. Therefore, a few researchers have employed numerical modelling. In order to provide confidence in using numerical models, experimental verification for a range of different topographic features is imperative. The objective of this study is to investigate the adequacy of a two‐dimensional Computational Fluid Dynamics (CFD) model to predict the wind‐driven‐rain distribution over small‐scale topography. The numerical model is applied to a number of topographic features, including a succession of cliffs, a small isolated hill, a small valley and a field with ridges and furrows. The numerical results are compared with the corresponding measurement results reported in the literature. It is shown that two‐dimensional numerical modelling can provide a good indication of the wind‐driven‐rain distribution over each type of micro‐scale topography that is considered in this study. It is concluded that more detailed verification procedures are currently inhibited due to the lack of available and detailed spatial and temporal rainfall data from field measurements. Copyright © 2005 John Wiley & Sons, Ltd.     

Interpretation of mean‐field bias correction of radar rain rate using the concept of linear regression

In this study, the correction problem of mean‐field bias of radar rain rate was investigated using the concept of linear regression. Three different relationships were reviewed for their slopes to be used as the bias correction factor: Relationship 1 (R1) is based on the conventional linear regression, relationship 2 (R2) is forced to pass the origin and relationship 3 (R3) is the line whose slope is the G/R ratio. In other words, R1 is the regression line connecting the intercept and the mass centre of measurement pairs, R2 is the regression line forced to pass the origin, and R3 is the line connecting the origin and the mass centre. The slopes of all three relationships were reviewed analytically to compare them, and thereby, the effect of zero measurements could be evaluated. Additionally, the effect of using switched independent and dependent variables on the derived slopes was also evaluated. The theoretically derived results were then verified by analysing the rainfall event on 10–11 August 2010 in Korea. Finally, the difference between the bias‐corrected radar rain rate and the rain gauge rain rate was quantified by root mean square error and mean error so that it could be used as a measure for the evaluation of bias correction factors. In conclusion, the slope of R2 was found to be the best for the bias correction factor. However, when deciding the slope of this R2, the radar rain rate should be used as the independent variable in the low rain rate region, and the rain gauge rain rate in the high rain rate region above a certain threshold. Copyright © 2013 John Wiley & Sons, Ltd.     

The electrical conductivity of clouds

Summary A modified Gerdien cell was designed, evaluated, and built for measurement of the polar conductivities in clouds. This conductivity dropsonde was attached to a U.S. Weather Bureau, 1680 mHz, radiosonde for telemetry and to measure pressure, temperature, and relative humidity profiles. The combined instruments were ejected from aircraft, and others were released from balloons into the region of interest.Eight flights were made during the 1967 thunderstorm season. Three of these drops were successful in measuring conductivity inside of electrically active clouds. Two fair-weather profiles were measured for comparison purposes, and three of the drops were faulty.These very preliminary results tend to indicate considerable electrical conductivity in thunderclouds. The data are too few to support a strong statement in favor of increased conductivity, but the instruments were sufficiently reliable to prove that the conductivity was not reduced, as is normally assumed, in the clouds investigated.This research was supported by the Atmospheric Sciences Section, National Science Foundation under Grant GA-701.     

Effect of remote clouds on surface UV irradiance

Clouds affect local surface UV irradiance, even if the horizontal distance from the radiation observation site amounts to several kilometers. In order to investigate this effect, which we call remote clouds effect, a 3-dimensional radiative transfer model is applied. Assuming the atmosphere is subdivided into a quadratic based sector and its surrounding, we quantify the influence of changing cloud coverage within this surrounding from 0% to 100% on surface UV irradiance at the sector center. To work out this remote clouds influence as a function of sector base size, we made some calculations for different sizes between 10 km × 10 km and 100 km × 100 km. It appears that in the case of small sectors (base size 20 km × 20 km) the remote clouds effect is highly variable: Depending on cloud structure, solar zenith angle and wavelength, the surface UV irradiance may be enhanced up to 15% as well as reduced by more than 50%. In contrast, for larger sectors it is always the case that enhancements become smaller by 5% if sector base size exceeds 60 km × 60 km. However, these values are upper estimates of the remote cloud effects and they are found only for special cloud structures. Since these structures might occur but cannot be regarded as typical, different satellite observed cloud formations (horizontal resolution about 1 km × 1 km) have also been investigated. For these more common cloud distributions we find remote cloud effects to be distinctly smaller than the corresponding upper estimates, e.g., for a sector with base size of 25 km × 25 km the surface UV irradiance error due to ignoring the actual remote clouds and replacing their influence with periodic horizontal boundary conditions is less than 3%, whereas the upper estimate of remote clouds effect would suggest an error close to 10%.     

Automated system for measuring snow surface energy balance components in mountainous terrain

The ability to continually monitor several meteorological parameters is needed to estimate snow surface energy balance components in mountainous terrain. In remote mountainous locations, limited accessibility and extreme weather conditions limit the use of delicate meteorological instrumentation. Robust instrumentation and radio telemetry are often needed to measure snow surface energy exchanges. This study examined the practicality and effectiveness of robust instrumentation in estimating radiative and turbulent exchanges in the forested Bear River Mountains of northern Utah. Measurement of reflected shortwave radiation was problematic due to possible selective absorption in the infra-red range. This resulted in overestimates of reflected shortwave radiation and decreased estimates of now surface albedo. During high snowfall, the pyranometer and net radiometer were occasionally covered with snow, resulting in inaccurate radiation measurements. Snow typically melted from instrument surfaces in less than one day under full sun. A relative humidity measurement accuracy of ± 4% may have resulted in a possible error of 20% in the calculation of vapour pressure. Snow depth measurement with an acoustical sensor was affected by new or blowing snow, which resulted in inaccurate snow depth measurement 16.2% of the time. The longest period without a valid snow depth measurement was 19.5 hours. A new snow temperature thermocouple ladder was designed and constructed and provided accurate within-pack temperature measurements throughout the pre-melt and melt season.     

Evolution of erythemal and total shortwave solar radiation in Valladolid,Spain: Effects of atmospheric factors

Erythemal ultraviolet (UVER; 280–400 nm) and total shortwave (SW; 305–2800 nm) solar irradiances were recorded from 2000 to 2009 in Valladolid, Spain. UVER and SW values under cloudless conditions are simulated by radiative transfer (TUV 4.6) and empirical models. These model estimations are tested with experimental measurements showing a great agreement (root mean square error around 7%). The aerosol effect on UVER irradiance is determined through a model study. UVER radiation and total ozone column (TOC) temporal evolutions show a negative relationship. TOC accounts for 80% of UVER variance and its radiation amplification factor is 1.1 at zenith of 65°. Cloud effects on solar radiation are shown and quantified by the cloud modification factor. Moreover the enhancement effect cases are analysed. SW radiation proves more sensitive to clouds than UVER. Clouds are seen to attenuate and enhance solar radiation by up to 93% and 22% in the UVER range, respectively.