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1.
A collocated SSM/I and radiosonde measurement data set provided by the NASDA(Japan) was used to retrieve the total precipitable water(PW) over oceans.The retrieval results obtained with several regression algorithms were compared against the radiosonde measurements.It is shown that:(a) the routinely operational algorithm of Alishouse et al.(1990) yields significant underestimation in high PW regime and overestimation in low PW regime;(b) a cubic correction by Colton and Poe(1994) is not sufficient and globally improves slightly the retrieval results;and(c) the regression algorithm with the form of brightness temperature(Tb) function In(280-Tb) gives a little largely scattered retrievals in whole PW range but without considerable over-and underestimates in low and high PW regimes.To improve the estimation of the oceanic precipitable water from the SSM/I measurements,a composite algorithm with different forms of Tb function in low.medium and high PW regimes is proposed and tested.  相似文献   

2.
Summary High spatial resolution data from an airborne microwave imaging radiometer operating at 92 and 183 GHz (0.32 and 0.16 cm wavelengths) are compared with ground-based radar data for a series of observations of precipitating convective systems. An inverse relationship between microwave brightness temperature (T B ) and radar-derived rain rate (RR) is observed. Differences in the empirical curves between midlatitude and tropical cloud systems are related to the differing microphysical and dynamical environments.ColdT B features in the aircraft images are collocated with high reflectivity values in the radar data. Over a water back-ground, which has a low surface emissivity at these frequencies, small convection produces an increase inT B at 92 GHz due to emission by liquid water in the cloud. As the convection deepens and ice forms,T B at both frequencies decreases rapidly with increasing rain rate. The large decrease inT B with increasing storm intensity is due to scattering of upwelling radiation by precipitation-sized ice particles within the clouds. With high rain rates, there is little difference betweenT B observed over both land and water backgrounds.TheT B features in the aircraft imagery are qualitatively similar to radar echoes in plan position indicator (PPI) images. Areas of extremely coldT B (<150 K) coincide with high radar reflectivities. The highest correlations between microwave and radar features with regard to location, intensity, and shape occur more frequently with mid-to upperlevel echoes rather than low-level reflectivity features.With 12 Figures  相似文献   

3.
Cloud observations with a polarimetric 33 GHz and 95 GHz radar   总被引：1，自引：0，他引：1  
Summary The University of Massachusetts' Microwave Remote Sensing Laboratory (MIRSL) has developed a unique high spatial resolution multiparameter radar under sponsorship from the Department of Energy's Atmospheric Radiation Measurement (ARM) program. The Cloud Profiling Radar System (CPRS) uses a single one-meter diameter dielectric lens antenna to make collocated polarimetric and Doppler measurements at both 33 GHz and 95 GHz. The polarization of each transmitted pulse at either frequency can be selected on a pulse-to-pulse basis. The radar and supporting hardware are mounted on a truck that serves as a mobile laboratory. The truck-based platform permits CPRS to operate in remote locations and also serves as an economical means of transporting the system.This paper describes the CPRS hardware and presents preliminary vertically pointing observations of mixed-phase stratus clouds obtained in the summer of 1993 during the first field test of the system. Measurements show Mie scattering in the ice region, melting layer and rain region of the clouds observed. To illustrate CPRS potential for particle sizing, models of differential reflectivity and differential mean Doppler velocity are used to estimate median volume diameter,D 0, from dual-wavelength reflectivity and Doppler measurments of rain.With 20 Figures  相似文献   

4.
Measurements on drop size were made in cumulus clouds over Pune (inland region) during the summer monsoon seasons. In this paper, the measurements of the cloud drop spectra made in non-raining clouds at different levels and for different thickness have been studied. Also, those on the days with rain and with no rain (the rain being observed within the clouds) have been compared. The average spectra broadened with height. The concentration of drops >50 μm (NL), liquid water content (LWC), mean volume diameter (MVD) and dispersion increased with height. The concentration of drops <20 μm (NS) and total concentration (NT) decreased with height. The spectra were broader, while NS and NT are smaller and the other parameters are greater for thicker clouds as compared to those for thinner. The spectra were broader, while NS and NT are smaller and the other parameters are greater on the days with rain with respect to those on the days with no rain. The distributions were bimodal at higher levels, for thicker clouds and on the days with rain, while they were unimodal at lower levels, for thinner clouds and on the days with no rain. The variations of the cloud drop spectra, preceding rain, at initial stage of rain and following rain are discussed.  相似文献   

5.
Summary The feasibility of using satellite data for climate research over the Greenland ice sheet is discussed. In particular, we demonstrate the usefulness of Advanced Very High Resolution Radiometer (AVHRR) Local Area Coverage (LAC) and Global Area Coverage (GAC) data for narrow-band albedo retrieval. Our study supports the use of lower resolution AVHRR (GAC) data for process studies over most of the Greenland ice sheet. Based on LAC data time series analysis, we can resolve relative albedo changes on the order of 2–5%. In addition, we examine Scanning Multichannel Microwave Radiometer (SMMR) and Special Sensor Microwave Imager (SSM/I) passive microwave data for snow typing and other signals of climatological significance. Based on relationships between in situ measurements and horizontally polarized 19 and 37 GHz observations, wet snow regions are identified. The wet snow regions increase in aerial percentage from 9% of the total ice surface in June to a maximum of 26% in August 1990. Furthermore, the relationship between brightness temperatures and accumulation rates in the northeastern part of Greenland is described. We found a consistent increase in accumulation rate for the northeastern part of the ice sheet from 1981 to 1986.With 16 Figures  相似文献   

6.
Using Microwave Sounding Unit (MSU) channel 2 (Ch. 2, 53.74 GHz) data, Spencer and Christy (1992a) determined that the earth exhibits no temperature trend in the period 1979–90, while other authors find a temperature increase of roughly 0.1 K. Based on a theoretical analysis Prabhakara et al. (1995) showed that the information about the global atmospheric temperature deduced from MSU Ch. 2 observations has a small contamination, T 2, as a result of the attenuation due to hydrometeors in the atmosphere. A method is developed in this study, that utilizes coincident measurements made by MSU in Ch. 1 (50.3 GHz), to estimate this T 2 over the global oceans. The magnitude of T 2 is found to be about 1 K over significant parts of the tropical oceanic rain belts and about 0.25 K over minor portions of the mid-latitude oceanic storm tracks. Due to events such as El Niôo, there is variability from year to year in the rain areas and rain intensity leading to significant change in the patterns of T 2. The patterns of T 2 derived for March 82 and March 83 reveal such a change. When averaged over the global oceans, from 50° N to 50° S, T 2 has a value of 0.25 and 0.29 K for March 1982 and 1983, respectively. Due to these reasons the interannual temperature change derived by Spencer and Christy from MSU Ch. 2 will contain a residual hydrometeor effect. Thus in evaluating decadal trend of the global mean temperature of the order of 0.1 K from MSU Ch. 2 data one has to take into account completely the contamination due to hydrometeors.  相似文献   

7.
Summary A new physical inversion-based algorithm for retrieving rain rate over the ocean with the Special Sensor Microwave Imager (SSM/I) is described. In a departure from other rain rate retrieval algorithms, the satellite observables inverted in the present algorithm are not the raw brightness temperatures but rather normalized polarizations for 19.35, 37.0, and 85.5 GHz, plus an 85.5 GHz scattering index which is sensitive primarily to ice particles aloft. The normalized polarizations are interpreted as footprint-averages of theoretically derived analytic functions of the column optical depth associated primarily with liquid water. The effective vertical depth of the rain layer is specified as a function of the SSM/I estimated column water vapor.The retrieval algorithm performs an iterative search for a high resolution (12.5 km) rain field which is simultaneously consistent with the 19.35 and 37.0 GHz normalized polarizations. The first-guess rain rate field is supplied by the 85.5 GHz scattering index. At gridpoints for which the rain column optical depth exceeds the dynamic range of the attenuation-based indices, the first-guess field is left essentially unmodified; elsewhere, the required consistency with the 19 and 37 GHz indices usually results in significant modification of the scattering-based rain rate estimates.The algorithm as described here is a prototype implementation which was developed with reference only to idealized theoretical models; empirical improvements to the numerical scheme and the model coefficients will be made in the future as results from the first Precipitation [algorithm] Intercomparison Project 1 (PIP-1) and the second phase of the GPCP (Global Precipitation Climatology Project) algorithm Intercomparison Project (AIP/2) are analyzed, as well as data from individual validation efforts. Although the algorithm is physically based and uses all SSM/I channels, it is computationally much less demanding than cloud/radiative transfer model-based inversion algorithms published else-where.With 9 Figures  相似文献   

8.
Observations in channel 1 (Ch. 1, 50.3 GHz) and channel 2 (Ch. 2, 53.74 GHz) of the Microwave Sounding Unit (MSU) over the convective areas of tropical oceans are analysed to reveal the nature of extinction (contamination) in these data. From this analysis we find Ch. 2 data are not free from the influence of clouds and rain. Extinction due to clouds and rain manifests primarily as emission in Ch. 1, and as absorption in Ch. 2. Scattering due to hydrometeors in these channels apparently is of secondary importance. Furthermore we show, in the convective areas of tropical oceans, contamination due to hydrometeors in MSU Ch. 2 data is significant and it is extensive in area. Based on this study we conclude Spencer, Christy, and Grody (this issue) underestimate this contamination.  相似文献   

9.
In recent studies (Spencer and Christy, 1990; and Spenceret al., 1990) it is suggested that observations at 53.74 GHz made by the Microwave Sounding Unit (MSU), flown on NOAA operational weather satellites, can yield a precise estimate of global mean temperature and its change as a function of time. Hansen and Wilson (1993) question their interpretation of temporal changes on the grounds that the microwave observations could be influenced by the opacity of the variable constituents in the atmosphere. This issue has broad interest because of the importance of detection of global climatic change.In order to help resolve this issue, in this study we utilize a radiative transfer model to simulate: (a) the observations of MSU Channel 1 (Ch. 1) at 50.3 GHz, in the weakly absorbing region of the 60 GHz molecular oxygen absorption band; and (b) the observations of MSU Channel 2 (Ch. 2) at 53.74 GHz, in the moderately strong absorption region of the same band. This radiative transfer model includes extinction due to clouds and rain in addition to absorption due to molecular oxygen and water vapor.The model simulations show that, over the oceans, extinction due to rain and clouds in Ch. 1 causes an increase in brightness temperature, while in Ch. 2 it causes a decrease. Over the land, however, both Ch. 1 and Ch. 2 show a decrease in brightness temperature due to rain and cloud extinction. These theoretical results are consistent with simultaneous observations in Ch. 1 and Ch. 2 made by MSU. Based on theory and observations we infer that a substantial number of the MSU observations at 53.74 GHz used by Spenceret al. contain rain and cloud contamination. As a result, their MSU derived global mean temperatures and long term trend is questionable.  相似文献   

10.
冰云是影响气候变化最为重要的因子之一,其生命周期的变化在很大程度上决定了冰云的气候辐射效应。冰云粒子下降末速度是影响冰云生命周期的关键参数。为了开展对冰云粒子下降末速度的研究,利用兰州大学半干旱气候与环境监测站Ka波段毫米波云雷达2013年8月至2015年7月连续观测数据,反演了冰云粒子的下降末速度（Vt）,并根据雷达反射率因子（Z）与Vt的关系计算了拟合因子a、b的值;在此基础上应用聚类分析方法,对比分析了4种不同特性冰云Z、Vt和拟合因子a、b的时、空分布特征,进而尝试通过参数垂直分布特征识别研究云中不同位置上云微物理过程的变化。结果表明:冰云粒子下降末速度的分布与雷达反射率因子有很好的对应,最大频率都出现在距离地面约7 km高度处,且具有显著的季节变化,粒子下降末速度在暖季较冷季可增大25%,峰值出现在6月和9月;云层较厚且持续时间长的第一、三类冰云,其雷达反射率因子、粒子下降末速度及拟合因子a和b的平均值都显著大于云层较薄且持续时间短的第二、四类云。垂直方向上,Z、Vt和拟合因子b从云顶到云底随着高度的降低呈现先增大后减小的趋势,体现了云粒子在云顶区域成核和水汽凝华效应,随着粒子在下落过程中碰并增长,云滴粒子逐渐增大,水汽的凝华和粒子的聚合起主要作用,最后在云底部分,云粒子蒸发、升华减小消亡的过程。由此表明中纬度干旱半干旱地区冰云是从云顶到云底自上而下的形成过程。   相似文献   

11.
Summary The Seasat Scanning Multichannel Microwave Radiometer (SMMR) measurements in the 18.0, 21.0 and 37.0 GHz channels, both horizontal and vertical polarizations, are primarily used for precipitable water, cloud liquid water content and rainfall rate determination. Linear regressions using a leaps and bounds procedure are used for the retrieval of precipitable water. The radiation simulated for all the ten SMMR channels with varied global environmental parameters were used for subset selection for water vapour retrieval. Only subsets with channels having uniform grid size (18, 21 and 37 GHz) were used for the analysis. A total of eight subsets using two to five frequencies of the SMMR are examined to determine their potential in the retrieval of atmospheric water vapour content. Our analysis indicates that the information concerning the 18 and 21 GHz channels are optimum for the water vapour retrieval. An attempt to use all the SMMR channels simultaneously gives no significant improvement. A comparison with the radiosonde observations gave an rms accuracy of 0.4 g/cm2. The rms accuracy of retrieved precipitable water using different subsets was within 10 percent.Global maps of precipitable water over oceans using two and five channels retrieval are given. These maps are generated on a 10 day average basis as well as on monthly basis for the period 7 July to 6 August 1978. An analysis of these Global maps reveals the possibility of global moisture distribution associated with oceanic currents and large scale general circulation in the atmosphere. A stable feature of the large scale circulation is noticed. The precipitable water is maximum over the Bay of Bengal and in the North Pacific over the Kuroshio current and shows general latitudinal pattern.With 5 Figures  相似文献   

12.
Summary Microwave rain rate retrieval algorithms have most often been formulated in terms of the raw brightness temperatures observed by one or more channels of a satellite radiometer. Taken individually, single-channel brightness temperatures generally represent a near-arbitrary combination of positive contributions due to liquid water emission and negative contributions due to scattering by ice and/or visibility of the radiometrically cold ocean surface. Unfortunately, for a given rain rate, emission by liquid water below the freezing level and scattering by ice particles above the freezing level are rather loosely coupled in both a physical and statistical sense. Furthermore, microwave brightness temperatures may vary significantly (30–70 K) in response to geophysical parameters other than liquid water and precipitation. Because of these complications, physical algorithms which attempt to directly invert observed brightness temperatures have typically relied on the iterative adjustment of detailed microphysical profiles or cloud models, guided by explicit forward microwave radiative transfer calculations.In support of an effort to develop a significantly simpler and more efficient inversion-type rain rate algorithm, the physical information content of two linear transformations of single-frequency, dual-polarization brightness temperatures is studied: thenormalized polarization difference P of Petty and Katsaros (1990, 1992), which is intended as a measure of footprint-averaged rain cloud transmittance for a given frequency; and ascattering index S (similar to the polarization corrected temperature of Spencer et al., 1989) which is sensitive almost exclusively to ice. A reverse Monte Carlo radiative transfer model is used to elucidate the qualitative response of these physically distinct single-frequency indices to idealized 3-dimensional rain clouds and to demonstrate their advantages over raw brightness temperatures both as stand-alone indices of precipitation activity and as primary variables in physical, multichannel rain rate retrieval schemes.As a byproduct of the present analysis, it is shown that conventional plane-parallel analyses of the well-known footprint-filling problem for emission-based algorithms may in some cases give seriously misleading results.With 11 Figures  相似文献   

13.
Summary In this paper a retrieval technique for estimating rainfall rates is introduced. The novel feature of this technique is the combination of two satellite radiometers — the Special Sensor Microwave/Imager (SSM/I) and the Advanced Very High-Resolution Radiometer (AVHRR) — with mesoscale weather prediction model data. This offers an adjustment of the model atmospheres to reality which is necessary for calculating brightness temperatures that can be compared with microwave satellite measurements.In sensitivity studies it was found that the estimation of precipitation is determined to a high degree by the particle size distribution of rain and snow, especially by the size distribution of solid hydrometeors. These studies also reveal the influence of the knowledge of the correct cloud coverage inside a SSM/I pixel and the importance of using a realistic temperature profile instead of using standard atmospheres.The retrieval technique is based on radiative transfer calculations using the model of Kummerow et al. (1989). The algorithm consists of two parts: First Guess (FG) brightness temperatures for the SSM/I frequencies are generated as a function of the cloud top height and the cloud coverage, derived from AVHRR data and predictions from a meso-scale model. The rainfall rate of different types of clouds containing raindrops, ice particles and coexisting ice and water hydrometeors is then calculated as a function of the cloud top height. As an example, a strong convective rain event over the western part of Europe and over the Alps is taken to evaluate the performance of this technique. Good agreement with radar data from the German Weather Service was achieved. Compared to statistical rainfall algorithms, the current algorithm shows a better performance of detecting rainfall areas.With 12 Figures  相似文献   

14.
Yafei YAN  Yimin LIU 《大气科学进展》2019,36(10):1089-1102
Cloud is essential in the atmosphere, condensing water vapor and generating strong convective or large-scale persistent precipitation. In this work, the relationships between cloud vertical macro- or microphysical properties, radiative heating rate, and precipitation for convective and stratiform clouds in boreal summer over the Tibetan Plateau (TP) are analyzed and compared with its neighboring land and tropical oceans based on CloudSat/CALIPSO satellite measurements and TRMM precipitation data. The precipitation intensity caused by convective clouds is twofold stronger than that by stratiform clouds. The vertical macrophysics of both cloud types show similar features over the TP, with the region weakening the precipitation intensity and compressing the cloud vertical expansion and variation in cloud top height, but having an uplift effect on the average cloud top height. The vertical microphysics of both cloud types under conditions of no rain over the TP are characterized by lower-level ice water, ice particles with a relatively larger range of sizes, and a relatively lower occurrence of denser ice particles. The features are similar to other regions when precipitation enhances, but convective clouds gather denser and larger ice particles than stratiform clouds over the TP. The atmospheric shortwave (longwave) heating (cooling) rate strengthens with increased precipitation for both cloud types. The longwave cooling layer is thicker when the rainfall rate is less than 100 mm d?1, but the net heating layer is typically compressed for the profiles of both cloud types over the TP. This study provides insights into the associations between clouds and precipitation, and an observational basis for improving the simulation of convective and stratiform clouds over the TP in climate models.  相似文献   

15.
The ability of the Tropical Rainfall Measuring Mission Microwave Imager(TRMM/TMI)forcloud liquid water(CLW)retrieval has been demonstrated in this study.Due to the greatsensitivity of the TMI 85.5 GHz channels to CLW,the liquid water path(LWP)ofnonprecipitating clouds over land can be successfully estimated using the VDISORT model basedon the iteration steps.Both the vertical-polarized 85. 5 GHz single-channel method and thepolarization-difference of 85.5 GHz method were applied to the LWP estimates over land regionsduring the Huaihe River Basin Energy and Water Cycle Experiment(HUBEX)in China.Theretrieval results show reasonable agreement with the ground-based microwave radiometermeasurements.When the surface emissivity or skin temperature is difficult to be made sure,thepolarization-difference method shows advantages of providing estimates of LWP especially for lowclouds because of its extremely insensitiveness to the surface skin temperature.  相似文献   

16.
对比了2017～2019年重庆沙坪坝MP-3000A型地基微波辐射计和Metop-A掩星资料气温、湿度廓线探测之间的差异,并对两次天气过程中微波辐射计的探测特征进行分析,结果表明：(1)微波辐射计与掩星气温在整个探测高度上均为显著正相关,且低层高于高层；夏半年偏差小于冬半年；,4km以下微波辐射计探测气温高于掩星气温,降雨时偏差更大。(2)微波辐射计与掩星相对湿度相关性稍高于气温；,夏半年相关性高于冬半年,,偏差小于冬半年；降水天气时,1km以下及4～-6km之间,微波辐射计相对湿度的负偏差值明显比无降水时大。(3)降水时段,微波辐射计探测5km以下为高湿区,暖湿气团上升过程中凝结潜热和绝热冷却作用,中低层出现了逆温层；辐射雾出现时,微波辐射计探测到近地面层相对湿度增大和气温降低。  相似文献   

17.
The thermal microwave radiation from the ocean surface as seen from space is a function of the surface temperature and wind speed and is modified by liquid water and water vapor in the intervening atmosphere. Further, if the ocean surface is frozen, the emissivity is drastically increased and the effect of the intervening atmosphere is generally negligible. The emissivity of first-year ice is somewhat larger than that of multi-year ice.The data from the Electrically Scanning Microwave Radiometers (ESMR's) on the Nimbus-5 and —6 satellites operating at wavelengths of 1.55 cm and 8 mm, respectively, can be interpreted in terms of rain rate, ice coverage and first-year versus multi-year ice determination. The rain-rate data are being used to establish a climatology of rainfall over the oceans. The ice data are being used by the United States Navy in support of international scientific efforts in the Antactic region. Both ice and rain data sets have been generated for the Global Atmospheric Research Project Data Systems Test.It is possible, by making multifrequency measurements, to separate the surface and atmospheric effects and to make useful measurements of sea surface temperature, surface wind speed, and atmospheric parameters along with improved measurements of rain and ice.  相似文献   

18.
Summary A new methodology for deriving daily averages of near surface specific humidity (Q a ) is developed. Remotely sensed parameters, total water vapor (W), boundary-layer water vapor (W b ), and sea-surface temperature (SST) are used to derive Q a . Genetic algorithm (GA) is used to find the empirical function relating the input (W, W b , and SST) and output (Q a ) parameters. The input data consist of 2 years (1999–2000) of daily W, W b , from SSM/I (Special Sensor Microwave Imager), and SST data from AVHRR (Advanced Very High Resolution Radiometer). COADS (Comprehensive Ocean Atmospheric Data Set) observations of Q a are used to develop and evaluate the new methodology. The performance of the algorithm is measured with COADS observations, which are not used in the development phase. The global mean rms error for daily averages Q a is 1.5 ± 0.40 g/kg. Slightly higher discrepancies between Q a derived from the new method and COADS observations are found over the Northwestern Pacific, North Atlantic oceans and Arabian Sea. This method improves upon the humidity retrieval of Liu (1986), Schulz et al (1993), and Chou et al (1997).  相似文献   

19.
Based on 1-year cloud measurements with radar and microwave radiometer broadband solar radiative transfer simulations were performed to quantify the impact of different ice crystal shapes of Arctic mixed-phase clouds on their radiative properties (reflectance, transmittance and absorptance). The ice crystal shape effects were investigated as a function of microphysical cloud properties (ice volume fraction fi, ice and liquid water content IWC and LWC, mean particle diameter DmI and DmW of ice/water particle number size distributions, NSDs).The required NSDs were statistically derived from radar data. The NSD was composed of a liquid and a solid mode defined by LWC, DmW (water mode) and IWC, DmI (ice mode). It was found that the ratio of DmI and DmW determines the magnitude of the shape effect. For mixed-phase clouds with DmI ≤ 27 μm a significant shape effect was obtained. The shape effect was almost insensitive with regard to the solar zenith angle, but highly sensitive to the ice volume fraction of the mixed-phase cloud. For mixed-phase clouds containing small ice crystals (DmI ≤ 27 μm) and high ice volume fractions (fi > 0.5) crystal shape is crucial. The largest shape effects were observed assuming aggregates and columns. If the IWC was conserved the shape effect reaches values up to 0.23 in cloud reflectance and transmittance. If the ice mode NSD was kept constant only a small shape effect was quantified (≤ 0.04).  相似文献   

20.
95GHz云雷达对一次冷锋云系结构的观测分析   总被引：2，自引：0，他引：2  
黄毅梅  周毓荃 《高原气象》2012,31(4):1129-1138
利用安徽寿县W-Band云雷达(95GHz,波长3.16mm)、地面微波辐射计、探空和地面观测等资料,对2008年11月5-7日一次冷锋云系的云结构进行了分析。结果表明,云雷达的多普勒速度可以初步确定粒子相态和大小以及是否存在雪晶或雨滴;在0℃层附近有回波暗带产生,这主要是由于波长为3mm的雷达对雪晶的衰减较强以及粒子的非Rayleigh散射引起的;云雷达观测可以清楚地识别混合云中的融化层。冷锋云系发展、演变过程及结构非常不均匀:锋面前部,在5～7km之间有一水凝物含量大值区,不断有长大的冰雪晶下落,使云底逐渐下伸,触地后产生间歇性阵性降水;降水过后,5km左右有一相对干层,上部为高层云,下部为散乱的多层云结构;冷锋临近,云层冷区没有水凝物含量大值区,回波强度较弱,暖区2km以下是干冷的东北气流,限制了雨滴通过暖雨过程增长,导致锋面降水强度较小,持续时间短。锋面后部4～7km高度,由于冰雪晶沉降,相对湿度较小,云层分裂成两层云;冷锋过后,出现了较强的降水,这主要是由暖雨过程产生的。  相似文献   

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