Tropical storm structure revealed by stereoscopic photographs from Skylab

A stereo pair of photographs taken by Skylab astronauts over Hurricane Ellen, September 19, 1973, resulted in the first stereo analysis over tropical storms. This pair is also the first evidence to indicate the existence of “supercell” convection in developing tropical storms. The photos are analyzed to determine the cloud top structure of the intense convection occurring in one quadrant of the storm. This type of supercell convection in tropical storms has recently been correlated with subsequent rapid deepening. The stereo analysis revealed that a circular cloud feature over the storm center was a dome which protruded 3–4 km above the undisturbed cirrus clouds. The center of the dome was capped by smaller scale convective turrets which protruded another 1–2 km above the dome. The existence of shear induced waves in the cloud tops is shown with wave amplitude ranging from 150–300 m and wave lengths ranging from 2–4 km. The existence of gravity waves at the cloud tops is also shown with wave amplitudes of 500–600 m and wavelengths of 10–12 km.     

Cloudiness over the Eastern Equatorial Pacific for summer 1983 from geostationary satellite data

The extraordinary El-Nino event of 1982–83 started to fade out in the late spring of 1983. However the sea surface temperature of the Eastern Equatorial Pacific still remained warmer than normal in the following summer. To investigate the characteristics of this late transition phase of the 1982–83 El-Nino, the GOES-West satellite data of July and August of 1983 are analyzed. The outgoing longwave radiation field and the distribution of cloudiness, which was derived by using a new threshold technique, are obtained. The longwave radiation field is compared to monthly average climatic indices commonly used at the Climatic Analysis Center. The results of cloud analysis showed some interesting features during the decaying phase of the 1982–83 El-Nino. The diurnal variation of cloudiness indicates that total cloud amounts decrease from 8 GMT to 20 GMT over most of the area. This overall study demonstrates preliminary results of the International Satellite Cloud Climatology Project of the World Climate Research Program.     

A comprehensive statistical study of cloud base height using ceilometer over western India

A comprehensive statistical analysis of the cloud base height (CBH) measured by ground-based Vaisala ceilometer (CL31) has been performed to study different layers of the cloud in the lower troposphere up to 7.5?km height over Ahmedabad, western India during 2014 and 2015. The total observations (～69%) of cloud by using ceilometer show annual cloud occurrence frequency of around 64%. Seasonal variation of CBH and cloud occurrence frequency reveal that the maximum/minimum cloud cover is found during southwest (SW) Indian summer monsoon/pre-monsoon season. Three CBHs (CBH1, CBH2, and CBH3) are presented in monsoon period due to high cloud occurrence, and two CBHs (CBH1 and CBH2) are observed in other seasons due to low cloud occurrence by ceilometer over the observational site. The CBH1 (～100–2000?m) and CBH2 (500–3000?m) are observed during SW monsoon and summer season, respectively. The CBH3 is occurred usually in SW monsoon season. Moreover, the cloud cover during the day and night time shows that the occurrence of cloud is more frequent in daytime than nighttime during pre-monsoon and post-monsoon season. The statistical analysis of cloud with ground-based observations is also performed in this study that may be useful for the development/improvement of regional weather and climate models to reduce the uncertainty in the prediction.     

基于对抗和迁移学习的灾害天气卫星云图分类

针对卫星云图中的灾害天气数据存在严重不平衡问题,提出一个结合生成对抗学习（GAN）和迁移学习（TL）的卷积神经网络（CNN）框架以解决上述问题进而提高基于卫星云图的灾害天气分类精度。该框架主要包含基于GAN的数据均衡化模块和基于迁移学习的CNN分类模块。上述2个模块分别从数据和算法层面解决数据的类间不平衡问题,分别得到一个相对均衡的数据集和一个可在不同类别数据上提取相对均衡特征的分类模型,最终实现对卫星云图的分类,提高其中灾害天气的卫星云图类别分类准确率。与此同时所提方法在自建的大规模卫星云图数据上进行了测试,消融性和综合实验结果证明了所提数据均衡方法和迁移学习方法是有效的,且所提框架模型对各个灾害天气类别的分类精度都有显著提升。      

Climatological characteristics of cloud cover over Europe from meteorological satellites

Climatological characteristics of cloud cover - means, variances, structure functions - previously computed for five years are compared with the results of a new test cloud cover data set of one year period. The effects on the cloud field of the Alps, the Carpathian basin and the land-ocean interface, further the seasonal changes of the general circulation are well reflected. The new test data set is based upon digitized data of one morning as well as one afternoon picture per day. Therefore some results are also obtained of the cloud cover variations during the day.     

A study of the onset of the Indian monsoon as seen from GEOS I.O. satellite

Wind fields deduced from cloud motions are extracted by an optical method from GOES I.O. pictures during FGGE : 1–10 February 1979, 16 May – 7 July 1979. These winds are compared with in-situ measurements with dropsondes. The onset of the monsoon is described from the point of view of winds and cloud cover.     

Ionospheric storm due to solar Coronal mass ejection in September 2017 over the Brazilian and African longitudes

Coronal mass ejection (CME) occurs when there is an abrupt release of a large amount of solar plasma, and this cloud of plasma released by the Sun has an intrinsic magnetic field. In addition, CMEs often follow solar flares (SF). The CME cloud travels outward from the Sun to the interplanetary medium and eventually hits the Earth’s system. One of the most significant aspects of space weather is the ionospheric response due to SF or CME. The direction of the interplanetary magnetic field, solar wind speed, and the number of particles are relevant parameters of the CME when it hits the Earth’s system. A geomagnetic storm is most geo-efficient when the plasma cloud has an interplanetary magnetic field southward and it is accompanied by an increase in the solar wind speed and particle number density. We investigated the ionospheric response (F-region) in the Brazilian and African sectors during a geomagnetic storm event on September 07–10, 2017, using magnetometer and GPS-TEC networks data. Positive ionospheric disturbances are observed in the VTEC during the disturbed period (September 07–08, 2017) over the Brazilian and African sectors. Also, two latitudinal chains of GPS-TEC stations from the equatorial region to low latitudes in the East and West Brazilian sectors and another chain in the East African sector are used to investigate the storm time behavior of the equatorial ionization anomaly (EIA). We noted that the EIA was disturbed in the American and African sectors during the main phase of the geomagnetic storm. Also, the Brazilian sector was more disturbed than the African sector.     

Estimation of the radiation budget sensitivity to cloud variations

At the estimation of the sensitivity three variable parameters must be taken into account: cloud amount, cloud albedo and cloud-top height. Cloud albedo is considered to be a parameter that varies according to a given formula. The effective cloud amount and outgoing longwave flux from cloudy atmosphere have been computed on the basis of the satellite measured planetary albedo and the outgoing flux data, using additional information about planetary albedo and the outgoing longwave flux in clear-sky conditions. The latter quantities have been computed from the mean contemporary climatic data. The estimation of the sensitivity is carried out in two cases: if the effective cloud amount and cloud-top height variations are independent or not. The corresponding statistical tests are presented.     

Cloud statistics using VAS

Statistics of cloud characteristics over North America during winter of 1985–86 have been calculated. The frequency of cloud cover with associated heights and infrared attenuation were charted using the CO₂ channel radiometric data from the geostationary VISSR Atmospheric Sounder (VAS). Cloud top pressures were determined from the ratio of VAS CO₂ channel radiances in a radiative transfer equation formulation. Cloud emissivities were then calculated from infrared window channel observations. CO₂ technique derived height and emissivity assignments have been found to be reliable in all cloud types, including thin cirrus clouds where other techniques have been inconsistent. Observations during November 1985 revealed that 25% of the United States was covered with thin clouds (radiative attenuation was less than 80%), 50% was covered with thick opaque clouds, and 25% had clear sky conditions. Geographical distribution of cloud cover over the United States for the winter of 1985–86 shows a strong latitudinal dependence. Cirrus reports in frequencies of 15% in the south increase to 30% in the northwest.     

Satellite measurements of cloud reflectance and optical thickness

We have computed the cloud reflectance and the optical thickness with the aid of atmospheric models from the first eleven months (April 1970 – February 1971) of Backscattered Ultraviolet (BUV) data over the pacific ocean. Both the cloud and the optical thickness are derived from the 380 nm channel by assuming that the entire IFOV (200 Km.) is filled by stratiform clouds. Our analysis show a large variability in the cloud reflectance in both the intertropic conversion zone (ITCZ) and the high latitudes. We also find that for 90% of the time in tropics, the clouds have optical thickness < 10. Our analysis of clouds with optical thickness between 10 and 20 show that in tropics the minimum frequency coincides with the dry zone at 2.5°s and the maximum frequency for clouds of optical thickness 10–20 is greater in summer than in winter and irrespective of the season, 50% of the time the clouds have optical thickness less than 13.     

Generalised variational assimilation of cloud-affected brightness temperature using simulated hyper-spectral atmospheric infrared sounder data

Assimilated channel brightness temperature data from infrared sounders accounting for cloud effects have a positive effect on weather forecasting, especially in weather-sensitive areas. When cloud effects are included, the channel brightness temperature deviations follow a non-Gaussian distribution. However, classical variational data assimilation follows a Gaussian distribution. When processing the cloud-affected brightness temperature, useful data are lost through the cloud detection process, thus assimilating some channel brightness temperatures with weight function peaks above the cloud top. Furthermore, strict quality control of brightness temperature removes outliers. By adopting the generalised variational assimilation method, which assumes that errors follow a non-Gaussian distribution, this paper assimilates the cloud-affected brightness temperature using simulated data for the hyper-spectral atmospheric infrared sounder (AIRS). A channel set is formed by dynamically selecting AIRS channels. The experiments for retrieving temperature and humidity data demonstrate that the generalised variational assimilated cloud-affected brightness temperature method performs better than the classical method.     

面向战斗机云作战的构造型仿真平台架构

随着大数据、云计算、物联网、移动互联网等信息技术的迅猛发展与广泛应用,新的作战模式不断涌现,以任务分布式指控流程为核心的云作战成为一种全新的跨域全维作战样式。在分析作战云与云作战特征的基础上,结合传统作战仿真流程提出了云作战体系仿真流程,并提出了云作战构造型仿真平台框架的总体方案设计与系统功能设计。通过云作战构造型仿真示例,对比了传统作战样式与云作战样式的观察-调整-决策-行动（OODA）循环,结果表明,云作战样式能够有效缩短OODA循环时间。      

Volcanism on Venus: Connecting link?

New observational data obtained from Venera-11 through Venera-14 and Pioneer-Venus data (1979–1982) call for searching for the interdependences of the phenomena occurring on this planet. It is proposed that the presence of electrical discharges in the near-surface layers of the atmosphere, the variable density of the above-cloud submicron haze, and the peculiarities of the cloud microphysics can be tied by a hypothesis that volcanic eruptions occur on Venus.     

Complex principal component analysis of the outgoing longwave radiation observed by meteosat during summer from 1983 to 1985

We have applied Complex Principal Component (CPC) analysis to METEOSAT ISCCP B2 data (3 hours resolution) for the IR atmospheric window channel and the Water Vapor (WV) band at 6.5 microns. CPC analysis of such a data set not only reveals the principal features of fluctuation of cloud cover for the region as a whole, but it also is useful for identifying traveling and standing waves over the African Tropical band. Applied to the whole METEOSAT field, CPC analysis describes both diurnal and seasonal fluctuations for the two channels with good stability from year to year. In the African Tropical band, CPC analysis applied in restricted spectral bands (3–4 days and 4–5 days) reveals the existence of traveling waves at particular areas of West Africa with substantial differences between the years 1983 and 84–85. Results of 84–85 are in very good agreement with those of previous studies using conventional meteorological data in 1979. This analysis reveals also the existence of a standing oscillation over Central Africa with a period around 3.5 days and good stability over the three years.     

Statistical approaches to cloud classification

For the determination of clouds from satellite data there exist in general more unknown parameters than independent observations. If the bispectral observations are used from the geostationary satellites in the solar (VIS-channel) and in the infrared (IR-channel) range to derive cloud parameters, information is needed whether a pixel radiance is from a cloud free or a cloudy scene. Statistical methods are applied to derive those informations. Various proposed statistical methods are discussed.The histogram analysis developed at the University of Cologne is described in detail: bispectral (two-dimensional) histograms are partitioned into clusters. Cloud cover results are shown. A comparison is given between the results of the histogram analysis, threshold methods (VIS- and IR threshold separately and both combined) and the spatial coherence method developed by Coakly and Bretherton. The cloud cover varies in this example by a factor of two depending on the definition of the threshold between cloud free and cloudy pixels. It is further shown that after a cluster analysis of a two-dimensional histogram the derived cloud cover is not as sensitive to the threshold as for a threshold method. The methods which are discussed here are those proposed for the International Satellite Cloud Climatology Project (ISCCP). The results are from the pilot study of the ISCCP.     

The morphology of fair weather cumulus cloud fields as remotely-sensed from satellites and some applications

The morphology of fair weather Cumulus cloud field over several ocean areas distributed globally has been studied using LANDSAT data. Distribution functions of cloud size, spacing, perimeter and other relevant parameters have been derived, as well as their correlations and moments.Examples of distribution functions of cloud size, cloud spacing and fractal dimension of the cloud fields over oceanic areas are given and applied to several problem in Cu convection.     

Estimation of cloud top height and effective cloud cover from infrared satellite soundings

The paper deals with a new method for simultaneous determination of cloud top height and effective cloud cover, using infrared radiance data of satellite-borne instruments. These cloud properties derived from the Selective Chopper Radiometer on the Nimbus 5 satellite are compared with nearly simultaneous observations by radiosondes and with satellite images. Encouraging results for Central-Europe during January, April, July, August and October 1974, as well as numerical simulations indicate that the method proposed here, would be useful also for global application. Another advantage of the described procedure are the small amount of computing time, and that no other data are required than 3 of infrared channel values, for each sounded spot.     

正态云模型雾化性质统计分析

对于超熵较大情况下的正态云模型,说明了云模型雾化过程.通过统计分析云滴离散的整体趋势,说明超熵增大过程中,云滴整体趋于离散.通过分析各论域区间内云滴离散趋势,说明靠近概念核心的云滴的离散速度相对缓慢.归纳云模型雾化性质:在超熵取值持续增大的过程中(HeEn/3),正态云表示的概念的论域范围持续增大,呈雾化状态,但靠近概念核心的论域区间内的云滴不失数量优势.雾化性质适用于建模偏离正态分布、缺乏共识的定量数据,期望表示概念语义值核心,熵描述概念语义的离散程度,超熵表示各种语义的共识程度,扩展了云模型知识表示的应用范围.     

Monitoring global surface temperature variations using cloud data sets

One of the by-products of cloud data sets such as that of the International Satellite Cloud Climatology Project (ISCCP) is global information on longwave window brightness temperatures for clear skies. These brightness temperatures depend mainly on the actual surface temperature with only a slight dependence on atmospheric water vapor. Thus, it may be possible to monitor long-term temperature variations using such data. The current methods for such monitoring depend on conventional surface observations and are subject to uncertainties due to inadequate spatial sampling. To test this idea monthly clear sky brightness temperatures from the six-year Nimbus-7 cloud data set are analyzed and compared to conventional estimates of surface temperature fluctuations.     

Remote sensing of clouds

The extraction of information on cloud cover from present-day multispectral satellite images poses a challenge to the remote sensing specialist. When approached one pixel at a time, the derived cloud cover parameters are inherently nonunique. More information is needed than is available in the radiances from each channel of an isolated pixel. The required additional information can be obtained for each scene, however, by analyzing the distribution of pixels in the multi-dimensional space of channel radiances. The cluster patterns in this space yield statistical information that points to the most likely solution for that scene. The geostationary and polar orbiting meteorological satellites all have, at a minimum, a solar reflection channel in the visible spectrum and a thermal infrared channel in the 8–12 micron window. With the information from the cluster patterns and application of the equations of radiative transfer, the measurements in those channels will yield cloud cover fraction, optical thickness, and cloud-top temperature for an assumed microphysical model of the cloud layer. Additional channels, such as the 3.7 micron channel on the AVHRR of the polar orbiting meteorological satellites, will will yield information on the microphysical model—e.g., distinguishing small liquid liquid droplets (typical of low level clouds) from large ice particles (typical of cirrus and the tops of cumulonimbus). New channels to be included in future satellite missions will provide information on cloud height, independent of temperature, and on a particle size and thermodynamic phase, independently of each other. A proposed STS mission using lidar will pave the way for the use of active sensors that will provide more precise information on cloud height and probe the structure of thin cirrus and the top layer of of the thicker cloud.