共查询到20条相似文献，搜索用时 31 毫秒
1.
Identifying the spatial extent of volcanic ash clouds in the atmosphere and forecasting their direction and speed of movement has important implications for the safety of the aviation industry, community preparedness and disaster response at ground level. Nine regional Volcanic Ash Advisory Centres were established worldwide to detect, track and forecast the movement of volcanic ash clouds and provide advice to en route aircraft and other aviation assets potentially exposed to the hazards of volcanic ash. In the absence of timely ground observations, an ability to promptly detect the presence and distribution of volcanic ash generated by an eruption and predict the spatial and temporal dispersion of the resulting volcanic cloud is critical. This process relies greatly on the heavily manual task of monitoring remotely sensed satellite imagery and estimating the eruption source parameters (e.g. mass loading and plume height) needed to run dispersion models. An approach for automating the quick and efficient processing of next generation satellite imagery (big data) as it is generated, for the presence of volcanic clouds, without any constraint on the meteorological conditions, (i.e. obscuration by meteorological cloud) would be an asset to efforts in this space. An automated statistics and physics-based algorithm, the Automated Probabilistic Eruption Surveillance algorithm is presented here for auto-detecting volcanic clouds in satellite imagery and distinguishing them from meteorological cloud in near real time. Coupled with a gravity current model of early cloud growth, which uses the area of the volcanic cloud as the basis for mass measurements, the mass flux of particles into the volcanic cloud is estimated as a function of time, thus quantitatively characterising the evolution of the eruption, and allowing for rapid estimation of source parameters used in volcanic ash transport and dispersion models.
相似文献2.
毫米波测云雷达的特点及其研究现状与展望 总被引：17，自引：2，他引：15
云在大气的能量分配、辐射传输,尤其是水循环系统中有不可忽视的作用。云探测对云物理、人工影响天气、气候变化和航空航天等领域有重要意义,是大气科学研究的热点之一。尽管目前已经发展了很多种遥感设备对云进行观测(如激光雷达、卫星、云幂仪等),但这些设备无法得到高时空分辨率的云水平和垂直结构,而毫米波雷达是云三维精细结构探测的重要工具。由于毫米波雷达具有更接近小粒子尺度的短波长,因此更适合用来探测弱云,同时毫米波雷达也存在衰减严重的缺点。介绍了毫米波雷达的特点以及其探测小粒子的优势;对比分析了其与新一代多普勒天气雷达、晴空风廓线雷达的差异,得出：毫米波雷达具有高时空分辨率,能够更精确地反映云的垂直和水平结构,比普通天气雷达更适合监测云的变化。概括了国内外毫米波测云雷达的发展现状以及在云物理研究方面的情况,并展望了国内毫米波雷达未来研究的方向。 相似文献
3.
Curtis D. Holder 《Geoforum》2006,37(1):82-93
This paper discusses the hydrological significance of socio-economic practices such as agricultural land use change and forest extraction to communities adjacent to the Sierra de las Minas Biosphere Reserve, Guatemala. Cloud forest hydrology differs from most environments because of the increased frequency of fog interception and fog precipitation. Fog precipitation occurs when intercepted cloud droplets coalesce on foliar and woody surfaces as fog filters through the canopy, and represents a significant proportion of the annual water inputs to cloud forests especially during the dry season. Interception data from this study showed that fog precipitation contributed greater than 7.4% of the hydrological inputs at 2550 m and less than 1% at 2100 m in the Sierra de las Minas. During the dry season fog precipitation contributed 19% of the hydrological inputs to the water budget of the cloud forest. Fog precipitation may be a significant hydrological input to the water resources of the local population. Socio-economic practices such as the conversion of cloud forest to agricultural land may decrease water resources for communities in Guatemala that demand greater quantities of water. 相似文献
4.
5.
雾水的D和18O同位素研究进展 总被引：1，自引：0，他引：1
凝结水的D、18O同位素研究目前主要集中在雾水方面,露水和土壤吸附水的相关研究仍属空白。由于形成时的温度较高,大多数雾水的D、18O同位素较当地雨水富集,但不同类型雾的同位素特征存在差异。平流式海洋雾为单级的蒸发—冷凝封闭循环系统的首次凝结,D、18O同位素较当地雨水显著富集;热带云雾林中的地形雾与降雨同时发生,且水分源于同一云团,δD、δ18O值差异较小;内陆辐射雾因部分水汽源于当地水分的再循环,过量氘和δD、δ18O值高于降雨。目前有少量研究用D、18O同位素指示雾水对植被、地下水和地表径流的补给作用,但以定性分析为主,基于端元混合模型的定量评价极少。露水和土壤吸附水的稳定同位素研究是干旱区凝结水研究的重要方向;D、18O同位素与其它同位素或化学指标的结合有助于促进凝结水生态水文效应的研究进展;短间隔、高密度的长期观测和用于稳定同位素分析的凝结水采样器的设计是需要进一步开展的工作。 相似文献
6.
Winter fog over the Indo-Gangetic Plains: mapping and modelling using remote sensing and GIS 总被引：1，自引：1，他引：0
Arun K. Saraf Ajoy K. Bora Josodhir Das Vineeta Rawat Kanika Sharma Sanjay K. Jain 《Natural Hazards》2011,58(1):199-220
Almost every year in the winter months (December–February), the vast Indo-Gangetic Plain south of the Himalaya is affected
by dense fog. This fog is considered as radiational fog, and sometime it becomes smog (when it mixes with smoke). The typical
meteorological, topographic and increasing pollution conditions over the Indo-Gangetic Plain are perhaps the common contributing
factors for fog formation. In the present study, the North Indian fog has been successfully mapped and analysed using NOAA-AVHRR
satellite data. In the winter seasons of 2005–06, 2006–07 and 2007–08, the fog-affected area has been found to cover about
575,800 km2, 594,100 km2 and 478,000 km2, respectively. Less fog in 2007–08 may be the consequence of high fluctuations in the meteorological parameters like temperature,
relative humidity and wind speed as related to the prevailing synoptic regime for that season. The dissipation and migration
pattern of fog in the study area has also been interpreted on the basis of the analysis of both meteorological and satellite
data. Further analysis of the fog-affected area allowed identifying more fog-prone regions. Analysis of past fog-affected
days and corresponding meteorological conditions enabled us to identify favourable conditions for fog formation viz. air temperature
3–13°C, relative humidity >87%, wind speed <2 m/s and elevation <300 m. Based on the observations of past fog formation and
corresponding governing parameters, fog for few selected days could be predicted in hind-sight and later verified with NOAA
images. 相似文献
7.
被动微波遥感反演地表温度研究进展 总被引：4，自引：0，他引：4
热红外遥感技术在地表温度反演中已经获得了丰厚的果实,反演精度可达到1 K,然而,大气中云雾和尘埃对热红外遥感探测地表温度影响很大,限制了热红外遥感反演地表温度的应用.相反,被动微波遥感受大气干扰小,可穿透云层获取地表辐射信息,并具有全天候、多极化等特点,在地表温度反演中具有独特的优越性.但是微波信号也受多种因素的影响,其反演地表温度的算法目前尚不成熟,有待进一步研究.根据不同微波辐射计特征,系统讨论并评估了被动微波反演地表温度的经验模型、物理模型以及半经验模型及其发展过程,指出目前研究的难点和缺点,为今后相关研究提供参考. 相似文献
8.
In order to study the scale error of low resolution meteorological satellite cloud detection and its impact on the calculation of downlink radiation, cloud detection using high resolution stationary satellite GF-4 data and error analysis were carried out. Firstly, the cloud detection of GF-4 data is carried out by using visible channel threshold method and time series method, and the error of cloud detection results of Himawari-8 and FY-2 (FY-2G, FY-2E) is analyzed based on the results of GF-4 cloud detection.In the study area, FY-2G, FY-2E and Himawari-8 cloud images could distinguish the clouds and clear sky. The main reason for the error was the scale effect produced by different spatial resolution satellites(the differences caused by cloud detection algorithms are not discussed here).Most of the errors occurred in the areas of thin clouds and broken clouds.High resolution data could detect broken clouds, while low resolution data lead to false and missed detection. On this basis, the error of remote sensing calculation of short wave radiation was analyzed,and it was found that the error of the actual cloud amount in the pixel would bring significant error to the estimation of the downward radiation.The relative error of the instantaneous downward radiation in the selected test area was -173.52%, and the maximum relative error of shortwave radiation was -20.20%.The results show that the high resolution stationary satellite data can significantly improve the estimation accuracy of the downlink shortwave radiation in the regions with more broken clouds. 相似文献
9.
利用MODIS和AMSR-E进行积雪制图的比较分析 总被引：21，自引：2，他引：19
MODIS和被动微波辐射计AMSR-E提供了识别积雪的不同方法.MODIS首先计算反映积雪在1.6μm强吸收特性的归一化差值积雪指数NDSI,在剔除卷云的影响后,得到MODIS积雪分布.AMSR-E则根据积雪在微波波段的差异性散射特性识别积雪.通过案例分析比较了MODIS和AMSR-E积雪分布,发现由于云的遮蔽使MODIS积雪分布面积会比实际小,但由于MODIS的空间分辨率很高,得到的积雪边界线轮廓清晰.而微波由于不受云的影响,得到的AMSR-E积雪分布比较符合实际,但积雪的边界线较粗. 相似文献
10.
祁连山区云光学特征的遥感反演与云水资源的分布特征分析 总被引：5，自引：0，他引：5
利用Terra和Aqua卫星上载的MODIS探测器接收资料和祁连山区及周边气象台站6 h降水量资料,应用6S辐射传输模式和Mie模式,针对2002—2005年以来的18次大范围云覆盖的祁连山区,反演了云的光学厚度、云粒子有效半径以及云液态含水量等参数,结合地理信息系统分析了其随海拔高度变化的分布特征及其与地面降雨量的关系.结果表明:祁连山区云的光学厚度、云粒子有效半径以及云液态含水量分布受地形影响具有显著的地域差异,最大值分布在海拔4 300 m以下的山区,是云水资源丰富区和易降水区;云宏观特征参数与地面6 h降水量成正相关关系,产生降水概率较大的云光学厚度在8~20之间,云粒子有效半径在6~12μm之间,云液态含水量在0.04 g·m-3就能产生降水.祁连山区云液态含水量可高达0.15 g·m-3,表明山区云水资源具有很大的开发潜力. 相似文献
11.
Incorporation of cloud- and precipitation-affected radiances from microwave satellite sensors in data assimilation system has a great potential in improving the accuracy of numerical model forecasts over the regions of high impact weather. By employing the multiple scattering radiative transfer model RTTOV-SCATT, all-sky radiance (clear sky and cloudy sky) simulation has been performed for six channel microwave SAPHIR (Sounder for Atmospheric Profiling of Humidity in the Inter-tropics by Radiometry) sensors of Megha-Tropiques (MT) satellite. To investigate the importance of cloud-affected radiance data in severe weather conditions, all-sky radiance simulation is carried out for the severe cyclonic storm ‘Hudhud’ formed over Bay of Bengal. Hydrometeors from NCMRWF unified model (NCUM) forecasts are used as input to the RTTOV model to simulate cloud-affected SAPHIR radiances. Horizontal and vertical distribution of all-sky simulated radiances agrees reasonably well with the SAPHIR observed radiances over cloudy regions during different stages of cyclone development. Simulated brightness temperatures of six SAPHIR channels indicate that the three dimensional humidity structure of tropical cyclone is well represented in all-sky computations. Improved correlation and reduced bias and root mean square error against SAPHIR observations are apparent. Probability distribution functions reveal that all-sky simulations are able to produce the cloud-affected lower brightness temperatures associated with cloudy regions. The density scatter plots infer that all-sky radiances are more consistent with observed radiances. Correlation between different types of hydrometeors and simulated brightness temperatures at respective atmospheric levels highlights the significance of inclusion of scattering effects from different hydrometeors in simulating the cloud-affected radiances in all-sky simulations. The results are promising and suggest that the inclusion of multiple scattering radiative transfer models into data assimilation system can simulate the cloud-affected microwave radiance data which provide detailed information on three dimensional humidity structure of the atmosphere in the presence of cloud hydrometeors. 相似文献
12.
A. B. Struminskii 《Astronomy Reports》2003,47(11):916-924
Solar proton events (SPEs) of 1989–1992 accompanied by ground-level enhancements of the cosmic-ray intensity are analyzed. A diffusive-propagation model can well approximate the solar proton intensity at energies of 84–200 MeV measured on board the GOES-7 satellite during the first 15–20 hours of the development of an SPE, assuming several episodes of proton injection into interplanetary space over some hours. The detection of π0-decay gamma-ray emission during the flares of June 11 and 15, 1991 on board the CGRO and GAMMA-1 space observatories is the sole experimental evidence for the existence of protons with energies >100 MeV near the Sun over such extended times. The number of protons in the source is estimated for various times based on the propagation model. Moreover, this value is in qualitative and quantitative agreement with the number of protons required to generate the observed gamma-ray emission for the June 15, 1991 event (and in qualitative agreement for the June 11, 1991 event). This provides evidence that processes of prolonged trapping and/or acceleration of protons in coronal structures may be possible in other such events. 相似文献
13.
近实时卫星降水反演数据具有覆盖范围广、空间连续性和时效性较强以及开放获取等优势, 是重要的全球性降水资料。针对2021年河南省“7·20”极端暴雨, 基于116个地面气象站观测资料及其空间插值数据, 综合解析了4种GPM近实时卫星降水数据(IMERG early、IMERG late、GSMaP NOW和GSMaP Gauge NOW)对极端强降水事件的表征能力。结果发现:①IMERG early、IMERG late对站网累积雨量的低估程度在20%左右, GSMaP NOW和GSMaP Gauge NOW的高估程度分别达到了约35%和70%, 但2种GSMaP数据更易探测到500 mm以上的累积雨量。②在雨量过程方面, 4种GPM数据对小时降水事件均具有较强的分类辨识能力, 但未捕捉到主要雨峰过程, 定量误差较突出, 与地面降水量之间表现出显著的负相关关系。GPM降水数据对小时雨量低于10 mm的降水事件以高估为主;对于小时雨量超过30mm的降水事件以低估为主, 甚至存在普遍低估。③在空间格局方面, 4种GPM数据的精度指标均具有较强的时间波动性, IMERG数据的空间相关系数和体积临界成功指数等指标总体上优于GSMaP数据, 但后者对较高量级的降水事件更敏感。④2种IMERG数据中, IMERG late相对IMERG early的精度具有较明显改善;2种GSMaP数据中, GSMaP Gauge NOW相对GSMaP NOW提高了对较高量级雨量的探测能力, 但也明显增大了较低量级雨量的定量估计误差。本文研究深化了对GPM近实时卫星降水数据性能的认识, 为完善GPM降水反演算法、提升其对极端降水的监测能力提供了重要反馈信息。 相似文献
14.
The presence of clouds can restrict the potential uses of remote sensing satellite imagery in extracting information and interpretation. Automatic detection and removal of clouds which hide significant information in the image is an important task in remote sensing. Hence, our aim is to detect clouds and restore the missing information in order to make the image ready for further analysis and applications. Due to the difference in nature and appearance, thick and thin clouds are dealt separately. Thick cloud is detected using an efficient Fuzzy C-Means (FCM) clustering algorithm, while thin cloud is detected using a simple region growing technique. In order to reconstruct the missing pixels, we utilize the prior knowledge about the statistics of the specific image class. Kernel principal component analysis (KPCA)-based image model is obtained using a set of training images. Missing area in the image is restored after an iterative projection operation and gradient descent algorithm. In short, an image lying out of the modelled image space is iteratively modified to obtain the restored image and that would be in the image space according to the obtained nonlinear low-dimensional and sparse KPCA image model. To illustrate the performance of the proposed method, a thorough experimental analysis on FORMOSAT multi-spectral images is done using MATLAB platform. When compared to the two recent existing techniques, our proposed method is superior and makes a promising tool for thick and thin cloud removal in multi-spectral satellite images. 相似文献
15.
Hailstorms represent one of the major sources of damage and insurance loss to residential, commercial, and agricultural assets in several parts of Central Europe. However, there is little knowledge of hail risk across Europe beyond local historical damage reports due to the relative rarity of severe hail events and the lack of uniform detection methods. Here we present a new stochastic catalog of hailstorms for Europe. It is based on satellite observations of overshooting cloud tops (OT) that indicate very strong convective updrafts and hail reports from the European Severe Weather Database (ESWD). Historic hail events are defined based on OT detections from satellite infrared brightness temperatures between 2004 and 2011 for the warm seasons (April–September). The satellite-based historical event properties are complemented by hailstone observations from ESWD to stochastically simulate more than 1 million individual events with an event footprint resolution of 10 km. The final hail event catalog presented in this paper is the first one with a spatial event distribution that is based on a single homogeneous observation source over Europe. Areas of high hail probability or hail risk are found over Central and Southern Europe, including mountainous regions such as the Alps or the Pyrenees. Another region of relatively high hail risk is present over central Eastern Europe. 相似文献
16.
基于MODIS的青藏高原季节性积雪去云方法可行性比较研究 总被引：3，自引：2，他引：1
青藏高原地处中纬度地区,季节性积雪分布破碎,地面观测站点稀少,中分辨率成像光谱仪（MODIS）可为该地区提供每日积雪监测数据,然而云是光学遥感最大的影响因素,为研究MODIS每日积雪产品去云方法在青藏高原的适用性,根据原理将去云方法归纳总结为五大类,并对每种方法的“潜在假设”开展分析讨论。结果显示：基于时间连续性的方法适用性强,去云效果明显,上下午积雪连续的平均概率为72.5%,而2~5d的连续积雪的概率为5.6%~43%不等,可靠性差;临近像元法可去除零散分布的云,平均正确率达到95.5%,但去除云量较少;基于高程的去云算法在山区适用性好,而在高原腹地由于坡度较小而错判概率较大;采用被动微波遥感数据进行去云则依赖于微波对云的识别率,往往误差较大;采用数学方法拟合积雪边界在积雪破碎、降雪融雪较快的青藏高原地区,物理意义较弱。通过分析研究表明,青藏高原地区MODIS日积雪产品的去云,需综合多种算法的区域适用性,充分考虑青藏高原地形及积雪本身的特征,逐步完善每日积雪去云工作。 相似文献
17.
Dr. Claire L. Parkinson 《GeoJournal》1989,18(1):9-20
In spite of the importance of sea ice to polar climates, sea ice/climate studies have been limited in the past due to the lack of consistent, long-term, global sea ice records. Satellite passive microwave technology, available since the early 1970s, now provides the potential of generating the desired long-term data sets. With passive microwave data, global sea ice distributions can be mapped on a routine basis every few days, to a spatial resolution on the order of 30 km. The sea ice records generated so far from such satellite data have already been used in many scientific investigations, helping to quantify global sea ice distributions and their seasonal and interannual variations, and to illuminate possible ice/ocean and ice/atmosphere interactions. The results to date augur well for the possibilities once the satellite passive microwave record is long enough to form a true climatic data base. 相似文献
18.
P. W. Webley K. Dean R. Peterson A. Steffke M. Harrild J. Groves 《Natural Hazards》2012,61(2):661-671
Over the last 40 years, there have been numerous volcanic eruptions across the North Pacific (NOPAC) region that posed a potential
threat to both local communities and transcontinental aircraft. The ability to detect these volcanic clouds using satellite
remote sensing and predict their movement by dispersion modeling is a major component of hazard mitigation. The Puff volcanic
ash transport and dispersion model, used by the Alaska Volcano Observatory, was used to illustrate the impact that these volcanic
ash clouds have made across the NOPAC and entire Polar region over the past 40 years. Nearly, 400 separate ash clouds were
analyzed that were either reported or detected to have reached above 6 km (20,000 ft) above sea level, an average of one ash
cloud every 1.25 months. Particular events showed that ash clouds can be tracked from Alaska to Greenland (Crater Peak, Mount
Spurr in 1992), from Kamchatka to Alaska (Kluvicheskoi Volcano in 1994), from Alaska to California (Mount Cleveland Volcano
in 2001) and from multiple events within 1 day (Mount Augustine Volcano in 2006). This study showed the vast number of events
that have impacted this Polar region and how tracking them is useful for hazard mitigation. 相似文献
19.
An environmental model to compute microwave brightness temperatures for downward looking radiometers on board satellite is described. The effects of water vapour, oxygen and clouds on the brightness temperature have been studied for frequencies from 5 to 50 GHz for a standard tropical atmosphere. The effect of look angle on brightness temperture has also been investigated. Based on the model it has been shown that while the radiometers on boardBhaskara at 19·35 and 22·235 GHz are capable of giving the atmospheric water vapour and liquid water contents, the ability to distinguish these quantities is more for the combination of the frequencies 22·235 and 31 GHz. 相似文献
20.
Cloud distribution over East Asia during the summer monsoon season interpreted through satellite pictures 总被引：1，自引：0，他引：1
Dr. T. Asakura 《GeoJournal》1979,3(2):147-152
Summer monsoon clouds over East Asia observed by the meteorological satellite Himawari and ESSA were analyzed in order to shed light on the dynamic climatology of the area during the Baiu season. The mean cloudiness over Monsoon Asia undergoes little change and is nearly 50%, but the monsoon cloud belt varies in time and space in accordance with the seasonal shift of the strongest westerly flow axis at the 500 mb level. The summer monsoon clouds form a belt in which a major amount of water vapor is transported, extending from South China to the Bering Sea. Monsoon rains occur in Japan when the belt of monsoon cloud is over Japan and ends when the cloud belt moves away. 相似文献