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The cloud top (or the top of the cloud) is the highest altitude of the visible portion of the cloud. It is traditionally expressed either in metres above the Earth (or planetary) surface, or as the corresponding pressure level in hectopascal (hPa, equivalent to the traditional but now obsolete millibar). ==Measurement== The cloud top is where the snow, rain and sleet come from. Cloud top height can be estimated from the ground by triangulation. However, this is often inconvenient as this is practically feasible only for isolated clouds in full view of (and some horizontal distance away from) the observers. Ground-based radars can be used to derive this cloud property (see this (paper ) for a comparison of this approach to a satellite-based method). An alternative (but also more expensive) approach is to acquire airborne observations either visually or using specific instruments such as a lidar. This technique is very appropriate to characterize individual clouds (and specifically to control or evaluate the accuracy of other methods) but becomes unmanageable to repetitively monitor clouds over large areas (see this (paper ) for an example using this approach). Cloud top height may be derived from satellite measurements, either through stereophotogrammetry (using pairs of images acquired at different observation angles) or by converting temperature measurements into estimations of height. An example of the stereo technique using the Multi-angle Imaging SpectroRadiometer (MISR) instrument can be found (here ), and using the Along Track Scanning Radiometer instruments (ATSR-1, ATSR-2 and AATSR) (here ). An example of the estimation of cloud top height from temperature measurements is available from (this paper ). Cloud top pressure can also be used as an indicator of cloud top height.〔(【引用サイトリンク】title=Cloud Parameter Definitions And Measurement Methods )〕 The Cooperative Institute for Meteorological Satellite Studies (CIMSS) provides real-time cloud top pressure maps of the conterminous United States derived from data obtained from the GOES 11 and GOES 12 satellites.〔(【引用サイトリンク】title=Cloud Top Pressure (GOES 11/12) )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cloud top」の詳細全文を読む スポンサード リンク
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