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Topic: Cloud base


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In the News (Thu 18 Apr 19)

  
  S'COOL Cloud Types Tutorial
The names used for the clouds are based on three factors: the altitude at which the cloud occurs, the shape of the cloud, and whether the cloud is producing precipitation.
Clouds with a base between 2,000 and 6,000 meters are mid-level clouds.
Cloud cover tends to be mostly cloudy to overcast, but distinct cloud pieces are visible, in contrast to the uniform and flat character of stratus clouds.
asd-www.larc.nasa.gov /SCOOL/tutorial/clouds/cloudtypes_transcript.html   (1482 words)

  
  Cloud - Wikipedia, the free encyclopedia
A cloud is a visible mass of condensation droplets or ice crystals suspended in the atmosphere above the surface of the Earth or another planetary body.
Clouds reflect all visible wavelengths of light equally and are usually white, but they can appear grey or even fl if they are so thick or dense that sunlight cannot pass through.
Clouds form when the invisible water vapour in the air condenses into visible water droplets or ice crystals.
en.wikipedia.org /wiki/Cloud   (1443 words)

  
 Cloud base - Wikipedia, the free encyclopedia
The Cloud base is the lowest portion of a cloud.
A ceilometer is used to measure the height of the cloud base.
Knowing the height of the cloud base is important in aviation as aircraft flying via Visual Flight Rules (VFR) must maintain a minimum distance from clouds and a minimum range of flight visibility [1].
en.wikipedia.org /wiki/Cloud_base   (113 words)

  
 ISCCP cloud types
Cloud amount for lower-level clouds is only that fraction of the area actually observed to be covered by clouds at that level.
If the cloud is optically thick, it radiates like a flbody so that the observed emission is equivalent to the actual temperature at the top (if the upper portion of the cloud is tenuous, then the radiating level will be within the cloud).
It is determined from the cloud base pressure and an atmospheric profile of temperature versus pressure.
isccp.giss.nasa.gov /cloudtypes.html   (903 words)

  
 Cloud liquid water content, drop sizes, and number of droplets
For convective clouds, the LWC increases with height (up to the level of glaciation) and it is higher when the cloud base temperature is higher.
The cloud base is assumed to be at 1 km (2).
The radius of cloud droplets is r (microns), the effective optical radius optically is r', N is the number of droplets per cubic centimetre, L is the liquid water content of the cloud (g/m
www-das.uwyo.edu /~geerts/cwx/notes/chap08/moist_cloud.html   (1090 words)

  
 NWS Louisville: Cloud Classifications and Characteristics
Altocumulus clouds with some vertical extent may denote the presence of elevated instability, especially in the morning, which could become boundary-layer based and be released into deep convection during the afternoon or evening.
Stratus clouds are uniform and flat, producing a gray layer of cloud cover which may be precipitation-free or may cause periods of light precipitation or drizzle.
clouds are hybrids of layered stratus and cellular cumulus, i.e., individual cloud elements, characteristic of cumulo type clouds, clumped together in a continuous distribution, characteristic of strato type clouds.
www.crh.noaa.gov /lmk/soo/docu/cloud_classifications.php   (1044 words)

  
 NSDL: Measuring Cloud Heights
Clouds can be classified by both their appearance and by the altitudes at which they occur.
Based on the time it takes the scattered and reflected pulse to return to the surface, the height of a cloud base can be accurately determined (Fig.
If the base of a low level cloud is generally found between 0-2 km, the base of a middle level cloud between 2-7 km, and the base of a high level cloud between 7-18 km, determine the type of clouds detected in the MPL image you selected.
avc.comm.nsdlib.org /cgi-bin/wiki_grade_interface.pl?Measuring_Cloud_Heights   (651 words)

  
 Educational Outreach >> For Teachers >> Glossary   (Site not responding. Last check: 2007-11-06)
A light is projected upward onto the cloud base; the reflected light is detected by a photocell, and the height is determined by triangulation (the unique point where three line meet).
a local region of clearing skies or reduced cloud cover, indicating an intrusion of drier air; often seen as a bright area with higher cloud bases on the west or southwest side of a wall cloud.
a funnel cloud or (rarely) a small, relatively weak tornado that can develop from a small shower or thunderstorm when the air aloft is unusually cold (hence the name).
k12.ocs.ou.edu /teachers/glossary/c.html   (1598 words)

  
 [No title]   (Site not responding. Last check: 2007-11-06)
How the heights of the base and top of the icing derived -------------------------------------------------------- Once the icing potential is calculated for each RUC column, the base and top of the icing layer are determined by simply finding the height of the lowest and highest grid points which have icing indicated.
Each RUC model grid point is assigned the cloud base height which is equivalent to the lowest cloud base height reported by any surface station within an allowable radius of influence.
It is important to note that a cloud base height will only be assigned if a cloud is indicated at grid point from the combination of satellite and surface observations.
www.rap.ucar.edu /icing/fip/all_bases_and_tops.explain   (730 words)

  
 Cloud at AllExperts
Cloud droplets tend to scatter light very efficiently, so that the intensity of the solar radiation decreases with depth into the cloud, hence the grey or even sometimes dark appearance of the clouds at their base.
Thin clouds may appear to have acquired the color of their environment or background, and clouds illuminated by non-white light, such as during sunrise or sunset, may be colored accordingly.
As a cloud matures, the droplets may combine to produce larger droplets, which may themselves combine to form droplets large enough to fall as rain.
en.allexperts.com /e/c/cl/cloud.htm   (1919 words)

  
 [No title]   (Site not responding. Last check: 2007-11-06)
These clouds over the Antarctic interior are found to be optically thin, usually with tg less than 1, in contrast to coastal clouds, which usually have tg greater than 20.
The optical thicknesses and base heights inferred from the emission spectra agree qualitatively with the visual reports of the weather observers, in that the optically thicker clouds are usually reported as nimbostratus and clouds with the highest retrieved bases are reported as cirrus or cirrostratus.
Stratus clouds tend to be reported as low; altostratus and altocumulus are intermediate in height.
www-k12.atmos.washington.edu /~sgwgroup/Maheshetal2001_metadata.txt   (745 words)

  
 SWA******* GADS Cloud Model *******SWA
For a T106-based GADS, the AGM cloud model (Emmitt and Wood, 1995) is based on the Slingo cloud parameterization scheme (Slingo, 1987).
This estimate is based upon the recently reported analysis of two years of HIRS data (Menzel et al., 1992), the cirrus climatology derived from SAGE data by Woodbury and McCormick (1986) and the Nimbus-7 global cloud climatology (Stowe et al., 1989).
All opaque cloud backscatter values are preset in the AGM to be 1x10-06 m-1 sr-1 for 9 um and 1.86x10-5 for 2 um.
www.swa.com /ALD/lsm/GADScloud.html   (1171 words)

  
 CLOUD TYPES
The funnel cloud is the visible portion of a tornado produced from clouds.
These clouds are located 75 to 90 kilometers above the surface and are rarely seen due to their extremely low moisture density.
The rapid lifting of humid air causes the cloud base to form at a lower elevation.
www.theweatherprediction.com /clouds   (705 words)

  
 Clouds Theme Page by Jim Cornish
The level at which condensation and cloud formation begins is defined by the flat cloud base, and its height will depend upon the humidity of the rising air.
Clouds are classified into a system that uses Latin words to describe the appearance of clouds as seen by an observer on the ground.
High-level clouds are typically thin and white in appearance, but can appear in a magnificent array of colours when the Sun is low on the horizon.
www.cdli.ca /CITE/cloudstypes.htm   (580 words)

  
 [No title]
The CVS parameters consist of the number of cloud layers, base and top heights and layer thickness for each layer, and the index of the levels where the cloud tops and bases are located to give the temperature and humidity at the cloud boundaries and within.
The RH threshold was derived based on comparisons of rawinsonde humidity profiles with aircraft observations of cloud top and base heights (Poore et al 1995) and surface estimates of cloud base heights (WR95).
Based on direct comparisons with radar and ceilometer data from Atlantic Stratocumulus Transition Experiment (ASTEX), marine boundary layer cloud base heights are underestimated by 200-300 m in the RAOBS results (Wang et al.
www.atd.ucar.edu /homes/junhong/paper/clim-cvs-rev.doc   (4662 words)

  
 Glossary
Frequently used as a synonym for wall cloud, although it actually is a generally circular ring of cloud surrounding the upper portion of a wall cloud.
Motions in the tail cloud are toward the wall cloud with rapid updraft at the junction of tail and wall cloud.
Tornadoes and funnel clouds are usually pendant from wall clouds or directly from the thunderstorm base, within a few miles to the southwest of the precipitation shaft.
movies.warnerbros.com /twister/cmp/glossary.html   (1359 words)

  
 Ask John   (Site not responding. Last check: 2007-11-06)
Base reflectivity is the echos being produced at the base of the clouds, or very near the base of the clouds.
Base Reflectivity is more inclined to pick up virga (precip that is not reaching the ground).
Or when you look up at the sky and see clouds, the bottom of the cloud is the base of the cloud or cloud base.
www.johndee.com /discus/messages/2080/2235.html   (302 words)

  
 Glossary
The cumulus cloud is the first stage of a developing thunderstorm.
A visible column of rain and/or hail falling from a cloud base.
Tornadoes and funnel clouds are usually pendant from wall clouds or directly from the thunderstorm base, within a few miles to the southwest of the precipitation shaft.
www.movies.warnerbrothers.com /twister/cmp/glossary.html   (1359 words)

  
 Estimating DLR Based on Cloud, Moisture, and Temperature Parameters
As for clouds with large optical thicknesses (see stratus, nimbostratus, and deep convective), we artificially model increased geometrical thickness of a cloud layer with increasing optical depth through an empirical formula that allows the base of these clouds to slope down to 1 km (for nimbostratus and deep convective) and to the surface (for stratus).
Tropical clouds are relatively consistent, especially in terms of base height, hence it might be wiser to assume cloud-base altitudes from climatalogical data.
Cloud fractional coverage at numerous layers would be needed, as would the respective optical depths and pressure levels of these clouds.
www.icess.ucsb.edu /esrg/ess_sum97/Students_ESS.1999/abatzoglou/report_abatzoglou.htm   (5174 words)

  
 Cloud Base Altitude
In this study, a cloud base echo is defined by the first signal gradient limited by the data acquisition system.
To obtain representative cloud base estimates, all shots in a volume scan are inspected for cloud echoes and the lowest cloud echo defines the cloud base altitude.
Figure 12 presents an RHI with a distribution profile of the first cloud return altitudes and an estimated cloud base which is measured within the resolution of the RHI scan.
lidar.ssec.wisc.edu /papers/akp_thes/node10.htm   (817 words)

  
 Overview
If no such cloud base is found then higher levels of the model are tested for a buoyant layer, mid-level convection being initiated from the lowest such level.
As horizontal resolution increases, parts of convective cloud systems may become better resolved (for example the stratiform regions) and be represented through an interaction between the dynamics and cloud scheme of the model.
The closure ensures that the amount of moisture which is vertically advected through cloud base by the large-scale ascent is fully available for generation of convective cells.
www.ecmwf.int /research/ifsdocs/PHYSICS/Chap5_Convection6.html   (1375 words)

  
 Wall Clouds: a lowering in the cloud base   (Site not responding. Last check: 2007-11-06)
Researchers have shown that wall clouds probably develop when some rain-cooled air is pulled upward, along with the more buoyant air, as the strengthening updraft attempts to replace ever-growing volumes of rising air.
Looking to the northwest, we see a detached scud cloud which had just emerged from the precipitation area and was moving rapidly southwestward (from right to left).
About 5 minutes later, the scud cloud entered the updraft area and was lifted into the cloud base.
www.palmod.uni-bremen.de /~gerrit/svetlana/WW2010-CD/files/wwhlpr/wall_clo.htm   (140 words)

  
 Wall Clouds and other Lowerings
The wall cloud is defined as an isolated cloud lowering attached to the rain free base.
The wall cloud is usually to the rear (generally south or southwest) of the visible precipitation area.
Shelf clouds tend to slope downward away from the precipitation while wall clouds tend to slope upward awayfrom the precipitation area.
www.tsgc.utexas.edu /stars/tscloud.html   (521 words)

  
 Clouds Theme Page by Jim Cornish
The level at which condensation and cloud formation begins is defined by the flat cloud base, and its height will depend upon the humidity of the rising air.
Clouds are classified into a system that uses Latin words to describe the appearance of clouds as seen by an observer on the ground.
High-level clouds are typically thin and white in appearance, but can appear in a magnificent array of colours when the Sun is low on the horizon.
www.stemnet.nf.ca /CITE/cloudstypes.htm   (580 words)

  
 MetLinkInternational Observation detail
Cloud becoming broken after dark then more continuous again after midnight with light to moderate rain from early hours this morning.
Previous 24 hours: Variable cloud amounts during yesterday, then cloud increasing after dark with a period of mainly moderate rain, sometimes heavy, moving in from W at 22:00GMT, becoming showery from 01:00GMT, and dying out by dawn.
Cloud persisting overnight and an overcast start this morning, then cloud breaking in the past hour or so RH max 94% min 73%.
www.metlink.org /data/obsdetail.php?ID=377   (4611 words)

  
 Wall Clouds: a lowering in the cloud base
About 5 minutes later, the scud cloud entered the updraft area and was lifted into the cloud base.
It was beneath the tail cloud and not the wall cloud!
Finally, tornadic wall clouds are characterized by strong, warm inflow from the southeast and east, usually much stronger inflow than that with non-tornadic storms.
ww2010.atmos.uiuc.edu /(Gh)/guides/mtr/svr/comp/wall/dvlp.rxml   (322 words)

  
 Cloud Types: common cloud classifications
For example, cloud names containing the prefix "cirr-", as in cirrus clouds, are located at high levels while cloud names with the prefix "alto-", as in altostratus, are found at middle levels.
High-level clouds are typically thin and white in appearance, but can appear in a magnificent array of colors when the sun is low on the horizon.
The bases of mid-level clouds typically appear between 6,500 to 20,000 feet (2,000 to 6,000 meters).
www.gfdl.noaa.gov /~io/WEATHER/clouds.html   (338 words)

  
 The cloud classification system (general)
These clouds are brighter and less fragmented in appearance due to their distance from the ground and the higher composition of ice crystals.
The cloud seems to be moving rapidly but because of its development at the rear actually progresses very slowly in the direction of the wind at that level.
The heights of cumulonimbus clouds vary depending on the conditions but are typically of the order of tens of kilometres from the base to the cloud tops.
www.australiasevereweather.com /techniques/moreadv/class.htm   (5094 words)

  
 [No title]   (Site not responding. Last check: 2007-11-06)
How the heights of the base and top of the icing derived -------------------------------------------------------- Once the icing potential is calculated for each AK-ETA column, the base and top of the icing layer are determined by simply finding the height of the lowest and highest grid points which have icing indicated.
How the cloud base height field is derived ------------------------------------------ The cloud base height field is based solely upon reported cloud base heights from surface observations (METARs) across Alaksa and Western and Canada.
Each AK-ETA model grid point is assigned the cloud base height which is equivalent to the lowest cloud base height reported by any surface station within the closest concentric circle, as described in "THE FIP-AK CONCEPT".
www.rap.ucar.edu /icing/cipak/all_bases_and_tops.explain   (697 words)

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