Earth from Space - Image Information

Photo #: ISS016-E-27426 Date: Feb. 2008
Geographic Region: AFRICA
Feature: PAN-LARGE THUNDERSTORM ANVIL

Cumulonimbus Cloud over Africa
Perhaps the most impressive of cloud formations, cumulonimbus (from the Latin for "pile" and "rain cloud") clouds form due to vigorous convection (rising and overturning) of warm, moist, and unstable air. Surface air is warmed by the Sun-heated ground surface and rises; if sufficient atmospheric moisture is present, water droplets will condense as the air mass encounters cooler air at higher altitudes. The air mass itself also expands and cools as it rises due to decreasing atmospheric pressure, a process known as adiabatic cooling. This type of convection is common in tropical latitudes year-round and during the summer season at higher latitudes.

As water in the rising air mass condenses and changes from a gas to a liquid state, it releases energy to its surroundings, further heating the surrounding air and leading to more convection and rising of the cloud mass to higher altitudes. This leads to the characteristic vertical "towers" associated with cumulonimbus clouds, an excellent example of which is visible in this astronaut photograph. If enough moisture is present to condense and heat the cloud mass through several convective cycles, a tower can rise to altitudes of approximately 10 kilometers at high latitudes and to 20 kilometers in the tropics before encountering a region of the atmosphere known as the tropopause--the boundary between the troposphere and the stratosphere.

The tropopause is characterized by a strong temperature inversion. Beyond the tropopause, the air no longer gets colder as altitude increases. The tropopause halts further upward motion of the cloud mass. The cloud tops flatten and spread into an anvil shape, as illustrated by this astronaut photograph. The photo was taken from a viewpoint that was at an angle from the vertical, rather than looking straight down towards the Earth's surface. The image, taken while the International Space Station was located over western Africa near the Senegal-Mali border, shows a fully formed anvil cloud with numerous smaller cumulonimbus towers rising near it. The high energy levels of these storm systems typically make them hazardous due to associated heavy precipitation, lightning, high wind speeds and possible tornadoes.

Images:	All Available Images Low-Resolution 154k
Mission:	ISS016
Roll - Frame:	E - 27426
Geographical Name:	AFRICA
Features:	PAN-LARGE THUNDERSTORM ANVIL
Center Lat x Lon:	N x E
Film Exposure:		N=Normal exposure, U=Under exposed, O=Over exposed, F=out of Focus
Percentage of Cloud Cover-CLDP:	50
Camera::	E4
Camera Tilt:	HO	LO=Low Oblique, HO=High Oblique, NV=Near Vertical
Camera Focal Length:	400
Nadir to Photo Center Direction:		The direction from the nadir to the center point, N=North, S=South, E=East, W=West
Stereo?:		Y=Yes there is an adjacent picture of the same area, N=No there isn't
Orbit Number:	761
Date:	20080205	YYYYMMDD
Time:	151024	GMT HHMMSS
Nadir Lat:	13.5N	Latitude of suborbital point of spacecraft
Nadir Lon:	12W	Longitude of suborbital point of spacecraft
Sun Azimuth:	228	Clockwise angle in degrees from north to the sun measured at the nadir point
Space Craft Altitude:	179	nautical miles
Sun Elevation:	47	Angle in degrees between the horizon and the sun, measured at the nadir point
Land Views:
Water Views:
Atmosphere Views:	CLOUDS
Man Made Views:
City Views:
Photo is not associated with any sequences

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