Weather Tutorial Page 5c

Aviation Weather

Tutorial

5(c). Clouds

Cross-section of a thunderstorm

In general, the following is a list of observations that a pilot can make regarding stable/unstable air and clouds.

Dust devils rising from the Earth's surface are a sign of dry, unstable air rising to a considerable height above. Get above the unstable air or the ride will be bumpy.
Clouds quickly towering upward accompanied by showers often indicate turbulence beneath and through the cloud. Fly around these clouds.
Thunderstorms are definite signs of turbulent, unstable air. Leave plenty of room between your flight path and these storm clouds.
Fair weather cumulus clouds will often have turbulence beneath and within the clouds. The tops of the clouds are usually where the approximate upper limit of convection is occurring. This means that flight above these clouds is normally smooth.
As an aircraft ascends (climbs) and the temperature uniformly and rapidly decreases, this indicates unstable air.
As an aircraft ascends (climbs) and the temperature remains unchanged, this indicates stable air.
Suspect unstable air if the air near the surface is warm and moist.

See the chart below for a brief description of each cloud type and its effects on flight.

**Cloud Types and Flight Effects Chart**
Cloud Type	Effects on Flight
cirrus	no significant icing; turbulence in dense, banded cirrus
cirrocumulus	may contain highly supercooled water droplets resulting in some turbulence and icing
cirrostratus	little if any icing; no turbulence; restricted visibility
altocumulus	small amounts of icing; some turbulence
altostratus	moderate amounts of icing; little to no turbulence; restricted sunlight
altocumulus castellanus	unstable air; rough turbulence with some icing
standing lenticular altocumulus clouds	very strong turbulence
nimbostratus	very little turbulence; can pose serious icing problems if temperatures are near or below freezing
stratus	little or no turbulence; hazardous icing conditions if temperatures are near or below freezing; when associated with fog or precipitation can create conditions of greatly reduced visibility
stratocumulus	some turbulence; possible icing at subfreezing temperatures; ceiling and visibility better than with low stratus clouds
cumulus	shallow layer of unstable air will give some turbulence, but no significant icing
towering cumulus	very strong turbulence with rain showers; some clear icing above freezing level
cumulonimbus	unstable air throughout; violent turbulence; strong possibility for icing

NASA Research
NASA works with the National Oceanographic and Atmospheric Administration (NOAA) to develop and deploy satellites that have proven to be critical for monitoring and forecasting the weather. These systems include geostationary operational environmental satellites (GOES) for short-range warning and "now-casting", and polar-orbiting satellites for longer-term forecasting. Both types of satellite are necessary for providing a complete global weather monitoring system.

GOES satellites orbit at about 35,800 km (22,300 miles) above the Earth, high enough to allow the satellites a full-disc view of the Earth. Because they stay above a fixed spot on the surface, they provide a constant vigil for the atmospheric "triggers" for severe weather conditions such as tornadoes, flash floods, hailstorms, and hurricanes. When these conditions develop the GOES satellites are able to monitor storm development and track their movements. GOES satellite imagery is also used to estimate rainfall during the thunderstorms and hurricanes for flash flood warnings, as well as estimates of snowfall accumulations and overall extent of snow cover. GOES observations have proven helpful in monitoring dust storms, volcano eruptions, and even the spread of forest fires.

TIROR Satellite Complementing the geostationary satellites are polar-orbiting satellites known as Advanced Television Infrared Observation Satellite (TIROS-N or ATN), constantly circling the Earth in an almost north-south orbit, passing close to both poles. The orbits are circular, with an altitude between 830 (morning orbit) and 870 (afternoon orbit) km, and are sun synchronous. The polar orbiters are able to monitor the entire Earth, tracking atmospheric variables and providing atmospheric data and cloud images. They track weather conditions that eventually affect the weather and climate of the United States. The satellites provide visible and infrared radiometer data that are used for imaging purposes, radiation measurements, and temperature profiles. The polar orbiters' ultraviolet sensors also provide ozone levels in the atmosphere and are able to detect the "ozone hole" over Antarctica during mid-September to mid-November.