Satellite

Water Vapour (6.8 µm)

Moisture or water vapour is present in the troposphere at different levels. This Water vapour absorbs and re-radiates electromagnetic radiation in the absorption band 6 -7 µm. This property is used for detecting presence of moisture in the middle and upper levels (600 -300 hPa) of the atmosphere. Dark region or black portion in WV imagery indicates an area of high temperature and the dryness of upper and middle atmosphere and bright region or white portion in WV imagery depicts an area of low temperature and moist upper and middle atmosphere or presence of tall/high cloud. WV image also provides information about the swirling middle tropospheric wind patterns and jet streams.

Summary

Sensitive to moisture

Shows variations in upper tropospheric moisture

Typically senses upper half of troposphere; higher in moist and lower in dry regions

Atmospheric wave structures are very apparent; short waves readily seen

Tracking features in sequences of water vapour images useful for inferring atmospheric motion (particularly moisture)