Appendix A: Glossary

APPENDIX A

GLOSSARY

ACTUAL TIME OF OBSERVATION For METAR reports, it is the time the last element of

the report is observed or evaluated. For SPECI reports, it is the time that the criteria for a SPECI

were met or noted.

ADIABATIC The word applied in the science of thermodynamics to a process during which no

heat is communicated to or withdrawn from the body or system concerned. Adiabatic changes of

atmospheric temperatures are those that occur only in consequence of compression or expansion

accompanying an increase or a decrease of atmospheric pressure.

AIRCRAFT MISHAP An inclusive term to denote the occurrence of an aircraft accident or

incident.

ALTIMETER SETTING Pressure of the reporting station converted in order to produce a

reading on altimeters of field elevation at 10 feet above the runway (normal installation height of

the altimeter). Altimeter settings are given in inches of mercury and represent sea level pressure.

ATMOSPHERIC PRESSURE The force exerted by the weight of the atmosphere from the

level of measurement to its outer limits.

AUGMENTED REPORT A meteorological report prepared by an automated surface weather

observing system for transmission with certified weather observers signed on to the system to

add information to the report.

AUTOMATED REPORT A meteorological report prepared by an automated surface weather

observing system for transmission, and with no certified weather observers signed on to the

system.

BLOWING DUST Dust raised by the wind to moderate heights above the ground and

restricting horizontal visibility to less than seven miles. If visibility reduced to between 5/8 and

5/16 then a duststorm; if less than 5/16, a severe duststorm.

BLOWING SAND Sand raised by the wind to moderate heights above the ground and

restricting horizontal visibility to less than seven miles. If visibility reduced to between 5/8 and

5/16 then a Sandstorm; if less than 5/16, a severe Sandstorm.

BLOWING SNOW Snow particles raised and stirred violently by the wind to moderate or great

heights. Visibility is poor (six miles or less) and the sky may become obscured when the

particles are raised to great heights.

BLOWING SPRAY Spray raised in such quantities as to reduce the visibility at eye level (6

feet on shore, 33 feet at sea) to six miles or less.

GLOSSARY A-1