Glossary of Some Meteorological Terms

Meteorological Terms	Explanation
Absolute Maximum	Highest value of the parameter ever recorded.
Absolute Minimum	Lowest value of the parameter ever recorded.
Air Temperature	Temperature read on a thermometer which is exposed to the air in a position sheltered from direct solar radiation.
Amount of Cloud	Percentage of the sky covered by any type of cloud.
Bright Sunshine	Period during which solar radiation reaches sufficient intensity to cast distinct shadows.
Day with Fog	A day with fog reported at any time during the day.
Day with Lightning	A day with lightning reported at any time during the day.
Day with Strong Monsoon Signal	A day with Strong Monsoon Signal issued at any time during the day.
Day with Thunderstorm	A day with thunderstorm reported at any time during the day.
Day with Tropical Cyclone Warning Signals	A day with Tropical Cyclone Warning Signals issued at any time during the day.
Dew point Temperature	Temperature to which air must be cooled at constant pressure and water vapor content in order that it shall be saturated with respect to water.
Diurnal Range	Difference between the daily maximum and minimum readings.
Duration of Rainfall	Duration of rainfall in an hour is the sum of the duration of precipitation recorded in an hour to the nearest 5 minutes. Duration for other periods is the sum of the hourly duration to the nearest whole hour.
Evaporation	Amount of water evaporated into the atmosphere from a free water surface.
Global Solar Radiation	Sum of direct solar radiation and diffuse sky radiation received by unit horizontal surface.
Maximum Air Temperature	Instantaneous maximum reading of the air temperature recorded in a specified period.
Maximum Gust	Peak value of wind speed recorded in a specified period.
Mean Daily Global Solar Radiation	Average of the daily values of total global solar radiation in a specified period.
Mean Daily Maximum Air Temperature	Average of the daily values of maximum air temperature in a specified period.
Mean Daily Minimum Air Temperature	Average of the daily values of minimum air temperature in a specified period.
Minimum Air Temperature	Instantaneous minimum reading of the air temperature recorded in a specified period.
Percentage of Possible Sunshine	Percentage ratio of actual amount of bright sunshine to the total possible between sunrise and sunset.
Potential Evapotranspiration	Maximum quantity of water capable of being lost, as water vapor, by a continuous stretch of vegetation covering the whole ground and well supplied with water.
Pressure	Atmospheric pressure reduced to mean sea level.
Prevailing Wind Direction	Wind direction which occurs more frequently than any other in a specified period.
Rainfall	Thickness of the layer of water which accumulates on a horizontal surface, as the result of precipitation, in the absence of infiltration or evaporation.
Reduced Visibility	Visibility below 8 kilometres, when there is no fog, mist, or precipitation.
Relative Humidity	Percentage ration of the actual vapour pressure in the air to the saturation vapour pressure with respect to water at the same temperature and pressure.
Sea Surface Temperature	Temperature of the water of the surface layer of the sea.
Soil Temperature	Temperature observed in the interior of the soil at different depths.
Thunderstorm	One or more sudden electrical discharges manifested by a flash of light(lightning) and a sharp or rumbling sound (thunder). It is regarded to have ceased when no further thunder is heard in 10-15 minutes after the last audible thunder.
Wet-bulb Temperature	Temperature read on a thermometer whose bulb is covered by a film of water or ice and which is exposed to the air in a position sheltered from direct solar radiation.
Wind Speed	Horizontal movement of air per unit time.