PPL » Meteorology » Temperature and Heat Exchange Processes
8.8 Temperature and Heat Exchange Processes
8.8.2 Outline the measurement of surface air temperature in New Zealand (as reported in aviation observations), and relate that to actual temperatures experienced above a sealed or grass runway.
The air temperature at an aerodrome is measured using a thermometer that is housed in a box called a Stevenson screen.
This box is constructed from wooden slats, double-sided and painted matte white to reduce the effects of scattered radiations from nearby buildings and objects.
The opening of the screen is sited to ensure that the sun is never allowed to shine directly on the instruments housed inside it.
It is also arranged that the thermometers are as close as possible to 1.5 m above the ground, and that the ground within 8 m of the screen consists of grassed lawn.
All this is aimed at ensuring that the temperatures measured are as close as possible to a standard that can then be used for comparison between observing stations.
The temperature on an aerodrome will often be higher than that recorded, due to direct solar radiation (insolation) and radiation from runways, taxiways, etc.
8.8.4 Define solar and terrestrial radiation.