Chapter 5 - Atmospheric Moisture Flashcards
How does a sling psychrometer work?
Consists of 2 thermometers. 1 has cotton wick around bulb that is saturated w water. Other has no covering, just measures air temp. The thermometers are mounted to pivoting device and slung through air. If air is unsaturated, water evaporates from Wet Bulb (temp falls). Difference btwn Wet & Dry bulb is WB Depression.
What is the instrument used to measure humidity?
Primarily the Psychrometer (sling or aspirated), although a Hair Hygrometer may also be used.
What is the difference between diabatic & adiabatic process?
Diabatic: Energy is added or removed from a system (Ex: water placed on stove). Note 2nd LoTD. Diabatic processes are often responsible for Fog formation.
Adiabatic: Temperature changes but no heat is added or removed. Note 1st LoTD. Adiabatic often responsible for Cloud formation.
What is ‘environmental lapse rate’?
ELR is the rate at which the ambient temperature decreases with height.
How is the ‘environmental lapse rate’ different form ‘adiabatic cooling rate’?
Dry Adiabatic Cooling Rate: Rate at which rising, unsaturated air cools
(1.0 C/100 m)
Wet ACR: aka Saturated ACR, rate at which saturated air cools (0.5 C/100 m)
ELR: rate at which ambient temperature decreases with height
What is the ‘heat index’ (aka ‘apparent temperature’)?
A measure of apparent (or felt) temperature used for warm conditions, incorporating temperature and humidity.
What is the ‘wind chill factor’?
An index of apparent (felt) temperature used for cold conditions that incorporates air temperature and wind speed.
What is Radiation Fog and how is it formed?
Radiation Fog aka ‘ground fog’ (and sometimes Tule fog) are near the surface and can create hazardous conditions for drivers. They often settle in areas of low elevation.
RF is caused Diabaticaly, by the nighttime loss of Long Wave Radiation which causes cooling to the dew point.
What is Advection Fog and how is it formed?
Advection Fog is associated with high winds. Is the fog that often covers London. Can be very thick.
AF forms Diabatically, when warm/moist air moves over cooler surface. Heat transfers downward, causing cooling which can lead to AF. Also can form over water when warm & cold current are in close proximity.
What is Upslope Fog and how is it formed?
When air flows along a sloping surface, it expands as cools as it moves upward (ex. over Rocky Mountains).
UF is formed Adiabatically.
