moist air Flashcards
moist air
dry air + water vapour
find pressure of a volume of water vapour
Rv x T (as water vapour have diff. states)
how to find pressure of moist air using partial pressures
- pressure of moist air = pressure of dry air + vapour pressure.
- the total pressure of moist air is equal to the sum of partial pressures of the components
mixing ratio (w) equation
- Mv/Md
- mass of vapour over mass of dry air
- g kg-1
- the lower the no, the drier it is
specific humidity (q) equation
- Mv/Md + Mv
- mass of vapour over mass of air
- q=w eventually. as Md is too low to make a difference
define saturation
condensation=evaporation
RH equation
w/ws x100 or e/es x100
how do we find the amount of vapour
w=ws x Td
true or false:
low Td indicates low moisture content in the air
true. when there’s low moisture content (w or e), there is a lower chance for this vapour to form dew. therefore a lower temp is needed for the vapour to liquify
there are two types of moist adiabatic process: saturated adiabatic process and pseudo-adiabatic process. compare these two processes
- saturated: when the condensate stay inside the parcel. heat is not lost hence process is reversible
- pseudo:when the condensate (liquid water) falls out of the parcel after saturation. this is because condensate carries heat energy so falling out means an exchange of energy with the environment –> not adiabatic
true or false:
when calculating the moist adiabatic lapse rate, we have to take account on the temperature
true.
temp affect the amount of water carried(warm air carries more water). the water content affect the latent heat produced during condensation hence affect the rate of cooling as parcel goes on. (more latent heat, lower cooling rate)
compare LCL and Td
LCL: level which air must cool at a higher altitude (lower pressure) to be saturated
Td: Temperature to which air must cool at constant pressure (as the air temp) to be saturated
