Topic 2: Atmospheric Water Flashcards
what is shortwave radiation expressed as
Qs or K
what is longwave radiation expressed as
QL or L
what does albedo replace in the net radiation equation?
outgoing shortwave
explain sensible heat
QH: energy flows from warm to cold; via conduction or advection/convection
explain latent heat
QE: energy transfer with phase change, consumed during evaporation, released during condensation
physics of evaporation
- -evaporation does not require the surface to be at saturation, what matters is vertical gradient of vapour pressure
- -difference between two vapour pressures can be positive (evap occurring) or negative (deposition) or zero (neither occurring in a net sense)
- -if surface is snow or ice latent heat requires latent heat of fusion
- -evaporation rates are high when lots of energy available and atmosphere is dry and windy
evaporation pan
measures the change in water height daily
lysimeter
measure the change in weight of soil or snow sample
water balance
can work well for small controlled basins. may also need to know about storage and precipitation. limitations: uncertainty in overall budget
energy balance
theoretical calculation
hydrological model: potential evapotranspiration
penman-montheith equation
three ways to think of ET
actual evapotranspiration ET
potential evapotranspiration ET0
crop evapotranspiration CT
what is PET
potential evapotranspiration; the rate at which ET would occur from a large area completely unlimited with supply of water
impact of soil moisture
- -directly reduces available moisture at surface
- -decreases moisture in plants, increasing surface resistance
- -a function of soil type
5 ways to describe humidity
- vapour pressure (Pa or mbar)
- mixing ratio (g H2O per kg dry air)
- specific humidity (g H2O per kg air)
- absolute humidity (g H2O per m3)
- Relative humidity (%)
does warm or cold air have lesser capacity to hold water vapour?
colder air
what is Dalton’s Law
total pressure of a mixture of gases= sum of pressure of constituents
actual vapour pressure vs saturation vapour pressure
actual: pressure resulting from the water molecules
saturation: partial pressure of the water molecules when air is saturated
list the 4 precipitation processes
- orographic uplift
- frontal uplift
- forced convergence
- buoyant convection
adiabatic processes
adiabatic cooling as air rises- no heat transfer with the environment.
dry adiabatic lapse rate vs warm adiabatic lapse rate
dry is faster -9.8C/km
moist -6C/km
how does a warm front work
buoyancy driven, warm wet air will rise over cold dry air
how does a cold front work
cold air will wedge under warm air, causing more severe weather
what is temperature advection
primary process that cyclones and anticyclones intensify, amplifies the shortwave making divergence and convergence stronger.
