precipitation II Flashcards
what is the equation for probability of occurence?
probability (P) = 1/T(return period) x 100
what is the equation for return period?
T=100/P
what is the probability that an 100 year storm occurs at least once in 100 years?
63%
what are the stages of snow metamorphosis?
snow (fresh)
névé (max 1 year)
— no longer snow—
firn (more than 1 year)
ice (multiple years)
what are 8 special characteristics of snow?
- mainly in northern hemisphere
- modifies energy and moisture fluxes
- albedo is high
- insulator
- reduces energy exchange between surface and atmosphere
- positive feedback, making air colder
- snowpack acts like soil
- changes structure quickly
what are snowfall measurements?
- depth of snowfall from one event
- depth of snow cover accumulated on the ground
- snow water equivalent
- timing and duration of snow cover on the ground
how to measure snow water equivalent?
- weighing a snow core
- snow pillow: measure changes of pressure in air cushion
why are snow and energy tighly related?
- snow requires energy to become hydrologically active
- sublimination may be significant
- albedo of snow within forests is low thus changes in forest cover can have strong effects on large scale albedo
how do we estimate snow melt rates?
- hard to do
- often based on simple temperature measurements (degree-day methods)
how does fast melting of snow during rainy conditions work?
- water vapor condenses at cold snow surface, releasing high amounts of latent heat
- condensed water infiltrates into snowpack and distributes energy by conduction of sensible heat
- after the water cooled to 0 degrees, it freezes, releasing more latent heat
how does the melting of snow under sunny and warm spring conditions work?
** advection is the main component
1. after the first patch of snow disappears, bare ground heats up (albedo)
2. warm spots deliver heat and humid air (high evaporation over wet soil) to the snow patches
3. condensation leads to accelerated ripening of the remaining snow
