precipitation I Flashcards
what are some factors to consider when using a rain gauge?
- height matters because the wind profile changes near the ground
- color matters: dark surfaces heat up and cause evaporation
- wind matters: wind deforms the pressure field around the rain gauges
- methods matter: wind protection, instantaneous measurements and tipping bucket
- location matters: no object should be closet than 2 times its height to the rain gauge
- people matter
- timing matters: frequent measurements keeps evaporation losses low
- technology matters: fails and doesn’t detect errors
- size matters: less inspections if large
what is a lysimeter?
device that records the amount of precipitation an area receives and the amount of water that drains the soil
–> weighing lysimeters can measure the precise amount of water that falls on them
what is the relative humidity equation?
RH= actual vapor pressure/saturation vapor pressure x 100%
what is the dew point?
temperature that you would have to cool air to reach saturation line and cause condensation
what happens when a point is in undersaturated and supersaturated location in the saturation vapor pressure curve?
undersaturated (under line): no cloud
supersaturated (over the line): air is not capable of holding that much water in it so it will condensate (clouds) or rain
what are the two types of uplifts?
- convective uplift: in a small cell, uplift of air until it cools and turns into clouds
- frontal/advective lift: water/air comes from elsewhere, either warmer air pushing upwards or cold air coming from below (pushing warm air up -> cooling)
what is an adiabatic lapse rate? and what are the dry and moist adiabatic lapse rates?
how much colder it gets with increasing height
dry adiabatic lapse rate: 10 degrees per thousand meters
moist adiabatic: 6 degrees per thousand meters
why is the moist adiabatic lapse rate slower than the dry adiabatic lapse rate?
because there is condensation which requires energy
what is orographic precipitation?
driven by height, usually on one side of the mountain
- moist adiabatic lapse rate going up one side and dry on the way down so warmer on the other side
where does it rain the most?
- mountain ranges on the wind side where moist air is pushed against
- coastal regions
- tropics because its warmer so air can hold more vapor
factors in distribution of precipitation?
- temperature
- seasonality
- topography
- distance from ocean
how do raindrops form?
water vapor gas gathers onto tiny airborne particle called a condensation nuclei -> collide with each other and grow -> once they are heavy enough, they fall
what are the airborne particles in rain droplets from?
dust, aerosols or salt
what are the types of precipitation?
- rain (0.5 - 5 mm diameter)
- drizzle (0.5 mm diameter)
- showers (vary in intensity)
- snow (when water vapor turns to ice without turning into liquid first)
- hail (when water droplets freeze in high, very cold clouds -> get bigger as they are coated with more layers or banging into each other)
where do we need more rain gauges?
- mountainous regions (orographic effects)
- tropics (small scale convective precipitation)
