precipitation I

Question 1

what are some factors to consider when using a rain gauge?

Answer 1

• 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

Question 2

what is a lysimeter?

Answer 2

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

Question 3

what is the relative humidity equation?

Answer 3

RH= actual vapor pressure/saturation vapor pressure x 100%

Question 4

what is the dew point?

Answer 4

temperature that you would have to cool air to reach saturation line and cause condensation

Question 5

what happens when a point is in undersaturated and supersaturated location in the saturation vapor pressure curve?

Answer 5

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

Question 6

what are the two types of uplifts?

Answer 6

• 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)

Question 7

what is an adiabatic lapse rate? and what are the dry and moist adiabatic lapse rates?

Answer 7

how much colder it gets with increasing height
dry adiabatic lapse rate: 10 degrees per thousand meters
moist adiabatic: 6 degrees per thousand meters

Question 8

why is the moist adiabatic lapse rate slower than the dry adiabatic lapse rate?

Answer 8

because there is condensation which requires energy

Question 9

what is orographic precipitation?

Answer 9

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

Question 10

where does it rain the most?

Answer 10

• mountain ranges on the wind side where moist air is pushed against
• coastal regions
• tropics because its warmer so air can hold more vapor

Question 11

factors in distribution of precipitation?

Answer 11

• temperature
• seasonality
• topography
• distance from ocean

Question 12

how do raindrops form?

Answer 12

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

Question 13

what are the airborne particles in rain droplets from?

Answer 13

dust, aerosols or salt

Question 14

what are the types of precipitation?

Answer 14

• 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)

Question 15

where do we need more rain gauges?

Answer 15

• mountainous regions (orographic effects)
• tropics (small scale convective precipitation)

Question 16

what are methods of spatial interpolation?

Answer 16

• arithmetic averages
• thiessen method -> polygons assigned to every point that is closest to the point
• isohyets: contour lines of equal rainfall depth
• kriging: computerized isohyet map

Question 17

what is a rainfall hyetograph?

Answer 17

graphical representation of the distribution of rainfall over time