Precipitation

what are the four conditions that must be present for the production of precipitation

1. condensation onto a nuclei

2. cooling of atmosphere

3. growth of water droplets

4. sufficient density of droplets

is rainfall considered totally pure

NO

why is precipitation not wholly pure

many pollutants have been found in rainfall

examples of pollutants in rainfall

metals, organics, suspended soilds

what is a side effect of air pollution emissions

acid rain

rain is considered naturally _____

acidic

why is rain naturally acidic

atmospheric CO₂ dissolves to form carbonic acid

what are the main contributors of acid rain

sulfur and nitrogen compounds

what is the most widely used tool to measure rainfall

tipping bucket rain gauge

what is the main feature of reference gauge design to minimize or control

the effect of wind on the catch

what is the most serious environmental factor for gauges at low rainfall intensities

wind

how can someone minimize the effect of wind on the gauge catchment

installing the gauges into a pit

what are 3 common errors when using tipping buckets

1. having an above ground gauge (wind induced under catch)

2. setting up under HIGH winds

3. bucket missing rainfall due to splashout

what is the most overlooked and significant error in rainfall measurement

high wind = 20% under catch

what are measurement devices (4)

1. tipping bucket

2. weighing precipitation gauge

3. optical gauge

4. Acoustic gauge

what does a weighing precipitation gauge measure

total precipitation from rain, snow, sleet and hail

what measuring device is accurate across all precipitation types

weighing precipitation gauge

what measuring device eliminates mechanical wear and drift because it has NO moving parts

optical gauge

which measuring device measures the impact of individual raindrops

acoustic gauge

what are four things to consider when placing a gauge to reduce error

1. must be free of obstacles (at least 2x the distance from anything)

2. must be vertical

3. higher off the ground = higher winds = more error

4. wind screens reduce turbulence

what is the Isohyetal method for rainfall variability

average of rain is weighted according to each proportion of space each isohyet occupies in a basin

what is the arithmetic average for calculating rainfall variability

summing the rainfall measurements from all rain gauges in a region and dividing by the total number of stations

what is the snow water equivalent (SWE)

depth of water that would result if you melted the entire snowpack instantly

what is the snow pillow a device for measuring

snowpack and converting the SWE values to meters

what is a snow pillow made up of

about 3 meters of antifreeze solution