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188 Cards in this Set

  • Front
  • Back
process by which liquid water is tranformed into water vapor and is transferred fromt he ground to the air
Two types of evaporation

direct transfer from open water surface
plants extract water from the soil through roots, use it, eject as vapor into the atmosphere through th stomata on their leaves
Three atmospheric conditions effecting evapotransipiration avaliable
2. wind speed
3. atmoshperhic humidity
Energy avalible for for evaporation needs to have
more incoming than outgoing energy
Can evaporation occur during the night?
most important factor in evapotranspiration
what is a moisture graident
rate of change in moisture amount as we move up from the Earth's surface
Evaporation will increase if...
1. decrease humidity
2. incrase wind
Potential Evapotranspiration
measure of water lost from a farm pond or city reservoir, water used by plants in a field
Actual Evapotranspiration
when water is not avaliable
Example of actual evapotranspiration
rural surfaces in the summer or autumn
cause of actual evapotranspiration
plants cant move water fast enough so the soil dries and plants wilt
is potential or actual evapotranspiration less?
actual evapotranspiration
how do we keep actual close to potential in the NC summers?
does an urban setting evaporate at a potential or actual rate?
potential or not at all
after it rains, the urban area ET's at a potential rate and then it no longer evaporates
-energy goes into surface heating instead of evaporation
why are cities warmer
because use their energy in surface heating (only use potential evaporation)
which area of NC has the greatest amount of evaporation?
coastal plain
which area has the least amount of evaporation in NC?
Hofmann forest on evaporation?
coastal area with rates similar to piedmont (Chapel Hill)
which month has the most water loss?
which months have the least water loss?
December and january
when is humidity highest in NC?
Humidity is effected by two things?
1. Dew point temperature
2. Relative Humidity
upper limit to the amount of moisture the air can hol da t a particular temperature
what happens if the atmosphere exceeds the staturation point?
air condense into water vapor and back to liquid water
Dew point
temperature to which the air must be cooled without change in mositure content for saturation to occur
Dew Point (simple definition)
amount of water vapor in the air
relative humidity
ratio of amount of mositure that the air is holding to that which it could hold (how close air is to saturation point)
what do public forcasts use for measuring relative humidity
temperature and humidity
what time of day is relative humidity the highest
what time is relative humidity the lowest
mid day
what time does relative humidity rise again
dew point is at its maximum in what season?
what area of NC has highest dew point
Cape hatteras (becuase its near water)
is there great variablity in Dew point over NC
why are we a humid state?
because of land and ocean water
our humidity is similar to that of
formed whenever air is cooled to our below dew point
-assoicated with verticle movements in the atmosphere (unless fog)
tiny drops of water suspended in the atmosphere
how far is visiblity in fog
1 KM (.62 miles)
how far is visiblity in heavy fog?
.25 miles
how far is visibility in mist?
more than 1 km
Radiative fog
if suface temperature goes below dew point fog forms
what type of fog is most common in NC?
radiative fog
when does radiative fog begin to form
soon after nightfall and gets thicker and eeper through the night
what evaporates the fog?
solar radiation
how long does radiative fog usually last?
rarely past noon
Advection fog
warm moist airstream blows over a cooler surface
-energy comes over air cooling it
-if cooled below dew point, fog forms
when is advection fog most common?
in winter
which geographic region gets the least fog?
coast (cape hatteras)
-turbulent winds
Charlottes fog conditions
-same as rest of piedmont
-few radiative fogs through the year
-advective fog in winter
what effects fog frequency?
ex. Ashville in vally: gets fog
radiative fog occurs most often when?
in the summer
Evaporative Fog
calm evening over water or a very wet land surface
-air temperature drops faster than that of water
when temperature drops how is evaporative fog effected?
it increases
how does the evaporative fog dissappear?
drops move to dryer air, and air becomes unsaturated
-fog goes away
stratus cloud
low level horizontal
cirrus cloud
higher and wispy horizontal
mid-level clouds (stratus or cumulus)
formation of clouds
rising air cools, if reaches dew point, clouds form
4 air movements effecting cloud formation
1.Orographic Uplift
2.Convcection Uplift
3.Cycloic Uplift
4.Frontal Uplift
orographic uplift
air froced to rise
what is the cause of orographic uplift
NC mountains
rainshadow of mountains creates
a dry side and lee side
Rocky Mountains
definate lee and dry side
App Mountains
different wind patterns create no rain shadow
driest place in the state
Ashville Basin
Rocky mountains have what type of clouds
verticle cumulus
what area in NC has the best Orographic uplift
app mountains but all areas have some form
convection uplift
closely related to seasons, air pressure differences and temperature
what season does convection uplift occur in most
summer (cloudless)
how does a convection uplift occur?
-day goes on and solar energy is abosbed at the ground
-ground creates convection current going up
-small cumulus clouds develop
-get bigger (cumulonimbus and storm)
-evening ground cools, clouds vanish
air convergence
inward spiraling air streams that squash air in center causing a stratus cloud
cyclonic uplift
caused by air convergence, inward spiraling air strams that squash air in center causing a stratus cloud
Frontal Uplift
two airstrams of different temps slide toether meet at weater front
-warm front rises over cold
which two uplifts cause rainy weather?
on average how much of the state is covered during most of the year?
which season has the least precipitation and the most sunshine?
how does it rain
rain drop has to be big enough to fall through rising air on the way to the ground
what increases the speed of rain drops
-size (bigger it is the faster it falls)
stratus clouds give what type of rain
light rain/drizzle
cumulonimbus clouds give what type of rain
big drops because need to get down from a higher altitude
-evaporation occurs at rain falls through dry atmosphere
shafts of light that form as rain falls but evaporates
precipitation is measured by
rain days
how many inches of rain does the piedmont normally get a year?
how many inches do the mountains normally get in a year?
80" in the mountains
wettest areas are areas with
orographic precipitation
the coast in terms of precipitation is
-wetter than piedmont
which areas are generally wettest in NC
west and east
which season is the wettest for the coastal plain
summer (wilmington wettest)
is there a huge difference between seasons in terms of precipitation
which season is wettest
summer, especially in coast
which season is the driest
rain day
day with .01 or more of precipitation
how many days of 3 does NC on average get rain
1 of 3
what season has the most rain
what season has the least rain
top layer of cloud is freezing, middle is not, and bottom is freezing, falls as ice
occurs if their is a thick cold layer
cold bottom layer
mix of snow, sleet, rain, freezing rain
-clouds and ground below freezing
-middle above freezing
most coomon form of frozen precipitation
cloud seeding
silver iodid/dry ice crystals in air droplets would grow
-must have cloud
precipitation augumentation
cloud seeding
why is it hard for NC to get rain in the summer
Bermuda high pressure
can we cloud seed without clouds?
if we have a light rain and gentle wooded slope how much rain is absorbed into the soil?
if we have a thunderstorm and a steep slope how much rain is absorbed into the soil?
none, runoff
what three things effect soil absorption
1. vegetation
2. type of soil
3. slope
Deep Drainage
water draining from bottom of the soil
does deep drainage occur faster than water absorption?
Field Capacity
amount in which soil can hold
what three things effect field capacity
type, depth, tillage
when is evapotranspiration low and and rainfall high?
early in the year when atmosphere is near capacity
wilting point
water content so small that neither plants nor atmosphere could extract more water
what season does the wilting point occur in?
does NC stay at field capacity?
when is the best time to irrigate?
late in the evening, or just before dawn
collection of water on top of impermiable rock
water table
top of layer
is the water table effected by one storm?
no, by wet seasons where water table rises
subsurface runoff
where the water goes during a dry spell
where we extract groundwater
where must the bottom of the well be to collect the groundwater?
below the water table
which season is the water table the highest?
what season is the water table the lowest?
end of summer
base flow
slow subsurface flow
where does the base flow go
down the water table, into the spring or stream
when does the base flow reach its maximum
in the winter and early spring
when is the base flow at its minimum
flood flow
rapid direct surface runoff that occurs only during/immediatly after a rain (excess of a base flow)
flood flow occurs most during which season
winter (more than summer)
is flood flow dangerous
damed river
do high or low clouds move faster?
what changes wind direction
-amount of friction
-amount of surface air
surface roughness
depends on local topograhy and number, size, and distribution of obstacles
if you increase surface roughness..
-wind slows
-wind twists
the most common wind direction for NC is
southwest winds (direction from which the wind is blowing)
is a southwest wind warm or cool?
warm and moist
which seasons in NC has a SW wind?
spring, and summer
which wind occurs during the winter
northernly (NW/NE)
during fall which wind is most prevelent
is an easternly wind common?
what is a factor in wind speed
what season has the fastest wind speed
late winter, early spring
which seasons have the slowest average wind speed?
late summer, early fall
ashville is known for what problem in wind
greatest seasonal difference from other areas of NC
what time during the day is wind heavier?
why is the day more windy than night?
hot and cold regions create wind
why is wind higher near the ocean?
smooth water friction creates faster wind tahn rough land
why does cape hatteras have a faster wind speed then most other coastal areas
because measurement is closer to the shore (ocean speed)
do mountains or valleys have a higher wind speed
mountain peeks
how often are there calm conditions in NC?
10% of the time
what times of year of has the most calm conditions?
late summer, and fall
what time of year has the least calm conditions
peak gust speed
highest 5 second average deteced within the hour
does peak gust find the maximum wind speed
no, because most wind gusts last less then a second
its difficult to stand in what wind speed?
25 miles per hour
its dangerous for some people (young and old) to be out in what wind speed?
30 miles per hour
year of first flight
kitty hawk
air flows
in response to horizontal differences in pressure
joins places with equal pressure
-goes from high to low
high pressure
-clockwise air flow
cyclonic storms
low pressure
-air flows counter clockwise directions
is the wind higher if the isobars are closer or farther apart?
global belt of high pressure
30 degrees north to 30 degrees south
what state is in the global belt of high pressure
equatorial trough
low pressure in between the global belt of high pressure
low pressure found in what areas
more around 60 degrees than the poles
why does NC have the westerlies
because low and high pressure is to the north and the south
high pressure
cold areas
low pressure
warm areas
general circulation of the atmosphere
set of currents near the ocean surface
what are the three factors in general circulation of the atmosphere?
temperature, pressure, and winds
Gulf Stream
warm northward parralel to our southern coast
how does the Gulf stream effect the winter in NC
increases cloudiness
Labrador Current
decreases cloudiness
does the Labrador Current effect us
not very much
Nor'esaterners are caused by what
interactions between gulf streams and labrador currents
cyclonic storms
30 degrees N to 30 degrees south
is NC near tropics
yes, but we dont have tropical weather
what is different in NC than in tropics
we have hot and cold seasons, and rain throughout the year
when were we close to the pole temperatures
13,000 years ago