Chapter 9 Wind: Small Scale and Local Systems Flashcards
what is the microscale?
diameter: < few meters
lasts: seconds-few minutes
-gusts, eddies (tiny whirls of air)
what is the mesoscale?
diameter: few meters-100km
lasts: few minutes-day
-thunderstorm/shower
-fog
-local winds
what is the synoptic scale?
diameter: 100km-2000km
lasts: days-2 weeks
-hurricane/tropical cyclones
-fronts
-high and low pressure system
what is the planetary scale?
diameter: 2000km+
lasts: permanent feature
-climate
what is a boundary layer?
lowest ~1km above Earth’s surface, where friction causes small wind patterns
what is a wind shear?
wind that changes speed and/or direction with height
creates Eddies
on the microscale winds influence: soil, snow, vegetation, and water
what is thermally driven circulation?
pressure difference aloft that creates winds at surface
-PGF causes winds to travel from high to low
what is a sea breeze?
breeze at surface from sea to land. caused from high (land) to low (sea) pressure aloft
what is a land breeze?
breeze at surface from land to sea. caused from high (sea) to low (land) pressure aloft
what is a valley breeze?
warm air rises on mountain slopes during the day
what is a mountain breeze?
cold, dense air sinks at night around mountain
what are mountain winds?
local but not due to heating difference
what are katabatic winds?
cold wind ruses down elevated slopes, mainly in antartica
what are chinook winds?
warm downslope winds on the leeward side “snow eaters”
what are the santa anna winds?
warm dry air that blows from east to northeast down canyons into southern California
dries out vegetation
what is a monsoon?
seasonal reversal in winds
-SE asia, synoptic
-SW US, mesoscale
driven by uneven heating
summer: sea breeze, wind from water to land
winter: land breeze, wind from land to water
rising motion over land=clouds, rain
how do we name wind?
based on where it is coming from
EXEPT:
onshore wind is coming onto the shore (sea to land)
offshore wind is coming off the shore (land to sea)
what are prevailing winds?
most frequently observed direction during a given period of time
what is a wind rose?
shows map of wind direction
what is a wind vane?
arrow shows direction
what is an anemometer?
measures wind speed as cups spin
what is an aerovane?
both wind speed and direction
what is a radiosonde?
GPS tracks the balloon motions with height
