pressure Flashcards
define surface pressure in meteorology
the weight of air above a unit area
equation for calculating pressure
p=m x g/A
when the pressure exerted by the mercury column is equal to the atmospheric pressure, what is the height of the column
29.92in
why do we use mercury column height as a measure of atmospheric pressure
mercury’s density doesn’t change significantly with height
what is the instrument used to measure atmospheric pressure
barometer
true or false
pressure is usually between 950 - 1050hPa
True
why does pressure decrease in an exponential fashion
because air density decreases with height
true or false
horizontal pressure gradient is greater than vertical pressure gradient.
False
- vertical pressure gradient is much greater (eg. 800hPa decrease in 15 km, while for hog, u might only get 12 hPa decrease in 200km)
- therefore pressure doesn’t vary much with countries
what is the formula for calculating R
1000 x R*/Mr
what is the R for moist air
Rd (1 +0.61q)
pressure decreases by 50% for every _____km increase in altitude
5.5
pressure decreases by a factor of ____ for every 16 km
10
the ________ of a layer fives a dirt measure of its average temperature
thickness
the thinner the layer (delta z), the _______ the average temp and the ______ the atmosphere
colder
denser
-as colder air is denser, its more compacted hence thinner
how are the thickness lines presented on the plotted chart?
dashed line
what causes the isobaric layers to be thicker?
increase in temp, air becomes less dense and expands, hence thicker
true or false
the greater the distance between two height level on the plotted chart (isobaric layer), the thicker the layer and the higher the temperautre
true
how can thickness contours help to identify fronts
cold front brings cold air, therefore packed thickness lines could mean a cold front.
what does thickness lower than 522 dam indicate?
likely to snow if there is precipitation
what does thickness lower than 528 dam indicate?
snow above 300m
what does thickness greater than 564 dam indicate?
probable heatwaves
1 hPa = ____ Pa
100
