WEAX 201 - Lesson 7: Geostropic Wind

what is beneficial about weather maps?

• obtain weather observations at…

• obtain weather observations at same time

only (…) variations affect wind

• horizontal pressure

station pressure must be reduced to ()

MSL

what are isobars?

• contours (lines of constant pressure)

when isobars are close together, it leads to (). which then leads to ()

• stronger pressure

• more wind

(When lines are packed tightly together, the pressure change is steep, generating a powerful push (pressure gradient force) that accelerates the air into strong winds. Wide gaps between lines mean a gentle change and light breezes)

what causes pressure gradients?

• temperature differences

• (uneven heating of the earth’s surface by the sun creating areas of warm, less dense air (low pressure) and cool, denser air (high pressure)

how do you identify lows and highs on a weather map?

• look for the labeled pressure center letters, H or L

how do you identify a trough on a weather map and what is it?

• () area of relatively () atmospheric pressure shaped like a () or ()

• elongated area of relatively low atmospheric pressure shaped like a U or V

how do you identify a ridge on a weather map and what is it?

• () area of relatively () atmospheric pressure or high geopotential height

• an upside-down () or a () like hump

• elongated area of relatively high atmospheric pressure or high geopotential height

• an upside-down U or a hill like hump

what is an isopleth?

• line on a map that connects () sharing an () value of a specific atmospheric or meteorological measurement

• line on a map that connects points sharing an equal value of a specific atmospheric or meteorological measurement

what is an isotherm?

• line on a map that connects () or represents conditions of () or () temperature

line on a map that connects points or represents conditions of equal or constant temperature.

what does a low pressure system or cyclone look like?

• isobars surround the center - the numbers on the lines get () as you move toward the middle

• () packed lines so pressure change is () and winds are ()

• isobars surround the center - the numbers on the lines get lower as you move toward the middle

• tightly packed lines so pressure change is rapid and winds are strong

what does a high pressure system or anticyclone look like?

• isobars surround the center - the numbers on the lines get () as you move toward the middle

• lines are () so pressure change is () and winds are ()

• isobars surround the center - the numbers on the lines get higher as you move toward the middle

• lines are far apart so pressure change is gradual and winds are light

the distribution of atmospheric pressure is mapped using…

• isobars (lines of equal air pressure)

what does wind originate from?

• pressure gradient force, caused by spatial differences in heating

air begins accelerating toward () - (PGF is () to pressure gradient)

• lower pressure

• perpendicular

how does airflow move in relation to the rotation of earth?

• toward the () in the northern hemisphere

• toward the () in the southern hemisphere

• toward the right in the northern hemisphere

• toward the left in the southern hemisphere

what is the coriolis effect?

• an apparent force, produced by (…)

• its strength depends on the () and ()

• an apparent force, produced by earth’s rotation

• its strength depends on the wind speed and latitude

coriolis deflection changes (), not () because it is strictly a () force

• wind direction, not speed

• perpendicular

the () the air moves, the () the coriolis effect

• faster, stronger

how is the coriolis effect in terms of the equator, latitude, and poles?

• () effect at equator for () movements

• increasing with () bc as you move towards () latitudes, () occurs which creates higher effect

• strongest at () bc it is completely () to the surface

• zero effect at equator for horizontal movements

• increasing with latitude bc as you move towards higher latitudes, deflection occurs which creates higher effect

• strongest at poles bc it is completely perpendicular to the surface

acts () to () of wind vector in the () hemisphere ( () in () hemisphere)

acts 90 degrees to right of wind vector in the northern hemisphere (left in southern hemisphere)

primarily influences (…) motions that are greater than 100 miles

• large-scale motions

what is geostrophic balance?

• state where the (…) pulling air toward () pressure is completely offset by the () force deflecting it due to earth’s rotation

• state where the horizontal PGF pulling air toward low pressure is completely offset by the coriolis force deflecting it due to earth’s rotation

what is geostrophic wind?

• results from balance between the () and the ()

• above () AGL, wind is approx geostrophic

• is () to isobars and upper-air contours

• results from balance between the pressure gradient force and the coriolis effect

• above 3000 AGL, wind is approx geostrophic

• is parallel to isobars and upper-air contours

for geostrophic wind, when standing with your back to the wind (face downwind), low pressure is located on the () in the N hemisphere and low pressure is located on the () in the S hemisphere

• left, right

the () together the isobars or height contour lines, the () is the airflow

• closer, stronger

how do you predict the wind direction?

• note ur in N hemisphere

• in N.H low NEEDS to be on ur left

• with the lines you could either go NE or SW, but u need to choose the one where the L will be on ur LEFT

• that is NE, but NE is the direction the wind is going but since wind is always where it is coming from it would be a SW wind

what direction is an cyclonic flow? N & S hemisphere

• CCW in N hemisphere

• CW in S hemisphere

what direction is an anticyclonic flow? N & S hemisphere

• CW in N hemisphere

• CCW in S hemisphere

what is zonal flow?

• when isobars are oriented () to ()

• () - (+)

• () - (-)

• when isobars are oriented west to east

• westerly (+)

• easterly (-)

prevailing wind in (…) is normally zonal

• cold air ()

• warm air ()

• mid-latitudes

• cold air north

• warm air south

what is meridional flow?

• when isobars are mainly oriented () to ()

• () - (+)

• () - (-)

• when isobars are mainly oriented north to south

• southerly (+)

• northerly (-)

prevailing wind meridional over AZ in ()/()

• brings () air ()

• july/august

• moist, northward