air mass air mass volume air defined temperature water content air masses cover hundreds thousands square miles adapt characteristics surface classified according latitude continental maritime source regions colder air masses termed polar arctic warmer air masses deemed tropical continental superior air masses dry maritime monsoon air masses moist weather fronts separate air masses different density temperature moisture characteristics air mass moves away source region underlying vegetation water bodies quickly modify character classification schemes tackle air mass characteristics modification classification classification widely accepted form air mass classification produced refined versions scheme different regions globe air mass classification involves letters letter describes moisture properties continental air masses dry maritime air masses moist second letter describes thermal characteristic source region tropical polar arctic monsoon superior air drying warming air formed significant downward motion atmosphere instance air mass originating desert southwest united_states summer designated air mass originating northern siberia winter indicated stability air mass shown letter air mass colder surface air mass warmer surface example polar air mass blowing denoted occasionally encounter use degree denoting given air mass having replacing colder replaced air mass usually polar air masses example series fronts pacific air mass denoted followed denoted convention utilizing symbols indication modification transformation type instance arctic air mass blowing shown convention indicates air masses certain situations instance polar air mass air mass gulf_of_mexico shown horizontal line fraction characteristics arctic polar air masses cold qualities arctic air developed ice snow covered ground arctic air deeply cold colder polar air masses arctic air shallow summer rapidly modify moves polar air masses develop higher latitudes land ocean stable generally shallower arctic air polar air ocean maritime loses stability gains moisture warmer ocean waters tropical air masses hot develop lower latitudes develop land continental drier develop oceans travel western periphery subtropical ridge maritime tropical air masses referred trade air masses monsoon air masses moist unstable superior air masses dry rarely reach ground normally reside maritime tropical air masses forming warmer drier layer moderate moist air mass forming known trade wind maritime tropical air mass air masses air masses cold dry continental source region continental polar air masses affect north_america form interior canada air masses type tropical air produced subtropical ridge large areas land typically originate low latitude northern africa major source air masses important sources producing air masses central arid semi arid australia lying continental tropical air masses extremely hot dry movement fronts weather boundary separating masses air different principal cause meteorological phenomena surface weather analyses fronts depicted colored lines symbols depending type air masses separated usually differ temperature humidity cold fronts feature narrow bands thunderstorms severe weather occasion preceded lines dry lines warm fronts usually preceded precipitation fog weather usually quickly passage fronts produce precipitation little invariably wind shift cold fronts fronts generally west east warm fronts greater density air wake cold fronts cold faster warm fronts warm mountains warm bodies water slow movement fronts stationary density contrast frontal boundary line separates regions differing wind velocity known common open ocean modification air masses modified variety ways surface underlying vegetation forest acts air mass heat underlying warmer waters significantly modify air mass distances short kilometres kilometres example southwest extratropical cyclones curved cyclonic flow bringing cold air relatively warm water bodies lead narrow lake effect snow bands bands bring strong localized precipitation large water bodies lakes efficiently store heat results significant temperature differences larger water surface air temperature difference warmth moisture transported upward vertically oriented clouds satellite picture produce snow showers temperature decrease height cloud depth directly affected water temperature large scale environment stronger temperature decrease height deeper clouds greater precipitation rate
Air mass