Accuratelyforecastingtheweatherisaveryhardthingtodo.Therearemanypartsofweatherdynamics—thestudyofhowwaterandairinmotioncauseweatherpatterns—toconsider.Eventhebestforecastcanbechangedbyasmallweatherdisturbancehalfwayaroundtheworld.Today’sforecastusecomplexcomputermodelsweatherinstrumentsanddetailedanalysesofdailyobservationstopredicttheweather.Howeverithasn’talwaysbeenthatway.Peoplelikeyourgrandparentsusefolkloreandproverbstohelpforecasttheweather.Theyrememberedwhatconditionscausedchangesandobservedthefactorsassociatedwithweather:atmosphericandcloudconditionstemperaturewindsandreactionsofplantsandanimals.Manypeoplebelievethatthiswayofforecastingweatherisaccuratemoreoftenthanmodemforecasting.
Grandma’sachingjointsmightindicatethearrivalofalow-pressuresystem.Shemightalsoobservethegeeseflyinglowerthanusualconfirmingthelow-pressuresystem.Finallyshemightfeeldampnessonherskinasignofhighhumidity(湿度).Basedonthesethreeobservationsgrandmamightwarnthatastormisbrewing.
Jointsandnervescanindicatedroppingairpressuredissolvedgasesinthebloodformbubblesunderlowairpressure.Thiscausespaininjointsandnerveendings.Geeseandotherbirdsrespondtochangesinairpressurebyadjustinghowhightheyfly.Inthefaircalmweatherofahigh-pressuresystemthebirdsflyhigherthaninthestormyweatherassociatedwithalow-pressuresystem.
Natureprovidesothercluestochangingweather.Adecreaseinairpressurecausesdeerandelktocomedownfromthemountainstolookforshelter.Someanimalsfeedmorethanusual.Thehigherhumiditybeforeastormcausessomeinsectstoleavethetreesandgatherneartheground.Someflowersclosesoraindoesn’tgetinsidethem.Inwinterrhododendronplantscurluptoprotectthemselvesasthetemperaturedrops.
Severalofthesayingsapplyinparticularareasoftheworld.Herearesomeofthem.
■Earlythunderearlyspring.
■Rainbowinthemorninggivesyoufairwarning.
■Whenteethandbonesacheexpectthecloudstofillthelake.
■Whenhighcloudsandlowcloudsdonotmatchtogetherprepareforablowandachangeintheweather