Lessn 3 Materials Hw accurate are weather frecasts? 1. Lk llhe current 5-dy weather frecast. Recrd the frecasted high temperatures. D 2. Check the weather reprt each day fr the next 5 days. Recrd the actual high fr the previus day. 3. Cmpare the frecasted dala with the actual data. lcal S-dey weather Frecast Explain Yur Results 4. What was the largest djfference between the frecast \... and actual temperatures? S. Draw a Cnclusin D yu see a pattern in the accuracy f the frecasts? Explain. 2 3 " 5 268 mvsciencenline.cm I ~plre It! Animatin Cpyright Pearsn Educatin, Inc. r its affiliates. All Rights Reserved. 1
I will knw the factrs that determine weather. Wrds t Knw weather barmetric pressure humidity circulatin Weather Yu prbably knw that a thermmeter can be used t measure air temperature. But it takes mre than a temperature reading t describe the weather. Weather is the state f the atmsphere, including its temperature, wind speed and directin, air pressure, misture, a munt f rain r snw, and ther factl's. Scientists called meterlgists study and predict weather. Me1erigislS cllect data frm many tls 10 tell abut the weather tday and t predict future weather. Almst all f the data they use are cllected autmatically at weather bservatin statins. Knwing and predicting the weather is very imprtant fr planning a ll srts f activities, including farming, fishing, a nd utdr cncerts. 2. Suggest W here might be a gd place 10 set up Ihis measuring ll? Explain.......... 1. Draw Cnclusins Use the gra ph ic rganizer belw t draw a cnclusin frm the texl abve. Fact Fact Cnclusin Cpyright Pearsn Educatin, Inc. r its affiliates. All Rights Reserved. ( mvsciencenline.cm I Envi's.n ttl ) 269 2
Barmetric Pressure When yu lk up n a clear day, yu see a high, blue sky. Yu are really lking thrugh 9,600 km (abut 6,000 mil f air. The blanket f air that surrunds Ea rth is its atmsphere. Like Lher mauer, air has mss and tkes up space. Air is mde up f a mixture f invisible gases. Over t f Earth's atmsphere is nitrgen. Mst f the rest is xygen, but sma ll amunts f carbn dixide gas a re als present. The prt f the atmsphere clsest t Earth's surface cntains water vapr. The amunt f water vapr depends n time a nd place. Fr example, air ver the cean r a frest has mre water vapr than air ver a desert. Gravity pulls the mass f air in the atmsphere tward Earth's surface. The pushing frce f the atmsphere is called barmetric pressure. Air pushes with equal frce in all directins. Many kilgrams f gs re pressing dwn n yur schl building. They d nt crush it because the air inside the building exerts pressure t. Air pushing dwn is balanced by ir pushing up and sideways. Air pressure decreases as yu g higher in the atmsphere. 3. (CHALLENGE ~ Suppse yu take tw readi ngs frm a barmeter. One reading is taken at the tp f a tll building and the ther at grund level. Which \ reading ishk~iyio b~ hig her? Why? A barmeter is n instrument that shws air pressure. Air prticles are represented here by smalt, blue spheres. As yu ~ mve upward thrugh the ~ afmsphere, air particles a are farther aprt. Th is a ~ means that higher in the afmsphere, the pressure a is lwer. a ~ a a a a a a a 12km II km IOkm 9!un Bkm 7km 6 km 5 km 3 km 2!un 1 km Okm 270 Cpyright Pearsn Educatin, Inc. r its affiliates. All Rights Reserved. 3
Temperature Air temperature als affects weather. As the sun warms Earth's surface, air that is in cntact with the surface becmes warmer. As the air particles mve farther apart, the a ir pushes dwn with less pressure. The warm air rises, causing an area f lw pressure t frm, and air frm areas with higher pressure mshes in. If the a ir near Earth's surface cls, the particles in the a ir becme mre clsely packed. This denser, cler a ir pushes dwn with mre pressure. An rca f high pressure frms. Air frm this area flws int lwer-pressure a reas. The temperature f the a ir als a ffects the type f precipitatin-rain, snw, r sleet. 4. Predict What wuld happen if the air utside the ht air balln were as ht as the ir inside? Line Graphs Lk at the graph f average mn thly high temperatures fr Frt Lauderdale, Flrida. 3' ;: 32 30.a 28 i 26 E 2. ~ 22 - Average High Temperatures in Frt Lauderdale, Flrida -./..., Jan Feb Mar Apr May Jun Jul Aug Sep Od Nv Dec Mnth G In Nvember, the average high tempera ture was abut 2rC. In December, it was abut 25 C. Plt the missing data pints and cmplete the graph abve. e Between which tw mnths did Frt Lauderdale have the greatest decrease in average temperature? Abut hw many degrees did the temperature decrease? Cpyright Pearsn Educatin, Inc. r its affiliates. All Rights Reserved. 271 4
Meterlgists measure wind speed using an inslrumenl ciled n anemmeter, Winds Wind is air mvement cused by differences in pressure. In general, air mves frm areas f high pressure t areas f lw pressure. Think abut a balln. When yu let air ut f a balln, air rushes ftm inside the balln where pressure is higher l where pressure is lwer utside the balln. Yu cn feel wind. Wind speed and directin affect weather. Lcal weather can be affected by special winds ciled jet streams. A jet stream is a narrw band f high-speed wind. A plar jet stream blws frm west t east high in the atmsphere ver Nrth America. The jet stream affects day-t-day weather and seasns. In the winter, the jet stream can bring cld air frm the nrth t states as fr suth as Kentucky. In the summer, the jet stream brings wolmer air noith int Canada. The name f a wind is the directin frm which it blws. A nrth wind cmes frm the nrth and mves tward the suth. Winds near the cean are smetimes named differently. N Wind directin can be bserved with a weather vane. The arrw pints twrd the directin the wind cmes frm. Tht is, il pints inf the wind. The vane belw shws tht there is a nrtherly wind. N w---<f).--e ~--------E 5. Draw On the blank weather vane diagram abve, draw an arrw t represent a su theasterly wind. s s 272 ( mvsciencenline.cm I a ] Will Knw... ) Cpyright Pearsn Educatin, Inc. r its affiliates. All Rights Reserved. 5
Water in the Atmsphere Three ther factrs fr determining weather are humidity, cluds, and precipitatin. Humidity is the amunt f water vapr in the air. The particles f water vapr are t small t he visible, hut when cnditins are right, they can cme tgether t frm small water drplets and ice crystals. These drplets and crystals are bigger than water vapr particles and can reflect light frm the sun. At this point, we can see the water as a clud. If the drplets r crystals get large enugh, they can fall t the grund as precipitatin, such as rain r snw. 6. Summarize W ha t d the factrs humidity, duds, and precipitatin have in cmmn? list tw things. Running Ht and Cld Wrk with an adult. Fill a bttle with ht water and then wait a minute r s. Gently pur the water ut and immediately cap the bttle. N w run cld water ver the bttle. What happens? Can yu reverse this prcess? 7. Describe Write tw r mre sentences that tell what is ging n in the picture belw. Use the wrds humidify, cluds, and precipitatin. Meterlgists use n instrument ciled 0 hygrmeter t measure humidify. Zs use hygrmeters t mnitr the air fr animls that need high humidity. 273 Cpyright Pearsn Educatin, Inc. r its affiliates. All Rights Reserved. 6
Circulatin Have yu ever used an electric fan t cl Q rm in the summer? Yu can a ls use a fa n t ma ke a hea ler mrc effi cient in the winter. The fan mves a ir a rund the rm. The wind may blw frm different directins, but winds d f llw sme large-scale patterns ver cntinents nd the cean. These patterns are determined by differences in temperature and pressure in diffe rent pa rts f the atmsphere. The la rge-scale mvement f a ir is called circula tin. Circulatin is the mvement f a ir tha t redistri butes heat n Earth. Fr example, the trade winds are Q persistent pattern f winds tha t blw near the equatr. The WQrmest parts f ur pla net are nea r the equa tr. The air abve this regin becmes wrm a nd rises, creating a lw pressure zne. High in the a tmsphere, this warm a ir travels away fr m the equa tr, cls dwn, a nd Sinks. Illhen blws back Lward the equa tr a lng the surface, causing the trade winds. In summe~ a ceiling fan shuld blw the air dwnward. This makes sweat evaprate faster and peple feel cler. 8. Demnstrate Belw is an example f a ru te frm Eurpe t the Americas. Draw arrws n the rute shwing the directin a sh ip might take t save the mst fuel. Explain yaur answer. 274 mvsciencenline.cm I Gt it? ~.~ 60-Secnd Vide Cpyright Pearsn Educatin, Inc. r its affiliates. All Rights Reserved. "',... 1$... 0...,"'" 1<'''' 7
In winfe" a ceiling fan shuld draw the air upward. In a heafed rm, the ht ir rises t the ceiling. The cld air blwing up pushes the ht air tward the wa ffs and then dwn, where peple can he warmed by if. 9. Draw arrws shwing the mtin f air in this rm. 10. Infer Hw des air circu latin help keep temperatures n \... ~ ~ st. ~~r t s. ~fearth m;ld? list fur factrs that can help determ ine weather at a particular place and time. Stp! I need help w;th. Wait! I have a questin abut Gl Nw I knw. _ Cpyright Pearsn Educatin, Inc. r its affiliates. All Rights Reserved. ( mysciencenline.cm I Gt it? QUiZ) 275 8