IN WHAT DIRECTIONDO WINDS BLOW–FROM HIGH TO LOWPRESSURE AREA ORVICE VERSA?
OBJECTIVESAfter performing this activity, you should beable to:1. Interpret a map to determine direction ofwind movement2. Explain why it is cold around in Decemberto February and warm around July.3. Illustrate why habagat brings lots of rain4. Give examples how the monsoons(amihan and habagat) affect people.
WHAT TO DOPart I. Study Figure 17. It showsthe air pressure and direction ofwinds in different parts of theworld in January. Low-pressureareas are marked by L and high-pressure areas are marked by H.Broken lines with arrowheadsshow the direction of the wind.
ANSWER THE FF.Q1. Choose a low-pressure area andstudy the direction of the winds aroundit. Do the winds move toward the low-pressure area or away from it?Q2. Choose a high-pressure area andstudy the direction of the winds aroundit. Do the winds move toward the high-pressure area or away from it?
Q3. In what direction do windsblow? Do winds blow from high-pressure areas to low-pressureareas? Or, from low-pressureareas to high pressure areas?Q4. Where is North in the map?South? West? East? Write thedirections on the map.
Q5. Study the wind direction near thePhilippine area. From what directiondoes the wind blow near thePhilippines in January?Q6. Study the wind direction near thePhilippine area. From what directiondoes the wind blow in the vicinity ofthe Philippines in July?
Figure 17 shows what happensduring the colder months. The windblows from the high-pressure area inthe Asian continent toward the lowpressure area south of thePhilippines. The cold air that weexperience from December toFebruary is part of this wind system.This monsoon wind is locally knownas amihan. (Northeast)
As you can see from Figure17, the wind passes oversome bodies of water before itreaches the Philippines. Thewind picks up moisture alongthe way and brings rain to theeastern part of the Philippines.
Now, what happens during the warmermonths? Study Figure 18 carefully. Whatdo you observe about the low-pressurearea and high-pressure area near thePhilippines? They have changed places.As a result, the direction of the wind alsochanges. This time the wind will movefrom the high-pressure area in Australiato the low-pressure area in the Asiancontinent. This monsoon wind is locallycalled habagat. (Southwest)
Trace the path of thehabagat before it reachesthe Philippines. Can youexplain why the habagatbrings so much rain? Whichpart of the Philippines doesthe habagat affect the most?
The monsoons, habagat andamihan, affect people indifferent ways. Try to explainthe following:Why do farmers welcomethe monsoons?Why are fisherfolk not sohappy about the monsoons?
Why do energy providersappreciate the monsoons?Why are fishpen ownersworried about themonsoons?How do the monsoonsaffect your own town?
THE INTERTROPICALCONVERGENCE ZONE (ITCZ)Many people who listen to weatherforecasts are confused about theintertropical convergence zone. Butit is easy to understand it once youknow that warm air rises, and airmoves toward the place wherewarm air is rising.
TAKE A LOOK AT THE DRAWING BELOW. Sun’s rays at the equator and at a higher latitude
Figure 19 shows the rays ofthe Sun at two different placesat noon. Study the drawingcarefully. Where would youobserve the Sun directlyabove you? When you are atthe equator? Or when you areat a higher latitude?
As you can see, the position of theSun at midday depends on whereyou are. At the equator, the Sunwill be directly overhead and therays of the Sun will hit the grounddirectly. At a higher latitude, theSun will be lower in the sky and theSun’s rays will strike the ground ata lower angle. Where do you thinkwill it be warmer?
It is clear that it is warmer at theequator than anywhere else.Because of that, the air over theequator will be warmer than the airover other parts of the Earth. Andyou already know what happens towarm air. It rises. And when warmair rises, air in the surroundings willthen move as a result.
As you can see from Figure 20, airfrom north of the equator and airfrom south of the equator will movetoward the place where warm air isrising. Thus, the intertropicalconvergence zone is the placewhere winds in the tropics meet orconverge. (Recall that the area nearthe equator is called the tropics.)
In time the rising warm airwill form clouds, which maylead to thunderstorms. Nowyou know why weatherforecasters often blame theITCZ for some heavyafternoon rains.
THE BAND OF WHITE CLOUDS IN THE FOLLOWINGPICTURE SHOWS THE LOCATION OF THE ITCZ.