9.2 Weather, Climate, and Astronomy

Why This Matters for the PUPCET

Weather, climate, and astronomy questions reward pure recall: match an instrument to what it measures, pick the right monsoon, arrange the planets. These are quick wins if you build clean memory tables — which is exactly what this section gives you. PAGASA itself (the Astronomical in its name is real: it tracks the skies, too) is a frequent answer choice.

Weather vs Climate

Weather is the day-to-day condition of the atmosphere — it changes by the hour. Climate is the long-term average of weather in a region, computed over at least 30 years. Memory hook: Weather is what you get; climate is what you expect. A rainy Tuesday in Baguio is weather; the fact that Baguio is cool year-round is climate.

Weather Elements and Instruments

The elements of weather and the instruments used to measure them are among the most frequently tested matching items:

Trap alert: the exam swaps anemometer (wind speed) with wind vane (wind direction), and barometer (pressure) with hygrometer (humidity). Anchor them with word roots: baro- = weight/pressure, hygro- = moisture, anemos = Greek for wind.

The Monsoons and Philippine Climate Types

Two monsoons dominate the Philippine year:

• Habagat — the southwest monsoon, roughly June to October. Warm, moist air from the ocean brings heavy rains, especially to the western side of the country. This is our wet season, enhanced by typhoons.
• Amihan — the northeast monsoon, roughly November to April/May. Cool, dry air from the Asian mainland brings cooler, drier weather — our dry season and the 'ber-month chill.

The ITCZ (Intertropical Convergence Zone) — the band near the equator where trade winds meet — also dumps rain on Mindanao and the Visayas as it shifts north and south through the year.

PAGASA classifies Philippine climate into four types (Modified Coronas classification) based on rainfall distribution:

Seasons and Earth's Tilt

Earth spins on an axis tilted 23.5° from vertical as it orbits (revolves around) the Sun in 365.25 days. The tilt — not distance from the Sun — causes the seasons: when the Northern Hemisphere tilts toward the Sun it gets more direct sunlight (summer); tilted away, winter. Key dates: the June solstice (longest day in the north, about June 21), December solstice (about December 22), and the equinoxes (about March 21 and September 23), when day and night are nearly equal worldwide. Near the equator the tilt's effect is small, so the Philippines has only two seasons — wet and dry — not four. Rotation (24 hours) causes day and night; revolution plus tilt causes seasons. Do not mix up the two motions.

The Solar System

Eight planets orbit the Sun, in order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Mnemonic: My Very Excellent Mother Just Served Us Noodles.

Facts the exam loves: Jupiter is the largest planet; Mercury is smallest and fastest (88-day year); Venus is the hottest (a runaway greenhouse effect from its carbon dioxide atmosphere, not its distance — it is hotter than Mercury) and the brightest 'evening/morning star'; Mars is the red planet (iron oxide dust) with Olympus Mons, the tallest volcano in the solar system; Saturn has the most spectacular rings; Earth is the only known planet with liquid water and life. The asteroid belt lies between Mars and Jupiter. Pluto was reclassified as a dwarf planet in 2006. The Sun, an ordinary star, holds about 99.8% of the solar system's mass. A light-year is a unit of distance, not time — the distance light travels in one year.

Moon Phases and Eclipses

The Moon shines by reflected sunlight and completes its phase cycle in about 29.5 days (a lunar month):

1. New moon — Moon between Earth and Sun; dark side faces us.
2. Waxing crescent — a growing sliver (waxing = growing).
3. First quarter — right half lit.
4. Waxing gibbous — more than half, still growing.
5. Full moon — entire face lit.
6. Waning gibbous — shrinking (waning = shrinking).
7. Last (third) quarter — left half lit.
8. Waning crescent — back toward new moon.

Eclipses need perfect alignment:

• Solar eclipse — order is Sun → Moon → Earth; happens only at new moon; the Moon's shadow falls on Earth. Types: total, partial, and annular (a 'ring of fire' when the Moon is too far to cover the Sun fully).
• Lunar eclipse — order is Sun → Earth → Moon; happens only at full moon; Earth's shadow darkens the Moon, often turning it coppery red ('blood moon'). Safe to watch with the naked eye, unlike a solar eclipse.

Trap alert: if the Moon comes between the Sun and Earth, the Sun is blocked — solar eclipse. Memory hook: in a solar eclipse, the Moon screens the Sun.

Constellations and Filipino Sky Culture

A constellation is an officially recognized pattern of stars — 88 in total — used to map the sky. An asterism is a smaller, unofficial pattern: the Big Dipper is an asterism inside the constellation Ursa Major. The Big Dipper's two pointer stars lead to Polaris, the North Star, which sits almost directly above the North Pole — sailors have used it to find north for centuries. Orion the hunter, with its three-star belt, is visible in Philippine evening skies around December to April; pre-colonial Filipinos called Orion's Belt Balatik and used its appearance to time planting, while the Pleiades star cluster marked harvest seasons. The twelve constellations along the Sun's yearly path form the zodiac. Stars only appear to move nightly because Earth rotates; Polaris stays fixed, which is why it guides navigators.

Final Exam Tips

• Match the instrument to the element using word roots; the exam's wrong options are usually just swaps of each other.
• Habagat = habagat (southwest) = wet; Amihan = northeast = cool and dry.
• Eclipse order: new moon → possible solar eclipse; full moon → possible lunar eclipse.
• Seasons come from the 23.5° tilt; day and night come from rotation; the year comes from revolution.
• PAGASA handles weather and astronomy for the Philippines — a fact hidden in its own name.