Solar Radiation, Heat Balance and Temperature
Class 11 · Geography
4 ideas in Class 11 Geography, explained in plain words, with games and quizzes to practise.
Insolation and Its Variations
Part of: Sunlight in, heat around
Insolation is sun energy arriving in short waves, about 1.94 calories per square cm per minute at the top of the sky. Earth sits farthest on 4 July and nearest on 3 January, but lands, seas and winds hide this gap. Slant rays heat less than upright rays, so tilt, latitude, day length, clear air and slope direction all shift how much each place gets.
Why it matters. Uneven sun energy starts winds, seasons and climate belts. Grasping slant versus upright rays unlocks the rest of climate study.
Key words
- Insolation
- : Sun energy arriving at earth in short waves
- Aphelion
- : Far point from the sun reached near 4 July
- Perihelion
- : Near point to the sun reached near 3 January
- Slant rays
- : Tilted sun beams spreading thin over wide ground
- Axis tilt
- : Lean of the earth shaping seasons and belts
Try it in two minutes
- Shine a torch straight on paper, then slanting, and mark patch sizes.
- Feel which patch would heat more per finger width.
- Tilt a globe and swing it round a lamp for seasons.
- Compare desert glare with cloudy noon dimness.
Try at home. Mark sunrise and sunset times for a week and link longer days with stronger warming.
Heating the Air
Part of: Sunlight in, heat around
Air warms mainly from below. Touch heating of low layers is conduction. Rising warm streams form convection, capped within the troposphere. Sideways drift of air is advection, which brings spells like the hot loo winds. Earth itself glows back long waves, which greenhouse gases drink, warming the sky from beneath.
Why it matters. Sun rays cross air almost untouched, so sky heat must come from the ground up. These four paths explain days, storms and loo spells.
Key words
- Conduction
- : Touch heating of low air by warm ground
- Convection
- : Rising warm streams heating the troposphere
- Advection
- : Sideways drift of air carrying heat spells
- Earth glow
- : Long-wave return from warmed ground
- Scattering
- : Flinging of light by tiny air bits painting skies
Try it in two minutes
- Warm hands over a hot plate without touching.
- Feel rising warmth as convection streams.
- Slide the plate sideways as drifting air for advection.
- Touch the plate edge gently for conduction.
Try at home. Name one daily event each for rising air, drifting air and ground glow.
Heat Budget and Temperature Controls
Part of: Budget, controls and upside-down air
Of each 100 sun units, 35 bounce off before touching ground, mostly from cloud tops, and 65 stay, split between air and ground. Ground pays back its share upward, part straight to space and part via air, so total return matches total gain and average heat holds steady. Latitude, height, sea nearness, air masses and sea streams then tune each place.
Why it matters. The budget proves why earth neither bakes nor freezes on average. Controls then explain hill coolness, sea softness and current effects.
Key words
- Albedo
- : Share of sun rays bounced back by a surface
- Heat budget
- : Even books of sun gain and space payback
- Lapse rate
- : Cooling pace with height, near six and half degrees per km
- Sea softening
- : Mild seasons near coasts from slow sea change
- Sea streams
- : Warm and cold flows tuning coastal heat
Try it in two minutes
- Count 100 seeds as sun units on a tray.
- Lift 35 as bounced by clouds and ice.
- Split 65 into air and ground piles.
- Pay ground pile back upward till books match.
Try at home. Retell the 100-unit tale with seeds, marking bounce, keep and payback piles.
Temperature Patterns and Inversion
Part of: Budget, controls and upside-down air
Isotherms join equal-heat places. In January they bend north over warm seas and south over cold lands, with Siberia bitter and southern seas even. Ranges swing past 60 degrees in far Eurasia but near 3 degrees in deep tropics. At times cold air pools below warm air, called inversion, on still clear winter nights and over poles, and valley cold pools even shield crops from frost.
Why it matters. Map bends reveal currents and land-sea contrasts at a glance. Inversion explains foggy mornings and frost-safe valleys.
Key words
- Isotherm
- : Line joining places of equal temperature
- January bend
- : Northward sea warp and southward land warp of heat lines
- Heat range
- : Gap between warmest and coldest monthly means
- Inversion
- : Cold air pooled below warm air against the norm
- Air drainage
- : Night cold sliding into valleys under gravity
Try it in two minutes
- Draw wavy equal-heat lines bending over land and sea.
- Mark bitter Siberia and mild oceans in January.
- Chill a tray slope and watch cold pool at the foot.
- Trap smoke under a lid as fog under inversion.
Try at home. Track three foggy mornings and note clear skies plus still air the night before.
What your child will practise
- Heat Budget and Temperature Controls: Candy Quick Fire (Quick Fire)
- Heating the Air: Desert Puzzle (Clue Puzzle)
- Heating the Air: Desert Quick Fire (Quick Fire)
- Insolation and Its Variations: Space Quick Fire (Quick Fire)
- Temperature Patterns and Inversion: Ocean Puzzle (Clue Puzzle)
- Quiz: Heat Budget and Temperature Controls (8 questions)
- Quiz: Heating the Air (8 questions)
- Quiz: Insolation and Its Variations (8 questions)
- Quiz: Temperature Patterns and Inversion (8 questions)