This MCQ module is based on: Precipitation Types, World Distribution & Exercises
TOPIC 21 OF 29
Precipitation Types, World Distribution & Exercises
🎓 Class 11
Social Science
CBSE
Theory
Ch 10 — Water in the Atmosphere
⏱ ~28 min
🌐 Language: [gtranslate]
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10.7 Precipitation — When the Air Can No Longer Hold Its Water
The process of continuous condensation in free air helps the condensed particles to grow in size — droplets coalesce, ice crystals collect, and clouds become heavier and heavier. Eventually, when the resistance of the air fails to hold them against the force of gravity, they fall onto the earth's surface. So after the condensation of water vapour, the release of moisture from the atmosphere is known as precipitation?. This may take place in either liquid or solid form depending on the temperature.
Forms of Precipitation — Five Faces of the Same Process
NCERT names five forms of precipitation, four of which are dictated mainly by the temperature profile of the atmosphere through which the falling particles pass.
Rainfall
Precipitation in the form of liquid water — when the temperature in the cloud and below is higher than 0 °C.
Snowfall
When the temperature is lower than 0 °C, moisture is released as hexagonal ice crystals that pack into flakes of snow.
Sleet?
Frozen raindrops and refrozen melted snow-water — small pellets of ice no bigger than the raindrops they came from.
Hail?
Rounded solid pieces of ice with several concentric layers — formed when raindrops are tossed repeatedly through colder layers.
Besides rain and snow, sleet and hail are limited in occurrence and sporadic in both time and space. Drizzle — very fine rain with droplets less than 0.5 mm in diameter — falls slowly and steadily from low stratus clouds and is also classified under precipitation.
📖 How Sleet Differs From Hail
Sleet is frozen raindrops or refrozen melted snow-water. When a layer of air with a temperature above freezing point overlies a subfreezing layer near the ground, raindrops leaving the warmer air encounter the colder air below, solidify, and reach the ground as small pellets of ice — not bigger than the raindrops from which they are formed.Hail forms inside a single cloud. Drops of rain after being released by the cloud become solidified into small rounded solid pieces of ice as they pass through colder layers; strong updraughts may toss the same drop up and down repeatedly, adding layer after layer of ice. Hailstones therefore have several concentric layers of ice one over the other — like the rings of a tree trunk in cross-section.
10.8 Three Types of Rainfall — By Origin
On the basis of origin — i.e., what makes the air rise in the first place — rainfall may be classified into three main types: (1) the convectional, (2) the orographic or relief, and (3) the cyclonic or frontal. Every shower in the world fits into one of these three categories (sometimes a combination).
(1) Convectional Rain — Heat Drives the Air Upward
The air, on being heated, becomes light and rises up in convection? currents. As it rises, it expands and loses heat — and consequently, condensation takes place and cumulus clouds are formed. With thunder and lightning, heavy rainfall takes place but this does not last long. Such rain is common in the summer or in the hotter part of the day. It is very common in the equatorial regions and in the interior parts of the continents, particularly in the northern hemisphere — the dramatic afternoon thunderstorm that arrives at four o'clock and is over by six.
(2) Orographic Rain — Mountains Forcing Air to Rise
When a saturated air mass comes across a mountain, it is forced to ascend — and as it rises, it expands; the temperature falls, and the moisture is condensed. The chief characteristic of this sort of rain is that the windward slopes receive greater rainfall. After giving rain on the windward side, when these winds reach the other slope, they descend, and their temperature rises. Then their capacity to take in moisture increases, and hence these leeward slopes remain rainless and dry.
🏔️ Rain Shadow Area
The area situated on the leeward side, which gets less rainfall, is known as the rain-shadow area?. This kind of rain is also known as relief rain. The wettest place on earth — Mawsynram in Meghalaya, with a long-term annual total of about 1,187 cm — sits exactly where the southwest monsoon is forced abruptly upward by the Khasi Hills. Just across, in Cherrapunji and Mawsynram's leeward, the totals tumble.
(3) Cyclonic Rain — Air Forced to Rise Along Fronts
You have already read about extra-tropical cyclones and cyclonic rain in Chapter 9. Cyclonic or frontal rain occurs when warm and cold air masses meet at a depression or cyclone. The lighter warm air is forced to rise over the cold dense air mass; as it rises, it cools, and the resulting condensation produces rain over a wide area for a long duration. This is the rain that comes with the winter depressions moving across the north Indian plains and with the temperate cyclones of Europe and North America.
The Three Origins of Rainfall
THINK ABOUT IT — Why Mawsynram Sees 1,187 cm and Leh Just 9 cm
L4 Analyse
Both Mawsynram (Meghalaya) and Leh (Ladakh) lie in the Indian subcontinent and both face the same southwest monsoon every summer. Yet Mawsynram is the wettest place on earth (annual total around 1,187 cm) while Leh is a high-altitude desert (annual total around 9 cm). Using NCERT's three rainfall types, explain in one paragraph why two places under one monsoon produce such opposite totals.
Mawsynram sits on the windward face of the Khasi Hills. The southwest monsoon, after travelling over the Bay of Bengal and arriving heavily charged with moisture, is funnelled into the V of the hills. NCERT's rule for orographic rain applies in textbook fashion — the saturated air mass is forced to ascend, expand and cool below dew point, and condensation is dumped on the windward face. Leh, by contrast, sits on the leeward side of not one but several mountain ranges (the Pir Panjal, the Greater Himalaya and the Zanskar). By the time the monsoon air reaches the Ladakh plateau it has already given up nearly all its moisture on the southern slopes; the descending air over Leh warms, expands and increases its capacity to hold moisture instead of releasing it — the classic rain-shadow effect. So both places obey the same orographic rule; they sit on opposite sides of it.
10.9 World Distribution of Rainfall
Different places on the earth's surface receive different amounts of rainfall in a year, and that too in different seasons. Several broad patterns emerge from the world rainfall map.
Latitudinal Pattern — Equator to Pole
In general, as we proceed from the equator towards the poles, rainfall goes on decreasing steadily. The coastal areas of the world receive greater amounts of rainfall than the interior of the continents. The rainfall is more over the oceans than on the landmasses of the world because oceans are great sources of water.
East Coast vs West Coast — Trade Winds and Westerlies
Between the latitudes 35° and 40° N and S of the equator, the rain is heavier on the eastern coasts and goes on decreasing towards the west. But between 45° and 65° N and S of the equator, due to the westerlies, the rainfall is first received on the western margins of the continents and goes on decreasing towards the east. Wherever mountains run parallel to the coast, the rain is greater on the coastal plain on the windward side and decreases towards the leeward side.
Major Precipitation Regimes — Heavy, Moderate and Scanty
On the basis of the total amount of annual precipitation, NCERT identifies the following major precipitation regimes of the world.
| Regime | Annual rainfall | Where it occurs |
|---|---|---|
| Heavy | Over 200 cm | The equatorial belt, the windward slopes of the mountains along the western coasts in the cool temperate zone, and the coastal areas of the monsoon land |
| Moderate | 100–200 cm | Interior continental areas; coastal areas of the continents (moderate amount) |
| Low | 50–100 cm | The central parts of the tropical land, and the eastern and interior parts of the temperate lands |
| Very Low / Scanty | Less than 50 cm | Areas lying in the rain-shadow zone of the interior of continents, and the high latitudes |
🌧️ The Two Extremes
At one end of the planetary scale sits Cherrapunji in Meghalaya, with a long-term annual rainfall of around 1,080 cm — orographic monsoon rain on a colossal scale. At the other end sits the Atacama Desert on the west coast of South America, where some weather stations have recorded less than 1 cm per year — air sinks here because of subtropical high pressure and the cold Peruvian Current chills the lower air, choking off both convection and frontal lift. Same physics, opposite outcomes.
Rainfall by latitude — typical annual totals (cm)
Seasonal Distribution Matters as Much as Annual Totals
Seasonal distribution of rainfall provides an important aspect to judge its effectiveness. In some regions rainfall is distributed evenly throughout the year — such as in the equatorial belt and in the western parts of cool temperate regions. In monsoon lands, almost all the rain falls in three or four months, leaving the rest of the year dry. The same 100 cm spread across twelve months supports a wet evergreen forest; the same 100 cm dumped in three months and absent for nine produces a savanna. Annual totals tell us how much; the calendar tells us how useful.
MAP STUDY — Sketching the World Rainfall Belts
L3 Apply
Take a blank world map. Without consulting an atlas, label five regions: (i) the equatorial heavy-rain belt; (ii) a tropical desert belt; (iii) a temperate east coast like the eastern USA; (iv) a temperate west coast like northwest Europe; and (v) a polar dry zone. Beside each, write the expected NCERT rainfall regime — heavy (>200 cm), moderate (100–200 cm), low (50–100 cm), or very low (<50 cm) — and the dominant rainfall type (convectional, orographic, cyclonic).
(i) Equatorial belt — heavy (>200 cm), convectional rain almost daily as the Sun heats the surface. (ii) Subtropical deserts like the Sahara and Atacama (around 20–30° N and S) — very low (<50 cm), no dominant rainfall type as the descending air of the subtropical high suppresses all three. (iii) Eastern USA (35–40° N) — moderate (100–200 cm), a mix of convectional summer thunderstorms and frontal/cyclonic winter rain; warm Gulf moisture is fed in by the trades. (iv) Northwest Europe (45–65° N west coast) — moderate (100–200 cm), cyclonic rain from a constant succession of mid-latitude depressions on the polar front. (v) Polar zone — very low (<50 cm); cold air can hold almost no vapour. Your sketch should show wet bands at the equator and poleward of 45°, dry bands at the subtropics and the poles.
SOURCE — From the NCERT Textbook
L2 Understand
NCERT writes: "Wherever mountains run parallel to the coast, the rain is greater on the coastal plain, on the windward side and it decreases towards the leeward side." Pick two real examples from anywhere in the world and show how this single sentence explains the rainfall pattern at each.
Example 1 — Western Ghats, India: The Sahyadri range runs parallel to India's west coast. The Konkan coastal plain (Mumbai, Mangaluru, Goa) receives 200–400 cm of orographic monsoon rain on the windward face. Just across, on the leeward Deccan plateau, totals fall to 50–80 cm — the classic Indian rain shadow that produces the relatively dry interiors of Karnataka and Maharashtra. Example 2 — Cascades, USA: The Cascade Range runs parallel to the Pacific coast of Washington and Oregon. The west-facing slope (Seattle, Olympic Peninsula) receives over 250 cm a year as Pacific air masses are forced up; the eastern, leeward side (eastern Washington — Yakima, Spokane) receives just 20–30 cm and supports semi-arid steppe vegetation. The same NCERT sentence — windward wet, leeward dry — explains both examples on opposite sides of the world.
🎯 Competency-Based Questions — Precipitation & World Rainfall
Case Stem. A research team monitors three weather stations along a single longitude in summer: Station A at 0° (equatorial), Station B at 25° N (interior subtropical desert), Station C at 50° N (mid-latitude west coast). Station A records short, very heavy late-afternoon thunderstorms almost daily; Station B records a single dust storm per week and zero rainfall in three months; Station C records gentle, all-day rain whenever a depression sweeps in from the Atlantic. Use this scenario to answer Q1–Q4.
Q1. Station A's rainfall is best classified as —
L3 ApplyAnswer: (c) Convectional. NCERT lists short, heavy afternoon downpours with thunder and lightning, common in equatorial regions, as the signature of convectional rain — driven by intense surface heating that creates rising cumulus.
Q2. Station B receives almost zero rain because —
L4 AnalyseIt lies under the descending air of the subtropical high pressure belt. Around 25° N, air that rose at the equator and lost its moisture in convectional showers comes down as warm, dry, descending air. There is nothing forcing the air upward — no heating strong enough, no mountain barrier, no front — so none of NCERT's three rainfall mechanisms can operate. Result: classic desert, less than 50 cm a year.
Q3. Station C's pattern of long, gentle rain associated with passing depressions is best described as —
L3 ApplyCyclonic / frontal rainfall. Between 45° and 65° N the prevailing westerlies bring a steady train of mid-latitude depressions, in which warm moist air rides up over colder air at the front. The rain band is wide and long-lasting — completely unlike the punchy convectional storm at Station A.
HOT Q. The same research team adds a fourth station, Station D, on the windward face of a coastal mountain at 22° N. Predict how its rainfall total and pattern would compare with Stations A, B and C — and explain why a single-mechanism label (convectional / orographic / cyclonic) may not capture its real behaviour.
L6 CreateHint: Station D would record one of the heaviest rainfall totals on earth — likely over 200 cm and possibly far higher (think Mawsynram-class). The dominant mechanism would be orographic, but it would not be the only one. The same coastal mountain would also see strong convectional rains in summer afternoons, and could be hit by tropical cyclones in the post-monsoon season — a third, cyclonic, contribution. So the real total is the sum of all three NCERT mechanisms acting together. This shows that the textbook's three-fold classification is a teaching device — useful for understanding origins, but in the field most stations show a mixture, with one mechanism dominant.
⚖️ Assertion–Reason Questions — Class 11
Options:
(A) Both A and R are true, and R is the correct explanation of A.
(B) Both A and R are true, but R is NOT the correct explanation of A.
(C) A is true, but R is false.
(D) A is false, but R is true.
(A) Both A and R are true, and R is the correct explanation of A.
(B) Both A and R are true, but R is NOT the correct explanation of A.
(C) A is true, but R is false.
(D) A is false, but R is true.
Assertion (A): Hailstones have several concentric layers of ice, one over the other.
Reason (R): Drops of rain after being released by the cloud become solidified as they pass through colder layers, and strong updraughts may toss the same drop up and down repeatedly, adding fresh layers of ice each time.
Answer: (A) — Both true and R is the correct explanation. Slicing a large hailstone in cross-section reveals tree-ring-like concentric layers, each marking one trip up through the colder part of the storm.
Assertion (A): The leeward slopes of mountains are drier than the windward slopes.
Reason (R): When moist air descends after crossing a mountain, its temperature rises and its capacity to take in moisture increases, so it absorbs rather than releases water.
Answer: (A) — Both true and R explains A. The descending air warms by adiabatic compression, its relative humidity drops, and it acts like a sponge that has just been wrung dry — sucking moisture out of the leeward landscape rather than depositing it.
Assertion (A): Between 45° and 65° N and S of the equator, rainfall is first received on the western margins of continents and decreases towards the east.
Reason (R): In this latitude band the prevailing winds are the westerlies, which bring moisture from the oceans onto the western (windward) coasts of the continents.
Answer: (A) — Both true and R is the correct explanation. NCERT explicitly attributes the west-coast wetness in mid-latitudes to the westerlies. This is why the British Isles, Norway, the Pacific Northwest of North America and the southern coasts of Chile and New Zealand are so reliably rainy.
10.10 NCERT Exercises — Full Model Answers
1. Multiple Choice Questions
(i) Which one of the following is the most important constituent of the atmosphere for human beings?
(a) Water vapour (b) Nitrogen (c) Dust particle (d) Oxygen
(a) Water vapour (b) Nitrogen (c) Dust particle (d) Oxygen
Answer: (d) Oxygen. Although water vapour drives weather and the carbon dioxide / nitrogen balance is essential for life, the constituent without which a human being cannot survive even five minutes is oxygen. We inhale roughly 21 per cent of every breath as O₂; cells across the body need it to release energy from food.
(ii) Which one of the following processes is responsible for transforming liquid into vapour?
(a) Condensation (b) Transpiration (c) Evaporation (d) Precipitation
(a) Condensation (b) Transpiration (c) Evaporation (d) Precipitation
Answer: (c) Evaporation. NCERT defines evaporation as the process by which water is transformed from the liquid to the gaseous state. Heat is the main cause; the energy needed (≈ 600 cal/g) is the latent heat of vaporisation.
(iii) The air that contains moisture to its full capacity:
(a) Relative humidity (b) Specific humidity (c) Absolute humidity (d) Saturated air
(a) Relative humidity (b) Specific humidity (c) Absolute humidity (d) Saturated air
Answer: (d) Saturated air. NCERT states: "The air containing moisture to its full capacity at a given temperature is said to be saturated. It means that the air at the given temperature is incapable of holding any additional amount of moisture at that stage." The temperature at which saturation occurs is the dew point.
(iv) Which one of the following is the highest cloud in the sky?
(a) Cirrus (b) Stratus (c) Nimbus (d) Cumulus
(a) Cirrus (b) Stratus (c) Nimbus (d) Cumulus
Answer: (a) Cirrus. Cirrus clouds form at altitudes of 8,000–12,000 m — the highest of the four basic NCERT types. Cumulus is at 4,000–7,000 m, stratus and nimbus are even lower.
2. Answer in About 30 Words
(i) Name the three types of precipitation.
Answer. On the basis of origin, the three types are: (1) Convectional rainfall — caused by surface heating and rising air; (2) Orographic / relief rainfall — caused by air being forced up a mountain barrier; (3) Cyclonic / frontal rainfall — caused by warm air rising over cold along a depression front.
(ii) Explain relative humidity.
Answer. Relative humidity is the percentage of moisture present in the atmosphere as compared to its full capacity at a given temperature. It changes with the air temperature — warmer air can hold more moisture, so relative humidity falls; cooler air can hold less, so relative humidity rises.
(iii) Why does the amount of water vapour decrease rapidly with altitude?
Answer. Water vapour enters the air at the surface — from oceans, lakes and plants. As altitude increases, both temperature and pressure fall sharply; cold high-altitude air can hold very little moisture, and there are no nearby vapour sources. Hence vapour concentration drops rapidly with height.
(iv) How are clouds formed? Classify them.
Answer. Clouds form when moist air rises and cools below its dew point in free air, and water vapour condenses on hygroscopic nuclei into tiny droplets or ice crystals. According to height, expanse, density and transparency, NCERT classifies them into four basic types — cirrus, cumulus, stratus and nimbus — and into altitude families: high (cirrus, cirrostratus, cirrocumulus), middle (altostratus, altocumulus), low (stratocumulus, nimbostratus) and clouds with extensive vertical development (cumulus and cumulonimbus).
3. Answer in About 150 Words
(i) Discuss the salient features of the world distribution of precipitation.
Answer. Five broad features stand out in the world rainfall map. First, rainfall decreases steadily from the equator towards the poles — the warmest air holds the most moisture. Second, oceans receive more rainfall than continents because they are vast water surfaces, and coastal areas receive more than continental interiors. Third, between 35° and 40° N and S the rain is heavier on the eastern coasts of continents and decreases westwards (because the trades blow from east to west); but between 45° and 65° N and S the pattern reverses — the westerlies make the western margins wet and the east drier. Fourth, where mountains run parallel to the coast, the windward plain is wet and the leeward is dry — the orographic rule. Fifth, on the basis of annual total, NCERT recognises four regimes — heavy (>200 cm) over the equatorial belt, windward cool-temperate west coasts and monsoon coasts; moderate (100–200 cm) over interior continental areas and most coasts; low (50–100 cm) over central tropical lands and eastern temperate interiors; and very low (<50 cm) in rain-shadow zones and high latitudes. Seasonal distribution is as important as the total — even rainfall (equatorial belt) supports evergreen forest; concentrated rainfall (monsoon) supports savanna or seasonal cropping.
(ii) What are the forms of condensation? Describe the process of dew and frost formation.
Answer. After condensation, the moisture in the atmosphere takes one of the following forms — dew, frost, fog, mist and clouds. NCERT classifies these on the basis of temperature (above or below 0 °C) and location (on a solid surface or in free air). Fog and clouds are condensation in free air on hygroscopic nuclei; mist is similar to fog but with thicker moisture coats and visibility of 1–2 km; clouds form at considerable elevations and are grouped as cirrus, cumulus, stratus and nimbus.
Dew formation: When moisture is deposited as water droplets on the cooler surfaces of solid objects — stones, grass blades, plant leaves — rather than on nuclei in the air above, it is known as dew. The ideal conditions are a clear sky (so the surface radiates heat freely to space at night), calm air (so the chilled layer is not stirred away), high relative humidity (so the dew point is easy to reach) and cold, long nights (giving the surface time to cool). For dew to form, the dew point must be above the freezing point.
Frost formation: Frost forms on cold surfaces when condensation takes place at or below 0 °C — i.e. the dew point is at or below freezing. The excess moisture is deposited not as droplets but as minute ice crystals. The conditions for white frost are exactly the same as for dew, except that the air temperature must be at or below the freezing point. Both dew and frost are surface phenomena, not free-air phenomena like fog and cloud — and the only thing separating them is whether the dew point sits above or below 0 °C.
Dew formation: When moisture is deposited as water droplets on the cooler surfaces of solid objects — stones, grass blades, plant leaves — rather than on nuclei in the air above, it is known as dew. The ideal conditions are a clear sky (so the surface radiates heat freely to space at night), calm air (so the chilled layer is not stirred away), high relative humidity (so the dew point is easy to reach) and cold, long nights (giving the surface time to cool). For dew to form, the dew point must be above the freezing point.
Frost formation: Frost forms on cold surfaces when condensation takes place at or below 0 °C — i.e. the dew point is at or below freezing. The excess moisture is deposited not as droplets but as minute ice crystals. The conditions for white frost are exactly the same as for dew, except that the air temperature must be at or below the freezing point. Both dew and frost are surface phenomena, not free-air phenomena like fog and cloud — and the only thing separating them is whether the dew point sits above or below 0 °C.
Project Work
Browse through the newspaper from 1st June to 31st December and note the news about extreme rainfall in different parts of the country.
Project Guide. Maintain a project diary for these seven months, the heart of India's southwest monsoon and post-monsoon seasons. Each time a newspaper carries a story about extreme rainfall — heavy daily totals, flash floods, urban flooding, cloudbursts or unseasonable rain — record the following: (1) date; (2) place and state; (3) rainfall figure quoted (24-hour total in mm or cm); (4) physical impact (deaths, crop loss, transport disruption); (5) the rainfall type (orographic in Mawsynram or the Konkan, convectional cloudburst in the hills, cyclonic over coastal Odisha or Andhra Pradesh, or a combination). At the end of the seven months, plot the events on a simple sketch map of India. You will see clearly that extreme rainfall is concentrated on (i) the windward Western Ghats, (ii) the northeastern hill states, and (iii) the eastern coast during the cyclone season — exactly where NCERT predicts the heaviest precipitation regimes lie. Submit a written summary of two pages plus the map.
📌 Chapter 10 — Quick Summary
- Water vapour in the atmosphere ranges from 0–4% by volume; sources are evaporation and transpiration.
- Evaporation needs heat — latent heat of vaporisation ≈ 600 cal/g for water. Rate depends on temperature, area of free water and air movement.
- Condensation is the reverse: cooling moist air below dew point releases latent heat and forms droplets on hygroscopic nuclei.
- Humidity is measured three ways: absolute (g/m³), specific (g/kg), and relative (per cent).
- Forms of condensation: dew (above 0 °C, on surface), frost (at/below 0 °C, on surface), fog (visibility < 1 km), mist (1–2 km), clouds (free air, considerable height).
- Cloud altitudes — high 8–12 km (cirrus etc.), middle 4–7 km (altostratus etc.), low 0–4 km (stratus etc.), and vertical development (cumulus, cumulonimbus).
- Precipitation takes the forms of rain, snow, sleet, hail and drizzle.
- Three rainfall types by origin: convectional (heating), orographic / relief (mountains, with rain shadow on leeward), cyclonic / frontal (depressions).
- World rainfall regimes: heavy >200 cm (equator, monsoon coasts, cool-temperate west coasts), moderate 100–200 cm, low 50–100 cm, very low <50 cm (rain shadow, polar zones). Cherrapunji ≈ 1,080 cm; Atacama < 1 cm.
10.11 Key Terms — Glossary
Humidity
Water vapour present in the air; varies 0–4% by volume.
Absolute Humidity
Weight of water vapour per unit volume of air (g/m³).
Specific Humidity
Weight of vapour per unit weight of air (g/kg).
Relative Humidity
Vapour present as a percentage of capacity at the given temperature.
Dew Point
Temperature at which a sample of air becomes saturated.
Saturated Air
Air holding moisture to its full capacity at a given temperature.
Evaporation
Liquid water transformed into water vapour, driven by heat.
Latent Heat of Vaporisation
Heat needed to vaporise unit mass of liquid without temperature change — about 600 cal/g for water.
Condensation
Vapour transformed back into liquid water; caused by loss of heat below dew point.
Hygroscopic Nuclei
Tiny particles (dust, smoke, salt) onto which vapour condenses in free air.
Hygrometer
Instrument used to measure relative humidity.
Dew
Liquid moisture deposited on cool surfaces above 0 °C.
Frost
Solid (ice-crystal) deposit on surfaces at/below 0 °C.
Fog
Cloud at ground level; visibility less than 1 km.
Mist
Lighter than fog; visibility 1–2 km; thicker moisture coats per nucleus.
Smog
Fog mixed with smoke — frequent over urban / industrial centres.
Cirrus
High, white, feathery clouds — 8,000–12,000 m, ice crystals.
Cumulus
Cotton-wool clouds with flat base — 4,000–7,000 m.
Stratus
Layered, sheet-like clouds covering large parts of the sky.
Nimbus
Dark, dense rain clouds, opaque to sunlight.
Cumulonimbus
Towering vertical cloud — thunderstorm engine.
Precipitation
Release of moisture from atmosphere — rain, snow, sleet, hail or drizzle.
Sleet
Frozen raindrops or refrozen melted snow water.
Hail
Solid ice pellets with concentric layers, formed in strong updraughts.
Convectional Rain
Heated air rises, cumulus forms, heavy rain with thunder/lightning.
Orographic Rain
Moist air forced up a mountain — windward wet, leeward dry.
Rain Shadow
Dry leeward area receiving little rainfall after orographic uplift.
Cyclonic / Frontal Rain
Rain along the front of a depression as warm air rises over cold.
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