Consider the following statements : 1. High clouds primarily reflect solar radiation and cool the surface of the Earth. 2. Low clouds have a high absorption of infrared radiation emanating from the Earth's surface and thus cause warming effect. Which of the statements given above is/are correct ?

Gives a comparative rule: high clouds are thin with low albedo (25–30%) and 'let through most of the incoming short-wave radiation' while low thick clouds have much higher albedo (70–80%).

A student can combine this with the basic fact that lower albedo means less reflection of incoming solar radiation to infer high clouds are less effective reflectors than low clouds.

Defines cirrus as high-altitude, thin, feathery, and always white — a morphological example of the 'high, thin' cloud type mentioned above.

Knowing cirrus are thin and composed of ice crystals, a student can expect limited bulk scattering/reflectance of solar rays compared with thicker clouds and check satellite albedo data for cirrus.

Also states cirrus are high (8,000–12,000 m) and made of ice crystals and thin, reinforcing the pattern that high clouds are geometrically thin.

Combine thin geometric thickness with typical optical depth concepts (thin layers reflect less) to judge that cirrus likely do not primarily reflect incoming solar radiation.

Provides a quantitative planetary energy-budget example: '27 units' are reflected from the top of the clouds, showing clouds as a significant overall reflector of solar radiation but not distinguishing cloud types.

A student can use this to reason that while clouds in aggregate reflect much solar energy, one must separate contributions by cloud type (high vs low) to assess whether high clouds 'primarily' cause that reflection.

Explains mechanisms (scattering, reflection, absorption) and links absorption by clouds to greenhouse effects, indicating clouds can both reflect incoming shortwave and absorb/emit longwave differently depending on particle size and composition.

Using this mechanism rule, a student can consider that ice-crystal, thin high clouds may scatter/absorb less shortwave and more strongly affect longwave, so they are less likely to be primary shortwave reflectors.

Gives a general rule: high clouds are thin (albedo 25–30%) and let through most incoming shortwave while blocking outgoing longwave (greenhouse effect); low thick clouds have high albedo (70–80%) and produce net cooling.

A student can combine these relative albedo and greenhouse roles with basic radiation budget reasoning (compare reflected shortwave vs. trapped longwave) to judge whether a high cloud would cool or warm the surface.

Identifies cirrus as high-altitude (8,000–12,000 m), thin, and white — properties relevant to their optical/thin radiative behavior.

Using the fact cirrus are high and thin, a student can infer they transmit more solar radiation and mainly interact with terrestrial infrared, which affects net surface forcing.

Defines high clouds (cirrus, cirrostratus, cirrocumulus) and notes cirrus are feathery and often produce halos — implying ice-crystal composition and optical thinness.

Knowing high clouds are ice-crystal and optically thin, a student can extend to how scattering/refraction and infrared absorption/emission by ice crystals influence net surface radiation.

Specifically notes halos are produced by refraction in ice crystals in cirrus/cirro-cumulus — confirming cirrus interaction with solar radiation via ice-crystal optics.

A student could use ice-crystal refraction/scattering implications to reason that these clouds transmit most direct sunlight (low SW reflection) but can alter outgoing IR.

Classifies clouds by height (high/middle/low) and lists cirrus among high clouds — useful for applying height-dependent radiative behaviour.

By combining this classification with basic facts (higher clouds are colder and radiate less downward IR), a student can infer how high-cloud temperature affects the balance of trapped vs. reflected radiation.

Presents the rule/example that ‘clouds absorb the radiation released from the Earth's surface’ (used in a UPSC question about cloudy nights).

A student could combine this with the fact that low clouds lie close to the surface to infer they can intercept/absorb terrestrial IR effectively.

States the general mechanism that atmospheric constituents absorb infrared emitted from the surface and re‑emit it, producing warming (greenhouse effect).

A student can extend the general IR‑absorption role of atmospheric components to consider clouds (liquid water/ice) as additional IR absorbers/emitters.

Notes that within the troposphere water vapour and other gases absorb much of the near infrared radiation.

Since low clouds (stratus/stratocumulus) are in the troposphere and contain water, a student could infer they likely interact with IR similarly to atmospheric water vapour.

Quantifies that a large portion of terrestrial (longwave) radiation is absorbed by the atmosphere (34 of 51 units), showing atmospheric absorption of outgoing longwave is significant.

A student could reason that clouds, as part of the atmosphere and substantial radiative components, contribute to that absorbed fraction, especially when low and dense.

Defines low cloud types (stratocumulus, nimbostratus, stratus) and describes them as dense/opaque (nimbus example) and low‑lying.

Knowing low clouds are dense and near the surface, a student could combine density + proximity to surface radiation to support the plausibility of strong longwave absorption.

Gives an explicit textbook rule contrasting cloud altitude: 'High clouds primarily reflect solar radiation and cool... Low clouds have a high absorption of infrared radiation... and thus cause a warming effect.'

A student could combine this rule with basic facts about radiative fluxes (solar vs. terrestrial IR) to judge whether low-cloud IR absorption outweighs their solar reflection for net surface warming.

States that thick cumulus and stratus clouds absorb incoming solar insolation by day and 'blanket' outgoing terrestrial heat, affecting surface temperature.

Use this pattern to consider the balance of daytime solar reduction versus nighttime longwave trapping (e.g., by latitude or diurnal cycle) to assess net effect.

Notes as a UPSC question option that 'Clouds absorb the radiation released from the Earth's surface' — a general statement about clouds trapping outgoing IR.

Combine with knowledge of which cloud types are low and their prevalence at night to infer whether they tend to raise night-time surface temperatures.

Describes nimbus clouds as 'extremely dense and opaque to the rays of the sun' and forming near the surface, indicating strong effects on incoming solar radiation.

Extend by considering that if low clouds are opaque to sunlight, their daytime cooling effect (by reducing insolation) must be weighed against their IR trapping to determine net warming/cooling.

Provides classification that identifies stratocumulus and nimbostratus as 'low clouds', tying the cloud types in the statement to textbook categories.

A student can use this to match the physical properties described elsewhere (opacity, altitude) to the specific low-cloud types when estimating their radiative roles.