Considering Earth’s radiation budget and diurnal cycle, which statements correctly describe how the Earth reflects and emits radiation during daytime and nighttime conditions?

Introduction / Context:
Remote sensing relies on understanding sources of electromagnetic energy. Earth’s surface and atmosphere interact with incoming shortwave solar radiation and continuously emit longwave thermal radiation. Recognizing how these components vary throughout the day is essential when interpreting optical and thermal images.

Given Data / Assumptions:

• Shortwave solar radiation dominates illumination in the visible and near-infrared during daytime.
• Earth’s surface emits thermal infrared radiation day and night based on temperature and emissivity.
• Clouds and atmosphere also reflect and emit radiation.

Concept / Approach:
During daytime, sensors detect a combination of reflected solar energy (shortwave) and emitted terrestrial energy (longwave). At night, the reflected component vanishes but thermal emission persists, enabling thermal imagers to operate without sunlight. Understanding this is crucial for selecting appropriate bands and interpreting radiance as reflectance or brightness temperature.

Step-by-Step Solution:
Daytime: confirm presence of reflected solar radiation from surfaces and clouds.Daytime: acknowledge concurrent thermal emission from surfaces (lower magnitude in shortwave, dominant in mid/thermal IR).Nighttime: only thermal emission remains detectable in passive measurements.Hence, all statements A–C are correct, so choose “All of these.”

Verification / Alternative check:
Visible images disappear at night; thermal IR images remain available, demonstrating continuous emission. Daytime thermal imagery records surface temperature patterns even under sunlight.

Why Other Options Are Wrong:

• Claiming negligible daytime reflection contradicts the very basis of optical remote sensing.

Common Pitfalls:
Confusing radiance units with reflectance; ignoring atmospheric contributions to both reflection and emission.

Final Answer:
All of these