Question

Microwave remote sensing is useful in monitoring
(A) Soil moisture
(B) Canopy structure
(C) Snow cover
(D) Moisture profiling in the atmosphere
(E) Ocean circultion
Choose the correct answer from the options given below :

• A. (A), (B) and (D) only.
• B. (B), (C) and (D) only.
• C. (A), (B), (C) and (D) only.
• D. (A), (B), (C), (D) and (E).

Hint:

Because microwaves can penetrate both clouds and vegetation, they are incredibly useful for tropical and forested regions where cloud cover often blocks visible and infrared satellite sensors.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Microwave remote sensing uses electromagnetic radiation with wavelengths ranging from $1\text{ mm}$ to $1\text{ m}$ (frequencies from $0.3$ to $300\text{ GHz}$).
Because of these longer wavelengths, microwaves can penetrate clouds, haze, and rain, allowing for all-weather, day-and-night imaging.

Step 3: Detailed Explanation:
Let us analyze each of the monitoring applications:
(A) Soil moisture:
The dielectric constant of water ($\approx 80$) is much higher than that of dry soil ($\approx 3 - 4$).
Microwaves are highly sensitive to these dielectric changes, making them the primary tool for mapping surface soil moisture.
(B) Canopy structure:
Microwaves can penetrate vegetative canopies.
The backscattered signal provides information on leaf area index (LAI), branch orientation, and canopy biomass.
(C) Snow cover:
Microwaves can penetrate snowpacks, allowing researchers to measure snow water equivalent (SWE) and map snow-covered areas.
(D) Moisture profiling in the atmosphere:
Satellite microwave sounders measure emissions from atmospheric water vapor to construct vertical moisture and temperature profiles.
(E) Ocean circulation:
Microwaves are used in radar altimetry to measure sea surface height, which helps map ocean currents and circulation patterns.

Step 4: Final Answer:
Microwave remote sensing is highly useful for all five applications (A, B, C, D, and E).
This corresponds to Option (D).