Snow hydrometeors: What does natural snow consist of in atmospheric science and remote sensing contexts?

Introduction / Context:
Understanding the microphysical forms of snow is vital for meteorology, avalanche science, hydrology, and remote sensing retrievals. Snow observed at the surface or aloft is not monolithic; it includes distinct particle types influencing radar backscatter, optical albedo, and accumulation characteristics.

Given Data / Assumptions:

• Snow forms via vapor deposition onto ice nuclei within clouds.
• Microphysical processes include aggregation and riming.
• Terminology distinguishes single crystals, rimed crystals, and snowflakes.

Concept / Approach:
Single snow crystals are pristine hexagonal forms (plates, columns, dendrites). Rimed snow crystals develop when supercooled droplets freeze on crystal surfaces, adding mass and altering shape. Snowflakes are aggregates of multiple crystals bound together, forming the large flakes often seen at the surface. Natural snowfall commonly contains a mixture of these, depending on temperature, humidity, and in-cloud liquid water content.

Step-by-Step Solution:
Recognize snow crystal as the fundamental ice particle.Account for riming: accretion of supercooled droplets produces rimed crystals (densified particles).Include aggregation: clusters of crystals produce snowflakes with large, fluffy structures.Conclude that real snowfall includes all these categories; choose the comprehensive option.

Verification / Alternative check:
Field microphotography and in situ probes (e.g., 2D-S, CIP) document coexisting pristine crystals, rimed crystals, and aggregates within the same cloud systems.

Why Other Options Are Wrong:
Single-category choices omit commonly co-occurring forms in natural snowfall.Only graupel: Graupel (heavily rimed pellets) is a subtype, not the entirety of snow.

Common Pitfalls:
Equating all snow to large flakes; overlooking riming/aggregation processes that change density and fall speed.

Final Answer:
All of these.