The correct option is Fog and Mist.
Explanation
Visibility in the lower atmosphere is primarily determined by the presence of suspended particles, such as water droplets or ice crystals, resulting from condensation near the earth's surface.
Analysis of Options:
- Dew and Frost Dew and Frost: These are forms of condensation where moisture deposits directly onto solid surfaces (such as blades of grass or rocks). Since the water vapor condenses on a surface rather than remaining suspended in the air, these phenomena do not obstruct atmospheric visibility.
- Fog and Mist Fog and Mist: These phenomena occur when condensation takes place on hygroscopic nuclei within the air mass near the ground.
- Fog: It is essentially a cloud formed at or very near the ground. It consists of very fine water droplets suspended in the air, reducing visibility to less than 1,000 meters (1 km).
- Mist: This is similar to fog but less dense, occurring when water droplets are larger and more dispersed. Visibility in mist is generally between 1 km and 2 km.
- Cirrus clouds Cirrus clouds: These are high-altitude clouds formed at elevations between 8,000 and 12,000 meters. They are composed of ice crystals and do not impact visibility in the lower atmosphere.
- Convectional rain Convectional rain: While intense rainfall can temporarily reduce visibility, it is a form of precipitation where water falls to the ground. It is not a suspended state of condensation defined by zero visibility in the same manner as fog.
Key Takeaway: Fog and Mist are forms of condensation characterized by suspended water droplets near the ground, distinguished by visibility range: Fog reduces visibility to below 1 km, whereas Mist allows visibility between 1 km and 2 km.