Natural Resource Management in South Asia

6

Atmosphere

Introduction

Earth’s atmosphere comprises the gases that envelop the earth. All these gases are held by its gravity. Primary components of these gases are nitrogen (78 per cent), oxygen (21 per cent), argon (0.93 per cent), carbon dioxide (0.038 per cent) and trace amounts of other gases and variable amount of water vapour. Together these gases form the air that supports all life forms. They also protect us from ultraviolet (UV) solar radiation and moderate temperature extremes between day and night.

 

Table 6.1 The Principal Layers of Earth’s Atmosphere

Layer	Range (km)
Exosphere	600–10,000 km,
Thermosphere	85–600 km
Mesosphere	50–85 km
Stratosphere	12–50 km
Troposphere	0–12 km

The atmosphere is densest at sea level (1.2 ...