ENV100Y5 Lecture Notes - Lecture 45: Northern Hemisphere, September Equinox, Axial Tilt

• School: UTM
• Department: Environment
• Course: ENV100Y5
• Professor: Barbara Murck

Document Summary

Chapter 14 - atmosphere & weather. Atmosphere= thin layer of gases that surrounds a planet or moon (retained by gravity ) Earth"s atmosphere- 8% n, 21% o, 1% other: nitrogen or oxygen amount does not change, onlywater vapour does. Most variable = water vapour. 2nd most- variable = aerosols. Absorbs radiation and moderates climate. Transports/recycles: water, heat, pollutants, nutrients. Moving pollutants isn"t really a good thing! But because it moves heat it allows us to live. Vertical differences in temperature, density, and composition. Human activity is changing the composition of the atmosphere. Troposphere:80% mass, 99% water vapour & aerosols. Tropos = change where weather occurs (well mixed!) Thickest at equator; thin at poles: exosphere => thermosphere => mesosphere => stratosphere => troposphere. Atmospheric properties include pressure, temperature, and humidity. Within troposphere, all three decline with increasing altitude. Gravitational effect: as altitude increases, there are fewer air molecules (it gets drier, colder, and harder to breathe)