PPT10 - Earth’s Albedo

PPT10 - Earth’s Albedo - Albedo = fraction...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Albedo = fraction of incident solar radiation directly reflected to outer space The term albedo (Latin for white) refers to the fraction of incident solar radiation that is directly reflected to outer space. Clouds account for a large fraction of the Earth’s albedo (26% out of a total of 30%) The Earth’s surface also reflects some of the incoming sunlight (4%). The reflection of the Earth’s surface depends on the type of surface (ice and deserts are very reflective; ocean and forests are not) Albedo of oceans depends on latitude and time of the day Albedo of different surfaces Highest albedo is for fresh snow and ice and some types of clouds The lowest albedo is for water (i.e. oceans) Note that the ocean’s albedo varies with latitude and time of the day. When the Sun is low over the horizon (i.e. early morning, late afternoon, or high latitudes), a higher fraction of sunlight is reflected by all surfaces. The albedo of the Earth’s surface is that relatively low (30%) because 70% of the surface of the Earth is covered by water, which has the lowest albedo and a large fraction of the continents is covered by forest, which an equally low albedo. Only ice and snow covered
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
areas have an albedo similar to clouds. Without clouds, Earth’s would have a much lower albedo Earth’s albedo depends on: - Cloud cover and type - Precipitation patterns & land cover - Cryosphere (ice reflects sunlight) - Tectonics (position & fragmentation of continents and sea level) - polar continents (more ice) - large land masses (more deserts) - sea level (depends on rate of seafloor spreading) The Earth’s albedo therefore depends on: - cloud cover (we will see that different types of clouds have different albedo) - precipitation patterns and resulting changes in terrestrial biosphere (e.g. desert vs rain forest, which reflect different proportion of incoming sunlight; more deserts means colder) - extent of the “cryosphere”, i.e. the amount of ice covering Earth’s surface (ice reflects sunlight more effectively. More ice cover tends to cool the planet) - tectonic processes affect continental ice cover, extent of deserts, and sea level. Continents drifting to the poles favor formation of continental ice and induces further cooling (higher albedo) Fragmentation of continents into smaller land masses results in less deserts and induces warming (lower albedo) fast spreading rates result in high sea level; oceans have lower albedo than land masses higher sea level induces warmer climate Cloud cover accounts today for ~ 87% of the Earth’s albedo. . More clouds: Higher albedo Cooler climate First, let’s have a look at the effect of clouds We have seen that cloud cover accounts today for a large fraction of the Earth’s albedo So, cloud cover could potentially be a very important factor affecting climate. Decreasing cloud cover should decrease Earth’s albedo and warm the planet (we can
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/20/2010 for the course EOSC 116 taught by Professor Randell during the Winter '09 term at The University of British Columbia.

Page1 / 15

PPT10 - Earth’s Albedo - Albedo = fraction...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online