Climate-Radiation Balance
Climate-Radiation Balance
Whether and climate Weather is the condition of the atmosphere in terms of temperature, humidity, winds and precipitation Climate is defined as the average weather over various time periods ranging from a few weeks to decades to geological timescales Whether and climate are ultimately determined by location, topography, and the exchange of radiant energy between the Sun, Earth, and space
Whether and Climate • Weather is the condition of the atmosphere in terms of temperature, humidity, winds and precipitation. • Climate is defined as the average weather over various time periods ranging from a few weeks to decades to geological timescales. • Whether and climate are ultimately determined by location, topography, and the exchange of radiant energy between the Sun, Earth, and space
Factors affecting the earths climate Incoming solar irradiance The earth system Surface Atmosphere (greenhouse gases particles, etc) Clouds
Factors affecting the earth’s climate • Incoming solar irradiance • The earth system – Surface – Atmosphere (greenhouse gases, particles, etc) – Clouds
Solar irradiation Solar constant Solar constant: The amount of solar energy received per unit of area outside the Earths atmosphere, normal to the direction of propagation of the light 1370J/s/m 1370watts/m
Solar irradiation: Solar constant Solar constant: The amount of solar energy received per unit of area outside the Earth’s atmosphere, normal to the direction of propagation of the light. 2 2 So = 1370J /s/ m = 1370watts/ m
Radiation Budget The earth's climate system constantly tries to maintain a balance between the energy from the Sun that is absorbed by the earth and the energy that goes from Earth back out to space. We refer to this process as earth's radiation budget. This radiation budget allows the earth to maintain the moderate temperature range essential for life as we know it The components of the earth system that are important to the radiation budget are the planet's surface, atmosphere, and clouds
Radiation Budget • The Earth's climate system constantly tries to maintain a balance between the energy from the Sun that is absorbed by the Earth, and the energy that goes from Earth back out to space. We refer to this process as Earth's "radiation budget." • This radiation budget allows the Earth to maintain the moderate temperature range essential for life as we know it. • The components of the Earth system that are important to the radiation budget are the planet's surface, atmosphere, and clouds
Radiation Budget at the Top of the atmosphere Incoming outgoing outgoing Solar Short wave Long wave Radiation Radiation Radiation 100% 30% 70%
Radiation Budget at the Top of the Atmosphere
Albedo(a The fraction of solar energy that is reflected back to space is called the albedo Different parts of the Earth(surface and cloud cover)have different albedo Over the whole earth, about 30 percent of incoming solar energy is reflected back to space
Albedo (a) • The fraction of solar energy that is reflected back to space is called the albedo. • Different parts of the Earth (surface and cloud cover) have different albedo. • Over the whole Earth, about 30 percent of incoming solar energy is reflected back to space
What contributes to the global albedo? Clouds account for two-thirds(67%)of the global albedo Backscattering from gaseous molecules and particles in the air: 20% o Earth's surface: 13%
What contributes to the global albedo? • Clouds account for two-thirds (67%) of the global albedo • Backscattering from gaseous molecules and particles in the air: 20% • Earth’s surface: 13%
HIGH ALBEDO (Snow, Ice, Sand LOW ALBEDO (Forests, Water)
Albedo for various types of surface Surface albedo Clouds(average over all types)0.35-0.40 Snow 0.60-0.80 Ocean 0.06-0.20 Deserts 0.25-0.40 Agricultural land 0.10-0.20 Forest 0.10-0.20
Albedo for various types of surface Surface albedo Clouds (average over all types) 0.35-0.40 Snow 0.60-0.80 Ocean 0.06-0.20 Deserts 0.25-0.40 Agricultural land 0.10-0.20 Forest 0.10-0.20