Presentation on theme: "Earth System and Climate: Introduction (ESC-I) Coordinators: V. Valsala, R. Murtugudde and M. Baba."— Presentation transcript:
Earth System and Climate: Introduction (ESC-I) Coordinators: V. Valsala, R. Murtugudde and M. Baba
Contents of ESC-Intro. course: Earth System Science and Global Climate ChangeG Global Energy Balance P Global Carbon CycleC Recycling of Elements; C, N, O 2, O 3 depletionC Global Biogeochemical Cycle- oceansC/B Short-term Climate variability, Global Warming P/C/B Should be covered in 7-hours
Continuous supply of energy for the earth systems- Solar Energy The solar energy drives the earth’s atmosphere and ocean.
Energy from sun’s radiation. Nearly all the energy being at wavelengths 0.2µm to 4µm
Electro Magnetic spectrum of solar radiation -----40% of energy-----------10% of energy-- ---------50% of energy------
Blackbody radiation flux Wein’s law λ max = 2898/T Stefan-Botlzmann law F = σT 4
Amount of radiation receives at surface of Earth
Solar constant (S ~ 1368 W/m2) S definition; Average energy ‘flux’ from the sun at a mean radius of earth Latitude Solar heat flux
Reflectivity of earth surface and atmosphere Albedo. Albedo The relative amount of solar insolation reflected back to the space by means of reflection by the earth surface as well as the atmosphere. Average albedo of earth ~ 0.3. Therefore net heat flux received from sun = 240W/m 2
With an average of 240w/m2 influx from the sun, how much would be the atmospheric temperature? Earth with no-atmosphere. E = σT 4 E = 240 w/m 2 σ = 5.7x10 -8 W/m 2 /k 4 T = 250 Kelvin (~ -20 0 C) Earth with atmosphere. E = σT 4 E = 240 w/m 2 = 5.7x10 -8 W/m 2 /k 4 T = 300 Kelvin (~ 15 0 C) Green house effect
The Green house effect. Earth Sun Short wave Long wave (heat) GH-effect helps the atmosphere to be warm at 15 0 C
The one-layer atmosphere model of Green-house effects Adopted from Lee Kump book Ts = 1.19*Te For average Te=255k, Ts = 303K ΔTg = Ts- Te
http://en.wikipedia.org/wiki/Atmosphere_of_Earth Composition of the atmosphere.
Atmospheric Structure How atmospheric pressure varies with altitude P = F/A (Pressure = Force exerted on unit area) The pressure exerted by atmosphere at sea- level is defined as one atmosphere (atm) The SI unit of pressure is Pascal (Pa). 1 Pa = 1x10 -5 bar = 9.9 x 10 -6 atm. Atmospheric pressure decreases with height.
Atmospheric Structure Atmospheric pressure decreases by a factor of 10 for every 16 km increase in altitude. 1 atm at surface 0.1atm at 16 km 0.01atm at 32 km …
The vertical structure of the Atmospheric temperature.
Percentage of radiation absorbed in the atmosphere.
Physical causes of greenhouse effect Molecules absorbs incident atmospheric radiation by mean of increasing its rotation. Example: Water vapor.
Physical causes of greenhouse effect Molecules absorbs incident atmospheric radiation by mean of vibration or bending. Example: CO2 But diatomic symmetric molecules have little capacity to absorb electromagnetic radiation. Therefore N 2 and O 2 are not greenhouse gases
Effects of clouds on radiation Types of clouds: (a) Cumulus clouds: white puffy clouds that look like balls of cotton. They are composed of water droplets and formed by convective activities. (b) Cumulonimbus clouds: Tall cumulus clouds giver rise to thunderstorms. (c) Stratus clouds: They are gray low- level water clouds that are more ore less continuous
Various type clouds with altitude and temperature
Opposing climate effects of cloud Have you noticed cloude days are colder whereas cloudy nights are warmer? o Albedo o Greenhouse effect
Vertical “gradient” of atmospheric temperature Lapse rate: Definition: “rate at which the temperature of the atmosphere decreases with height” Stability of the atmosphere: Warm air is lighter than hot air leads to vertical motion by virtue of buoyancy (gravity). Warm air Cold air Warm air height UnstableStable
Lapse rate Dry (adiabatic) lapse rate Moist (adiabatic) lapse rate
Radiative-Convective equilibrium; with green house effect & no climate feed back These model predicts the green house warming ΔTg = 33 0 C i.e. with CO2 = 300 ppm In test simulations with doubling the CO2, i.e. with 600 ppm (expected true value in near future), the additional ΔTg = 1.2 0 C Why doubling CO2 produce meager changes in temperature? Radiation absorption spectrum by CO2 and other greenhouse gases (H 2 0 vapor) are different
Radiative-Convective equilibrium; with climate feedbacks Climate feedbacks are extremely important because they can either amplify or moderate the radiative effect of changes in greenhouse gas concentrations. We examined the feedbacks in chapter-2 in an imaginary “Daisy world” We analogically attribute such feedbacks to the earth system here.
Water vapor feedback o Water vapor is an excellent absorber of IR radiation. o Unlike CO2, water vapor are at the edges of condensation, and if condenses and rain- out, the average vapor concentration in atmosphere reduces. This can cause reduction in GH-warming o On the other hand, if average surface temperature increases by global warming, water vapor concentration increases and that will increase GH-warming further.
Radiative-Convective equilibrium; with water vapor feedbacks o Average surface temperature changes in doubling the CO2 experiment without climate feedback was 1.2 0 C. o Whereas the above experiment with watervapor feedback causes the surface temperature rise by additional 1.2 0 C. o Therefore the total change in temperature with water vapor feedback is 2.4 0 C. o The feedback factor = 2.4/1.4 = 2 (strong positive feedback).
Snow-ice albedo feedback Ts Snow and Ice Albedo +ve Snow-ice feedback o If surface Ts increases snow melts and albedo decreases o If albedo decreases surface temperature increases o This leads to a positive feedback loop which is unstable.
Infrared-flux and Temperature feedback o If surface temperature Ts increases, the outgoing long wave radiation (infrared- flux increase) o This tends to cool down the surface temperature Ts Long- wave Longwave-Temperature feedback -ve
Climate feed backs of radiation-convection Ts Atm. H 2 O GH- effect (a) Water vapor feed back Ts Snow and Ice Albedo +ve (b) Snow-ice feedback Ts Long- wave (c) Longwave-Temperature feedback -ve
Conclusion o Green house and radiation budget. o Earth is warmed by green house effect (from -15 0 C to 15 0 C) o H 2 O and CO 2 are major GH-gases o Clouds affect radiation budget both by reflection and GH-effect. o Water vapor feedback (+) o Snow-ice feedback (+) o Outgoing Longwave Radiation (IR flux) – surface temperature feedback (-)
Assignment1. Surface heat budget. (a)Plot the global and annual mean shortwave radiation reaching the earth surface (b) Plot the global and annual mean outgoing longwave radiation (c) Plot the global and annual mean sensible heat flux (d) Plot the global and annual mean latent heat flux (e) Plot the global and annual mean Precipitation rate (f) Plot the global and annual mean Evaporation rate (g) From figure a to f, comment the total balance of heat fluxes on annual mean time-scale. (h) From figure a to f, discuss on the symmetry-asymmetry structures of the patterns and interpret its causes. (i)Plot the vertical profile of climatological atmospheric air-temperature for summer and winter at following locations. (1) at x=180e,y=0; (2) at x=80e, y=40s; (3) at x=300e, y=40n; Make a short note on the profiles.