Monday, Oct. 2: Clear-sky radiation; solar attenuation, Thermal nomenclature

Sun Earth Y-axis: Spectral radiance, aka monochromatic intensity units: watts/(m^2*ster*wavelength) Blackbody curves provide the envelope to Sun, earth emission

Sun Earth visible

1 Angstrom= m. wavelengths < 0.1 micron (1000 angstroms) wavelengths 2O Ozone < 0.31 micron Depth of penetraion into earth’s atmosphere of solar UV Visible spectrum 0.39 to 0.76 micron

Thermal Radiation: scattering negligible absorption,emission is what matters Math gets complicated: thousands of absorption lines, each varying individually with pressure, temperature natural Natural Doppler broadening: Half-width goes as T 1/2 Lorentz (Pressure) broadening: Half-width goes as P/T ( ) (Freq shift)/half-width absorption < 20 km, pressure broadening > 50 km Doppler broadening

Continuing efforts to improve database on line absorption strengths and Halfwidths: H20 continuum, Microwave lines, are examples 16 micron 7 micron

Radiation transmits through an atmospheric layer According to: I = intensity r= air density r = absorbing gas amount k =mass extinction coeff.  rk = volume extinction coeff. Inverse length unit Extinction=scattering+absorption Path length ds +J ds emission Thermal ~ 0

T = e -  sec   Beer’s Law used to assess solar constant in pre-satellite days, now used to calibrate instrumentation & determine aerosol&cloud optical depth from ground Langley plot Ln (I inf /I  ) =  sec 

dI = -I k abs sec  dz Transmission through a layer, ignoring scattering and emission: After integration: T = e -  sec   T = transmissivity;  = optical depth, or thickness Beer’s Law or Lambert’s Law Consequence: most radiation is absorbed/emitted at an optical depth of 1.

Limb Effects darkening brightening affects ALL terrestrial remote sensing

Limb Sounding as a Remote Sensing Technique: first get the temperature from Planck function radiance then use radiance in an absorbing/emitting wavelength to get atmospheric concentration at that height HIRDLS

To calculate the broadband infrared emission, One simplification is to group lines together, Use spectral-band-average values for absorption - “band” models. A more elegant solution is to group lines by their absorption lines strengths, and integrate over that. Only works in infrared

attenuation emission Full radiative transfer equation for infrared/microwave (I.e. ignores scattering): Plane-parallel approximation: the earth is flat. -> the temperature, atmospheric density is a function of height (or pressure) alone. Curvature of earth ignored, atmosphere assumed to be horizontally homogeneous. Flux density with “flux transmissivity”

Radiative heating rate profiles: Manabe & Strickler, or- Cooling to space approximation: Ignore all intervening layers Rodgers & Walshaw, 1966, QJRMS

Remote temperature sensing CO 2 particularly suited (well-mixed & emissive) (what part of the Earth is this from ?)

Weighting function

If scattering is also included: 3 radiatively-important scatterer parameters: optical depth ( how much stuff Is there ?) single-scattering albedo  k sca /(k scat + k abs ) ( how much got Scattered rather than absorbed ?) asymmetry parameter g, or phase function P(cos  : (describe how it scatters)

Wednesday: results from top of atmosphere radiation Balance questions up to 4.40 some other aerosol, greenhouse gas, results

Whether/how solar radiation scatters when it impacts gases,aerosols,clouds,the ocean surface depends on 1. ratio of scatterer size to wavelength: Size parameter x = 2*pi*scatterer radius/wavelength X large X small Sunlight on a flat ocean Sunlight on raindrops IR scattering off of air, aerosol Microwave scattering off of clouds Microwave (cm) Scattering neglected