teaching:radiative_transfer

teaching:radiative_transfer:cloud_detection

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:03+0000

Cirrus cloud detection In satellite images it is often difficult to see thin clouds, e.g. cirrus clouds. To detect cirrus clouds a common procedure is to look at the radiance difference between two channels (around 10 µm and 12 µm). Calculate the radiance at 10 µm and at 12 µm for ice clouds in the optical thickness range from 0.1 to 10 and plot the results (radiances and difference). Explain how the cloud detection could work.

teaching:radiative_transfer:cloudbow

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:04+0000

Impact on cloud optical thickness and droplet size on radiance field, visibility of cloudbow Calculate the upwelling radiance at 500nm the top of the atmosphere for an atmosphere including a liquid water cloud layer. Use the discrete ordinate method with intensity correction for your simulation (

teaching:radiative_transfer:disort_nstr1

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:03+0000

Discrete ordinate method: Impact of number of streams on clearsky radiance field at surface Task: Calculate the radiance field for a clearsky atmosphere at the surface using the DISORT solver (version 1 which includes the DOM solution method which was derived in the lecture). Perform the calculation for a pure Rayleigh atmosphere (only molecular absorption and scattering) and for an atmosphere including aerosol. What changes when you include aeorsol? Investigate the impact of the number of stre…

teaching:radiative_transfer:disort_nstr2

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:03+0000

Discrete ordinate method: Impact of intensity correction on cloudy radiance field at TOA Calculate the radiance field for a cloudy atmosphere at the top of the atmosphere using the DISORT solver. Perform the calculation first for a pure Rayleigh atmosphere (only molecular absorption and scattering) and then include a cloud layer. What changes when you include the cloud? Use version 1 of disort with and without delta scaling (

teaching:radiative_transfer:exam

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:04+0000

Results of radiative transfer exam written on 17 February 2011 mean grade: 2.3 You may look at your exams in my office. In case you want to retake the exam please come to my office to find a date.

teaching:radiative_transfer:glory

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:04+0000

Glory simulation The glory is an optical phenomenon which can be observed from the airplane or from a mountain, when the sun is in the back of the observer (). Very high angular resolution about the backscatter region (~177°-180°, corresponding to umu~0.998-1 if the sun is in the zenith) is required to resolve the glory (see

teaching:radiative_transfer:halo

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:03+0000

Ice clouds - halo and crystal shape Investigate the radiance field in presence of an ice cloud. What do you observe? What is the impact of the crystal shape? An ice cloud can be defined in the libRadtran input file as follows: ic_properties hey interpolate ic_habit solid-column

teaching:radiative_transfer:irrad_rad_delta_sc

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:03+0000

Irradiance and radiance at surface below a water cloud with and without delta scaling Calculate the solar irradiance spectrum in the spectral range from 400nm -- 800nm. Use rte_solver disort with and without delta-scaling (deltam on/off). Assume that the cloud scattering phase function can be approximated by a Heney-Greenstein phase function (see

teaching:radiative_transfer:legendre

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:04+0000

Legendre decomposition of phase function and delta scaling Task: The file includes a typical scattering phase function for cloud water droplets. It has been computed using Mie theory (mie tool in libRadtran). In order to apply the discrete ordinate method the phase function is expanded in a Legendre series. The number of terms in the Legendre series is equal to the number of streams (nstr). Investigate how many Legendre terms are required to represent the phase function as a Legendre series.

teaching:radiative_transfer:legendre_hg

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:04+0000

Legendre decomposition of Heney Greenstein phase function The Heney-Greenstein function p_HG=(1-g*g)/(1+g*g-2*g*mu)**(3/2) is often used to approximate scattering phase functions of aerosols or clouds. Show that the Legendre coefficients of p_HG are P_l=g^l. Investigate how many Legendre coefficients are required for asymmetry parameters of 0, 0.5, 0.7, 0.8, 0.85, 0.9.

teaching:radiative_transfer:mie_calc

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:04+0000

Mie calculations Extinction efficiency Asymmetry parameter Phase function - comparison to geometrical optics [From Hansen and Travis (1974), Fig.5, S. 538]

teaching:radiative_transfer:mie_phase

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:04+0000

Scattering phase function as function of particle size (water cloud) Perform Mie calculations at one wavelength (e.g. 550 nm) for gamma distributions with effective radii in the range from 1 to 20 µu. Use the option 'pmom' to output the Legendre polynomials of the phase function. Use the tool 'phase' to calculate the phase function. Finally plot the phase functions for the various particle sizes and describe the results!

teaching:radiative_transfer:mie_reff_dep

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:04+0000

Optical properties of liquid water for various effective radii * Plot gamma size distributions with an effective variance of 0.1 for effective radii in the range from 1 to 80 µm. * Perform Mie calculations for wavelengths from 100 to 10000 nm for gamma distributions with effective radii from 1 to 20. Plot the real and the imaginary part of the refractive index, the extinction coefficient, the asymmetry parameter, and the single scattering albedo.

teaching:radiative_transfer:mie_reff_dep_ice

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:04+0000

Optical properties of ice for various effective radii * Perform Mie calculations for wavelengths from 100 to 10000 nm for the gamma distributions with effective radii from 1 to 20. Plot the real and the imaginary part of the refractive index, the extinction coefficient, the asymmetry parameter, and the single scattering albedo. Use the refractive index of ice.

teaching:radiative_transfer:mie_single_vs_dist

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:04+0000

Extinction efficiency for single particle and for particle size distribution Perform a Mie calculation for the size parameter range from 1 to 1000 for a single sphere with a radius of 10 µm. Plot the extinction efficiency as a function of size parameter and describe the result.

teaching:radiative_transfer:planck

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:04+0000

Planck radiation Task: Plot the Planck function at 6000 K and at 300 K and calculate the solar irradiance at the top of the atmosphere assuming that the sun has a temperature of 6000 K and emits blackbody radiation. from pylab import * def planck(lam, T): c= 2.99792458e8 # speed of light k= 1.380662e-23 # Boltzmann constant h= 6.626180e-34 # Planck constant return 2*pi*h*c*c/(lam**5 * (exp(h*c/(lam*k*T))-1.)) lam=arange(0.05, 1000, 0.01)*1e-6 d= 1.49e11 # distance…

teaching:radiative_transfer:radiative_transfer

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:04+0000

Radiative transfer lecture WS 2010/2011 [Summary of the lecture (10th February 2011)] Exam (17 February 2011) Literature This list is by far not complete. It includes some literature which has been used for the lecture. Radiative transfer * Zdunkowski et al., Radiation in the atmosphere (2007) * [DISORT report] * Chandrasekhar, Radiative transfer (1960)

teaching:radiative_transfer:rs_tau_reff

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:03+0000

Remote sensing of cloud optical thickness and effective radius Nadir radiances (TOA, viewing direction 'umu 1', straight downwards) at the two wavelengths 750 nm and 2160 nm In the following we simulated the backscattered radiation for a given optical thickness of a cloud and a given effective radius. From it we try to find a connection between radiation and optical properties of the cloud.

teaching:radiative_transfer:runit

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:04+0000

Running libRadtran See also: and To run an input file and write the output into a file do: uvspec < input_file.inp > output_file.out If irradiances are calculated, the standard output includes the following columns: * wavelength (lambda) *

teaching:radiative_transfer:shell

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:04+0000

Shell scripts Loops When you want to loop over input parameters (e.g. sza, nstr ...) this can be done with a simple shell script see (FAQ about loops)

teaching:radiative_transfer:sizedist_sens

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:04+0000

Sensitivity of optical properties on particle size distribution * Plot gamma size distributions for an effective radius of 10 µm and effective variances of 0.01, 0.05, 0.1, 0.15. (Petra, Heiner) * Perform Mie calculations for wavelengths from 100 to 10000 nm for the different gamma distributions. Plot the real and the imaginary part of the refractive index, the extinction coefficient, the asymmetry parameter, and the single scattering albedo.

teaching:radiative_transfer:solar_irrad

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:03+0000

Solar irradiance spectrum Task: Compute the direct and the diffuse solar irradiance spectrum at the surface in the spectral range from 200 to 3500 nm. Plot the result together with the extraterrestrial solar spectrum and the estimate of solar irradiance using the Planck function. Which spectral features result from absorption in the Earth atmosphere?

teaching:radiative_transfer:thermal

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:04+0000

TOA radiance at 10 μm as function of cloud height Calculate the radiance at the top of the atmosphere at a wavelength of 10 μm assuming that the atmosphere includes a cloud layer. How does the radiance depend on cloud altitude? Hints: * Use the libRadtran input file and the plotting script from

teaching:radiative_transfer:thermal_irrad

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:03+0000

Outgoing longwave radiation spectrum Task: Compute the emitted irradiance spectrum at the Earth surface and at the top of the atmosphere from 3.5 µm to 100 μm. Plot the result together with the Planck function at the surface temperature. # specify libRadtran data path data_files_path /home/claudia/libRadtran/data # Location of atmospheric profile file. atmosphere_file us-standard mol_abs_param lowtran albedo 0.0 …

teaching:radiative_transfer:uv_irrad

Anonymous (anonymous@undisclosed.example.com) — 2018-05-04T08:40:04+0000

Impact of various parameters on UV irradiance Task: In the spectral range from 300 nm to 500 nm investigate the influence of the following parameters on the irradiance spectrum: solar zenith angle, surface albedo, ozone column. libradtran_path='/local/libRadtran-1.5-beta/bin' for var in 0 15 30 45 60 ; do sed 's/SSS/'$var'/' < uv-zenith.inp > uv-$var.inp | $libradtran_path/uvspec -i uv-$var.inp > tmp/uv$var.out done