Line-by-Line modeling of radiation transfer in the thermal IR

Written report (as part of Homework 3) due: 29 Sep

Line-by-line (LBL) calculations of radiative transfer in an absorbing/emitting atmosphere is an “exact” method for computing a monochromatic radiance by explicitly accounting for contribution from all individual lines and continuum of gases that can absorb at each wavenumber of interest.

Here, we will be running a LBLRTM code and interpreting the model results. The LBLRTM was developed at the ATMOSPHERIC AND ENVIRONMENTAL RESEARCH INC (see Lecture 7).

Instruction: To browse the FORTRAN source code of LBLRTM click on VIEW LBLRTM

Task 1

Instruction: to run LBLRTM with various water vapor continuum options, click on RUN LBLRTM H20

Consider the Tropical Atmosphere model from 0 km to 13 km.

  • Compute and plot the transmission spectra with all continuum absorption turned on (“all continuum”) and with the continuum turned off (“no continuum”). Compare and discuss the major effects of the water continuum on the transmission in the thermal IR.
  • Estimate contributions and discuss the relative importance of the self-broadening and foreign-broadening continuum of water vapor in the 8-12 um IR window region.


Task 2

Instruction: to run LBLRTM code for this task click on RUN LBLRTM

Select the "7 Molecules" LBLTRM setup. Compute and plot the transmission function from 0 km to 13 km for the Tropics, Arctic Summer, and Mid-latitude Summer Atmospheres in the 0 -2000 cm-1 spectral region with a spectral averaging of 10 cm-1. Briefly discuss and explain major differences between transmission functions of these standard atmospheres.

Repeat your computations with the 1 cm-1 spectral resolution. Briefly discuss how the spectral resolution affects the differences in transmission for considered atmospheric models.