## Modeling of radiative fluxes and heating/cooling rates in the IR

### Written report (as part of Homework 4) due: 8 Oct.

Instruction: to calculate the profile of IR fluxes click on RUN IR-RAD
Task 1
1. Calculate the IR upwelling and downwelling fluxes for the Midlatitude Summer Atmosphere (with H2O and O3 turned on). Plot them as a function of pressure (take ~ p=10 mb for the upper level so only the troposphere and stratosphere are plotted). For a different perspective, change the y-axis of the plot to altitude.

Why does the downwelling flux have a change in slope around 200 mb?

2. Repeat the same calculations but with H2O turned off. Compare your results with case A. Explain the differences.
3. Repeat the same calculations but with O3 turned off. Compare your results with cases A and B. Explain the differences.

Task 2
1. For the Tropical Atmosphere, Midlatitude Summer Atmosphere, and Subarctic Summer Atmosphere, compute the IR net fluxes at the surface, near tropopause, and top of the atmosphere. Then calculate and compare the net flux divergence ( ΔFnet in W/m2) in the troposphere and above. Explain your results.
2. Consider the Midlatitude Summer Atmosphere. Note that the flux divergence over the entire atmosphere does not equal the flux emitted at the top of the atmosphere -what else is cooling, i.e. what makes the longwave flux balance?
3. Write a FORTRAN code to compute the IR heating/cooling rates using IR flux profiles from the IR-RAD output. Then compute the IR heating/cooling rates for these three atmospheres in the 10 lowest layers. Briefly explain the differences in radiative heating/cooling profiles between these atmospheres.

Task 3
1. Investigate how a doubling of the present CO2 concentration affects the IR fluxes at the top of the atmosphere (TOA) and at the surface for the Midlatitude Summer Atmosphere by computing the change in the downwelling fluxes at the surface and the change in TOA upwelling fluxes. Briefly explain your results.

2. Calculate and plot the difference between the IR radiative heating rate profile for doubled CO2 and present CO2 cases. Consider the atmosphere below the 10 mb pressure level. Explain the change in the IR heating rate profile.