understanding anything entirely, howevger ths paqragraph

presents pleasant understanding even. ]]>

thank you very much. ]]>

Van Minh Nham,

The link to define_atmos_0_5.m is given in post

https://scienceofdoom.com/2013/01/10/visualizing-atmospheric-radiation-part-five-the-code/

That might satisfy your needs. (The file has the ending .doc, but it’s really a .m file.)

]]>thank you very much. ]]>

It seems that Spectralcalc will give you the Hitran data at:

http://www.spectralcalc.com/spectral_browser/db_data.php

Select Hitran2008 from the line list.

Select H20 from the species.

Select the range of wave numbers (I used 1 to 2500)

Select datafile format as csv.

then click on ‘Extract data’

then rigth click on ‘View lines’ and save as *.csv

To read it into matlab I had to delete the header information and just keep the first 10 columns (the rest are codes and some have alphanumeric characters)

Then to figure out what columns did SOD use for his values of:

S, gama, iso,nair,v I downloaded the same data for CO2 and plotted all the columns until I matched the SOD variables that he uses in his co2 matlab file for HITRAN_0_3.m:

column 1 is the species code (H20 or CO2, etc)

iso is column 2, the isopotologue code

v is column 3, labeled as frequency

S is column 4, labeled as intensity

gama is column 6, labeled as air_halfwidth

nair is column 9, labeled as t_exponent

the list of isopotologue concentrations is from the document describing the 2004 Hitran edition:

http://www.cfa.harvard.edu/hitran/docs.html

for H2O there are 6 with the following concentrations:

isoprop=[0.997317 0.0199983 0.000372 0.00031069 0.000000623 0.000000116];

I was then able to recreate the CO2 transmittance graphs (using CO2 data) and create similar ones for H2O (using H2O data). Now I am off going to figure out how to define H2O concentrations in the atmosphere, and how to do combined CO2 and H2O runs.

Thanks to all for making this available to me 🙂

]]>I went ahead and got the HITRAN_0_3.m program you posted running, by adding the Ttropo parameter to define_atmos_0_2.m (the one I had) and calling it define_atmos_0_3.m, then I used your hitran_co2_keyparams1.txt file and saved it as Co2.mat, assigning the columns to ‘iso’,’S’,’v’,’gama’, and ‘nair’. It all seemed to work. THANKS!!

Then I had the hardest time trying to create a Bgamma curve using the wavenumber, I figured the wavenumber was 1/wavelength (some people use 2*pi/wavelength) and could not get the integral of the Bgamma curve (spectral radiance) to match sigma*T^4 (stefan Bolztman law). Never got it working using wavenumbers, had to convertt them to wavelengths. After some reading I figured that the Stefan Boltzman energy radiated per surface area goes in all directions from the surface, and the Bgamma curve is only perpendicular to the surface. The integral of the Bgamma curve vs gamma = sigma*T^4 divided by pi.

Ok, after all that I could generate the black body radiation at 296K and integrate it, then run the HITRAN_0_3 program (with the wave number range increased to vmin=1 to vmax=2500 and get the transmittance. Then I multiplied the transmittance to the black body curve, integrated it, and got the ratio of the two integrals and then I call that the effective transmittance, and -ln(that) I call the grey optical thickness. I hope I did not go off the deep end there. The results for CO2 ppm’s of 70,140,280,560,1120 then seem to follow the relation tautotal = 0.0495*(CO2ppm)^0.2618

If the total optical thickness for the atmosphere is about 1.9 then that means that at ~ 280ppm the percent contributed by CO2 is 0.216/1.9 or 12%

1) Could you post, or direct me to where I could get a similar file as the CO2 data, but for H2O?

2) I ran the HITRAN_0_3 at 0 CO2 ppm and got transmittance of 1.0. So it does not appear to include any other species. Is the air (N2 and O2) totally transparent to IR? or do we also need to get similar files for air? Or O2 and N2?

Could you comment on the approach?. And thanks again for making the programs available so we can use them.

]]>And the result would not be very sensitive to surface temperature – so if you did it for 288K it would be very close to the answer for 263K.

But if you just average the spectrum from fig 15 over an unweighted 4-100 μm you would get a very different number.

]]>If you took the average of this transmittance over the terrestrial spectrum (4 – 100 μm, or 100 cm^{-1} – 2500 cm^{-1}) then you would have something useful for the effective transmittance of CO2.

One important point to note is that to get a correct answer you would need to “Planck-weight” the average for a given surface temperature.

This is because the importance of transmittance at 5 μm is much less than the importance of transmittance at 10 μm, because the emission of radiation is much less at 5 μm than 10 μm.

Perhaps I might get around to doing it at some stage.

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