[RegCNET] How to calculate the SW optical parameters?

[Solmon Fabien]

Hello Xingtao Su

1) You have to assume or calculate an effective radius for each bin .
For that we considered a sub-bin distribution corresponding to an
average emission distribution ( 3 mode distribution of Alfaro). This is
an approximation because the real distribution willl of course change
during transport due to deposition process (cf ACPD discussion about
Zakey 'a paper) , but we have no way to accound for that in rgecm (
except multiplying the number of bins)). If you have data or information
over your region,  you can for your particular region assume an other
distribution to calculate the bin effective radius.

2) The mie calculation should be done iteratively over the spectral
range of the different spectral windows of regm. Eg for a given band  eg
340-640nm consider a 10 nm spectral increment to calculate optical
properties and then average to get an effective value rather than doing
a single Mie  calculation for the band central wavelenght.


Hope it helps

all the best


Fabien

On 05/05/2011 04:00 PM, suxingtao at sina.com wrote:
>
> Dear Fabien, Ashraf, Xunqiang and all RegCM users,
>
> I am sorry to trouble you. Now I am studying the climatic effects of dust aerosols over East Asia. We all know that the dust shortwave optical parameters (asymmetry factor, single scattering albedo and mass extinction coefficient) which are obtained from Mie calculations are specified at 19 discrete spectral intervals in mod_aerosol.f90. 
>
> Now I want to modify these parameters according to the complex refractive indices of East Asian dust aerosols in present RegCM4.0 model. In my opinion, in order to calculate the mass extinction coefficients, we should know the effective radius of each dust size-bin (0.01-1.0micron, 1.0-2.5micron, 2.5-5.0micron, 5.0-20.0micron).
>

>  But I don’t know how to calculate the effective radius of each bin.
>

>  Moreover, in order to calculate the asymmetry factor and single scattering albedo, we should know the weight of each bin.
>
>

> How to get the weight? If my opinion is wrong, how to calculate these three parameters?
>
> I am grateful to you for any help. Thanks very much in advance.
>
>  
>
> Yours Sincerely, 
>
> Xingtao Su
>
> PLA University of Sci. and Tech., Nanjing, China
>
>  

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