Re: MEGAN model online with WRF-Chem

[Gabriele Pfister]

Hi Megan

the MEGAN online scheme in WRF-Chem uses inputs from DSW.nc and TAS.nc only to calculate the impact of past weather on biogenic emissions. The dependence of the biogenic emissions on the current weather conditions is derived from WRF temperature and solar radiation at that same time step. Clouds are considered in that they impact the WRF temperature and solar radiation. 

Gabi

On Wed, Dec 20, 2017 at 1:58 PM, Christiansen, Megan <megan-chr...@uiowa.edu> wrote:

Hi Gabi,

I have been reading up on how the MEGAN model interacts with WRF-Chem and found this flowchart in my notes from the tutorial and have a couple questions

MEGAN data includes DSW.nc and TAS.nc, both averaged from 1991-2000. If MEGAN starts with surface temperature and downward solar radiation, does it update with Temp and SR from the model first? 

If clouds are generated in the model, does that affect the emissions calculated by MEGAN?

Thanks,
Megan Christiansen

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Gabriele Pfister

Atmospheric Chemistry Observations & Modeling

National Center for Atmospheric Research

Email: pfi...@ucar.edu

Phone: +1 303 497 2915

Web: https://staff.ucar.edu/users/pfister

[Gabriele Pfister]

Hi Megan,

the code does also use the LAI information. You can look at the subroutine module_bioemi_megan2.F in the ./chem directory to see details on this calculation and also Guenther at al. (ACP, 2006)

​. ​

​Note that the current implementation of MEGAN in WRF-Chem is based on an older and not the most recent MEGAN version. Updates are planned for the upcoming releases. ​

Gabi

On Thu, Dec 21, 2017 at 2:34 PM, Christiansen, Megan <megan-chr...@uiowa.edu> wrote:

Hi Gabi,

Thank you for the information. I also have a question about LAI. When running MEGAN online with WRF-Chem, does MEGAN use the monthly LAI downloaded with the code or the LAIs from the met_em files?

I ask because Brad Pierce has daily LAI values from MODIS that can be used to update the LAI in the met_em files, but if MEGAN does not use these values then I am not sure how to update the LAI for MEGAN.

Thanks,
Megan

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From: Gabriele Pfister <pfi...@ucar.edu>
Sent: Wednesday, December 20, 2017 3:36:10 PM
To: Christiansen, Megan
Cc: wrf-chem-bio_emiss
Subject: Re: MEGAN model online with WRF-Chem

 

[Gabriele Pfister]

No sorry, not yet in V3.9.1. 

Gabi

On Thu, Dec 21, 2017 at 2:58 PM, Christiansen, Megan <megan-chr...@uiowa.edu> wrote:

Hi Gabi,

Thanks, I have been reading this paper and will look at the subroutine. We are trying to switch over to WRF-Chem 3.9.1 in the hopes that MEGAN 2.1 is now implemented, but it sounds like that is not quite ready?

Thanks,
Megan

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From: Gabriele Pfister <pfi...@ucar.edu>
Sent: Thursday, December 21, 2017 3:54:21 PM