How to use the latest LAI for MEGAN

[lwcugb]

Name and Institution (Required)

Name:Wei Li
Institution:NOAA ARL

Confirm you have reviewed the following documentation

• Support guidelines
• User manuals
• Debugging GEOS-Chem and HEMCO errors
• Current and past Github issues

Description of your issue or question

I am trying to run HEMCO standalone to generate MEGAN emissions in 2023. The latest YUAN_LAI data provided is in 2020 and the latest raw data on their website is in 2021 and they will not update it anymore (http://globalchange.bnu.edu.cn/research/laiv061). Is there any other LAI data source that I can use for 2023? I guess MERRA2 LAI is not separated to 73 types and could be used.

Thanks!
Wei

[yantosca]

Thanks for writing @lwcugb. We rely on developers to provide us with data sets for input into GEOS-Chem. The Surface-Atmosphere Exchange Working Group may be able to point you into the right direction.

Tagging WG Co-Chairs: @jgeddes85 @cdholmes @amospktai

[jgeddes85]

Great question, @lwcugb. As a matter of fact, this concern was briefly discussed at the last GEOS-Chem steering committee meeting (you can see notes on this here, look under "Working Group Flash Updates", Section G).

Unfortunately, I am not aware of anyone that has worked to update the LAI inputs past 2020 yet. As @yantosca points out, we still rely on individual developers and research groups to update the products as needed and share these with the community. If someone has worked on this (@jennyfisher?), perhaps they will see your question and share an update.

A discussion about longer-term strategies to keep the LAI updated has been initiated with the Surface-Atmosphere-Exchange Working Group, but I don't have a satisfying answer for you at the moment. For now, our recommendation is that you use an LAI climatology for years beyond data availability. Having said that, I'm not sure a climatology option is easily available with LAI data in the current model release (I don't see any recent climatological LAI files from the last couple of LAI updates, though they had been available in the past). To get your work started, you may just need to use the default option which is to repeat the LAI from 2020 for all future years. We continue to work on a solution to this issue, which will become even more urgent as we expect well-used LAI products from MODIS to retire in the near future.

Finally, I can also invite you to follow the instructions in the README file provided by @jennyfisher with the latest batch of LAI that was processed (/HEMCO/Yuan_XLAI/v2021-06/README), in case you are interested in trying to update the data to 2021 yourself and sharing that with the community.

Thanks again for your question. It is on our "radar", and perhaps we can further strategize as a Working Group at the GEOS-Chem meeting in June.

[lwcugb]

Thanks @jgeddes85 for the explanation. I may use 2020 to start my work for now as you suggested. I will also try to update it to 2021.

[jennyfisher]

Nope, I haven't worked on updated LAI recently either, sorry!

[amospktai]

My group has been working on updating LAI (from various sources) for use with GCHP, and I’ll ask my students what they’ve come up with…