Research Note #20 - Preparing Emission Data with PREP-CHEM-SRC and CONVERT_EMISS for WRF-Chem

It took quite a while before I could post this, mainly because everything becomes more and more complicated. The deeper I dig into WRF-Chem, the more complex the problems are. Successfully compiling PREP_CHEM_SRC didn't make things easier as more questions keep coming into my mind about how the system actually works, thanks to the oblivious manual. Well, at least the emission data could be prepared and seems to be simulated in the model now.

Here are the steps to prepare emission data for WRF-Chem using PREP-CHEM-SRC and CONVERT_EMISS utilities.

1. Download and Link the Emission Data

Download the latest emission data from this link. It was in the same directory with PREP-CHEM-SRC source codes. Extract the data inside any desired directory and it is recommended to make a soft link to the location to avoid long-directory listing in the input namelist file which will be explained soon. Locate the softlink in the same directory with the PREP-CHEM-SRC utility (and its namelist input file), and name it 'datain' (the name is actually up to you). 

$ mkdir wrf/EMISSION

$ cd wrf/EMISSION

$ tar -xzvf global_emissions_v3_24aug2015.tar.gz

$ cd PREP-CHEM-SRC-1.5/bin

$ ln -sf ../../Global_emissions_v3/ datain

The directory should similar like this (after executing ls command):

[c24223@ofp05 bin]$ ls -alh

total 3.9M

drwxr-s--- 4 c24223 gi55 4.0K Feb  7 19:06 .

drwxr-s--- 8 c24223 gi55 4.0K Aug 25  2015 ..

drwxr-s--- 3 c24223 gi55  12K Jan 31 20:24 build

lrwxrwxrwx 1 c24223 gi55   26 Jan 31 20:24 datain -> ../../Global_emissions_v3/

-rw-r----- 1 c24223 gi55 6.0K Feb  6 20:38 prep_chem_sources.inp

-rwxr-x--- 1 c24223 gi55 3.9M Jan 31 20:22 prep_chem_sources_RADM_WRF_FIM_.exe

drwxr-s--- 6 c24223 gi55 4.0K Apr 30  2015 .svn

2. Configure using Namelist Input File

This step is really important to determine what kind of emission data, map projections, grid configuration, output format etc. used by the utility. These configurations are stored inside namelist input file: prep_chem_sources.inp. 

Ideally, we could run the utility without any changes to namelist file, but unfortunately, it is not the case this time. The main contents of the file contain paths of emission data from step #1, and it seems the developers didn't update it according the latest path in the data. Therefore, you MUST re-check and confirm the path inside the namelist file by your own, otherwise you will get errors while executing the utility.

A sample of 'working' configuration for my case could be download here. 

Some important points are before using the namelist file above:

• The emission dataset used this post is published does not contain MEGAN emission data.
• I didn't use bbem/bbem plumerise and volcanic emission data.
• The map projection used in my simulation is mercator/ii. 
• For more detailed information about the configurations in the namelist file, read this guide (it is much better than the original emission guide of WRF-Chem).

3. Execute prep_chem_src utility

This step is quite straight forward, except that some nasty things could happen during the process. 

$ ./prep_chem_sources_RADM_WRF_FIM_.exe

You could just sit down nicely until the utility finishes preparing the emission data. Anyway, if you find that the utility crashes midway with some scary segmentation fault messages, you should check the compilation of it. One possible cause is, the compiler option used while compiling the utility. For more detail, check the previous post about installing prep_chem_src utility.

Another possible reason is the program overloads the memory because of compilation or grid settings in the namelist file, causing crash. If it's the case, execute 'ulimit -s unlimited' and try again.

Anyway, if the program successfully works, you will see files similar like the following in the directory:

-rw-r----- 1 c24223 gi55  27M Feb  7 20:03 matrixfire-T-2018-01-01-000000-g1-ab.bin

-rw-r----- 1 c24223 gi55  35M Feb  7 20:03 matrixfire-T-2018-01-01-000000-g1-bb.bin

-rw-r----- 1 c24223 gi55 6.5K Feb  7 20:02 matrixfire-T-2018-01-01-000000-g1.ctl

-rw-r----- 1 c24223 gi55 168M Feb  7 20:03 matrixfire-T-2018-01-01-000000-g1-gocartBG.bin

-rw-r----- 1 c24223 gi55  70M Feb  7 20:03 matrixfire-T-2018-01-01-000000-g1.gra

-rw-r----- 1 c24223 gi55  71M Feb  7 20:03 matrixfire-T-2018-01-01-000000-g1.vfm

So, here are some explanations for the files:

• g1-ab.bin file is anthropogenic emission data (+ biogenic emission data, if you use it) for WRF-Chem
• g1-bb.bin file is biomass burning (+ plume rise, if you use it) emission data for WRF-Chem
• g1-gocartBG.bin is GOCART background emission data for WRF-Chem
• g1.gra and g1.vfm are binary files in GrADS format to visualize the emission data
• g1.ctl is GrADS control/descriptor file

You can now check the emission data using GrADS (don't forget to add 'options big_endian' into the descriptor file).

 --- To be continued ---