Grid definition and population


(Tammy xu) #1

Since I want to use benMAP for the northern hemisphere instead of the default US setup, I was wondering :

1)The user manual states that CMAQ model data can be one of the options for concentration input. Is benMAP able to import CMAQ output directly?Or does benMAP have a processing tool that can convert netcdf file from CMAQ to the shapefile and csv file benMAP needs? ( for the concentration with 108*108 grid ) Or did I misinterpret the manual?

  1. If I got the shape file with the 108*108 grid definition from CMAQ, what technique would you recommend to assign population data to each matching cell in order to get population for each row and column?

Thank you in advance for these big questions and I look forward to the answers. Have a good day!

Regards,

Tammy


(Ali) #2

Hi Tammy,

Unfortunately, we cannot import CMAQ model data directly into BenMAP. Because we use the Column/Row index, you’ll have to open up your netcdf file (I’ve used Panoply in the past) and then assign a Column/Row index across your 108x108 grid.

As for your second question, you don’t have to assign your population to the 108x108 grid, that’s BenMAP’s job! BenMAP will look at any population grid you have and area-weight it to your air quality grid.

And I have a few quick questions, too:
Is there any reason you don’t want to use the US Setup? Are you looking at Canada and Mexico, too? What grid definition would you be able to obtain your population data? Since the US Setup has so much built-in data already that we use for our rule-making decisions, I think this would be the easiest and most reliable way to go.

If anyone else would like to chime in (Neal), please add anything I missed!

Best,
Ali


(Tammy xu) #3

Hi Ali,

Thank you so much for your detailed reply!

  1. Just to make sure: Do you mean if I have input a shapefile that’s defined on 108km x108km grid and want to input a population file that’s defined on 1km x 1km grid , all I need to do is to match the population to it’s column/row index across the 1km x 1km grid?

  2. Yes, I want to explore the use of benMAP on a larger scale (including US). For countries that are out of US I need to create new setups.

  3. As for the population data, I’m considering using Gridded Population of the World (GPW), which could be found here: http://sedac.ciesin.columbia.edu/data/set/gpw-v4-population-count .However, the data is defined by arc seconds in GeoTiff format. Is there any other source of population data for countries outside of US that’s more compatible with benMAP or easier to reformat? What’s the source of data provided in the self-paced training materials?

Thanks again!

Regards,

Tammy


(Ali) #4

Hi Tammy,

You don’t need to match the column/row index from one grid to another - BenMAP-CE performs the area-weighting to assign how the grids spatially overlap…that’s the “Crosswalk” step when you load the Grid Definitions into BenMAP-CE. The shape files have the geo-referencing for BenMAP-CE to know how the two grids need to overlap.

Also, the source of the country-specific population on the BenMAP website is the same CIESIN data you’d like to use. We went through the process of converting it all over to a grid definition you can now use in BenMAP-CE.

Good luck in your analysis!
Ali


(Tammy xu) #5

Thank you so much and happy new year!