# EFMAP for different days

**URL:** <https://forum.cmascenter.org/t/efmap-for-different-days/5773>\
**Category:** MEGAN\
**Created:** [April 30, 2025, 10:37pm UTC](https://forum.cmascenter.org/t/efmap-for-different-days/5773 "2025-04-30T22:37:44Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![amin](https://avatars.discourse-cdn.com/v4/letter/a/8e7dd6/32.png) [@amin](https://forum.cmascenter.org/u/amin)\
**Post date:** [April 30, 2025, 10:37pm UTC](https://forum.cmascenter.org/t/efmap-for-different-days/5773/1 "2025-04-30T22:37:44Z")

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Hello All,

I created the OutputGridEF.csv and EFMAP.ncf files using MEGAN v3.2. Since these files have one emission factor for each gridcell and only one time-step, respectively, I’m just wondering how CMAQ-INLINEMEGAN (or maybe SMOKE) can use and read this emission factors and create the emissions for “different days of the year” for each pollutant? I assume that the natural emissions (like ISOPRENE) should be different for each day during the year.

Thanks

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**Author:** ![willison.jeff](https://avatars.discourse-cdn.com/v4/letter/w/c89c15/32.png) [@willison.jeff](https://forum.cmascenter.org/u/willison.jeff)\
**Post date:** [May 1, 2025, 12:48pm UTC](https://forum.cmascenter.org/t/efmap-for-different-days/5773/2 "2025-05-01T12:48:42Z")

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The fundamental approach described by Guenther et al. (2012) hasn’t changed for MEGAN 3.2. Please see equation 1 of [that paper](https://gmd.copernicus.org/articles/5/1471/2012/gmd-5-1471-2012.pdf). The values in EFMAP.ncf correspond to the emission factor at standard conditions (epsilon), while the time dependent term is emission activity (gamma). Epsilon is computed by the preprocessor, while gamma is computed inline by CMAQ or offline with the MEGVEA program.