# CMAQ - Computing Emissions at Stations

**URL:** <https://forum.cmascenter.org/t/cmaq-computing-emissions-at-stations/2255>\
**Category:** CMAQ\
**Created:** [April 15, 2021, 6:37pm UTC](https://forum.cmascenter.org/t/cmaq-computing-emissions-at-stations/2255 "2021-04-15T18:37:36Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![SharMM](https://avatars.discourse-cdn.com/v4/letter/s/96bed5/32.png) [@SharMM](https://forum.cmascenter.org/u/SharMM)\
**Post date:** [April 15, 2021, 6:37pm UTC](https://forum.cmascenter.org/t/cmaq-computing-emissions-at-stations/2255/1 "2021-04-15T18:37:36Z")

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Hi,  
How can I ask CMAQ to compute output at given points (say monitoring stations) in addition to the grid receptors?

Thanks  
MMS

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**Author:** ![hogrefe.christian](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@hogrefe.christian](https://forum.cmascenter.org/u/hogrefe.christian)\
**Post date:** [April 15, 2021, 7:27pm UTC](https://forum.cmascenter.org/t/cmaq-computing-emissions-at-stations/2255/2 "2021-04-15T19:27:21Z")

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To generate data at specific locations while running CMAQ, you can use the `VERTEXT` option in the run script:

> #\> Vertical Extraction Options  
> setenv VERTEXT Y  
> setenv VERTEXT\_COORD\_PATH ${WORKDIR}/lonlat.csv

This will create vertical profiles of the species in the CCTM\_CONC files at the location of the points specified in lonlat.csv.

After running CMAQ, you could also use a tool like `writesite` distributed with CMAQ to extract data from the gridded output files generated by CMAQ for locations of interest:

[writesite](https://github.com/USEPA/CMAQ/tree/master/POST/writesite)

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**Author:** ![cjcoats](https://avatars.discourse-cdn.com/v4/letter/c/ac8455/32.png) [@cjcoats](https://forum.cmascenter.org/u/cjcoats)\
**Post date:** [April 15, 2021, 9:11pm UTC](https://forum.cmascenter.org/t/cmaq-computing-emissions-at-stations/2255/3 "2021-04-15T21:11:32Z")

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Note that generally [M3Tools program _gridprobe_](https://cjcoats.github.io/ioapi/GRIDPROBE.html) can be used to do bilinear interpolation from a (time stepped) gridded I/O API file to a set of Lat-Lon specified points, with output either to an ASCII time series file or to an observations-format I/O API file, or both.

This will be very useful if you wish to examine meteorology at the sites also…