# Spatial allocation of road emissions and unit conversion

I have a grid shapefile that has a resolution of 1km x 1km.

This grid is then used to spatially allocate road emissions.

My goal is to get the emissions in the unit: μg m-2 s-1(microgram per square meter per second) since this is the emission unit for aerosols in the WRF/Chem

I manage to get the emissions for a certain grid cell by multiplying the total emissions in (micrograms/s) to the ratio of the road length present inside the grid cell to the total road length

Now I have the emission for that grid cell in μg s-1 (micrograms/second).

My question may be silly or simple, but I am thinking if I still need to divide my emissions by 1000 (since 1km = 1000m) to get the final emission unit I need

(Final unit needed: μg m-2 s-1(microgram per square meter per second))

Am I right? Hoping someone could help me with this. Thanks!

You have got your emissions over a square kilometer. To get to square meters you divide by 1000000 since $$1km^2=10^6m^2$$.