Regarding air mass origin and population with HYSPLIT

[Zainab]

Hello,

I need to calculate:
1. Air mass origin for a long term data for 15th Jan 2017- 2nd April 2018 at an hourly interval.
2. Average population density for each trajectory for 15th Jan 2017- 2nd April 2018 at an hourly interval.
3. Time over land for each trajectory for 15th Jan 2017- 2nd April 2018 at an hourly interval.

Method described in Raatikainen et al. 2009:
Air mass origin, expressed as a compass heading from Hyytiala, is an average of trajectory point headings weighted by their distances from Hyytiala. Weights were used to decrease the effect of trajectory points close to Hyytiala, but the weights had only a small effect on results.

One simple way to estimate anthropogenic influence onaerosol mass concentrations is to calculate average population densities (number of people per km2) for each trajectory. A population density map for year 2000 was downloaded from SEDAC web pages.1 Because of the high resolution of the population density map (2.5 arc min, which is about 5 km in distance) and the fact that population densities can change a lot in relatively short distances, trajectory coordinate points were interpolated for every three minutes from the original one-hour time resolution.

However, I am unable to understand how this is to be done. The kind of plots that I finally want to arrive at is as given in Figure 7 of the paper. Please find the the paper attached. Please guide to the best approach to handle this.

Thanks and regards,
Zainab.