calpuff_add_area_sources: Add area sources to a list for later use in CALPUFF
In rich-iannone/PuffR: A set of tools to help with CALPUFF dispersion modelling.

Add area sources to a list for later use in CALPUFF

calpuff_add_area_sources(src_name, species_name, lat_dec_deg = NULL,
  lon_dec_deg = NULL, x_coord_km = NULL, y_coord_km = NULL,
  UTM_zone = NULL, UTM_hemisphere = NULL, effective_height, base_elev,
  init_sigma_z, emission_rate, emission_units)

`src_name`	the name of the source emitting the species.
`species_name`	the name of the species undergoing emissions.
`lat_dec_deg`	a vector of 4 latitude values for the area source in units of decimal degrees.
`lon_dec_deg`	a vector of 4 longitude values for the area source in units of decimal degrees.
`x_coord_km`	a vector of 4 UTM easting values for the area source in km units.
`y_coord_km`	a vector of 4 UTM northing values for the area source in km units.
`UTM_zone`	the UTM zone for the area source.
`UTM_hemisphere`	the UTM hemisphere for the area source.
`effective_height`	the effective height of the area source in meters above ground level (m AGL).
`base_elev`	the ground elevation at the location of the area source in meters above sea level (m ASL).
`init_sigma_z`	the initial sigma z value for the area source in meters.
`emission_rate`	the rate of constant emissions from the area source; units are defined in the 'emission_units' argument.
`emission_units`	the units applied to the value defined in the 'emission_rate' argument. The possible selections are: (1) "g/m2/s", (2) "kg/m2/hr", (3) "lb/m2/hr", (4) "tons/m2/yr", (5) "Odour Unit * m/s", (6) "Odour Unit * m/min", (7) "metric tons/m2/yr", (8) "Bq/m2/s", and (9) "GBq/m2/yr".