If you have already set the "grid" keyword in your request, you can add the "area" : "coordinates" keyword. You can set pre-defined area regions e.g. 'europe' or set the area using coordinates North/West/South/East.

See the description of the area keyword for more information.

Some examples:

 "area": "europe",
#area:  N/W/S/E

#europe
"area": "75/-20/10/60",

#africa
"area": "40/-20/-40/60",