[EMAC] integrate aircraft/volcanic emissions

[axel-lauer]

EMAC aircraft and volcanic emissions are 3-dim emission fields (unit = kg m-3 s-1) given on different vertical levels. In contrast to other 3-dim emissions that are given in kg m-2 s-1, aircraft and volcanic emissions have to be integrated vertically and cannot be simply summed up.

Tasks (branch dev_emac_import_airc_volc)

• calculate vertical integral of aircraft emissions (variable AIRC_NO_s.py)
• calculate vertical integral of volcanic emissions (variable VOLC_SO2_s)
• test with more than 1 year of data

[schlunma]

VOLC_SO2_s gives correct magnitude now, AIRC_NO_s has not been tested due to lack of data with non-zero aircraft emissions.