  We investigate the performance of the MAGIC telescopes under three simulated
atmospheric conditions: an increased aerosol content in the lower part of the
troposphere, the presence of thin aerosol over-densities at different heights,
and an extremely clean atmosphere. Weshow how the effective area of the
telescope system is gradually reduced in the presence of varying concentrations
of aerosols whereas the energy threshold rises. Clouds at different heights
produce energy and altitude-dependent effects on the performance of the system.
