  The James Webb Space Telescope (JWST) will provide an opportunity to
investigate the atmospheres of potentially habitable planets. Aerosols,
significantly mute molecular features in transit spectra because they prevent
light from probing the deeper layers of the atmosphere. Earth occasionally has
stratospheric/high tropospheric clouds at 15-20 km that could substantially
limit the observable depth of the underlying atmosphere. We use solar
occultations of Earth's atmosphere to create synthetic JWST transit spectra of
Earth analogs orbiting dwarf stars. Unlike previous investigations, we consider
both clear and cloudy sightlines from the SCISAT satellite. We find that the
maximum difference in effective thickness of the atmosphere between a clear and
globally cloudy atmosphere is 8.5 km at 2.28 microns with a resolution of 0.02
microns. After incorporating the effects of refraction and Pandexo's noise
modeling, we find that JWST would not be able to detect Earth like
stratospheric clouds if an exo-Earth was present in the TRAPPIST-1 system, as
the cloud spectrum differs from the clear spectrum by a maximum of 10 ppm.
These stratospheric clouds are also not robustly detected by TauREx when
performing spectral retrieval for a cloudy TRAPPIST-1 planet. However, if an
Earth size planet were to orbit in a white dwarf's habitable zone, then, we
predict that JWST's NIRSpec would be able to detect its stratospheric clouds
after only 4 transits. We conclude that stratospheric clouds would not impede
JWST transit spectroscopy or the detection of biosignatures for Earth-like
atmospheres.
