  The transmission spectra of exoplanet atmospheres observed with the Hubble
Space Telescope (HST) in the near-infrared range (1.1-1.65$\mu$m) frequently
show evidence for some combination of clouds and hazes. Identification of
systematic trends in exoplanet clouds and hazes is potentially important for
understanding atmospheric composition and temperature structure. Here we report
on the analysis of spectral modulation using a large, uniformly processed
sample of HST/WFC3 transit spectra from 62 exoplanets. The spectral retrieval
includes the capability to detect and represent atmospheres in which the
composition departs from thermochemical equilibrium. By using this unique
catalog and measuring the dampening of spectral modulations compared to
strictly clear atmospheres, we identify two populations. One is completely
cloud/haze free spanning a wide temperature range, while the other population,
identified as ``Partial cloud/hazes'', follows a trend from mostly cloudy/hazy
around 500~K to mostly clear at $\sim$1500~K. We also find that a partially
transparent aerosol component is frequently present and that it is typically
vertically distributed throughout the atmospheric column. Our findings also
suggest that while clouds and hazes are common in exoplanet atmospheres, the
majority of planets have some level of detectable spectral modulation.
Additionally, the empirical trend that clouds and hazes are minimized at
1460.86K$^{+316}_{-405}$ revealed in our catalog has predictive utility for
modelling the performance of large-scale transiting exoplanets survey, such as
planned with the Ariel mission. This trend can also be used for making a
probability-based forecast of spectral modulation for a given source in the
context of future JWST observations. Future observations including the optical
and/or a broader spectral coverage may be useful to further quantify the trend
reported here.
