  Upcoming James Webb Space Telescope (JWST) observations will allow us to
study exoplanet and brown dwarf atmospheres in great detail. The physical
interpretation of these upcoming high signal-to-noise observations requires
precise atmospheric models of exoplanets and brown dwarfs. While several
one-dimensional and three-dimensional atmospheric models have been developed in
the past three decades, these models have often relied on simplified
assumptions like chemical equilibrium and are also often not open-source, which
limits their usage and development by the wider community. We present a
python-based one-dimensional atmospheric radiative-convective equilibrium
model. This model has heritage from the Fortran-based code (Marley et al.,1996}
which has been widely used to model the atmospheres of Solar System objects,
brown dwarfs, and exoplanets. In short, the basic capability of the original
model is to compute the atmospheric state of the object under
radiative-convective equilibrium given its effective or internal temperature,
gravity, and host--star properties (if relevant). In the new model, which has
been included within the well-utilized code-base PICASO, we have added these
original features as well as the new capability of self-consistently treating
disequilibrium chemistry. This code is widely applicable to Hydrogen-dominated
atmospheres (e.g., brown dwarfs and giant planets).
