We explore the local well-posedness theory for the 2D inviscid Boussinesq system
when the vorticity is given by a singular patch. We give a significant improvement
on the result of Hassainia and Hmidi (J. Math. Anal. Appl. 430:2 (2015),
777–809) by replacing their compatibility assumption on the density with
a constraint on its platitude degree on the singular set. The second main
contribution focuses on the same issue for the partial viscous Boussinesq
system. We establish a uniform LWP theory with respect to the vanishing
conductivity. This issue is much more delicate than the inviscid case and one
should carefully deal with various difficulties related to the diffusion effects
which tend to alter some local structures. The weak a priori estimates are
not trivial and refined analysis on transport-diffusion equation subject to a
logarithmic singular potential is required. Another difficulty stems from
some commutators arising in the control of the co-normal regularity that we
counterbalance in part by the maximal smoothing effects of transport-diffusion
equation advected by a velocity field which scales slightly below the Lipschitz
class.