  We present ALMA and VLA spatial maps of the Uranian atmosphere taken between
2015 and 2018 at wavelengths from 1.3 mm to 10 cm, probing pressures from
$\sim$1 to $\sim$50 bar at spatial resolutions from 0.1'' to 0.8''. Radiative
transfer modeling was performed to determine the physical origin of the
brightness variations across Uranus's disk. The radio-dark equator and
midlatitudes of the planet (south of $\sim$50$^\circ$ N) are well fit by a deep
H$_2$S mixing ratio of $8.7_{-1.5}^{+3.1}\times10^{-4}$ ($37_{-6}^{+13}\times$
Solar) and a deep NH$_3$ mixing ratio of $1.7_{-0.4}^{+0.7}\times10^{-4}$
($1.4_{-0.3}^{+0.5}\times$ Solar), in good agreement with literature models of
Uranus's disk-averaged spectrum. The north polar region is very bright at all
frequencies northward of $\sim$50$^\circ$N, which we attribute to strong
depletions extending down to the NH$_4$SH layer in both NH$_3$ and H$_2$S
relative to the equatorial region; the model is consistent with an NH$_3$
abundance of $4.7_{-1.8}^{+2.1} \times 10^{-7}$ and an H$_2$S abundance of
$<$$1.9\times10^{-7}$ between $\sim$20 and $\sim$50 bar. Combining this
observed depletion in condensible molecules with methane-sensitive
near-infrared observations from the literature suggests large-scale downwelling
in the north polar vortex region from $\sim$0.1 to $\sim$50 bar. The
highest-resolution maps reveal zonal radio-dark and radio-bright bands at
20$^\circ$S, 0$^\circ$, and 20$^\circ$N, as well as zonal banding within the
north polar region. The difference in brightness is a factor of $\sim$10 less
pronounced in these bands than the difference between the north pole and
equator, and additional observations are required to determine the temperature,
composition and vertical extent of these features.
