  After two decades of measurements, neutrino physics is now advancing into the
precision era. Withthe long-baseline experiments designed to tackle current
open questions, a new query arises: can atmospheric neutrino experiments also
play a role? To that end, we analyze the expected sensitivity of current and
near-future water(ice)-Cherenkov atmospheric neutrino experiments in the
context of standard three-flavor neutrino oscillations. In this first in depth
combined atmospheric neutrino analysis, we analyze the current shared
systematic uncertainties arising from the common flux and neutrino-water
interactions. We then implement the systematic uncertainties of each experiment
in detail and develop the atmospheric neutrino simulations for
Super-Kamiokande, with and without neutron-tagging capabilities, IceCube
Upgrade, ORCA, and Hyper-Kamiokande detectors. We carefully review the
synergies and features of these experiments to examine the potential of a joint
analysis of these atmospheric neutrino data in resolving the $\theta_{23}$
octant at 99% confidence level, and determining the neutrino mass ordering
above 5$\sigma$ by 2030. Additionally, we assess the capability to constrain
$\theta_{13}$ and the CP -violating phase ($\delta_{CP}$) in the leptonic
sector independently from reactor and accelerator neutrino data. A combination
of the atmospheric neutrino measurements will enhance the sensitivity to a
greater extent than the simple sum of individual experiment results reaching
more than 3$\sigma$ for some values of $\delta_{CP}$ . These results will
provide vital information for next-generation accelerator neutrino oscillation
experiments such as DUNE and Hyper-Kamiokande.
