  Using topology, we unveil the existence of new unidirectional modes in
compressible rotating stratified fluids. We relate their emergence to the
breaking of time-reversal symmetry by rotation and vertical mirror symmetry by
stratification and gravity. We stress the role of the Coriolis force's
nontraditional part, induced by a rotation field tangent to the surface. In
contrast with horizontally trapped equatorial waves induced by the traditional
component of Coriolis force perpendicular to the surface, we find vertically
trapped modes that are trapped along interfaces between regions with distinct
stratification properties. We show that such modes are generalized atmospheric
Lamb waves whose direction of propagation can be selected by the nontraditional
component of the Coriolis force.
