An assessment of the role of surface sensible heat flux and the atmosphere inversion on the breakup time in a highly complex terrain

The life cycle of the stable boundary layer (SBL) strongly modulates air quality in urban valleys embedded in complex terrain. We investigate inversion-breakup timing in a narrow tropical-Andean valley using a process-oriented observational energy-budget framework. The framework combines proxies for the energy required to erode nocturnal stability ($Q_{req}$) and the energy supplied to the valley atmosphere by surface sensible heat flux ($Q_{prov}$). $Q_{req}$ is derived from lower-tropospheric thermodynamic stability metrics obtained from continuous microwave-radiometer profiles, while $Q_{prov}$ is estimated from time-integrated eddy-covariance sensible heat flux. Additional in situ and remote-sensing observations are used to characterize boundary-layer structure, winds, and PM2.5 variability. Results show a non-linear $Q_{req}$--$Q_{prov}$ relationship and regime-dependent heating efficiency, with nearly linear behavior in most cases and a rapid increase of $Q_{prov}$ at high $Q_{req}$ in less efficient regimes. Elevated wind shear near the top of the SBL is associated with earlier erosion for lower $Q_{prov}$, indicating a relevant role of mechanically generated turbulence. Regional convective-cloud forcing, diagnosed from velocity-potential and OLR anomalies, further modulates breakup timing through radiative effects. Later breakup is consistently linked to higher PM2.5 burden and more frequent same-day accumulation.