Vertical Structure of the Lower Troposphere in a Changing Arctic

• Main Author: Watkins, Daniel M.
• Other Authors: Hutchings, Jennifer, Skyllingstad, Eric, Shell, Karen, de Szoeke, Simon, College of Earth, Ocean, and Atmospheric Sciences
• Format: Doctoral or Postdoctoral Thesis
• Language: English; unknown
• Published: Oregon State University
• Subjects: Climate change; Ice; permafrost; Tundra
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/zs25xh61x

The Arctic climate system is changing dramatically as a response to rising atmospheric greenhouse gas concentrations. Key indicators of Arctic change include thinning and retreating of Arctic pack ice, thawing permafrost, greening tundra, and rising surface temperatures. The structure of the atmospheric boundary layer influences and is influenced by processes at the surface. As the Arctic surface changes, so to will the atmospheric boundary layer. The structure of the lower troposphere, including the boundary layer, affects the exchange of heat, moisture, and momentum between the atmosphere and the surface. Understanding the spatial variability and annual cycle of lower tropospheric structure therefore plays a critical role in modeling, interpreting, and forecasting Arctic climate change. In pursuit of this understanding, I produce an observational climatology of Arctic lower tropospheric temperature inversions, examine the relationship between detailed measurements and bulk estimates of inversion properties, and analyze trends in stability using the ERA5 reanalysis and two climate model ensembles. Temperature inversions are layers of enhanced static stability that can occur worldwide but are especially common in Arctic settings. The vertical position and intensity of inversion layers affects cloud evolution, aerosol propagation, and surfaces fluxes. I develop a climatology of surface-based and elevated temperature inversions using radiosonde observations from 46 locations spanning the 2000-2019 period. The climatology reveals detailed structure with distinct regional differences, both in seasonal means and in the annual cycle. Using a novel algorithm, I classify elevated inversions based on their similarity to surface-based inversions to identify distinct features of upper-air and stable boundary layer elevated inversions. With these results, I show that the observed annual increase in elevated inversion base heights from winter to summer is a result of a difference in occurrence frequency of stable boundary ...