Ground-Based Remote Sensing of the Summer Atmospheric Boundary Layer in Reno, Nevada, USA, Using Infrared Spectroscopy

Abstract

AbstractThe atmospheric boundary layer (ABL) is the lowermost part of the atmosphere in the vicinity of the Earth's surface. It plays a vital role in the exchange of heat, momentum, humidity and other trace substances with the Earth's surface. The boundary layer is extremely important for air quality and health related issues as it is associated with the first few kilometers above the surface. Boundary layer height diurnally evolves as solar radiation waxes and wanes. Though balloon soundings of atmospheric temperature, pressure, and winds are performed in many world-wide locations, they are only done twice a day, primarily for large scale weather forecasting applications, leaving much of the boundary layer evolution and structure without assessment. Ground-based remote sensing methods have been developed to provide detailed knowledge of the boundary layer. This thesis presents the surface-based Fourier Transform Infrared (FTIR) spectrometer measurements of the downwelling thermal infrared radiance spectrum emitted by various gases in the cloud-free atmosphere. Measurements were carried out both in early morning hours and late in the afternoon where the temperature profile changes from inverted due to overnight radiative cooling by the surface, to super adiabatic due to intense solar heating at the surface. The measured spectra are compared to the model spectra to infer the structure of the boundary layer.A simple approximate analytical expression for the weighting function, which is crucial to solve the radiative transfer equation (RTE) and retrieve the temperature and gaseous concentration profiles of the ABL, has been developed. The validity of the analytical form of the weighting function was evaluated by comparison with a numerical model.