This research focuses on advanced spectroscopic techniques for quantitative analysis of light-matter interaction in the Earth's atmosphere with an emphasis on atmospheric-aerosol monitoring applications. Research opportunities include the development and application of high-accuracy, ultrasensitive cavity-enhanced methods with visible diode lasers and broadband sources. A major goal of this work is to provide quality-assured techniques and spectroscopic reference data to support climate change science. For example, we are conducting cavity ring-down absorption spectroscopy (CRDS) and photoacoustic spectroscopy (PAS) to characterize the radiative properties of natural and anthropogenic atmospheric aerosols and particulate matter including soot, secondary organics, and inorganic particulate matter. Therefore, we combine the CRDS and PAS methods with laboratory-based aerosol generation and particle counting techniques to measure the extinction, absorption, and albedo of complex heterogeneous aerosol mixtures which are relevant to understanding and predicting climate change. Furthermore we are using the methods developed to evaluate new materials for generating aerosol materials with known optical properties for future standards development.