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In this study, we investigated aerosol chemical composition, spectral properties of aerosol extracts, and source contributions to the aerosol light-absorbing brown carbon (BrC) in central Los Angeles from July 2018 to March 2019, during warm and cold seasons. Spectrophotometric measurements (water and methanol extracts; 200 < λ < 1100) and chemical analyses were performed on collected particulate matter (PM), and relationships of BrC light absorption (Abs₃₆₅) to source tracer chemical species were evaluated. Mass absorption efficiency (MAE) of both water and methanol extracted solutions exhibited an increasing trend from warm period to cold season, with an annual average value of 0.61 ± 0.22 m².g⁻¹ and 1.38 ± 0.89 m².g⁻¹, respectively. Principal component analysis (PCA) were coupled with multiple linear regression (MLR) to identify and quantify sources of BrC light absorption in each of the …