Source Apportionment of Ambient Methane Enhancements in Los Angeles, California, To Evaluate Emission Inventory Estimates.

Rapid increase in atmospheric methane (CH) mixing ratios over the past century is attributable to the intensification of human activities. Information on spatially explicit source contributions is needed to develop efficient and cost-effective CH emission reduction and mitigation strategies to addresses near-term climate change. This study collected long-term ambient CH measurements at Mount Wilson Observatory (MWO) in Los Angeles, California, to estimate the annual CH emissions from the portion of Los Angeles County that is within the South Coast Air Basin (SCLA).

Carbon dioxide and methane measurements from the Los Angeles Megacity Carbon Project - Part 1: calibration, urban enhancements, and uncertainty estimates.

We report continuous surface observations of carbon dioxide (CO) and methane (CH) from the Los Angeles (LA) Megacity Carbon Project during 2015. We devised a calibration strategy, methods for selection of background air masses, calculation of urban enhancements, and a detailed algorithm for estimating uncertainties in urban-scale CO and CH measurements. These methods are essential for understanding carbon fluxes from the LA megacity and other complex urban environments globally.

Midlatitude atmospheric OH response to the most recent 11-y solar cycle.

The hydroxyl radical (OH) plays an important role in middle atmospheric photochemistry, particularly in ozone (O(3)) chemistry. Because it is mainly produced through photolysis and has a short chemical lifetime, OH is expected to show rapid responses to solar forcing [e.g.

Atmospheric hydroxyl radical (OH) abundances from ground-based ultraviolet solar spectra: an improved retrieval method.

The Fourier Transform Ultraviolet Spectrometer (FTUVS) instrument has recorded a long-term data record of the atmospheric column abundance of the hydroxyl radical (OH) using the technique of high resolution solar absorption spectroscopy. We report new efforts in improving the precision of the OH measurements in order to better model the diurnal, seasonal, and interannual variability of odd hydrogen (HO(x)) chemistry in the stratosphere, which, in turn, will improve our understanding of ozone chemistry and its long-term changes. Until the present, the retrieval method has used a single strong OH absorption line P(1)(1) in the near-ultraviolet at 32,341 cm(-1).