Figure shows mappings of the spatial distributions of total column concentrations due to routine emissions, for selected time periods, that represent widely varying column concentrations. For example, on May 23, total column concentrations were relatively low due to relatively strong, persistent winds from the south over the entire state of Texas. In contrast, on August 5 and 28, southerly winds from the Gulf encounter northerly winds, establishing stagnation zones with relatively high column concentrations of methane with complex spatial distributions in northern Texas. This variation in the spatial and temporal distribution of total column concentrations presents challenges in detecting emission events.