Carlos Ochoa

The role of a peri-urban forest on air quality improvement in the Mexico City megalopolis

Air quality improvement by a forested, peri-urban national park was quantified by combining the Urban Forest Effects (UFORE) and the Weather Research and Forecasting coupled with Chemistry (WRF-Chem) models. We estimated the ecosystem-level annual pollution removal function of the parks trees, shrub and grasses using pollution concentration data for carbon monoxide (CO), ozone (O(3)), and particulate matter less than 10 microns in diameter (PM(10)), modeled meteorological and pollution variables, and measured forest structure data. Ecosystem-level O(3) and CO removal and formation were also analyzed for a representative month. Total annual air quality improvement of the parks vegetation was approximately 0.02% for CO, 1% for O(3,) and 2% for PM(10), of the annual concentrations for these three pollutants. Results can be used to understand the air quality regulation ecosystem services of peri-urban forests and regional dynamics of air pollution emissions from major urban areas.

Changes in Intense Precipitation Events in Mexico City

AbstractThe authors analyzed an extensive precipitation dataset available for the Mexico City basin that included hourly precipitation in various sectors of the city from 1993 to 2007. Observations indicated that significant changes occurred in the timing and number of intense events (precipitation rate >20 mm h−1) over this time period. Alternative hypotheses that changes in the emission of aerosol pollutants or in the land use can result in the observed variations are tested. The Weather Research and Forecasting Model was used to simulate September precipitation from 2002 to 2011 at the peak of the wet season. Changes were introduced to the microphysical scheme as a proxy for differences in the aerosol population and the droplet activation spectra. Simulations were also performed with the land use of the urban areas set up to represent older and more current conditions. Results indicate that increased pollution (decreased urban area) led to an average precipitation decrease over the mountain areas of 20...