Mexico is one of the most diverse countries in the world in terms of its climate and meteorology. With its great latitudinal range and diverse topography, climates range from Mediterranean in Baja California in the northwest to the tropical rain forest of Chiapas in the southeast. The scorching aridity of the Sonoran Desert contrasts with the frigid glacial barrens of the volcanic peaks of Popocatépetl (5400 meters) and the Pico de Orizaba (5700 meters) as well as the thousands of kilometers of tropical beaches.
Diversity is not the only defining characteristic of Mexico’s weather and climate. Hurricanes batter both coasts, and tornadoes can even wreak havoc in the northeast. Anthropogenic influences are also striking: Mexico City’s air quality problems are typical of one of Earth’s most populous urban clusters. Desertification and conflicts over water usage threaten many of the arid regions in the north. Surprisingly, Mexican academic programs and scientific investigation in the atmospheric sciences are not commensurate with this diversity of atmospheric phenomena available for study.
Observational networks—meteorological, hydrological, and maritime—do exist; however, they are used primarily for weather and hydrological forecasting and/or hazard warnings. For instance, the Servicio Meteorológico Nacional (Mexican Weather Service) has numerous automatic weather stations, radars, and atmospheric soundings principally for weather prediction. Research-based, observational networks for the atmospheric sciences, however, have been lacking. Fortunately, in recent years, this has begun to change.
A New Network
To motivate the expansion of long-term research on climatology, meteorology, air chemistry, and air quality, as well as training students and researchers, the Universidad Nacional Autónoma de México (UNAM) has created the University Network of Atmospheric Observatories (Red Universitaria de Observatorios Atmosféricos (RUOA)). These observatories, located in a variety of urban and natural settings, will provide research-quality data in areas ranging from atmospheric chemistry, aerobiology, and greenhouse gases to tropospheric water vapor, cloud physics, and electric fields.
These sites also serve as a basis for technological development. For example, a multiaxis differential optical absorption spectrometer (MAX-DOAS) system, which uses scattered solar radiation for gas column measurements, was designed and constructed at UNAM. Long-term measures of air quality and greenhouse gas concentrations will help scientists understand their spatial and temporal variability and inform policy makers in the areas of public health, ecological conservation, and climate change. Also, RUOA will be an educational and training space for technicians and operators from other meteorological and air quality networks in Mexico.
At present, RUOA consists of six atmospheric observatories in urban zones:
- the UNAM campus site in Mexico City
- Juriquilla, Querétaro
- Aguascalientes, Aguascalientes
- Saltillo, Coahuila
- Hermosillo, Sonora
- Morelia, Michoacán
In addition, three observatories operate in unique natural protected zones: the deciduous forest on the Pacific coast of Jalisco in Chamela; the rain forest of Los Tuxtlas, Veracruz; and the high-altitude (4 kilometers above sea level) volcanic environment of Altzomoni, State of Mexico.
The permanent maintenance of the RUOA observatories, which includes the calibration, validation, and publication of the data produced, is the responsibility of the participating research groups at UNAM’s Centro de Ciencias de la Atmósfera. Many of these groups have experience developing, analyzing, or correcting data from other meteorological or air quality networks in Mexico. All data will be freely available, a large portion of them in real time at the RUOA website.
RUOA is linked to several national and international projects. The Mexico City Air Quality Network has instruments in two RUOA observatories and measures the air quality in close collaboration with UNAM. The Mexican weather service has meteorological instruments in two RUOA observatories located in natural protected areas. In addition, the Mexican Aerobiology Network shares infrastructure and information with RUOA, so that both networks can identify and classify a wide variety of pollen types. Also, carbon dioxide and methane monitors installed in RUOA support a funded project named “Temporal and Spatial Variability of CO2 and CH4 in Mexico” to evaluate changes in greenhouse gases.
A plan for a high-altitude site (Altzomoni) to contribute to the World Meteorological Organization’s Global Atmosphere Watch program is already in progress. The Altzomoni Observatory has recently been accepted to be part of the international Network for the Detection of Atmospheric Composition Change.
Finally, the recently formed Black Carbon Network (RCN) is a system for measuring black carbon nationwide, and with support from RUOA, it covers four cities and a pristine background site. RCN and RUOA have been comparing information in order to evaluate Mexico’s contribution to global warming with short-lived climate forcers. Five RUOA observatories are also hosts for TlalocNet, a national network of GPS meteorology stations for continuously measuring water vapor columns.
Available Instrumentation and Data
Each of the RUOA measuring sites observes a diverse array of surface and atmospheric variables. Urban observatories have sensors that measure the absorption and scattering aerosols and black carbon. There are also technologies to measure ion concentrations in real time for particles smaller than 1 micrometer. In addition, observatories have ceilometers to detect and range clouds, hydrometeors, or air masses that have a substantial amount of particles. Those instruments also serve to estimate the height and thickness of clouds and the evolution of the planetary boundary layer.
At some stations, samples are regularly collected to distinguish allergens from other biological particulate matter, to identify volatile organic compounds, and to analyze the chemical composition of wet deposition. The analysis of heavy metals, organic acids, and acid rain precursors (nitrogen oxides and sulfur), as well as nine inorganic ions, is important in understanding the incorporation of air pollutants in rainwater and how it is associated with atmospheric dispersion of pollutants over a large region.
Wind data (speed and direction), temperature, humidity, pressure, solar radiation, and precipitation will also be measured at the observatories. All of the variables are registered in an acquisition system. A field mill monitor detects atmospheric electric field variation and the presence of lightning within a 50-kilometer radius. Additionally, disdrometers measure the amount of precipitation and provide detailed information on raindrops, discriminating between different types of hydrometeors (liquid or solid). The sensors also indicate the range of visibility of fog events. Moreover, data from GPS receivers at the observatories, together with surface pressure and temperature measurements, are used to estimate precipitable water vapor for both meteorological research and long-term climate studies.
UNAM has designed instruments for determining the concentrations of several gases (nitrogen dioxide, formaldehyde, and sulfur dioxide) by measuring ultraviolet/visible light absorption at different elevation angles in an atmospheric column. These MAX-DOAS instruments have been installed at five sites to assess the distribution of pollution at several altitudes as well as to validate satellite data.
Furthermore, RUOA observatories have analyzers that continuously measure concentrations of carbon dioxide, methane, carbon monoxide, and water in air because continuous measurement of gases that participate in the radiative balance has become increasingly important for understanding their effects on the global climate. Observatories in urban zones have standard air quality gas (ozone, sulfur dioxide, carbon monoxide, nitrogen dioxide) and particle (PM10 and PM2.5) monitors. They also have passive samplers that collect atmospheric aerosols used to study organic compounds that persist in the environment.
UNAM is the most important university in Mexico, as well as the largest university in Latin America. Its RUOA observatories offer new data to fill a need for atmospheric information on the Tropic of Cancer, which is relatively unstudied in America. This information is relevant to the scientific and other communities interested in atmospheric phenomena related to the diversity of climate, weather, and chemistry of the atmosphere.
We thank the UNAM staff: Amparo Martínez for the initial administration and management logistic of RUOA and Héctor Soto, Omar López, and Delibes Flores for technical support in the instrumentation and data management of the RUOA observatories. We also thank Enrique Cabral and Luis Tlazcani for installation of TlalocNet GPS sites and UNIATMOS for managing the Web page and the geographical information system. External support was provided by Autonomous University of Aguascalientes and Antonio Narro University.
O. Peralta, D. Adams, T. Castro, M. Grutter, and A. Varela, Atmospheric Sciences Center, National Autonomous University of Mexico, Mexico City, Federal District, Mexico; email: [email protected]
Citation: Peralta, O., D. Adams, T. Castro, M. Grutter, and A. Varela (2016), Mexico’s University Network of Atmospheric Observatories, Eos, 97, doi:10.1029/2016EO045273. Published on 12 February 2016.