Monsoon storm clouds gather near mountains abutting the Sonora Desert. Credit: free parking :-|, CC BY-NC 2.0

Climatologists and meteorologists first met to examine weather and climate issues in northwestern Mexico in 2013. Since then, the Red Universitaria de Observatorios Atmosféricos (RUOA) was constructed in Hermosillo and currently provides quality meteorological data and lidar-based boundary layer heights. Additionally, the Trans-boundary, Land and Atmosphere Long-term Observational and Collaborative Network (TLALOCNet) was recently implemented. It includes seven near-real-time GPS meteorology sites in northwest Mexico with high-frequency precipitable water vapor (PWV).

Against the backdrop of this new data-gathering infrastructure, organizers of the Third Annual Regional Climatology and Meteorology Meeting for Northwest Mexico, held in June 2015, chose to focus on the study of the North American monsoon. The purpose of the meeting, which took place at the Universidad Nacional Autónoma de México (UNAM) in Mexico City, was to address research challenges associated with the monsoon, with specific focus on modeling versus observation.

Participants explored three principle questions:

  • What is the relative importance of local surface forcing versus larger-scale dynamics for determining monsoon convection?
  • What is the relative importance of local water vapor sources versus larger-scale moisture transport?
  • Which processes are most critical in regional and weather forecast models for correctly representing monsoon rainfall?

The meeting format included a roundtable discussion at the close of each day to summarize, discuss, and debate issues from the day’s presentations. Participants were encouraged to present speculative results and ideas to stimulate debate and instigate new directions for research. Evenly divided between modeling and observational studies, the issues addressed included the importance of local water vapor fluxes from vegetated surfaces, large-scale forcing associated with sea surface temperature variability, and the use of GPS PWV for studying the monsoon’s onset, making process-oriented studies of convection, and constraining and initializing regional models.

The oak savanna biome at the Sierra Los Locos, Sonora, meteorological site. Credit: Enrique Vivoni. Used with permission.

In particular, contentious debate arose over the issue of local water vapor sources (i.e., moisture recycling) versus large-scale oceanic transport in convective monsoon rainfall. Given that vegetation moisture recycling is an active area of research within the tropical meteorological community, this debate provided the motivation for the collaborative GPS Vegetation-Atmosphere Feedback Experiment for 2015. This 3-month campaign used existing TLALOCNet and RUOA infrastructure, as well as three additional GPS meteorology sites, two collocated with meteorological flux towers in central Sonora. One of these towers is pictured here. High temporal resolution PWV and surface flux data, along with a 4-day intensive radiosonde campaign, will be employed to characterize the vegetation green-up and its influence on water vapor flux and convective activity. Results will be reported following the campaign.

This year’s meeting drew more participants and participating institutions, from both Mexico and the United States, than the two previous annual meetings. Mexican and U.S. institutions represented included the Universidad de Sonora, Centro de Investigación Científica de Educación Superior de Ensenada, Unidad Académica Sisal/UNAM, Instituto Tecnológico de Sonora, Universidad Veracruzana, the Ciencias de la Atmósfera/UNAM, the University of Arizona, Arizona State University, the University of NebraskaLincoln, the Desert Research Institute, and the University of Washington.

Coordinación de la Investigación Científica, UNAM, provided funding for the meeting. National Science Foundation grant AGS-1261226 supported University of Arizona/University of Washington attendees, and Robert B. Daugherty of the Water for Food Institute supported University of Nebraska–Lincoln’s attendees. UNAVCO provided GPS receivers.

—David K. Adams, Arturo Quintanar Isaias, and C. Lizárraga, Departamento de Física, Universidad de Sonora, Hermosillo, Mexico

Citation: Adams, D. K., A. Q. Isaias, and C. Lizárraga (2016), The North American monsoon: Models versus observations, Eos, 97, doi:10.1029/2016EO043151. Published on 20 January 2016.

Text © 2016. The authors. CC BY-NC 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.