The surface-based component of the LA observing system includes a network of Greenhouse Gas (GHG) monitoring stations that is intended to encompass the portions of the South Coast Air Basin producing the most intense GHG emissions (the urbanized portions of Los Angeles, Orange, Riverside, and San Bernardino counties). Measurements began a few years ago at several sites within the basin such as Mt Wilson, Caltech, and Palos Verdes. Sustained measurements have also been underway for many years from the Scripps Pier in La Jolla. However until recently those measurements were not coordinated. Between 2013 and 2015 we completed installation of a 14-node measurement network within and around the LA basin.
Every site is equipped with at least one in situ gas analyzer providing high-accuracy, continuous measurements of carbon dioxide (CO2) mixing ratios. Nearly every site also includes measurements of methane (CH4) and about half of the sites currently measure carbon monoxide (CO). Two of the sites were deployed in the high desert and on an island to help track the relatively clean “background” air conditions and to track the outflow of polluted air from the basin. The in situ instruments being used in our network include various versions of gas analyzers from Picarro and Los Gatos Research. These instruments sample the air using pumps and air hose inlets located on towers or tall buildings. Every site is also equipped with one or more weather stations to help interpret the greenhouse gas measurements. Wind speed and direction measurements are essential for interpreting greenhouse gas data collecting on building roof-tops because we need to determine the upwind corner of the building (which varies over time) to be sure we’re sampling the surrounding air rather than air trapped in eddies around the building or from polluted air being emitted from the building itself.
In addition to the continuous in situ gas analyzers, whole-air gas flasks are automatically collected roughly twice weekly at a subset of sites for subsequent laboratory analysis for many gas species and also radio-isotope analysis including 14C (critical for separating the contribution of CO2 and CH4 generated from fossil-fuel active vs biogenic sources). Remote-sensing measurements of column-averaged mixing ratios are currently provided from three sites: the CLARS instrument on Mt. Wilson provides two-dimensional scans of the LA basin about every 90 minutes during daylight hours and the TCCON FTS instrument at Caltech in Pasadena provides near-continuous solar observations. Both of these remote sensing instruments measure column-averaged mixing ratios of CO2, methane, and carbon dioxide.
In addition to GHG observations, measurements of key meteorological variables including winds and Planetary Boundary Layer Height (PBLH) are being made with an existing measurement network that is being augmented with remote sensing instruments at Caltech and other locations. PBLH instruments include 1 Sigma Space Mini Micro Pulse Lidar (MiniMPL) and 1 Vaisala ceilometer.
Measurement systems across this LA network are currently operated by a collaboration between NASA JPL, Earth Networks, Scripps, the California Air Resources Board, Caltech, and NOAA.
Our collaborators in France are conducting a similar activity in Paris with greenhouse gas monitoring sites in and around the Region Ile De France. See MEGAPARIS CO2 website for description of the first phase of the project and Carbocount-City website for the next phase. Other new related efforts include Multi-CO2 and Paris 2030. The Paris network is currently being reconfigured as shown in the figure below. The green and purple sites are operating. Setup of the yellow sites is in progress.
Discussions are currently underway with collaborators at the University of Sao Paulo and other institutions in Brazil regarding a potential coordinated effort there. We will add more information here when its available.