CO2 variability from in situ and vertical column measurements in Mexico City

UNAM started a program to measure, among many other atmospheric parameters, greenhouse gas concentrations at six stations in the Mexican territory as part of the "Red Universitaria de Observatorios Atmosfericos", RUOA (www.ruoa.unam.mx). In this work we present recent time series of CO2 measured at the station located in the university campus in Mexico City, and compare them to total vertical columns of this gas measured at the same location. In situ measurements are continuously carried out with a cavity ring-down spectrometer (Picarro Inc., G2401) since July 2014 and the columns are retrieved from solar absorption measurements taken with a Fourier transform infrared spectrometer (Bruker, Vertex 80) when conditions allow. The retrieval method is described and results of the comparison of both techniques and a detailed analysis of the variability of this important greenhouse gas is presented. Simultaneous surface and column CO2 data are useful to constrain models and estimate emissions.