LED-CE-DOAS and MAX-DOAS measurements of glyoxal and NO2 at Milliken Library during CalNEX

The University of Colorado Light Emitting Diode Cavity Enhanced Differential Optical Absorption Spectroscopy (CU LED-CE-DOAS) and a CU Ground based MAX-DOAS instrument were deployed on top of Milliken Library at the CalNex-LA site (May.June 2010). The CU LED-CE-DOAS is a novel instrument that was deployed for the first time in the field to measure in-situ concentrations of nitrogen dioxide (NO2) and glyoxal (CHOCHO) at roof top level. The CU Ground MAX-DOAS measured vertical column integral amounts of the same gases, along with formaldehyde (HCHO) among other gases. For a period of time two CE-DOAS instruments were operated simultaneously with one in closed and one in open cavity mode. Open cavity mode allows air to flow between the mirrors of the cavity and does not utilize an inlet or aerosol filter. NO2 measurements by the two instruments are compared. Here we present the diurnal profiles for glyoxal and NO2 measured by CE-DOAS for the duration of the Cal-NEX campaign. The temporal evolution of in situ CE-DOAS measurements of NO2 and glyoxal is used in combination with that of the vertical column density measured by MAX-DOAS to assess transport to the site, as well as to estimate the boundary layer height.