Diurnal variation of midlatitudinal NO<sub>3</sub> column abundance over table mountain facility, California

Abstract

Abstract. The column abundance of NO 3 was measured over Table Mountain Facility, CA (34.4 • N, 117.7 • W) from May 2003 through September 2004, using lunar occultation near full moon with a grating spectrometer. The NO 3 column retrieval was performed with the differential optical absorption spectroscopy (DOAS) technique using both the 623 and 662 nm NO 3 absorption bands. Other spectral features such as Fraunhofer lines and absorption from water vapor and oxygen were removed using solar spectra obtained at different airmass factors. We observed a seasonal variation, with nocturnally averaged NO 3 columns between 5 − 7 × 10 13 molec cm −2 during October through March, and 5 − 22 × 10 13 molec cm −2 during April through September. A subset of the data, with diurnal variability vastly different from the temporal profile obtained from onedimensional stratospheric model calculations, clearly has boundary layer contributions; this was confirmed by simultaneous long-path DOAS measurements. However, even the NO 3 columns that did follow the modeled time evolution were often much larger than modeled stratospheric partial columns constrained by realistic temperatures and ozone concentrations. This discrepancy is attributed to substantial tropospheric NO 3 in the free troposphere, which may have the same time dependence as stratospheric NO 3 .

The impact of Los Angeles basin pollution and stratospheric intrusions on the surrounding San Gabriel Mountains as seen by surface measurements, lidar, and numerical models

“…16d. This decrease in the surface ozone concentration, associated with an increase in the relative humidity, resembles the case study presented in Chouza et al (2019) and suggest low-level transport of marine air as the source of it. By 13:00 UTC on 13 June, the stratospheric intrusion reaches the surface over TMF, causing a decrease in the surface relative humidity and an increase in the surface ozone mixing ratio.…”

“…In 2018, TMTOL was fully automated, and a new channel covering the range between 100 and 1000 m a.g.l. was added to the system (Chouza et al, 2019). These two modifications greatly improved the capabilities of the system for air quality and transport studies in the planetary boundary layer (PBL).…”

“…Long runs of multiple hours or days can be routinely performed without over-stressing the operators, and the retrieved profile extends downwards into the PBL, in contrast to the former setup that allowed only measurements down to 1000 m a.g.l. In addition to the validation with tethered balloons reported in Chouza et al (2019), routine validations of this new very-near-range receiver have been conducted with an unmanned aerial vehicle (UAV)-borne electrochemical concentration cell (ECC) ozonesonde that provides ozone profiles between the ground and 120 m a.g.l. The overlap of 20 m between the UAV measurements and TMTOL allows us to verify that the lidar measurement is not biased due to changes in the receiver overlap function.…”

Low-level summertime isoprene observed at a forested mountaintop site in southern China: implications for strong regional atmospheric oxidative capacity

“…may lower the observed isoprene levels as compared with the forest canopy underneath the site, it is still interesting to find that the daytime isoprene concentration (377±46 pptv) in the hottest months of the year (July-August) was 50 %-100 % lower than the values observed at the same latitude subtropical forested sites in Southern China (e.g. yearly value of 760 pptv at Dinghu Mountain, and summer average of 1028 pptv at a rural park) (Chen et al, 2010;Wu et al, 2016). Furthermore, O 3 and NO x levels at this site were generally higher than the observations available in other forest stud- ies worldwide (Table 1).…”

Diurnal variability of total column NO<sub>2</sub> measured using direct solar and lunar spectra over Table Mountain, California (34.38° N)

“…The grating spectrometer used for the NO2 spectral measurement is similar to the one used by Chen et al (2011) and is installed in the same observatory. A heliostat and a telescope are used to direct and launch light into a fibre optic bundle placed at the focal plane of the telescope (Figure 1).…”