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A low-power lidar system based in Manchester, United Kingdom has been developed to measure temperature profiles in the nocturnal urban boundary layer. The lidar transmitter uses a 355nm diode-pumped solid state Nd:YAG laser and two narrow-band interference filters in the receiver filter out rotational Raman lines that are dependent on temperature. The spectral response of the lidar is calibrated using a monochromator. Temperature profiles measured by the system are calibrated by comparison to co-located radiosondes.

The Clean Air for London (ClearfLo) Project took place in and around London, United Kingdom. The aim of the project was to learn how both atmospheric dynamics and chemistry affect air pollution in the south east of England. During the winter and summer of 2012 many different types of instrument including lidars were deployed throughout London city centre, suburbs and into rural areas. Amongst these instruments was the Boundary Layer Aerosol/Ozone Lidar owned by the National Centre for Atmospheric Sciences (NCAS) in the United Kingdom. Ozone and aerosol data are presented from data collected during July and August 2012 and compared to back trajectories to identify their origins.

On 22 June 2019 the Raikoke volcano in the Kuril islands erupted, sending a plume of ash and sulphur dioxide into the stratosphere. A Raman lidar system at Capel Dewi Atmospheric Observatory, UK (52.4° N, 4.1° W) has been used to measure the extent and optical depth of the stratospheric aerosol layer following the eruption. The elastic channel allowed measurements up to 25 km, but the Raman channel was only sensitive to the troposphere. Therefore, backscatter ratio profiles were derived by comparison with aerosol-free profiles derived from nearby radiosondes, corrected for aerosol extinction with a lidar ratio of 40-50 sr. Small amounts of aerosol were measured prior to the arrival of the volcanic cloud, probably from pyroconvection over Canada. Volcanic ash may have first arrived as a thin layer at 14 km late on 3 July, and was certainly detected from 13 July onwards, eventually extending up to 20.5 km. Aerosol optical depths reached around 0.05 by early August, decaying thereafter to around 0.01 by the end of 2019 and remaining around that level until May 2020. The location of peak backscatter varied considerably but was generally around 15 km. However, on one notable occasion on 25 August, a layer around 300 m thick with peak lidar backscatter ratio around 1.5 was observed as high as 21 km. [ABSTRACT FROM AUTHOR]

Methane emission fluxes from facility-scale sources may be poorly quantified, leading to uncertainties in the global methane budget. Accurate atmospheric measurement based flux quantification is urgently required to address this. This paper describes the test of a new near-field Gaussian plume inversion (NGI) technique, suitable for facility-scale flux quantification, using a controlled release of methane gas. Two unmanned aerial vehicle (UAV) platforms were used to perform 22 flight surveys downwind of a point-source release of methane gas from a regulated and flow-metered cylinder. One UAV was tethered to an instrument on the ground, while the other UAV carried an on-board high-precision prototype instrument, both of which used the same near-infrared laser technology. The performance of these instruments from UAV sampling is described. Both instruments were calibrated using certified standards, to account for variability in the instrumental gain factor. Furthermore, a modified approach to correcting for the effect of water vapour applied and is described here in detail. The NGI technique was used to derive emission fluxes for each UAV flight survey. We found good agreement of most NGI fluxes with the known controlled emission flux, within uncertainty, verifying the flux quantification methodology. The lower NGI flux uncertainty bound was, on average, 17 % ± 10(1σ) % of the controlled emission flux and the upper NGI flux uncertainty bound was, on average, 218 % ± 100(1σ) % of the controlled emission flux. These highly conservative uncertainty ranges incorporate factors including the variability in the position of the plume and the potential for under-sampling. While these average uncertainties are large compared to methods such as tracer dispersion, we suggest that UAV sampling can be highly complementary to a toolkit of flux approaches and may perform well in situations where site access for tracer release is problematic. We see tracer release applied to UAV sampling as an effective combination in future flux quantification studies. Successful flux quantification using this UAV sampling methodology demonstrates its future utility in identifying and quantifying emissions from methane sources such as oil and gas infrastructure facilities, livestock agriculture and landfill sites, where site access may be difficult. [ABSTRACT FROM AUTHOR]