Evaluation of UV aerosol retrievals from an ozone lidar

Abstract

Abstract. Aerosol retrieval using ozone lidars in the ultraviolet spectral region is challenging but necessary for correcting aerosol interference in ozone retrieval and for studying the ozone–aerosol correlations. This study describes the aerosol retrieval algorithm for a tropospheric ozone lidar, quantifies the retrieval error budget, and intercompares the aerosol retrieval products at 299 nm with those at 532 nm from a high spectral resolution lidar (HSRL) and with those at 340 nm from an AErosol RObotic NETwork radiometer. After the cloud-contaminated data are filtered out, the aerosol backscatter or extinction coefficients at 30 m and 10 min resolutions retrieved by the ozone lidar are highly correlated with the HSRL products, with a coefficient of 0.95 suggesting that the ozone lidar can reliably measure aerosol structures with high spatiotemporal resolution when the signal-to-noise ratio is sufficient. The actual uncertainties of the aerosol retrieval from the ozone lidar generally agree with our theoretical analysis. The backscatter color ratio (backscatter-related exponent of wavelength dependence) linking the coincident data measured by the two instruments at 299 and 532 nm is 1.34±0.11, while the Ångström (extinction-related) exponent is 1.49±0.16 for a mixture of urban and fire smoke aerosols within the troposphere above Huntsville, AL, USA.

Impact of the 2016 Southeastern US Wildfires on the Vertical Distribution of Ozone and Aerosol at Huntsville, Alabama

“…Aerosol extinction coefficients at the non‐absorption line (299 nm) are retrieved by assuming a constant aerosol extinction‐to‐backscatter ratio, which is 60 steradians (sr) for this study. Validation experiments through comparing with co‐located high spectral resolution lidar observations suggest that the RO 3 QET lidar is capable of capturing aerosol variability up to 6 km altitude at high spatiotemporal resolution (Kuang et al., 2020).…”

“…The continuous profiling of ozone and aerosols provides details missed by isolated measurements and is an asset for model evaluation by coordinating measurements (Langford et al, 2018(Langford et al, , 2019. In addition, the ultraviolet (UV) backscatter (or extinction) profiles retrieved from ozone lidar can quantify the aerosol variability at the high spatiotemporal resolution, and these measurements serve as a tracer for fire smoke (Kuang et al, 2020;Langford et al, 2020). To our best knowledge, there has been little or no attempt to evaluate CTMs using this range-resolved UV aerosol optical product.…”

Tropospheric NO<sub>2</sub> measurements using a three-wavelength optical parametric oscillator differential absorption lidar

“…5a with the setting of the lidar ratio = 50 and e = 1, 2 and 3. The lidar ratio is wavelengthdependent, and its value in the visible band is in general smaller than in the UV band for the same type of aerosols (Kuang et al, 2020;Reid et al, 2017). Absorption of NO 2 and O 3 at 438, 439.5 and 441 nm can be calculated using their mixing ratio profiles in Fig.…”

“…In addition, measurements of tropospheric NO 2 from satellites or aircraft are also influenced and limited by clouds (Bovensmann et al, 1999;Liang et al, 2017). Ground-based measurements of column NO 2 from instruments such as Pandora using differential optical absorption spectroscopy (DOAS) are often used for the validation of satellite instruments (Herman et al, 2009;Lamsal et al, 2014;Kollonige et al, 2018). In situ measurements of near-surface NO 2 can best monitor local emissions.…”

Retrieval of UVB aerosol extinction profiles from the ground-based Langley Mobile Ozone Lidar (LMOL) system

“…The increase in frequency and severity of North American wildfires significantly affects air quality by increasing the amount of particulates and ozone in the air (Schoennagel et al, 2017). Ground-based lidars have the ability of simultaneously detecting O3 and aerosol with high temporal and vertical resolution to better understand air quality exceedances that can be exacerbated by transported wildfire emission (Aggarwal et al, 2018;Strawbridge et al, 2018;Kuang et al, 2020). On the other hand, the determination of the aerosol properties in UVB wavelength region is of great importance to understand the effect of aerosol on UV radiation which is linked to human health and atmospheric chemistry (Bais et al, 1993;Carlund et al, 2017;Moozhipurath and Skiera, 2020).…”