This is the first comprehensive assessment of the aerosol optical depth (AOD) product retrieved from the near‐UV observations by the Ozone Monitoring Instrument (OMI) onboard the Aura satellite. The OMI‐retrieved AOD by the UV aerosol algorithm (OMAERUV version 1.4.2) was evaluated using collocated Aerosol Robotic Network (AERONET) level 2.0 direct Sun AOD measurements over 8 years (2005–2012). A time series analysis of collocated satellite and ground‐based AOD observations over 8 years shows no discernible drift in OMI's calibration. A rigorous validation analysis over 4 years (2005–2008) was carried out at 44 globally distributed AERONET land sites. The chosen locations are representative of major aerosol types such as smoke from biomass burning or wildfires, desert mineral dust, and urban/industrial pollutants. Correlation coefficient (ρ) values of 0.75 or better were obtained at 50% of the sites with about 33% of the sites in the analysis reporting regression line slope values larger than 0.70 but always less than unity. The combined AERONET‐OMAERUV analysis of the 44 sites yielded a ρ of 0.81, slope of 0.79, y intercept of 0.10, and 65% OMAERUV AOD falling within the expected uncertainty range (largest of 30% or 0.1) at 440 nm. The most accurate OMAERUV retrievals are reported over northern Africa locations where the predominant aerosol type is desert dust and cloud presence is less frequent. Reliable retrievals were documented at many sites characterized by urban‐type aerosols with low to moderate AOD values, concentrated in the boundary layer. These results confirm that the near‐UV observations are sensitive to the entire aerosol column. A simultaneous comparison of OMAERUV, Moderate Resolution Imaging Spectroradiometer (MODIS) Deep Blue, and Multiangle Imaging Spectroradiometer (MISR) AOD retrievals to AERONET measurements was also carried out to evaluate the OMAERUV accuracy in relation to those of the standard aerosol satellite products. The outcome of the comparison indicates that OMAERUV, MODIS Deep Blue, and MISR retrieval accuracies in arid and semiarid environments are statistically comparable.

A carbonaceous aerosol plume associated with wildfires in British Columbia in August 2017 reached the stratosphere a few days following the fires onset. The Earth Polychromatic Imaging Camera (EPIC) sensor onboard the Deep Space Climate Observatory (DSCOVR) satellite observed the spatial and temporal evolution of the plume for about 6 weeks. EPIC's near‐hourly observations of the Earth's sunlit disk allowed for monitoring the smoke plume several times per day. High ultraviolet aerosol index values pointed to the presence of an aerosol layer in the upper troposphere and lower stratosphere, confirmed with Cloud‐Aerosol Lidar with Orthogonal Polarization (CALIOP) lidar observations. EPIC aerosol optical depth retrievals and CALIOP information on layer height were used to estimate the stratospheric portion of the aerosol mass, reaching a maximum of 268 ± 86 Kt 3 days after the onset of the wildfires. About 10% of this aerosol mass reached the stratosphere on 13 August, whereas the remaining 90% did so over the following 2 days. Observed daytime and inferred nighttime rates of stratospheric aerosol mass increase showed a more rapid daytime increase, consistent with variability in diurnal insolation, suggesting that solar radiation driven processes may have contributed to the observed stratospheric aerosol mass increase. Global modeling results support the possible role of diabatic aerosol self‐lofting. Ozone Mapping and Profiler Suite Limb Profiler (OMPS‐LP) aerosol retrievals showed the spread of stratospheric aerosols in the Northern Hemisphere, reaching peak concentration between October 2017 and January 2018, when about half the Northern Hemisphere experienced a detectable enhancement of stratospheric aerosols with respect to preinjection conditions. The lifetime and aerosol mass of this smoke event were comparable to those of a moderate volcanic eruption.

The Geostationary Environment Monitoring Spectrometer (GEMS) is scheduled to be in orbit in 2019 onboard the GEO-KOMPSAT 2B satellite and will continuously monitor air quality over Asia. The GEMS will make measurements in the UV spectrum (300–500 nm) with 0.6 nm resolution. In this study, an algorithm is developed to retrieve aerosol optical properties from UV-visible measurements for the future satellite instrument and is tested using 3 years of existing OMI L1B data. This algorithm provides aerosol optical depth (AOD), single scattering albedo (SSA) and aerosol layer height (ALH) using an optimized estimation method. The retrieved AOD shows good correlation with Aerosol Robotic Network (AERONET) AOD with correlation coefficients of 0.83, 0.73 and 0.80 for heavy-absorbing fine (HAF) particles, dust and non-absorbing (NA) particles, respectively. However, regression tests indicate underestimation and overestimation of HAF and NA AOD, respectively. In comparison with AOD from the OMI/Aura Near-UV Aerosol Optical Depth and Single Scattering Albedo 1-orbit L2 Swath 13 km × 24 km V003 (OMAERUV) algorithm, the retrieved AOD has a correlation coefficient of 0.86 and linear regression equation, AOD_GEMS = 1.18AOD_OMAERUV + 0.09. An uncertainty test based on a reference method, which estimates retrieval error by applying the algorithm to simulated radiance data, revealed that assumptions in the spectral dependency of aerosol absorptivity in the UV cause significant errors in aerosol property retrieval, particularly the SSA retrieval. Consequently, retrieved SSAs did not show good correlation with AERONET values. The ALH results were qualitatively compared with the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) products and were found to be well correlated for highly absorbing aerosols. The difference between the attenuated-backscatter-weighted height from CALIOP and retrieved ALH were mostly closed to zero when the retrieved AOD is higher than 0.8 and SSA is lower than 0.93. Although retrieval accuracy was not significantly improved, the simultaneous consistent retrieval of AOD, SSA and ALH alone demonstrates the value of this stand-alone algorithm, given their nature for error using other methods. The use of these properties as input parameters for the air mass factor calculation is expected to improve the retrieval of other trace gases over Asia.

Frequent observations of aerosols from space are essential for studying aerosol effects on climate and air quality applications. We present results of aerosol properties derived from observations made by the Earth Polychromatic Imaging Camera (EPIC) sensor onboard the Deep Space Climate Observatory satellite. EPIC's near‐hourly measured radiances at 340 and 388 nm from sun rise to sunset have been used as input to the EPIC near‐UV aerosol algorithm (EPICAERUV) for retrieving aerosol extinction optical depth (AOD), single scattering albedo (SSA), above‐cloud aerosol optical depth (ACAOD), and ultraviolet Aerosol Index. Comparisons of AERONET and EPIC daily mean AOD values at eight selected representative sites yield correlation coefficients in the range from 0.68 to 0.89 and root mean square errors from 0.10 to 0.31. A similar comparison of EPIC‐retrieved SSA against the AERONET inverted SSA product revealed nearly 51% (76%) of matchups in agreement within ±0.03 (±0.05). Furthermore, the retrievals of ACAOD are also found to compare reasonably well, with 50%–70% of matchups falling within expected uncertainty against the direct airborne measurements acquired during the ObseRvations of Aerosols above CLouds and their intEractionS campaign. Using the EPICAERUV aerosol product, we analyzed the spatial and temporal patterns of specific smoke events caused by wildfires over North America over the last four years.

Atmospheric aerosols are significant sources of uncertainty in air mass factor (AMF) calculations for trace gas retrievals using ultraviolet measurements from space. Current trace gas retrievals typically do not consider aerosols explicitly as cloud products partially account for aerosol effects. Here, we propose a new measurement‐based approach to correct for aerosols explicitly in the AMF calculation, apply it to Ozone Monitoring Instrument (OMI) formaldehyde (HCHO) retrievals and quantify the aerosol‐induced HCHO vertical column density difference for three aerosol types (smoke, dust, and sulfate) during 2006–2007. We use OMI aerosol retrievals for aerosol optical properties and vertical profiles to construct lookup tables of scattering weights as functions of geometry, surface pressure, surface albedo, and aerosol information. The average difference between the National Aeronautics and Space Administration operational OMI HCHO product (not considering aerosols) and the results obtained in this study on a global scale are 27%, 6%, and −0.3% for smoke, dust, and sulfate aerosols, respectively. The region with the largest aerosol effects is East China, where the explicit smoke aerosol correction enhances mean HCHO vertical column densities by 35%, with corrections to individual observations sometimes larger than 100%. The quantified aerosol effects are applicable under clear‐sky conditions. This study highlights the need to implement aerosol corrections in the AMF calculation for HCHO retrievals. This is particularly relevant in regions with high levels of pollution where aerosols interfere the most with formaldehyde satellite observations.

The hour‐to‐hour variability of 388 nm aerosol optical depth (AOD) and single scattering albedo (SSA) derived from near UV observations by the Earth Polychromatic Imaging Camera (EPIC) on the Deep Space Climate Observatory has been evaluated at multiple locations around the world. AOD retrievals by the EPIC near UV algorithm (EPICAERUV) have been compared to ground based AOD measurements at 16 Aerosol Robotic Network (AERONET) stations representative of the most commonly observed aerosol types over geographic regions in three continents. Obtained results show that, in general, the EPICAERUV algorithm reproduces closely the hour‐to‐hour AOD variability reported by AERONET ground‐truth observations. Although most sites in the analysis show high correlation between the AOD hourly measurements by the ground‐based and space‐borne measuring techniques. Best algorithm performance is observed in the presence of carbonaceous and desert dust aerosols. The diurnal cycle of the retrieved SSA product was also analyzed. Although, a direct comparison of hourly EPICAERUV retrievals to equivalent ground‐based observations was not possible, the satellite result shows that diurnal SSA variability as large as 0.05 can be observed mostly associated with carbonaceous aerosols. EPICAERUV observed diurnal cycle of retrieved AOD on a regional basis was examined for the unusually active seasons of aerosol production of Saharan desert dust aerosols in 2020, and during the 2023 Canadian wildfires. Results presented in this study confirm the EPIC near UV aerosol product is well suited for observing diurnal variability of aerosols and, therefore, it is an important resource for climate and air quality studies.