This paper describes modification of smoothness constraints on the imaginary part of the refractive index employed in the AERONET aerosol retrieval algorithm. This modification is termed relaxed due to the weaker strength of this new smoothness constraint. Applying the modified version of the smoothness constraint results in a significant reduction of retrieved light absorption by brown-carbon-containing aerosols.

The evolution of the atmospheric boundary layer height (ABLH) has an important impact on meteorology. However, the complexity of the phenomena occurring within the ABL and the influence of advection and local accumulation processes often prevent an unambiguous determination of the ABLH. The paper reports results from an inter-comparison effort involving different sensors and techniques to measure the ABLH. Correlations between the ABLH and other atmospheric variables are also assessed.

A new method is presented to retrieve the sea spray aerosol size distribution by combining submicron size and nephelometer scattering based on Mie theory. Using available sea spray tracers, we find that this approach serves as a comparable substitute to supermicron size distribution measurements, which are limited in availability at marine sites. Application of this technique can expand sea spray observations and improve the characterization of marine aerosol impacts on clouds and climate.

We present the pollution detection algorithm (PDA), a new method to identify local primary pollution in remote atmospheric aerosol and trace gas time series. The PDA identifies periods of contaminated data and relies only on the target dataset itself; i.e., it is independent of ancillary data such as meteorological variables. The parameters of all pollution identification steps are adjustable so that the PDA can be tuned to different locations and situations. It is available as open-access code.

Mid-level and high clouds can be considered natural laboratories for studying cloud glaciation in the atmosphere. While they can be conveniently observed from ground with lidar, such measurements require a clear line of sight between the instrument and the target cloud. Here, observations of clouds with two spaceborne lidars are used to assess where ground-based lidar measurements of mid- and upper-level clouds are least affected by the light-attenuating effect of low-level clouds.

The comparison of water vapor lidar measurements with co-located radiosondes and aerosol backscatter profiles indicates that laser-induced aerosol fluorescence in smoke layers injected into the stratosphere can introduce very large and chronic wet biases above 15 km, thus impacting the ability of these systems to accurately estimate long-term water vapor trends. The proposed correction method presented in this work is able to reduce this fluorescence-induced bias from 75 % to under 5 %.

Two cloud-masking approaches, a local and a regional approach, using high-resolution satellite data are developed and validated for the region of Paris to improve applicability for analyses of urban effects on low clouds. We found that cloud masks obtained from the regional approach are more appropriate for the high-resolution analysis of locally induced cloud processes. Its applicability is tested for the analysis of typical fog conditions over different surface types.

Landscape fires are a substantial emitter of greenhouse gases and aerosols. Previous studies have indicated savanna emission factors to be highly variable. Improving fire emission estimates, and understanding future climate- and human-induced changes in fire regimes, requires in situ measurements. We present a drone-based method that enables the collection of a large amount of high-quality emission factor measurements that do not have the biases of aircraft or surface measurements.

Iodide chemical ionization mass spectrometry (CIMS) is commonly used in atmospheric chemistry laboratory studies and field campaigns. Deployment of the NOAA iodide CIMS instrument in the summer of 2021 indicated a significant and overlooked temperature dependence of the instrument sensitivity. This work explores which analytes are influenced by this phenomena. Additionally, we recommend controls to reduce this effect for future field deployments.

Space profiling lidars offer a unique insight into cloud properties in Earth’s atmosphere, and are considered the most reliable source of cloud information. However, lidar-based cloud climatologies are infrequently sampled: every 7 to 91 d, and only along the ground track. This study evaluated how accurate are the cloud data from existing (CALIPSO, ICESat-2, Aeolus) and planned (EarthCARE) space lidars, when compared to a cloud climatology obtained with observations taken every day.

Aerosol parameter retrievals have always been a research focus. In this study, we used an advanced aerosol algorithms (GRASP, developed by Oleg Dubovik) to test the ability of DPC/Gaofen-5 (the first polarized multi-angle payload developed in China) images to obtain aerosol parameters. The results show that DPC/GRASP achieves good results (R > 0.9). This research will contribute to the development of hardware and algorithms for aerosols

We present a computationally very efficient method for the synergetic use of level 2 remote-sensing data products. We apply the method to IASI vertical profile and TROPOMI total column space-borne methane observations and thus gain sensitivity for the tropospheric methane partial columns, which is not achievable by the individual use of TROPOMI and IASI. These synergetic effects are evaluated theoretically and empirically by inter-comparisons to independent references of TCCON, AirCore, and GAW.

SO₂ is adverse to human health and the environment. A single SO₂ sonde was developed to provide direct SO₂ measurement with a greater vertical extent, a lower limit of detection, and less uncertainty relative to the previous dual-sonde method. The single sonde was tested in the field near volcanoes and anthropogenic sources where the sonde measured SO₂ ranging from 0.5 to 940 ppb. This lighter-weight payload can be a great candidate to attach to small drones and unmanned aerial vehicles.

Atmospheric chemistry plays a key role in the understanding of aerosol formation and air pollution. We designed chamber experiments for the characterization of secondary organic aerosol (SOA) from a biogenic precursor with inorganic seed. Our results highlight the advantages of a combination of online FIGAERO-CIMS and offline LC-Orbitrap MS analytical techniques to characterize the chemical composition of SOA in chamber studies.

The equivalence between the data fusion performed using the Kalman filter and the Complete Data Fusion has been proved, and a generalization of the Complete Data Fusion formula, that is valid also in the case that the noise error covariance matrices of the fused products are singular, is derived. The two methods are also equivalent to the measurement–space–solution data fusion method, and for moderately nonlinear problems, the three methods are all equivalent to the simultaneous retrieval.