Effect of aerosol vertical distribution on aerosol-radiation interaction: A theoretical prospect

Equivalent radius of atmosphere aerosol in haze weather based on laser scattering

The investigation of atmospheric aerosols holds paramount importance within the environmental realm. This significance arises from the intricate nature of aerosol distribution and size in real-life hazy weather conditions. In this work, we have employed the equivalent radius of the aerosols in haze weather obtained from the volume spectrum, and then the scattering characteristics of these aerosols are obtained using the equivalent radius. Pearson correlation coefficients have been used for revealing a strong correlation by comparing Aeronet website data and simulation results with a minimum value of 0.657.

Aerosol optical properties over the South Atlantic and southern ocean during the 2010-2012 summer seasons as part of the global maritime aerosol network

Aerosols have implications to climate and biogeochemical cycles in the global oceans. At sites under indirect influence of dust emitted by the Patagonian semi-desert, a debate exists on the potential fertilization effects of iron enriched aerossol. Considering this subject we conducted measurements of aerosols optical properties using a Microtops II sun photometer to access aerosol size distributions and other intrinsic properties oversea from Atlantic Southern mid-latitudes to Antarctica. Oceanographic cruises were developed between December 2010 to April 2011 and October 2011 to April 2012, in the context of the Brazilian Antarctic Program, and between November 2011 to December 2011. This survey was taken as part of the Global Maritime Aerosol Network (MAN/NASA). Our data of AOD (500 nm) along the South American coast depicts a steady decrease southwards following the decreased latitudinal continental extent. However, the influence of the aerosols blown from Patagonia semi-desert region was clear from latitude 53⁰S to 64⁰S. The predominance of aerosol fine mode was observed in Central Atlantic and close to the Drake Passage. An unexpected aerosol coarse mode predominance was found close to the Antarctic Peninsula. We attribute that to a possible weathering of rock outcrops due to the strong westerly winds in that region.

Aerosol breezes drive cloud and precipitation increases

Aerosol-cloud interactions are a major source of uncertainty in weather and climate models. These interactions and associated precipitation feedbacks are modulated by spatial distributions of aerosols on global and regional scales. Aerosols also vary on mesoscales, including around wildfires, industrial regions, and cities, but the impacts of variability on these scales are understudied. Here, we first present observations of covarying mesoscale aerosol and cloud distributions on the mesoscale. Then, using a high-resolution process model, we show that horizontal aerosol gradients of order 100 km drive a thermally-direct circulation we call an "aerosol breeze". We find that aerosol breezes support initiation of clouds and precipitation over the low-aerosol portion of the gradient while suppressing their development on the high-aerosol end. Aerosol gradients also enhance domain-wide cloudiness and precipitation, compared with homogenous distributions of the same aerosol mass, leading to potential biases in models that do not adequately represent this mesoscale aerosol heterogeneity.

Spatial distribution vegetation density, land surface temperature, and land surface moisture of Banda Aceh, Indonesia after 17 years of tsunami: a multitemporal analysis approaches

Although some studies on vegetation cover in relation to the land surface temperature (LST) and land surface moisture (LSM) have been carried out, but not yet been investigated in relation to the pre-disaster and after-tsunami disasters. This paper investigates the spatial extent of vegetation cover density, land surface temperature, and land surface moisture of Banda Aceh from 2000 to 2020 to represent the pre-disaster phase, during the disaster, post-disaster, rehabilitation, and reconstruction stages, and current conditions using remote sensing data. NDVI, LST, and NDMI indexes were utilized, and the mapping process of multitemporal images of Banda Aceh was carried out. The results show that after the tsunami, the distribution of vegetation density varies, tending to decrease for densely vegetated areas before increasing more than 5 years later. For medium categories, the vegetation density increased by 22% in 2020 and almost 26% in 2015. Meanwhile, dense vegetation grew by 19% and 13%, respectively, according to data for 2015 and 2020. In a similar outlook, the increasing vegetation density has demonstrated that the LST across Banda Aceh is dominated by 27-30 °C, with 2005 data occupying the coldest area. The city's moderate moisture content covered 85.43% of its surface. The low to medium vegetation density, LST, and LSM indexes from 2000 to 2010 is shown by overlaying a combination of three spatial extent indexes. It is shown that Banda Aceh's medium-to-high density, medium LSM, and medium-to-high LST spatially. Banda Aceh's dynamic changes in vegetation, LST, and LSM over the past two decades have been proven in this research; the Banda Aceh's spatial variation in vegetation density, LST, and LSM is influenced by the tsunami.

Design and Verification of a Double-Grating Spectrometer System (DGSS) for Simultaneous Observation of Aerosols, Water Vapor and Clouds

Simultaneous observation of aerosols, water vapor, and clouds is conducive to the analysis of their interactions, and the consistency of observation equipment, instrument performance, and observation time is crucial. Molecular oxygen A-band (758–778 nm) and water vapor absorption band (758–880 nm) are two bands with similar wavelengths, and the hyperspectral remote sensing information of these two bands can be exploited to invert the vertical profile of aerosol and water vapor. In this paper, a double-grating spectrometer system (DGSS) was developed. DGSS uses a telescope system and fiber to introduce multi-angle, double-band sunlight, and it splits light synchronously (non-sequentially) to different positions of the detector through a slit plate and two gratings. The DGSS was calibrated in the laboratory and observed in the external field. The results indicated that the spectral resolution reached 0.06 nm (molecular oxygen A-band, 758–778 nm) and 0.24 nm (water vapor absorption band, 758–880 nm). Meanwhile, the spectra of the two bands (three angles in each band) are not aliased on the detector. Besides, the multi-angle simultaneous observation of the high-resolution spectra of the two bands is realized, which proves the effectiveness of this method. This study will provide a scientific basis for the observation of aerosol, water vapor, and cloud ground-based networks.

Effect of Aerosol Vertical Distribution on the Modeling of Solar Radiation

Default aerosol extinction coefficient profiles are commonly used instead of measured profiles in radiative transfer modeling, increasing the uncertainties in the simulations. The present study aimed to determine the magnitude of these uncertainties and contribute towards the understanding of the complex interactions between aerosols and solar radiation. Default, artificial and measured profiles of the aerosol extinction coefficient were used to simulate the profiles of different radiometric quantities in the atmosphere for different surface, atmospheric, and aerosol properties and for four spectral bands: ultraviolet-B, ultraviolet-A, visible, and near-infrared. Case studies were performed over different areas in Europe and North Africa. Analysis of the results showed that under cloudless skies, changing the altitude of an artificial aerosol layer has minor impact on the levels of shortwave radiation at the top and bottom of the atmosphere, even for high aerosol loads. Differences of up to 30% were, however, detected for individual spectral bands. Using measured instead of default profiles for the simulations led to more significant differences in the atmosphere, which became very large during dust episodes (10–60% for actinic flux at altitudes between 1 and 2 km, and up to 15 K/day for heating rates depending on the site and solar elevation).

Direct radiative effects of airborne microplastics

Microplastics are now recognized as widespread contaminants in the atmosphere, where, due to their small size and low density, they can be transported with winds around the Earth^1-25. Atmospheric aerosols, such as mineral dust and other types of airborne particulate matter, influence Earth's climate by absorbing and scattering radiation (direct radiative effects) and their impacts are commonly quantified with the effective radiative forcing (ERF) metric²⁶. However, the radiative effects of airborne microplastics and associated implications for global climate are unknown. Here we present calculations of the optical properties and direct radiative effects of airborne microplastics (excluding aerosol-cloud interactions). The ERF of airborne microplastics is computed to be 0.044 ± 0.399 milliwatts per square metre in the present-day atmosphere assuming a uniform surface concentration of 1 microplastic particle per cubic metre and a vertical distribution up to 10 kilometres altitude. However, there are large uncertainties in the geographical and vertical distribution of microplastics. Assuming that they are confined to the boundary layer, shortwave effects dominate and the microplastic ERF is approximately -0.746 ± 0.553 milliwatts per square metre. Compared with the total ERF due to aerosol-radiation interactions²⁷ (-0.71 to -0.14 watts per square metre), the microplastic ERF is small. However, plastic production has increased rapidly over the past 70 years²⁸; without serious attempts to overhaul plastic production and waste-management practices, the abundance and ERF of airborne microplastics will continue to increase.

Aerosol Layering in the Free Troposphere over the Industrial City of Raciborz in Southwest Poland and Its Influence on Surface UV Radiation

Atmospheric aerosol and ultraviolet index (UVI) measurements performed in Racibórz (50.08° N, 18.19° E) were analyzed for the period June–September 2019. Results of the following observations were taken into account: columnar characteristics of the aerosols (aerosol thickness, Angstrom exponent, single scattering albedo, asymmetry factor) obtained from standard CIMEL sun-photometer observations and parameters of aerosol layers (ALs) in the free troposphere (the number of layers and altitudes of the base and top) derived from continuous monitoring by a CHM-15k ceilometer. Three categories of ALs were defined: residues from the daily evolution of the planetary boundary layer (PBL) aerosols, from the PBL-adjacent layer, and from the elevated layer above the PBL. Total column ozone measurements taken by the Ozone-Monitoring Instrument on board NASA’s Aura satellite completed the list of variables used to model UVI variability under clear-sky conditions. The aim was to present a hybrid model (radiative transfer model combined with a regression model) for determining ALs’ impact on the observed UVI series. First, a radiative transfer model, the Tropospheric Ultraviolet–Visible (TUV) model, which uses typical columnar characteristics to describe UV attenuation in the atmosphere, was applied to calculate hypothetical surface UVI values under clear-sky conditions. These modeled values were used to normalize the measured UVI data obtained during cloudless conditions. Next, a regression of the normalized UVI values was made using the AL characteristics. Random forest (RF) regression was chosen to search for an AL signal in the measured data. This explained about 55% of the variance in the normalized UVI series under clear-sky conditions. Finally, the UVI values were calculated as the product of the RF regression and the relevant UVIs by the columnar TUV model. The root mean square error and mean absolute error of the hybrid model were 1.86% and 1.25%, respectively, about 1 percentage point lower than corresponding values derived from the columnar TUV model. The 5th–95th percentile ranges of the observation/model differences were [−2.5%, 2.8%] and [−3.0%, 5.3%] for the hybrid model and columnar TUV model, respectively. Therefore, the impact of ALs on measured surface UV radiation could be demonstrated using the proposed AL characteristics. The statistical analysis of the UVI differences between the models allowed us to identify specific AL configuration responsible for these differences.

Assessment of Approximations in Aerosol Optical Properties and Vertical Distribution into FLEX Atmospherically-Corrected Surface Reflectance and Retrieved Sun-Induced Fluorescence

Physically-based atmospheric correction of optical Earth Observation satellite data is used to accurately derive surface biogeophysical parameters free from the atmospheric influence. While water vapor or surface pressure can be univocally characterized, the compensation of aerosol radiometric effects relies on assumptions and parametric approximations of their properties. To determine the validity of these assumptions and approximations in the atmospheric correction of ESA’s FLEX/Sentinel-3 tandem mission, a systematic error analysis of simulated FLEX data within the O 2 absorption bands was conducted. This paper presents the impact of key aerosol parameters in atmospherically-corrected FLEX surface reflectance and the subsequent Sun-Induced Fluorescence retrieval (SIF). We observed that: (1) a parametric characterization of aerosol scattering effects increases the accuracy of the atmospheric correction with respect to the commonly implemented discretization of aerosol optical properties by aerosol types and (2) the Ångström exponent and the aerosol vertical distribution have a residual influence in the atmospherically-corrected surface reflectance. In conclusion, a multi-parametric aerosol characterization is sufficient for the atmospheric correction of FLEX data (and SIF retrieval) within the mission requirements in nearly 85% (70%) of the cases with average aerosol load conditions. The future development of the FLEX atmospheric correction algorithm would therefore gain from a multi-parametric aerosol characterization based on the synergy of FLEX and Sentinel-3 data.