Accuracy Enhancement of the Two-Stream Radiative Transfer Model for Computing Absorption Bands at the Presence of Aerosols

The two-stream model is the fastest radiative transfer model among those based on the discrete ordinate method. Although its accuracy is not high enough to be used in applications, the two-stream model gets more attention in computationally demanding tasks such as line-by-line simulations in the gaseous absorption bands. For this reason, we designed the cluster low-streams regression (CLSR) technique, in which a spectrum computed with a two-stream model, is refined by using statistical dependencies between two- and multistream radiative transfer models. In this paper, we examine the efficiency of this approach for computing Hartley-Huggins, O2 A-, water vapour and CO2 bands at the presence of aerosols. The numerical results evidence that the errors of the CLSR method is not biased and around 0.05 %, while the performance enhancement is two orders of magnitude.

Modelling, Investigation, and Feasibility of Stratospheric Broadband mm-Wave 5G and beyond Networks for Aviation

Recent advances in communication systems provide an enabling technology for aircraft connection and safety. A promising communication system that uses stratospheric platforms provides an efficient and improved communication performance and can be an efficient solution for establishing communication networks for aviation. Therefore, in this paper, a novel communication network based on stratospheric basestation (SB) is proposed to provide fifth-generation (5G) and beyond services for civil aviation aircrafts to improve global flight connectivity, control, and safety. The proposed aircraft–SB network is demonstrated, and its coverage geometry is modelled and investigated. As the 5G and beyond networks use millimeter wave frequency bands (mm-wave), the performance of different atmospheric losses including gaseous absorption, rain, and fog/cloud is analyzed to investigate the system’s practical feasibility at different 5G proposed frequencies ranging from 3.5 to 66 GHz through a flight model including three distinct stages which are takeoff/landing, climbing/descending, and cruise stages. Also, handover scenarios in the proposed aircraft–SB network are investigated and analyzed at the proposed 5G frequencies. In addition, the aircraft–SB 5G network is compared to the most recent low-Earth orbit (LEO) Internet satellites where the proposed system is expected to provide low latency, less atmospheric attenuation, longer aircraft–SB link duration, and very low handover rate.

Comparisons of spectral aerosol single scattering albedo in Seoul, South Korea

Quantifying aerosol absorption at ultraviolet (UV) wavelengths is important for monitoring air pollution and aerosol amounts using current (e.g., Aura/OMI) and future (e.g., TROPOMI, TEMPO, GEMS, and Sentinel-4) satellite measurements. Measurements of column average atmospheric aerosol single scattering albedo (SSA) are performed on the ground by the NASA AERONET in the visible (VIS) and near-infrared (NIR) wavelengths and in the UV-VIS-NIR by the SKYNET networks. Previous comparison studies have focused on VIS and NIR wavelengths due to the lack of co-incident measurements of aerosol and gaseous absorption properties in the UV. This study compares the SKYNET-retrieved SSA in the UV with the SSA derived from a combination of AERONET, MFRSR, and Pandora (AMP) retrievals in Seoul, South Korea, in spring and summer 2016. The results show that the spectrally invariant surface albedo assumed in the SKYNET SSA retrievals leads to underestimated SSA compared to AMP values at near UV wavelengths. Re-processed SKYNET inversions using spectrally varying surface albedo, consistent with the AERONET retrieval improve agreement with AMP SSA. The combined AMP inversions allow for separating aerosol and gaseous (NO2 and O3) absorption and provide aerosol retrievals from the shortest UVB (305 nm) through VIS to NIR wavelengths (870 nm).

ARTS, the Atmospheric Radiative Transfer Simulator – version 2.2, the planetary toolbox edition

This article describes the latest stable release (version 2.2) of the Atmospheric Radiative Transfer Simulator (ARTS), a public domain software for radiative transfer simulations in the thermal spectral range (microwave to infrared). The main feature of this release is a planetary toolbox that allows simulations for the planets Venus, Mars, and Jupiter, in addition to Earth. This required considerable model adaptations, most notably in the area of gaseous absorption calculations. Other new features are also described, notably radio link budgets (including the effect of Faraday rotation that changes the polarization state) and the treatment of Zeeman splitting for oxygen spectral lines. The latter is relevant, for example, for the various operational microwave satellite temperature sensors of the Advanced Microwave Sounding Unit (AMSU) family.

Comparisons of spectral aerosol absorption in Seoul, South Korea

Quantifying the aerosol absorption at ultraviolet (UV) wavelengths is important for monitoring air pollution using current (e.g., Aura/OMI) and future (e.g., TROPOMI, TEMPO, GEMS, and Sentinel-4) satellite measurements. Measurements of column atmospheric aerosol absorption (i.e., column effective imaginary refractive index (k), single scattering albedo (SSA), and aerosol absorption optical depth (AAOD)) are performed on the ground by the NASA AERONET in the visible (VIS) and near-infrared (NIR) wavelengths and in the UV-VIS-NIR by the SKYNET networks. Previous comparison studies have focused on visible and NIR wavelengths due to the lack of co-incident measurements of aerosol and gaseous absorption properties in the UV. This study compares the SKYNET-retrieved SSA in the UV with the SSA derived from a combination of AERONET, MFRSR, and Pandora (AMP) retrievals in Seoul, South Korea in spring and summer of 2016. The results show that the spectrally invariant surface albedo assumed in the SKYNET SSA retrievals leads to underestimated SSA compared to AMP values at near UV wavelengths. Re-processed SKYNET inversions using spectrally varying surface albedo, consistent with the AERONET retrieval improves agreement with AMP SSA. The combined AMP inversions allow for separating aerosol and gaseous (NO2 and O3) absorption and provides aerosol retrievals from the shortest UVB (305 nm) through visible to NIR wavelengths (870 nm).