Solar 27-day signatures in standard phase height measurements above central Europe

We report on the effect of solar variability at the 27-day and the 11-year timescales on standard phase heightmeasurements in the ionospheric D region carried out in cen-tral Europe. Standard phase height corresponds to the re-flection height of radio waves (for constant solar zenith dis-tance) in the ionosphere near 80 km altitude, where NO isionized by solar Lyman-αradiation. Using the superposedepoch analysis (SEA) method, we extract statistically highlysignificant solar 27-day signatures in standard phase heights.The 27-day signatures are roughly inversely correlated to so-lar proxies, such as the F10.7 cm radio flux or the Lyman-αflux. The sensitivity of standard phase height change to so-lar forcing at the 27-day timescale is found to be in goodagreement with the sensitivity for the 11-year solar cycle,suggesting similar underlying mechanisms. The amplitude ofthe 27-day signature in standard phase height is larger duringsolar minimum than during solar maximum, indicating thatthe signature is not only driven by photoionization of NO. Weidentified statistical evidence for an influence of ultra-longplanetary waves on the quasi 27-day signature of standardphase height in winters of solar minimum periods

Solar Activity Driven 27-Day Signatures in Ionospheric Electron and Molecular Oxygen Densities

The complex interactions in the upper atmosphere, which control the height-dependent ionospheric response to the 27-day solar rotation period, are investigated with the superposed epoch analysis technique. 27-day signatures describing solar activity are calculated from a solar proxy (F10.7) and wavelength-dependent extreme ultraviolet (EUV) fluxes (Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Solar EUV Experiment), and the corresponding 27-day signatures describing ionospheric conditions are calculated from electron density profiles (Pruhonice ionosonde station) and O2 density profiles (Global-scale Observations of the Limb and Disk). The lag analysis of these extracted signatures is applied to characterize the delayed ionospheric response at heights from 100 to 300 km and the impact of major absorption processes in the lower (dominated by O2) and upper ionosphere (dominated by O) is discussed. The observed variations of the delay in these regions are in good agreement with model simulations in preceding studies. Additionally, the estimated significance and the correlation of the delays based on both ionospheric parameters are good. Thus, variations such as the strong shift in 27-day signatures for the O2 density at low heights are also reliably identified (up to half a cycle). The analysis confirms the importance of ionospheric and thermospheric coupling to understand the variability of the delayed ionospheric response and introduces a method that could be applied to additional ionosonde stations in future studies. This would allow to describe the variability of the delayed ionospheric response spatially, vertically and temporally and therefore may contribute further to the understanding of processes and improve ionospheric modeling

Model results of OH airglow considering four different wavelength regions to derive night-time atomic oxygen and atomic hydrogen in the mesopause region

Based on the zero-dimensional box model Module Efficiently Calculating the Chemistry of the Atmosphere/Chemistry As A Box model Application (CAABA/MECCA-3.72f), an OH airglow model was developed to derive night-time number densities of atomic oxygen ([O(3P)]) and atomic hydrogen ([H]) in the mesopause region ( ∼ 75–100 km). The profiles of [O(3P)] and [H] were calculated from OH airglow emissions measured at 2.0 µm by the Sounding of the Atmosphere using Broadband Emission Radiography (SABER) instrument on board NASA\u27s Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite. The two target species were used to initialize the OH airglow model, which was empirically adjusted to fit four different OH airglow emissions observed by the satellite/instrument configuration TIMED/SABER at 2.0 µm and at 1.6 µm as well as measurements by the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) instrument on board the Environmental Satellite (ENVISAT) of the transitions OH(6-2) and OH(3-1). Comparisons between the "best-fit model" obtained here and the satellite measurements suggest that deactivation of vibrationally excited OH(ν) via OH(ν ≥ 7)+O2 might favour relaxation to OH(ν′ ≤ 5)+O2 by multi-quantum quenching. It is further indicated that the deactivation pathway to OH(ν′ = ν − 5)+O2 dominates. The results also provide general support of the recently proposed mechanism OH(ν)+O(3P) → OH(0 ≤ ν′ ≤ ν − 5)+O(1D) but suggest slower rates of OH(ν = 8,7,6,5)+O(3P), partly disagreeing with laboratory experiments. Additionally, deactivation to OH(ν′ = ν − 5)+O(1D) might be preferred. The profiles of [O(3P)] and [H] derived here are plausible between 80 and 95 km but should be regarded as an upper limit. The values of [O(3P)] obtained in this study agree with the corresponding TIMED/SABER values between 80 and 85 km but are larger from 85 to 95 km due to different relaxation assumptions of OH(ν)+O(3P). The [H] profile found here is generally larger than TIMED/SABER [H] by about 50 % from 80 to 95 km, which is primarily attributed to our faster OH(ν = 8)+O2 rate

A Method for Retrieving Stratospheric Aerosol Extinction and Particle Size from Ground-Based Rayleigh-Mie-Raman Lidar Observations

We report on the retrieval of stratospheric aerosol particle size and extinction coefficient profiles from multi-color backscatter measurements with the Rayleigh-Mie-Raman lidar operated at the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) in northern Norway. The retrievals are based on a two-step approach. In a first step, the median radius of an assumed monomodal log-normal particle size distribution with fixed width is retrieved based on a color index formed from the measured backscatter ratios at the wavelengths of 1064nm and 532 nm. An intrinsic ambiguity of the retrieved aerosol size information is discussed. In a second step, this particle size information is used to convert the measured lidar backscatter ratio to aerosol extinction coefficients. The retrieval is currently based on monthly-averaged lidar measurements and the results for March 2013 are discussed. A sensitivity study is presented that allows for establishing an error budget for the aerosol retrievals. Assuming a monomodal log-normal aerosol particle size distribution with a geometric width of S = 1.5, median radii on the order of below 100 nm are retrieved. The median radii are found to generally decrease with increasing altitude. The retrieved aerosol extinction profiles are compared to observations with the OSIRIS (Optical Spectrograph and InfraRed Imager System) and the OMPS-LP (Ozone Mapping Profiling Suite Limb Profiler) satellite instruments in the 60° N to 80° N latitude band. The extinction profiles that were retrieved from the lidar measurements show good agreement with the observations of the two satellite instruments when taking the different wavelengths of the instruments into account. © 2020 by the authors

The Height-Dependent Delayed Ionospheric Response to Solar EUV

Based on the analysis of electron density Ne profiles (Grahamstown ionosonde), a case study of the height-dependent ionospheric response to two 27-day solar rotation periods in 2019 is performed. A well-defined sinusoidal response is observed for the period from 27 April 2019 to 24 May 2019 and reproduced with a Thermosphere-Ionosphere-Electrodynamics General Circulation Model simulation. The occurring differences between model and observations as well as the driving physical and chemical processes are discussed based on the height-dependent variations of Ne and major species. Further simulations with an artificial noise free sinusoidal solar flux input show that the Ne delay is defined by contributions due to accumulation of O+ at the Ne peak (positive delay) and continuous loss of O2+ in the lower ionosphere (negative delay). The neutral parts' 27-day signatures show stronger phase shifts. The time-dependent and height-dependent impact of the processes responsible for the delayed ionospheric response can therefore be described by a joint analysis of the neutral and ionized parts. The return to the initial ionospheric state (and thus the loss of the accumulated O+) is driven by an increase of downward transport in the second half of the 27-day solar rotation period. For this reason, the neutral vertical winds (upwards and downwards) and their different height-dependent 27-day signatures are discussed. Finally, the importance of a wavelength-dependent analysis, statistical methods (superposed epoch analysis), and coupling with the middle atmosphere is discussed to outline steps for future analysis

A Python Package to Calculate the OLR-Based Index of the Madden- Julian-Oscillation (OMI) in Climate Science and Weather Forecasting

The Madden-Julian Oscillation (MJO) is a prominent feature of the intraseasonal variability of the atmosphere. The MJO strongly modulates tropical precipitation and has implications around the globe for weather, climate and basic atmospheric research. The time-dependent state of the MJO is described by MJO indices, which are calculated through sometimes complicated statistical approaches from meteorological variables. One of these indices is the OLR-based MJO Index (OMI; OLR stands for outgoing longwave radiation). The Python package mjoindices, which is described in this paper, provides the first open source implementation of the OMI algorithm, to our knowledge. The package meets state-of-the-art criteria for sustainable research software, like automated tests and a persistent archiving to aid the reproducibility of scientific results. The agreement of the OMI values calculated with this package and the original OMI values is also summarized here. There are several reuse scenarios; the most probable one is MJO-related research based on atmospheric models, since the index values have to be recalculated for each model run

Particle aging and aerosol–radiation interaction affect volcanic plume dispersion: evidence from the Raikoke 2019 eruption

A correct and reliable forecast of volcanic plume dispersion is vital for aviation safety. This can only be achieved by representing all responsible physical and chemical processes (sources, sinks, and interactions) in the forecast models. The representation of the sources has been enhanced over the last decade, while the sinks and interactions have received less attention. In particular, aerosol dynamic processes and aerosol–radiation interaction are neglected so far. Here we address this gap by further developing the ICON-ART (ICOsahedral Nonhydrostatic – Aerosols and Reactive Trace gases) global modeling system to account for these processes. We use this extended model for the simulation of volcanic aerosol dispersion after the Raikoke eruption in June 2019. Additionally, we validate the simulation results with measurements from AHI (Advanced Himawari Imager), CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization), and OMPS-LP (Ozone Mapping and Profiling Suite-Limb Profiler). Our results show that around 50 % of very fine volcanic ash mass (particles with diameter d<30 µm) is removed due to particle growth and aging. Furthermore, the maximum volcanic cloud top height rises more than 6 km over the course of 4 d after the eruption due to aerosol–radiation interaction. This is the first direct evidence that shows how cumulative effects of aerosol dynamics and aerosol–radiation interaction lead to a more precise forecast of very fine ash lifetime in volcanic clouds

Obstacles to prompt and effective malaria treatment lead to low community-coverage in two rural districts of Tanzania

BACKGROUND\ud \ud Malaria is still a leading child killer in sub-Saharan Africa. Yet, access to prompt and effective malaria treatment, a mainstay of any malaria control strategy, is sub-optimal in many settings. Little is known about obstacles to treatment and community-effectiveness of case-management strategies. This research quantified treatment seeking behaviour and access to treatment in a highly endemic rural Tanzanian community. The aim was to provide a better understanding of obstacles to treatment access in order to develop practical and cost-effective interventions.\ud \ud METHODS\ud \ud We conducted community-based treatment-seeking surveys including 226 recent fever episodes in 2004 and 2005. The local Demographic Surveillance System provided additional household information. A census of drug retailers and health facilities provided data on availability and location of treatment sources.\ud \ud RESULTS\ud \ud After intensive health education, the biomedical concept of malaria has largely been adopted by the community. 87.5% (78.2-93.8) of the fever cases in children and 80.7% (68.1-90.0) in adults were treated with one of the recommended antimalarials (at the time SP, amodiaquine or quinine). However, only 22.5% (13.9-33.2) of the children and 10.5% (4.0-21.5) of the adults received prompt and appropriate antimalarial treatment. Health facility attendance increased the odds of receiving an antimalarial (OR = 7.7) but did not have an influence on correct dosage. The exemption system for under-fives in public health facilities was not functioning and drug expenditures for children were as high in health facilities as with private retailers.\ud \ud CONCLUSION\ud \ud A clear preference for modern medicine was reflected in the frequent use of antimalarials. Yet, quality of case-management was far from satisfactory as was the functioning of the exemption mechanism for the main risk group. Private drug retailers played a central role by complementing existing formal health services in delivering antimalarial treatment. Health system factors like these need to be tackled urgently in order to translate the high efficacy of newly introduced artemisinin-based combination therapy (ACT) into equitable community-effectiveness and health-impact

Solar Activity Driven 27‐Day Signatures in Ionospheric Electron and Molecular Oxygen Densities

The complex interactions in the upper atmosphere, which control the height‐dependent ionospheric response to the 27‐day solar rotation period, are investigated with the superposed epoch analysis technique. 27‐day signatures describing solar activity are calculated from a solar proxy (F10.7) and wavelength‐dependent extreme ultraviolet (EUV) fluxes (Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Solar EUV Experiment), and the corresponding 27‐day signatures describing ionospheric conditions are calculated from electron density profiles (Pruhonice ionosonde station) and O2 density profiles (Global‐scale Observations of the Limb and Disk). The lag analysis of these extracted signatures is applied to characterize the delayed ionospheric response at heights from 100 to 300 km and the impact of major absorption processes in the lower (dominated by O2) and upper ionosphere (dominated by O) is discussed. The observed variations of the delay in these regions are in good agreement with model simulations in preceding studies. Additionally, the estimated significance and the correlation of the delays based on both ionospheric parameters are good. Thus, variations such as the strong shift in 27‐day signatures for the O2 density at low heights are also reliably identified (up to half a cycle). The analysis confirms the importance of ionospheric and thermospheric coupling to understand the variability of the delayed ionospheric response and introduces a method that could be applied to additional ionosonde stations in future studies. This would allow to describe the variability of the delayed ionospheric response spatially, vertically and temporally and therefore may contribute further to the understanding of processes and improve ionospheric modeling.Key Points: 27‐day signatures are extracted from ionospheric Ne and nO2 via superposed epoch analysis and a lag analysis is applied. The height‐dependent delay of the extracted 27‐day signatures is characterized by major absorption processes of O and O2. Good correlations between observed delays of Ne and nO2 confirm modeling results in preceding studies

IN-SITU EXPLORATION OF EARTH’S ATMOSPHERE USING NOVEL SPACECRAFT DESIGN

Altitudes between 40 and 140 km are not accessible for conventional aircraft and spacecraft for long-term duration. In particular the region around 100 km, the upper mesosphere and lower thermosphere (UMLT), is of great interest to scientists and engineers since it forms the transition from earth to space. Important physical phenomena take place at this region that have a strong influence on the atmospheric layers below. The scientific need to explore this region is very high. So far, the UMLT region has been accessible mainly to remote sensing observations, which are subject to vertical and horizontal smoothing of the measured information, and require an underlying model and possibly not existing a priori information about the subject of interest. Therefore, in-situ measurements in the UMLT region on a global scale would be of inestimable value. However any conventional spacecraft will quickly suffer from free molecular friction at UMLT altitudes, leading to rapid orbital decay. We intend to highlight the scientific need for in-situ measurements in the UMLT region and discuss several mission case studies. The impact of the special conditions at that altitude on the spacecraft design require a careful consideration