Atmospheric Mixing Research Articles

Evaluation of the Potential Use of Satellite-Derived XCO2 in Detecting CO2 Enhancement in Megacities with Limited Ground Observations: A Case Study in Seoul Using Orbiting Carbon Observatory-2

Exact assessment of urban atmospheric CO2 enhancement, which is higher than background CO2 concentrations, is critical to mitigate carbon emissions in the city. However, ground-based atmospheric CO2 measurements covering the diverse landscape across the city are still limited. This study utilizes the column integrated CO2 concentration (XCO2) data obtained from the NASA Orbiting Carbon Observatory-2 (OCO-2) to evaluate urban CO2 enhancements over Seoul Capital Area (SCA) of South Korea for the period 2014–2018. In this study, Jirisan National Park (JNP), which is the cleanest area on the same orbit track with SCA, is defined as the background area considering its strong vegetation activity and low anthropogenic carbon emissions. By comparing XCO2 between SCA and JNP based on wind speed, we find an apparent increase in XCO2 by 1.71 to 2.21 ppm over SCA only on the days with wind speed less than 4 m s−1. Strong wind speed (e.g., over 4 m s−1) disrupts the identification of XCO2 enhancements over SCA due to atmospheric mixing between SCA and JNP. In addition, we compare estimated XCO2 differences between SCA and JNP from OCO-2 with other low-resolution data. This increase in XCO2 over SCA is only observed in OCO-2. Overall, our results suggest that high-resolution satellite remote sensing of XCO2 constrained by wind speed has strong potential to open up the possibility of identifying atmospheric CO2 enhancements in the city where ground-based observations are limited.

A new Littlest Seesaw model

We propose and discuss a new Littlest Seesaw model, realized in the tri-direct CP approach, in which the couplings of the two right-handed neutrinos to the lepton doublets are proportional to (0, −1, 1) and (1,5/2, −1/2) respectively with the relative phase η = −π/2. This model can give an excellent description of lepton flavour mixing, including an atmospheric neutrino mixing angle in the second octant, in terms of only two input parameters. We show that the observed baryon asymmetry can be generated for the lightest right-handed neutrino mass M1 = 1.176 × 1011 GeV in SM and M1 = 3.992 × 1010 GeV in MSSM with . We construct an explicit Littlest Seesaw model based on the flavour symmetry S4 × Z5 × Z8 in which the desired alignments and the phase η = −π/2 are achieved.

Temporal variations of atmospheric black carbon and its relation to other pollutants and meteorological factors at an urban traffic site in Istanbul

This study aimed to investigate the variability of Black Carbon (BC) at one traffic site in Istanbul as a function of other pollutants, traffic density and meteorological parameters in order to identify the source and determinants of concentration. This was carried out through the statistical analyses of data measured in the period of May 2016–December 2018. The mean concentration of BC was observed as 6.5 ± 3.5 μg m−3. Daytime BC was observed to be higher than nighttime during the weekdays but slightly lower at the weekend, similar to oxides of nitrogen (NOx). However, nighttime traffic during the weekend was found to be higher than the weekdays. The diurnal pattern showed two peaks of BC corresponding to the traffic rush hours in the morning and evening. Since the traffic density did not change during the day, the sharp decrease after the morning rush hour is attributed to enhanced atmospheric mixing, due to an increased wind speed and boundary layer depth. In addition, polar plots indicated that the only major source of BC is in the vicinity of the monitoring site, consistent with road traffic. Moreover, episodic north-easterly atmospheric transport events from the ship activity in the Bosphorus in summer can contribute to elevated BC concentrations. These results suggest that vehicular emissions heavily impact the environmental concentrations of BC and affect NOx concentrations more than other pollutants. BC concentrations are highly correlated with NOx, reflecting a common source in diesel vehicle emissions. Since the proportion of diesels in total vehicles in Istanbul is increasing every year, there may be future increases in BC and NOx unless exhaust after-treatment works effectively on newer vehicles entering the fleet.

Seasonal variations of atmospheric CH4 at Jingdezhen station in Central China: Understanding the regional transport and its correlation with CO2 and CO

Greenhouse gases observation networks have been extensively established in the eastern, southern, western, and northern China, but rare in the developing central China. We conducted in-situ measurement of atmospheric CH4 mixing ratios with high precision at JDZ (Jingdezhen) station (29.37°N, 117.22°E, 87.3 m a.s.l) in central China between December 2017 and November 2018. The “regionally representative data” and “polluted events” are separated from the complete dataset, based on the analysis of diurnal discrepancy among different levels, the impacts of wind directions and speeds, and the statistical identification procedure. The average CH4 mixing ratio of regionally representative compositions during the study period was 2037.4 ppb, lower than that of polluted conditions (2086.3 ppb). The lowest levels of CH4 for regionally representative conditions are observed in summer, while highest values are obtained during June–August for polluted events. Cluster analysis of backward trajectories indicated that air-mass transport arising from northwestern China, eastern China and Jiangxi made the significant contribution to the variability in regionally representative air. Air masses passing through Jiangxi province and Yangtze River Delta (YRD) regions carried the polluted air with higher CH4 mixing ratios to the observational station in summer, probably owing to large quantities of CH4 emission from rice cultivation over these areas. △CH4 and △CO exhibit strong correlations in all month during the study period. Moreover, the △CO/△CH4 ratio showed the distinct seasonal characteristics, with the rapid decrease from the peak (2.74 ± 0.05, ppb/ppb) in January to the trough (0.40 ± 0.02, ppb/ppb) in July, and then the gradual increase to high levels in winter. It is possibly attributed to the maximum CH4 emission during summertime and the maximum CO emission during wintertime, as well as the significantly faster reaction rate of CO with OH in summer. The enhancements of CH4 (△CH4) and CO2 (△CO2) in polluted conditions relative to the regionally representative conditions present strong correlation only in winter, with the △CH4 /△CO2 slope of (3.92 ± 0.08) ppb/ppm, similar with the average △CH4 /△CO2 ratio observed in winter (4.15 ± 0.40, ppb/ppm) reported for LAN regional station during 2007 and 2013.

노천소각 발생 시 드론을 이용한 대기 안정도에 따른 연직 PM2.5 분포 비교

Biomass burning in rural areas is one of the major particulate matter (PM) emission sources. Open burning events frequently occur during post- and pre-agricultural activities in early and late winter, resulting in high PM2.5 concentration episodes immediately near emission sources. We have investigated the wintertime vertical PM2.5 distribution on three open burning days and three non burning days in the morning in the lower atmospheric boundary layer according to atmospheric stabilities. A drone has been utilized to measure the vertical distributions of air temperature, PM2.5, BC (black carbon), and O₃ concentrations at 40, 80, 120, 160, 200, and 250 m heights in a rural area near an industrial complex. On open burning days, ground PM2.5 concentrations increased up to 169 μg m-3 at 9 AM while the closest urban PM2.5 concentration was only 33 μg m-3. On non burning days, the difference in ground PM2.5 concentrations at most 23 μg m-3. The PM2.5 on open burning days was accumulated in the stable boundary layer (below 80 m above ground level) at 8 and 9 AM in the morning due to the suppressed vertical mixing of emitted PM2.5. The vertical gradients of PM2.5 concentration, then, became reduced after solar heating on ground activates atmospheric mixing. Consequently, the atmospheric stability in the early morning plays an important role in vertical mixing of emitted PM2.5 and increasing ground PM2.5 concentrations during open burning events.

Quantifying the Feedback Between Rice Architecture, Physiology, and Microclimate Under Current and Future CO2 Conditions

AbstractTo assess the micrometeorological consequences of rice variety choices in relation to rising CO2 associated to climate change, we quantified the interplay between rice architecture, physiology, and microclimate in current (~385 μmol mol−1) and future (~580 μmol mol−1) CO2 microenvironments. Two rice varieties contrasting in canopy structure and physiology were grown embedded in irrigated rice paddies, under elevated CO2 (using a Free‐Air CO2 Enrichment facility) and ambient CO2 conditions. The high‐yielding indica variety Takanari is more photosynthetically active and characterized by a more open canopy than a commonly cultivated variety Koshihikari. Our results show a strong diurnal interplay between solar angle, canopy structure, plant physiology, and the overlying atmosphere. Plant architecture was identified as a strong determinant of the relation between plant physiology and microclimate that in turn affects the surface forcing to the overlying atmosphere. Takanari was able to maintain lower canopy temperature both in current and future CO2 owing to the greater atmospheric mixing and stomatal conductance than Koshihikari. In the perspective of food security, a shift to such a higher‐yielding variety would have consequences on the regional surface energy balance, which subsequently might alter regional weather.

Two-Higgs-doublet models with a flavored Z2 symmetry

Two Higgs-doublet models usually consider an ad-hoc $\mathbb{Z}_2$ discrete symmetry to avoid flavor changing neutral currents. We consider a new class of two Higgs-doublet models where $\mathbb{Z}_2$ is enlarged to the symmetry group ${\cal{F}}\rtimes \mathbb{Z}_2$, i.e. an inner semi-direct product of a discrete symmetry group ${\cal{F}}$ and $\mathbb{Z}_2$. In such a scenario the symmetry constrains the Yukawa interactions but goes unnoticed by the scalar sector. In the most minimal scenario, $\mathbb{Z}_3 \rtimes \mathbb{Z}_2 = D_3$, flavor changing neutral currents mediated by scalars are absent at tree and one-loop level, while at the same time predictions to quark and lepton mixing are obtained, namely a trivial CKM matrix and a PMNS matrix (upon introduction of three heavy right-handed neutrinos) containing maximal atmospheric mixing. Small extensions allow to fully reproduce mixing parameters, including cobimaximal mixing in the lepton sector (maximal atmospheric mixing and a maximal $CP$ phase).

SU(5) grand unified theory with A4 modular symmetry

We present the first example of a grand unified theory (GUT) with a modular symmetry interpreted as a family symmetry. The theory is based on supersymmetric $SU(5)$ in 6d, where the two extra dimensions are compactified on a $T_2/\mathbb{Z}_2$ orbifold. We have shown that, if there is a finite modular symmetry, then it can only be $A_4$ with an (infinite) discrete choice of moduli, where we focus on $\tau = \omega=e^{i2\pi/3}$, the unique solution with $|\tau|=1$. The fields on the branes respect a generalised CP and flavour symmetry $A_4\ltimes \mathbb{Z}_2$ which is isomorphic to $S_4$ which leads to an effective $\mu-\tau$ reflection symmetry at low energies, implying maximal atmospheric mixing and maximal leptonic CP violation. We construct an explicit model along these lines with two triplet flavons in the bulk, whose vacuum alignments are determined by orbifold boundary conditions, analogous to those used for $SU(5)$ breaking with doublet-triplet splitting. There are two right-handed neutrinos on the branes whose Yukawa couplings are determined by modular weights. The charged lepton and down-type quarks have diagonal and hierarchical Yukawa matrices, with quark mixing due to a hierarchical up-quark Yukawa matrix.

Moving beyond Fine Particle Mass: High-Spatial Resolution Exposure to Source-Resolved Atmospheric Particle Number and Chemical Mixing State.

Background:Most epidemiological studies address health effects of atmospheric particulate matter (PM) using mass-based measurements as exposure surrogates. However, this approach ignores many critical physiochemical properties of individual atmospheric particles. These properties control the deposition of particles in the human lung and likely their toxicity; in addition, they likely have larger spatial variability than PM mass.Objectives:This study was designed to quantify the spatial variability in number, size, source, and chemical mixing state of individual particles in a populous urban area. We quantified the population exposure to these detailed particle properties and compared them to mass-based exposures.Methods:We performed mobile sampling using an advanced single-particle mass spectrometer to measure the spatial variability of number concentration of source-resolved particles and particle mixing state in Pittsburgh, Pennsylvania. We built land-use regression (LUR) models to estimate their spatial patterns and coupled them with demographic data to estimate population exposure.Results:Particle number concentration had a much larger spatial variability than mass concentration within the city. Freshly emitted particles from traffic and cooking drive the variability in particle number, but mass concentrations are dominated by aged background particles composed of secondary materials. In addition, people exposed to elevated number concentrations of atmospheric particles are also exposed to more externally mixed particles.Conclusions:Our advanced measurement technique provides a new exposure picture that resolves the large intra-city spatial heterogeneity in traffic and cooking particle number concentrations in the populous urban area. Our results provide a complementary and more detailed perspective compared with bulk measurements of composition. In addition, given the influence of particle mixing state on properties such as particle deposition in the lung, the large spatial gradients of chemical mixing state may significantly influence the health effects of fine PM. https://doi.org/10.1289/EHP5311

Active growth of non-hydrothermal subaqueous and subaerial barite (BaSO4) speleothems in Lechuguilla Cave (New Mexico, USA)

Barite (BaSO4) speleothems have been reported from caves around the globe and interpreted to have chiefly formed in phreatic, hypogene, hydrothermal settings. Here we report two contrasting types of barite speleothems (bluish tabular crystals in a shallow pool and actively dripping greenish stalactites), which today form at lower temperatures in the non-hydrothermal and vadose environment of Lechuguilla Cave, New Mexico, USA. Scanning electron microscopy analysis, along with energy- and wavelength-dispersive X-ray spectroscopy (EDS, WDS), as well as X-ray diffraction (XRD), characterize the habit and chemical composition as barite. Fractionation of the minor element calcium is related to growth along different crystal faces whereas variations in strontium concentration are mirrored in blue color zoning of the pool crystals. Two possible modes of non-hydrothermal barite precipitation are discussed: (1) intense evaporation driven by thermal atmospheric convection cells or (2) mixing of barium-rich, sulfate-poor water with water rich in sulfate. Both processes, in isolation or in combination, lead to supersaturation and could explain formation of the investigated barite speleothems. Observations of three types of microbes on the pool barite crystals showing evidence of incrustation raises the question whether there is a potential involvement of microbial activity in the temperate barite precipitation in Lechuguilla Cave.

Quantifying Influences of Nocturnal Mixing on Air Quality Using Atmospheric Radon Measurement-Case Study in Jinhua City, China

ABSTRACT The atmospheric mixing state and emission rates play decisive roles in public exposure to urban air pollution. This study utilizes atmospheric radon measurements taken with the SM200 “stability monitor,” which reflect changes in the atmospheric mixing state, to evaluate and forecast air quality. Using six months (March–August 2016) of atmospheric radon measurements in Jinhua, China, we classify the nocturnal atmospheric stability conditions into four distinct categories, “well-mixed”, “weakly stable”, “moderately stable”, and “most stable”, by applying a modified radon-based stability technique. We calculate the atmospheric self-cleaning ability index (ASI) and evaluate it with the four-category stability scheme, and the results confirm that the atmospheric radon measurements reliably represent the atmospheric mixing state. Analyzing PM2.5, PM10, SO2, NO2, CO, and O3 measurements from three nearby stations during the campaign, we find that the pollutant concentrations and air quality index (AQI) values assigned using the aforementioned stability scheme are consistent with the defined atmospheric mixing states. We subsequently demonstrate that the modified radon-based stability method is suitable for targeting the most unfavorable air quality conditions and determining where the emissions originated. Finally, we propose a simple ASI-based model for predicting regional severe air pollution.

Improved method for characterising temporal variability in urban air quality part I: Traffic emissions in central Poland

Four years of observations in Central Poland are used to assess the ability of a recently-improved radon-based stability classification technique to investigate temporal variability in urban air quality (specifically NOx and CO). After isolating periods of greatest synoptic non-stationarity, observations were assigned (in whole 24-h blocks) to one of four atmospheric mixing categories. Wind speed more than doubled from the most stable to the most well mixed nocturnal conditions in non-winter months, reducing nocturnal radon accumulation by a factor of five. A strong seasonality in NOx and CO concentrations was observed, contributed to by changing atmospheric mixing depths (day and night) and additional cold-season combustion sources. Peak daily NO concentrations typically increased by a factor of 2–4 from the most well-mixed to most stable conditions, with smaller changes for NO2 and CO (factor of 1.5–2). For non-winter months urban air quality was typically best in the afternoons, when mixing was deepest, but also improved in the 3–4 h after midnight due to advection of cleaner air from outside the city. Specific air quality influences were attributed to parts of Łódź and localised sources in the region, but the topographic setting of the monitoring site also played an important role. Emissions from nearby point sources were often brought to the site in katabatic flows when gradient winds were light. Observed daytime local CO contributions in summer were almost entirely attributable to vehicle emissions, whereas an additional afternoon source of around 48 mg m−2 h−1 in winter was attributed to combustion for heating (likely more at night). Winter local afternoon CO contributions attributable to local domestic combustion were estimated to be up to a factor of three less than the CO being advected to the study region from upwind European source regions.

The Hubble PanCET program: an extensive search for metallic ions in the exosphere of GJ 436 b

Context. The quiet M2.5 star GJ 436 hosts a warm Neptune that displays an extended atmosphere that dwarfs its own host star. Predictions of atmospheric escape in such planets state that H atoms escape from the upper atmosphere in a collisional regime and that the flow can drag heavier atoms to the upper atmosphere. It is unclear, however, what astrophysical mechanisms drive the process. Aims. Our objective is to leverage the extensive coverage of observations of the far-ultraviolet (FUV) spectrum of GJ 436 obtained with the Cosmic Origins Spectrograph (COS) to search for signals of metallic ions in the upper atmosphere of GJ 436 b, as well as study the activity-induced variability of the star. Methods. We analyzed flux time-series of species present in the FUV spectrum of GJ 436 and successfully performed geocoronal contamination removal in the COS Lyman-α profiles obtained near the Earth’s night-side. Results. GJ 436 displays flaring events with a rate of ~10 d−1. There is evidence for a possibly long-lived active region or longitude that modulates the FUV metallic lines of the star with amplitudes up to 20%. Despite the strong geocoronal contamination in the COS spectra, we detected in-transit excess absorption signals of ~50 and ~30% in the blue and red wings, respectively, of the Lyman-α line. We rule out a wide range of excess absorption levels in the metallic lines of the star during transit. Conclusions. The large atmospheric loss of GJ 436 b observed in Lyman-α transmission spectra is stable over the timescale of a few years, and the red wing signal supports the presence of a variable hydrogen absorption source besides the stable exosphere. The previously claimed in-transit absorption in the Si III line is likely an artifact resulting from the stellar magnetic cycle. The non-detection of metallic ions in absorption could indicate that the escape is not hydrodynamic or that the atmospheric mixing is not efficient in dragging metals high enough for sublimation to produce a detectable escape rate of ions to the exosphere.

Visibility and Line‐of‐Sight Extinction Estimates in Gale Crater During the 2018/MY34 Global Dust Storm

AbstractNorthern line‐of‐sight extinction within Gale Crater during the 2018 global dust storm was monitored daily using Mars Science Laboratory's Navcam. Additional observations with Mastcam (north) and Navcam (all directions) were obtained at a lower cadence. Using feature identification and georeferencing, extinction was estimated in all possible directions. Peak extinction of >1.1 km−1 was measured between sols 2086 and 2090, an order of magnitude higher than previous maxima. Northern and western directions show an initial decrease, followed by a secondary peak in extinction, not seen in column opacity measurements. Due to foreground topography, eastern direction results are provided only as limits, and southern results were indeterminable. Mastcam red and green filter results agree well, but blue filter results show higher extinctions, likely due to low signal‐to‐noise. Morning results are systematically higher than afternoon results, potentially indicative of atmospheric mixing.

Comparing MSL Curiosity Rover TLS‐SAM Methane Measurements With Mars Regional Atmospheric Modeling System Atmospheric Transport Experiments

AbstractThe detection of methane at Gale crater by the Tunable Laser Spectrometer–Sample Analysis at Mars instrument aboard the Curiosity rover has garnered significant attention because of the implications for the presence of Martian organisms (Webster et al., 2015, https://doi.org/10.1126/science.1261713). Methane's photochemical lifetime is several centuries unless there is a fast, as‐yet‐unknown destruction mechanism (Lefèvre and Forget, 2009, https://doi.org/10.1038/nature08228). This is much longer than the atmospheric mixing time scale, and thus, the gas should be well‐mixed except when near a source or shortly after a release. Although most measurements report low background levels of ~0.4 parts per billion by volume, observed spikes of several parts per billion by volume or greater and a subsequent return to the background level are intriguing (Webster et al., 2015, https://doi.org/10.1126/science.1261713). The Mars Regional Atmospheric Modeling System is used to simulate, via passive tracers, the transport and mixing of methane released inside and outside of the crater from instantaneous and steady state releases, and to test whether the results are consistent with in situ observations made by the Mars Curiosity rover. The simulations indicate that the mixing time scale for air within the crater is approximately 1 sol. The timing of methane measurements within the crater is also important, because modeled methane abundance varies by ~1 order of magnitude over a diurnal cycle under all the scenarios considered. While the observed low background levels can be reproduced by the model under some circumstances, it is difficult to reconcile the measured peaks with the modeled transport and mixing. For periods of high methane abundance lasting longer than a few hours there must be a continuous release of methane inside the crater to counteract mixing, or there must be a large, methane‐rich air mass continually transported into the crater. The few scenarios that can produce peaks are problematic, because they would result in background methane values above what is observed.

Assessing PM2.5 model performance for the conterminous U.S. with comparison to model performance statistics from 2007-2015

Previous studies have proposed that model performance statistics from earlier photochemical grid model (PGM) applications can be used to benchmark performance in new PGM applications. A challenge in implementing this approach is that limited information is available on consistently calculated model performance statistics that vary spatially and temporally over the U.S. Here, a consistent set of model performance statistics are calculated by year, season, region, and monitoring network for PM2.5 and its major components using simulations from versions 4.7.1-5.2.1 of the Community Multiscale Air Quality (CMAQ) model for years 2007–2015. The multi-year set of statistics is then used to provide quantitative context for model performance results from the 2015 simulation. Model performance for PM2.5 organic carbon in the 2015 simulation ranked high (i.e., favorable performance) in the multi-year dataset, due to factors including recent improvements in biogenic secondary organic aerosol and atmospheric mixing parameterizations in CMAQ. Model performance statistics for the Northwest region in 2015 ranked low (i.e., unfavorable performance) for many species in comparison to the 2007–2015 dataset. This finding motivated additional investigation that suggests a need for improved speciation of wildfire PM2.5 emissions and modeling of boundary layer dynamics near water bodies. Several limitations were identified in the approach of benchmarking new model performance results with previous results. Since performance statistics vary widely by region and season, a simple set of national performance benchmarks (e.g., one or two targets per species and statistic) as proposed previously are inadequate to assess model performance throughout the U.S. Also, trends in model performance statistics for sulfate over the 2007 to 2015 period suggest that model performance for earlier years may not be a useful reference for assessing model performance for recent years in some cases. Comparisons of results from the 2015 base case with results from five sensitivity simulations demonstrated the importance of parameterizations of NH3 surface exchange, organic aerosol volatility and production, and emissions of crustal cations for predicting PM2.5 species concentrations.

Biased estimates of the isotope ratios of steady‐state evaporation from the assumption of equilibrium between vapour and precipitation

AbstractStable water isotope ratios are measured as a tracer of environmental processes in materials such as leaves, soils, and lakes. Water in these archives may experience evaporation, which increases the abundance of heavy isotopologues proportionally to the gradients in humidity and isotope ratio between the evaporating water and the surrounding atmosphere. The isotope ratio of the atmosphere has been difficult to measure until recently, and measurements remain scarce. As a result, several assumptions have been adopted to estimate isotope ratios of atmospheric water vapour. Perhaps the most commonly employed assumption in terrestrial environments is that water vapour is in isotopic equilibrium with precipitation. We evaluate this assumption using an eight‐member ensemble of general circulation model (GCM) simulations that include explicit calculation of isotope ratios in precipitation and vapour. We find that across the model ensemble, water vapour is typically less depleted in heavy isotopologues than expected if it were in equilibrium with annual precipitation. Atmospheric vapour likely possesses higher‐than‐expected isotope ratios because precipitation isotope ratios are determined by atmospheric conditions that favour condensation, which do not reflect atmospheric mixing and advection processes outside of precipitation events. The effect of this deviation on theoretical estimates of isotope ratios of evaporating waters scales with relative humidity. As a result, the equilibrium assumption gives relatively accurate estimates of the isotope ratios of evaporating waters in low latitudes but performs increasingly poorly at increasing latitudes. Future studies of evaporative water pools should include measurements of atmospheric isotope ratios or constrain potential bias with isotope‐enabled GCM simulations.

PetitRADTRANS

We present the easy-to-use, publicly available, Python package petitRADTRANS, built for the spectral characterization of exoplanet atmospheres. The code is fast, accurate, and versatile; it can calculate both transmission and emission spectra within a few seconds at low resolution (λ/Δλ = 1000; correlated-k method) and high resolution (λ/Δλ = 106; line-by-line method), using only a few lines of input instruction. The somewhat slower, correlated-k method is used at low resolution because it is more accurate than methods such as opacity sampling. Clouds can be included and treated using wavelength-dependent power law opacities, or by using optical constants of real condensates, specifying either the cloud particle size, or the atmospheric mixing and particle settling strength. Opacities of amorphous or crystalline, spherical or irregularly-shaped cloud particles are available. The line opacity database spans temperatures between 80 and 3000 K, allowing to model fluxes of objects such as terrestrial planets, super-Earths, Neptunes, or hot Jupiters, if their atmospheres are hydrogen-dominated. Higher temperature points and species will be added in the future, allowing to also model the class of ultra hot-Jupiters, with equilibrium temperatures Teq ≳ 2000 K. Radiative transfer results were tested by cross-verifying the low- and high-resolution implementation of petitRADTRANS, and benchmarked with the petitCODE, which itself is also benchmarked to the ATMO and Exo-REM codes. We successfully carried out test retrievals of synthetic JWST emission and transmission spectra (for the hot Jupiter TrES-4b, which has a Teq of ∼1800 K).

Return flows from beaver ponds enhance floodplain-to-river metals exchange in alluvial mountain catchments

River to floodplain hydrologic connectivity is strongly enhanced by beaver- (Castor canadensis) engineered channel water diversions. The hydroecological impacts are wide ranging and generally positive, however, the hydrogeochemical characteristics of beaver-induced flowpaths have not been thoroughly examined. Using a suite of complementary ground- and drone-based heat tracing and remote sensing methodology we characterized the physical template of beaver-induced floodplain exchange for two alluvial mountain streams near Crested Butte, Colorado, USA. A flowpath-oriented perspective to water quality sampling allowed characterization of the chemical evolution of channel water diverted through floodplain beaver ponds and ultimately back to the channel in ‘beaver pond return flows’. Subsurface return flow seepages were universally suboxic, while ponds and surface return flows showed a range of oxygen concentration due to in-situ photosynthesis and atmospheric mixing. Median concentrations of reduced metals: manganese (Mn), iron (Fe), aluminum (Al), and arsenic (As) were substantially higher along beaver-induced flowpaths than in geologically controlled seepages and upstream main channel locations. The areal footprint of reduced return seepage flowpaths were imaged with surface electromagnetic methods, indicating extensive zones of high-conductivity shallow groundwater flowing back toward the main channels and emerging at relatively warm bank seepage zones observed with infrared. Multiple-depth redox dynamics within one focused seepage zone showed coupled variation over time, likely driven by observed changes in seepage rate that may be controlled by pond stage. High-resolution times series of dissolved Mn and Fe collected downstream of the beaver-impacted reaches demonstrated seasonal dynamics in mixed river metal concentrations. Al time series concentrations showed proportional change to Fe at the smaller stream location, indicating chemically reduced flowpaths were sourcing Al to the channel. Overall our results indicated beaver-induced floodplain exchanges create important, and perhaps dominant, transport pathways for floodplain metals by expanding chemically-reduced zones paired with strong advective exchange.

Climatology of mixing layer height in China based on multi-year meteorological data from 2000 to 2013

Atmospheric aerosol levels are high in different regions of China. Changes in atmospheric stability and mixing layer height (MLH) may affect the vertical aerosol distribution during pollution events. Here, we continuous studied the spatiotemporal distribution of MLH in China over 2000–2013 to characterize the regional-scale properties of atmospheric boundary layers. MLH was larger in the Southern Coastal and Southeastern China (1241.5 ± 73.5 and 632.7 ± 61.8 m, respectively), but lower in Eastern and Southwestern China (518.1 ± 63.6 and 462.7 ± 88.5 m, respectively). We divided the monitoring stations into 11 regions; these regions could be classified into three types with an increasing linear trend (95% confidence level), with a decreasing linear trend (95% confidence level), and with fluctuation changes. In all regions, MLH was higher in spring and summer than in autumn and winter. The spatial distribution of the diurnal MLH increased significantly at 1400 BJT (Beijing time) in all regions, with the strongest radiation being noted during the daytime. Higher levels of PM2.5 with corresponding lower MLH were noted during winter, indicating that lower MLH could confine the pollutant diffusion to near the surface. By contrast, in spring, higher MLH could be potentially due to the dynamic condition. In general, the poor air quality days occurred more frequently in winter than in other seasons. As the air quality worsened, most MLH showed a decreasing trend in almost all regions. This work provides information that aids in further understanding not only MLH distribution in China but also specific PM–MLH interaction to facilitate regional atmospheric environment monitoring and prediction.