Radiation Balance Research Articles

Bright and Stable Yellow Quantum Dot Light-Emitting Diodes Through Core-Shell Nanostructure Engineering.

Solution-processed and efficient yellow quantum dot light-emitting diodes (QLEDs) are considered key optoelectronic devices for lighting, display, and signal indication. However, limited synthesis routes for yellow quantum dots (QDs), combined with inferior stress-relaxation of the core-shell interface, pose challenges to their commercialization. Herein, a nanostructure tailoring strategy for high-quality yellow CdZnSe/ZnSe/ZnS core/shell QDs using a "stepwise high-temperature nucleation-shell growth" method is introduced. The synthesized CdZnSe-based QDs effectively smoothed the release stress of the core-shell interface and revealed a near-unit photoluminescence quantum yield, with nonblinking behavior and matched energy level, which accelerated radiative recombination and charge injection balance for device operation. Consequently, the yellow CdZnSe-based QLEDs exhibited a peak external quantum efficiency of 23.7%, a maximum luminance of 686050cdm-2, and a current efficiency of 103.2cdA-1, along with an operating half-lifetime of 428523h at 100cdm-2. To the best of the knowledge, the luminance and operational stability of the device are found to be the highest values reported for yellow LEDs. Moreover, devices with electroluminescence (EL) peaks at 570-605nm exhibited excellent EQEs, surpassing 20%. The work is expected to significantly push the development of RGBY-based display panels and white LEDs.

High contributions of fossil fuel sources to char-EC/soot-EC at a high-altitude site: Direct radiative effects and transport pathway

Char-EC and soot-EC in the atmosphere produced from different fuel combustion have distinct optical properties which lead to different radiative forcing. Pollutants transported into high-altitude environment could have a long-lasting radiative effect due to being free of deposition. In this study, the mass absorption cross-section (MAC), the sources, transport pathways and the direct radiative effects (DREs) of soot-EC and char-EC were investigated at a peak of Mountain Hua (Mt. Hua) in China. The measurement results showed that soot-EC and char-EC account for 15.7 % and 84.3 % of EC, respectively. The mean MAC (λ = 633 nm) of soot-EC (13.7 ± 3.8 m2/g) was much higher than that of char-EC (5.4 ± 2.5 m2/g), indicating a stronger light absorption ability for soot-EC. During the study period, 62.1 % char-EC was from anthracite chunk coal, 24.3 % of it from liquid fuel combustion. By contrast, 59.0 % soot-EC from liquid fuel combustion and 36.6 % of it from anthracite chunk coal. EC (both char-EC and soot-EC) produced from anthracite chunk coal reached the peak of the Mt. Hua primarily through the raising of the planetary boundary layer (PBL), while the EC produced from liquid fuel arrived the peak mainly by the regional transport above the PBL of the site. Although soot-EC has a stronger ability (2.8 times higher) to absorb the light compared with char-EC, its DRE (5.7 ± 3.9 W m−2) was lower than that of char-EC (11.6 ± 6.9 W m−2) due to the smaller mass quantity. Liquid fuel consumption contributed 3.5 ± 2.9 W m−2 DRE of soot-EC, while the combustion of anthracite chunk coal contributed 7.5 ± 5.7 W m−2 DRE of char-EC. This study highlights the differences in DREs of soot-EC and char-EC from fossil fuel combustion and the DRE mass efficiency of soot-EC and char-EC. The results emphasize the divergent climate warming effects caused by the combustion of different fossil fuels and imply that setting path to a green transition of energy use would benefit reducing the EC perturbation to the radiation balance of earth-atmosphere.

Revisiting the Link Between Thunderstorms and Upper Tropospheric Water Vapor

AbstractAs the Earth's temperatures continue to rise due to increasing greenhouse gases in the atmosphere, a large portion of the warming is due to positive feedbacks from increasing atmospheric water vapor or specific humidity (SH). Some of this water vapor in the boundary layer is transported via deep convection to the upper troposphere (as droplets and ice crystals), moistening the upper troposphere. These small changes in SH in the upper troposphere have a significant impact on the Earth's radiation balance. We compared global daily lightning from the WWLLN data set, and SH data from the ERA5 reanalysis product for 2019, at a spatial resolution of 5°. Our findings show high spatial and temporal correlations between the lightning activity and the SH concentrations in the upper troposphere. The best correlations (r2 = 0.72, p << 0.001) are between lightning activity and UTWV at the 200 mb level (∼12 km altitude), although the correlations with SH at 300 and 400 mb were only slightly lower. Lightning and SH migrate with the seasons north and south of the equator with both parameters showing maxima in the summer hemisphere around 10° latitude. Furthermore, the correlation increases slightly (r2 = 0.73) if a 1‐day lag is considered between the lightning activity and the UTWV. We find that the daily global SH in the upper troposphere can be best estimated using daily global lightning frequency and a power law having an exponent of 0.33.

Evaluation of MERRA-2 and CAMS reanalysis for black carbon aerosol in China

Black carbon (BC) constitutes a pivotal component of atmospheric aerosols, significantly impacting regional and global radiation balance, climate, and human health. In this study, we evaluated BC data in two prominent atmospheric composition reanalysis datasets: the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) and the Copernicus Atmosphere Monitoring Service (CAMS), and analyzed the causes of their deviations. This assessment is based on observational data collected from 34 monitoring stations across China from 2006 to 2022. Our research reveals a significant and consistent decline in BC concentrations within China, amounting to a reduction exceeding 67.33%. However, both MERRA-2 and CAMS reanalysis data fail to capture this declining trend. The average annual decrease of BC in MERRA-2 from 2006 to 2022 is only 0.06 μg/m3 per year, while the BC concentration in CAMS even increased with an average annual value of 0.014 μg/m3 per year. In 2022, MERRA-2 had overestimated BC concentration by 20% compared to observational data, while CAMS had overestimated it by approximately 66%. In the regional BC concentration analysis, the data quality of the reanalysis data is better in the South China (RM = 0.59, RC = 0.53), followed by the North China (RM = 0.50, RC = 0.42). Reanalysis BC data in Northwest China and the Tibetan Plateau are difficult to use for practical analysis due to their big difference with observation. In a comparison of the anthropogenic BC emissions inventory used in the two atmospheric composition reanalysis datasets with the Multi-resolution Emission Inventory model for Climate and air pollution research (MEIC) emissions inventory, we found that: Despite the significant decline in China's BC emissions, MERRA-2 still relies on the 2006 emissions inventory, while CAMS utilizes emission inventories that even show an increasing trend. These factors will undoubtedly lead to greater deviations between reanalysis and observational data.

Contrasting characteristics of continental and oceanic deep convective systems at different life stages from CloudSat observations

The deep convective system (DCS) has large impacts on the radiation balance, global circulation and consequent the climate change. However, a reasonable representation of the DCS characterization in numerical models is limited by the understanding of its evolutionary mechanism. In this study, we investigate the land-ocean DCS contrast using three years (2015–2017) of cloud profiling radar (CPR) observations from the CloudSat satellite based on a connected area DCS identification approach. We identify the DCS life stages through a buoyancy determination, and conduct a composite image method to provide robust internal statistical structure of the morphology, radar reflectivity and microphysical properties of oceanic and continental DCS during each life stage. Reasonable evolutionary mechanisms of DCSs over ocean and land is proposed. It is found that the continental DCS height is strongly influenced by the intense of convection, and its volume decrease when heavy precipitation occurs. While the oceanic DCS can maintain a larger volume due to the sufficient water vapor supply. It often presents with dispersed stratified precipitation and the main procedure of its dissipation is the cloud edge entrainment. Our results may provide a pathway to evaluate the life cycle and evolution mechanism of DCS from model simulation.

Carbon Dioxide and Heat Fluxes during Reforestation in the North Caucasus

Human impact on natural ecosystems has significantly increased in recent decades. As a result, the structure and functioning of ecosystems are seriously altered. This in turn affects regional weather and climate conditions through changes in the radiation, water, and carbon balance of ecosystems. Investigating the process of natural ecosystem restoration after disturbances is an important issue in the context of climate change. During monitoring observations of greenhouse gas (GHG) fluxes in a reforestation area in the Chechen Republic, new experimental data on their seasonal variability were obtained, and their sensitivity to changes in environmental conditions was assessed. Forest restoration and land reclamation are essential components of the low-carbon development and decarbonization strategy of the world economy. Observations of GHG fluxes were conducted in the reclaimed area, which was planted with tree seedlings. One year of eddy covariance flux measurements (May 2022–June 2023) demonstrated that CO2 uptake by the reforestation area in a humid continental climate with hot summers and cold winters is determined by the moisture conditions of the growing season. The cumulative net ecosystem exchange (NEE) for the entire measurement period at the carbon farm was 613.7 gC·m−2. The uptake of CO2 by the reforestation area was observed only due to active seedling growth during periods of sufficient soil moisture (May 2023). During this time, total NEE uptake was 48.7 gC·m−2. Sensible and latent heat fluxes were also dependent on weather conditions, primarily on incoming solar radiation and moisture conditions. For the successful implementation of climate projects aimed at the creation of artificial forest ecosystems with high CO2 uptake capacity, it is essential to develop appropriate hydro-meliorative measures that ensure a sufficient amount of available soil moisture.

Aerosol absorption using in situ filter-based photometers and ground-based sun photometry in the Po Valley urban atmosphere

Abstract. Light-absorbing aerosols (LAAs) are short-lived climate forcers with a significant impact on Earth's radiative balance. LAAs include dust aerosols, black carbon (BC) and organic light-absorbing carbonaceous aerosol (collectively termed brown carbon, BrC), which have also been proven to be highly toxic. In this study, aerosol absorption at five wavelengths (ranging from ultraviolet to infrared) was monitored continuously using filter-based photometers during two winter seasons in 2020 and 2021 in the city of Modena (southern central Po Valley, northern Italy), at two regulatory air quality monitoring sites, along with other pollutants (coarse particulate matter, PM10; fine particulate matter, PM2.5; O3; NO; NO2; and C6H6) and the vehicular traffic rate. The aerosol optical depth (AOD) and other column aerosol optical properties were concurrently monitored at four wavelengths by an AErosol RObotic NETwork (AERONET) sun photometer under urban background conditions within Modena. In situ absorption levels were apportioned to both sources (fossil fuel and biomass burning) and species (BC and BrC), while columnar absorption was apportioned to BC, BrC and mineral dust. The combined analysis of the atmospheric aerosol and gas measurements and of the meteorological conditions (in situ and from the ERA5 reanalysis) identified the location of potential urban sources of BC and BrC, most likely related to traffic and biomass burning. In situ data show different diurnal/weekly patterns for BrC from biomass burning and BC from traffic, with minor differences between the background and the urban traffic conditions. AERONET version 3 absorption aerosol optical depth (AAOD) retrievals at four wavelengths allowed the estimation of the absorptive direct radiative effect due to LAAs over the same period under the reasonable assumption that the AOD signal is concentrated within the mixing layer. AERONET retrievals showed a modest correlation of columnar absorption with planetary boundary layer (PBL)-scaled in situ observations, although the correlation improved significantly during a desert dust transport event that affected both in situ aerosol and columnar absorption, particularly in the blue spectrum range. A low correlation occurred between the contribution of BrC to aerosol absorption for the in situ and the columnar observations, with the BrC contribution being generally larger for in situ observations. Finally, evidence of a highly layered atmosphere during the study period, featuring significant spatial mixing and modest vertical mixing, was shown by ERA5-based atmospheric temperature profiles and by the large correlation of concurrent AERONET AOD retrievals in Modena and in Ispra (on the northwestern side of the Po Valley, ca. 225 km from Modena).

Threefold reduction of modeled uncertainty in direct radiative effects over biomass burning regions by constraining absorbing aerosols.

Absorbing aerosols emitted from biomass burning (BB) greatly affect the radiation balance, cloudiness, and circulation over tropical regions. Assessments of these impacts rely heavily on the modeled aerosol absorption from poorly constrained global models and thus exhibit large uncertainties. By combining the AeroCom model ensemble with satellite and in situ observations, we provide constraints on the aerosol absorption optical depth (AAOD) over the Amazon and Africa. Our approach enables identification of error contributions from emission, lifetime, and MAC (mass absorption coefficient) per model, with MAC and emission dominating the AAOD errors over Amazon and Africa, respectively. In addition to primary emissions, our analysis suggests substantial formation of secondary organic aerosols over the Amazon but not over Africa. Furthermore, we find that differences in direct aerosol radiative effects between models decrease by threefold over the BB source and outflow regions after correcting the identified errors. This highlights the potential to greatly reduce the uncertainty in the most uncertain radiative forcing agent.

Cooling the Coldest Continent: The 4 December 2021 Total Solar Eclipse over Antarctica

Abstract Total solar eclipses (TSEs) are impressive astronomical events that have attracted people’s curiosity since ancient times. Their abrupt alterations to the radiation balance have stimulated studies on “eclipse meteorology,” most of them documenting events in the Northern Hemisphere while only one TSE (23 November 2003) has been described over Antarctica. On 4 December 2021—just a few days before the austral summer solstice—the moon blocked the sun over the austral high latitudes, with the path of totality arching from the Weddell Sea to the Amundsen Sea, thus producing a ∼2-min central TSE. In this work we present high-resolution meteorological observations from Union Glacier Camp (80°S, 83°W), the only location with a working station under totality, and South Pole station. These observations were complemented with meteorological records from 37 surface stations across Antarctica. Notably, the largest cooling (∼5°C) was observed over the East Antarctic dome, where obscurity was ∼85% while many sectors experienced insignificant temperature changes. This heterogenous cooling distribution, at odds with the seemingly homogeneous land surface of Antarctica, is partially captured by a simple radiative model. To further diagnose the effect of the eclipse on the surface meteorology, we ran multiple pairs of simulations (eclipse enabled and disabled) using the Weather Research and Forecasting (WRF) Model. The overall pattern and magnitude of the simulated cooling agree well with the observations and reveal that, in addition to the solar radiation deficit and cloud cover, low-level winds and the height of the planetary boundary layer are key determinants of the temperature changes and their spatial variability.

Changes in biodiversity impact atmospheric chemistry and climate through plant volatiles and particles

Climate extremes in tandem with biodiversity change affect plant emissions of biogenic volatile organic compounds, as a result, the formation of biogenic secondary organic aerosols. The resulting biogenic secondary organic aerosols can have a wide variety of impacts, such as on Earth’s radiative balance or cloud- and precipitation formation. However, at present, it is unclear how changing biodiversity will lead to changes in biogenic volatile organic compound emissions, biogenic secondary organic aerosols and their corresponding effects. We present a conceptual framework of the relationships between biodiversity and biogenic volatile organic compound emissions based on our current mechanistic understanding and combining knowledge from the fields of biology and atmospheric chemistry. Parts of this framework are tested in a case study using a tree diversity experiment. The relative differences in tree monocultures and mixtures show that the overall concentration of biogenic volatile organic compounds decreases with increasing biodiversity, but results for biogenic secondary organic aerosols are mixed and overall non-significant. A deeper understanding of how changing biodiversity influences biogenic organic compound emissions and biogenic secondary organic aerosol formation requires in-depth investigations of microclimate conditions, accurate monitoring of above- and below-ground biotic and abiotic stress, and manipulating stress conditions across long-term biodiversity experiments.

Comparative study of energy balance in urban and forest areas in Central Amazonia

Data from two experimental sites in central Amazonia were used, one located in a forested region and the other in an urban region. The values of the radiation and energy balance components were measured at both sites. The observed components of the radiation balance in the forest, and urban areas were quite different. The city, the radiative (albedo and emissivity) and thermal (absorptivity) parameters of the surface produced greater reflection of solar radiation and emission of longwave radiation. Urban pollution reduced the incident solar radiation and increased the longwave radiation emitted by the atmosphere. The energy balance presented marked differences in the partition between sensible and latent heat flux between forest and city. In the forest, much of the available energy is converted into latent heat flux, due to the process of evapotranspiration. Whereas, in the city, energy is equally divided into sensible and latent heat fluxes.

Empirical record, geochronology and theoretical determinates of Mesozoic climate in the Junggar Basin, NW China, in relation to other basins in NE China

Abstract Mesozoic continental basins of northern China, including the Junggar Basin, provide some of the most spectacular and important fossil assemblages in the world, but their climatic and environmental contexts have been shrouded in uncertainty. Here we examine the main factors that determine those contexts: palaeolatitude; the effects of changing atmospheric gases on the radiative balance; and orbitally paced variations in insolation. Empirical evidence of these factors is accumulating rapidly and promises to upend many long-standing paradigms. We focus primarily on the Junggar Basin in Xinjiang, NW China, with the renowned Shishugou Biota, and the basins in Liaoning, Hebei and Inner Mongolia with their famous Jehol and Yanliao biotas. Accurate geochronology is necessary to disentangle these various factors, and we review the Late Triassic to Early Cretaceous U–Pb ages for these areas and supply a new laser ablation inductively coupled plasma mass spectrometry age for the otherwise un-dated Sangonghe Formation of Early Jurassic age. We review climate-sensitive facies patterns in North China and show that the climatic context changed synchronously in northwestern and northeastern China consistent with a previously proposed huge Late Jurassic–earliest Cretaceous true polar wander event, with all the major plates of East Asia docked with Siberia and moving together since at least the Triassic when the North China basins were at Arctic latitudes. We conclude that this true polar wander shift was responsible for the coal beds and ice-rafted debris being produced at high latitudes and the red beds and aeolian strata being deposited at low latitudes within the same basin. The climatic and taphonomic context in which the famous Shishugou, Yanliao and Jehol biotas were preserved was thus a function of true polar wander, as opposed to local tectonics or climate change.

Quantitative analysis of the Martian atmospheric dust cycle: Transported mass, surface dust lifting and sedimentation rates

The atmospheric dust cycle on Mars plays a dominant role in the planetary radiative balance, atmospheric photochemistry escape, and redistribution of materials on the surface. Although this planetary dust cycle has been extensively modelled and characterized with both orbital and in situ observations, to date little is known about the total mass of dust that is circulated, the actual dust lifting and settling rates, and the main dust sources and sinks. Using orbital global and seasonal measurements of atmospheric dust opacity, a data reduction methodology that can describe the annual dust redistribution cycle on a planetary scale with 95% accuracy is presented. The method was applied to the 9.3 μm infrared observations of the Thermal Emission Spectrometer (TES) aboard the Mars Global Surveyor (MGS) during two full Martian Years (MY) 25 and 26, and partly MY 24 and MY 27, disregarding the global dust storm that occurred in MY 25. By comparison with terrestrial observations, a mass-to-extinction conversion factor of 1.9 ± 0.3 g m−2 is proposed, assuming a dust density of 2.6 g cm−3. The analysis shows an estimation of 400 1012 g of dust transported globally in the atmosphere for a typical Mars year, which is comparable to the minimum total annual mass of dust transported on Earth. The methodology proposed here is based on remote sensing and cannot disentangle completely local surface lifting and sedimentation rates from dust advection. However, this analysis provides upper bounds which can be compared with in-situ observations. The analysis of the dust sedimentation cycle suggests that the annual cycle might produce a dust layer of about 50–100 μm on the surface of some particular zones, as Valle Marineris or Meridiani Planum. This estimation agrees with in-situ observations of rovers on Mars. The potential dust sources are mainly located from latitudes of 20°S to 60°S. Our results find the 70% of the sources previously identified by the existing planetary circulation models. This kind of large-scale analysis can be applied to other remote sensing observations to refine these calculations and study the annual and geographical variability of the dust-mass transport on Mars.

Optical Properties of Individual Tar Balls in the Free Troposphere.

Tar balls are brown carbonaceous particles that are highly viscous, spherical, amorphous, and light absorbing. They are believed to form in biomass burning smoke plumes during transport in the troposphere. Tar balls are also believed to have a significant impact on the Earth's radiative balance, but due to poorly characterized optical properties, this impact is highly uncertain. Here, we used two nighttime samples to investigate the chemical composition and optical properties of individual tar balls transported in the free troposphere to the Climate Observatory "Ottavio Vittori" on Mt. Cimone, Italy, using multimodal microspectroscopy. In our two samples, tar balls contributed 50% of carbonaceous particles by number. Of those tar balls, 16% were inhomogeneously mixed with other constituents. Using electron energy loss spectroscopy, we retrieved the complex refractive index (RI) for a wavelength range from 200 to 1200 nm for both inhomogeneously and homogeneously mixed tar balls. We found no significant difference in the average RI of inhomogeneously and homogeneously mixed tar balls (1.40-0.03i and 1.36-0.03i at 550 nm, respectively). Furthermore, we estimated the top of the atmosphere radiative forcing using the Santa Barbara DISORT Atmospheric Radiative Transfer model and found that a layer of only tar balls with an optical depth of 0.1 above vegetation would exert a positive radiative forcing ranging from 2.8 W m-2 (on a clear sky day) to 9.5 W m-2 (when clouds are below the aerosol layer). Understanding the optical properties of tar balls can help reduce uncertainties associated with the contribution of biomass-burning aerosol in current climate models.

Sulfuric Acid Nucleation Potential Model Applied to Complex Reacting Systems in the Atmosphere

AbstractAtmospheric aerosol particles impact Earth's radiation balance by acting as seeds for cloud droplet formation. Over half of global cloud seed particles are formed by nucleation, a process where gas‐phase compounds react to form stable particles. Reactions of sulfuric acid (SA) with a wide variety of atmospheric compounds have been previously shown to drive nucleation in the lower troposphere. However, global climate models poorly predict particle nucleation rates since current nucleation models do not describe nucleation for systems containing tens to hundreds of precursor compounds. The nucleation potential model (NPM) was recently developed to model SA nucleation of complex mixtures by measuring an effective base concentration using a 1‐nm condensation particle counter. This technique for estimating particle nucleation rates can be deployed at a much higher spatial and temporal resolution than current methods which require detailed knowledge of all nucleation reactions and measurements, typically using a mass spectrometer, of all nucleation precursor gases. This work expands NPM by showing that this model can capture enhancement and suppression of SA nucleation rates within a complex mixture of organic and inorganic acids, ambient air, and across a range of atmospherically relevant relative humidities. In addition, an expression for calculating atmospheric nucleation rates was also derived from the NPM. Ultimately, NPM provides a simple way to measure and model the extent compounds in a complex mixture enhance SA nucleation rates using a condensation particle counter.

Aqueous Radical Initiated Oxidation of an Organic Monolayer at the Air-Water Interface as a Proxy for Thin Films on Atmospheric Aerosol Studied with Neutron Reflectometry.

Neutron reflectometry has been used to study the radical initiated oxidation of a monolayer of the lipid 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) at the air-solution interface by aqueous-phase hydroxyl, sulfate, and nitrate radicals. The oxidation of organic films at the surface of atmospheric aqueous aerosols can influence the optical properties of the aerosol and consequently can impact Earth's radiative balance and contribute to modern climate change. The amount of material at the air-solution interface was found to decrease on exposure to aqueous-phase radicals which was consistent with a multistep degradation mechanism, i.e., the products of reaction of the DSPC film with aqueous radicals were also surface active. The multistep degradation mechanism suggests that lipid molecules in the thin film degrade to form progressively shorter chain surface active products and several reactive steps are required to remove the film from the air-solution interface. Bimolecular rate constants for oxidation via the aqueous phase OH radical cluster around 1010 dm3 mol-1 s-1. Calculations to determine the film lifetime indicate that it will take ∼4-5 days for the film to degrade to 50% of its initial amount in the atmosphere, and therefore attack by aqueous radicals on organic films could be atmospherically important relative to typical atmospheric aerosol lifetimes.

Sink, Source or Something In‐Between? Net Effects of Precipitation on Aerosol Particle Populations

AbstractInteractions between atmospheric aerosols, clouds, and precipitation impact Earth's radiative balance and air quality, yet remain poorly constrained. Precipitating clouds serve as major sinks for particulate matter, but recent studies suggest that precipitation may also act as a particle source. The magnitude of the sources versus sinks, particularly for cloud condensation nuclei (CCN) numbers, remain unquantified. This study analyzes multi‐year in situ observations from tropical and boreal forests, as well as Arctic marine environment, showing links between recent precipitation and enhanced particle concentrations, including CCN‐sized particles. In some cases, the magnitude of precipitation‐related source equals or surpasses corresponding removal effect. Our findings highlight the importance of cloud‐processed material in determining near‐surface particle concentrations and the value of long‐term in situ observations for understanding aerosol particle life cycle. Robust patterns emerge from sufficiently long data series, allowing for quantitative assessment of the large‐scale significance of new phenomena observed in case studies.

SI-traceable validation of a laser spectrometer for balloon-borne measurements of water vapor in the upper atmosphere

Abstract. Despite its crucial role in the Earth's radiative balance, upper-air water vapor (H2O) is still lacking accurate, in situ, and continuous monitoring. Especially in the upper troposphere–lower stratosphere (UTLS), these measurements are notoriously difficult, and significant discrepancies have been reported in the past between different measuring techniques. Here, we present a laboratory assessment of a recently developed mid-IR quantum-cascade laser absorption spectrometer, called ALBATROSS, for balloon-borne measurements of H2O in the UTLS. The validation was performed using SI-traceable reference gas mixtures generated based on the permeation method and dynamic dilution. The accuracy and precision of ALBATROSS were evaluated at a wide range of pressures (30–250 mbar) and H2O amount fractions (2.5–35 ppm), representative of the atmospheric variability in H2O in the UTLS. The best agreement was achieved by implementing a quadratic speed-dependent Voigt profile (qSDVP) line shape model in the spectroscopic retrieval algorithm. The molecular parameters required by this parameterization were determined empirically using a multi-spectrum fitting approach over different pressure conditions. In the laboratory environment, ALBATROSS achieves an accuracy better than ±1.5 % with respect to the SI-traceable reference at all investigated pressures and H2O amount fractions. The measurement precision was found to be better than 30 ppb (i.e., 0.1 % at 35 ppm H2O) at 1 s resolution for all conditions. This performance, unprecedented for a balloon-borne hygrometer, demonstrates the exceptional potential of mid-IR laser absorption spectroscopy as a new reference method for in situ measurements of H2O in the UTLS.

Modeling Slope Microclimates in the Mars Planetary Climate Model

AbstractA large number of surface features (e.g., frost, gullies, slope streaks, recurring slope lineae) are observed on Martian slopes. Their activity is often associated with the specific microclimates on these slopes, which have been mostly studied with one‐dimensional radiative balance models to date. We develop here a parameterization to simulate these microclimates in 3D Global Climate Models. We first demonstrate that any Martian slope can be thermally represented by a poleward or equatorward slope, that is, the daily average, minimum, and maximum surface temperatures depend on the North‐South component of the slope. Based on this observation, we implement here a subgrid‐scale parameterization to represent slope microclimates (radiative fluxes, volatile condensation, ignoring slope winds for now) in the Mars Planetary Climate Model and validate it through comparisons with surface temperature measurements and frost detections on sloped terrains. With this new model, we show that slope microclimates do not have a significant impact on the seasonal CO2 and H2O cycles on a global scale. Furthermore, short‐scale slopes (i.e., less than ∼1 km in length) do not significantly impact the thermal state of the atmosphere. Ninety‐one percent of the active gullies are found where our model predicts CO2 frost, suggesting that their activity is related to processes involving CO2 ice. However, the low thicknesses (≤tens of cm) predicted at mid‐latitudes rule out mechanisms involving large amounts (∼meters) of ice. This model opens the way to new studies on surface‐atmosphere interactions in present and past climates.

A Surface Radiation Balance Dataset from Siple Dome in West Antarctica for Atmospheric and Climate Model Evaluation

Abstract A field campaign at Siple Dome in West Antarctica during the austral summer 2019/20 offers an opportunity to evaluate climate model performance, particularly cloud microphysical simulation. Over Antarctic ice sheets and ice shelves, clouds are a major regulator of the surface energy balance, and in the warm season their presence occasionally induces surface melt that can gradually weaken an ice shelf structure. This dataset from Siple Dome, obtained using transportable and solar-powered equipment, includes surface energy balance measurements, meteorology, and cloud remote sensing. To demonstrate how these data can be used to evaluate model performance, comparisons are made with meteorological reanalysis known to give generally good performance over Antarctica (ERA5). Surface albedo measurements show expected variability with observed cloud amount, and can be used to evaluate a model’s snowpack parameterization. One case study discussed involves a squall with northerly winds, during which ERA5 fails to produce cloud cover throughout one of the days. A second case study illustrates how shortwave spectroradiometer measurements that encompass the 1.6-μm atmospheric window reveal cloud phase transitions associated with cloud life cycle. Here, continuously precipitating mixed-phase clouds become mainly liquid water clouds from local morning through the afternoon, not reproduced by ERA5. We challenge researchers to run their various regional or global models in a manner that has the large-scale meteorology follow the conditions of this field campaign, compare cloud and radiation simulations with this Siple Dome dataset, and potentially investigate why cloud microphysical simulations or other model components might produce discrepancies with these observations. significance statement Antarctica is a critical region for understanding climate change and sea level rise, as the great ice sheets and the ice shelves are subject to increasing risk as global climate warms. Climate models have difficulties over Antarctica, particularly with simulation of cloud properties that regulate snow surface melting or refreezing. Atmospheric and climate-related field work has significant challenges in the Antarctic, due to the small number of research stations that can support state-of-the-art equipment. Here we present new data from a suite of transportable and solar-powered instruments that can be deployed to remote Antarctic sites, including regions where ice shelves are most at risk, and we demonstrate how key components of climate model simulations can be evaluated against these data.