Atmospheric Thermal Structure Research Articles

From the Surface to the Stratosphere: Large‐Scale Atmospheric Response to Antarctic Meltwater

AbstractThe ocean response to Antarctic Ice Sheet (AIS) mass loss has been extensively studied using numerical models, but less attention has been given to the atmosphere. We examine the global atmospheric response to AIS meltwater in an ensemble of experiments performed using two fully coupled climate models under a pre‐industrial climate. In response to AIS meltwater, the experiments yield cooling from the surface to the tropopause over the subpolar Southern Ocean, warming in the Southern Hemisphere polar stratosphere, and cooling in the upper tropical troposphere. Positive feedbacks, initiated by disrupted ocean‐atmosphere heat exchange, result in a change in the top‐of‐atmosphere radiative balance caused primarily through surface and near‐surface albedo changes. Changes in the atmospheric thermal structure alter the jet streams aloft. The results highlight the global influence of AIS melting on the climate system and the potential for impacts on mid‐latitude climate patterns and delayed regional warming signals.

Two-dimensional Models of Microphysical Clouds on Hot Jupiters. I. Cloud Properties

We present a new two-dimensional, bin-scheme microphysical model of cloud formation in the atmospheres of hot Jupiters that includes the effects of longitudinal gas and cloud transport. We predict cloud particle size distributions as a function of planetary longitude and atmospheric height for a grid of hot Jupiters with equilibrium temperatures ranging from 1000 to 2100 K. The predicted 2D cloud distributions vary significantly from models that do not consider horizontal cloud transport and we discuss the microphysical and transport timescales that give rise to the differences in 2D versus 1D models. We find that the horizontal advection of cloud particles increases the cloud formation efficiency for nearly all cloud species and homogenizes cloud distributions across the planets in our model grid. In 2D models, certain cloud species are able to be transported and survive on the daysides of hot Jupiters in cases where 1D models would not predict the existence of clouds. We demonstrate that the depletion of condensible gas species varies as a function of longitude and atmospheric height across the planet, which impacts the resultant gas-phase chemistry. Finally, we discuss various model sensitivities including the sensitivity of cloud properties to microphysical parameters, which we find to be substantially less than the sensitivity to the atmospheric thermal structure and horizontal and vertical transport of condensible material.

Atacama Large Aperture Submillimeter Telescope (AtLAST) science: Planetary and cometary atmospheres.

The study of planets and small bodies within our Solar System is fundamental for understanding the formation and evolution of the Earth and other planets. Compositional and meteorological studies of the giant planets provide a foundation for understanding the nature of the most commonly observed exoplanets, while spectroscopic observations of the atmospheres of terrestrial planets, moons, and comets provide insights into the past and present-day habitability of planetary environments, and the availability of the chemical ingredients for life. While prior and existing (sub)millimeter observations have led to major advances in these areas, progress is hindered by limitations in the dynamic range, spatial and temporal coverage, as well as sensitivity of existing telescopes and interferometers. Here, we summarize some of the key planetary science use cases that factor into the design of the Atacama Large Aperture Submillimeter Telescope (AtLAST), a proposed 50-m class single dish facility: (1) to more fully characterize planetary wind fields and atmospheric thermal structures, (2) to measure the compositions of icy moon atmospheres and plumes, (3) to obtain detections of new, astrobiologically relevant gases and perform isotopic surveys of comets, and (4) to perform synergistic, temporally-resolved measurements in support of dedicated interplanetary space missions. The improved spatial coverage (several arcminutes), resolution (~ 1.2'' - 12''), bandwidth (several tens of GHz), dynamic range (~ 10 5) and sensitivity (~ 1 mK km s -1) required by these science cases would enable new insights into the chemistry and physics of planetary environments, the origins of prebiotic molecules and the habitability of planetary systems in general.

The radiative and dynamical impact of clouds in the atmosphere of the hot Jupiter WASP-43 b

Context. Hot Jupiters are tidally locked gaseous exoplanets that exhibit large day-night temperature contrasts. Their cooler nightsides are thought to host clouds, as has been suggested by numerous observations. However, the exact nature of these clouds, their spatial distribution, and their impact on atmospheric dynamics, thermal structure, and spectra is still unclear. Aims. We investigate the atmosphere of WASP-43 b, a short period hot Jupiter recently observed with James Webb Space Telescope (JWST), to understand the radiative and dynamical impact of clouds on the atmospheric circulation and thermal structure. We aim to understand the impact of different kinds of condensates potentially forming in WASP-43 b, with various sizes and atmospheric metallicities. Methods. We used a 3D global climate model (GCM) with a new temperature-dependent cloud model that includes radiative feedbacks coupled with hydrodynamical integrations to study the atmospheric properties of WASP-43 b. We produced observables from our GCM simulations and compared them to spectral phase curves from various observations to derive constraints on the atmospheric properties. Results. We show that clouds have a net warming effect, meaning that the greenhouse effect caused by clouds is stronger than the albedo cooling effect. We show that the radiative effect of clouds has various impacts on the dynamical and thermal structure of WASP-43 b. Depending on the type of condensates and their sizes, the radiative-dynamical feedback will modify the horizontal and vertical temperature gradient and reduce the wind speed. For super-solar metallicity atmospheres, fewer clouds form in the atmosphere, leading to a weaker feedback. Comparisons with spectral phase curves observed with HST, Spitzer, and JWST indicate that WASP-43 b's nightside is cloudy and rule out sub-micron Mg2SiO4 cloud particles as the main opacity source. Distinguishing between cloudy solarand cloudy super-solar-metallicity atmospheres is not straightforward, and further observations of both reflected light and thermal emission are needed.

The Lower Atmospheric Characteristics of Dust Storms Using Ground-Based Sensor Data: A Comparative Analysis of Two Cases in Jinan, China

Two severe dust storm (DS) events (15–17 March and 28–29 March) hit northern China in 2021 consecutively. The lower atmospheric vertical dynamic and thermal structures during the two cases were compared using the ground-based sensor data from the microwave radiometer and radar wind profiler, combined with the environmental and meteorological observations data in Jinan, China. It was found that both cases occurred under the background of cold vortexes over northeastern China. The dust was transported through the cold air on the northwest route. During the dust period, 2–3 km was the west or northwest airflow, and below 2 km was the northeast wind. The variation in the dynamic structure determined the duration of the DS. During the DS maintenance phase, the vertical wind shear (VWS) below 3 km measured approximately 10 m∙(s∙km)−1. The increased VWS during the dust intrusion period facilitated the transportation of dust. In contrast, the more significant VWS was not conducive to the maintenance of DS, and the shift to south wind control in the upper middle layer indicated the weakening of DS. In both cases, we observed a cliff-like decrease in relative humidity as a prominent indicator of dust outbreaks, occurring approximately 2–5 h beforehand. The diurnal difference between the vertical temperature and relative humidity during the dust maintenance period was found to be insignificant.

Cenozoic Indo-Pacific warm pool controlled by both atmospheric CO2 and paleogeography

The Indo-Pacific warm pool (IPWP) is crucial for regional and global climates. However, the development of the IPWP and its effect on the regional climate during the Cenozoic remain unclear. Here, using a compilation of sea surface temperature (SST) records (mainly since the middle Miocene) and multimodel paleoclimate simulations, our results indicated that the extent, intensity and warmest temperature position of the IPWP changed markedly during the Cenozoic. Specifically, its extent decreased, its intensity weakened, and its warmest temperature position shifted from the Indian to western Pacific Ocean over time. The atmospheric CO2 dominated its extent and intensity, while paleogeography, by restricting the distribution of the Indian Ocean and the width of the tropical seaways, controlled the shift in its warmest temperature position. In particular, the eastward shift to the western Pacific Ocean from the middle to late Miocene inferred from compiled SST records likely resulted from the constriction of tropical seaways. Furthermore, by changing the atmospheric thermal structure and atmospheric circulation, the reduced extent and intensity of the IPWP decreased the annual precipitation in the western Indian Ocean, eastern Asia and Australia, while the shift in the warmest temperature position from the Indian to western Pacific Ocean promoted aridification in Australia. Qualitative model-data agreements are obtained for both the IPWP SST and regional climate. From the perspective of past warm climates with high concentrations of atmospheric CO2, the expansion and strengthening of the IPWP will occur in a warmer future and favor excessive precipitation in eastern Asia and Australia.

The Role of Non‐Local Effects on Surface Sensible Heat Flux Under Different Types of Thermal Structures Over the Arctic Sea‐Ice Surface

AbstractThe effects of atmospheric thermal structure on the surface energy flux are poorly understood over the Arctic sea‐ice surface. Here, we explore the mechanism of sensible heat exchange under different types of thermal structures over the Arctic sea‐ice surface by using data collected during the Multidisciplinary drifting Observatory for the Study of Arctic Climate expedition. The quadrant analysis indicates that strong surface temperature inversions below 100 m enhance non‐local effects on the positive (upward) sensible heat flux () through entrainment of large eddies from the convective boundary layer aloft. However, strong surface inversions restrict the contributions of large eddies to the negative (downward) due to intensified surface stability. By inspecting the existing parameterization schemes, we found that the European Center for Medium‐Range Weather Forecasts Integrated Forecasting System scheme fails to predict the impacts of non‐local processes on the positive , and an adjustment term to correct the bias of parameterized is proposed.

Potential Atmospheric Compositions of TRAPPIST-1 c Constrained by JWST/MIRI Observations at 15 μm

The first James Webb Space Telescope observations of TRAPPIST-1 c showed a secondary eclipse depth of 421 ± 94 ppm at 15 μm, which is consistent with a bare rock surface or a thin, O2-dominated, low-CO2 atmosphere. Here we further explore potential atmospheres for TRAPPIST-1 c by comparing the observed secondary eclipse depth to synthetic spectra of a broader range of plausible environments. To self-consistently incorporate the impact of photochemistry and atmospheric composition on atmospheric thermal structure and predicted eclipse depth, we use a two-column climate model coupled to a photochemical model and simulate O2-dominated, Venus-like, and steam atmospheres. We find that a broader suite of plausible atmospheric compositions are also consistent with the data. For lower-pressure atmospheres (0.1 bar), our O2–CO2 atmospheres produce eclipse depths within 1σ of the data, consistent with the modeling results of Zieba et al. However, for higher-pressure atmospheres, our models produce different temperature–pressure profiles and are less pessimistic, with 1–10 bar O2, 100 ppm CO2 models within 2.0σ–2.2σ of the measured secondary eclipse depth and up to 0.5% CO2 within 2.9σ. Venus-like atmospheres are still unlikely. For thin O2 atmospheres of 0.1 bar with a low abundance of CO2 (∼100 ppm), up to 10% water vapor can be present and still provide an eclipse depth within 1σ of the data. We compared the TRAPPIST-1 c data to modeled steam atmospheres of ≤3 bars, which are 1.7σ–1.8σ from the data and not conclusively ruled out. More data will be required to discriminate between possible atmospheres or more definitively support the bare rock hypothesis.

Three-Dimensional Distributions of the Direct Effect of anExtended and Intense Dust Aerosol Episode (16–18 June 2016) over the Mediterranean Basin on Regional Shortwave Radiation, Atmospheric Thermal Structure, and Dynamics

In the present study, we used the FORTH deterministic spectral Radiation Transfer Model (RTM) to estimate detailed three-dimensional distributions of the Direct Radiative Effects (DREs) and their consequent modification of the thermal structure of the regional atmosphere during an intense dust episode that took place from 16 to 18 June 2016 over the Mediterranean Basin (MB). The RTM operated on a 3-hourly temporal and 0.5 × 0.625° spatial resolution, using 3-D aerosol optical properties (i.e., aerosol optical depth, single scattering albedo, and asymmetry parameter) and other surface and atmospheric properties from the MERRA-2 reanalysis and cloud properties (i.e., cloud amount, cloud optical depth, and cloud top height) from the ISCCP-H dataset. The model ran with and without dust aerosols, yielding the upwelling and downwelling solar fluxes at the top of the atmosphere, in the atmosphere, and at the Earth’s surface as well as at 50 levels in the atmosphere. The dust direct radiative effect (DDRE) was estimated as the difference between the two (one taking into account all aerosol types and one taking into account all except for dust aerosols) flux outputs. The atmospheric heating rates and subsequent convection induced by dust radiative absorption were calculated at 50 levels to determine how the DDRE affects the thermal structure and dynamics of the atmosphere. The results showed that such a great and intense dust transport event significantly reduces the net surface solar radiation over the MB (by up to 62 W/m2 on a daily mean basis, and up to 200 W/m2 on an hourly basis, at 12:00 UTC) while increasing the atmospheric solar absorption (by up to 72 W/m2 daily and 187 W/m2 hourly, at 12:00 UTC). At the top of the atmosphere, both heating (over desert areas) and cooling (over oceanic and other continental areas) are observed due to the significantly different surface albedos. Transported dust causes considerable heating of the region’s atmosphere, which becomes maximum at altitudes where the dust loadings are highest (0.14 K/3 h on 17 June 2016, 12:00 UTC, at 3–5 km above sea level). The dust solar absorption and heating induce a buoyancy as strong as 0.014 m/s2, resulting in considerable changes in vertical air motions and possibly contributing to the formation of middle- and high-level clouds over the Mediterranean Basin.

Distinct features of mid-winter North Pacific storm track suppression associated with central and eastern Pacific El Niños

The North Pacific storm track (NPST) represents intense activity of synoptic-scale eddies that are important for Northern Hemisphere mid-latitude weather systems. According to the linear baroclinic instability theory, the strength of the NPST should peak in January and February but is substantially weaker than that in late fall and early spring, a phenomenon termed mid-winter suppression (MWS). This study investigates the characteristics of the MWS associated with central-Pacific (CP) and eastern-Pacific (EP) El Niños mainly based on composite analyses in the HadISSTv1.1 and ERA-5 datasets. It is found that over the southern North Pacific (NP; south of 40°N), the peak of the NPST delays until January and thus the MWS does not appear during CP El Niño as that in climatology. In contrast, a prominent MWS-like feature is identified in January over this region during EP El Niño. Over the northern NP (north of 40°N), the MWS is largely enhanced in January and February during CP El Niño. Quantitative diagnosis of eddy kinetic energy conversion further reveals that different features of the MWS are mainly caused by baroclinic conversion anomalies. The two types of El Niño may affect the NPST and MWS by modifying the atmospheric thermal structure and exciting cross-Pacific wave trains, which are associated with different convective anomalies.

Long-term variabilities in thermal structure, CO2 concentration and associated cooling rates in the Earth's middle atmosphere: Observations and model simulations

Enhanced anthropogenic activities in the recent decades are ensuing in the large-scale accumulation of carbon dioxide (CO2) concentration in the Earth's atmosphere. CO2 in the atmosphere induces warming in the troposphere and cooling in the middle atmosphere. A systematic analysis of the middle atmospheric thermal structure and its variability at decadal scale is need of the hour to perceive the consequences of increased anthropogenic activity in totality. In this regard, long-term variations of temperature, CO2 concentration and associated cooling rates in the middle and upper atmosphere (30–110 km) are investigated using Sounding of Atmosphere by Broadband Emission Radiometry (SABER) on board Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) satellite observations during 2002–2021 and Specified Dynamics-Whole Atmosphere Community Climate Model (SD-WACCM) simulations during 2002–2017 over 50 N–50 S latitudes. The results show that CO2 concentration measured by SABER is significantly underestimated by the WACCM simulations, especially above 90 km altitude. In order to find the long-term trends in each variable, Multivariate Linear Regression (MLR) technique is employed to the residual data obtained after removing seasonal variations. SABER observations show decreasing trend in temperature with a rate of 0.5–2.5 K/decade and an increase in CO2 vmr of 16–18 ppmv/decade. The effect of Solar Cycle, QBO and ENSO on each of the variables is also investigated. The significance of the present study lies in evaluating the SD-WACCM simulations of long-term variabilities in the thermal structure, CO2 vmr and associated cooling rates using two decades of observations.

Correction to: The climate and compositional variation of the highly eccentric planet HD 80606 b – the rise and fall of carbon monoxide and elemental sulfur

The gas giant HD 80606 b has a highly eccentric orbit (e $\sim$ 0.93). The variation due to the rapid shift of stellar irradiation provides a unique opportunity to probe the physical and chemical timescales and to study the interplay between climate dynamics and atmospheric chemistry. In this work, we present integrated models to study the atmospheric responses and the underlying physical and chemical mechanisms of HD 80606 b. We first run three-dimensional general circulation models (GCMs) to establish the atmospheric thermal and dynamical structures for different atmospheric metallicities and internal heat. Based on the GCM output, we then adopted a 1D time-dependent photochemical model to investigate the compositional variation along the eccentric orbit. The transition of the circulation patterns of HD 80606 b matched the dynamics regimes in previous works. Our photochemical models show that efficient vertical mixing leads to deep quench levels of the major carbon and nitrogen species and the quenching behavior does not change throughout the eccentric orbit. Instead, photolysis is the main driver of the time-dependent chemistry. While CH$_4$ dominates over CO through most of the orbits, a transient state of [CO]/[CH$_4$}] $>$ 1 after periastron is confirmed for all metallicity and internal heat cases. The upcoming JWST Cycle 1 GO program will be able to track this real-time CH$_4$--CO conversion and infer the chemical timescale. Furthermore, sulfur species initiated by sudden heating and photochemical forcing exhibit both short-term and long-term cycles, opening an interesting avenue for detecting sulfur on exoplanets.

Revealing the atmospheres of highly irradiated exoplanets: from ultra-hot Jupiters to rocky worlds

Spectroscopy of transiting exoplanets has revealed a wealth of information about their atmospheric compositions and thermal structures. In particular, studies of highly irradiated exoplanets at temperatures much higher than those found in our solar system have provided detailed information on planetary chemistry and physics because of the high level of precision which can be obtained from such observations. Here we use a variety of techniques to study the atmospheres of highly irradiated transiting exoplanets and address three large, open questions in exoplanet atmosphere spectroscopy. First, we use secondary eclipse and phase curve observations to investigate the thermal structures and heat redistribution of ultra-hot Jupiters, the hottest known exoplanets. We demonstrate how these planets form an unique class of objects influenced by high-temperature chemical effects such as molecular dissociation and H− opacity. Second, we use observations of helium in the upper atmosphere of the exo-Neptune HAT-P-11b to probe atmospheric escape processes. Third, we develop tools to interpret JWST observations of highly irradiated exoplanets, including a data analysis pipeline to perform eclipse mapping of hot Jupiters and a method to infer albedos of and detect atmospheres on hot, terrestrial planets. Finally, we discuss remaining open questions in the field of highly irradiated exoplanets and opportunities to advance our understanding of these unique bodies in the coming years.

The climate and compositional variation of the highly eccentric planet HD 80606 b – the rise and fall of carbon monoxide and elemental sulfur

ABSTRACTThe gas giant HD 80606 b has a highly eccentric orbit (e ∼ 0.93). The variation due to the rapid shift of stellar irradiation provides a unique opportunity to probe the physical and chemical timescales and to study the interplay between climate dynamics and atmospheric chemistry. In this work, we present integrated models to study the atmospheric responses and the underlying physical and chemical mechanisms of HD 80606 b. We first run 3D general circulation models (GCMs) to establish the atmospheric thermal and dynamical structures for different atmospheric metallicities and internal heat. Based on the GCM output, we then adopted a 1D time-dependent photochemical model to investigate the compositional variation along the eccentric orbit. The transition of the circulation patterns of HD 80606 b matched the dynamics regimes in previous works. Our photochemical models show that efficient vertical mixing leads to deep quench levels of the major carbon and nitrogen species and the quenching behaviour does not change throughout the eccentric orbit. Instead, photolysis is the main driver of the time-dependent chemistry. While CH4 dominates over CO through most of the orbits, a transient state of [CO]/[CH4] > 1 after periastron is confirmed for all metallicity and internal heat cases. The upcoming JWST Cycle 1 GO program will be able to track this real-time CH4–CO conversion and infer the chemical timescale. Furthermore, sulfur species initiated by sudden heating and photochemical forcing exhibit both short-term and long-term cycles, opening an interesting avenue for detecting sulfur on exoplanets.

The Effect of Interior Heat Flux on the Atmospheric Circulation of Hot and Ultra-hot Jupiters

Many hot and ultra-hot Jupiters have inflated radii, implying that their interiors retain significant entropy from formation. These hot interiors lead to an enhanced internal heat flux that impinges upon the atmosphere from below. In this work, we study the effect of this hot interior on the atmospheric circulation and thermal structure of hot and ultra-hot Jupiters. To do so, we incorporate the population-level predictions from evolutionary models of hot and ultra-hot Jupiters as input for a suite of general circulation models (GCMs) of their atmospheric circulation with varying semimajor axis and surface gravity. We conduct simulations with and without a hot interior, and find that there are significant local differences in temperature of up to hundreds of Kelvin and in wind speeds of hundreds of meters per second or more across the observable atmosphere. These differences persist throughout the parameter regime studied, and are dependent on surface gravity through the impact on photosphere pressure. These results imply that the internal evolution and atmospheric thermal structure and dynamics of hot and ultra-hot Jupiters are coupled. As a result, a joint approach including both evolutionary models and GCMs may be required to make robust predictions for the atmospheric circulation of hot and ultra-hot Jupiters.

Impact of Clouds and Blowing Snow on Surface and Atmospheric Boundary Layer Properties Over Dome C, Antarctica.

Clouds and blowing snow (BLSN) occur frequently over Antarctica, where it is critical to understand their feedbacks to surface and atmospheric boundary layer processes. Dome C, an elevated East Antarctic station, dominated by lengthy periods of surface longwave (LW) radiative cooling, is selected to reveal cloud and BLSN impacts within a largely stable environment. The sky condition is classified as clear, cloudy, or BLSN, using 3years of Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations satellite data. Co-located and contemporaneous in situ observations are used to investigate the relationship of sky condition with surface and atmospheric boundary layer thermal structure, focusing on seasonal variability. Results show that increased downwelling LW radiation from clouds abate surface radiative cooling losses, contributing to warming during all seasons. An increase of 3°C in the mean surface air temperature is observed during spring, whereas, a more dramatic rise (around 10°C), due to accompanying large-scale subsidence, is observed during fall and winter in association with clouds. For all seasons, the wind speed and wind speed shear are strongest during BLSN events, and the surface-based inversion is weakened by cooling which peaks in a shallow above-surface turbulent layer. The stronger background stability during fall and winter seasons, restricts turbulence and BLSN depths generally to the lowest tens of meters. The Earth's cryosphere is among the most rapidly evolving yet least well-observed regions, and knowledge of clouds and BLSN interactions with the typical stable atmospheric boundary layer can help further understand energy and moisture exchanges.

Thermal Structure of the Middle and Upper Atmosphere of Mars From ACS/TGO CO2Spectroscopy

AbstractTemperature and density in the upper Martian atmosphere, above ∼100 km, are key diagnostic parameters to study processes of the species' escape, investigate the impact of solar activity, model the atmospheric circulation, and plan spacecraft descent or aerobraking maneuvers. In this paper, we report vertical profiling of carbon dioxide (CO2) density and temperature from the Atmospheric Chemistry Suite (ACS) solar occultations onboard the ExoMars Trace Gas Orbiter. A strong CO2absorption band near 2.7 μm observed by the middle infrared spectrometric channel (ACS MIR) allows the retrieval of the atmospheric thermal structure in an unprecedentedly large altitude range, from 20 to 180 km. We present the latitudinal and seasonal climatology of the thermal structure for 1.5 Martian years (MYs), from the middle of MY 34 to the end of MY 35. The results show the variability of distinct atmospheric layers, such as a mesopause (derived from 70 to 145 km) and homopause, changing from 90 to 100 km at aphelion to 120–130 km at perihelion. Some short‐term homopause fluctuations are also observed depending on the dust activity.

Martian Atmospheric Thermal Structure and Dust Distribution During the MY 34 Global Dust Storm From ACS TIRVIM Nadir Observations

AbstractThe Thermal InfraRed channel in honor of professor Vassili Ivanovich Moroz (TIRVIM) of the Atmospheric Chemistry Suite onboard ExoMars Trace Gas Orbiter has continuously monitored the Martian atmosphere from 13 March 2018 until 2 December 2019, covering almost a complete Martian Year (MY). In the nadir mode of observations, infrared spectra obtained by TIRVIM in the spectral range 600–1,300 cm−1 permit retrievals of vertical temperature profiles from the surface up to 60 km of altitude, surface temperatures and column aerosol optical depths. Here we report the retrieved atmospheric thermal structure and the column dust content during the global dust storm (GDS) of MY 34 monitored from Ls = 182.2° to Ls = 211.8° (Solar Longitude), capturing the evolution of the GDS and the response of the atmospheric thermal structure to the changing dust loading. The global storm caused asymmetric atmosphere heating, predominantly in the southern hemisphere, and changed diurnal contrast of atmospheric thermal structure. We also observe a reduced diurnal contrast of surface temperatures at the peak of the GDS.

Effects of black carbon aerosol on air quality and vertical meteorological factors in early summer in Beijing

Black carbon (BC) aerosols have effects on the atmospheric thermal vertical structure due to its radiation absorption characteristics, hereby influencing the boundary layer characteristics and pollutant diffusion. This study focuses on the BC effects under different atmospheric conditions on air quality and vertical meteorological conditions. Four days flight observation combined with surface wind profiler radar data were used to investigate the vertical profiles of BC and wind speed over Beijing urban area in early summer. The vertical profiles of BC concentration and wind speed in the boundary layer had a negative correlation, both having abrupt changes near the boundary layer height under stagnant weather conditions. The chemical transport model showed the increase of BC under stagnant conditions could cause aggravation of the stability of the boundary layer, thereby increasing the accumulation of pollutants. In particular, BC leads to the changes in the temperature profile, which will modify relative humidity and indirectly lead to the changes in the vertical profile of aerosol optical properties. However, if the early accumulation of BC was absent under more turbulent conditions, the effects of BC on air quality and meteorological conditions were limited.

Evaluation of FY-4A Temperature Profile Products and Application to Winter Precipitation Type Diagnosis in Southern China

FY-4A GIIRS temperature profile products have provided unprecedented information for studying the atmospheric characteristics of thermal structures since 2020. The main objective of this paper is to evaluate GIIRS temperature profile products by using radiosonde observations and then apply them to the diagnosis of winter precipitation types in southern China. GIIRS temperature profile products for four types (clear sky perfect quality, cloudy sky perfect quality, cloudy sky good quality and cloudy sky bad quality) show different performances. Relatively, the cloud can affect the quality and quantity of GIIRS products. At different pressure levels, the perfect flagged data under the clear or cloudy sky show the best agreement with radiosonde observations, yielding the highest Pearson correlation coefficient and lowest mean bias as well as root mean square error. The good flagged data have a slight deviation from the perfect data. The impact on the quantity of the GIIRS temperature data is greater than that on the quality with an increase in cloud top height. A case investigation was carried out to analyze the performance of GIIRS temperature profiles for the diagnosis of precipitation types in a winter storm of 2022. The GIIRS temperature profiles represent the reasonable atmospheric thermal structures in the rain and snow in Hubei and Hunan provinces. The GIIRS temperature below 700 hPa is an important indictor to precipitation type diagnosis. Furthermore, two critical thresholds for GIIRS temperatures, which are below −2 °C at 850 hPa and below 0 °C at 925 hPa, respectively, are proposed for the occurrence of snowfall in this winter storm. In addition, the distribution of GIIRS temperature at different pressure levels is consistent with radiosonde observations in a freezing rain event in Guiyang, all of which show the warm rain mechanism by combining the cloud top information.