Atmospheric Thermal Inversions Research Articles

Flight delays due to air pollution in China

Using a newly-compiled dataset of airport traffic, air pollution, and weather from 2015 to 2017, we evaluate the effect of PM2.5 pollution levels on flight departure delays in China. We instrument for PM2.5 levels using changes in atmospheric thermal inversions and wind direction. We find that a one-standard-deviation increase in the daily PM2.5 concentration levels leads to roughly 4.5–6.4 additional minutes in departure delays per flight. We estimate that reductions in China's PM2.5 pollution levels due to the Air Pollution Prevention and Control Action Plan avoided 13–18% of the increases in national average flight delays and saved US $54 to $69 million in passenger time in 2017 alone.

Atmospheric characterization of the ultra-hot Jupiter WASP-33b

Ultra-hot Jupiters are highly irradiated gas giant exoplanets on close-in orbits around their host stars. The dayside atmospheres of these objects strongly emit thermal radiation due to their elevated temperatures, making them prime targets for characterization by emission spectroscopy. We analyzed high-resolution spectra from CARMENES, HARPS-N, and ESPaDOnS taken over eight observation nights to study the emission spectrum of WASP-33b and draw conclusions about its atmosphere. By applying the cross-correlation technique, we detected the spectral signatures of Ti i, V i, and a tentative signal of Ti ii for the first time via emission spectroscopy. These detections are an important finding because of the fundamental role of Ti- and V-bearing species in the planetary energy balance. Moreover, we assessed and confirm the presence of OH, Fe i, and Si i from previous studies. The spectral lines are all detected in emission, which unambiguously proves the presence of an inverted temperature profile in the planetary atmosphere. By performing retrievals on the emission lines of all the detected species, we determined a relatively weak atmospheric thermal inversion extending from approximately 3400 to 4000 K. We infer a supersolar metallicity close to 1.5 dex in the planetary atmosphere, and find that its emission signature undergoes significant line broadening with a Gaussian full width at half maximum of about 4.5 km s−1. Also, we find that the atmospheric temperature profile retrieved at orbital phases far from the secondary eclipse is about 300 to 700 K cooler than that measured close to the secondary eclipse, which is consistent with different day- and nightside temperatures. Moreover, retrievals performed on the emission lines of the individual chemical species lead to consistent results, which gives additional confidence to our retrieval method. Increasing the number of species included in the retrieval and expanding the set of retrieved atmospheric parameters will further advance our understanding of exoplanet atmospheres.

Assessment of Individual-Level Exposure to Airborne Particulate Matter during Periods of Atmospheric Thermal Inversion.

Air pollution exposure is harmful to human health and reducing it at the level of an individual requires measurements and assessments that capture the spatiotemporal variability of different microenvironments and the influence of specific activities. In this paper, activity-specific and general indoor and outdoor exposure during and after a period of high concentrations of particulate matter (PM), e.g., an atmospheric thermal inversion (ATI) in the Ljubljana subalpine basin, Slovenia, was assessed. To this end, personal particulate matter monitors (PPM) were used, worn by participants of the H2020 ICARUS sampling campaigns in spring 2019 who also recorded their hourly activities. ATI period(s) were determined based on data collected from two meteorological stations managed by the Slovenian Environmental Agency (SEA). Results showed that indoor and outdoor exposure to PM was significantly higher during the ATI period, and that the difference between mean indoor and outdoor exposure to PM was much higher during the ATI period (23.0 µg/m3) than after (6.5 µg/m3). Indoor activities generally were associated with smaller differences, with cooking and cleaning even having higher values in the post-ATI period. On the other hand, all outdoor activities had higher PM values during the ATI than after, with larger differences, mostly >30.0 µg/m3. Overall, this work demonstrated that an individual-level approach can provide better spatiotemporal resolution and evaluate the relative importance of specific high-exposure events, and in this way provide an ancillary tool for exposure assessments.

Air pollution and political trust in local government: Evidence from China

While it is well-established that air pollution damages health and inhibits productivity, the political cost of air pollution remains poorly understood. We estimate the causal effect of air pollution on political trust in local government in China, which underpins the stability of the authoritarian state. Combining a nationally representative longitudinal survey with satellite derived PM2.5 concentrations, we find that a one μg/m³ exogenous increase in PM2.5 concentrations, due to atmospheric thermal inversion, reduces trust in local government by 4.1 per cent of one standard deviation. This implies that if China were to reduce PM2.5 emissions to the annual standard of 35 μg/m³ mandated by the Chinese government, this would boost trust in local government by 21.2 per cent evaluated at the mean. We examine the underlying transmission channels and find that prolonged exposure to PM2.5 lowers citizens’ life satisfaction and evaluation of local government performance, induces adverse health effects, imposes additional financial burden and, albeit to a lesser extent, reduces household income.

ARES I: WASP-76 b, A Tale of Two HST Spectra*

Abstract We analyze the transmission and emission spectra of the ultra-hot Jupiter WASP-76 b, observed with the G141 grism of the Hubble Space Telescope’s (HST) Wide Field Camera 3 (WFC3). We reduce and fit the raw data for each observation using the open-source software Iraclis before performing a fully Bayesian retrieval using the publicly available analysis suite TauREx 3. Previous studies of the WFC3 transmission spectra of WASP-76 b found hints of titanium oxide (TiO) and vanadium oxide (VO) or non-gray clouds. Accounting for a fainter stellar companion to WASP-76, we reanalyze this data and show that removing the effects of this background star changes the slope of the spectrum, resulting in these visible absorbers no longer being detected, eliminating the need for a non-gray cloud model to adequately fit the data but maintaining the strong water feature previously seen. However, our analysis of the emission spectrum suggests the presence of TiO and an atmospheric thermal inversion, along with a significant amount of water. Given the brightness of the host star and the size of the atmospheric features, WASP-76 b is an excellent target for further characterization with HST, or with future facilities, to better understand the nature of its atmosphere, to confirm the presence of TiO and to search for other optical absorbers.

Neutral Iron Emission Lines from the Dayside of KELT-9b: The GAPS Program with HARPS-N at TNG XX

Abstract We present the first detection of atomic emission lines from the atmosphere of an exoplanet. We detect neutral iron lines from the dayside of KELT-9b (T eq ∼ 4000 K). We combined thousands of spectrally resolved lines observed during one night with the HARPS-N spectrograph (R ∼ 115,000), mounted at the Telescopio Nazionale Galileo. We introduce a novel statistical approach to extract the planetary parameters from the binary mask cross-correlation analysis. We also adapt the concept of contribution function to the context of high spectral resolution observations, to identify the location in the planetary atmosphere where the detected emission originates. The average planetary line profile intersected by a stellar G2 binary mask was found in emission with a contrast of 84 ± 14 ppm relative to the planetary plus stellar continuum (40% ± 5% relative to the planetary continuum only). This result unambiguously indicates the presence of an atmospheric thermal inversion. Finally, assuming a modeled temperature profile previously published, we show that an iron abundance consistent with a few times the stellar value explains the data well. In this scenario, the iron emission originates at the 10−3–10−5 bar level.

An emission spectrum for WASP-121b measured across the 0.8–1.1 μm wavelength range using the Hubble Space Telescope

Abstract WASP-121b is a transiting gas giant exoplanet orbiting close to its Roche limit, with an inflated radius nearly double that of Jupiter and a dayside temperature comparable to a late M dwarf photosphere. Secondary eclipse observations covering the 1.1–$1.6\, \mu{\rm m}$ wavelength range have revealed an atmospheric thermal inversion on the dayside hemisphere, likely caused by high-altitude absorption at optical wavelengths. Here we present secondary eclipse observations made with the Hubble Space Telescope Wide Field Camera 3 spectrograph that extend the wavelength coverage from $1.1\, \mu{\rm m}$ down to $0.8\, \mu{\rm m}$. To determine the atmospheric properties from the measured eclipse spectrum, we performed a retrieval analysis assuming chemical equilibrium, with the effects of thermal dissociation and ionization included. Our best-fitting model provides a good fit to the data with reduced $\chi ^2_\nu =1.04$. The data diverge from a blackbody spectrum and instead exhibit emission due to H− shortward of $1.1\, \mu{\rm m}$. The best-fitting model does not reproduce a previously reported bump in the spectrum at $1.25\,\mu{\rm m}$, possibly indicating this feature is a statistical fluctuation in the data rather than a VO emission band as had been tentatively suggested. We estimate an atmospheric metallicity of $[{\rm M}/{\rm H}]= {1.09}_{-0.69}^{+0.57}$, and fit for the carbon and oxygen abundances separately, obtaining $[{\rm C}/{\rm H}]= {-0.29}_{-0.48}^{+0.61}$ and $[{\rm O}/{\rm H}]= {0.18}_{-0.60}^{+0.64}$. The corresponding carbon-to-oxygen ratio is ${\rm C/O} = 0.49_{-0.37}^{+0.65}$, which encompasses the solar value of 0.54, but has a large uncertainty.

NO THERMAL INVERSION AND A SOLAR WATER ABUNDANCE FOR THE HOT JUPITER HD 209458B FROM HST/WFC3 SPECTROSCOPY

ABSTRACT The nature of the thermal structure of hot Jupiter atmospheres is one of the key questions raised by the characterization of transiting exoplanets over the past decade. There have been claims that many hot Jupiters exhibit atmospheric thermal inversions. However, these claims have been based on broadband photometry rather than the unambiguous identification of emission features with spectroscopy, and the chemical species that could cause the thermal inversions by absorbing stellar irradiation at high altitudes have not been identified despite extensive theoretical and observational effort. Here we present high-precision Hubble Space Telescope WFC3 observations of the dayside thermal emission spectrum of the hot Jupiter HD 209458b, which was the first exoplanet suggested to have a thermal inversion. In contrast to previous results for this planet, our observations detect water in absorption at 6.2σ confidence. When combined with Spitzer photometry, the data are indicative of a monotonically decreasing temperature with pressure over the range of 1–0.001 bars at 7.7σ confidence. We test the robustness of our results by exploring a variety of model assumptions, including the temperature profile parameterization, presence of a cloud, and choice of Spitzer data reduction. We also introduce a new analysis method to determine the elemental abundances from the spectrally retrieved mixing ratios with thermochemical self-consistency and find plausible abundances consistent with solar metallicity (0.06–10 × solar) and carbon-to-oxygen ratios less than unity. This work suggests that high-precision spectrophotometric results are required to robustly infer thermal structures and compositions of extrasolar planet atmospheres and to perform comparative exoplanetology.

Evidence against a strong thermal inversion in HD 209458b from high-dispersion spectroscopy

Broadband secondary-eclipse measurements of hot Jupiters have indicated the existence of atmospheric thermal inversions, but their presence is difficult to determine from broadband measurements because of degeneracies between molecular abundances and temperature structure. We apply high-resolution (R = 100 000) infrared spectroscopy to probe the temperature-pressure profile of HD 209458 b. This bright, transiting hot-Jupiter has long been considered the gold standard for a hot Jupiter with an inversion layer, but this has been challenged in recent publications. We observed the thermal dayside emission of HD 209458 b with CRIRES / VLT during three nights, targeting the carbon monoxide band at 2.3 microns. Thermal inversions give rise to emission features, which means that detecting emission lines in the planetary spectrum, as opposed to absorption lines, would be direct evidence of a region in which the temperature increases with altitude. We do not detect any significant absorption or emission of CO in the dayside spectrum of HD 209458 b, although cross-correlation with template spectra either with CO absorption lines or with weak emission at the core of the lines show a low-significance correlation signal with a signal-to-noise ratio of 3 - 3.5. Models with strong CO emission lines show a weak anti-correlation with similar or lower significance levels. Furthermore, we found no evidence of absorption or emission from H2O at these wavelengths. The non-detection of CO in the dayside spectrum of HD 209458 b is interesting in light of a previous CO detection in the transmission spectrum. That there is no signal indicates that HD 209458 b either has a nearly isothermal atmosphere or that the signal is heavily muted. Assuming a clear atmosphere, we can rule out a full-disc dayside inversion layer in the pressure range 1 bar to 1 mbar.

NEW ANALYSIS INDICATES NO THERMAL INVERSION IN THE ATMOSPHERE OF HD 209458b

An important focus of exoplanet research is the determination of the atmospheric temperature structure of strongly irradiated gas giant planets, or hot Jupiters. HD 209458b is the prototypical exoplanet for atmospheric thermal inversions, but this assertion does not take into account recently obtained data or newer data reduction techniques. We re-examine this claim by investigating all publicly available Spitzer Space Telescope secondary-eclipse photometric data of HD 209458b and performing a self-consistent analysis. We employ data reduction techniques that minimize stellar centroid variations, apply sophisticated models to known Spitzer systematics, and account for time-correlated noise in the data. We derive new secondary-eclipse depths of 0.119 +/- 0.007%, 0.123 +/- 0.006%, 0.134 +/- 0.035%, and 0.215 +/- 0.008% in the 3.6, 4.5, 5.8, and 8.0 micron bandpasses, respectively. We feed these results into a Bayesian atmospheric retrieval analysis and determine that it is unnecessary to invoke a thermal inversion to explain our secondary-eclipse depths. The data are well-fitted by a temperature model that decreases monotonically between pressure levels of 1 and 0.01 bars. We conclude that there is no evidence for a thermal inversion in the atmosphere of HD 209458b.

Radon progeny in hydrometeors at the earth's surface

During atmospheric thermal inversions, dew and hoarfrost concentrate gamma emitting radionuclides of the short-lived (222)Rn progeny ((214)Pb and (214)Bi), causing an increase in the total natural gamma background from the ground. To highlight this phenomenon, a volcanic zone of high (222)Rn flux was studied during the winter season 2010-11. High-specific short-lived radon progeny activities up to 122 Bq g(-1) were detected in hydrometeors forming at the earth's surface (ESHs), corresponding to a mean increase of up to 17 % of the normal gamma background value. A theoretical model, depending on radon flux from soil and predicting the radon progeny concentrations in hydrometeors forming at the ESHs is presented. The comparison between model and field data shows a good correspondence. Around nuclear power plants or in nuclear facilities that use automatic NaI or CsI total gamma spectroscopy systems for monitoring radioactive contamination, hydrometeors forming at the ESHs in sites with a high radon flux could represent a relevant source of false alarms of radioactive contamination.

Effects of public health interventions on industrial emissions and ambient air in Cartagena, Spain

Background, aim, and scope Ten years of public health interventions on industrial emissions to clean air were monitored for the Mediterranean city of Cartagena. During the 1960s, a number of large chemical and non-ferrous metallurgical factories were established that significantly deteriorated the city’s air quality. By the 1970s, the average annual air concentration of sulfur dioxide (SO2) ranged from 200 to 300 µg/m3 (standard conditions units). In 1979, the Spanish government implemented an industrial intervention plan to improve the performance of factories and industrial air pollution surveillance. Unplanned urban development led to residential housing being located adjacent to three major factories. Factory A produced lead, factory B processed zinc from ore concentrates, and factory C produced sulfuric acid and phosphates. This, in combination with the particular abrupt topography and frequent atmospheric thermal inversions, resulted in the worsening of air quality and heightening concern for public health. In 1990, the City Council authorized the immediate intervention at these factories to reduce or shut down production if ambient levels of SO2 or total suspended particles (TSP) exceeded a time-emission threshold in pre-established meteorological contexts. The aim of this research was to assess the appropriateness and effectiveness of the intervention plan implemented from 1992 to 2001 to abate industrial air pollution.

Biodirected mutagenic chemical assay of PM 10 extractable organic matter in Southwest Mexico City

The concentration of breathable particles (PM 10) in urban areas has been associated with increases in morbidity and mortality of the exposed populations, therein the importance of this study. Organic compounds adsorbed to PM 10 are related to the increased risk to human health. Although some studies have shown the lack of correlation between specific mutagenic compounds in an organic complex mixture (OCM) and the mutagenic response in several bioassays, the same organic compounds selectively separated in less complex groups can show higher or lower mutagenic responses than in the OCM. In this study, we fractionated the OCM, from the PM 10 in four organic fractions of increasing polarity (F1–F4). The Salmonella bioassay with plate incorporation was applied for each one using TA98, with and without S9 (mammalian metabolic activation), and YG1021 (without S9) strains. The most polar fraction (F4) contained the greatest mass followed by F1 (non-polar), F2 and F3 (moderately polar). The concentrations of the OCM as well as the F4 were the only variables correlated with PM 10, atmospheric thermal inversions, fire-prone area, NO 2, SO 2, CO, rain and relative humidity. This indicated that polar organic compounds were originated in gas precursors formed during the atmospheric thermal inversions as well as the product of the incomplete combustion of vehicular exhausts and of burned vegetation. The percentages of the total PAH, and the individual PAH with molecular weight ≥ 228 g mol −1 (except retene) correlated with the percentages of indirect-acting mutagenicity in TA98 + S9. The percentages of the total nitro-PAH and most of the analyzed individual nitro-PAH correlated with percentages of the direct-acting mutagenicity in both TA98 − S9 and YG1021, the latter being more sensitive. In general, the highest mutagenic activity (indirect and direct) was found in F3 (moderately polar) and in F4 (polar). The non-polar fraction (F1) did not exhibit any kind of mutagenicity. In 77% of the cases, mutagenic activity was higher in the sum fractions with respect to their OCM. The combinations between F1, F2 and F4, with F3 under different or equal proportions suggested that mutagenicity reduction, in the combined matter of January (with TA98 + S9 and YG1021) and of May (with YG1021), was due to concentrations of mutagens and non-mutagens in each fraction, and not to an antimutagenic effect. The organic compounds present in the non-polar fractions showed no antagonism, inhibition or reduction in the most mutagenic fractions in both indirect- and direct-acting mutagenicity, and the less polar organic compounds in F3 reduced mutagenicity in F4, in both months.

Epidemiological characteristics of Legionella infection in South Australia: implications for disease control

About one third of adults surveyed in South Australia have shown evidence of past silent infection with Legionella pneumophila serogroup 1. However, the annual notification rate for symptomatic disease is only about 0.5 per 100,000 residents in non-epidemic years. The male to female ratio is 2.5 to one and approximately 50% of the cases are at least 60 years of age. Cases have presented more in summer and in the metropolitan areas. Twenty cases of Legionnaires' disease occurred during the summer of 1985-86. A cooling tower was held to be the principal source with aerosols being dispersed up to three kilometers away during an atmospheric thermal inversion. A subsequent outbreak of 22 L. longbeachae serogroup 1 infections had no marked geographic clustering. The outbreak commenced in spring and cases were distinguished as active gardeners. L. longbeachae was found in garden soil and it is hypothesised that this soil inhabitant can become aerosolised and inhaled during gardening. The potential for primary prevention of Legionnaires' disease is discussed in relation to water-handling equipment and the need for early precautionary treatment of all community-acquired pneumonia as suspect Legionnaires' disease is emphasised.

Inhalable urban atmospheric particulate matter in a semi-arid climate: The case of Santiago De Chile

The city of Santiago is characterized by low average rainfall and atmospheric thermal inversion layers. Air pollution levels are high. Dichotomous sampling of inhalable particulate matter (IPM) has been conducted at a fixed station on the Universidad de Santiago de Chile (USACH) campus from October 1981 to March 1983. The air sampling inlet cutoff was 15 μm, the fractioning cut being located at a 2.5 μm aerodynamic diameter. The samples were analyzed qualitatively by X-ray fluorescence (XRF) spectrometry. Information on the IPM component of urban air pollution in Santiago by particle sizing sampling methods was not previously available, nor had XRF spectrometry been applied to local IPM samples. A multivariate statistical analysis of the body of data comprising sample masses and XRF elemental intensities is presented and discussed. The group of elements Al, Si, K, Ca, Ti and Fe shows strong statistical correlations in the coarse particle fraction; correlations in the fine particle fraction include Br/Pb. Evidence for seasonal variations in the air pollution pattern is presented. Pollution by sulfur is discussed.

Variations in oceanic net long-wave radiation caused by atmospheric thermal structure

Observations of clear sky net long-wave radiation at sites off Oregon and off northwest Africa were compared with vertical profiles of air temperature. Atmospheric thermal inversions appeared to reduce the net long-wave radiation by at least 0.02 cal cm−2 min−1. If empirical formulas are used to estimate the irradiance, account should be taken of this effect in regions with persistent inversions.