Tropospheric Radiation Research Articles

Beyond Runaway: Initiation of the Post-runaway Greenhouse State on Rocky Exoplanets

Abstract The runaway greenhouse represents the ultimate climate catastrophe for rocky, Earth-like worlds: when the incoming stellar flux cannot be balanced by radiation to space, the oceans evaporate and exacerbate heating, turning the planet into a hot wasteland with a steam atmosphere overlying a possibly molten magma surface. The equilibrium state beyond the runaway greenhouse instellation limit depends on the radiative properties of the atmosphere and its temperature structure. Here, we use 1D radiative-convective models of steam atmospheres to explore the transition from the tropospheric radiation limit to the post-runaway climate state. To facilitate eventual simulations with 3D global circulation models, a computationally efficient band-gray model is developed, which is capable of reproducing the key features of the more comprehensive calculations. We analyze two factors that determine the equilibrated surface temperature of post-runaway planets. The infrared cooling of the planet is strongly enhanced by the penetration of the dry adiabat into the optically thin upper regions of the atmosphere. In addition, thermal emission of both shortwave and near-IR fluxes from the hot lower atmospheric layers, which can radiate through window regions of the spectrum, is quantified. Astronomical surveys of rocky exoplanets in the runaway greenhouse state may discriminate these features using multiwavelength observations.

Anthropogenic Photolabile Chlorine in the Cold-Climate City of Montreal

Chlorine atoms play a key role in the oxidative potential of the atmosphere and biogeochemical cycling of selected elements. This study provides a decadal analysis (2010−2019) of chloride ions in PM2.5 particles in the city of Montreal, where these are most concentrated systematically in the winter (up to 1.6 µg/m3). We also herein present the measurement of photolabile chlorine, which includes chlorine-containing compounds (e.g., Cl2, HOCl, ClNO2, ClNO3, and BrCl) that release chlorine atoms upon interaction with radiation, in urban Montreal, Canada using Cl2-RPGE (Cl2 Reactive Phase Gas Extraction) tubes and quantifying the chlorinated product by GC-MS. Photolabile chlorine in urban Montreal was measured during a discontinuous period primarily in summer 2018 and winter 2019 with a time resolution of 30 min, with concentrations ranging from 3 to 545 ng/m3 expressed as Cl2. The reported values are considered lower limits, as compounds such as HOCl and ClNO2 can only be partially converted in the current setup. The largest peak of gaseous photolabile chlorine occurred in the winter, when significant sources of anthropogenic salt are used in snow removal in the city. This coincides with observed chloride ion measurements in airborne particles, implying that anthropogenic salt addition produces photoactive chlorine. The maximum chlorine signal was consistently obtained during the daytime, which is in accordance with the tropospheric radiation profile. Complementary photochemistry laboratory experiments indicated that upon tropospheric radiation (340 ≤ λ ≤ 400 nm; UVA), an increase (20–100%) was observed, confirming the formation of Cl atoms from photolabile chlorine compounds. Thus, this portable technique is adequate for Cl atoms and photolabile chlorine-containing compounds upon photolysis using UVA lamps. High-resolution S/TEM and energy-dispersive X-ray spectroscopy (EDS) were used to evaluate collected particle morphology and composition. The behavior of complementary pollutants (O3, CO, PM2.5, and NOx) was also briefly discussed. We herein discuss the measurement of photolabile halogens within a northern urban metropolitan environment and the impact of anthropogenic sources on chlorine concentrations.

Biofuel blending reduces particle emissions from aircraft engines at cruise conditions.

Aviation-related aerosol emissions contribute to the formation of contrail cirrus clouds that can alter upper tropospheric radiation and water budgets, and therefore climate. The magnitude of air-traffic-related aerosol-cloud interactions and the ways in which these interactions might change in the future remain uncertain. Modelling studies of the present and future effects of aviation on climate require detailed information about the number of aerosol particles emitted per kilogram of fuel burned and the microphysical properties of those aerosols that are relevant for cloud formation. However, previous observational data at cruise altitudes are sparse for engines burning conventional fuels, and no data have previously been reported for biofuel use in-flight. Here we report observations from research aircraft that sampled the exhaust of engines onboard a NASA DC-8 aircraft as they burned conventional Jet A fuel and a 50:50 (by volume) blend of Jet A fuel and a biofuel derived from Camelina oil. We show that, compared to using conventional fuels, biofuel blending reduces particle number and mass emissions immediately behind the aircraft by 50 to 70 per cent. Our observations quantify the impact of biofuel blending on aerosol emissions at cruise conditions and provide key microphysical parameters, which will be useful to assess the potential of biofuel use in aviation as a viable strategy to mitigate climate change.

Improved modeling of cloudy‐sky actinic flux using satellite cloud retrievals

AbstractClouds play a critical role in modulating tropospheric radiation and thus photochemistry. We develop a methodology for calculating the vertical distribution of tropospheric ultraviolet (300–420 nm) actinic fluxes using satellite cloud retrievals and a radiative transfer model. We demonstrate that our approach can accurately reproduce airborne‐measured actinic fluxes from the 2013 Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) campaign as a case study. The results show that the actinic flux is reduced below moderately thick clouds with increasing cloud optical depth and can be enhanced by a factor of 2 above clouds. Inside clouds, the actinic flux can be enhanced by up to 2.4 times in the upper part of clouds or reduced up to 10 times in the lower parts of clouds. Our study suggests that the use of satellite‐derived actinic fluxes as input to chemistry‐transport models can improve the accuracy of photochemistry calculations.

Acid-Base and Photoinduced Processes on Magnesium-Containing Minerals and their Influence on the Troposphere Cleaning

Acid-base, adsorption and photosorption properties of microparticles surface of magnesium-containing compounds produced by dispersion of natural minerals after exposure to the air were studied. It was revealed that the reduction in predominant basicity of minerals surface in a range of periclase (MgO), brucite (Mg (OH)2) and magnesite (MgCO3) can be considered as a result of the presence of iron, silicon and magnesium oxide compounds. Quantum-chemical calculations made during the investigation, the decrease of pressure in the process of long-term contact of Freon 22 with the surface of MgO, irreversible character of adsorption and the absence of fluorine and chlorine-containing products in a gaseous phase give evidence of CFC destructive adsorption on the surface of magnesium oxide. The interaction of chlorine and fluorine derivatives of methane with the surface of aerosol particles from minerals in the darkness and under the influence of sunlight tropospheric radiation was studied. The evaluation of such interactions influence on the process of the Earth troposphere purification from carbon dioxide and dichlorofluoromethane during their adsorption and photosorption on the surface of precipitated aerosol was made.

Seventh Annual NOAA-Industry Space Weather Summit Meets

The Seventh Annual NOAA Space Weather Prediction Center (SWPC)/Commercial Space Weather Interest Group (CSWIG)/American Commercial Space Weather Association (ACSWA) Summit was held on Tuesday 16 April 2013 during the Space Weather Workshop. Government personnel and commercial space weather representatives attended in person and by telecom, and many were participating for the first time. The ACSWA (http://www.acswa.us/) Executive Committee [Dr. Geoff Crowley (Atmospheric and Space Technology Research Associates, ASTRA), Dr. Devrie Intriligator (Carmel Research Center, CRC), Dr. Robert Schunk (Space Environment Corporation, SEC), and Dr. Kent Tobiska (Space Environment Technologies, SET)] was in attendance. Dr. Devrie Intriligator and Mr. Brent Gordon, Acting Director of SWPC, welcomed the group. Mr. Gordon reported that the National Weather Service (NWS) continues its search for a permanent SWPC Director. There have been two unsuccessful hiring attempts since January 2012, and there is currently a NOAA-wide hiring freeze. The SWPC forecast office is using the WSA (Wang Sheeley Arge)–Enlil modeling system in their daily operations andhas introduced twonewproducts: a plain language forecast and a technical discussion report. Both are available fromSWPC’s Product Subscription Service (http://pss.swpc. noaa.gov). The forecast office is also working closely with NASA/Community Coordinated Modeling Center on its recommendation for a Geospace model to transition into operations at SWPC. SWPC has also made progress on the Whole Atmosphere Model/Integrated Dynamics through Earth’s Atmosphere model. The budget at SWPC continues to be a serious concern. Due to sequestration and other cuts, SWPC is facing a major reduction in its operating budget for fiscal year 13. SWPC faces serious reductions to its modeling efforts that could set them back several years on the planned implementation dates. The Deep Space Climate Observatory (DSCOVR) project, the follow-on L1 spacecraft to ACE, continues to move toward its planned November 2014 launch date. NOAA will move the ground data processing from the National Environmental Satellite, Data, and Information Service to SWPC, i.e., the same ground configuration as used for ACE data recovery. Mr. Gordon reported that the Sunjammer solar sail mission would be comanifested with the DSCOVR launch. Sunjammer will attempt to reach a stable point approximately twice the distance of L1 from Earth. The UK is collaborating on the project by providing two space weather instruments for the mission, a magnetometer and a plasma detector. These data will not be available in real time to SWPC and its customers. Mr. Gordon also reported on the NOAA Small Business Innovation and Research (SBIR) program. A SBIR Phase II award was given to Propagation Research Associates, Inc., to continue their work on detecting and nowcasting ionosphere scintillation. A new SBIR Phase I award was given to NorthWest Research Associates for “Delivering a Solar Flare Forecast Model that Improves Flare Forecast (Timing and Magnitude) Accuracy by 25%.” Mr. David Bouwer (SET) reported on the operational use of the DOC/NOAA/NWS External Space Weather Data Store (E-SWDS) server and recommended new and future E-SWDS capabilities such as WSA-Enlil and GOES Extreme Ultraviolet sensor data access. Dr. Intriligator reiterated the commercial space weather community needs for long-term, stable space-based and ground-based space weather data, including GOES; coronagraph; solar irradiance; neutron monitor; and magnetospheric, ionospheric, and tropospheric radiation. Dr. Schunk discussed the importance of the government complementing its current space weather capabilities through commercial data buys and buys of services. A lively discussion ensued on potential data and services buys from commercial companies. A sentiment was expressed ©2013. American Geophysical Union. All Rights Reserved. 1542-7390/13/10.1002/swe.20101

Dosimetry of cosmic radiation in the troposphere based on the measurements at the summit of Mt. Fuji

Abstract Dose rate of cosmic-ray origin neutrons (abbreviated to “cosmic neutrons”) at aviation altitude was estimated based on the measurements at Mt. Fuji. Cosmic neutrons were measured in a facility of the Mt. Fuji Weather Station located at the summit of Mt. Fuji, the highest mountain in Japan (3776 m in altitude), in the summer of 2008 and 2009. The average of 1 cm ambient dose equivalent H*(10) for two measurements was verified by numerical model simulation and then used to empirically estimate the solar force field potential (FFP). The H*(10) rates at aviation altitude estimated from the measurements at Mt. Fuji were compared to those obtained in in-flight measurements onboard a civilian aircraft flying near Mt. Fuji at the time between the two measurements at the mountain. According to the results obtained, we expect that the empirical estimation based on the measurements at Mt. Fuji will work effectively for dosimetry of cosmic radiation in troposphere.

Photochemical properties of powdered titanium dioxide produced from monocrystal rutile under ambient air

It is shown that the photochemical activity of titanium dioxide is significantly higher under the action of solar tropospheric radiation when it is not produced by the traditional way, but from the rutile monocrystal. The magnitudes and spectral dependences of the quantum yield of oxygen photoadsorption and carbon dioxide photodesorption for the titanium dioxide produced from a monocrystal are determined. A mechanism of a sharp increase of the titanium dioxide photoadsorption activity in the oxide surface absorption range is proposed.

Infrared radiative transfer modelling in a 3D scattering cloudy atmosphere: Application to limb sounding measurements of cirrus

The Monte Carlo cloud scattering forward model (McClouds_FM) has been developed to simulate limb radiative transfer in the presence of cirrus clouds, for the purposes of simulating cloud contaminated measurements made by an infrared limb sounding instrument, e.g. the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). A reverse method three-dimensional Monte Carlo transfer model is combined with a line-by-line model for radiative transfer through the non-cloudy atmosphere to explicitly account for the effects of multiple scattering by the clouds. The ice cloud microphysics are characterised by a size distribution of randomly oriented ice crystals, with the single scattering properties of the distribution determined by accurate calculations accounting for non-spherical habit. A comparison of McClouds_FM simulations and real MIPAS spectra of cirrus shows good agreement. Of particular interest are several noticeable spectral features (i.e. H 2 O absorption lines) in the data that are replicated in the simulations: these can only be explained by upwelling tropospheric radiation scattered into the line-of-sight by the cloud ice particles.

Evidence of scattering of tropospheric radiation by PSCs in mid‐IR limb emission spectra: MIPAS‐B observations and KOPRA simulations

Polar stratospheric clouds (PSCs) were observed by the high resolution mid infrared Michelson Interferometer for Passive Atmospheric Sounding, Balloon borne version (MIPAS‐B), on a flight from Kiruna/Sweden on January 11, 2001. Highly resolved spectral features in the limb measurements could only be explained by tropospheric radiation scattered into the line of sight by large PSC particles. Furthermore, model calculations showed that for PSCs with particles of radius ≥1 μm, a significant part of the broadband continuum radiance signal is due to scattering. Inclusion of scattering in the retrieval process resulted in reasonable values of otherwise largely overestimated PSC volume density profiles.

Methane and Nitrous Oxide: Their Effects on the Terrestrial Climate

Abstract Simplified band models are developed for methane (CH4) and nitrous oxide (N2O) bands in the longwave radiation spectrum. The band models are then employed in a radiation model to calculate the seasonally and latitudinally varying contributions of CH4, and N2O to the radiative energy balance of the earth-troposphere system. From the energy balance calculations, it is concluded that the longwave opacity (i.e., the so-called “greenhouse effect”) due to present-day observed concentrations of CH4. and N2O contribute nearly 2 K to hemispherical mean surface temperature with possible larger contributions to polar surface temperatures. The paper also discusses stratospheric effects of CH4 and N2O and examines the sensitivity of tropospheric radiation energy balance to large increases in CH4 and N2O.

The Role of Stratospheric Ozone in the Zonal and Seasonal Radiative Energy Balance of the Earth-Troposphere System

The role of ozone in the tropospheric-surface energy balance is discussed in the context of its latitudinally and seasonally varying modulation of solar and longwave energy fluxes. We analyze in detail the various radiative energy inputs to the stratosphere and the radiative fluxes from the stratosphere to the troposphere. To a very close approximation, on an annual and hemispherical mean, longwave emission from the stratosphere balances the absorbed radiant energy. The stratosphere absorbs about twice as much longwave radiation from the troposphere as it does solar radiation. About 20% of the longwave flux from the stratosphere to the troposphere is directly due to O2. A change in O3 concentrations perturbs the stratospheric and tropospheric-surface energy balances through a number of distinct mechanisms involving changes in solar and longwave fluxes and which are separated into direct effects due to the change of O3 and indirect effects due to the accompanying change of stratospheric temperature. The relative importance of average versus spatial varying changes in ozone is examined. We confirm the result of past analyses that, for a uniform change in ozone, the global average perturbation in radiative fluxes to the troposphere and surface is small since the perturbations in solar and infrared fluxes nearly cancel. However, this result probably severely underestimates the contribution of changes in the distribution of ozone to global climate. First, there generally are significant latitudinal and seasonal variations in the perturbation radiative fluxes to the troposphere. Second, vertical redistribution of Oe can produce larger perturbation fluxes to the troposphere than do uniform changes, and possibly of opposite sign. Third, most of the perturbation solar heating is deposited at or near the earth's surface, whereas much of the perturbation longwave fluxes are deposited in the upper troposphere with consequences for changes in the tropospheric lapse rates. Thus, it is difficult to evaluate the changes in tropospheric radiation needed to determine a change of climate due to a change of O3. Not even the net global average perturbation radiative fluxes to the troposphere can be calculated without knowing the change of the vertical ozone profile, and the vertical and latitudinal variations of the troposphere-surface perturbation heating rates are likely to be more important for climate change than the net global values.

AMTEX期間中における対流圏放射収支に及ぼす雲の影響

Radiative budgets of the troposphere are highly dependent on cloud conditions present. Thus, estimates of quantities for these budgets taken from climatological studies are not applicable to specific cases of cyclone development and/or strong air mass modification.A radiative scheme, using cloud information obtained from the operational Three Dimensional Nephanalysis (3DNEPH) Model of the U.S. Air Force Global Weather Central, has been developed to study radiative transfer during different synoptic conditions during the Air-Mass Transformation Experiment (AMTEX).Comparisons of calculated downward irradiance components with measured values indicate that the model provides acceptable results when the cloud data, which are spatial averages, are representative of the location where the model is applied.Effect of clouds on tropospheric radiation budgets, and time and spatial variations of atmospheric radiation budget components over the AMTEX region are discussed.

Computations of the tropospheric radiation budget in the Caribbean and Gulf of Mexico area for clear sky conditions

Computations of solar heating and infrared cooling for clear sky conditions in the area of the Central American Seas are presented, as based on conventional radiosondes in 1960. Results are discussed with regard to latitude mean data available in the literature.