The Spectral Dimension of Arctic Outgoing Longwave Radiation and Greenhouse Efficiency Trends From 2003 to 2016

Fourteen years of spectral fluxes derived from collocated Atmospheric Infrared Sounder (AIRS) and Clouds and the Earth’s Radiant Energy System (CERES) observations are used in conjunction with AIRS retrievals to examine the trends of zonal mean spectral outgoing longwave radiation (OLR) and greenhouse efficiency (GHE) in the Arctic. AIRS retrieved profiles are fed into a radiative transfer model to generate synthetic clear‐sky spectral OLR. Trends are derived from the simulated clear‐sky spectral OLR and GHE and then compared with their counterparts derived from collocated observations. Spectral trends in different seasons are distinctively different. March and September exhibit positive trends in spectral OLR over the far‐IR dirty window and mid‐IR window region for most of the Arctic. In contrast, spectral OLR trends in July are negative over the far‐IR dirty window and can be positive or negative in the mid‐IR window depending on the latitude. Sensitivity studies reveal that surface temperature contributes much more than atmospheric temperature and humidity to the spectral OLR and GHE trends, while the contributions from the latter two are also discernible over many spectral regions (e.g., trends in the far‐IR dirty window in March). The largest increase of spectral GHE is seen north of 80°N in March across the water vapor v2 band and far‐IR. When the secular fractional change of spectral OLR is less than that of surface spectral emission, an increase of spectral GHE can be expected. Spectral trend analyses reveal more information than broadband trend analyses alone.Key PointsObserved Arctic zonal mean trends of spectral flux and greenhouse efficiency are studied for the first timeSpectral trends are seasonally dependent and reveal more information than broadband trendsChanges in surface temperature contribute the most to overall spectral trends, but changes due to air temperature and humidity trends are discerniblePeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151304/1/jgrd55648_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151304/2/jgrd55648.pd

Determination of characteristic turbulence length scales from large-eddy simulation of the convective planetary boundary layer

Turbulente Austauschprozesse in der atmosphärischen Grenzschicht spielen eine Schlüsselrolle beim vertikalen Impuls-, Energie- und Stofftransport in der Erdatmosphäre. In meso- und globalskaligen Atmosphärenmodellen sind turbulente Austauschprozesse jedoch subskalig und müssen unter Verwendung geeigneter Schliessungsansätze parametrisiert werden. Hierbei spielt die Spezifikation der charakteristischen Turbulenzlängenskala in Abhängigkeit vom Stabilitätszustand der Atmosphäre eine entscheidende Rolle. Gegenwärtig verwendete Ansätze, die auf der Verwendung der turbulenten Mischungslänge für neutrale Schichtung sowie dimensionsloser Stabilitätsfunktionen basieren, zeigen vor allem Defizite im oberen Bereich der konvektiven Grenzschicht sowie in der Entrainmentzone, wo starke vertikale Gradienten auftreten. In der vorliegenden Arbeit wurden hochaufgelöste dreidimensionale Grobstruktursimulationen der trockenen und feuchten Grenzschicht für ein weites Spektrum von Labilitätsbedingungen durchgeführt. Erste und zweite Momente atmosphärischer Strömungsvariablen wurden aus den simulierten hydro- und thermodynamischen Feldern berechnet und diskutiert. Die Spektraleigenschaften turbulenter Fluktuationen der Strömungsvariablen, das raumzeitliche Verhalten kohärenter Strukturen sowie charakteristische Turbulenzlängenskalen wurden abgeleitet. Eine Verifizierung der charakteristischen Turbulenzlängenskalen erfolgte durch Vergleich mit Ergebnissen früherer numerischer Simulationen, mit Turbulenzmessungen in der atmosphärischen Grenzschicht sowie mit Laborexperimenten. Mit Hilfe der nichtlinearen Datenmodellierung wurden leicht verwendbare Approximationen der charakteristischen Turbulenzlängenskalen abgeleitet und deren statistische Signifikanz diskutiert. Unter Verwendung dieser Approximationen wurde ein existierendes Parametrisierungsmodell revidiert und mit Hilfe von Grobstruktursimulationen verifiziert. Desweiteren wurde der Einfluß der turbulenten Mischungslänge auf die Prognose mesokaliger Felder untersucht. Hierzu wurde mit dem Lokal-Modell des Deutschen Wetterdienstes eine entsprechende Sensitivitätsstudie durchgeführt. Anhand von Satellitendaten und Analysedaten aus der 4D-Datenassimilation wurden die Simulationsergebnisse verifiziert

Evaluating Volatile Induced Surface Features on Vesta and Ceres

This work evaluates volatile induced surface features on Vesta and Ceres, two of the largest asteroids present within the asteroid belt. Both the planetary objects have similar surface acceleration but different regolith nature. Vesta is a relatively dry body whereas Ceres is rich with water ice. Direct measurement of volatiles is challenging due to harsh space conditions. However, when they are mixed with regolith, it produces peculiar landforms due to melting and/or sublimation and affects the overall evolution of a planetary body. Therefore, in this study the surface features which have direct or indirect link to ice and/or volatiles are examined in order to understand the volatile distribution. For this, regional and global scale investigations related to ponded deposits, pit chains and mass wasting analysis were conducted on Vesta and Ceres. In the vicinity of Marcia and Cornelia impact craters of Vesta, two types of pond deposits were observed. Type 1 melt ponds have smooth, shallow deposits (depth <100 m) and are produced from the downslope movement of volatile bearing impact melt material. In contrast, type 2 dust ponds deposit consist of rough surface with ~200 m depth. These deposits are produced from the mobility of granular dust via infrequent high-amplitude seismic diffusivity and/or short-lived volatile outgassing activity. Due to low amounts of volatiles, the dusty material did not achieve kinetic sieving and thus do not attain typical smooth pond morphology. The findings of this study strongly support the hypothesis related to presence of low amounts of volatiles within Vesta’s regolith. To understand the volatile distribution on Ceres, the analysis of pit chains is carried out within three impact craters namely; Occator, Azacca and Urvara. Radial pit chain pattern of Occator is related to subsurface laccolith swelling of volatile rich cryomagmatic material. Linear pit chain clusters at floors of Azacca and Urvara are attributed to seasonal thermal contraction of ice layer present near the surface. Additionally, based on the pit chains depth the depicted average minimum thickness of regolith within Azacca, located at equator is ~200 m. On the contrary, within Occator and Urvara, the localized thickness is 30 m and 800 m, respectively, which is attributed to their distinct subsurface condition. Hence, this investigation favors the presence of ice layer within the subsurface layer and reveals that it is not distributed homogeneously on Ceres. Lastly, the global scale comparative examination of the mass wasting process on Vesta and Ceres shows few common and some distinct characteristics. In general, granular sliding on Vesta and flow-like movements on Ceres are observed as dominant population. Further, slides and slumping features are restricted to mid-latitudes on Ceres which implies ice-rock fractionation at regional scale. Additionally, the volatile concentration also influences the deposit mobility on Vesta and Ceres and is analyzed by estimating height, width and effective coefficient of friction; H/L. The outcome suggests that deposits become immobile at shorter distances on Vesta in comparison to Ceres (avg. distance 4.5 km and 11.2 km, respectively). The difference in morphology and mobility is related to contrast in the amounts of volatiles present within regolith of both the bodies. While comparing the effective coefficient of friction of Vesta and Ceres with planetary objects in outer solar system, the examination shows that lower temperature may have more influence on mobility. Together, all the above-mentioned studies summarize the volatile induced surface landforms and provide evidences related to their distribution on Vesta and Ceres. This work also presents the first-time comparative investigation that reveals the influence of volatile content on the morphological characteristics of Vesta and Ceres

Deciphering Surfaces of Trans-Neptunian and Kuiper Belt Objects using Radiative Scattering Models, Machine Learning, and Laboratory Experiments

Decoding surface-atmospheric interactions and volatile transport mechanisms on trans-Neptunian objects (TNOs) and Kuiper Belt objects (KBOs) involves an in-depth understanding of physical and thermal properties and spatial distribution of surface constituents – nitrogen (N2), methane (CH4), carbon monoxide (CO), and water (H2O) ices. This thesis implements a combination of radiative scattering models, machine learning techniques, and laboratory experiments to investigate the uncertainties in grain size estimation of ices, the spatial distribution of surface compositions on Pluto, and the thermal properties of volatiles found on TNOs and KBOs. Radiative scattering models (Mie theory and Hapke approximations) were used to compare single scattering albedos of N2, CH4, and H2O ices from their optical constants at near-infrared wavelengths (1 – 5 µm). Based on the results of Chapters 2 and 3, this thesis recommends using the Mie model for unknown spectra of outer solar system bodies in estimating grain sizes of surface ices. When using an approximation for radiative transfer models (RTMs), we recommend using the Hapke slab approximation model over the internal scattering model. In Chapter 4, this thesis utilizes near-infrared (NIR) spectral observations of the LEISA/Ralph instrument onboard NASA’s New Horizons spacecraft. Hyperspectral LEISA data were used to map the geographic distribution of ices on Pluto’s surface by implementing the principal component reduced Gaussian mixture model (PC-GMM), an unsupervised machine learning technique. The distribution of ices reveals a latitudinal pattern with distinct surface compositions of volatiles. The PC-GMM method was able to recognize local-scale variations in surface compositions of geological features. The mapped distribution of surface units and their compositions are consistent with existing literature and help in an improved understanding of the volatile transport mechanism on the dwarf planet. In Chapter 5, we propose a method to estimate thermal conductivity, volumetric heat capacity, thermal diffusivity, and thermal inertia of N2, CH4, and CO ices, and mixtures thereof in a simulated laboratory setting at temperatures of 20 to 60 K – relevant to TNOs and KBOs. A new laboratory experimental facility – named the Outer Solar System Astrophysics Lab (OSSAL) – was built to implement the proposed method. This thesis provides detailed technical specifications of that laboratory with an emphasis on facilitating the design of similar cryogenic facilities in the future. Thus, this research was able to incorporate a set of methods, tools, and techniques for an improved understanding of ices found in the Kuiper Belt and to decipher surface-atmospheric interactions and volatile transport mechanisms on planetary bodies in the outer solar system

Deciphering Surfaces of Trans-Neptunian and Kuiper Belt Objects using Radiative Scattering Models, Machine Learning, and Laboratory Experiments

Decoding surface-atmospheric interactions and volatile transport mechanisms on trans-Neptunian objects (TNOs) and Kuiper Belt objects (KBOs) involves an in-depth understanding of physical and thermal properties and spatial distribution of surface constituents – nitrogen (N2), methane (CH4), carbon monoxide (CO), and water (H2O) ices. This thesis implements a combination of radiative scattering models, machine learning techniques, and laboratory experiments to investigate the uncertainties in grain size estimation of ices, the spatial distribution of surface compositions on Pluto, and the thermal properties of volatiles found on TNOs and KBOs. Radiative scattering models (Mie theory and Hapke approximations) were used to compare single scattering albedos of N2, CH4, and H2O ices from their optical constants at near-infrared wavelengths (1 – 5 µm). Based on the results of Chapters 2 and 3, this thesis recommends using the Mie model for unknown spectra of outer solar system bodies in estimating grain sizes of surface ices. When using an approximation for radiative transfer models (RTMs), we recommend using the Hapke slab approximation model over the internal scattering model. In Chapter 4, this thesis utilizes near-infrared (NIR) spectral observations of the LEISA/Ralph instrument onboard NASA’s New Horizons spacecraft. Hyperspectral LEISA data were used to map the geographic distribution of ices on Pluto’s surface by implementing the principal component reduced Gaussian mixture model (PC-GMM), an unsupervised machine learning technique. The distribution of ices reveals a latitudinal pattern with distinct surface compositions of volatiles. The PC-GMM method was able to recognize local-scale variations in surface compositions of geological features. The mapped distribution of surface units and their compositions are consistent with existing literature and help in an improved understanding of the volatile transport mechanism on the dwarf planet. In Chapter 5, we propose a method to estimate thermal conductivity, volumetric heat capacity, thermal diffusivity, and thermal inertia of N2, CH4, and CO ices, and mixtures thereof in a simulated laboratory setting at temperatures of 20 to 60 K – relevant to TNOs and KBOs. A new laboratory experimental facility – named the Outer Solar System Astrophysics Lab (OSSAL) – was built to implement the proposed method. This thesis provides detailed technical specifications of that laboratory with an emphasis on facilitating the design of similar cryogenic facilities in the future. Thus, this research was able to incorporate a set of methods, tools, and techniques for an improved understanding of ices found in the Kuiper Belt and to decipher surface-atmospheric interactions and volatile transport mechanisms on planetary bodies in the outer solar system

Goce precise non-gravitational force modeling for POD applications

GOCE was launched in 2009 at 250 km altitude to recover Earth’s static gravity field. As part of the GOCE-Italy project, we carried out the precise modeling for the radiation pressure and the aerodynamic effects on this satellite. This analysis has been performed to reduce the mismodeling of the non-gravitational forces, in order to be able to estimate the ocean tides parameters from the LEO satellites orbital perturbation. A new software ARPA (Aerodynamics and Radiation Pressure Analysis), which takes advantage of the raytracing technique, has been designed and developed to accurately model the non-gravitational perturbations. ARPA can compute the Solar Radiation Pressure (SRP), Earth Radiation Pressure (ERP), the spacecraft Thermal Re-Radiation (TRR) and the aerodynamic forces and torques acting on any satellite with a high level of accuracy. The adopted methodologies and procedure are presented in this thesis, and the results of the tests on GOCE are illustrated and discussed. The NAPEOS (NAvigation Package for Earth Observation Satellites) software, developed and maintained at ESA/ESOC, was upgraded to make use of the new ARPA inputs and adopted to perform the tests on GOCE. The tests were performed on 30 consecutive daily arcs, starting at the beginning of the GOCE science phase on 1st November 2009. The results for the radiation test cases show a significant reduction of the empirical accelerations, especially in the cross-track direction, of about the 20% for the SRP, 12% for the ERP albedo, 13% for the ERP infrared and 20% for the TRR with respect to the standard NAPEOS force modeling (cannon-ball). For the aerodynamics, an important reduction of the post-fit RMS from 7.6 to 7.3 mm has been observed with the new ARPA model, and the a reduction from 4.6 to 4.2 cm of the distance of the orbits computed with ARPA from the official reduced-dynamics GOCE orbits (Precise Science Orbit) has been computed. The obtained results confirm the goodness of the modeling and techniques of ARPA for all the non-gravitational perturbations computed for GOCE. Even though the results are presented for the GOCE satellite, the new technique and software are adaptable to satellite of any shape, whether in Earth-bound orbit, or orbiting another planet, or cruising in interplanetary space

Ceres water regime: surface temperature, water sublimation and transient exo(atmo)sphere

Recent observations of water emission around Ceres suggest the presence of an ice layer on or beneath the surface of this asteroid. Several mechanisms have been suggested to explain these plumes, among which cometary-like sublimation seems to be plausible, since there is a correlation between the magnitude of the emission and the change in the heliocentric distance along the orbit. In this work, we applied a comet sublimation model to study the plausible scenarios that match with Herschel observations of the water flux (1026 molecules s-1). Each scenario is characterized by a well-defined set of physical and orbital parameters. Moreover, a study of the dynamic evolution of the H2O plume has been performed, showing that an optically thin transient atmospheric envelope, with a typical timescale of some tens of days, can be maintained by the H2O surface emission. Our simulations could be useful theoretical support for the Dawn NASA mission by giving a better understanding of the physical conditions for water sublimation and ice stability

Planetary Geological Science and Aerospace Systems Engineering Applications of Thermal Infrared Remote Sensing for Earth, Mars, and the Outer Bodies

abstract: Many planetary science missions study thermophysical properties of surfaces using infrared spectrometers and infrared cameras. Thermal inertia is a frequently derived thermophysical property that quantifies the ability for heat to exchange through planetary surfaces. To conceptualize thermal inertia, the diffusion equation analogies are extended using a general effusivity term: the square root of a product of conductivity and capacity terms. A hypothetical thermal inductance was investigated for diurnal planetary heating. The hyperbolic heat diffusion equation was solved to derive an augmented thermal inertia. The hypothetical thermal inductance was modeled with negligible effect on Mars. Extending spectral performance of infrared cameras was desired for colder bodies in the outer solar system where peak infrared emission is at longer wavelengths. The far-infrared response of an infrared microbolometer array with a retrofitted diamond window was determined using an OSIRIS-REx—OTES interferometer. An instrument response function of the diamond interferometer-microbolometer system shows extended peak performance from 15 µm out to 20 µm and 40% performance to at least 30 µm. The results are folded into E-THEMIS for the NASA flagship mission: Europa Clipper. Infrared camera systems are desired for the expanding smallsat community that can inherit risk and relax performance requirements. The Thermal-camera for Exploration, Science, and Imaging Spacecraft (THESIS) was developed for the Prox-1 microsat mission. THESIS, incorporating 2001 Mars Odyssey—THEMIS experience, consists of an infrared camera, a visible camera, and an instrument computer. THESIS was planned to provide images for demonstrating autonomous proximity operations between two spacecraft, verifying deployment of the Planetary Society’s LightSail-B, and conducting remote sensing of Earth. Prox-1—THESIS was selected as the finalist for the competed University Nanosatellite Program-7 and was awarded a launch on the maiden commercial SpaceX Falcon Heavy. THESIS captures 8-12 µm IR images with 100 mm optics and RGB color images with 25 mm optics. The instrument computer was capable of instrument commanding, automatic data processing, image storage, and telemetry recording. The completed THESIS has a mass of 2.04 kg, a combined volume of 3U, and uses 7W of power. THESIS was designed, fabricated, integrated, and tested in ASU’s 100K clean lab.Dissertation/ThesisDoctoral Dissertation Geological Sciences 201