Planetary Surface Research Articles

High pCO2 Reduces Sensitivity to CO2 Perturbations on Temperate, Earth-like Planets Throughout Most of Habitable Zone.

The nearly logarithmic radiative impact of CO2 means that planets near the outer edge of the liquid water habitable zone (HZ) require ∼106 × more CO2 to maintain temperatures that are conducive to standing liquid water on the planetary surface than their counterparts near the inner edge. This logarithmic radiative response also means that atmospheric CO2 changes of a given mass will have smaller temperature effects on higher pCO2 planets. Ocean pH is linked to atmospheric pCO2 through seawater carbonate speciation and calcium carbonate dissolution/precipitation, and the response of pH to changes in pCO2 also decreases at higher initial pCO2. Here, we use idealized climate and ocean chemistry models to demonstrate that CO2 perturbations large enough to cause catastrophic changes to surface temperature and ocean pH on temperate, low-pCO2 planets in the innermost region of the HZ are likely to have much smaller effects on planets with higher pCO2, as may be the case for terrestrial planets with active carbonate-silicate cycles receiving less instellation than the Earth. Major bouts of extraterrestrial fossil fuel combustion or volcanic CO2 outgassing on high-pCO2 planets in the mid-to-outer HZ should have mild or negligible impacts on surface temperature and ocean pH. Owing to low pCO2, Phanerozoic Earth's surface environment may be unusually volatile compared with similar planets receiving lower instellation.

Abiotic methane generation through reduction of serpentinite-hosted dolomite: Implications for carbon mobility in subduction zones

Abiotic methane has been increasingly detected at the surface of Earth and other terrestrial planets, exerting a strong effect on the study of chemolithoautotrophic life and thus astrobiology. In contrast, abiotic methane generation in subduction zones, which is intimately linked to questions such as the mechanisms of deep carbon mobility, has received scarce attention. Experiments elucidated the significant production of abiotic methane through reduction of carbonate minerals under subduction zone conditions, whereas detailed geological conditions and processes for the reduction in natural rocks are hitherto poorly understood. Here, we report carbonate reduction and genesis of abiotic methane in dolomitized serpentinites (referred to as ophidolomites) from a fossil subduction zone (SW Tianshan, China). Detailed petrological, Raman spectroscopic, strontium and carbon isotopic, and thermodynamic results provide evidence for dolomite reduction into the phase assemblage of calcite + brucite + methane, likely associated with retrograde serpentinization starting at 7–9 kbar and 410–430 °C in the subduction zone. Microthermometric data for dolomite-hosted fluid inclusions are consistent with petrographic observations, indicative of fluid entrapment postdating the onset of dolomite reduction during exhumation. Model calculations suggest that water-rich fluids characterized by relatively high hydrogen fugacities can create favorable conditions for the reduction process, which, however, do not exclude the possibility of carbonate methanation by hydrogen-rich fluids as reported in previous studies. The widespread occurrence of methane in these rocks gives credence to the intricate redox transformations of subducted carbon, implying that the elevated hydrogen fugacities may facilitate abiotic synthesis of methane through dolomite reduction at convergent plate boundaries. Our work shows that alteration of dolomite-bearing lithologies represents a potential source for abiotic methane in subduction zones, which may have implications for the transfer of subducted carbon.

Imaging Mars analog minerals' reflectance spectra and testing mineral detection algorithms

Mineral mapping of a planetary surface is of prime importance to better understanding its composition and constraining its geologic evolution. Visible-to-Near-Infrared (VNIR) hyperspectral remote sensing is the primary tool to detect the composition of the martian surface at high spatial resolution. However, it is not straightforward to validate the mapping results since mineralogical groundtruth is typically unavailable. Furthermore, determining whether common approaches used to decode terrestrial VNIR data are applicable to Mars requires rigorous evaluation. In this work, we collected a suite of laboratory hyperspectral images with groundtruth, consisting of binary mixtures of Mars Global Simulant (MGS-1) and various hydrous minerals. The spectral effects of mixing MGS-1 with hydrous minerals were analyzed through conventional spectral parameters. It is observed that MGS-1 substantially reduces the spectral contrast of hydrous minerals. We then conducted a systematic comparison of seven benchmark target detection algorithms on the laboratory datasets, including Constrained Energy Minimization, Adaptive Coherence Estimator, Matched filter, Hierarchical Constrained Energy Minimization, Sparse Representation for Target Detection, Joint Sparse Representation and Multi-task Learning method, and Multi-task Joint Sparse and low-rank Representation (MTJSLR) method. Extensive experiments demonstrate that MTJSLR outperforms other competitors in successfully detecting low modal abundance hydrous minerals. The detection limits for nontronite, montmorillonite, kaolinite, gypsum, and calcite are 2.5%, 2.5%, 1%, 5%, and 5%, respectively. Carbonates are more challenging to detect than phyllosilicates even at the same abundance, which could partially contribute to the relative paucity of observed carbonates on Mars relative to phyllosilicates.

In Situ Geochronology for the Next Decade: Mission Designs for the Moon, Mars, and Vesta

Abstract Geochronology is an indispensable tool for reconstructing the geologic history of planets, essential to understanding the formation and evolution of our solar system. Bombardment chronology bounds models of solar system dynamics, as well as the timing of volatile, organic, and siderophile element delivery. Absolute ages of magmatic products provide constraints on the dynamics of magma oceans and crustal formation, as well as the longevity and evolution of interior heat engines and distinct mantle/crustal source regions. Absolute dating also relates habitability markers to the timescale of evolution of life on Earth. However, the number of terrains important to date on worlds of the inner solar system far exceeds our ability to conduct sample return from all of them. In preparation for the upcoming Decadal Survey, our team formulated a set of medium-class (New Frontiers) mission concepts to three different locations (the Moon, Mars, and Vesta) where sites that record solar system bombardment, magmatism, and habitability are uniquely preserved and accessible. We developed a notional payload to directly date planetary surfaces, consisting of two instruments capable of measuring radiometric ages, an imaging spectrometer, optical cameras to provide site geologic context and sample characterization, a trace-element analyzer to augment sample contextualization, and a sample acquisition and handling system. Landers carrying this payload to the Moon, Mars, and Vesta would likely fit into the New Frontiers cost cap in our study (∼$1B). A mission of this type would provide crucial constraints on planetary history while also enabling a broad suite of complementary investigations.

Enhanced Lunar Topographic Mapping Using Multiple Stereo Images Taken by Yutu-2 Rover with Changing Illumination Conditions

In a planetary-rover exploration mission, stereovision-based 3D reconstruction has been widely applied to topographic mapping of the planetary surface using stereo cameras onboard the rover. In this study, we propose an enhanced topographic mapping method based on multiple stereo images taken at the same rover location with changing illumination conditions. Key steps of the method include dense matching of stereo images, 3D point-cloud generation, point-cloud co-registration, and fusion. The final point cloud has more complete coverage and more details of the terrain than that conventionally generated from a single stereo pair. The effectiveness of the proposed method is verified by experiments using the Yutu-2 rover, in which two data sets were acquired by the navigation cameras at two locations and under changing illumination conditions. This method, which does not involve complex operations, has great potential for application in planetary-rover and lander missions.

Science and exploration of the moon enabled by surface telerobotics

Tele-operated rovers have been a feature of space exploration for decades. Ground control teams that operate these rovers generally comprise a robot operations team supported by science and robot engineering groups. But, in the future, astronauts will also remotely operate rovers. Several studies have proposed that astronauts should be able to control rovers from orbiting spacecraft such as the Deep Space Gateway (DSG). This concept of operations offers several benefits to human exploration. Firstly, it will enable astronauts to expand their sphere of influence beyond the confines of a spacecraft. Secondly, it will enable astronauts to safely perform surface work via an avatar. Thirdly, it will reduce the expenditure of life support consumables, and fourthly, it will spare astronauts from spending time on radiation-ravaged planetary surfaces. But integrating tele-operated rovers into human space exploration raises important questions. What system configurations are effective? Which modes of operation and control are most appropriate? When is it appropriate to rely (or not) on tele-operated rovers? The proposed research sought to answer the first two of these questions. It was designed to simulate three mission phases: pre-mission planning, site survey, and surface asset deployment. The study employed a derived terrain model located in the Lunares hab facility (located in Pila, Poland). Operators drove a Turtle rover through task sequences to survey sites while avoiding hazards/obstacles. This study simulated remote rover operations that assessed crew workload, crew situation awareness, robot asset acquisition, task sequence success, system issues, and rover performance. This study demonstrated basic competence in teleoperated rover driving, but more work must be conducted to produce a system that can behave reliably over many weeks and/or kilometers. Results indicated interactive monitoring is an effective strategy for crew-centric surface telerobotics. Safeguarded driving using this mode of operation enabled participants to perform each task successfully – success being measured by the metric of completing assigned tasks and completing the course. Participants maintained good situational awareness (SA) with low effort using interactive visualization of the rover state. From post-test debriefs it was determined participants maintained a high level of SA during operations and that the activity employed via the operator interface was a contributing factor to achieving these high levels. Since the test sessions were designed to be increasingly difficult in terms of task complexity it was expected that SA would decrease and task loading would increase across tasks and the data confirms this was the case.

Boulders on Mercury

Boulders on the surfaces of planets, satellites and small bodies, as well as their geological associations, provide important information about surface processes. We analyzed all available images of the surface of Mercury that have sufficient resolution and quality to detect boulders, and we mapped all the boulders observed. The lower size limit of detectable boulders was ~5 m. All boulders found on Mercury are associated with fresh impact craters hundreds of meters in diameter or larger. We compared boulder population on Mercury with population of boulders of the same size on the Moon, and found that boulders on Mercury are ~30 times less abundant than in the lunar highlands. This exact quantitative estimate is inherently inaccurate due to the limitation in the source data; however, the significant relative rarity of boulders on Mercury can be firmly and reliably established. We discuss possible causes of the observed difference. Higher thermal stresses and more rapid material fatigue due to diurnal temperature cycling on Mercury may cause rapid disintegration of the upper decimeters of the boulder surface and thus contribute to more rapid boulder obliteration; however, these factors alone cannot account for the observed difference. A proposed thicker regolith on Mercury is likely to significantly reduce boulder production rate. A higher micrometeoritic flux on Mercury is likely to result in micrometeoritic abrasion being a dominant contributor to boulder degradation; this high abrasion rate likely shortens the boulder lifetime. A combination of these factors appears to be able to account for the relative rarity of boulders on Mercury.

A new laboratory emissivity and reflectance spectral library for the interpretation of Mars thermal infrared spectral data

New spectral orbital thermal infrared data of Mars are being acquired by the thermal infrared channel TIRVIM (in honor of Vassily Ivanovich Moroz) of the Atmospheric Chemistry Suite (ACS) of spectrometers on board of ExoMars2016 mission. TIRVIM encompasses the spectral range of 1.7–17 μm. A major challenge brought by the analysis of these data of planetary bodies with atmospheres is the ability to extract from the data the relevant information about the surface. Thus, laboratory work plays an essential role, providing end-member and mixture spectral data of planetary analogs to fit the orbital data by means of deconvolution techniques. At the Planetary Spectroscopy Laboratory (PSL) of the German Aerospace Center (DLR), we are performing new laboratory experiments on Martian analogs in order to provide a new and updated library of spectra optimized for the interpretation of TIRVIM data. Emissivity measurements, recorded at increasing temperatures, are coupled with reflectance measurements on fresh and thermally processed samples acquired between 1.7 and 17 μm. Building on measurements previously collected on Martian analogues, we have paid particular attention to the study of the spectral behaviour of mixtures of carbonates and phyllosilicates. The main goal of this analysis is to study the variation of the main carbonate spectral features in mixtures with a phyllosilicate component, an important factor for understanding the story of carbonates detections on planetary surfaces and to provide insights for new detections. The results obtained in this work show that the presence of a phyllosilicate component affect the appearance of the carbonate spectral features in the spectral range studied, with a stronger effect in the range between 1.7 and 5 μm. Effects of mineral type and particle size are also investigated and shown to strongly affect the spectral behaviour of laboratory samples. Finally, deconvolution techniques of laboratory emissivity spectra are studied in preparation for the interpretation of atmospherically corrected TIRVIM spectral data, showing that modelled mixtures spectra represent an acceptable reproduction of laboratory spectra of mixtures.

Ozone-Depleting Substances, Economic Growth, and Energy Consumption in Latin America and the Caribbean: An Analysis Applying a Panel Vector Autoregression (PVAR)

After the Montreal Protocol in 1989, countries agreed to reduce their ozone-depleting substances (ODS) emissions to improve environmental conditions by reducing UV radiation from our planet's surface. The policies to control ODS have influenced how countries' industries produce, ergo affecting their energy consumption. This study explores the causal relationship between economic growth, energy consumption, and ODS emissions. Retrieving data from Latin America and the Caribbean from 1998 to 2018, a panel VAR is built and analyzed using GMM robust estimates. The main results show a bidirectional causality between GDP and energy consumption, a unidirectional causality from GDP to ODS emissions, and an Environmental Kuznets Curve (EKC) for ODS emissions. Policies and actionable campaigns are discussed.

A Grain-Scale Study of Mojave Mars Simulant (MMS-1).

Space exploration has attracted significant interest by government agencies and the scientific community in recent years in an attempt to explore possible scenarios of settling of facilities on the Moon and Mars surface. One of the important components in space exploration is related with the understanding of the geophysical and geotechnical characteristics of the surfaces of planets and their natural satellites and because of the limitation of available extra-terrestrial samples, many times researchers develop simulants, which mimic the properties and characteristics of the original materials. In the present study, characterization at the grain-scale was performed on the Mojave Mars Simulant (MMS-1) with emphasis on the frictional behavior of small size samples which follow the particle-to-particle configuration. Additional characterization was performed by means of surface composition and morphology analysis and the crushing behavior of individual grains. The results from the study present for the first time the micromechanical tribological response of Mars simulant, and attempts were also made to compare the behavior of this simulant with previously published results on other types of Earth and extra-terrestrial materials. Despite some similarities between Mars and Moon simulants, the unique characteristics of the MMS-1 samples resulted in significant differences and particularly in severe damage of the grain surfaces, which was also linked to the dilation behavior at the grain-scale.

Integration of Raman, emission, and reflectance spectroscopy for earth and lunar mineralogy

Spectroscopy plays a vital role in the identification and characterization of minerals on terrestrial and planetary surfaces. We review the three different spectroscopic techniques for characterizing minerals on the Earth and lunar surfaces separately. Seven sedimentary and metamorphic terrestrial rock samples were analyzed with three field-based spectrometers, i.e., Raman, Fourier transform infrared (FTIR), and visible to near infrared and shortwave infrared (Vis–NIR–SWIR) spectrometers. Similarly, a review of work done by previous researchers on lunar rock samples was also carried out for their Raman, Vis–NIR–SWIR, and thermal (mid-infrared) spectral responses. It has been found in both the cases that the spectral information such as Si-O-Si stretching (polymorphs) in Raman spectra, identification of impurities, Christiansen and Restrahlen band center variation in mid-infrared spectra, location of elemental substitution, the content of iron, and shifting of the band center of diagnostic absorption features at 1 and 2 μm in reflectance spectra are contributing to the characterization and identification of terrestrial and lunar minerals. We show that quartz can be better characterized by considering silica polymorphs from Raman spectra, emission features in the range of 8 to 14 μm in FTIR spectra, and reflectance absorption features from Vis–NIR–SWIR spectra. KREEP materials from Apollo 12 and 14 samples are also better characterized using integrated spectroscopic studies. Integrated spectral responses felicitate comprehensive characterization and better identification of minerals. We suggest that Raman spectroscopy and visible and NIR-thermal spectroscopy are the best techniques to explore the Earth’s and lunar mineralogy.

Quantifying physical parameterization uncertainties associated with land-atmosphere interactions in the WRF model over Amazon

The Weather Research and Forecasting (WRF) model can be used to diagnose regional land-atmosphere (L-A) coupling strength in the absence of sufficient observations but subjected to uncertainties associated with model physical parameterizations. In this study, we propose a framework to quantify and reduce model physical parameterization uncertainties associated with surface fluxes and L-A coupling. An ensemble of WRF simulations with different physical schemes is used to simulate surface fluxes and land-atmosphere coupling strength over the Amazon region. The physical parameterizations investigated include cloud microphysics (MP), land surface processes (LSM), planetary boundary layer (PBL), surface layer (SL), and cumulus (CU). We perform 120 ensemble simulations using the WRF model and different combinations of six MPs, three LSMs, six PBLs and SLs and three CUs. The measurements from the GoAMAZON field campaign and satellite data are used to evaluate model performance. A Multi-way analysis of variance (ANOVA) approach is applied to quantify the relative importance of different physics processes on L-A coupling. The Tukey's test is used to sort schemes that have no significant differences into one group. The suite of physics that result in the best simulations of the corresponding variables are selected based on the Taylor skill score. Results show that the relative importance of processes and their interaction vary with the variables of interest. For example, CU was the most important process in modulating soil moisture, 2 m-humidity, latent heat, and net radiation. LSM showed dominant effects on 2 m-temperature and also has the largest impact on sensible heat and the lifting condensation level. The best physical parameterization ensembles show much narrower ranges of the variables of interest than the priori ensemble. Results of this study show the roles of different physical processes in modulating L-A interactions, quantify model uncertainties from physical processes, and provide insights for improving the model physics parameterizations.

Laboratory Investigations Coupled to VIR/Dawn Observations to Quantify the Large Concentrations of Organic Matter on Ceres

Organic matter directly observed at the surface of an inner planetary body is quite infrequent due to the usual low abundance of such matter and the limitation of the infrared technique. Fortuitously, the Dawn mission has revealed, thanks to the Visible and InfraRed mapping spectrometer (VIR), large areas rich in organic matter at the surface of Ceres, near Ernutet crater. The origin of the organic matter and its abundance in association with minerals, as indicated by the low altitude VIR data, remains unclear, but multiple lines of evidence support an endogenous origin. Here, we report an experimental investigation to determine the abundance of the aliphatic carbon signature observed on Ceres. We produced relevant analogues containing ammoniated-phyllosilicates, carbonates, aliphatic carbons (coals), and magnetite or amorphous carbon as darkening agents, and measured their reflectance by infrared spectroscopy. Measurements of these organic-rich analogues were directly compared to the VIR spectra taken from different locations around Ernutet crater. We found that the absolute reflectance of our analogues is at least two orders of magnitude higher than Ceres, but the depths of absorption bands match nicely the ones of the organic-rich Ceres spectra. The choices of the different components are discussed in comparison with VIR data. Relative abundances of the components are extrapolated from the spectra and mixture composition, considering that the differences in reflectance level is mainly due to optical effects. Absorption bands of Ceres’ organic-rich spectra are best reproduced by around 20 wt.% of carbon (a third being aliphatic carbons), in association with around 20 wt.% of carbonates, 15 wt.% of ammoniated-phyllosilicate, 20 wt.% of Mg-phyllosilicates, and 25 wt.% of darkening agent. Results also highlight the pertinence to use laboratory analogues in addition to models for planetary surface characterization. Such large quantities of organic materials near Ernutet crater, in addition to the amorphous carbon suspected on a global scale, requires a concentration mechanism whose nature is still unknown but that could potentially be relevant to other large volatile-rich bodies.

Willenbring Receives 2020 Earth and Planetary Surface Processes Marguerite T. Williams Award

Jane K. Willenbring received the inaugural Marguerite T. Williams Award at AGU’s virtual Fall Meeting 2020. The award is given in recognition of “significant contributions to research and community-building by a mid-career scientist in the field of Earth and planetary surface processes.”

Anderson Receives 2020 G. K. Gilbert Award in Surface Processes

Suzanne P. Anderson received the 2020 G. K. Gilbert Award in Surface Processes at AGU’s virtual Fall Meeting 2020. The award recognizes “sustained and outstanding contributions to the field of Earth and planetary surface processes from a mid-career or senior scientist.”

Intermittent short-arm centrifugation is a partially effective countermeasure against upright balance deterioration following 60-day head-down tilt bed rest.

This study investigated whether artificial gravity (AG), induced by short-radius centrifugation, mitigated deterioration in standing balance and anticipatory postural adjustments (APAs) of trunk muscles following 60-day head-down tilt bed rest. Twenty-four participants were allocated to one of three groups: control group (n = 8); 30-min continuous AG daily (n = 8); and intermittent 6 × 5 min AG daily (n = 8). Before and immediately after bed rest, standing balance was assessed in four conditions: eyes open and closed on both stable and foam surfaces. Measures including sway path, root mean square, and peak sway velocity, sway area, sway frequency power, and sway density curve were extracted from the center of pressure displacement. APAs were assessed during rapid arm movements using intramuscular or surface electromyography electrodes of the rectus abdominis; obliquus externus and internus abdominis; transversus abdominis; erector spinae at L1, L2, L3, and L4 vertebral levels; and deep lumbar multifidus muscles. The relative latency between the EMG onset of the deltoid and each of the trunk muscles was calculated. All three groups had poorer balance performance in most of the parameters (all P < 0.05) and delayed APAs of the trunk muscles following bed rest (all P < 0.05). Sway path and sway velocity were deteriorated, and sway frequency power was less in those who received intermittent AG than in the control group (all P < 0.05), particularly in conditions with reduced proprioceptive feedback. These data highlight the potential of intermittent AG to mitigate deterioration of some aspects of postural control induced by gravitational unloading, but no protective effects on trunk muscle responses were observed.NEW & NOTEWORTHY This study presents novel insights into the effect of artificial gravity (AG) on the deterioration of standing balance and anticipatory postural adjustments (APAs) of trunk muscles induced by 60-day strict head-down bed rest. The results indicated severe balance dysfunction and delayed APAs during rapid arm movement. AG partially mitigated the deterioration in standing balance and may thus be considered as a potential countermeasure for future planetary surface explorations. Optimization of AG protocols might enhance effects.

Crew time and workload in the EDEN ISS greenhouse in Antarctica

The goal of the EDEN ISS project is to research technologies for future greenhouses as a substantial part of planetary surface habitats. In this paper, we investigate crew time and workload needed to operate the space analogue EDEN ISS greenhouse on-site and remotely from the Mission Control Center. Within the almost three years of operation in Antarctica, different vegetable crops were cultivated, which yielded an edible biomass of 646 kg during the experiment phase 2018 and 2019.Operating in such a remote environment, analogue to future planetary missions, both greenhouse systems and remote support capabilities must be carefully developed and assessed to guarantee a reliable and efficient workflow. The investigation of crew time and workload is crucial to optimize processes within the operation of the greenhouse. For the Antarctic winter seasons, 2019 and 2020, as well as the summer season 2019/2020, the workload of the EDEN ISS greenhouse operators was assessed using the NASA Task Load Index. In addition, crew time was measured for the winter season 2019.The participants consisted of on-site operators, who worked inside the EDEN ISS greenhouse in Antarctica and the DLR remote support team, who worked in the Mission Control Center at the DLR Institute of Space Systems in Bremen (Germany).The crew time results show that crew time for the whole experiment phase 2019 required by the on-site operator team 2019 is approximately four times higher than the crew time of the corresponding remote support team without considering planning activities for the next mission. The total crew time for the experiment phase 2019 amounts to 694.5 CM-h or 6.31 CM-h/kg. With the measurements of the experiment phase 2019 it was possible to develop a methodology for crew time categorization for the remote support activities, which facilitates the analysis and increases the comparability of crew time values. In addition, the development of weekly and monthly crew time demand over the experiment phase is presented.The workload investigations indicate that the highest workload is perceived by the remote support team 2019 + 2020, followed by the summer maintenance team 2019/2020. The on-site operator team 2019 and on-site operator team 2020 showed the lowest values. The values presented in this paper indicate the need to minimize crew time as well as workload demands of the operators involved in the operation of future planetary surface greenhouses.

Elements of ballistic calculation for spacecraft gravity assist

The purpose of the study is an analytical description of the section of the ballistic trajectory corresponding to the normal fall of the spacecraft on the surface of an atmosphereless planet. In this case, the motion of a normally falling body is characterized by an increasing acceleration of gravity. The problem of the speed, time and acceleration of the normal fall of a body on the planet's surface in the absence of an atmosphere is reduced to solving a second-order differential equation, which is solved by the standard method. A feature of the solution is the formal use of the tabular integral at an intermediate stage. It turned out, however, that his formula is unreliable, namely, the derivative of the right-hand side is not equal to the integrand. It follows from this that the possible existing solutions to this problem, based on the use of the indicated tabular integral, are incorrect. The article presents the correction of this tabular integral, which is an incidental result of the study. In this work, the time equation of motion of a body normally falling on the surface of the planet in the absence of an atmosphere, as well as the time equations of its speed and acceleration are obtained. The results obtained can be useful in calculating passive gravity assist during interplanetary flights and calculating the sheer fall of small celestial bodies and spent structural element s of spacecraft.

The impact of improved air-quality due to COVID-19 lockdown on surface meteorological parameters and planetary boundary layer over Gadanki, a tropical rural site in India

The nation-wide lockdowns imposed in India during March‐–May 2020 (in four phases) to curb the spread of the novel Corona virus, greatly enhanced the near-surface air-quality due to lowering of industrial, transport and human activities. The present study focuses on the changes in the vertical structure of aerosol concentration and how those changes impacted radiation balance, the planetary boundary layer (PBL) height and surface meteorological parameters. Instrumented tower and Ceilometer measurements made at Gadanki (13.45°N, 79.18°E), located in a rural environment, coupled with satellite-derived Aerosol Optical Depth (AOD) data have been used to understand the changes in lockdown period. Significant reduction in backscatter density during the lockdown compared to 2019 indicates that aerosol reduction during the lockdown is not only limited to the surface, rather observed in the entire PBL. Except for the fourth phase of lockdown during which several relaxations have been given for vehicular movement and other anthropogenic activities, the reduction in backscatter density is seen in all phases of lockdown. However, the reduction is prominently seen in the second and third phases. The AOD also reduced by 40% around Gadanki, comparable to that of in urban regions. Due to the reduction in aerosols during the lockdown period, the insolation increases by 60 Wm−2, which is expected to increase the temperature. However, the increased loss of long-wave radiation (due to reduction in trapping gases) and more rain events during the lockdown period decreased the temperature by ~1 °C. Measurements also suggest that the most of net radiation is partitioned into the latent heat flux increasing the humidity and lowering the PBL height (due to reduced strength of thermals and sensible heat flux).

УРАХУВАННЯ АЛЬТИМЕТРИЧНОЇ ІНФОРМАЦІЇ ПРИ ВИЗНАЧЕННІ РЕЛЬЄФУ ПОВЕРХНІ ПЛАНЕТИ МЕТОДОМ УДОСКОНАЛЕНОЇ ФОТОКЛИНОМЕТРІЇ ЗА ПОЛЕМ НАХИЛІВ

Purpose: The paper discusses the possibility for increasing the planet’s surface relief retrieving accuracy with the improved photoclinometry method through the reference of the desired relief to the altimetry data. The general approach to solving the problem is proposed. The use of altimeters having both wide and narrow beam patterns are discussed, but the narrow beam pattern altimeter data is studied more in detail. The spatial resolution of the retrieved relief calculated with the improved photoclinometry method conforms to the one of the source images. Altimetry allows absolute reference to the surface heights and improves the accuracy of the relief determination. Design/metodology/approach: The work is based on the improved photoclinometry method for the planet’s surface relief retrieving from images. This method is mathematically rigorous and uses the Bayesian statistical approach, that allows calculation of the most probable relief according to available observations. Findings: An approach to determining the optimal statistical estimate of the surface heights from images in the frames of the improved photoclinometry method is proposed and an expression for the optimal filter which converts source images along with the wide beam pattern altimetry data into the most probable relief of the planet surface area is presented. The reference technique for the narrow beam pattern altimeter data is formulated. The efficiency of the method has been verified with the computer simulation. The relief of the surface area in Mare Imbrium on the Moon was retrieved using three images and laser altimeter data taken by the “Lunar Reconnaissance Orbiter” spacecraft. Conclusions: Accounting for the narrow beam pattern altimeter data increases the accuracy of the relief determination. Using the narrow beam pattern altimeter data turns out to be more preferable over the involving wide beam pattern altimeter data. Computer simulation has shown that accounting for the narrow beam pattern altimeter data significantly increases the accuracy of the calculated heights as against using images exclusively and helps to speed up the calculation procedure. Key words: planet surface relief; photometry; altimetry; optimal filtering; statistical estimation of random value