Remotely sensed land surface temperature (LST) enables global modelling and monitoring carbon dioxide (CO2) fluxes from peatlands. We aimed to provide the first overview of the LST potential for monitoring ecosystem respiration (Reco) in disturbed (drained and extracted) peatlands. We used chamber measured data (2017–2020) from five disturbed and two intact northern peatlands and LST data from Landsat 7, 8, and MODIS missions. First, we studied the strength of relationships between fluxes and their in-situ drivers: thermal and moisture conditions. Second, we examined the association between LST and in-situ temperatures. Third, we compared chamber measured Reco with the modelled Reco based on (i) in-situ measured surface temperature and (ii) MODIS LST. In-situ temperatures were a stronger driver of CO2 fluxes in disturbed sites (Spearman correlation R=0.8–0.9) than in intact ones (R=0.5–0.7). LST had a higher association with in-situ measured temperatures (mean R=0.74 for MODIS) in disturbed sites and weaker in the intact peatlands (mean R=0.34 for Landsat and 0.36 for MODIS). Reco models driven by MODIS LST and in-situ surface temperature yielded similar accuracy: R-squared was 0.26, 0.64, 0.65 and 0.28, 0.68, 0.58 for intact, drained and extracted sites, correspondingly. Therefore, LST has a great potential to be utilized in Reco models as a proxy of thermal regime in disturbed and intact northern peatlands.

Ground scatter (GS) echoes in Super Dual Auroral Radar Network (SuperDARN) observations have been always expected to occur under high-enough electron density in the ionosphere providing sufficient bending of HF radio wave paths toward the ground. In this study we provide direct evidence statistically supporting this notion by comparing the GS occurrence rate for the Rankin Inlet SuperDARN radar and the F region peak electron density NmF2 measured at Resolute Bay by the CADI ionosonde and incoherent scatter radars RISR-N/C. We show that the occurrence rate increases with NmF2 roughly linearly up to about ~4·1011 m-3, and the trend saturates at larger NmF2. One expected consequence of this relationship is correlation in seasonal and solar cycle variations of the GS echo occurrence rate and NmF2. GS occurrence rates for a number of SuperDARN radars at middle latitudes, in the auroral zone and in the polar cap are considered separately for daytime and nighttime. The data indicate that the daytime occurrence rates are maximized in winter and nighttime occurrence rates are maximized in summer for middle latitude and auroral zone radars in the Northern Hemisphere, consistent with the Winter Anomaly (WA) phenomenon. The effect is most evident in the North American and Japanize sectors, and the quality of WA signatures deteriorates in the European and, especially, in the Australian sectors. The effect does not exist in the South American sector and in the polar caps of both hemispheres.

Two distinct rainfall stages over the Central Highlands (CH) of Vietnam during the rainy season have been objectively defined using the high-resolution Vietnam Gridded Precipitation dataset for 1983–2010 (28 years): a second rainy season (SRS) embedded in the conventional rainy season. Surprisingly, the pronounced interannual variation in the SRS onset date has led to three apparent regimes: an early (late) SRS with a 1 month longer (shorter) rainfall period occurring in early July (until mid-August) and a normal SRS starting in late July. Almost all the early SRS years occur during El Niño developing phases, particularly during the Niño3.4 sea surface temperature (SST) increase from January through December. Water vapor budget analyses reveal that the interannual variation in the divergent water vapor flux is in response to the warmer July tropical Pacific SST anomalies, resulting in rainfall enhancement over the CH and eventually inducing early SRS onset.

Crustal velocity variation within impact-related seismic zones is commonly attributed to mechanisms such as pore pressure changes, dense fracture network, and compositional variation. In this study, we combine seismic tomography, rock physics analysis, and potential field modeling to quantitatively investigate the mechanisms that influence crustal velocity variation in the Charlevoix Seismic Zone (CSZ), a meteorite impact-related seismic zone in eastern Canada. Earthquakes in the CSZ align along two broad NE-SW trending clusters related to reactivated paleo-rift faults. Within the impact structure, the earthquakes are diffusely distributed and lower velocity bodies are ubiquitous which can be attributed to crustal damage from tectonic inheritance exacerbated by the meteorite impact. The Bouguer gravity anomaly decreases southeastward across the St. Lawrence River due to density disparity between rocks in the Grenville Province and the Appalachians. We find a higher velocity body northeast of the impact structure that does not exhibit an observable gravity anomaly, which suggests the presence of a rock (e.g. anorthosite) of comparable density but a higher elastic moduli within another rock (e.g. charnockite). Outside the impact structure, compositional variations control velocity changes, whereas inside the impact structure, velocity variations can be explained by porosity enhancement of up to 10% by low (0.1) aspect ratio cracks. Our results suggest that intense fracturing and compositional alteration, rather than pore pressure, control velocity variations, hence earthquake processes in the CSZ.

The presence, spatial extent and persistence of low-level clouds (LLCs) largely impact on the diurnal surface radiation and energy balance, as well as, the regional climate. Notwithstanding, there is limited understanding on their evolution and processes, particularly in southern West Africa. This paper assesses the development of LLCs and their dominant formative factors, as well as, their relationship with radiation and energy balance. Firstly, ceilometer and radiosondes deployed during the DACCIWA (Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa) field campaign were used in identifying the LLC. Afterwards, the cloud fraction was employed to characterize different LLC phases. Averagely, break-up, dissipation and build-up of LLC were marked at 0900 GMT, 1200 GMT and 2200 GMT respectively. Moreover, composites of LLC diurnal evolution and their relationship with net radiation, energy storage and surface stability showed that LLCs significantly impact on net radiation flux, by reducing downwelling shortwave radiation. Additionally, LLC onsets were characterized by a near-steady state in net radiation flux, whereas the rate of energy storage within the lower layers marginally oscillated about equilibrium. Finally, with observations from selected intensive observation periods (IOPs), the dominant factors influencing LLC development were evaluated. Horizontal cold air advection, with enhancement by nocturnal low-level jets, was observed to primarily influence the development of LLCs for the study period. Findings of this paper are necessary for improving the understanding of LLC characteristics, formation and interactions with surface properties, particularly over southern West Africa.

The role of individual and collective human action is increasingly recognized as a prominent and arguably paramount determinant in shaping the behavior, trajectory, and vulnerability of multisector systems. This human influence operates at multiple scales: from short-term (hourly to daily) to long-term (annually to centennial) timescales, and from the local to the global, pushing systems towards either desirable or undesirable outcomes. However, the effort to represent human systems in multisector models has been fragmented across philosophical, methodological, and disciplinary lines. To cohere insights across diverse modeling approaches, we present a new typology for classifying how human actors are represented in the broad suite of coupled human-natural system models that are applied in MultiSector Dynamics (MSD) research. The typology conceptualizes a “sector” as a system-of-systems that includes a diverse group of human actors, defined across individual to collective social levels, involved in governing, provisioning, and utilizing products, goods, or services towards some human end. We trace the salient features of modeled representations of human systems by organizing the typology around three key questions: 1) Who are the actors in MSD systems? 2) What are their actions? 3) How and for what purpose are these actors and actions operationalized in a computational model? We use this typology to critically examine existing models and chart the frontier of human systems modeling for MSD research.

The Atlantic’s Meridional Overturning Circulation (AMOC) is weak when the northern summer insolation is strong and vice-versa in the 23-kyr precessional frequency band. The mechanism behind this response is unknown and does not conform in any obvious way to Milankovitch theory. The link between the AMOC and precession is attributed here to the trade winds that blow out from Africa across the Atlantic. The trade winds, like the AMOC itself, are weak when the northern summer insolation is strong. The trade winds are shown here to have a direct impact on the AMOC’s return flow. A return flow altered this way should warm and cool the Earth in a way that has not been previously considered.

In December 2020, Chang’e-5 returned samples from mare basalt unit Em4/P58 in northern Oceanus Procellarum. With an absolute model age of 1.21-1.53 Ga (Hiesinger et al. 2003; Qian et al., 2018, 2021a). Elevation analysis of the interior of Rima Sharp and Mairan, plus geomorphological observations suggest lava backfilling of Rima Sharp with younger lava from Rima Mairan. Analysis of the magnetic field at the surface also shows that the younger lava from the southern Mairan vents, which covered the southeastern part of Em4/P58 is unmagnetized. Our new magnetic anomaly analysis shows that Em4/P58 unit can be divided into magnetized (northwest) and unmagnetized (southeast) parts. The comprehensive analysis of magnetic anomaly and topography shows that lava from southern rille is likely to have reached the Chang’e-5 landing site. Samples returned by Chang’e-5 will help constrain the source of lava flow and the evolution of the lunar magnetic field over time.

Cumulus entrainment substantially regulates the earth’s climate but remains poorly constrained in global climate models. Recent studies have shown that cumulus bulk entrainment (or dilution) is particularly sensitive to continentality, with the entrainment rate in simulated maritime cumuli nearly double that of continental cumuli. The present study examines the impacts of such land–ocean entrainment contrasts on the current climate using 21-year simulations with the Geophysical Fluid Dynamics Laboratory’s (GFDL) High-Resolution Atmospheric Model (HIRAM). In response to a 25% reduction in entrainment over land, precipitation over tropical land regions increases by up to 40%. Along with directly facilitating enhanced convective precipitation, this entrainment reduction induces a positive soil moisture–precipitation feedback that further enhances convective precipitation over land. A 25% entrainment reduction over the oceans leads to more widespread modifications of convection patterns, with the strongest signal in the tropical Pacific. Deep convection shifts upstream (eastward) there, inducing enhanced large-scale ascent over the central Pacific with compensating subsidence and reduced humidity and precipitation over the western Pacific. Land–ocean variations in entrainment project onto the Pacific Walker circulation, with the 25% land reduction strengthening it by 4% and the 25% ocean reduction weakening it by 14%. These changes are driven by variations in convective and large-scale stratiform heating over the Pacific. While reduced entrainment over land enhances diabatic heating in the Maritime Continent to strengthen the Walker circulation, reduced entrainment over the oceans decreases diabatic heating in the western Pacific to weaken the Walker circulation.

A document by Piero Campalani. Click on the document to view its contents.

In this study we develop a tool to simultaneously invert multi-source magnetic transfer functions (TFs), including magnetotelluric (MT) tippers (with period ranging from a few minutes to 3 hours), solar quiet (Sq) global-to-local (G2L) transfer functions (TFs; with period ranging from 6 hours to 24 hours) of ionospheric origin, and magnetospheric global Q-responses (with period ranging from a few days to a few months). We further jointly invert the aforementioned multi-source TFs to constrain the local conductivity structures beneath three islands located in South Atlantic, Indian Ocean and North Pacific. The recovered conductivity profiles suggest upper mantle plumes beneath Tristan da Cunha and Oahu islands. Besides, our results indicate resistive lithosphere of different thicknesses beneath these three islands, showing a progressive thickening of oceanic lithosphere with age.

In the predominantly oxic, upland soils, periods of high wetness trigger anaerobic processes such as iron (Fe) reduction within the soil microsites, with implications for organic matter decomposition, the fate of pollutants, and nutrient cycling. In fluctuating O conditions, Fe reduction is maintained by the re-oxidation of ferrous iron, which renews the electron acceptor, Fe, for microbial Fe reduction. To characterize such processes, it is fundamental to relate the redox cycling of iron between the two redox states to the hydro-climatic conditions. Here, we link iron cycling to soil moisture variability through a model of iron-redox dynamics and find the hydrologic regime that maximizes Fe reduction, under non-limiting organic carbon availability. Away from the optimal cycle, the duration of the oxic or the anoxic phase limits the regeneration of Fe or its reduction rate, respectively. We relate the average duration of the oxic and anoxic intervals to the frequency and mean depth of precipitation events that drive the dynamics of soil moisture, effectively linking iron cycling to the hydrologic regime. We then compare a tropical (Luquillo CZO) and a subtropical (Calhoun CZO) forest to provide insights into the soil moisture control on iron-redox dynamics in these ecosystems. The tropical site maintains a high potential for iron reduction throughout the year, due to quick and frequent transitions between oxic and anoxic conditions, whereas the subtropical site is strongly affected by seasonality, which limits iron reduction to winter and early-spring months with higher precipitation and lower evaporative demand.

Utilizing atmospheric temperature observed from Mars Years 33 to 36 by the Imaging Ultraviolet Spectrograph (IUVS) onboard the Mars Atmosphere and Volatile Evolution (MAVEN), we derive the diurnal and semidiurnal thermal tides from 90 to 160 km. The seasonal variations of diurnal (DW1) and semidiurnal (SW2) tides in the thermosphere and mesosphere, observed by the Mars Climate Sounder (MCS), along with vertical phase velocities, indicate different sources for the migrating tide in the lower and upper atmosphere. The seasonal variation of diurnal eastward wavenumber 2 (DE2) tide in the thermosphere corresponds well to its counterpart in the lower atmosphere. Vertical phase velocities indicate that the DE2 propagates upward from the lower atmosphere to ~150 km, except near the perihelion (solar longitude 210° to 270°). The upward propagation of this DE2 tide could potentially impact the vertical coupling between the Martian lower and upper atmosphere.

The commonly applied pedotransfer functions (PTFs), which predict soil hydraulic properties (SHPs) from easily measured soil properties such as texture information, often account only for capillary forces. Recent advances in soil hydraulic modeling suggest that, to improve the prediction of SHPs under dry conditions, the impact of adsorption forces has to be taken into account. However, the lack of observations in particularly dry conditions, due to the difficult and time-consuming measurement, hinders the development of PTFs that predict SHPs from saturation to oven dryness. In this paper, we first present a simple method for predicting complete SHPs with limited measurements that cover only a relatively high matric potential range. With this method, we extended a public dataset to cover dry conditions, and then applied it to develop PTFs that can predict SHPs from saturation to oven dryness. This was achieved by applying the complete soil hydraulic model proposed by Wang et al. (2021), which accounts for both capillary and adsorptions forces and overcomes the unrealistic decrease near saturation for fine-textured soils. The impact of vapor diffusion was also considered. We further applied this method in extending an existing capillary-based PTF to dry conditions. The results showed that: 1) the proposed method performs very well in describing SHPs over the entire moisture range; 2) the PTFs developed with the extended observations and the complete model show a superior prediction performance, especially for the hydraulic conductivity; and 3) the extended capillary-based PTF improves the performance in describing SHPs under dry conditions.

Root exudates alter the rhizosphere’s physical properties, but the impact that these changes have on solute transport is unknown. In this study, we tested the effects of chia mucilage and wheat root exudates on the transport of iodide and potassium in saturated or unsaturated soil. Saturated solute breakthrough experiments, conducted in loamy sand soil or coarser textured quartz sand, revealed that increasing the exudate concentration in soil resulted in increasingly non-equilibrium solute transport. This behavior was demonstrated by an initial solute breakthrough after fewer pore volumes and the arrival of the peak solute concentration after greater pore volumes in soil mixed with exudates compared to soil without exudates. These patterns were more pronounced for the quartz sand than in the loamy sand soil and in soil mixed with mucilage than in soil mixed wheat root exudates. Parameter fits to these breakthrough curves with a mobile-immobile transport model indicated the fraction of immobile water increased as the concentration of exudates increased. For example, in quartz sand the estimated immobile fraction increased from 0 without exudates to 0.75 at a mucilage concentration of 0.2%. The solutes’ breakthrough under unsaturated conditions was also altered by the exudates, demonstrated by a smaller volume of water extracted from soil mixed with exudates, compared to soil without exudates, before the arrival of the peak solute concentration. The results indicate that exudates alter the rhizosphere’s transport properties; we hypothesize that this is due to exudates creating low-conducting flow paths that result in a physical non-equilibrium solute transport.

Using over 6 years of magnetic field data (2014.10-2020.12) collected by the Mars Atmosphere and Volatile EvolutioN (MAVEN), we conduct a statistical study on the three-dimensional average magnetic field structure around Mars. We find that this magnetic field structure conforms to the pattern typical of an induced magnetosphere, that is, the interplanetary magnetic field (IMF) which is carried by the solar wind and which drapes, piles up, slips around the planet, and eventually forms a tail in the wake. The draped field lines from both hemispheres along the direction of the solar wind electric field (E) are directed towards the nightside magnetic equatorial plane, which looks like they are “sinking” toward the wake. These “sinking” field lines from the +E-hemisphere (E pointing away from the plane) are more flared and dominant in the tail, while the field lines from the –E-hemisphere (E pointing towards) are more stretched and “pinched” towards the plasma sheet. Such highly “pinched” field lines even form a loop over the pole of the –E-hemisphere. The tail current sheet also shows an E-asymmetry: the sheet is thicker with a stronger tailward J×B force at +E-flank, but much thinner and with a weaker J×B (even turns sunward) at –E-flank. Additionally, we find that IMF Bx can induce a kink-like field structure at the boundary layer; the field strength is globally enhanced and the field lines flare less during high dynamic pressure; however, the rotation of the planet, against expectations, modulate the configuration of the tail current sheet insignificantly.

In this study, the combined application of geodesic kernel and Gaussian process regression was investigated to estimate nonstationary hydraulic conductivity fields in two-dimensional hydrogeological systems. Particularly, a semi-analytical form of the geodesic distance based on the intrinsic geometry of the manifold was derived and used to define positive definite geodesic covariance matrices that are employed for Gaussian process regression. Furthermore, the proposed approach was applied to a series of synthetic hydraulic conductivity estimation problems and the results show that the incorporation of secondary information, such as geophysical or geological interpretations, can considerably improve the estimation accuracy, especially in nonstationary fields. Moreover, groundwater flow and solute transport simulations based on the estimated hydraulic conductivity fields revealed that the accuracy of the simulations was strongly affected by the inclusion of secondary information. These results suggest that incorporating secondary information into manifold geometry can remarkably improve the estimation accuracy and provide new insights on the underlying structure of geological data. This proposed approach has crucial implications for hydrogeological applications, such as groundwater resource management, safety assessments, and risk management strategies related to groundwater contamination.

We conducted microcosm incubation experiments in contrasting biogeochemical areas of the South Indian Ocean and Indian sector of the Southern Ocean to determine the phytoplankton response to aerosol related nutrient release. Dry depositions of 2 mg.L-1 of dust from Patagonia or 25 mg.L-1 of ash from the Icelandic stratovolcano Eyjafjallajökull were added to trace metal clean incubations of surface seawater, along with nutrients (Si, Fe, N or P) at five stations. We interpreted the biological response based on abiotic experiments of aerosols nutrient release. We showed that both types of aerosols increased significantly the primary production by resolving some main local nutrient limitations of the Southern Ocean, at least for iron and to a lesser extend for silicon. Phytoplanktonic communities reacted differently to the additions; however added nutrients/aerosols were mostly beneficial for diatom growth, responsible for 40 to 100 % of the algal biomass increase, depending on the region and aerosols. Nonetheless, the aerosols did not relieve main N limitation of the LNLC area, as neither dust nor ash released significant amounts of NOx. According to these findings, characteristic localized high deposition of volcanic eruptions be of equal or higher importance to phytoplankton compared to desert dust, despite ashes’ lower nutrient solubility to the ocean.