The symbiosis between crops and arbuscular mycorrhizal fungi (AMF) have become an attractive route towards achieving carbon neutral agriculture and reducing the use of chemical fertilizers. Yet, our understanding of how active AMF infections influence the uptake, allocation, and exchange of carbon is limited. Here, we combine X-ray CT and PET imaging to observe and quantify the flow of carbon from leaves to roots to hyphae. Comparison of maize grown with and without AMF allows us to measure changes in the amount of 11CO2 taken up in leaves and subsequently the amount of 11C allocated to below-ground roots. Then, co-registered CT and PET images are used to identify hot spots which may indicate active AMF infection sites. Finally, analysis of 11C kinetics at these hot spots are used to assess the amount of carbon exchanged between maize roots and hyphae. By combining structural and biochemical information, we begin to deepen our understanding of the different types of changes in carbon flow in Maize-AMF systems and how we can improve sustainable agriculture efforts.

As global temperatures increase, Antarctica is likely to experience increased frequency, duration, and intensity of extreme temperature events. Here we investigate how the characteristics of summer extreme temperature events - heatwaves and incidence of melt days - may change over Antarctica using daily historical and SSP5-8.5 Coupled Model Intercomparison Project phase 6 (CMIP6) output from 1950-2099. CMIP6 models robustly project that Antarctica’s lowest elevation regions and the West Antarctic ice sheet will reach 0C for an average of 6-12 days during summer by 2099. Modelled summer heatwaves become more intense across the entire continent, but less frequent and shorter everywhere except the East Antarctic Plateau due to declining temperature variability as surface temperatures approach the melting point of ice. Our results imply that the increasing frequency of 0C days and greater heatwave intensity will contribute to increasing ice sheet surface melt and accelerating global sea level rise over the coming century.

Publicly accessible data has been used to construct a county-scale supply chain model of United States gasoline consumption and quantify the scope 3 CO2; emissions from gasoline consumption. Our model tracks the movement of refined fuels from county of refinement to county of blending and eventually to county of consumption via multiple infrastructure networks – pipelines, tankers, trains, and trucks. Where quantities of the fuel moved across different linkages and different transportation modes are known, they are used as is. However, for the vast majority of the country, the exact quantities of fuel moved between county of refining and county of blending or county of blending and county of consumption, as well as the mode of transportation, is not known with certainty. Linear optimization is used to model those links with constraints related to total supply and demand at lower spatial resolutions (State-level and Petroleum Administration for Defense (PAD) Districts). This is the first real attempt at a spatially-resolved scope 3 style CO2 emissions data product specific to United States gasoline consumption. This model can improve understanding of the complex liquid fuel supply chain, and has significant implications for local policy. With a complete model of scope 3 CO2 emissions, it is also possible to analyze how the differences between scope 1 and scope 3 emissions vary across the country. Finally, this model lays the foundation to model the evolution of the U.S. gasoline supply chain – its dependencies, critical linkages, and pinch points – and the evolution of scope 1 and scope 3 CO2 emissions using the full extent of available public data.

LST is routinely retrieved from the GOES-R Advanced Baseline Imager (ABI) long wave spectral channels. Since the product is available only under clear sky conditions, large gaps exist in the data stream which correspond to contamination by clouds. However, continuous estimates of LST data are still vitally needed for several applications such as drought monitoring ,vegetation growth, and crop yield estimation etc. Studies have shown that LST tracks with corresponding changes in incident solar radiation or more specifically changes in surface absorbed solar radiation with good correlation irrespective of sky conditions (clear or cloudy). In the present study, a scheme is developed to fill in the large spatio-temporal gaps in the LST time series using surface solar absorption parameter (SSA) retrieved in near real time from other satellites. Validation of retrieved LST values over all of the SURFRAD stations reveal RMS errors of less than 1 K.

Nitrous oxide (N2O), a potent greenhouse gas and ozone depleting substance, plays a crucial role in the atmosphere. Anthropogenic emissions from agriculture contribute to a rising trend in global N2O emissions and atmospheric concentrations. However, due to insufficient direct observations, regional N2O emissions derived in bottom-up and top-down studies are highly uncertain. The U.S. Midwest is one of the most intensive agriculture areas worldwide and hence may contribute significantly to the observed trend. Recent top-down studies suggest that bottom-up estimates underestimate agricultural emissions in that area by up to an order of magnitude. Here we quantify nitrous oxide emissions in the Midwest in October 2017 and June-July 2019 with a top-down approach. Unique continuous aircraft-based measurements of N2O conducted during the ACT-America campaign together with forward WRF-Chem model simulations are used to scale the EDGAR inventory thus quantifying emissions. On average we had to upscale October 2017 and June-July 2019 agricultural EDGAR 4.3.2/5.0 emissions by a factor of 6.3/3.5 and 11.4/9.9, resulting in 0.42 nmol m-2 s-1 and 1.06 nmol m-2 s-1 emissions in the Midwest, respectively. Finally, calculations of direct soil N2O emissions from the DayCent biogeochemical model are compared to our estimates.

Global Navigation Satellite System (GNSS) signals reflected at the water surface are received together with direct GNSS signals by two low-const receivers deployed to an unmanned aerial vehicle (UAV). From relative delay of the reflected signals with respect to the direct ones, the height of the UAV above the water surface can be determined by GNSS Reflectometry (GNSS-R). The height estimation is originally conducted independently for each epoch, but by forcing temporally continuous constraints on differences of two receiver clocks, estimates of whole epochs during the study period are then contributed in the recursive estimates of the height. Applying the new method to GNSS-R altimetry data during an approximately 3-min hovering period at around 120-m altitude, the mean and RMS differences from the measured and estimated heights become improved from 0.72 and 5.87 m to 0.35 and 3.74 m. The accuracy of measurements is also found strongly depends on elevation angles of GNSS satellites, and also is sensitive to contaminations of unexpected reflections such as from lands or ships.

Many communities along the East and Gulf coasts of the United States are experiencing moderate to severe erosion. Decadal shoreline erosion rates determined by the North Carolina Division of Coastal Management indicate that >65% of the NC shoreline is eroding, with 20% losing shore at ~1 m per year. Chronic long-term erosion and episodic rapid impacts from storms have encouraged most coastal NC communities to conduct beach nourishments for mitigation. One concern is that there is limited knowledge of how offshore sand shoals – often sources for nourishments – are evolving in response to storm conditions and dredging activity. In September 2018, Hurricane Florence impacted southern NC and northern SC, and many communities experienced enhanced erosion. Future offshore sand removal for beach nourishment is inevitable here and elsewhere along the East Coast. A borrow area on the continental shelf seaward of Bogue Inlet (NC) offers an opportunity to see how the seabed is changing as a result of anthropogenic and oceanographic processes. Hurricane Florence made landfall as a Category 1 near Wilmington, NC on the morning of September 14, 2018. Prior to making landfall the storm was a powerful Category 2 hurricane, down from Category 4 status days prior. Hurricane-force winds were experienced over a large region, yielding powerful storm surge and waves over 8 m near the study area. Given the water depths of the ODMDS, seabed reworking was anticipated. The project collected geophysical data and sediment samples over a portion of the ODMDS offshore of Bogue Banks, NC in February 2019. Multibeam bathymetry, backscatter and seismic reflection data were obtained along with 24 sediment samples. These data add to previously collected data over the same area in 2013 and 2018. Grain-size analysis has been completed on all collected samples. Preliminary analysis of the post-hurricane data in comparison to earlier results indicate that the seabed has been reshaped since the last survey in March 2018, likely in response to Hurricane Florence. The broad dome-shape of the ODMDS remains, however, there is conspicuous morphological change. In shallower areas large sand waves (crests oriented roughly N-S, wavelength 20-30 m) differ from earlier mapping. Despite notable reworking, the anthropic signature of dredging in 2013 remains on the seascape.

In this study, the impact of soil freezing–thawing processes on August rainfall in southern China (SC) during 1979–2008 and related physical mechanisms are investigated using the Grid-Point Atmospheric Model version 2.0 (GAMIL2.0). This model with considering the supercooled water in soil freezing-thawing scheme reproduces the climatology and trends of August precipitation in the SC region. Moisture-budget analysis is employed to quantity the contributions of different factors to the change of precipitation in SC. The results indicate that evaporation contributes significantly to the climatologically August rainfall in SC. The dynamic component of vertical moisture advection, which is related to changes in atmospheric circulation, plays an important role in August precipitation trends. The possible physical mechanism is that the GAMIL2.0 considering the supercooled water simulated much higher soil/air temperature on August especially in the north of 40°N, weakened the meridional thermal contrast, decreased the 200hpa zonal winds, strengthened 850hpa northerly wind, which is more benificial to the convergence in SC and lead to the precipitation increased. This study provides a new interpretation of the ‘southern flooding’ during 1979–2008 from the point of frozen soil changing.

There is an approximately one-year observation gap of terrestrial water storage anomalies (TWSAs) between the Gravity Recovery and Climate Experiment (GRACE) satellite and its successor GRACE Follow-On (GRACE-FO). This poses a challenge for water resources management, as discontinuity in the TWSA observations may introduce significant biases and uncertainties in hydrological model predictions and consequently mislead decision making. To tackle this challenge, a Bayesian convolutional neural network (BCNN) is proposed in this study to bridge this gap using climatic data as inputs. Enhanced by integrating recent advances in deep learning, BCNN can efficiently extract important features for TWSA predictions from multi-source input data. The predicted TWSAs are compared to the hydrological model outputs and three recent TWSA prediction products. Results suggest the superior performance of BCNN in bridging the gap. The extreme dry and wet events during the gap period are also successfully identified by BCNN.

Motivated by previous measurements of very low tropospheric ozone concentrations in the Tropical West Pacific (TWP) and the implied low oxidizing capacity of this key region for transport into the stratosphere (e.g. Rex et al. 2014), we set up an atmospheric research station in Palau (7° N 134° E). Our analysis of regular balloon-borne tropospheric ozone observations at Palau from 01/2016-10/2019 confirms the year-round dominance of a low ozone background in the mid-troposphere. Layers of enhanced ozone are often anti-correlated with water vapor and occur frequently. Moreover, the occurrence of respective layers shows a strong seasonality. Dry and ozone-rich air masses between 5 and 10 km altitude were observed in 71 % of the profiles from February until April compared to 25 % from August until October. By defining monthly atmospheric background profiles for ozone and relative humidity based on observed statistics, we found that the deviations from this background reveal a bimodal distribution of RH anomalies. A previously proposed universal bimodal structure of free tropospheric ozone in the TWP could not be verified (Pan et al. 2015). Back trajectory calculations confirm that throughout the year the mid-tropospheric background is controlled by local convective processes and the origin of air masses is thus close to or East of Palau in the Pacific Ocean. Dry and ozone-rich air originates in tropical Asia and reaches Palau in anticyclonic conditions over an area stretching from India to the Philippines. This supports the hypothesis of several studies which attribute ozone enhancement against the low ozone background to remote pollution events on the ground such as biomass burning (e.g. Andersen et al. 2016). A potential vorticity analysis revealed no stratospheric influence and we thus propose large-scale descent within the tropical troposphere as responsible for dehydration of air masses on their way to Palau.

The Madden-Julian Oscillation (MJO) is the leading mode of intra-seasonal climate variability, having profound impacts on a range of weather and climate phenomena. Here, we use a wavelet-based spectral Principal Component Analysis (wsPCA) to evaluate the skill of 20 state-of-the-art CMIP6 models in capturing the magnitude and dynamics of the MJO. The advantages of wsPCA are its ability to focus on desired frequencies and capture each propagative physical mode with one principal component (PC). We show that the MJO contribution to the total intra-seasonal climate variability is substantially underestimated in most CMIP6 models. The joint distribution of the modulus and angular frequency of the complex wavelet PC series associated with MJO is used to rank models relatively to the observations through the Wasserstein distance. Using Hovmöller phase-longitude diagrams, we show that precipitation variability associated with MJO is underestimated in most CMIP6 models for the Amazonia, Southwest Africa, and Maritime Continent.

In this paper, we analyzed the fine structure of the rotational discontinuity (RD) in the magnetopause of the open magnetosphere by using the MMS four-point magnetic field measurements. It is found that RD is very common within the magnetopause when reconnection occurs at the magnetopause. Furthermore, RD usually occurs closer to the magnetosheath side of the magnetopause. RD is very thin and its thickness is usually much smaller than 0.1 Re. The magnetic field rotation maximums and magnetic strength minimums within the RD. The radius of curvature of the magnetic field lines reaches its minimum value in the RD (~0.03-0.62 Re). In addition, the radius of curvature of magnetic field line of RD is usually larger than the thickness of RD structure, indicating that the magnetic field lines are partly lying in the RD. Generally，the field-aligned current dominates in the RD.

In atmospheric models with kilometer-scale grids the resolution approaches the scale of convection. As a consequence the most energetic eddies in the atmosphere are partially resolved and partially unresolved. The modeling challenge to represent convection partially explicitly and partially as a subgrid process is called the convective gray zone problem. The gray zone issue has previously been discussed in the context of regional models, but the evolution in regional models is constrained by the lateral boundary conditions. Here we explore the convective gray zone starting from a defined global configuration of the Met Office Unified Model using initialized forecasts and comparing different model formulations to observations. The focus is on convection and turbulence, but some aspects of the model dynamics are also considered. The global model is run at nominal 5km resolution and thus contributions from both resolved and subgrid turbulent and convective fluxes are non-negligible. The main conclusion is that in the present assessment, the configurations which include scale-aware turbulence and a carefully reduced and simplified mass-flux convection scheme outperform both the configuration with fully parameterized convection as well as a configuration in which the subgrid convection parameterization is switched off completely. The results are more conclusive with regard to convective organization and tropical variability than extratropical predictability. The present study thus endorses the strategy to further develop scale-aware physics schemes and to pursue an operational implementation of the global 5km-resolution model to be used alongside other ensemble forecasts to allow researchers and forecasters to further assess these simulations.

To date, actively flowing lava has only been observed on Earth and on Jupiter’s moon Io. This lack of observation means that for the vast majority of volcanic systems in the Solar System, solidified lava-flow morphologies are used to infer important information about eruption and emplacement parameters. These include: lava supply rate, lava composition, lava rheology, and determination of laminar or turbulent emplacement regimes. Commonly used models that relate simple lava flow morphologic properties (e.g., width, thickness, length) to emplacement characteristics are based on assumptions that are readily misinterpreted. For example, the simplifying assumption of fully turbulent lava flow allows for a thermally mixed flow interior, but ignores the lava properties that naturally work to suppress full turbulence (such as thermal boundary layers encasing active lava flows, and a temperature-dependent lava rheology). However, full turbulence in silicate lava flows erupted into environments that have temperatures lower than the lava solidification temperature requires a rare combination of characteristics. We model Bingham Plastic, Newtonian, and Herschel-Bulkley fluids in rectangular channels, tubes, and sheets with computational fluid dynamics (COMSOL) software to obtain flow solutions and general flow rate equations and compare them to field measurements of volcanic velocity and flow rates. We present these as more realistic alternatives to older simpler rate-from-morphology models. We find that several lava rheology properties work together to delay the onset of turbulence as compared to isothermal Newtonian materials, and that while turbulent lavas flows certainly exist, they are not as prevalent as the published literature might indicate. Results obtained from models that assume full turbulence in silicate flows on the terrestrial planets should therefore be interpreted cautiously.

The Southern African Magnetotelluric Experiment (SAMTEX) involved the collection of data at over 700 sites in Archean to Proterozoic southern Africa, spanning features including the Kalahari Craton, Bushveld Complex and voluminous kimberlites. Here, we present the first 3D inversions of the full SAMTEX dataset. In this paper, we focus on assessing the robustness of the 3D models by comparing two different inversion codes, jif3D and ModEM, and two different subsets of the data, one containing all acceptable data and the other containing a smaller selection of undistorted, high-quality data. Results show that the main conductive and resistive features are imaged by all inversions, including deep resistive features in the central Kaapvaal Craton and southern Congo Craton and a lithospheric-scale conductor beneath the Bushveld Complex. Despite this, differences exist between the jif3D and ModEM inverse models that derive mainly from the differences in regularization between the models, with jif3D producing models that are very smooth laterally and with depth, while ModEM produces models with more discrete conductive and resistive features. Analysis of the differences between these two inversions can provide a good indication of the model resolution. More minor differences are apparent between models run with different subsets of data, with the models containing all acceptable data featuring higher wavelength conductivity variations than those run with fewer stations but also demonstrating poorer data fit.

In the 2011 Tohoku-Oki earthquake, the rupture in the subduction megathrust reached the trench axis and triggered a large tsunami. The shallow portion of the subduction megathrust fault was regarded as an aseismic stable zone. The frictional properties along the shallow subduction plate boundary are an important foundation for understanding the cause of the dynamic fault rupture in the earthquake near the trench. The critical taper model of a sedimentary wedge best describes the first-order mechanics of a subduction zone wedge. The tapered wedge geometry (slope angle α and basal dip angle β) is responsible for the strength of a shallow megathrust. However, to apply the critical taper model for the investigation of spatial heterogeneity, we need to improve handling β, since β is derived from the subsurface structure and its value depends on the number of accurately depth-converted seismic profiles. Here, the effect of décollement dip angle β in the critical taper model of a sedimentary wedge is examined. The effect is negligible for a high pore fluid pressure ratio, allowing the frictional variation to be obtained with only bathymetry data. We applied the model to the Japan Trench. The frictional variation indicates that a smaller frictional area corresponds to an area with a larger coseismic shallow rupture during the 2011 earthquake than those of the southern and northern areas. The method can be applied to other trenches to predict seismic potential.

The low-frequency intraseasonal oscillations (ISOs) dominate the subseasonal variability of the Indian summer monsoon and involve rainbands propagating northward from the equator. These oscillations modulate the active–break cycle of the monsoons and have two distinct regimes, one where rainfall maximum is located near the equator and the second one in which it is located around central India. The interaction of vorticity and divergence is an important feature for the northward propagation of ISOs. With a correlation study, we show that the low-frequency modes in vorticity and divergence are coupled in the boundary layer and upper troposphere. We use multichannel singular spectrum analysis to extract the low-frequency oscillatory modes in vorticity and divergence. The examination of the spatiotemporal structure of these modes reveals that vorticity has coherent northward propagation at all pressure levels. In contrast, divergence only shows propagation in the boundary layer and the upper troposphere. The vorticity low-frequency mode has a near barotropic structure, while the divergence mode has a baroclinic structure. We point out the contrasting features of vorticity and divergence for the two regimes of the ISO. The barotropic vorticity leads the rainfall for the equatorial region, whereas, for the central Indian region, the vorticity lags the rainfall. Meanwhile, the rainfall is in phase with baroclinic divergence for both regimes. These findings are relevant to understanding the initiation and propagation of ISOs and can contribute to the further development of simple models of these phenomena.

Monazite fission-track presents itself as a novel, low-temperature thermochronometer with annealing studies placing its closure temperature between ~45 and 25 °C. Previously, monazite has been unsuitable for fission-track dating due to high abundance of gadolinium and insufficient investigation of the etching protocol. Gadolinium causes self-shielding via thermal neutron capture and substantial associated nuclear heating during irradiation which prevented robust monazite fission-track dating using the traditional external detector method. Further, early etching studies were found to be extremely corrosive to monazite grains. However, developments in LA-ICP-MS fission-track analysis allow for measurement of 238U and improvements in monazite fission-track etching protocols mean that dating monazite through the fission-track method is now viable. In this study, we present monazite fission-track data from an elevation profile (2260 m, 2000 m, 1600 m, and 1200 m) from the Catalina metamorphic core complex (Catalina MCC), in southern AZ, USA. We follow the etching protocol described in Jones et al. (2019), etching the monazites in 6 M HCl for 90 minutes at 90 °C. We measure the 238U concentration via LA-ICP-MS and compare the dates to other multi-method thermochronology from the same rocks. Traditional low-temperature thermochronology (apatite and zircon fission-track, apatite and zircon (U-Th-Sm)/He) from the Catalina MCC reveals cooling at 25-20 Ma and 18-10 Ma. Preliminary monazite fission-track analysis yields a date of 6.1 ± 0.4 Ma, far younger than all the traditional thermochronometric data, in-line its far lower closure temperature. The 6 Ma monazite fission-track date is consistent with the youngest phase of hematite (U-Th)/He dates observed in the nearby Rincon metamorphic core complex and suggest that these dates correspond to the latest phase of exhumation in response to Basin and Range extension and/or climate enhanced erosion. These preliminary results show that monazite fission-track can reveal shallow crustal processes and contribute to constraining thermal histories below ~60 oC, which are traditionally difficult to resolve.