Oat crown rust caused by Puccinia coronata Cda f. sp. avenae Erikss (Pca), is a major constraint to oat (Avena sativa L.) production in many parts of the globe, with host resistance applied as a common strategy to curb crown rust epidemics. Combining multiple sources of crown rust resistance (for example, Pc genes conferring seedling resistance) in a single genetic background can be expedited by marker-assisted selection using molecular markers that are tightly linked with resistance loci. Pc96 is a race-specific crown rust resistance gene originating from cultivated oat that has been deployed in North American oat breeding programs. SNP markers linked with Pc96 were identified using multiple interval mapping with 899 polymorphic SNPs in a recombinant inbred line population developed from a cross between the oat crown rust differential known to carry Pc96 and the differential line carrying Pc54. A single resistance locus was identified on chromosome 7D between 60.4 and 91.6 cM with a peak LOD at 87.3 cM. The resistance locus and linked SNPs were validated in two additional biparental populations, Ajay x Pc96 and Pc96 x Kasztan. Genotype state at a combination of two linked SNPs predicted the absence of Pc96 in a broad group of germplasm with 5% miss-classification. SNPs that are closely linked to the gene may be beneficial as PCR-based molecular markers in marker-assisted selection.

Flux transfer events (FTEs) are transient magnetic flux ropes at Earth’s dayside magnetopause formed due to magnetic reconnection. As they move across the magnetopause surface, they can generate disturbances in the ultra-low frequency (ULF) range, which then propagate into the magnetosphere. This study provides evidence of ULF waves in the Pc2 wave frequency range caused by FTEs during dayside reconnection using a global 3D hybrid-Vlasov simulation (Vlasiator). These waves resulted from FTE formation and propagation at the magnetopause are particularly associated with large, rapidly moving FTEs. The wave power is stronger in the morning than afternoon, showing local time asymmetry. In the pre and postnoon equatorial regions, significant poloidal and toroidal components are present alongside the compressional component. The noon sector, with fewer FTEs, has lower wave power and limited magnetospheric propagation.

This study examines the impact of ocean advection and surface freshwater flux on the non-seasonal, upper-ocean salinity variability in two climate model simulations with eddy-resolving and eddy-parameterized ocean components (HR and LR, respectively). We assess the realism of each simulation by comparing their sea surface salinity (SSS) variance with satellite and Argo float estimates. Our results show that, in the extratropics, the HR variance is about five times larger than that in LR and agrees with the Argo estimates. In turn, the extratropical satellite SSS variance is smaller than that from HR and Argo by about a factor of two, potentially reflecting the low sensitivity of radiometers to SSS in cold waters. Using a simplified salinity conservation equation for the upper-50-m ocean layer, we find that the advection-driven variance in HR is, on average, one order of magnitude larger than the surface flux-driven variance, reflecting the action of mesoscale processes.

Joule heating deposits a significant amount of energy into the high-latitude ionosphere and is an important factor in many magnetosphere-ionosphere-thermosphere coupling processes. We consider the relationship between localized temperature enhancements in polar cap measured with the Resolute Bay Incoherent Scatter Radar-North (RISR-N) and the orientation of the IMF. Based on analysis of 10 years of data, RISR-N most commonly observes ion heating in the noon sector under northwards IMF Bz. We interpret heating events in that sector as being primarily driven by sunwards plasma convection associated with lobe reconnection. We attempt to model two of the observed temperature enhancements with a data-driven first principles model of ionospheric plasma transport and dynamics, but fail to fully reproduce the ion temperature enhancements. However, evaluating the ion energy equation using the locally measured ion velocities reproduces the observed ion temperature enhancements. This result indicates that current techniques for estimating global plasma convection pattern are not adequately capturing mesoscale flows in the polar cap, and this can result in underestimation of the energy deposition into the ionosphere and thermosphere.

The 15 Jan 2022 Hunga Tonga-Hunga Ha’apai volcano eruption drove global atmospheric waves that propagated into space and impacted the ionosphere. Here we show immediate large-scale electrodynamic effects of the eruption using observations from NASA’s Ionospheric Connection Explorer. We report extreme zonal and vertical ExB ion drifts thousands of kilometers away from Tonga within an hour of the eruption, before the arrival of any atmospheric wave. The measured drifts were magnetically connected to the ionospheric E-region just 400 km from Tonga, suggesting that the expanding wavefront created strong electric potentials which were transmitted along Earth’s magnetic field. A simple theoretical model suggests that the observed drifts are consistent with an expanding wave with a large (>200 m/s) neutral wind amplitude. These observations are the first direct detection in space of the immediate electrodynamic effects of a volcanic eruption and will help constrain future models of impulsive lower atmospheric events.

Naturally emitted reactive trace gases are thought to impact tropospheric composition, predominantly through the emission and chemistry of isoprene (C5H8). Other species are thought to play a less important role. Here the GEOS-Chem model is used to compare the impacts of isoprene and iodine emissions on present-day tropospheric composition. Removing isoprene emissions leads to a 4.4% decrease in tropospheric O3 burden, a smaller absolute change than the 5.7% increase from removing iodine emissions. Iodine has a negligible impact on global mean OH concentrations and methane lifetime (-0.2% and +0.1%). Isoprene has a substantial impact on both (-7% and +6.5%). Isoprene emissions and chemistry are seen as essential for tropospheric chemistry models, but iodine is often not. We suggest iodine should receive greater attention in model development and experimental research to allow improved predictions of past, present and future tropospheric O3.

In this study, we report results from three analogue models with similar initial setup and different amounts of bulk shortening, to simulate a development of a pop-up structure in fold-and-thrust belts at different stages. Samples are taken in different places of the deformed models for analysis using anisotropy of magnetic susceptibility. Shortening of the models resulted in the formation of a pop-up structure, which is bounded by backthrust(s) and complex forekink zone(s). Several forethrusts at different degrees of maturity developed in front of the pop-up structure. Three distinct types of magnetic fabric can be identified throughout the models: (i) a compactional oblate fabric that changes as function of distance towards a localized deformation zone (e.g., thrust or kinkzone), (ii) a thrust-induced fabric with magnetic foliation parallel to the thrust surface, and (iii) a complex forekink zone fabric with broad girdle distributions of principal axes and magnetic lineation perpendicular to shortening direction. The latter indicate interplay between folding and thrusting of the shortened sand layers. Additionally, a decrease in degree of anisotropy with appearance of a quantitatively more prolate fabric can be observed towards the thrusts and kinkzones. Additionally at thrusts, a variation in strain is reflected by the magnetic fabric and can be inherited in a thrust-induced fabric. In conclusion, strain is changing as function of distance towards localized deformation zones with characteristic fabric, and differences in magnetic fabric are distinct between data away and within deformation zones as deformation zones mature.

High resolution eddy resolving models are shown to be necessary for simulating submesoscale variability of the ocean. Although how these resolved submesoscale features impact the larger scale simulations is not yet clear. Here, using satellite observation and model experiments based on Modular Ocean Model (MOM5), we investigate the impact of model resolution in the sea level variability of the north Indian Ocean in the seasonal and intraseasonal time scale. While one model experiment uses uniform 0.25 o horizontal resolution with 40 vertical levels, in the second experiment model resolution is increase to uniform 0.05 o in horizontal with 50 vertical levels. The high resolution model shows significant improvement in simulating mean sea level and its variability especially along the coast of India, in the equatorial regime and in the western Arabian Sea. The Great Whirl and its extension become more realistic as the resolution increases. We show that these improvements are owing to the better representation of the mesoscale variability of the upper ocean water column. Further, we show that the coarser model tends to get biased towards wind-driven Ekman circulation in the open ocean and produce stronger seasonal signal along the coast.

In recent years, various models have been developed to describe Arctic coastal erosion. Many models are process-based, simulating multiple physical processes and combining them interactively to resemble Arctic coastal erosion. One limitation of the current process-based models is the difficulties in including the hydrodynamic forces. The morphological changes by the hydrodynamics are either simplified or simulated by some empirical relation. The reason for excluding detailed hydrodynamic forcing is the absence of thermal energy conservation in the systems of equations inside the available software. Most hydrodynamic models are designed considering the warmer climate, where waves, tides and storm surges cause changes in morphology. The available models cannot be applied where permafrost is a significant environmental parameter. This paper explains a methodology that allows us to use the models designed for warmer climates to simulate Arctic coastal erosion. The open-source software XBeach is used to simulate the waves, sediment transport and morphological changes. We developed different submodules for the processes related to permafrost thawing-freezing, slumping, wave-cut niche, bluff failure, etc. The submodules are coupled with the XBeach following a workflow where ice concentration, storm surge and bluff collapse work as an on-off switch. The submodules communicate with each other at three-hour intervals. The input parameters of the model are calibrated with field measurements. The model is then validated by another set of mutually exclusive field measurements under different geological conditions. The model can simulate the short term (one year) and long term (a few years) with the same level of fidelity.

In this paper, we use standard extreme temperature indices to detect and attribute external forcing in Madagascar. These indices are calculated from observations and multi-model ensemble mean responses on anthropogenic-plus-natural (ALL), greenhouse gases (GHG), natural (NAT) and anthropogenic (ANT) which is subtracted from ALL and NAT forcings over 1950-2018. Correlation analysis emphasizes that the observed changes are more influenced by ENSO events especially in minimum temperature. The observed changes are regressed or combined with model simulations from sixth phase of the Coupled Model Inter-comparison Project (CMIP6) to assess human impacts in indices. CMIP6 models with ALL, GHG, ANT forcings correspond well with the observations for the frequency indices that the intensity indices. Moreover, decadal trends indicate the existence of anthropogenic warming according to observations and multi-model ensembles with ALL, GHG, and ANT forcings. Detection and attribution parties identify and justify the causes of the observed changes. We do this by performing the single-signal and two-signal analysis using the Regularized Optimal Fingerprinting (ROF) method with Total Least Square (TLS) regression. We estimate internal climate variability by means of control model simulations. As a result, we note an inconsistency in the warming trend with the NAT forcing. The influence of ALL, GHG and ANT forcings is detectable for standard extreme temperature indices between 1950 and 2018. Nearly, observed changes are attributed to GHG and ANT forcings except for coldest night and warm nights in Madagascar.

The long-term climatology of high-frequency quasi-monochromatic gravity waves is presented using multi-year airglow images observed at Andes Lidar Observatory (ALO, 30.3ºS, 70.7ºW) in northern Chile. A large number of high-frequency gravity waves were retrieved from OH airglow images. The distribution of primary wave parameters including horizontal wavelength, vertical wavelength, intrinsic wave speed, and intrinsic wave period are obtained and are in the ranges of 20–30 km, 15–25 km, 50–100 ms-1, and 5–10 min, respectively. The waves tend to propagate against the local background winds and show clear seasonal variations. In austral winter (Ma–Aug), the observed wave occurrence frequency is higher and preferential wave propagation is equator-ward. In austral summer (Nov–Feb), the wave occurrence frequency is lower and the waves mostly propagate pole-ward. Critical-layer filtering plays an important role in determining the preferential propagation direction in certain months, especially for waves with a small observed phase speed (less than typical background winds). The wave occurrence and preferential propagation direction are shown to be related to the locations of convection activities nearby and their relative distance to ALO. However, other possible wave sources such as secondary wave generation and possible ducted propagation cannot be ruled out. The estimated momentum fluxes have typical values of a few to 10 m2s-2 and show seasonal variations with a clear anti-correlation with local background wind directions.

Further extension of skillful prediction of tropical cyclones (TCs) relies on in-depth studies about the intrinsic predictability of TCs. In this study, convection-resolving ensemble forecasts based on the Hurricane Weather Research and Forecasting model were adopted with perturbed initial conditions to study the error growth and intrinsic predictability of TCs. The new aspect of our study is the focus on the sensitivity of TC track and intensity predictability to initial errors in different regions, including (1) the inner core and outer rainbands (0-350 km), (2) the near environment (350-1300 km), and (3) the far environment (1300-3500 km). The results of TC track predictability show that the most sensitive region of initial errors for TC track forecasts is case-dependent. For the TC case with striking track forecast errors (e.g., Typhoon Chan-hom, 2020), the initial errors in the combined region of the TC inner core and outer rainbands produce the largest track uncertainties compared to those in the near and far environment. However, for the TC case with a highly predictable track (e.g., Typhoon Maysak, 2020), the most sensitive region of initial errors is the near environment at early lead times and the far environment later. By contrast, the most sensitive region for TC intensity is the inner core for both cases. The surface wind structure of TC inner core at larger scales (wavenumbers 0-2) can be predicted for more than 3.5 days, while the structure at smaller scales can only be predicted for a few hours.

NASA’s Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) laser altimeter launched in Fall 2018, providing an invaluable addition to the polar altimetry record generated by ESA’s CryoSat-2 radar altimeter. The simultaneous operation of these two satellite altimeters enables unique comparison studies of sea ice altimetry, utilizing the different frequencies and profiling strategies of the two instruments. Here, we use freeboard data from ICESat-2 to assess Antarctic snow freeboard retrievals from CryoSat-2. We first discuss updates made to a previously-published CryoSat-2 retrieval process and show how this Version 2 algorithm improves upon the original method by comparing the new retrievals to ICESat-2 in specific along-track profiles as well as on the basin-scale. In two near-coincident along-track profiles, we find mean snow freeboard differences (standard deviations of differences) of 0.3 (9.3) and 7.6 cm (9.6 cm) with 25 km binned correlation coefficients of 0.77 and 0.89. Monthly mean freeboard differences range between -2.9 (10.8) and 6.6 cm (16.8 cm) basin wide, with the largest differences typically occurring in Austral fall months. Monthly mean correlation coefficients range between 0.57 and 0.80. While coincident data show good agreement between the two sensors, they highlight issues related to geometric and frequency sampling differences that can impact the freeboard distributions.

Human inputs of pollutants to the atmosphere and subsequent deposition may decrease pH in the coastal waters. Significant rate of decrease in pH and increase in pCO2 by 3 to 5 times is noticed in the coastal Bay of Bengal (BoB) than the global trend in the last few decades. We provide evidence for the first time for a rapid decrease in surface water pH due to atmospheric deposition of pollutants in the coastal BoB. The decrease in pH in the coastal BoB over the last decade is associated with concomitant increase in aerosol optical depth (AOD), total suspended particles (TSP) in air, sulphate and nitrate concentrations in TSP. This study suggests that contamination of surface coastal BoB by atmospheric pollutants not only acidifies surface ocean but also potentially amplifies CO2 emission with immediate implications to regional weather and climate.

Pulsating auroras (PsAs) are considered to be caused by energetic (~10 keV) electron precipitations. Additionally, soft electron precipitations (~1 keV) have often been observed in PsAs. These soft electron precipitations enhance the electron density in the ionospheric F region. However, to date, the relationship between PsAs and soft electron precipitation has not been well understood. In this study, using the data taken by the European incoherent scatter radar and the auroral all-sky imager at Tromso;, we conducted two case studies to investigate, in detail, the relationship between the electron density height profile and the type of aurora. Additionally, we conducted statistical studies for 14 events to elucidate how often F region electron density enhancement occurs with a PsA. We consequently found that 76% of electron density height profiles showed a local peak in the F region, with electron temperature enhancements. It was also found that 89% of the F region peak altitudes were above the peak altitude of the ionization rate produced by electrons of characteristic energy below 100 eV. The occurrence rate of these profiles in the hourly magnetic local time (MLT) exceeded 80% in the 22–3 MLT sectors. We suggest that the electron density enhancement in the F region would have been caused by electrostatic electron cyclotron harmonic waves in the magnetosphere. Another candidate would have been polar patches that had traveled from the dayside ionosphere.

We have measured the salt content changes of soil samples in laboratory experiments to simulate the salt and water migration that may cause duricrust formation on Mars. Although the cold, dry surface of modern Mars lacks abundant, liquid water, salts may stabilize scant liquid water as thin films through freezing point depression, allowing them to migrate along temperature and water concentration gradients driven by evaporation at the surface, and to transport salts where they precipitate and cement loose soil grains into crusts. Our work also demonstrates that spectral data complements salt content changes we measured, by showing changes in the hydration states inferred in the 1950 nm water band. We simulated salt and water migration, required in salt crust formation, in Mars analog regolith, through desiccating wet loess doped with either MgCl2, MgSO4, or CaSO4 at a temperature range of -196 °C to 150 °C. Our experiments allowed exploring temperature and depth dependencies on water and salt behaviors in 2 cm tall cylindrical soil sample tubes. The 1000 nm to 2400 nm spectral slope and the area of the 1950 nm water band correlate with salt concentration. MgSO4 exhibits the greatest migration, CaSO4 hydrates with weak migration, and MgCl2 migrates with moderate hydration. Spectral analysis may be useful in estimating salt and water migration, and in turn, aiding in interpreting hydrological and climatic history of the regolith of Mars.

Approximately eight months of co-located spaceborne lidar and lightning observations were analyzed in a pathfinder study to understand the advantages and challenges of using these combined observations to understand thunderstorms. Data from the Lightning Imaging Sensor (LIS) and the Cloud-Aerosol Transport System (CATS) lidar were used when they overlapped on the International Space Station during March-October 2017. Using simple matching criteria, 8246 LIS flashes occurred within 25 km of the CATS ground track. CATS cloud-top heights near these flashes showed similar behavior with latitude when compared to a spaceborne radar-based climatology, but the lidar cloud tops were approximately 2-km higher than 20-dBZ radar echo tops. CATS cloud phase near LIS flashes was consistent with ice or mixed-phase more than 90% of the time, showing the value of using lightning observations to validate lidar-based feature masks. In addition, correlations between a proxy for LIS flash rate and CATS ice water path, cloud optical depth, and cloud-top height were low (0.38-0.42) but positive and highly statistically significant (> 99%), suggesting lidar retrievals of cloud properties can be meaningfully compared with lightning observations despite lidar’s known inability to penetrate deeply into optically thick clouds like thunderstorms. Finally, CATS was used to help diagnose LIS false alarms due to surface-based glint. The false alarm rate was approximately 0.1%, which demonstrated the excellent performance of the surface glint filter in the LIS processing code. The results suggest that fruitful scientific insights can be expected from larger combined lidar/lightning datasets.

In the last few years, the relationship between reconnection and turbulence has received significant attention. A surprising recent result is that laminar reconnection has been shown to exhibit a power law spectrum consistent with the Kolmogorov law of turbulence1. However, there still exists an unanswered question: “Is magnetic reconnection fundamentally an energy cascade?”. The energy cascade can be measured directly as a function of spatial scale length using the generalized von-Karman Howarth equation based on the framework of incompressible Hall MHD2. In this study, we apply this technique to 2.5D kinetic particle-in-cell (PIC) simulations of strong turbulence and laminar reconnection, comparing the two to study the flow of energy across spatial scales (lags). Both the turbulence and reconnection simulations show similar behavior, implying that reconnection fundamentally involves an energy cascade. The largest lags are dominated by a steady decrease in energy (second order structure functions) which drives the global system dynamics. At smaller lags, a relatively constant flow (cascade) of energy occurs from large to small scales which can be associated with an MHD inertial range. At still smaller lags, the rate of energy flow decreases considerably, and this energy flux is dominated by Hall physics. In the reconnection simulation, the cascade of energy is strongly correlated with the reconnection rate, with both shutting off at similar times. References: Adhikari et al., Phys. Plasmas 27, 042305 (2020); https://doi.org/10.1063/1.5128376 Hellinger et al., ApJ Letters 857, L19 (2018); http://doi.org/10.3847/2041-8213/aabc06