bluuebunny/crossref_metadata_2025 huggingface dataset:
Greenhouse gas fluxes from Downy Birch stems during the spring sap-run period and their dependence on dissolved gas concentrations in xylem sap
Authors: Ranniku Reti , Truupõld Joosep , Espenberg Mikk , Escuer-Gatius Jordi , Ali Kazmi Fahad , Mander Ülo , Soosaar Kaido
Published: March 2024

Tree stems are known to emit greenhouse gases CH4, CO2 and N2O to the atmosphere but the processes and drivers behind these fluxes are still contested. Soil water is taken up by tree roots and moves up the xylem due to a negative pressure gradient caused by transpiration through the leaves. Consequently, dissolved gases in the soil water move up the stem and are potentially diffused to the atmosphere through the bark. Periods of soil freeze-thaw in the spring are crucial hot-moments of GHG release from the soil, as well as stems. As birch trees go through a sap running period between the thawing of the soil and bud break, they provide an opportunity to study stem GHG fluxes during the peak time of emissions, together with the concentrations of dissolved gases in the birch sap.We quantified the fluxes of CH4, CO2 and N2O from Downy birch (Betula pubescens), as well as Norway spruce (Picea abies) for comparison, in a temperate nutrient-rich drained peatland forest in April and May 2023. In addition, we studied the relationship between birch stem fluxes and dissolved gas concentrations inside the xylem sap. Stem fluxes were determined using static chambers attached to the tree stems and automatic LI-COR gas analysers. Dissolved gas samples were extracted from the collected birch sap and soil water after water-atmosphere equilibration, and were analysed in the lab using gas-chromatography. In addition, we analysed the relationships between the chemical and microbiological composition of the soil and soil and stem GHG fluxes.Birch stem CH4, CO2 and N2O fluxes peaked in the end of April, following the the temporal trend of soil and air temperature, with higher fluxes during warmer days, likely related to increased microbial activity in the soil. Dissolved CH4 concentrations in the birch sap peaked with a delay in relation to peak stem emissions, indicating that xylem sap flow rate needs to be studied to comprehend the water dynamics inside the stem. Relationships between stem fluxes and dissolved gas concentrations were strongest at the bottom part of the tree. A more detailed analysis together with examination of the underlying soil chemistry and microbiology will be presented to further explain the processes behind soil and tree stem GHG flux dynamics.
Stratospheric composition variability observed from the International Space Station (ISS) by the Stratospheric Aerosol and Gas Experiment III (SAGE III/ISS)
Authors: Flittner David , Roell Marilee , Manion Robbert , Leavor Kevin
Published: March 2024

After completion of the robot installation on the International Space Station (ISS) in early March 2017 as an external hosted science payload, the Stratospheric Aerosol and Gas Experiment (SAGE) III became the newest member to the family of space-based solar occultation instruments operated by NASA to investigate the Earth’s upper atmosphere since the late 1970s. One of three identical instruments, the SAGE III/ISS mission was revived in the early 2010s with a primary objective to monitor the vertical distribution of aerosol, ozone and other trace gases to enhance understanding of ozone recovery and climate change processes in the upper atmosphere. The 51.6-degree inclined orbit of the ISS is well-suited for solar occultation and provides near-global observations on a monthly basis with coverage of low and mid-latitudes similar to that of the SAGE II mission, which operated over two decades – outliving its platform.  International commitment to continuing ISS as a science outpost throughout this decade enables SAGE III to serve as a bridge to future stratospheric composition missions.The nominal science products, derived from sampling spectra covering 290nm to 1030nm and a photo-diode near 1550 nm, include high resolution vertical profiles of ozone, nitrogen dioxide and water vapor, along with multi-wavelength aerosol extinction. Although in the visible portion of the spectrum the brightness of the Sun is a million times that of the full Moon, the SAGE III instrument design covers this large dynamic range, performing lunar occultations on a routine basis to augment the solar products. The standard lunar products include ozone and nitrogen trioxide. Routine observations began June 2017 and continue to the present. This has enabled observations of significant perturbations of the stratosphere induced by multiple episodic terrestrial events - wildfires (two of which were record setting) and volcanic eruptions - and dynamical forcings such as phase changes of the Quasi-Biennial Oscillation (QBO).  Here is presented stratospheric variability as represented in the standard SAGE III/ISS data products since 2017.  The stability of observations afforded by the solar occultation technique is superb for quantifying long-term changes in stratospheric composition.  Thus, comparisons with variability recorded by previous SAGE missions are also shown. 
Methane and Nitrous Oxide Fluxes in Soil and Stems of Malaysian Tropical Peat Swamp Forest
Authors: Soosaar Kaido , Melling Lulie , Ranniku Reti , Sangok Faustina E. , Pärn Jaan , Wong Guan Xhuan , William Sebestian Kalang , Kasak Kuno , Espenberg Mikk , Öpik Maarja , Mander Ülo
Published: March 2024

Tropical peat swamp forests are crucial global carbon (C) reserves. Prevailing waterlogged conditions in peat soils prevent the complete decomposition of dead plant material. As a result, more organic matter is produced than decomposed, leading to the gradual accumulation of peat. However, the destabilisation of tropical peatlands through climate warming, droughts, and changes in land use threaten this C sink capacity. Anaerobic conditions in peat soils lead to methane (CH4) production through decomposition and nitrous oxide (N2O) production under moderate levels of soil oxygen content. Earlier evidence suggests that tree stems in tropical peat swamp forests are significant sources of CH4; however, little information is available on their exchange of N2O.This study investigated CH4 and N2O exchange of soil and stems of Combretocarpus rotunditus and Shorea albida trees in a peat swamp forest in Sarawak, Malaysia, from September 2022 to September 2023. To describe the temporal dynamics of greenhouse gas (GHG) exchange, we measured gas fluxes from the soil and stems at different heights (10, 80 and 170 cm from the tree's base) using the manual static chamber method and spectroscopic gas analysis. The chemical composition of the soil was analysed and several environmental parameters, including groundwater level, soil moisture content, soil and air temperature, were simultaneously measured with the GHG fluxes to determine the relationships between the fluxes and environmental factors.Soil CH4 emissions varied between 52.3 and 807 μg C m−2 h−1, with higher values observed during the wet season in conjunction with higher groundwater levels. On the other hand, the soil N2O fluxes were relatively low and did not show a distinct seasonal pattern, ranging from -1.33 to 3.54 μg N m−2 h−1. Annual average soil CH4 and N2O emissions were 392 μg C m−2 h−1 and 0.65 μg N m−2 h−1, respectively. The highest average stem CH4 emissions (1.48 μg C m−2 h−1) were recorded at the lowest parts of trees, with a vertical decrease in emissions and an overall uptake observed at the highest measurement point. In contrast, stem N2O emissions were small, with no clear trend with measurement height.In summary, we observed moderate and variable soil CH4 emissions with limited generalisable relation to measured environmental parameters. Soil and stem N2O emissions were relatively small. These results indicate the need for further comprehensive soil and stem GHG analyses in tropical peat swamp systems to better understand the GHG dynamics of this critical ecosystem.
Enhancing NESDIS Global Automated Snow and Ice Cover Mapping System
Authors: Romanov Peter
Published: March 2024

A new version of the Global Multisensor Automated Snow and Ice Mapping System (GMASI) has been implemented into operations at NESDIS is summer 2023. The new system is an upgrade of the previous version of the GMASI which was operated since 2006. The system provides information on the snow and ice distribution for NOAA numerical weather prediction and climate models as well as for a number of other atmosphere and land remote sensing products. The retrieval algorithm uses satellite observations in the visible/infrared and in the microwave spectral bands and delivers daily spatially continuous (gap-free) maps of the snow and ice cover.  Compared to previous version, the new system incorporates data from a larger set of microwave sensors and features an enhanced retrieval algorithm. The spatial resolution of the output maps has been improved from es improved from 4km to 2km.  In the presentation we provide details of the data processing algorithm and of the output product focusing on the improvements and upgrades. We demonstrate that the output of the new GMASI system closely matches the accuracy of snow maps produced within NOAA Interactive Multisensor Snow and Ice Mapping System (IMS) and agrees well to in situ station snow depth report. Improvements to the retrieval algorithm mostly affected reproduction of small-scale features in the snow and ice cover distribution, particularly in alpine areas.  In the same time, large-scale climatologically-important cryosphere features as the continental and hemisphere snow and ice extent estimated with the new snow and ice maps remain consistent with the previous version of the product. 
Sea-ice variability on the Southeast Greenland shelf during the Late Holocene
Authors: Xiao Xiaotong , Wan Xia , Sha Longbin , Andresen Camilla S.
Published: March 2024

Arctic sea ice is a critical element of the climate system by regulating the global heat budget due to the albedo effect and sensitive to changes in atmospheric and oceanic circulation. The Southeast Greenland Shelf is a climatologically sensitive area where sea ice changes are not only affected by local sea ice formation but also drift ice and cold freshwater outflow from the Arctic Ocean by East Greenland Current (EGC), which makes this area challenging for paleo-sea ice reconstruction. Here, we analyze biomarker concentrations from a sediment core located on the Southeast Greenland Shelf to reconstruct the sea-ice variability to capture the neoglacial climate change. The biomarker record shows a long-term cooling trend over last 3.5 kyr, and four centurial periods were established combined with terrigenous (glaciers) and oceanic (currents) variations. We suggest a north-south heterogeneous sea-ice variability on the East Greenland shelf from 3.5-1.2 kyr BP. Moreover, a widespread sea-ice expansion within North Atlantic regions, concurrent with the glacier advances prior to Little Ice Age, is proposed to be a pre-Little Ice Age cooling from 1.2 kyr BP. This predate cooling seemly ascribed to a swing to the negative Arctic Oscillation might be triggered by a drop of solar irradiation and a strong latitudinal insolation gradient and maintained by internal progresses.
Geochemical fingerprints of dolomitization in Upper Jurassic Arabian carbonate platform: Evidence from carbon, oxygen, strontium and magnesium isotopes
Authors: Jia Xiaolan , Li Weiqiang , Xia Zhiguang , Alsuwaidi Mohammad
Published: March 2024

The formation of extensive dolomite across ancient carbonate platform is widely attributed to the replacement of the calcium-carbonate so-called dolomitization. However, it is still unclear whether the extensive dolomite formation is controlled by one single or multiple mechanisms, as whether the mineralogical, petrological, and geochemical records of dolomite preserve the pristine signature or diagenetic effect is still under debate. In this study, we integrate carbon, oxygen, strontium and magnesium isotopes to provide new insights into ancient dolomite origin interpretation. Dolomite in the Upper Jurassic Arab Formation on the Arabian Plate has widely been studied due to the complete carbonate-evaporite cycle and relevance to oil reservoirs. Sabkha and seepage reflux dolomitization models have been proposed despite the high temperatures inferred from clumped isotopes and fluid inclusions, as well as some geochemical data such as oxygen and strontium isotopes, are inconsistent with near-surface dolomitization conditions. Here we performed integrated isotope study of the Upper Jurassic Arab Formation, and found that (1) Mg isotope data range from -2.25 ‰ to -1.78 ‰, suggesting the Mg cations for Arab dolomite formation were delivered from Late Jurassic seawater, which is consistent with the idea that dolomite is a valid archive of seawater Mg isotope composition through geological times; (2) in each cycle, more depleted Mg isotope signatures in dolomite formed at shallower depth than that formed at deeper depth, indicating top-down dolomitization process which is controlled by percolation of dense and saline fluids, suggesting the advective flow model and related seepage reflux dolomitization; (3) parts of Sr isotopic ratios are out of Late Jurassic seawater range, revealing hydrothermal or burial dolomitization probably altered the dolomite formed from near-surface conditions, which can also be verified by depleted oxygen isotopic values. This study indicates that ancient carbonate platform with massive dolomite distribution are probably generated by multi-mechanism dolomitization processes and it is necessary to integrate Mg isotope with traditional isotope methods to unravel the dolomite problem.
Exploring origin of life chemistry and exoplanet biosignatures with GCMs
Authors: Olson Stephanie , Jernigan Jonathan , Lafleche Emilie , Brown Haleigh
Published: March 2024

Studies of exoplanet habitability involving GCMs typically consider the potential for long-lived surface liquid water—or, in other words, climates that Earth-life may find survivable. However, the presence of life and remotely detectable biosignatures on an exoplanet additionally requires an independent origin of life and that life subsequently thrives rather than simply survives. The origin and proliferation of life are both strongly influenced by climate, and both can therefore be informed by GCM studies in parallel with traditional habitability metrics. Wet-dry cycles are thought to be an essential ingredient for the origin of life. Cyclic wetting and drying may arise from either diurnal or seasonal cycles, and thus the likelihood of an origin of life may differ between worlds with very different rotation rates, obliquities, or eccentricities. At the same time, seasonal mixing in aqueous environments can trigger highly productive blooms and amplify biosignatures relative to scenarios lacking temporal variability.  We used ExoPlaSim (an atmospheric GCM) and cGENIE-PlaSim (a 3D model for ocean dynamics and marine biogeochemistry coupled to a 3D atmospheric GCM) to explore diurnal and seasonal cycles on other worlds—with an eye towards origin of life chemistry and biosignatures. This presentation will ultimately identify the planetary scenarios most conducive to exoplanet life detection. 
Estimates of wave attenuation from ICESat-2 observations
Authors: Voermans Joey , Brouwer Jill , Fraser Alexander , Meylan Michael , Liu Qingxiang , Babanin Alexander
Published: March 2024

Energetic waves originating from the Southern Ocean can propagate great distances into the Antarctic ice pack. Along the way, they can significantly alter the composition of the ice whilst, at the same time, sea ice can significantly alter the characteristics of the wave field. Importantly, sea ice attenuates wave energy, thereby reducing their capacity to break the ice. Understanding of the rate of attenuation of wave energy in sea ice is thus critical to achieve accurate representation of sea ice in operational forecasting models. Observations of wave attenuation are, however, sparse as logistics to the harsh and remote Antarctic Marginal Ice Zone are limited. To this end, satellite remote sensing provides significant opportunities as it can cover large spatial areas, albeit at relatively low temporal resolution.Recent studies have shown the capabilities of ICESat-2 to not only measure surface height over land, ocean and sea ice at high accuracy, but also to distill wave field properties from these observations. Here, we use the quality-controlled data of Brouwer et al. (2022) to estimate the wave attenuation rate from ICESat-2 observations. We show that the magnitude of the estimated attenuation rates from ICESat-2 observations are largely consistent with those observed by others. As ICESat-2 provides a near-instantaneous snapshot of waves in sea ice, the data reveals unique spatial resolution of the attenuation rates across the Marginal ice Zone that cannot easily be obtained with surface buoys. Spatial variability of the estimated attenuation rates appears to be correlated with sea ice properties obtained from satellite derived products, such as sea ice thickness and sea ice concentration.
Antarctic 20th-Century Sea Level Mitigation Dominated By Uncertainty in 19th-Century East Antarctic Snow Accumulation
Authors: Eswaran Advik , Truax Olivia , Fudge Tyler
Published: March 2024

Increasing Antarctic snow accumulation can mitigate sea level rise, but considerable uncertainty surrounds both past snowfall trends and future sea level projections. Here, we present a reconstruction of 19th and 20th century Antarctic accumulation, and the 20th century cumulative impact on global mean sea level. Using the Last Millenium Reanalysis framework to integrate ice core accumulation and water isotope records with a multi-model ensemble of CMIP5 climate simulations, we produce annually resolved reconstructions from 1801-2000 CE. Reconstructions demonstrate significant skill through strong satellite-era correlation with instrumental reanalysis; we find a positive Antarctic accumulation trend over the 20th century, translating to a modest amount (~1 mm) of sea level mitigation. Mitigation is primarily driven by an accelerating trend since around 1970. These findings contrast with previous 20th century mitigation estimates of ~10-12 mm; we determine that this discrepancy is due to unconstrained baseline estimates of 19th century accumulation in East Antarctica. Our results suggest that uncertainties in East Antarctic accumulation history preclude a confident estimate of Antarctic sea level mitigation, thus highlighting the need for new, high-quality accumulation records from East Antarctica.
Anion Transport Through Bentonite Under Various Geochemical Conditions
Authors: Krol Magdalena , Chowdhury Farhana , Papry Sifat , Asad Md Abdullah , Mondal Pulin , Rashwan Tarek , Molnar Ian
Published: March 2024

The use of bentonite clay in industrial applications is widespread: it is used as an engineered barrier for long-term management of radioactive wastes, CO2 storage, landfill liners, and contaminant containment. These applications have diverse environmental conditions ranging from various temperatures, pHs, saline contents, and ionic concentrations. Since bentonite is a low permeability clay, anion transport is diffusion dominated but geochemical reactions can also play a significant role and transport will be affected by environmental conditions. In this study, anion transport (bisulfide) under various conditions was examined using experimental and numerical techniques to understand the various geochemical and surface mediated reactions that are occurring in the bentonite. The case study presented is for the use of bentonite in long term storage of nuclear waste but can be extended to other applications.First, diffusion experiments were performed to examine the transport and reactive nature of bisulfide (HS-) through bentonite compacted at dry density of 1090-1330 kg m-3. Experimental data of bisulfide transport were fitted using the inverse solution technique of Hydrus-1D model and different fitting parameters (e.g., diffusion, sorption, and reaction sink). Simulation results suggest that the HS- sorption/reaction affecting itsdiffusive transport through bentonite can be modeled using a simple nonlinear adsorption process.Second, batch experiments were performed to understand the maximum allowable sorption that could take place under key geochemical conditions, including temperature, pH, and ionic strength. The results of batch sorption experiments performed suggest that HS- sorption increases with increasing temperature but decreases with increasing pH and ionic strength.Lastly, since transport and reactive processes are interconnected, the results of these experiments were incorporated into a 1D transport COMSOL model to understand which geochemical process governs bisulfide transport through bentonite. Various processes were examined including linear and non-linear sorption, reactive transport, and anion exclusion. The model was validated using the experiments and showed that HS- was retained in the bentonite due to reactive processes and anion exclusion effects.
Hydrokinetic resource assessment for the Canadian Arctic
Authors: Bhattacharjee Koyena , Sushama Laxmi , Cousineau Julien
Published: March 2024

Increasing renewable energy development has rekindled interest in hydrokinetic or in-stream river potential for power production using zero head turbines. This is also of interest for remote regions such as the Canadian Arctic where decentralized power production from renewable energy sources is an economically viable option in offsetting the high cost of diesel power production. However, one of the major obstacles is the absence of streamflow data at necessary spatial and temporal scales for these regions. This study estimates the hydrokinetic power potential for current-based systems in the rivers of the Canadian Arctic region, primarily Nunavut and adjoining regions, for the current and near-future periods, based on streamflow estimated using a routing scheme applied to runoff generated by ultra-high-resolution simulations of the Global Environmental Multiscale (GEM) model, for a high emission scenario. GEM simulation for current climate, validated against gridded and station observation data, suggest reasonable performance of the model, particularly streamflow-relevant variables such as precipitation, snow water equivalent, soil and air temperatures given improved representation of processes and surface heterogeneity due to the higher resolution. This is also reflected in the comparison of simulated streamflow characteristics with available observations from HYDAT.Hydrokinetic power estimates over the study region show patterns similar to those of flow velocity as expected, with maximum hydropower being noted during the summer season for the central regions of Nunavut. Since the near-future period spans only till 2040, the changes in flow velocity and hydrokinetic power are minimal with an overall decrease of 2.5% for the southern and western regions of Nunavut and an increase of 2.5 to 5 % for some of the northernmost regions of Nunavut. The study further identifies ideal locations for the installation of hydrokinetic turbines for energy extraction, which require daily flow velocities above pre-defined thresholds, by considering indirectly also the impact of river ice on flow velocities. The results of this study provide useful information on hydrokinetic resources for the high-altitude regions of Canada by introducing a science-based approach and serve as a foundation for additional detailed investigations for site-specific studies to support the implementation of hydrokinetic energy conversion systems.
Teleseismic imaging results reveal Proto-South China Sea subduction remnants
Authors: Huiyan Shi , Tonglin Li
Published: March 2024

The subduction and disappearance process of the Proto-South China Sea is closely related to the opening of the South China Sea. Studying its subduction process and dynamic mechanism helps to explore the Cenozoic evolution model of the South China Sea. We collected teleseismic travel time data from Southeast Asia over the past 20 years, preprocessed the original data through data filtering, picking first arrival , and crustal correction, and obtained a three-dimensional velocity model of Southeast Asia using the Fast Marching Teleseismic Tomography(FMTT) method. The velocity imaging results reveal the presence of high-velocity anomalies in the mantle and mantle transition zones beneath Borneo and the Philippines. It is worth noting that the distribution range of serpentinite and serpentinite belt discovered in this area is highly consistent with the range of high-velocity anomaly bodies. Therefore, it is highly likely that the high-velocity anomalous bodies discovered in this area are remnants of the Proto-South China Sea subduction plate in the mantle transition zone. The morphology of residual subduction plates indicates that the Proto-South China Sea was subducted and closed from south to north, which may have had a certain impact on the Cenozoic seafloor spreading of the South China Sea; The detailed distribution range of residual plates further delineates the location of the disappearance of the Proto-South China Sea.
A New Era of Air Quality Monitoring from Space overNorth America with TEMPO: Commissioning and Early Nominal Operation Results
Authors: Liu Xiong , Chance Kelly , Suleiman Raid , Houck John , Davis John , Gonzalez Abad Gonzalo , Nowlan Caroline , Wang Huiqun , Chong Heesung , Hou Weizhen ,   TEMPO Team
Published: March 2024

We present an overview of the initial data products of TEMPO during its commissioning and early nominal operation and preliminary comparison with correlative satellite and ground-based observations.TEMPO is NASA’s first Earth Venture Instrument (EVI) and first host payload. It measures hourly daytime atmospheric pollution over North America from Mexico City to the Canadian oil sands, and from the Atlantic to the Pacific, at high spatiotemporal resolution (~10 km2 at boresight) from the geostationary (GEO) orbit. It uses UV/visible spectroscopy (293-493 nm, 538-741 nm) to measure O3 profiles including lower tropospheric O3 and columns of NO2, H2CO, SO2, C2H2O2, H2O, BrO, IO, as well as clouds aerosols, and UVB. TEMPO provides a tropospheric measurement suite that includes the key elements of tropospheric air pollution chemistry and captures the inherent high variability in the diurnal cycle of emissions and chemistry. The TEMPO instrument was built by Ball in 2018. It was integrated into the host commercial communication satellite Intelsat 40e (IS-40e) by Maxar. IS-40e was successfully launched on April 7 by a SpaceX Falcon 9 rocket on to the GEO orbit at 91°W. The TEMPO Instrument powered up for the first time on orbit in early June to start its commissioning. After a month of dry out and activation, TEMPO first light of solar and earth measurements occurred on July 31-August 2. Nominal operation started on 19 October 2023 after the commissioning phase and the post-launch acceptance review. Science data products are archived and distributed at NASA’s ASDC and will be released to the public in approximately February 2024 for L1b and in April 2024 for L2/3. TEMPO is part of a geostationary constellation to measure air quality along with GEMS (launched in Feb. 2020) over Asia and Sentinel-4 (to launch in 2024) over Europe.
Preliminary GEMS L2 validation results using ground-based measurements during the ASIA-AQ/SIJAQ campaign
Authors: Hong Hyunkee , Lee Hanlim , Jeong Ukkyo , Kim Joowan , Kim Serin , Kim Donghee
Published: March 2024

To validate L2 data of the Geostationary Environment Monitoring Spectrometer (GEMS) and to understand the causes of particulate matter generation in winter season, the National Institute of Environmental Research (NIER) in Korea and the National Aeronautics and Space Administration (NASA) in the U.S. will carry out a field campaign over four Asian countries (South Korea, the Philippines, Malaysia, and Thailand) in February through March 2024. In this campaign, NIER will install 12 ground-based remote sensing instruments such as Pandora, Max-DOAS, and AQ-Profiler in and around the Seoul metropolitan area and  retrieve nitrogen dioxide (NO2), formaldehyde, ozone vertical column density, NO2 vertical profile as well as aerosol properties (aerosol optical depth, single scattering albedo, size distribution, etc.). Especially, to investigate pixel inhomogeneity, we installed four instruments around an industrial complex within one GEMS pixel. During this campaign, NASA will observe NO2 and HCHO vertical column density using air-borne remote sensing instruments (e.g., GCAS: GeoCAPE airborne Simulator). Through this campaign, we plan to validate the performance of GEMS L2 data using ground-based and airborne measurements.
Optimization of kNDVI for improved biosphere monitoring with the AVHRR sensor 
Authors: León Hairo , Moreno-Martínez Álvaro , Piles Maria , Medina Katy , Loarte Edwin , Castillo-Vergara Francisco
Published: March 2024

Vegetation indices (VIs) calculated from spectral values have been widely used for monitoring the terrestrial biosphere. These indices serve as proxies for determining certain biophysical parameters, useful for monitoring vegetation. Due to its ease of application, the Normalized Difference Vegetation Index (NDVI) has been used as a proxy of various biophysical parameters. However, NDVI can only capture linear relationships between the difference of the near infrared (NIR) and red bands with various biophysical parameters. To address this limitation, the NDVI kernel (kNDVI) was proposed with certain reference values for optimal estimation, but it requires to be adjusted according to the object of study. 20 points distributed in different countries of Europe and Africa were chosen considering that the reflectivity information was representative of the whole study area and that it allowed us to distinguish diverse types of vegetation cover. Reflectivity data were obtained from the NIR and red bands of the AVHRR sensor at a temporal resolution every 8 days for the year 2012. Therefore, in an initial analysis, areas with little or no vegetation, such as areas covered by water bodies, glaciers, coastal strips and deserts, were discarded. Subsequently, we performed the optimization of this index using a Bayesian function that provides statistical improvements of its performance in estimating leaf area index (LAI) and compared it with the LAI product obtained from MOD15A2H.  

The results showed a good overall performance of the index, since the correlation coefficient of kNDVI and LAI was 0. 55, 0.70 and 0.52 for forests, agricultural areas and pastures, respectively. Likewise, the validation of the equation obtained for the estimation of LAI using the optimized kNDVI, yielded correlation values greater than 0.70 (in agricultural areas). Based on this, we confirm the overall satisfactory performance of the index and highlight its suitability for monitoring terrestrial ecosystems as well as for LAI estimation. However, we recommend a more specific or regionalized analysis according to the different cover types that could contribute to improving the estimates. These results were implemented in Google Earth Engine (GEE), to facilitate the analysis and discussion of the products obtained 
Near real-time construction of Solar Coronal Parameters based on MAS simulation by Deep Learning 
Authors: Rahman Sumiaya , Jeong Hyun-Jin , Siddique Ashraf , Moon Yong-Jae
Published: March 2024

Magnetohydrodynamic (MHD) models provide a quantitative 3D distribution of the solar corona parameters (density, radial velocity, and temperature). However, this process is expensive and time-consuming. For this, we apply deep learning models to reproduce the 3D distribution of solar coronal parameters from 2D synoptic photospheric magnetic fields. We consider synoptic photospheric magnetic fields as an input to obtain 3D solar coronal parameters simulated by the MHD Algorithm outside a Sphere (MAS) from June 2010 to January 2023. Each parameter is individually trained using 150 deep learning models, corresponding to 150 solar radial distances ranging from 1 to 30 solar radii. Our study yields significant findings. Firstly, our model accurately reproduces 3D coronal parameter structures across the 1 to 30 solar radii range, demonstrating an average correlation coefficient value of approximately 0.96. Secondly, the 150 deep-learning models exhibit a remarkably shorter runtime (about 16 seconds for each parameter), with an NVIDIA Titan XP GPU, in comparison to the conventional MAS simulation time. As the MAS simulation is a regularization model, we may significantly reduce the simulation time by using our results as an initial magnetic configuration to obtain an equilibrium condition. In the future, we hope that the generated solar coronal parameters can be used for near real-time forecasting of heliospheric propagation of solar eruptions.
Estimating Crop Evapotranspiration Variability in Processing Tomatoes Using High-Resolution Aerial Imagery and pySEBAL Algorithm
Authors: Peddinti Srinivasa Rao , Kisekka Isaya
Published: March 2024

In the pursuit of optimizing use of limited water resources in agriculture, leveraging high-resolution aerial imagery to estimate ETa (actual crop evapotranspiration) is of interest to farmers and water managers. However, there remains a dearth of information regarding the efficacy of energy balancing algorithms—initially developed for satellite remote sensing for estimating ETa from aerial imagery. This study presents an approach that estimates ETa for processing tomatoes employing high-resolution aerial data and the pySEBAL (Surface Energy Balance Algorithm for Land) remote sensing algorithm. During the 2021 growing season, an aircraft captured multispectral and thermal imagery over a processing tomato farm near Esparto, California, USA. Simultaneously, low-frequency biometeorological data essential for energy balance assessment, along with high-frequency turbulent fluxes, were measured by an eddy covariance flux tower installed within the field. Extensive evaluation of ETa and other energy balance components showed that pySEBAL produced accurate, high-resolution estimates of ETa. The root mean square error (RMSE) for the energy balance components were as follows: 33 Wm-2 for the latent heat flux, 29 Wm-2 for the sensible heat flux, 24 Wm-2 for the net radiation, and 10 Wm-2 for the soil heat flux. Moreover, the RMSE for ETa was 0.26 mm d-1. Notably, each component exhibited an R2 value exceeding 0.92. Furthermore, the ETa mapping of the processing tomato field delineated spatial variability linked to irrigation schedules, crop development, areas affected by disease, and soil heterogeneity, visually representing these aspects. This research underscores the pivotal role of high-resolution spatial aerial imagery and the pySEBAL algorithm in estimating ETa variability within fields, demonstrating high potential for improving precision irrigation management and maximizing the judicious utilization of water resources in agriculture.
Hydroclimatic characteristics on the Chinese Loess Plateau over the past 250 years inferred from tree rings
Authors: Cai Qiufang , Liu Yu
Published: March 2024

    Recurrent droughts in history, especially climatic aridity since the mid-20th century have aroused great social anxiety about the water resources in the Chinese Loess Plateau (CLP). Given lacking of extended instrumental-like records, new precipitation reconstructions in the CLP are badly needed for objectively evaluating the current precipitation situation, understanding the spatial-temporal differences, and serving for predicting the future. Here we present a tree-ring-based 248-year regional precipitation reconstruction (P8–7) in the Heichashan Mountain, which can significantly represent the past dry-wet variations in the eastern CLP (ECLP). P8–7 explains 48.72% of the instrumental record, reveals a wetting trend since the early 2000s and attains the second wettest period over the past 248 years in 2014–2020 AD. The 1920s/2010s is recorded as the driest/wettest decade. 1910–1932 AD ranks as the driest period over the past centuries. The 19th century is comparatively wet while the 20th century is dry. Precipitation in the ECLP and western CLP (WCLP) has changed synchronously over most time of the past two centuries. However, regional difference exists in the 1890s–1920s when a gradually drying occurred in the ECLP, while not evident in the WCLP, although the 1920s megadrought occurred in the CLP. Moreover, the 20th-century drying in the ECLP begins in the 1950s, later than the WCLP. It reveals that P8–7 variability is primarily influenced by the Asian Summer Monsoon and related large-scale circulations. The seismic phase shift of the contemporaneous Northern Hemispheric temperature may also be responsible for the 1920s megadrought.
New Constraints on Rock Glacier Geometry and Kinematics in the Western USA from Airborne- and Satellite-based Synthetic Aperture Radar
Authors: Handwerger Alexander L. , Munroe Jeffrey S.
Published: March 2024

Rock glaciers occur in high numbers in alpine landscapes around the world. These mixtures of ice and rock move downslope at rates from mm/yr to m/yr and can remain active for decades to millennial timescales. Here, we use airborne and satellite interferometric synthetic aperture radar (InSAR) to track the motion of more than 300 rock glaciers in Colorado and Utah, USA. We present a first-of-its-kind inventory of rock glaciers measured with the NASA/JPL Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) for our field site in Colorado. UAVSAR provides high resolution (0.6 x 1.6 m pixel spacing) measurements of surface motion along multiple viewing geometries, which allows us to accurately delineate rock glacier boundaries and invert for true 3D surface motion (as opposed to the typical 1D line-of-sight InSAR measurement). We collected UAVSAR data two months apart (July and September) on 8 different flight paths during the summer of 2023. We found that the rock glaciers are moving at rates up to 50 cm/yr during the summer period. We also apply volume conservation techniques to infer the subsurface geometry of multiple rock glaciers and better constrain rock glacier sediment flux. To gain a broader perspective of rock glacier motion over longer time periods (i.e., yearly to near-decadal), we also processed and analyzed satellite InSAR data from the ESA Sentinel-1 A/B satellites between 2015-2024 in Colorado and Utah. The satellite data showed that rock glaciers display seasonal and annual velocity changes, which we infer are driven by liquid water availability (i.e., snowmelt and rainfall). Our findings illustrate that rock glaciers exhibit complex kinematic patterns and geometries. Our new UAVSAR measurements provide key information for constraining rock glacier volume and sediment flux, particularly when combined with field- (e.g., GPS) and lab-measurements (10Be surface-exposure dating).
Instability in upper-ocean structure and its implications for Deep Water formation during marine isotope stage
Authors: Thibodeau Benoit , Doherty John , Alonso-García Montserrat , Band Shraddha , Gonazalez-Lanchas Alba , Not Christelle , Ren Haojia
Published: March 2024

The marine isotope stage (MIS) 11 interglacial, which occurred approximately 424 to 374 thousand years ago, is a period of significant climatological interest due to its unusual duration and intensity of warm conditions under relatively subdued orbital forcing, a phenomenon often referred to as the “MIS 11 paradox”. This study focuses on understanding the factors behind this paradox and its implications for the formation of Deep Water in the North Atlantic.We examined the upper-ocean structure in the Iceland Basin during MIS 11, a key region for modern deep-water formation. By analyzing geochemical measurements, including stable nitrogen isotopic ratios and carbon and oxygen isotopic ratios of planktic foraminifera, we reconstructed the upper-ocean structure and its potential role in driving the Atlantic Meridional Overturning Circulation (AMOC) during MIS 11.The findings reveal that MIS 11 experienced an initial AMOC intensification, followed by a secondary strengthening prior to the onset of the climatic optimum. The secondary intensification was attributed to the gradual reduction of northern-hemisphere sea ice, allowing for a northward extension of surface-ocean currents. This resulted in the maintenance of an anomalously deep summer mixed layer in the polar Nordic Seas during MIS 11 compared to the Holocene. The deep-water formation in the Nordic Seas played a crucial role in extending the enhanced warming of the northern hemisphere and delaying the onset of the next glacial interval.While the contemporary Atlantic Ocean primarily relies on deep-water formation in the eastern subpolar region, the study suggests that the relative importance of deep-water formation in polar regions may increase under extreme scenarios of anthropogenic warming. By studying MIS 11 as a potential analog for Earth's contemporary climate system, we provide valuable insights into the long-term fate of the AMOC and its implications for global climate.This study also highlights the significance of understanding the convective behavior of the subpolar Atlantic for a comprehensive understanding of the AMOC during MIS 11. We present new geochemical measurements and reconstructions of upper-ocean structure in the Iceland Basin, shedding light on the potential link between summer mixed-layer depth and deep-water formation.
Towards continental-scale mapping of supratidal forests to support blue carbon initiatives for Australia
Authors: Owers Christopher , Carvalho Rafael , Kelleway Jeffrey
Published: March 2024

Australia’s coastal wetlands include a diversity of vegetation structures and compositions across intertidal and supratidal elevations. While there have been significant recent advances in continental-wide information on mangrove and saltmarsh, neighbouring supratidal forests represent a significant missing link in knowledge of the distribution of coastal ecosystems in Australia. Without the ability to classify supratidal forests using remotely sensed imagery, it is currently not possible to identify where this ecosystem exists across Australia or to track changes over time, including increases in extent from restoration projects. This knowledge gap impacts a range of end-users, including federal and state/territory government portfolios responsible for monitoring and managing coastal wetland sites across Australia. In addition, the Clean Energy Regulator and project developers require access to current and historic coastal wetland extent to track and report on changes of supratidal forest extent for new Blue Carbon methods under Australia’s Emissions Reduction Fund. Access to publicly available, nationally consistent supratidal forest maps would further benefit coastal wetland managers, including state and territory governments, NRM groups and local councils across Australia.We have developed an initial ecosystem extent workflow and associated maps of supratidal forest distribution, with the view to develop a continental scale national supratidal forest mapping workflow for Australia. This workflow and associated maps are based upon an emerging conceptual understanding of supratidal forest characteristics and biophysical drivers from multiple settings around the country. New field measurements will be used to calibrate and validate an improved workflow and national map products. The final outputs from this project will align with Australia’s Ocean Accounts, providing a missing piece in national mapping and reporting on Australia’s ocean-based natural assets. Addressing this data gap is crucial for effective management and protection of coastal wetland ecosystems and their associated services.
Analyzing the relationship between the leaf anatomical traits and PM adsorption capacity of 150 major landscape tree species in Korea
Authors: Je Sun Mi , Jeong Su Gyeong , Chang Hanna , Son Joung-a
Published: March 2024

The literature extensively discusses the potential of trees to enhance urban air quality by removing particulate matter (PM), highlighting it as one of the numerous advantages of trees in urban settings. To optimize the layout of green spaces in urban and peri-urban areas with restricted open space, it is crucial to choose appropriate tree species capable of maximizing PM removal. Regarding the PM absorption capacity in leaves, recent findings have primarily focused on establishing connections with complex leaf shapes, large surface areas, trichome shapes or other associations. Depending on which tree species were tested, factors that had a major influence on the adsorption capacity of PM used to show differently. So, we evaluated the relationship between leaf anatomical traits (microstructural properties) and PM adsorption capacity in 150 species in Korea. As a result of our study, a weak relationship was observed between microstructures (trichome density located in the main vein, lateral vein, lamina, stomatal density, roughness, leaf length, leaf area) and the PM adsorption capacity in 150 tree species. We suggest that the microstructures associated with PM adsorption capacity are likely a combination of complex factors rather than a single major factor. To gain clearer insights, we plan to conduct analyses on the same genus with similar microstructure characteristics but varying morphological differences, such as density and length. Additionally, we intend to analyze two to three composite characteristics of microstructure. 
Annually resolved Northwestern Pacific tropical cyclone series since the mid-14th century: intensified activities during the Maunder Minimum 
Authors: Lin Kuan-Hui Elaine , Tseng Wan-Ling , Hsu Huang-Hsiung , Wang Pao K.
Published: March 2024

This study used Reconstructed East Asian Climate Historical Encoded Series (REACHES) database (Wang et al. 2018) to reconstruct historical tropical cyclone (TC) series documented in 1368-1911. Records documented with ‘typhoon’ (Chinese character颱) or ‘hurricane’ (颶) were retrieved, with descriptions of other compounding effects such as strong wind, torrential rain and storm surge to consist of the data set. To avoid repetition and duplicate counting of the same TC event, records that have temporal (± 1 days) and spatial (±2∘degree latitude/longitude) proximity were combined accounting for one single TC event. The method was based on a systematic database approach and data quality was checked and validated through comparison with other independent reconstructed series and IBTrACS (Tropical Cyclone Best Track Data) 1884-2020. The REACHES TC series was then merged with the IBTrACS data to form a l368-2020 long TC series for Northwestern Pacific region. The reconstructed TC series demonstrates clear multi-decadal to centennial variabilities. In the last six hundred years, there were in average 3 TC documented in every year. 1600s was the most TC active period (8 TC in 1627, 7 in 1640, 7 in 1652, 6 in 1662, 7 in 1664, 9 in 1668, 12 in 1669, 10 in 1671, and 8 in 1672). The TC series was then compared with other forcings (volcanic eruption, solar, and SST) and ENSO.  All of the forcings may have a role in the frequent TC activities during Maunder Minimum. Further research from model-data comparison and simulations will shed lights on TC behaviors in the warming climate.