bluuebunny/crossref_metadata_2025 huggingface dataset:
Robust InSAR Tropospheric Delay Correction Using Global Atmospheric Models
Authors: Cao Yunmeng , Jónsson Sigurjón , Li Zhiwei
Published: March 2021

Tropospheric delays are the main source of error when measuring ground displacements using InSAR. Increasingly, global atmospheric models (GAMs), e.g., ERA5 and MERRA2 reanalysis data, are used to reduce tropospheric signals in InSAR deformation observations. However, due to the coarse spatial resolution of current GAMs (~10s of kilometers), it is still challenging to obtain tropospheric corrections for high-resolution InSAR data (~10s of meters). Here we present an advanced GAM-based correction method, aimed at improving InSAR geodesy, that incorporates spatial stochastic models of the troposphere in the corrections. We first estimate stochastic models of the tropospheric parameters (temperature, pressure, and partial pressure of water vapor) at different GAM altitude layers and we then interpolate the parameters according to the correlation between pixels of interest and the GAM grid locations (3D). The interpolation accounts for spatial variabilities of the tropospheric random field, instead of subjectively using an inverse distance method or using a local spline function, which are commonly used in current GAM-correction methods. We also estimate the integral of the tropospheric delays along the satellite line-of-sight (LOS) direction directly, instead of calculating the projected zenith-delays, because the troposphere is not purely stratified. Our new method can easily be applied using any of the present GAMs; here we implemented it with the latest ECMWF ERA5 reanalysis outputs. We validate the new method for both interferograms and time-series analysis products (deformation velocities and time-series solutions), using hundreds of the Sentinel-1 images over the island of Hawaii from 2015 to 2020. The results show that the average standard deviation of non-deforming interferograms reduces from 2.55 cm to 1.91 cm when applying the new method, compared with standard deviations of 2.47 cm (PyAPS), 2.44 cm (d-LOS), and 2.10 cm (GACOS), after using three common GAM correction methods. In addition, the new method improves most (87%, i.e., 243 out of 280) of the interferograms, while only about half (52%, 53%, and 66%) are improved by the earlier correction methods. The results demonstrate the importance of considering (1) tropospheric stochastic models in GAM-corrections, (2) horizontal heterogeneities when estimating the LOS delays, and (3) tropospheric delays when mapping long-wavelength or small-magnitude deformation using InSAR.
Inferring rock glacier genesis and dynamics from age-layer modelling and borehole age-profile
Authors: Leysinger Vieli Gwendolyn J.-M. C. , Vieli Andreas , Cicoira Alessandro
Published: March 2021

The genesis of rock glaciers differs fundamentally from ‘normal’ glaciers and results in much older landforms that are often reaching ages of several millennia. Recent datings of rock glacier material from boreholes indicate early Holocene ages for rock glaciers and allow the derivation of age-depth profiles at the borehole location. We use here a 2-dimensional numerical modelling approach that calculates age-layers (isochrones) within the rock glacier body and that considers the accretion, melt and flow-advection of rock glacier material. We apply this model to the case of Lazaun rock glacier (Southern Ötztal Alps) for which a well dated profile from a borehole exists, with ages at the bottom older than 9000 years (Krainer et al. 2015). With our modelling we are able to reproduce the observed age-depth profiles well and are able to infer a long-term accumulation rate that is around 1 cm/yr which is an order of magnitude higher than a previous estimate that does not account for deformation. The modelling is consistent with the classic rock glacier genesis of material accretion in the upstream talus slope and confirms the dominance of deformation in the shear-zone at the bottom layer of the rock glacier.
We conclude that combining age-layer modelling with dated depth-profiles of rock glaciers allows for important new insights into our understanding of rock glacier evolution and dynamics.

REFERENCES  
Krainer, K., Bressan, D., Dietre, B., Haas, J., Hajdas, I., Lang, K. & Tonidandel, D. (2015). A 10,300-year-old permafrost core from the active rock glacier Lazaun, southern Oetztal Alps (South Tyrol, Northern Italy). Quaternary Research, 83 , 324-335. 

 
Explosive Cyclones in the CORDEX-CORE projections for Southern Hemisphere domains
Authors: Reboita Michelle , Machado Crespo Natália , Reale Marco , Torres José Abraham , Porfírio da Rocha Rosmeri
Published: March 2021

Explosive cyclones (ECs) are extratropical systems, often associated with extreme events,  which experience a fast deepening (~24 hPa/24 h) over a relatively short time range. Here, we analyze changes in the austral winter characteristics of ECs in three domains (Africa-AFR, Australia-AUS and South America-SAM) as projected by Regional Climate Model (RegCM4) under RCP8.5 emission scenario in the CORDEX-CORE framework. RegCM4 was nested in three global climate models (GCMs) from CMIP5 (HadGEM2-ES, MPI-ESM-MR and NorESM-1M) and executed with 25 km of grid spacing. The cyclone database was obtained with the application of an automatic detection and tracking scheme to the 6-hourly mean sea level pressure fields. Extratropical cyclones with explosive features are then selected using the Sanders and Gyakum criterium. Following IPCC recommendation, we analyze the reference 1995–2014 period and the end-of-century 2080–2099 period. ECs represent ~13-17% of the total number of cyclones in ERA-Interim reanalysis during the austral winter, while the simulation ensembles, in general, underestimate this value. While in the AFR domain GCMs ensemble represents better the percentage of ECs compared to ERA-Interim, in AUS and SAM domains RegCM4 has a better performance than GCMs. The percentage of ECs compared to the  total number of cyclones in each domain is projected to increase, with higher positive trends for the SAM domain (7.4% in GCMs and 5.6% in RegCM4) than  AFR (3.3% in GCMs and 3.9% in RegCM4) and AUS (3.9% in GCMs and 1.7% in RegCM4). Compared to the present climate, ECs in the future will be stronger and faster but with a shorter lifetime.
Agriculture effects on geochemical soil properties and stability of soil organic carbon on tropical Andosols
Authors: Anindita Sastrika , Sleutel Steven , Finke Peter
Published: March 2021

The impact of soil age on geochemical properties and carbon cycling has been studied via chronosequences. However, only few studies have addressed how land-use and soil age might interactively shape properties of Andosols and in turn their capability to retain organic carbon (OC). Geochemical soil analyses and laboratory incubation experiments were carried out to assess soil characteristics and mineralization of soil organic carbon (SOC) in Indonesian soils with two contrasting land uses, viz. pine forest and horticulture. Both of these land uses are the results of conversion of primary forest which had similar parent materials, soil age, as well as weathering intensity. Results showed that intensive agricultural practices (+ 40-50 years) did not result in a significant loss of SOC or the increase of bulk density compared to forest. On the other hand, they were found to increase pH, exchangeable cations, base saturation, and most strikingly non-crystalline materials (i.e. Alo + ½ Feo) leading to phenotype formation in agricultural soils. Positive correlations were found between non-crystalline materials with properties such as soil specific surface area and micropores volume, and it was also positively correlated with SOC, particularly in the subsoil. This study highlighted the resilience of Andosols to soil degradation under agricultural practices and its ability to stabilize SOC.
Does biochar contribute to soil organic matter accumulation? – A tropical perspective
Authors: Schnee Laura Sophie , Ngakou Albert , Filser Juliane
Published: March 2021

Tropical soils are often deeply weathered and vulnerable to degradation. Biochar appears a promising means to improve soil quality while sequestering carbon into the soil. Yet, sustainable soil amelioration depends on stable soil organic matter (SOM) stocks for nutrient retention, water uptake and as habitat for soil life. In a literature meta-analysis, we investigated, if biochar amendment to tropical soils led to SOM increases additional to biochar C. We found a mean additional C accumulation (MAC) of 0.29% soil dry weight (% dw). MAC was independent of study duration, climate, and biochar addition rate, but strongly linked to soil type and nutrient status prior to the experiment: In Nitisols, MAC was highest (0.99% dw) and initial C and N contents were higher in these soils. MAC was slightly negative in Ferralsols and Oxisols (– 0.01% dw and –0.2% dw respectively). MAC as a percentage of initial C content was < 50% for most soil types, but –50% in Ferralsols, Oxisols and Ultisols. Changes to soil microbiomes were more conclusive and included elevated enzyme activities and shifts from bacterial to fungi dominated microbiomes. We conclude that soil nutrient status prior to amendment, which is often linked to microbial activity, determines if the alteration of soil conditions caused by the biochar can be buffered ecologically, so that fresh organic residues are transformed into SOM. Additionally, we remarked that research on biochar – SOM interactions in tropical soils largely depends on cooperations with institutions from North America and Europe for funding and analytical infrastructure. Researchers, institutions, and funding bodies need to be creative and cautious to realise equitable participation of all partners in international research projects designed to render added value for societies around the world.
Observations of plumes from the 2019 Raikoke eruption with the Infrared Atmospheric Sounding Interferometer (IASI)
Authors: Taylor Isabelle A. , Grainger Roy G. , Mather Tamsin A.
Published: March 2021

Raikoke, a remote volcano in the Kuril Islands, erupted on the 21st June 2019. The eruption injected significant quantities of SO2 into the atmosphere along with volcanic ash. These plumes have been studied with tools developed for the Infrared Atmospheric Sounding Interferometer (IASI) by the Earth Observation Data Group (EODG) at the University of Oxford. IASI is a hyperspectral sensor onboard of three meteorological satellites (Metop A, B and C). Each instrument obtains near global coverage twice a day and has a spectral range which includes sensitivity to both SO2 and ash: making them useful for studying the Raikoke plumes. A fast linear SO2 retrieval was first applied to flag pixels with elevated amounts of SO2. With this tool it was possible to follow the Raikoke plume as it circulated the northern hemisphere above 30 degrees, with parts of the plume still visible around 2 months after the eruption took place. Next an iterative SO2 retrieval was used to quantify the amount and height of the SO2 in each pixel. In the first few days after the eruption took place, very high column amounts are recorded, in some cases exceeding 600 DU. Using this retrieval, a preliminary estimate of 1.6 Tg was obtained for the total amount of SO2 emitted (measured on the 23rd of June). Height information from this technique shows that there were probably multiple injection heights during the eruption and that SO2 was emitted into both the troposphere and stratosphere. The tropospheric plume remains visible for just a few days after the eruption, while the stratospheric portion of the plume persists for several weeks.
Particle transport in the central Ionian Sea
Authors: Berline Leo , Doglioli Andrea , Petrenko Anne , Barrillon Stephanie , Espinasse Boris , Le Moigne Frederic , Simon-Bot François , Melilotus Thyssen , Carlotti François
Published: March 2021

In the upper layers of the Ionian Sea, young Mediterranean Atlantic Waters (MAW) flowing eastward from the Sicily channel meet old MAW. In May 2017, during the PEACETIME cruise, fluorescence and particle content sampled at high resolution revealed unexpected heterogeneity in the central Ionian. Surface salinity measurements, together with altimetry-derived and hull-mounted ADCP currents, describe a zonal pathway of AW entering the Ionian Sea, consistent with the so-called cyclonic mode in the North Ionian Gyre. The ION-Tr transect, located ~19-20°E- ~36°N turned out to be at the crossroad of three water masses, mostly coming from the west, north and from an isolated anticyclonic eddy northeast of ION-Tr. Using Lagrangian numerical simulations, we suggest that the contrast in particle loads along ION-Tr originates from particles transported from these three different water masses. Waters from the west, identified as young AW carried by a strong southwestward jet, were intermediate in particle load, probably originating from the Sicily channel. Water mass originating from the north was carrying abundant particles, probably originating from northern Ionian, or further from the south Adriatic. Waters from the eddy, depleted in particles and Chl-a may originate from south of Peloponnese, where the Pelops eddy forms.

The central Ionian Sea hence appears as a mosaic area, where waters of contrasted biological history meet. This contrast is particularly clear in spring, when blooming and non-blooming areas co-occur.

High resolution measurements reveal a high heterogeneity in properties such as particles abundances. To interpret these distributions, combination of multiparametric in situ measurements with remote sensing and Lagrangian modeling appears necessary.
Assessing orbital vs. volcanic control on carbon cycle during the Early Cretaceous
Authors: Martinez Mathieu , Aguirre-Urreta Beatriz , Lescano Marina , Dera Guillaume , Omarini Julieta , Tunik Maisa , Frederichs Tomas , Pälike Heiko , O'Dogherty Luis , Aguado Roque , Company Miguel , Sandoval Jose
Published: March 2021

The interval from the Valanginian to the Barremian stages (137–121 Ma; Early Cretaceous) is punctuated by several episodes of environmental changes, accompanied by shifts in weathering intensity on the continents and changes in the Tethyan neritic carbonate production. We synthetize here the astrochronology of two recent studies performed in the Neuquén basin, Vocontian Basin and Subbetic Domain (Aguirre-Urreta et al., 2019; Martinez et al., 2020), anchored to CA-ID-TIMS U-Pb ages, which conclusions have been included in the Geologic Time Scale 2020 (Gale et al, in press). We applied this time scale to a compilation of carbon-isotope ratio from belemnites and proxies of detrital supply in the Tethyan area (Vocontian Basin and Subbetic Domain). From this compilation, we show that the episodes of environmental changes are paced by a 2.4-Myr cycle and, with a lower amplitude, a 1.2-Myr cycle. In addition, the new time scale shows the synchronicity between the Weissert Event and the Parana-Etendeka Large Igneous Province. In the series of carbon-isotope ratios measured on belemnite rostra, the amplitude of the 2.4-Myr cycle is twice higher during the Valanginian than in the Late Barremian and three times higher than in the Hauterivian and Early Barremian, suggesting that the activity of the Parana-Etendeka Large Igneous Province amplified the initial orbital forcing to trigger the environmental changes observed during the Mid-Valanginian.

Reference:

Aguirre-Urreta, B., Martinez, M., Schmitz, M., Lescano, M., Omarini, J., Tunik, M., Kuhnert, H., Concheyro, A., Rawson, P.F., Ramos, V.A., Reboulet, S., Noclin, N., Frederichs, T., Nickl, A.-L., Pälike, H., 2019. Interhemispheric radio-astrochronological calibration of the time scales from the Andean and the Tethyan areas in the Valanginian–Hauterivian (Early Cretaceous). Gondwana Research 70, 104-132. https://doi.org/10.1016/j.gr.2019.01.006.

Gale, A.S., Mutterlose, J., Batenburg, S., in press. Chapter 27: The Cretaceous Period, in: Gradstein, F.M., Ogg, J.G., Schmitz, M.D., Ogg, G.M. (Eds.) Geologic Time Scale 2020. Elsevier BV, Amsterdam, The Netherlands, pp. 1023–1086.

Martinez, M., Aguado, R., Company, M., Sandoval, J., O’Dogherty, L., 2020. Integrated astrochronology of the Barremian Stage (Early Cretaceous) and its biostratigraphic subdivisions. Global and Planetary Change 195, 103368. https://doi.org/10.1016/j.gloplacha.2020.103368.
Extreme events on Gulf of Bothnia
Authors: Siiriä Simo-Matti , Fredriksson Sam , Roiha Petra , Alenius Pekka , Oikkonen Annu
Published: March 2021

The future changes in the physical conditions in the Gulf of Bothnia can have considerable impact on various human activities in the area. In this presentation we concentrate on marine heatwaves and ice conditions. The general changing trends of ice conditions, temperature and salinity give an idea of the changes to come. It is, however, also important to know the possible changes in extremes, and their frequencies in the future. To name a few examples, aquaculture activities can be affected by sudden exceptional warm or cold periods of water, and wind-energy construction benefits from knowing what kind of ice conditions can be expected.

In the SmartSea project we have made simulations of future scenarios for predicting the possible changes in the conditions in the Gulf of Bothnia. We have simulated a historical control period of 1976-2006 with three different downscaled global circulation models, and use these as comparisons for runs made with same model forcings for the years 2006-2060 with RCP 4.5 and RCP 8.5 scenarios. These scenarios are used to detect the type and frequency of extreme events, such as marine heatwaves or extreme ice conditions in the control period, and the change of these in the future for both RCP’s.
One-third of global food production at risk for unprecedented climate conditions due to climate change
Authors: Kummu Matti , Heino Matias , Taka Maija , Varis Olli , Viviroli Daniel
Published: March 2021

The majority of food production is based on agricultural practices developed for the stable Holocene climatic conditions, which now are under risk for rapid change due to climate change. Although various studies have assessed the potential changes in climatic conditions and their projected impacts on yields globally, there is no clear understanding on the climatic niche of the current food production. Nor, which areas are under risk of falling outside this niche.

In this study we aim first at defining the novel concept Safe Climatic Space (SCS) by using a combination of three key climatic parameters. SCS is defined here as the climate conditions to which current food production systems (here crop production and livestock production separately) are accustomed to, an analogue to Safe Operating Space (SOS) concepts such as Planetary Boundaries and human climate niche. We use a combination of selected key climatic factors to define the SCS through the Holdridge Life Zone (HLZ) concept. It allows us to first define the SCS based on three climatic factors (annual precipitation, biotemperature and aridity) and to identify which food production areas would stay within it under changed future climate conditions. 

We show that a rapid and unhalted growth of GHG emissions (SSP5-8.5) could force 31% (25-37% with 5th-95th percentile confidence interval) of global food crop production and 34% (26-43%) of livestock production beyond the SCS by 2081-2100. Our results underpin the importance of committing to a low emission scenario (SSP1-2.6), whereupon the extent of food production facing unprecedented conditions would be a fraction: 8% (4-10%) for crop production and 4% (2-8%) for livestock production. The most vulnerable areas are the ones at risk of leaving SCS with low resilience to cope with the change, particularly South and Southeast Asia and Africa’s Sudano-Sahelian Zone. 

Our findings reinforce the existing research in suggesting that climate change forces humanity into a new era of reduced validity of past experiences and dramatically increased uncertainties. Future solutions should be concentrated on actions that would both mitigate climate change as well as increase resilience in food systems and societies, increase the food production sustainability that respects key planetary boundaries, adapt to climate change by, for example, crop migration and foster local livelihoods especially in the most critical areas.
The impacts of peat slides on upland blanket peatland hydrology, ecology and soil structure. A paired catchment approach. 
Authors: Halpin Rob , Bourke Mary , Long Mike , Trafford Andrew
Published: March 2021

Rainfall-induced landslides are difficult to forecast and often evolve into highly destructive flows, as such, they are one of the most dangerous natural hazards globally. While our understanding of peatland hydrology has improved greatly in the past two decades, there has been less focus on the response of peat hydrology following perturbations such as wildfires and landslides.  Here we report on a new paired catchment experiment in Ireland. Our focus is to quantify the hydrological changes following peat landslides and further, to establish the short-term and longer-term impacts on local peatland hydrology, ecology and recovery.

The two paired sites are located in Co. Leitrim, Ireland, in two adjacent, small upland blanket bog catchments. The first peat catchment (0.2km2) is an area of a recent (June 2020) slope failure. According to preliminary estimates ~178,000 – 188,000 tonnes of peat were transported downstream during the peat slide event, resulting in a large landslide scar section (~0.059 km2) in a special area of conservation [SAC]. Preliminary impacts are assessed to include: habitat loss, decreased slope stability, impacts on hydrology and water quality, as well as increased local erosion.

This catchment is paired with an adjacent upland blanket peat catchment (0.11 km2) which is deemed to have been under the same anthropogenic pressures (grazing, upslope forestry plantation).

A hydrometric suite, including weather station, piezometers, and water level recorders to evaluate the surface and subsurface hydrology has been installed at both sites. In addition, we are monitoring the response of landslide deposits (e.g. rafted peat, some with still-standing sika spruce), ecology, soil structure, permeability and shear strength in both catchments.

Here we will report on the initial results of our monitoring.
Understanding the Dynamics of a Heavy Rainfall Event using Multivariate Ensemble Sensitivity Analysis 
Authors: George Babitha , Kutty Govindan
Published: March 2021

Ensemble forecasts have proven useful for investigating the dynamics in a wide variety of atmospheric systems and they might be useful for diagnosing the source of forecast uncertainty in multi-scale flows. Ensemble Sensitivity Analysis (ESA) uses ensemble forecasts to evaluate the impact of changes in initial conditions on subsequent forecasts. ESA leads to a simple univariate regression by approximating the analysis covariance matrix with the corresponding diagonal matrix. On the contrary, the multivariate ensemble sensitivity computes sensitivity based on a more general multivariate regression that retains the full covariance matrix. The purpose of this study is to examine the performance of multivariate ensemble sensitivity over univariate by applying it to a heavy rainfall event that happened over the Himalayan foothills in June 2013. The ensemble forecasts and analyses are generated using the Advanced Research version of the Weather Research and Forecasting (WRF) model DART based Ensemble Kalman Filter. Initial results are promising and the sensitivity shows similar patterns for both univariate and multivariate methods. The reflectivity forecast for both methods are characterized by lower temperatures and increased moisture in the control area at 850 hPa level. Compared to multivariate, univariate ensemble sensitivity overestimates the magnitude of sensitivity for temperature. But the sensitivity for the moisture is the same in both methods.
Feasibility of Using Sentinel-3 in Estimating Lake Nasser Water Depths
Authors: Khairy Marwa , Hossen Hickmat , Elsahabi Mohamed , Ghaly Shenouda , Scozzari Andrea , Negm Abdelazim
Published: March 2021

Abstract  After the construction of the Grand Ethiopian Renaissance Dam (GERD), Nasser Lake (NL)became one of the most challenging hot spots at both local and global level. It is one of the biggest manmade reservoirs in the world and the most important in Egypt. It is created  in the southern part of the Nile River in Upper Egypt after the construction of Aswan High Dam (AHD). The water level in NL might fluctuate between 160 to 182 m above the mean sea level. Monitoring NL  water depth is an expensive and time-consuming activity. This work investigates the possibility to use information from the Sentinel missions to estimate the depth of NL as an inland water body, in the frame of estimating storage variations from satellite measurements. In this preliminary study, we investigated the relationship between the radiance /reflectance of optical imagery from two instruments SLSTR and OLCI instruments hosted by the Sentinel-3A platform and in situ water depth data using the Lyzenga equation. The results  indictaed  that there was a reasonable correlation between Sentinel-3 optical data and in situ water depth data. Also, Heron's formula was used to estimate water storage variations of NL with limited in situ data. In addition, equations governing the relationship between water level and both surface area and water volume were worked out. This study is in the framework of a bilateral project between ASRT of Egypt and CNR of Italy which is still running.

 

Keywords: Sentinel, SLSTR, OLCI, Inland water body, Nasser Lake, Egypt, Water Depth, GERD, AHD, Egypt
Sea level variability on interannual, decadal and longer time scales along the tropical Atlantic
Authors: Kemgang Ghomsi Franck Eitel , Raj Roshin P. , Rouault Mathieu , von Schuckmann Karina
Published: March 2021

Regional sea levels often behave significantly differently from the global average, making it difficult to establish future sea-level projections. In the Atlantic Ocean, the regional average steric (thermosteric, halosteric) sea level plays an important role in the variability of the overall trend, associated with heat and freshwater, redistribution due to circulation, and freshwater input from melting land ice and river runoff over the past two decades. This contribution varies in space and time. Based on sea level measurements obtained by satellite altimetry from CMEMS products and salinity and temperature data from Argo floats for the period 2005-2015, we found that the Gulf of Guinea and the Atlantic Niño boxes experienced a large thermosteric relative to the Amazon box, which experienced a larger halosteric contribution to sea-level change. This remarkably large halosteric contribution is associated with a cooling in the upper 700 m range. Currently, local atmospheric forcing, such as wind variability, may not explain this warming while the Tropical Northern Atlantic (TNA) index tends to explain the freshening.
Deep learning approach to reconstruct satellite ocean color time series in the global ocean
Authors: Roussillon Joana , Fablet Ronan , Drumetz Lucas , Gorgues Thomas , Martinez Elodie
Published: March 2021

Phytoplankton plays a key role in the carbon cycle and constitutes the basis of the marine food web. Its seasonal and interannual cycles are relatively well-known on a global scale thanks to continuous ocean color satellite observations acquired since 1997. The satellite-derived chlorophyll-a concentrations (Chl-a, a proxy of phytoplankton biomass) time series are still too short to investigate phytoplankton biomass low-frequency variability. However, it is a vital prerequisite before being able to confidently detect anthropogenic signals, as natural decadal variability can accentuate, weaken or even mask out any anthropogenic trends. Machine learning appears as a promising tool to reconstruct Chl-a past signals (including periods before satellite Chl-a era), and deep learning models seem particularly relevant to explore the spatial and/or temporal structure of the data.

Here, different neural network architectures have been tested on a 18-year satellite and re-analysis dataset to infer Chl-a from physical predictors. Their ability to reconstruct spatial and temporal (seasonal and interannual) variations on a global scale will be presented. Convolutional neural networks (CNN) better capture Chl-a spatial fields than models that do not account for the structure of the data, such as multi-layer perceptrons (MLPs). We also assess how the selection of training period may affect the reconstruction performance. This is a necessary step before being able to reconstruct any past Chl-a multi-decadal time series with confidence, which is the ultimate goal of this work.

Our study also addresses the carbon footprint associated with the use of GPU resources when training the CNN. GPUs are energy intensive, and their use in geosciences is expected to grow fast. Systematically reporting the computational energy costs in the geoscience community studies would provide an overview of models energy-efficiency on different kinds of datasets and may encourage actions to reduce consumption when possible.
Turbulence characteristics of Solar Prominences due to Rayleigh Taylor Instabilities
Authors: Changmai Madhurjya , Keppens Rony
Published: March 2021

The purpose of our study is to deepen our understanding on the turbulence that arises from Rayleigh Taylor Instabilities in quiescent solar prominences. Quiescent prominences in the solar corona are cool and dense condensates that show internal dynamics over a wide range of spatial and temporal scales. These dynamics are dominated by vertical flows in the prominence body where the mean magnetic field is predominantly in the horizontal direction and the magnetic pressure suspends the dense prominence material. We perform numerical simulations using  MPI-AMRVAC (http://amrvac.org) to study the Rayleigh Taylor Instabilitiy at the prominence-corona transition region using the Ideal-magentohydrodyamics approach. High resolution simulations achieve a resolution of ∼23 km for ∼21 min transitioning from a multi-mode perturbation instability to the non-linear regime and finally a fully turbulent prominence. We use statistical methods to quantify the rich dynamics in quiescent prominence as being indicative of turbulence.
Impact of climate change on the future of tourism areas in the Canary Islands
Authors: Carrillo Judit , González Albano , Pérez Juan C. , Expósito Francisco J. , Díaz Juan P.
Published: March 2021

Tourism is an essential sector of the economy of the Canary Islands. Tourism Climate Index (TCI) and Holiday Climate Index (HCI) are good indicators of environmental conditions for leisure activities. Regional climate model (RCM) has been addressed to analyze the impact of climate change on the indices of tourist areas. The initial and boundary conditions for future scenarios are prescribed through three CMIP5 models (GFDL, IPSL and MIROC)  surface and lateral boundary conditions within the Meteorological Research and Forecast (WRF), with a high resolution, 3x3 km. Two time periods (2030 – 2059, and 2070-2099) and two Representative Concentration Pathways (RCPs 4.5 and 8.5) are considered. Tourism indicators are projected to improve significantly during the winter and shoulder seasons, but will worsen in the summer months, including October, in the southeast, which is where hotels are currently located.
Quantitative study of atmospheric rivers in the Indian subcontinent
Authors: V. Lyngwa Rosa , Ahmad Nayak Munir
Published: March 2021

The principal sources of freshwater in India include precipitation, glaciers, and snowmelt. The former dominates the country’s annual river water contribution, which is important for agriculture and livelihood of the residents, and the latter two sources contribute at a much lower fraction in comparison to precipitation to even meet the minimum requirements. However, there is a large degree of variations in their spatio-temporal distribution throughout the country. India receives a major portion of its annual precipitation during the boreal summer (June – September). The well-known but relatively unexplored contributors to precipitation in India are atmospheric rivers (ARs). This study aims to understand the main climatological and dynamical differences between the Indian summer monsoon (ISM) and ARs in boreal summer. Zonal (‘u’) and meridional (‘v’) wind speeds, integrated water vapor transport (IVT), and integrated water vapor (IWV) are used to identify distinct features in ARs in the Indian sub-continent that can be used to distinguish them from ISM. The major differences between the two synoptic features were found in the increased zonal wind speed and moisture inputs during AR events, which often result in extreme precipitation and floods. Besides understanding them, the identification of ARs in this region and accounting for their existential contribution to moisture during peak rainfall seasons is critical for further hydrological impacts studies.
AEROCOM/AEROSAT: an intercomparison of AAOD & SSA in model and satellite data
Authors: Schutgens Nick , Zhong Qirui ,   AEROCOM/AEROSAT teams
Published: March 2021

Absorbing aerosol has the capacity to warm the climate, but the amount of warming is highly uncertain. AAOD (Absorptive Aeorosl Optical Depth) is an optical measure of the abundance of this absorbing aerosol, comprising mineral dust, black and brown carbon and can be retrieved from satellite measurements providing an almost global view on absorbing aerosol.

In this study we evaluate AEROCOM models with satellite observations of AAOD and SSA (Single Scattering Albedo) and interpret the discrepancies. Over source regions, diversity in model AAOD is mostly due to emissions even though models employ different assumptions regarding the imaginary refractive index. On the one hand this suggests emissions to be a major error source, on the other hand it suggests that the AEROCOM ensemble as a whole may have a bias with regards to MAC (Mass Absorption Coefficient). We show that in the models AAOD scales almost linearly with emissions (either black carbon or dust) and this allows the use of observations as a constraint.  In contrast, model diversity in AOD is shown to depend in almost equal measure on emissions, lifetimes and MECs (Mass Extinction Coefficient). We also analyse mineral dust and black carbon lifetimes by considering the contrast in AAOD over source regions and over outflow regions, and again provide observations constraints.

While the older Phase II models generally underestimate AAOD, Phase III models tend to straddle the observations, with some models over-estimating and other models underestimating AAOD. Emissions seem to be the driving factor in this difference. The amount of diversity is larger in the Phase III than Phase II models.

This study was conducted using four satellite datasets of AAOD and SSA. These datasets were extensively evaluated with AERONET. Dearth of observations prevents global assesment of the satellite retrievals. However, we show that model evaluation is relatively independent of the chosen dataset, even though we identify significant biases between the datasets.
Decadal altitudinal glacier mass balance for the Maipo and Santa basins of South America
Authors: von Ah Florian , Miles Evan , Dussaillant Inés , Shaw Thomas E. , Molnar Peter , Pellicciotti Francesca
Published: March 2021

Andean glaciers are an important part of the water cycle of high elevation catchments and supply fresh water to large populations downstreams, especially during dry periods. They are experiencing dramatic mass loss due to a warming climate, and their catchments are among the most vulnerable. However, relatively few glaciers are monitored systematically due to accessibility and cost, limiting our understanding of mass accumulation and ablation rates. In this study, we estimated the decadal altitudinal mass balance of glaciers in the Maipo River Basin in central Chile and the Rio Santa Basin in the Cordillera Blanca in Peru for the periods of 2000-2009 and 2009-2018. We accomplished this by 1) correcting current ice thickness estimates for recent thinning, 2) deriving glacier velocities from Landsat data using the Glacier Image Velocimetry (GIV) toolbox, and 3) modelling ice flux divergence using the continuity approach to correct observed glacier thinning for flow. We validated the altitudinally-resolved mass balance with the few available observational datasets, then determined each domain’s equilibrium line altitude, accumulation area ratio, and ablation balance ratio for each period, which identifies the portion of annual ablation that is compensated by accumulation.

Our results highlight the influence of the Chilean ‘Mega-drought’ (2010-present) on glacier health in the Maipo River Basin, causing a dramatic reduction in glacier mass balance (decrease of 0.5 m w.e. a-1) below 5000 m a.s.l., raising the regional equilibrium line altitude from 4210 m a.s.l. during 2000-2009 to 4470 m a.s.l. ± 15 m during 2009-2018, and lowering accumulation area ratios from 0.65 to 0.55. In contrast, the Santa Basin glaciers showed very similar altitudinal mass balance patterns for both decades, with equilibrium line altitudes at ~5100 m a.s.l. and accumulation area ratios of ~0.5, indicating a basin already out of balance prior to 2000. 

Large populations rely on glaciers’ water supply in both basins and the two basins’ glaciers contrast in terms of water supply sustainability. In the Maipo Basin, glaciers experienced little mass change in the first period (ablation balance ratio of 1.01) and experienced only slightly unsustainable mass loss in the second period (ablation balance ratio of 0.9) despite the Megadrought. The ablation balance ratio for the Santa Basin was lower for both periods (0.75) indicating that these glaciers are moderately unhealthy despite their recent retreat, and water managers should expect further reductions in glacier water supply. Our results will help to constrain glacier models to understand the timing of glacier change for this data-sparse region.
Lagrangian diffusivity estimated from coherent mesoscale eddies in an idealized basin circulation model
Authors: Zhang Wenda , Wolfe Christopher
Published: March 2021

Lagrangian methods have been used to estimate the lateral eddy diffusivity in the ocean using surface drifter and subsurface float tracks and using the numerical particles advected by satellite-derived velocity fields. The diffusivity is estimated from the rate of dispersion of these particles. Accurate point-wise estimates of diffusivity generally require averages over a large number of drifters or floats, but the distribution of drifters and floats is generally sparse and many tracks of drifters are contaminated by winds. On the other hand, the convergence time for the particle-based diffusivity is on the order of a month for both in situ and numerical particles, which makes the estimates inefficient and allows for the accumulation of measurement error. Studies of vortex-dominated 2D turbulence have found that particle dispersion is dominated by the movement of coherent eddies, and that the dispersion rate of coherent eddies themselves can provide accurate estimates of the Lagrangian diffusivity. We found that the potential vorticity diffusivity in two-layer quasigeostrophic turbulence can also be accurately estimated by the rate of dispersion of coherent eddies, and this estimate converges more than four times faster than the diffusivity estimated from particles inserted uniformly in the flow. If this result also holds for oceanic mesoscale turbulence, it can form the basis for a potentially useful technique for diagnosing mesoscale diffusivity based on the tracks of coherent mesoscale eddies.

This presentation examines the relation between the dispersion of coherent eddies and tracer diffusivity in an idealized configuration of Massachusetts Institute of Technology general circulation model which contains multiple gyres, boundary currents, and a zonally reentrant channel flow analogous to the Antarctic Circumpolar Current. The coherent eddies are identified and tracked from the sea surface height snapshots, and the diffusivity estimated from coherent eddies is compared to the tracer diffusivity diagnosed by a tracer inversion method. The diffusivity inferred from dispersion of coherent eddies generally converges within 15 days. Direct comparison of two diffusivity estimates is not straightforward, since the tracer-based diffusivity varies vertically. Approaches for reconciling the two estimates are discussed. This study shows the possibility of relating the Lagrangian movement of coherent eddies to the Eulerian tracer diffusivity.
Dayside ionospheric electrodynamics in association with high-latitude dayside aurora (HiLDA)
Authors: Cai Lei , Kullen Anita , Karlson Tomas , Vaivads Andris , Zhang Yongliang
Published: March 2021

The Defense Meteorological Satellite Program (DMSP) Special Sensor Ultraviolet Spectrographic Imager (SSUSI) has observed the large-scale high-latitude dayside aurora (HiLDA) during its long lifetime of hours. HiLDA has dynamical changes in form, size, location, and development of fine structures. However, the associated electrodynamics is not fully understood. In general, HiLDA occurs in the dayside polar cap during IMF By+ (By-) prevailing conditions in the sunlit northern (southern) hemisphere.  The prevailing conditions drive strong upward field-aligned current in the polar cap. Within the upward field-aligned current region, the field-aligned potential drop can be set up and accelerate the electrons, forming the monoenergetic electron precipitation (up to 10s keV) and producing HiLDA.

 

This study investigates the ionospheric flows, currents, and auroral precipitation in association with HiLDA, benified from the simultaneous measurements from the DMSP satellites, the AMPERE project, and ground-based magnetometers and SuperDARN coherent radars. We will show HiLDA interacts with duskside oval-aligned arcs or transpolar arcs. The interactions are associated with the cusp and the dayside reconnection at the duskside flank/high latitudes. The reconnection produces strong dusk-dawn convection with flow shears in the polar cap, which generates the upward Region 0 current. We find that HiLDA is formed in the high-latitude part of the upward Region 0 current. We apply the Knight relation and identify the lobe electrons (< 0.3 cm-3) as the source of HiLDA. The fine structures revealed in the emission intensity of HiLDA may suggest the uneven distribution of the electron density in the high-latitude lobe.
Automatic landslide detection using the Random Forest classification - the importance of the train-test split ratio
Authors: Pawluszek-Filipiak Kamila , Borkowski Andrzej
Published: March 2021

Landslide identification is the fundamental step to reduce the potential damaging effects of landslide activities. A variety of techniques and approaches has been developed to detect landslides. Conventional landslide identification is a complex and laborious task due to a large amount of the field work and materials that have to be investigated. Additionally, the conventional geomorphological mapping mainly provides a subjective representation of landscape complexities at different scales. Sometimes, in certain conditions, such as densely-vegetated terrain, conventional landslide mapping is ineffective or even impossible.

Therefore, innovative methods that allow for the reduction of subjectivism, time, and effort have increasingly become the subject of interest in landslide research. These methods mainly focus on semi-automated or automatic landslide mapping and include analysis of remote sensing data, such as optical images, Digital Elevation Models (DEMs) derived by Light Detection and Ranging etc. Among them, the pixel-based approach (PBA) and the object-based image analysis (OBIA) methods can be distinguished, for which supervised classification methods are usually utilized.

The accuracy of supervised classification methods strongly corresponds to the training samples - its quality and amount. Supervised classification methods require the collection of training as well as testing data to generate and assess the accuracy of the classification results. It is a challenging task, especially in forested areas, to capture ground truths of the good quality to train the classifier and to identify landslides. Considering this, we decided to investigate the following research question: What is the appropriate training–testing dataset split ratio in supervised classification to detect landslides in a testing area based on DEMs? Since PBA and OBIA approaches are nowadays widely utilized, we investigated this issue for both methods. The Random Forest classifier was implemented for both methods. The experiments were performed in Poland in the Outer Carpathians.

Accuracy measures calculated for the region growing validation indicated that the training area should be similarly large to the testing area in DEM-based automatic landslide detection. Additionally, we found that the OBIA approach performs slightly better than PBA when the quantity of training samples is lower. Besides this, we also attempted to increase the detection performance and to generate final landslide inventory. For this purpose, the intersection of the OBIA and PBA results together with median filtering and the removal of small elongated objects were carried out. We achieved the Overall Accuracy of 80% and F1 Score of 0.50.
Algorithm for interpolation of magnetic field variations
Authors: Vishniakov Dmitrii , Lygin Ivan , Arutyunyan David
Published: March 2021

To solve many geological and geophysical problems, it is very important to study variations of the Earth's magnetic field. The observed variations are usually obtained from data from observatories or temporary variation stations. However, while performing various regional magnetic prospecting works, the network of observatories is not complete enough to account for the variation field correctly.

In this regard, it is becoming necessary to interpolate the data on variations from the points of irregular network. At the same time, obtaining the optimal algorithm is an ambiguous task, its solution requires taking a whole list of factors into account that determine regularity of distribution of physical parameters over the area.

This project represents an interpolation algorithm using method of complex weighting coefficients. The technique was tested on data from the Intermagnet observatories for central Europe, and the obtained accuracy was ± 2 nT. Comparative analysis with known interpolation methods by interpolation methods was carried out.