bluuebunny/crossref_metadata_2025 huggingface dataset:
Assimilation of CryoSat-2 radar Freeboard data in a global ocean-sea ice modelling system.
Authors: Chenal Aliette , Testut Charles-Emmanuel , Garnier Florent , Laurent Parent , Gilles Garric
Published: March 2022

Sea ice is a key element in our climate system, and it is very sensitive to the current observed climate change. Sea ice volume is a sensitive indicator of the health of Arctic although very challenging to estimate precisely since it is a combination of sea ice area and sea ice thickness. Arctic sea ice volume has decreased by as much as 75% at the end of the summer season if compared with the conditions 40 years ago. The ongoing decline of Arctic sea ice exposes the ocean to anomalous surface heat and freshwater fluxes that can have potential implication for the Arctic region and beyond, for the general oceanic circulation itself.

For more than a decade, Mercator Ocean International develops and produces Global Ocean Reanalysis with a 1/4° resolution system. Based on the NEMO modelling platform, observations are assimilated by a reduced-order Kalman filter. In-situ CORA database, altimetric data, sea surface temperature, and sea ice concentration are jointly assimilated to constrain the ocean and sea ice model.

In previous reanalysis, long-term sea ice volume drift has been observed in the Arctic. To obtain a better constraint on the sea ice thickness, Cryosat-2 radar Freeboard data are assimilated jointly with the sea ice concentration in a multidata/multivariate sea ice analysis. The coupled ocean and ice assimilation system runs on a 7-day cycle, using IAU (Incremental Analysis Update) and a 4D increment. The “white ocean” is modelled with the multi-categories LIM3.6 sea ice numerical model. The aim of this study is to initiate the development of the future operational multi-variate and multi-data sea ice analysis system with freeboard radar assimilation.

After describing this global sea ice reanalysis system, we present results on the abilities of this configuration to reproduce sea ice extent and volume interannual variability in both hemispheres. Comparisons between experiments with and without assimilation show that the joint assimilation of CryoSat-2 radar freeboard and sea ice concentration reduces most of model biases of sea ice thickness, e.g., in the north of the Canadian Arctic Archipelago and in the Beaufort Sea in the Arctic. Moreover, radar freeboard assimilation does not hinder the good results in simulating sea ice extent previously obtained with the assimilation of only sea ice concentration. Validation with non-assimilated satellite data and in-situ data supports these findings. Lastly, snow depth significantly influences the Freeboard measurement: this study also reveals the importance of including snow information on freeboard retrieval and on the ice volume assimilation methodology.

These experiments take place in a context of increasing interest in polar regions and prepare the launch of Copernicus Sentinel expansion satellite missions.
Regional climate modeling for Georgia with RegCM4.7
Authors: Elizbarashvili Mariam , Kalmár Tímea , Tsintsadze Magda , Mshvenieradze Tsezari
Published: March 2022

In this study, the latest version of the Abdus Salam International Center for Theoretical Physics (ICTP) Regional Climate Model RegCM4.7.0 is used to simulate climate of Georgia for the period 1986-2005.

Georgia is the mountainous country located in the south-western part of the Greater Caucasus. Its area is 69.875 km2. Mountains cover significant part of the territory 54% of them is located at 1,000 m elevation. From the west Georgia is washed by the Black Sea, from the south it borders with Turkey and Armenia, from the south-east – with Azerbaijan and from the north – with the Russian Federation.

Georgia displays diverse climate and vegetation types: there are almost all climate types from high mountains eternal snow and glaciers to steppe continental climate of eastern Georgia and the Black Sea coastal subtropical humid climate.

To simulate climate with high horizontal resolution and represent more special details for the complex terrain of Georgia the double-nested dynamic downscaling method has been used. First, RegCM was driven by ERA-Interim data at a grid spacing of 50 km. For 50 km resolution simulation, we defined central latitude and central longitude of model domain clat=42.27, clon=42.70 degrees as well as 30 number of points in the N/S direction and 60 number of points in the E/W direction. The 12-km resolution RegCM simulation was nested in the simulation at 50 km resolution. For 12 km resolution simulation, we chose central latitude and central longitude of model domain clat=42, clon =43 degrees as well as 48 N/S 100 E/W points. We selected domain size to be large enough to account for the relevant large-scale processes (such as the large-scale flow modulations due to orographic features and water bodies) but at the same time small enough in size to minimize the use of computational resources.  

We have used the default BATS (Biosphere-atmosphere transfer scheme) land surface parameterization scheme, Emanuel cumulus convective parameterization scheme, SUBEX (Sub-grid Explicit Moisture Scheme) moisture scheme and Holstlag planetary boundary layer scheme for the simulations.

The simulated surface annual and seasonal air temperature and precipitation as well as extreme climate events are compared with Climatic Research Unit (CRU), ERA5 reanalysis, GPCP data sets. For extreme events analyzes, we chose and used some indices, defined by the Expert Team on Climate Change Detection and Indices, recommended by the World Meteorological Organization.

This work was supported by Shota Rustaveli National Science Foundation of Georgia (SRNSFG) № FR-19-8110.

 
Soil organic carbon loss promoted by long-term warming and simulated chronic nitrogen enrichment in the Tibetan Plateau
Authors: Sun Huimin , Schmidt Michael , Nie Ming
Published: March 2022

Global air and soil temperature and nitrogen (N) enrichment are expected to increase in the future, which have the potential to change quantity and quality of soil organic carbon (SOC) pool and alter terrestrial C cycling. However, the underlying mechanism remain unclear especially in the alpine meadow ecosystem on the Tibetan Plateau, which is quite sensitive to global change and is of great importance in regulating future SOC emissions. Using a 9-year two-way factorial experiment involving warming and multilevel N enrichments in the Tibetan Plateau, we showed that both warming and N enrichment promotes soil and microbial C loss. We examined abundance of relative functional genes and found that N enrichment enhanced the ability of microorganisms to degrade labile SOC and reduced the ability to degrade less labile SOC. A long-term laboratory incubation combined with a two-pool model analysis and molecular component examination were conducted to examine potential mechanisms underlying the stabilization variations in different C pools. Diffuse reflectance infrared Fourier transform spectroscopy and biomarker analysis will be used to reveal SOC composition changes and underlying degradation mechanisms. This study highlights the crucial role of soil C stabilization mechanisms in regulating SOC – climate feedback when exposed to warming and chronic atmospheric N enrichment.
Dynamic Tomography Principle: An Adaptive Variable-Scale Approach to GNSS Atmospheric Water Vapor Tomography
Authors: Zhang Wenyuan , Moeller Gregor , Zhang Shubi , Zheng Nanshan , Ding Nan
Published: March 2022

Atmospheric water vapor is an important greenhouse gas in the Earth’s atmosphere and significantly impact the thermodynamics of the atmosphere. Due to its dramatic spatio-temporal variability, knowing the three-dimensional (3D) distribution of it is a key goal of atmospheric observation that has been very difficult to attain. However, Global Navigation Satellite System (GNSS) tomography is a promising technique that retrieves the 3D observation of atmospheric water vapor using data from all satellite constellations with a dense station network. In the last decades, various tomography algorithms were developed based on the fixed-scale tomography (FST) system with an unchangeable tomographic domain and voxel. Here we demonstrate the development of a new adaptive variable-scale tomography (AVST) system to determine the optimal dynamic boundary of tomography area and the adaptive resolution of tomography voxel in different atmospheric layers. First, the optimal regular tomography region of each layer is constructed by the boundary optimal approach based on the convex hull algorithm. Subsequently, we define a water vapor index (WVI) and introduce a WVI invariance discretized principle to obtain the variable-scale voxels in different layers.

The proposed method is applied to reconstruct the 3D adaptive water vapor fields over Hong Kong region using the GNSS data in August 2017. For validations, we compared the tomographic water vapor profiles with the reference profiles from radiosonde, and assessed the tomographic overall distributions using independent ERA5 data. The results show that AVST approach is superior to the FST method in both water vapor profiles and 3D distributions, with the mean root-mean-square-error (RMSE) improved by 30% and 23%, respectively. Such improvements highlight the significant potential of the proposed principle for reconstructing the 3D adaptive atmospheric water vapor fields to advance rainfall forecast and meteorological research.
The role of meteorology in the near-surface ozone enhancements over Europe during the COVID-19 lockdown of early spring 2020
Authors: Ordóñez Carlos , Garrido-Pérez José M. , García-Herrera Ricardo
Published: March 2022

Over the last two years non-pharmaceutical intervention measures in the form of social distancing and lockdowns have been applied to reduce the transmission of SARS-CoV-2. While the exact nature and duration of these measures have varied substantially over the European continent, most countries were under strict lockdowns at the beginning of the pandemic, from mid-March to late April 2020. This caused unprecedented falls in industrial activity and vehicle use, two of the main sources of air pollution.

Here we investigate the effects of that lockdown on the near-surface ozone concentrations. For that purpose, we use 1-h daily maximum nitrogen dioxide (NO2) and maximum daily 8-h running average ozone (MDA8 O3) observations at ~1300 background sites of the European Environment Agency's air quality database (AirBase) as well as a meteorological reanalysis.

We find that the lockdown caused a substantial reduction in NO2 concentrations across Europe, while O3 increased over northwestern and central Europe compared to the same period in 2015-2019. In some countries like Germany, O3 concentrations were typical of the summer season. Atmospheric conditions were also anomalously stable, dry and warm over large parts of the continent, which could potentially rise the O3 concentrations. Consequently, to separate the effect of meteorology and emissions, we have built statistical models fed by reanalysis meteorological data and estimated the expected O3 concentrations during that period in the absence of a lockdown. The results indicate that a considerable fraction of the observed O3 changes can be explained by elevated temperatures, low atmospheric humidity and high solar radiation.

While this analysis shows a dominant role of the meteorology during the early-spring lockdown, we will discuss other factors such as changes in chemical regimes (caused mainly by sharper decreases in emissions of nitrogen oxides than those of volatile organic compounds) that may have yielded regional ozone enhancements during the pandemic.
Study and Comparison of Solid Bricks Used by Merinids and those For Restoration Within the Chellah Historical Site
Authors: Belhaj Siham , Belhaj Omaima essaad
Published: March 2022

Solid brick is a very old construction material used in the construction of monuments and buildings, the manufacture of solid brick is essentially based on the use of terracotta, this used earth conditions the specific characteristics of the brick and its mechanics behavior and its lifespan in the monument.

 In this work and recognizing the importance of characterizing the traditional building materials we plan to study some samples of solid bricks made and used during the Marinid dynasty recovered from the historic site of Chellah which is located in the named city of Rabat as a shared heritage in 2012 and also the solid bricks used in restoration to deduce the similarities and differences.

We will study them under an optical electron microscope and we will expose them to the X-ray diffraction and fluorescence tests, this will allow us to identify the pathologies and degradations of the two types of bricks and the origins of the materials used and their primary compositions.
Field Studies on Effects of Bioaugmentation on Phytoextraction of Germanium, Rare Earth Elements and Potentially Toxic Elements
Authors: Okoroafor Precious Uchenna , Ikwuka God'sfavour , Zaffar Nazia , Ngalle Epede Melvice , Wiche Oliver
Published: March 2022

Soil inoculation with plant growth promoting rhizobacteria (PGPR) promises benefits for agriculture as well as phytoremediation and phytomining of potentially toxic elements (PTEs) and critical raw materials (CRMs) in soil. Thus, we investigated on a field scale the effects of soil inoculation on biomass production as well as on phytoextraction of germanium (Ge), sum total of rare earth elements (REET), copper (Cu), lead (Pb), zinc (Zn), cadmium (Cd), cobalt (Co), nickel (Ni), Iron (Fe), calcium (Ca) and phosphorus (P). Zea mays (ZM) and Helianthus annuus (HA) were used as test plants and the commercially available PGPR RhizoVital®42 containing Bacillus amyloliquefaciens FZB42 as source of inoculum. Post-harvest, biomass/m2, shoot element content/m2, root concentration and water-soluble soil element fraction of root soils were compared for plants grown on inoculated versus uninoculated reference soil. Results indicated increase of 24 % and 26 % for ZM and HA grown on inoculated soils respectively, albeit insignificant at p ≤ 0.05. Inoculation with PGPR enhanced the ZM shoot content of P, K, Co, Cd and Ge by percentages between 20 and 80 % (significant only for Ge) and decreased shoot content of Pb, REET and Cu by 35 %, 28 % and 59 % respectively. For HA grown on inoculated soil, shoot content of Ca, Ni, Cu, Zn, Ge, REET and Pb increased by over 28 % with negligible decrease observed for Cd. Water soluble element concentrations revealed increased concentrations of more than 15 % for K, Fe, Zn, Cd, Pb, Ge and REET in inoculated post-harvest root soils of ZM with negligible changes of less than ≤ 5% observed for P, Ca, Co, Ni and Cu. For HA , increase of ≥ 28 % for water soluble element concentrations occurred only for P and Ca, with concentrations of Ni, Cu, Zn, Cd, Pb and REET decreasing by percentages between 11 and 41 %. Also, increased root concentrations of ≥ 22 % for ZM growing on inoculated soils occurred only for P, Ca, Cu and Cd while decreased concentration of ≥ 12 % occurred only for Fe, Co, Ni, Pb and REET. Summarily, results suggest that bioaugmentation with commercially available PGPR RhizoVital®42, containing Bacillus amyloliquefaciens FZB42 has the potential to enhance biomass production as well as enhance or inhibit phytoextraction of some elements. Also, effects of PGPR on phytomining and phytoremediation is plant specific for some elements, depending mostly on plant physiological  characteristics.
The Little Ice Age CO2 drop:  Natural, Anthropogenic or Artefact? 
Authors: King Amy , Bauska Thomas , Brook Ed , Kalk Mike , Strawson Ivo , Epifanio Jenna , Hoffman Helene , Wolff Eric
Published: March 2022

We present new measurements of methane (CH4) and carbon dioxide (CO2) in the Skytrain ice core, with gas ages dated around 1610AD. The aim of these measurements is to improve our understanding of why there is a significant difference between measured CO2 at that time in current ice core records.

A pronounced feature of the Law Dome record (accumulation 60 cm ice eq. yr; gas age distribution 8 years,) is a rapid decrease in CO2 of ~10 ppm over 50 years with a distinct minimum at 1610. The cause of this decrease is much debated, with complex carbon cycle feedbacks required in explanation. However, other ice cores do not show the same event. The West Antarctic Ice Sheet (WAIS) divide record (accumulation 22 cm ice eq. yr; gas age distribution 19 years) shows a steadier decline in CO2 of approximately 6 ppm over the same period, with the record also ~2-3 ppm higher than Law Dome throughout 900-1800 CE. A follow-up study using the Dronning Maud Land (DML) ice core (accumulation 7 cm ice eq. yr; gas age distribution 65 years) attempted to prove which core showed the real atmospheric signal, but results were inconclusive due to the wide gas-age distribution of the record. While Skytrain (accumulation 14 cm ice eq. yr) does not match the accumulation rate of Law Dome, we present these new, high-resolution gas measurements over the period to work towards answering the following questions: (1) if the Law Dome record is correct, what caused this amplitude of CO2 change over a short timescale? (2) Does one of the records suffer from contamination? (3) Is our understanding of gas smoothing processes in these ice cores inaccurate? We will then use these measurements, from a well-validated ‘needle-crusher’ CO2 device at the ice core labs at Oregon State University, USA, to validate a new semi-continuous ice-grating device (for which we present a preliminary outline) at the new ice core gas analysis lab at the British Antarctic Survey, UK.
Accuracy assessment of IMERG and TRMM remote sensing precipitation data under the influence of monsoon over the upper and middle Lancang River basin, China
Authors: Lu Chengxuan , Fang Guohua , Ye Jian , Yang Zitong
Published: March 2022

Rationale: After the Tropical Rainfall Measuring Mission (TRMM) was successfully launched by NASA and JAXA in 1997, NASA released the first GPM-era global precipitation product (IMERG) in April 2014, aiming to obtain precipitation data with ultra-fine temporal and spatial resolution around the world. Examining the key precipitation data in different climatic areas influenced by the monsoon can effectively help users and algorithm developers maximise the accuracy and characteristics of new satellite remote sensing products. Objective: To this end, this study used the upper and middle Lancang River basin (UMLRB), a transnational river with complex climatic conditions, as the research area to explore the applicability and precipitation distribution of IMERG and TRMM, and evaluate their accuracy. Methods: In this study, various performance indexes were used to comprehensively evaluate the retrieval accuracy of IMERG and TRMM remote sensing precipitation data in UMLRB; these indexes can be divided into two categories according to the evaluation objectives. One type of indexes mainly evaluates the amplitude consistency of precipitation, and the other type of indexes is mainly used to evaluate the occurrence consistency of precipitation. Results: The results indicated that: (1) The temporal distribution of precipitation in different climatic regions was correctly detected by IMERG and TRMM in the UMLRB, and the dry and wet seasons in the climate transition zone were distinct. (2) IMERG and TRMM tended to overestimate moderate rain (1.0-20 mm/d) while underestimating heavy rain (20-50mm/d) and extreme precipitation (> 50mm/d). (3) In terms of the amplitude consistency of precipitation, the detection results of IMERG in the alpine climate zone were not completely consistent with those of TRMM, while those in the climate transition zone were consistent with TRMM. (4) The stronger the precipitation intensity, the worse the accuracy of IMERG and TRMM, especially between heavy rain (20-50 mm/d) and extreme precipitation (> 50mm/d). (5) The IMERG, which had greater application potential in complex climatic conditions, had higher accuracy than TRMM.” Conclusions/Recommendations: Therefore, before using remote sensing precipitation data to study watershed hydrometeorology in monsoon-affected areas, their seasonal distribution, precipitation intensity, and the type of remote sensing data should be carefully considered to verify their accuracy.
Direct validation of dune instability theory
Authors: Narteau Clément , Lü Ping , Claudin Philippe , Dong Zhibao , Rodriguez Sébastien , An Zhishan , Fernandez-Cascales Laura , Gadal Cyril , Courrech du Pont Sylvain
Published: March 2022

We designed a landscape-scale experiment at the edge of the Gobi desert, China, to quantify the development of incipient dunes under the natural action of winds (Lü et al., 2021). High-resolution topographic data documenting 42 months of bedform dynamics are examined to provide a spectral analysis of dune pattern formation. We identified two successive phases in the process of dune growth, from the initial flat sand bed to a meter-high periodic pattern. We focus on the initial phase, when the linear regime of dune instability applies, and measure the growth rate of dunes of different wavelengths. We identify the existence of a maximum growth rate, which readily explains the mechanism by which dunes select their size, leading to the prevalence of a 15 m-wavelength pattern. We quantitatively compare our experimental results to the prediction of the dune instability theory using transport and flow parameters independently measured in the field. The remarkable agreement between theory and observations demonstrates that the linear regime of dune growth is permanently expressed on low-amplitude bed topography, before larger regular patterns and slip faces eventually emerge. Our experiment underpin existing theoretical models for the early development of eolian dunes, which can now be used to provide reliable insights into atmospheric and surface processes on Earth and other planetary bodies.

 

Bibliography:

Lü P., C. Narteau, Z. Dong, P. Claudin, S. Rodriguez, Z. An, L. Fernandez-Cascales, C. Gadal, S. Courrech du Pont, Direct validation of dune instability theory, Proceedings of the National Academy of Sciences, 118, 17 (2021).
The Combined QBO and ENSO Influence on Tropical Cyclone Activity over the North Atlantic Ocean
Authors: Jaramillo Alejandro , Dominguez Christian , Raga Graciela , Quintanar Arturo I.
Published: March 2022

The Quasi-Biennal Oscillation (QBO) and the El Niño-Southern Oscillation (ENSO) largely modulate the zonal wind in the tropics. Previous studies showed that QBO phases produce changes in deep convection through an increase/decrease in the tropopause height over the tropics and subtropics. This study investigates the combined effects of QBO and ENSO on tropical cyclone (TC) activity by modulating tropopause height. We found that tropopause height increases over the Gulf of Mexico, the Caribbean region, and the Western North Atlantic Ocean during La Niña + QBOW, allowing deeper tropical convection to develop over those regions. As a consequence, TC activity over those regions is not only increased in number but also enhanced in intensity. Conversely, during El Niño + QBOE, most deep tropical convection is inhibited over those same regions due to the decrease in tropopause height over the subtropics. We conclude that QBO effects on TCs and deep convection should be studied in combination with ENSO. Since TCs are among the most dangerous natural hazards, causing severe economic losses and high mortality, this signal of the QBO+ENSO on TCs could be key for planning activities before the beginning of the season, which might help reduce disaster risk and economic impacts on society, enhancing resilience.
INVC-Investigation of the water vapor channel within the Yarlung Zangbo Grand Canyon, China 
Authors: Chen Xuelong , Xu Xiangde , Wang Gaili , Chen Deliang , Ma Yaoming , Liu Liping , Hu Xie , Liu Yajing , Li Luhan , Li Maoshan , Ming Gong , Luo Siqiong , Wang Xin
Published: March 2022

The Yarlung Zangbo Grand Canyon (YGC) is an important pathway for water vapor transport from south Asia to the Tibetan Plateau (TP). This area exhibits one of the highest frequencies of convective activity in China, and precipitation often brings natural disasters to local communities that can dramatically affect their livelihoods. In addition, the produced precipitation has produced vast glaciers and large rivers around the YGC. In 2018, the Second Tibetan Plateau Scientific Expedition and Research Programme tasked a research team to conduct an "Investigation of the water vapor channel of the Yarlung Zangbo Grand Canyon" in the southeastern Tibetan Plateau. This team subsequently established a three-dimensional comprehensive observation system of land-air interaction, water vapor transport, cloud cover, and rainfall activity in the YGC. This paper introduces the developed observation system and summarizes preliminary results obtained during the first two years of the project. Using this observation network, we focus herein on the development of heavy rainfall events in southeast Tibet that are associated with water vapor transported from the south. This project also helps to monitor geohazards in the key area of the Sichuan-Tibet railway that traverses the northern YGC.
Anisotropic fault permeability upscaling and modeling of fault CO2 migration scenarios during geologic carbon sequestration
Authors: Saló-Salgado Lluís , Davis Steve , Juanes Ruben
Published: March 2022

Accurate assessment of fault-related CO2 migration hazard is required to deploy geologic carbon storage at the gigaton scale. First, we present a novel methodology, PREDICT, to model the intrinsic permeability of faults in siliciclastic sequences. PREDICT models realizations of the fault core consistent with the stratigraphy, and computes the probability distributions for the directional components (dip-normal, strike-parallel and dip-parallel) of the fault-scale permeability tensor. PREDICT accounts for uncertainty in the geologic variables influencing fault permeability and was developed for scenario building and risk management.

Second, we show how to leverage PREDICT to build geologically-realistic fault leakage scenarios using a model of the Miocene offshore Texas, Gulf of Mexico. The process includes selection of anisotropic, upscaled fault permeability values from PREDICT’s output, upscaling of multiphase-flow fault properties (relative permeability and capillary pressure), and CO2-brine numerical simulation for hundreds of years. CO2 migration through the fault and into overlying units is tracked in each scenario, and results are compared with SGR-based fault property modeling.
Simulation of fluvial fan development using a coupled soilscape-landscape evolution model
Authors: Welivitiya Welivitiyage Don Dimuth Prasad , Hancock Gregory
Published: March 2022

In this study the evolution of a fluvial fan on a synthetic landform under erosion, weathering and deposition was simulated using SSSPAM coupled soil-landscape evolution model. A constant rainfall was simulated on a synthetic landform and a fluvial fan depositional structure was allowed to form at the latter part of the landform. At each time step the geomorphological and particle size distribution information of the fan was recorded. Using this recorded information, the evolutionary characteristics of the fan was studied and compared with experimental and field observation data. Also the surface and subsurface sediment characteristics of the fan were studied. Different fan profile sections were also derived from the recorded data and analysed. The simulation produced a fluvial fan semicircular in shape, with concave up long profiles and convex up cross profiles. The surface sediment sizes of the simulated fan were coarsest near the fan apex and fines toward the fan toe with coarse grained sediment filaments extending radially from the fan apex. These geomorphological features and surface sediment distribution agrees well with field observations of natural fluvial fans. The results of the simulation also show that the fluvial fan develops as a result of the channel bringing sediments in to the fan periodically changing its path due to steepening of channel gradient by sediment deposition. The position of the channel is fixed at the fan apex and the channel path constantly changes along any radial direction form the fan apex. This process is remarkably similar to the process of “Fan head trenching” described in literature which is the dominant process in fluvial fan development in the field. Finally, the analysis of fan cross-sections revealed complex sediment layering patterns in the fan profile. The simulation results of SSSPAM coupled soilscape-landscape evolution model provide qualitatively correct geomorphological and sedimentary characterization of the fluvial fan development process.
Estimating core-mantle boundary temperature from lateral variations in shear velocity and seismic attenuation
Authors: Deschamps Frederic , Borgeaud Anselme
Published: March 2022

The temperature at the Earth’s core-mantle boundary (CMB), TCMB, is a key property for a better understanding of our planet dynamics and evolution, but remains poorly constrained. Because the CMB is a material boundary between silicate rocks and molten iron, TCMB cannot be deduced directly from a single phase diagram. Estimates from mineral physics extrapolate either the solidus of mantle rocks to large pressure, or the ICB temperature to lower pressure, assuming that the outer core is adiabatic. Here, we propose a new approach to the determination of TCMB based on the analysis of observed lateral variations in shear-wave seismic velocity, VS, and attenuation, measured with the quality factor QS, in the lowermost mantle. Shear velocity is sensitive to the presence of post-perovskite (pPv), a high pressure phase of bridgmanite that is stable at lowermost mantle conditions. Because the stability field of pPv strongly depends on temperature, the presence of this phase and its impact on VS provides a constraint on the horizontally averaged temperature in the lowermost mantle. On another hand, seismic attenuation is a thermally activated process, implying that its amplitude depends on temperature. At a given depth, and using an appropriate modeling of QS, its deviation from a global average can then give access to the average temperature at this depth. Our approach is based on the knowledge of several parameters, of which the temperature of the phase transition to pPv, TpPv, appears to be the most sensitive. We then performed a preliminary application using models of VS and QS obtained for beneath the Central America and the Northern Pacific, and found that for TpPv = 3150 K, the CMB temperature should be in the range 3500-3800 K.
A Deep Learning Bias Correction Approach for Rainfall Numerical Prediction
Authors: Ma Leiming
Published: March 2022

Numerical weather prediction (NWP) models are currently popularly used for operational weather forecast in meteorological centers. The NWP models describe the flow of fluids by employing a set of governing equations, physical parameterization schemes and initial and boundary conditions. Thus, it often face bias of prediction due to insufficient data assimilation, assumptions or approximations of dynamical and physical processes. To make gridded forecast of rainfall with high confidence, in this study, we present a data-driven deep learning model for correction of rainfall from NWP model, which mainly includes a confidence network and a combinatorial network. Meanwhile, a focal loss is introduced to deal with the characteristics of longtail-distribution of rainfall. It is expected to alleviate the impact of the large span of rainfall magnitude by transferring the regression problem into several binary classification problems. The deep learning model is used to correct the gridded forecasts of rainfall from the European Centre for Medium-Range Weather Forecast Integrated Forecasting System global model (ECMWF-IFS) with a forecast lead time of 24 h to 240 h in Eastern China. First, the rainfall forecast correction problem is treated as an image-to-image translation problem in deep learning under the neural networks. Second, the ECMWF-IFS forecasts and rainfall observations in recent years are used as training, validation, and testing datasets. Finally, the correction performance of the new machine learning model is evaluated and compared to several classical machine learning algorithms. By performing a set of experiments for rainfall forecast error correction, it is found that the new model can effectively forecast rainfall over East China region during the flood season of the year 2020. Experiments also demonstrate that the proposed approach generally performs better in bias correction of rainfall prediction than most of the classical machine learning approaches .
 Fertilization effects on drought responses in sessile oak and Scots pine seedlings 
Authors: Ouyang Shengnan , Shen Weijun , Saurer Matthias , Duan Honglang , Ding Guijie , Tie Liehua , Li Maihe , Arthur Gessler
Published: March 2022

Severe drought acutely impairs plant hydraulic functioning and impedes processes of carbon (C) and nutrient as well as their allocation. However, how fertilization would modify the allocation of C and nutrient between sink and source organs during drought stress remains largely unknown.

We used three-year old potted seedlings of sessile oak and Scots pine in a greenhouse experiment where they were subjected to three different fertilization treatments (non-fertilized, moderate and high fertilization) and two water regimes (well-watered and severe drought) across two consecutive growing seasons. 13C and 15N labeling were labeled to trace the C and nitrogen (N) allocation. Leaf gas exchanges and predawn water potential, biomass of the different plant organs and NSC concentration, as well as relative 13C and 15N allocation to root, stems and leaves were assessed in the two growing seasons.

Our results showed that sessile oak grown under fertilization suffered faster from drought and showed earlier death than unfertilized seedlings. Fertilization significantly improved aboveground growth, increased shoot: root ratio and reduced NSC storage in sessile oak. This leads to drought-induced C depletion and increased mortality under severe drought. Progressing drought altered C and N translocation strategies in sessile oak by prioritizing C allocation to and N retention in the roots under moderate fertilization, but not in high fertilization. In sessile oak, seasonal dynamics of C and N allocation is coupled and independent of drought and fertilization. By contrast, fertilization and drought, both had only minor impacts on Scots pine C allocation and the tradeoff of C allocation between growth and reserves, as well as the uptake of added N by root. Severe drought strongly decreased NSC in stem and root of Scots pine, while NSC concentrations in leaf and fine root kept stable and high and at the status of mortality.

We conclude that sessile oak shows a more plastic response to environment changes than Scots pine by adjusting its C and N relations on the whole plant level. The impact of fertilization on tree seedlings drought responses seems to be species-specific and is also modified by the degree of drought and fertilization.
Research on the seismic signal characteristics of debris flow: an in-field monitoring approach
Authors: Zhou kailai , Cui Yifei , Yan Yan , Liu Dingzhu
Published: March 2022

Debris flow hazard often brings huge economic losses and fatalities downstream. Despite the traditional in-field monitoring system developed, the apparatus is vulnerable to being damaged in the process of hazards, resulting in limited in-situ data collected to analyze the dynamic process. Recently, with the development of seismology, the seismic signals from geophones become an effective method to analyze the process of debris flow for hazard assessment. The scientific challenge lies in how to get the seismic signals of the whole process of debris flow accurately for analyzing the seismic signal characteristics and of debris flow. In this study, two debris flow gullies (Er gully and Chediguan gully in Wenchuan county) are selected to install the monitoring apparatus after field investigation, and two monitoring sites are selected for each gully. The ground vibration monitoring system consists of geophone and Data-Cube. The geophone is fixed in the concrete base which is clinging to the bedrock firmly to collect the seismic signals and save the seismic signals in the Data-Cube. In addition, each monitoring site is equipped with an infrared camera for recording the geomorphologic changes of the monitoring section in the gully, and a rain gauge is installed at the monitoring site upstream of each gully to obtain rainfall information during the whole observation period. The ambient noise in raw seismic signals will be filtered out, and the filter seismic signals are combined with rainfall information to analyze the moment of potential hazards. Then identify debris flow by checking the video of the infrared camera and analyzing the spectrum, spectrogram, and power spectra density of these potential hazards. Finally, the seismic signal characteristics of the debris flow are extracted and analyzed. Based on this, the monitoring and early warning work of debris flow hazards can be guided.
Diurnal and Seasonal Patterns of Urban Dry Islands Quantified with a Global Dataset
Authors: Meili Naika , Paschalis Athanasios , Manoli Gabriele , Fatichi Simone
Published: March 2022

Research quantifying urban-rural differences in humidity, the so called urban dry or moisture islands (UDIs, UMIs), has been mostly confined to case-studies of single cities or regions. An analysis of the typical diurnal and seasonal patterns of UDIs at larger scale is still missing even though changes in humidity can impact human well-being, building energy consumption, and urban ecology. In this study, we use a large data set (1089 stations) of globally distributed near surface air temperature and humidity measurements to quantify the typical diurnal and seasonal patterns of UDIs, which developed due to rapid urbanization in many parts of the world, using a time for space substitution. We distinguish between “relative” and “absolute” UDIs quantified as the urban-rural difference in relative and actual humidity measurements, respectively, to account for differences in their diurnal and seasonal patterns.

We find that absolute UDI is largest during daytime with the highest humidity decrease in the late afternoon hours, while relative UDI is generally largest at night. Peak relative humidity decrease occurs during the late evening hours with magnitudes of around -10 to -11% between 20-00 local time in summer. Both relative and absolute UDI are largest during the warm season. Separating the contribution of actual humidity decrease and change in temperature to the formation of relative UDI, we find that relative UDI is mostly caused by absolute UDI during daytime and by temperature, i.e., urban heat island (UHI), during nighttime. The quantification of UDIs, as presented here, is crucial for subsequent impact analyses of urbanization on outdoor thermal comfort, urban ecology, and building energy consumption.
Interchange instability analysis based on magnetosphere-ionosphere coupling theory
Authors: Sadeghzadeh Sina , Yang Jian , Mousavi Ameneh
Published: March 2022

A localized flux tube with reduced entropy (PV5/3, where P and V stand for the plasma pressure and flux tube volume, respectively) as compared to its neighbors is defined as a plasma-sheet bubble. Bubbles are susceptible to interchange instability. The interchange instability plays a key role in the transport of plasma from the magnetotail to the near-Earth region. A strong dawn-to-dusk electric field is formed inside the bubble which creates a shear flow. The E×B drift causes the bubble to grow earthward and the magnetic tension force drives it towards the equilibrium location where its total entropy matches the entropy of the surrounding area. According to the Vasyliunas equation, when the angle (α) between ∇V and ∇PV5/3 is either 0 (being parallel) or 180° (being antiparallel), the Birkeland current cannot be flown between the plasma sheet and the ionosphere. In this study, using the linear instability analysis we investigate the excitation and development of interchange modes in the low-beta plasma sheet (β<<1) when 0<α<180°. To this end, a boundary layer (with thickness δ) separating regions of higher and lower entropy is assumed in a small region of the ionosphere. The first-order electric potential (Φ) within this layer is numerically calculated based on time-sequence technique. The complete analytical solution for the temporal variation of Φ clearly shows that the unstable interchange modes with large wavelengths compared to the boundary layer (i.e., λ>>δ) can be generated.
Imaging the meso-scale structure of the upper mantle beneath the southern and central Atlantic ocean
Authors: Romanowicz Barbara , Munch Federico , Rudolph Max , Mukhopadhyay Sujoy
Published: March 2022

Although seismic tomography has provided important constraints on the long-wavelength structure of the mantle and its planform of convection, much is yet not well understood about the dynamic interaction of tectonic plates and deep mantle circulation at intermediate wavelengths (i.e., below plate-scale). In particular, a better understanding of the seismic structure of the oceanic upper mantle could potentially help unraveling the relationships between different scales of mantle convection, hotspot volcanism, and surface observables (e.g., MORB geochemistry, gravity gradients and bathymetry). We here present a new tomographic model of the shear-wave velocity and radial anisotropy structure beneath the central and southern Atlantic ocean constructed from the inversion of surface and body waves waveforms down to 30s period. Preliminary results confirm the existence of quasi-periodically distributed low-velocity regions in the upper mantle (200–350 km depth) organized in horizontally elongated bands some of which are parallel to the direction of absolute plate motion, as previously found in a lower resolution global tomographic models SEMum2 (French et al., 2013) and SEMUCB_WM1 (French and Romanowicz, 2014). Many of these elongated structures overlie vertically elongated plumelike conduits that appear to be rooted in the lower mantle, located, when projected vertically to the surface, in the vicinity of major hotspots.  However, there is no direct vertical correspondence between the imaged plumelike conduits and hotspots locations suggesting a complex interaction between the upwelling flow and the lithosphere/asthenosphere system. We discuss possible relations of this structure with trace element geochemistry of the corresponding hotspots.
Evaluation of the novel Drought Potential Index (DPI) over Japan
Authors: Abhishek Abhishek , Kinouchi Tsuyoshi
Published: March 2022

Despite receiving an annual rainfall of about 1718 mm (twice as the global average of 810 mm), Japan has erratically faced water shortages at various levels. Since most of these events last less than six months, their detailed assessment remains largely unexplored. Here, firstly we correct the GRACE- and GRACE-FO-derived terrestrial water storage anomaly (TWSA) for co- and post-seismic corrections corresponding to the Tohoku-Oki earthquake (Mw=9.1) that occurred on March 11th, 2011. Secondly, we fill the 34 missing values (23 due to battery management and 11 between the two missions) in the TWSA time series using the ANN and LSTM models. Lastly, we employ the Drought Potential Index (DPI) recently devised by Abhishek et al. (Journal of Hydrology, Volume 603, Part A, 2021, 126868) to quantity the drought potential of the region. The seismic correction using the least square fitting of the TWSA in the spectral domain results in a 76% increase (raw: -3.50 mm yr-1 vs. corrected: -0.83 mm yr-1) in linear trends from May 2002 to April 2020. The seismic correction accounts for an increase of 54.45 mm of TWSA during March 2011, with continually decreasing post-seismic relaxations until 2017. Both ANN and LSTM performed reasonably well (r>0.85, NSE>0.70) during calibration and validation phases, and therefore, an average of the two modeled TWSA was used during the data gaps. The maximum water storage deficit (DPI = 1) was observed during July 2014, followed by September 2016 and October 2012 (DPI≈0.85 for both). Some other years of significant water-stressed conditions include 2005, 2007, 2008, and 2013. The crux of this effective water storage-based DPI is that, unlike traditional assessment of water deficit, it considers the monthly potential water deficit and is therefore capable of capturing the droughts that evolve during dry and wet seasons. DPI can also indicate the long-term tendency and transition of the study region to a drought-prone area.
Influence of the NAO on wintertime surface air temperature over the East Asia: multidecadal variability and decadal prediction
Authors: Li Jianping , Xie Tiejun , Tang Xinxin , Wang Hao , Sun Cheng , Feng Juan , Zheng Fei , Ding Ruiqiang
Published: March 2022

In this paper, we investigate the influence of the winter NAO on the multidecadal variability of winter East Asian surface air temperature (EASAT) and its decadal prediction. The observational analysis shows that the winter EASAT and East Asian minimum SAT (EAmSAT) display strong in-phase fluctuations and a significant 60–80-year multidecadal variability, apart from a long-term warming trend. The winter EASAT experienced a decreasing trend in the last two decades, which is conducive to the occurrence of winter extremely cold events in East Asia in recent years. The winter NAO leads the detrended winter EASAT by 12–18 years with a maximumly significant positive correlation at the leading time of 15 years. Further analysis shows that ENSO may affect winter EASAT interannual variability, but does not affect the robust leading relationship between the winter NAO and EASAT. We present the coupled oceanic-atmospheric bridge (COAB) mechanism of the NAO influences on winter EASAT multidecadal variability through its accumulated delayed effect of ~15 years on the Atlantic Multidecadal Oscillation (AMO) and Africa–Asia multidecadal teleconnection (AAMT) pattern. Based on the COAB mechanism an NAO-based linear model for predicting winter decadal EASAT is constructed, with good hindcast performance. The winter EASAT for 2020–2034 is predicted to keep on fluctuating downward until ~2025, implying a high probability of occurrence of extremely cold events in coming winters in East Asia, and then turn towards sharp warming. The predicted 2020/21 winter EASAT is almost the same as the 2019/20 winter.

Keywords: winter East Asian surface air temperature (EASAT), North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation (AMO), Africa-Asia multidecadal teleconnection (AAMT) pattern, coupled oceanic-atmospheric bridge (COAB), multidecadal variability.
Variability of the Upper Ocean Energy Field in the Amundsen Basin, Arctic Ocean
Authors: Wu Wen-Chuan , Fang Ying-Chih , Rabe Benjamin
Published: March 2022

The dynamics of the Arctic Ocean are changing significantly with increasing global greenhouse gas emissions. Under the current warming scenario, the thinning of sea ice could affect Arctic thermohaline dynamics for the foreseeable future, which would affect the development of the energy cascade. Here, we analyze in situ Lagrangian measurements of the wintertime upper-ocean thermohaline field that were taken during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. Horizontal wavenumber spectra of density are examined from 13 approximately 100-km long transects from October 2019 – May 2020 to determine the steepness of spectra for different spatial scales. Unlike the relatively well-defined frequency spectra, horizontal wavenumber spectra yield variable patterns depending on the region of observations. This issue motivates us to investigate the current state of horizontal wavenumber spectra in the multiyear ice zone of the central Arctic. Our preliminary results show that the wavenumber spectra are not consistent in space and time, implying an interplay of stratification, mixed layer depth, and external forcing, such as ice dynamics.