bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of the value of spatially improved SMAP soil moisture products in enhancing streamflow forecast skills
Authors: Wakigari Shimelis Asfaw , Leconte Robert
Published: March 2022

Soil moisture (SM) measurements over large areas are vital for many operational applications such as flood forecasting, irrigation scheduling, and drought monitoring. Although obtaining SM over extensive areas was difficult until recently, the advent of satellite remote sensing technologies such as passive microwave satellites (e.g., SMOS and SMAP) opened a new way. Nevertheless, the utilization of SM products of these satellites is often impeded because of their coarse spatial resolution (i.e., about 40 km). A number of studies have been attempted to improve the coarse resolution satellite SM products via downscaling. However, despite of many downscaling efforts, subsequent use of downscaled satellite SM products for operational applications has not yet been fully explored. Thus, the objective of this study is to evaluate the value of SMAP SM in enhancing short-term streamflow forecast skills. The random forest machine learning technique was used to downscaled SMAP SM from 36 km to a range of resolutions from 1 to 9 km (i.e., 9, 3, and 1 km). Thereafter, a host of experiments were carried out to update a physically-based distributed hydrological model through direct ingestion of the original SMAP SM (e.g., 36 km), SMAP enhanced SM (i.e., 9 km), and downscaled SMAP SM at different spatial resolutions (e.g., 9, 3 and 1 km). A non-updated model was used as a benchmark for comparison. The result shows that the downscaled SMAP SM has presented better spatial detail than its corresponding native resolution and updating the model state with SMAP SM products (i.e., with the native and downscaled products) shows promising potential for improving short term flood forecasting. Finally, this will in turn helps in better water resources management.
Can examining past variability help us understand catchment response to future climate change?
Authors: Stephens Clare , Marshall Lucy , Johnson Fiona , Lin Laurence , Band Larry , Ajami Hoori
Published: March 2022

It is common to test hydrologic models under contrasting historical periods as an indicator of likely performance under climate change. For example, a model calibrated under average conditions may be tested under increasingly dry subsets of the observational record. Any decline in performance as the testing conditions deviate further from the calibration conditions is then assumed to represent likely performance degradation under climate change scenarios with comparable rainfall decreases. Many studies have inherently applied the assumption that past rainfall variability can be used as a proxy for future climate change, but the analogy may be flawed for three main reasons:

Due to lagged hydrologic response to meteorological shifts, catchment behaviour under long-term wetting or drying may not be fully represented over shorter wet or dry periods.

Subsets of the past record selected based on rainfall are unlikely to reflect future temperature increases.

Past observations do not include expected increases in carbon dioxide levels.

If any of these factors substantially impacts catchment response, subsets of the historical record with equivalent rainfall will not be accurate proxies for future climate scenarios. We tested the impact of each factor using the ecohydrologic model RHESSys. RHESSys dynamically simulates vegetation growth, subsurface flow and nutrient cycling and is thus able to capture the key processes that could drive nonstationary catchment response in the future. We found that all three future climate factors (rainfall change persistence, temperature, and carbon dioxide) altered catchment response substantially, especially for drier future scenarios. For our study catchment, persistence of dry conditions over many decades led to different subsurface water storage levels than the same rainfall experienced over shorter timeframes, leading to different streamflow. The impacts of increased temperature and carbon dioxide concentrations on vegetation further altered runoff behaviour. This means that long-term climate change effects will not necessarily emerge over short historical periods with equivalent rainfall. In our example, ignoring persistence in rainfall changes, rising temperatures, and higher carbon dioxide levels could lead us to underestimate model performance degradation in terms of Nash-Sutcliffe efficiency by as much as 0.41. Therefore, the uncertainty introduced in hydrologic models by future climate change has probably been underestimated in the current literature.
A new version of Global Satellite Mapping of Precipitation (GSMaP) product released in December 2021
Authors: Kubota Takuji , Aonashi Kazumasa , Ushio Tomoo , Shige Shoichi , Yamaji Moeka , Yamamoto Munehisa , Hirose Hitoshi , Takayabu Yukari
Published: March 2022

The Global Satellite Mapping for Precipitation (GSMaP) produces high-resolution and high-frequent global rainfall map based on multi-satellite passive microwave radiometer observations with information from the Geostationary InfraRed (IR) instruments (Kubota et al. 2020). Output product of GSMaP algorithm is 0.1-degree grid for horizontal resolution and 1-hour for temporal resolution. The GSMaP near-real-time version product (GSMaP_NRT) has been in operation at JAXA since November 2007 in near-real-time basis, and browse images and binary data available at JAXA GSMaP web site (http://sharaku.eorc.jaxa.jp/GSMaP/).

A new version of the GSMaP product was released in December 2021. We plan the reprocessing of the GSMaP standard version in a period during the past 24 years since Jan. 1998. The GSMaP algorithms consist of passive microwave (PMW) algorithms, a normalization module for PMW retrievals, a PMW-IR Combined algorithm, and a Gauge-adjustment algorithm. Features in the new version are summarized as follows. In the PMW algorithm, retrievals extended to the pole-to-pole. Databases used in the algorithm were updated. A method using frozen precipitation depths was newly installed (Aonashi et al. 2021). Heavy orographic rainfall retrievals were improved upon a basic idea of Shige and Kummerow (2016). The normalization module for PMW retrievals (Yamamoto and Kubota 2020) were newly implemented to make more homogeneous PMW retrievals, in particular, for microwave sounders. A basic idea of the PMW-IR combined algorithm is using morphing and Kalman filter (Ushio et al. 2009). In addition, a histogram matching method by Hirose et al. (2022) was implemented in the new version to reduce the IR retrievals with reference to the PMW retrievals. In the gauge-adjustment algorithm, a precipitation estimate is adjusted using the NOAA CPC Global Unified Gauge-Based Analysis of Daily Precipitation (Mega et al. 2019). Artificial patterns appeared in past versions were mitigated in the new version. Preliminary validation results using the gauge-adjustment ground radar data over the Japan land areas confirmed better results in the new version of the satellite only products.

Furthermore, the GSMaP real-time version (GSMaP_NOW) with the new algorithm was also released in December 2021.The GSMaP algorithm for the new version was also applied to the GSMaP_NOW system after 6th December 2021. Accuracy improvements were confirmed also in the GSMaP_NOW products by validations with the gauge-adjustment ground radar data over Japan.
Subseasonal Effects of Large-Scale Soil Moisture Anomalies over Southeastern South America
Authors: Chug Divyansh , Chen Chu-chun , Dominguez Francina , Grimm Alice
Published: March 2022

Soil moisture has been recognized as a source of predictability for subseasonal-to-seasonal forecasts. We perform a series of soil moisture (SM) sensitivity tests using the Community Earth System Model (CESM2) to understand the effect of antecedent land surface state on intra-seasonal hydroclimate variability over South America. Using extended empirical orthogonal function (EEOF) analysis with remotely-sensed and reanalyzed datasets, we establish a link between the dominant oscillatory mode of intraseasonal hydroclimate variability (EEOF-1) and antecedent SM anomalies. Large-scale dry SM anomalies are observed to persist over southeastern South America (SESA) prior to the intra-seasonal increase in precipitation. The modeled response of monthly mean conditions shows that SM exerts a strong influence on the surface energy budget and the evolution of the boundary layer in this region. A reduction of initial SM over the SESA region induces a thermal low and anomalous cyclonic circulation that would inhibit the moisture-rich northerly flow associated with the increase in intra-seasonal precipitation and decrease the variability associated with EEOF-1. Reduced availability of moisture at the surface also decreases the atmospheric moisture content through reduced recycling of local moisture. The overall impact of the surface anomaly through thermal and recycling pathways can support or compete with each other depending on the scale and the location of the initial perturbation. The goal of this study is to identify the mechanisms through which accurate initialization of SM in subseasonal forecasts can enhance predictability in this socio-economically vital region of South America.
Evidence for Anisotropy in the Innermost Inner Core from the Earthquake Coda-correlation Wavefield
Authors: Costa de Lima Thuany , Tkalčić Hrvoje , Waszek Lauren
Published: March 2022

Progress on seismic imaging of the Earth’s inner core (IC) is fairly limited by the uneven distribution of sources and receivers; large earthquakes are primarily confined to plate margins, and seismic stations are unevenly deployed on the Earth’s surface. Advances in data processing techniques and new methods are required to bridge new opportunities to probe the centre of our planet and provide us with valuable information on the IC seismic structure and its surrounding dynamics. In this study, we present a newly-developed method based on the global earthquake coda-correlation wavefield to investigate the anisotropic structure of the IC. Anisotropy in seismic velocity is the directional dependence of seismic waves. Under IC pressure and temperature conditions, different phases of iron – the core’s main mineral constituent can stabilize and form elastic anisotropy. Thus, improved constraints on its strength and distribution are required to understand the crystallographic structure of iron in the IC, which is linked to the evolution of its solidification and deformation processes. Here, we stack the cross-correlation functions of the late-coda seismic wavefield (the correlation wavefield) that reverberates within the Earth up to 10 hours after large earthquakes. We analyse the travel times of the I2* correlation feature, a mathematical manifestation of similarity among IC seismic phases with the same slowness detected in global correlograms at small interstation distances (<10°). The I2* spatial sampling offers an unprecedented data coverage of the IC’s central portion, also known as the innermost IC (IMIC), which overcomes the shortage of the traditional approach using PKIKP ray paths sampling. By comparing the time residuals of different paths of I2* propagating through the IC, we confirm the presence of a deep IC structure with anisotropy fundamentally different from the IC’s outer layers. Our observations support an IMIC cylindrical anisotropy model with a slow direction oriented 55° from the Earth’s spin axis. This new evidence reinforces previous inferences on the existence of the IMIC, with implications for our understanding of the core’s geodynamical evolution. In the future, a similar approach could be applied to advance our understanding of anisotropy in the Earth’s mantle.
Photoassimilation rates of sub-arctic moss and lichens species in pine ecosystems of the Central Siberia 
Authors: Polosukhina Daria , Makhnykina Anastasia , Prokushkin Anatoly
Published: March 2022

Bryophytes and lichens usually dominate the ground floor layer of boreal forests and tundra, and contribute up to 50% of ecosystem gross CO2 exchange (Bisbee et al. 2001; Goulden & Crill 1997). While Sphagnum spp. are the most important contributors in wetland C uptake, feathermosses and lichens play a significant role in drained habitats (Nilsson & Wardle 2005; O’Connell et al. 2003; Bjerke et al. 2013). Given their important ecological roles in such widespread biomes, it is surprising that still a few studies have attempted to understand the intrinsic factors that control moss-lichen cover carbon exchange dynamics specifically under ongoing climate change in high latitudes.

The aim of this work was to determine photoassimilation activity the widespread species of moss-lichen stratum during the growing season. The study has been conducted in Central Siberia near Zotino tall tower observatory (ZOTTO, 60 ° N, 89 ° E) in lichen- and feathermoss-dominated pine forests. The intensity of CO2 photoassimilation of ground vegetation dominants (Cladonia stellaris O., Cladonia rangiferina L., Cetraria islandica L., Pleurozium schreberi W. ex B., Hylocomium splendens H., Dicranum scoparium H.) was determined in situ by infrared gas analyzer Walz GFS-3000 (Heinz Walz GmbH, Effeltrich, Germany) during the most part of a growing season (from June to September).

Bryophytes demonstrated more intense photosynthetic activity throughout the growing season. From June to September, among the studied moss species, the highest values of photoassimilation were observed for P. schreberi, and the lowest for H. splendens. The maximum values were recorded in August for all studied species and amounted to 4.36 ± 0.13 μmol / m2 / s, and the lowest values were recorded in June to 1.4± 0.08 μmol / m2 / s . Among lichens, C. stellaris was the most photosynthetically active, and C. rangiferina showed the least CO2 photoassimilation rates. Moss-lichen layer dominants maintained relatively high photoassimilation activity throughout the growing season.

The research was funded by Krasnoyarsk Regional Fund of Science within the framework of the project № 2021 102007845  and RFBR, Krasnoyarsk Territory and Krasnoyarsk Regional Fund of Science, project number 44-243003.
CCMOC: A New View of the Earth's Outer Core Through the Global Coda Correlation Wavefield
Authors: Ma Xiaolong , Tkalčić Hrvoje
Published: March 2022

Increasing seismic evidence has accumulated, suggesting that the Earth’s outer core consists of distinct layers of low P-wave velocities relative to the Preliminary Reference Earth Model (PREM) in the top and bottom of the liquid core. Seismically detected low velocity in the outer core could be linked with the stratification, essential for understanding the geodynamo and thermochemical evolution of the liquid core. However, a consistent globally-averaged radial structure of the outer core has not been obtained due to the incomplete coverage of sampling body waves. To remedy this problem, we explore the seismic structure of Earth's outer core by employing a new theoretical and observational concept termed coda correlation wavefield. We construct the global correlogram in the 15-50 sec period range by stacking cross-correlations of the long-duration coda waves from the selected ten large earthquakes. We then assemble a dataset of prominent correlation features from the global correlogram that are sensitive to the outer core. The waveforms of these features are fit by computing synthetic correlograms through various outer core models. The obtained optimal model displays P-wave velocities in both the outer core's top and bottom, consistent with Coda Correlation Reference Earth Model (CCREM) and reduced relative to PREM. The low seismic speeds in the top of the outer core could likely imply the formation of a thermal and/or compositional stratification.
Mean transit times help understand the volume of catchment water required to sustain streamflow in contrasting southeast Australian rivers
Authors: Zhou Zibo , Cartwright Ian , Morgenstern Uwe
Published: March 2022

Streams may be connected to a large store of water, such as regional groundwater, and/or sustained by smaller near-river stores (such as riparian groundwater). Documenting the sources of water in streams is important for understanding catchment water balances, protecting riverine environments from pollution, and predicting the efforts of near-river pumping. Additionally, streams connected to large water stores will be buffered against the impacts of short-term climate variability (such as droughts that last a few years). Many techniques that document groundwater-stream water interaction allow the location and fluxes of baseflow to be determined but do not constrain from where in the catchment the baseflow is derived. The mean transit time (MTT) represents the time taken for water to migrate from where it is recharged in the catchment to where it discharges into the stream. Estimating the MTTs of stream water allows the volume (V) of the water store that sustains streamflow (Q) to be estimated (V=Q×MTT). This study compares the water stores sustaining streamflow in contrasting rivers in southeast Australia based on tritium MTTs calculated using lumped parameter models. Perennial streams (Oven, Yarra, Latrobe, and Gellibrand Catchments) have long MTTs (4 to 179 years) that are higher at low streamflows. By contrast, the MTTs of similar size intermittent streams (Deep Creek, Wimmera, and Gatum Catchments) range from <1 to 35 years (and are mostly less than 20 years). The estimated volumes of the catchment contributing to streamflow are 3 to 5 orders of magnitude smaller than those in comparable perennial streams. These differences reflect the limited connection between the intermittent streams and the deeper regional groundwater system compared with the perennial streams, especially at low flows. Rather, intermittent streams may be sustained mainly by smaller younger reservoirs in the riparian zone. These intermittent streams will be more susceptible to short-term climate variabilities and changes to flow regimes may have significant impacts on water supplies and the health of the riverine system. Intermittent streams are globally distributed in a range of environments, especially in semi-arid areas. Climate change and water stress have resulted in many perennial streams gradually becoming intermittent and this trend is expected to increase. In southeast Australia, around 30% of catchments have not recovered following multiple drought years between 1996 and 2010 (the Millennium Drought), and streamflow has kept declining. The increased intermittence fundamentally changes the catchment water balance, specifically making regional groundwater less important, and increases the reliance of these streams on more vulnerable small young water stores.
Imaging of Deep Planetary Interiors from Inter-source Correlations via a Single Seismograph
Authors: Wang Sheng , Tkalčić Hrvoje
Published: March 2022

Global seismic imaging of the Earth's interior has come a long way in exploring and understanding the Earth’s internal structure and dynamics with the worldwide proliferation of seismographs. However, investigating planetary interiors, including detections of their deep structures, remains challenging because of the limited number of seismographs that are and will be deployed in the foreseeable future. Besides, the existing imaging methods based on observations of a direct seismic wavefield from seismic sources require the emergence of the seismic waves with distinguishable amplitudes. That condition restricts the seismic station locations for practical wave reflections or refractions from internal planetary interfaces to a limited angular distance range from the source.

Here, we explore a new way to image deep planetary interiors, especially the planetary cores, using a single seismograph. We first develop a novel procedure for constructing global inter-source correlograms and show that they contain many prominent features sensitive to the internal planetary structures. We demonstrate that a single station is sufficient to produce a global correlogram for the Earth. We then utilize a single-station correlogram and show the steps for detecting and quantifying the Earth’s and Martian cores interfaces. This provides a new paradigm for imaging deep planetary interiors on global scales.
Identifying the dominant local factors of 2000-2019 changes in dust loading over East Asia
Authors: Che Huizheng , Yao Wenrui , Gui Ke , Wang Yaqiang , Zhang Xiaoye
Published: March 2022

East Asian dust aerosols play a vital role in the local and regional climate through its direct, indirect, and semidirect effects, but the dominant factors affecting the interannual variation of dust aerosols over East Asia and their regional differences remain unclear. This study verified the accuracy of MEERA-2 dust data in East Asia, analyzed the interannual trends of dust in East Asia from 2000 to 2019 using the MERRA-2 dust column mass density (DCMD) and identified the dominant factors affecting the interannual variation during the dusty season (March–July) by developing the regional multiple linear regression models, combined with correlation and partial correlation analysis. The comparison with the dust index (DI) calculated from ground-based observations of dust events frequency indicated that MERRA-2 DCMD exhibited high spatial agreement (R > 0.8) with ground-based observations in most regions (especially in the dust source region of North China). The trend analysis revealed that DCMD in East Asia decreased significantly after 2000, particularly in the dusty season (March–July). These significant decreases were generally highly correlated with increases in normalized differential vegetation index (NDVI), volumetric soil moisture (VSM), and precipitation (PPT) and with decreases in wind speed (WS). Furthermore, WS dominated the interannual variation in the dust concentration over the East Asian dust source regions and their downstream. By contrast, PPT, through its wet deposition effect, dominated the variation in the rest of the regions away from the dust source regions. The study findings may help clarify the associations between local meteorological and surface factors and long-term variations in dust aerosols over East Asia.
Real-time Flood Forecasting Using Numerical Weather Prediction System Through NICAM-LETKF Data Assimilation in the Prek Thnot River, Cambodia
Authors: Try Sophal , Sayama Takahiro , Sok Ty , Phy Sophea Rum , Oeurng Chantha
Published: March 2022

Flood is widely recognized as the most common and frequent natural phenomenon which currently threatens huge damage worldwide. The Prek Thnot River (PTR) in Cambodia is one of the flood-prone areas where severe floods occur every year and cause damage to residents downstream. This study aims to evaluate the forecasting performance of flooding in the PTR using near real-time datasets from satellite observation (i.e., GSMaP and GPM) and forecasted rainfall from NICAM-LETKF numerical weather prediction (so called GSMaPxNEXRA) dataset. GSMaPxNEXRA data is produced by Global Cloud Resolving Model with Data Assimilation. This study used a fully distributed rainfall-runoff-inundation (RRI) model for river discharge and water level simulations. The RRI model was calibrated and validated with gauged observed rainfall during flood events in 2000, 2001, 2007, 2010, and 2020 with satisfactory and acceptable results. The most recent flood event in 2020 was considered to evaluate real-time flood forecasting. The near real-time simulation indicated the results discharge and water level with statistical indicators KGE = 0.80 and 0.07 and r2 = 0.83 and 0.87 for GPM and KGE = 0.48 and -0.12 and r2 = 0.54 and 0.67 for GSMaP. The GPM rainfall product outperforms GSMaP rainfall in the PTR. Flood forecast from the GSMaPxNEXRA showed an accuracy with KGE = 0.79 and r2 = 0.89 (1-day forecast) to KGE = 0.66 and r2 = 0.76 (5-day forecast). On the other hand, the performance of 1-day to 5-day forecast indicated with coefficient of extrapolation (CE) and coefficient of persistence (CP) between CE = -2.62 and CP = -2.65 for 1-day forecast to CE = 0.71 and CP = -0.06 for 5-day forecast. To conclude, real-time flood forecasting in the PTR was successfully assessed and evaluated in this study; however, the accuracy of flood prediction should be further improved in the future by considering data assimilation and machine learning.
Double TGFs and optical pulses observed by ASIM 
Authors: Ostgaard Nikolai , Mezentsev Andrey , Marisaldi Martino , Sarria David , Ullaland Kjetil , Yang Shiming , Genov Georgi , Neubert Torsten , Chanrion Olivier , Christiansen Freddy , Cummer Steve , Lu Gaopeng , Reglero Victor , Luque Alejandro
Published: March 2022

Atmosphere Space Interaction Monitor (ASIM) has now observed more than 1000 Terrestrila Gamma-ray falshes (TGFs) since the launch in 2018. ASIM has two payloads, the Modular X- and Gamma-ray Sensor (MXGS) and the Modular Multi-Spectral Imaging Assembly (MMIA). MXGS consists of two detector layers, one pixelated detector in the low energy range (50 keV to 400 keV) and another in the high energy range (300 keV to >30 MeV), with temporal resolution of 1µs and 28 ns, respectively.  MMIA has three photometers (337 nm, 180-230 nm, 777 nm) and two cameras (337 nm and 777 nm). During nighttime we observe both the TGFs and the lightning that produced them. Multiple and double TGFs  separated by 1-2 ms have frequently been observed by ASIM. In this paper we present three events of double TGFs. All of them are associated with  optical pulses from a hot leader (777 nm), and the first and second pulses come from the same location, indicating that the double TGFs are produced by the same leader as it propagates upward. 
Large-scale experiment on dike breaching with complex measures on the crown
Authors: Huang Wei , Shi Deliang , Wei Hongyan , Ni Yufang , Duan Wengang
Published: March 2022

Dike breaching is the main component of flood defending system. To temporally enhance the capacity of the river, small levees will be build on the dike crown to increase the elevation of the dike crest. Also, the dike top usually be paved with concrete as transportation road. Under these two condition, break mechanism are different from those without complex measures on the crown, which has not been investigated yet. Large-scale experiment has been carried to investigate the breaching mechanism. Results show that with small levees, the flow forms a little fall at the downstream edge of the levee top and a much larger fall on the downstream face of the dike. The “headcut” backward retreat is the main breaching mechanism in the early stage of breaching. During the rapid development stage of breaching, the vertical erosion, lateral erosion and gravity collapse are the breaching mechanism. The existence of the external small levee protected the top of the dike from erosion for a long time, which largely delayed the breaching processes. As the top was paved, the breaching processes likes that of dike with small levees. Two falls forms at the edge of the road and at the downstream face respectively. When the backward retreat of “headcut” at the downstream face of the dike reaches the base of the dike, the underneath soil is washed away and lead to concrete of the road collapse. Once the road is collapsed completely, two falls merged into one, thereafter the breaching processes likes dikes without complex measures on the crown. The paved road also delayed the breaching processes. This study can provide scientific support to dike breaching emergency management.
Numerical simulation of directional JONSWAP sea waves taking into account four- and five-wave nonlinear resonances
Authors: Kokorina Anna , Slunyaev Alexey
Published: March 2022

We perform the direct numerical simulation of surface gravity waves in the deep sea with the initial conditions specified by waves with a given JONSWAP spectrum and the directional spreading according to the cos2 distribution. The High Order Spectral Method employed for the simulation, allows to control the order of nonlinearity through the parameter of the scheme, M. In particular, the value M = 1 corresponds to the linear solution, M = 3 – to the account of the cubic nonlinearity due to the four-wave nonlinear interactions. Most of the direct numerical simulations of the HOSM available in the literature, are performed with the parameter M = 3, which is sufficient to take into account the modulational instability. In this work we examine the role of even higher order nonlinear effects due to 5-wave interactions. To this end, a series of comparative numerical simulations have been performed with M = 3 and M = 4. The obtained wave data are examined with respect to the probability distribution functions for the wave heights, and the typical rogue wave shapes. So far, no new dynamical effects between waves associated with the high-order nonlinearity is found. The high-order nonlinearity seems to affect the dynamics of very steep waves leading to the generation of even slightly higher waves. The main part of the wave height probability distribution function remains unchanged.

 

The research is supported by the RFBR grants Nos. 20-05-00162 and 21-55-15008.

[1] A. Sergeeva (Kokorina), A. Slunyaev, Rogue waves, rogue events and extreme wave kinematics in spatio-temporal fields of simulated sea states. Nat. Hazards Earth Syst. Sci. 13, 1759-1771 (2013).

[2] A. Slunyaev, A. Sergeeva (Kokorina), I. Didenkulova, Rogue events in spatiotemporal numerical simulations of unidirectional waves in basins of different depth. Natural Hazards 84(2), 549-565 (2016).

[3] A. Slunyaev, A. Kokorina, Account of occasional wave breaking in numerical simulations of irregular water waves in the focus of the rogue wave problem. Water Waves 2(2), 243-262 (2020).

[4] A. Slunyaev, A. Kokorina, Numerical Simulation of the Sea Surface Rogue Waves within the Framework of the Potential Euler Equations. Izvestiya, Atmospheric and Oceanic Physics 56, No. 2, 179–190 (2020).
Deep convection in the Subpolar Gyre, how much data is needed to estimate its intensity?
Authors: Fedorov Aleksandr M. , Bashmachnikov Igor L. , Iakovleva Diana A. , Kuznetcova Daria A. , Raj Roshin P.
Published: March 2022

Deep convection in the Subpolar Gyre (SPG) of the North Atlantic forms a link between the upper and lower limbs of the Atlantic Meridional Overturning Circulation (AMOC). The intensity of convection is estimated using mixed layer depth (MLD) derived from in situ vertical profiles of potential density. Given limited areas of convective chimneys, the robustness of the estimates from an available set of vertical profiles needs to be verified before studying mechanisms of interannual variability of convection intensity. For reaching this goal, we first computed the frequency of deep convection events observed in situ and split the convective regions into three domains: the central part of the Irminger Sea (I-DC), the southwestern part of the Labrador Sea (L-DC), and a domain south of Cape Farewell (F-DC). For each domain, we identified two types of development of the convective regions using k-means cluster analysis. Then, for each convection domain and each convection type, the minimum number of randomly scattered casts required for a robust estimate of the maximum MLD during the convective period are derived as a criterion of a robust estimate of the convection intensity. The results showed that, for all the convection domains, a sufficient number of casts during a cold season was collected since the late 1990s for some years, while uninterrupted time series are obtained since the mid-2000s. The main modes of spatio-temporal variability of salinity and temperature in the upper North Atlantic, preceding the years with high/low convection intensity, are accessed through constructing the composite maps of their anomalies and the empirical orthogonal function (EOF) analysis. The first EOF of temperature closely corresponds to the composite map of temperature anomalies, while its principal component has a high correlation with interannual variability of convection in the I-DC and F-DC convection domains, and a moderate one in the L-DC domain. At the same time, a high correlation with the SPG index is also observed. The results suggest that the variability of these dynamic patterns may play an important role in shaping convection intensity in the SPG.

Funding: The research was funded by Saint Petersburg State University (SPSU), project no. 75295423.
Indian Ocean influence on the ENSO-Indian monsoon teleconnection is mostly apparent 
Authors: Bodai Tamas , Sundaresan Aneesh , Lee June-Yi , Lee Sun-Seon
Published: March 2022

“Decadal influence” on the El Nino--Southern Oscillation-Indian summer monsoon (ENSO-ISM) teleconnection have been much studied but with plurality and ambiguity about the concept of influence. We provide formal definitions of the apparent influence of a specific factor which enable us to test them as null-hypotheses. Using the recently released Community Earth System Model v2 (CESM2) Large Ensemble (LE) data, we show that a 50% chance for the detection of the apparent Indian Ocean (IO) influence under stationary conditions might take 2000 years of data. However, we find that this influence is mostly apparent indeed, as it originates from fluctuations of the decadal apparent -- as opposed to climatological -- ENSO variability, which causally influences an IOD-like apparent mean state. We also show that no unattributed so-called “decadal influence”, reflected in a deviation from a linear regression model of the teleconnection as a null-hypothesis, can be detected in 20th c. observations even regionally.  Only the LE data is sizable enough to reveal this effect.
Upscaling microbial stoichiometric adaptability in SOM turnover using the SESAM model: specifics of phosphorous dynamics.
Authors: Wutzler Thomas , Yu Lin , Zaehle Sönke , Schrumpf Marion , Ahrens Bernhard , Reichstein Markus
Published: March 2022

In order to understand the coupling of land ecosystem carbon (C), nitrogen (N), and phosphorous (P) cycles, it is necessary to understand microbial element use efficiencies (C, N and P) of soil organic matter (SOM) decomposition. While important controls of those efficiencies by microbial community adaptations have been shown at the scale of a soil pore, an abstract simplified representation of community adaptations is needed at the ecosystem scale. The conceptual soil enzyme allocation model (SEAM) explicitly models community adaptation strategies of resource allocation to extracellular enzymes and enzyme limitations on SOM decomposition. It thus provides a scaling from representing several microbial functional groups to a single holistic microbial community. The model has been further abstracted using quasi-steady-state assumption for extracellular enzyme pools to the SESAM model. While initially, P optimality considerations have been treated analogue to N, we found with simulating a sequence of sites with a P availability gradient that model extensions were required for P. Here we discuss effects of explicitly considering two assumptions on SOM dynamics: (1) oxidative enzymes can acquire P from SOM without necessary stoichiometric decomposition of C and N, and (2) for the case where P is limiting, in addition to P cost, also the C and N cost of enzyme production are important for optimality. We found that neglecting these two assumptions did not significantly change system behavior and predictions in the case where P was not limiting soil microbes. However, it changed model predictions of ecosystem-scale SOM dynamics for the case where P started to become limiting.

This modeling study links knowledge of constraints at soil microbial scale to SOM dynamics at ecosystem scale. It highlights the important role of adaptability of soil microbial communities to resource supply and stoichiometry for the development of SOM stocks and nutrient availability.
Multifunctionality of coastal wetlands in a hazard context
Authors: Karstens Svenja , Kiesel Joshua , Petersen Lennart , Etter Kilian , Vafeidis Athanasios , Gross Felix
Published: March 2022

The ability to trap and accumulate sediment and thereby to change the bathymetry makes coastal wetlands bioengineers of their own environment. While wind and wave attenuation directly contribute to hazard mitigation, the influence on bathymetry and thus shoreline change acts on longer time scales. In addition, sediment trapping impacts not only hazard mitigation but also blue carbon storage or the nutrient removal potential. The wetland in Stein at the Kiel Bay (German Baltic Sea) is a primary example of a site that offers ‘nature based coastal protection’, while at the same time the site is exposed to increasing anthropogenic pressures. Space for natural development at the study site is limited as the wetland is squeezed by a dyke in the hinterland, a marina and construction sites in the east, a popular tourist beach in the west and waterway dredging in the north. We aim to achieve a deeper understanding of short-term vs long-term processes of sediment trapping and vegetation propagation at this site.

We are combining remote sensing methods with vegetation mapping in field and on-site measurements (e.g. water level, oxygen saturation and waves). Vegetation mapping exposed a striking biodiversity with inter alia Tripolium pannonicum, Atriplex littoralis, Lathyrus japonicus, Bolboschoenus maritimus or Honckenya peploides besides the dominating Phragmites australis. Habitat variety is further enhanced by a manifold topography with small-scale basins, micro-cliffs and micro-depressions. Aerial images from 2007 to 2019 are analyzed to get insights into past development of vegetation patches and shoreline evolution. Preliminary results reveal that the wetland edge is relatively stable, while beach lake size varies significantly. However, this data lacks the spatiotemporal resolution to identify whether changes occurred gradually or after extreme events such as storm surges or winter ice. In contrast, our weekly to monthly UAV flights offer sufficient spatial and temporal resolution to monitor changes in microtopography. We anticipate that our results will help to better understand ecosystem dynamics as a response of gradual and abrupt disturbances, which may foster confidence in more sustainable coastal adaptation strategies.
Fibre-optic observation of volcanic tremor through floating ice sheet resonance
Authors: Fichtner Andreas , Klaasen Sara , Thrastarson Sölvi , Cubuk-Sabuncu Yesim , Paitz Patrick , Jonsdottir Kristin
Published: March 2022

We report on the indirect observation of low-frequency tremor at Grimsvötn, Iceland, via resonance of an ice sheet, floating atop a volcanically heated subglacial lake.

Entirely covered by Europe’s largest glacier, Vatnajökull, Grimsvötn is among Iceland’s largest and most active volcanoes. In addition to flood hazards, ash clouds pose a threat to settlements and air traffic, as direct interactions between magma and meltwater cause Grímsvötn to erupt explosively. To study the seismicity and structure of Grimsvötn in detail, we deployed a 12.5 km long fibre-optic cable around and inside the caldera, which we used for Distributed Acoustic Sensing (DAS) measurements in May 2021.

The experiment revealed a previously unknown level of seismicity, with nearly 2’000 earthquake detections in less than one month. Furthermore, the cable segment within the caldera recorded continuous and nearly monochromatic oscillations at 0.23 Hz. This corresponds to the expected fundamental-mode resonance frequency of flexural waves within the floating ice sheet, which effectively acts as a damped harmonic oscillator with Q around 15.

In spite of the ice sheet being affected by ambient noise at slightly lower frequencies, the resonance amplitude does not generally correlate with the level of ambient noise throughout southern Iceland. It follows that an additional and spatially localised forcing term is required to explain the observations. A linear inversion reveals that the forcing acts continuously, with periods of higher or lower activity alternating over time scales of a few days.

A plausible explanation for the additional resonance forcing is volcanic tremor, most likely related to geothermal activity, that shows surface expressions in the form of cauldrons and fumaroles along the caldera rim. Being largely below the instrument noise at channels outside the caldera, the ice sheet resonance acts as a magnifying glass that increases tremor amplitudes to an observable level, thereby providing a new and unconventional form of seismic volcano monitoring.
Dry drier drought – Understanding drought in a changing society and climate
Authors: Wanders Niko
Published: March 2022

Droughts have major economic, social and environmental impacts around the world, and they are expected to increase in severity and magnitude because of changes in climate and its variability. In recent years we have seen incredible developments in the field of drought research and we have significantly improved our understanding of this complex phenomenon. While observations have become more abundant, we have also seen significant improvements in hydrological models that are better constrained by these observations. These model improvements also include the addition of new, relevant processes, needed to fully understand drought feedbacks.

In this talk I will discuss my experience with modeling drought at larger scales and including human-water interactions at these scales. These models are also used to study the impact of climate change on drought and show the impact of rising temperatures on society’s exposure to these impactful events. Spatial resolutions of hydrological models have improved significantly and the complexity of processes that we are able to simulate has increased, leading to exciting new insights. At the same time, we have to communicate these findings with not only the scientific community, but also the general public. This brings new challenges for scientists and affects our science.

I’ll highlight recent advances in the field of drought research and hydrological modelling, as well as frontiers and interesting developments in the field. I’ll mention some key challenges that we still have to face to better understand the impact and feedbacks of extreme hydroclimatic events.
The role of root physiological and structural plasticity for carbon allocation in plant-soil systems
Authors: Colombi Tino , Chakrawal Arjun
Published: March 2022

Plant roots are essential for acquiring water and nutrients from soils and constitute a major input source for soil organic matter. Plants invest a significant proportion of the photosynthetically fixed carbon into the growth and maintenance of their root system. The carbon supplied from the shoot fuels both anabolic (i.e., biosynthesis including root growth) and catabolic (i.e., respiration and fermentation) processes in roots. The partitioning of carbon between anabolic and catabolic processes can be expressed as the carbon use efficiency of roots. Root carbon use efficiency determines how much of the total carbon allocated to roots remains in the plant-soil system in the form of root biomass and how much carbon is lost via catabolic pathways. Hence, the carbon use efficiency of roots plays a pivotal yet underexplored role for root growth and associated ecosystem functions such as primary production and carbon sequestration. Here, we present a conceptual framework to assess carbon allocation patterns in plant-soil systems that explicitly accounts for the interactions among root physiology, root trait plasticity, whole plant growth, and soil conditions. Using our framework, we illustrate how soil conditions such as soil aeration, soil moisture, and soil strength interfere with root carbon use efficiency and carbon allocation patterns between different plant organs. We show how edaphic stress and the resulting decrease in root carbon use efficiency may limit root growth, thereby reducing whole plant productivity and inputs of organic matter to soil. Moreover, we provide theoretical and experimental evidence that the plasticity of root structural traits such as cortical cell size and cortical cell number enables plants to maintain their growth upon decreased carbon use efficiency of roots. This suggests that root trait plasticity is a key mechanism that allows plants to adjust to edaphic stress and heterogenous soil environemnts. We, therefore, propose that the framework presented here may provide new insights into the complex interactions between root physiology, soil (micro-)environments, and associated soil functions.
Metasomatism between serpentinite and pelitic schist in the Yuli belt, eastern Taiwan: fluid-rock interactions during subduction metamorphism
Authors: Dewangga Dominikus Deka , Tsai Chin-Ho , Lee Hao-Yang , Iizuka Yoshiyuki , Lo Wen-Han , Lee Chi-Yu
Published: March 2022

Metasomatic rocks in orogenic mélanges bear critical information about fluid-rock interactions and element mobilities during subduction processes. The Yuli belt contains a few mélange units that crop out high-pressure blocks of metaigneous rocks and serpentinites enclosed in metasedimentary rocks. Metasomatic rocks are found along contacts between the serpentinites and metasedimentary rocks. However, the protolith and formation of those metasomatic rocks are largely unknown. Meter-scale metasomatic zones occur at the contact between pelitic schists (PS) and serpentinites (SP) in the Tsunkuanshan area. Five zones from PS to SP are newly identified: (I) chlorite-albite schist, (II) amphibole-albite rock, (III) albite-chlorite schist, (IV) epidote-chlorite schist, and (V) chlorite-talc schist. Minor garnet and amphibole (glaucophane core - barroisite mantle - actinolite rim) are present in the zone I and II, respectively. Field and petrographic observations combined with whole-rock major elements data suggest that this rock association likely was formed by chemical exchanges between the SP and PS. However, the zone II shows enrichment of Si, Na, and Ca, but Al depletion relative to the other metasomatic rocks. This anomaly might be due to infiltration of external fluids. Rare earth element patterns of the PS, zone I, II, III, and IV are similar, indicating a similar protolith origin. Hence, the original boundary between the PS and SP is likely between the zone IV and V. We estimate the chemical mass balance from the PS to the metasomatic rocks (zone I, II, III, and IV) using the sparse isocon method (Kuwatani et al., 2020). The result shows that the chemical components in zone I, III, and IV are gained relative to the PS, whereas those in zone II are of loss. We interpret that the zone I, III, IV, and V were produced by diffusive exchanges of components between the PS and SP, whereas formation of the zone II was likely created by Na-Ca rich fluid infiltrations. The newly-found occurrence of glaucophane within the zone II indicates fluid-rock interactions during subduction metamorphism.

Keywords: Chemical mass balance, sparse isocon method, Na-Ca rich fluids, Yuli belt.