bluuebunny/crossref_metadata_2025 huggingface dataset:
Closing the water budget at the global scale using observations, remote sensing, and reanalyses
Authors: Lehmann Fanny , Vishwakarma Brahma Dutt , Bamber Jonathan
Published: March 2021

Despite the accuracy of GRACE terrestrial water storage estimates and the variety of global hydrological datasets providing precipitations, evapotranspiration, and runoff data, it remains challenging to find datasets satisfying the water budget equation at the global scale.

We select commonly used and widely-assessed datasets. We use several precipitations (CPC, CRU, GPCC, GPCP, GPM, MSWEP, TRMM, ERA5 Land, MERRA2), evapotranspiration (land surface models CLSM, Noah, VIC from GLDAS 2.0, 2.1, and 2.2; GLEAM, MOD16, SSEBop, ERA5 Land, MERRA2), and runoff (land surface models CLSM, Noah, VIC from GLDAS 2.0, 2.1, and 2.2; GRUN, ERA5 Land, MERRA2) datasets to assess the water storage change over more than 150 hydrological basins. Both mascons and spherical harmonics coefficients are used as the reference terrestrial water storage from different centres processing GRACE data. The analysis covers a wide range of climate zones over the globe and is conducted over 2003-2014.

The water budget closure is evaluated with Root Mean Square Deviation (RMSD), Nash-Sutcliffe Efficiency (NSE), and seasonal decomposition. Each dataset is assessed individually across all basins and dataset combinations are also ranked according to their performances. We obtain a total of 1080 combinations, among which several are suitable to close the water budget. Although none of the combinations performs consistently well over all basins, GPCP precipitations provide generally good results, together with GPCC and GPM. A better water budget closure is generally obtained when using evapotranspiration from Catchment Land Surface Models (GLDAS CLSM), while reanalyses ERA5 Land and MERRA2 are especially suitable in cold regions. Concerning runoff, the machine learning GRUN dataset performs remarkably well across climate zones, followed by ERA5 Land and MERRA2 in cold regions. We also highlight highly unrealistic values in evapotranspiration computed with version 2.2 of GLDAS (using data assimilation from GRACE) in most of the cold basins. Our results are robust as changing the GRACE product from one centre to the other does not affect our conclusions.
Estimation of the Exchangeable Sodium Percentage from the Sodium Adsorption Ratio for salt-affected soils in Bolivia
Authors: Andrade Foronda Demis
Published: March 2021

In order to obtain a more cost-time efficient way to determine the sodicity of salt-affected soils, this study aims to generate a regression model to predict the Exchangeable Sodium Percentage (ESP) from the Sodium Adsorption Ratio (SARe). Based on a database with 84 soil samples from the High Valley of Cochabamba (Bolivia), two linear models were generated: ESP= 0.9725 SAR + 1.5766 (R2=0.85, RSE=4.47) and ESP= 0.9197 SAR + 0.3813 (R2=0.71, RSE=0.91) with square root transformation. Subsequently, through a set of 18 testing samples and a T-test of paired samples between the predicted ESP and measured ESP values, the efficiency of the generated models was verified with a value of p= 0.063 and 0.209, respectively, in contrast to p= 0.285 from the US Salinity Lab referential model. To improve the performance of the generated models, could be necessary a stratification according to soil sodicity levels and additional samples for the calibration dataset.
Impact of climate change on water availability in Tropical Andean catchments: a case study in the Vilcanota catchment, Peru
Authors: Meier Selina , Munoz Randy , Huggel Christian
Published: March 2021

Water scarcity is increasingly becoming a problem in many regions of the world. On the one hand, this can be attributed to changes in precipitation conditions due to climate change. On the other hand, this is also due to population growth and changes in consumer behaviour. In this study, an analysis is carried out for the highly glaciated Vilcanota River catchment (9808 km2 – 1.2% glacier area) in the Cusco region (Peru). Possible climatic and socioeconomic scenarios up to 2050 were developed including the interests from different water sectors, i.e. agriculture, domestic and energy.

The analysis consists of the hydrological simulation at a monthly time step from September 2043 to August 2050 using a simple glacio-hydrological model. For historic conditions (1990 to 2006) a combination of gridded data (PISCO precipitation) and weather stations was used. Future scenario simulations were based on three different climate models for both RCP 2.6 and 8.5. Different glacier outlines were used to simulate changes in glacier surface through the time for both historic (from satellite data) and future (from existing literature) scenarios. Furthermore, future water demand simulations were based on the SSP1 and SSP3 scenarios.

Results from all scenarios suggest an average monthly runoff of about 130 m3/s for the Vilcanota catchment between 2043 and 2050. This represents a change of about +5% compared to the historical monthly runoff of about 123 m3/s. The reason for the increase in runoff is related to the precipitation data from the selected climate models. However, an average monthly deficit of up to 50 m3/s was estimated between April and November with a peak in September. The seasonal deficit is related to the seasonal change in precipitation, while the water demand seems to have a less important influence.

Due to the great uncertainty of the modelling and changes in the socioeconomic situation, the data should be continuously updated. In order to construct a locally sustainable water management system, the modelling needs to be further downscaled to the different subcatchments in the Vilcanota catchment. To address the projected water deficit, a new dam could partially compensate for the decreasing storage capacity of the melting glaciers. However, the construction of the dam could meet resistance from the local population if they cannot be promised and communicated multiple uses of the new dam. Sustainable water management requires the cooperation of all stakeholders and all stakeholders should be able to benefit from it so that they will support future projects.
Comparison of stationary and non-stationary frequency models for assessing design discharges in variable climate: north-west England case study
Authors: Hesarkazzazi Sina , Arabzadeh Rezgar , Hajibabaei Mohsen , Rauch Wolfgang , R. Kjeldsen Thomas , Prosdocimi Ilaria , Castellarin Attilio , Sitzenfrei Robert
Published: March 2021

Successive occurrence of floods across north-west England over the course of the past few years has resulted in the need for the local authorities and decision makers to (re-) assess several flood management schemes. However, ongoing decision-making on how flood control measures are constructed, is frequently still made on the basis of the assumption that the flood characteristics of catchments have remained constant over time (i.e., stationarity). To verify the validity of this assumptions, non-parametric tests alongside change-permitting flood frequency frameworks based on Generalized Logistic distribution model (as the recommended model in the UK catchments) have been applied to a dataset of extreme peak river flow measurements across the region (39 catchments with up to 75 years of records). Allowing the location parameter of the model to change linearly with time, cumulative annual rainfall and cumulative annual temperature as covariates, one stationary as well as six non-stationary models have been introduced. The regional non-stationary frequency results indicate a notable improvement over the stationary predictions, estimating design flood quantiles (i.e., 100-year events) up to 75% larger than classic stationary estimates. Moreover, the vast majority of rivers demonstrate statistically significant changes (mainly driven by cumulative annual rainfall), specifically in the late 1990s. This indicates that non-stationary models should be taken into consideration, along with the traditional stationary ones to help understanding the changes in the peak river flow regimes across the north-west England.
Characterization of the engineering geological units with the shear wave velocity parameter: statistical analysis of data from the Italian seismic microzonation studies
Authors: Romagnoli Gino , Carbone Gianluca , Catalano Stefano , Cesarano Massimo , Fabozzi Stefania , Falcone Gaetano , Moscatelli Massimiliano , Naso Giuseppe , Peronace Edoardo , Porchia Attilio , Tarquini Emanuele , Albarello Dario
Published: March 2021

The availability of a unique database, where all data of the seismic microzonation studies carried out in about 1900 municipalities of Italy (https://www.webms.it/) are achieved with a standardized format, allowed statistical elaborations in terms of subsoil parameters. In particular, we analysed borehole logs and geophysical data in order to characterize them with the shear wave velocity (Vs) vertical profile, and the code of standardized engineering geological units, according to the Italian Guidelines for Seismic Microzonation (Seismic Microzonation Working Group, 2015; 2018). The Vs parameter, extracted from about 3700 geophysical surveys, was correlated to the engineering geological units from the borehole logs, with 1meter step. The correlation was performed for about 1700 available Down-Hole (DH) surveys and for about 2000 Multichannel Analyses of Surface Waves (MASW). For these latter, we selected only MASW surveys located near boreholes, no more than 100 m away. The statistical analysis on the distribution and dispersion of Vs parameter allowed to calculate the Vs values related to the mode, mean, median, standard deviation, first quartile, third quartile, minimum and maximum, and the trend with depth of Vs for each engineering geological unit. Validation with external datasets (e.g. Italian Vs30 map, Mori et al., 2020) demonstrates that the characterization of engineering geological units in term of Vs, based on velocity profiles extracted by the Italian seismic microzonation dataset, allow to reliably characterize the engineering geological model, where no geophysical data are available. Statistics of subsoil parameters will represent a fundamental tool for computing local seismic ground motion parameters (e.g. PGA, HSM) in the areas not covered by seismic microzonation studies.

References

- Mori, F., Mendicelli, A., Moscatelli, M., Romagnoli, 796 G., Peronace, E., Naso, G., 2020. A new Vs30 map for Italy based on the seismic microzonation dataset. Engineering Geology 275, 105745. https://doi.org/10.1016/j.enggeo.2020.105745.

- Seismic Microzonation Working Group, 2015. Guidelines for Seismic Microzonation http://www.protezionecivile.gov.it/httpdocs/cms/attach_extra/GuidelinesForSeismicMicrozonation.pdf

- Seismic Microzonation Working Group, 2018. Standard di rappresentazione e archiviazione informatica Versione 4.1. http://www.protezionecivile.gov.it/attivita-rischi/rischio-sismico/attivita/commissione-supporto-monitoraggio-studi-microzonazione/standard-rappresentazione-archiviazione-informatica
Can biochar restore soil quality in a degraded forest and vineyard soil in a one-year percolation lysimeters study, in Portugal?
Authors: Isaka Suyan , Hendrychová Markéta , Campos Isabel , Bastos Ana Catarina , Gonzales Pelayo Oscar , Caetano Ana , Abrantes Nelson , Martins Martinho , Jongen Marjan , Ferreira Carla , Verheijen Frank
Published: March 2021

The use of biochar has increased worldwide in the last years due to its good results for several soil quality indicators. However, restoration potential depends on the type and amount of biochar for each specific soil and land use. In order to investigate this restoration potential differential, we conducted an experiment where we amended two contrasting degraded soils with the same biochar. We installed a controlled and fully randomized percolation lysimeter experiment (3 replicates) with 15 lysimeters on a moderately steep slope angle, monitored for one year. Two types of soil were collected, a low organic matter, hydrophilic vineyard soil and a high organic matter, hydrophobic forest soil. Biochar was applied at 4% for both soils, and an additional treatment at 2% for the forest soil only. Selected soil quality indicators are: soil organic matter, medium weight diameter, aggregate stability, bulk density, pH, electric conductivity, potassium (K), phosphorus (P), soil water repellency, biomass quality. The present study comprises four data collections in different seasons along the year, enabling to compare the development of the biochar effects on different types of soil and its short- and medium-term behaviour.
Challenges in constructing a source function for high-temperature marine INPs
Authors: Steinke Isabelle , DeMott Paul , Deane Grant , Hill Tom , Maltrud Matthew , Raman Aishwarya , Burrows Susannah M.
Published: March 2021

Sea spray emissions are an important source for ice nucleating particles (INPs) over remote ocean regions. Over the past years, our understanding of marine organic surfactants acting as INPs has advanced a lot. However, there are still significant knowledge gaps regarding the role of larger marine biogenic particles (e.g. polymers, diatom fragments, protists and bacteria) which are potentially the drivers of episodically observed high INP concentrations.
In this study, we use a combination of ARM (Atmospheric Radiation Measurement) observations and output from E3SM (Energy Exascale Earth System Model) simulation runs to investigate the impact of larger marine biogenic particles acting as INPs. We use heterotrophic bacteria and nanogels (polymeric particles) as two hypothesized classes of marine INPs which can get transported across the sea-air interface. Based on the offline-calculated concentrations of these ice nucleating entities in the ocean surface layer, we conduct sensitivity studies to estimate INP concentration ranges, relying on current knowledge of enrichment factors and ice nucleation activities (e.g., ns values from McCluskey et al. (2018)). In comparison to observations of episodic high INP concentrations, our estimated concentrations are consistently lower. However, one of the main conclusions of our study is that large uncertainties regarding the links between ocean biology, organic matter in sea spray and ice nucleation properties, remain. Therefore, comprehensive observational datasets, including sea spray size distributions, aerosol and INP compositions, and ice nucleation efficiencies of individual marine species, are needed. 
Effects of Glacial Isostatic Adjustment on Surface Topography, Flow Accumulation,  Stream Power & Sediment Transport Indexes in the Canadian Prairies
Authors: Wu Patrick , Li Tanghua , Steffen Holger
Published: March 2021

Glacial Isostatic Adjustment (GIA) induced by the melting of the Pleistocene Ice Sheets causes differential land uplift, relative sea level and geoid changes. Thus, GIA in North America may affect water flow-accumulation and the rate of sedimentation and erosion in the South Saskatchewan River Basin (SSRB), but so far this has not been well investigated.

 

Our aim here is to use surface topography in the SSRB and simple models of surface water flow to compute flow-accumulation, wetness index, stream power index and sediment transport index - the latter two affect the rates of erosion and sedimentation. Since the river basin became virtually ice-free around 8 ka BP, we shall study the effects of GIA induced differential land uplift during the last 8 ka on these indexes.

 

Using the present-day surface topography ETOPO1 model, we see that the stream power index and sediment transport index in the SSRB may not be high enough to alter the surface topography significantly today and probably during the last 8 ka except for places around the Rocky Mountains. The effect of using 1 and 3 arc minute grid resolution of the ETOPO1 model does not significantly alter the value of these indexes. However, we note that using 1 arc minute grid is much more computationally intensive, so only a smaller area of the SSRB can be included in the computation.

 

Next, we assume that sedimentation and erosion did not occur in the SSRB during the last 8 ka BP, and the change in surface topography is only due to GIA induced differential uplift. We use land uplift predicted by a large number of GIA models to study the changes in stream power & sediment transport indexes in the last 8 ka BP. Our base GIA model is ICE6G_C(VM5a). Then we investigate the effects of using uplift predicted by other GIA models that can still fit the observed relative sea level (RSL), uplift rate and gravity-rate-of-change data in North America reasonably well. These alternate GIA models have lateral heterogeneity in the mantle and lithosphere included – in particular we test those that give the largest differential uplift in the SSRB. We found that the effect of these other GIA earth models is not large on the stream power & sediment transport indexes. Finally, we investigate the sensitivity of these indexes on the ice models that are consistent with GIA observations. The results of this study will be useful to our understanding of water flow accumulation, sedimentation and erosion in the past, present and future and for water resource management in North America.
Development of a numerical model for predicting the volatilization flux from unsaturated soil
Authors: Kondo Monami , Sakamoto Yasuhide , Komai Takeshi , Kawabe Yoshishige , Nakamura Kengo , Watanabe Noriaki
Published: March 2021

In recent years, exposure to volatile chemical substances (VCSs) from contaminated soil has become a serious problem so it has become increasingly important to study the transport phenomena of VCSs. In this study we focused on the transport phenomena of VCSs at the boundary layer between the soil surface and the atmosphere, and defined it as volatilization flux, which express the amount of volatilized substances per unit volume per unit time. In order to estimate the phenomena of mercury transport in unsaturated soil and mercury released from soil to the atmosphere, it is necessary to consider in detail the spatiotemporal fluctuations of factors that affect the volatilization of mercury and the physical transport phenomena in soil.

The present study developed a model for predicting the volatilization flux from the unsaturated soil contaminated by VCSs. The model considers a series of phenomena under the unsaturated condition such as gas-liquid two-phase flow consisting of convection and diffusion. The effects of various transport phenomena on the surface soil on changes in the magnitude of this flux due to variations in meteorological factors such as temperature and soil moisture content were quantitatively evaluated. This developed prediction model can be utilized to estimate dynamic variations in the flux under real-environmental conditions.
Land use and cover changes related to green and blue infrastructure planning for water resources management based on a Budyko framework
Authors: Fan Ping Yu , Chun Kwok Pan , Mijic Ana , Tan Mou Leong , Yetemen Omer , Evaristo Jaivime
Published: March 2021

Based on the interplays between land use and water resources, the green and blue infrastructure (GBI) is a central landscape approach for hydrological environment management. However, evidence-based principles of regional GBI planning are not well developed. The Budyko framework is widely used to explore water balance in land-use change studies. It provides a method to relate land use changes and streamflow variations based on two indices – the evaporative index (EI) and the dryness index (DI). Using the Dongjiang River Basin (DJ) as an example, we use the Geographically Weighted Principal Components Analysis (GWPCA) with adaptive kernels to classify the dominant land types based on local spatial variances. Then, we apply the Emerging Hot Spots Analysis (EHSA) to identify spatial-temporal hotspots of EI and DI for the Budyko analysis. From the EHSA, two wet years (1998 and 2016) and three dry years (2004, 2009, and 2018) are focused to investigate how land uses are related to water resources in different climatic conditions. On both catchment and hotspot scales, movements within the Budyko space are observed. These movements illustrate the associations between land use and hydrological response. These data-driven relationships can be used to explain the underlying mechanism of catchment forms (land surface property) and functions (evapotranspiration and runoff) for setting best practices for land use planning. Specifically, our results show that planners should consider to 1) reduce the area of croplands and trees, while increase the extent of grassland and water body on a catchment scale; and 2) increase rain fed croplands, broadleaved evergreen trees, and grasslands in the upstream catchment. Overall, this study highlights the scale considerations in land use planning, and land use strategies are developed based on reanalysis data and remote sensing products for catchment water resources management.
Unsteady vortex behavior in the Asian monsoon anticyclone
Authors: Siu Leong Wai , Bowman Kenneth
Published: March 2021

The Asian monsoon anticyclone (AMA), which is primarily driven by the latent heat released by monsoon precipitation, is one of the dominant features of the Northern Hemisphere summer circulation in the upper troposphere and lower stratosphere. Due to variations in the diabatic heating, interactions with Rossby waves propagating along the subtropical jet, and internal dynamics within the anticyclone, the circulation of the AMA is unsteady. Here we use the ERA-Interim dataset and trajectories computed with ERA-Interim winds to show that the AMA contains two or three distinct synoptic-scale subvortices 69% of the time, while a single circulation center is present only 23% of the time. More than three simultaneous subvortices are uncommon. Observed behaviors of the subvortices include 1) splitting of a single vortex into two vortices; 2) merger of two vortices into a single vortex; 3) vortex shedding in the eastward direction; 4) vortex shedding in the westward direction; and 5) formation, movement, and dissipation of a vortex. The evolution of the subvortices is closely tied to stirring and transport.
Enhanced heavy oil recovery and CO2 storage in a reservoir with high-water-cut: laboratory to field
Authors: Zhou Xiang , Tan Yongsheng , Jiang Qi
Published: March 2021

In this study, in order to enhance heavy oil recovery in the heavy oil reservoir with a high-water-cut after water flooding process, experimental and numerical simulation studies are conducted. In the experimental studies, firstly, the properties of the heavy oil-CO2 system were measured under different saturation pressures at the reservoir temperature. Secondly, to mimic the high-water-cut condition in the real reservoir, water flooding process was conducted for each core; then four long core experiments insist of one CO2 huff `n` puff process and three CO2 flooding processes were implemented. The CO2 huff `n` puff process is conducted to compare the production performance with that in the CO2 flooding process to optimize the method. Regarding the CO2 flooding process, different gas (pure CO2, flue gas) and different production categories (constant production pressure, pressure depletion) were applied to study the heavy oil production performance in the heavy oil reservoir with high-water-cut. The experimental results indicate that, the CO2 flooding coupling with pressure depletion process is the best choice to reduce the water-cut and enhance the heavy oil recovery, which is 41.84% of the original oil in place and the water-cut reduced to lower than 70%. In the numerical simulation studies, the WinProp module in CMG is applied to simulate the properties of the heavy oil-CO2 system, which is generated by recombining CO2 into heavy oil, and high agreement simulation results were obtained. Then the results of the optimized experiment were history matched using GEM module. Finally, the upscaling studied was conducted. The CO2 flooding processes are carried out in the studied reservoir to maximum the heavy oil recovery factor. Moreover, the CO2 storage ratio is studied using GEM model.
Probabilistic Geomagnetic Storm Forecasting via Deep Learning
Authors: Tasistro-Hart Adrian , Grayver Alexander , Kuvshinov Alexey
Published: March 2021

By causing time variation in Earth's external magnetic field, geomagnetic storms can induce damaging currents in ground-based conducting infrastructure, such as power and communication lines.  The physical link between solar activity and Earth's magnetosphere, while complicated, provides the basis for attempts to forecast geomagnetic storms. Fortunately, we have abundant observational data of both the solar disk and solar wind, which are ameable to the application of data-hungry neural networks to the forecasting problem. To date, almost all neural networks trained for geomagnetic storm forecasting have utilized solar wind observations from the Earth-Sun first Lagrangian point (L1) or closer and have generated deterministic output without uncertainty estimates. Furthermore, existing models generate forecasts for indices that are also sensitive to induced internal magnetic fields, complicating the forecasting problem with another layer of non-linearity. In this work, we present neural networks trained on observations from both the solar disk and the L1 point. Our architecture generates reliable probabilistic forecasts over Est, the external component of the disturbance storm time index, showing that neural networks can learn measures of confidence in their output. 
Automatic Recognition of Power Line Harmonic Radiation Observed by the EFD On board the ZH-1 Satellite
Authors: Han ying , Yuan jing , Wang qiao , Yang dehe , Sun xuhui
Published: March 2021

The power line harmonic generated by human activities can be found from the vast amount of the data observed by EFD on board the ZH-1 satellite. To study the human activities and remove the nonnegligible amount of interferences in the study of ionospheric precursors of earthquakes, we are desperate for finding the power line harmonic from the vast amount of data Hence, a novel automatic power line recognition method is proposed. Firstly, we utilize fourier transform on EFD data to obtain the power spectral density(PSD). Secondly, it is well known that harmonic radiation from power lines presents one or more horizontal linear characteristics on the PSD image and the color of the line is close to the color of the background in the image.In order to highlight the color contrast between the line and the background, we transform the PSD image from the RGB to the HSV color space and utilize the Saturation compoment of the HSV space as the object image.To obtain the edge regions, we process the object image with canny techniques. Finally, we use the Hough transform to detect the power line from the edge regions. To evaluate the proposed method, the experiment is performed for the dataset composed of 100 PSD images and each PSD image includes several interference lines. And the experimental result verifies the effectiveness of the proposed method with an accuracy of 86%.
Preliminary research on a method of outcrops extraction on Karst Gabin ecosystem based on digital image processing: the case of the Mengzi Gabin basin
Authors: Yin Zhe , Shan Zhijie
Published: March 2021

Rock outcrops are common features of the karst ecosystem The bare rock rate is an important indicator for rocky desertification grades classification, and its accurate extraction can benefit for understanding the distribution characteristics of rock outcrops in desertification areas and the classification of rocky desertification grades. In order to explore the distribution pattern of surface bare rocks in the typical geomorphic environment of the Karst gabin basin, the Mengzi gabin basin was carried out as the research site. The combination of UAV shooting images and digital image processing technology were used, the characteristics of bare rock rate on the karst fault basin after vegetation restoration were shaped. Our results showed that digital image processing technology can be used for extraction of bare rock rate in Karst area, and the effective combination of UAV technology and digital image processing technology can quickly obtain bare rock rate data of typical landform in Karst gabin basins. After performing drone aerial photography on 26 typical landform information under different bare rock distribution conditions on the Mengzi gabin basin, the results of the image processing analysis showed that the bare rock rate is between 2.7%-28.9%. The research provide technical support for the assessment of the karst ecosystem degradation and the evaluation of the current status of rocky desertification in karst gabin basin
A simulation of the influence of DE3 tide on nitric oxide infrared cooling
Authors: Ren Zhipeng , Wan Weixing , Xiong Jiangang , Li Xing
Published: March 2021

Using GCITEM-IGGCAS model, we simulate the influence of the eastward propagating non-migrating diurnal tide with zonal wavenumber-3 (DE3) on nitric oxide (NO) infrared cooling rate. We find that the DE3 tide can drive a DE3 signal in lower thermospheric NO cooling rate, and the simulated altitudinal and seasonal variations are according with that of DE3 signal in equatorial lower thermospheric NO cooling rate observed by Oberheide et al. [2013], which is based on the TIMED/SABER observations during the solar minimum year 2008. This signal mainly shows an annual variation, which is stronger between June and September, and weaker near November. The maximum of the absolute signal, whose value is about 0.35*10-9 W/m3, occurs near the height of 130 km, but the relative signal mainly shows its peak with a value of 40% near the height of 100 km. Due to the difference of the driving mechanism, the distribution of NO signals in different latitudinal regions shows obvious difference. The middle- and low-latitude NO signal show smooth variation, while the high-latitude signal is discontinuous. The DE3 signal in NO cooling rate is mainly controlled by DE3 temperature tide and DE3 NO tide, meanwhile, the influences of DE3 neutral density tide on the DE3 signal can be ignored. The relative contributions of the DE3 NO tide and of the DE3 temperature tide vary with geographic latitude. The DE3 cooling rates in middle- and low- latitude and in high-latitude are respectively mainly driven by the DE3 temperature tide DE3 NO tide. DE3 tide may not only drive the DE3 signal, but also affect the lower thermospheric zonal mean NO cooling rate. The maximum of the absolute influence, whose value is about 0.12*10-9 W/m3, occurs above the height of 140 km, but the relative influence mainly shows its peak with a value of 10% near the height of 100 km.
An analysis of urban heat island impact toward increasing of afternoon thunderstorm frequency in Taipei, Taiwan
Authors: Rachma Siti Talitha , Lin Yuan-Chien
Published: March 2021

Each year, average of Earth’s temperature rises and the urbanized cities, are warming at a significant rate than the surrounding rural areas. This phenomenon is called Urban Heat Island (UHI). UHI is a consequence of human activities in urban area and it has possibilities to impact weather and climate on regional or global scale. Precipitation is one of the basic hydro-meteorological phenomena that could be affected by UHI trend with thunderstorm as a part of precipitation. As the UHI level rises from year to year, the pattern of precipitation could change. However, this issue is still underdeveloped, thus, this work tries to comprehensively understand the hydrological response to UHI.

 

This research selects Taipei city as the study area and explores the connection between UHI and precipitation pattern’s change. The data used here are hourly temperature and precipitation data collected from 21 Taipei weather stations collected from Central Weather Bureau (CWB) Taiwan. In order to reveal specific details and trend of non-linear relation from both time domain and frequency, Hilbert-Huang Transform (HHT) is adopted in this study. The HHT results are compared between each station. Later, empirical orthogonal function (EOF) also being used to extract main spatial pattern of precipitation in Taipei city.

 

The results show that the urbanization in Taipei city contribute to increasing trend of 0.5 – 1 oC in daily UHI and also increase of 27% in the afternoon thunderstorm frequency for this past 20 years. The increase of thunderstorm would result into a bigger rain water flow to the river and a fewer time for it to percolate to the ground. If there are more thunderstorms in the future, it is possible the phenomenon could lead to the lack of groundwater discharge and depletion of groundwater reserve. This result could be utilized in the future to understand more about UHI mitigation and thunderstorm in Taipei.

 

Keywords: urban heat island, thunderstorm, Hilbert-Huang Transform, empirical orthogonal function
Convolutional Neural Networks for Classification of Sea Ice Types in Sentinel-1 SAR Data
Authors: Korosov Anton , Boulze Hugo , Brajard Julien
Published: March 2021

A new algorithm for classification of sea ice types on Sentinel-1 Synthetic Aperture Radar (SAR) data using a convolutional neural network (CNN) is presented.  The CNN is trained on reference ice charts produced by human experts and compared with an existing machine learning algorithm based on texture features and random forest classifier. The CNN is trained on a dataset from winter 2020 for retrieval of four classes: ice free, young ice, first-year ice and old ice. The accuracy of our classification is 91.6%. The error is a bit higher for young ice (76%) and first-year ice (84%). Our algorithm outperforms the existing random forest product for each ice type. It has also proved to be more efficient in computing time and less sensitive to the noise in SAR data.

 

Our study demonstrates that CNN can be successfully applied for classification of sea ice types in SAR data. The algorithm is applied in small sub-images extracted from a SAR image after preprocessing including thermal noise removal. Validation shows that the errors are mostly attributed to coarse resolution of ice charts or misclassification of training data by human experts.

 

Several sensitivity experiments were conducted for testing the impact of CNN architecture, hyperparameters, training parameters and data preprocessing on accuracy. It was shown that a CNN with three convolutional layers, two max-pool layers and three hidden dense layers can be applied to a sub-image with size 50 x 50 pixels for achieving the best results. It was also shown that a CNN can be applied to SAR data without thermal noise removal on the preprocessing step. Understandably, the classification accuracy decreases to 89% but remains reasonable.

 

The main advantages of the new algorithm are the ability to classify several ice types, higher classification accuracy for each ice type and higher speed of processing than in the previous studies. The relative simplicity of the algorithm (both texture analysis and classification are performed by CNN) is also a benefit. In addition to providing ice type labels, the algorithm also derives the probability of belonging to a class. Uncertainty of the method can be derived from these probabilities and used in the assimilation of ice type in numerical models. 

Given the high accuracy and processing speed, the CNN-based algorithm is included in the Copernicus Marine Environment Monitoring Service (CMEMS) for operational sea ice type retrieval for generating ice charts in the Arctic Ocean. It is already released as an open source software and available on Github: https://github.com/nansencenter/s1_icetype_cnn.
Accounting for soil structure in pedo-transfer functions: swelling vs non swelling clays
Authors: Tafasca Salma , Ducharne Agnès , Valentin Christian
Published: March 2021

Tropical clay Oxisols have a strong granular structure, as opposed to other clay-textured soils, such as Vertisols. Their highly aggregated structure favors infiltration and drainage, while Vertisols favor runoff, due to their high content of swelling clays. Most global scale pedotransfer functions (PTFs) are derived from soils of temperate regions where Oxisols are absent, which does not allow to represent this type of tropical soils.

In ORCHIDEE, which is a state-of-the-art land surface model (LSM), soil hydraulic properties are derived from a soil texture map, using PTFs of temperate regions (Carsel and Parrish, 1988), which does not allow to represent tropical clay Oxisols. This has been shown to induce large negative evapotranspiration biases in areas effectively covered by clay Oxisols, and mapped as clay (Tafasca et al., 2020). In order to distinguish the two types of clays of different behavior, we introduce a new soil class to represent clay Oxisols. This is equivalent to splitting the clay soil texture in two sub-classes: clay Oxisols and swelling clay. First, we modify the Reynolds soil texture map (Reynolds et al., 2000) such as to represent clay Oxisols based on the FAO Soil Order Map of the World. Then we obtain the corresponding Van Genuchten parameters based on previous studies from the litterature. We evaluate the new PTFs and the modified soil texture map using the ORCHIDEE LSM.

Using the new soil texture mapping increases evapotranspiration by 11%, allowing to correct important negative bias in tropical areas. In these zones, the mean annual river discharge decreases, consistently with the observations.

 
Comparing different block propagation modelling approaches using the Platrock simulation platform 
Authors: Acary Vincent , Bourrier Franck , Toe David , Kneib Francois
Published: March 2021

Block propagation models are routinely used for the quantitative assessment of rockfall hazard. In these models, one of the major diﬃculties is the development of physically consistent and ﬁeld applicable approaches to model the interaction between the block and the natural terrain. For most of propagation models, a thorough calibration of the input parameters is not available over the wide range of configurations encountered in practice. Consequently, the parameters choice is strongly depending on expert knowledge. In addition, most of models exhibit substantial sensitivity to some parameters, i.e. small changes of these parameters entail large differences in the simulation results.

The trajectory analysis platform Platrock, freely available upon request (contact: franck.bourrier@inrae.fr), allows performing 2D and 3D simulations using both material point rebound models and models, based on non-smooth mechanics, that explicitly account for block shape. This platform provides several simulation tools for detailed analyses of block propagation on study sites.

The possibilities of the predictive capabilities of different block propagation modelling approaches integrated into the Platrock platform have been assessed on a well-documented study site, where a benchmark of propagation models has been done in the context of C2ROP research project. This analysis emphasized the capacities of trajectory analyses to traduce block propagation but also demonstrated their substantial sensitivity to model parameters. The results from these simulations cannot be relevantly interpreted if they are not accompanied with calibration proofs, sensitivity analysis, and detailed interpretation of the results from the expert in charge of the study.
On the use of complex rays to analyse the sonic boom of the Carancas meteorite at I08BO station located into shadow zone
Authors: Zelias Annie , Gainville Olaf , Coulouvrat François
Published: March 2021

The International Monitoring System (IMS) network of the Comprehensive nuclear-Test-Ban Treaty (CTBT) detects powerful natural and artificial infrasonic sources. One of these sources are meteorites which produce multi-arrival pressure signatures similar to explosion onces. Long range sonic boom modeling allows to distinguish these sources from one another. Our documented case is the Carancas meteorite that impacted the ground in Peru on September 15th, 2007, near the IMS infrasound station I08BO. Since this station is located within the shadow zone, classical ray tracing cannot be used to capture the characteristics of the recorded arrivals. Analytic continuation into complex plane of emission parameters of the ray tracing method allows to analyse the propagation in shadow zone for fully three dimensional problems. Contribution of complex ray ordinary differential equations integration and optimisation algorithm allows to compute complex eigenrays. Simulated infrasound wave arrival times, azimuths and apparent velocities at the station are compared with Carancas records.
A Process-Based Validation of GPM IMERG and Its Sources Using a Mesoscale Rain Gauge Network in the West African Forest Zone
Authors: Maranan Marlon , Fink Andreas H. , Knippertz Peter , Amekudzi Leonard K. , Atiah Winifred A. , Stengel Martin
Published: March 2021

Using a two-year dataset (2016–17) from 17 one-minute rain gauges located in the moist forest region of Ghana, the performance of the Integrated Multisatellite Retrievals for GPM, version 6b (IMERG), is evaluated based on a subdaily time scale, down to the level of the underlying passive microwave (PMW) and infrared (IR) sources. Additionally, the spaceborne cloud product Cloud Property Dataset Using SEVIRI, edition 2 (CLAAS-2), available every 15 minutes, is used to link IMERG rainfall to cloud-top properties. Several important issues are identified: 1) IMERG’s proneness to low-intensity false alarms, accounting for more than a fifth of total rainfall; 2) IMERG’s overestimation of the rainfall amount from frequently occurring weak convective events, while that of relatively rare but strong mesoscale convective systems is underestimated, resulting in an error compensation; and 3) a decrease of skill during the little dry season in July and August, known to feature enhanced low-level cloudiness and warm rain. These findings are related to 1) a general oversensitivity for clouds with low ice and liquid water path and a particular oversensitivity for low cloud optical thickness, a problem which is slightly reduced for direct PMW overpasses; 2) a pronounced negative bias for high rain intensities, strongest when IR data are included; and 3) a large fraction of missed events linked with rainfall out of warm clouds, which are inherently misinterpreted by IMERG and its sources. This paper emphasizes the potential of validating spaceborne rainfall products with high-resolution rain gauges on a subdaily time scale, particularly for the understudied West African region.
Inhomogeneous surface of West Siberian peatland diagnosed by skin temperature distribution
Authors: Repina Irina , Stepanenko Victor , Varentsov Alexander , Artamonov Arseniy , Natalia Kuksova
Published: March 2021

Skin temperature (Ts) plays a central role in shaping the land surface energy balance and is also widely available from remote sensing for model evaluation and data assimilation. Both offline land models and land–atmosphere coupled models still have difficulty in realistically simulating or predicting Ts. In the case of an inhomogeneous surface, under the same atmospheric conditions, there are patches of different skin temperature and different daily variability. This observational study reports variations of surface fluxes (turbulent, radiative, and soil heat) and ancillary atmospheric/surface/soil data based on in-situ measurements conducted at Mukhrino ﬁeld station located in the middle taiga zone of the West Siberian Lowland. To measure the surface temperature, we used an infrared camera (TIR, ~8–14 mkm wavelength range) based on an unmanned aerial vehicle. This UAV-based system provides high-resolution multi-sensors data acquisition. It also provides maximal flexibility for data collection at low cost with minimal atmospheric influence, minimal site disturbance, flexibility in measurement planning, and ease of access to study sites (e.g., peatlands) in contrast with traditional data collection methods. e demonstrate that the temperature of the boggy surface has significant variability: depending on the time of day, temperature contrasts can reach more than 10 degrees, which is associated with different surface moisture and albedo. A technique has been developed for restoring the surface albedo from the data of IR measurements. Ground measurements have shown that the variations of temperature and humidity across the subsurface layer can be very large. Furthermore, these variations are directly related to the concept of a difference between the roughness length for momentum versus that for heat. Information about the ratio of z0/z0h is necessary in order to be able to use surface skin temperature from satellite remote sensing for the computation of surface fluxes. The relationship between the difference in skin temperature and soil contact temperature with the heat balance, especially with sensible heat fluxes and heat flux through the soil, is considered. The parametrizations obtained in this work can be used in Earth System models to represent wetland ecosystems.

The work was supported by RFBR grant 18-05-60126, by the Moscow Center for Fundamental and Applied Mathematics and within the grant of the Tyumen region Government in accordance with the Program of the World-Class West Siberian Interregional Scientific and Educational Center (National Project "Nauka").
Assessment of the influence of aerosol climatology on the forecast of the air temperature.
Authors: Poliukhov Aleksei , Denis Blinov , Natalia Chubarova , Marina Shatunova
Published: March 2021

Our report provides an examination of aerosol climatologies and their impact on the weather forecast accuracy. We used non-hydrostatiс mesoscale COSMO-Ru model with Tanre (Tanre et al., 1984), Tegen (Tegen et al., 1997), MACv2 (Kinne S, 2019) and CAMS (Flemming, et al., 2017) aerosol climatologies for the central months of the season for the territory of Eurasia in 2017. We estimated the forecast accuracy for the surface air temperature, the temperature at 850 hPa and 500 hPa. It is found that the change in the calculation of surface air temperature over land can reach one degree when using Tegen and MACv2 compared to Tanre. Changes don’t exceed 0.4 degrees at altitudes of 850 and 500 hPa. Also, we presented the comparison results for total radiation with measurements on the Meteorological Observatory of Moscow State University and Tiksi (Russia), Eilat (Israel) and Lindenberg (Germany) Observatories. It is shown that when using aerosol climatology, the deviation of calculations from the measurement data does not exceed 25 W/m2 (Poliukhov et al., 2019).

Acknowledgements

The reported study was funded by RFBR, project number 19-35-90129.

References:

Flemming, J., Benedetti, A., Inness, A., Engelen, R. J., Jones, L., Huijnen, V., ... & Peuch, V. H. (2017). The CAMS interim reanalysis of carbon monoxide, ozone and aerosol for 2003–2015, Atmospheric Chemistry and Physics, 17 (3), 1945 - 1983.

Kinne S. (2019), The MACv2 aerosol climatology, Tellus B: Chemical and Physical Meteorology. 71(1), 1-21.

Poliukhov, A. A., Chubarova, N. E., Blinov, D. V., Tarasova, T. A., Makshtas, A. P., & Muskatel, H. (2019). Radiation Effects of Different Types of Aerosol in Eurasia According to Observations and Model Calculations. Russian Meteorology and Hydrology, 44(9), 579-587.

Tanre D., Geleyn J. F., Slingo J. (1984), First results of the introduction of an advanced aerosol-radiation interaction in the ECMWF low-resolution global model, Aerosols and their climatic, 133-177.

Tegen I. et al. (1997), Contribution of different aerosol species to the global aerosol extinction optical thickness: Estimates from model results, Journal of Geophysical Research: Atmospheres. 102(20), 23895-23915.