bluuebunny/crossref_metadata_2025 huggingface dataset:
Multi-fluid single-column modelling of Rayleigh-Bénard convection
Authors: Shipley Daniel , Weller Hilary , Clark Peter , McIntyre William
Published: March 2020

Atmospheric convection remains one of the weakest parts of weather and climate models, especially in the tropics. As model resolutions increase, the assumptions underlying traditional convection parametrisations break down; however, we are still far from fully resolving all convective processes, showing a need for convection parametrisation well into the future.

A multi-fluid framework for parametrising convection has been proposed, based on conditionally filtering the Navier-Stokes equations. This results in a set of equations for multiple fluids, where each fluid has its own dynamic and thermodynamic fields. The approach is fully 3D and time-dependent, allowing for both convective memory and net mass transport due to convection. However, the approach differs from higher-order turbulence closures in that it attempts to capture the important coherent structures of convection via the partitioning into multiple fluids. In addition to the usual sub-filter fluxes, the equations contain terms involving the exchange of momentum, entropy, moisture, and tracers between different fluids. The problem of parametrising convection then becomes the problem of parametrising these exchange terms. This means that within this framework the convection is fundamentally a part of the dynamics: there is no separate “convection scheme" which is called by the dynamical core.

As a first step towards using this framework to parametrise atmospheric convection, we consider a highly simplified model: dry, 2D Rayleigh-Bénard convection in the Boussinesq limit. This model captures the essentials of buoyant convection, with additional symmetry constraints which help with building a parametrisation. In the single-column limit of the single-fluid case, no circulation can exist. This leads to a very poor solution, in particular vastly underestimating the heat transport.

In a two-fluid model, the separate dynamical fields for each fluid mean that a circulation can exist even at the coarsest resolutions. We show that a simple two-fluid single-column model can capture all the essentials of the horizontally-averaged time-mean high resolution solution, including the buoyancy, vertical velocity, and pressure profiles, as well as much better representation of the heat flux. We explore the consequences of different choices for the parametrisations of the exchange terms, showing that a good representation of volume, momentum, and buoyancy exchange, and of the pressure difference between the fluids, is required. For this simple case, this is achieved entirely without parametrisation of subfilter terms, showing that the multi-fluid approach is capturing the coherent structures of convection well.
Biogeochemical Asynchrony: Ecosystem Drivers of Seasonal Concentration Regimes across the Great Lakes Basin
Authors: Van Meter Kimberly , Basu Nandita , Byrnes Danyka
Published: March 2020

Changes in seasonal climate regimes, and related changes in seasonal nutrient dynamics, are occurring across a range of climates and land use types. Although it is known that seasonal patterns in nutrient availability are key drivers of both stream metabolism and eutrophication, there has been little success in developing a comprehensive understanding of seasonal variations in nutrient export across watersheds or of the relationship between nutrient seasonality and watershed characteristics. In the present study, we have used concentration and discharge data from more than 200 stations across US and Canadian watersheds to identify (1) archetypal seasonal concentration regimes for nitrate, soluble reactive phosphorus, and total phosphorus, and (2) dominant watershed controls on these regimes across a gradient of climate, land use, and topography. Our analysis shows that less impacted watersheds, with more forested and wetland area, most commonly exhibit concentration regimes that are in phase with discharge, with concentration lows occurring during summer low-flow periods. Agricultural watersheds also commonly exhibit in-phase behavior, though the seasonality is usually muted compared to that seen in less impacted areas. With increasing urban area, however, nutrient concentrations frequently become essentially aseasonal or even exhibit clearly out-of-phase behavior. In addition, our data indicate that seasonal SRP concentration patterns may be strongly influenced by proximal controls such as the presence of dams and reservoirs. In all, these results suggest that human activity is significantly altering nutrient concentration regimes, with large potential consequences for both in-stream metabolism and eutrophication risk in downstream water bodies.
The impacts of liquid precipitation on sea ice surface ablation
Authors: Dou Tingfeng
Published: March 2020

Snow plays an important role in the Arctic climate system, modulating heat transfer in terrestrial and marine environments and controlling feedbacks. Changes in snow depth over Arctic sea ice, particularly in spring, have a strong impact on the surface energy budget, influencing ocean heat loss, ice growth and surface ponding. Snow conditions are sensitive to the phase (solid or liquid) of deposited precipitation. However, variability and potential trends of rain-on snow events over Arctic sea ice and their role in sea-ice losses are poorly understood. Time series of surface observations at Utqiagvik, Alaska, reveal rapid reduction in snow depth linked to late-spring rain-on-snow events. Liquid precipitation is critical in preconditioning and triggering snow ablation through reduction in surface albedo as well as latent heat release determined by rainfall amount, supported by field observations beginning in 2000 and model results. Rainfall was found to accelerate warming and ripening of the snowpack, with even small amounts (such as 0.3mm recorded on 24 May 2017) triggering the transition from the warming phase into the ripening phase. Subsequently, direct heat input drives snowmelt, with water content of the snowpack increasing until meltwater output occurs, with an associated rapid decrease in snow depth. Rainfall during the ripening phase can further raise water content in the snow layer, prompting onset of the meltwater output phase in the snowpack. First spring rainfall in Utqiagvik has been observed to shift to earlier dates since the 1970s, in particular after the mid-1990s. Early melt season rainfall and its fraction of total annual precipitation also exhibit an increasing trend. These changes of precipitation over sea ice may have profound impacts on ice melt through feedbacks involving earlier onset of surface melt.
Analysis on sub-daily characteristics of one hour precipitation based on observed data
Authors: Huafang Lyu
Published: March 2020

In order to reveal sub-daily characteristics of precipitation, this study analyzes statistical characteristics of hourly precipitation by using statistical methods. The hourly precipitation observed data was collected from 34 representative precipitation stations of Sichuan Province of China during 2001-2007. The results show that the average one hour precipitation is 0.148 mm, and the probability density function of precipitation intensity y = 0.2235e-0.083x. The average daily precipitation time is 2.6 hours, and the probability of precipitation event each hour follows a sine wave. As well as the maximum probability time when precipitation occurs in a day is 3 AM to 4 AM, and the minimum probability time is 14 PM to 15 PM. It suggests a method for precipitation downscaling from daily into hourly.
Analysis of aerosol properties at recent (2015-2018) high PM concentration events in two super-mega cities, Seoul and Beijing
Authors: Cha Yesol , Song Chang-Keun
Published: March 2020

To meet public concerns of health caused by the high concentration of PM highly raised, this research has been done to find out unique physical, chemical, and optical characteristics of aerosols in the case of recent four years high PM concentration events over the East Asian region, especially in Korea and China. Severe air pollution over the East Asian region has occurred by the rapid development of urban areas and industrialization. Also, the meteorological conditions in East Asia are strongly correlated with a high concentration of air pollution and seasonal variation of aerosols. There are three types of aerosol properties (physical, chemical, and optical property), and each property is essential to understand the characteristics of regional and seasonal high PM concentrations. This research has been done to find out unique physical, chemical, and optical characteristics of aerosols in the case of high PM concentration events, especially in two super-mega cities (Seoul and Beijing) of Korea and China, by using various observations measured during recent four years. To analyze those characteristics of aerosols at high concentration events occur, various measurement data are used, like ambient surface air monitoring data (for physical properties) from national network in both Korea and China, Intensive Monitoring Data (for chemical properties), AERONET, GOCI satellite (for optical properties), and meteorological data during recent years (2015 – 2018). This study can provide observational evidence to confirm that each different region has different physical, chemical and optical characteristics of aerosol with the different time periods. The comprehensive results analyzed from this study and integrated methodologies suggested in this study might be useful to make a better in-depth understanding of the relations between various aerosol properties in certain regions and periods.

 

 

Key words : Aerosol, High concentration events, Physical/Chemical/Optical Properties of aerosols
Scaling the piping process
Authors: Dirkx Willem-Jan , Van Beek Rens , Bierkens Marc
Published: March 2020

Scaling the piping process

 

W.J. Dirkx*a, L.P.H. van Beeka, M.F.P. Bierkensa,b

 

*Corresponding author

a University of Utrecht, Department  of Physical Geography, Faculty of Geosciences, P.O. 80.115, 3508 TC,    

  Utrecht, the Netherlands

bDepartmentStochastic hydrology and geohydrology, Deltares, P.O. 85467, 3508 AL, Utrecht, the Netherlands.

 

Seepage underneath river embankments during high water events can lead to erosion by piping. Elevated hydraulic gradients will drive groundwater flow, which when large enough, may breach the confining layer by bursting and wash out finer non-cohesive sediments, especially if the outflow is concentrated in a single point. As material is removed, a pipe may form and continue to progress upstream eventually undermining the embankment. Although often approached as a geotechnical or engineering problem in terms of embankment failure, the process can also be approached from different scales as a geohydrological problem. On the scale of an entire delta there are multiple channel belts that define the regional groundwater flow patterns. On the scale of a single stretch of river embankment the interaction between the river, present channel belts, their orientation, and channel belt architectural elements dominate the exact location of bursting and associated discharge. From there on the process scale becomes important, where the grain size distribution within the facies where the piping is taking place. And the process is dominated by regional bulk hydraulic conductivity in terms of discharge magnitude and grain size distribution at the tip of the pipe in terms of erodibility. In this study, a set of embedded models for the various scales is developed and tested that simulates the formation of a single pipe at these various scales in a holistic approach. Geohydrological conditions are linked to a representation of saturated hydraulic conductivity based on the local grain size distribution to model the feedback between groundwater flow, subsurface conditions and piping at these various scales. Thus, the model assesses the influence of subsurface heterogeneity on piping and its performance was assessed on the basis of field observations and laboratory experiments. Our results show the validity of the model and stress the need to treat piping as a three-dimensional geohydrological problem.
Ground-based lightning and AWS network system for alert of torrential rainfall and typhoon combined with micro-satellite constellation
Authors: Takahashi Yukihiro , Sato Mitsuteru , Kubota Hisayuki , Ishida Testuro , Algodon Meryl , Castro Ellison , Estrebillo Loren , Purwadi Purwadi , Perez Gay , Yamashita Kozo , Matsumoto Jun , Hamada Jun-ichi
Published: March 2020

We have been developing a ground-based lightning and AWS network system under the projects of a SATREPS “ULAT” and e-ASIA in order to realize precise real-time monitoring and issuing alert for torrential rainfall and typhoon extreme based on international cooperation among Japan, Philippines, Indonesia and other SE-Asian countries supported by JST, JICA, PHL-Microsat and other funding. The intensification of lightning activity is precursor of typhoon growth. In these projects, we are constructing ground-based lightning and AWS—automated weather station—network system with 12 sites for VLF radio wave measurement in nation-wide of Philippines and with 50 sites for electrostatic field measurement in Metro Manila together with infrasound sensor. We are going to complete the installation of the sensors at most of the planned ~60 sites by the end of this year. We already started with installed sensors and achieved preliminary results for typhoon and thunderstorm measurement. We are also doing practice in operating our micro-satellite which can make rapid target pointing at high accuracy. Using the photos captured from the satellite, now we can reproduce the detailed 3-D structure of the cloud at best quality even compared to the latest radar system.
What controls microbial growth in tropical soils? The role of carbon and phosphorus.
Authors: Ranits Christian , Fuchslueger Lucia , Van Langenhove Leandro , Janssens Ivan , Peñuelas Josep , Richter Andreas
Published: March 2020

Tropical forest ecosystems are important components of global biogeochemical cycling. Many tropical rainforests grow in old and highly weathered soils, depleted in phosphorus (P) and net primary productivity in tropical forests is often limited by P availability. It is unclear, however, if heterotrophic microbial communities in tropical soils are also limited by P or rather by carbon (C). Elemental limitations of microorganisms in soil have often been approached by measurements of respiration rates in response to additions of nutrients or carbon. However, it has been argued lately, that microbial growth rather than respiration should be used to assess limitations.

In this study we therefore ask the question whether the growth of heterotrophic microbial communities in tropical soil is limited by available phosphorus or by carbon. We collected soils from three sites along a topographic gradient (plateau, slope, bottom) differing in soil texture, total and available P concentrations from a well-studied, P-poor region in Nouragues, French Guiana. We incubated these soils in the laboratory with C in the form of cellulose, inorganic phosphorus and with a combination of both, and studied microbial growth by measuring the 18O incorporation from labelled water into microbial DNA. Moreover, we measured microbial respiration and determined microbial biomass C, N (nitrogen) and P.

Our results demonstrate that, although microbial biomass C and N was similar in soil collected from all three topographic sites, soil respiration rates were significantly higher in soils from the plateau indicating a more active microbial community. Microbial C and N did not respond to cellulose and inorganic P additions, only microbial P increased significantly when P was added in all soils. Although microbial biomass C was not increased, C and P additions stimulated microbial respiration in clay rich plateau soils. In slope soils microbial communities initially only increased respiration activity in response to P additions, however at the end of the incubation also C showed significant differences in respiration activity, with strongest increases when C and P were added in combination. In sandier bottom soils microorganisms responded with increased activity to C addition, but also here respiration showed strongest increases in response to combined carbon and phosphorus additions. We will discuss these findings in relation to the pattern of gross growth rates in these soils and evaluate the stoichiometric limitations of microbial activity and turnover.
Improved interpolation scheme at receiver positions for 2.5D frequency-domain marine CSEM forward modelling
Authors: Li Gang , Duan Shuangmin , Cai Hongzhu , Han Bo , Ye Yixin
Published: March 2020

We present an improved interpolation scheme for 2.5D marine controlled-source electromagnetic (CSEM) forward modeling problem. As the resistivity contrast between the seawater and seafloor sediment layers is significant, it is usually difficult to compute the EM fields accurately at receivers which are usually located at the seafloor. In this study, a new interpolation scheme at receivers is proposed, in which the interpolation of EM fields at the cell nodes for the whole computational domain to arbitrary receiver locations is discussed in detail. Numerical tests indicate that, our improved interpolation is more accurate for simulating the EM responses at receivers located on the seafloor, compared with the linear or rigorous interpolation.
Lagged response of Adélie penguin population dynamics to environmental variability in the Ross Sea, Antarctica
Authors: Chen Xintong , Li Xianglan
Published: March 2020

Adélie penguin (Pygoscelis adeliae) are known as an eco-indicator species of the Southern Ocean marine ecosystem. Environmental variability drives penguin population dynamics through its effects on vital rates (e.g., survival, dispersal, or breeding success). Recent studies suggested that inter-annual variation strongly affected Adélie penguin abundance in individual colonies, and aggregating abundance across space provided more reliable trends of population dynamics. By considering the similarity of the regional sea-ice concentration, we divided the Ross Sea region into six areas to investigate the effects of environmental changes on penguin population dynamics from 1982–2013. Time lagged analysis of 0–6 years between penguin abundance and environmental factors were conducted in our study. We found that penguin abundance was significantly correlated with environmental factors at different lag times (p <0.05). In the western Ross Sea region, penguin abundance was positively correlated with temperature over the past 5 years (p <0.05), and positively correlated with sea-ice concentration at a lag of 4–6 years (p <0.05). In the northernmost region of the Ross Sea, penguin abundance was significantly correlated with chlorophyll concentration 4 years earlier (p <0.01). Generalized additive model (GAM) results showed that in mid-Victoria Land, the relationship between sea-ice concentration and penguin abundance was quadratic. Penguin abundance peaked when sea-ice concentration was approximately 40%. On Franklin Island, temperature positively affected penguin abundance when temperature was lower than -3°C, and the contribution decreased considerably when temperature was higher than -2.5°C. Optimal ranges of environmental factors for Adélie penguin population might exist and differ spatially in the Ross Sea. Our study highlighted the lagged response of penguin population to environmental factors to further understand the effects of climate changes on the Antarctic biosphere.
Fate and transport of nitrogen in soils, sediment and water of the Lena Delta, Northeast Siberia
Authors: Sanders Tina , Fuchs Matthias , Dähnke Kirstin
Published: March 2020

Soils and sediments in the Lena Delta in Northeast Siberia store large amounts of organic matter including organic bound nitrogen. This nitrogen is not directly available for plants and primary production, but can be remineralised in the soils or in sediments after erosion to the Lena River. Our study aims to estimate the load of reactive nitrogen from terrestrial sources into the Arctic Ocean. Therefore, water and sediment samples were collected along a transect (~200 km) from the centre of the Delta to the open Laptev Sea in summer 2019. On the collected samples, we will measure dissolved organic and inorganic nitrogen, particulate nitrogen and CN ratio. In addition, the 15N stable isotope values of these components will be determined to identify nitrogen sources, sinks and processes of nitrogen transformation. Additionally, we carried out incubation experiments in the field to determine the potential remineralisation rates of various soil types in Lena water and nutrients fluxes of the sediments. The load of dissolved inorganic nitrogen in the Lena water in the delta was very low and low nitrate and silicate concentration indicate uptake by phytoplankton. Outside the Lena Delta, a lens of nutrient depleted freshwater covered the salty Arctic Ocean water, which had higher loads of reactive nitrogen. The organic matter content of the soils and sediment is highly variable and ranges from 1 to 45 %. This organic matter is the source of reactive nitrogen, which is determined in incubation experiments and using nitrogen stable isotopes. We found that especially the unvegetated soils and sediment are sources of reactive nitrogen in the end of vegetation period, and are potentially sources of nitrous oxide emissions.
Nutrient Recovery from Agricultural Wastewater by Integrated Electrokinetic Processes
Authors: Pan Shu-Yuan , Wei Chao-Yu , Wade Anwar Jamaal , Tseng Po-Chih
Published: March 2020

Agricultural wastewater including anaerobic digestate is annually generated in a huge quantity in Taiwan. The management of agricultural wastewater should be emphasized on the recovery and production of value-added resources, such as macronutrients (nitrogen, phosphorus, and potassium), for realizing the circular bioeconomy. In this paper, we will illustrate the development of energy-efficient electrokinetic processes for nutrient recovery from agricultural wastewater. First, we evaluate the performance of electrokinetic separations processes for recovery of macronutrients. We also discuss major challenges in managing nutrient reuse by the developed electrokinetic methods. Then, we elucidate the process chemistry and reaction kinetics by the processes. Lastly, we consider the interconnectivity among water, energy and the produced macronutrients in the context of large-scale deployment.
Identification of the Earth Tide’s Influences and its Main Influencing-Components on Groundwater Level in an Unconfined-Aquifer
Authors: Guo Jian , Xu Mo , Shi Haoxin , Ge Jianhong
Published: March 2020

It is well known that various kinds of factors are causing the fluctuation of the groundwater level. The influence of earth tide on groundwater is first observed in confined-aquifer, while in unconfined-aquifer, understanding the influence of earth tide on the micro-fluctuation of the water level is crucial for obtaining key geo-hydrological parameters of the aquifer. In this study, the groundwater level of a monitoring well in Kualiangzi Village, Zhongjiang County, Deyang, as well as the data of local earth tides and rainfall were collected. And then the identification of the earth tide’s influences and its main influencing-components on groundwater level were studied by means of spectral analysis, cross-correlation analysis and harmonic analysis. The results show that the local groundwater levels are featured periodic changes of 1-day, 1/2 day and 1/3 day, which are corresponded to the earth tide. Moreover, the amplitude of the groundwater levels are negatively correlated with the earth tide, and there is no obvious hysteresis between them. The main influencing-components of earth tide are K1 diurnal wave and S2 semidiurnal wave.
Forecasting of an extreme flood in mountainous area of North China based on WRF-Hydro with distributing parameters
Authors: Wang Wei , Liu JIa , Li Chuanzhe , Qiu Qingtai , Liu Yuchen
Published: March 2020

The flood events in the mountainous area of northern China has the characteristics of high intensity and strong sudden occurrence, and atmospheric-hydrological coupling system can improve the forecast accuracy and prolong the lead time. This paper discusses the simulations of the enhanced WRF-Hydro model on a historical flood that occurrs in a mesoscale catchment of Taihang mountain on July 21, 2012. Firstly, the precipitation accuracy of WRF, WRF data assimilation, co-kriging merging method of radar QPE data are as three different input sources for WRF-Hydro. The results show that the rainfall of merging QPE can achieve better simulations in time and space. In addition, the rainfall of WRF assimilation data is obviously better than that of WRF, but still underestimates the rainfall values. The extreme event rainstorm mainly proceeds in 5 hours, and for the assimilation data, the spatio-temporal simulations of the rainfall data in the first 2 hours are slightly poor. Hence we compare the combination of the first few hours to use the merging QPE and following by assimilation precipitation as the model input. In addition, according to the parameters of the WRF-Hydro model, a gridding parameter calibration method based on topographic index is constructed.
Low-temperature thermochronologic constraints on the tectonic evolution of the Subei and Shibaocheng areas, northern Tibetan Plateau
Authors: Li Jianfeng , Zhang Zhicheng , Zhao Yue
Published: March 2020

        The northern Tibetan Plateau, between the Kunlun and the Altyn Tagh faults, contains high relief topography, such as the Eastern Kunlun Range, the Altyn Tagh Range and the Qilian mountain belt, and plays an important role in researching the tectonic evolution and topographic growth of the Tibetan Plateau. We present new apatite fission track (AFT) and 40Ar/39Ar thermochronologic data from the Subei and Shibaocheng areas near the eastern Altyn Tagh fault. Two Cenozoic exhumation phases have been identified from our AFT thermochronology. The AFT cooling ages of ~ 60–40 Ma farther away from the faults represented a slow widespread denudation surface as response to the Indo-Eurasia collision and signified that the Subei and Shibaocheng areas denudated as a whole in the northern Tibetan Plateau. Another phase with AFT cooling ages between about 20.5 Ma to 13.6 Ma on the hanging walls near the faults, located in the Danghenanshan and Daxueshan Mountains, recorded widespread fault activities resulted from local uplift and exhumation in late Miocene (~ 8 Ma) acquired from AFT thermal history modeling. A Cretaceous exhumation (~ 120–70 Ma) acquired from AFT thermal history modeling may have made great contributions to the growth of the pre-Cenozoic northern Tibetan Plateau.
Detection and deformation monitoring of landslides by InSAR: applications along Jinsha River, China
Authors: Xiao Ruya , Li Yongsheng , Yu Chen , Li Zhenhong , He Xiufeng
Published: March 2020

In recent years, massive landslides and the related secondary hazards such as the dammed lakes occurred in the mountainous areas of southwestern China, e.g., the Wenchuan earthquake-triggered landslide dammed lake at Tangjiashan in 2008 and the Jinsha River Baige landslide in October and November 2018 near the junction of Sichuan and Tibet Province, has attracted wide attention of the geoscience community. Geologists and disaster scientists have recognized the important role of remote sensing technology in the early detection and deformation monitoring of geohazards. Some leading countries, such as Italy and Norway, have completed nationwide InSAR monitoring projects and the results have been well applied in the field of geohazards prevention and monitoring.
We applied InSAR technology in the detection and deformation monitoring of geological hazards in the Jinsha River, mainly including 1) General survey: the mean deformation rate from InSAR stacking with atmospheric corrections conducted for a wide-range area would be helpful to narrow down the area of detailed investigation, as well as to initially establish a geological hazard inventory. 2) Detailed investigation: For potential geohazards delineated in the general survey, or the areas require special attention, multi-temporal, multi-band and high-resolution InSAR should be utilized. The exhaustive deformation time series and the retrospect results provide information for geologists to carry out risk assessments. 3) Field monitoring: For the key areas, or in the rapid response for hazards, ground-based radar equipment can be used to carry out monitoring work to quickly obtain deformation over a relatively large area of interest in a short period of time.
In this work, we will provide general survey results of landslides on the scale of hundreds of kilometres along the Jinsha River, as well as detailed results of InSAR time series analysis of Baige Landslide, Woda Landslide, and some other potential landslide failures with rapid moving trends. The deformation monitoring results of Baige landslide using ground-based radar after the first failure will also be included in this work. Finally, we will also list several challenges at this stage and the possible solutions.
Heterogenous snow cover derived uncertainty in Arctic carbon budget
Authors: Park Hotaek , Kim Youngwook
Published: March 2020

The winter of northern Arctic regions is characterized by strong winds that lead to frequent blowing snow and thus heterogeneous snow cover, which critically affects permafrost hydrothermal processes and the associated feedbacks across the northern regions. However until now, observations and models have not documented the blowing snow impacts. The blowing snow process has coupled into a land surface model CHANGE, and the improved model was applied to observational sites in the northeastern Siberia for 1979–2016. The simulated snow depth and soil temperature showed general agreements with the observations. To quantify the impacts of blowing snow on permafrost temperatures and the associated greenhouse gases, two decadal experiments that included or excluded blowing snow, were conducted for the observational sites and over the pan-Arctic scale. The differences between the two experiments represent impacts of the blowing snow on the analytical components. The blowing snow-induced thinner snow depth resulted in cooler permafrost temperature and lower active layer thickness; this lower temperature limited the vegetation photosynthetic activity due to the increased soil moisture stress in terms of larger soil ice portion and hence lower ecosystem productivity. The cooler permafrost temperature is also linked to less decomposition of soil organic matter and lower releases of CO2 and CH4 to the atmosphere. These results suggest that the most land models without a blowing snow component likely overestimate the release of greenhouse gases from the tundra regions. There is a strong need to improve land surface models for better simulations and future projections of the northern environmental changes.
Estimation of shallow groundwater evaporation from dried-up areas of Lake Urmia, Iran
Authors: Darehshouri Sahand , Michelsen Nils , Schüth Christoph , Schulz Stephan
Published: March 2020

Lake Urmia, located in the northwest of Iran, had an initial volume of about 19 km3 and a surface area of 5,700 km2 (Alipour, 2006). Once one of the largest hypersaline lakes in the world, this UNESCO Biosphere Reserve site currently shows a remarkable water level decline. About 70% of the lake area (Tourian et al., 2015) and more than 90% of its volume were lost between 2000 and 2014 (Schulz et al., 2020). The lack of a precise water balance of the Lake Urmia catchment is one of the challenges authorities are facing in their efforts to restore the lake to its ecological level. Here, key issues are that lake evaporation rates are mostly assumed and that evaporation of shallow groundwater from dried-up areas (up to 3,000 km2) is often ignored. The objective of this study is to obtain evaporation rate estimates for the dried-up parts of the Urmia lake bed. To this end, we set up a laboratory experiment with undisturbed soil columns collected from dried-up areas of the lake. With the help of a custom-made low-cost environmental chamber, the columns were subject to day- and night-time weather conditions typical for the area. Performed measurements comprise water level logging and monitoring of mass losses from the columns due to evaporation. First experimental results will be presented.

 

References

Alipour, S., 2006. Hydrogeochemistry of seasonal variation of Urmia Salt Lake, Iran. Saline Systems 2, 9. doi:10.1186/1746-1448-2-9

Schulz, S., Darehshouri, S., Hassanzadeh, E., Tajrishy, M., Schüth, C., 2020. Climate change or irrigated agriculture – what drives the water level decline of Lake Urmia. Sci. Rep. 1–10. doi:10.1038/s41598-019-57150-y

Tourian, M.J., Elmi, O., Chen, Q., Devaraju, B., Roohi, S., Sneeuw, N., 2015. A spaceborne multisensor approach to monitor the desiccation of Lake Urmia in Iran. Remote Sens. Environ. 156, 349–360. doi:10.1016/j.rse.2014.10.006

 
Complex topography and media implementation using hp-adaptive DG-FEM for seismic wave modeling
Authors: Xu Yang , Chen Xiaofei , Han Dechao , Zhang Wei
Published: March 2020

Numerical simulation of seismic wavefield is helpful to understand the propagation law of seismic wave in complex media. In addition, accurate simulation of seismic wave propagation is of great importance for seismic inversion. The discontinuous Galerkin finite element method(DG-FEM) combines the advantages of finite element method(FEM) and finite volume method(FVM) to effectively simulate the propagation characteristics of seismic waves in complex medium.

In this study, we use the hp-adaptive DG -FEM to perform accurate simulation of seismic wave propagation in complex topography and medium, and compare the results with the analytical solution of the Generalized Reflection/Transmission(GRT) coefficient method. Furthermore, ADE CFS-PML is modified and applied to DG-FEM, which greatly reduces the impact of artificial boundaries.
Heat-wave health impacts forecasting model in Korea: development and evaluation
Authors: Park Jongchul , Chae Yeora
Published: March 2020

Currently, heat-wave warning systems are based on temperature in many countries. However, heat-wave impacts depend not just on temperature but by socio-economic contexts, including age, occupation, income, household type, etc. This study developed a heatwave health impacts forecast model by considering socio-economic characteristics. In addition, this study evaluated the developed forecasting model by using Area Under the Curve (AUC).
This study used health and meteorological data from 2011 to 2017. For the health data, we used two different measures, the number of mortality and the number of emergency department visits with heat-wave related diseases (respiratory diseases, cardiovascular diseases, trauma, infectious diseases, mental and behavioral disorders). Those numbers were obtained from the National Statistical Office and the National Health Insurance Corporation, respectively. For meteorological data, we used temperature and humidity data, which were interpolated at 1 km spatial resolution.
We analyzed the health impacts of heat-wave on health by age, type of work, and income. In addition, we analyzed the weighted effects of humidity on health. The results showed age over 65, outdoor workers and low-income groups are relatively vulnerable to heat-wave. Moreover, high relative humidity was a factor that increased the risk of mortality for the population of age over 65. 
Based on the analysis results, we categorized warning level to 5 levels (from 0 to 4), level 0 means low risk and level 4 means high risk. Warning levels were classified by considering the increased risk of disease and mortality with temperature. We developed warning levels for three different groups, the general public, the elderly, and the outdoor workers.
The performance of the model measured based on AUC by using 2018 Heat-related illness monitoring data obtained from the Korea Centers for Disease Control. In the assessment for the risk level 4, the AUC ranged from 0.71 to 0.92, with an average of 0.80. The AUC value of above the risk level 3 also ranged from 0.71 to 0.92, with an average of 0.85.
These results indicate that the health impact forecasting model suggested in the study is applicable as an operational forecast model. The results are expected to be used to develop a heat-wave early warning system in Korea.
Contribution of urban park to thermal comfort and CO2 mitigation in a hot-humid environment
Authors: Lee Keunmin , Hong Je-Woo , Kim Jeongwon , Hong Jinkyu
Published: March 2020

Urban parks provide a wide range of services for healthcare and social welfare. In particular, they function as a key link connected to urban ecosystems, mitigating various environmental problems such as urban heat island effect and greenhouse emission. It is, therefore, urgent to improve our understanding of the role of the urban park in regulating their surrounding environment. We observed surface turbulent fluxes at an artificially constructed Seoul Forest Park (SFP) in Seoul, for two years from June 2013 to May 2015. The objectives of the study are to 1) quantify water, energy and CO2 exchanges from urban park into the atmosphere and 2) quantify the effect of the urban park on microclimate through comparison before and after the park construction and comparison with urbanized surrounding areas and 3) identify abiotic and biotic factors controlling the temperature reduction and CO2 offset.

Our analysis shows that SFP in summer daytime has cooler surface air temperature up to -0.6 ℃ with a Bowen ratio of 0.15 than surrounding commercial-residential zone in Seoul. SFP also acts as local sinks, and its carbon uptake gives economic benefits in terms of a carbon tax and reduction of heatwaves. Our findings indicate the important role of urban parks in mitigating urban heat island intensity and CO2 emission from urban areas and in providing eco-social benefits with us.
Zinc and Nickel signature for abiogenic and biogenic magnetite: implications for the origin of magnetite in banded iron formations
Authors: Han Xiaohua , Tomaszewski Elizabeth , Schönberg Ronny , Pan Yongxin , Byrne James , Kappler Andreas
Published: March 2020

There are longstanding and ongoing controversies about the abiogenic or biogenic origin of magnetite in banded iron formations (BIFs). The trace element composition of magnetite was proposed as a promising tracer for distinguishing biogenic from abiogenic magnetite, which, however, remains to be explored quantitatively. Here, we compared the partitioning of trace elements Zinc (Zn) and Nickel (Ni) in both abiogenic and biogenic magnetite produced either by an abiotic reaction of ferrihydrite with by Fe2+aq or by Fe(III)-reducing bacteria Shewanella oneidensis MR-1. We compared the transformation of three different ferrihydrite (Fh) starting materials: 1) Control Fh without added trace elements, 2) ferrihydrite with co-precipitated Zn (ZnFh) and 3) ferrihydrite with co-precipitated Ni (NiFh) – both in either NaHCO3 or HEPES buffer. We monitored Fe concentration and speciation in both aqueous and solid phases over time using the spectrophotometric ferrozine assay, analyzed Fh transformation products by Mössbauer spectroscopy as well as X-ray diffraction and quantified Zn and Ni in solution and in the minerals by iCAP-Qc quadrupole mass spectrometer after acidic dissolution of the minerals. In summary our results revealed that both Zn and Ni are much more depleted in abiogenic magnetite than those in biogenic magnetite, independent of whether magnetite was precipitated in NaHCO3 or HEPES buffer. Although further analyses are needed, this suggests that the trace element distribution could be a chemical signature to distinguish biogenic from abiogenic magnetite in BIFs.
Semi-Lagrangian advection scheme for the dynamical downscaling of the East Asian summer monsoon in a regional spectral model
Authors: Chang Eun-Chul , Yeo Namgu , Cha Dong-Hyun
Published: March 2020

The regional model program (RMP) that is the regional atmospheric model component of the Global/Regional Integrated Model system (GRIMs), which has the spectral dynamical core, have been participated in the Regional Model comparison project (RMIP) and the COordinated Regional Climate Downscaling Experiment (CORDEX) East Asia. The spectral method has advantages of accuracy, because numerical problems related to the spatial truncation in the grid system does not occur. However, the spectral system has the Gibbs phenomenon, which is the problem that negative values of positive definite quantities (e.g., moisture, tracer gases) can be generated by the spectral space transformation in a spectral model system. In this study, the non-iteration dimensional-split semi-Lagrangian (NDSL) advection scheme is applied to the RMP for the dynamical downscaling of the East Asian summer monsoon. In a regional climate simulation, the RMP with the NDSL scheme simulated enhanced precipitation by improving moisture field in the lower troposphere. The improvement is also induced by the revised vertical momentum which is affected by evaporation and condensation adjustment from the corrected moisture field.
Short-Term Realization of the ITRS with GNSS/SLR/VLBI/DORIS
Authors: Xu Changhui , Cheng Yingyan , Dang Yamin
Published: March 2020

International Terrestrial Reference Frame (ITRF) is the realization of the International Terrestrial Reference System (ITRS), which can be used for the variety applications such as earth research, surveying and mapping. 2000 National Geodetic Coordinate System (CGCS2000) has been established and widely applied as a long-term reference frame in China, however, a software for short-term reference frame establishment is also developed to provide high accuracy applications based on the fusion of GNSS/SLR/VLBI/DORIS. We analyzed the covariance from sinex format of the GNSS/SLR/VLBI/DORIS and the quality of local ties. The errors between the local ties and the ITRF2014 within 1cm was 89% in north direction and 85% east direction. We used inner constraints as the method of datum realization and Helmert variance component estimation for giving the weight of different space geodetic GNSS/SLR/VLBI/DORIS. Finaly, short-term terrestrial reference frame realization software can produce the weekly, monthly and annual frame products for high accuracy applications.
Spatially-distributed IDF curves for Center-Southern Chile using IMERG
Authors: Zambrano-Bigiarini Mauricio , Soto Escobar Cristóbal , Baez-Villanueva Oscar M.
Published: March 2020

The Intensity-Duration-Frequency (IDF) curves are crucial for urban drainage design and to mitigate the impact of extreme precipitation events and floods. However, many regions lack a high-density network of rain gauges to adequately characterise the spatial distribution of precipitation events. In this work we compute IDF curves for the South-Central Chilean region (26-56°S) using the latest version of the Integrated Multi-satellitE Retrievals for GPM (IMERGv06B) for 2001-2018, with a spatial resolution of 0.10° and half-hourly temporal frequency.

First, we evaluated the performance of IMERGv06B against 344 rain gauge stations at daily, monthly and annual temporal scales using a point-to-pixel approach. The modified Kling-Gupta efficiency (KGE’) and its components (linear correlation, bias, and variability ratio) were selected as continuous indices of performance. Secondly, we fit maximum precipitation intensities from 14 long-term rain gauge stations to three probability density functions (Gumbel, Log-Pearson Type III, and GEV II) to evaluate: i) the impact of using 15-year rainfall time series in the computation of IDF curves instead of using the typical long-term periods (~ 30 years); and ii) to select the best distribution function for the study area. The Gumbel distribution was selected to obtain the maximum annual intensities for each grid-cell within the study area for 12 durations (0.5, 1, 2, 4, 6, 8, 10, 12, 18, 24, 48, and 72 h) and 6 return periods (T=2, 5, 10, 25, 50, and 100 years).

The application of the Wilcoxon Mann-Whitney test indicates that differences between IDF curves obtained from 15 years of records at the 14 long-term rain gauges and those derived from 25 years of record (or more) are not statistically significant, and therefore, 15 years of record are enough (although not optimal) to compute the IDF curves. Also, our results show that IMERGv06B is able to represent the spatial distribution of precipitation at daily, monthly and annual temporal scales over the study area. Moreover, the obtained precipitation intensities showed high spatial variability, mainly over the Near North (26.0-32.2°S) and the Far South (43.7-56.0°S). Additionally, the intensities from Central Chile (32.2-36.4°S) to the Near South (36.4-43.7°S) were systematically higher compared to the intensities described in older official governmental reports, suggesting an increase in precipitation intensities during recent decades.
Human Perception of and Response to Wildfire Smoke
Authors: Fowler Mariah , Sadegh Mojtaba
Published: March 2020

Wildfire smoke presents a growing threat in the Western U.S.; and human health, transportation, and economic systems in growing western communities suffer due to increasingly severe and widespread fires. While modelling wildfire activity and associated wildfire smoke distributions have substantially improved, understanding how people perceive and respond to emerging smoke hazards has received little attention. Understanding and incorporating human perceptions of threats from wildfire smoke is critical, as decision-makers need such information to mitigate smoke-related hazards. We surveyed 614 randomly selected people (in-person) across the Boise Metropolitan Area in Idaho and 1,623 Boise State University affiliates (online), collecting information about their level of outside activity during smoke event(s), knowledge about the source of air quality information and effective messaging preference, perception of wildfire smoke as a hazard, and smoke-related health experiences. This relatively large dataset provides a novel perspective of people’s perception of smoke hazards and provides crucial policy-relevant information to decision-makers. Dataset is available to the public and can be used to address a wide range of research questions.
Wind-thermal environment in idealized 2D street canyon with different aspect ratios and thermal conditions
Authors: Ling Hong , Chen Lan , Lin Yuanyuan , Hang Jian
Published: March 2020

Environmental problems such as low wind speed, poor air quality and urban heat island effect are deteriorating in cities due to the rapid urbanization. Optimizing the ventilation condition in the urban canopy is an effective way to improve the urban air quality and thermal environment. To study the impact of building structure and thermal condition on local flow regime and micro thermal environment, wind tunnel experiments and CFD simulations were conducted with scale-model of idealized 2D street canyons. A series of street canyon models with aspect ratios of 1.1, 2.4, 4 and 5.67 were set up for both wind tunnel experiments and CFD simulations, with the scaled ration of 1:200. Laser Doppler Anemometer was deployed in the working section of the wind tunnel to monitor the velocity components. CFD simulations using ANSYS Fluent 15.0 were performed to study the turbulence characteristics under wind driven force and thermal buoyancy force. A solar ray tracing model and radiation models in Fluent was employed to simulate the heat effect of solar radiation in street canyons. The wind tunnel experiments and modelling revealed that a clockwise vortex existed in regular and deep street canyon while two counter-rotating vortexes appeared in extremely deep canyon. Moreover, different turbulence structures and significant spatial variation of air temperature existed in canyons with different solar elevation.