bluuebunny/crossref_metadata_2025 huggingface dataset:
Features and controlling factors of drainage networks in the Tibetan Plateau
Authors: Li Minhui , Wu Baosheng , Chen Yi
Published: March 2020

Tibetan Plateau is the source of many major rivers in Asia. Drainage networks of these rivers vary in shapes and features due to complex climatic and geomorphic conditions. In this study, we extracted drainage networks in the source area of Yellow River, Yangtze River and Yarlung Zangbo River from 90-m-resolution SRTM DEM. We chose 62 sub-basins in the Yellow River, 96 sub-basins in the Yangtze River and 120 sub-basins in the Yarlung Zangbo River and tested self-similarity of drainage networks in two ways. First, we tested self-similarity for traditional Horton laws. Based on Horton-Strahler order, the results indicate that rivers with low levels generally obey Horton laws while rivers with high levels show deviation. Second, we tested statistical self-similarity in the topology of river networks. Random self-similar networks (RSN) model which combines self-similarity and randomness shows topological features of river networks statistically. Real networks were decomposed into generators that produce the network. The results demonstrate that the generators of RSN model obey a geometric distribution and the parameter p, which describes the distribution of generators, ranges from 0.401 to 0.587. Self-similarity holds in a statistical sense in the selected basins in the Tibetan Plateau. Motivated by the need to understand the controlling factors of drainage networks in Tibetan Plateau, these sub-basins were divided into groups according to possible controlling factors, such as climate, tectonic and geology. Analysis shows that Horton ratios and generators of low-level rivers are affected by precipitation, but the relationship between these parameters of high-level rivers and these factors is not obvious. In order to further explore the controlling factors, we analyzed three typical rivers (Tao River, Yalong River and Lasa River) in more details. For Yalong River, Tao River and Lasa River, bifurcation ratios are 4.46, 5.00 and 4.37 while the length ratios are 2.35, 2.71 and 2.30 respectively. The Normalized Concavity Index for Tao River, Lasa River and Yalong River are -0.129, -0.082 and 0.009 respectively, indicating that the profiles of the first two rivers are concave-up and that of Yalong River is convex-up. The influence of climate is well reflected in the structure and longitudinal profiles of the drainage network in the Tibetan Plateau. Strong tectonic activities in the eastern margin of the Tibetan Plateau destroy the network of Yalong River, resulting in river capture to maintain equilibrium.
Could crop albedo modification reduce regional warming over Australia?
Authors: Kala Jatin , Hirsch Annette
Published: March 2020

Climate observations and projections for Australia show an increase in warm temperature extremes, including the frequency, duration and intensity of heatwaves. Recent global scale studies have suggested that agricultural land-use management options, such as increasing crop albedo, could reducing local warming. Australia has approximately 3,727,210 km2 of cropland agricultural land-use, the majority of which is in southwest Western Australia and southeast Australia. This presents a potential opportunity to reduce regional warming via crop albedo enhancement. We use a regional climate model at 10 km resolution, to show that crop albedo enhancement of up to 0.1 could reduce monthly mean daily maximum temperatures by -1.0°C to -1.2°C, and monthly highest maximum temperatures by up to -1.4°C to -1.6°C during the cropping season. This cooling is approximately 3 times higher over Australia than global climate models predict. We highlight stronger cooling over southwest Western Australia as compared to southeast Australia, the opposite to global model studies which poorly resolve southwestern agricultural regions. The regional cooling was driven by a reduction in surface net shortwave radiation leading to a decrease in both sensible and latent heat flux of up to 50 W m-2 and 20 W m-2 respectively, when albedo is increased by up to 0.1. There were no cloud feedbacks or effects on precipitation. Our results highlight the importance of using regional climate models at a sufficiently high spatial resolution when investigating agricultural land-use management to reduce regional warming.
Improve Tropical Cyclone Prediction of TWRF with the Application of Advanced Observation Data
Authors: Chen Der-Song , Hsiao Ling-Feng , Xie Jia-Hong , Hong Jing-Shan , Fong Chin-Tzu , Yeh Tien-Chiang
Published: March 2020

With violent wind and severe rainfall, the tropical cyclone is one of the most disastrous weather systems over ocean and the coastal area. To provide accurate tropical cyclone (TC) track and intensity forecasts is one of the most important tasks of the national weather service of countries affected. Taiwan is one of the areas frequently influenced by tropical cyclones. Improving the tropical cyclone forecast is the highest priority task of Taiwan’s Central Weather Bureau (CWB).

Recent improvement of the TC forecast is due to the improvement of the numerical weather prediction. A version of the Advanced Research Weather Research and Forecasting Model (WRF), named TWRF (Typhoon WRF), was developed and implemented in CWB for operational TC forecasting from 2011. During the years, partial update cycling, cyclone bogus scheme, relocation scheme, 3DVAR with outer loop, analysis blending scheme, new trigger Kain–Fritsch cumulus scheme, and so on have been studied and applied in TWRF (Hsiao et al. 2010, 2012, 2015) to improve the model. We also improved the model by changing the TWRF configuration from a triple nested to a double nested grid and increasing the model resolution from 45/15/5 km 45-levels to 15/3 km 52-levels from 2016. Results showed increasing the model resolution improving the track, intensity and rainfall forecast. However, The averaged 24/48/72 hours TC track forecast errors of TWRF are 91/147/223, 84/133/197, 74/127/215, 64/122/202, 70/120/194 and 70/122/180 km in year 2014, 2015, 2016, 2017, 2018 and 2019 respectively.

In this study, WRF Four-dimensional data assimilation (FDDA) is adopted to assimilate the temperature, pressure, water vapor content which processed from the FORMOSAT-7 constellation, high-temporal frequency atmospheric motion vector (AMV) retrieved from Himawari-8 satellite images and radar data to generate a model balanced TC structure and thermodynamic state at the initial time. The specific goal is to improve the track, structure and intensity prediction of TCs and their associated rainfall distribution in Taiwan. The detail will be presented in the conference.

Keywords: tropical cyclone, Himawari-8 AMV, Four-dimensional data assimilation, FORMOSAT-7, radar data.

Corresponding author address:

Der-Song Chen,  song@cwb.gov.tw

Central Weather Bureau, 64 Gongyuan Rd., Taipei, Taiwan, R.O.C., 10048.
Risk and vulnerability of Mongolian grasslands to climate change and grazing
Authors: Nandintsetseg Banzragch , Boldgiv Bazartsersen , Chang Jinfeng , Ciais Philippe , Shinoda Masato , Mei Yong , Stenseth Nils Christian
Published: March 2020

Robust changes in climatic hazards, including droughts, heatwaves and dust storms, are evident in many parts of the world and they are expected to increase in magnitude and frequency in the future. At the same time, socio-ecological damage from climate-related disasters has increased worldwide, including the Eurasian steppes, notably Mongolian grasslands (MGs), which occur in arid and harsh cold climate and still support traditional nomadic livelihood and culture through the food supply, and agricultural and ecosystem services. In the 2000s, increasing climate disasters (droughts combined with anomalously harsh winters (dzuds in Mongolian), and dust storms) resulted in massive livestock deaths, causing socioeconomic stagnation. In this context, assessments of risk and vulnerability of MGs to climate change and grazing may support disaster risk management by helping to identify hazard risk hotspots, allowing herders in risky areas to be prepared for events, and to mitigate the future potential impacts. Here, we examine the risk and vulnerability of the MG ecosystem to droughts at the national-level during a 40-year (1976–2015) using simulations of a gridded process-based ecosystem model by contrasting the recent (1996–2015) and past (1976–1995) 20-years. In general, the model realistically simulates temporal and spatial variations of vegetation biomass and soil moisture that were captured by field and satellite observations during 2000–2015 over MGs. We apply a probabilistic risk analysis in which risk is the product of the probability of hazardous drought during June-August and ecosystem vulnerability. Results reveal that during 1976–2015, increases in droughts with rapid warming and slight drying occurred over MGs, particularly in the recent 20-year, accompanied by ever-increasing grazing intensity, which together resulted in declining trends in grassland productivity. During the recent 20-year, the risk of drought to productivity slightly increased over extended areas in MGs compared to the past 20-year. The increase in the risk to MGs predominantly caused by the climate change-induced increase in the probability of hazardous drought, and less by the vulnerability. Regionally, recent droughts modify the risk to grasslands particularly in northcentral and northeast Mongolia. Given the benefits of MGs for both ecosystem services and socio-economic consequences, recent increases in drought hazards and associated risk to MGs signal an urgent need to implement drought management policies that sustain MGs.
Spatial and temporal heterogeneity in aerosol radiative effects over ecological area in south China: Composition and transmission implications
Authors: Yining Ma , Jinyuan Xin
Published: March 2020

Abstract: Ecological region in southern China has been perennially affected by monsoon climate and anthropogenic emissions, resulting in complex aerosol components and frequent long-range transport. In this study, a Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model is applied to estimate aerosol radiative forcing (ARF) and multiple aerosol observation datasets is used to estimate the aerosol chemical components and optical properties. The aerosol loading and the radiative effects in the ecological region exhibited strong seasonal changes. The average major components (NH4+, NO3−, SO42−) in Total water soluble ionic (TWSI) ,organic carbon (OC) concentration, the ratio of organic carbon to element carbon (OC/EC) and biogenic secondary organic aerosol (BSOA) tracers were 3.20±1.22 μg·m-3, 2.19±1.39 μg·m-3, 3.17 and 74.00±35.23 ng·m-3 in the dry season and 2.22±0.91 μg·m-3, 3.14±1.62 μg·m-3, 7.13 and 186.34±113.82 ng·m-3 in the wet season, respectively. The average radiative forcing at the top of atmosphere (TOA) is -11.73±11.36 W/m2 and -0.41±10.08 W/m2 in dry and wet season. When the aerosol single scattering albedo (SSA) less than 0.9, the retrieve frequency in wet season reached account for 75%. The increase of OC and BSOA transformed by forests in the wet season weaken the cooling effects. However, the dry season is mainly composed of anthropogenic inorganic aerosols, which enhances the scattering effect. The aerosol observation baseline also verified the seasonal variation of ARF in the ecological region. Driven by multiple factors such as meteorological conditions, emission sources, and the mixed state of particulate matter, the transport patterns of air masses in ecological area exhibits completely opposite affects to ARF.
Long-term intensification of the East Asian Summer Monsoon (EASM) lifecycle based on observation and CMIP6
Authors: Park Jina , Kim Hyungjun , Wang Shih-Yu(Simon) , Jung Jee-Hoon , Lim Kyo-Sun , Yoon Jin-Ho
Published: March 2020

In 2018, Japan experienced successive extremes, flood and following heat wave. The East Asian summer monsoon (EASM) has lifecycle and depending on the cycle, the basic condition of rainfall and heat event is decided. Thus, to examine the variability to the basic condition which is capable to make extreme event favorable, the long-term change of the EASM lifecycle is analyzed based on observation datasets and historical simulations of the Couple Model Intercomparison Project Phase 6 (CMIP6).

 According to the observation, the active phase of EASM has intensified and the break phase becomes longer, resulting in a shorter but stronger rainy season followed by a longer dry spell. This intensification in the precipitation evolution is accompanied by increased lower tropospheric southwesterly wind and convergence of water vapor flux, suggesting a dynamical cause. The widely reported westward extension of the Western North Pacific Subtropical High associated with the warming climate is a likely driver. Some of the CMIP6 models were able to capture the climatology of the EASM lifecycle and its intensification similar to those observed, but the majority of models still did not properly simulate the EASM lifecycle.
Preliminary investigation of the possibility of GIC development in Greece
Authors: Boutsi Adamantia Zoe , Balasis Georgios , Daglis Ioannis A.
Published: March 2020

Geomagnetically Induced Currents (GIC) constitute an integral part of the space weather research and a subject of ever-growing attention for countries located in the low and middle latitudes. A series of recent studies highlights the importance of considering GIC risks for the Mediterranean region. The HellENIc GeoMagnetic Array (ENIGMA) is a network of 4 ground-based magnetometer stations in the areas of Thessaly, Central Greece, Peloponnese and Crete in Greece that provides geomagnetic measurements for the study of pulsations, resulting from the solar wind - magnetosphere coupling. ENIGMA magnetometer array enables effective remote sensing of geospace dynamics and the study of space weather effects on the ground (i.e. GIC). ENIGMA contributes data to SuperMAG, a worldwide collaboration of organizations and national agencies that currently operate approximately 300 ground-based magnetometers. In this presentation, we exploit ENIGMA data in order to study the spatio-temporal variations of the geomagnetic field that emanate during active geospace conditions. Moreover, we investigate the possibility that these variations produce hazardous currents and provide an estimation of their intensity, focusing on the most intense magnetic storms of the present solar cycle.
Unprecedented coastal upwelling in the southern coast of the Korean peninsula during summer 2013
Authors: Jung Jihun , Cho Yang-Ki
Published: March 2020

Unprecedented coastal upwelling in the southern coast of the Korean peninsula was reported in the summer of 2013. The offshore water temperature was 2℃ higher than that of climate (10-year mean) due to the hot summer in 2013. However, the water temperature at the coastal region was 2℃ lower. The upwelling continued for a month despite of weakening of upwelling-favorable wind. In this study, observational data and numerical model results were analyzed to investigate what caused the upwelling and sustained it for a long time. The upwelling was induced by upwelling-favorable wind in July. Coastal upwelling resulted in dynamic uplift of bottom cold water due to geostrophic adjustment. The dynamic uplift decreased sea level in the coastal region. The sea level difference between coastal and offshore regions resulted in an intensified cross-shore pressure gradient which induced geostrophic current accompanied by geostrophic adjustment along the coast. This positive feedback between dynamic uplift and geostrophic adjustment sustained the coastal upwelling for a long time regardless of upwelling-favorable wind.
Seasonal variability and differences in n-alkane deltaD values between dicotyledonous tree and monocotyledonous grass
Authors: Zhang Xiaolong , Xu Baiqing , Günther Franziska , Gleixner Gerd
Published: March 2020

Understanding seasonal variability in n-alkane δD values (δDwax) among plant forms/lineages and the underlying physiological and biochemical factors that causes it is crucial for δDwax-based quantitative paleoclimate reconstruction. Herein, we present parallel controlled study of Stipa bungeana (monocotyledonous grass) and Quercus aquifolioides (dicotyledonous tree) by conducting semimonthly paired δD analysis of precipitation, soil and leaf water, and n-alkanes over two years. We show that δDwax in both plants inherit precipitation hydrogen isotopic compositions throughout the growing season. However, it is synchronous in S. bungeana and belated in Q. aquifolioides. We reveal previously unrecognized phenomenon that, for trees alkanes with higher concentration percentages utilize lighter deuterium preferentially, whereas grasses do not. We conclude that dicotyledonous trees have a selection mechanism whereby leaf water hydrogen is utilized for n-alkane biosynthesis, whereas monocotyledonous grasses do not. This fundamentally explains δDwax discrepancy between dicotyledonous trees and monocotyledonous grasses, having significant implications for δDwax paleoapplication.
Sea spray and land use affect clay mineral and soil organic matter properties in soil on machair (Harris, Scotland)
Authors: Rennert Thilo , Herrmann Ludger
Published: March 2020

‘Machair’ describes a landscape form that is present along the Atlantic seaboard of Scotland and Ireland, and that is characterized by a gently sloping coastal plain developed from aeolian carbonate and quartzose sand. We characterized three grassland soil profiles along a coastal transect on Harris (Outer Hebrides, Scotland) by standard methods (colour, texture, pH, wet-chemical extractions), infrared spectroscopy, X-ray diffractometry, X-ray fluorescence spectrometry and differential scanning calorimetry. Our aim was to understand the impacts of humankind, matter input, weathering and accumulation of soil organic matter (SOM) on chemical processes and soil properties. One of the profiles differed distinctly from the other two, in particular regarding depth, texture, carbonate and SOM contents, and properties of SOM (relative content of rather labile permanganate-oxidizable SOM, transformation state), presumably caused by earlier land use as arable land. We classified the soil with the least depth as Hypereutric Leptosol, and the others as Cambic and Calcaric Phaeozem. Thermally stable SOM was present in all samples, likely pointing to pyrogenic SOM, i.e. black carbon. The mineralogical composition differed among the profiles and reflected the intermediate character of the local rocks. In all topsoil horizons, we identified Mg-hydroxy-interlayered minerals (HIMs), which are rather rare, given the commonly low abundance of Mg ions in the soil solution relative to Ca, or Al in acidic soil. The share of Mg-HIMs of the total minerals in the clay fraction ranged from 25% in a subsoil to 71% in a topsoil horizon. We suggest that sea spray is the source of subsequently intercalated Mg. This composition of the clay fraction, which is possibly typical of soil on certain machair sites, and is the result of a pedogenic process, surely affects soil properties and processes such as cation exchange capacity and SOM storage and thus element cycles.
The Effect of the State-of-the-Art Mapping Functions on Precise Point Positioning
Authors: Durmus Faruk Can , Erdogan Bahattin
Published: March 2020

Global Navigation Satellite Systems (GNSS) are effectively used for different applications of Geomatic Engineering. There are lots of model error sources that affect the performance of the point positioning. Especially for the Precise Point Positioning (PPP) technique, which depends on the absolute point positioning, these errors should be modelled since PPP technique utilizes un-differenced and ionosphere-free combinations. Studies about PPP technique show that the effect of tropospheric delay caused by water vapor and dry air in the troposphere, which affects GNSS signals, is an important parameter should be modelled. Total zenith delay consists of both hydrostatic and wet delay. Hydrostatic delay can be accurately estimated by using atmospheric surface pressure and temperature with empirical models. Although there are many empirical models currently used for the determination of the zenith wet delay, the accuracies of these models are inadequate due to the temporal and spatial variation of atmospheric water vapor. Moreover, the tropospheric delay occurs along the path of GNSS signals and the Mapping Functions (MFs) are used to convert the tropospheric signal delay along the zenith direction to the slant direction. In this study, it is aimed to measure the effect of the globally produced MFs as Niell Mapping Function (NMF), Vienna Mapping Function 1 (VMF1), Global Mapping Function (GMF) and Global Pressure Temperature model 2 (GPT2) for GNSS positioning accuracy. Only GPS satellite system has been taken into account. For the analysis it has planned to process approximately 294 permanent stations from Crustal Dynamics Data Information System (CDDIS) archive with Jet Propulsion Laboratory’s GipsyX v1.2 software. In order to reveal the effect of different season the GPS observations in January, April, July and October, 2018 have been obtained. The solutions were derived for different session durations as 2, 4, 6, 8, 12 and 24 hours for each global MFs and root mean square values have been estimated for each session durations. According to the first results that based on the six points, which the ellipsoidal heights of them are between 20 m and 105 m, although the results of north and east components are close to each other; the results of VMF1 are better than other global MFs for up component.

 

Keywords: State-of-the-Art Mapping Function, Troposphere, Precise Point Positioning, Accuracy, GipsyX
A new Berriasian to Turonian carbon isotope stratigraphy for the Boreal Realm
Authors: Bornemann André , Erbacher Jochen , Blumenberg Martin
Published: March 2020

An upper Berriasian to mid-Turonian composite carbon isotope record has been compiled based on 13 drill cores and more than 4500 measurements. The total record comprises a composite thickness of about 1300 m. All cores are situated in the larger Hanover area, which represents the depocenter of the Lower Saxony Basin in early Cretaceous times.

Some intervals have already been published such as the Berriasian to early Aptian interval published by Thöle et al. (2019, Deposit. Rec.), the Albian to Cenomanian transition (Bornemann et al., 2017, Sedimentol.) and the Cenomanian/Turonian Wunstorf cores (Voigt et al., 2008, Newsl. Strat.; Erbacher et al., 2020, ZDGG). Tie points among the studied cores have been defined based on multiple criteria including litho-, chemo- and biostratigraphy.

The record can be considered to be almost complete, albeit a small gap in the early Albian cannot be ruled out at the moment. A number of global carbon isotope key events including the Valanginian Weisssert Event, the OAEs 1a (Aptian), 1b (lower Albian) and 1d (upper Albian) as well as the Mid-Cenomanian Event (MCE) and the OAE 2 (Cenomanian-Turonian Boundary Event) have been identified allowing for a detailed comparison with Tethyan records covering this time interval. Thus, this new detailed chemostratigraphy provides a unique opportunity to potentially overcome many still existing Boreal-Tethyan correlation issues.
Rain and small earthquakes maintain a slow-moving landslide in a persistent critical state
Authors: Bontemps Noélie , Larose Eric , Lacroix Pascal , Jara Jorge , Taipe Edu
Published: March 2020

In tectonically active mountain belts, landslides contribute significantly to erosion. Statistical analysis of regional inventories of earthquake-triggered-landslides after large earthquakes (Mw>5.5) reveal a complex interaction between seismic shaking, landslide material, and rainfall. However, the contributions of each component have never been quantified due to a lack of in-situ data for active landslides. We exploited a 3-year geodetic and seismic dataset for a slow-moving landslide in Peru affected by local earthquakes and seasonal rainfalls. Here we show that in combination, they cause greater landslide motion than either force alone. We also show the rigidity of the landslide’s bulk clearly decreasing during Ml≥5 earthquakes. The recovery is affected by rainfall and small earthquakes (Ml<3.6), which prevent the soil from healing, highlighting the importance of the timing between forcings. These new quantitative insights into the mechanics of landslides open new perspectives for the study of the mass balance of earthquakes.
Impact assessment of reservoir operation for potential adaptation in the upper Chao Phraya River basin
Authors: Padiyedath Gopalan Saritha , Hanasaki Naota
Published: March 2020

The increased flood occurrence in the lower reaches of Chao Phraya River Basin, a major river system of Thailand, has caused tremendous economic as well as agricultural losses in the past. Reservoir operation is one of the most influential factors that can alleviate flood damage by controlling the natural flow. Hence, this study examines the effect of reservoir operation on the flood peak reduction for the baseline (1990-1999) as well as future (2090-2099) scenarios under representative concentration pathway (RCP) 6 emission scenario using the H08 global hydrological model with reservoir operation module. The main objectives of the study are; (i) analyze the effect of two largest existing reservoirs of Bhumibol and Sirikit at Nakhon Sawan (catchment area: 109973 km2), where major tributaries of the Chao Phraya River join together, and (ii) analyze the effect of a hypothetical dam, located in the upper reaches of Yom River (one of the tributaries of Chao Phraya River), at Sukhothai (catchment area: 12769 km2) and Nakhon Sawan for the baseline and future scenarios. For this purpose, the H08 model was calibrated at Nakhon Sawan and validated at 26 gauging stations within the catchment with an average daily and monthly Nash-Sutcliffe efficiency values of 50 and 66% respectively. The results of baseline scenario simulation revealed that the two major reservoirs cause an enormous reduction in the daily peak discharge by 21-52% at Nakhon Sawan, whereas the impact of the hypothetical dam was negligible (3-14%) due to its reduced storage capacity compared with the major reservoirs. On the other hand, the proposed hypothetical dam exhibited significant potential for the flood peak reduction by 15-53% at Sukhothai. Therefore, it can be envisaged that the hypothetical dam could reduce flood damage at the lower reaches of Yom River where flooding is regular due to gentle slope. Further, the simulated change in daily peak discharge without the reservoir effect for the future scenario was -0.55 to 5.78 and -0.72 to 7.68 times higher at Nakhon Sawan and Sukhothai respectively compared with the baseline scenario. The impact of two existing as well the hypothetical reservoirs on flood peak reduction was similar compared with the baseline scenario at Nakhon Sawan as well as at Sukhothai. This further indicates that the changes in discharge due to climate change are larger than those achieved by the reservoir operations for the future scenario even though the simulated discharge highly depends on which general circulation model was used as input.
Dynamic emergence of domino effects in systems of interacting tipping elements in ecology and climate
Authors: Klose Ann Kristin , Karle Volker , Winkelmann Ricarda , Donges Jonathan F.
Published: March 2020

In ecology, climate and other fields, systems have been identified that can transition into a qualitatively different state when a critical threshold or tipping point in a driving process is crossed. An understanding of those tipping elements is of great interest given the increasing influence of humans on the biophysical Earth system. Tipping elements are not independent from each other as there exist complex interactions, e.g. through physical mechanisms that connect subsystems of the climate system.
Based on earlier work on such coupled nonlinear systems, we systematically assessed the qualitative long-term behavior of interacting tipping elements. We developed an understanding of the consequences of interactions on the tipping behavior allowing for domino effects and tipping cascades to emerge under certain conditions.
The application of these qualitative results to real-world examples of interacting tipping elements shows that domino effects with profound consequences can occur: the interacting Greenland ice sheet and thermohaline ocean circulation might tip before the tipping points of the isolated subsystems are crossed. The eutrophication of the first lake in a lake chain might propagate through the following lakes without a crossing of their individual critical nutrient input levels.  
The possibility of emerging domino effects calls for the development of a unified theory of interacting tipping elements and the quantitative analysis of interacting real-world tipping elements.
Testing isotopologues as diabatic heating proxy for atmospheric data analyses
Authors: Khosrawi Farahnaz , Toride Kinya , Yoshimura Kei , Diekmann Christopher , Ertl Benjamin , Schneider Matthias
Published: March 2020

The strong coupling between atmospheric circulation, moisture pathways and atmospheric diabatic heating is a great challenge in atmospheric research since this coupling is responsible for most climate feedback mechanisms and controls the evolution of severe weather events. Although diabatic heating rates are the major driving force of atmospheric circulation on weather and climate time scales, the diabatic heating rates obtained from current meteorological reanalyses show significant inconsistencies. This is mainly indebted to the fact that diabatic heating rates cannot be directly observed. Isotopologue observations assimilated into meteorological reanalyses can make an invaluable contribution since the isotopologue composition depends on the history of phase transition. Therefore, isotopologue observations can provide information that is closely linked to latent heating processes. Here, we analyse idealized experiments performed with the isotopes-incorporated General Spectral Model (IsoGSM) to investigate whether the additional assimilation of isotopologue observations can improve the diabatic heating rates. To do so, we use a Local Transform Ensemble Kalman Filter (LETKF) for data assimilation, and mock the high-density isotopologue MUSICA IASI observational data. The MUSICA IASI data apply the retrieval recipe of MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water) to the thermal nadir spectra recorded by the IASI (Infrared Atmospheric Sounding Interferometer) satellite instrument. The mocked isotopologue observations are then assimilated into the model in addition to temperature, humidity and wind profiles obtained from radiosonde and satellite data. By comparing the ensemble runs with and without the additional assimilation of the isotopologue data we can reveal the potential of MUSICA IASI isotopologue data for constraining uncertainties in diabatic heating rates.
A Pump-Probe Analysis of Nonlinear Elastic Behavior on the San Andreas Fault
Authors: Delorey Andrew
Published: March 2020

Fracture networks in the subsurface influence nearly every aspect of earthquakes and natural hazards.  These aspects, including stress, permeability and material failure, and are important for hazard assessment. However, our ability to monitor fracture behavior in the Earth is insufficient for any type of decision-making regarding hazard avoidance.  I propose a new method for probing the evolution of fracture networks in situ to inform public safety decisions and understand natural systems. 

In heterogeneous, fractured materials, like those found in the Earth, the relationship between stress and strain is highly nonlinear.  This nonlinearity in the upper crust is almost entirely due to fractures.  By measuring to what extent Earth materials exhibit nonlinear elastic behavior, we can learn more information about them.  Directly, measuring physical properties may be more useful than just detecting that fractures are present or how they are shaped and oriented.  We measure nonlinearity by measuring the apparent modulus at different strains. 

In this study we use a pump-probe analysis, which involves continuously probing velocity (as a proxy for modulus) while systematically straining the material.  We will use solid Earth tides as a strain pump and empirical Green’s functions (EGF) as a velocity probe.  We apply this analysis to the San Andreas Fault near Parkfield, California.  We chose Parkfield because there is a long-term deployment of borehole seismic instruments that recorded before and after a M6 earthquake.  We find evidence that nonlinear behavior is correlated with the seismic cycle and therefore it may contain information on the both the evolution and current state of stress on faults. 
Estimating the changes in the Moho interface beneath the Tibetan Plateau based on GRACE data
Authors: Rao Weilong , Sun Wenke
Published: March 2020

         The Tibetan Plateau (TP) experiences complex mass transfer and redistribution due to the effects from internal earth dynamics and external climate change, such as, land water change, crustal uplift, surface denudation, and Moho interface change. These phenomenas are accompanied by the gravity field change and could be observed by the Gravity Recovery and Climate Experiment (GRACE). This study applies GRACE data to estimate the corresponding mass changes expressed by water equivalent height (EWH) anomaly of the TP. In addition, we use ICESat data and hydrological models to estimate the effects of hydrological factors (lake, glaciers, snow, soil moisture, and groundwater), to separate them from the comprehensive mass field to obtain the tectonic information. The total hydrological contribution to the average EWH change is -0.30±0.21 cm/yr. We further estimate the rates of tectonic uplift and denudation based on GNSS and denudation, with results of 0.71±0.46 mm/yr and 0.38±0.10 mm/yr, respectively. Removing the effects of hydrological change, surface displacements and GIA from the GRACE data, we obtain the EWH change contributed from interior mass change of 0.21±0.27 cm/yr, which is equivalent to a mean Moho interface uplift rate of 3.63±4.32 mm/yr. Final results show that the crustal thickness of the northern TP is thinning because of the upwelling of Moho interface and the southern TP is thickening along with Moho deepening, coinciding with the tomographic results.

Key words: the Tibetan plateau, mass transfer, land water change, Moho interface change, GRACE
Investigating the divergence between Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) in defining drought over different climate zones of India.
Authors: Singh Gauranshi Raj , Dhanya Chandrika Thulaseedharan , Chakravorty Aniket
Published: March 2020

Drought quantification is carried out by indicators like (1) Standardized Precipitation Index (SPI) and (2) Standardized Precipitation Evapotranspiration Index (SPEI), which encompass the historical characteristics of meteorological variants (precipitation and temperature). The behavioral pattern of these variables has changed significantly due to the recent changes in the climate, posing a question of the mutual agreement among SPI and SPEI in defining drought over regions with different climatic characteristics. India is chosen as the study area owing to the long term data availability, diverse climatic zones (from tropical monsoon belts to dry arid regions), and increasing drought likelihood in the mainland area. Daily, gridded precipitation (0.25º × 0.25º) and temperature (1º × 1º) data, from January 1951 to December 2013, was utilized for the calculation of SPI and SPEI. While the average annual precipitation in India is consistently declining, the yearly average temperature exhibits three distinct trends (decreasing from 1951 to 1975, neutral from 1975 to 1990, increasing abruptly from 1990 onwards). Such variations in the trend behavior are replicated in the increasing divergence of the two indices, represented as percentage area under drought. A robust regional divergence between the indices is detected from east to west, highlighting the arid and semi-arid regions as hotspots of significant deviations.  SPEI showcases an overall increasing drought hazard in India since the 1970s in terms of frequency, magnitude, and duration, when compared to SPI.
Simple catchments and where to find them: The storage discharge relationship as a proxy for catchment complexity
Authors: Jehn Florian Ulrich , Breuer Lutz , Kraft Philipp , Bestian Konrad , Houska Tobias
Published: March 2020

Hydrology and especially hydrological models often treat catchments as if they were leaky buckets. But, do we find such catchments in the real world or is this just a convenient simplification? Moreover, if we find them, what attributes allow these catchments to show such a simple behavior? To study this, we look at time series of 27 years for 90 catchments in Hesse, Germany, which includes droughts and years of abundant precipitation. In addition, the state Hesse provides a wide range of catchment attributes like geology, soils and land use, while still having a relatively similar climate. Using discharge, evapotranspiration and precipitation, we calculate the cumulative storage change for all years separately and use it as a proxy for the storage. We group the 90 catchments by the complexity of their storage-discharge relationship, which we define as how good the relationship can be modelled by an exponential function. We find that climate and physical attributes of the catchments seem to have similar influence on the overall complexity of the storage-discharge relationship. However, we could also identify catchments that depict consistent behavior, mostly independent of climate. Those catchments either behave always complex or always simple in all the years considered. They differ in their permeability, conductivity, geology, soil and to a lesser extent their shape. We show that bucket like catchments exist in the real world and that they can be found by looking for oval catchments with good permeability in regions of igneous geology and clay silt soil texture.
Mechanism of Phase Inversion in Arctic Stratiform Clouds
Authors: Liu Pei-Hsin , Chen Jen-Ping , Dong Xiquan , Lin Yi-Chiu
Published: March 2020

Arctic stratiform clouds (ASC) often exhibit phase inversion structure (i.e., liquid top and mixed- or ice-phase below) and can persist for a very long time. According to past studies, the phase inversion structure is the result of persistent liquid cloud generation aloft and gravitational ice precipitation; however, observation reveals that the largest cloud reflectivity appears in the middle of the cloud, implying that the gravitational ice precipitation cannot fully explain the mechanism of phase inversion structure. Also, the role of ice nucleation in ASC is not fully addressed before. Ice nucleation processes are affected by temperature, ice nuclei (IN) species and number concentration. As the result, strong inversion or strong vertical gradient of IN number concentration may favor ice nucleation to occur in the lower levels and result in phase inversion.

This study aims to find out the mechanism of phase inversion and the dominant ice nucleation processes in ASC. Weather Research and Forecasting (WRF) model with detailed ice nucleation mechanisms is applied. The ice nucleation scheme used in the model takes different ice nucleation processes and IN species into account. Dust and soot, taken from MERRA-2, are the two main IN considered in this study and are fitted into lognormal distributions for providing the initial and boundary conditions. The 2008 Mar 04-05 case, chosen from the Atmospheric Radiation Measurement (ARM) program, is simulated. From observation, ASC and the phase inversion structure persisted for half a day. Temperature decreases with height in cloud, indicating that temperature inversion is not the mechanism of phase inversion in this case. More dust in the lower levels is seen from the model simulation results. In this case, strong vertical gradient of IN number concentration serves as the main mechanism of phase inversion, suggesting that ice nucleation process plays an important role in ASC. The role of soot particles will also be addressed.
Melt inclusions in metamorphic rocks: how localized melting promoted the formation of the Gore Mountains mega garnets (Adirondacks, US)
Authors: Ferrero Silvio , Wannhoff Iris , Darling Robert , Wunder Bernd , Oscar Laurent , O' Brien Patrick J. , Ziemann Martin A. , Günter Christina
Published: March 2020

Melt inclusions have been for almost 150 years an exclusive feature of magmatic rocks. However, intensive research activity in the last decade has shown that melt inclusions, or nanogranitoids, are also a widespread feature of high grade metamorphic rocks. Such inclusions rapidly became fundamental tools to unravel partial melting and melt-related processes taking place during orogenesis.

One of the latest discoveries in this field has been the identification of nanogranitoids and glass inside the mega almandine-pyrope garnets of Barton Mine (Gore Mountain, NY State, US). These crystals are arguably the world’s largest garnets and occur within garnet hornblendite. Their size is ca. 35 cm in average, while garnet diameters up to 1 m were reported in historical record. Fluid is often invoked in the formation of large crystals, but so far no study has identified clear witnesses for the presence of fluid during garnet formation, e.g. primary fluid inclusions.

Polycrystalline inclusions of primary nature were instead reported by Darling et al. (1997) to occur inside the garnet: such inclusions are the main target of our study. Their shape ranges from tubular (2-100 µm in length) to negative crystal shape (2-50 µm). They mainly contain cristobalite/quartz, kumdykolite and amphibole. Minor phases such as biotite/phlogopite, enstatite, rutile, ilmenite and a second, Ca-richer plagioclase (or its rare polymorphs dmisteinbergite and svyatoslavite) may be also present. The inclusions were re-homogenized to a silicate-rich glass via piston cylinder experiments at 1.0-1.5 GPa and 925-940°C. Experimental results prove that such inclusions are former droplets of melt, in agreement with the finding of preserved residual glass in one single inclusion before the experimental runs. The melt composition measured in situ via electron microprobe is tonalitic-trondhjemitic with 5-6 wt% H2O.

The identification of melt inclusions points toward a melt rather than a fluid as the medium which favored extreme garnet growth under low nucleation rate conditions. The elements necessary to grow garnets – mainly Fe, Al, Si, Mg- are indeed far more effectively transported by a silicate melt rather than simple aqueous fluid, at least at the limited depth envisioned for this process. In conclusion, the finding of melt inclusions in metamorphic rocks brought us forward along the path toward the solution of the enigma represented by the formation of these giant garnets.

References
Darling, R.S., Chou, I.M., Bodnar, R.J., 1997. An Occurrence of Metastable Cristobalite in High-Pressure Garnet Granulite. Science 276, 91.
Coastal flooding in the Balearic Islands during the 21st century caused by sea level rise and extreme events
Authors: Luque Lozano Pau , Gómez-Pujol Lluís , Marcos Marta , Orfila Alejandro
Published: March 2020

Sea-level rise induces a permanent loss of land with widespread ecological and economic impacts, most evident in urban and densely populated areas. The eventual coastline retreat combined with the action of waves and storm surges will end in more severe damages over coastal areas. These effects are expected to be particularly significant over islands, where coastal zones represent a relatively larger area vulnerable to marine hazards.

Managing coastal flood risk at regional scales requires a prioritization of resources and socioeconomic activities along the coast. Stakeholders, such as regional authorities, coastal managers and private companies, need tools that help to address the evaluation of coastal risks and criteria to support decision-makers to clarify priorities and critical sites. For this reason, the regional Government of the Balearic Islands (Spain) in association with the Spanish Ministry of Agriculture, Fisheries and Environment has launched the Plan for Climate Change Coastal Adaptation. This framework integrates two levels of analysis. The first one relates with the identification of critical areas affected by coastal flooding and erosion under mean sea-level rise scenarios and the quantification of the extent of flooding, including marine extreme events. The second level assesses the impacts on infrastructures and assets from a socioeconomic perspective due to these hazards.

In this context, this paper quantifies the effects of sea-level rise and marine extreme events caused by storm surges and waves along the coasts of the Balearic Islands (Western Mediterranean Sea) in terms of coastal flooding and potential erosion. Given the regional scale (~1500 km) of this study, the presented methodology adopts a compromise between accuracy, physical representativity and computational costs. We map the projected flooded coastal areas under two mean sea-level rise climate change scenarios, RCP4.5 and RCP8.5. To do so, we apply a corrected bathtub algorithm. Additionally, we compute the impact of extreme storm surges and waves using two 35-year hindcasts consistently forced by mean sea level pressure and surface winds from ERA-Interim reanalysis. Waves have been further propagated towards the nearshore to compute wave setup with higher accuracy. The 100-year return levels of joint storm surges and waves are used to map the spatial extent of flooding in more than 200 sandy beaches around the Balearic Islands by mid and late 21st century, using the hydrodynamical LISFLOOD-FP model and a high resolution (2 m) Digital Elevation Model.
Development of a versatile portable MAX-DOAS instrument
Authors: Kausch Wolfgang , Kimeswenger Stefan , Przybilla Norbert , Noll Stefan
Published: March 2020

Multi-AXis Differential Optical Absorption Spectroscopy has become a versatile and mature measurement technique for determining various components of the Earth’s atmosphere, e.g. O3, SO2, NO2 properties. Since the concentration of these trace gases might strongly vary locally and in time, easy in-situ measurements with a mobile device are highly desirable.

We are currently developing a portable MAX-DOAS instrument setup consisting of three small telescopes with a diameter of 50mm. Each of these telescopes is equipped with an individual fiber-fed low-resolution spectrograph (Stellarnet Blue Wave devices, 2048 pixel CCD) to enable simultaneous measurements ranging from 300 to 1000nm in one shot. The entire wavelength range is therefore covered by three spectral arms: (a) The UV arm, equipped with a Stellarnet BLUE-Wave UV2 spectrograph ranging from 300 to 500nm; (b) the VIS arm consisting of a NIR4 device (500…700nm), and (c) The NIR arm, based on a Stellarnet NIR2 ranging from 600 to 1000nm. All spectrographs are fed with wavelength-optimised fibers and equipped with the smallest possible slit (14 µm slit width) to maximise the throughput and the spectral resolving power (λ-dispersion UVB + VIS: 0.2nm; NIR: 0.4nm).

The three telescopes are aligned in parallel and installed on a small astronomical azimuthal mount (Skywatcher AZ-EQ5, powered by a mobile 12V Lithium-Polymer battery) to enable measurements in all directions. The mount control software will be based either on the ASCOM or the INDILIB platform. For the control of the spectrographs we use the programme SpectraWiz (by Stellarnet). As DOAS analysis software we have chosen QDOAS, provided by the Royal Belgian Institute for Space Aeronomy. All software is freely available and is installed on a Dell Latitude 5450 Rugged laptop, which is optimised for outdoor applications.

The chosen setup enables a mobile usage easily transportable by a small car. Since the development is currently ongoing, especially with respect to the automation of the measurements and the data processing, we report on the status of the project in this presentation.