scholarly journals Different drought types and the spatial variability in their hazard, impact, and propagation characteristics

2021 ◽  
Author(s):  
Erik Tijdeman ◽  
Veit Blauhut ◽  
Michael Stoelzle ◽  
Lucas Menzel ◽  
Kerstin Stahl
Keyword(s):  
Spatial Variability ◽  
Large Scale ◽  
Hydrological Cycle ◽  
Spatial Scales ◽  
Time Lag ◽  
Severe Drought ◽  
Drought Management ◽  
Propagation Characteristics ◽  
Drought Impacts ◽  
Drought Hazard

Abstract. Droughts often have a severe impact on environment, society, and economy. Only a multifaceted assessment of such droughts and their impacts can provide insights in the variables and scales that are relevant for drought management. Motivated by this aim, we compared hazard and propagation characteristics as well as impacts of major droughts between 1990–2019 in Southwestern Germany. We bring together high-resolution datasets of air temperature, precipitation, soil moisture simulations, streamflow and groundwater level observations, as well as text-based information on drought impacts. Various drought characteristics were derived from the hydrometeorological and drought impact time series and compared across variables and spatial scales. Results revealed different drought types sharing similar hazard and impact characteristics. The most severe drought type identified is an intense multi-seasonal drought type peaking in summer, i.e. the events in 2003, 2015 and 2018. This drought type appeared in all domains of the hydrological cycle and coincided with high air temperatures, causing a high number and variability of drought impacts. The regional average drought signals of this drought type exhibit typical drought propagation characteristics such as a time lag between meteorological and hydrological drought, whereas propagation characteristics of local drought signals are variable in space. This spatial variability in drought hazard increased when droughts propagated through the hydrological cycle, causing distinct differences among variables, and regional average and local drought information. Accordingly, single variable or regional average drought information is considered to be not sufficient to fully explain the variety of drought impacts that occurred. In addition to large-scale drought monitoring, drought management needs to consider local drought information from different hydrometeorological variables and could be type based.

scholarly journals Sampling density and date influence spatial representation of tree ring reconstructions

2020 ◽  
Author(s):  
Justin T. Maxwell ◽  
Grant L. Harley ◽  
Trevis J. Matheus ◽  
Brandon M. Strange ◽  
Kayla Van Aken ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Spatial Variability ◽  
Tree Ring ◽  
Tree Rings ◽  
Large Scale ◽  
The United States ◽  
Severe Drought ◽  
Ring Network ◽  
Tree Ring Data ◽  
The Us

Abstract. Our understanding of the natural variability of hydroclimate before the instrumental period (ca. 1900 in the United States; US) is largely dependent on tree-ring-based reconstructions. Large-scale soil moisture reconstructions from a network of tree-ring chronologies have greatly improved our understanding of the spatial and temporal variability in hydroclimate conditions, particularly extremes of both drought and pluvial (wet) events. However, certain regions within these large-scale reconstructions in the US have a sparse network of tree-ring chronologies. Further, several chronologies were collected in the 1980s and 1990s, thus our understanding of the sensitivity of radial growth to soil moisture in the US is based on a period that experienced multiple extremely severe droughts and neglects the impacts of recent, rapid global change. In this study, we expanded the tree-ring network of the Ohio River Valley in the US, a region with sparse coverage. We used a total of 72 chronologies across 15 species to examine how increasing the density of the tree-ring network influences the representation of reconstructing the Palmer Meteorological Drought Index (PMDI). Further, we tested how the sampling date influenced the reconstruction models by creating reconstructions that ended in the year 1980 and compared them to reconstructions ending in 2010 from the same chronologies. We found that increasing the density of the tree-ring network resulted in reconstructed values that better matched the spatial variability of instrumentally recorded droughts and to a lesser extent, pluvials. By sampling tree in 2010 compared to 1980, the sensitivity of tree rings to PMDI decreased in the southern portion of our region where severe drought conditions have been absent over recent decades. We emphasize the need of building a high-density tree-ring network to better represent the spatial variability of past droughts and pluvials. Further, chronologies on the International Tree-Ring Data Bank need updating regularly to better understand how the sensitivity of tree rings to climate may vary through time.

scholarly journals Introducing the “VALOR” analysis framework for auroral field-aligned current sheets using observations from Swarm Alpha and Charlie

2021 ◽  
Author(s):  
Leonie Pick ◽  
Joachim Vogt ◽  
Adrian Blagau ◽  
Nele Stachlys
Keyword(s):  
Magnetic Field ◽  
Linear Correlation ◽  
Large Scale ◽  
Spatial Scales ◽  
Time Lag ◽  
Field Vector ◽  
Auroral Oval ◽  
Association Measure ◽  
Field Aligned Current ◽  
Scale Estimate

<p>The investigation of auroral field-aligned current (FAC) sheets is crucial in the context of space weather research since they serve as main transmitters of energy and momentum across geospace domains. Different magnetosphere-ionosphere coupling modes are reflected by the FACs’ multiscale nature with spatial scales, i.e., latitudinal extensions, ranging from below 1 km to hundreds of kilometers. The multiscale property can be addressed conveniently using ESA’s three-spacecraft mission Swarm. According to common practice a linear correlation analysis is performed on lagged and band-pass filtered scalar FAC density estimates from two nearby spacecraft.</p><p>We introduce the framework VALOR (Vectorial Association of Linearly Oriented Residua) which generalizes the common approach in two ways. First, VALOR utilizes the full magnetic field vector primarily observed at both spacecraft without filtering. Second, VALOR allows to test statistical association measures other than linear correlation in dependence of both time and along-track spacecraft lag. The method is further refined by considering the current sheet’s polarization, i.e., the directional preference of the associated magnetic field perturbation, which additionally constrains the sheet’s orientation.</p><p>Here, we apply VALOR to 1 Hz magnetic field observations from Swarm Alpha and Charlie and base the association measure on a vectorial version of the mean squared deviation. By means of a sample auroral oval crossing event we demonstrate that the incorporation of vectorial and polarization information helps to focus the association measure in the time-lag parameter plane leading to a smaller FAC spatial scale estimate. This result seems to hold in a statistical context including over 9000 quasi-perpendicular auroral oval crossings from 2014 to 2020. The fact that the VALOR derived FAC locations reflect the known ellipsoidal shapes of the auroral ovals speaks to the overall plausibility of the method as well as the independently supported finding that large-scale FACs (>300 km) dominate the dawn and dusk sectors while smaller scale FACs gain importance at noon and midnight. Among the various opportunities for future work are an application to 50 Hz high-resolution Swarm data as well as the investigation of the solar controlling parameters.</p>

scholarly journals A Remote Sensing Survey of the Role of Landform on the Organization of Orographic Precipitation in Central and Southern Mexico

2008 ◽  
Vol 9 (6) ◽  
pp. 1267-1283 ◽  
Author(s):  
Jason P. Giovannettone ◽  
Ana P. Barros
Keyword(s):  
Spatial Variability ◽  
Large Scale ◽  
Spatial Scales ◽  
Coastal Region ◽  
La Niña ◽  
Southern Mexico ◽  
La Nina ◽  
Basin Scale ◽  
Sierra Madre ◽  
Average Rainfall

Abstract Data from NASA’s TRMM satellite and NOAA’s GOES satellites were used to survey the orographic organization of cloud precipitation in central and southern Mexico during the monsoon with two main objectives: 1) to investigate large-scale forcing versus local landform controls, and 2) to compare the results with previous work in the Himalayas. At large scales, the modes of spatial variability of cloudiness were estimated using the empirical orthogonal function (EOF) analysis of GOES brightness temperatures. Terrain modulation of synoptic-scale high-frequency variability (3–5- and 6–9-day cycles normally associated with the propagation of easterly waves) was found to cause higher dispersion in the EOF spectrum, with the first mode explaining less than 30% of the spatial variability in central and southern Mexico as opposed to 50% and higher in the Himalayas. A detailed analysis of the first three EOFs for 1999, an average La Niña year with above average rainfall, and for 2001, a weak La Niña year with below average rainfall, shows that landform (mountain peaks and land–ocean contrast) and large-scale circulation (moisture convergence) alternate as the key controls of regional hydrometeorology in dry and wet years, or as active and break (midsummer drought) phases of the monsoon, respectively. The diurnal cycle is the dominant time scale of variability in 2001, as it is during the midsummer drought in all years. Strong variability at time scales beyond two weeks is only present during the active phases of the monsoon. At the river basin scale, the data show increased cloudiness over the mountain ranges during the afternoon, which moves over the low-lying regions at the foot of the major orographic barriers [the Sierra Madre Occidental (SMO)/Sierra Madre del Sur (SMS) and Trans-Mexican Volcanic Belt (TMVB)], specifically the Balsas and the Rio de Santiago basins at nighttime and in the early morning. At the ridge–valley scale (∼100–200 km), robust day–night (ridge–valley) asymmetries suggest strong local controls on cloud and precipitation, with convective activity along the coastal region of the SMO and topographically forced convection at the foothills of headwater ridges in the Altiplano and the SMS. These day–night spatial shifts in cloudiness and precipitation are similar to those found in the Himalayas at the same spatial scales.

scholarly journals Parameterization of the Spatial Variability of Rain for Large-Scale Models and Remote Sensing

2015 ◽  
Vol 54 (10) ◽  
pp. 2027-2046 ◽  
Author(s):  
Z. J. Lebo ◽  
C. R. Williams ◽  
G. Feingold ◽  
V. E. Larson
Keyword(s):  
Spatial Variability ◽  
Large Scale ◽  
Rain Rate ◽  
Numerical Models ◽  
Spatial Scales ◽  
Warm Pool ◽  
Radar Data ◽  
Model Output ◽  
Wide Range ◽  
Averaged Model

AbstractThe spatial variability of rain rate R is evaluated by using both radar observations and cloud-resolving model output, focusing on the Tropical Warm Pool–International Cloud Experiment (TWP-ICE) period. In general, the model-predicted rain-rate probability distributions agree well with those estimated from the radar data across a wide range of spatial scales. The spatial variability in R, which is defined according to the standard deviation of R (for R greater than a predefined threshold Rmin) σ(R), is found to vary according to both the average of R over a given footprint μ(R) and the footprint size or averaging scale Δ. There is good agreement between area-averaged model output and radar data at a height of 2.5 km. The model output at the surface is used to construct a scale-dependent parameterization of σ(R) as a function of μ(R) and Δ that can be readily implemented into large-scale numerical models. The variability in both the rainwater mixing ratio qr and R as a function of height is also explored. From the statistical analysis, a scale- and height-dependent formulation for the spatial variability of both qr and R is provided for the analyzed tropical scenario. Last, it is shown how this parameterization can be used to assist in constraining parameters that are often used to describe the surface rain-rate distribution.

What it takes to increase Europe’s resilience to drought – Insights from a pan European survey on recent drought perception, impacts and management

2021 ◽  
Author(s):  
Veit Blauhut ◽  
Michael Stoelzle ◽  
Lauri Ahopelto ◽  
Manuela Brunner ◽  
Doris Wendt ◽  
...  
Keyword(s):  
Water Management ◽  
Management Strategies ◽  
Drought Management ◽  
National Scale ◽  
Current Management ◽  
European Survey ◽  
Drought Impacts ◽  
Drought Hazard ◽  
Effects Of Drought ◽  
The Relationship

<p>In recent years, drought impacts have been more severe and frequent than past impacts throughout Europe. Due to the heterogeneity of Europe’s hydro- climatological situation as well as the multiple nations on the continent, drought events and their impacts vary with respect to location, sector, extent, duration and scale. In order to understand recent effects of drought and their possible drivers, national representatives distributed a uniform questionnaire to water management stakeholders of 28 contributing countries. Here, we focus on obtaining information on stakeholders’ drought perception,impacts, and current management strategies on a national and sub-national scale. With the survey, we analyse how strong the relationship between perceptions and actual hazard information is. Actual drought hazard information from the European Drought Observatory for the years 2018 and 2019 is compared with the questionnaire’s results. The results of the study highlight the diversity among national drought perceptions and the value of  already existing drought management strategies. An absence of coordinated drought management is mostly attributed to a lack of resources and macro- governmental guidance. Supported by the national perspectives, possible macro-governmental pathways to increase national and sub-national awareness and resilience are discussed. The results support the need for national  drought policies, which could be pushed forward with international drought management directives.</p>

Suborbital Measurements of Spectral Aerosol Optical Depth and Its Variability at Subsatellite Grid Scales in Support of CLAMS 2001

2005 ◽  
Vol 62 (4) ◽  
pp. 993-1007 ◽  
Author(s):  
J. Redemann ◽  
B. Schmid ◽  
J. A. Eilers ◽  
R. Kahn ◽  
R. C. Levy ◽  
...  
Keyword(s):  
Spatial Variability ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Large Scale ◽  
Spatial Scales ◽  
The United States ◽  
Horizontal Distance ◽  
Airborne Measurements ◽  
Low Level ◽  
Modis Aod

Abstract As part of the Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) experiment, 10 July–2 August 2001, off the central East Coast of the United States, the 14-channel NASA Ames Airborne Tracking Sunphotometer (AATS-14) was operated aboard the University of Washington’s Convair 580 (CV-580) research aircraft during 10 flights (∼45 flight hours). One of the main research goals in CLAMS was the validation of satellite-based retrievals of aerosol properties. The goal of this study in particular was to perform true over-ocean validations (rather than over-ocean validation with ground-based, coastal sites) at finer spatial scales and extending to longer wavelengths than those considered in previous studies. Comparisons of aerosol optical depth (AOD) between the Aerosol Robotic Network (AERONET) Cimel instrument at the Chesapeake Lighthouse and airborne measurements by AATS-14 in its vicinity showed good agreement with the largest r-square correlation coefficients at wavelengths of 0.38 and 0.5 μm (>0.99). Coordinated low-level flight tracks of the CV-580 during Terra overpass times permitted validation of over-ocean Moderate Resolution Imaging Spectroradiometer (MODIS) level 2 (MOD04_L2) multiwavelength AOD data (10 km × 10 km, nadir) in 16 cases on three separate days. While the correlation between AATS-14- and MODIS-derived AOD was weak with an r square of 0.55, almost 75% of all MODIS AOD measurements fell within the prelaunch estimated uncertainty range Δτ = ±0.03 ± 0.05τ. This weak correlation may be due to the small AODs (generally less than 0.1 at 0.5 μm) encountered in these comparison cases. An analogous coordination exercise resulted in seven coincident over-ocean matchups between AATS-14 and Multiangle Imaging Spectroradiometer (MISR) measurements. The comparison between AATS-14 and the MISR standard algorithm regional mean AODs showed a stronger correlation with an r square of 0.94. However, MISR AODs were systematically larger than the corresponding AATS values, with an rms difference of ∼0.06. AATS data collected during nine extended low-level CV-580 flight tracks were used to assess the spatial variability in AOD at horizontal scales up to 100 km. At UV and midvisible wavelengths, the largest absolute gradients in AOD were 0.1–0.2 per 50-km horizontal distance. In the near-IR, analogous gradients rarely reached 0.05. On any given day, the relative gradients in AOD were remarkably similar for all wavelengths, with maximum values of 70% (50 km)−1 and more typical values of 25% (50 km)−1. The implications of these unique measurements of AOD spatial variability for common validation practices of satellite data products and for comparisons to large-scale aerosol models are discussed.

scholarly journals Moving from drought hazard to impact forecasts

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Samuel J. Sutanto ◽  
Melati van der Weert ◽  
Niko Wanders ◽  
Veit Blauhut ◽  
Henny A. J. Van Lanen
Keyword(s):  
River Flow ◽  
Meteorological Drought ◽  
Early Warning Systems ◽  
Drought Indices ◽  
Warning Systems ◽  
Drought Management ◽  
Drought Impact ◽  
Drought Impacts ◽  
Drought Hazard ◽  
Drought Early Warning

Abstract Present-day drought early warning systems provide the end-users information on the ongoing and forecasted drought hazard (e.g. river flow deficit). However, information on the forecasted drought impacts, which is a prerequisite for drought management, is still missing. Here we present the first study assessing the feasibility of forecasting drought impacts, using machine-learning to relate forecasted hydro-meteorological drought indices to reported drought impacts. Results show that models, which were built with more than 50 months of reported drought impacts, are able to forecast drought impacts a few months ahead. This study highlights the importance of drought impact databases for developing drought impact functions. Our findings recommend that institutions that provide operational drought early warnings should not only forecast drought hazard, but also impacts after developing an impact database.

Estimating spatial variability in developing assemblages of epibiota on subtidal hard substrata

1998 ◽  
Vol 49 (5) ◽  
pp. 429 ◽  
Author(s):  
T. M. Glasby
Keyword(s):  
Environmental Impact ◽  
Spatial Variability ◽  
Large Scale ◽  
Sampling Design ◽  
Spatial Scales ◽  
Rocky Reefs ◽  
Natural Substratum ◽  
Spatial Replication ◽  
Supporting Structures ◽  
Hard Substrata

A nested hierarchical sampling design was used to estimate the scales of natural variability in developing assemblages of subtidal epibiota on rocky reefs. The appropriate spatial scales were needed for sampling to test for environmental impact in this habitat. Sandstone settlement plates were used to mimic the natural substratum. They were designed and deployed in such a way that the effects of any supporting structures were minimized. Differences in recruitment of epibiota were found at all of the spatial scales examined (10s, 100s and 1000s of metres). When differences were found at the smallest spatial scale, they were generally still detected at the two larger scales. The results highlighted the need for adequate small- and large-scale spatial replication for studies of environmental impact.

Improved representation of forest snow processes in coarse-resolution models: lessons learnt from upscaling hyper-resolution simulations

2021 ◽  
Author(s):  
Giulia Mazzotti ◽  
Clare Webster ◽  
Richard Essery ◽  
Johanna Malle ◽  
Tobias Jonas
Keyword(s):  
Spatial Variability ◽  
Snow Cover ◽  
Large Scale ◽  
Snow Water Equivalent ◽  
Spatial Scales ◽  
Canopy Structure ◽  
Coarse Resolution ◽  
Wide Range ◽  
Snow Model ◽  
High Level

<p>Forest snow cover dynamics affect hydrological regimes, ecosystem processes, and climate feedbacks, and thus need to be captured by model applications that operate across a wide range of spatial scales. At large scales and coarse model resolutions, high spatial variability of the processes shaping forest snow cover evolution creates a major modelling challenge. Variability of canopy-snow interactions is determined by heterogeneous canopy structure and can only be explicitly resolved with hyper-resolution models (<5m).</p><p>Here, we address this challenge with model upscaling experiments with the forest snow model FSM2, using hyper-resolution simulations as intermediary between experimental data and coarse-resolution simulations. When run at 2-m resolution, FSM2 is shown to capture the spatial variability of forest snow dynamics with a high level of detail: Its accurate performance is verified at the level of individual energy balance components based on extensive, spatially distributed sub-canopy measurements of micrometeorological and snow variables, obtained with mobile multi-sensor platforms. Results from hyper-resolution simulations over a 150,000 m<sup>2</sup> domain are then compared to spatially lumped, coarse-resolution runs, where 50m x 50m grid cells are represented by one model run only. For the spatially lumped simulations, we evaluate alternative upscaling strategies, aiming to explore the representation of forest snow processes at model resolutions coarser than the spatial scales at which these processes vary and interact.</p><p>Different upscaling strategies exhibited large discrepancies in simulated (1) distribution of snow water equivalent at peak of winter, and (2) timing of snow disappearance. Our results indicate that detailed canopy structure metrics, as included in hyper-resolution runs, are necessary to capture the spatial variability of forest snow processes even at coarser resolutions. They further demonstrate the relevance of accounting for unresolved sub-grid variability in snowmelt calculations even at relatively small spatial aggregation scales. By identifying important model features, which allow coarse-resolution simulations to approximate spatially averaged results of corresponding hyper-resolution simulations, this work provides recommendations for modelling forest snow processes in medium- to large-scale applications.</p>

scholarly journals Lessons from the 2018–2019 European droughts: A collective need for unifying drought risk management

2021 ◽  
Author(s):  
Veit Blauhut ◽  
Michael Stoelzle ◽  
Lauri Ahopelto ◽  
Manuela I. Brunner ◽  
Claudia Teutschbein ◽  
...  
Keyword(s):  
Management Strategies ◽  
Drought Risk ◽  
Drought Management ◽  
Drought Impacts ◽  
Drought Hazard ◽  
Survey Results ◽  
The Relationship ◽  
Hydrologic Conditions ◽  
Drought Risk Management ◽  
High Diversity

Abstract. Drought events and their impacts vary spatially and temporally due to diverse pedo-climatic and hydrologic conditions, as well as variations in exposure and vulnerability, such as demographics and response actions. While hazardous severity and frequency of past drought events have been studied in detail, little is known about the effect of drought management strategies on the actual impacts, and how the hazard is perceived by relevant stakeholders for inducing action. In a continental study, we characterised and assessed the impacts and the perceptions of two recent drought events (2018 and 2019) in Europe and examined the relationship between management strategies and drought perception, hazard and impacts. The study was based on a pan-European survey involving national representatives from 28 countries and relevant stakeholders responding to a standard questionnaire. The survey focused on collecting information on stakeholders’ perceptions of drought, impacts on water resources and beyond, water availability and current drought management strategies at national and regional scales. The survey results were compared with the actual drought hazard information registered by the European Drought Observatory (EDO) for 2018 and 2019. The results highlighted high diversity in drought perceptions across different countries and in values of implemented drought management strategies to alleviate impacts by increasing national and sub-national awareness and resilience. The study concludes with an urgent need to further reduce drought impacts by constructing and implementing a European macro-level drought governance approach, such as a directive, which would strengthen national drought management and lessen harm to human and natural potentials.

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