scholarly journals Future discharge drought across climate regions around the world modelled with a synthetic hydrological modelling approach forced by three general circulation models

2015 ◽  
Vol 15 (3) ◽  
pp. 487-504 ◽  
Author(s):  
N. Wanders ◽  
H. A. J. Van Lanen
Keyword(s):  
General Circulation ◽  
Reference Model ◽  
Control Period ◽  
General Circulation Models ◽  
Hydrological Drought ◽  
Drought Duration ◽  
Data Set ◽  
Drought Characteristics ◽  
The World ◽  
Drought Occurrence

Abstract. Hydrological drought characteristics (drought in groundwater and streamflow) likely will change in the 21st century as a result of climate change. The magnitude and directionality of these changes and their dependency on climatology and catchment characteristics, however, is uncertain. In this study a conceptual hydrological model was forced by downscaled and bias-corrected outcome from three general circulation models for the SRES A2 emission scenario (GCM forced models), and the WATCH Forcing Data set (reference model). The threshold level method was applied to investigate drought occurrence, duration and severity. Results for the control period (1971–2000) show that the drought characteristics of each GCM forced model reasonably agree with the reference model for most of the climate types, suggesting that the climate models' results after post-processing produce realistic outcomes for global drought analyses. For the near future (2021–2050) and far future (2071–2100) the GCM forced models show a decrease in drought occurrence for all major climates around the world and increase of both average drought duration and deficit volume of the remaining drought events. The largest decrease in hydrological drought occurrence is expected in cold (D) climates where global warming results in a decreased length of the snow season and an increased precipitation. In the dry (B) climates the smallest decrease in drought occurrence is expected to occur, which probably will lead to even more severe water scarcity. However, in the extreme climate regions (desert and polar), the drought analysis for the control period showed that projections of hydrological drought characteristics are most uncertain. On a global scale the increase in hydrological drought duration and severity in multiple regions will lead to a higher impact of drought events, which should motivate water resource managers to timely anticipate the increased risk of more severe drought in groundwater and streamflow and to design pro-active measures.

scholarly journals Future discharge drought across climate regions around the world modelled with a synthetic hydrological modelling approach forced by three General Circulation Models

2013 ◽  
Vol 1 (6) ◽  
pp. 7701-7738 ◽  
Author(s):  
N. Wanders ◽  
H. A. J. van Lanen
Keyword(s):  
General Circulation ◽  
Reference Model ◽  
Control Period ◽  
General Circulation Models ◽  
Hydrological Drought ◽  
Severe Drought ◽  
Drought Duration ◽  
Increased Risk ◽  
The World ◽  
Drought Occurrence

Abstract. Hydrological droughts characteristics (drought in groundwater and streamflow) likely will change in the 21st century as a results of climate change. Magnitude and directionality of these changes and their dependency on climatology and catchment characteristics, however, is largely unknown. In this study a conceptual hydrological model was forced by downscaled and bias-corrected outcome from three General Circulation Models for the A2 emission scenario (GCM forced models), and the WATCH Forcing Data re-analysis dataset(reference model). The threshold level method was applied to investigate drought occurrence, duration and deficit volume. Results for the control period (1971–2000) show that the drought characteristics of each GCM forced model reasonably agree with the reference model for most of the climate types, suggesting that the climate model's results after post-processing produce realistic outcome for global drought analyses. For the near future (2021–2050) and far future (2071–2100) the GCM forced models show a decrease in drought occurrence for all major climates around the world and increase of both average drought duration and deficit volume of the remaining drought events. The largest decrease in hydrological drought occurrence is expected in cold (D-)climates where global warming results in a decreased length of the snow season and an increased precipitation. In the dry B-climates the smallest decrease in drought occurrence is expected to occur, which probably will lead to even more severe water scarcity. However, in the extreme climate regions (desert and polar), the analysis for the control period showed that projections are in these regions most uncertain. On a global scale the increase in hydrological drought duration and severity will lead to a higher impact of drought events, which urges water resources managers to timely anticipate on the increased risk on more severe drought in groundwater and streamflow and to design pro-active measures.

scholarly journals Uncertainties in runoff projection and hydrological drought assessment over Gharesu basin under CMIP5 RCP scenarios

2020 ◽  
Vol 11 (S1) ◽  
pp. 145-163 ◽  
Author(s):  
S. M. Ashrafi ◽  
H. Gholami ◽  
M. R. Najafi
Keyword(s):  
River Basin ◽  
General Circulation ◽  
General Circulation Models ◽  
Hydrological Drought ◽  
Drought Severity ◽  
Historical Period ◽  
Drought Duration ◽  
Rcp Scenarios ◽  
Drought Assessment ◽  
Drought Characteristics

Abstract Hydrological drought plays an important role in planning and managing water resources systems to meet increasing water demands due to population growth. In this study, the effects of climate change on the hydrological drought characteristics of the Gharasu basin, as one of the major sub-basins of the Karkheh river basin, are investigated. This river basin has experienced severe droughts, and floods, in recent years. The uncertainties in projected drought conditions are characterized based on a suite of 34 general circulation models (GCMs). Based on hydrological simulations over the historical period, 12 GCMs are selected to estimate projected runoff values and the corresponding streamflow drought index (SDI) in the future period. The ‘run theory’ is applied to evaluate the drought characteristics under Representative Concentration Pathways (RCPs) 4.5 and 8.5 emission scenarios. Results show that uncertainties of drought projection under RCP8.5 are higher than under RCP4.5, where among different drought characteristics, the maximum uncertainty is detected for drought severity and maximum drought duration. Moreover, the uncertainty of drought projection in wet periods is greater than that in dry periods.

scholarly journals Hydrological drought across the world: impact of climate and physical catchment structure

2013 ◽  
Vol 17 (5) ◽  
pp. 1715-1732 ◽  
Author(s):  
H. A. J. Van Lanen ◽  
N. Wanders ◽  
L. M. Tallaksen ◽  
A. F. Van Loon
Keyword(s):  
Large Scale ◽  
Hydrological Drought ◽  
Temperate Climate ◽  
Minor Effect ◽  
Hydrological Models ◽  
Drought Duration ◽  
Groundwater System ◽  
Drought Characteristics ◽  
The World ◽  
Groundwater Systems

Abstract. Large-scale hydrological drought studies have demonstrated spatial and temporal patterns in observed trends, and considerable difference exists among global hydrological models in their ability to reproduce these patterns. In this study a controlled modeling experiment has been set up to systematically explore the role of climate and physical catchment structure (soils and groundwater systems) to better understand underlying drought-generating mechanisms. Daily climate data (1958–2001) of 1495 grid cells across the world were selected that represent Köppen–Geiger major climate types. These data were fed into a conceptual hydrological model. Nine realizations of physical catchment structure were defined for each grid cell, i.e., three soils with different soil moisture supply capacity and three groundwater systems (quickly, intermediately and slowly responding). Hydrological drought characteristics (number, duration and standardized deficit volume) were identified from time series of daily discharge. Summary statistics showed that the equatorial and temperate climate types (A- and C-climates) had about twice as many drought events as the arid and polar types (B- and E-climates), and the durations of more extreme droughts were about half the length. Selected soils under permanent grassland were found to have a minor effect on hydrological drought characteristics, whereas groundwater systems had major impact. Groundwater systems strongly controlled the hydrological drought characteristics of all climate types, but particularly those of the wetter A-, C- and D-climates because of higher recharge. The median number of droughts for quickly responding groundwater systems was about three times higher than for slowly responding systems. Groundwater systems substantially affected the duration, particularly of the more extreme drought events. Bivariate probability distributions of drought duration and standardized deficit for combinations of Köppen–Geiger climate, soil and groundwater system showed that the responsiveness of the groundwater system is as important as climate for hydrological drought development. This urges for an improvement of subsurface modules in global hydrological models to be more useful for water resources assessments. A foreseen higher spatial resolution in large-scale models would enable a better hydrogeological parameterization and thus inclusion of lateral flow.

scholarly journals Climate Change Effects on Spatiotemporal Patterns of Hydroclimatological Summer Droughts in Norway

2011 ◽  
Vol 12 (6) ◽  
pp. 1205-1220 ◽  
Author(s):  
Wai Kwok Wong ◽  
Stein Beldring ◽  
Torill Engen-Skaugen ◽  
Ingjerd Haddeland ◽  
Hege Hisdal
Keyword(s):  
Climate Change ◽  
General Circulation ◽  
Dominant Role ◽  
Summer Precipitation ◽  
Meteorological Drought ◽  
Threshold Level ◽  
General Circulation Models ◽  
Drought Duration ◽  
Drought Characteristics ◽  
The Impact

Abstract This study examines the impact of climate change on droughts in Norway. A spatially distributed (1 × 1 km2) version of the Hydrologiska Byråns Vattenbalansavdelning (HBV) precipitation-runoff model was used to provide hydrological data for the analyses. Downscaled daily temperature and precipitation derived from two atmosphere–ocean general circulation models with two future emission scenarios were applied as input to the HBV model. The differences in hydroclimatological drought characteristics in the summer season between the periods 1961–90 and 2071–2100 were studied. The threshold level method was adopted to select drought events for both present and future climates. Changes in both the duration and spatial extent of precipitation, soil moisture, runoff, and groundwater droughts were identified. Despite small changes in future meteorological drought characteristics, substantial increases in hydrological drought duration and drought affected areas are expected, especially in the southern and northernmost parts of the country. Reduced summer precipitation is a major factor that affects changes in drought characteristics in the south while temperature increases play a more dominant role for the rest of the country.

scholarly journals Comparison of Projection in Meteorological and Hydrological Droughts in the Cheongmicheon Watershed for RCP4.5 and SSP2-4.5

2021 ◽  
Vol 13 (4) ◽  
pp. 2066
Author(s):  
Jin Hyuck Kim ◽  
Jang Hyun Sung ◽  
Eun-Sung Chung ◽  
Sang Ug Kim ◽  
Minwoo Son ◽  
...  
Keyword(s):  
General Circulation ◽  
Drought Index ◽  
Standardized Precipitation Index ◽  
Coupled Model ◽  
Meteorological Drought ◽  
General Circulation Models ◽  
Hydrological Drought ◽  
Drought Indices ◽  
Drought Period ◽  
Drought Characteristics

Due to the recent appearance of shares socioeconomic pathway (SSP) scenarios, there have been many studies that compare the results between Coupled Model Intercomparison Project (CMIP)5 and CMIP6 general circulation models (GCMs). This study attempted to project future drought characteristics in the Cheongmicheon watershed using SSP2-4.5 of Australian Community Climate and Earth System Simulator-coupled model (ACCESS-CM2) in addition to Representative Concentration Pathway (RCP) 4.5 of ACCESS 1-3 of the same institute. The historical precipitation and temperature data of ACCESS-CM2 were generated better than those of ACCESS 1-3. Two meteorological drought indices, namely, Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) were used to project meteorological drought while a hydrological drought index, Standardized Streamflow Index (SDI), was used to project the hydrological drought characteristics. The metrological data of GCMs were bias-corrected using quantile mapping method and the streamflow was obtained using Soil and Water Assessment Tool (SWAT) and bias-corrected meteorological data. As a result, there were large differences of drought occurrences and severities between RCP4.5 and SSP2-4.5 for the values of SPI, SPEI, and SDI. The differences in the minimum values of drought index between near (2021–2060) and far futures (2061–2100) were very small in SSP2-4.5, while those in RCP4.5 were very large. In addition, the longest drought period from SDI was the largest because the variation in precipitation usually affects the streamflow with a lag. Therefore, it was concluded that it is important to consider both CMIP5 and CMIP6 GCMs in establishing the drought countermeasures for the future period.

scholarly journals Hydrological drought across the world: impact of climate and physical catchment structure

2012 ◽  
Vol 9 (10) ◽  
pp. 12145-12192 ◽  
Author(s):  
H. A. J. Van Lanen ◽  
N. Wanders ◽  
L. M. Tallaksen ◽  
A. F. Van Loon
Keyword(s):  
Large Scale ◽  
Hydrological Drought ◽  
Temperate Climate ◽  
Minor Effect ◽  
Hydrological Models ◽  
Spatial And Temporal Patterns ◽  
Drought Duration ◽  
Drought Characteristics ◽  
The World ◽  
Groundwater Systems

Abstract. Large-scale hydrological drought studies have demonstrated spatial and temporal patterns in observed trends and considerable difference exists among global hydrological models in their ability to reproduce these patterns. A controlled modeling experiment has been set up to systematically explore the role of climate and physical catchment structure (soils and groundwater systems) to better understand underlying drought-generating mechanisms. Daily climate data (1958–2001) of 1495 grid cells across the world were selected that represent Köppen-Geiger major climate types. These data were fed into a hydrological model. Nine realizations of physical catchment structure were defined for each grid cell, i.e. three soils with different soil moisture supply capacity and three groundwater systems (quickly-, intermediary- and slowly-responding). Hydrological drought characteristics (number, duration and standardized deficit volume) were identified from time series of daily discharge. Summary statistics showed that the equatorial and temperate climate types (A- and C-climates) had about twice as many drought events as the arid and polar types (B- and E-climates) and the duration of more extreme droughts were about half the length. Soils were found to have a minor effect on hydrological drought characteristics, whereas groundwater systems had major impact. Groundwater systems strongly controlled the hydrological drought characteristics of all climate types, but particularly those of the wetter A-, C- and D-climates because of higher recharge. The median number of drought for quickly-responding groundwater systems was about three times higher than for slowly-responding systems, which substantially affected the duration, particularly of the more extreme drought events. Bivariate probability distributions of drought duration and standardized deficit for combinations of Köppen-Geiger climate, soil and groundwater system showed that responsiveness of groundwater systems is as important as climate for hydrological drought development. This urges for an improvement of subsurface modules in global hydrological models to be more useful for water resources assessments. A foreseen higher spatial resolution would enable a better hydrogeological parameterization and inclusion of lateral flow.

Event detection and visualization of ocean eddies simulated by ocean general circulation model

2019 ◽  
Vol 10 (03) ◽  
pp. 1950018
Author(s):  
Daisuke Matsuoka ◽  
Fumiaki Araki ◽  
Hideharu Sasaki
Keyword(s):  
High Resolution ◽  
General Circulation ◽  
Numerical Study ◽  
Circulation Model ◽  
General Circulation Models ◽  
Ocean Currents ◽  
Time Step ◽  
Data Set ◽  
Ocean Eddies ◽  
Ocean General Circulation

Numerical study of ocean eddies has been carried out by using high-resolution ocean general circulation models. In order to understand ocean eddies from the large volume data produced by simulations, visualizing only eddy distribution at each time step is insufficient; time-variations in eddy events and phenomena must also be considered. However, existing methods cannot precisely find and track eddy events such as amalgamation and bifurcation. In this study, we propose an original approach for eddy detection, tracking, and event visualization based on an eddy classification system. The proposed method detects streams and currents as well as eddies, and it classifies discovered eddies into several categories using the additional stream and current information. By tracking how the classified eddies vary over time, detecting events such as eddy amalgamation and bifurcation as well as the interaction between eddies and ocean currents becomes achievable. We adopt the proposed method for two ocean areas in which strong ocean currents exist as case studies. We visualize the detected eddies and events in a time series of images, allowing us to acquire an intuitive understanding of a region of interest concealed in a high-resolution data set. Furthermore, our proposed method succeeded in clarifying the occurrence place and seasonality of each type of eddy event.

scholarly journals Future Changes in Precipitation and Drought Characteristics over Bangladesh Under CMIP5 Climatological Projections

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2219 ◽  
Author(s):  
Kamruzzaman ◽  
Jang ◽  
Cho ◽  
Hwang
Keyword(s):  
Climate Change ◽  
21St Century ◽  
General Circulation ◽  
General Circulation Models ◽  
Northern Region ◽  
Medium Term ◽  
Rcp Scenarios ◽  
Drought Characteristics ◽  
The Future ◽  
Northwestern Region

: The impacts of climate change on precipitation and drought characteristics over Bangladesh were examined by using the daily precipitation outputs from 29 bias-corrected general circulation models (GCMs) under the representative concentration pathway (RCP) 4.5 and 8.5 scenarios. A precipitation-based drought estimator, namely, the Effective Drought Index (EDI), was applied to quantify the characteristics of drought events in terms of the severity and duration. The changes in drought characteristics were assessed for the beginning (2010–2039), middle (2040–2069), and end of this century (2070–2099) relative to the 1976–2005 baseline. The GCMs were limited in regard to forecasting the occurrence of future extreme droughts. Overall, the findings showed that the annual precipitation will increase in the 21st century over Bangladesh; the increasing rate was comparatively higher under the RCP8.5 scenario. The highest increase in rainfall is expected to happen over the drought-prone northern region. The general trends of drought frequency, duration, and intensity are likely to decrease in the 21st century over Bangladesh under both RCP scenarios, except for the maximum drought intensity during the beginning of the century, which is projected to increase over the country. The extreme and medium-term drought events did not show any significant changes in the future under both scenarios except for the medium-term droughts, which decreased by 55% compared to the base period during the 2070s under RCP8.5. However, extreme drought days will likely increase in most of the cropping seasons for the different future periods under both scenarios. The spatial distribution of changes in drought characteristics indicates that the drought-vulnerable areas are expected to shift from the northwestern region to the central and the southern region in the future under both scenarios due to the effects of climate change.

Albedo observations of the Earth’s surface for climate research

1983 ◽  
Vol 309 (1508) ◽  
pp. 285-294 ◽  
Keyword(s):  
General Circulation ◽  
Surface Albedo ◽  
Climate Models ◽  
General Circulation Models ◽  
Data Set ◽  
Primary Input ◽  
Climate Research ◽  
Earth’S Climate ◽  
Atmospheric Distortion ◽  
Spectrally Resolved

The primary input of energy to the Earth’s climate system occurs at the surface and can be highly sensitive to the surface albedo. Albedo changes have been proposed as one cause of climatic variation, but results from climate models are not yet consistent. It is very difficult to establish an agreed global data set with which to initiate comparative climatic simulations. Albedo observations must be spectrally resolved because reflexion of solar radiation is a strong function of wavelength and incident and reflected beams are modified by the atmosphere. Parametrization of system albedos in energybalance models draws on satellite data. The use of satellite observations is less easy in general circulation climate models. The removal of atmospheric distortion is particularly difficult. The establishment of a surface albedo data set generally follows one of two approaches: geographical categorization or remote monitoring. Surface albedo specification in current general circulation models is diverse. This paper reviews the ways in which remotely derived albedo measurements are used now and may, in the future, be improved for climate research.

scholarly journals Future Changes in Precipitation and Drought Characteristics over Bangladesh under CMIP5 Climatological Projections

2019 ◽  
Author(s):  
Mohammad Kamruzzaman ◽  
Min-Won Jang ◽  
Jaepil Cho ◽  
Syewoon Hwang
Keyword(s):  
Climate Change ◽  
21St Century ◽  
General Circulation ◽  
General Circulation Models ◽  
Northern Region ◽  
Medium Term ◽  
Rcp Scenarios ◽  
Drought Characteristics ◽  
The Future ◽  
Northwestern Region

The impacts of climate change on precipitation and drought characteristics over Bangladesh were examined by using the daily precipitation outputs from 29 bias-corrected general circulation models (GCMs) under the representative concentration pathway (RCP) 4.5 and 8.5 scenarios. A precipitation-based drought estimator, namely, the Effective Drought Index (EDI), was applied to quantify the characteristics of drought events in terms of the severity and duration. The changes in drought characteristics were assessed for the beginning (2010–2039), middle (2040–2069), and end of this century (2070–2099) relative to the 1976–2005 baseline. The GCMs were limited in regard to forecasting the occurrence of future extreme droughts. Overall, the findings showed that the annual precipitation will increase in the 21st century over Bangladesh; the increasing rate was comparatively higher under the RCP8.5 scenario. The highest increase of rainfall is expected to happen over the drought-prone northern region. The general trends of drought frequency, duration, and intensity are likely to decrease in the 21st century over Bangladesh under both RCP scenarios, except for the maximum drought intensity during the beginning of the century, which is projected to increase over the country. The extreme and medium-term drought events did not show any significant changes in the future under both scenarios except for the medium-term droughts, which decreased by 55% compared to the base period during the 2070s under RCP8.5. However, extreme drought days will likely increase in most of the cropping seasons for the different future periods under both scenarios. The spatial distribution of changes in drought characteristics indicates that the drought-vulnerable areas are expected to shift from the northwestern region to the central and the southern region in the future under both scenarios due to the effects of climate change.

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