scholarly journals Future shift of the relative roles of precipitation and temperature in controlling annual runoff in the conterminous United States

2017 ◽  
Author(s):  
Kai Duan ◽  
Ge Sun ◽  
Steven G. McNulty ◽  
Peter V. Caldwell ◽  
Erika C. Cohen ◽  
...  
Keyword(s):  
United States ◽  
Climate Models ◽  
Coupled Model ◽  
Annual Runoff ◽  
Dominant Factor ◽  
Future Climate Change ◽  
Primary Control ◽  
Evaporative Demand ◽  
South Central ◽  
Runoff Change

Abstract. This study examines the relative roles of climatic variables in altering annual runoff in the conterminous United States (CONUS) in the 21st century, using an ecohydrological model driven with historical records and future scenarios constructed from 20 Coupled Model Intercomparison Project Phase 5 (CMIP5) climate models. The results suggest that precipitation has been the primary control of runoff variation during the latest decades, but the role of temperature will outweigh that of precipitation in most regions if future climate change follows the projections of climate models instead of the historical tendencies. Besides these two key factors, increasing humidity is projected to partially offset the additional evaporative demand caused by warming and consequently enhance runoff. Overall, the projections from 20 climate models suggest a high degree of consistency on the increasing trends in temperature, precipitation, and humidity, which will be the major climatic driving factors accounting for 43 % ~ 50 %, 20 % ~ 24 %, and 16 % ~ 23 % of runoff change, respectively. Spatially, while temperature rise is recognized as the largest contributor in most of the CONUS, precipitation is expected to be the dominant factor driving runoff to increase across the Pacific Coast and the Southwest. The combined effects of increasing humidity and precipitation may also surpass the detrimental effects of warming and result in a hydrologically wetter future in the East. However, severe runoff depletion is more likely to occur in the Midwest and South-Central.

scholarly journals Future shift of the relative roles of precipitation and temperature in controlling annual runoff in the conterminous United States

2017 ◽  
Vol 21 (11) ◽  
pp. 5517-5529 ◽  
Author(s):  
Kai Duan ◽  
Ge Sun ◽  
Steven G. McNulty ◽  
Peter V. Caldwell ◽  
Erika C. Cohen ◽  
...  
Keyword(s):  
United States ◽  
Climate Models ◽  
Coupled Model ◽  
Annual Runoff ◽  
Stress Index ◽  
Dominant Factor ◽  
Future Climate Change ◽  
Primary Control ◽  
Evaporative Demand ◽  
Runoff Change

Abstract. This study examines the relative roles of climatic variables in altering annual runoff in the conterminous United States (CONUS) in the 21st century, using a monthly ecohydrological model (the Water Supply Stress Index model, WaSSI) driven with historical records and future scenarios constructed from 20 Coupled Model Intercomparison Project Phase 5 (CMIP5) climate models. The results suggest that precipitation has been the primary control of runoff variation during the latest decades, but the role of temperature will outweigh that of precipitation in most regions if future climate change follows the projections of climate models instead of the historical tendencies. Besides these two key factors, increasing air humidity is projected to partially offset the additional evaporative demand caused by warming and consequently enhance runoff. Overall, the projections from 20 climate models suggest a high degree of consistency on the increasing trends in temperature, precipitation, and humidity, which will be the major climatic driving factors accounting for 43–50, 20–24, and 16–23 % of the runoff change, respectively. Spatially, while temperature rise is recognized as the largest contributor that suppresses runoff in most areas, precipitation is expected to be the dominant factor driving runoff to increase across the Pacific coast and the southwest. The combined effects of increasing humidity and precipitation may also surpass the detrimental effects of warming and result in a hydrologically wetter future in the east. However, severe runoff depletion is more likely to occur in the central CONUS as temperature effect prevails.

scholarly journals Future shift of the relative roles of precipitation and temperature in controlling annual runoff in the conterminous United States

2016 ◽  
Author(s):  
Kai Duan ◽  
Ge Sun ◽  
Steven G. McNulty ◽  
Peter V. Caldwell ◽  
Erika C. Cohen ◽  
...  
Keyword(s):  
United States ◽  
21St Century ◽  
Climate Models ◽  
Hydrological Cycle ◽  
Annual Runoff ◽  
Primary Control ◽  
Considerable Uncertainty ◽  
Temperature And Precipitation ◽  
Runoff Change ◽  
Precipitation And Temperature

Abstract. Precipitation and temperature are the two key climatic variables that control the hydrological cycle and water availability for humans. This study examines the potential shift of the relative roles of precipitation and temperature in controlling annual runoff in the conterminous United States (CONUS), using a water-centric ecohydrological model driven with historical records and climate scenarios constructed from 20 CMIP5 (Coupled Model Intercomparison Project Phase 5) climate models. The results suggest that precipitation has been the primary control of runoff variability and trend during the latest decades. However, the influence of temperature is projected to increase in a continued warming future in the 21st century. Despite considerable uncertainty and regional diversity, the multi-model ensemble reveals a high degree of consistency in the general increasing trend of both precipitation and temperature in the future, imposing positive and negative effects on annual runoff, respectively. The magnitude of temperature effect tends to exceed that of precipitation, and thus leads to an overall decrease of 8 ~ 30 mm yr−1 (3 % ~ 11 %) runoff by 2100. Overall, temperature and precipitation changes are expected to contribute to runoff change by 58 % ~ 65 % and 31 % ~ 39 % separately, indicating that the role of rising temperature may outweigh that of precipitation in the later part of the 21st century. Across the CONUS, runoff decrease and increase in 34 % ~ 52 % and 11 % ~ 12 % of the land area are expected to be dominated by long-term changes in temperature and precipitation, respectively. We found that the vast croplands and grasslands across the central and forests in the northwestern regions might be particularly vulnerable to water supply decline caused by the changing climate.

Assess 21st century Flash Drought in the United States using high resolution regional climate models

2021 ◽  
Author(s):  
Brandi Gamelin ◽  
Jiali Wang ◽  
V. Rao Kotamarthi
Keyword(s):  
Climate Change ◽  
United States ◽  
Soil Moisture ◽  
Climate Models ◽  
Wrf Model ◽  
The United States ◽  
Future Climate Change ◽  
Climate Change Scenarios ◽  
Regional Variability ◽  
Groundwater Levels

<p>Flash droughts are the rapid intensification of drought conditions generally associated with increased temperatures and decreased precipitation on short time scales.  Consequently, flash droughts are responsible for reduced soil moisture which contributes to diminished agricultural yields and lower groundwater levels. Drought management, especially flash drought in the United States is vital to address the human and economic impact of crop loss, diminished water resources and increased wildfire risk. In previous research, climate change scenarios show increased growing season (i.e. frost-free days) and drying in soil moisture over most of the United States by 2100. Understanding projected flash drought is important to assess regional variability, frequency and intensity of flash droughts under future climate change scenarios. Data for this work was produced with the Weather Research and Forecasting (WRF) model. Initial and boundary conditions for the model were supplied by CCSM4, GFDL-ESM2G, and HadGEM2-ES and based on the 8.5 Representative Concentration Pathway (RCP8.5). The WRF model was downscaled to a 12 km spatial resolution for three climate time frames: 1995-2004 (Historical), 2045-2054 (Mid), and 2085-2094 (Late).  A key characteristic of flash drought is the rapid onset and intensification of dry conditions. For this, we identify onset with vapor pressure deficit during each time frame. Known flash drought cases during the Historical run are identified and compared to flash droughts in the Mid and Late 21<sup>st</sup> century.</p>

scholarly journals Robust increase of Indian monsoon rainfall and its variability under future warming in CMIP-6 models

2020 ◽  
Author(s):  
Anja Katzenberger ◽  
Jacob Schewe ◽  
Julia Pongratz ◽  
Anders Levermann
Keyword(s):  
Climate Change ◽  
Global Warming ◽  
Climate Models ◽  
Monsoon Rainfall ◽  
Global Climate ◽  
Coupled Model ◽  
Global Climate Models ◽  
Future Climate Change ◽  
Global Mean Temperature ◽  
Almost All

Abstract. The Indian summer monsoon is an integral part of the global climate system. As its seasonal rainfall plays a crucial role in India's agriculture and shapes many other aspects of life, it affects the livelihood of a fifth of the world's population. It is therefore highly relevant to assess its change under potential future climate change. Global climate models within the Coupled Model Intercomparison Project Phase 5 (CMIP-5) indicated a consistent increase in monsoon rainfall and its variability under global warming. Since the range of the results of CMIP-5 was still large and the confidence in the models was limited due to partly poor representation of observed rainfall, the updates within the latest generation of climate models in CMIP-6 are of interest. Here, we analyse 32 models of the latest CMIP-6 exercise with regard to their annual mean monsoon rainfall and its variability. All of these models show a substantial increase in June-to-September (JJAS) mean rainfall under unabated climate change (SSP5-8.5) and most do also for the other three Shared Socioeconomic Pathways analyzed (SSP1-2.6, SSP2-4.5, SSP3-7.0). Moreover, the simulation ensemble indicates a linear dependence of rainfall on global mean temperature with high agreement between the models and independent of the SSP; the multi-model mean for JJAS projects an increase of 0.33 mm/day and 5.3 % per degree of global warming. This is significantly higher than in the CMIP-5 projections. Most models project that the increase will contribute to the precipitation especially in the Himalaya region and to the northeast of the Bay of Bengal, as well as the west coast of India. Interannual variability is found to be increasing in the higher-warming scenarios by almost all models. The CMIP-6 simulations largely confirm the findings from CMIP-5 models, but show an increased robustness across models with reduced uncertainties and updated magnitudes towards a stronger increase in monsoon rainfall.

Estimation of the annual runoff frequency distribution under a non-stationarity condition within the Budyko framework

2020 ◽  
Author(s):  
Hanbo Yang ◽  
Ziwei Liu
Keyword(s):  
Frequency Distribution ◽  
Regional Difference ◽  
Coupled Model ◽  
Annual Runoff ◽  
The Past ◽  
The North ◽  
Runoff Change ◽  
The Mean ◽  
Type Frequency ◽  
Stationarity Conditions

<p>In the past decades, climate change has been leading to non-stationarity in hydrological variables. Therefore, a simple framework within the Budyko framework is proposed to estimate the annual runoff frequency distribution and provide a new method for hydrological design under non-stationarity conditions. In this framework, the mean and standard deviation of annual runoff are derived by the Choudhury-Yang equation. Furthermore, the P-Ш type frequency curve is selected to calculate the annual runoff on a design return period. Based on this framework, the change in water resources in 207 three-level basins across China during 2020-2050 are estimated according to the Coupled Model Inter-comparison Project Phase 5. The results show that the mean annual runoff will decrease by 2.7% for all basins, and the regional difference will decline, i.e., the mean annual runoff will increase in the north of China and decrease in the south of China. However, the inter-annual variability of annual runoff will increase in more than 70% of basins. Additionally, in the wet year, approximately half of the total basins show decreased runoff change, and in the dry year, decreased change appears in ~65% basins. These findings offer a simple and effective way to re-examine the effects of non-stationarity in hydrological design.</p>

scholarly journals Historically-based run-time bias corrections substantially improve model projections of 100 years of future climate change

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Gerhard Krinner ◽  
Viatcheslav Kharin ◽  
Romain Roehrig ◽  
John Scinocca ◽  
Francis Codron
Keyword(s):  
Climate Change ◽  
Climate Models ◽  
Coupled Model ◽  
Atmospheric Model ◽  
Climate Impact ◽  
Future Climate ◽  
Future Climate Change ◽  
Historical Period ◽  
Underlying Assumption ◽  
Bias Corrections

Abstract Climate models and/or their output are usually bias-corrected for climate impact studies. The underlying assumption of these corrections is that climate biases are essentially stationary between historical and future climate states. Under very strong climate change, the validity of this assumption is uncertain, so the practical benefit of bias corrections remains an open question. Here, this issue is addressed in the context of bias correcting the climate models themselves. Employing the ARPEGE, LMDZ and CanAM4 atmospheric models, we undertook experiments in which one centre’s atmospheric model takes another centre’s coupled model as observations during the historical period, to define the bias correction, and as the reference under future projections of strong climate change, to evaluate its impact. This allows testing of the stationarity assumption directly from the historical through future periods for three different models. These experiments provide evidence for the validity of the new bias-corrected model approach. In particular, temperature, wind and pressure biases are reduced by 40–60% and, with few exceptions, more than 50% of the improvement obtained over the historical period is on average preserved after 100 years of strong climate change. Below 3 °C global average surface temperature increase, these corrections globally retain 80% of their benefit.

scholarly journals Whither the 100th Meridian? The Once and Future Physical and Human Geography of America’s Arid–Humid Divide. Part II: The Meridian Moves East

2018 ◽  
Vol 22 (5) ◽  
pp. 1-24 ◽  
Author(s):  
Richard Seager ◽  
Jamie Feldman ◽  
Nathan Lis ◽  
Mingfang Ting ◽  
Alton P. Williams ◽  
...  
Keyword(s):  
United States ◽  
Great Plains ◽  
Climate Models ◽  
Potential Evapotranspiration ◽  
Coupled Model ◽  
Moisture Flux ◽  
The United States ◽  
Farm Size ◽  
Current Century ◽  
Northern United States

Abstract The 100th meridian bisects the Great Plains of the United States and effectively divides the continent into more arid western and less arid eastern halves and is well expressed in terms of vegetation, land hydrology, crops, and the farm economy. Here, it is considered how this arid–humid divide will change in intensity and location during the current century under rising greenhouse gases. It is first shown that state-of-the-art climate models from phase 5 of the Coupled Model Intercomparison Project generally underestimate the degree of aridity of the United States and simulate an arid–humid divide that is too diffuse. These biases are traced to excessive precipitation and evapotranspiration and inadequate blocking of eastward moisture flux by the Pacific coastal ranges and Rockies. Bias-corrected future projections are developed that modify observationally based measures of aridity by the model-projected fractional changes in aridity. Aridity increases across the United States, and the aridity gradient weakens. The main contributor to the changes is rising potential evapotranspiration, while changes in precipitation working alone increase aridity across the southern and decrease across the northern United States. The “effective 100th meridian” moves to the east as the century progresses. In the current farm economy, farm size and percent of county under rangelands increase and percent of cropland under corn decreases as aridity increases. Statistical relations between these quantities and the bias-corrected aridity projections suggest that, all else being equal (which it will not be), adjustment to changing environmental conditions would cause farm size and rangeland area to increase across the plains and percent of cropland under corn to decrease in the northern plains as the century advances.

scholarly journals Estimating the Permafrost-Carbon Climate Response in the CMIP5 Climate Models Using a Simplified Approach

2013 ◽  
Vol 26 (14) ◽  
pp. 4897-4909 ◽  
Author(s):  
Eleanor J. Burke ◽  
Chris D. Jones ◽  
Charles D. Koven
Keyword(s):  
Climate Change ◽  
Radiative Forcing ◽  
Climate Models ◽  
Coupled Model ◽  
Climate Feedback ◽  
Cmip5 Models ◽  
Future Climate Change ◽  
Permafrost Region ◽  
Climate Response ◽  
Simplified Approach

Abstract Under climate change, thawing permafrost may cause a release of carbon, which has a positive feedback on the climate. The permafrost-carbon climate response (γPF) is the additional permafrost-carbon made vulnerable to decomposition per degree of global temperature increase. A simple framework was adopted to estimate γPF using the database for phase 5 of the Coupled Model Intercomparison Project (CMIP5). The projected changes in the annual maximum active layer thicknesses (ALTmax) over the twenty-first century were quantified using CMIP5 soil temperatures. These changes were combined with the observed distribution of soil organic carbon and its potential decomposability to give γPF. This estimate of γPF is dependent on the biases in the simulated present-day permafrost. This dependency was reduced by combining a reference estimate of the present-day ALTmax with an estimate of the sensitivity of ALTmax to temperature from the CMIP5 models. In this case, γPF was from −6 to −66 PgC K−1(5th–95th percentile) with a radiative forcing of 0.03–0.29 W m−2 K−1. This range is mainly caused by uncertainties in the amount of soil carbon deeper in the soil profile and whether it thaws over the time scales under consideration. These results suggest that including permafrost-carbon within climate models will lead to an increase in the positive global carbon climate feedback. Under future climate change the northern high-latitude permafrost region is expected to be a small sink of carbon. Adding the permafrost-carbon response is likely to change this region to a source of carbon.

scholarly journals Effects of snow ratio on annual runoff within Budyko framework

2015 ◽  
Vol 12 (1) ◽  
pp. 939-973 ◽  
Author(s):  
D. Zhang ◽  
Z. Cong ◽  
G. Ni ◽  
D. Yang ◽  
S. Hu
Keyword(s):  
Coupled Model ◽  
Temporal Distribution ◽  
Winter Precipitation ◽  
Annual Runoff ◽  
Proposed Model ◽  
Runoff Change ◽  
Ratio Change ◽  
Intercomparison Project ◽  
The Relationship

Abstract. Warmer climate may lead to less winter precipitation falling as snow. Such a switch in the state of precipitation not only alters temporal distribution of intra-annual runoff, but tends to yield less total annual runoff. Long-term water balance for 282 catchments across China is investigated, showing that decreasing snow ratio reduces annual runoff for a given total precipitation. Within the Budyko framework, we develop an equation to quantify the relationship between snow ratio and annual runoff from a water–energy balance viewpoint. Based on the proposed equation, attribution of runoff change during past several decades and possible runoff change induced by projected snow ratio change using climate experiment outputs archived in the Coupled Model Intercomparison Project Phase 5 are analyzed. Results indicate that annual runoff in northwest mountainous and north high-latitude areas are sensitive to snow ratio change. The proposed model is applicable to other catchments easily and quantitatively for analyzing the effects of possible change in snow ratio on available water resources and evaluating the vulnerability of catchments to climate change.

scholarly journals Effects of snow ratio on annual runoff within the Budyko framework

2015 ◽  
Vol 19 (4) ◽  
pp. 1977-1992 ◽  
Author(s):  
D. Zhang ◽  
Z. Cong ◽  
G. Ni ◽  
D. Yang ◽  
S. Hu
Keyword(s):  
Coupled Model ◽  
Temporal Distribution ◽  
Annual Runoff ◽  
Proposed Model ◽  
Runoff Change ◽  
Northern High Latitude ◽  
Ratio Change ◽  
Intercomparison Project ◽  
The Relationship

Abstract. A warmer climate may lead to less precipitation falling as snow in cold seasons. Such a switch in the state of precipitation not only alters temporal distribution of intra-annual runoff but also tends to yield less total annual runoff. Long-term water balance for 282 catchments across China is investigated, showing that a decreasing snow ratio reduces annual runoff for a given total precipitation. Within the Budyko framework, we develop an equation to quantify the relationship between snow ratio and annual runoff from a water–energy balance viewpoint. Based on the proposed equation, attribution of runoff change during the past several decades and possible runoff change induced by projected snow ratio change using climate experiment outputs archived in the Coupled Model Intercomparison Project Phase 5 (CMIP5) are analyzed. Results indicate that annual runoff in northwestern mountainous and northern high-latitude areas are sensitive to snow ratio change. The proposed model is applicable to other catchments easily and quantitatively for analyzing the effects of possible change in snow ratio on available water resources and evaluating the vulnerability of catchments to climate change.

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