Changes In Mean Annual Precipitation Research Articles

Stable isotope evidence for long-term stability of large-scale hydroclimate in the Neogene North American Great Plains

Abstract. The Great Plains of North America host a stark climatic gradient, separating the humid and well-watered eastern US from the semi-arid and arid western US, and this gradient shapes the region's water availability, its ecosystems, and its economies. This climatic boundary is largely set by the influence of two competing atmospheric circulation systems that meet over the Great Plains – the wintertime westerlies bring dominantly dry air that gives way to moist, southerly air transported by the Great Plains low-level jet in the warmer months. Climate model simulations suggest that, as CO2 rises, this low-level jet will strengthen, leading to greater precipitation in the spring but less in the summer and, thus, no change in mean annual precipitation. Combined with rising temperatures that will increase potential evapotranspiration, semi-arid conditions will shift eastward, with potentially large consequences for the ecosystems and inhabitants of the Great Plains. We examine how hydroclimate in the Great Plains varied in the past in response to warmer global climate by studying the paleoclimate record within the Ogallala Formation, which underlies nearly the entire Great Plains and provides a spatially resolved record of hydroclimate during the globally warmer late Miocene. We use the stable isotopes of oxygen (δ18O) as preserved in authigenic carbonates hosted within the abundant paleosol and fluvial successions that comprise the Ogallala Formation as a record of past hydroclimate. Today, and coincident with the modern aridity gradient, there is a sharp meteoric water δ18O gradient with high (−6 ‰ to 0 ‰) δ18O in the southern Great Plains and low (−12 ‰ to −18 ‰) δ18O in the northern plains. We find that the spatial pattern of reconstructed late Miocene precipitation δ18O is indistinguishable from the spatial pattern of modern meteoric water δ18O. We use a recently developed vapor transport model to demonstrate that this δ18O spatial pattern requires air mass mixing over the Great Plains between dry westerly and moist southerly air masses in the late Miocene – consistent with today. Our results suggest that the spatial extents of these two atmospheric circulation systems have been largely unchanged since the late Miocene and any strengthening of the Great Plains low-level jet in response to warming has been isotopically masked by proportional increases in westerly moisture delivery. Our results hold implications for the sensitivity of Great Plains climate to changes in global temperature and CO2 and also for our understanding of the processes that drove Ogallala Formation deposition in the late Miocene.

Responses of water use efficiency of Chinese fir to mixed planting and meteorological factors

Chinese fir in China are generally inefficient plantations with single species, unreasonable stand density, and low productivity. The introduction of broadleaved species is usually adopted as a strategy to improve Chinese fir plantations. Taking the pure forests and mixed forests of the Guanshan Forest Farm in Jiangxi Province as example, we quantified the intrinsic water-use efficiency (iWUE) of trees based on the stable isotope carbon method, as well as its response to meteorological factors, and investigated the improvement of stand quality after introducing Phoebe zhennan into Chinese fir plantation. The results showed that the basal area increment was 0.23 cm2 in pure forest, being higher than that of 0.19 cm2 in mixed forest. The δ13C and iWUE of pure forest were -27.4‰ and 52.9%, respectively, being lower than those of -26.7‰ and 62.8% in the mixed forest. Tree δ13C in pure forest was more sensitive to changes in mean annual precipitation and mean annual relative humidity, while that in mixed forest was not significantly correlated with meteorological factors. Pure forest iWUE was positively correlated with mean annual temperature, mean annual atmospheric CO2 concentration, and mean annual maximum temperature, and negatively correlated with mean annual precipitation and mean annual relative humidity, while mixed forest iWUE was positively correlated with mean annual atmospheric CO2 concentration only. Our results indicated that pure forests was more sensitive to climate than mixed forests.

Projection of future extreme meteorological droughts using two large multi-member climate model ensembles

Several studies have looked at the evolution of droughts in a changing climate in various locations and have typically found that droughts are expected to become more severe in the future. However, relatively little work has been done on extreme droughts. This study focuses on the evolution of extreme meteorological droughts over near (2036–2065) and far (2071–2100) future time periods. Monthly precipitation from two large multi-member climate model ensembles: the Canadian Earth System Model (CanESM2) 50-member ensemble and the Community Earth System Model (CESM1) 40-member ensemble, was used to calculate the Standard Precipitation Index (SPI) to quantify and explore the evolution of future meteorological droughts. The use of these large ensembles allows for the calculation of the 20- and 100-year droughts return period and offers a unique perspective into those rare events.Both climate models project increases in extreme meteorological drought frequency over many of the world’s regions. The spatial patterns of regions with worsening droughts generally match those of projected change in mean annual precipitation, although the former is more extensive, indicating that changes in internal variability will increase drought frequency even in some regions projected to see increased mean annual precipitation. The projected increase in meteorological drought frequency is more significant for short-term JJA droughts, and for the larger return periods. Large increases in frequency are observed in many regions, all the way up to 20 times for the historical100-year JJA drought indicating a return period shift from 100 to 5 year.Considering the significant predicted increases in temperature, it follows that future changes for both agricultural (soil water deficit) and hydrological droughts (low stream levels), which result from the interaction between precipitation deficit and temperature (as well as other variables), will be even more severe.

Dryland soil mycobiome response to long‐term precipitation variability depends on host type

Abstract Climate change is projected to cause shifts in precipitation regimes globally, leading to intensified periods of precipitation and droughts. Most studies that have explored the influence of changing precipitation regimes on ecosystems have focused on changes in mean annual precipitation, rather than the variance around the mean. Soil fungi are ubiquitous organisms that drive ecosystem processes, but it is unknown how they respond to long‐term increased interannual precipitation variability. Here, we investigated the influence of long‐term increased precipitation variability and host type on soil fungal diversity and community composition in a dryland ecosystem. We collected 300 soil samples from two time points and different host type substrate types at a long‐term precipitation variability experiment at the Jornada Long Term Ecological Research site. Next, we used amplicon sequencing to characterize soil fungal communities. Soil fungal alpha diversity and community composition were strongly affected by host type and sampling year, and increased precipitation variability caused a modest, statistically insignificant, decrease in soil fungal evenness. Furthermore, results from our structural equational model showed that the decrease in grass‐associated soil fungal richness was likely an indirect result of host decline in response to increased precipitation variability. Synthesis. Our work demonstrates effects of increase in interannual precipitation variability on soil fungi, and that plant hosts play a key role in mediating soil fungal responses.

Palaeoenvironmental reconstruction for the Permian (lower Gondwana) succession of the Godavari Valley Coalfield in southern India based on a combined palynofacies, carbon isotope, and biomarker study

The study presents integrated palynofacies, organic carbon isotope, and biomarker data to reconstruct palaeoenviromental setting for the Permian sediments (borehole MGK-6) of the Kachinapalli block of the Godavari Valley Coalfield, southern India. The palynofacies data reveal three distinct palynofacies (A–C) as follows. Palynofacies A is dominated by abundant arborescent vegetation (glossopterids and conifers) along with structured organic matter, suggesting freshwater forest swamps in proximal settings. Palynofacies B is dominated by abundant degraded organic matter and amorphous organic matter, suggesting lakeshore/flooded palaeomires in slightly dismal settings. It has a high water level in the hinterland, which enables bacterial degradation of organic matter and establishes low-oxygenation conditions within the water column. These conditions would have provided grounds for the accumulation of either degraded or amorphous organic matter. Palynofacies C is dominated by the abundance of charcoal/opaque phytoclasts, indicating prolonged transportation or post-depositional alteration, suggesting a highly-oxidizing condition in distal settings. The bulk organic δ13C range (−25.1‰ to −20.9‰) in the borehole MGK-6 is in close agreement with the global Permian records. This study also shows a weak but statistically significant correlation with the major forms of palynofacies A and C. The interlinked behaviour of bulk organic δ13C and palynofacies suggests that the changes in palaeobiogeography/palaeodepositional settings were most likely driven by the change in mean annual precipitation. The biomarker study shows the presence of n-alkane from C15 to C31 with unimodal and bimodal distribution patterns, revealing the source materials as vascular plants and microbially-altered organic matter. The combined palynofacies, organic carbon isotope, and biomarker data provide vital clue to salient findings for the development of environmental conditions of Godavari Valley Coalfield during lower Gondwana sedimentation.

Remotely sensed assessment of increasing chronic and episodic drought effects on a Costa Rican tropical dry forest

AbstractTropical dry forests (TDFs) have experienced pronounced droughts and increased temperatures for the last century. To assess whether these climatic shifts have influenced dry forest vegetation and ecosystem functioning, we integrated ground observations from a Costa Rican long‐term forest dynamics monitoring plot with remotely sensed measures of forest productivity and canopy functioning from a diverse set of satellite data. Previously reported long‐term climate data (1921–1997) show a reduction in annual rainfall, but since 1980 there has been no directional change in mean annual precipitation. However, the 2015 El Niño Southern Oscillation (ENSO)‐induced drought was unprecedented. Temperatures have increased by 1.1°C since 1931. However, the Landsat wet season (1987–2017) Enhanced Vegetation Index (EVI) (canopy greenness) and the dry season (1985–2017) fraction of non‐photosynthetic canopy cover all indicate that TDFs have become more deciduous but also more productive during the wet season. These changes are consistent with a shift in the functional composition observed in the long‐term plot as more drought‐deciduous tree species have increased in abundance. Nonetheless, more continuous 16‐d MODIS (the Moderate Resolution Imaging Spectroradiometer) measures of the EVI over the past 17 yr (2001–2017) showed no change in the total annual forest productivity. Further, while the 2015 ENSO event temporarily reduced forest EVI, it did not cause a longer‐term impact on forest productivity. Instead, high spatial resolution Worldview‐2 satellite imagery showed that forest phenology shifted in the subsequent years even though the region returned to normal precipitation. Our results indicate that while the species composition of TDFs may be sensitive to the long‐term trend of gradually increasing temperatures and aridity, the annual forest functioning has so far been resilient to long‐term drying and a large episodic extreme drought event. This study demonstrates the feasibility of synthesizing satellite images of different characteristics to study the vegetation dynamics of a long‐term forest dynamics plot. Our synoptically sensed results show that the longer‐term changing climate has been and is currently shifting the ecological functioning, and also provide a baseline to assess the impacts of an extreme drought year on TDFs.

Intensification characteristics of hydroclimatic extremes in the Asian monsoon region under 1.5 and 2.0 °C of global warming

Abstract. Understanding the influence of global warming on regional hydroclimatic extremes is challenging. To reduce the potential risk of extremes under future climate states, assessing the change in extreme climate events is important, especially in Asia, due to spatial variability of climate and its seasonal variability. Here, the changes in hydroclimatic extremes are assessed over the Asian monsoon region under global mean temperature warming targets of 1.5 and 2.0 ∘C above preindustrial levels based on representative concentration pathways (RCPs) 4.5 and 8.5. Analyses of the subregions classified using regional climate characteristics are performed based on the multimodel ensemble mean (MME) of five bias-corrected global climate models (GCMs). For runoff extremes, the hydrologic responses to 1.5 and 2.0 ∘C global warming targets are simulated based on the variable infiltration capacity (VIC) model. Changes in temperature extremes show increasing warm extremes and decreasing cold extremes in all climate zones with strong robustness under global warming conditions. However, the hottest extreme temperatures occur more frequently in low-latitude regions with tropical climates. Changes in mean annual precipitation and mean annual runoff and low-runoff extremes represent the large spatial variations with weak robustness based on intermodel agreements. Global warming is expected to consistently intensify maximum extreme precipitation events (usually exceeding a 10 % increase in intensity under 2.0 ∘C of warming) in all climate zones. The precipitation change patterns directly contribute to the spatial extent and magnitude of the high-runoff extremes. Regardless of regional climate characteristics and RCPs, this behavior is expected to be enhanced under the 2.0 ∘C (compared with the 1.5 ∘C) warming scenario and increase the likelihood of flood risk (up to 10 %). More importantly, an extra 0.5 ∘C of global warming under two RCPs will amplify the change in hydroclimatic extremes on temperature, precipitation, and runoff with strong robustness, especially in cold (and polar) climate zones. The results of this study clearly show the consistent changes in regional hydroclimatic extremes related to temperature and high precipitation and suggest that hydroclimatic sensitivities can differ based on regional climate characteristics and type of extreme variables under warmer conditions over Asia.

Impact of climate change on water availability and its propagation through the Western U.S. power grid

Climate change is expected to affect the availability of water for electricity generation, yet the propagation of climate impacts across a large and diverse power grid remains unexplored. In this study, we evaluate how projected changes in water availability affect electricity generation at hydroelectric and thermal power plants and how the coincident impacts propagate locally and throughout the interconnected power grid of western United States. We also evaluate whether the prospect of climate-driven change could affect regional power dependencies. Hydrologic simulations derived from three Global Circulation Models (CCSM4, INMCM4, and GFDL-CM3), two radiative scenarios (RCP4.5 and RCP8.5) and the VIC hydrology model are used to force a large-scale, distributed water management model (MOSART-WM), which translates water availability into power generation constraints at hydropower plants and water-dependent thermoelectric plants. Power system dynamics are evaluated using the production cost model PLEXOS. We find that the interregional connections across the contemporary Western U.S. electricity infrastructure play an essential role in managing variations in regional generation due to hydrological variability. Projected WECC-scale changes in mean annual precipitation ranging from −3.8% to +17% are moderated to −6% to +4% in mean annual production cost changes. Climate change impacts on water availability in the Northwest drive future changes in other regions’ generation and in regional power flows. Northwest total generation influences interannual variability in other regions’ net generation, explaining about 40%, 50%, and 35% of the variability in Southwest, Rockies, and Southern California regions respectively. The propagation of Northwest climate change impact throughout the grid is exacerbated by the occurrence of dry years in Northern California. Generation from the Desert Southwest emerges as a critical resource to compensate for variations in water availability, and generation, in these regions. Though the regional power flow directions seem insensitive to long-term variations in water availability, our analysis highlights the need to consider other compounding regional factors, such as changes in Southern California’s net load and changes in regional fuel prices.

Variations in grizzly bear habitat selection in relation to the daily and seasonal availability of annual plant-food resources

Determining how resource availability changes daily, seasonally and annually, and how wildlife react to these changes, is valuable for managing wildlife. For vegetative resources phenological information can be used to determine availability and model the distribution of available resources. This study develops a set of annually varying species distribution models using maximum entropy modeling for eight grizzly bear key plant-food species using 1635 food occurrences collected between 2001 and 2017. Seasonal availability (phenology) of plant-food species were then estimated daily at a 30 m resolution for the period 2000–2017 using ground data collected at 15 sites in 2015 and 2018 combined with newly created fine scale phenology product DRIVE (Daily Remote Inference of Vegetation). These food availability layers were then used to develop resource selection functions with grizzly bear GPS collar data to describe daily and seasonal habitat selection and to compared how this changes over a three-year period based on changes in mean annual precipitation. Results demonstrated that grizzly bears selected areas where key plant-food species were available and that habitat selection varied between wet and dry years dependant on season and species. In dry spring conditions, selection for root species was stronger and occurred earlier than for an average and wet year. In the wet summer, length of selection for forb species increased, while strength of selection for wet and dry years was species dependant. In the fall, strength of selection for berry species between wet and dry years was species dependant, but overall selection for berry species was prolonged in the dry fall year. This research aids in predicting how inter-annual differences in climate affect grizzly bear habitat selection and provides insights to managers regarding how changes in management practices that encourage growth of understory vegetation could be used to maximize food resources regionally for grizzly bears and other wildlife.

Spatio-temporal climate and agroclimate diversities over the Zagreb city area

The Zagreb city is rich in green urban infrastructure that has an important role in climate change mitigation and adaptation. Knowledge on climate change and agroclimate has an important role in planning of green areas. Therefore, the aim is to evaluate the temporal and spatial diversities of agroclimate indicators over Zagreb city. Warming and no change in mean annual precipitation, as well as prolonged vegetation periods and reduced evapotranspiration were observed at all locations in the recent 1991-2018 compared to reference 1961-1990 period. The results indicate different intensity in climate change of observed indicators and existance of diffrences in indicators between city centre, suburb and hilly slopes thatshould be considered while planning green urban infracture.

Overlooked Trends in Observed Global Annual Precipitation Reveal Underestimated Risks

Numerous human and environmental systems are sensitive to the spatial and temporal distribution of precipitation, including agriculture, water supply, and ecosystems. Trends in observed precipitation form an important line of evidence to understand how changes may increase system vulnerabilities. Linear trends reported in US and global climate assessments reflect changes in mean annual precipitation. Mean trends may not reflect changes across other quantiles in the precipitation probability distribution, including the tails (very high and low precipitation levels), leading to systematic mischaracterization of climate risk. Here we reanalyze global annual precipitation using quantile regression to reveal overlooked trends. We find trends in the tails inconsistent with the mean in 44.4% of land area and 40.7% of rainfed agricultural regions. Previously undetected trends offer a more accurate view of the changing climate. This work enables reappraisals of risk aggregated over thresholds in human and environmental systems, enabling revaluation of threats and identification of appropriate adaptation strategies.

Effect of changing vegetation and precipitation on denudation – Part 2: Predicted landscape response to transient climate and vegetation cover over millennial to million-year timescales

Abstract. We present a numerical modeling investigation into the interactions between transient climate and vegetation cover with hillslope and detachment limited fluvial processes. Model simulations were designed to investigate topographic patterns and behavior resulting from changing climate and the associated changes in surface vegetation cover. The Landlab surface process model was modified to evaluate the effects of temporal variations in vegetation cover on hillslope diffusion and fluvial erosion. A suite of simulations were conducted to represent present-day climatic conditions and satellite derived vegetation cover at four different research areas in the Chilean Coastal Cordillera. These simulations included steady-state simulations as well as transient simulations with forcings in either climate or vegetation cover over millennial to million-year timescales. Two different transient variations in climate and vegetation cover including a step change in climate or vegetation were used, as well as 100 kyr oscillations over 5 Myr. We conducted eight different step-change simulations for positive and negative perturbations in either vegetation cover or climate and six simulations with oscillating transient forcings for either vegetation cover, climate, or oscillations in both vegetation cover and climate. Results indicate that the coupled influence of surface vegetation cover and mean annual precipitation shifts basin landforms towards a new steady state, with the magnitude of the change being highly sensitive to the initial vegetation and climate conditions of the basin. Dry, non-vegetated basins show higher magnitudes of adjustment than basins that are situated in wetter conditions with higher vegetation cover. For coupled conditions when surface vegetation cover and mean annual precipitation change simultaneously, the landscape response tends to be weaker. When vegetation cover and mean annual precipitation change independently from one another, higher magnitude shifts in topographic metrics are predicted. Changes in vegetation cover show a higher impact on topography for low initial surface cover values; however, for areas with high initial surface cover, the effect of changes in precipitation dominate the formation of landscapes. This study demonstrates the sensitivity of catchment characteristics to different transient forcings in vegetation cover and mean annual precipitation, with initial vegetation and climate conditions playing a crucial role.

Formation of a Rain Shadow: O and H Stable Isotope Records in Authigenic Clays From the Siwalik Group in Eastern Bhutan

AbstractWe measure the oxygen and hydrogen stable isotope composition of authigenic clays from Himalayan foreland sediments (Siwalik Group), and from present day small stream waters in eastern Bhutan to explore the impact of uplift of the Shillong Plateau on rain shadow formation over the Himalayan foothills. Stable isotope data from authigenic clay minerals (<2 μm) suggest the presence of three paleoclimatic periods during deposition of the Siwalik Group, between ∼7 and ∼1 Ma. The mean δ18O value in paleometeoric waters, which were in equilibrium with clay minerals, is ∼2.5‰ lower than in modern meteoric and stream waters at the elevation of the foreland basin. We discuss the factors that could have changed the isotopic composition of water over time and we conclude that (a) the most likely and significant cause for the increase in meteoric water δ18O values over time is the “amount effect,” specifically, a decrease in mean annual precipitation. (b) The change in mean annual precipitation over the foreland basin and foothills of the Himalaya is the result of orographic effect caused by the Shillong Plateau's uplift. The critical elevation of the Shillong Plateau required to induce significant orographic precipitation was attained after ∼1.2 Ma. (c) By applying scale analysis, we estimate that the mean annual precipitation over the foreland basin of the eastern Bhutan Himalayas has decreased by a factor of 1.7–2.5 over the last 1–3 million years.

Changes in the occurrence of extreme precipitation events at the Paleocene–Eocene thermal maximum

Future global warming is widely anticipated to increase the occurrence of extreme precipitation events, but such hydrological changes have received limited attention within paleoclimate studies. Several proxy studies of the hydrological response to the Paleocene–Eocene Thermal Maximum hyperthermal, ∼56 Ma, have recently invoked changes in the occurrence of extreme precipitation events to explain observations, but these changes have not been studied for the geologic past using climate models. Here, we use a coupled atmosphere–ocean general circulation model, HadCM3L, to study regional changes in metrics for extreme precipitation across the onset of the PETM by comparing simulations performed with possible PETM and pre-PETM greenhouse gas forcings. Our simulations show a shift in the frequency–intensity relationship of precipitation, with extreme events increasing in importance over tropical regions including equatorial Africa and southern America. The incidence of some extreme events increases by up to 70% across the PETM in some regions. While the most extreme precipitation rates tend to relate to increases in convective precipitation, in some regions dynamic changes in atmospheric circulation are also of importance. Although shortcomings in the ability of general circulation models to represent the daily cycle of precipitation and the full range of extreme events precludes a direct comparison of absolute precipitation rates, our simulations provide a useful spatial framework for interpreting hydrological proxies from this time period. Our results indicate that changes in extreme precipitation behaviour may be decoupled from those in mean annual precipitation, including, for example in east Africa, where the change in mean annual precipitation is small but a large increase in the size and frequency of extreme events occurs. This has important implications for the interpretation of the hydrological proxy record and our understanding of climatic, as well as biogeochemical, responses to global warming events.

Allocation of forest biomass across broad precipitation gradients in China\u2019s forests

Forests act as major sinks for atmospheric CO2. An understanding of the relationship between forest biomass allocation and precipitation gradients is needed to estimate the impacts of changes in precipitation on carbon stores. Biomass patterns depend on tree size or age, making it unclear whether biomass allocation is limited by tree age at regional scales. Using a dataset of ten typical forest types spanning a large age scale, we evaluated forest biomass allocation–precipitation correlations with the aim of testing whether biomass allocation patterns vary systematically in response to altered precipitation. With increasing mean annual precipitation, a significant quadratic increase occurred in ≤30 yr and >60 yr groups in stem biomass, >60 yr group in branch biomass, and >60 yr groups in leaf biomass; and a significant cubic increase occurred in 30–60 yr and all age forest groups in stem biomass, ≤30 yr, 30–60 yr and all age forest groups in branch biomass, ≤30 yr and all age forest groups in leaf biomass, and in each group in root biomass, indicating that organ biomass is strongly limited by precipitation. Thus, forest biomass responds predictably to changes in mean annual precipitation. The results suggest that forest organ biomass–precipitation relationships hold across independent datasets that encompass a broad climatic range and forest age.

The role of urban growth, climate change, and their interplay in altering runoff extremes

AbstractChanges in climate and urban growth are the most influential factors affecting hydrological characteristics in urban and extra‐urban contexts. The assessment of the impacts of these changes on the extreme rainfall–runoff events may have important implications on urban and extra‐urban management policies against severe events, such as floods, and on the design of hydraulic infrastructures.Understanding the effects of the interaction between climate change and urban growth on the generation of runoff extremes is the main aim of this paper. We carried out a synthetic experiment on a river catchment of 64 km2 to generate hourly runoff time series under different hypothetical scenarios. We imposed a growth of the percentage of urban coverage within the basin (from 1.5% to 25%), a rise in mean temperature of 2.6 °C, and an alternatively increase/decrease in mean annual precipitation of 25%; changes in mean annual precipitation were imposed following different schemes, either changing rainstorm frequency or rainstorm intensity. The modelling framework consists of a physically based distributed hydrological model, which simulates fast and slow mechanisms of runoff generation directly connected with the impervious areas, a land‐use change model, and a weather generator. The results indicate that the peaks over threshold and the hourly annual peaks, used as hydrological indicators, are very sensitive to the rainstorm intensity. Moreover, the effects of climate changes dominate on those of urban growth determining an exacerbation of the fast runoff component in extreme events and a reduction of the slow and deep runoff component, thus limiting changes in the overall runoff.

Climate trends of temperature and precipitation in Nisava river valley (Serbia) for 1960-2015 period

Since climate plays a crucial role on our planet and is an inseparable part of all human activities, it is necessary to precisely record all parameters in order to estimate current climate conditions, climate characteristics of a certain region, as well as to try to predict and calculate further trends of climate change. Therefore, for the purpose of this paper, air temperature and precipitation of four meteorological stations in the Nisava river valley in Southeastern Serbia (municipalities of Dimitrovgrad, Pirot, Bela Palanka and Nis) have been considered for the period 1960-2015 along with statistical methods for analysis of these parameters and prediction of their trends. Results have shown that there is a positive trend in mean annual air temperatures and average seasonal air temperatures for the whole region which can influence natural processes and human activities. For precipitation, it can be concluded that no significant change in mean annual precipitation for the observed period has occurred. However, there is a great difference in the amount of precipitation between consecutive years, especially from 2000 onwards which can cause very dry years or years with floods.

A Study of Climate Change Impact on Precipitation of Sheonath River Basin

Objectives: Climate change impact assessment on precipitation data. Methods/Statistical analysis: This study is done for estimating the impact of climate change on the precipitation of Jondhara station, in the Seonath river basin, Chhattisgarh, India under A2 and B2 scenario of the HadCM3 GCM model. Statistical Downscaling Model (SDSM) was applied in this work. Selection of predictor variables is the most important steps in the statistical downscaling processes because it mostly affects the quality of the generated scenarios. Linear scaling method was used for the bias correction of the downscaled data in the study. Findings: The values ofR2 and NSE were0.78 and 0.78respectively, for the calibration period (1980-1991) and for the validation period (1992-2001) are 0.70 and 0.69 respectively. These parameters show the good applicability of the model performance. The change in mean annual precipitation during the period 2020- 2049, 2050-2079 and 2080– 2099 are -0.28%, -0.61%, and -2.39% respectively for A2 Scenario in comparison to the baseline period. Similarly, the values are increased 0.22%, 2.22%, and 2.00% respectively for theB2 scenario. Application/Improvements: This paper elaborates the effect of climate change on the precipitation of the Seonath river basin.

Inter-model comparison of hydrological impacts of climate change on the Upper Blue Nile basin using ensemble of hydrological models and global climate models

The aim of this study was to investigate the impacts of future climate change on discharge and evapotranspiration of the Upper Blue Nile (UBN) basin using multiple global circulation models (GCMs) projections and multiple hydrological models (HMs). The uncertainties of projections originating from HMs, GCMs, and representative concentration pathways (RCPs) were also analyzed. This study is part of the Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP) initiative (phase 2), which is a community driven modeling effort to assess global socio-economic impacts of climate change. The baseline period of 1981–2010 was used to identify climate change signals in two future periods: mid future (2036–2065) and far future (2070–2099). Our analyses showed that two out of four GCMs indicated a statistically significant increase in projected precipitation in the far future period. The projected change in mean annual precipitation varied between 4 and 10% relative to the baseline period. The HMs did not agree on the direction of climate change impacts on mean annual discharge. Furthermore, simulated changes in mean annual discharge by all HMs, except SWIM which simulated up to 6.6% increase for the far future period, were not statistically significant. All the HMs generally simulated a statistically significant increase in annual mean actual evapotranspiration (AET) in both periods. The HMs simulated changes in AET ranging from 1.9 to 4.4% for the far future period. In the UBN basin GCM structure was the main contributor of uncertainty in mean annual discharge projection followed by HM structure and RCPs, respectively. The results from this research suggest to use multiple impact models as well as multiple GCMs to provide a more robust assessment of climate change impacts in the UBN basin.

Impact of Climate Change on Drought in the Upstream Yangtze River Region

Based on Coupled Model Intercomparison Project Phase 5 (CMIP5) dataset and a variable infiltration capacity (VIC) hydrological model, this study assesses the possible influence of climate change in the upstream region of the Yangtze River on droughts in the future 30 years. Long-term daily soil moisture content were simulated by VIC model at a 50 km × 50 km resolution from 1951 to 2013. Regional historical drought events were then recognized based on soil moisture anomaly percentage index and validated with field data. Five relatively independent representative global circulation models were selected and the outputs of them were downscaled temporally and spatially as the inputs of VIC model for daily soil moisture content simulations both in the period of 1971–2000 for the present-day climate and in the period of 2021–2050 for the future. The results show that the projected annual mean temperature is likely to increase from 1.4 °C to 1.8 °C. The projected change in mean annual precipitation could be increased slightly by 0.6% to 1.3%, but the trend of precipitation change in summer and autumn might be opposite of that. Comparing the drought characteristics values recognized in 1971–2000, seven to eight additional regional drought events are likely to happen in 2021–2050. Drought duration and drought intensity are also likely to extend for 18 d to 25 d and increase by 1.2% to 6.2%, respectively. But, drought area could decrease slightly by 1.3% to 2.7% on average. These changes in drought characteristics values suggest that regional drought could become more severely prolonged and frequent in future.