Vegetation–climate feedbacks modulate rainfall patterns in Africa under
future climate change

Abstract. Africa has been undergoing significant changes in climate and vegetation in recent decades, and continued changes may be expected over this century. Vegetation cover and composition impose important influences on the regional climate in Africa. Climate-driven changes in vegetation structure and the distribution of forests versus savannah and grassland may feed back to climate via shifts in the surface energy balance, hydrological cycle and resultant effects on surface pressure and larger-scale atmospheric circulation. We used a regional Earth system model incorporating interactive vegetation–atmosphere coupling to investigate the potential role of vegetation-mediated biophysical feedbacks on climate dynamics in Africa in an RCP8.5-based future climate scenario. The model was applied at high resolution (0.44 × 0.44°) for the CORDEX-Africa domain with boundary conditions from the CanESM2 general circulation model. We found that increased tree cover and leaf-area index (LAI) associated with a CO2 and climate-driven increase in net primary productivity, particularly over subtropical savannah areas, not only imposed important local effect on the regional climate by altering surface energy fluxes but also resulted in remote effects over central Africa by modulating the land–ocean temperature contrast, Atlantic Walker circulation and moisture inflow feeding the central African tropical rainforest region with precipitation. The vegetation-mediated feedbacks were in general negative with respect to temperature, dampening the warming trend simulated in the absence of feedbacks, and positive with respect to precipitation, enhancing rainfall reduction over the rainforest areas. Our results highlight the importance of accounting for vegetation–atmosphere interactions in climate projections for tropical and subtropical Africa.

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Vegetation-climate feedbacks modulate rainfall patterns in Africa under future climate change

10.5194/esd-2015-88 ◽

2016 ◽

Cited By ~ 1

Author(s):

M. Wu ◽

G. Schurgers ◽

M. Rummukainen ◽

B. Smith ◽

P. Samuelsson ◽

...

Keyword(s):

Climate Change ◽

Surface Energy ◽

Net Primary Productivity ◽

Hydrological Cycle ◽

Regional Climate ◽

Local Effect ◽

Future Climate ◽

Future Climate Change ◽

Vegetation Patterns ◽

Climate Projections

Abstract. Africa has been undergoing significant changes in climate patterns and vegetation in recent decades, and continued changes may be expected over this century. Vegetation cover and composition impose important influences on the regional climate in Africa. Climate change-driven changes in regional vegetation patterns may feed back to climate via shifts in surface energy balance, hydrological cycle and resultant effects on surface pressure patterns and larger-scale atmospheric cir culation. We used a regional Earth system model incorporating interactive vegetation-atmosphere coupling to investigate the potential role of vegetation-mediated biophysical feedbacks on climate dynamics in Africa in an RCP8.5-based future climate scenario. The model was applied at high resolution (0.44 x 0.44 degrees) for the CORDEX-Africa domain with boundary conditions from the CanESM2 GCM. We found that changes in vegetation patterns associated with a CO2 and climate-driven increase in net primary productivity, particularly over sub-tropical savannah areas, not only imposed important local effect on the regional climate by altering surface energy fluxes, but also resulted in remote effects over central Africa by modulating the land-ocean temperature contrast, Atlantic Walker circulation and moisture inflow feeding the central African tropical rainforest region with precipitation. The vegetation-mediated feedbacks were in general negative with respect to temperature, dampening the warming trend simulated in the absence of feedbacks, and positive with respect to precipitation, enhancing rainfall reduction over rainforest areas. Our results highlight the importance of vegetation-atmosphere interactions in climate projections for tropical and sub-tropical Africa.

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Integrated Water Balance and Water Quality Management Under Future Climate Change and Population Growth: A Case Study of Upper Litani Basin, Lebanon

10.21203/rs.3.rs-1169379/v1 ◽

2022 ◽

Author(s):

Rana Salim Abou Slaymane ◽

M. Reda Soliman

Keyword(s):

Water Quality ◽

Water Resources ◽

Water Balance ◽

General Circulation ◽

Waste Water Treatment ◽

Water Quality Management ◽

Circulation Model ◽

Future Climate ◽

Future Climate Change ◽

Baseline Scenario

Abstract The impacts of the growing population at Lebanon including Lebanese, Palestinian and Syrian refugees, associated with the changing climate parameters such that the precipitation are putting the Bekaa Valley’s water resources in a stymie situation. The water resources are under significant stress limiting the water availability and deteriorating the water quality at the Upper Litani River Basin (ULRB) within the Bekaa Valley region. These impacts are assessed by Water Evaluation And Planning model to assure the water balance and quality at baseline scenario in 2013, and future scenarios reaching 2095, serving by the Watershed Modeling System to get the flow throughout the Litani River’s ungauged zones. Moreover, a General Circulation Model is used to predict the future climate up to 2100 under several emissions scenarios which shows a critical situation at the high emission scenario where the precipitation will be reduced about 87 mm from 2013 to 2095. The aim of this research is to reduce the water pollution that limits the availability of usable water, and to minimize the gap between the demand and supply of water within the ULRB in order to maintain water resources sustainability, and preserves its quality, even after 80 years. In particular, this may be achieved by removing encroachments on the river, by adding waste water treatment plants, by reducing the amount of lost water in damaged water network, and by avoiding the overconsumption of groundwater.

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Impacts of Climate Change on the Water Availability, Seasonality and Extremes in the Upper Indus Basin (UIB)

Sustainability ◽

10.3390/su12041283 ◽

2020 ◽

Vol 12 (4) ◽

pp. 1283 ◽

Cited By ~ 3

Author(s):

Asim Khan ◽

Manfred Koch ◽

Adnan Tahir

Keyword(s):

General Circulation ◽

Extreme Values ◽

Regional Climate ◽

Total Duration ◽

Future Climate ◽

Indus Basin ◽

Mean Annual Precipitation ◽

Climate Projections ◽

Climatic Data ◽

Upper Indus Basin

Projecting future hydrology for the mountainous, highly glaciated upper Indus basin (UIB) is a challenging task because of uncertainties in future climate projections and issues with the coverage and quality of available reference climatic data and hydrological modelling approaches. This study attempts to address these issues by utilizing the semi-distributed hydrological model “Soil and water assessment tool” (SWAT) with new climate datasets and better spatial and altitudinal representation as well as a wider range of future climate forcing models (general circulation model/regional climate model combinations (GCMs_RCMs) from the “Coordinated Regional Climate Downscaling Experiment-South Asia (CORDEX-SA) project to assess different aspects of future hydrology (mean flows, extremes and seasonal changes). Contour maps for the mean annual flow and actual evapotranspiration as a function of the downscaled projected mean annual precipitation and temperatures are produced and can serve as a “hands-on” forecast tool of future hydrology. The overall results of these future SWAT hydrological projections indicate similar trends of changes in magnitudes, seasonal patterns and extremes of the UIB—stream flows for almost all climate scenarios/models/periods—combinations analyzed. In particular, all but one GCM_RCM model—the one predicting a very high future temperature rise—indicated mean annual flow increases throughout the 21st century, wherefore, interestingly, these are stronger for the middle years (2041–2070) than at its end (2071–2100). The seasonal shifts as well as the extremes follow also similar trends for all climate scenario/model/period combinations, e.g., an earlier future arrival (in May–June instead of July–August) of high flows and increased spring and winter flows, with upper flow extremes (peaks) projected to drastically increase by 50 to >100%, and with significantly decreased annual recurrence intervals, i.e., a tremendously increased future flood hazard for the UIB. The future low flows projections also show more extreme values, with lower-than-nowadays-experienced minimal flows occurring more frequently and with much longer annual total duration.

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Over 5,000 Years of Ensemble Future Climate Simulations by 60-km Global and 20-km Regional Atmospheric Models

Bulletin of the American Meteorological Society ◽

10.1175/bams-d-16-0099.1 ◽

2017 ◽

Vol 98 (7) ◽

pp. 1383-1398 ◽

Cited By ~ 119

Author(s):

Ryo Mizuta ◽

Akihiko Murata ◽

Masayoshi Ishii ◽

Hideo Shiogama ◽

Kenshi Hibino ◽

...

Keyword(s):

Twentieth Century ◽

Extreme Events ◽

General Circulation ◽

Dynamical Downscaling ◽

Circulation Model ◽

Future Climate ◽

Future Climate Change ◽

Atmospheric Models ◽

Large Ensemble ◽

Climate Simulations

Abstract An unprecedentedly large ensemble of climate simulations with a 60-km atmospheric general circulation model and dynamical downscaling with a 20-km regional climate model has been performed to obtain probabilistic future projections of low-frequency local-scale events. The climate of the latter half of the twentieth century, the climate 4 K warmer than the preindustrial climate, and the climate of the latter half of the twentieth century without historical trends associated with the anthropogenic effect are each simulated for more than 5,000 years. From large ensemble simulations, probabilistic future changes in extreme events are available directly without using any statistical models. The atmospheric models are highly skillful in representing localized extreme events, such as heavy precipitation and tropical cyclones. Moreover, mean climate changes in the models are consistent with those in phase 5 of the Coupled Model Intercomparison Project (CMIP5) ensembles. Therefore, the results enable the assessment of probabilistic change in localized severe events that have large uncertainty from internal variability. The simulation outputs are open to the public as a database called “Database for Policy Decision Making for Future Climate Change” (d4PDF), which is intended to be utilized for impact assessment studies and adaptation planning for global warming.

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Methane chemistry in a nutshell – The new submodels CH4 (v1.0) and TRSYNC (v1.0) in MESSy (v2.54.0)

10.5194/gmd-2020-137 ◽

2020 ◽

Author(s):

Franziska Winterstein ◽

Patrick Jöckel

Keyword(s):

Water Vapour ◽

Atmospheric Chemistry ◽

General Circulation ◽

Hydrological Cycle ◽

Circulation Model ◽

Optimization Techniques ◽

Specific Humidity ◽

Climate Projections ◽

Sensitivity Studies ◽

The Impact

Abstract. Climate projections including chemical feedbacks rely on state-of-the-art chemistry-climate models (CCMs). Of particular importance is the role of methane (CH4) for the budget of stratospheric water vapor (SWV), which has an important climate impact. However, simulations with CCMs are, due to the large number of involved chemical species, computationally demanding, which limits the simulation of sensitivity studies. To allow for sensitivity studies and ensemble simulations with a reduced demand for computational resources, we introduce a simpliﬁed approach to simulate the core of methane chemistry in form of the new Modular Earth Submodel System (MESSy) submodel CH4. It involves an atmospheric chemistry mechanism reduced to the sink reactions of CH4 with predeﬁned ﬁelds of the hydroxyl radical (OH), excited oxygen (O(1D)), and chlorine (Cl), as well as photolysis and the reaction products limited to water vapour (H2O). This chemical production of H2O is optionally feed back onto the speciﬁc humidity (q) of the connected General Circulation Model (GCM), to account for the impact onto SWV and its effect on radiation and stratospheric dynamics. The submodel CH4 is further capable of simulating the four most prevalent CH4 isotopologues for carbon and hydrogen (CH4 and CH3D as well as 12CH4 and 13CH4), respectively. Furthermore, the production of deuterated water vapour (HDO) is, similar to the production of H2O in the CH4 oxidation, optionally feed back to the isotopological hydrological cycle simulated by the submodel H2OISO, using the newly developed auxiliary submodel TRSYNC. Moreover, the simulation of a user deﬁned number of diagnostic CH4 age- and emission classes is possible, which output can be used for ofﬂine inverse optimization techniques. The presented approach combines the most important chemical hydrological feedback including the isotopic signatures with the advantages concerning the computational simplicity of a GCM, in comparison to a full featured CCM.

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Investigating future changes in Southern China precipitation characteristics based on dynamically downscaled CMIP5 climate projections

10.5194/egusphere-egu2020-2987 ◽

2020 ◽

Author(s):

Ying Lung Liu ◽

Chi-Yung Tam ◽

Sai Ming Lee

Keyword(s):

Interannual Variability ◽

General Circulation ◽

Hydrological Cycle ◽

Southern China ◽

Lower Troposphere ◽

Circulation Model ◽

Boreal Summer ◽

Annual Number ◽

Climate Projections ◽

The Mean

In this study, general circulation model (GCM) products were dynamically downscaled using the Regional Climate Model system version 4 (RegCM4), in order to study changes in the hydrological cycle - including extreme events - due to a warmer climate by the end of the 21st century over Southern China. The performance of 22 GCMs participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) in simulating the climate over the East Asian- western north Pacific region was first evaluated. It was found that MPI-ESM-MR, CNRM-CM5, ACCESS1-3, and GFDL- CM3 can reasonably reproduce the seasonal mean atmospheric circulation in that region, as well as its interannual variability. Outputs from these GCMs were subsequently downscaled, using the RegCM4, to a horizontal resolution of 25 km &#215; 25km, for the period of 1979 to 2003, and also from 2050 to 2099, with the latter based on GCM projection according to the RCP8.5 scenario. Results show that the whole domain would undergo warming at the lower troposphere by 3 &#8211; 4 &#176;C over inland China and ~2 &#176;C over the ocean and low-latitude locations. Compared to the 1979-2003 era, during 2050-2099 boreal summer, the mean precipitation is projected to increase by 1 &#8211; 2 mm/day over coastal Southern China. There is also significantly enhanced interannual variability for the same season. In boreal spring, a similar increase in both the seasonal mean and also its year-to-year variations is also found, over more inland locations at about 25&#176;N. Extreme daily precipitation is projected to become more intense, based on analyses of the 95th percentile for these seasons. On the other hand, it will be significantly drier during autumn over a broad area in Southern China: the mean rainfall is projected to decrease by ~1 mm/day. In addition, changes in the annual number of consecutive dry days (CDD) throughout the whole calendar year was also examined. It was found that CDD over the more inland locations will increase by ~5 days. Thus, there will be a lengthening of the dry season in the region. Global warming&#8217;s potential impact on sub-daily rainfall is also examined. For the rainfall diurnal cycle (DC), there is no significant change in both spatial and temporal patterns. Moisture budget analyses are also carried out, in order to ascertain the importance of change in background moisture, versus that in wind circulation, on the intensification of MAM and JJA mean rainfall as well as their interannual variability. The implication of these results on water management and climate change adaptation over the Southern China region will be discussed.

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Seasonal Simulation of Tropospheric Ozone over the Midwestern and Northeastern United States: An Application of a Coupled Regional Climate and Air Quality Modeling System

Journal of Applied Meteorology and Climatology ◽

10.1175/jam2521.1 ◽

2007 ◽

Vol 46 (7) ◽

pp. 945-960 ◽

Cited By ~ 17

Author(s):

Ho-Chun Huang ◽

Xin-Zhong Liang ◽

Kenneth E. Kunkel ◽

Michael Caughey ◽

Allen Williams

Keyword(s):

United States ◽

Air Quality ◽

Tropospheric Ozone ◽

General Circulation ◽

Climate Model ◽

Regional Climate ◽

Future Climate ◽

Climate Projections ◽

Northeastern United States ◽

Ozone Episodes

Abstract The impacts of air pollution on the environment and human health could increase as a result of potential climate change. To assess such possible changes, model simulations of pollutant concentrations need to be performed at climatic (seasonal) rather than episodic (days) time scales, using future climate projections from a general circulation model. Such a modeling system was employed here, consisting of a regional climate model (RCM), an emissions model, and an air quality model. To assess overall model performance with one-way coupling, this system was used to simulate tropospheric ozone concentrations in the midwestern and northeastern United States for summer seasons between 1995 and 2000. The RCM meteorological conditions were driven by the National Centers for Environmental Prediction/Department of Energy global reanalysis (R-2) using the same procedure that integrates future climate model projections. Based on analyses for several urban and rural areas and regional domains, fairly good agreement with observations was found for the diurnal cycle and for several multiday periods of high ozone episodes. Even better agreement occurred between monthly and seasonal mean quantities of observed and model-simulated values. This is consistent with an RCM designed primarily to produce good simulations of monthly and seasonal mean statistics of weather systems.

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Evaluation of climate change impacts and adaptation strategies for maize cultivation in the Himalayan foothills of India

Journal of Water and Climate Change ◽

10.2166/wcc.2015.070 ◽

2015 ◽

Vol 6 (3) ◽

pp. 596-614 ◽

Cited By ~ 18

Author(s):

Proloy Deb ◽

Anthony S. Kiem ◽

Mukand S. Babel ◽

Sang Thi Chu ◽

Biplab Chakma

Keyword(s):

Climate Change ◽

General Circulation ◽

Circulation Model ◽

Maize Yield ◽

Future Climate ◽

Future Climate Change ◽

Daily Maximum ◽

Study Region ◽

Supplementary Irrigation ◽

The Future

This study evaluates the impacts of climate change on rainfed maize (Zea mays) yield and evaluates different agro-adaptation measures to counteract its negative impacts at Sikkim, a Himalayan state of India. Future climate scenarios for the 10 years centered on 2025, 2055 and 2085 were obtained by downscaling the outputs of the HadCM3 General Circulation Model (GCM) under for A2 and B2 emission scenarios. HadCM3 was chosen after assessing the performance analysis of six GCMs for the study region. The daily maximum and minimum temperatures are projected to rise in the future and precipitation is projected to decrease (by 1.7 to 22.6% relative to the 1991–2000 baseline) depending on the time period and scenarios considered. The crop simulation model CERES-Maize was then used to simulate maize yield under future climate change for the future time windows. Simulation results show that climate change could reduce maize productivity by 10.7–18.2%, compared to baseline yield, under A2 and 6.4–12.4% under B2 scenarios. However, the results also indicate that the projected decline in maize yield could be offset by early planting of seeds, lowering the farm yard manure application rate, introducing supplementary irrigation and shifting to heat tolerant varieties of maize.

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Methane chemistry in a nutshell – the new submodels CH4 (v1.0) and TRSYNC (v1.0) in MESSy (v2.54.0)

Geoscientific Model Development ◽

10.5194/gmd-14-661-2021 ◽

2021 ◽

Vol 14 (2) ◽

pp. 661-674

Author(s):

Franziska Winterstein ◽

Patrick Jöckel

Keyword(s):

Water Vapour ◽

Atmospheric Chemistry ◽

General Circulation ◽

Hydrological Cycle ◽

Circulation Model ◽

Optimization Techniques ◽

Specific Humidity ◽

Climate Projections ◽

Sensitivity Studies ◽

The Impact

Abstract. Climate projections including chemical feedbacks rely on state-of-the-art chemistry–climate models (CCMs). Of particular importance is the role of methane (CH4) for the budget of stratospheric water vapour (SWV), which has an important climate impact. However, simulations with CCMs are, due to the large number of involved chemical species, computationally demanding, which limits the simulation of sensitivity studies. To allow for sensitivity studies and ensemble simulations with a reduced demand for computational resources, we introduce a simplified approach to simulate the core of methane chemistry in form of the new Modular Earth Submodel System (MESSy) submodel CH4. It involves an atmospheric chemistry mechanism reduced to the sink reactions of CH4 with predefined fields of the hydroxyl radical (OH), excited oxygen (O(1D)), and chlorine (Cl), as well as photolysis and the reaction products limited to water vapour (H2O). This chemical production of H2O is optionally fed back onto the specific humidity (q) of the connected general circulation model (GCM), to account for the impact onto SWV and its effect on radiation and stratospheric dynamics. The submodel CH4 is further capable of simulating the four most prevalent CH4 isotopologues for carbon and hydrogen (CH4 and CH3D, as well as 12CH4 and 13CH4). Furthermore, the production of deuterated water vapour (HDO) is, similar to the production of H2O in the CH4 oxidation, optionally passed back to the isotopological hydrological cycle simulated by the submodel H2OISO, using the newly developed auxiliary submodel TRSYNC. Moreover, the simulation of a user-defined number of diagnostic CH4 age and emission classes is possible, the output of which can be used for offline inverse optimization techniques. The presented approach combines the most important chemical hydrological feedback including the isotopic signatures with the advantages concerning the computational simplicity of a GCM, in comparison to a full-featured CCM.

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Parameterization dependence of the hydrological cycle in a general circulation model of intermediate complexity

10.5194/egusphere-egu21-1328 ◽

2021 ◽

Author(s):

Oliver Mehling ◽

Elisa Ziegler ◽

Heather Andres ◽

Martin Werner ◽

Kira Rehfeld

Keyword(s):

General Circulation Model ◽

General Circulation ◽

Hydrological Cycle ◽

Mean Absolute Error ◽

Circulation Model ◽

Absolute Error ◽

Bayesian Optimization ◽

Model Parameters ◽

Climate Projections ◽

Intermediate Complexity

The global hydrological cycle is of crucial importance for life on Earth. Hence, it is a focus of both future climate projections and paleoclimate modeling. The latter typically requires long integrations or large ensembles of simulations, and therefore models of reduced complexity are needed to reduce the computational cost. Here, we study the hydrological cycle of the the Planet Simulator (PlaSim) [1], a general circulation model (GCM) of intermediate complexity, which includes evaporation, precipitation, soil hydrology, and river advection.Using published parameter configurations for T21 resolution [2, 3], PlaSim strongly underestimates precipitation in the mid-latitudes as well as global atmospheric water compared to ERA5 reanalysis data [4]. However, the tuning of PlaSim has been limited to optimizing atmospheric temperatures and net radiative fluxes so far [3].Here, we present a different approach by tuning the model&#8217;s atmospheric energy balance and water budget simultaneously. We argue for the use of the globally averaged mean absolute error (MAE) for 2 m temperature, net radiation, and evaporation in the objective function. To select relevant model parameters, especially with respect to radiation and the hydrological cycle, we perform a sensitivity analysis and evaluate the feature importance using a Random Forest regressor. An optimal set of parameters is obtained via Bayesian optimization.Using the optimized set of parameters, the mean absolute error of temperature and cloud cover is reduced on most model levels, and mid-latitude precipitation patterns are improved. In addition to annual zonal-mean patterns, we examine the agreement with the seasonal cycle and discuss regions in which the bias remains considerable, such as the monsoon region over the Pacific.We discuss the robustness of this tuning with regards to resolution (T21, T31, and T42), and compare the atmosphere-only results to simulations with a mixed-layer ocean. Finally, we provide an outlook on the applicability of our parametrization to climate states other than present-day conditions.[1] K. Fraedrich et al., Meteorol. Z. 14, 299&#8211;304 (2005) [2] F. Lunkeit et al., Planet Simulator User&#8217;s Guide Version 16.0 (University of Hamburg, 2016) [3] G. Lyu et al., J. Adv. Model. Earth Syst. 10, 207&#8211;222 (2018) [4] H. Hersbach et al., Q. J. R. Meteorol. Soc. 146, 1999&#8211;2049 (2020)

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