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The interactions between the terrestrial biosphere, atmospheric chemistry, and climate involve complex feedbacks that have traditionally been modeled separately. We present a new framework that couples the Yale Interactive terrestrial Biosphere (YIBs) model, a dynamic plant-chemistry model, with the RegCM-Chem model. RegCM-Chem–YIBs integrates meteorological variables and atmospheric chemical composition from RegCM-Chem with land surface parameters from YIBs. The terrestrial carbon flux calculated by YIBs is fed back into RegCM-Chem interactively, thereby representing the interactions between fine particulate matter (PM 2.5), ozone (O 3), and carbon dioxide (CO 2). For testing purposes, we carry out a 1-year simulation (2016) at a 30 km horizontal resolution over East Asia with RegCM-Chem–YIBs. The model accurately captures the spatio-temporal distribution of climate, chemical composition, and ecological parameters. In particular, the estimated O 3 and PM 2.5 are consistent with ground observations, with correlation coefficients (R) of 0.74 and 0.65, respectively. The simulated CO 2 concentration is consistent with observations from six sites (R ranged from 0.89 to 0.97) and exhibits a similar spatial pattern when compared with carbon assimilation products. RegCM-Chem–YIBs produces reasonably good gross primary productivity (GPP) and net primary productivity (NPP), showing seasonal and spatial distributions consistent with satellite observations, and mean biases (MBs) of 0.13 and 0.05 kg C m -2 yr -1. This study illustrates that RegCM-Chem–YIBs is a valuable tool to investigate coupled interactions between the terrestrial carbon cycle, atmospheric chemistry, and climate change at a higher resolution on a regional scale. [ABSTRACT FROM AUTHOR]

The interactions between the terrestrial biosphere, atmospheric chemistry, and climate involve complex feedbacks that have traditionally been modeled separately. We present a new framework that couples the Yale Interactive terrestrial Biosphere (YIBs), a dynamic plant-chemistry model, with the RegCM-Chem model. RegCM-Chem-YIBs integrates meteorological variables and atmospheric chemical composition from RegCM-Chem with land surface parameters from YIBs. The terrestrial carbon flux calculated by YIBs, are fed back into RegCM-Chem interactively, thereby representing the interactions between fine particulate matter (PM2.5), ozone (O3), and carbon dioxide (CO2). For testing purposes, we carry out a one-year simulation (2016) at a 30 km horizontal resolution over East Asia with RegCM-Chem-YIBs. The model accurately captures the spa-tio-temporal distribution of climate, chemical composition, and ecological parameters. In particular, the estimated O3 and PM2.5 are consistent with ground observations, with correlation coefficients (R) of 0.74 and 0.65, respec-tively. The simulated CO2 concentration is consistent with observations from six sites (R ranged from 0.89 to 0.97) and exhibits a similar spatial pattern when compared to carbon assimilation products. RegCM-Chem-YIBs produces reasonably good gross primary productivity (GPP) and net primary productivity (NPP), showing seasonal and spatial distributions consistent with satellite observations, and mean biases (MBs) of 0.13 and 0.05 kg C m-2 year-1. This study illustrates that the RegCM-Chem-YIBs is a valuable tool to investigate coupled interactions between the terrestrial carbon cycle, atmospheric chemistry, and climate change at a higher resolution in regional scale. [ABSTRACT FROM AUTHOR]

The interactions between the terrestrial biosphere, atmospheric chemistry, and climate involve complex feedbacks that have traditionally been modeled separately. We present a new framework that couples the Yale Interactive terrestrial Biosphere (YIBs), a dynamic plant-chemistry model, with the RegCM-Chem model. RegCM-Chem-YIBs integrates meteorological variables and atmospheric chemical composition from RegCM-Chem with land surface parameters from YIBs. The terrestrial carbon flux calculated by YIBs, are fed back into RegCM-Chem interactively, thereby representing the interactions between fine particulate matter (PM2.5), ozone (O3), and carbon dioxide (CO2). For testing purposes, we carry out a one-year simulation (2016) at a 30 km horizontal resolution over East Asia with RegCM-Chem-YIBs. The model accurately captures the spa-tio-temporal distribution of climate, chemical composition, and ecological parameters. In particular, the estimated O3 and PM2.5 are consistent with ground observations, with correlation coefficients (R) of 0.74 and 0.65, respec-tively. The simulated CO2 concentration is consistent with observations from six sites (R ranged from 0.89 to 0.97) and exhibits a similar spatial pattern when compared to carbon assimilation products. RegCM-Chem-YIBs produces reasonably good gross primary productivity (GPP) and net primary productivity (NPP), showing seasonal and spatial distributions consistent with satellite observations, and mean biases (MBs) of 0.13 and 0.05 kg C m-2 year-1. This study illustrates that the RegCM-Chem-YIBs is a valuable tool to investigate coupled interactions between the terrestrial carbon cycle, atmospheric chemistry, and climate change at a higher resolution in regional scale. [ABSTRACT FROM AUTHOR]

Plants emit biogenic volatile organic compounds (BVOCs) in response to changes in environmental conditions (e.g. temperature, radiation, soil moisture). In the large family of BVOCs, isoprene is by far the strongest emitted compound and plays an important role in ozone chemistry, thus affecting both air quality and climate. In turn, climate change may alter isoprene emissions by increasing temperature as well as the occurrence and intensity of severe water stresses that alter plant functioning. The Model of Emissions of Gases and Aerosols from Nature (MEGAN) provides different parameterizations to account for the impact of water stress on isoprene emissions, which essentially reduces emissions in response to the effect of soil moisture deficit on plant productivity. By applying the regional climate–chemistry model RegCM4chem coupled to the Community Land Model CLM4.5 and MEGAN2.1, we thus performed sensitivity simulations to assess the effects of water stress on isoprene emissions and near-surface ozone levels over the Euro-Mediterranean region and across the drier and wetter summers over the 1992–2016 period using two different parameterizations of the impact of water stress implemented in the MEGAN model. Over the Euro-Mediterranean region and across the simulated summers, water stress reduces isoprene emissions on average by nearly 6 %. However, during the warmest and driest selected summers (e.g. 2003, 2010, 2015) and over large isoprene-source areas (e.g. the Balkans), decreases in isoprene emissions range from -20 % to -60 % and co-occur with negative anomalies in precipitation, soil moisture and plant productivity. Sustained decreases in isoprene emissions also occur after prolonged or repeated dry anomalies, as observed for the summers of 2010 and 2012. Although the decrease in isoprene emissions due to water stress may be important, it only reduces near-surface ozone levels by a few percent due to a dominant VOC-limited regime over southern Europe and the Mediterranean Basin. Overall, over the selected analysis region, compared to the old MEGAN parameterization, the new one leads to localized and 25 %–50 % smaller decreases in isoprene emissions and 3 %–8 % smaller reductions in near-surface ozone levels. [ABSTRACT FROM AUTHOR]

Evidence that during the Last Glacial Maximum (LGM) glaciers extended well into the piedmont plains is still identifiable in the alpine foreland as a system of well-preserved moraines. Glaciers are strongly controlled by temperature and precipitation, and therefore, they are excellent indicators of climate change. Here, we use a regional climate model (RCM) to investigate some of the physical processes sustaining Alpine glaciers during the last phase of the LGM during Greenland Stadial 2 at 21 ka. We find a predominance of convection during summer and increased southwesterly stratiform precipitation over the southern Alps when compared to pre-industrial (PI) conditions. This precipitation pattern, along with lower temperatures, determined summer snowfall extending to low elevations, with a consequent substantial drop of the equilibrium line altitude (ELA), which is consistent with the estimated LGM glacier extent. Our RCM-based estimates of 21 ka ELA at the LGM yield excellent consistency with Alpine ELA reconstructions, further demonstrating the great potential of this technique for use in palaeoclimate studies. [ABSTRACT FROM AUTHOR]

Mitigation of carbonaceous aerosol emissions is expected to provide climate and health co-benefits. The accurate representation of carbonaceous aerosols in climate models is critical for reducing uncertainties in their climate feedback. In this regard, emission fluxes and aerosol life cycle processes are the two primary sources of uncertainties. Here, we demonstrate that the incorporation of a dynamic ageing scheme and emission estimates that are updated for the local sources improves the representation of carbonaceous aerosols over the Indian monsoon region in a regional climate model, RegCM, compared with its default configuration. The respective mean black carbon (BC) and organic carbon (OC) surface concentrations in 2010 are estimated to be 4.25 and 10.35 µ g m -3 over the Indo-Gangetic Plain (IGP) in the augmented model. The BC column burden over the polluted IGP is found to be 2.47 mg m -2 , 69.95 % higher than in the default model configuration and much closer to available observations. The anthropogenic aerosol optical depth (AOD) increases by more than 19 % over the IGP due to the model enhancement, also leading to a better agreement with observed AOD. The respective top-of-the-atmosphere, surface, and atmospheric anthropogenic aerosol short-wave radiative forcing are estimated at -0.3 , -9.3 , and 9.0 W m -2 over the IGP and -0.89 , -5.33 , and 4.44 W m -2 over Peninsular India (PI). Our results suggest that the combined effect of two modifications leads to maximum improvements in the model performance in regions where emissions play a dominant role. [ABSTRACT FROM AUTHOR]

Evidence that during the Last Glacial Maximum (LGM) glaciers extended well into the piedmont planes is still identifiable in the alpine foreland as a system of well-preserved moraines. Glaciers are strongly affected by temperature and precipitation and therefore they are excellent indicators of climate change. Here we use a regional climate model (RCM) to investigate the physical processes sustaining the glacier extent during the LGM. We find a predominance of convection during summer and increased southwesterly stratiform precipitation over the southern Alps compared to pre-industrial conditions. This precipitation pattern, along with lower temperatures, determined summer snowfall extending to low elevations with a consequent substantial drop of the equilibrium line altitude (ELA) consistent with the estimated LGM glacier extent. Our RCM based estimates of the ELA at the LGM yield excellent consistency with Alpine glacier reconstructions, further demonstrating the great potential of this technique for use in paleoclimate studies. [ABSTRACT FROM AUTHOR]

Mitigation of carbonaceous aerosol emissions is expected to provide climate and health co-benefits. The accurate representation of carbonaceous aerosols in climate models is critical for reducing uncertainties in their climate feedbacks. In this regard, emission fluxes and aerosol life-cycle processes are the two primary sources of uncertainties. Here we demonstrate that incorporating a dynamic ageing scheme and emission estimates that are updated for the local sources improve the representation of carbonaceous aerosols over the Indian monsoon region in a regional climate model, RegCM, compared to its default configuration. The mean BC and OC surface concentrations in 2010 are estimated to be 4.25 and 10.35 μg m-3, respectively, over the Indo-Gangetic Plain (IGP), in the augmented model. The BC column burden over the polluted IGP is found to be 2.47 mg m-2, 69.95 % higher than in the default model configuration and much closer to available observations. The anthropogenic AOD increases by more than 19 % over the IGP due to the model enhancement, also leading to a better agreement with observed AOD. The top-of-the-atmosphere, surface, and atmospheric anthropogenic aerosol shortwave radiative forcing are estimated at -0.3, -9.3, and 9.0 W m-2, respectively, over the IGP and -0.89, -5.33, and 4.44 W m-2, respectively, over Peninsular India. Our results suggest that both the accurate estimates of emission fluxes and a better representation of aerosol processes are required to improve the aerosol life cycle representation in the climate model. [ABSTRACT FROM AUTHOR]

We describe the development of a non-hydrostatic version of the regional climate model RegCM4, called RegCM4-NH, for use at convection-permitting resolutions. The non-hydrostatic dynamical core of the Mesoscale Model MM5 is introduced in the RegCM4, with some modifications to increase stability and applicability of the model to long-term climate simulations. Newly available explicit microphysics schemes are also described, and three case studies of intense convection events are carried out in order to illustrate the performance of the model. They are all run at a convection-permitting grid spacing of 3 km over domains in northern California, Texas and the Lake Victoria region, without the use of parameterized cumulus convection. A substantial improvement is found in several aspects of the simulations compared to corresponding coarser-resolution (12 km) runs completed with the hydrostatic version of the model employing parameterized convection. RegCM4-NH is currently being used in different projects for regional climate simulations at convection-permitting resolutions and is intended to be a resource for users of the RegCM modeling system. [ABSTRACT FROM AUTHOR]

Air pollution and wintertime fog over South Asia is a major concern due to its significant implications for air quality, visibility and health. Using a regional climate model coupled with chemistry, we assess the contribution of the hygroscopic growth of aerosols (ambient–dry) to the total aerosol optical depth and demonstrate that the increased surface cooling due to the hygroscopic effects of aerosols further increases the humidity in the boundary layer and thus enhances the confinement of pollutants through aerosol–boundary layer interactions. This positive feedback mechanism plays an important role in the prevalence of wintertime fog and poor air quality conditions over South Asia, where water vapour contributes more than half of the aerosol optical depth. The aerosol–boundary layer interactions lead to moistening of the boundary layer and drying of the free troposphere, which amplifies the long-term trend in relative humidity over the Indo-Gangetic Plain during winter. Hence, the aerosol–water vapour interaction plays a decisive role in the formation and maintenance of the wintertime fog conditions over South Asia, which needs to be considered for planning mitigation strategies. [ABSTRACT FROM AUTHOR]

Identification of flood prone areas is instrumental for a large number of applications, ranging from engineering to climate change studies, and provides essential information for planning effective emergency responses. In this work we describe an integrated hydrological and hydraulic modeling approach for the assessment of flood-prone areas in Italy and we present the first results obtained over the Po river (Northern Italy) at a resolution of 90 m. River discharges are obtained through the hydrological model CHyM driven by GRIPHO, a newly-developed high resolution hourly precipitation dataset. Runoff data is then used to obtain Synthetic Design Hydrographs (SDHs) for different return periods along the river network. Flood hydrographs are subsequently processed by a parallelized version of the CA2D hydraulic model to calculate the flow over an ad hoc re-shaped HydroSHEDS digital elevation model which includes information about the channel geometry. Modeled hydrographs and SDHs are compared with those obtained from observed data for a choice of gauging stations, showing an overall good performance of the CHyM model. The flood hazard maps for return periods of 50, 100, 500 are validated by comparison with the official flood hazard maps produced by the River Po Authority (Adbpo) and with the Joint Research Centre's (JRC) pan-European maps. The results show a good agreement with the available official national flood maps for high return periods. For lower return periods the results and less satisfactory but overall the application suggests strong potential of the proposed approach for future applications. [ABSTRACT FROM AUTHOR]

We revisit the issue of the response of precipitation characteristics to global warming based on analyses of global and regional climate model projections for the 21st century. The prevailing response we identify can be summarized as follows: increase in the intensity of precipitation events and extremes, with the occurrence of events of "unprecedented" magnitude, i.e., a magnitude not found in the present-day climate; decrease in the number of light precipitation events and in wet spell lengths; and increase in the number of dry days and dry spell lengths. This response, which is mostly consistent across the models we analyzed, is tied to the difference between precipitation intensity responding to increases in local humidity conditions and circulations, especially for heavy and extreme events, and mean precipitation responding to slower increases in global evaporation. These changes in hydroclimatic characteristics have multiple and important impacts on the Earth's hydrologic cycle and on a variety of sectors. As examples we investigate effects on potential stress due to increases in dry and wet extremes, changes in precipitation interannual variability, and changes in the potential predictability of precipitation events. We also stress how the understanding of the hydroclimatic response to global warming can provide important insights into the fundamental behavior of precipitation processes, most noticeably tropical convection. [ABSTRACT FROM AUTHOR]

The latest version of RegCM4 with CLM4.5 as a land surface scheme was used to assess the performance and sensitivity of the simulated West African climate system to different convection schemes. The sensitivity studies were performed over the West African domain from November 2002 to December 2004 at a spatial resolution of 50 km × 50 km and involved five convective schemes: (i) Emanuel; (ii) Grell; (iii) Emanuel over land and Grell over ocean (Mix1); (iv) Grell over land and Emanuel over ocean (Mix2); and (v) Tiedtke. All simulations were forced with ERA-Interim data. Validation of surface temperature at 2 m and precipitation were conducted using data from the Climate Research Unit (CRU), Global Precipitation Climatology Project (GPCP) and the Tropical Rainfall Measurement Mission (TRMM) during June to September (rainy season), while the simulated atmospheric dynamic was compared to ERA-Interim data. It is worth noting that the few previous similar sensitivity studies conducted in the region were performed using BATS as a land surface scheme and involved less convective schemes. Compared with the previous version of RegCM, RegCM4-CLM also shows a general cold bias over West Africa whatever the convective scheme used. This cold bias is more reduced when using the Emanuel convective scheme. In terms of precipitation, the dominant feature in model simulations is a dry bias that is better reduced when using the Emanuel convective scheme. Considering the good performance with respect to a quantitative evaluation of the temperature and precipitation simulations over the entire West African domain and its subregions, the Emanuel convective scheme is recommended for the study of the West African climate system. [ABSTRACT FROM AUTHOR]

We revisit the issue of the response of the precipitation characteristics to global warming based on analyses of global and regional climate model projections for the 21st century. The prevailing response we identify can be summarized as follows: increase in the intensity of precipitation events and extremes, with the occurrence of events of unprecedented magnitude, i.e. magnitude not found in present day climate; decrease in the number of light precipitation events and in wet spell lengths; increase in the number of dry days and dry spell lengths. This response, which is mostly consistent across the models we analized, is tied to the difference between precipitation intensity responding to increases in local humidity conditions, especially for heavy and extreme events, and mean precipitation responding to slower increases in global evaporation. These changes in hydroclimatic characteristics have multiple and important impacts on the Earth's hydrologic cycle and on a variety of sectors, and as examples we investigate effects on the potential stress due to increases in dry and wet extremes, changes in precipitation interannual variability and changes in potential predictability of precipitation events. We also stress how the understanding of the hydroclimatic response to global warming can shed important insights into the fundamental behavior of precipitation processes, most noticeably tropical convection. [ABSTRACT FROM AUTHOR]

The COordinated Regional Downscaling EXperiment (CORDEX) is a diagnostic model intercomparison project (MIP) in CMIP6. CORDEX builds on a foundation of previous downscaling intercomparison projects to provide a common framework for downscaling activities around the world. The CORDEX Regional Challenges provide a focus for downscaling research and a basis for making use of CMIP6 global climate model (GCM) output to produce downscaled projected changes in regional climates and assess sources of uncertainties in the projections, all of which can potentially be distilled into climate change information for vulnerability, impacts and adaptation studies. CORDEX Flagship Pilot Studies advance regional downscaling by targeting one or more of the CORDEX Regional Challenges. A CORDEX-CORE framework is planned that will produce a baseline set of homogeneous high-resolution, downscaled projections for regions worldwide. In CMIP6, CORDEX coordinates with ScenarioMIP and is structured to allow cross comparisons with HighResMIP and interaction with the CMIP6 VIACS Advisory Board. [ABSTRACT FROM AUTHOR]

We implement and evaluate a new parameterization scheme for stratiform cloud microphysics and precipitation within regional climate model RegCM4. This new parameterization is based on a multiple-phase one-moment cloud microphysics scheme built upon the implicit numerical framework recently developed and implemented in the ECMWF operational forecasting model. The parameterization solves five prognostic equations for water vapour, cloud liquid water, rain, cloud ice, and snow mixing ratios. Compared to the pre-existing scheme, it allows a proper treatment of mixed-phase clouds and a more physically realistic representation of cloud microphysics and precipitation. Various fields from a 10-year long integration of RegCM4 run in tropical band mode with the new scheme are compared with their counterparts using the previous cloud scheme and are evaluated against satellite observations. In addition, an assessment using the Cloud Feedback Model Intercomparison Project (CFMIP) Observational Simulator Package (COSP) for a 1-year sub-period provides additional information for evaluating the cloud optical properties against satellite data. The new microphysics parameterization yields an improved simulation of cloud fields, and in particular it removes the overestimation of upper level cloud characteristics of the previous scheme, increasing the agreement with observations and leading to an amelioration of a long-standing problem in the RegCM system. The vertical cloud profile produced by the new scheme leads to a considerably improvement of the representation of the longwave and shortwave components of the cloud radiative forcing. [ABSTRACT FROM AUTHOR]

Common ragweed (Ambrosia artemisiifolia L.) is a highly allergenic and invasive plant in Europe. Its pollen can be transported over large distances and has been recognized as a significant cause of hay fever and asthma (D'Amato et al., 2007; Burbach et al., 2009). To simulate production and dispersion of common ragweed pollen, we implement a pollen emission and transport module in the Regional Climate Model (RegCM) version 4 using the framework of the Community Land Model (CLM) version 4.5. In this online approach pollen emissions are calculated based on the modelling of plant distribution, pollen production, species-specific phenology, flowering probability, and flux response to meteorological conditions. A pollen tracer model is used to describe pollen advective transport, turbulent mixing, dry and wet deposition. The model is then applied and evaluated on a European domain for the period 2000-2010. To reduce the large uncertainties notably due to the lack of information on ragweed density distribution, a calibration based on airborne pollen observations is used. Accordingly a cross validation is conducted and shows reasonable error and sensitivity of the calibration. Resulting simulations show that the model captures the gross features of the pollen concentrations found in Europe, and reproduce reasonably both the spatial and temporal patterns of flowering season and associated pollen concentrations measured over Europe. The model can explain 68.6, 39.2, and 34.3% of the observed variance in starting, central, and ending dates of the pollen season with associated root mean square error (RMSE) equal to 4.7, 3.9, and 7.0 days, respectively. The correlation between simulated and observed daily concentrations time series reaches 0.69. Statistical scores show that the model performs better over the central Europe source region where pollen loads are larger and the model is better constrained. From these simulations health risks associated to common ragweed pollen spread are evaluated through calculation of exposure time above health-relevant threshold levels. The total risk area with concentration above 5 grainsm-3 takes up 29.5% of domain. The longest exposure time occurs on Pannonian Plain, where the number of days per year with the daily concentration above 20 grainsm-3 exceeds 30. [ABSTRACT FROM AUTHOR]

The Coordinated Regional Climate Downscaling Experiment (CORDEX) (Giorgi et al. 2009) moved towards the implementation of its phase 2 (hereafter referred to as CORDEX2, Giorgi and Gutowski 2015). One initiative of this phase II is CORDEX-CORE, by which a minimum set of regional climate models (RCMs) downscaled a common set of Global Climate Model (GCM) scenario simulations over most CORDEX domains. The downscaled simulations will have a spatial resolution spanning from 12 to 25 km and will cover the 140-year period 1960-2100 for multiple greenhouse gas representative concentration pathways (RCP). The scientific aim of this ambitious project is to provide homogenous downscaled climate change information across the globe, which will lead to increased understanding of the variability and change of regional climate phenomena; to a more rigorous evaluation and improvement of downscaling techniques; and to the production of a high quality homogenous dataset for impact and vulnerability studies and for use by stake-holders and decision makers.As part of the CORDEX-CORE program, RegCM user community completed an ensembles of scenario simulations with the RegCM4 system over 9 CORDEX domains. Such effort has been distributed across various users and the ICTP directly contributed to it by carrying out the experiments for a sub-set of the CORDEX domains. Specifically, scenario projections have been completed for six CORDEX domains: the African, North, Central and South American, the pan European ones and the Australasia. Two scenario (RCP 8.5 and 2.6) are downscaled driven by a minimum of 3 GCMs for 130 years at a horizontal grid spacing of 25 km for all region except Europe where a 12km resolution has been used.The aim of this work is to provide a critical contribution to the next generation assessments of impacts and vulnerabilities worldwide. Toward this direction all the simulations have been validated for the refernce period and added value has been shown for wet and dry extremes in several region of complex topography or where land surface feedback plays a n important role like for example the Amazon forest. Added value is also seen for wind intensity, cyclon track simulation and position and intensity of several jeat streams. Climate change (CC) signals are compared with the same signals coming from the GCM and regional specific feature are evident for both the mean and extreme analysis. In the regions and for those processes where added value is found in the control period, the regional climate change signal departs more from the large scale CC signal coming from the GCM. Process oriented analysis will be presented for each of the 9 CORDEX regions. [ABSTRACT FROM AUTHOR]

The year 2019 marks the thirtieth anniversary of the development of the first Regional Climate Model (RCM) and thus offers an excellent opportunity to reflect on the progress in regional modeling research and on the main challenges lying ahead. RCMs were developed mostly to provide fine scale climate information for application to impact studies, but they have evolved into general and multi-purpose modeling tools. Among the main achievements in RCM research the focus is on: the development of community RCMs portable on different computing architectures and applicable to a wide variety of studies and regional contexts; the increase of model simulation length up to centennial scales, and spatial resolutions up to convection-permitting scales (few km); the development of fully coupled Regional Earth System Models (RESMs); the inception of intercomparison projects culminating in the international Coordinated Regional Climate Downscaling EXperiment (CORDEX); the extensive use of RCM simulations for impact assessments; and the involvement of the scientific community from developing countries in climate modeling research. Among the outstanding issues in need of more attention the focus is on the Added Value of using this downscaling technique and on various technical aspects concerning RCM simulations. Future directions in RCM research are discussed, with highlight on: transition to convection-permitting modeling systems; further development of RESMs including the human component; next phase of the CORDEX project and the use of RCMs in the distillation of actionable information for contribution to climate service activities. [ABSTRACT FROM AUTHOR]

Rapid growth in industrialization, land use change and other anthropogenic-related activities has led to large amounts of polluting aerosols over India. These anthropogenic aerosols are continuously increasing in terms of their species composition and concentration levels. Increasing anthropogenic aerosol emissions can have substantial impacts on climate as well as human health. India being one of the most heavily polluted and populous regions of the world has been under the scanner to curb down the anthropogenic aerosol emissions by implementing mitigation measures. In this work, we use the International Centre for Theoretical Physics (ICTP) Regional Climate Model – version 4 (RegCM4) to examine the responses of Indian summer monsoon (ISM) climate to anthropogenic aerosols (black carbon, organic carbon, and sulfates) from the current legislation (CLE) "baseline" scenario for the period (2005-2015) and from short-lived climate pollutant (SLCP) "mitigation" scenario for the near future period (2020-2030) taken from ECLIPSE inventory. Our results show a reduction in carbonaceous aerosols (black carbon and organic carbon) in the mitigation scenario, but an increase in AOD (>0.05) over India due to increased sulfate emissions. The reduction in anthropogenic emissions of SLCPs over the Middle East under the mitigation scenario enhances the radiative effects of dust on the ISM. Specifically, the increase in dust-induced tropospheric warming over the Middle-East deserts and subsequent increase in sulfate aerosol cooling over India increases the strength of the ISM. Further analysis suggests the possible role of aerosols in extending the active phases of the ISM and partially contributing to precipitation extremes following mitigation measures. [ABSTRACT FROM AUTHOR]

This study investigates the greenhouse gas-induced winter and summer precipitation change signals over the Carpathian region with special focus on topographical effects and underlying processes. Six high-resolution (~12 km grid spacing) regional climate model projections - as members of EURO-CORDEX and Med-CORDEX initiatives - are analyzed for the future period 2070-2099 with respect to the reference period 1976-2005 under the RCP8.5 scenario. We found that the Carpathian Mountains significantly affect the seasonal precipitation change patterns both in winter and summer, but with different underlying mechanisms. In the winter, the topographic forcing is mostly of dynamical nature. It is tied to the topographic shadowing effect related to changes in wind circulations, which causes an increase in precipitation on the upwind side of the mountains with respect to the main direction of the wind change. In the summer, the topographic forcing is mostly of thermodynamical nature, being related to an increase in convective potential over the mountain peaks associated to high elevation heating and moistening. This process is similar to that found previously for the Alps, with the important difference that it is of lower intensity, because of the lower elevations of the Carpathians compared to the Alps. In fact, while over the Alps the topographic forcing actually reversed the sign of summer precipitation change over the mountain peaks (from negative to positive), in the Carpathians, it only attenuates the negative summer precipitation signal. Our results draw attention to the fact that the high-resolution representation of topography in climate models is crucial for the provision of fine scale precipitation projections. [ABSTRACT FROM AUTHOR]