Erika Coppola

Climatology, Hydrology

PhD Meteorology, University of Reading
32.19

Publications

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    ABSTRACT: The Mediterranean is expected to be one of the most prominent and vulnerable climate change “hot spots” of the 21st century, and the physical mechanisms underlying this finding are still not clear. Furthermore complex interactions and feedbacks involving ocean-atmosphere-land-biogeochemical processes play a prominent role in modulating the climate and environment of the Mediterranean region on a range of spatial and temporal scales. Therefore it is critical to provide robust climate change information for use in Vulnerability/Impact/Adaptation assessment studies considering the Mediterranean as a fully coupled environmental system. The Med-CORDEX initiative aims at coordinating the Mediterranean climate modeling community towards the development of fully coupled regional climate simulations, improving all relevant components of the system, from atmosphere and ocean dynamics to land surface, hydrology and biogeochemical processes. The primary goals of Med-CORDEX are to improve understanding of past climate variability and trends, and to provide more accurate and reliable future projections, assessing in a quantitative and robust way the added value of using high resolution and coupled regional climate models. The coordination activities and the scientific outcomes of Med-CORDEX can produce an important framework to foster the development of regional earth system models in several key regions worldwide.
    No preview · Article · Sep 2015 · Bulletin of the American Meteorological Society
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    ABSTRACT: We investigate the combined impact of ENSO and PDO on North American winter climate in current and future climate projections from 11 global models in the Climate Model Intercomparison Project Phase 5 (CMIP5) dataset. We first analyze winter sea surface temperature, sea level pressure (SLP) and precipitation anomalies for the historical period 1951–2005, and find that the CMIP5 models reproduce well the constructive interference between ENSO and the PDO compared to observations (i.e. positive ENSO and PDO or negative ENSO and PDO). On the other hand, the destructive interference (positive ENSO and negative PDO or negative ENSO and positive PDO) is less accurately reproduced. Consistently with observations, ENSO events show generally more impact on North American winter climate than PDO events, although there is a robust increase of rainfall in the Southeastern US during the negative PDO phase. For the twenty first century projections, we focus on the 2050–2099 period under the RCP8.5 greenhouse gas concentration scenario and we find an overall strengthening of both the ENSO and PDO signals, and particularly the PDO one, on the SLP and related teleconnections. This results in an enhanced influence of the negative PDO phase on flood conditions in the Southeastern United States, and in drier conditions over the Southwest coasts of North America.
    Full-text · Article · Jul 2015 · Climate Dynamics
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    ABSTRACT: An ensemble of future climate projections performed with the regional climate model RegCM4 is used to assess changes in inter-annual variability of precipitation over Southern Mexico and Central America (SMECAM). Two different Global Climate Models (GCMs) from the coupled model intercomparison project phase 5 are used to provide boundary conditions for two different RegCM4 configurations. This results in four regional climate projections extending from 1970 to 2100 for the greenhouse gas representative concentration pathway RCP8.5. The precipitation variability over the SMECAM region and its dependence on the gradient between Atlantic and Pacific sea surface temperature (SST) anomalies are verified by reproducing SST anomaly patterns during wettest and driest years similar to those seen in observational datasets. RegCM4 does a comparably better job than the driving GCMs. This strong relationship between precipitation and SST anomalies does not appear to change substantially under future climate conditions. For the rainy season, June to September, we find a future change in inter-annual variability of precipitation towards a much greater occurrence of very dry seasons over the SMECAM region, with this change being more pronounced in the regional than in the global model projections. A greater warming of the Tropical Northeastern Pacific (TNP) compared to the Tropical North Atlantic (TNA), which causes stronger wind fluxes from the TNA to the TNP through the Caribbean Low Level Jet, is identified as the main process responsible for these drier conditions.
    Full-text · Article · Jul 2015 · Climate Dynamics
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    Csaba Torma · Filippo Giorgi · Erika Coppola
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    ABSTRACT: We present an analysis of the added value (AV) of downscaling via regional climate model (RCM) nesting with respect to the driving global climate models (GCMs). We analyze ensembles of driving GCM and nested RCM (two resolutions, 0.44° and 0.11°) simulations for the late 20th and late 21st centuries from the CMIP5, EURO‐CORDEX, and MED‐CORDEX experiments, with a focus on the Alpine region. Different metrics of AV are investigated, measuring aspects of precipitation where substantial AV can be expected in mountainous terrains: spatial pattern of mean precipitation, daily precipitation intensity distribution, and daily precipitation extremes tails. Comparison with a high‐quality, fine‐scale (5 km) gridded observational data set shows substantial AV of RCM downscaling for all metrics selected, and results are mostly improved compared to the driving GCMs also when the RCM fields are upscaled at the scale of the GCM resolution. We also find consistent improvements in the high‐resolution (0.11°) versus medium‐resolution (0.44°) RCM simulations. Finally, we find that the RCM downscaling substantially modulates the GCM‐produced precipitation change signal in future climate projections, particularly in terms of fine‐scale spatial pattern associated with the complex topography of the region. Our results thus point to the important role that high‐resolution nested RCMs can play in the study of climate change over areas characterized by complex topographical features. RCMs produce substantial added value over complex topography regionsHigh resolution improves precipitation spatial patterns simulation and extremesRCMs are important tools for climate studies over complex topographical regions
    Full-text · Article · May 2015 · Journal of Geophysical Research Atmospheres
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    ABSTRACT: In this study, we present the projected seasonal mean summer monsoon over India and adjoining regions for the twenty-first century under the representative concentration pathway (RCP) 4.5 and RCP 8.5 scenarios using the regional model RegCM4 driven by the global model GFDL-ESM2M. RegCM4 is integrated from 1970 to 2099 at 50 km horizontal resolution over the South Asia CORDEX domain. The simulated mean summer monsoon circulation and associated rainfall by RegCM4 are validated against observations in the reference period 1975 to 2004 based on the Global Precipitation Climatology Project (GPCP) and India Meteorological Department (IMD) data sets. Regional model results are also compared with those of the global model GFDL which forces the RegCM4, showing that the regional model in particular improves the simulation of precipitation trends during the reference period. Future projections are categorized as near future (2010–2039), mid future (2040–2069), and far future (2070–2099). Comparison of projected seasonal (June–September) mean rainfall from the different time slices indicate a gradual increase in the intensity of changes over some of the regions under both the RCP4.5 and RCP8.5 scenarios. RegCM4 projected rainfall decreases over most of the Indian land mass and the equatorial and northern Indian Ocean, while it increases over the Arabian Sea, northern Bay of Bengal, and the Himalayas. Results show that the monsoon circulation may become weaker in the future associated with a decrease in rainfall over Indian land points. The RegCM4 projected decrease in June, July, August, September (JJAS) rainfall under the RCP8.5 scenario over the central, eastern, and peninsular India by the end of the century is in the range of 25–40 % of their mean reference period values; it is significant at the 95 % confidence level and it is broadly in line with patterns of observed change in recent decades. Surface evaporation is projected to increase over the Indian Ocean, thereby supplying more moisture into the atmosphere. As per the RegCM4 projection, the northward flank of the southwesterly winds (i.e., over the central and north India) may become stronger and veer towards the north over the Arabian Sea, traverse trans-India over the foothills of the Himalayas and northern Bay of Bengal, and reach up to Burma. The changes in circulation lead to a change in the moisture distribution and result in a decrease of moisture convergence over central and peninsular India, the Indian Ocean, and the southern part of Bay of Bengal and an increase over the Arabian Sea, northern Bay of Bengal, and the Himalayas.
    Full-text · Article · Nov 2014 · Theoretical and Applied Climatology
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    ABSTRACT: We simulate the observed statistical relationship between ENSO and the rainfall regime of the upper Blue Nile using the tropical-band version of the regional climate model RegCM4 (or Reg-TB). An ensemble of nine simulations for the 28-year period 1982–2009 is completed to investigate the role of ENSO in modulating rainfall over the upper Blue Nile catchment. Reg-TB shows a good skill in simulating the climatology of temperature, outgoing long-wave radiation patterns as well as related atmospheric circulation features during the summer season (i.e. the rainy season over the Blue Nile catchment). The model also succeeds in reproducing the observed negative correlation between Pacific SST and rainfall anomalies over the Blue Nile catchment, and in particular the association of droughts over the Blue Nile with El Niño events that start in April–June. We thus propose that observations and model forecasts of Pacific SST during this season could be used in seasonal forecasting of summer rainfall over the upper Blue Nile region.
    Full-text · Dataset · Nov 2014
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    F. Giorgi · E. Coppola · F. Raffaele
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    ABSTRACT: We analyze trends of six daily precipitation-based and physically interconnected hydroclimatic indices in an ensemble of historical and 21st century climate projections under forcing from increasing greenhouse gas (GHG) concentrations (RCP8.5), along with gridded (land only) observations for the late decades of the 20th century. The indices include metrics of intensity (SDII) and extremes (R95) of precipitation, dry (DSL) and wet (WSL) spell length, the hydroclimatic intensity index HY-INT and a newly introduced index of precipitation area (PA). All the indices in both the 21st century and historical simulations provide a consistent picture of a predominant shift towards a hydroclimatic regime of more intense, shorter, less frequent and less widespread precipitation events in response to GHG-induced global warming. The trends are larger and more spatially consistent over tropical than extratropical regions, pointing to the importance of tropical convection in regulating this response, and show substantial regional spatial variability. Observed trends in the indices analyzed are qualitatively and consistently in line with the simulated ones, at least at the global and full tropical scale, further supporting the robustness of the identified prevailing hydroclimatic responses. The HY-INT, PA and R95 indices show the most consistent response to global warming, and thus offer the most promising tools for formal hydroclimatic model validation and detection/attribution studies. The physical mechanism underlying this response and some of the applications of our results are also discussed.
    Full-text · Article · Oct 2014
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    L. Mariotti · I Diallo · E Coppola · F Giorgi
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    ABSTRACT: We analyze a mini ensemble of regional climate projections over the CORDEX Africa domain carried out with RegCM4 model as part of the Phase I CREMA experiment (Giorgi 2013). RegCM4 is driven by the HadGEM2-ES and MPI-ESM global models for the RCP8.5 and RCP4.5 greenhouse gas and aerosol concentration scenarios. The focus of the analysis is on seasonal and intraseasonal monsoon characteristics. We find two prominent change signals. Over West Africa and the Sahel MPI produces a forward shift in the monsoon season in line with previous findings, and this shift is also simulated by the RegCM4. Furthermore, the regional model produces a widespread decrease of monsoon precipitation (when driven by both MPI and HadGEM) associated with decreased easterly wave activity in the 6-9 days regime and with soil moisture-precipitation interactions. South of the equator we find an extension of the dry season with delayed onset and anticipated recession of the monsoon and a narrowing and strengthening of the ITCZ precipitation band. This signal is consistent in all global and regional model projections, although with different spatial detail. We plan to enlarge this mini-ensemble as a further contribution to the CORDEX project to better assess the robustness of the signals found in this paper.
    Full-text · Article · Jul 2014 · Climatic Change
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    ABSTRACT: We analyze changes of four extreme hydroclimatic indices in the RCP8.5 projections of the Phase I CREMA experiment, which includes 21st century projections over 5 CORDEX domains (Africa, Central America, South America, South Asia, Mediterranean) with the ICTP regional model RegCM4 driven by three CMIP5 global models. The indices are: Heat Wave Day Index (HWD), Maximum Consecutive Dry Day index (CDD), fraction of precipitation above the 95th intensity percentile (R95) and Hydroclimatic Intensity index (HY-INT). Comparison with coarse (GPCP) and high (TRMM) resolution daily precipitation data for the present day conditions shows that the precipitation intensity distributions from the GCMs are close to the GPCP data, while the RegCM4 ones are closer to TRMM, illustrating the added value of the increased resolution of the regional model. All global and regional model simulations project predominant increases in HWD, CDD, R95 and HY-INT, implying a regime shift towards more intense, less frequent rain events and increasing risk of heat wave, drought and flood with global warming. However, the magnitudes of the changes are generally larger in the global than the regional models, likely because of the relatively low “climate sensitivity” of the RegCM4, especially when using the CLM land surface scheme. In addition, pronounced regional differences in the change signals are found. The data from these simulations are available for use in impact assessment studies.
    Full-text · Article · Jul 2014 · Climatic Change
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    ABSTRACT: We provide an overall assessment of the surface air temperature and precipitation present day (1976–2005) and future (2070–2099) ensemble climatologies in the Phase I CREMA experiment. This consists of simulations performed with different configurations (physics schemes) of the ICTP regional model RegCM4 over five CORDEX domains (Africa, Mediterranean, Central America, South America, South Asia), driven by different combinations of three global climate models (GCMs) and two greenhouse gas (GHG) representative concen-tration pathways (RCP8.5 and RCP4.5). The biases (1976–2005) in the driving and nested model ensembles compared to observations show a high degree of spatial variability and, when comparing GCMs and RegCM4, similar magnitudes and more similarity for precipitation than for temperature. The large scale patterns of change (2070–2099 minus 1976–2005) are broadly consistent across the GCM and RegCM4 ensembles and with previous analyses of GCM projections, indicating that the GCMs selected in the CREMA experiment are representative of the more general behavior of current GCMs. The RegCM4, however, shows a lower climate sensitivity (reduced warming) than the driving GCMs, especially when using the CLM land surface scheme. While the broad patterns of precipitation change are consistent across the GCM and RegCM4 ensembles, greater differences are found at sub-regional scales over the various domains, evidently tied to the representation of local processes. This paper serves to provide a Climatic Change
    Full-text · Article · Jun 2014 · Climatic Change
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    ABSTRACT: Interannual variability over South America (SA) is mainly controlled by the El Niño-Southern Oscillation (ENSO) phenomenon. This study investigates the ENSO precipitation signal during austral spring (September–October–November-SON) over SA. Three global circulation models-GCMs-(MPI, GFDL and HadGEM2) are used for RegCM4 (Regional Climate Model version 4) downscaling of the present (1975–2005) near-future (2020–2050) and far-future (2070–2098) climates using two greenhouse gas stabilization scenarios (RCP4.5 and RCP8.5). For the present climate, only HadGEM2 simulates a frequency of El Niño (EN) and La Niña (LN) years similar to the observations. In terms of ENSO frequency changes, only in the far-future RCP8.5 climate there is greater agreement among GCMs, indicating an increase (decrease) of EN (LN) years. In the present climate, validation indicates that only the RegCM4 ensemble mean provides acceptable precipitation biases (smaller than ±20 %) in the two investigated regions. In this period, the GCMs and RegCM4 agree on the relationship between ENSO and precipitation in SA, i.e., both are able to capture the observed regions of positive/negative rainfall anomalies during EN years, with RegCM4 improving on the GCMs' signal over southeastern SA. For the near and far future climates, in general, the projections indicate an increase (decrease) of precipitation over southeastern SA (northern-northeastern SA). However, the relationship be-tween ENSO and rainfall in most of RegCM4 and GCM members is weaker in the near and far future climates than in the present day climate. This is likely connected with the GCMs' projection of the more intense ENSO signal displaced to the central basin of Pacific Ocean in the far future compared to present climate.
    Full-text · Article · May 2014 · Climatic Change
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    ABSTRACT: We analyze the local and remote impacts of climate change on the hydroclimate of the Amazon and La Plata basins of South America (SA) in an ensemble of four 21st century projections (1970–2100, RCP8.5 scenario) with the regional climate model RegCM4 driven by the HadGEM, GFDL and MPI global climate models (GCMs) over the SA CORDEX domain. Two RegCM4 configurations are used, one employing the CLM land surface and the Emanuel convective schemes, and one using the BATS land surface and Grell (over land) convection schemes. First, we find considerable sensitivity of the precipitation change signal to both the driving GCM and the RegCM4 physics schemes (with the latter even greater than the first), highlighting the pronounced uncertainty of regional projections over the region. However, some improvements in the simulation of the annual cycle of precipitation over the Amazon and La Plata basins is found when using RegCM4, and some consistent change signals across the experiments are found. One is a tendency towards an extension of the dry season over central SA deriving from a late onset and an early retreat of the SA monsoon. The second is a dipolar response consisting of reduced precipitation over the broad Amazon and Central Brazil region and increased precipitation over the La Plata basin and central Argentina. An analysis of the relative influence on the change signal of local soil-moisture feedbacks and remote effects of Sea Surface Temperature (SST) over the Niño 3.4 region indicates that the former is prevalent over the Amazon basin while the latter dominates over the La Plata Basin. Also, the soil moisture feedback has a larger role in RegCM4 than in the GCMs.
    Full-text · Article · Apr 2014 · Climatic Change
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    Full-text · Dataset · Apr 2014
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    ABSTRACT: The Po River is a crucial resource for the Italian economy, since 40% of the gross domestic product comes from this area. It is thus crucial to quantify the impact of climate change on this water resource in order to plan for future water use. In this paper a mini ensemble of 8 hydrological simulations is completed from 1960 to 2050 under the A1B emission scenario, by using the output of two regional climate models as input (REMO and RegCM) at two different resolutions (25km-10km and 25km-3km). The river discharge at the outlet point of the basin shows a change in the spring peak of the annual cycle, with a one month shift from May to April. This shift is entirely due to the change in snowmelt timing which drives most of the discharge during this period. Two other important changes are an increase of discharge in the wintertime and a decrease in the fall from September to November. The uncertainty associated with the winter change is larger compared to that in the fall. The spring shift and the fall decrease of discharge imply an extension of the hydrological dry season and thus an increase in water stress over the basin. The spatial distributions of the discharge changes are in agreement with what is observed at the outlet point and the uncertainty associated with these changes is proportional to the amplitude of the signal. The analysis of the changes in the anomaly distribution of discharge shows that both the increases and decreases in seasonal discharge are tied to the changes in the tails of the distribution, i.e. to the increase or decrease of extreme events.
    Full-text · Article · Mar 2014 · Science of The Total Environment
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    ABSTRACT: This study investigates the performance of two planetary boundary layer (PBL) parameterisations in the regional climate model RegCM4.2 with specific focus on the recently implemented prognostic turbulent kinetic energy parameterisation scheme: the University of Washington (UW) scheme. When compared with the default Holtslag scheme, the UW scheme, in the 10-year experiments over the European domain, shows a substantial cooling. It reduces winter warm bias over the north-eastern Europe by 2 A degrees C and reduces summer warm bias over central Europe by 3 A degrees C. A part of the detected cooling is ascribed to a general reduction in lower tropospheric eddy heat diffusivity with the UW scheme. While differences in temperature tendency due to PBL schemes are mostly localized to the lower troposphere, the schemes show a much higher diversity in how vertical turbulent mixing of the water vapour mixing ratio is governed. Differences in the water vapour mixing ratio tendency due to the PBL scheme are present almost throughout the troposphere. However, they alone cannot explain the overall water vapour mixing ratio profiles, suggesting strong interaction between the PBL and other model parameterisations. An additional 18-member ensemble with the UW scheme is made, where two formulations of the master turbulent length scale in unstable conditions are tested and unconstrained parameters associated with (a) the evaporative enhancement of the cloud-top entrainment and (b) the formulation of the master turbulent length scale in stable conditions are systematically perturbed. These experiments suggest that the master turbulent length scale in the UW scheme could be further refined in the current implementation in the RegCM model. It was also found that the UW scheme is less sensitive to the variations of the other two selected unconstrained parameters, supporting the choice of these parameters in the default formulation of the UW scheme.
    No preview · Article · Oct 2013 · Climate Dynamics
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    M. B. Sylla · F. Giorgi · E. Coppola · L. Mariotti
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    ABSTRACT: We intercompare three gridded observed daily rainfall datasets over Africa (FEWS (Famine Early Warning System), GPCP (Global Precipitation Climatology Project) and TRMM (Tropical Rainfall Measuring Mission)) in order to assess uncertainties in observation products towards the evaluation of the performance of a Regional Climate Model (RegCM3) in simulating daily precipitation characteristics over a domain encompassing the whole African continent. We find that different observation products exhibit substantial systematic differences in mean rainfall, but especially in higher order daily precipitation statistics, such as frequency of wet days, precipitation intensity and extremes as well as maximum length of wet and dry spells. For example, FEWS shows mostly higher frequency and lower intensity events than TRMM and GPCP. Thus, the different datasets provide quite different representations of daily precipitation behavior. As a result, although RegCM3 captures pretty well the monsoon rainband evolution and exhibits a representation of daily precipitation statistics within the range of the observations, it performs differently with respect to the various products. For instance, it simulates more intense but less frequent events over East and Southern Africa than in FEWS and vice versa compared to TRMM. We thus highlight the uncertainty in observations as a key factor preventing a rigorous and unambiguous evaluation of climate models over Africa. Improving the quality and consistency of observation products is thus paramount for a better understanding of the response of African climate to global warming. Copyright © 2012 Royal Meteorological Society
    Full-text · Article · Jun 2013 · International Journal of Climatology
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    ABSTRACT: The climate variability over the South America (SA) is mainly controlled by the El Niño-Southern Oscillation (ENSO) phenomenon. ENSO positive phase (El Niño; EN) is typically associated with below (above) normal precipitation over northern and northeastern (southeastern) of SA. The opposite signal is normally observed during the ENSO negative phase (La Niña; LN). In the context of CORDEX, the objective of this study is to investigate the ENSO precipitation signal over SA in the present and future climates. For this, we used an ensemble of RegCM4 projections driven by three global models (MPI-ESM-MR, GFDL-ESM2M and HadGEM2-ES). Basically, we investigated two scenarios (rcp4.5 and rcp8.5) during austral spring (September-October-November; SON) for present (P: 1975-2005), near future (N: 2020-2050), and far future (F: 2070-2098) climates. EN and LN years are defined according to the Oceanic Niño Index (ONI) that needs to be higher (lower) than a positive (negative) threshold for least 5 consecutive over-lapping seasons. For present climate, the number of EL and LN years simulated by HadGEM2-ES has a good agreement with the observations, while MPI-ESM-MR and GFDL-ESM2M underestimate the number of EN years. All global models project an increase (decrease) of EN (LN) years in the rcp8.5 far future climate scenario - except for GFDL-ESM2M which shows a slight decrease of EN years; on the other hand, for the near future climate there is a large discrepancy in this signal. For present climate, the composites indicate that all RegCM4 simulations capture the positive anomalies of rainfall over Southeastern of SA (SESA) associated with EN years. Individual RegCM4 simulations show some differences in the spatial pattern and intensity of rainfall anomalies during EN years compared with observations. The RegCM4 simulations ensemble for present climate shows a good representation of the observed anomalies. For near and future climates, all RegCM4 projections indicate an increase of SON precipitation over SESA and a decrease over the north-northeast of SA. However, the precipitation anomalies associated with EN years are weaker than that observed and simulated in present climate; this would be explained by EN events weaker in the future than in present climate as projected by global models.
    No preview · Article · Apr 2013
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    ABSTRACT: The hydroclimatic regime variability over the Amazon and La Plata Basin, the two main basins of South America (SA), are affect by local climate feedbacks and climate patterns associated with SST anomalies. The local and remote impacts of climate change over SA are evaluated using the regional model RegCM4 driven by HadGEM, GFDL and MPI global climate models (RegHad_CLM, RegGFDL, and RegMPI, respectively). All simulations used CLM (Community Land Model) land surface scheme and Emanuel convective scheme, with 50 km of horizontal resolution; except for one simulation driven by HadGEM that used the BATS (RegHad_BATS) as a land surface scheme and a mixed convection scheme (Grell over land and Emanuel over ocean). Climate changes were evaluated by comparing the future (2070-2098) with the present climate (1975-2004) during the rainy season (December to April). For the present day climate, the regional simulations reproduce reasonably well the precipitation annual cycle over Amazon and La Plata Basin. In particular the RegCM4 runs driven by MPI and GFDL are quite good over the Amazon and RegCM4 runs driven by HadGEM for La Plata Basin. For the future climate projections, all the global models show a precipitation decrease over the central Amazon Basin, northeast Brazil, and northern of SA (ranging from -5 to -25%) for the end of century, except the GFDL. Over the La Plata Basin, mainly over northern Argentina, and western of Amazon Basin simulations indicate an increase of precipitation (ranging from 25 to 50%). These patterns are intensified in the RegCM4-CLM simulations. The exceptions are the RegHad_BATS results that shows a general precipitation reduction over almost all Amazon basin. Over the La Plata Basin all regional models presented a positive coupling between sea surface temperature (SST) in Niño 3.4 region and precipitation. With exception of RegHad_CLM, all simulations show a negative SST/Precipitation regression over the central and northeastern Brazil. The soil moisture feedback on precipitation is evaluated too by mean of a statistical approach. The RegCM-CLM simulations have a common feature and they show a similar behavior when the future changes are investigated. The RegCM-BATS shows a different soil moisture feedback picture. Of course this can be explained by the differences in the two land-surface schemes and in the precipitation change signal that comes out from the two sets of simulations.
    No preview · Article · Apr 2013
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    ABSTRACT: In this study we analyze a set of regional climate model (RCM) simulations applying dynamical downscaling of global climate model (GCM) simulations over the Mediterranean region. The RCM simulations are completed with the Regional Climate Model RegCM, version RegCM4.3, and cover one of the domains specified by the international initiative Coordinated Regional Downscaling Experiment (CORDEX). Two GCMs were selected from the Coupled Model Intercomparison Project Phase 5 (CMIP5) ensemble to provide the driving fields for the RegCM: HadGEM2-ES and MPI-ESM-MR. The simulations consist of an ensemble including multiple physics configurations and different "Reference Concentration Pathways" (RCP4.5 and RCP8.5). In total 13 simulations were carried out with 6 model physics configurations with varying convection and land surface schemes. The simulations were completed as part of the CORDEX REgCM4 hyper-Matrix (CREMA) experiment. The horizontal grid spacing of the RCM simulations is 50 km and the simulated period in all cases is 1970-2100. The Mediterranean region was divided into 6 subregions: Spain, Alps, Balkan, Turkey, Adriatic and full Mediterranean Basin. Mean temperature and precipitation changes are assessed from monthly through seasonal to annual scale mainly focusing on the period of 2070-2099 with respect to the 1976-2005 corresponding model reference period. We analyze changes in mean climate as well as climate variability and different indexes of extreme events. The results show a clear warming trend by the end of the XXIst century over all subregions, especially in the warm season, along with a corresponding drying. The change of the interannual variability of precipitation and temperature show a prevailing increase, especially over the Iberian peninsula. Changes in extremes are spatially coherent for temperature, but more variable for precipitation. Although these results are generally consistent with previous scenario runs, we also find that the model exhibits significant sensitivity to the physics configuration used, particularly in the summer season, while in the winter the GCM boundary forcing appears to be more dominant.
    No preview · Article · Apr 2013
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    ABSTRACT: This study is based on the RegCM4.3 simulated climate projections for the South Asia CORDEX domain. The lateral boundary forcing of GFDL-ESM2M is used in the control run and the emission scenario RCP8.5 obtained from the CMIP5 archive. In all the experiments, Emanuel convective parameterization scheme has been used over the land and Grell convection scheme over the ocean. The model has been integrated at 50km resolution starting from the initial condition of 1st January 1970 upto 1st January 2100. The model simulated surface air temperature and rainfall are validated for the current climate over the reference period 1975-2004. The future simulations are divided into four 30-years time slices of 2010-2039, 2040-2069 and 2070-2099 referred to as the near-future, mid-future and far-future periods respectively. Comparison of JJAS mean model projected rainfall for the different periods in the future interestingly reveals systematic changes over most of the Indian regions. The farther we go into the future the larger is the change from the reference period. Seasonal mean rainfall weakens over the central India, northern Indian Ocean and equatorial Indian Ocean. On the other hand, it strengthens more and more over the Arabian Sea and northern Bay of Bengal. A major fraction of the changes happen to come from the convective component of the rainfall, which is attributed to the fact that Asian Summer Monsoon is largely driven by the atmospheric convection. Nevertheless, non-convective precipitation component partly contributes to the enhancement of rainfall in the Arabian Sea and northern Bay of Bengal and to its weakening in the north Indian Ocean. Atmospheric circulation, surface evaporation, and large scale moisture convergence over the region are found to change along the same line and explain the changes observed with rainfall.
    No preview · Article · Apr 2013

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