Erika Coppola

Climatology, Hydrology

PhD Meteorology, University of Reading
31.90

Publications

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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.
    Climate Dynamics 07/2015; 45(1-2). DOI:10.1007/s00382-014-2258-6 · 4.62 Impact Factor
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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
    Journal of Geophysical Research Atmospheres 05/2015; 120(9):3957–3972. DOI:10.1002/2014JD022781 · 3.44 Impact Factor
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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.
    Theoretical and Applied Climatology 11/2014; DOI:10.1007/s00704-014-1310-0 · 1.74 Impact Factor
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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.
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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.
    10/2014; 119(20). DOI:10.1002/2014JD022238
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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.
    Climatic Change 07/2014; 125(1):53-65. DOI:10.1007/s10584-014-1097-0 · 4.62 Impact Factor
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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.
    Climatic Change 07/2014; 125(1):39-51. DOI:10.1007/s10584-014-1117-0 · 4.62 Impact Factor
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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
    Climatic Change 06/2014; 125(1):23-38. DOI:10.1007/s10584-014-1137-9 · 4.62 Impact Factor
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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.
    Climatic Change 05/2014; 125(1):95-109. DOI:10.1007/s10584-014-1119-y · 4.62 Impact Factor
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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.
    Climatic Change 04/2014; DOI:10.1007/s10584-014-1140-1 · 4.62 Impact Factor
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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.
    Science of The Total Environment 03/2014; 493. DOI:10.1016/j.scitotenv.2014.03.003 · 4.10 Impact Factor
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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.
    Climate Dynamics 10/2013; 43(7-8). DOI:10.1007/s00382-013-2003-6 · 4.62 Impact Factor
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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
    International Journal of Climatology 06/2013; 33(7):1805-1817. DOI:10.1002/joc.3551 · 3.40 Impact Factor
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    ABSTRACT: Regional climate models can be used to examine the impact of global warming at the regional level for the possible emission scenarios. According to IPCC AR4, a number of studies noticed large inter model differences leading to large uncertainties in the projected future changes in different aspects of monsoon rainfall. The aim of this study to understand the different response of similarly forced model RegCM4.3 with different convection scheme over the Ocean. In this study, RegCM4.3 is used to generate the climate scenarios for South Asia CORDEX domain using boundary forcing of global coupled climate models GFDL-ESM2M and MPI-ESM-MR in control runs and two emission scenarios RCP4.5 and RCP8.5 obtained from CMIP5 archive. Emanuel convective parameterization scheme has been used over the land in all the experiments. Over the Ocean, experiments are designed using both Emanual and Grell convection schemes. Rest of the model configuration is based on the different sensitivity experiments conducted to reduce the model temperature and precipitation biases. The model has been integrated at 50km resolution starting from the initial condition of 1st Jan 1970 and the climate simulation continued till 1st Jan 2100. Results indicate that all India JJAS mean temperature change is consistent with clear projection of warming, whereas the projected JJAS precipitation change shows large spread and uncertainty in trends. Even the similar forcing experiments with difference only in the convective scheme over ocean show large difference in their projected precipitation. Climatology of JJAS precipitation over Indian land and low level westerlies for the historical period (1979-2005) is well represented. However, there are differences in the precipitation distribution at regional level within the experiments mainly over the Northwest and southern part of Peninsular India. In case of Emanuel over ocean, enhanced convection over Indian land is mainly associated with the weak westerlies over the Bay of Bengal. The positive anomalies of westerly jet are captured over the Arabian Sea in both the cases where Grell convection over ocean is used in RegCM4.3. Grell scheme over ocean has significantly improved the pattern of westerly flow in RegCM4.3 simulations forced with the considered GCMs.
  • Laura Mariotti · Erika Coppola · Filippo Giorgi
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    ABSTRACT: The Phase I CREMA experiment is the first contribution of the RegCM regional modelling community to the Coordinated Regional Downscaling Experiment (CORDEX). It consists of a series of scenario simulations over five CORDEX domains completed with the RegCM4 RCM driven by different CMIP5 GCMs. For the African domain three simulations have been completed from 1970 up to 2099, two have been driven by HADGEM2ES for RCP4.5 and RCP8.5 with one RegCM configuration and one driven by MPI-ESMMR for RCP8.5 with a different RegCM configuration. While the temperature changes are strongly driven by the global model, the precipitation change patterns of the regional model are different compared to the global models. According to Mariotti et al. 2011, it is confirmed that the local processes and internal model physics are key elements in determining the precipitation change signal simulated by the nested regional model in this large domain experiment, especially over equatorial and tropical regions. In particular over Western Africa, the Sahel region and Southern Africa, there is a reduction of the precipitation in the early season of the monsoon and an increase in the late part of the season for the future scenario (Seth et al. 2010).
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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.
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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.
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    ABSTRACT: Future climate projections performed with the Regional Climate Model (RegCM4) are used to analyze the future changes on inter-annual variability of precipitation and temperature over Mexico and Central America. Two different global circulation models from the Couple Model Intercomparison Project phase 5 (CMPI5) are used as boundary conditions for two different RegCM4 configurations, which result in four different climate projections. Through a comparison of the precipitation annual cycles in reference period with future simulations, a shift in the annual cycle is found over Northwestern Mexico and Central America. During the rainy season (June to September), it is found an increase in the inter-annual variability of precipitation and temperature, together with a warming greater than 4°C in the mean seasonal temperature and a drying of more than 20%. An increased warming on the Eastern Pacific Ocean compared to the Tropical North Atlantic Ocean potentially generates a strengthened North Atlantic Subtropical High Pressure and also a stronger Caribbean Low Level Jet. This future ENSO-like state appears to be the mechanism driving the drying over the region
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    ABSTRACT: For the phase I CREMA experiment the regional climate model RegCM4 has been used to simulate the present and future time period over 5 domains across the word (Africa, South America, Central America, West Asia and Mediterranean) to contribute to CORDEX for a total of 34 simulations, spanning the period 1970-2100. Three GCMs have been used taken from the CMIP5 ensemble and they are HADGEM2ES, MPI-ESMMR and GFDL-ESM2M. The selection has been made according to the best RegCM4 performances when driven by those GCMs. For the present day period (1975-2205) the RCMs are evaluated and compared with the GCMs in term of ensemble mean biases, root mean square error and correlation by mean of Taylor diagrams for the two seasons DJF and JJA. For the temperature and precipitation biases the global and regional models are quite comparable. When the 5 domains are taken into account in the Taylor diagrams the individual regional model simulations show consistent improvements compared to the global model. This is confirmed by all the domains and by all the model configurations. For precipitation the situation is more complex and requires a detailed analysis for the different domains and model settings. The change signal has been also analyzed for the period 2070-2100 compared to the reference period 1975-2005. The ensemble mean change for the regional models show a stronger warming signal over Western Africa for DJF and Central and Southern Africa for JJA when compared with the global model mean change and a weaker warming signal over the Mediterranean domain for JJA. For precipitation, the regional ensemble mean change shows a stronger drying over the Western and Eastern Africa and north-east South America continent for the JJA season and an opposite wet signal for Northern Europe when compared with the global ensemble mean change. Also in the central part of India the regional ensemble shows a weaker monsoon for the future when compared to the global ensemble change that show and increase of precipitation during the JJA season. A stronger drying is also evident in Mexico and Central America from the regional simulations. For DJF the regional change signal shows a wetter Mexico and a wetter south Brazil and Argentina compared to the dryer signal coming from the GCMs and a dryer east Brazil. Some of these differences can be attributed to the land-surface feedback mechanism that are modulated by local processes and internal model physics like for example has been shown from a previous study in Western Africa (Mariotti et al. 2011).

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