RegCM4 Simulations Research Articles

Projected changes in Köppen‒Trewartha climate zones under 1.5–4 °C global warming targets over mid-high latitudes of Northern Asia using an ensemble of RegCM4 simulations

Mid-high latitude Northern Asia is one of the most vulnerable and sensitive areas to global warming, but relatively less studied previously. We used an ensemble of a regional climate model (RegCM4) projections to assess future changes in surface air temperature, precipitation and Köppen‒Trewartha (K‒T) climate types in Northern Asia under the 1.5–4 °C global warming targets. RegCM4 is driven by five CMIP5 global models over an East Asia domain at a grid spacing of 25 km. Validation of the present day (1986–2005) simulations shows that the ensembles of RegCM4 (ensR) and driving GCMs (ensG) reproduce the major characters of the observed temperature, precipitation and K‒T climate zones reasonably well. Greater and more realistic spatial detail is found in RegCM4 compared to the driving GCMs. A general warming and overall increases in precipitation are projected over the region, with these changes being more pronounced at higher warming levels. The projected warming by ensR shows different spatial patterns, and is in general lower, compared to ensG in most months of the year, while the percentage increases of precipitation are maximum during the cold months. The future changes in K‒T climate zones are characterized by a substantial expansion of Dc (temperature oceanic) and retreat of Ec (sub-arctic continental) over the region, reaching ∼20% under the 4 °C warming level. The most notable change in climate types in ensR is found over Japan (∼60%), followed by Southern Siberia, Mongolia, and the Korean Peninsula (∼40%). The largest change in the K‒T climate types is found when increasing from 2 to 3 °C. The results will help to better assess the impacts of climate change and in implementation of appropriate adaptation measures over the region.

Quantifying uncertainties related to observational datasets used as reference for regional climate model evaluation over complex topography — a case study for the wettest year 2010 in the Carpathian region

Gridded observational datasets are often used for the evaluation of regional climate model (RCM) simulations. However, the uncertainty of observations affects the evaluation. This work introduces a novel method to quantify the uncertainties in the observational datasets and how these uncertainties affect the evaluation of RCM simulations. Besides precipitation and temperature, our method uses geographic variables (e.g. elevation, variability of elevation, effect of station), which are considered as uncertainty sources. To assess these uncertainties, a complex analysis based on various statistical tools, e.g. correlation analysis and permutation test, was carried out. Furthermore, we used a special metric, the reduction of error (RE) to identify where the RCM shows improvement compared to the lateral boundary conditions (LBCs). We focused on the Carpathian region, because of its unique orographic and climatic conditions. The method is applied to two observational datasets (CarpatClim and E-OBS) and to RegCM simulations for 2010, the wettest year in this region since 1901.The results show that CarpatClim is wetter than E-OBS, while temperature is similar over the lowland; however, E-OBS is significantly warmer than CarpatClim over the mountains. By the RE metric, RegCM has improvement against the LBCs over mountains for temperature and areas with dense station network for precipitation. Nevertheless, there are significant differences in the results depending on which observational dataset was used concerning precipitation. The evaluation method can be applied to other datasets, different time periods and areas. It is also suitable to find dataset errors, which is also exemplified in this paper.

Assessing the performance of the non-hydrostatic RegCM4 with the improved urban parameterization over southeastern China

This study evaluates the performance of the non-hydrostatic RegCM4 model (RegCM4-NH) incorporating the building energy model (BEM) in simulating urban climate over the Pearl River Delta (PRD) and Yangtze River Delta (YRD) regions. Specifically, it focuses on examining how the inclusion of BEM can ameliorate the severe warm bias in urban grids observed in high-resolution RegCM4 simulations by improving the surface energy balance. The prognostic calculation of interior building temperature and the consideration of ventilation and heat transfer between the building and the environment can collectively lead to a better estimate of anthropogenic heat flux (AHF). The effect of BEM does not appear to be uniform, showing spatial and temporal variations. While the magnitude of AHF reduction is roughly proportional to the urban density, the maximum reduction occurs at nighttime, which results in an asymmetric response to the minimum and maximum temperatures. Although the degree of lowering temperature is not sufficient to remove the systematic warm bias, adding physical realism to the model is helpful to make further improvements. The performance evaluation of RegCM4-NH with BEM targeted in vast urban agglomerations for the first time will be a valuable reference to facilitate the wider use of RegCM4-NH in the study of urban surface impacts.

Climate change projection over Mainland Southeast Asia and the Lancang‐Mekong River basin based on a set of RegCM4 simulations

AbstractWe investigate the projected climate change over Mainland Southeast Asia (also known as the Indochina Peninsula) and the Lancang‐Mekong River basin, a region with complex topography and unique weather and climate systems, but limited availability of published high‐resolution regional climate model (RCM) studies. The study is based on an unprecedented ensemble of 21st century projections with the RegCM4 RCM driven by five different general circulation models (GCMs) at a grid spacing of 25 km under the representative concentration pathways RCP4.5 and RCP8.5. We focus on mean temperature and precipitation in the dry season November–March (NDJFM), the wet season May–September (MJJAS), and the whole year. Intercomparison between the RegCM4 simulations with the driving GCMs is provided to illustrate the added value of the RegCM4 experiments. RegCM4 reproduces greater and more realistic spatial detail of the present day temperature and precipitation distribution compared to the driving GCMs, but some biases are found, such as an overestimation of precipitation over high topography regions. The spatial pattern of biases shows some consistencies across the GCMs and, for NDJFM the RegCM4, although weak correlation is found between the GCM and nested RegCM4 biases. A generally lower warming is projected in the future by the RegCM4 in different seasons and the whole year. For precipitation, while prevailing increases are found in the GCM projections, large areas of decrease occur in the RegCM ones, in particular during the wet season, possibly due to the more detailed topographical representation. The change patterns of precipitation show consistencies across the GCMs and the RegCM4, especially in MJJAS. The projected changes of extreme indices indicate a general decrease/increase of extreme cold/warm events. Drought events are projected to be more frequent over the southwestern, while a general increase of heavy rain events prevails over most parts of the region.

Global/Regional Impacts on Present and Near-Future Climate Regimes in the Metropolitan Region of Belém, Eastern Amazon

Impact studies have contributed to a better integrated scientific understanding of the climate and environment of the Amazon, in the present, past, and future. This work aims to describe the regional impacts of human-induced landcover changes on the RAINY (January to April) and DRY (July to November) regime of the Metropolitan Region of Belém (MRB), the first frontier of Amazonian occupation. Furthermore, a dynamic downscaling (RegCM4 driven by HadGEM2-ES under the RCP8.5 scenario) was performed to investigate future global climate change impacts. A present climate (1985/2020) quantitative analysis showed that the disorderly urban enlargement in Belém and the forest suppression that led to the uncontrolled expansion of pasture/agriculture area over MRB has conditioned a local warmer climate with a significant increasing air temperature trend in both seasonal regimes. Another clear piece of evidence was the systematic intensification of the precipitation during the RAINY period. RegCM4 simulations indicate that the region will be impacted by the global climate change, such that warmer conditions in the DRY and intensified rainfall in the RAINY regime are expected to persist in the coming decades (2021/2045). Our findings for the MRB (area 3565 km2 for a population about 2.5 million inhabitants) are relevant and should be considered in the tasks of long-term planning and elaboration of advanced strategies to mitigate future climate-related risks and urban disaster management.

Climate change projection over the Tibetan Plateau based on a set of RCM simulations

Tibetan Plateau (TP, with the height > 3000 m) is a region with complex topographical features and a large diversity of climate both in space and time. The use of higher resolution regional climate models (RCMs) to downscale global climate model simulations is of high importance. In the present study, future climate change over TP and the surrounding areas is investigated based on the ensemble of a set of the 21st century climate change projections using the RCM RegCM4. The model is driven by five different GCMs at a grid spacing of 25 km under RCP4.5. The focus is on the December‒January‒February (DJF), June‒July‒August (JJA), and annual mean temperature and precipitation, with comparisons against the driving GCMs also provided. Overall, the RegCM4 greatly improves the simulation by providing finer scale spatial details of both temperature and precipitation distributions over the region. The topographic effects are well reproduced by RegCM4 but not the GCMs. For the projected future changes, general warming and increase in precipitation are found in both GCM and RegCM4 simulations. However, substantial differences exist in both the spatial distribution and magnitude of the changes. The added value of RegCM4 for temperature, in addition to the finer spatial details, is characterized by a more pronounced warming in DJF over TP compared to its surrounding areas. The projected changes of precipitation show also differences between RegCM4 and the driving GCMs. The increase of precipitation is more pronounced and over the basins in DJF for RegCM4, and in general with a better agreement across the simulations compared to the driving GCMs.

Simulations of Indian summer monsoon using RegCM: a comparison with ERA and GFDL analysis

A comprehensive understanding of the variation of Indian summer monsoon (ISM) features is necessary for accurate prediction of seasonal and sub-seasonal scale meteorological parameters. In this study, the summer monsoon features over India are investigated using RegCM simulations over South Asia Coordinated Regional Downscaling Experiment (SA-CORDEX) domain with 45-km spatial resolution. The initial-boundary data are derived from the European Centre for Medium Range Weather Forecasts Re-Analysis (ERA) and Geophysical Fluid Dynamics Laboratory (GFDL) analysis for the period 1989 to 2005. For both model simulations, mixed convection scheme (Emmanuel over ocean and Grell over land), Holtslag planetary boundary layer (PBL) scheme and biosphere atmospheric transfer system (BATS) land surface scheme are used throughout the experiment. The simulation results are validated with Climatic Research Unit (CRU) observations of precipitation and temperature. The spatial distribution of precipitation and temperature is reasonably simulated with ERA and GFDL analysis as compared with CRU observation. However, the simulation of precipitation and temperature with ERA analysis iscloser to CRU observations as compared with GFDL analysis. The seasonal scale (JJAS) simulation of precipitation with ERA and GFDL illustrates wet bias (2 mm per day) as compared to CRU observation, whereas temperature simulated with ERA indicated warm bias (1 °C) and GFDL depicts cold bias (2 °C) against CRU observations. The wind magnitude and distribution of ERA simulations show considerably higher magnitude over the western Himalaya which is connected to low values of specific humidity over the same terrain as compared with GFDL.

Sectoral emissions contributions to anthropogenic aerosol scenarios over the Indian subcontinent and effects of mitigation on air quality, climate, and health

Over the last few decades, there have been substantial changes in sectoral anthropogenic emissions over India, modifying the region’s air quality and radiation budget. However, these sectoral contributions are still poorly understood. This study attempts to estimate the anthropogenic aerosols and SO2 emissions from different sectors over the Indian subcontinent and their implications for regional climate and human health using the RegCM4.4 regional climate model and the Greenhouse Gas-Air Pollution Interactions and Synergies (GAINS) global model. We consider current emissions as well as emissions with a mitigation scenario for the year 2030. The RegCM simulations with ECLIPSE v5a as emissions inventory for 2000 and 2015 show high SO2 emissions from the energy sector, substantially contributing to anthropogenic aerosol optical depth (AODanthro) and climate forcing. The residential and transport sectors’ imprint on climate forcing is increased in 2015 compared to 2000. Higher AODanthro (0.35-0.45) occurrence days substantially decrease under a mitigation scenario by 5-10% over the Indo-Gangetic Plain. In particular, over 5�megacities (Delhi, Kolkata, Mumbai, Chennai, and Bangalore) of India, the concentrations of black carbon, organic carbon, and particulate matter ≤2.5 µm in diameter (PM2.5) are substantially reduced under the mitigation scenario; however, SO2 is increased. The reduction of pollutants contributes to significantly reducing life expectancy loss in all cities. This study advocates the need for future emission control policies with a synergy between air quality and climate change.

Performance of RegCM4 simulations over Croatia and adjacent climate regions

AbstractWe investigate the impact of horizontal resolution, convection parameterization and lateral boundary conditions on the ability of a regional climate model ‐ RegCM4 to simulate the observed temperature and precipitation climatology over Croatia and surrounding regions. An ensemble of RegCM4 simulations over Europe has been generated including two resolutions (50 and 12.5 km), two different deep convection schemes and different boundary conditions (a reanalysis and four global climate models). Using two observational data sets (with and without the undercatch correction) shows that the magnitude of RegCM4 errors in winter precipitation also depends on observational uncertainty. While the mean precipitation amounts in high‐resolution simulations are generally overestimated in the cold part of the year, low‐resolution RegCM4 simulations are comparable to most of other EURO‐CORDEX models. When forced by ERA‐Interim, RegCM4 performs relatively poorly in reproducing temporal correlations against observations, but performs well in terms of spatial correlation. Whereas precipitation amounts from high‐resolution simulations need further improvements, the RegCM4 skill in simulating near‐surface temperature is high and well suited for impact studies.

Temperature Changes over the CORDEX-MENA Domain in the 21st Century Using CMIP5 Data Downscaled with RegCM4: A Focus on the Arabian Peninsula

This paper examined the temperature changes from the COordinated Regional climate Downscaling Experiment (CORDEX) over the Middle East and North Africa (MENA) domain called CORDEX-MENA. The focus is on the Arabian Peninsula in the 21st century, using data from three Coupled Model Intercomparison Project Phase 5 (CMIP5) models downscaled by RegCM4, a regional climate model. The analysis includes surface observations along with RegCM4 simulations and changes in threshold based on extreme temperature at the end of the 21st century relative to the base period (1971–2000). Irrespective of the driving CMIP5 models, the RegCM4 simulations show enhanced future temperature changes for RCP8.5 as compared to RCP4.5. The Arabian Peninsula will warm at a faster rate (0.83°C per decade) as compared to the entire domain (0.79°C per decade) for RCP8.5 during the period 2071–2100. Moreover, the number of hot days (Tmax ≥ 50°C) (cold nights: Tmin ≤ 5°C) will increase (decrease) faster in the Arabian Peninsula as compared to the entire domain. This increase (decrease) of hot days (cold nights) will be more prominent in the far future (2071–2100) as compared to the near future (2021–2050) period. Moreover, the future changes in temperature over the main cities in Saudi Arabia are also projected. The RegCM4-based temperature simulation data from two suitable CMIP5 models are recommended as a useful database for further climate-change-related studies.

Projected changes in autumn rainfall over West China: Results from an ensemble of dynamical downscaling simulations

Autumn rainfall in West China, the last rainy season of China, exerts profound impacts on the economic society, therefore, researches on its changes in the context of a warmer world are crucial for better adaptation to climate change. Using the dynamical downscaling performed by the regional climate model RegCM4 from four global climate models, this study firstly evaluated the fidelity of the RegCM4 simulations on the mean and extreme aspects of autumn rainfall in West China, and then projected their changes during the middle and the end of the 21st century under the RCP4.5 scenario. The evaluations indicate a good performance of the RegCM4 downscaling simulations in reproducing the observed spatial distribution of autumn rainfall amount, wet days, maximum consecutive 5‐day precipitation (RX5day), total extremely wet‐day precipitation (R95p), and consecutive dry days (CDD). Under the RCP4.5 scenario, relative to 1986–2005, the amount of autumn rainfall and the frequency of wet days are projected to increase in the northwestern part of West China and to decrease in its southeastern flank, concurrent with greater changes by the end of the 21st century than by the middle of the 21st century. Such an increase is closely associated with the enhancement of zonal water vapour transport and atmospheric unstable stratification, while the projected decrease is largely related to the reduction of moisture supply. Similar changes are also projected for the precipitation extremes Rx5day and R95p. Corresponding to the changing pattern of autumn rainfall, the CDD is projected to decrease in the northwestern part and to increase in the southeastern part of West China.

Future Changes in the Aridity of South America from Regional Climate Model Projections

Future changes of the aridity of South America (SA) are investigated. The projected changes of the Budyko and United Nations Environment Programme (UNEP) indices in the mid- and end of the twenty-first century from the ensemble mean RegCM4 simulations using the scenario RCP 8.5 are presented. The RegCM4 model driven by the global models of HadGEM2, MPI, and GFDL for the period 1970–2100 carries out the simulations. For both Budyko and UNEP indices, an aridity increase over SA is projected. Over Brazil, the higher changes were found in the Amazon, North Brazil, and Northeast Brazil (NEB). In the Amazon and North Brazil, an increase of the aridity of 33.8% and 36.9% (for the UNEP index) and 4.6% and 13.9% (for the Budyko index), respectively, are noted at the end of the twenty-first century suggesting an increase of the process of savannization in future climate. In NEB, a rise of 37.3% and 14.1%, respectively, for the UNEP and the Budyko indices, is found, indicating an expansion of areas of the dry land regime.

Analysis of regional climate model simulations for Central Europe as a potential tool to assess weather-related air quality conditions

Potentially adverse air quality is discussed via its relation to wind conditions and boundary layer thickness. The main goal of the study is to evaluate different RegCM simulations for 1981–1990, d...

Projected changes in heat wave characteristics in the Carpathian Basin comparing different definitions

Heat waves (HWs) associated with climate change and increased near-surface air temperature can be considered as a climatic hazard for people and the environment. This study evaluates six HW detecting methods and the estimated HW characteristics (duration, frequency and intensity) from observational (CarpatClim database) and modelled (RegCM simulations with the representative concentration pathway (RCP) 4.5 and 8.5) datasets. The RegCM model results show a considerable future increase (by 2016-2045; 2061-2090) in HW days compared to the reference period (1971-2000). In case of RCP4.5, HW days become 3-6 times more frequent, while the increase is 5-9 fold for RCP8.5 by the end of the century. As a consequence of climate change, HW durations are also projected to become 1-2 (3-4) days longer on average for RCP4.5 (RCP8.5) in the Carpathian Basin.

Projected changes in heat wave characteristics in the Carpathian Basin comparing different definitions

Heat waves (HWs) associated with climate change and increased near-surface air temperature can be considered as a climatic hazard for people and the environment. This study evaluates six HW detecting methods and the estimated HW characteristics (duration, frequency and intensity) from observational (CarpatClim database) and modelled (RegCM simulations with the representative concentration pathway (RCP) 4.5 and 8.5) datasets. The RegCM model results show a considerable future increase (by 2016-2045; 2061-2090) in HW days compared to the reference period (1971-2000). In case of RCP4.5, HW days become 3-6 times more frequent, while the increase is 5-9 fold for RCP8.5 by the end of the century. As a consequence of climate change, HW durations are also projected to become 1-2 (3-4) days longer on average for RCP4.5 (RCP8.5) in the Carpathian Basin.

Role of resolution in regional climate change projections over China

This paper investigates the sensitivity of projected future climate changes over China to the horizontal resolution of a regional climate model RegCM4.4 (RegCM), using RCP8.5 as an example. Model validation shows that RegCM performs better in reproducing the spatial distribution and magnitude of present-day temperature, precipitation and climate extremes than the driving global climate model HadGEM2-ES (HadGEM, at 1.875° × 1.25° degree resolution), but little difference is found between the simulations at 50 and 25 km resolutions. Comparison with observational data at different resolutions confirmed the added value of the RCM and finer model resolutions in better capturing the probability distribution of precipitation. However, HadGEM and RegCM at both resolutions project a similar pattern of significant future warming during both winter and summer, and a similar pattern of winter precipitation changes including dominant increase in most areas of northern China and little change or decrease in the southern part. Projected precipitation changes in summer diverge among the three models, especially over eastern China, with a general increase in HadGEM, little change in RegCM at 50 km, and a mix of increase and decrease in RegCM at 25 km resolution. Changes of temperature-related extremes (annual total number of daily maximum temperature > 25 °C, the maximum value of daily maximum temperature, the minimum value of daily minimum temperature in the three simulations especially in the two RegCM simulations are very similar to each other; so are the precipitation-related extremes (maximum consecutive dry days, maximum consecutive 5-day precipitation and extremely wet days’ total amount). Overall, results from this study indicate a very low sensitivity of projected changes in this region to model resolution. While fine resolution is critical for capturing the spatial variability of the control climate, it may not be as important for capturing the climate response to homogeneous forcing (in this case greenhouse gas concentration changes).

Coupling of Community Land Model with RegCM4 for Indian Summer Monsoon Simulation

Three land surface schemes available in the regional climate model RegCM4 have been examined to understand the coupling between land and atmosphere for simulation of the Indian summer monsoon rainfall. The RegCM4 is coupled with biosphere–atmosphere transfer scheme (BATS) and the National Center for Atmospheric Research (NCAR) Community Land Model versions 3.5, and 4.5 (CLM3.5 and CLM4.5, respectively) and model performance is evaluated for recent drought (2009) and normal (2011) monsoon years. The CLM4.5 has a more distinct category of surface and it is capable of representing better the land surface characteristics. National Centers for Environmental Prediction (NCEP) and Department of Energy (DOE) reanalysis version 2 (NNRP2) datasets are considered as driving force to conduct the experiments for the Indian monsoon region (30°E–120°E; 30°S–50°N). The NNRP2 and India Meteorological Department (IMD) gridded precipitation data are used for verification analysis. The results indicate that RegCM4 simulations with CLM4.5 (RegCM4–CLM4.5) and CLM3.5 (RegCM4–CLM3.5) surface temperature (at 2 ms) have very low warm biases (~1 °C), while with BATS (RegCM4–BATS) has a cold bias of about 1–3 °C in peninsular India and some parts of central India. Warm bias in the RegCM4–BATS is observed over the Indo-Gangetic plain and northwest India and the bias is more for the deficit year as compared to the normal year. However, the warm (cold) bias is less in RegCM4–CLM4.5 than other schemes for both the deficit and normal years. The model-simulated maximum (minimum) surface temperature and sensible heat flux at the surface are positively (negatively) biased in all the schemes; however, the bias is higher in RegCM4–BATS and lower in RegCM4–CLM4.5 over India. All the land surface schemes overestimated the precipitation in peninsular India and underestimated in central parts of India for both the years; however, the biases are less in RegCM4–CLM4.5 and more in RegCM4–CLM3.5 and RegCM4–BATS. During both the years, BATS scheme in RegCM4 failed to represent low precipitation over the leeward than windward side of the Western Ghats, while CLM schemes (both versions) in the RegCM4 are able to depict this feature. In the topographic regions, such as the Western Ghats, northeast India and state of Jammu and Kashmir, RegCM4–BATS overestimates the rainfall amount with higher bias. Statistical analysis using anomaly correlation coefficient, root mean square error, equitable threat score, and critical success index confirms that RegCM4–CLM performs better than RegCM4–BATS in the simulation of the Indian summer monsoon.

Sensitivity of simulated South America climate to the land surface schemes in RegCM4

This work evaluates the impact of two land surface parameterizations on the simulated climate and its variability over South America (SA). Two numerical experiments using RegCM4 coupled with the Biosphere–Atmosphere Transfer Scheme (RegBATS) and the Community Land Model version 3.5 (RegCLM) land surface schemes are compared. For the period 1979–2008, RegCM4 simulations used 50 km horizontal grid spacing and the ERA-Interim reanalysis as initial and boundary conditions. For the period studied, both simulations represent the main observed spatial patterns of rainfall, air temperature and low level circulation over SA. However, with regard to the precipitation intensity, RegCLM values are closer to the observations than RegBATS (it is wetter in general) over most of SA. RegCLM also produces smaller biases for air temperature. Over the Amazon basin, the amplitudes of the annual cycles of the soil moisture, evapotranspiration and sensible heat flux are higher in RegBATS than in RegCLM. This indicates that RegBATS provides large amounts of water vapor to the atmosphere and has more available energy to increase the boundary layer thickness and cause it to reach the level of free convection (higher sensible heat flux values) resulting in higher precipitation rates and a large wet bias. RegCLM is closer to the observations than RegBATS, presenting smaller wet and warm biases over the Amazon basin. On an interannual scale, the magnitudes of the anomalies of the precipitation and air temperature simulated by RegCLM are closer to the observations. In general, RegBATS simulates higher magnitude for the interannual variability signal.

Climate change effects on the marine characteristics of the Aegean and Ionian Seas

This paper addresses the effects of estimated climate change on the sea-surface dynamics of the Aegean and Ionian Seas (AIS). The main aim is the identification of climate change impacts on the severity and frequency of extreme storm surges and waves in areas of the AIS prone to flooding. An attempt is made to define design levels for future research on coastal protection in Greece. Extreme value analysis is implemented through a nonstationary generalized extreme value distribution function, incorporating time harmonics in its parameters, by means of statistically defined criteria. A 50-year time span analysis is adopted and changes of means and extremes are determined. A Regional Climate Model (RegCM3) is implemented with dynamical downscaling, forced by ECHAM5 fields under 20C3M historical data for the twentieth century and the SRES-A1B scenario for the twenty-first century. Storm surge and wave models (GreCSSM and SWAN, respectively) are used for marine climate simulations. Comparisons of model results with reanalysis and field data of atmospheric and hydrodynamic characteristics, respectively, are in good agreement. Our findings indicate that the dynamically downscaled RegCM3 simulation adequately reproduces the present general circulation patterns over the Mediterranean and Greece. Future changes in sea level pressure and mean wind fields are estimated to be small, yet significant for marine extremes. In general, we estimate a projected intensification of severe wave and storm surge events during the first half of the twenty-first century and a subsequent storminess attenuation leading to the resettlement of milder extreme marine events with increased prediction uncertainty in the second half of the twenty-first century.

Sensitivity experiments of RegCM4 simulations to different convective schemes over Central Africa

In this study, version 4 of the International Centre for Theoretical Physics (ICTP) regional climate model named RegCM4 is used to perform 6 years simulation including 1 year for spin-up (from January 2001 to December 2006) over Central Africa using four convective schemes: The Emmanuel scheme (MIT), the Grell scheme with Arakawa-Schulbert closure assumption (GAS), the Grell scheme with Fritsch-Chappell closure assumption (GFC) and the Anthes-Kuo scheme (Kuo). We have investigated the ability of the model to simulate precipitation, surface temperature, wind and aerosols optical depth. Emphasis in the model results were made in December–January–February (DJF) and July–August–September (JAS) periods. Two subregions have been identified for more specific analysis namely: zone 1 which corresponds to the sahel region mainly classified as desert and steppe and zone 2 which is a region spanning the tropical rain forest and is characterized by a bimodal rain regime. We found that MIT scheme shows a better index of agreement in temperature, but it generally has a tendency to an overestimation of other simulated parameters. Overall, GAS scheme is more suitable to downscale the aforementioned parameters except temperature, as well as the diurnal cycle of precipitation everywhere over the study domain irrespective of the seasons. In JAS, model results are similar in the representation of regional wind circulation. Apart from the MIT scheme, all the convective schemes give the same tendencies in aerosols optical depth simulations. Additional experiment reveals that the use of BATS instead of Zeng scheme to calculate ocean flux appears to improve the quality of the model simulations.