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We analyse the effects of deforestation and the projected differential sea surface temperature (SST) anomalies between the tropical North Atlantic and the eastern North Pacific on the mid‐summer drought (MSD) over southern Mexico and Central America. To address these issues, we performed a set of three 6‐year (1996–2001) sensitivity experiments with RegCM4 driven by the ERA‐Interim reanalysis and employing different SST (projected end of century patterns under the RCP8.5 scenario) and vegetation (turning forest landuse into grass) configurations. The model domain follows the specifications of the COrdinated Regional Downscaling EXperiment (CORDEX) for Central America. Results indicate that projected SST patterns cause the MSD signal to almost disappear from the regional mean annual cycle, with its spatial extent decreasing from ~82 to ~48%. In the vegetation sensitivity experiment, the MSD intensity increases along the Pacific coast and Central America, while the MSD spatial extent remains almost unchanged. These regional changes in MSD can be explained in terms of the regional precipitation response to deforestation, primarily due to changes in vertical moisture advection. [ABSTRACT FROM AUTHOR]

The interannual variability of the boreal winter (DJF) subtropical jet stream (STJ) is analyzed over the Coordinated Regional Downscaling Experiment—Central America, Mexico, and Caribbean domain (CORDEX-CAM) during 1980–2010. We use simulations with the regional climate model RegCM4 (version 7) at 25 km resolution driven by ERA-Interim (RegERA) and three global models (RegGCMs). The simulations are evaluated using zonal winds at 200 hPa level from ERA-Interim and MERRA2, which show similar results, and no significant trends in the STJ. Despite some biases, RegERA captures the STJ variability and its relationship with several teleconnections. The polarities of the principal mode of variability of the Pacific and Atlantic jets are significantly anti-correlated; they represent the longitudinal extension/retraction and the poleward/equatorward migration of the jet cores, respectively. During El Niño and the + PNA (Pacific North America), the North Pacific jet exit region and the North Atlantic jet show maximum speeds equatorward of their climatological positions. During these conditions, there is an extended and strong STJ over the domain; this pattern also tends to occur during the negative phases of the Arctic and North Atlantic oscillations. The RegGCMs simulate better the principal modes of the Atlantic jet variability than those of the Pacific jet exit region; nevertheless, they reproduce the observed sign of the variations of the jet speeds and their latitudinal changes in the two basins. They also partially capture the sign of the temperature and precipitation anomalies in the domain, which respond to the STJ polarities and their interaction with the teleconnections. [ABSTRACT FROM AUTHOR]

Regional climate projections are developed four Central America and the Caribbean, based on a multiparameter ensemble formed by four configurations with different convective cumulus schemes with the regional model RegCM4 at 25 km grid spacing, driven by the HadGEM2‐ES global model under the RCP4.5 and RCP8.5 scenarios. The precipitation change projections indicate drier conditions compared to present in the near future (2020–2049) and far future (2070–2099) time slices. These drier conditions are statistically significant at the 90% confidence level over the eastern Caribbean, central Atlantic Ocean, and the western Pacific Ocean and are more pronounced in the far future time slice. For temperature, the warmer conditions are statistically significant at the 95% confidence level over the study region. The drier and warmer signals are greater in extension and magnitude in the RCP8.5 than for RCP4.5. Projected changes in precipitation and temperature extreme indices show a reduction of consecutive wet days and an increment of consecutive dry days, with a reduction of cold days and nights and an increase of warm days and nights. Lower precipitation along with increased intensity of extreme events are projected over the Greatest Antilles region. [ABSTRACT FROM AUTHOR]

The climate features over Central America and the Caribbean are simulated with the regional climate model RegCM4 to analyze the performance of the model in reproducing precipitation and temperature patterns over the region. Results from RegCM4 and the driving global climate model (GCM) HadGEM2-ES (HadG) are compared against gridded observations for a period from January 1980 to December 2004 using a perturbed physics ensemble formed by four configurations of the RegCM4 using different combinations of four convection schemes run over land and ocean areas: Kain Fritsch (Kf), Emanuel (Em), Grell (Ge), and Tiedtke (Tk). The added value of RegCM4 relative to the GCM simulation is also estimated, with focus over four subregions, using several metrics calculated on the RegCM4 as well as the GCM grids. The RegCM4 downscaling, expressed by the ensemble mean ENS, adds significant details to the HadG simulation of the temperature field patterns, showing smaller biases of up to ± 1.6 °C at the RCM resolution. Regarding the spatial patterns of precipitation, the HadG has overall higher correlation values with observations than ENS. However, the regional model provides more detailed spatial distributions, decreasing the bias by more than 1 mm/day over some of the islands. It also captures extreme precipitation events that are underestimated in the HadG simulation, even after upscaling to the GCM resolution grid. Concerning the performance of the different RegCM4 convection scheme combinations, KfEm and EmEm show the highest skill values for precipitation, while for temperature TkEm and GeEm are the best performing. This highlights that no individual scheme outperforms the others in all respects, while the application of the averaged ensemble technique provides the best results. [ABSTRACT FROM AUTHOR]

A sensitivity study of the performance of the RegCM4 regional climate model driven by the ERA Interim reanalysis is conducted for the Central America and Caribbean region. A set of numerical experiments are completed using four configurations of the model, with a horizontal grid spacing of 25 km for a period of 6 years (1998-2003), using three of the convective parameterization schemes implemented in the model, the Emanuel scheme, the Grell over land-Emanuel over ocean scheme and two configurations of the Tiedtke scheme. The objective of the study is to investigate the ability of each configuration to reproduce different characteristics of the temperature, circulation and precipitation fields for the dry and rainy seasons. All schemes simulate the general temperature and precipitation patterns over land reasonably well, with relatively high correlations compared to observation datasets, though in specific regions there are positive or negative biases, greater in the rainy season. We also focus on some circulation features relevant for the region, such as the Caribbean low level jet and sea breeze circulations over islands, which are simulated by the model with varied performance across the different configurations. We find that no model configuration assessed is best performing for all the analysis criteria selected, but the Tiedtke configurations, which include the capability of tuning in particular the exchanges between cloud and environment air, provide the most balanced range of biases across variables, with no outstanding systematic bias emerging. [ABSTRACT FROM AUTHOR]

Recent global-scale analyses of the CMIP3 model projections for the twenty-first century indicate a strong, coherent decreased precipitation response over Central America and the Intra-America Seas region. We explore this regional response and examine the models’ skill in representing present-day climate over this region. For much of Central America, the annual cycle of precipitation is characterized by a rainy season that extends from May to October with a period of reduced precipitation in July and August called the mid-summer drought. A comparison of the climate of the twentieth century simulations (20c3m) with observations over the period 1961–1990 shows that nearly all models underestimate precipitation over Central America, due in part to an underestimation of sea surface temperatures over the tropical North Atlantic and an excessively smooth representation of regional topographical features. However, many of the models capture the mid-summer drought. Differences between the A1B scenario (2061–2090) and 20c3m (1961–1990) simulations show decreased precipitation in the future climate scenario, mostly in June and July, just before and during the onset of the mid-summer drought. We thus hypothesize that the simulated twenty-first century drying over Central America represents an early onset and intensification of the mid-summer drought. An analysis of circulation changes indicates that the westward expansion and intensification of the North Atlantic subtropical high associated with the mid-summer drought occurs earlier in the A1B simulations, along with stronger low-level easterlies. The eastern Pacific inter-tropical convergence zone is also located further southward in the scenario simulations. There are some indications that these changes could be forced by ENSO-like warming of the tropical eastern Pacific and increased land–ocean heating contrasts over the North American continent. [ABSTRACT FROM AUTHOR]

Under the CORDEX initiative, simulations were performed using the latest version of the ICTP Regional Climate model (RegCM4.7) at a spatial resolution of 25 km over Central America/Mexico. These simulations cover the 130-year period, 1970-2099, for two representative concentration pathways, the 2.6 (RCP2.6) and 8.5 (RCP8.5) emission scenarios. They were driven by three General Circulation Models (GCMs: HadGEM2-ES, MPI-ESM-MR and GFDL-ESM2M) from phase 5 of the Coupled Model Inter-comparison Project (CMIP5). For validation, RegCM4.7 is driven by lateral boundary conditions from the ECMWF ERA-Interim global reanalysis (RegCM4.7-ERAI) for 1980–2014. In all these simulations, the potential changes in tropical cyclone (TC) activity for the North Atlantic and the Northeast Pacific basins are investigated, using an algorithm to identify and track the TCs. The RegCM4.7 simulations driven by GCMs are evaluated for the period of 1971–2005, in comparison with the RegCM4.7-ERAI and the observed TC data from the International Best Track Archive for Climate Stewardship (IBTrACS). Preliminary results show that RegCM4.7 simulations driven by GCMs are capable of capturing the TC distribution but show a notable underestimation of very intense TCs. The analysis of the influence of global warming on the TC activity will compare the 30-year period of 2070–2099 under the two representative concentration pathways to the period of 1976–2005. [ABSTRACT FROM AUTHOR]