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Eric Alfaro

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Papers by Eric Alfaro

Atmospheric Circulation Types Controlling Rainfall in the Central American Isthmus

International Journal of Climatology, 2022

Rainfall mechanisms in the Central American Isthmus are controlled by complex physical interactio... more Rainfall mechanisms in the Central American Isthmus are controlled by complex physical interactions across spatial and
temporal scales, which are reflected on the dynamics of atmospheric circulation patterns affecting the region. However,
physical mechanisms and their relationships with thermodynamic distributions connected to overturning circulations remain
elusive. Here, a set of 6 recurrent daily atmospheric patterns, or weather types (WT), is defined using a k-means++ clustering
algorithm on standardized fields of Convective Available Potential Energy (CAPE) and winds at 925, 850 and 200 hPa. The
relationships between these weather types, their temporal characteristics, and anomalous distributions of moisture flux
divergence, equivalent potential temperature (saturated and unsaturated) and observed rainfall are used to describe physical
processes controlling the latter, for all seasons. Regional observed rainfall is analyzed from a set of 174 automatic stations
from all countries from Mexico to Panama. By modulating vertically integrated moisture fluxes, these weather types, and the
different climate drivers linked to them, control the temporal and spatial rainfall characteristics in the region, especially over
the Pacific side of the isthmus. During some stages of the regional rainy season, described by two weather types, thermal
anomalies in convective quasi-equilibrium characteristic of the upward branch of the Hadley cell, force westerly flow over
Central America, enhancing rainfall. While during other stages, the enhancement of the trades and the displacement of
convection to the ITCZ area over the eastern tropical Pacific, characteristic of the midsummer drought, diminishes rainfall.
This study sets the stage for a better understanding of the mechanistic relationship between these weather types and rainfall
characteristics in general, like on-set, demise, and duration of rainy seasons. Hence, these results can inform process-based
model diagnostics aiming at bias-correcting climate predictions at multiple timescales.

Atmospheric Circulation Types Controlling Rainfall in the Central American Isthmus

by Hugo Hidalgo and Eric Alfaro

International Journal of Climatology, 2022

Rainfall mechanisms in the Central American Isthmus are controlled by complex physical interactio... more Rainfall mechanisms in the Central American Isthmus are controlled by complex physical interactions across spatial and
temporal scales, which are reflected on the dynamics of atmospheric circulation patterns affecting the region. However,
physical mechanisms and their relationships with thermodynamic distributions connected to overturning circulations remain
elusive. Here, a set of 6 recurrent daily atmospheric patterns, or weather types (WT), is defined using a k-means++ clustering
algorithm on standardized fields of Convective Available Potential Energy (CAPE) and winds at 925, 850 and 200 hPa. The
relationships between these weather types, their temporal characteristics, and anomalous distributions of moisture flux
divergence, equivalent potential temperature (saturated and unsaturated) and observed rainfall are used to describe physical
processes controlling the latter, for all seasons. Regional observed rainfall is analyzed from a set of 174 automatic stations
from all countries from Mexico to Panama. By modulating vertically integrated moisture fluxes, these weather types, and the
different climate drivers linked to them, control the temporal and spatial rainfall characteristics in the region, especially over
the Pacific side of the isthmus. During some stages of the regional rainy season, described by two weather types, thermal
anomalies in convective quasi-equilibrium characteristic of the upward branch of the Hadley cell, force westerly flow over
Central America, enhancing rainfall. While during other stages, the enhancement of the trades and the displacement of
convection to the ITCZ area over the eastern tropical Pacific, characteristic of the midsummer drought, diminishes rainfall.
This study sets the stage for a better understanding of the mechanistic relationship between these weather types and rainfall
characteristics in general, like on-set, demise, and duration of rainy seasons. Hence, these results can inform process-based
model diagnostics aiming at bias-correcting climate predictions at multiple timescales.

Visualization of 40 Years of Tropical Cyclone Positions and Their Rainfall Impacts in Central America

Scientific Visualization

This article focuses on a visualization of tropical cyclone track data occurring over a 40-year p... more This article focuses on a visualization of tropical cyclone track data occurring over a 40-year period (1970–2010) and their relationship with (extremely) heavy rainfall reported by 88 Central American weather stations. The purpose of the visualization is to associate the paths of tropical cyclones in oceanic areas with heavy rainfall inland. Thus, the potential for producing a set of rainfall patterns might somehow help in predicting where different impacts like flooding might occur when tropical cyclones develop in specific oceanic regions. The visualization will serve as a key tool for CIGEFI scientists to apply in their work to determine critical positions of the tropical cyclones associated with extremely heavy rainfall events at daily timescales.

Variability of the Caribbean low-level jet during boreal winter and summer

ABSTRACT An index capturing the anomalies of the zonal wind at 925 hPa from 1950 to 2010 was defi... more ABSTRACT An index capturing the anomalies of the zonal wind at 925 hPa from 1950 to 2010 was defined to explore the relationship between the fluctuations of the Caribbean low-level jet (CLLJ) and the main climate variability modes affecting the Intra-Americas Sea Region. El Niño Southern Oscillation (ENSO) events, here defined using the Niño 3.4 index, are found to be the most important variability modes for the jet anomalies, in agreement with previous studies. However, the Pacific Decadal Oscillation (PDO) and the Pacific/North American (PNA) teleconnection pattern also show significant correlations with the CLLJ anomaly index during February. The North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO) reveal a possible interaction with the jet anomalies that could be connected with the cold fronts and cold air surges arriving to the Caribbean basin from the Northern Hemisphere during winter. A composite technique is used to explain the correlations with the Pacific indexes. We found that ENSO events are connected to CLLJ anomalies by modulating the sea-level pressure (SLP) near the east coast of the United States and the Aleutian Low. The pattern displayed by the SLP anomalies (SLPa) is also associated with the PNA. During warm (cold) ENSO phases, negative (positive) anomalies in the SLP field over the east coast of North America produce cyclonic (anticyclonic) circulations at low levels. However, the ENSO signal in the SLPa and the PNA pattern are modulated by the phases of the PDO. Results indicate that when the ENSO and PDO are in phase (out of phase), the SLPa signal is enhanced (weakened or cancelled), affecting the CLLJ anomalies in both direction and intensity, also changing the spatial distribution of precipitation.

Influencia del océano Atlántico tropical sobre el comportamiento de la primera parte de la estación lluviosa en Venezuela

The Statistical Ocean Model System, based in Canonical Correlation Analysis, was used to study th... more The Statistical Ocean Model System, based in Canonical Correlation Analysis, was used to study the relationships between the Tropical Atlantic and Pacific Oceans and the precipitation anomalies in Venezuela for the first part of the rainy season during 1951-1995. The Tropical Atlantic Ocean had the main influence over the April-July (AMJJ) precipitation anomalies with annual cycles associated showing only one maximum in June, mainly. The atmospheric mechanism responsible for this oceanic modulation over the precipitation anomalies could be variations in the latitudinal position of the Inter-Tropical Convergence Zone.

Prediction of MJ rainfall season using CCA models

The prediction of the May-June (MJ) precipitation as the first peak of the rainy season is import... more The prediction of the May-June (MJ) precipitation as the first peak of the rainy season is important in the Central American isthmus because wetter (drier) MJ seasons tend to be associated with early (late) onsets of the rainy season on the Pacific slope. Having a late start of the rains, followed by a drier season in MJ in conjunction with a deep Mid-Summer Drought (MSD), would affect significantly key socioeconomic sectors in the isthmus like hydropower generation, water supply for human consumption (as main cities in the isthmus are located on the Pacific slope) and agriculture. Using 162 gauge stations, we built skillful Canonical Correlation Analysis (CCA) prediction models for MJ season as the first peak of the rainy season, using as predictands monthly rainfall accumulations and Standardized Precipitation Index (SPI) values over Central America. Sea Surface Temperature anomalies (SSTA) were used as predictors handling a domain bounded by 63° N-10° S and 152° E-15° W, along wi...

Uso de un modelo de aguas someras para analizar la influencia del Atlántico Tropical Norte y del Pacı́fico Ecuatorial del Este sobre la circulación atmosférica en los mares Intra-Americanos

espanolSe uso un modelo numerico de aguas someras para simular la circulacion anomala en la regio... more espanolSe uso un modelo numerico de aguas someras para simular la circulacion anomala en la region de los Mares Intra-Americanos (MIA) inducida por dos funciones forzantes asociadas con fuentes de calor localizadas en las regiones oceanicas del Atlantico Tropical Norte y del Pacifico Ecuatorial del Este, respectivamente. A pesar de su simplicidad, el modelo de aguas someras represento algunas de las caracteristicas principales de la circulacion inducida sobre los MIA por las funciones forzantes descritas anteriormente. La principal respuesta, en terminos de anomalias, se observo cuando estas fuentes de calor eran de signo opuesto, es decir, Atlantico Tropical Norte anomalamente frio (calido) y Pacifico Ecuatorial del Este anomalamente calido (frio). Estos patrones podrian estar asociados con una mayor (menor) cizalladura vertical del viento sobre los MIA. EnglishA shallow water model was used to simulate the anomalous circulation over the Intra American Seas (IAS), due to heat forci...

Projected Changes in Temperature and Precipitation Over the United States, Central America, and the Caribbean in CMIP6 GCMs

Earth Systems and Environment

The Coupled Model Intercomparison Project Phase 6 (CMIP6) dataset is used to examine projected ch... more The Coupled Model Intercomparison Project Phase 6 (CMIP6) dataset is used to examine projected changes in temperature and precipitation over the United States (U.S.), Central America and the Caribbean. The changes are computed using an ensemble of 31 models for three future time slices (2021–2040, 2041–2060, and 2080–2099) relative to the reference period (1995–2014) under three Shared Socioeconomic Pathways (SSPs; SSP1-2.6, SSP2-4.5, and SSP5-8.5). The CMIP6 ensemble reproduces the observed annual cycle and distribution of mean annual temperature and precipitation with biases between − 0.93 and 1.27 °C and − 37.90 to 58.45%, respectively, for most of the region. However, modeled precipitation is too large over the western and Midwestern U.S. during winter and spring and over the North American monsoon region in summer, while too small over southern Central America. Temperature is projected to increase over the entire domain under all three SSPs, by as much as 6 °C under SSP5-8.5, a...

Standardized Drought Indices for Pre-Summer Drought Assessment in Tropical Areas

Atmosphere

The main climatic indices used for the determination of pre-summer drought severity were develope... more The main climatic indices used for the determination of pre-summer drought severity were developed for temperate zones with very different climatic conditions from those found in the tropical climate zones, particularly with respect to seasonal rainfall variations. The temporal evolution of pre-summer drought leads the authors to compute the indices for each year over a defined period according to the climatic normals of each meteorological station and to consider the months inside the dry episode differently, according to the law of emptying the water reserves. As a function of this, standardized drought indices are proposed for the evaluation of the pre-summer drought in tropical zone. Two new indices were tested: one developed from precipitation and the other also considering temperature. These indices were validated by correlation with Advanced very-high-resolution radiometer (AVHRR) normalized difference vegetation index (NDVI) time series and used to identify the most severe d...

Examination of WRF-ARW Experiments Using Different Planetary Boundary Layer Parameterizations to Study the Rapid Intensification and Trajectory of Hurricane Otto (2016)

Atmosphere

Hurricane Otto (2016) was characterised by remarkable meteorological features of relevance for th... more Hurricane Otto (2016) was characterised by remarkable meteorological features of relevance for the scientific community and society. Scientifically, among the most important attributes of Otto is that it underwent a rapid intensification (RI) process. For society, this cyclone severely impacted Costa Rica and Nicaragua, leaving enormous economic losses and many fatalities. In this study, a set of three numerical simulations are performed to examine the skill of model estimations in reproducing RI and trajectory of Hurricane Otto by comparing the results of a global model to a regional model using three different planetary boundary layer parameterizations (PBL). The objective is to set the basis for future studies that analyse the physical reasons why a particular simulation (associated with a certain model setup) performs better than others in terms of reproducing RI and trajectory. We use the regional model Weather Research and Forecasting—Advanced Research WRF (WRF-ARW) with bound...

Rasgos oceanográficos en el Golfo Dulce, Pacífico de Costa Rica: una revisión para la toma de decisiones en conservación marina

Revista de Biología Tropical

Se indagó, de septiembre del 2005 a noviembre del 2007, las propiedades oceanográficas físicas, q... more Se indagó, de septiembre del 2005 a noviembre del 2007, las propiedades oceanográficas físicas, químicas y biológicas (zooplancton) más relevantes del Golfo Dulce, Pacífico Sur de Costa Rica, y las tipologías meteorológicas de la zona, con el objetivo de analizarlas y hacerlas disponibles como referencia en el establecimiento de actividades adecuadas para su conservación, dado que es un ecosistema acuático único en Costa Rica. El patrón de circulación de las aguas en el Golfo Dulce es el típico de estuarios tipo fiordo, con una estratificación de flujo en la columna de agua. Las corrientes marinas superficiales alcanzaron velocidades cercanas a los 18cm/s en la región de entrada al Golfo, que disminuyeron al ampliarse el área del golfo donde las velocidades llegaron a alcanzar poco más de 5cm/s en el extremo noroeste, Rincón. Predominó el flujo superficial de este-oeste, mientras que en la zona de Puerto Jiménez la velocidad fue moderada de 5.4cm/s con dirección sur. Se detectaron v...

Aridity Trends in Central America: A Spatial Correlation Analysis

Atmosphere

Trend analyses are common in several types of climate change studies. In many cases, finding evid... more Trend analyses are common in several types of climate change studies. In many cases, finding evidence that the trends are different from zero in hydroclimate variables is of particular interest. However, when estimating the confidence interval of a set of hydroclimate stations or gridded data the spatial correlation between can affect the significance assessment using for example traditional non-parametric and parametric methods. For this reason, Monte Carlo simulations are needed in order to generate maps of corrected trend significance. In this article, we determined the significance of trends in aridity, modeled runoff using the Variable Infiltration Capacity Macroscale Hydrological model, Hagreaves potential evapotranspiration (PET) and near-surface temperature in Central America. Linear-regression models were fitted considering that the predictor variable is the time variable (years from 1970 to 1999) and predictand variable corresponds to each of the previously mentioned hydro...

Regional precipitation estimations in Central America using the Weather Research and Forecast model

Revista de Biología Tropical

Using the regional climate model WRF, and the NCEP-NCAR Reanalysis Project data as boundary and i... more Using the regional climate model WRF, and the NCEP-NCAR Reanalysis Project data as boundary and initial conditions, regional precipitation for Central America was estimated by means of the dynamical downscaling technique for two selected periods: January 2000 and September 2007. Four-nested domains, d01, d02, d03 and d04 with a grid-resolution of 90 km, 30 km, 10 km, and 3.3 km respectively, were configured over this region. The runs were reinitialized every 5 days with 6 h of spin-up time for adjustment of the model. A total of eight experiments (four per month) were tested in order to study: a) two important Cumulus Parameterization Schemes (CPS): Kain-Fritsch (KF) and Grell-Devenyi (GD); and b) the physical interaction between nested domains (one-and two-way nesting), during each simulated month. The modeled precipitation was in agreement with observations for January 2000, and also captured the mean climate features of rainfall concerning magnitude, and spatial distribution, such as the particular precipitation contrast between the Pacific and the Caribbean coast. Outputs of the coarse domains (d01, d02, and d03) for September 2007 revealed differences between experiments within the domains when a visual comparison of the spatial distribution was made. However, for the inner grid (d04), all the experiments, showed a similar spatial distribution and magnitude estimation, mainly in those runs using one-way nesting configuration. The results for the month of September differed substantially with the observations, which could be related to associated deficiencies in the boundary condition that do not reproduce well the transition periods from warm to cold ENSO episodes for the selected periods of study. In all the experiments, the KF scheme calculated more precipitation than the GD scheme and it was associated to the ability of the GD scheme to reproduce spotty but intense rainfall, and apparently, this scheme was reluctant to activate, showing frequent events of low intensity rain. However, when rainfall did develop, it was very intense. Also, the time series did not replicate specific precipitation events. Thus, the 5-days integration period used in this study was not enough to reproduce short-period precipitation events. Finally, physical interaction issues between the nested domains were reflected in discontinuities in the precipitation field, which have been associated with mass field adjustment in the CPS.

Valoración socioeconómica del impacto de la variabilidad climática sobre la pesca artesanal en Costa Rica

Uniciencia

La mayor cantidad de pesca en Costa Rica la realiza la flota artesanal con el 81,41% del total en... more La mayor cantidad de pesca en Costa Rica la realiza la flota artesanal con el 81,41% del total en el periodo 1990-2009. Muchas son las presiones que esta flota debe afrontar para desarrollar su actividad. Una de ellas es el desconocimiento de cuál es el papel de la variabilidad climática en los cambios en la pesca y qué medidas pueden adoptar para mitigarla. En el presente artículo se aplica una metodología que relaciona las variaciones de la producción de la pesca artesanal con los cambios en la temperatura superficial del mar y valora los posibles efectos resultantes en los ingresos de los grupos pescadores en un periodo de 10 años. Se obtuvo como resultado que no todos los grupos comerciales de la pesca artesanal son sensibles a las variaciones en la temperatura superficial del mar. En el presente estudio de caso, se obtuvo que el tiburón fue el grupo comercial más sensible y que los ingresos del sector pescador son 53% más altos en eventos fríos que aquellos obtenidos en eventos...

DynACof: A process-based model to study growth, yield and ecosystem services of coffee agroforestry systems

Environmental Modelling & Software

The DynACof model was designed to model coffee agroforestry systems and study the trade-offs to e... more The DynACof model was designed to model coffee agroforestry systems and study the trade-offs to e.g. optimize the system facing climate changes. The model simulates net primary productivity (NPP), growth, yield, mortality, energy and water balance of coffee agroforestry systems according to shade tree species and management. Several plot-scale ecosystem services are simulated by the model, such as production, canopy cooling effect, or potential C sequestration. DynACof uses metamodels derived from a detailed 3D process-based model (MAESPA) to account for complex spatial effects, while running fast. It also includes a coffee flower bud and fruit cohort module to better distribute fruit carbon demand over the year, a key feature to obtain a realistic competition between sinks. We compared the model outputs with a highly comprehensive database on a coffee agroforestry farm in Costa Rica. The fluxes simulated by the model were close to the measurements over a 5-year period (RMSE= 1.60 gC m-2 d-1 for gross primary productivity; 0.63 mm d-1 for actual evapo-transpiration, 1.34 MJ m-2 d-1 for sensible heat flux and 1.88 MJ m-2 d-1 for net radiation), and DynACof satisfactorily simulated the yield, NPP, mortality and carbon stock for each coffee organ type over a 35-year rotation.

Mapping Environmental and Socioeconomic impacts of hydrometeorological hazards across Central America. Study case: Honduras

Política Económica para el Desarrollo Sostenible

tra bajo una licencia Creative Commons Reconocimiento-NoComercial-SinObraDerivada 3.0 Costa Rica ... more

Comparison of parameters of the generalized extreme value distribution associated with extreme rainfall events in Central America

Uniciencia

The generalized extreme value distribution (GEVD) was used to model extreme rainfall events in Ce... more The generalized extreme value distribution (GEVD) was used to model extreme rainfall events in Central America for a period of 30 years, beginning in 1971. Data consisted of daily rainfall records of 103 meteorological stations located throughout the isthmus. Central America was divided into 3 regions: Pacific, Caribbean and an intermediate zone. A bootstrap hypothesis test was used to compare the parameters of location, scale and form of the 3 regions. The results of the study showed significant differences between the 3 regions, mainly in terms of location and scale parameters.

A review of the main drivers and variability of Central America’s Climate and seasonal forecast systems

Revista de Biología Tropical

Central America is a region susceptible to natural disasters and climate change. We reviewed the ... more Central America is a region susceptible to natural disasters and climate change. We reviewed the literature on the main atmospheric and oceanographic forces and climate modulators affecting Central America, for different spatial and time scales. We also reviewed the reported correlation between climate variability, natural hazards and climate change aspects (in the past and future). In addition, we examined the current state of seasonal prediction systems being applied to the region. At inter-annual scales, El Niño/Southern Oscillation is the main climate modulator; however, other indices such as the Tropical North Atlantic, Atlantic Multi-Decadal Oscillation and Pacific Decadal Oscillation, have shown a correlation with precipitation anomalies in the region. Current seasonal forecast systems in the region have shown a constant development, including incorporation of different approaches ranging from statistical to dynamical downscaling, improving prediction of variables such as pre...

Análisis del Impacto en Costa Rica de los Ciclones Tropicales Ocurridos en el Mar Caribe desde 1968 al 2007

Diálogos Revista Electrónica

El estudio de la actividad de los ciclones tropicales, así como su caracterización histórica en l... more El estudio de la actividad de los ciclones tropicales, así como su caracterización histórica en la región centroamericana, es una prioridad para apoyar las actividades de mitigación del impacto que estos fenómenos provocan en las diversas zonas del istmo. Basado en lo anterior, en este trabajo se definen para Costa Rica, los años de alto o bajo impacto por el paso de ciclones tropicales en el Caribe considerando variables asociadas a la trayectoria del evento, la permanencia del mismo cerca del istmo y la frecuencia de los fenómenos en la cuenca. El análisis mostró que la mayor probabilidad de ocurrencia de los ciclones tropicales cerca de América Central se presenta durante el trimestre agosto-setiembre-octubre. Se observó también, que durante los años que mostraron altas ocurrencias de ciclones cerca de América Central, el Atlántico Tropical Norte presentó campos con anomalías positivas en la temperatura superficial del mar y la humedad relativa en 700 hPa, y negativas en la presi...

Humedales del Parque Nacional Chirripó, Costa Rica: características, relaciones geomorfológicas y escenarios de cambio climático

Revista de Biología Tropical, 2018

The geomorphological, climatological and hydrological characteristics of the high Andean wetlands... more The geomorphological, climatological and hydrological characteristics of the high Andean wetlands of the Chirripó National Park (PNCh) are analyzed. The PNCh is located in south-central Costa Rica, Central America. This analysis includes a geomorphological survey on a 1: 25 000 scale of the relief forms and processes, particularly those of glacial origin. The National Wetland Inventory carried out by the Wetlands Project (UNDP-SINAC-GEF) was also used, along with different climate change projections corresponding to the scenarios for the 2039-2059 and 2079-2099 horizons. The main objective is to characterize the current state of these ecosystems, to explain how and why they are formed, as well as to assess the possible implications in the hydrological cycle and the water supply of these wetlands due to future climate variations. The results showed the relevance of these natural reservoirs in maintaining the ecological dynamics of the PNCh. We also studied the services of water provi...