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ResumenEl presente artículo sintetiza los principales procesos histórico-científicos que permitieron el desarrollo de las primeras observaciones meteorológicas elaboradas en la región caribeña de Costa Rica. Se parte de las descripciones y mediciones realizadas por el Bachiller Osejo (1833) hasta la clausura parcial del Servicio Meteorológico y Sismológico Nacional (1949). Durante más de un siglo, dichas observaciones fueron elaboradas, sistematizadas y analizadas por diversos actores. Entre ellos, destacan científicos y estudiosos nacionales y extranjeros, instituciones científicas como el Instituto Físico-Geográfico Nacional y empresas como la United Fruit Company. Los datos recopilados fueron reanalizados e interpretados con el propósito de caracterizar el clima de la región en el pasado. Los resultados de este estudio aportan una línea base de comparación histórica ante el problema actual del cambio climático regional. AbstractThis article summarizes the main historical and scientific processes that allowed the development of the first meteorological observations made in the Caribbean region of Costa Rica. It is part of the descriptions and measurements made by Bachelor Osejo (1833) to the partial closure of the National Weather and Seismological Service (1949). For over a century, these observations were made, systematized and analyzed by various stakeholders. Among them are domestic and foreign scientists and scholars, scientific institutions such as the National Physical Geographic Institute and companies like United Fruit Company. The collected data were re-analyzed and interpreted in order to characterize the climate of the region in the past. The results of this study provide a baseline for historical comparison to the current problem of regional climate change.

Artículo científico -- Universidad de Costa Rica, Escuela de Física. 2014 The Central America region hosts a valuable amount of World Heritage Sites (WHS), many of them located in areas of floods, landslides, drought, high winds, intense precipitations, and earthquakes. The effective management of WHS requires the understanding of this type of environmental phenomena and their potential impacts on these sites. The objective of this work is twofold. To make an analysis of some of the atmospheric systems (easterly waves, cold fronts and tropical cyclones [TCs]) hitting Central America, to estimate their effects on socio-economic activities and potential impacts on WHS during the period 2002–2012. The second objective is to identify, for a case study, the potential effects of hydro-meteorological events associated with a tropical storm on the Diquis Delta region in southern Costa Rica. This site, an important unique archeological site of stone spheres, has been proposed by this country as a WHS. To achieve both, public data bases like HURDAT (North Atlantic Hurricane Database), and information from regional newspapers and National Emergency Committees, among other sources, were used for the study of socio-economic impacts caused by these natural hazards. To accomplish the latter, course resolution NCEP/NCAR (National Center for Environmental Prediction/National Center for Atmospheric Research) Reanalysis atmospheric data served to initialize version 5 of a numerical atmospheric mesoscale model (MM5). This approach permitted to obtain higher resolution gridded data for a set of atmospheric variables for a case study associated with the formation of tropical storm Alma upon the Pacific basin. The MM5 resulted winds and precipitation, among other variables, were then used to evaluate potential impacts on the WHS region. Among the systems analyzed for Central America, TCs were the ones that most severely impacted regional social life and worsened the already weak regional economies. During the period analyzed, TCs affected regions where WHS are very relevant to cultural life and touristic income. The MM5 derived data shows its potential for providing detailed spacetime atmospheric data to help quantify and anticipate impacts for WHS protection and management. The overall results are expected to bring the attention of organizations and governments about the importance of socio-economic and cultural losses associated with the impacts caused by natural hazards near WHS in the region. Universidad de Costa Rica UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Física

A climatology of moisture sources linked with Central American precipitation was computed based upon Lagrangian trajectories for the analysis period 1980–2013. The response of the annual cycle of precipitation in terms of moisture supply from the sources was analysed. Regional precipitation patterns are mostly driven by moisture transport from the Caribbean Sea (CS). Moisture supply from the eastern tropical Pacific (ETPac) and northern South America (NSA) exhibits a strong seasonal pattern but weaker compared to CS. The regional distribution of rainfall is largely influenced by a local signal associated with surface fluxes during the first part of the rainy season, whereas large-scale dynamics forces rainfall during the second part of the rainy season. The Caribbean Low Level Jet (CLLJ) and the Chocó Jet (CJ) are the main conveyors of regional moisture, being key to define the seasonality of large-scale forced rainfall. Therefore, interannual variability of rainfall is highly dependent of the regional LLJs to the atmospheric variability modes. The El Niño–Southern Oscillation (ENSO) was found to be the dominant mode affecting moisture supply for Central American precipitation via the modulation of regional phenomena. Evaporative sources show opposite anomaly patterns during warm and cold ENSO phases, as a result of the strengthening and weakening, respectively, of the CLLJ during the summer months. Trends in both moisture supply and precipitation over the last three decades were computed, results suggest that precipitation trends are not homogeneous for Central America. Trends in moisture supply from the sources identified show a marked north–south seesaw, with an increasing supply from the CS Sea to northern Central America. Long-term trends in moisture supply are larger for the transition months (March and October). This might have important implications given that any changes in the conditions seen during the transition to the rainy season may induce stronger precipitation trends. Universidad de Costa Rica/[805-B3-600]/UCR/Costa Rica Universidad de Costa Rica/[805-B5-295]/UCR/Costa Rica Universidad de Costa Rica/[805-B0-065]/UCR/Costa Rica Universidad de Costa Rica/[805-A8-606]/UCR/Costa Rica Universidad de Costa Rica/[805-B0-130]/UCR/Costa Rica Universidad de Costa Rica/[805-A9-224]/UCR/Costa Rica Universidad de Costa Rica/[805-A7-002]/UCR/Costa Rica Universidad de Costa Rica/[805-B6-143]/UCR/Costa Rica Universidad de Costa Rica/[808-A9-180]/UCR/Costa Rica Environmental Physics Laboratory/[]/EPhysLab/España UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigaciones Geofísicas (CIGEFI)

artículo científico -- Universidad de Costa Rica,Centro de Investigaciones Geofísicas. 2013. Este documento es privado debido a limitaciones de derechos de autor. Runoff climate change projections for the 21st century were calculated from a suite of 30 General Circulation Model (GCM) simulations for the A1B emission scenario in a 0.5 0.5 grid over Central America. The GCM data were downscaled using a version of the Bias Correction and Spatial Downscaling (BCSD) method and then used in the Variable Infiltration Capacity (VIC) macroscale hydrological model. The VIC model showed calibration skill in Honduras, Nicaragua, Costa Rica and Panama, but the results for some of the northern countries (Guatemala, El Salvador and Belize) and for the Caribbean coast of Central America was not satisfactory. Bias correction showed to remove effectively the biases in the GCMs. Results of the projected climate in the 2050–2099 period showed median significant reductions in precipitation (as much as 5–10%) and runoff (as much as 10–30%) in northern Central America. Therefore in this sub-region the prevalence of severe drought may increase significantly in the future under this emissions scenario. Northern Central America could warm as much as 3 C during 2050–2099 and southern Central America could reach increases as much as 4 C during the same period. The projected dry pattern over Central America is consistent with a southward displacement of the Intertropical Convergence Zone (ITCZ). In addition, downscaling of the NCEP/NCAR Reanalysis data from 1948 to 2012 and posterior run in VIC, for two locations in the northern and southern sub-regions of Central America, suggested that the annual runoff has been decreasing since ca. 1980, which is consistent with the sign of the runoff changes of the GCM projections. However, the Reanalysis 1980–2012 drying trends are generally much stronger than the corresponding GCM trends. Among the possible reasons for that discrepancy are model deficiencies, amplification of the trends due to constructive interference with natural modes of variability in the Reanalysis data, errors in the Reanalysis (modeled) precipitation data, and that the drying signal is more pronounced than predicted by the emissions scenario used. A few studies show that extrapolations of future climate from paleoclimatic indicators project a wetter climate in northern Central America, which is inconsistent with the modeling results presented here. However, these types of extrapolations should be done with caution, as the future climate responds to an extra forcing mechanism (anthropogenic) that was not present prehistorically and therefore the response could also be different than in the past. info:eu-repo/grantAgreement/Universidad de Costa Rica/Marine Science and Limnology Research Center (CIMAR)/808-A9-180/Costa Rica// info:eu-repo/grantAgreement/Universidad de Costa Rica/Center for Geophysical Research (CIGEFI)/805-A8-606/Costa Rica// info:eu-repo/grantAgreement/Universidad de Costa Rica/Center for Geophysical Research (CIGEFI)/805-A9-532/Costa Rica// info:eu-repo/grantAgreement/Universidad de Costa Rica/Center for Geophysical Research (CIGEFI)/805-A9-224/Costa Rica// info:eu-repo/grantAgreement/Florida Ice and Farm Company///Costa Rica// info:eu-repo/grantAgreement/Panamerican Institute of Geography and History//GEOF.02.2011/// UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigaciones Geofísicas (CIGEFI)

The tropics are characterized by a variety of atmospheric and oceanic systems dominated by multi-scale interaction processes. This is Part I of a two-part review study on climate and climate variability of the Eastern Tropical Pacific (ETP). Here, the mean fields of incoming short wave radiation, surface energy fluxes, sea surface temperature, sea level pressure, salinity, wind patterns at 10m height, wind stress curl, precipitation, and evaporation are analyzed and synthetized using available data including that from the last decade. Given the strong interaction between the ETP and Caribbean Sea-Atlantic Ocean, mean field discussions are presented for two different domains, a relatively large domain from 24° S - 36° N and between 129° W - 17° W, and a smaller domain embedding only the Caribbean Sea and the easternmost part of the ETP. Most results on the climate of these two regions can be used as the base line for climate change studies. Interannual variability of tropical cyclones is also investigated over the domain of the latter two basins in the smaller domain. The study is complemented with a short review of some low frequency modes, such as, El Niño-Southern Oscillation, the Pacific Decadal Oscillation, and the Atlantic Multi-decadal Oscillation. Such low-frequency modes are known to modulate regional systems, including tropical cyclone frequency.

This is Part II of a two-part review about climate and climate variability focused on the Eastern Tropical Pacific (ETP) and the Caribbean Sea (CS). Both parts are aimed at providing oceanographers, marine biologists, and other ocean scientists, a guiding base for ocean-atmosphere interaction processes affecting the CS, the ETP, and the waters of Isla del Coco. Isla del Coco National Park is a Costa Rican World Heritage site. Part I analyzed the mean fields for both basins and a larger region covering 25º S - 35º N, 20º W - 130º W. Here we focus on a smaller area (65º W - 95º W, 0º - 20º N), as a complement to Part 1. Incoming solar radiation and surface energy fluxes reveal the complex nature of the ETP and CS for convective activity and precipitation on seasonal and intraseasonal time scales. Both regions are relevant as sources of evaporation and the associated moisture transport processes. The American Monsoon System influences the climate and climate variability of the ETP and CS, however, the precise way systems affect regional precipitation and transport of moisture, within the Intra Americas Sea (IAS) are not clear. Although the Caribbean Low-Level Jet (CLLJ) is known to act as a conveyor belt for moisture transport, intraseasonal and seasonal modes of the CLLJ and their interactions with other IAS systems, have to be further investigated. Trans-isthmic jets, exert a variable seasonal wind stress force over the ocean surface co-generating regions of great marine productivity. Isolated convection, the seasonal migration of the Intertropical Convergence Zone, the hurricane season, the Mid-Summer Drought, the seasonal and intraseasonal behavior of low-level jets and their interactions with transients, and the southward incursion of cold fronts contribute to regional seasonal precipitation. Many large-scale systems, such as El Niño-Southern Oscillation, the Atlantic Multidecadal Oscillation and the Madden-Julian Oscillation (MJO, also influence the variability of precipitation by modulating regional features associated with convection and precipitation. Monthly tropical storm (TS) activity in the CS and ETP basins is restricted to the period May-November, with very few cases in December. The CS presents TS peak activity during August, as well as for the number of hurricanes and major hurricanes, in contrast to the ETP that shows the same features during September. Esta es la Parte II de una revisión en dos partes del clima y la variabilidad climática, enfocada en el Pacífico Tropical del Este (PTE) y el Mar Caribe (MC). Ambas partes del trabajo tienen como objetivo proveer a oceanógrafos, biólogos marinos y otros científicos marinos, una guía base de las interacciones océano-atmósfera que afectan el PTE, el MC y las aguas de la Isla del Coco, Patrimonio de la Humanidad de Costa Rica. La Parte I analizó para el PTE y MC y para las región 25º S - 35º N, 20º W - 130º W, los campos medios anuales. En este trabajo el área de interés es 65º W - 95° W, 0º - 20º N, como complemento a la Parte I. La radiación solar y los flujos superficiales de energía muestran una compleja naturaleza del PTE y MC, en relación con la actividad convectiva y la precipitación en escalas de tiempo estacionales e intra-estacionales. Ambas regiones son importantes como fuentes de evaporación y para los procesos de transporte regional de humedad. El Sistema Monsónico de América (SMA) influencia el clima y variabilidad climática del PTE y CS, sin embargo, la forma precisa en que los sistemas actúan para afectar la precipitación regional y el transporte de humedad, en la región de los Mares Intra Americanos (MIA), no es clara. A pesar de que la Corriente en Chorro del Caribe (CCC) actúa como una cinta transportadora de humedad, los modos estacionales e intra-estacionales de la CCC y sus interacciones con otro sistemas en la región del MIA, tienen que ser aún investigados. Las corrientes trans-istmicas ejercen un variable esfuerzo estacional del viento sobre la superficie oceánica cogenerando regiones de gran productividad marina. Convección aislada, la migración estacional de la Zona de Convergencia Intertropical, la temporada de huracanes, el veranillo, el comportamiento estacional e intra-estacional de las corrientes de bajo nivel y su interacción con sistemas transitorios y la incursión en latitudes bajas de frentes fríos contribuyen a la precipitación estacional en la región. Muchos sistemas de gran escala, como el Niño-Oscilación del Sur, la Oscilación Multidecenal del Atlántico y la Oscilación de Madden-Julian contribuyen también a la variabilidad de la precipitación, al modular características regionales asociadas a la convección y la precipitación. La actividad mensual de tormentas tropicales (TT) se restringe en el PTE y MC al periodo mayo-noviembre, con muy pocos casos en diciembre. El MC presenta picos de TT durante agosto, lo mismo que el número de huracanes y el de huracanes fuertes, en contraste con el PTE que muestra estas características durante septiembre. El final de la temporada de TT es más abrupta en el PTE que en el MC, en donde octubre es un periodo menos activo que septiembre-octubre en el MC.

Con el fin de determinar el efecto del calcio y diferentes láminas de riego en plantas de repollo (Brassica oleracea), se sometieron 80 plantas a un diseño completamente al azar, factorial de 3x3, donde el primer factor correspondió a tres niveles de calcio (80, 120 y 160kg x ha-1 de Ca) y el segundo a láminas de riego determinadas por coeficientes (0,8; 1 y 1,2 de la evaporación medida en un evaporímetro construido), más un testigo con una lámina de uno y sin aplicación de calcio, para un total de diez tratamientos. El experimento tuvo una duración de 130 días en invernadero y diez días en laboratorio, para evaluar el comportamiento en poscosecha. Los tratamientos indujeron diferencias significativas para la altura, el área foliar, el peso fresco de hojas, tallo y cabeza, el peso seco de raíz y cabeza, el pH y la pérdida de peso fresco y, altamente significativas para los sólidos solubles totales y el análisis económico. Con la aplicación de la lámina de 0,8 y 160kg x ha-1 de Ca, se obtuvo mayor peso fresco de cabeza y mayor cantidad de fitomasa fresca por cada peso invertido (33,76g x $), por tanto, éste tratamiento es recomendable para ser implementado por los productores de repollo. El suministro de lámina de 1 y 160kg x ha-1 de Ca permitió conservar el repollo en mejores condiciones durante la poscosecha.With the purpose of determining the effect of calcium and different water tables in cabbage (Brassica oleracea) 80 plants were put under a completely randomized design, factorial of 3x3, where the first factor corresponded to three calcium levels (80, 120 and 160kg x ha -1) and the second one to three water tables, determined by using three evaporation coefficients (0.8; 1 and 1.2 of evaporation, measured with an evaporimeter) and a treatment with a water table of 1, without calcium application, for a total of ten treatments. The research was carried out during 130 days in a greenhouse and during ten days under laboratory conditions, to evaluate the post-harvest behavior. The treatments induced significant differences for height, leaf area, fresh weight of leaves, stem and head, dry weight of roots and head, pH and loss of fresh weight; and highly significant differences in total soluble solids and within the economic analysis. With the application of a water table of 0.8 and 160kg x ha-1 of Ca the greatest fresh weight of heads was obtained and a higher fresh phytomass for each inverted peso (33.76g x $). Therefore, this treatment is recommended to be implemented by cabagge producers. The water table of 1 and 160kg x ha-1 of Ca, allowed conserving cabbage in better conditions during post-harvest.

Data from the Global Precipitation Climatology Project covering Central America, the Caribbean Sea, the eastern tropical Pacific and northern South America are used to compute four indexes that describe characteristics of the Inter-Tropical Convergence Zone: the latitudinal center of mass of precipitation, the longitudinal center of mass of precipitation, the average precipitation in a region bounded by 10° S–25° N and 100° W–55° W, and the spread of the precipitation patterns.Avery strong correlation is found between summer latitudinal center of mass and a summer index of the Caribbean Low-Level Jet suggesting connections between Pacific and Caribbean climatic processes. The sign of the correlation implies that when the jet is stronger (weaker) there is a lower (higher) latitudinal center of mass and at the same time less (more) precipitation in the Pacific slope of Central America. The connection between the Caribbean and Pacific climate is not only related to high-level wind convergence, but it is proposed here that local convection and the establishment of a zonal circulation may be playing a role in the process. The circulation seems to be consistent during years when latitudinal center of mass is lower than normal, apparently reinforcing the jet, and presents weaker strength during years of high latitudinal center of mass. The proposed mechanism is explained in some detail. Universidad de Costa Rica/[805-B3-413]/UCR/Costa Rica Universidad de Costa Rica/[808-A9-180]/UCR/Costa Rica Universidad de Costa Rica/[805-A9-532]/UCR/Costa Rica Universidad de Costa Rica/[805-B3-600]/UCR/Costa Rica Universidad de Costa Rica/[808-B0-654]/UCR/Costa Rica Universidad de Costa Rica/[805-B0-065]/UCR/Costa Rica Universidad de Costa Rica/[805-B4-227]/UCR/Costa Rica Universidad de Costa Rica/[805-A7-002]/UCR/Costa Rica Universidad de Costa Rica/[805-A9-224]/UCR/Costa Rica UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigaciones Geofísicas (CIGEFI)

An important goal of the Climate Variability and Predictability (CLIVAR) research on the American monsoon systems is to determine the sources and limits of predictability of warm season precipitation, with emphasis on weekly to interannual time scales. This paper reviews recent progress in the understanding of the American monsoon systems and identifies some of the future challenges that remain to improve warm season climate prediction. Much of the recent progress is derived from complementary international programs in North and South America, namely, the North American Monsoon Experiment (NAME) and the Monsoon Experiment South America (MESA), with the following common objectives: 1) to understand the key components of the American monsoon systems and their variability, 2) to determine the role of these systems in the global water cycle, 3) to improve observational datasets, and 4) to improve simulation and monthly-to-seasonal prediction of the monsoons and regional water resources. Among the recent observational advances highlighted in this paper are new insights into moisture transport processes, description of the structure and variability of the South American low-level jet, and resolution of the diurnal cycle of precipitation in the core monsoon regions. NAME and MESA are also driving major efforts in model development and hydrologic applications. Incorporated into the postfield phases of these projects are assessments of atmosphere–land surface interactions and model-based climate predictability experiments. As CLIVAR research on American monsoon systems evolves, a unified view of the climatic processes modulating continental warm season precipitation is beginning to emerge.

The collection of articles in this volume reviewing eastern tropical Pacific oceanography is briefly summarized, and updated references are given. The region is an unusual biological environment as a consequence of physical characteristics and patterns of forcing – including a strong and shallow thermocline, the ITCZ and coastal wind jets, equatorial upwelling, the Costa Rica Dome, eastern boundary and equatorial current systems, low iron input, inadequate ventilation of subthermocline waters, and dominance of ENSO-scale temporal variability. Remaining unanswered questions are presented.

The North American Monsoon Experiment (NAME) is an internationally coordinated process study aimed at determining the sources and limits of predictability of warm-season precipitation over North America. The scientific objectives of NAME are to promote a better understanding and more realistic simulation of warm-season convective processes in complex terrain, intraseasonal variability of the monsoon, and the response of the warm-season atmospheric circulation and precipitation patterns to slowly varying, potentially predictable surface boundary conditions. During the summer of 2004, the NAME community implemented an international (United States, Mexico, Central America), multiagency (NOAA, NASA, NSF, USDA) field experiment called NAME 2004. This article presents early results from the NAME 2004 campaign and describes how the NAME modeling community will leverage the NAME 2004 data to accelerate improvements in warm-season precipitation forecasts for North America.

In 2013, the vast majority of the monitored climate variables reported here maintained trends established in recent decades. ENSO was in a neutral state during the entire year, remaining mostly on the cool side of neutral with modest impacts on regional weather patterns around the world. This follows several years dominated by the effects of either La Niña or El Niño events. According to several independent analyses, 2013 was again among the 10 warmest years on record at the global scale, both at the Earths surface and through the troposphere. Some regions in the Southern Hemisphere had record or near-record high temperatures for the year. Australia observed its hottest year on record, while Argentina and New Zealand reported their second and third hottest years, respectively. In Antarctica, Amundsen-Scott South Pole Station reported its highest annual temperature since records began in 1957. At the opposite pole, the Arctic observed its seventh warmest year since records began in the early 20th century. At 20-m depth, record high temperatures were measured at some permafrost stations on the North Slope of Alaska and in the Brooks Range. In the Northern Hemisphere extratropics, anomalous meridional atmospheric circulation occurred throughout much of the year, leading to marked regional extremes of both temperature and precipitation. Cold temperature anomalies during winter across Eurasia were followed by warm spring temperature anomalies, which were linked to a new record low Eurasian snow cover extent in May. Minimum sea ice extent in the Arctic was the sixth lowest since satellite observations began in 1979. Including 2013, all seven lowest extents on record have occurred in the past seven years. Antarctica, on the other hand, had above-average sea ice extent throughout 2013, with 116 days of new daily high extent records, including a new daily maximum sea ice area of 19.57 million km2 reached on 1 October. ENSO-neutral conditions in the eastern central Pacific Ocean and a negative Pacific decadal oscillation pattern in the North Pacific had the largest impacts on the global sea surface temperature in 2013. The North Pacific reached a historic high temperature in 2013 and on balance the globally-averaged sea surface temperature was among the 10 highest on record. Overall, the salt content in nearsurface ocean waters increased while in intermediate waters it decreased. Global mean sea level continued to rise during 2013, on pace with a trend of 3.2 mm yr-1 over the past two decades. A portion of this trend (0.5 mm yr-1) has been attributed to natural variability associated with the Pacific decadal oscillation as well as to ongoing contributions from the melting of glaciers and ice sheets and ocean warming. Global tropical cyclone frequency during 2013 was slightly above average with a total of 94 storms, although the North Atlantic Basin had its quietest hurricane season since 1994. In the Western North Pacific Basin, Super Typhoon Haiyan, the deadliest tropical cyclone of 2013, had 1-minute sustained winds estimated to be 170 kt (87.5 m s-1) on 7 November, the highest wind speed ever assigned to a tropical cyclone. High storm surge was also associated with Haiyan as it made landfall over the central Philippines, an area where sea level is currently at historic highs, increasing by 200 mm since 1970. In the atmosphere, carbon dioxide, methane, and nitrous oxide all continued to increase in 2013. As in previous years, each of these major greenhouse gases once again reached historic high concentrations. In the Arctic, carbon dioxide and methane increased at the same rate as the global increase. These increases are likely due to export from lower latitudes rather than a consequence of increases in Arctic sources, such as thawing permafrost. At Mauna Loa, Hawaii, for the first time since measurements began in 1958, the daily average mixing ratio of carbon dioxide exceeded 400 ppm on 9 May. The state of these variables, along with dozens of others, and the 2013 climate conditions of regions around the world are discussed in further detail in this 24th edition of the State of the Climate series. © 2014, American Meteorological Society. All rights reserved.

The annual cycle of precipitation over the southern part of Mexico and Central America exhibits a bimodal distribution with maxima during June and September–October and a relative minimum during July and August, known as the midsummer drought (MSD). The MSD is not associated with the meridional migration of the intertropical convergence zone (ITCZ) and its double crossing over Central America but rather with fluctuations in the intensity and location of the eastern Pacific ITCZ. During the transition from intense to weak (weak to intense) convective activity, the trade winds over the Caribbean strengthen (weaken). Such acceleration in the trade winds is part of the dynamic response of the low-level atmosphere to the magnitude of the convective forcing in the ITCZ. The intensification of the trade winds during July and August and the orographic forcing of the mountains over most of Central America result in maximum precipitation along the Caribbean coast and minimum precipitation along the Pacific...

This work is related to the study of several aspects of some of the geophysical effects of the 22 April 1991 earthquake in the Atlantic Coast of Costa Rica. Changes in the shore line nearby Limón, associated to the uplift of the earth‘s crust, and sediment plumes and coastal currents are analyzed by means of LANDSAT (2 Abril 1991) and SPOT (19 June 1991) imagery. This analysis is complemented with hydrometeorological data and field work. In relation to the uplift of the earth's crust, the SPOT image shows an area of variable width to the north of Limón and in the neighborhood of the Pájaros and Uvita islands, that is not identified in the LANDSAT image prior to the event. Field work confirmed, that such an area is a mixture of dead coral reefs and consolidated sand. This uplift is of noncontinuous nature and is in the order of 40-50 cm near La Estrella river, 40 cm in the Muelle Alemán and approximately 2 m in Playa Bonita. Post-event precipitation rates and river flows were generally above normal means, such that together with the landslides, produced inusual sediment transport rates in the rivers of the region. These sediment discharges, specially in Banano and La Estrella rivers show well defined sediment concentration patterns that led to identify coastal currents with a principal component towards the north, in contrast to what has been published in the scientific literature. El presente trabajo estudia varios aspectos de algunos efectos geofísicos del terremoto del 22 de abril de 1991 en la Costa Atlántica de Costa Rica. Los cambios en la línea de costa al norte de Limón, asociados al levantamiento de la corteza terrestre durante el sismo, las descargas de sedimentos de los ríos de la región y las corrientes costeras asociadas, son analizados mediante imágenes LANDSAT (2 de abril de 1991) y SPOT (19 dejunio de 1991). El análisis anterior se complementa con la ayuda de datos hidrometeorológicos y trabajo de campo. En relación con el levantamiento de la corteza terrestre, la imagen SPOT muestra una zona costera de ancho variable en el litoral norte de Limón y en los alrededores de las islas Pájaros y Uvita, que no se identifica en la imagen LANDSAT antes del terremoto. El trabajo de campo confirmó que esa zona está constituida principalmente por arrecifes coralinos muertos y arena consolidada. El levantamiento ocurrido no es continuo y del orden de 40-50 cm. cerca del río La Estrella, 40 cm. en el Muelle Alemán y cerca de 2 m. en Playa Bonita. Las lluvias y caudales post-evento, fueron en general superiores a lo normal, lo que asociado a los deslizamientos ocurridos, provocaron un arrastre inusual de sedimentos en los ríos de la región. La descarga de estos ríos, en especial, en el Banano y La Estrella, presentan patrones de concentración bien definidos y permiten identificar corrientes costeras cercanas con componente principal hacia el norte, en contraste con lo que ha sido publicado en la literatura científica.

We report on balloon sonde measurements of water vapor and ozone using the cryogenic frost point hygrometer and electrochemical concentration cell ozonesondes made at Alajuela, Costa Rica (10.0 N, 84.2 W) during two NASA airborne campaigns: the Tropical Convective Systems and Processes (TCSP) mission in July 2005 and the Tropical Composition, Clouds, and Climate Coupling Experiment (TC4), July - August 2007. In both campaigns we found an upper troposphere that was frequently supersaturated but no evidence that deep convection had reached the tropopause. The balloon sondes were complemented by campaigns of 4 times daily high-resolution radiosondes from mid-June through mid-August in both years. The radiosonde data reveal vertically propagating equatorial waves that caused a large increase in the variability of temperature in the tropical tropopause layer (TTL). These waves episodically produced cold point tropopauses (CPTs) above 18 km, yet in neither campaign was saturation observed above approx 380 K or 17 km. The averages of the water vapor minima below this level were 5.2 ppmv in TCSP and 4.8 ppmv in TC4, and the individual profile minima all lay at or above approx 360 K. The average minima in this 360 C380 K layer provide a better estimate of the effective stratospheric entry value than the average mixing ratio at the CPT. We refer to this upper portion of the TTL as the tropopause saturation layer and consider it to be the locus of the final dehydration of nascent stratospheric air. As such, it is the local equivalent to the tape head of the water vapor tape recorder.

In this chapter, indexes of the Intra-Americas or Caribbean Low-Level Jet (IALLJ or CLLJ, respectively), Niño 3, Tropical North Atlantic (NATL), Atlantic Multidecadal Oscillation (AMO), and Outgoing Long Wave Radiation (OLR) are quantified for the period 1950–2007, to study their relationship with tropical cyclone (TC) frequency for summer–autumn of the Northern Hemisphere. A remarkable inverse relationship is found between both, the strength of the wind speed at 925 hPa and the vertical wind shear at low levels, and the monthly relative frequency of TCs for two selected areas in the Caribbean. The July peak in wind speed and low-level vertical wind shear are associated with a minimum in the monthly relative frequency of TCs. On the contrary, a decrease in the wind speed and vertical shears are associated with a maximum value of the relative frequency of TCs. Stronger (weaker) than normal IALLJ summer winds (July–August) during warm (cold) ENSO events imply a stronger (weaker) than normal vertical wind shear at low-levels in the Caribbean. This condition may inhibit (allow) deep convection, disfavoring (favoring) TC development during these months. Correlation values of the monthly mean CLLJ core winds and the monthly normalized values of NATL – Niño 3 index for 1950–2007 showed statistical significance greater than 99% during July–August. During El Niño years, low-level wind increases at the jet core strengthening the low level convergence near Central America at the jet exit and the low-level divergence in the central Caribbean at the jet entrance. The descending motion associated with the latter acts as an inhibiting factor for convection and TC development. TC activity in the Caribbean is not only sensitive to ENSO influences, but to the strength of the CLLJ vertical wind shear, to barotropic energy conversions induced by the lateral wind shear, to the intensity of the regional scale descending motion associated with the jet entrance, and to the SST cooling generated by the CLLJ at the sea surface. Climatology of a group of General Circulation Models used in the 2007 report of the IPCC were tested to study their ability to capture the low-level wind annual cycle over the Caribbean and the known CLLJ structure. Some models do not capture basic characteristics of the jet. A discussion of cyclone potential over the Caribbean, based on the relationships developed using the models climatology, is presented for the period 2010–2050. As a study case, the findings were contrasted with the observed 2008 climate over the IAS region. Rainy season for 2008 in Central America evolved in a way consistent with the presence of La Niña event and the meridional migration of the ITCZ. Wind anomalies associated with the IALLJ were larger (smaller) than normal during February (July) 2008, in agreement with earlier findings in regards to the relationship of the IALLJ and ENSO phases. The year of 2008 was very active for tropical storm formation in the Caribbean basin (10–22. 5∘N, 60–82. 5∘W). From 16 named storms observed in the Atlantic, 10 entered the Caribbean basin. Eight (five) Atlantic cyclones were hurricanes (strong hurricanes) and from the five hurricanes crossing the Caribbean basin, four were strong. Universidad de Costa Rica/[805-A7-002]/UCR/Costa Rica Universidad de Costa Rica/[805-A7-755]/UCR/Costa Rica Universidad de Costa Rica/[805-A8-401]/UCR/Costa Rica Universidad de Costa Rica/[805-A8-606]/UCR/Costa Rica Universidad de Costa Rica/[805-A9-532]/UCR/Costa Rica Universidad de Costa Rica/[808-A9-070]/UCR/Costa Rica Universidad de Costa Rica/[808-A9-180]/UCR/Costa Rica UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigaciones Geofísicas (CIGEFI) UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Ciencias del Mar y Limnología (CIMAR)

A relevant climate feature of the Intra-Americas Sea (IAS) is the low-level jet (IALLJ) dominating the IAS circulation, both in summer and winter; and yet it is practically unknown with regard to its nature, structure, interactions with mid-latitude and tropical phenomena, and its role in regional weather and climate. This paper updates IALLJ current knowledge and its contribution to IAS circulation-precipitation patterns and presents recent findings about the IALLJ based on first in situ observations during Phase 3 of the Experimento Climático en las Albercas de Agua Cálida (ECAC), an international field campaign to study IALLJ dynamics during July 2001. Nonhydrostatic fifth-generation Pennsylvania State University National Center for Atmospheric Research Mesoscale Model (MM5) simulations were compared with observations and reanalysis. Large-scale circulation patterns of the IALLJ northern hemisphere summer and winter components suggest that trades, and so the IALLJ, are responding to land-ocean thermal contrasts during the summer season of each continent. The IALLJ is a natural component of the American monsoons as a result of the continent's approximate north-south land distribution. During warm (cold) El Niño-Southern Oscillation phases, winds associated with the IALLJ core (IALLJC) are stronger (weaker) than normal, so precipitation anomalies are positive (negative) in the western Caribbean near Central America and negative (positive) in the central IAS. During the ECAC Phase 3, strong surface winds associated with the IALLJ induced upwelling, cooling down the sea surface temperature by 1-2 degrees C. The atmospheric mixed layer height reached 1 km near the surface wind maximum below the IALLJC. Observations indicate that primary water vapor advection takes place in a shallow layer between the IALLJC and the ocean surface. Latent heat flux peaked below the IALLJC. Neither the reanalysis nor MM5 captured the observed thermodynamic and kinematic IALLJ structure. So far, IALLJ knowledge is based on either dynamically initialized data or simulations of global (regional) models, which implies that a more systematic and scientific approach is needed to improve it. The Intra-Americas Study of Climate Processes is a great regional opportunity to address trough field work, modeling, and process studies, many of the IALLJ unknown features.

A relevant climate feature of the Intra‐Americas Sea (IAS) is the low‐level jet (IALLJ) dominating the IAS circulation, both in summer and winter; and yet it is practically unknown with regard to its nature, structure, interactions with mid‐latitude and tropical phenomena, and its role in regional weather and climate. This paper updates IALLJ current knowledge and its contribution to IAS circulation–precipitation patterns and presents recent findings about the IALLJ based on first in situ observations during Phase 3 of the Experimento Climático en las Albercas de Agua Cálida (ECAC), an international field campaign to study IALLJ dynamics during July 2001. Nonhydrostatic fifth‐generation Pennsylvania State University National Center for Atmospheric Research Mesoscale Model (MM5) simulations were compared with observations and reanalysis. Large‐scale circulation patterns of the IALLJ northern hemisphere summer and winter components suggest that trades, and so the IALLJ, are responding to land–ocean thermal contrasts during the summer season of each continent. The IALLJ is a natural component of the American monsoons as a result of the continent's approximate north–south land distribution. During warm (cold) El Niño–Southern Oscillation phases, winds associated with the IALLJ core (IALLJC) are stronger (weaker) than normal, so precipitation anomalies are positive (negative) in the western Caribbean near Central America and negative (positive) in the central IAS. During the ECAC Phase 3, strong surface winds associated with the IALLJ induced upwelling, cooling down the sea surface temperature by 1–2 °C. The atmospheric mixed layer height reached 1 km near the surface wind maximum below the IALLJC. Observations indicate that primary water vapor advection takes place in a shallow layer between the IALLJC and the ocean surface. Latent heat flux peaked below the IALLJC. Neither the reanalysis nor MM5 captured the observed thermodynamic and kinematic IALLJ structure. So far, IALLJ knowledge is based on either dynamically initialized data or simulations of global (regional) models, which implies that a more systematic and scientific approach is needed to improve it. The Intra‐Americas Study of Climate Processes is a great regional opportunity to address trough field work, modeling, and process studies, many of the IALLJ unknown features. Universidad de Costa Rica/[805-98-506]/UCR/Costa Rica Universidad de Costa Rica/[805-A7-002]/UCR/Costa Rica Universidad de Costa Rica/[805-A7-755]/UCR/Costa Rica UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigaciones Geofísicas (CIGEFI)

The ability of two general circulation models (ECHAM4.5 and CCM3.6) to simulate key climate features of Central America is determined by the evaluation of both precipitation and low-level wind fields for the period 1990-1999. According to the evaluation, ECHAM4.5 exhibits a more realistic representation of the regional climate. Therefore, its output is used in order to provide the initial and boundary conditions necessary to perform a dynamical downscaling using the regional model MM5v3. Mediante la evaluación del campo vectorial de viento en bajo nivel y de precipitación derivados de dos modelos de circulación general (ECHAM4.5 y CCM3.6), para el período 1990-1999, se determinó la habilidad de dichos modelos para simular aspectos dinámicos y termodinámicos asociados al clima centroamericano y su variabilidad climática. Para ello, primeramente se analizan las características de la atmósfera consideradas como fundamentales contribuyentes del régimen climático regional. De acuerdo con los resultados de esta evaluación, el ECHAM4.5 exhibe una representación más realista de varios aspectos del ciclo anual y estacional de la atmósfera tropical de interés, por lo que la información de gran escala (≈ 5 × 103 km) de este modelo se utiliza en la parte II de este trabajo para proveer las condiciones iniciales y de contorno como funciones de espacio y tiempo necesarias para efectuar un proceso de reducción de escala dinámica de hasta 30 km de resolución espacial con el modelo regional MM5v3.

Con el fin de determinar el efecto del calcio y diferentes láminas de riego en plantas de repollo (Brassica oleracea), se sometieron 80 plantas a un diseño completamente al azar, factorial de 3x3, donde el primer factor correspondió a tres niveles de calcio (80, 120 y 160kg.ha-1 de Ca) y el segundo a láminas de riego determinadas por coeficientes (0,8; 1 y 1,2 de la evaporación medida en un evaporímetro construido), más un testigo con una lámina de uno y sin aplicación de calcio, para un total de diez tratamientos. El experimento tuvo una duración de 130 días en invernadero y diez días en laboratorio, para evaluar el comportamiento en poscosecha. Los tratamientos indujeron diferencias significativas para la altura, el área foliar, el peso fresco de hojas, tallo y cabeza, el peso seco de raíz y cabeza, el pH y la pérdida de peso fresco y, altamente significativas para los sólidos solubles totales y el análisis económico. Con la aplicación de la lámina de 0,8 y 160kg.ha-1 de Ca, se obtuvo mayor peso fresco de cabeza y mayor cantidad de fitomasa fresca por cada peso invertido (33,76g.$), por tanto, éste tratamiento es recomendable para ser implementado por los productores de repollo. El suministro de lámina de 1 y 160kg.ha-1 de Ca permitió conservar el repollo en mejores condiciones durante la poscosecha. With the purpose of determining the effect of calcium and different water tables in cabbage (Brassica oleracea) 80 plants were put under a completely randomized design, factorial of 3x3, where the first factor corresponded to three calcium levels (80, 120 and 160kg·ha -1) and the second one to three water tables, determined by using three evaporation coefficients (0.8; 1 and 1.2 of evaporation, measured with an evaporimeter) and a treatment with a water table of 1, without calcium application, for a total of ten treatments. The research was carried out during 130 days in a greenhouse and during ten days under laboratory conditions, to evaluate the post-harvest behavior. The treatments induced significant differences for height, leaf area, fresh weight of leaves, stem and head, dry weight of roots and head, pH and loss of fresh weight; and highly significant differences in total soluble solids and within the economic analysis. With the application of a water table of 0.8 and 160kg·ha-1 of Ca the greatest fresh weight of heads was obtained and a higher fresh phytomass for each inverted peso (33.76g·$). Therefore, this treatment is recommended to be implemented by cabagge producers. The water table of 1 and 160kg·ha-1 of Ca, allowed conserving cabbage in better conditions during post-harvest. Incluye referencias bibliográficas

Este trabajo trata sobre la investigación realizada por el Ing. Luis Matamoros Sandoval, quien en 1902 publicó en Costa Rica sus investigaciones en Sismología en un artículo denominado "El interior de la corteza terrestre: una nueva teoría sobre el origen de los temblores". En su trabajo, Matamoros sigue la corriente de pensamiento aristotélica y la mezcla con las hipótesis del fraile español Benito Feijoo, quien propone la electricidad como la causante física de intensos terremotos con una gran área de percepción. Matamoros justifica sus resultados con matemática combinada con principios fundamentales de la física, los cuales explica en parte con cierto grado de dificultad, pues utiliza criterios y conceptos que no estaban soportados por el conocimiento de la física tradicional. Pese a los errores conceptuales, el trabajo es valioso por ser el primer intento científico local formal por explicar el origen de los temblores, proceso que aún en los grandes centros científicos de la época era fuente de continua especulación.

The increase in marine, land surface, atmospheric and satellite data during recent decades has led to an improved understanding of the air–sea interaction processes in the eastern tropical Pacific. This is also thanks to extensive diagnoses from conceptual and coupled ocean–atmosphere numerical models. In this paper, mean fields of atmospheric variables, such as incoming solar radiation, sea level pressure, winds, wind stress curl, precipitation, evaporation, and surface energy fluxes, are derived from global atmospheric data sets in order to examine the dominant features of the low level atmospheric circulations of the region. The seasonal march of the atmospheric circulations is presented to depict the role of radiative forcing on atmospheric perturbations, especially those dominating the atmosphere at low levels. In the tropics, the trade winds constitute an important north–south energy and moisture exchange mechanism (as part of the low level branch of the Hadley circulation), that determines to a large extent the precipitation distribution in the region, i.e., that associated with the Inter-Tropical Convergence Zone (ITCZ). Monsoonal circulations also play an important role in determining the warm season precipitation distribution over the eastern tropical Pacific through a large variety of air–sea–land interaction mechanisms. Westward traveling waves, tropical cyclones, low latitude cold air intrusions, and other synoptic and mesoscale perturbations associated with the ITCZ are also important elements that modulate the annual rainfall cycle. The low-level jets of the Gulf of California, the Intra-Americas Sea (Gulf of Mexico and Caribbean Sea) and Chocó, Colombia are prominent features of the eastern tropical Pacific low-level circulations related to sub-regional and regional scale precipitation patterns. Observations show that the Intra-Americas Low-Level Jet intensity varies with El Niño/Southern Oscillation (ENSO) phases, however its origin and role in the westward propagation and development of disturbances that may hit the eastern tropical Pacific, such as easterly waves and tropical cyclones, are still unclear. Changes in the intensity of the trade winds in the Caribbean Sea and the Gulf of Mexico (associated with eastern tropical Pacific wind jets) exert an important control on precipitation by means of wind–topography interactions. Gaps in the mountains of southern Mexico and Central America allow strong wind jets to pass over the continent imprinting a unique signal in sea surface temperatures and ocean dynamics of the eastern tropical Pacific. The warm pools of the Americas constitute an important source of moisture for the North American Monsoon System. The northeastern tropical Pacific is a region of intense cyclogenetic activity, just west of the coast of Mesoamerica. Over the oceanic regions, large-scale properties of key variables such as precipitation, moisture, surface energy fluxes and wind stress curl are still uncertain, which inhibits a more comprehensive view of the region and stresses the importance of regional field experiments. Progress has been substantial in the understanding of the ocean and atmospheric dynamics of the eastern tropical Pacific, however, recent observational evidence such as that of a shallow meridional circulation cell in that region, in contrast to the classic concept of the Hadley-type deep meridional circulation, suggests that more in situ observations to validate theories are still necessary. Universidad de Costa Rica/[805-94-204]/UCR/Costa Rica Universidad de Costa Rica/[805-98-506]/UCR/Costa Rica Universidad de Costa Rica/[112-99-305]/UCR/Costa Rica UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigaciones Geofísicas (CIGEFI)

This work examines some of the effects of climate and climate variability in the Arenal River basin of Costa Rica, the site of the largest hydropower complex in the country. The Arenal system, which drains part of the north-central portion of Costa Rica covers a total area of approximately 493 km2 ; it is mainly managed for electric power generation and produces nearly a quarter of the total annual electricity in Costa Rica. Monthly, pentad (5-day means), and daily precipitation data are used to study signals associated with climate and shorter-term atmospheric disruptions in the basin. Although the study area is relatively small, strong spatial and temporal contrasts of precipitation patterns are found. A clear distinction in the seasonal distribution of precipitation is observed over short distances (~30–40 km), between the northwestern (NW) low lands of the basin compared to the southeastern (SE) sector. The former region exhibits a bimodal precipitation distribution, with maxima in June and September–October, and relative minima in July and December–April. The July minimum suggests a weak mid-summer drought or “veranillo” signal. The latter region has practically no dry season with the highest precipitation values occurring during the second part of the calendar year. As determined by principal component analysis of anomalies of monthly precipitation data, the main disruption of the normal pattern of precipitation appears to be related to the ENSO signal in the NW region, whereas the SE sector shows a positive correlation with Caribbean low-level wind changes. Some of the latter changes are associated with warm or cold ENSO episodes that seem to modulate wind intensities of the low-level jet over the Caribbean. Precipitation effects in the basin for selected extreme cases, such as that of hurricane Mitch, and other so-called “temporales” are also analyzed. The importance of these systems as fundamental components of the basin’s hydrological cycle is well established. ENSO related variability of the regional summer circulation (such as that of the low-level jet in the western Caribbean), and the appearance of cases of extreme strong trade winds during the winter circulation are also important forcing mechanisms for precipitation variability in the basin. In these cases, the interaction between the basin complex topography, and changes in the flow pattern and intensity seem to be of fundamental importance for precipitation variance. Some socioeconomic impacts of precipitation variability, as well as a discussion about the potential use of climate variability information for water management in the basin are presented Universidad de Costa Rica/[805-94-204]/UCR/Costa Rica Universidad de Costa Rica/[805-98-506]/UCR/Costa Rica Universidad de Costa Rica/[112-99-305]/UCR/Costa Rica UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigaciones Geofísicas (CIGEFI) UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Física