The collection of articles in this volume reviewing eastern tropical Pacific oceanography is brie... more 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.
For the first time in serveral years, the El Nino-Southern Oscillation did not dominate regional ... more For the first time in serveral years, the El Nino-Southern Oscillation did not dominate regional climate conditions around the globe. A weak La Ni a dissipated to ENSOneutral conditions by spring, and while El Nino appeared to be emerging during summer, this phase never fully developed as sea surface temperatures in the eastern conditions. Nevertheless, other large-scale climate patterns and extreme weather events impacted various regions during the year. A negative phase of the Arctic Oscillation from mid-January to early February contributed to frigid conditions in parts of northern Africa, eastern Europe, and western Asia. A lack of rain during the 2012 wet season led to the worst drought in at least the past three decades for northeastern Brazil. Central North America also experienced one of its most severe droughts on record. The Caribbean observed a very wet dry season and it was the Sahel's wettest rainy season in 50 years. Overall, the 2012 average temperature across glo...
Recibido em: 2 de Mayo de 2019 -Aceptado em: 16 de Septiembre de 2019 Otto (2016) es el primer hu... more Recibido em: 2 de Mayo de 2019 -Aceptado em: 16 de Septiembre de 2019 Otto (2016) es el primer huracán en la historia documentada de ciclones tropicales de haber alcanzado directamente Costa Rica. Este trabajo analiza las descargas eléctricas (DE) de Otto en noviembre 2016 en su paso desde el Caribe hasta el Pacífico, usando datos de la World Wide Lightning Location Network; lo cual constituye una investigación pionera en esta región de Centroamérica. Las DE asociadas a Otto capturan muy bien las fases de intensificación y degradación de este huracán, que como variable podría ser parametrizada en los modelos numéricos para mejorar el entendimiento y evolución de estos sistemas. Otto presentó tres picos máximos de descargas; uno en categoría 1 en la escala Saffir-Simpson, otro en categoría 2 y el último en la categoría 3 (OH3), poco antes de su entrada a tierra entre Costa Rica y Nicaragua. La región de mayor cantidad de DE se desplazó del centro hacia las zonas más externas del huracán conforme éste se intensificó. En el caso de OH3, el máximo de DE se ubicó en las bandas externas de Otto (250-300 km). Durante su evolución, las de máximas DE observadas estaban relacionadas con temperaturas del tope de las nubes menores a los -70 °C.
In mid-2018, a group of researchers from the Geophysical Research Center and the School of Physic... more In mid-2018, a group of researchers from the Geophysical Research Center and the School of Physics of the University of Costa Rica started a project to share knowledge about weather and climate sciences with the cabécar community of Pú Ksogë (9,591 ° N, 82.978 ° W, 114.4 masl), Talamanca, Limón, Costa Rica. The initiative was supported by leaders and educational authorities of that indigenous community at the end of that year. With local labor input and the respective authorization, an automatic meteorological station (Siwá Etka) was installed and left in operation on the grounds of the community school at the beginning of 2019. Details of this project and the first atmospheric data observed in the history of that community are described in this paper. The lack of adequate community control and the lack of interest of the school authorities in the care of the instruments caused problems that did not allow the project to continue, and the station had to be uninstalled in October 2019. The experience had positive phases, but other aspects such as cell phone and internet connectivity, sometimes of very low quality or non-existent at all, also influenced the decision to discontinue the initiative. Contacts made with an association for local development in the region could be an alternative to give continuity to the project.
[Mangrove characterization of Central America with remote sensors]
Revista de biología tropical, 2001
Satellite images were used to study the mangrove distribution patterns in two different climatic ... more Satellite images were used to study the mangrove distribution patterns in two different climatic regions of Central America: Gulf of Fonseca in Honduras-El Salvador and Sierpe-Térraba in Costa Rica. The Gulf of Fonseca has higher temperature and solar radiation, and lower precipitation, which can explain the higher structural development and species mixing of the Sierpe-Térraba mangrove. In the latter the transition between species or between heights in the same species is clear. The automatic classification made by the Geographic Information System (IDRISI) fits well the field mangrove distribution, but it was necessary to regroup some subdivisions that represent the same land use as identified by transects and an aerial video. Mixed species and clouds produced less satisfactory results in Sierpe-Térraba indicating a need for better satellite image resolution.
This work explores statistical connections between the displacements and strength of the Intertro... more This work explores statistical connections between the displacements and strength of the Intertropical Convergence Zone (ITCZ) and the Caribbean Low Level Jet (CLLJ). Indicators of the position and of the strength of the ITCZ include the latitude (LATC) and longitude (LONC) of the center of mass of precipitation and the domain precipitation (Pdomain) in a region bounded by coordinates-10 and 25 degrees latitude and-100 and-55 degrees longitude, respectively. Preliminary analyses show that there is a strong correlation (0.82) between summer (JJA) LATC and JJA CLLJ index, and this correlation is lower in other seasons (0.63 for Autumn, 0.20 for Winter and 0.49 for Spring). These correlations were verified in the zonal wind composites at 925 hPa for the 5 lowest and 5 highest years of LATC. LONC does not seem to have the same strong relationship with the CLLJ. At daily level, composites show precipitation in the Central America region is influenced by Pdomain, LATC, CLLJ index, and to a less extent to LONC. Composites of Sea Surface Temperature for the 5 years of highest and lowest LATC show some relationship with ENSO, although there is a disproportionate influence of the 1997-98 El Niño that may be affecting the results. There is however a consistent feature: during years of high LATC, there are warm anomalies in the tropical Atlantic off the coast of Venezuela, that are not present during years of low LATC.
A climatology of moisture sources linked with Central American precipitation was computed based u... more 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 Caribbean 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.
Precursors of quasi-decadal dry-spells in the Central America Dry Corridor
Climate Dynamics, Jan 30, 2019
Although the hydric stress in Central America is generally low, there is a region relatively drie... more Although the hydric stress in Central America is generally low, there is a region relatively drier and prone to drought known as the Central America Dry Corridor (CADC). The area of interest is located mainly in the Pacific slope of Central America, from Chiapas in southern Mexico, to the Nicoya Peninsula in the Costa Rican North Pacific. Most of the region has experienced significant warming trends (1970–1999). On the contrary precipitation and the Palmer Drought Severity Index (PDSI) have mainly displayed non-significant trends. Analysis using the Standardized Precipitation Index and PDSI in the CADC, suggests a significant periodicity of severe and sustained droughts of around 10 years. The drought response has been associated with tropical heating that drives an atmospheric response through strengthening of the Hadley cell, which in turn produces higher pressure in the subtropical highs, and intensification of the trade winds (indexed by the Caribbean Low Level Jet). It is important to determine the commonness of severe and sustained droughts in the CADC to improve water resources planning, as this is a region that depends on subsistence agriculture and presents high social and economic vulnerabilities.
Annals of the New York Academy of Sciences, Dec 1, 2008
A relevant climate feature of the Intra-Americas Sea (IAS) is the low-level jet (IALLJ) dominatin... more 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 landocean 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.
Hydroclimatological Processes in the Central American Dry Corridor
2015 AGU Fall Meeting, Dec 17, 2015
Atmospheric circulation types controlling rainfall in the Central American Isthmus
International Journal of Climatology
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 six 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 analysed from a set of 174 automatic stations from all coun...
We explored the relationship between the precipitation anomalies during May to June as the first ... more We explored the relationship between the precipitation anomalies during May to June as the first peak of the rainy season in the Pacific slope of Central America, and sea surface temperature (SST) fluctuations in the surrounding oceans, using canonical correlation analysis (CCA). With this approach, we studied variations in total precipitation, frequency of rainy days and the monthly occurrence of days with rainfall above (below) the 80th (20th) percentile, due to changes in the nearby SST. Composites of the sea-level pressure (SLP), geopotential heights (200 hPa), relative humidity (700 hPa), horizontal moisture flux and wind at 850 hPa were estimated to provide a dynamical analysis. The composites are calculated using the information obtained with CCA. In addition, we used a general circulation model forced with fixed SST to explore the sensitivity of the model to the SST patterns found using CCA. The results show that the SST over the tropical North Atlantic controls the precipitation fluctuations at interannual scales, due to its connection with the tropical upper tropospheric trough. Warmer (colder) temperatures result in SLP below normal in the Caribbean region, associated with an increase in the heights at 200 hPa. This vertical configuration reduces the wind shear between 850 and 200 hPa and increases the input of humidity to mid-levels, creating favourable conditions for deep convection, and favouring the generation of tropical cyclone activity. In the Pacific, a positive anomalous low-level moisture flux is observed from the ocean to the continental parts of the region and may enhance the formation of mesoscale systems. The classic prediction schemes show a lead time of 1 or 2 months; this is an advantage for climate services operative work. The atmospheric model outcomes replicate the main results found in the composite analysis, reflecting its potential use for model output statistics predictive schemes. KEY WORDS seasonal climate prediction; Central America; tropical North Atlantic; sea surface temperature; canonical correlation analysis; heavy rainfall events
Diurnal cycle on the Caribbean slope of Costa Rica: An observational study
On the Interannual Variablity of the Tropical Tropopause Layer Over Central America
We investigate year-to-year differences in the vertical structure and variability of the Tropical... more We investigate year-to-year differences in the vertical structure and variability of the Tropical Tropopause Layer (TTL) over Central America using data from the four Ticosonde balloon-sounding campaigns in Costa Rica (10°N, 84°W) since 2004. In each of the campaigns the temperature and wind profiles reveal a rich mix of laminations in the lower stratosphere. Water vapor and ozone profiles from
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Papers by Jorge A Amador