Repositorio de publicaciones: Centro de Investigaciones Geofísicas
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Detection of the forest fires of April 1997 in Guanacaste, Costa Rica, using GOES-8 images
(International Journal of Remote Sensing, 1999) Alfaro, R; Fernández, W; Connell, B
A satellite sensor product that combines the GOES-8 radiometer images 3.9 mu m and 10.7 mu m wavelengths was used to detect grassland and forest fires which occurred in Guanacaste, Costa Rica, in April 1997. This product is shown to be useful in the detection of forest fires in Central America. This will help to identify the areas that are burned yearly and diminish the serious consequences these fires cause to the environment and aviation.
Numerical simulations of mountain wave generation past and isaolated obstacle
(Tópicos Meteorológicos y Oceanográficos, 1999) Gutiérrez, J
Numerical experiments concerning high Froude number flow without background rotation past an isolated threedimensional obstacle are performed and comparisons with the results obtained and R. Smith´s linear theory are made. Linear and non-linear effects are investigated.
Imágenes satelitales en la predicción de eventos esporádicos de escala sinóptica: Antecedentes del huracán César como un evento sinóptico.
(Tópicos Meteorológicos y Oceanográficos, 1999) Banichevich, A; Castro, V
It is shown the kind of information that meteorological satellite images con give, particulary for the case of geostationary satllite GOES – 8for the event of hurricane Cesar.
Some possible plasma effects associated with atmospheric electric discharges
(Revista Geofísica, 1999) Bonatti, J; Fernández, W
An analysis of possible emissions of molecular radiation caused by a very high electric field related to a thunderstorm is made. The possible occurrence of a water maser effect is studied. The main objective is to determine the spectral range for observational purposes, since there is a lack of experimental data for the phenomenon under study.
The Mid-Summer Drought over México and Central America
(Journal of Climate, 1999) Magaña, V; Amador, J; Medina, S
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 coast of Central America.
Changes in the divergent (convergent) low-level winds over the “warm pool” off the west coast of southern Mexico and Central America determine the evolution of the MSD. Maximum deep convective activity over the northern equatorial eastern Pacific, during the onset of the summer rainy season, is reached when sea surface temperatures exceed 29°C (around May). After this, the SSTs over the eastern Pacific warm pool decrease around 1°C due to diminished downwelling solar radiation and stronger easterly winds (during July and August). Such SST changes near 28°C result in an substantial decrease in deep convective activity, associated with the nonlinear interaction between SST and deep tropical convection. Decreased deep tropical convection allows increased downwelling solar radiation and a slight increase in SSTs, which reach a second maximum (∼28.5°C) by the end of August and early September. This increase in SST results once again in stronger low-level convergence, enhanced deep convection, and, consequently, in a second maximum in precipitation.
The MSD signal can also be detected in other variables such as minimum and maximum surface temperature and even in tropical cyclone activity over the eastern Pacific.