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- Author or Editor: Oswaldo Garcia x
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Abstract
Rainfall estimates obtained for the GATE experiment by two satellite rainfall estimation techniques are compared for different time and space scales. The Kilonsky-Ramage technique uses polar-orbiting satellites for 1° resolution rainfall estimates over the tropics. The Griffith-Woodley technique uses geostationary satellite data to generate much higher resolution estimates. There is good correspondence between the A scale isohyetal patterns and rainfall volumes estimated by both techniques for periods ranging from 1 to 80 days. Largest discrepancies appear over Africa and nearby ocean areas, where the Griffith-Woodley estimates are higher. Correlation coefficients between the two estimates are higher when only oceanic points are compared, ranging up to 0.92 for the entire GATE period. When continental areas of the A scale are included, correlation coefficients are lower, reaching 0.66 for phase 2. The large discrepancies over Africa and nearby ocean areas are seen to be associated with a nocturnal peak of rainfall which is not detected by the daytime passes of the polar orbiting satellite used in the Kilonsky-Ramage calculations.
Comparison of results of both techniques with shipboard radar ground-truth over the GATE B scale show that both techniques produce comparable rainfall volume estimates at this scale, generally within 15% of the radar estimates. Overall, results indicate that the Kilonsky-Ramage technique can produce low cost and fairly reliable estimates of rainfall over the tropical oceans.
Abstract
Rainfall estimates obtained for the GATE experiment by two satellite rainfall estimation techniques are compared for different time and space scales. The Kilonsky-Ramage technique uses polar-orbiting satellites for 1° resolution rainfall estimates over the tropics. The Griffith-Woodley technique uses geostationary satellite data to generate much higher resolution estimates. There is good correspondence between the A scale isohyetal patterns and rainfall volumes estimated by both techniques for periods ranging from 1 to 80 days. Largest discrepancies appear over Africa and nearby ocean areas, where the Griffith-Woodley estimates are higher. Correlation coefficients between the two estimates are higher when only oceanic points are compared, ranging up to 0.92 for the entire GATE period. When continental areas of the A scale are included, correlation coefficients are lower, reaching 0.66 for phase 2. The large discrepancies over Africa and nearby ocean areas are seen to be associated with a nocturnal peak of rainfall which is not detected by the daytime passes of the polar orbiting satellite used in the Kilonsky-Ramage calculations.
Comparison of results of both techniques with shipboard radar ground-truth over the GATE B scale show that both techniques produce comparable rainfall volume estimates at this scale, generally within 15% of the radar estimates. Overall, results indicate that the Kilonsky-Ramage technique can produce low cost and fairly reliable estimates of rainfall over the tropical oceans.
Abstract
Tle highly reflective cloud (HRC) dataset is a daily index of organized deep convection, at one degree resolution, from 17 years of polar-orbiting, satellite imagery. These data are used to analyze and discuss the climatological geographical distribution of deep convection observed over the Asian summer monsoon season and its component months (June, July, August and September). Intraseasonal variations of convection for selected regions am examined using normalized pentad time series of regional median HRC values. We also compare HRC data over two regions (western coastal India and western coastal Burma/Thailand) with the results from a two-dimensional numerical model, consisting of a simple differentially heated land-ocean system which predicts that a preponderance of deep convection occurs over the coastal zone. The Buma/Thailand regional comparison supports the model result. Comparison of the model with the western coastal India region is less conclusive, which may be due to the limitations of the model.
We conclude that monsoon deep convection, and its attendant sources of latent heat momentum, and mass sources important to large-scale monsoon dynamics is localized and persistent from year to year. If, as hypothesized by others, tropical cumulonimbus activity is important to stratospheric-tropospheric exchange, this study shows the preferred areas of such exchange during the monsoon. The locations of areas with large HRC amounts are consistent with upstream lifting of low-level, conditionally unstable air by low, coastal mountains. Intraseasonal variability follows variations in sea surface temperature and low-level flow. Upper-level dynamics are also recognized as an important contribution.
Abstract
Tle highly reflective cloud (HRC) dataset is a daily index of organized deep convection, at one degree resolution, from 17 years of polar-orbiting, satellite imagery. These data are used to analyze and discuss the climatological geographical distribution of deep convection observed over the Asian summer monsoon season and its component months (June, July, August and September). Intraseasonal variations of convection for selected regions am examined using normalized pentad time series of regional median HRC values. We also compare HRC data over two regions (western coastal India and western coastal Burma/Thailand) with the results from a two-dimensional numerical model, consisting of a simple differentially heated land-ocean system which predicts that a preponderance of deep convection occurs over the coastal zone. The Buma/Thailand regional comparison supports the model result. Comparison of the model with the western coastal India region is less conclusive, which may be due to the limitations of the model.
We conclude that monsoon deep convection, and its attendant sources of latent heat momentum, and mass sources important to large-scale monsoon dynamics is localized and persistent from year to year. If, as hypothesized by others, tropical cumulonimbus activity is important to stratospheric-tropospheric exchange, this study shows the preferred areas of such exchange during the monsoon. The locations of areas with large HRC amounts are consistent with upstream lifting of low-level, conditionally unstable air by low, coastal mountains. Intraseasonal variability follows variations in sea surface temperature and low-level flow. Upper-level dynamics are also recognized as an important contribution.
Abstract
The winter season rainfall data for the Dominican Republic for the years 1960–67 are examined in detail. Frontal zones dissipating over the area are found to he the primary rain-producing mechanism during the winter months. A relatively small number of fronts produce a large share of the total rainfall. Rainfall producing fronts are most pronounced in November and least evident in February.
Mountains are seen to play a crucial role in the intensity and distribution of precipitation throughout the country. The interactive effects of synoptic-scale frontal zones with the local terrain seem to account for the large peak of precipitation observed along the north coast of the country during November.
Synoptic-scale conditions that seem to favor enhanced frontal precipitation include the establishment of strong ridging north of the Greater Antilles, with a corresponding strengthening of the trades over the area. Upper level westerlies in the vicinity of the Greater Antilles also tend to become more pronounced during heavy rain occurrences.
The use of a nonlinear diagnostic balance model in a detailed case study suggests that synoptic-scale warm advection and diabatic heating (primarily latent) are the dominant forcing functions producing ascent in the Dominican Republic region. Terrain influence is a very important modifying factor.
Abstract
The winter season rainfall data for the Dominican Republic for the years 1960–67 are examined in detail. Frontal zones dissipating over the area are found to he the primary rain-producing mechanism during the winter months. A relatively small number of fronts produce a large share of the total rainfall. Rainfall producing fronts are most pronounced in November and least evident in February.
Mountains are seen to play a crucial role in the intensity and distribution of precipitation throughout the country. The interactive effects of synoptic-scale frontal zones with the local terrain seem to account for the large peak of precipitation observed along the north coast of the country during November.
Synoptic-scale conditions that seem to favor enhanced frontal precipitation include the establishment of strong ridging north of the Greater Antilles, with a corresponding strengthening of the trades over the area. Upper level westerlies in the vicinity of the Greater Antilles also tend to become more pronounced during heavy rain occurrences.
The use of a nonlinear diagnostic balance model in a detailed case study suggests that synoptic-scale warm advection and diabatic heating (primarily latent) are the dominant forcing functions producing ascent in the Dominican Republic region. Terrain influence is a very important modifying factor.
Abstract
In May 2014 a team of atmospheric and geodetic scientists from UNAVCO and the University Corporation for Atmospheric Research (UCAR) sent and helped set up a global positioning system (GPS) receiver to measure atmospheric water vapor at the Grupo de Óptica Atmosférica de Camagüey (GOAC) at the Camagüey Meteorological Center in Camagüey, Cuba. The GPS receiver immediately began to produce observations of precipitable water, which are being shared with the international meteorological community. Obtaining permission from both sides to send a highly sensitive instrument from the United States to Cuba was not easy. This paper describes the series of events that led to this achievement, beginning with a North Atlantic Treaty Organization (NATO) workshop in Rome, Italy, in 1994 in which Alan Robock met a young Cuban scientist named Juan Carlos Antuña and accepted him as a graduate student at the University of Maryland, College Park. The GPS meteorology connection began with a March 2007 visit of a delegation from the United States headed by then American Meteorological Society (AMS) President Richard Anthes to Havana, Cuba, at the invitation of the Cuban Meteorological Society president, Andrés Planas. These two threads led to this remarkable cooperation between Cuban and U.S. scientists. Several visits to Cuba beginning in 2010 by Robock, who met former President of Cuba Fidel Castro and the science advisor to the president of Cuba, played a significant role.
This is another instance (the visit of the AMS delegation to China in 1974 was a prime example) of how communication and visits between meteorologists in countries that are at odds on many other issues can lead to lasting collaborations that benefit both countries as well as the international community.
Abstract
In May 2014 a team of atmospheric and geodetic scientists from UNAVCO and the University Corporation for Atmospheric Research (UCAR) sent and helped set up a global positioning system (GPS) receiver to measure atmospheric water vapor at the Grupo de Óptica Atmosférica de Camagüey (GOAC) at the Camagüey Meteorological Center in Camagüey, Cuba. The GPS receiver immediately began to produce observations of precipitable water, which are being shared with the international meteorological community. Obtaining permission from both sides to send a highly sensitive instrument from the United States to Cuba was not easy. This paper describes the series of events that led to this achievement, beginning with a North Atlantic Treaty Organization (NATO) workshop in Rome, Italy, in 1994 in which Alan Robock met a young Cuban scientist named Juan Carlos Antuña and accepted him as a graduate student at the University of Maryland, College Park. The GPS meteorology connection began with a March 2007 visit of a delegation from the United States headed by then American Meteorological Society (AMS) President Richard Anthes to Havana, Cuba, at the invitation of the Cuban Meteorological Society president, Andrés Planas. These two threads led to this remarkable cooperation between Cuban and U.S. scientists. Several visits to Cuba beginning in 2010 by Robock, who met former President of Cuba Fidel Castro and the science advisor to the president of Cuba, played a significant role.
This is another instance (the visit of the AMS delegation to China in 1974 was a prime example) of how communication and visits between meteorologists in countries that are at odds on many other issues can lead to lasting collaborations that benefit both countries as well as the international community.
