Tropical Cyclone and Easterly Wave Relationship in Regional Precipitation over the Tropical and Subtropical North America

2021 ◽  
Author(s):  
Christian Dominguez
Keyword(s):  
North America ◽  
South America ◽  
Negative Impact ◽  
Southern Oscillation ◽  
Rainfall Variability ◽  
Seasonal Rainfall ◽  
Seasonal Precipitation ◽  
Tropical Eastern Pacific ◽  
Threshold Distance ◽  
Northern South America

<p>Tropical cyclones (TCs) and easterly waves (EWs) produce significant seasonal rainfall over the tropical and subtropical North America. When TC activity over the tropical eastern Pacific (TEP) or the Intra Americas Seas (IAS) is below-normal (above-normal), regional precipitation may be below (above-normal). However, it is not only the number of TCs what may change seasonal precipitation, but the trajectory of the systems. TCs induce intense precipitation over continental regions if they are close enough to shorelines, for instance, if the TC center is located less than 500 km-distant from the coast. However, if TCs are more remote than this threshold distance, the chances of rain over continental regions decrease, particularly in arid and semi-arid regions. In addition, a distant TC may induce subsidence or produce moisture divergence that inhibits, at least for a few days, convective activity farther away than the threshold distance.</p><p>EWs can produce up to 50% of seasonal rainfall and contribute substantially to interannual regional rainfall variability. An observational analysis shows that the El Niño Southern Oscillation (ENSO) affects EW frequency and therefore, their contribution to seasonal rainfall. In recent years, TC activity over the Main Development Region (MDR) of the tropical North Atlantic has a negative impact on regional seasonal precipitation over northern South America. High TC activity over MDR corresponds to below-normal precipitation because it reduces the EW activity reaching northern South America through the recurving of TC tracks. Recurving TC tracks redirect moisture away from the tropical belt and into the mid-latitudes. However, this relationship only holds under neutral ENSO conditions and the positive phase of the Atlantic Multidecadal Oscillation. A 10-member regional model multi-physics ensemble simulation for the period 1990–2000 was analyzed to show the relationships are robust to different representations of physical processes. This new understanding of seasonal rainfall over the tropical Americas may support improved regional seasonal and climate outlooks.</p>

scholarly journals Easterly wave contributions to seasonal rainfall over the tropical Americas in observations and a regional climate model

2019 ◽  
Vol 54 (1-2) ◽  
pp. 191-209 ◽  
Author(s):  
Christian Dominguez ◽  
James M. Done ◽  
Cindy L. Bruyère
Keyword(s):  
South America ◽  
Climate Model ◽  
Negative Impact ◽  
Southern Oscillation ◽  
Rainfall Variability ◽  
Rain Gauge ◽  
Regional Model ◽  
Seasonal Rainfall ◽  
Seasonal Precipitation ◽  
Northern South America

Abstract Easterly waves (EWs) are important moisture carriers and their variability can impact the total May–November rainfall, defined as seasonal precipitation, over the Tropical Americas. The contribution of EWs to the seasonal precipitation is explored over the tropical Americas using rain gauge stations, reanalysis data and a regional model ensemble during the 1980–2013 period. In the present study, EWs are found to produce up to 50% of seasonal rainfall mainly over the north of South America and contribute substantially to interannual regional rainfall variability. An observational analysis shows that the El Niño Southern Oscillation (ENSO) affects EW frequency and therefore, their contribution to seasonal rainfall. In recent years, tropical cyclone (TC) activity over the Main Development Region (MDR) of the tropical North Atlantic has a negative impact on regional seasonal precipitation over northern South America. High TC activity over MDR corresponds to below-normal precipitation because it reduces the EW activity reaching northern South America through the recurving of TC tracks. Recurving TC tracks redirect moisture away from the tropical belt and into the mid-latitudes. However, this relationship only holds under neutral ENSO conditions and the positive phase of the Atlantic Multidecadal Oscillation. A 10-member regional model multi-physics ensemble simulation for the period 1990–2000 was analyzed to show the relationships are robust to different representations of physical processes. This new understanding of seasonal rainfall over the tropical Americas may support improved regional seasonal and climate outlooks.

scholarly journals First record of Ramphocorixa rotundocephala Hungerford, 1927 (Hemiptera, Corixidae) for Colombia

Check List ◽  
2021 ◽  
Vol 17 (2) ◽  
pp. 503-506
Author(s):  
Mabel Giovana Pimiento-Ortega ◽  
Isabella González-Gamboa ◽  
Yimy Herrera-Martínez
Keyword(s):  
North America ◽  
South America ◽  
Procambarus Clarkii ◽  
Aquatic Insect ◽  
First Record ◽  
Adult Males ◽  
Northern South America ◽  
The Town

In the course of research conducted on Procambarus clarkii (Girard, 1852) in Colombia, Ramphocorixa rotundocephala Hungerford, 1927 was collected in Güitoque Lake, outside the town of Gachantivá, Boyacá. The species was identified from the adult males found there. This species of aquatic insect occurs mostly in Central and North America, but there are also two records from Venezuela in South America. This is the first record of this species and its genus for Colombia. This finding increases this species’ known distribution on the continent and the diversity of hemipterans in northern South America.

scholarly journals Tracking the moisture transport from the Pacific towards Central and northern South America since the late 19th century

2019 ◽  
Vol 10 (2) ◽  
pp. 319-331 ◽  
Author(s):  
David Gallego ◽  
Ricardo García-Herrera ◽  
Francisco de Paula Gómez-Delgado ◽  
Paulina Ordoñez-Perez ◽  
Pedro Ribera
Keyword(s):  
South America ◽  
20Th Century ◽  
19Th Century ◽  
Moisture Transport ◽  
Southern Oscillation ◽  
Westerly Jet ◽  
Eastern Equatorial Pacific ◽  
The Pacific ◽  
Northern South America ◽  
The Stability

Abstract. In this paper, we develop an instrumental index based on historical wind direction observations aimed to quantify the moisture transport from the tropical Pacific to Central and northern South America at a monthly scale. This transport is mainly driven by the so-called “Chocó jet”, a low-level westerly jet whose core is located at 5∘ N and 80∘ W. The Chocó jet is profoundly related to the dynamics of the Intertropical Convergence Zone in the eastern equatorial Pacific and it is responsible for up to 30 % of the total precipitation in these areas. We have been able to produce an index for this transport starting in the 19th century, adding almost a century of data to previous comparable indices. Our results indicate that the seasonal distribution of the precipitation in Central America has changed throughout the 20th century as a response to the changes in the Chocó jet, decreasing (increasing) its strength in July (September). Additionally, we have found that in general, the relationship between the Chocó jet and the El Niño–Southern Oscillation has been remarkably stable throughout the entire 20th century, a finding particularly significant because the stability of this relation is usually the basis of the hydrologic reconstructions in northern South America.

scholarly journals Tracking the Choco jet since the 19th Century by using historical wind direction measurements

2018 ◽  
Author(s):  
David Gallego ◽  
Ricardo García-Herrera ◽  
Francisco de Paula Gómez-Delgado ◽  
Paulina Ordoñez-Perez ◽  
Pedro Ribera
Keyword(s):  
South America ◽  
Central America ◽  
20Th Century ◽  
19Th Century ◽  
Wind Direction ◽  
Southern Oscillation ◽  
Westerly Jet ◽  
Eastern Equatorial Pacific ◽  
Northern South America ◽  
The 19Th Century

Abstract. In this paper, we demonstrate that the methodology recently developed to quantify the strength of monsoonal circulations by using historical wind direction observations can be applied to compute a new index for the intensity of the Choco jet. This is a low-level westerly jet observed from May to November whose core is located at 5º N and 80º W that modulates the moisture transport from the Pacific into Central America and northern South America. The Choco jet is profoundly related to the dynamics of the Intertropical Convergence Zone in the eastern equatorial Pacific and it is responsible of up to 30 % of the total precipitation in these areas. We have been able to produce an index for this jet starting in the 19th century, adding almost a century of data to previous comparable indices. Our results indicate that the seasonal distribution of the precipitation in Central America has changed along the 20th century as a response to the changes in the Choco jet, with has diminished (increased) its strength in July (September). Additionally, we have found that the relation between the Choco jet and the El Niño/Southern Oscillation has been remarkably stable along the entire 20th century, a finding particularly significant because the stability of this relation is usually the basis of the hydrologic reconstructions in northern South America.

scholarly journals Madden–Julian oscillation influence on sub-seasonal rainfall variability on the west of South America

2020 ◽  
Vol 54 (3-4) ◽  
pp. 2167-2185 ◽  
Author(s):  
G. Cristina Recalde-Coronel ◽  
Benjamin Zaitchik ◽  
William K. Pan
Keyword(s):  
South America ◽  
Rainfall Variability ◽  
Seasonal Rainfall ◽  
Madden Julian Oscillation ◽  
The West

Analysis of determinants of forest - savanna transition in the northern South America

2021 ◽  
Author(s):  
Santiago Valencia ◽  
Juan Camilo Villegas ◽  
Juan F. Salazar
Keyword(s):  
South America ◽  
Environmental Change ◽  
Soil Properties ◽  
Rainfall Variability ◽  
Fire Frequency ◽  
Dry Season ◽  
Tree Cover ◽  
Annual Rainfall ◽  
Northern South America ◽  
Rainy Days

<p>Forest - savanna transition is the most widespread and perhaps more dynamic ecotone in the tropics, and extremely sensitive to climate and environmental change. Both kinds of tropical ecosystems are globally strategic and their presence and dynamics have important ecological, climatic and biogeochemical implications, even at the global scale. However, the processes and mechanisms that control this transition vary among regions and remain not fully understood. In general, this transition is influenced by multiple interactions between vegetation and environmental factors such as climate, soil properties, fire, and herbivory. However, the magnitude of these effects can vary substantially across continents, which can result in different responses to environmental change. For this reason, more regional studies are needed to describe and understand the factors and interactions that control forest - savanna transition, particularly in Northern South America, where climate alone has failed to explain this transition. Based on a combination of LiDAR and satellite-derived data, we developed a statistical analysis on the interactive effects of rainfall, soil properties, and fire on the forest - savanna transition in Northern South America, in the savanna region between Colombia and Venezuela, using tree cover as an indicator variable that differentiates forest from savanna. Specifically, we analyze the relationships of tree cover (from GEDI) with soil sand content (from SoilGrids), fire frequency (from Fire_CCI v5.1) as well as three rainfall variability components (from CHIRPS): mean dry-season rainfall, length of the dry season, and frequency of rainy days within the dry season. Our results show that tree cover increased with mean dry-season rainfall and frequency of rainy days within the dry season, whereas it decreased with increased fire frequency. In particular, mean dry-season rainfall followed by fire frequency are the most important predictors of tree cover gradient in the transition. Importantly, our results also suggest that areas with high annual rainfall (2000 to 2800 mm) have low tree cover (i.e. savanna) if the local rainfall climatology consists of infrequent (< 0.35) and low total rainfall (< 650 mm) in the dry season. This highlights the role of water availability and fire disturbance in determining the limits between forest and the second largest area of savanna in South America. Further, our results support that future projections for forest - savanna transition should include not only changes in mean annual rainfall but also changes in rainfall variability, which is expected to be more impacted by climate change. </p>

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