Abstract
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.
Highlights
The Northern Hemisphere eastern equatorial Pacific is an interesting area from a climatological point of view
The objective of this paper is to develop a new index representative of the Chocó jet strength by exclusively using the raw wind direction measurement currently incorporated in International Comprehensive Ocean-Atmosphere Data Set (ICOADS)
We have found that the strength of the Chocó jet can be estimated through an index starting in the 1850s by using in situ wind direction measurements contained in ICOADS
Summary
The Northern Hemisphere eastern equatorial Pacific is an interesting area from a climatological point of view. In the eastern equatorial Pacific, the Intertropical Convergence Zone (ITCZ) is predominantly located in the Northern Hemisphere (Wodzicki and Rapp, 2016) In this region, the Southern Hemisphere trade winds cross the Equator and the change in the sign of the Coriolis term, facilitated by the coast orientation and the land–sea temperature gradients, deflects the trades to the east, entering northern South America at 5◦ N as a low-level westerly jet, whose core is located at the 925 hPa level (Fig. 1a) introducing huge amounts of moisture into the continent (Poveda and Mesa, 1999, 2000). As we will show below, this method provides an extension of almost one century to the current available indices for this jet
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
