Abstract
The summer spatial structure and sub-monthly temporal evolution of one of the key dynamical features of Central American climate, the Caribbean Low-Level Jet (CLLJ), is investigated by means of extended empirical orthogonal functions (EEOFs). The Caribbean 925-hPa zonal wind from the CFSR reanalysis for the period 1979 – 2010 is used for the analysis. This approach reveals new insights into the dynamical processes and spatio-temporal evolution of the CLLJ summer intensification, and through lead and lag linear regressions, significant climate links in the broader Caribbean region are identified. The results show that the CLLJ generates significant precipitation and temperature responses with a distinct temporal evolution over the Caribbean-Atlantic domain to that over the tropical Pacific, which hints at different underlying controlling mechanisms over these two large-scale regions. These anomalies are linked with the mid and upper tropospheric circulation, where a vertical cell over the Caribbean (ascending at the jet exit and subsiding at its entrance) varies in phase with large-scale divergence over the Pacific Ocean. Extratropical hemispheric-wide waves and the weakening of a thermal low in northeast Mexico-central US are identified as potential triggering factors for the CLLJ summer intensification. Two leading modes of tropical variability, El Niño Southern Oscillation and the Madden-Julian Oscillation, are found to modulate the CLLJ by intensifying it and prolonging its life cycle. Details of the underlying mechanisms are provided. These results help to advance the understanding of the processes that modulate local climate variations, which is an important issue in view of the rapid climate change the region is undergoing.
Highlights
Wet-season (May-October) precipitation is of utmost importance for southern Mexico and Central America as it provides more than 80% of the annual total rainfall of the region, and it is a vital resource for the regional economy, agriculture, ecosystems as well as the livelihood of the Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.nearly 180 million inhabitants (United Nations 2019)
The Caribbean Low-Level Jet (CLLJ) is identified by applying the Extended Empirical Orthogonal Function (EEOF) analysis (Weare and Nasstrom 1982) to pentad 925-hPa zonal wind anomalies over the Caribbean domain (10◦–20◦ N, 60◦–84◦W), which encloses the region where the climatological CLLJ core is located
This is supported by comparing the temporal autocorrelation of the first principal component (PC) from both EEOF and EOF analyses, which provides an estimate of the timescale of the most recurrent mode of CLLJ summer variability (Fig. 3)
Summary
The CLLJ is typically described on a monthly or seasonal scale, primarily by using a circulation index based on area-averaged 925-hPa zonal wind over the climatological position of the jet core (e.g., Wang 2007; Whyte et al 2008; Cook and Vizy 2010; Maldonado et al 2018), or alternatively, albeit much less commonly, by Empirical Orthogonal Function (EOF) analysis of the 925hPa (zonal) wind over the Caribbean region (e.g., Whyte et al 2008; Muñoz and Enfield 2011) Common to both methods is the assumption of stationarity of the spatial pattern of the winds during the examined season.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
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 call
