Intraseasonal modulation of spring-strong wind events associated with convection in northeastern Argentina

Abstract

The relationship between intraseasonal variability (IS; 10–90 days) and days which registered convection-associated strong surface wind events (CSSWE) over northeastern Argentina (NEA) was studied. The climatological behaviour of these strong wind events showed a higher duration and occurrence in austral spring. CSSWE were categorized as a function of the wet and dry phases of the spring-season intraseasonal (spring-SIS) index, which describes the activity of the leading pattern of IS-filtered outgoing longwave radiation (IS-OLR) during that season in eastern South America. A modulation of the IS variability over localized and mesoscale phenomena as the CSSWE was found, showing significant peaks of wind variability in that timescale, and especially the submonthly timescale. The CSSWE were categorized according to the phases of the spring-SIS pattern and most of them occurred before or during a wet phase, especially for the longer CSSWE. Moreover, the detection of CSSWE days during and before a dry phase was scarce. Rossby wave trains were observed to organize the circulation on intraseasonal timescales that configure regional cyclonic anomalies in such way that favours the development of CSSWE, promoting mid-level ascents over NEA and northerly advection of humidity to the region. Together with the composites of IS-OLR anomalies and the spectra of wind velocity, they support the fact that the higher-frequency IS variability is the primary influence for the development of CSSWE.