ENSO Influence on Intraday Solar Irradiance in Uruguay During the Most Affected Period (Nov-Dec)
Abstract
This work explores how El Niño Southern Oscillation (ENSO) modulates intraday to interannual solar irradiance patterns in Southeastern South America during the November-December period, when ENSO impacts on the region, in particular on radiation, are known to peak. Based on 24 years of hourly Global Horizontal Irradiance (GHI) estimates from an accurate satellite-based model, diurnal cycles of the clearness index (kt) were analyzed and grouped using K-means clustering. Four characteristic intraday patterns were identified: overcast (OC), clear-sky (CL), clear-morning/cloudy-afternoon (CL-AM), and cloudy-morning/clear-afternoon (CL-PM). Their frequencies vary significantly with ENSO phase: CL days dominate during La Niña years, while El Niño years exhibit more OC and CL-AM days. This provides a first indication of ENSO-related modulation of intraday irradiance variability. Ongoing work will extend the analysis to other periods, particularly February-May, and address spatial variability over a broader region and underlying physical mechanisms.
Keywords
GHI, daily profiles, ENSO, intraday variability, clustering