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Understanding and Predicting Wet Season Precipitation in the Ecuadorian Andes
  • Carly Narotsky
Carly Narotsky
University of North Carolina at Asheville

Corresponding Author:cnarotsk@alumni.unca.edu

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Abstract

Farmers in the indigenous Andean community of Cañar, Ecuador rely on an abundant wet season each growing year and are concerned that their wet seasons are becoming less rainy. The normal seasonal rainfall pattern in this region, the Andes of southern Ecuador, is driven primarily by the seasonal migration of the Intertropical Convergence Zone (ITCZ). Existing scientific literature suggests that the ITCZ’s seasonal migration pattern could be affected by anthropogenic climate change, thereby impacting the seasonal precipitation in the region. This study explores the possibility that the ITCZ’s migration pattern has already changed, which would validate the concerns of the Cañari people. This is accomplished by tracking the movement of the ITCZ over the past few decades using Outgoing Longwave Radiation (OLR) data. No obvious trend in the seasonal mean position of the ITCZ has been detected. However, OLR maps indicate an abnormal ITCZ signature during strong warm phases of the El Niño-Southern Oscillation (ENSO), consistent with previous studies. The interannual variability in the region’s seasonal precipitation is also associated with varying phases of ENSO. An additional component of this study is the development of a statistical model using ENSO indices as input, among other atmospheric indices, to provide seasonal precipitation forecasts for the tropical Andean wet season each year. Besides ENSO, another potentially useful index for seasonal prediction is the phase of the Quasi-Biennial Oscillation, which has been linked to precipitation variability in the tropics. The seasonal forecasting model is expected to help Ecuadorian highland farmers decide which of their crops to plant each year, based on the water needs of each crop.