FORECASTING ZONDA WIND OCCURENCE WITH VERTICAL SOUNDING DATA

FEDERICO OTERO; DIEGO ARANEO

ADVANCES IN ATMOSPHERIC SCIENCES

SCIENCE PRESS

Lugar: Marrickville NSW; Año: 2021

0256-1530

Zonda wind is a typical downslope windstorm over the eastern slopes of Central Andes, in Argentina, which produces extremely warm and dry conditions creating substantial socioeconomic impacts. The aim of this work is to obtain an index for predicting the probability of Zonda wind occurrence. The Principal Component Analysis (PCA) is applied to the vertical soundings data on both sides of the Andes. Through the use of a binary logistic regression, we seek to apply the PCA to discriminate those soundings associated to Zonda wind events from those that are not, obtaining a probabilistic forecasting tool for Zonda occurrence. This index model is capable to discriminate between Zonda and Non-Zonda events with an effectiveness close to 91%. The best model consists in four variables each side of the Andes. From an event-based statistic, the probability of detection locates the mixed model above 97% with a probability of false detection lower than 7% and a missing ratio below 1%. From an alarm-based view, models present values below 7% in the false alarm rate, lower than 1.5% in the missing alarm ratio and higher than 93% in the correct alarm ratio. The zonal component of the wind on both sides and the windward temperature are the key variables in class discrimination. This vertical structure present two wind maximums and a lapse rate that tend to becomes unstable at med-levels on the leeside and a wind maximum at 700 hPa accompanied by a relatively more stable layer near the top of the barrier.