Análisis estadístico y métodos de clasificación del viento zonda en San Juan

This paper intends to evaluate possible methods of objective classification (OCM) of zonda wind (foehn) events and update the statistics of this phenomenon in the city of San Juan. First, a classification was performed according to the “three point method”, where subjectively analyze temporal changes in wind speed and direction, temperature and humidity to diagnose the presence of zonda. On the other hand, OCM help to understand what are the most relevant variables, providing a physical basis for defining the zonda wind occurrence in this region. Following the classification methodologies by other authors, the most appropriate variables were selected, being a combination of the speed and direction of wind and temperature anomalies and relative humidity. Three OCM are proposed; The method of the maximum temperature (CTMAX) including daily maximum temperature, monthly average maximum temperature and minimum dew point temperature for the same day variables; the method of daily anomalies (CAD), which has as variables the daily temperature and dew point temperature anomalies and the method of seasonal anomalies (CADE), with seasonal temperature and dew point temperature anomalies. All methods were able to identify many of the Zonda wind events in San Juan. Next, these methods were compared with the subjectively classification methods. The diurnal and monthly cycle, the onset, offset and the average duration were compared. After comparing the methods, those events subjectively classified were taken and new classification was made according to the maximum wind speed. A weather description was made, and the differences were discussed with respect to the new classification, the daily and annual cycle, duration and onset. Then, the percentage frequency of wind directions for different zonda wind intensities was described. Finally, the percentage distribution of the gusts and wind speed for the entire zonda wind data was analyzed.