Santa Ana Winds: Fractal-Based Analysis in a Semi-Arid Zone of Northern Mexico

Yeraldin Serpa-Usta,Mariangela López-Lambraño,Ena Gámez-Balmaceda,John Freddy Remolina López,Luisa Martínez-Acosta,Dora-Luz Flores,Alvaro Alberto López-Lambraño,Juan Pablo Medrano-Barboza,Alvaro López-Ramos

doi:10.3390/atmos13010048

Abstract

A fractal analysis based on the time series of precipitation, temperature, pressure, relative humidity, and wind speed was performed for 16 weather stations located in the hydrographic basin of the Guadalupe River in Baja California, Mexico. Days on which the phenomenon known as Santa Ana winds occurs were identified based on the corresponding criteria of wind speed (≥4.5 m/s) and wind direction (between 0° and 90°). Subsequently, the time series was formed with data representing the days on which this phenomenon occurs in each of the analyzed weather stations. A time series was additionally formed from the days in which the Santa Ana winds condition does not occur. Hurst exponents and fractal dimension were estimated applying the rescaled range method to characterize the established time series in terms of characteristics of persistence, anti-persistence, or randomness along with the calculation of the climate predictability Index. This enabled the behavior and correlation analysis of the meteorological variables associated with Santa Ana winds occurrence. Finally, this type of research study is instrumental in understanding the regional dynamics of the climate in the basin, and allows us to establish a basis for developing models that can forecast the days of occurrence of the Santa Ana winds, in such a way that actions or measures can be taken to mitigate the negative consequences generated when said phenomenon occurs, such as fires and droughts.

Highlights

The Santa Ana winds are a meteorological phenomenon that affects the SouthwesternUnited States and Northwestern Mexico, mainly in fall and winter [1]
The estimated values of the Hurst exponent are reported for variables of pressure (P), temperature (T), precipitation (R), relative humidity (H), and wind speed (W) from the time series obtained with the databases used
Regarding wind speed and relative humidity [30], reported average values were 0.64 and 0.61, respectively, similar to those found in the studied region

Summary

Introduction

United States and Northwestern Mexico, mainly in fall and winter [1] They are a warm, dry, Föhn-type wind from the east or northeast, blowing from the Sierra Nevada eastern desert to the Southern California coast [2]. Meteorological indicators of the winds are high wind speeds (up to 30 mph), northeast wind directions, and low relative humidity, along with a strong pressure gradient between the Great Basin and the California coast [4,5,6,8,10,11,12] They tend to form in winter but the most dangerous events usually occur in the fall, before the winter rains begin. At this time, vegetation tends to be extremely dry, causing a high risk of fires due to the very low humidity condition and the strong winds that can cause and spread flames, arousing great interest in fire dynamics research in Southern California [11,13,14]

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