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

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.

Association between Meningococcal Meningitis and Santa Ana Winds in Children and Adolescents from Tijuana, Mexico, a need for Vaccination.

Background Based on several previous studies (regional and national), Tijuana, Baja-California, Mexico (across the border from San Diego, California, USA), has shown the highest rate of Meningococcal Meningitis (MeM) in the country, however, the reason for this has not yet been known. In the “African Meningitis Belt”, the Harmattan seasons are associated with MeM outbreaks. The Santa Ana winds seasons (SAWs) are hot and dry winds (similar to Harmattan seasons) that occur seasonally in southwestern California, USA, and North of Baja-California, Mexico. Objectives Our aim was to demonstrate, as a short communication, a potential association of SAWs with MeM in Tijuana, Baja-California, Mexico, which in turn, may partially explain the high rate of this disease in the region. Methods Based on own previously published data obtained from thirteen years of active surveillance of MeM, and a 65 years review showing the occurrence of SAWs, we estimated the risk ratio (RR) of total cases number by MeM vs. bacterial non-MeM (bacterial meningitis not caused by Neisseria meningitidis) during seasons with and without SAWs. Results We found an association of SAWs seasons with MeM, but not with bacterial non-MeM (RR = 2.06, p = 0.02 (95% CI 1.1 to 3.8), which may partially explain the high endemicity of this deadly disease in this part of the globe. Conclusion This study shows a new potential climatic association with MeM, and provides more information that justifies universal meningococcal vaccination in Tijuana, Mexico.

Weather Patterns Driving Atmospheric Rivers, Santa Ana Winds, Floods, and Wildfires During California Winters Provide Evidence for Increasing Fire Risk

Floods caused by atmospheric rivers and wildfires fanned by Santa Ana winds are common occurrences in California with devastating societal impacts. Planning for these types of events is critical to protect life and property, and extending the lead-times of predictability for these types of events improves emergency response. A better understanding of linkages between large-scale atmospheric circulation patterns and extreme weather represents an important step towards improving predictability and preparedness on subseasonal-to-seasonal (S2S) timescales and for climate change adaptation. In this work, we show that winter weather variability in California, including the occurrence of extreme and impactful events, is linked to four atmospheric circulation regimes over the North Pacific Ocean previously named and identified as the “NP4 modes”. These modes interact on daily timescales to produce recurring winter weather patterns that are major drivers of atmospheric river landfalls, Santa Ana winds, floods, and wildfires. Many recent California natural hazard events resulted from compounding and cascading extremes including frequent atmospheric river landfalls (wet, fuel-producing years) or lack thereof (drought) and followed by Sana Ana-driven wildfires that render the landscape susceptible to hydrologic hazards posed by short-duration high-intensity precipitation events. This historical perspective of atmospheric circulation and impacts over 70 years reveals that weather patterns are changing in a way that enhances wildfire risk in California, while the frequency of weather patterns linked to historical floods is not diminishing. These changes highlight the rising hazards of compounding weather extremes in California’s present and future.

Hot and cold flavors of southern California’s Santa Ana winds: their causes, trends, and links with wildfire

Santa Ana winds (SAWs) are associated with anomalous temperatures in coastal Southern California (SoCal). As dry air flows over SoCal’s coastal ranges on its way from the elevated Great Basin down to sea level, all SAWs warm adiabatically. Many but not all SAWs produce coastal heat events. The strongest regionally averaged SAWs tend to be cold. In fact, some of the hottest and coldest observed temperatures in coastal SoCal are linked to SAWs. We show that hot and cold SAWs are produced by distinct synoptic dynamics. High-amplitude anticyclonic flow around a blocking high pressure aloft anchored at the California coast produces hot SAWs. Cold SAWs result from anticyclonic Rossby wave breaking over the northwestern U.S. Hot SAWs are preceded by warming in the Great Basin and dry conditions across the Southwestern U.S. Precipitation over the Southwest, including SoCal, and snow accumulation in the Great Basin usually precede cold SAWs. Both SAW flavors, but especially the hot SAWs, yield low relative humidity at the coast. Although cold SAWs tend to be associated with the strongest winds, hot SAWs tend to last longer and preferentially favor wildfire growth. Historically, out of large (> 100 acres) SAW-spread wildfires, 90% were associated with hot SAWs, accounting for 95% of burned area. As health impacts of SAW-driven coastal fall, winter and spring heat waves and impacts of smoke from wildfires have been recently identified, our results have implications for designing early warning systems. The long-term warming trend in coastal temperatures associated with SAWs is focused on January–March, when hot and cold SAW frequency and temperature intensity have been increasing and decreasing, respectively, over our 71-year record.

340. Association between Meningococcal Meningitis and Santa Ana Winds in Mexican Children and Adolescents from Tijuana, Baja-California, Mexico

Background The Tijuana, Baja-California, and San Diego, California, USA -border, is considered to be the most transited in the world. Based on our active surveillance studies, Tijuana has the highest incidence of meningococcal meningitis (MeM) in Mexico (Chacon-Cruz E. et al.: Ther. Adv. Vaccines 2016; 4: 15–9. J. Infect. Dis. Treat. 2017; 3: 1–4. Emerg. Infect. Dis. 2011; 17: 543–6. And Ther. Adv. Vaccines 2019; 6: 1–7), and an outbreak of MeM in 2013 (Chacon-Cruz et al. Ther. Adv. Vaccines 2014; 2: 71–6). The Santa Ana Winds (SAWs) are episodic pulses of easterly, downslope, offshore flows over the coastal topography of the California Border Region: Southern California and Northern Baja-California (Mexico), occurring mostly from October to April, and are associated with very dry air, often with anomalous warming at low elevations, similar to the Harmattan winds associated with MeM outbreaks in Africa. We hypothesized that the high incidence of MeM in Tijuana is, in part, associated with SAWs. This association has never yet been described. Methods Based on 13 years of active/prospective surveillance (2005–2018) in children > 7 days and < 16 years of age at the General Hospital of Tijuana, we identified 51 cases of MeM (25% lethality), and 30 non-meningococcal meningitis (NMeM). Association between cases per month of MeM and NMeM, with SAWs seasons (from a 65 years review: Guzman-Morales J, et al. Geophys. Res. Lett. 2016; 43: 2827–34), was calculated by Risk Ratio (RR). A z test was also used to compare proportions of MeM during SAWs seasons vs. non-SAWs seasons. Results From 51 MeM, 44 (86.27%) occurred during SAWs seasons (z test = 7.32, p< 0.0002). Cases per month during 13 years (91 months for SAWs seasons and 60 months for non-SAWs seasons) were as follow (See Figure-1): SAWs seasons: non-SAWs seasons: MeM 0.483 cases/month 0.107 cases/month NMeM 0.186 cases/month 0.216 cases/month RR =1.76, p=0.0002 (95% CI 1.23 to 2.49) Conclusion 1. In Tijuana, Baja-California, Mexico, there is a strong association of Meningococcal Meningitis with seasons when Santa Ana Winds occur. 2. Routine immunization against vs. Neisseria meningitidis should be seriously considered in the region. Disclosures All Authors: No reported disclosures

Dust Deposition on the Gulf of California Caused by Santa Ana Winds

Numerical simulations revealed a profound interaction between the severe dust storm of 2007 caused by Santa Ana winds and the Gulf of California. The weather research and forecasting model coupled with a chemistry module (WRF-CHEM) and the hybrid single-particle Lagrangian integrated trajectory model (HYSPLIT) allowed for the estimation of the meteorological and dynamic aspects of the event and the dust deposition on the surface waters of the Gulf of California caused by the erosion and entrainment of dust particles from the surrounding desert regions. The dust emission rates from three chosen areas (Altar desert, Sonora coast, and a region between these two zones) and their contribution to dust deposition over the Gulf of California were analyzed. The Altar Desert had the highest dust emission rates and the highest contribution to dust deposition over the Gulf of California, i.e., it has the most critical influence with 96,879 tons of emission and 43,539 tons of dust deposition in the gulf. An increase of chlorophyll-a concentrations is observed coinciding with areas of high dust deposition in the northern and western coast of the gulf. This kind of event could have a significant positive influence over the mineralization and productivity processes in the Gulf of California, despite the soil loss in the eroded regions.

Santa Ana Winds and Wildfires Influence Air Pollution

Inhaling particulate matter is hard on human health. New research shows that Southern California’s Santa Ana winds can clear or exacerbate fine-particulate pollution depending on wildfire conditions.