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Santa Ana Winds

MICHELLE TRANSUE

Each year, thousands of people visit Great Basin National Park in east central Nevada. Many go to stand in the shadow cast by the 13,036 foot Wheeler Peak or to gaze at the Milky Way in one of the darkest places in the country. Few of these people, however, may know that the atmospheric conditions of the Great Basin provide the origin of a meteorological phenomenon knows as the Santa Ana Winds. Dangerous wildfires, choppy surf, aviation hazards, and increases in air pollutants and allergens are just some of the concerns associated with this phenomenon. These winds, which have long been a fixture of local legend and folklore, have considerable impact on the residents of nearby Southern California. In his novel, Red Wind, Raymond Chandler describes those "hot dry winds that come down through the mountain passes and curl your hair and make your nerves jump and your skin itch. On nights like that, every booze party ends in a fight. Meek little wives feel the edge of the carving knife and study their husbands' necks. Anything can happen." In fact, according to surfline.com, noted serial killer Richard Rameriz, aka "The Night Stalker," went on a healthy killing spree when these relentless blowers acted up in 1984, and the Los Angeles Police Department often report an upsurge in violent acts such as road rage and domestic abuse when the winds linger too long.

With the highest elevation of the four deserts in North America, the Great Basin experiences a decrease in temperature during the months of October through March. As a result of this cooling temperature, a high pressure begins to build. The expanding and cooling air rises and its water vapor is precipitated out. Eventually, this cool dehydrated air will spill out from the basin, and is forced by gravity down the slopes of the Sierra Nevada Mountains into lower lying areas. As is descends, this air warms adiabatically and picks up speed. Warming can occur at up to five degrees Fahrenheit per one thousand feet. Categorized as a Foehn Wind, the Santa Ana Winds can characteristically raise surface temperatures rapidly as they progress over the landscape.

Low lying areas like Southern California, thus, experience hot, dry, easterly and northeasterly winds that may reach up to 104 F at the coast line. This differs greatly from the cool westerly winds they usually receive off the Pacific Ocean. It is not uncommon for the atmospheric conditions of coastal Southern California to be warmer and less humid than that of nearby dessert locations. December appears to be the month in which Santa Ana Winds are most frequent.

This fast moving (possibly hurricane force), hot, dry air has serious environmental consequences for Southern California. The shrub like foliage that covers much of California can be dried considerably, placing hundreds of thousands of acres at an increased wildfire risk. These resultant fires are often deadly and extremely difficult to control. Residents of the posh beach community of Malibu, California, unfortunately, became all too familiar with scenario this past January. Celebrity Suzanne Somers watched as her multi-million dollar home was reduced to rubble. Additionally, Santa Ana Winds will bring with them heavy amounts of grit, dust, pollens and pollutants that they acquired during their journey from the Great Basin.

While the Santa Ana Winds can be potentially very destructive, they do bring with them some benefits. Their presence can cause deeper cold ocean water to rise to the surface bringing a host of nutrients that can aid marine life. The winds are also sometimes credited for Southern California's decrease in smog and high visibility during the winter months. Often the surfers of Southern California welcome the Santa Ana winds as they help to make for good surf if they coincide with quality swells.

The wide range of effects stemming from the Santa Ana Winds makes forecasting them an important task. While December seems to be the month in which Santa Ana Winds occur with greatest frequency, there is considerable variation in the number of events and their severity when compared on an annual basis. Meteorologists often look at three parameters when forecasting the winds. The first is a comparison of the surface pressure measurements at the Great Basin and those at stations along coastal California. The greater the surface pressure difference, the great the chances of a wind developing. The second parameter is the relative humidity seen at coastal stations. Lower relative humidity at these stations correlates to an increase risk of Santa Ana Winds. The third piece of information used the forecasting is the wind direction. In order for Santa Ana Winds to be declared, the wind direction must fall between north-northwesterly and easterly.

Experts are constantly looking at new ways to help predict the frequency, severity, and impact of the Santa Ana Winds. Satellite imaging can be used to detect the presence of Santa Ana Winds. Multi-angle Imaging SpectroRadiometers can capture images of dust particles caught in the winds. Meteorologists are also looking at other atmosphere indicators that correlate to the development of Santa Ana Winds. Sudden changes in wind direction can lead to changes in corresponding dewpoint temperatures. Looking at the dewpoints may help forecast wind trends in wind speeds and directions.

In conclusion, the Santa Ana Winds are a meteorological phenomenon that presents a challenge for meteorologists, fire and emergency responders, and residents of Southern California. If a fire should ignite, understanding the affects that the fire has on the winds is crucial. The fire will warm the air even further thus causing it to rise. This will then allow more air to rush in and create additional gusts of winds, further complicating the situation. Studying the development and progression of these rapidly and sometimes unexpectedly warm, dry and fast moving winds will have a positive impact on both the health and safety of people in and around the city of Los Angeles, California.