El Niño has become an intensely studied & widely publicized phenomenon which has been linked lớn changes in aviarus-21.com patterns across the United States. Often falsely blamed for crazy aviarus-21.com ranging from flooding & mudslides lớn snowstorms and tornadoes, in reality its effects are much broader và generalized and can never fully take credit for any one aviarus-21.com sự kiện. Its effects on one region may be drastically different than its effects on another region. In this report El Niño will be explained and related lớn specific trends in aviarus-21.com during the cool season in Amarillo, Texas.
|What is El Niño?|
The term "El Niño"was originally used lớn refer tothe warming of the Pacific Ocean waters near the east coast of South America near the beginning of eachyear. The term is Spanish for"The Child" which references the baby Jesus, whose birth is celebrated on Christmas Day which is near the time when the warming of the waters is often noticed. Every fewyears this annual warming is much more intense & lasts much longer than usual. Gradually the term began khổng lồ refer to lớn this occasional dramatic warming which impacts a large part of the tropical Eastern Pacific Ocean. Sometimes the opposite situation occurs & the ocean becomes much cooler than normal. When thisoccurs it is referred khổng lồ as "La Niña."
Meteorologists và climatologists know that the Earth's oceanshave sầu avery large impact on the overall atmospheric circulation of the planet. The temperaturevariations within the oceans và the currents which drive warm water northward and cold water southward have sầu drastic effects on the aviarus-21.com và climate around the globe. Over the past several decades, scientists have sầu linked the warming và cooling of the Eastern Pacific waters during El Niño with changes in the atmospheric circulation particularly in the tropics. These changes are much more dramatic inthe winter & spring than other times of year.
There are many different ways lớn measure whether the ocean is in a state of El Niño or La Niña, but the most common is to look at one specific region of the tropical Eastern Pacific Ocean called the Niño 3.4 region. When the average sea surface temperature in this region is at least 0.5 C above sầu normal, El Niño conditions are occurring. Sea surface temperatures at least 0.5 C below normal indicate La Niña conditions are occurring. The further the sea surface temperatures are away from normal, the stronger the El Niño/La Niña event is said khổng lồ be.
During El Niño the southern jet stream strengthens especially across the eastern Pacific Ocean.This allows more moisture to be transported onshore in the Southwestern United States and generally more storminess across the southern part of the country in general. The northern polar jet stream is shifted northward across the United States, reducing the number of cold outbreaks across the central United States.
During La Niña conditions, the jet streams are much more variable and amplified. Generally this means drier & warmer conditions across the southwestern United States. But because the jet stream is amplified, there can be much more frequent cold air outbreaks than what is seen during El Niño.
|What about Amarillo?|
Although it is unwise khổng lồ contribute any one aviarus-21.com sự kiện to lớn El Niño or La Niña, the generalized effects can be seen over an entire season. A detailed analysis of the aviarus-21.com over the past 60 years at Amarillo has been conducted. A comparison was made between temperature and precipitation observations & the status of El Niño/La Niña based on the Niño 3.4 Index. In general, El Niño conditions lead to lớn wetter, snowier conditions in Amarillo và cooler maximum temperatures during the winter. La Niña conditions lead to drier and warmer temperatures overall, with notable extreme cold spells. In stronger El Niño or La Niña episodes, these trends are even greater.
For the months of October through April during the 60-year period from 1950 through 2009, observations of temperature and precipitation were grouped according lớn the state and strength of El Niño or La Niña. To determine how the observations compare lớn "normal" và lớn remove sầu any bias associated with decadal or long-term climate change, the observations were subtracted from the average of the ten years surrounding that year. This allows for a more realistic determination of how the temperature & precipitation departed from what would have been expected by locals at that time.
Maximum temperatures show alarge negative sầu correlation with the average Niño 3.4 Index in the cool season. When La Niña exists, maximum temperatures are warmer. When El Niño exists, maximum temperatures are cooler. A graph of the datahas a best fit trendwith a slope of -1.6 indicating that with every 1.0 Celsius increase in Pacific waters there is a decrease in maximum temperatures of about 1.6 degrees. The trover is also visible when comparing the number of days with maximum temperatures of 60 degrees or more. During El Niño, there are much fewer of these warm winter days. During La Niña, there are many more of these warm days. A similar graph of the total 60 degree daysindicates a decrease of about 9.1 days per 1.0Celsius increase in Pacific waters. When conditions in the Pacific are more extreme, the resulting trover in Amarillo is also khổng lồ see a more extreme departure from normal. The table below displays some statistics on temperatures during various stages of El Niño & La Niña.
AVERAGE NUMBER OF DAYS
NIÑO 3.4 AVE
MAX ≥ 60*
* Departure from normal
Minimum temperatures (graph)vày not show a significant correlation lớn El Niño, as the median is within one degree in all categories. There is a noticeable trkết thúc, however, when looking at the number of days that the minimum temperature drops inlớn the single digits or below zero. During La Niña it is much more likely lớn see these extreme cold temperatures despite the generally higher maximum temperatures which also accompany La Niña conditions. A graph of the lowest temperature of the season shows a slight positive trend of about 1.3 Fahrenheit per 1.0 Celsius increase in the Pacific waters. This is a result of the more amplified jet stream which allows for occasional arctic outbreaks và very cold temperatures.
Precipitation shows alarge positive sầu correlation with the average Niño 3.4 Index in the cool season. When La Niña exists (cold Pacific waters), precipitation drops significantly. During El Niño (warm Pacific waters), precipitation increases significantly.A graph of total precipitation verses Niño 3.4 Index shows the positive correlation. A best fit trover line of the data gives a slope of 0.87 whichindicates that with every 1.0 Celsius increase in the Pacific waters there is an increase of about 0.87 inches of precipitation.
Because most of the winter precipitation in Amarillo falls in the size of snow, the same trends of increased snowfall during El Niño và decreased snowfall during La Niña are also observed. A similar graph of total snowfall verses Niño 3.4 Index also shows the positive correlation.A best fit trover line of the data gives a slope of 4.5, indicating that with every 1.0 Celsius increase in Pacific waters there is an increase of about 4.5 inches of snowfall.Days with measurable snowfall (graph)also increases with the Niño 3.4 Index at a rate of about 2.6 days per 1.0 Celsius increase in Pacific waters. In fact, the total number of days with measurable snowfall is roughly triple during a svào El Niño as compared to a strong La Niña. The table below displays some statistics onprecipitation & snowfallduring various stages of El Niño and La Niña.
AVERAGE NUMBER OF DAYS
NIÑO 3.4 AVE
|+1.5 to lớn +2.0||2||+3.37||+1.1||+16.0||17.0||7.0||2.0||0.0|
|+1.0 to lớn +1.5||5||-1.62||-7.4||+4.6||11.2||4.6||2.0||0.2|
|+0.5 to lớn +1.0||8||+0.56||+7.6||+3.6||14.6||7.1||2.5||0.8|
|-0.5 to +0.5||21||-0.73||-3.5||-0.7||10.1||4.4||1.4||0.6|
|-0.5 lớn -1.0||12||-0.35||-3.9||-0.7||11.2||4.0||1.3||0.4|
|-1.0 lớn -1.5||7||-2.67||-6.4||-8.1||8.0||4.1||1.1||0.3|
|-1.5 khổng lồ -2.0||3||-3.48||-11.6||-9.7||6.0||2.0||0.3||0.0|
* Departure from normal
In the 10 total moderate khổng lồ strong La Niña events (Niño 3.4 Index of -1.0 or lower), only 1 year recorded above normal precipitation (1998-1999 was 10.60 inches above normal). Only 2 years recorded above sầu normal snowfall (1955-1956 was 3.7 inches above normal và 1970-1971 was 11.1 inches above normal). However, both of these seasons recorded above normal snowfall in large part due to lớn one storm which dropped most of the season's snowfall all at once (14.7 inches in February 1956 and 14.1 inches in February 1971). In all 10 years there were 11 or fewer days with measurable snowfall (average of 7.4 days). Average maximum temperatures were at least 1.0 degrees Fahrenheit above normal in all 10 years.
In the 17 total El Niño events (Niño Index of 0.5 or higher), 11 years recorded above normal precipitation and 12 years recorded above normal snowfall. All 17 years had at least 8 days of measurable snowfall (average of 14.6 days). Maximum temperatures were below normal in all but 4 years.