LARGEST IMPACT ON WINTER WEATHER CONDITIONS : EL NIÑO AND LA NIÑA
By Matt Makens Atmospheric Scientist
The changing seasons due to Earth ’ s tilt is our most significant weather driver . This makes sense ; it is hot in the summer compared to the cold of winter . Aside from this normal seasonal pattern , having either El Niño or La Niña in place is the second most significant impact on our weather patterns . Though dozens of other features can influence the patterns , they act to modify El Niño or La Niña ’ s impact rather than having full control .
I often take these features for granted because I deal with them daily . As a bit of a personal reality check , I was recently asked where these terms came from and what they are .
The term “ El Niño ” originated hundreds of years ago from Peruvian fishermen who noticed a periodic warming of the Pacific Ocean waters along the western coast of South America . This warming typically occurred around December , close to Christmas , leading the fishermen to name the phenomenon “ El Niño ,” meaning “ The Child ” in Spanish , a reference to the Christ Child . Initially , the term was used to describe the warmer-thanusual ocean currents that disrupted their fishing patterns . Over time , “ El Niño ” has come to represent a broader climate pattern associated with significant global weather impacts , including droughts in others ( drought for much of the U . S .). The name La Niña was adopted in the late 20th century as scientists began to recognize the importance of these cooler phases in the broader climate cycle known as the El Niño-Southern Oscillation ( ENSO ). Because it is colder , this area of the ocean does not create rising motion or storm development above .
Regardless of what we call them , throughout the last century , much work has been done to observe how each pattern develops and how each impacts global weather . The very early work of what is now the Climate Prediction Center was focused on improving weather forecasts for the agricultural industry , and much of that work was observing connections between the weather in the U . S . and ocean / atmosphere patterns across the globe . Early data was limited to sea surface temperatures and surface to very low-level observations . Atmospheric data from balloons and planes became more prevalent and reliable after World War II .
We have a good grasp of these connections today as global networks , especially satellite data since the 1970s , have increased the amount and accuracy of data available . Clues have
Figure 1
altered precipitation patterns and increased storm activity across various regions . Being warmer , this ocean area creates lots of rising motion and storm development .
The term “ La Niña ,” meaning “ The Girl ” in Spanish , was coined as the counterpart to “ El Niño .” While El Niño describes the periodic warming of the Pacific Ocean waters , La Niña refers to the opposite phenomenon — a significant ocean surface cooling . This cooling leads to different global weather patterns , often characterized by increased rainfall in some regions and been discovered , such as something as obscure as how much rain falls on Bahia , Brazil , in the early spring can indicate the likelihood of either El Niño or La Niña the following year ; that is just one example . With a vast network of data and an extensive history of valuable data , we see connections previously hidden from view .
Even with all our knowledge today , we know that we are missing some of the connections that impact us across the States , and this is a source of error in any long-range forecast
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