When I came back to New Mexico for the holidays, I was a bit shocked at how warm it was. After living in subzero temperatures in the Chicago area, it felt like summertime in New Mexico.
Many people think of New Mexico as a hot, dry desert filled with cacti. While some parts of New Mexico are like this, the area my family lives in is high desert, similar in climate to southern Colorado. We get snow. The past few years have been white Christmases. But this year, the ground was bare and it was warm.
So what was the cause of this unseasonably warm and dry weather? It's the lesser-known cousin of El Niño: La Niña. In Spanish, "la niña" means "the little girl." La Niña, like El Niño, is a periodic climate cycle — but has the opposite effects of El Niño. La Niña is characterized by abnormally cooler subsurface ocean temperatures building up in the equatorial waters in the Pacific leading to chaotic weather patterns. Dry areas become dryer and warmer, wet areas become wetter and cooler.
According to NOAA, the winter of 2010-2011 will be a La Niña winter. On average, La Niña takes place every three to five years and can last for nine to 12 months. The effects are most noticeable during the winter months.
La Niña sometimes takes place after an El Niño, and is preceded by a buildup of cooler subsurface waters in the tropical Pacific Ocean. Easterly moving atmospheric and oceanic waves bring the cold water to the surface. Over a period of time, the trade winds strengthen on the coast of North, South, and Central America, and sea surface temperatures drop.
So how does this affect the Southwest? Unlike the West and East Coasts being bombarded by storms this winter, New Mexico is experiencing a lovely and mild winter. However, the effects of La Niña may come back to haunt the Southwest. New Mexico, already a place with a dry climate, has become dryer than usual this winter. Most stream flow in New Mexico and throughout the Southwest is created from snowmelt. The build-up of snow in the winter and subsequent melting in the spring and summer is vital to providing water to crops, people and the natural ecosystem. In a dry winter with little precipitation or snow pack, it could create ideal conditions for wildfires in the spring and summer.
La Niña is a complex series of events that are still being examined. It is not entirely clear if global warming causes La Niñas, but additional research is being done.
Photos: Heather Altherr