Stories tagged El Nino

Jun
25
2010

Adios El Niño, Hello La Niña?: The Pacific has switched from warm (red) to cold (blue).
Adios El Niño, Hello La Niña?: The Pacific has switched from warm (red) to cold (blue).Courtesy NASA

How to measure ocean temperature

There are many ways to measure the temperature of an ocean. Oceans are big and temperatures at different locations vary. To get a sense of whether the ocean is warming or cooling, lots of spread out measurements need to be made.

  • Thermometers under buoys or ships Since about 1990 an extensive array of moored buoys across the equatorial Pacific Ocean has beamed temperature data from a 1 meter depth up to a satellite. Lots of ships are also recording their intake water temperatures but the depths and locations vary making this data harder to use.
  • Satellite remote sensing NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) SST satellites have been providing global SST (Sea Surface Temperature) data since 2000. Unlike buoys, the satellites can sense the surface temperature everywhere. The temp measured is of the surface only, though. The surface "skin" temp can be quite different than the temp of the water below because of things like evaporation, wind, sunshine, and humidity. Also, cloud cover prevents satellites from sensing surface temperatures.
  • Acoustic Tomography Sound, especially low frequencies, can travel long distances under water. Since the speed of sound under water varies with temperature, measuring how long sound takes to travel a certain distance will give you the average temperature of the water over that distance. Acoustic Thermometry of Ocean Climate (ATOC) is using trans-basin acoustic transmissions to observe the world's oceans, and the ocean climate in particular.
  • Ocean Surface Topography By bouncing microwaves off the the ocean surface and using GPS location, satellites can precisely measure the height of any spot on the ocean surface. Reasoning that water expands and contracts as it heats and cools, then so too would the height of the sea surface. I think Ocean Surface Topography is the easiest and best technique for measuring ocean temperature.
    In a 2005 study researchers compared satellite measurements of sea surface height in the northeast Pacific Ocean from 1993-2004 to recordings of sea surface temperature in the region during the same period. The sea surface height measurements proved to be as accurate as temperature measurements as indicators of ocean conditions resulting from long-term climate cycles as well as being more consistent. PhysOrg

El Niño and La Niña effect on hurricanes

Ocean temperature information is useful in predicting hurricane season severity and forecasting individual storm severity. The image above shows that the Pacific Ocean is changing from hot to cold.

A La Niña is essentially the opposite of an El Niño. During a La Niña, trade winds in the western equatorial Pacific are stronger than normal, and the cold water that normally exists along the coast of South America extends to the central equatorial Pacific. La Niñas change global weather patterns and are associated with less moisture in the air, resulting in less rain along the coasts of North and South America. They also tend to increase the formation of tropical storms in the Atlantic.

"For the American Southwest, La Niñas usually bring a dry winter, not good news for a region that has experienced normal rain and snowpack only once in the past five winters," said Patzert. NASA

El Niño has returned

How strong an El Niño will eventually develop and how long it is likely to last is not yet known. Learn more about El Niño in 2009 in ScienceNow Daily News.

That's right, folks, whether you wanted him around or not, El Niño has come, and he's going to break your head open! (Climatologically speaking he will.)

One way to describe El Niño might be to say that it's a global weather phenomenon associated with an upwelling of warm water off of the Pacific coast of South America, occurring every two two five years, which causes all sorts of oddness around the world, from droughts in Australia to major flooding in South America, to heavy rains and increased wave erosion in the Pacific Northwest.

Another way to describe El Niño might be this:

(Actually, I'd encourage someone to write something better than this wimpy little post on El Niño. There's a lot to say about it, and it affects billions of people around the world. Check it out, teach us something we didn't know.)

Jul
14
2007

In hot water: These thermal imaging maps show the difference between normal surface water temperatures and El Nino surface water temperatures in the Pacific Ocean. (Photo from the National Oceanic and Atmospheric Administraion Photo Library)
In hot water: These thermal imaging maps show the difference between normal surface water temperatures and El Nino surface water temperatures in the Pacific Ocean. (Photo from the National Oceanic and Atmospheric Administraion Photo Library)
As if our TV meteorologists didn’t have enough warnings and ratings to rattle our cages with, here come two more.

The Climate Prediction Center as announced that it has created a rating scale to measure the impacts up oncoming El Nino or La Nina weather patterns. The new ratings will likely first be issued starting this fall.

Not only will the weather patterns carry a rating on their severity, but warnings and advisories will also be issued through the new program, much like we get thunder storm or tornado warnings or watches. Here are the details:

• A watch will be issued when conditions are ripe for the creation of El Nino or La Nino patterns within the ensuing three to six months.

• An advisory will be issued when the conditions are underway.

• The rating scale will go from 1 to 5 and be done to measure the impact of the El Nino or La Nina after it’s passed, much like the F-scale used to measure tornados.

The strength of the weather conditions is determined by the warmth or coolness of the surface waters in the South Pacific. The names were given to the weather conditions by fishermen from Peru who noticed fluctuations in their catches based on the changing water temperatures.

The new scale will have a bigger impact on allowing researchers to compare weather conditions after they’ve happened, not in predicting how severe new ones will be.

Strong El Ninos and La Ninas can impact weather conditions worldwide. You can learn more about them at the Science Museum of Minnesota's Science on a Sphere display.