It is based on contributions from the leading centres around the world monitoring and predicting this phenomenon and expert consensus facilitated by WMO and IRI.
Skip to main content. Sea surface temperatures in the eastern-central Pacific are predicted to be below-average to average during September-November , in the range of For October-December , they are predicted to range from Full September Update. Past Updates. Read more. Climate Patterns in the Pacific Research conducted over recent decades has shed considerable light on the important role played by interactions between the atmosphere and ocean in the tropical belt of the Pacific Ocean in altering global weather and climate patterns.
Global Seasonal Climate Update. Read more about Global Seasonal Climate Update. ISBN As the ocean surface temperature changes in response to atmospheric conditions, it modifies rainfall patterns. This increases moisture rising in the air, resulting in more rainstorms. In the US, winter temperatures tend to be warmer than normal in the Northwest with decreased rainfall, while the Southeast experiences wetter-than-average conditions.
You may recall that parts of the Southwest, including California, experienced historic flooding and landslides during In the US, winter temperatures tend to be cooler than average in the Northwest and warmer than average in the Southeast. The promise of the future is that continued research on ENSO and related problems will be rewarded with new scientific breakthroughs that translate into a broad range of applications for the benefit of society.
The physical processes are complicated, but they involve unstable air-sea interaction and planetary-scale oceanic waves. Nor do sunspots as far as we know. The first half of the s was unusual in that four years were all unusually warm in the equatorial Pacific. Kevin E. Trenberth and Timothy J. Geophysical Research Letters, Vol. January 1, Another video is available Explaining the El Nino. Finally, see the graphics comparing today's conditions with others. Most current theories of ENSO involve planetary scale equatorial waves.
The time it takes these waves to cross the Pacific is one of the factors that sets the time scale and amplitude of ENSO climate anomalies. The narrower width of the Atlantic and Indian Oceans means the waves can cross those basins in less time, so that ocean adjusts more quickly to wind variations.
Conversely, wind variations in the Pacific Ocean excites waves that take a long time to cross the basin, so that the Pacific adjusts to wind variations more slowly. This slower adjustment time allows the ocean-atmosphere system to drift further from equilibrium than in the narrower Atlantic or Indian Ocean, with the result that interannual climate anomalies e.
There is another way in which the width of the Pacific allows ENSO to develop there as compared to the other basins. In the narrower Atlantic and Indian Oceans, bordering land masses influence seasonal climate more significantly than in the broader Pacific.
The Indian Ocean in particular is governed by monsoon variations, under the strong influence of the Asian land mass. Seasonally changing heat sources and sinks over the land are associated with the annual migration of sun.
Heating of the land in the summer and cooling of the land in the winter sets up land-sea temperature contrasts that affect the atmospheric circulation over the neighboring ocean. This land influence competes with ocean and atmosphere interactions which are essential for generating ENSO.
They also publish a monthly Climate Diagnostics Bulletin. The Climate Analysis Center at the U. National Center for Environmental Prediction provides up to date Regional Climate Monitoring information from many parts of the world.
A variety of indices are used to characterize ENSO because it effects so many elements of the atmosphere-ocean climate system. The measurements needed for these indices are straightforward, and we have long historical records, especially for the the SOI. However, other indices are effective at characterizing other aspects of ENSO. For example, the anomalous mb zonal winds show how the low-level atmospheric flow is responding to low-level pressure anomalies associated with ENSO and other mechanisms.
Often the mb flow about 1. An index involving the mb zonal flow is used to describe the upper tropospheric winds, whose anomalies tend to be opposite to those at mb and below. The mb flow is particularly important because it is changes at around this level in the tropics that tend to have the biggest consequences for the atmospheric circulation outside of the tropics. The mb temperature represents a proxy for the anomalous heat content of the tropical troposphere. In an overall sense, there is greater heating of the troposphere, and more deep cumulus convection, than normal during warm ENSO events El Ninos.
Finally, there is one more widely used index for the atmosphere and that relates to the outgoing longwave radiation or OLR. The deeper the cumulus convection, the colder the cloud tops, which means the thermal or infrared radiation to space is reduced. It is straightforward to monitor OLR via satellite; its value in the tropical Pacific near the dateline is an effective way to gauge the frequency and magnitude of the thunderstorm activity that changes with ENSO.
Current values of these indices provided on-line by the Climate Prediction Center. In general, warm ENSO episodes are characterized by an increased number of tropical storms and hurricanes in the eastern Pacific and a decrease in the Gulf of Mexico and the Caribbean Sea. Tropical weather products pages are available from the University of Michigan and from the University of Hawaii.
The world expert in this area of study is Prof. Bill Gray of Colorado State University. See the latest articles on this topic from climate. Coral bleaching results when sea temperature rises above a threshold about 28C beyond which corals expel colorful symbiotic algae hence the bleaching.
Deprived of metabolic by-products generated by algae for extended periods, corals die. We don't know the answer to this question. However, computer climate models, one of the primary research tools for studies of global warming, are hampered by inadequate representation of many key physical processes such as the effects of clouds on climate and the role of the ocean.
So, depending on which model you choose to believe, you can get different answers.
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