El Nino Occurrences Research Articles

Asian Summer Monsoon—ENSO Feedback on the Cane–Zebiak Model ENSO

Abstract The Asian summer monsoon heating anomalies are parameterized in terms of the concurrent ENSO SST anomalies and used as additional forcing in the Cane–Zebiak (CZ) Pacific ocean–atmosphere anomaly model. The Asian heating parameterization is developed from the rotated principal component analysis of combined interannual variability of the tropical Pacific SSTs, residually diagnosed tropical diabatic heating at 400 mb (from ECMWF’s analyses), and the 1000-mb tropical winds during the 1979–97 summer months of June, July, and August. Analysis of the 95 000-yr-long model integrations conducted with and without the interactive Asian sector heating anomalies reveals that their influence on the Pacific surface winds leads to increased ENSO occurrence—an extra ENSO event every 20 yr or so. An examination of the ENSO distribution w.r.t. the peak SST anomaly in the eastern equatorial Pacific shows increased El Nino occurrence in the 2.2–3.6 K range (and −1.0 to −1.6 K range in case of cold events) along with...

Some causes of rapid changes in temperature patterns

It was shown in another recent publication by the author that, for each sunspot cycle, there exists in the surface-atmosphere system (SAS) two quasi-sinusoidal temperature variations each at the frequency of the sunspot cycle. The first of these two variations is much smaller than the other one and is always in phase with the associated sunspot cycle. However, the second of the two variations is relatively huge and is always not in phase with the associated sunspot cycle. Here we illustratively describe how the smaller temperature variations associated with sunspot cycles participate in causing large and rapid changes in temperature patterns. Furthermore it is noted that El Nino events as well as the processes responsible for switchings of (temperature) amplitude-modulation states into each other are other key causes of rapid changes in temperature patterns. Finally we set up clear relationships between El Nino occurrence patterns and sunspot cycles, and then use these relationships to make an attempt at predicting the expected timing of the next El Nino event. Some physical justification for this attempted prediction is also given.

Understanding a Possible Correlation between El Nino Occurrence Frequency and Global Warming

Understanding a Possible Correlation between El Nino Occurrence Frequency and Global Warming

Former El Niño events: records from western South America

The quasi-periodic alterations of the climate in South America and of the oceanographical conditions in the eastern Pacific Ocean, referred to as the “El Niño” phenomenon, are part of a global anomaly in the ocean-atmosphere interactive system (the El Niño-Southern Oscillation, ENSO). As this phenomenon is responsible for the major interannual climatic variability and has a great potential to document links between the atmospheric and oceanic circulations, it is important to understand its mechanism, its boundary conditions and the causes of the variations of its intensity. Many answers to such questions can be sought in the historical and geological record of El Niño occurrences. Former impacts of the El Niño phenomenon along the western coast of South America are documented by remnants of catastrophic rainfalls and associated river floods, records of lake salinity variations, beach ridge sequences and numerous evidences of alterations in the biotic and physical coastal environment. For the last millennium or so, relatively precise (although discontinuous) archaeological and historical data are available. Continuous, high-resolution, proxy records are provided by glaciological data (last 1500 yr) from the Quelccaya ice cap of southern Peru and are potentially available from coral cores from the Galapagos Islands. No marine varves that would permit a detailed and sequential study of El Niño-related oceanographic anomalies during the late Quaternary have yet been obtained off western South America. The reconstruction of the sequence of the main ENSO events during the last millennia is thus hampered by the fact that there are too few continuous records and that these have not necessarily registered every El Niño occurrence and/or the relative intensity of each event. The discontinuous records of major El Niño events are more numerous, but often lack the required chronological accuracy. Obviously, both series of data need to be cross-checked and compared with information (e.g. dendroclimatology and marine varves) from other regions of the globe where climate teleconnections with the ENSO phenomenon can be assessed.

Low-Frequency Changes in El Niño-Southern Oscillation

Abstract Although there are indications from numerical models that El Nino-Southern Oscillation (ENSO) may be an internal mode of the coupled Pacific ocean-atmosphere system, sensitive to climatic background parameters, it has not yet been possible to find significant changes in ENSO variability between the Little Ice Age and the present. Yet a number of authors have found qualitative indications in anecdotal and proxy records of shorter, century-scale variations in the return-interval statistics for El Nino episodes. To objectively determine what nonstationarities exist, we statistically examine the El Nino occurrences since 1525, compiled by Quinn et al. We have stratified the return intervals both for strong events and for all events according to two null hypotheses. 1) return intervals are stationary over periods of 200–500 years, and 2) the intervals are stationary on a centenary time scale, between epochs of contrasting solar variability. Two-parameter Weibull distributions are fit to subsamples of ...

El Nino effects on hydrogen ion concentration of a California reservoir

Hydrogen ion concentration, [H+], of discharge water from Pardee reservoir in the central Sierra Nevada, California was greater than expected in years of El Nino occurrence over the period 1954–86. This pattern is in addition to the general increase in [H+] over the same period attributed to acidic atmospheric deposition. Monthly means of [H+] also show differences between El Nino and non-El Nino years. Total annual runoff does not seem to be a controlling factor; the source and timing of storms are probably more important. Storms are usually from the west or northwest, but during El Nino years tropical-like storms from a more-southerly direction appear to carry acidic pollutants to the central Sierra Nevada.

Monthly Mean Sea-Level Variability Along the West Coast of North America

Abstract Linear statistical estimators are used to examine 29 years of nonseasonal, monthly-mean, tide-gauge sea-level data along the west coast of North America. The objective is exploration of the structure, and causes of nearshore ocean variability over time scales of months to years at 20 stations from Alaska to Mexico. North of San Francisco, 50–60% of the sea-level variability reflects a simple inverse barometric response to local atmospheric pressure. These inverted barometer effects account for only 10–15% of the variance at stations to the south. The dominant signal of inverse-barometer-corrected sea level represents a nearly uniform rise or fall of sea level everywhere along the eastern rim of the North Pacific. The interannual aspects of this large-scale sea-level variability are closely related to El Nino occurrences in the eastern tropical Pacific which appear to propagate poloward with phase speeds of ∼40 cm s−1. Higher frequency aspects of this large-scale sea-level variability appear to re...