Collm (52°N, 15°E) midlatitude mesosphere/lower thermosphere (MLT) zonal winds are investigated with respect to a possible influence of the Southern Oscillation (SO). It is found that in winter the prevailing wind is positively correlated with the Southern Oscillation index (SOI), which qualitatively fits to the response of the low-latitude stratosphere on the SO. In summer, however, there is a negative correlation between MLT zonal winds and SOI. A possible mechanism, which includes slightly enhanced planetary wave propagation to the MLT in summers of low SOI is discussed. / Windmessungen aus Collm (52°N, 15°E) wurden hinsichtlich eines möglichen Einflusses der Southern Oscillation (SO) in ihnen untersucht. Es zeigt sich, dass im Winter der mittlere Zonalwind positiv mit dem \"Southern Oscillation Index\" SOI korreliert ist, was qualitativ mit der Reaktion der Stratosphäre auf ENSO übereinstimmt. Im Sommer findet sich jedoch ein negativer Zusammenhang zwischen hochatmosphärischem Zonalwind und SOI. Ein möglicher Mechanismus, der die Ausbreitung planetarer Wellen beinhaltet, wird diskutiert.

No description available.

El Ni??o-Southern Oscillation (ENSO) is the most important coupled ocean-atmospheric phenomenon to cause global climate variability on interannual time scales. Efforts to understand recent, apparently anomalous ENSO behaviour are hampered by the lack of long, high-quality climate records. While instrumental data generally covers the past 150 years, record length is insufficient for the assessment of past changes in the frequency, magnitude, and duration of ENSO. Here, multiproxy networks of high-resolution tree-ring, coral, ice and documentary records derived from eastern and western Pacific ENSO ???centres of action??? are analysed (A.D. 1525-2002). Considerable improvements in ENSO reconstruction are achieved from expanding the use of records from the western Pacific. In particular, ~500 years of a continuous 3,722 year ENSO sensitive tree-ring record from New Zealand is introduced. Although extreme ENSO events are seen throughout a 478-year discrete event analysis, 43% of extreme, 20% of very strong and 28% of all protracted ENSO events occur within the 20th century. Principal component analysis was used to extend instrumental records of the Southern Oscillation Index (SOI) Ni??o 3.4 Sea Surface Temperature (Ni??o 3.4 SST) and a newly developed coupled ocean-atmospheric ENSO index (CEI) by 347 years. Significantly, of the three indices reconstructed here, CEI reconstructions were largely found to be the best predictors of ENSO. The results suggest that ENSO may be more effectively characterised using a coupled ocean-atmosphere index, particularly for December-May periods. Compared to the pre-instrumental period, the late 19th and early 20th centuries indicate a clear trend toward increased ENSO variability over the past 150 years. Significantly, spectral analysis of reconstructed indices reveals a marked change in the frequency and intensity of ENSO beginning ~A.D. 1850, coinciding with the end of the Little Ice Age and the boom in global industrialisation. This suggests that ENSO may operate differently under natural (pre-industrial) and anthropogenically influenced background states. This study asserts that recent ENSO variability appears anomalous in the context of the past five centuries. Given the considerable socio-economic impacts of ENSO events, future investigation into the implications an increasingly anthropogenically-warmed world may have on ENSO is vital.

El Ni??o-Southern Oscillation (ENSO) is the most important coupled ocean-atmospheric phenomenon to cause global climate variability on interannual time scales. Efforts to understand recent, apparently anomalous ENSO behaviour are hampered by the lack of long, high-quality climate records. While instrumental data generally covers the past 150 years, record length is insufficient for the assessment of past changes in the frequency, magnitude, and duration of ENSO. Here, multiproxy networks of high-resolution tree-ring, coral, ice and documentary records derived from eastern and western Pacific ENSO ???centres of action??? are analysed (A.D. 1525-2002). Considerable improvements in ENSO reconstruction are achieved from expanding the use of records from the western Pacific. In particular, ~500 years of a continuous 3,722 year ENSO sensitive tree-ring record from New Zealand is introduced. Although extreme ENSO events are seen throughout a 478-year discrete event analysis, 43% of extreme, 20% of very strong and 28% of all protracted ENSO events occur within the 20th century. Principal component analysis was used to extend instrumental records of the Southern Oscillation Index (SOI) Ni??o 3.4 Sea Surface Temperature (Ni??o 3.4 SST) and a newly developed coupled ocean-atmospheric ENSO index (CEI) by 347 years. Significantly, of the three indices reconstructed here, CEI reconstructions were largely found to be the best predictors of ENSO. The results suggest that ENSO may be more effectively characterised using a coupled ocean-atmosphere index, particularly for December-May periods. Compared to the pre-instrumental period, the late 19th and early 20th centuries indicate a clear trend toward increased ENSO variability over the past 150 years. Significantly, spectral analysis of reconstructed indices reveals a marked change in the frequency and intensity of ENSO beginning ~A.D. 1850, coinciding with the end of the Little Ice Age and the boom in global industrialisation. This suggests that ENSO may operate differently under natural (pre-industrial) and anthropogenically influenced background states. This study asserts that recent ENSO variability appears anomalous in the context of the past five centuries. Given the considerable socio-economic impacts of ENSO events, future investigation into the implications an increasingly anthropogenically-warmed world may have on ENSO is vital.

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (p. [181]-185).

Thesis (M.S.)--University of California, Santa Cruz, 1996. / Typescript. Includes bibliographical references (leaves 77-78).

Recent scientific investigations of sub-millennial paleoceanographic variability have attempted to use the population statistics of single planktic foraminiferal δ18O in an attempt to characterize the variability of high-frequency signals such as the El Niño Southern Oscillation (ENSO). However, this approach is complicated by the relatively short lifespan of individual foraminifera (~2-4 weeks) compared to the time represented by a sediment sample of a marine core (decades to millennia). The resolving ability of individual foraminiferal analyses (IFA) is investigated through simulations on an idealized virtual sediment sample. We focus on ENSO-related sea-surface temperatures (SST) anomalies in the tropical Pacific Ocean (Niño3.4 region). We constrain uncertainties on the range and standard deviation associated with the IFA technique using a bootstrap Monte Carlo approach. Sensitivity to changes in ENSO amplitude and frequency and the influence of the seasonal cycle on IFA are investigated through the construction of synthetic time series containing different characteristics of variability. We find that the standard deviation and range of the population of individual foraminiferal δ18O may be used to detect ENSO amplitude changes at particular thresholds (though the uncertainty in range is much larger than in standard deviation); however, it is highly improbable that IFA can resolve changes in ENSO frequency. We also determine that the main driver of the IFA signal is ENSO amplitude as opposed to changes in the seasonal cycle although this is specific to Niño3.4 where the SST response to ENSO is maximal. Our results suggest that rigorous uncertainty analysis is crucial to the proper interpretation of IFA data and should become a standard in individual foraminiferal studies. / text

Thesis (Ph. D.)--University of Washington, 1999. / Includes bibliographical references (leaves 137-142).

Thesis (Ph. D.)--University of California, Los Angeles, 1997. / Vita. Includes bibliographical references (leaves 200-208).

Thesis (Ph. D.)--Oregon State University, 1988. / Typescript (photocopy). One mounted photograph. Includes bibliographical references (leaves 272-287).