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Warm Pool (warm + pool)
Selected AbstractsEl Niño, climate change, and Southern African climateENVIRONMETRICS, Issue 4 2001Simon J. Mason Abstract The El Niño phenomenon involves a large-scale warming of the equatorial eastern and central Pacific Ocean. Recent developments in the El Niño,Southern Oscillation (ENSO) phenomenon have raised concerns about climate change. In this review paper, these recent developments are critically assessed and forecasts of possible future changes are reviewed. Since the late-1970s, El Niño episodes have been unusually recurrent, while the frequency of strong La Niña events has been low. Prolonged/recurrent warm event conditions of the first half of the 1990s were the result of the persistence of an anomalously warm pool near the date line, which, in turn, may be part of an abrupt warming trend in tropical sea-surface temperatures that occurred in the late-1970s. The abrupt warming of tropical sea-surface temperatures has been attributed to the enhanced-greenhouse effect, but may be indicative of inter-decadal variability: earlier changes in the frequency of ENSO events and earlier persistent El Niño and La Niña sequences have occurred. Most forecasts of ENSO variability in a doubled-CO2 climate suggest that the recent changes in the tropical Pacific are anomalous. Of potential concern, however, is a possible reduction in the predictability of ENSO events given a warmer background climate. El Niño events usually are associated with below-normal rainfall over much of southern Africa. Mechanisms for this influence on southern African climate are discussed, and the implications of possible changes in ENSO variability on the climate of the region are assessed. Recent observed changes in southern African climate and their possible relationships with trends in ENSO variability are investigated. The El Niño influence on rainfall over southern Africa occurs largely because of a weakening of tropical convection over the subcontinent. A warming of the Indian Ocean during El Niño events appears to be important in providing a teleconnection from the equatorial Pacific Ocean. The abrupt warming of the tropical Pacific and Indian oceans in the late-1970s is probably partly responsible for increasing air temperatures over southern Africa, and may have contributed to a prolongation of predominantly dry conditions. A return to a wet phase appears to have occurred, despite the persistence of anomalously high sea-surface temperatures associated with the late-1970s warming, and a record-breaking El Niño in 1997/98. Copyright © 2001 John Wiley & Sons, Ltd. [source] Secular and multidecadal warmings in the North Atlantic and their relationships with major hurricane activityINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 2 2010David B. Enfield Abstract Analysis of recent literature finds weaknesses in arguments to the effect that the Atlantic multidecadal oscillation (AMO),roughly 50,90 year fluctuations in North Atlantic sea surface temperatures,is externally forced by anthropogenic aerosols and greenhouse gases rather than an internal climate mode, plus indications from other sources that the contrary may be true. We are led to the conclusion that the AMO is probably comprised of both natural and anthropogenic forcing in ways that preclude a physically based separation of the two, using the limited historical data sets. A straightforward quadratic fitting of trend to temperature data accounts for some of the 20th century nonlinearity in secular warming and separates the secular and multidecadal components of variability without inherent assumptions about the nature of the multidecadal fluctuations. Doing this shows that the 20th century secular ocean warming in the North Atlantic is about equal to the peak-to-peak amplitude of the multidecadal fluctuations. However, over the last quarter-century (1975,2000) the most recent multidecadal warming has been almost three times the secular sea surface temperature (SST) increase over the main development region (MDR) for major Atlantic hurricanes. In the last quarter-century the multidecadal increase in late summer Atlantic warm pool (AWP) size (area of SSTs in excess of 28 °C) has been 36%, and the secular increase, 14%. Projections to the year 2025 show that the cumulative change in summer warm pool size since 1975 will depend critically on whether a subsequent cooling in the multidecadal cycle occurs, comparable to the warming between 1975 and 2000 AD. This places a high premium on understanding to what extent the AMO is a man-made or a natural phenomenon. Copyright © 2009 Royal Meteorological Society [source] Trend and variability of China precipitation in spring and summer: linkage to sea-surface temperaturesINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 13 2004Fanglin Yang Abstract Observational records in the past 50 years show an upward trend of boreal-summer precipitation over central eastern China and a downward trend over northern China. During boreal spring, the trend is upward over southeastern China and downward over central eastern China. This study explores the forcing mechanism of these trends in association with the global sea-surface temperature (SST) variations on the interannual and interdecadal time scales. Results based on singular value decomposition (SVD) analyses show that the interannual variability of China precipitation in boreal spring and summer can be well defined by two centres of action for each season, which are covarying with two interannual modes of SSTs. The first SVD modes of precipitation in spring and summer, which are centred in southeastern China and northern China respectively, are linked to an El Niño,southern oscillation (ENSO)-like mode of SSTs. The second SVD modes of precipitation in both seasons are confined to central eastern China, and are primarily linked to SST variations over the warm pool and the Indian Ocean. Features of the anomalous 850 hPa winds and 700 hPa geopotential height corresponding to these modes support a physical mechanism that explains the causal links between the modal variations of precipitation and SSTs. On the decadal and longer time scale, similar causal links are found between the same modes of precipitation and SSTs, except for the case of springtime precipitation over central eastern China. For this case, while the interannual mode of precipitation is positively correlated with the interannual variations of SSTs over the warm pool and Indian Ocean, the interdecadal mode is negatively correlated with a different SST mode, i.e. the North Pacific mode. The latter is responsible for the observed downward trend of springtime precipitation over central eastern China. For all other cases, both the interannual and interdecadal variations of precipitation can be explained by the same mode of SSTs. The upward trend of springtime precipitation over southeastern China and downward trend of summertime precipitation over northern China are attributable to the warming trend of the ENSO-like mode. The recent frequent summertime floods over central eastern China are linked to the warming trend of SSTs over the warm pool and Indian Ocean. Copyright © 2004 Royal Meteorological Society [source] Momentum transport processes in the stratiform regions of mesoscale convective systems over the western Pacific warm poolTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 616 2006David B. Mechem Abstract Momentum transport by the stratiform components of mesoscale convective systems (MCSs) during the Tropical Ocean,Global Atmosphere Coupled Ocean,Atmosphere Response Experiment in December 1992 is investigated using a cloud-resolving model. The mesoscale momentum transport by the stratiform regions of MCSs is examined in two distinct large-scale flow regimes associated with the intraseasonal oscillation over the western Pacific warm pool. Model simulations for 14 December 1992 characterize the ,westerly onset' period, which has relatively weak low-level westerlies with easterlies above. Simulations for 23,24 December represent the ,strong westerly' regime, when westerlies extend from the upper troposphere to the surface, with a jet 2,3 km above the surface. In the westerly onset simulation, the extensive stratiform region of a MCS contained a broad region of descent that transported easterly momentum associated with the mid-level easterly jet downward. Thus, the stratiform regions acted as a negative feedback to decrease the large-scale mean westerly momentum developing at low levels. In the strong westerly regime, the mesoscale downward air motion in the stratiform regions of large MCSs transported westerly momentum downward and thus acted as a positive feedback, strengthening the already strong westerly momentum at low levels. Momentum fluxes by the mesoscale stratiform region downdraughts are shown to have a systematic and measurable impact on the large-scale momentum budget. Copyright © 2006 Royal Meteorological Society. [source] Response of the Asian summer monsoon to changes in El Niño propertiesTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 607 2005H. Annamalai Abstract Diagnostics from observed precipitation and National Centers for Environmental Prediction,National Center for Atmospheric Research re-analysis products reveal that after the 1976,77 climate shift in the Pacific there was a dramatic change in the response of the Indian summer monsoon (ISM) to El Niño, particularly during the months of July and August. Based on 1950,75 (PRE76) and 1977,2001 (POST76) El Niño composites: the western North Pacific monsoon (WNPM) was stronger than normal in both periods; the ISM was weaker than normal during the entire monsoon season in PRE76, but in POST76 was weaker only during the onset and withdrawal phases. In terms of observed sea surface temperature (SST) during July,August, the major differences between the two periods are the presence of cold SST anomalies over the Indo,Pacific warm pool and the intensity of warm SST anomalies in the central Pacific in POST76. The effect of these differences on the ISM is investigated in a suite of experiments with an Atmospheric General Circulation Model (AGCM) that has a realistic monsoon precipitation climatology. Separate ten-member ensemble simulations with the AGCM were conducted for PRE76 and POST76 El Niño events with SST anomalies inserted as follows: (i) tropical Indo,Pacific (TIP), (ii) tropical Pacific only (TPO), and (iii) tropical Indian Ocean only (TIO). Qualitatively, TPO solutions reproduce the observed differences in the monsoon response in both periods. Specifically, during July,August of POST76 the cold SST anomalies in conjunction with remote subsidence suppress precipitation (3,5 mm day,1) over the maritime continent and equatorial central Indian Ocean. Inclusion of Indian Ocean SST anomalies in the TIP runs further suppresses precipitation over the entire equatorial Indian Ocean. The low-level anticyclonic circulation anomalies that develop as a Rossby-wave response to these convective anomalies increase the south-westerlies over the northern Indian Ocean, and favour a stronger ISM and WNPM. During PRE76 the non-occurrence of cold SST anomalies over the Indo,Pacific warm pool reinforces El Niño's suppression on the ISM. In contrast, TIO solutions show a reduced ISM during July,August of POST76; the solutions, however, show a significant effect on the WNPM during both PRE76 and POST76 periods. It is argued that SSTs over the entire tropical Indo,Pacific region need to be considered to understand the El Niño Southern Oscillation,monsoon linkage, and to make predictions of rainfall over India and the western North Pacific. Copyright © 2005 Royal Meteorological Society [source] Field Play: The Normalization of an Alternate Cognizance in Seriously Ill ChildrenANTHROPOLOGY OF CONSCIOUSNESS, Issue 1-2 2000Kelvin Saxton Children who grow up with a life-threatening illness live and face death in a way that is foreign to those of us who have reached adulthood in relative health. The experiences that form their identities create a range of knowledge, and processes for acquiring that knowledge, quite apart from the mainstream. In the pace of its acquisition, and the depth of its content, this knowledge is hard for the rest of us to comprehend. Indeed, the primary symptom of this alternate cognizance is that it sets these children apart from their families, peers, and greater communities. The child as a whole is marginalized in interpersonal relations by essentializing the child as the illness. The experience of the illness itself further isolates the child. Through firsthand observation, we find that the Hole in the Wall Gang summer camps provide a nearly unique environment for the normalization of this alternate cognizance. At camp, all those things that set them apart from the rest of the world mark them as normal members of a society. Other children share their physical qualities, have similar experiences and immediately understand their perspective on life. Small adjustments to social and physical environments have a lasting effect. A warm pool to swim in, a caring touch, an open smile,the children take the memory of these with them when they leave. They begin to understand that they are a desired part of a large and varied community. A new definition of normal is created and they are included. [source] | ||||||||||