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Asian Monsoon (asian + monsoon)
Selected AbstractsTime series analyses reveal transient relationships between abundance of larval anchovy and environmental variables in the coastal waters southwest of TaiwanFISHERIES OCEANOGRAPHY, Issue 2 2009CHIH-HAO HSIEH Abstract We investigated environmental effects on larval anchovy fluctuations (based on CPUE from 1980 to 2000) in the waters off southwestern Taiwan using advanced time series analyses, including the state-space approach to remove seasonality, wavelet analysis to investigate transient relationships, and stationary bootstrap to test correlation between time series. For large-scale environmental effects, we used the Southern Oscillation Index (SOI) to represent the El Niño Southern Oscillation (ENSO); for local hydrographic conditions, we used sea surface temperature (SST), river runoff, and mixing conditions. Whereas the anchovy catch consisted of a northern species (Engraulis japonicus) and two southern species (Encrasicholina heteroloba and Encrasicholina punctifer), the magnitude of the anchovy catch appeared to be mainly determined by the strength of Eng. japonicus (Japanese anchovy). The main factor that caused the interannual variation of anchovy CPUE might change through time. The CPUE showed a negative correlation with combination of water temperature and river runoff before 1987 and a positive correlation with river runoff after 1988. Whereas a significant negative correlation between CPUE and ENSOs existed, this correlation was driven completely by the low-frequency ENSO events and explained only 10% of the variance. Several previous studies on this population emphasized that the fluctuations of larval anchovy abundance were determined by local SST. Our analyses indicated that such a correlation was transient and simply reflected ENSO signals. Recent advances in physical oceanography around Taiwan showed that the ENSOs reduced the strength of the Asian monsoon and thus weakened the China Coastal Current toward Taiwan. The decline of larval anchovy during ENSO may be due to reduced China Coastal Current, which is important in facilitating the spawning migration of the Japanese anchovy. [source] Estimation of mean residence times of subsurface waters using seasonal variation in deuterium excess in a small headwater catchment in JapanHYDROLOGICAL PROCESSES, Issue 3 2007Naoki Kabeya Abstract We measured deuterium excess (d = ,D , 8,18O) in throughfall, groundwater, soil water, spring water, and stream water for 3 years in a small headwater catchment (Matsuzawa, 0·68 ha) in the Kiryu Experimental Watershed in Japan. The d value represents a kinetic effect produced when water evaporates. The d value of the throughfall showed a sinusoidal change (amplitude: 6·9, relative to Vienna standard mean ocean water (V-SMOW)) derived from seasonal changes in the source of water vapour. The amplitude of this sinusoidal change was attenuated to 1·3,6·9, V-SMOW in soil water, groundwater, spring water, and stream water. It is thought that these attenuations derive from hydrodynamic transport processes in the subsurface and mixing processes at an outflow point (stream or spring) or a well. The mean residence time (MRT) of water was estimated from d value variations using an exponential-piston flow model and a dispersion model. MRTs for soil water were 0,5 months and were not necessarily proportional to the depth. This may imply the existence of bypass flow in the soil. Groundwater in the hillslope zone had short residence times, similar to those of the soil water. For groundwater in the saturated zone near the spring outflow point, the MRTs differed between shallow and deeper groundwater; shallow groundwater had a shorter residence time (5,8 months) than deeper groundwater (more than 9 months). The MRT of stream water (8,9 months) was between that of shallow groundwater near the spring and deeper groundwater near the spring. The seasonal variation in the d value of precipitation arises from changes in isotopic water vapour composition associated with seasonal activity of the Asian monsoon mechanism. The d value is probably an effective tracer for estimating the MRT of subsurface water not only in Japan, but also in other East Asian countries influenced by the Asian monsoon. Copyright © 2006 John Wiley & Sons, Ltd. [source] Hydrology and water resources in monsoon Asia: a consideration of the necessity of establishing a standing research community of hydrology and water resources in the Asia Pacific regionHYDROLOGICAL PROCESSES, Issue 14 2003Katumi Musiake Abstract Hydrological and water resources issues appear very differently in different regions, and are strongly affected by geographical conditions. Hydrological knowledge and methodologies obtained in a specific region cannot necessarily be adapted to other regions. The purpose of this paper is to clarify one way to address adequately the regional characteristics of hydrology and water resources in monsoon Asia, especially the ,too much water' problems in the region. For this purpose, geomorphological factors, climatic factors and human intervention in the natural environment are taken into consideration as the three major factors governing the regional characteristics of the hydrology,water resources system. To identify geomorphological features macroscopically between the Asia Pacific region and other continental regions, the concepts ,tectonic zone' and ,stable region', which are two major subdivisions of continental masses in the world, are introduced. Also, a new climatic subdivision termed ,warm-humid' is proposed to express the abundant precipitation due to the Asian monsoon. Then, hydrological characteristics common or similar in ,warm-humid tectonic zones' in the Asia Pacific region, contrasted with those in stable regions, are enumerated together with the human intervention corresponding to these characteristics, and research targets peculiar to warm-humid tectonic zones are discussed. Finally, the establishment of a standing research community called ,Asia Pacific Association of Hydrology and Water Resources' is proposed to promote the exchange of operational knowledge and experience in water resources management, cooperative research activities, and professional education in the Asia Pacific region. Copyright © 2003 John Wiley & Sons, Ltd. [source] Sensitivity of the regional climate of East/Southeast Asia to convective parameterizations in the RegCM3 modelling system.INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 14 2008Part 1: Focus on the Korean peninsula Abstract This study investigates the capability of the regional climate model, RegCM3, to simulate fine-scale regional climate over a narrow peninsula or archipelago. The model is run in one-way double-nested mode with one mother domain and two nested domains. The mother domain encompasses the eastern and southern regions of Asia and adjacent oceans with a grid spacing of 60 km. The first nested domain focuses on the Korean peninsula and the second one covers the Philippine archipelago with a grid spacing of 20 km. The simulation spans a period of 5 years and 1 month, from November 2000 to December 2004. The sensitivity of the two convection schemes, namely, the Grell scheme (Grell) and the MIT-Emanuel scheme (EMU), is studied. Model results obtained with both the Grell and EMU show reasonable performance in capturing the seasonal variation and the spatial characteristics of the East Asian monsoon. However, the Grell simulation appears to have persistent cold and dry biases in the summer season. There is a definite improvement in these model deficiencies by the implementation of EMU. Although the temperature fields in the Grell and EMU simulations are essentially the same in terms of the spatial distribution, the EMU simulation is quantitatively in better agreement with the observed estimates, indicating a substantial reduction in the cold bias. Further, in comparison with the Grell simulation, the EMU simulation shows an improvement in the timing and amplitude of the rain band propagating northward. The spatial distributions of precipitation also have good quality, capturing the localized maxima over Korea. The frequency distributions of daily temperature and precipitation simulated by EMU are closer to observations than those of the Grell simulation. It is found that the convective precipitation derived from different convection parameterizations is a major contributor to the performance of the model in summer. Copyright © 2008 Royal Meteorological Society [source] Connections of Siberian snow onset dates to the following summer's monsoon conditions over Southeast AsiaINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 12 2005Hengchun Ye Abstract This is an exploratory study of possible links between the conditions of early season Eurasian snowfall and the following year's Southeast Asian summer monsoon. Forty years (1950,1995) of historical records are used to examine the statistical connections between early season snow cover onset dates over northern Eurasia and the following year's summer monsoon over Southeast Asia. We found that the time of snow onset is significantly associated with warm season rainfall over Southeast Asia. The most persistent connection is between northeastern Siberian snow onsets and summer monsoon strength over India and northeastern China. This connection seems to be more clearly shown during the mature stage and monsoon withdrawal and is reflected in all three aspects of monsoon characteristics. In other words, the earlier snow cover onset (more snow cover during the early season) over northeastern Siberia, the more precipitation and moisture convergence, the higher prevalence of a southwesterly monsoon wind, and the later monsoon withdrawal over Southeast Asia. The revealed connection is likely through atmospheric circulation associated with early season land surface snow cover processes independent of El Ñino conditions. The authors suggest that more studies are needed to fully understand the circuitous connections between Eurasian snowfall and the Southeastern Asian monsoon. Copyright © 2005 Royal Meteorological Society. [source] Timing and style of Late Pleistocene glaciation in the Queer Shan, northern Hengduan Mountains in the eastern Tibetan Plateau,JOURNAL OF QUATERNARY SCIENCE, Issue 6 2010Liubing Xu Abstract Glacial landforms and sediments provide evidence for the existence of two Late Pleistocene major glacial advances in the Queer Shan, northern Hengduan Mountains in the eastern Tibetan Plateau. In the current study, optically stimulated luminescence and electron spin resonance dating results reveal that the two glacial advances occurred during Marine Isotope Stage (MIS) 3 and the Last Glacial Maximum (LGM) in MIS 2, respectively. Geomorphic evidence shows that the glacial advance during MIS 3 was more extensive than that in MIS 2. This glacial advance is synchronous with other glaciated areas in the Himalaya and Tibet, but contrasts with global ice volumes that reached their maximum extent during the LGM. Glaciers in the Queer Shan are of the summer accumulation type and are mainly fed by precipitation from the south Asian monsoon. Palaeoclimate proxies show that during MIS 3 the south Asian monsoon strengthened and extended further north into the Tibetan Plateau to supply more precipitation as snow at high altitudes. This in turn led to positive glacier mass balances and caused glaciers to advance. However, during the LGM, despite cooler temperature than in MIS 3, the weakened south Asian monsoon and the associated reduced precipitation were not as favourable for glacier expansion as in MIS 3. Copyright © 2010 John Wiley & Sons, Ltd. [source] North Atlantic forcing of climate and its uncertainty from a multi-model experimentTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 601 2004M. J. Rodwell Abstract To understand recent climate change in the North Atlantic region and to produce better climate forecasts with uncertainty estimates it is important to determine the atmospheric ,response' to Atlantic sea-surface temperature (SST) forcing. There have been conflicting results regarding the strength, character and tropical-versus-extratropical origin of this response. For model-based studies, this may indicate differing sensitivities to Atlantic SST, but the comparison is complicated by changes in experimental design. Here, a highly controlled experiment with five atmospheric models is undertaken. The influence of realistic (if reasonably strong) and optimally chosen North Atlantic (equator to 70°N) SST anomalies is isolated. Unexpected global agreement between the models is found (e.g. the North Atlantic Oscillation (NAO), Eurasian temperatures, rainfall over the Americas and Africa, and the Asian monsoon). The extratropical North Atlantic region response appears to be associated with remote Caribbean and tropical Atlantic SST anomalies, and with local forcing. Some features such as the European winter-temperature response would be stronger than atmospheric ,noise' if the prescribed SST anomalies persisted for just two years. More generally, Atlantic air,sea interaction appears to be important for climate variability on the 30-year timescale and, thus, to be important in the climate-change context. The multi-model mean response patterns are in reasonable agreement with observational estimates, although the model response magnitudes may be too weak. The similarity between their responses helps to reconcile models. Inter-model differences do still exist and these are discussed and quantified. © Crown copyright, 2004. [source] Trends and abrupt changes of precipitation maxima in the Pearl River basin, ChinaATMOSPHERIC SCIENCE LETTERS, Issue 2 2009Q. Zhang Abstract We applied the Mann-Kendall (MK) test and Bayesian model to systematically explore trends and abrupt changes of the precipitation series in the Pearl River basin. The results showed that no significant trends were detected for annual precipitation and summer or winter precipitation totals. Significant negative trends were identified for the number of rainy days across the Pearl River basin; significant positive trends were observed regarding precipitation intensity (PI). In particular, the precipitation totals and frequencies of extremely high precipitation events are subject to significant positive trends. In addition, the number of extremely low precipitation events was also increasing significantly. Factors affecting the changes in precipitation patterns are the weakening Asian monsoon and consequently increasing moisture transport to Southern China and the Pearl River basin. In summary, the main findings of this study are: (1) increased precipitation variability and high-intensity rainfall was observed though rainy days and low-intensity rainfall have decreased, and (2) the amount of rainfall has changed little but its variability has increased over the time interval divided by change points. These finds indicate potentially increased risk for both agriculture and in locations subject to flooding, both urban and rural, across the Pearl River basin. Copyright © 2009 Royal Meteorological Society [source] East Asian monsoon instability at the stage 5a/4 transitionBOREAS, Issue 2 2002SHANGFA XIONG The physics involved in the abrupt climate changes of the late Quaternary have eluded paleoclimatologists for many years. More paleoclimatic records characteristic of different elements of the global climate system are needed for better understanding of the cause-feedback relationships in the system. The East Asian monsoon is an important part of the global climate system and the mechanical links between the East Asian monsoon and other climatic elements around the world may hold a key to our knowledge of abrupt climate changes in East Asia and probably over a larger part of the globe. Previous studies have detected millennial-scale winter monsoon oscillations during the last glaciation and probably also during the last interglaciation in loess sequences across China. However, less attention has been paid to the abrupt summer monsoon changes and the stage 5a/4 transition, an important period for the evolution of the East Asian monsoon when the global climate shifted towards the last glaciation. Here we report on two loess sections from eastern China which were dated using a thermoluminescence (TL) technique. The pedogenic and other sediment parameters suggest that the summer monsoon experienced a two-step abrupt retreat at the stage 5a/4 transition. The variations in the proxies for the winter monsoon are synchronized with the summer monsoon proxies during this brief interval, implying a direct and immediate link between high latitude and low latitude mechanisms. These changes may be correlated with similar climatic oscillations observed in the North Atlantic, Europe and Antarctica, raising the possibility that the forcing factors that induced these changes are global in extent. [source] Observational relationships between summer and winter monsoons over East Asia.INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2005Part II: results Abstract Using the framework presented in part I of this study, three possible summer-to-winter monsoon and four possible winter-to-summer monsoon relationships are identified. A generalized relationship between summer and winter monsoons is virtually non-existent, and some of the possible relationships are in fact tied to the influence of the El Niño,southern oscillation (ENSO). Indeed, relationships between summer and winter monsoons are specific in terms of both the winter monsoon strength and the ENSO conditions. It is found that the strength of winter monsoon is unlikely to be an important forcing regarding the possible winter-to-summer monsoon relationships, since the summer monsoon is unlikely to be weak following a non-ENSO-coupled winter monsoon, regardless of the winter monsoon strength. On the other hand, possible summer-to-winter relationships are noted only when the summer monsoon is not weak, regardless of the ENSO condition. An alternation or opposite tendency in the summer monsoon strength is noted between the onset year (tends to be unlikely weak) and the following year (tends to be unlikely strong) of an El Niño. Therefore, certain possible relationships between summer and winter monsoons are obvious when the winter monsoon tends to be weaker during the mature phase of an El Niño. For a La Niña, the signature in the summer monsoon strength is less clear, as indicated from the assessment of summer monsoon indices. Nevertheless, when the winter monsoon tends to be strong when coupled with a La Niña, the following summer monsoon also tends to be weaker. A biennial alternation of the summer and winter monsoons is noted, i.e. that a stronger summer monsoon precedes a weaker winter monsoon and a weaker winter monsoon is followed by a stronger summer monsoon. This biennial alternation is associated with a transition of ENSO warm phase to ENSO cold phase, representing the biennial signal in the interannual variability of the monsoons as well as in ENSO. Concurrent with this biennial alternation is an evident variation in the subtropical-high strength. It appears that the commonly recognized tropical biennial oscillation (TBO) is not tied to the biennial signal in the interannual variability of the East Asian monsoons, because the TBO is constituted by a strong (weak) summer monsoon followed by strong (weak) winter monsoon process. Furthermore, it is suggested that a complete biennial oscillation in the interannual variability of the monsoons is not observed because of the breakdown of a cycle (or oscillation) in the summer monsoon following a La Niña onset. Copyright © 2005 Royal Meteorological Society. [source] | ||||||||||