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Winter Monsoon (winter + monsoon)

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Earth and Environmental Science100%

Selected Abstracts

Observational relationships between summer and winter monsoons over East Asia.

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2005
Part I: Basic framework
Abstract This paper is the first of a two-part study to investigate the possible relationships between summer and winter monsoons over East Asia during the period 1958 to 1999. It documents the approach employed in the study. Assuming the existence of relationships, the central theme of the study is to answer the questions: Is there evidence for the relationships and, if so, what are the relationships? In particular, the approach used to interpret the available evidence to make inferences about the conditions of the summer monsoon is described. Six winter monsoon categories are defined in terms of the monsoon strength and the conditions of the El Niño,southern oscillation. The conditions of the summer monsoons preceding and following each winter monsoon category are assessed to identify the possible summer-to-winter monsoon and winter-to-summer monsoon relationships respectively. Summer monsoons are classified into unlikely strong (notS) or unlikely weak (notW) according to the bias in the relative occurrence of positive and negative anomalies of several summer monsoon indices. The rainfall condition over China and the characteristics of the subtropical high are also used to provide supplementary evidence for the summer monsoon strength and to describe the accompanying synoptic situations. Copyright © 2005 Royal Meteorological Society. [source]

Observational relationships between summer and winter monsoons over East Asia.

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2005
Part 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]

Stable isotope records of plant cover change and monsoon variation in the past 2200 years: evidence from laminated stalagmites in Beijing, China

BOREAS, Issue 2 2003
JU ZHI HOU
Two stalagmites collected from the Shihua cave in the southwestern suburb of Beijing were dated by annual layer counting. The results are consistent with thermal ionization mass spectrometry 230Th dating. Stable carbon isotope variation of stalagmites is dominated by plant cover change, which largely reflects climate change and monsoon variation. Oxygen isotopes are mainly affected by precipitation, which is related to summer and winter monsoon intensity. The combination of carbon and oxygen isotopes can therefore be a proxy of plant cover change and monsoon variation. Our stable isotope results show that lower carbon isotope values of the stalagmites between 200 BC and AD 1000 probably imply dense plant cover and an episode dominated by humid summer monsoon. From ,1000 to AD 1450, the dominant monsoon alternated between the winter monsoon and the summer monsoon. Since ,AD 1450, a significant jump in carbon isotope ratios and increasing oxygen isotope ratios has been demonstrated, indicating less plant cover and the probable dominance of dry winter monsoon. The results are consistent with historical documents of the region. [source]

East Asian monsoon instability at the stage 5a/4 transition

BOREAS, Issue 2 2002
SHANGFA 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 2005
Part I: Basic framework
Abstract This paper is the first of a two-part study to investigate the possible relationships between summer and winter monsoons over East Asia during the period 1958 to 1999. It documents the approach employed in the study. Assuming the existence of relationships, the central theme of the study is to answer the questions: Is there evidence for the relationships and, if so, what are the relationships? In particular, the approach used to interpret the available evidence to make inferences about the conditions of the summer monsoon is described. Six winter monsoon categories are defined in terms of the monsoon strength and the conditions of the El Niño,southern oscillation. The conditions of the summer monsoons preceding and following each winter monsoon category are assessed to identify the possible summer-to-winter monsoon and winter-to-summer monsoon relationships respectively. Summer monsoons are classified into unlikely strong (notS) or unlikely weak (notW) according to the bias in the relative occurrence of positive and negative anomalies of several summer monsoon indices. The rainfall condition over China and the characteristics of the subtropical high are also used to provide supplementary evidence for the summer monsoon strength and to describe the accompanying synoptic situations. Copyright © 2005 Royal Meteorological Society. [source]

Observational relationships between summer and winter monsoons over East Asia.

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2005
Part 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]

Mollusk record of millennial climate variability in the Loess Plateau during the Last Glacial Maximum

BOREAS, Issue 1 2002
NAIQIN WU
A high-resolution terrestrial mollusk record from the Loess Plateau of China has been studied to characterize climate variability during the Last Glacial Maximum (LGM). The rapid successions in mollusk taxa in the Weinan loess sequence reveal that climate changes occurred at least four times in this period. In the loess region, millennia-scale climate fluctuations existed, as documented in the grain size and weathering intensity records. Our results show such millennia-scale fluctuations reflecting changes in both temperature and precipitation, rather than a simple cold and warm alternation. Changes in temperature and precipitation were not in phase during the LGM. Temperature varied earlier than precipitation, which could have been the effect of winter and summer monsoon interactions. Our data also reveal that the East Asian summer monsoons could reach the southeast part of the Loess Plateau during the whole of the LGM. The intensification of winter monsoons during the LGM led to short duration of summer monsoons annually impacting on the Loess Plateau, but the intrinsic intensity of summer monsoons would not have changed significantly, thus providing the thermo-hydrological conditions for temperate-humidiphilou s mollusks to persistently grow and develop in the glacial age. [source]