scholarly journals Variability of summer precipitation over Eastern China during the last millennium

2009 ◽  
Vol 5 (2) ◽  
pp. 129-141 ◽  
Author(s):  
C. Shen ◽  
W.-C. Wang ◽  
Y. Peng ◽  
Y. Xu ◽  
J. Zheng
Keyword(s):  
Eastern China ◽  
Summer Precipitation ◽  
Internal Variability ◽  
Last Millennium ◽  
Model Data ◽  
Proxy Data ◽  
The Past ◽  
Temperature Regimes ◽  
Temporal And Spatial Variability ◽  
Temporal And Spatial

Abstract. We use measurements of recent decades, 1500-yr proxy data, and millennium model simulations with a variety of climate facings to study the temporal and spatial variability of summer precipitation over eastern China. Spectral analysis of the proxy data using multi-taper method reveals three statistically significant bidecadal (15–35-yr), pendadecadal (40–60-yr), and centennial (65–170-yr) oscillation bands. The results of wavelet filtering show that the amplitudes of these bands vary substantially through time depending on the temperature regimes. Weak centennial oscillation and strong pentadecadal oscillation occur in warm conditions, whereas both the centennial and pentadecadal oscillations are strong in cold conditions. A model/data intercomparison suggests that pentadecadal and bidecadal oscillations could be associated with internal variability of the climate system. It is also found that the increased frequency of drought-in-north/flood-in-south spatial pattern over eastern China during the last two decades is unusual in the past five centuries.

scholarly journals Variability of summer precipitation over eastern China during the last millennium

2008 ◽  
Vol 4 (3) ◽  
pp. 611-643 ◽  
Author(s):  
C. Shen ◽  
W.-C. Wang ◽  
Y. Peng ◽  
Y. Xu ◽  
J. Zheng
Keyword(s):  
Eastern China ◽  
Summer Precipitation ◽  
Internal Variability ◽  
Model Data ◽  
Solar Forcing ◽  
Proxy Data ◽  
The Past ◽  
Temperature Regimes ◽  
Temporal And Spatial Variability ◽  
Temporal And Spatial

Abstract. We use measurements of recent decades, 1500-yr proxy data, and millennium model simulations with a variety of climate facings to study the temporal and spatial variability of summer precipitation over eastern China. Spectral analysis of the proxy data using multi-taper method reveals three statistically significant bidecadal (15–35-yr), pendadecadal (40–60-yr), and centennial (65–170-yr) oscillation bands. The results of wavelet filtering show that the amplitudes of these bands vary substantially through time depending on the temperature regimes. Weak centennial oscillation and strong pentadecadal oscillation occur in warm conditions, whereas the oscillations are both strong in cold conditions. A model/data intercomparison suggests that the centennial oscillation might be linked to the fluctuation of solar forcing (Gleissberg cycle), and the pentadecadal and bidecadal oscillations could be associated with internal variability of the climate system. It is also found that the increased frequency of drought-in-north/flood-in-south spatial pattern over eastern China during the last two decades is unusual in the past five centuries.

scholarly journals Modeling of severe persistent droughts over eastern China during the last millennium

2014 ◽  
Vol 10 (3) ◽  
pp. 1079-1091 ◽  
Author(s):  
Y. Peng ◽  
C. Shen ◽  
H. Cheng ◽  
Y. Xu
Keyword(s):  
Southern Oscillation ◽  
Asian Summer Monsoon ◽  
Eastern China ◽  
Volcanic Eruptions ◽  
Internal Variability ◽  
Last Millennium ◽  
Proxy Data ◽  
Monsoon Variability ◽  
Primary Driver ◽  
Climate Forcings

Abstract. We use proxy data and modeled data from 1000 year model simulations with a variety of climate forcings to examine the occurrence of severe event of persistent drought over eastern China during the last millennium and diagnose the mechanisms. Results show that the model was able to roughly simulate most of these droughts over the study area during the last millennium such as those that occurred during the periods of 1123–1152, 1197–1223, 1353–1363, 1428–1449, 1479–1513, and 1632–1645. Our analyses suggest that these six well-captured droughts may caused by the East Asian summer monsoon (EASM) weakening. Study on the wavelet transform and spectral analysis reveals these events occurred all at the statistically significant 15–35-year timescale. A modeled data intercomparison suggests the possibility that solar activity may be the primary driver in the occurrence of the 1129–1144, 1354–1365, 1466–1491 and 1631–1648 droughts as identified by the model. However another possibility that these events may be related to internal variability cannot be excluded. Although the El Niño–Southern Oscillation (ENSO) plays an important role in monsoon variability, a temporally consistent relationship between the droughts and SST pattern in the Pacific Ocean could not be found either in the modeled or proxy data. Our analyses also indicate that large volcanic eruptions play a role as an amplifier in the drought of 1631–1648 and caused the droughts of 1830–1853 and 1958–1976, which was identified by the model.

scholarly journals The Paleoclimate reanalysis project

2015 ◽  
Vol 11 (5) ◽  
pp. 4159-4204 ◽  
Author(s):  
S. A. Browning ◽  
I. D. Goodwin
Keyword(s):  
Data Assimilation ◽  
World View ◽  
Internal Variability ◽  
Temporal Variations ◽  
Global Ocean ◽  
Model Data ◽  
Proxy Data ◽  
The Past ◽  
Spatial Fields ◽  
Past Millennium

Abstract. Recent advances in proxy-model data assimilation have made feasible the development of proxy-based reanalyses. Proxy-based reanalyses aim to make optimum use of both proxy and model data while presenting paleoclimate information in an accessible format – they will undoubtedly play a pivotal role in the future of paleoclimate research. In the Paleoclimate Reanalysis Project (PaleoR) we use "off-line" data assimilation to constrain the CESM1 (CAM5) Last Millennial Ensemble (LME) simulation with a globally distributed multivariate proxy dataset, producing a decadal resolution reanalysis of the past millennium. Discrete time periods are "reconstructed" by using anomalous (±0.5σ) proxy climate signals to select an ensemble of climate state analogues from the LME. Prior to assimilation the LME simulates internal variability that is temporally inconsistent with information from the proxy archive. After assimilation the LME is highly correlated to almost all included proxy data, and dynamical relationships between modelled variables are preserved; thus providing a "real-world" view of climate system evolution during the past millennium. Unlike traditional regression based approaches to paleoclimatology, PaleoR is unaffected by temporal variations in teleconnection patterns. Indices representing major modes of global ocean–atmosphere climate variability can be calculated directly from PaleoR spatial fields. PaleoR derived ENSO, SAM, and NAO indices are consistent with observations and published multiproxy reconstructions. The computational efficiency of "off-line" data assimilation allows easy incorporation and evaluation of new proxy data, and experimentation with different setups and model simulations. PaleoR spatial fields can be viewed online at http://climatefutures.mq.edu.au/research/themes/marine/paleor/.

scholarly journals Modeling of severe persistent droughts over eastern China during the last millennium

2013 ◽  
Vol 9 (6) ◽  
pp. 6345-6373 ◽  
Author(s):  
Y. Peng ◽  
C. Shen ◽  
H. Cheng ◽  
Y. Xu
Keyword(s):  
Southern Oscillation ◽  
Eastern China ◽  
Low Frequency ◽  
Summer Precipitation ◽  
Volcanic Eruptions ◽  
Monsoon Circulation ◽  
Contrast Study ◽  
Last Millennium ◽  
Proxy Data ◽  
Spatial Coverage

Abstract. We use proxy data and modeled data from 1000 yr model simulations with a variety of climate forcings to examine the occurrence of severe events of persistent drought over eastern China during the last millennium and to diagnose the mechanisms. Results show that the model was able to simulate many aspects of the low-frequency (periods greater than 10 yr) variations of precipitation over eastern China during the last millennium, including most of the severe persistent droughts such as those in the 1130s, 1200s, 1350s, 1430s, 1480s, and the late 1630s–mid-1640s. These six droughts are identified both in the proxy data and in the modeled data and are consistent with each other in terms of drought intensity, duration, and spatial coverage. Our analyses suggest that monsoon circulation can lock into a drought-prone mode that may last for years to decades and supports the suggestion that generally reduced monsoon in eastern Asia were associated with the land–sea thermal contrast. Study on the wavelet transform and spectral analysis reveals six well-captured events occurred all at the drought stages of statistically significant 15–35 yr timescale. A modeled data intercomparison suggests that solar activity is the primary driver in the occurrence of the 1130s, 1350s, 1480s, and late 1630s–mid-1640s droughts. Although the El-Niño–Southern Oscillation (ENSO) plays an important role in monsoon variability, a temporally consistent relationship between the droughts and SST pattern in the Pacific Ocean could not be found in the model. Our analyses also indicate that large volcanic eruptions play a role as an amplifier in the drought of 1635–1645 and caused the model to overestimate the decreasing trends in summer precipitation over eastern China during the mid-1830s and the mid-1960s.

scholarly journals How Do Volcanic Eruptions Influence Decadal Megadroughts over Eastern China?

2020 ◽  
Vol 33 (19) ◽  
pp. 8195-8207 ◽  
Author(s):  
Liang Ning ◽  
Kefan Chen ◽  
Jian Liu ◽  
Zhengyu Liu ◽  
Mi Yan ◽  
...  
Keyword(s):  
Asian Summer Monsoon ◽  
Eastern China ◽  
Volcanic Eruptions ◽  
Internal Variability ◽  
Last Millennium ◽  
Decadal Scale ◽  
Community Earth System Model ◽  
Sea Surface Temperature Anomalies ◽  
Asian Summer ◽  
The Western Pacific

AbstractThe influence and mechanism of volcanic eruptions on decadal megadroughts over eastern China during the last millennium were investigated using a control (CTRL) and five volcanic eruption sensitivity experiments (VOLC) from the Community Earth System Model (CESM) Last Millennium Ensemble (LME) archive. The decadal megadroughts associated with the failures of the East Asian summer monsoon (EASM) are associated with a meridional tripole of sea surface temperature anomalies (SSTAs) in the western Pacific from the equator to high latitudes, suggestive of a decadal-scale internal mode of variability that emerges from empirical orthogonal function (EOF) analysis. Composite analyses further showed that, on interannual time scales, within a decade after an eruption the megadrought was first enhanced but then weakened, due to the change from an El Niño state to a La Niña state. The impacts of volcanic eruptions on the magnitudes of megadroughts are superposed on internal variability. Therefore, the evolution of decadal megadroughts coinciding with strong volcanic eruptions demonstrate that the impacts of internal variability and external forcing can combine to influence hydroclimate.

Analysis of Time-Spatial Characteristics of Summer Precipition in Chongqing Region during 45 a

2012 ◽  
Vol 599 ◽  
pp. 690-696
Author(s):  
Fan Hua Min ◽  
Bai Cheng Xia ◽  
De Liu ◽  
Yu Han
Keyword(s):  
Annual Variation ◽  
Summer Precipitation ◽  
Morlet Wavelet ◽  
Precipitation Data ◽  
Common Features ◽  
Maximum Value ◽  
Temporal And Spatial Variability ◽  
Spatial Differences ◽  
The Common ◽  
Temporal And Spatial

Using 1966~2010 year Jun.~Aug. precipitation data over 34 stations of Chongqing region, the temporal and spatial variability features were studied by applying the methods of EOF, REOF, Morlet wavelet analysis. The results indicate that the summer precipitation spatial differences are great. The summer precipitation distribution exhibits the common features as well as the spatial differences, which can be classified into four types as Northeast, Northwest, Southeast and Southwest Chongqing. The inter-annual variation characteristic in the four types is not correspondent. Northeast and Southwest ones are like a parabolic curve which have a maximum value and Southwest and Northwest ones exist upward tendency. The periods of the four types are not unanimous.

scholarly journals Timescale-dependence of the relationship between the East Asian summer monsoon strength and precipitation over eastern China in the last millennium

2017 ◽  
Author(s):  
Jian Shi ◽  
Qing Yan ◽  
Huijun Wang
Keyword(s):  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Eastern China ◽  
Summer Precipitation ◽  
Ice Age ◽  
Last Millennium ◽  
Decadal Timescale ◽  
Asian Summer

Abstract. Precipitation/humidity proxies are widely used to reconstruct the historical East Asian summer monsoon (EASM) variation based on the assumption that summer precipitation over eastern China is closely and stably linked to the strength of EASM. However, whether the observed EASM-precipitation relationship (e.g., increased precipitation with a stronger EASM) was stable throughout the past time remains unclear. In this study, we used model outputs from the Paleoclimate Modelling Intercomparison Project Phase Ⅲ and Community Earth System Model to investigate the stability of the EASM-precipitation relationship over the last millennium on different timescales. The model results indicate that the EASM strength (defined as the regionally averaged meridional wind) enhanced in the Medieval Climate Anomaly (MCA; ~ 950–1250 A.D.), during which there was increased precipitation over eastern China, and weakened during the Little Ice Age (LIA; ~ 1500‒1800 A.D.), during which there was decreased precipitation, consistent with precipitation/humidity proxies. However, the simulated EASM-precipitation relationship is only stable on a centennial and longer timescale and is unstable on a multi-decadal timescale. The nonstationary multi-decadal EASM-precipitation relationship broadly exhibits a quasi-60-year period, which may be attributed to the internal variability of the climate system and have no significant correlation to external forcings. Our results have implications for understanding the discrepancy among various EASM proxies on a multi-decadal timescale and highlight the need to rethink reconstructed decadal EASM variations based on precipitation/humidity proxies.

Volcanoes and ENSO: a re-appraisal with the Last Millennium Reanalysis

2021 ◽  
Author(s):  
Feng Zhu ◽  
Julien Emile-Geay ◽  
Kevin Anchukaitis ◽  
Greg Hakim ◽  
Andrew Wittenberg ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Southern Oscillation ◽  
Internal Variability ◽  
Explosive Volcanism ◽  
Last Millennium ◽  
Statistical Association ◽  
The Past ◽  
Volcanic Events ◽  
Underlying Mechanisms ◽  
The Many

<p>The potential for explosive volcanism to affect the state of the El Niño-Southern Oscillation (ENSO) has been debated since the 1980s. Several observational studies, largely based on tree rings, have since found support for a positive ENSO phase in the year following large eruptions. Models of different complexities also simulate such a response, detectable above the backdrop of internal variability – though they disagree on the underlying mechanisms. In contrast, recent coral data from the heart of the tropical Pacific suggest no uniform ENSO response to all eruptions over the last millennium. Here we leverage paleoclimate data assimilation to integrate the latest paleoclimate evidence into a consistent dynamical framework and re-appraise this relationship. Our analysis finds only a weak statistical association between volcanism and ENSO, suggestive of either no causal association, or of an insufficient number of large volcanic events over the past millennium to obtain reliable statistics. While currently available observations do not support the model-based inference that tropical eruptions promote an ENSO response, there are hints of a response to hemispherically asymmetric forcing, consistent with the "ITCZ shift" mechanism. We discuss the difficulties of conclusively establishing a volcanic influence on ENSO given the many degrees of freedom affecting the response, including eruption season, spatial characteristics of the forcing, and ENSO phase preconditioning.</p>

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