Characteristics, processes, and causes of the spatio-temporal variabilities of the East Asian monsoon system
TL;DR: In this article, the authors reviewed recent advances in the study of the characteristics, processes, and causes of spatio-temporal variabilities of the East Asian monsoon (EAM) system.
Abstract: Recent advances in the study of the characteristics, processes, and causes of spatio-temporal variabilities of the East Asian monsoon (EAM) system are reviewed in this paper. The understanding of the EAM system has improved in many aspects: the basic characteristics of horizontal and vertical structures, the annual cycle of the East Asian summer monsoon (EASM) system and the East Asian winter monsoon (EAWM) system, the characteristics of the spatio-temporal variabilities of the EASM system and the EAWM system, and especially the multiple modes of the EAM system and their spatio-temporal variabilities. Some new results have also been achieved in understanding the atmosphere-ocean interaction and atmosphere-land interaction processes that affect the variability of the EAM system. Based on recent studies, the EAM system can be seen as more than a circulation system, it can be viewed as an atmosphere-ocean-land coupled system, namely, the EAM climate system. In addition, further progress has been made in diagnosing the internal physical mechanisms of EAM climate system variability, especially regarding the characteristics and properties of the East Asia-Pacific (EAP) teleconnection over East Asia and the North Pacific, the “Silk Road” teleconnection along the westerly jet stream in the upper troposphere over the Asian continent, and the dynamical effects of quasi-stationary planetary wave activity on EAM system variability. At the end of the paper, some scientific problems regarding understanding the EAM system variability are proposed for further study.
Citations
More filters
TL;DR: In this article, the authors studied the effect of teleconnection patterns on the precipitation anomaly in the eastern part of East Asia and found that the effect was mainly dominated by the Pacific-Japan and Silk-Road teleconnections.
Abstract: East Asia is greatly impacted by drought. North and southwest China are the regions with the highest drought frequency and maximum duration. At the interannual time scale, drought in the eastern part of East Asia is mainly dominated by two teleconnection patterns (i.e., the Pacific–Japan and Silk Road teleconnections). The former is forced by SST anomalies in the western North Pacific and the tropical Indian Ocean during El Nino decaying year summers. The precipitation anomaly features a meridional tripolar or sandwich pattern. The latter is forced by Indian monsoon heating and is a propagation of stationary Rossby waves along the Asian jet in the upper troposphere. It can significantly influence the precipitation over north China. Regarding the long-term trend, there exists an increasing drought trend over central parts of northern China and a decreasing tendency over northwestern China from the 1950s to the present. The increased drought in north China results from a weakened tendency of summer ...
271 citations
Additional excerpts
...5b; Huang et al. 2012)....
[...]
01 Apr 2011
TL;DR: The midlatitude component of the East Asian winter monsoon (EA WM) is characterized by the cold-core Siberian-Mongolian High (SMH) at the surface whose variability affects all scales of the extratropical circulations as discussed by the authors.
Abstract: The midlatitude component ofthe East Asian winter monsoon (EA WM) is characterized by the cold-core Siberian-Mongolian High (SMH) at the surface whose variability affects all scales of the extratropical circulations. The SMH has been weakening in recent decades, which appears to correlate with the negative phase ofNAOIAO due to increased warm air advection over the Eurasian continent and the resultant reduction in snow cover. However, it is not clear that this recent decrease in the EA WM intensity is unique in the most recent 400 years. Periodical cold air outbreaks that cause high-impact weather are associated with the intra seasonal and synoptic variation of the SMH, and they often continue as cold monsoonal surges into the tropics and affect the tropical component of the EA WM. There is some evidence that intraseasonal variability has decreased in 1990s although extreme weather events in the past few years counter this trend, An important mechanism for the intraseasonal and higher frequency enhancement of the SMH comes from upper level blocking ridges over the Atlantic and the Pacific. The Atlantic blocking triggers a Rossby wave train that has a downstream effect of enhancing the SMH, The Pacific blocking forces the SMH through slow retrogression of the blocking center.
190 citations
TL;DR: In this paper, the interannual variation of the wintertime fog-haze days across central and eastern China from 1972 to 2014 and its relationship with East Asian winter monsoon (EAWM) were investigated based on the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data and the surface observation data from the weather stations in China.
Abstract: The interannual variation of the wintertime fog–haze days across central and eastern China from 1972 to 2014 and its relationship with East Asian winter monsoon (EAWM) are investigated based on the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data and the surface observation data from the weather stations in China. The results show that the wintertime fog–haze days across central and eastern China have close relation with EAWM in the interannual time scale. The stronger (weaker) the EAWM is, the less (more) the wintertime fog–haze days are. In strong (weak) EAWM winters, both near-surface winds and vertical shear of horizontal zonal winds strengthen (weaken). The strengthened (weakened) near-surface winds enhance (reduce) the outward transport of fog and haze and are unfavourable (favourable) for their accumulation over central and eastern China. The enlarged (receded) vertical shear of horizontal zonal winds intensifies (abates) the atmospheric baroclinic instability and vertical diffusion, leading to less (more) fog and haze in near-surface. In addition, a strong (weak) EAWM is also unfavourable (favourable) for the maintenance of the fog and haze in the lower troposphere through the anomalous divergence (convergence) associated with the intense anticyclonic (cyclonic) anomalies in the upper troposphere over southern China.
179 citations
Cites background from "Characteristics, processes, and cau..."
...Because of the cold high, the northwesterlies prevail over eastern China to the north of about 30∘N in lower troposphere, while the northeasterlies to the south of about 30∘N (Huang et al., 2012)....
[...]
TL;DR: This paper evaluated the historical precipitation variability based on 20 general circulation models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) archive over the 20th century relative to two observational data sets and quantifies CMIP5 improvements over CMIP3.
Abstract: Precipitation variability has great economic, social, and environmental impacts across the globe, and in particular in China. This paper evaluates the historical precipitation variability based on 20 general circulation models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) archive over the 20th century relative to two observational data sets and quantifies CMIP5 improvements over CMIP3. Multimodel ensemble means and individual models are assessed. Three future emission scenarios are used (representative concentration pathways (RCP) 8.5, RCP 4.5, and RCP 2.6), and 21st century CMIP5 estimates are put into context based on the 20th century biases. We find that CMIP5 models can reproduce the spatial pattern of precipitation over China during the 20th century, which represents an improvement over CMIP3. However, the models overestimate the magnitude of seasonal and annual precipitation in most regions of China, especially along the eastern edge of the Tibetan Plateau, and underestimate summer precipitation over southeastern China. For China as a whole, CMIP5's overestimation of annual precipitation is greater than CMIP3, which can be traced back to a greater underestimation of summer precipitation in CMIP3. There is a large spread among individual models, with the greatest uncertainties in simulating summer precipitation. Trends and correlations also suggest a better agreement of CMIP5 with observations than CMIP3. Throughout the 20th century, both the observations and models show an increasing trend in precipitation over parts of northwestern China and a decreasing trend over the Tibetan Plateau. There is poor agreement in precipitation trends over the southeast and northeast regions. In general, multimodel means cannot capture the amplitude of observed multidecadal precipitation variability. In the 21st century, precipitation is generally projected to increase across all of China under all three scenarios. RCP 8.5 exhibits the largest significant trend at a rate of +1.5 mm/yr, corresponding to 16% precipitation increase by the end of the century. The RCP 2.6 scenario shows the smallest increases, at +0.5 mm/yr (6%) by 2100. The greatest increases are projected to occur over the Tibetan Plateau and eastern China in summer, suggesting an altered monsoonal circulation in the future. However, due to the uncertainties in CMIP5, future precipitation projections should be interpreted with caution.
166 citations
TL;DR: In this paper, a concise summary of the studies on interdecadal variability of the East Asian winter monsoon (EAWM) from three main perspectives is presented, and it is inferred that global warming may be one of the most important natural factors influencing long-term variability in the EAWM.
Abstract: This paper presents a concise summary of the studies on interdecadal variability of the East Asian winter monsoon (EAWM) from three main perspectives. (1) The EAWM has been significantly affected by global climate change. Winter temperature in China has experienced three stages of variations from the beginning of the 1950s: a cold period (from the beginning of the 1950s to the early or mid 1980s), a warm period (from the early or mid 1980s to the early 2000s), and a hiatus period in recent 10 years (starting from 1998). The strength of the EAWM has also varied in three stages: a stronger winter monsoon period (1950 to 1986/87), a weaker period (1986/87 to 2004/05), and a strengthening period (from 2005). (2) Corresponding to the interdecadal variations of the EAWM, the East Asian atmospheric circulation, winter temperature of China, and the occurrence of cold waves over China have all exhibited coherent interdecadal variability. The upper-level zonal circulation was stronger, the mid-tropospheric trough over East Asia was deeper with stronger downdrafts behind the trough, and the Siberian high was stronger during the cold period than during the warm period. (3) The interdecadal variations of the EAWM seem closely related to major modes of variability in the atmospheric circulation and the Pacific sea surface temperature. When the Northern Hemisphere annular mode/Arctic Oscillation and the Pacific decadal oscillation were in negative (positive) phase, the EAWM was stronger (weaker), leading to colder (warmer) temperatures in China. In addition, the negative (positive) phase of the Atlantic multi decadal oscillation coincided with relatively cold (warm) temperatures and stronger (weaker) EAWMs. It is thus inferred that the interdecadal variations in the ocean may be one of the most important natural factors influencing long-term variability in the EAWM. although global warming may have also played a significant role in weakening the EAWM.
161 citations
References
More filters
TL;DR: The NCEP/NCAR 40-yr reanalysis uses a frozen state-of-the-art global data assimilation system and a database as complete as possible, except that the horizontal resolution is T62 (about 210 km) as discussed by the authors.
Abstract: The NCEP and NCAR are cooperating in a project (denoted “reanalysis”) to produce a 40-year record of global analyses of atmospheric fields in support of the needs of the research and climate monitoring communities. This effort involves the recovery of land surface, ship, rawinsonde, pibal, aircraft, satellite, and other data; quality controlling and assimilating these data with a data assimilation system that is kept unchanged over the reanalysis period 1957–96. This eliminates perceived climate jumps associated with changes in the data assimilation system. The NCEP/NCAR 40-yr reanalysis uses a frozen state-of-the-art global data assimilation system and a database as complete as possible. The data assimilation and the model used are identical to the global system implemented operationally at the NCEP on 11 January 1995, except that the horizontal resolution is T62 (about 210 km). The database has been enhanced with many sources of observations not available in real time for operations, provided b...
28,145 citations
European Centre for Medium-Range Weather Forecasts1, Lawrence Livermore National Laboratory2, Chinese Academy of Sciences3, Japan Meteorological Agency4, Met Office5, University of Reading6, Max Planck Society7, Royal Netherlands Meteorological Institute8, National Center for Atmospheric Research9, National Oceanic and Atmospheric Administration10
TL;DR: ERA-40 is a re-analysis of meteorological observations from September 1957 to August 2002 produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) in collaboration with many institutions as mentioned in this paper.
Abstract: ERA-40 is a re-analysis of meteorological observations from September 1957 to August 2002 produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) in collaboration with many institutions. The observing system changed considerably over this re-analysis period, with assimilable data provided by a succession of satellite-borne instruments from the 1970s onwards, supplemented by increasing numbers of observations from aircraft, ocean-buoys and other surface platforms, but with a declining number of radiosonde ascents since the late 1980s. The observations used in ERA-40 were accumulated from many sources. The first part of this paper describes the data acquisition and the principal changes in data type and coverage over the period. It also describes the data assimilation system used for ERA-40. This benefited from many of the changes introduced into operational forecasting since the mid-1990s, when the systems used for the 15-year ECMWF re-analysis (ERA-15) and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) re-analysis were implemented. Several of the improvements are discussed. General aspects of the production of the analyses are also summarized.
A number of results indicative of the overall performance of the data assimilation system, and implicitly of the observing system, are presented and discussed. The comparison of background (short-range) forecasts and analyses with observations, the consistency of the global mass budget, the magnitude of differences between analysis and background fields and the accuracy of medium-range forecasts run from the ERA-40 analyses are illustrated. Several results demonstrate the marked improvement that was made to the observing system for the southern hemisphere in the 1970s, particularly towards the end of the decade. In contrast, the synoptic quality of the analysis for the northern hemisphere is sufficient to provide forecasts that remain skilful well into the medium range for all years. Two particular problems are also examined: excessive precipitation over tropical oceans and a too strong Brewer-Dobson circulation, both of which are pronounced in later years. Several other aspects of the quality of the re-analyses revealed by monitoring and validation studies are summarized. Expectations that the ‘second-generation’ ERA-40 re-analysis would provide products that are better than those from the firstgeneration ERA-15 and NCEP/NCAR re-analyses are found to have been met in most cases. © Royal Meteorological Society, 2005. The contributions of N. A. Rayner and R. W. Saunders are Crown copyright.
7,110 citations
TL;DR: The Arctic Oscillation (AO) as mentioned in this paper is the signature of modulations in the strength of the polar vortex aloft, and it resembles the NAO in many respects; but its primary center of action covers more of the Arctic, giving it a more zonally symmetric appearance.
Abstract: The leading empirical orthogonal function of the wintertime sea-level pressure field is more strongly coupled to surface air temperature fluctuations over the Eurasian continent than the North Atlantic Oscillation (NAO). It resembles the NAO in many respects; but its primary center of action covers more of the Arctic, giving it a more zonally symmetric appearance. Coupled to strong fluctuations at the 50-hPa level on the intraseasonal, interannual, and interdecadal time scales, this "Arctic Oscillation" (AO)can be interpreted as the surface signature of modulations in the strength of the polar vortex aloft. It is proposed that the zonally asymmetric surface air temperature and mid-tropospheric circulation anomalies observed in association with the AO may be secondary baroclinic features induced by the land-sea contrasts. The same modal structure is mirrored in the pronounced trends in winter and springtime surface air temperature, sea-level pressure, and 50-hPa height over the past 30 years: parts of Eurasia have warmed by as much as several K, sea-level pressure over parts of the Arctic has fallen by 4 hPa, and the core of the lower stratospheric polar vortex has cooled by several K. These trends can be interpreted as the development of a systematic bias in one of the atmosphere's dominant, naturally occurring modes of variability.
3,800 citations
"Characteristics, processes, and cau..." refers background in this paper
...…of these two wave guides of quasi-stationary planetary waves has a significant influence on Arctic Oscillation (AO), which is closely related to EAWM system variability (e.g., Gong et al., 2001; Gong and Ho, 2003) through the Northern Annular Mode (NAM, Thompson and Wallace, 1998, 2000)....
[...]
TL;DR: In this paper, a review of existing literature on the subject reveals the existence of at least four such patterns: the North Atlantic and North Pacific Oscillations identified by Walker and Bliss (1932), a zonally symmetric seesaw between sea level pressures in polar and temperature latitudes, first noted by Lorenz (1951), and what we will refer to as the Pacific/North American pattern, which has been known to operational long-range forecasters in this country since the 1950's.
Abstract: Contemporaneous correlations between geopotential heights on a given pressure surface at widely separated points on earth, referred to as teleconnections in this paper, are studied in an attempt to identify and document recurrent spatial patterns which might be indicative of standing oscillations in the planetary waves during the Northern Hemisphere winter, with time scales on the order of a month or longer. A review of existing literature on the subject reveals the existence of at least four such patterns: the North Atlantic and North Pacific Oscillations identified by Walker and Bliss (1932). a zonally symmetric seesaw between sea level pressures in polar and temperature latitudes, first noted by Lorenz (1951), and what we will refer to as the Pacific/North American pattern, which has been known to operational long-range forecasters in this country since the 1950's. A data set consisting of NMC monthly mean sea level pressure and 500 mb height analyses for a 15-year period is used as a basis fo...
3,781 citations
"Characteristics, processes, and cau..." refers background in this paper
...Of course, this meridional tripole pattern of circulation anomalies over East Asia is also associated with thermal anomalies over the North Atlantic through the EU pattern teleconnection over middle and high latitudes, as proposed by Wallace and Gutzler (1981)....
[...]
...…Asia/Pacific (EAP) teleconnection of summer circulation anomalies over East Asia (e.g., Nitta, 1987; Huang and Li, 1987, 1988) but also the interdecadal variation of the Eurasian (EU) teleconnection of summer circulation anomalies over middle and high latitudes (e.g., Wallace and Gutzler, 1981)....
[...]
TL;DR: In this article, the authors compared the structure and seasonality of the Southern Hemisphere (SH) annular mode and the Northern Hemisphere (NH) mode, referred to as the Arctic Oscillation (AO), based on data from the National Centers for Environmental Prediction and National Center for Atmospheric Research reanalysis and supplementary datasets.
Abstract: The leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep, zonally symmetric or ‘‘annular’’ structures, with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude. The structure and dynamics of the Southern Hemisphere (SH) annular mode have been extensively documented, whereas the existence of a Northern Hemisphere (NH) mode, herein referred to as the Arctic Oscillation (AO), has only recently been recognized. Like the SH mode, the AO can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields. In this paper the structure and seasonality of the NH and SH modes are compared based on data from the National Centers for Environmental Prediction‐National Center for Atmospheric Research reanalysis and supplementary datasets. The structures of the NH and SH annular modes are shown to be remarkably similar, not only in the zonally averaged geopotential height and zonal wind fields, but in the mean meridional circulations as well. Both exist year-round in the troposphere, but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave‐mean flow interaction: midwinter in the NH and late spring in the SH. During these ‘‘active seasons,’’ the annular modes modulate the strength of the Lagrangian mean circulation in the lower stratosphere, total column ozone and tropopause height over mid- and high latitudes, and the strength of the trade winds of their respective hemispheres. The NH mode also contains an embedded planetary wave signature with expressions in surface air temperature, precipitation, total column ozone, and tropopause height. It is argued that the horizontal temperature advection by the perturbed zonal-mean zonal wind field in the lower troposphere is instrumental in forcing this pattern. A companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades.
3,278 citations
"Characteristics, processes, and cau..." refers background in this paper
...…of these two wave guides of quasi-stationary planetary waves has a significant influence on Arctic Oscillation (AO), which is closely related to EAWM system variability (e.g., Gong et al., 2001; Gong and Ho, 2003) through the Northern Annular Mode (NAM, Thompson and Wallace, 1998, 2000)....
[...]