An empirical seasonal prediction model of the east asian summer monsoon using enso and nao zhiwei wu,1,2 bin wang,2 jianping li,1 and feifei jin2 received 8 january 2009. An index measuring the interannual variation of the east. The thick and thin blue lines indicate sevenday running mean and daily mean values, respectively. Asian monsoon monitoring by jmatokyo climate center. A new east asian winter monsoon index, which reflects the 300hpa meridional wind shear associated with the jet stream, was defined to describe the variability of the winter monsoon in midlatitude. Indian and western north pacific east asian monsoons.
Late quaternary upwelling intensity and east asian monsoon. Increases in aerosol concentrations over eastern china due. Furthermore, it is pointed out that the index is very useful for understanding. Intensified east asian winter monsoon during the last. Chinese cave records and the east asia summer monsoon. Africa and north america, but its estimate by current generation of terrestrial biosphere models tbms has seldom been systematically evaluated. One obstacle that prevents a better understanding of future behavior is a poor knowledge of its past. East asian summer monsoon easm is one of the most dominant climate systems in east asia. A study of holocene asian summer and winter monsoon change. Decadal variation of relationship between east asian.
A new index measuring the east asian winter monsoon is defined using the mean wind shears of uppertropospheric zonal wind based on the belief that the physical processes of both higher and lower latitudes, and at both lower and upper troposphere, should be considered to depict the variability of monsoon. Sensitivity of east asian monsoon climate to the uplift of. East asian monsoon world scientific series on meteorology. Our record shows that fluctuations of eam intensity and spatial extent covaried over the past 125 ka. Numerous studies have well documented that the huge asian. It can also be used to delimit the geographical distribution of the global monsoon systems. The calculation of east asian summer monsoon index easmi 7 the change in the strength of easm is commonly represented by the east asian summer monsoon index easmi. East asian monsoon news and updates from the economic times. Two indices are chosen to describe the winter monsoon. This index represents very well the seasonal mean winter temperature over korea, japan, and eastern china.
Pdf a new east asian winter monsoon index and associated. It affects approximately onethird of the global population, influencing the. Contrast between the indian and western north pacificeast asian monsoons. We here reconstruct the past change of the east asian monsoon since 20 ma using samples from ocean drilling program odp site 1146 in the northern south china sea based on a multiproxy approach including a monomineralic quartz isolation procedure, identification of clay minerals by xray diffraction xrd and grainsize analysis of isolated terrigenous materials. Data of all 3 daily monsoon indices for the period 19792006 are available to download. Vegetation functional properties determine uncertainty of. Weakening relationship between east asian summer monsoon. It is driven by temperature differences between the east asian continent and the pacific ocean. Monsoon index the difinition of wnpmi and imi monsoons. Quantitative reconstruction of the east asian winter monsoon. Since the east asian domain includes the tropical western north pacific summer monsoon wnpsm and the subtropical continent monsoon, two well. Asian monsoon failure and megadrought during the last. Monsoon winds exist in other parts of the world, too.
In this study, we show that the surface wind speed associated with the east asian monsoon has significantly weakened in both winter and summer in the recent three decades. Based on observational data and asian monsoon intensity datasets from china, the relationships between the east asian winter monsoon index and winter temperature, the east asian summer monsoon index and meiyu precipitation over the middle and lower reaches of the yangtze river, were analyzed. It covers both subtropics and midlatitudes and its rainfall tends to be concentrated in rain belts that stretch for many thousands of. A study of holocene asian summer and winter monsoon change by.
It covers both subtropics and midlatitudes and its rainfall tends to be concentrated in rain belts that stretch for many thousands of kilometers and affect china, japan, korea, and the surrounding areas. Steady decline of east asian monsoon winds, 19692000. East asian monsoon subtropical forests have comparable nep to that of subtropical forests of the southeastern united states and intensively managed western european forests. The east asian winter monsoon the global monsoon system. Index variable regions meanings of the original index modi. Seasonalmonthly mean monsoon index indian summer monsoon index definition other figures and index data note. The results show that there existed an anomalous cyclonic. This can be seen first in the crosssnapshot correlation map between the chinese.
Atmosphere free fulltext east asian summer monsoon. Predictability of east asian summer monsoon in seasonal. Models are mostly successful in simulating the basic features of the eawm with varied location of monsoon northwesterlies nw. The downloaded pdo index included four series from treering proxy 2932, and one series from chinese historical documents 33. The eastasian monsoon consists of the summer monsoon sm, characterized by the influx of warm, moist wind from the pacific air mass, and. A new monsoon index, the dynamical normalized seasonality dns, is introduced to study the issue of monsoons. The thermal contrast between the asian continent and the adjacent oceans is the primary aspect of the east asian winter monsoon eawm that can be well represented in the sea level pressure slp field. Oct 17, 2017 thereby, the meridional winds at 850 hpa can be used as the index to describe the east asian monsoon. The atmospheric circulation anomalies in east asia and key external forcing factors that influence the easm in 2018 are explored in this paper.
Pdf decadal variations of the east asian winter monsoon in. It affects approximately onethird of the global population, influencing the climate of japan including okinawa, korean peninsula, taiwan, hong kong, macau, and much of mainland china. Apr 23, 2010 the asian monsoon is the weather system that has the greatest effect on the greatest number of people in the world. The asian australian monsoon, which includes the indian ocean, stretches from northern australia to russias pacific coast. Millennial and orbitalscale changes in the east asian. These figures show monthly patterns of the correlation shadings between grid point precipitation and the east asian western north pacific monsoon index. In the research periods, all the in dices show similar interannual. The progresses of recent studies on the variabilities of. Indian monsoon im and western north pacific monsoon wnpm. Jun 28, 2019 the east asian monsoon consists of the summer monsoon sm, characterized by the influx of warm, moist wind from the pacific air mass, and the winter monsoon wm, characterized by the influx of. A dynamical index for the east asian winter monsoon. This paper elaborates on the meanings of 18 existing eawm strength indices and classifies them into four categories. Impact of global warming on the east asian winter monsoon as.
Highresolution speleothem records from china have provided insights into the factors that control the strength of the east asian monsoon 1,2,3,4. Throughout southeast asia, the monsoon season generally refers to the southwest monsoon, the time of the year when the prevailing winds blow up from the warm, wet equatorial seas, bringing in rains and storms. Enso influence on the dynamical seasonal prediction of the. The linkages between monsoon forcings at different timescales remain unclear.
Impact of global warming on the east asian winter monsoon. A new monsoon index and the geographical distribution of the. Why is the east asian summer monsoon extremely strong in. These figures show monthly patterns of the correlation shadings between gridpoint precipitation and the east asian western north pacific monsoon index, and the regression vectors of gridpoint 850mb winds on the monsoon index. East asian monsoon index climate prediction center. Aug 06, 2016 the east asian monsoon is a monsoonal flow that carries moist air from the indian ocean and pacific ocean to east asia. The anomalous easm can cause extremely high temperatures, floods or drought. Here, we present a rainfall reconstruction based on the surface area of a closedbasin lake located at the modern northwestern boundary of the eam. The east asia monsoon system consists of a southwesterly summer monsoon and a northerly winter monsoon. Quantitative reconstruction of the east asian winter.
Four east asian winter monsoon eawm indices are compared in this paper. An evaluation of east asian summer monsoon forecast with. An empirical seasonal prediction model of the east asian. Increases in aerosol concentrations over eastern china due to. In 2018, summer precipitation was above normal in north and northwest china and below normal around the yangtze river valley, due to an extremely strong east asian summer monsoon easm. Climate prediction center east asian monsoon index. A new east asian winter monsoon index, which reflects the 300hpa meridional wind shear associated with the jet stream, was defined to describe the variability of the winter monsoon in midlatitude east asia. The speedy simulated a west african summer monsoon index, b south asian summer monsoon hadley index, c western north pacific summer monsoon index, and d strength of the east asian midlevel trough in winter see identification in the text associated with changing insolation 335352 w m. From 1969 to 2000, the annual mean wind speed over china has decreased steadily by 28%, and the prevalence of windy days daily mean wind speed 5 ms has decreased by 58%. East asian winter monsoon and arctic oscillation east asian winter monsoon and arctic oscillation gong, dao. The east asian winter monsoon 103 siberian high index reached the lowest values since 1871. The covariability of easm and eawm on multiple timescales significantly affect east asia. This huge monsoon wind system then stretches into the indian ocean.
High carbon dioxide uptake by subtropical forest ecosystems. The asianaustralian monsoon, which includes the indian ocean, stretches from northern australia to russias pacific coast. Pdf a dynamical index for the east asian winter monsoon. We suggest that the east asian summer monsoon has been forced by changes in solar insolation associated with precession and obliquity, while icevolume forcing is probably a primary factor in determining the strength and timing of the east asian winter monsoon but. This southwest monsoon generally starts in may or june, reaching a fever pitch between august and october typhoon season in vietnam and the philippines then tapering off by november. Mar, 2017 this study examined the forecast skill for the east asian winter monsoon eawm using the following stateoftheart dynamical seasonal prediction systems. May 15, 2012 the calculation of east asian summer monsoon index easmi 7 the change in the strength of easm is commonly represented by the east asian summer monsoon index easmi. The east asian monsoon exerts a profound influence on environmental change in the east asian region. Time series of the two indices for summerjjas, june, july, august and september of 19482006 are shown below. East asian monsoon world scientific series on asia. Based on the eap east asiapacific teleconnection in the summer circulation anomalies over the northern hemisphere, an index measuring the strength of the east asian summer monsoon, i.
An intensity index for the east asian winter monsoon. East asian monsoon signals reflected in temperature and. The term also increasingly refers to regions where there is a clear alternation between winter dry and summer rainy seasons. East asian monsoon world scientific series on asiapacific. The east asian summer monsoon easm, which is an important influencing summer climate of east asia, is associated with largescale change of the landsea thermal contrast. East asian monsoon news and updates from the economictimes. The easmi introduced by li and zeng is used in this study to quantify the decadal. The east asian monsoon is a monsoonal flow that carries moist air from the indian ocean and pacific ocean to east asia. A joint monsoon index for east asianaustralian monsoons during. Naturally then, knowing better how climate change might affect the monsoon is tremendously important. A new monsoon index and the geographical distribution of. The rain occurs in a concentrated belt that stretches eastwest except in east china where it is tilted eastnortheast over korea and japan.
The east asian monsoon affects large parts of indochina, philippines, china, taiwan, korea and japan. It covers both subtropics and midlatitudes and its rainfall tends to be concentrated in rain belts that stretch for many thousands of kilometers and affect china, japan, korea. Kikuchi could mjo predictions help forecast the asian summer monsoon. Simulations and seasonal prediction of the asia summer monsoon in the ncep climate forecast system monsoon indices references send your comments to. The prediction skill and source of the predictability of the east asian summer monsoon easm system are examined in this work based on four state. The east asian monsoon eam is a regional factor affecting the east asian climate and the oceanographic processes of the marginal seas along the western pacific. The east asian monsoon consists of the summer monsoon sm, characterized by the influx of warm, moist wind from the pacific air mass, and the winter monsoon wm, characterized by the influx of. Various factors have been hypothesized as the dominant asian monsoon forcings, however, the forcings can change from interannual to millennial timescales. Pdf a joint monsoon index for east asianaustralian monsoons. Regional average values of the msw index were calculated for three monsoon regions of comparable size.
How well do existing indices measure the strength of the. How to measure the strength of the east asian summer monsoon. The asianpacific oscillation apo can modulate the easm because it not only represents the uppertropospheric zonal landsea thermal contrast over asia and the pacific region, but it also affects the sea surface. Northward extent of east asian monsoon covaries with. It is characterised by a warm, rainy summer monsoon and a cold, dry winter monsoon. He, sp, wang, hj 2012 an integrated east asian winter monsoon index and its interannual variability. The midlatitude component ofthe east asian winter monsoon eawm is characterized by the coldcore siberianmongolian high smh at the surface whose variability affects all scales of the extratropical circulations. Interaction of mjo with asian summer monsoon us clivar. The ncep ncar reanalysis product is downloaded from the noaa. A proper monsoon index for seasonal and interannual. Although the upper level winds exhibit difference, the easm index is consistent in the eight reanalyses, which are based upon the zonal wind over 850 hpa. The total nep of east asian monsoon subtropical forests was estimated to be 0. Correlation and anticorrelation of the east asian summer.
A joint monsoon index for east asianaustralian monsoons. View or download all content the institution has subscribed to. Go to previous content download this content share this content add this content to favorites go to next content. In boreal summer, the mjo has considerable interaction with the circulation and varability of asian summer monsoon. The present paper provides an overview of major problems of the east asian summer monsoon. Apr 01, 2014 east asian monsoon subtropical forests have comparable nep to that of subtropical forests of the southeastern united states and intensively managed western european forests.
The authors also recommend a simple index, the reversed wang and fan index, which is nearly identical to. Finally, it reaches its end on the indian coast of africa. A new east asian winter monsoon index and associated. The variabilities of the east asian summer monsoon arc an important research issue in china, japan, and korea. An intensity index for the east asian winter monsoon ams journals. Annamalai and slingo 2001, including the genesis of synoptic systems goswami et al. This dns index can describe both seasonal variation and interannual variability of different monsoon regions. May 30, 2019 the prediction skill and source of the predictability of the east asian summer monsoon easm system are examined in this work based on four state. The asian monsoon is the weather system that has the greatest effect on the greatest number of people in the world. Monsoon climate, especially monsoonassociated precipitation, is importan t to the maintenance of living environments and socially sustainable development in the populous regions of east asia an et al. The easmi introduced by li and zeng 2002 is used in this study to quantify the decadal. The east asian summer monsoon easm index is defined as an. The thermal contrast between the asian continent and the adjacent oceans is the primary aspect of the east asian winter monsoon eawm that can. The east asian summer monsoon has complex space and time structures that are distinct from the south asian summer monsoon.
The olr index is calculated after wang and fan 1999. Comparison of east asian winter monsoon indices table 1. A new index measuring the east asian winter monsoon is defined using the mean wind shears of uppertropospheric zonal wind based on the belief that the physical processes of both higher and lower. The summer monsoon system over east asia including the south china sea scs cannot be just thought of as the eastward and northward extension of the indian monsoon. East asian monsoon news and updates from the economic. Defining the intensity of the east asian winter monsoon eawm with a simple index has been a difficult task. Monsoons have been defined as a shift of prevailing winds between summer jja and winter djf seasons. We suggest that the east asian summer monsoon has been forced by changes in solar insolation associated with precession and obliquity, while icevolume forcing is probably a primary factor in determining the strength and timing of the east asian winter monsoon but with less important insolation forcing.
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