Atmospheric sciences, Yonsei university

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2013.0408-0410.FOCRAII . On the Relationship between East Asia Jet and North Pacific Atmospheric Circulation Pattern during the Boreal Winter. Jae-Heung Park, Soon-Il An. Atmospheric sciences, Yonsei university. Contents. - PowerPoint PPT Presentation

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Atmospheric sciences, Yonsei university2013.0408-0410.FOCRAII

Jae-Heung Park, Soon-Il AnOn the Relationship between East Asia Jet and North Pacific Atmospheric Circulation Pattern during the Boreal WinterHello, every one.My name is Jae-Heung Park form Yonsei university in Korea.The title of my presentation is On the Relationship between East Asia Jet And North Pacific Atmosphere Circulation Pattern during the Boreal Winter.Although the subject of this study is a little different from that of this FOCRAIIplease, be interested in my presentation. Then lets start my presentation.1ContentsAtmospheric sciences, Yonsei universityOn the Relationship between East Asia Jet and North Pacific Atmospheric Circulation Pattern during the Boreal WinterIntroduction

Data

Result

Discussion

5. Summary Contents are like this.Introduction, data, result, and discussion & Summary.2Atmospheric sciences, Yonsei universityIntro.Recently, as global warming continues, NPGO/NPO frequently appears compared to the past. This result is corresponding to the tropical climate change such as frequent generation of CP El Nino and temperature increase in Warm Pool. Since atmosphere leads oceans in the North Pacific, NPO becomes more important. (Yeh et al, 20011; Di Lorenzo et al 2010; Park et al, 2012; Furtado et al, 2011)

However, contrary to the study of AL, that of NPO or other atmosphere pattern is not arranged well. They are needed to be focused more.

In the North Pacific1st mode:: Pacific Decadal Oscillation (PDO) Aleutian Low (AL)2nd mode :: North Pacific Gyre Oscillation (NPGO) North Pacific Oscillation (NPO)On the Relationship between East Asia Jet and North Pacific Atmospheric Circulation Pattern during the Boreal WinterIn the North Pacific, There are two famous climate modes.First modes Pacific decadal oscillation, PDO, in ocean and Aleutian Low, AL, in atmosphere.Which are characterized by horseshoe and monopole pattern.Seconds are North Pacific Gyre oscillation, NPGO in ocean. And North Pacific Oscillation in atmosphere.They are distinguished by tri-pole and dipole pattern respectively.

Recently, as global warming continues,The second mode NPGO and NPO appears more compared to the past.And some scientists argued that this result is corresponding to the tropical climate change such asCentral Pacific El Nino and Warm Pool temperature increase.

It is known that over the North Pacific, atmosphere affects and lead ocean.Thus, NPO or other atmosphere pattern should be more investigated,However, contrary to the study of AL, that of NPO or other atmosphere patternIs not well arranged well. They are needed to be more focused.

3Atmospheric sciences, Yonsei universityIntro.Previous studies Wallace and Gutzler (1981) :: WPO (GPH 500hPa) & NPO (PSL) Nigam (2003) :: WPO & Asian-Pacific Jet (whole range of Pacific) Linkin and Nigam (2007) :: NPO & WPO.

In this study, we investigate the relationship between East Asia jet stream and atmosphere pressure over the North Pacific. It is suggested that this relationship can be connected to the Tropics.

On the Relationship between East Asia Jet and North Pacific Atmospheric Circulation Pattern during the Boreal WinterIn the past,Wallace and Gutzler, Nigam, Linkin and Nigam, studied the relationshipNPO at surface, WPO at mid-atmosphere, and jet stream at upper atmosphere.and told that they are related to each other.

In this study. We investigate the relationship between East Asia jet stream and atmosphere pressureOver the north Pacific.And It is suggested that this relationship can be connected to the tropical climate change.4Atmospheric sciences, Yonsei universityData:: NCEP-R1 reanalysis data (1949~2007, 708montly data DJF mean 58 yearly data)

:: Used variable - Zonal wind (U) - Geopotential Height (GPH) - Sea Level Pressure (SLP) - Omega - Temperature On the Relationship between East Asia Jet and North Pacific Atmospheric Circulation Pattern during the Boreal WinterIn this study, NCEP-R1 reanalysis data is used,Ranging from 1949 to 2007.Used variables are zonal wind, GPH, PSL, Omega, and temperature.All variables are averaged focused on winter, December to February.5ResultAtmospheric sciences, Yonsei universityEast Asia Jet (EA Jet)East Asian Jet stream (> 70m/s)

2. Parallel to the latitude

Upstream region of North Pacific

EA Jet Axis Index

EA Jet region (120-160E, 25-45N):: It indicates the north-south movement of EA jetFind latitudes where the strongest U exists at each longitude within EA jet regionAverage the latitudes

On the Relationship between East Asia Jet and North Pacific Atmospheric Circulation Pattern during the Boreal WinterThis figure shows winter-mean zonal wind at 200 hPa.The core is located at south part of Japan, and we named this region as EA jet region, marked by rectangular.EA jet region is relatively located at upstream part of North Pacific. The speed exceed 70 meter per second.And the axis is parallel to the latitude.

Here, we focused on the north-south movement of jet rather than its speed.So, we made EA jet axis index which indicates north-south displacement of EA jet.To obtain the index, first, the latitude where the strongest zonal wind exist at each longitude within EA jet region are found, and these latitudes are averaged.

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ResultAtmospheric sciences, Yonsei universityComposite Analysis :: zonal wind (200hPa) is composited with respect to the highest and lowest 10% of EA Jet axis index

When EA jet is located at north (south). zonal wind is strong (weak)

Shapes of jet in both period are similar in EA jet region, however, they are different in jet exit region. :: when EA jet locates at north(south), jet axis over the eastern North Pacific is toward northward(southward).

It implies that small difference of north-south displacement of EA jet is associated to the large change in atmosphere flow over the North Pacific.Solid EA jet axis index (mean=32.5N, std. 0.53) Dotted 9-year running mean of the index increasing trend(95% significant level) EA jet is moving northward. On the Relationship between East Asia Jet and North Pacific Atmospheric Circulation Pattern during the Boreal WinterThis graph shows EA jet axis index, solid line, and its 9-year running mean, dotted line.There is a increasing trend with 95% significant level, it is known that East Asia jet is moving northward.

Based on the highest and lowest 10% of this index, Zonal wind is composited.

Comparing the two figures, we can known thatWhen jet locates at further north, zonal wind becomes strong.And although the figure of EA jet region in both period is similar to each other, However, those are quite different in the jet exit region.

When EA jet located at north, jet axis in the exit region is toward northward.And reverse is true.

It implies that EA jet north-south movement is related to atmosphere flow over the north Pacific.

7ResultAtmospheric sciences, Yonsei university

Regression Analysis :: EA Jet axis index is regressed onto the GPH(200hPa) & SLP.1. Dipole pattern. (Northwest-low, Southeast-high) Similarity to NPO (scorr.=0.63)

2. Equivalent barotropic structure.

3. Simple regression relationship (SLPa) If EA jet axis moves northward by 3 7.5hPa (250Pa x 3) increase and decrease at each center.

:: Shading (95% significant level) Statistically apparent relationship between EA jet location and dipole pressure pattern over the North Pacific.

:: This result indicates EA jet location plays an important role in making dipole structure.

What controls EA jet displacement??On the Relationship between East Asia Jet and North Pacific Atmospheric Circulation Pattern during the Boreal WinterThe EA jet axis index is regressed onto the GPH and SLP.In both figure, northwest-southeast diploe pattern is shown.Considering the location of North center, it seems to be similar to the NPO.Their correlation is 0.63.

Using simple regression relationship, we can notice that If EA jet moves northward by 3 degree, then SLP decrease and increase at each center by 7.5hPa.

This results indicates that jet location plays an important role in inducing such a dipole pattern.Then, here raised a question What controls EA jet displacement.8ResultAtmospheric sciences, Yonsei university

Relationship between EA Jet & Hadley Circulation:: Subtropical jet is located at the inner section of Hadley circulation boundary.

:: At the boundary, tropopause height decreases abruptly.

jet:: Using this information, Hadley circulation boundary (HCB) index is made. (local Hadley circulation, 120-160E, same to longitudinal range of EA jet region)

:: The correlation between EA jet axis index and HCB index is 0.79 (95%) (closely linked)

Hadley circulation controls the location of EA jet.On the Relationship between East Asia Jet and North Pacific Atmospheric Circulation Pattern during the Boreal WinterGenerally, subtropical jet is located at the inner section of Hadley circulation boundary.At the boundary, Tropopause height decreases abruptly.

This shows tropopause height change with respect to latitude.Here, red elliptic indicates the location of Hadley circulation boundary.

So using this information, Hadley circulation boundary index is made and when it is correlated to EA jet axis index, the correlation coefficient is 0.79.

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ResultAtmospheric sciences, Yonsei universityCorrelation Map :: HCB index is correlated to Omega(500hPa) and Surface Air Temperature(SAT).1. The correlation center is located in the western tropical Pacific.

2. Minus omega indicates upward motion or convection. If SAT is high and convection is strong in the region, then HCB moves northward. (EA jet moves to the north accordingly.)

3. Convection in the western tropical Pacific is an upward branch of Hadley and Walker circulations. The strong convection in the western tropical Pacific strong Hadley and Walker circulations cold sat & Northward movement ITCZ over the eastern Pacific

4. Omega index (100-145E, 0-20N)

On the Relationship between East Asia Jet and North Pacific Atmospheric Circulation Pattern during the Boreal WinterThe graphs shown the correlation maps between HCB index and Omega and SAT. The correlation center is locate in the western tropical pacific.

It is noted that minus omega means upward motion or convection.Thus, these graphs say that if SAT is high and convection is strong in the western tropical pacific.Then HCB moves northward and EA jet is also moves northward accordingly.

Convection in the western tropical Pacific is so important, because the convection in this region is a upward branch of Hadley and walker circulation. So this convection is referred as Pumping center of tropical atmosphere.

when the convection is strong, it means that Hadley and walker circulation is strong as well.At this moment, cold sst in the eastern tropical Pacific is induced by strong trade wind.Then, ITCZ locates at further north in the eastern Pacific.

We also make an Omega index based on the western Pacific region.

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1. Dipole structure (Northwest-Southeast axis)

2. Similar to the regression pattern.

Convection in the western tropical Pacific can affect the pressure over north Pacific via EA jet movement. ResultAtmospheric sciences, Yonsei universityComposite Analysis:: SLP composite based on Omega index (above 1.5 std. below -1.5 std.)

solid :: Omega indexdotted :: 9-year running mean of the index decreasing trend, 95%Convection gets stronger in the western tropical Pacific.On the Relationship between East Asia Jet and North Pacific Atmospheric Circulation Pattern during the Boreal WinterIts 9-year running mean shows a significant decreasing trend. This indicates convection develops more in the western tropical Pacific.

Next, SLP is composited regarding Omega index.Only the period when its standard deviation is above and below 1.5% after normalization.And the graph shows above minus below. Consider the relationship between Omega and vertical wind,Then, When convection is strong in the western Pacific, low locates at northwest and high locates at southeast.

This pattern is very similar to the regression pattern shown earlier.So it can be concluded that convection in the western tropical Pacific affects the pressure Over the North Pacific via the location modulation of EA jet.

11Atmospheric sciences, Yonsei university

WarmingConvectionCoolingITCZLHDiscussion & SummaryOn the Relationship between East Asia Jet and North Pacific Atmospheric Circulation Pattern during the Boreal Winter

As global warming, SST and convection in the western tropical Pacific increase.The convection is upward branch of Hadley & Walker circulation, 1. Hadley circulation boundary moves northward. (EA jet) 2. Walker circulation gets stronger so that SST in eastern tropical Pacific cools.ITCZ over the eastern tropical Pacific moves northward, and corresponding meridional circulation moves northward as well.Jet stream over the whole pacific changes its axis, and secondary circulation induces low pressure at north and high pressure at south. So far, I told that the connection between western tropical Pacific and north Pacific atmosphere via EA jet.This slide shows a simple description of this study.

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