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Persistent anomalous flows over the subtropical western Pacific insummer

Shiyu Zhuang,Liren Ji,

科学通报(英文版) , 1998,
Abstract: The distribution of global persistent anomaliesshows that the subtropical western Pacific is a key region with high-frequency occurrence of persistent anornalics. Analyscs of streamfunction anomalies, 013 anomalies etc. suggest that the convective heating related to Indian nlon.uwn might he responsible for the development of WPA. The results of numerical experiment by two linear bamtmpic rnodcls support the observation.
A Premonitory Sign of Anomalous SSTs over the Eastern Equatorial Pacific and a Forecasting Experiment
“短期气候预测专刊”

ZHANG Qing-Yun,CHANG Rui,
ZHANG Qing-Yun
,CHANG Rui

大气和海洋科学快报 , 2009,
Abstract: A premonitory sign of an anomalous SST over the eastern equatorial Pacific shows up in the North Pacific Subtropical Mode Water (STMW) 18 months earlier, and the air-sea relationship between the STMW and the anomalous SST over the eastern equatorial Pacific is shown. This premonitory connection involves an air-sea coupling between the longtime persistent mid-latitude sea surface temperature anomaly (SSTA) induced by the remote re-emergence of the STMW and the following spring subtropical atmospheric circulation anomalies. An examination of the air-sea interaction reveals that the following spring subtropical atmospheric circulation, which responds to the longtime persistent SSTA, is dominated by the anomalous negative (positive) geopotential height downstream of the negative (positive) SSTA in the strong (weak) STMW case. Thus, the tropics adjust to these anomalies through coupled dynamics, producing positive (negative) SST anomalies over the eastern equatorial Pacific. A cold water event that occurred over the eastern equatorial Pacific during winter 2008-09 was successfully forecasted by the weak summer STMW index in 2007. The evolution of this process for the air-sea interactions from the autumn of 2007 to December 2008 is presented.
Longitudinal Displacement of the Subtropical High in the Western Pacific in Summer and its Influence
YANG Hui,SUN Shuqing,
YANG Hui
,SUN Shuqing

大气科学进展 , 2003,
Abstract: Using the relative vorticity averaged over a certain area, a new index for measuring the longitudinal position of the subtropical high (SH) in the western Pacific is proposed to avoid the increasing trend of heights in the previous indices based on geopotential height. The years of extreme westward and eastward extension of SH using the new index are in good agreement with those defined by height index. There exists a distinct difference in large-scale circulation between the eastward and westward extension of SH under the new definition, which includes not only the circulation in the middle latitudes but also the flow in the lower latitudes. It seems that when the SH extends far to the east (west), the summer monsoon in the South China Sea is stronger (weaker) and established earlier (later). In addition, there exists a good relationship between the longitudinal position of SH and the summer rainfall in China. A remarkable negative correlation area appears in the Changjiang River valley, indicating that when the SH extends westward (eastward), the precipitation in that region increases (decreases). A positive correlation region is found in South China, showing the decrease of rainfall when the SH extends westward. On the other hand, the rainfall is heavier when the SH retreats eastward. However, the anomalous longitudinal position of SH is not significantly related to the precipitation in North China. The calculation of correlation coefficients between the index of longitudinal position of SH and surface temperature in China shows that a large area of positive values, higher than 0.6 in the center, covers the whole of North China, even extending eastward to the Korean Peninsula and Japan Islands when using NCEP/NCAR reanalysis data to do the correlation calculation. This means that when the longitudinal position of the SH withdraws eastward in summer, the temperature over North China is higher. On the other hand, when it moves westward, the temperature there is lower. This could explain the phenomenon of the seriously high temperatures over North China during recent summers, because the longitudinal position of SH in recent summers was located far away from the Asian continent. Another region with large negative correlation coefficients is found in South China.
Adjoint Sensitivity Analyses on the Persistent Anomalous Circulation during the Summer of 1991
1991年夏季持续性异常环流的共轭敏感性分析

Yang Yan,Li Zhijin,Ji Liren,
杨燕
,李志锦,纪立人

大气科学 , 1998,
Abstract: The concept of optimal sensitivity perturbation is developed basing on analyses to adjoint sensitivity The persistent anomalous features of the East Asian summer circulation in 1991, including the Ural blocking, the East Asian dipole blocking and the variation of the subtropical high pressure, which have caused severe floods in the Yangtqe River and Huaihe River valleys are analyzed with the adjoint model Every initial perturbations with the strongest influence upon the above each anomaly, respectively, are obtained The results revealed the most important factors in these systems form a new aspect and showed the efficiency and great potential of further applications of the method of the adjoint sensitivity analysis in the diagnoses of the physical processes of atmospheric general circulation
Summer Diatom Blooms in the North Pacific Subtropical Gyre: 2008–2009  [PDF]
Tracy A. Villareal, Colbi G. Brown, Mark A. Brzezinski, Jeffrey W. Krause, Cara Wilson
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0033109
Abstract: The summertime North Pacific subtropical gyre has widespread phytoplankton blooms between Hawaii and the subtropical front (~30°N) that appear as chlorophyll (chl) increases in satellite ocean color data. Nitrogen-fixing diatom symbioses (diatom-diazotroph associations: DDAs) often increase 102–103 fold in these blooms and contribute to elevated export flux. In 2008 and 2009, two cruises targeted satellite chlorophyll blooms to examine DDA species abundance, chlorophyll concentration, biogenic silica concentration, and hydrography. Generalized observations that DDA blooms occur when the mixed layer depth is < 70 m are supported, but there is no consistent relationship between mixed layer depth, bloom intensity, or composition; regional blooms between 22–34°N occur within a broader temperature range (21–26°C) than previously reported. In both years, the Hemiaulus-Richelia and Rhizosolenia-Richelia DDAs increased 102–103 over background concentrations within satellite-defined bloom features. The two years share a common trend of Hemiaulus dominance of the DDAs and substantial increases in the >10 μm chl a fraction (~40–90+% of total chl a). Integrated diatom abundance varied 10-fold over <10 km. Biogenic silica concentration tracked diatom abundance, was dominated by the >10 μm size fraction, and increased up to 5-fold in the blooms. The two years differed in the magnitude of the surface chl a increase (2009>2008), the abundance of pennate diatoms within the bloom (2009>2008), and the substantially greater mixed layer depth in 2009. Only the 2009 bloom had sufficient chl a in the >10 μm fraction to produce the observed ocean color chl increase. Blooms had high spatial variability; ocean color images likely average over numerous small events over time and space scales that exceed the individual event scale. Summertime DDA export flux noted at the Hawaii time-series Sta. ALOHA is probably a generalized feature of the eastern N. Pacific north to the subtropical front.
Relationship between the zonal displacement of the western Pacific subtropical high and the dominant modes of low-tropospheric circulation in summer

Riyu Lu,Ying Li,Ryu Chan-Su,

自然科学进展 , 2008,
Abstract: The zonal displacement of the western Pacific subtropical high remarkably influences the climate anomalies in China. In this paper, a new zonal index of the subtropical high is defined by modifying previous indices, and is used to investigate the relationship between the zonal displacement of the subtropical high and the dominant modes of 850-hPa circulations. It is found that the zonal displacement of the subtropical high is significantly correlated with the first two leading modes of circulations. In particular, the correlation coefficient between the index and the time series associated with the second mode is as high as 0.78 in 1958-2003 (46 years). Since the second mode is not associated with significant anomalies of sea surface temperatures, the above results imply the difficulty in seasonal forecasting of the zonal displacement for the subtropical high. In addition, the interannual variability in the zonal displacement of the subtropical high is considerably enhanced since 1978, due to the effects of both dominant modes, especially the second mode. This is likely to account for the frequent occurrence of anomalous climate in China during the recent two decades.
A Teleconnection Pattern Related with the Development of the Okhotsk High and the Northward Progress of the Subtropical High in East Asian Summer
东亚夏季一个与鄂霍次克海阻高建立及副高北上相关的遥相关类型(英)

WANG Yafei,Fujiyaoshi YASUSHI,Kato KURANOSHIN,
WANG Yafei
,Fujiyaoshi YASUSHI,Kato KURANOSHIN

大气科学进展 , 2003,
Abstract: This study examines the relationship between the subtropical high in the West Pacific and the Okhotsk high in summer, and explains why the subtropical high cannot progress northward when the Okhotsk high is active. The findings are as follows. (1) A teleconnection pattern, namely, the significant correlation dipole between the index of the Okhotsk high and 500 hPa geopotential height (Z500), over East Asia, tends to occur in summer. (2) The teleconnection is closely related to the wave train propagation from the Okhotsk Sea via Japan to the subtropical regions when the Okhotsk high is developing. (3) The wave train propagation associated with the development of the Okhotsk high can generate a large cyclonic anomaly over the sea east of Japan, even in late summer. The cyclonic anomaly plays an important role in weakening the northern part of the subtropical high. The anomalous southern position of the main body of the subtropical high in the summer of 1998 is partly due to this effect.
Simulating Influence of Positive Sea Surface Temperature Anomalies over the Eastern Equatorial Pacific on Subtropical High over the Western Pacific
赤道东太平洋海温正异常对西太平洋副高影响的数值模拟研究

Long Zhenxia,Li Chongyin,
龙振夏
,李崇银

大气科学 , 2001,
Abstract: IAP 2-level AGCM and LASG 9-level spectral AGCM are employed to simulate the effect of positive SSTAs with different duration (the SSTAs are prescribed only in January, January- February, January-April and January-August with the climatological SST in the other period respectively) over the eastern equatorial Pacific on the subtropical high over the western Pacific. The results suggest that despite the diversity of SSTAs duration, both the distribution and the temporal evolution of the anomalous subtropical high are similar, and so are the rainfall anomalies (therefore the latent release anomalies); the ITCZs are characterized by late northward displacement from the indian Ocean to the western Pacific in May. The agreement between the rainfall anomalies and the subtropical high anomalies over the western Pacific suggests the possible physical link between these two variables. The results also suggest that the atmospheric internal dynamical process is responsible for the insensitivity of atmospheric responses to the duration of SSTAs over the eastern equatorial Pacific. On one hand, the Rossby wave sources maintain the disturbances at middle-high latitudes which are excited in the tropics, on the other hand, the insensitivity of Rossby wave source to the duration of SSTAs over the eastern equatorial Pacific leads to the insensitivity of atmospheric responses to the duration of SSTAs over the eastern equatorial Pacific. The results show when the positive SSTAs are prescribed over the eastern equatorial Pacific, although the atmospheric internal dynamical process plays an important role, there is also obvious influence of positive SSTAs over the eastern equatorial Pacific in summer on the summer subtropical high over the western Pacific, therefore, the predictability of summer subtropical high over the western Pacific is determined by both the SSTA over the equatorial eastern Pacific and the atmospheric internal dynamical process. The different model results also suggest that the above results are model-independent.
Adjoint Sensitivity Analyses on the Anomalous Circulation Features in East Asian Summer Monsoon

Yang Yan,Li Zhijin,Ji Liren,

大气科学进展 , 1997,
Abstract: The concept of optimal sensitivity perturbation (OSP) is developed based on adjoint sensitivity analysis theory. The persistent anomalous features in East Asian summer monsoon system, including the Ural blocking, the Okhotsk Sea dipole blocking and the variations of subtropical high are analyzed and the OSP for each of them evaluated. The results provide us with some new insight into the most significant influential factors for these features. It also demon-strates the great potential for further applications of this method in diagnostics of atmospheric processes
Role of the Pacific and the Indian Ocean in Interdecadal Variation of the South China Sea Summer Monsoon Onset
太平洋和印度洋在南海夏季风爆发年代际变化中的作用

YU Lejiang,HU Dunxin,FENG Junqiao,
于乐江
,胡敦欣,冯俊乔

大气科学 , 2011,
Abstract: The role of the western Pacific and the Indian Ocean in the South China Sea (SCS) summer monsoon onset is investigated by analyzing various atmospheric and oceanic datasets. The Results show that the impact factor of the SCS summer monsoon onset exhibits interdecadal variation. From 1951 to 1970, the impact factor exists in the Indian Ocean, from 1970 to 1998 it occurs in the western Pacific Ocean. The interdecadal variation of impact factor results from the significant abrupt change of the Arctic Oscillation (AO) and the intensity of the Western Pacific Subtropical High (WPSH). For the period of 1951 through 1970, an anomalous westerly wind over the northern Indian Ocean induced by a negative AO index and the weak WPSH that are helpful to the SCS summer monsoon onset make the zonal wind over the northern Indian Ocean the main factor controlling the SCS summer monsoon onset. Meanwhile, during the period, the southern Indian Ocean Subtropical Dipole (IOSD) is closely related to the SCS summer onset. The positive IOSD (with positive SST anomaly in the southwestern Indian Ocean, a negative SST anomaly in the other regions) results in anomalous westerly wind over the northern Indian Ocean and early onset of the SCS summer monsoon, and vice versa. For the period of 1971 to 1998, an anomalous easterly wind induced by a positive AO index and stronger WPSH offer an unhelpful condition for the SCS summer monsoon onset when the heat content in the western Pacific warm pool become the main factor controlling the SCS summer monsoon onset. The positive (negative) anomalous heat content in the western Pacific warm pool leads to earlier (later) onset of the SCS summer monsoon.
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