scholarly journals Local and Remote Factors Affecting the SST–Precipitation Relationship over the Western North Pacific during Summer

2014 ◽  
Vol 27 (13) ◽  
pp. 5132-5147 ◽  
Author(s):  
Riyu Lu ◽  
Shu Lu
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
East Asian ◽  
Sea Surface ◽  
Circulation Anomaly ◽  
Factors Affecting ◽  
Monsoon Variability ◽  
East Asian Climate ◽  
Atmospheric Variations ◽  
Sst Anomalies

The western North Pacific (WNP) monsoon variability plays an important role in East Asian climate, and it highlights the importance of understanding atmosphere–ocean interaction determining WNP variability. A key characteristic of atmosphere–ocean interaction is the local relationship between sea surface temperatures and precipitation (SST–P), which over the WNP exhibits a weak and negative correlation; this indicates that atmospheric variations lead to SST anomalies. This study investigates the underlying physical causes of this relationship, and it suggests that the inverse SST–P relationship over the WNP results from a local anomalous lower-tropospheric anticyclone or cyclone. A strong and negative SST–P correlation corresponds to a strong cyclonic/anticyclonic anomaly, while a weak SST–P relationship is related to a weak circulation anomaly. This study suggests that the remote effects play a crucial role in forming the inverse SST–P relationship over the WNP, while local SSTs tend to result in a positive SST–P correlation and partially offset the remote effects. Furthermore, the negative SST–P relationship over the WNP tends to be associated with rapid transitions of SST anomalies in the equatorial central and eastern Pacific, implying that atmosphere–ocean interaction over the WNP during summer may be affected by and in turn modify the evolution of ENSO.

Decadal Variability of the Anticyclone in the Western North Pacific

2020 ◽  
Vol 33 (20) ◽  
pp. 9031-9043
Author(s):  
Mingmei Xie ◽  
Chunzai Wang
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Decadal Variability ◽  
East Asian ◽  
Hadley Circulation ◽  
Walker Circulation ◽  
Decadal Time Scale ◽  
Anomalous Anticyclone ◽  
East Asian Climate ◽  
Decadal Mode

AbstractThe western North Pacific anomalous anticyclone (WNPAC) significantly affects East Asian climate. Previous studies have elucidated interannual variability of the WNPAC associated with El Niño, but decadal variability of the WNPAC remains unknown. The present paper investigates the dominant modes of decadal variability of the WNPAC by using observational data. The first decadal mode, characterized by an anomalous anticyclone centered over the western North Pacific, is associated with the Pacific decadal oscillation (PDO). The relationship between the first mode and the PDO shifted from in phase to out of phase around 1966. From 1900 to 1966 when the PDO and the first mode are in phase, the anticyclone is maintained by the effects of both the strengthened Aleutian low through meridional atmospheric forcing and Indian Ocean warming through enhanced zonal Walker circulation. From 1967 to 2012, the anticyclone is induced by cold SST anomalies over the central equatorial Pacific when the PDO and the first mode are out of phase. The second decadal mode is characterized by an anomalous anticyclone extending from southeastern China to the Philippine Sea and is associated with the Maritime Continent (MC). This anticyclone resides in the sinking branch of the local Hadley circulation, triggered by enhanced convection associated with the MC warming from 1900 to 2012. The finding of the decadal WNPAC in this paper may provide a new way to explain East Asian climate on a decadal time scale.

scholarly journals Coupling Modes of Climatological Intraseasonal Oscillation in the East Asian Summer Monsoon

2016 ◽  
Vol 29 (17) ◽  
pp. 6363-6382 ◽  
Author(s):  
Zehao Song ◽  
Congwen Zhu ◽  
Jingzhi Su ◽  
Boqi Liu
Keyword(s):  
East Asia ◽  
North Pacific ◽  
East Asian Summer Monsoon ◽  
Western North Pacific ◽  
Diabatic Heating ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Intraseasonal Oscillation ◽  
Rainfall Anomaly ◽  
Asian Summer

Abstract The present study used harmonic and multivariate empirical orthogonal function (MV-EOF) analyses to identify the existence of climatological intraseasonal oscillation (CISO) in the diabatic heating, precipitation, and circulation of the East Asian summer monsoon (EASM). The strongest CISO signals are found in the north of the western North Pacific, possibly because of the horizontal gradient of diabatic heating induced by the seasonal land–sea thermal contrast. Further, the phase relationship between the diabatic heating components maintains the EASM CISO. The first two coupling modes of EASM CISO in the circulation are robust during May through August, with a period of 40–80 days, and exhibit phase locking to the stepwise establishment of the EASM, which reveals the coaction of the Mongolian cyclone (MC) around Lake Baikal at 850 hPa, the western North Pacific subtropical high (WNPSH) at 500 hPa, and the South Asian high (SAH) over the Tibetan Plateau (TP) at 200 hPa. The first mode shows that the jointly enhanced MC, WNPSH, and SAH correspond to a tripole rainfall anomaly with strong mei-yu and baiu fronts over East Asia. The second mode, however, indicates the eastward and northwestward propagation of MC and WNPSH, respectively, with suppressed SAH, as well as a dipole rainfall anomaly over East Asia. Both the observations and numerical simulation verify the importance of daily diabatic heating and SST in maintaining the CISO modes over the WNP, where the condensation heating related to atmospheric forcing determines the local intraseasonal air–sea interaction.

scholarly journals Association of the Poleward Shift of East Asian Subtropical Upper-Level Jet with Frequent Tropical Cyclone Activities over the Western North Pacific in Summer

2017 ◽  
Vol 30 (14) ◽  
pp. 5597-5603 ◽  
Author(s):  
Xian Chen ◽  
Zhong Zhong ◽  
Wei Lu
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
East Asian ◽  
Teleconnection Pattern ◽  
Reanalysis Dataset ◽  
Poleward Shift ◽  
Upper Level ◽  
Upper Level Jet

The NCEP–NCAR reanalysis dataset and the tropical cyclone (TC) best-track dataset from the Regional Specialized Meteorological Center (RSMC) Tokyo Typhoon Center were employed in the present study to investigate the possible linkage of the meridional displacement of the East Asian subtropical upper-level jet (EASJ) with the TC activity over the western North Pacific (WNP). Results indicate that summertime frequent TC activities would create the poleward shift of the EASJ through a stimulated Pacific–Japan (PJ) teleconnection pattern as well as the changed large-scale meridional temperature gradient. On the contrary, in the inactive TC years, the EASJ is often located more southward than normal with an enhanced intensity. Therefore, TC activities over the WNP are closely related to the location and intensity of the EASJ in summer at the interannual time scale.

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