scholarly journals Recent Shift in the State of the Western Pacific Subtropical High due to ENSO Change

2020 ◽  
Vol 33 (1) ◽  
pp. 229-241 ◽  
Author(s):  
Zongci Huang ◽  
Wenjun Zhang ◽  
Xin Geng ◽  
Fei-Fei Jin
Keyword(s):  
El Niño ◽  
El Nino ◽  
Western Pacific Subtropical High ◽  
Western Pacific ◽  
Recent Period ◽  
Decadal Shift ◽  
Dipole Structure ◽  
Ep El Niño ◽  
Oscillating Period ◽  
The Tropical Pacific

AbstractThe boreal summer western Pacific subtropical high (WPSH) exhibits a remarkable decadal shift in its spatial pattern and periodicity around the late 1990s. In the former period, the WPSH is primarily characterized by a large-scale uniform pattern over Asia and its surrounding area with an oscillating period of ~4–5 yr. However, the WPSH-related atmospheric circulations shift to a dipole structure and oscillate at ~2–3 yr in the recent period. We found that this decadal shift is largely contributed by the ENSO regime change. During the former period, the tropical Pacific was dominated by the conventional eastern Pacific (EP) El Niño–Southern Oscillation (ENSO) with an oscillating period of ~4–5 yr. Strong anticyclone anomalies usually are maintained over the western North Pacific (WNP) during the EP El Niño decaying summer, accounting for most of the WPSH temporal and spatial variability. In contrast, the recent period features much more frequent occurrence of central Pacific (CP) El Niño events in the tropical Pacific with a ~2–3-yr oscillating period. A dipole structure in the WNP and Indian Ocean is evident during both developing and decaying summers of CP El Niño, consistent with the WPSH leading mode after the late 1990s. The results have important implications for seasonal prediction of the WPSH and associated Asian summer climate anomalies.

scholarly journals Water vapor anomaly over the tropical western Pacific in El Niño winters from radiosonde and satellite observations

2021 ◽  
Author(s):  
Minkang Du ◽  
Kaiming Huang ◽  
Shaodong Zhang ◽  
Chunming Huang ◽  
Yun Gong ◽  
...  
Keyword(s):  
Water Vapor ◽  
El Niño ◽  
El Nino ◽  
Walker Circulation ◽  
Western Pacific ◽  
Monsoon Circulation ◽  
Circulation Anomaly ◽  
Tropical Western Pacific ◽  
Ep El Niño ◽  
The Walker Circulation

Abstract. Using radiosonde observations at five stations in the tropical western Pacific and reanalysis data for 15 years from 2005 to 2019, we report an extremely negative anomaly in atmospheric water vapor during the super El Niño winter of 2015/16, and compare the anomaly with that in the other three El Niño winters. Strong specific humidity anomaly is concentrated below 8 km of the troposphere with a peak at 2.5–3.5 km, and column integrated water vapor mass anomaly over the five radiosonde sites has a large negative correlation coefficient of −0.63 with oceanic Niño3.4 index, but with a lag of about 2–3 months. In general, the tropical circulation anomaly in the El Niño winter is characterized by divergence (convergence) in the lower troposphere over the tropical western (eastern) Pacific, thus the water vapor decreases over the tropical western Pacific as upward motion is suppressed. The variability of the Hadley circulation is quite small and has little influence on the observed water vapor anomaly. The anomaly of the Walker circulation makes a considerable contribution to the total anomaly in all the four El Niño winters, especially in the 2006/07 and 2015/16 eastern-Pacific (EP) El Niño events. The monsoon circulation shows a remarkable change from one to the other event, and its anomaly is large in the 2009/10 and 2018/19 central-Pacific (CP) El Niño winters and small in the two EP El Niño winters. The observed water vapor anomaly is caused mainly by the Walker circulation anomaly in the supper EP event of 2015/16 but by the monsoon circulation anomaly in the strong CP event of 2009/10. Owing to the anomalous decrease in upward transport of water vapor during the El Niño winter, less cloud amount and more outgoing longwave radiation over the five stations are clearly presented in satellite observation.

scholarly journals CP El Niño and PDO Variability Affect Summer Precipitation over East China

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Wan-Jiao Song ◽  
Qi-Guang Wang
Keyword(s):  
El Niño ◽  
El Nino ◽  
Summer Precipitation ◽  
Western Pacific Subtropical High ◽  
Western Pacific ◽  
Subtropical High ◽  
East China ◽  
Central Pacific ◽  
Cp El Niño ◽  
Precipitation Anomalies

The summer precipitation produced by the East Asian summer monsoon (EASM) is significantly affecting agriculture and socioeconomics. Based on the Precipitation Reconstruction dataset in East China from 1950 to 2017, we investigate the spatiotemporal variations of summer precipitation, influencing environmental factors and their relation with the EASM and the Pacific Decadal Oscillation (PDO) in both central Pacific (CP) El Niño developing and decaying years. Results indicate the following: (1) The evolutions of CP El Niño events modulate the summer precipitation anomalies in East China. In the cool PDO phase, CP El Niño causes enhanced precipitation anomalies in the decaying years but less precipitation anomalies in the developing years, and vice versa for the warm PDO phase. (2) Atmospheric circulation anomalies drive the moisture transportation and combine the motion of western Pacific subtropical high resulting in the variation of precipitation patterns. Anomalous cyclone over the western North Pacific and the sustained Western Pacific Subtropical High (WPSH) are favorable for the increment of summer precipitation. (3) The different CP El Niño-EASM relationship is caused by the influences of PDO on the evolution of CP El Niño. CP El Niño develops slowly (decays rapidly) and is associated with rapidly developing (slowly decaying) anomalous warming in the north Indian Ocean during the developing (decaying) years.

scholarly journals Relationship Analysis between Runoff of Dadu River Basin and El Niño

2018 ◽  
Vol 246 ◽  
pp. 01074
Author(s):  
Zujian Zou ◽  
Yubin He
Keyword(s):  
River Basin ◽  
El Niño ◽  
El Nino ◽  
Western Pacific Subtropical High ◽  
Western Pacific ◽  
Subtropical High ◽  
Tibet Plateau ◽  
Rainfall Runoff ◽  
Dadu River ◽  
The Western Pacific

The Dadu River Basin is located in the transitional zone between the Qinghai-Tibet Plateau and the Sichuan Basin. It is alternately affected by various weather systems such as the western Pacific subtropical high, the Qinghai-Tibet high (anti-cyclone), the southwest warm and humid air current, and the southeast monsoon. The western Pacific subtropical high is one of the main influencing factors of rainfall runoff in the basin. During the El Niño period, the western Pacific subtropical high moved eastward and the position was southward. The warm and humid airflow and the southeast monsoon northward changed, and the rainfall runoff in the Dadu River Basin changed.By analyzing the development of the El Niño phenomenon, Divide an El Niño process into different stages of occurrence, development, and end. Combining the characteristics of the Dadu River runoff in each stage, Studying the runoff situation of the Dadu River Basin under different strengths and weaknesses of the El Niño phenomenon. Using the correlation method to establish a model of the relationship between the abundance of the Dadu River Basin and the El Niño strength and weakness. Providing new ideas and new methods for the accurate prediction of the incoming water of the Dadu River under the abnormal climatic conditions of El Niño. It provides technical support for reservoir dispatching, flood control dispatching and economic dispatching of cascade hydropower stations, and provides experience for other river basins to cope with complex climate situations and improve water regime forecasting levels.

scholarly journals The Changing Impact Mechanisms of a Diverse El Niño on the Western Pacific Subtropical High

2019 ◽  
Vol 46 (2) ◽  
pp. 953-962 ◽  
Author(s):  
Mengyan Chen ◽  
Jin‐Yi Yu ◽  
Xin Wang ◽  
Wenping Jiang
Keyword(s):  
El Niño ◽  
El Nino ◽  
Western Pacific Subtropical High ◽  
Western Pacific ◽  
Subtropical High ◽  
The Western Pacific

scholarly journals Evolution of the Madden–Julian Oscillation in Two Types of El Niño

2016 ◽  
Vol 29 (5) ◽  
pp. 1919-1934 ◽  
Author(s):  
Xiong Chen ◽  
Jian Ling ◽  
Chongyin Li
Keyword(s):  
El Niño ◽  
El Nino ◽  
Moisture Flux ◽  
Early Summer ◽  
Western Pacific ◽  
Madden Julian Oscillation ◽  
Central Pacific ◽  
Cp El Niño ◽  
Ep El Niño ◽  
The Western Pacific

Abstract Evolution characteristics of the Madden–Julian oscillation (MJO) during the eastern Pacific (EP) and central Pacific (CP) types of El Niño have been investigated. MJO activities are strengthened over the western Pacific during the predeveloping and developing phases of EP El Niño, but suppressed during the mature and decaying phases. In contrast, MJO activities do not show a clear relationship with CP El Niño before their occurrence over the western Pacific, but they increase over the central Pacific during the mature and decaying phases of CP El Niño. Lag correlation analyses further confirm that MJO activities over the western Pacific in boreal spring and early summer are closely related to EP El Niño up to 2–11 months later, but not for CP El Niño. EP El Niño tends to weaken the MJO and lead to a much shorter range of its eastward propagation. Anomalous descending motions over the Maritime Continent and western Pacific related to El Niño can suppress convection and moisture flux convergence there and weaken MJO activities over these regions during the mature phase of both types of El Niño. MJO activities over the western Pacific are much weaker in EP El Niño due to the stronger anomalous descending motions. Furthermore, the MJO propagates more continuously and farther eastward during CP El Niño because of robust moisture convergence over the central Pacific, which provides adequate moisture for the development of MJO convection.

scholarly journals Dipole Structure of Mixed Layer Salinity in Response to El Niño‐La Niña Asymmetry in the Tropical Pacific

2019 ◽  
Vol 46 (21) ◽  
pp. 12165-12172 ◽  
Author(s):  
Cong Guan ◽  
Shijian Hu ◽  
Michael J. McPhaden ◽  
Fan Wang ◽  
Shan Gao ◽  
...  
Keyword(s):  
Mixed Layer ◽  
El Niño ◽  
El Nino ◽  
Tropical Pacific ◽  
La Niña ◽  
Dipole Structure ◽  
La Nina ◽  
The Tropical Pacific

scholarly journals Changes in Sea Salt Emissions Enhance ENSO Variability

2016 ◽  
Vol 29 (23) ◽  
pp. 8575-8588 ◽  
Author(s):  
Yang Yang ◽  
Lynn M. Russell ◽  
Sijia Lou ◽  
Maryam A. Lamjiri ◽  
Ying Liu ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
El Niño ◽  
El Nino ◽  
Sea Salt ◽  
La Niña ◽  
Western Pacific ◽  
Interannual Variations ◽  
Enso Variability ◽  
La Nina ◽  
The Tropical Pacific

Abstract Two 150-yr preindustrial simulations with and without interactive sea salt emissions from the Community Earth System Model (CESM) are performed to quantify the interactions between sea salt emissions and El Niño–Southern Oscillation (ENSO). Variations in sea salt emissions over the tropical Pacific Ocean are affected by changing wind speed associated with ENSO variability. ENSO-induced interannual variations in sea salt emissions result in decreasing (increasing) aerosol optical depth (AOD) by 0.03 over the equatorial central-eastern (western) Pacific Ocean during El Niño events compared to those during La Niña events. These changes in AOD further increase (decrease) radiative fluxes into the atmosphere by +0.2 (−0.4) W m−2 over the tropical eastern (western) Pacific. Thereby, sea surface temperature increases (decreases) by 0.2–0.4 K over the tropical eastern (western) Pacific Ocean during El Niño compared to La Niña events and enhances ENSO variability by 10%. The increase in ENSO amplitude is a result of systematic heating (cooling) during the warm (cold) phase of ENSO in the eastern Pacific. Interannual variations in sea salt emissions then produce the anomalous ascent (subsidence) over the equatorial eastern (western) Pacific between El Niño and La Niña events, which is a result of heating anomalies. Owing to variations in sea salt emissions, the convective precipitation is enhanced by 0.6–1.2 mm day−1 over the tropical central-eastern Pacific Ocean and weakened by 0.9–1.5 mm day−1 over the Maritime Continent during El Niño compared to La Niña events, enhancing the precipitation variability over the tropical Pacific.

scholarly journals Water vapor anomaly over the tropical western Pacific in El Niño winters from radiosonde and satellite observations and ERA5 reanalysis data

2021 ◽  
Vol 21 (17) ◽  
pp. 13553-13569
Author(s):  
Minkang Du ◽  
Kaiming Huang ◽  
Shaodong Zhang ◽  
Chunming Huang ◽  
Yun Gong ◽  
...  
Keyword(s):  
Water Vapor ◽  
El Niño ◽  
El Nino ◽  
Walker Circulation ◽  
Reanalysis Data ◽  
Western Pacific ◽  
Monsoon Circulation ◽  
Circulation Anomaly ◽  
Tropical Western Pacific ◽  
Ep El Niño

Abstract. Using radiosonde observations at five stations in the tropical western Pacific and reanalysis data for the 15 years from 2005 to 2019, we report an extremely negative anomaly in atmospheric water vapor during the super El Niño winter of 2015/16 and compare the anomaly with that in the other three El Niño winters of the period. A strong specific humidity anomaly is concentrated below 8 km of the troposphere with a peak at 2.5–3.5 km, and a column-integrated water vapor mass anomaly over the five radiosonde sites has a large negative correlation coefficient of −0.63 with the oceanic Niño3.4 index but with a lag of about 2–3 months. In general, the tropical circulation anomaly in the El Niño winter is characterized by divergence (convergence) in the lower troposphere over the tropical western (eastern) Pacific; thus, the water vapor decreases over the tropical western Pacific as upward motion is suppressed. The variability of the Hadley circulation is quite small and has little influence on the observed water vapor anomaly. The anomaly of the Walker circulation makes a considerable contribution to the total anomaly in all four El Niño winters, especially in the 2006/07 and 2015/16 eastern Pacific (EP) El Niño events. The monsoon circulation shows a remarkable change from one event to another, and its anomaly is large in the 2009/10 and 2018/19 central Pacific (CP) El Niño winters and small in the two EP El Niño winters. The observed water vapor anomaly is caused mainly by the Walker circulation anomaly in the super EP event of 2015/16 but is caused by the monsoon circulation anomaly in the strong CP event of 2009/10. The roles of the Hadley, Walker, and monsoon circulations in the EP and CP events are confirmed by the composite EP and CP El Niños based on the reanalysis data for 41 years. Owing to the anomalous decrease in upward transport of water vapor during the El Niño winter, lower cloud amounts and more outgoing longwave radiation over the five stations are clearly presented in satellite observation. In addition, a detailed comparison of water vapor in the reanalysis, radiosonde, and satellite data shows a fine confidence level for the datasets; nevertheless, the reanalysis seems to slightly underestimate the water vapor over the five stations in the 2009/10 winter.

scholarly journals A review of ENSO theories

2018 ◽  
Vol 5 (6) ◽  
pp. 813-825 ◽  
Author(s):  
Chunzai Wang
Keyword(s):  
El Niño ◽  
El Nino ◽  
Enso Event ◽  
Tropical Pacific ◽  
Kelvin Waves ◽  
Western Pacific ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Negative Feedbacks ◽  
The Tropical Pacific

Abstract The El Niño and the Southern Oscillation (ENSO) occurrence can be usually explained by two views of (i) a self-sustained oscillatory mode and (ii) a stable mode interacting with high-frequency forcing such as westerly wind bursts and Madden-Julian Oscillation events. The positive ocean–atmosphere feedback in the tropical Pacific hypothesized by Bjerknes leads the ENSO event to a mature phase. After ENSO event matures, negative feedbacks are needed to cease the ENSO anomaly growth. Four negative feedbacks have been proposed: (i) reflected Kelvin waves at the ocean western boundary, (ii) a discharge process due to Sverdrup transport, (iii) western-Pacific wind-forced Kelvin waves and (iv) anomalous zonal advections and wave reflection at the ocean eastern boundary. These four ENSO mechanisms are respectively called the delayed oscillator, the recharge–discharge oscillator, the western-Pacific oscillator and the advective–reflective oscillator. The unified oscillator is developed by including all ENSO mechanisms, i.e. all four ENSO oscillators are special cases of the unified oscillator. The tropical Pacific Ocean and atmosphere interaction can also induce coupled slow westward- and eastward-propagating modes. An advantage of the coupled slow modes is that they can be used to explain the propagating property of interannual anomalies, whereas the oscillatory modes produce a standing oscillation. The research community has recently paid attention to different types of ENSO events by focusing on the central-Pacific El Niño. All of the ENSO mechanisms may work for the central-Pacific El Niño events, with an addition that the central-Pacific El Niño may be related to forcing or processes in the extra-tropical Pacific.

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