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 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 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 Interannual and Interdecadal Variability of Thailand Summer Monsoon Season

2005 ◽  
Vol 18 (11) ◽  
pp. 1697-1708 ◽  
Author(s):  
Nkrintra Singhrattna ◽  
Balaji Rajagopalan ◽  
K. Krishna Kumar ◽  
Martyn Clark
Keyword(s):  
Summer Monsoon ◽  
El Niño ◽  
Large Scale ◽  
Monsoon Rainfall ◽  
El Nino ◽  
Southern Oscillation ◽  
Negative Relationship ◽  
Walker Circulation ◽  
Planning And Management ◽  
The Walker Circulation

Abstract Summer monsoon rains are a critical factor in Thailand’s water resources and agricultural planning and management. In fact, they have a significant impact on the country’s economic health. Consequently, understanding the variability of the summer monsoon rains over Thailand is important for instituting effective mitigating strategies against extreme rainfall fluctuations. To this end, the authors systematically investigated the relationships between summer monsoon precipitation from the central and northern regions of Thailand and large-scale climate features. It was found that Pacific sea surface temperatures (SSTs), in particular, El Niño–Southern Oscillation (ENSO), have a negative relationship with the summer monsoon rainfall over Thailand in recent decades. However, the relationship between summer rainfall and ENSO was weak prior to 1980. It is hypothesized that the ENSO teleconnection depends on the SST configuration in the tropical Pacific Ocean, that is, an eastern Pacific–based El Niño pattern, such as is the case in most of the post-1980 El Niño events, tends to place the descending limb of the Walker circulation over the Thailand–Indonesian region, thereby significantly reducing convection and consequently, rainfall over Thailand. It is believed that this recent shift in the Walker circulation is instrumental for the nonstationarity in ENSO–monsoon relationships in Thailand. El Niños of 1997 and 2002 corroborate this hypothesis. This has implications for monsoon rainfall forecasting and, consequently, for resources planning and management.

Two Tropical Routes for the Remote Influence of the Northern Tropical Atlantic on the Indo−western Pacific Summer Climate

2020 ◽  
pp. 1-51
Author(s):  
Yuhei Takaya ◽  
Naoaki Saito ◽  
Ichiro Ishikawa ◽  
Shuhei Maeda
Keyword(s):  
El Niño ◽  
El Nino ◽  
Walker Circulation ◽  
La Niña ◽  
Western Pacific ◽  
Tropical Atlantic ◽  
Summer Climate ◽  
La Nina ◽  
The Impact ◽  
Northern Tropical Atlantic

AbstractThis study investigates the influence of sea surface temperature (SST) in the northern tropical Atlantic (NTA) on the Indo−western Pacific summer climate by analyzing record-high NTA SSTs summer in 2010. In that time, a decaying El Niño and developing La Niña were accompanied by widespread anomalous climate conditions in the Indo-western Pacific. These conditions are typical of summers that follow El Niño events and are often explained as being due to the influence of Indian Ocean warming induced by the El Niño. Meanwhile, the record high NTA SSTs that also resulted from the influence of the El Niño, the negative phase of the North Atlantic Oscillation as well as the interdecadal-and-longer NTA SST variability, is one of possible causes of anomalous conditions in the Indo−western Pacific. The results of sensitivity experiments using a coupled atmosphere−ocean model clearly indicate that the high NTA SSTs had a considerable influence on the summer weather in the Indo−western Pacific via two tropical routes: an eastbound route that involved a reinforcement of the atmospheric equatorial Kelvin wave and a westbound route that involved altering the Walker circulation over the Atlantic−Pacific region. The altered Walker circulation facilitated the transition to La Niña, amplifying the impact on the western North Pacific monsoon. Further evaluation reveals that both the interannual and interdecadal-and-longer variability of the NTA SST contributed to the anomalous Indo−western Pacific summer. The results highlight the interannual to multidecadal predictability of the Indo−western Pacific summer climate that originates in the NTA.

scholarly journals On the initiation of the walker circulation during 1982/1983 enso event

2009 ◽  
Vol 24 (1) ◽  
pp. 63-68 ◽  
Author(s):  
José Augusto Paixão Veiga ◽  
Vadlamudi Brahmananda Rao ◽  
Sérgio Henrique Franchito
Keyword(s):  
El Nino ◽  
Walker Circulation ◽  
Ocean Surface ◽  
Enso Event ◽  
Western Pacific ◽  
Sea Surface ◽  
Eastern Pacific ◽  
El Niño Event ◽  
Surface Gradient ◽  
The Walker Circulation

The GEOS-1 data from multiyear reanalysis are using. An altered Walker Circulation is initiated by the rising motion created over the warm ocean surface on the eastern Pacific. This occurred during the major El Niño event of 1982-1983. To compensate the rising motion, a sinking motion is generated over western Pacific completing the formation of the altered Walker Circulation. Thus, the initiation of the altered Walker Circulation is by the sea surface gradient as originally envisioned by Bjerknes.

scholarly journals Links between Tropical Pacific SST and Cholera Incidence in Bangladesh: Role of the Western Tropical and Central Extratropical Pacific

2009 ◽  
Vol 22 (7) ◽  
pp. 1641-1660 ◽  
Author(s):  
Benjamin A. Cash ◽  
Xavier Rodó ◽  
James L. Kinter
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Tropical Pacific ◽  
Western Pacific ◽  
Monsoon Circulation ◽  
Global Response ◽  
The Indian Ocean ◽  
The Western Pacific ◽  
Sst Anomalies

Abstract Recent studies arising from both statistical analysis and dynamical disease models demonstrate a link between the incidence of cholera, a paradigmatic waterborne bacterial illness endemic to Bangladesh, and the El Niño–Southern Oscillation (ENSO). The physical significance of this relationship was investigated by examining links between the regional climate of Bangladesh and western Pacific sea surface temperatures (SST) associated with ENSO using a pacemaker configuration of the Center for Ocean–Land–Atmosphere Studies atmospheric general circulation model. The global SST response to ENSO SST anomalies in the western Pacific alone is found to be relatively weak and unrealistic when compared to observations, indicating that the global response to ENSO is driven primarily by anomalies in the central and eastern tropical Pacific. Despite the weak global response to western Pacific SST anomalies, however, a signal is found in summer rainfall over India and Bangladesh. Specifically, reduced rainfall typically follows winter El Niño events. In the absence of warm SST anomalies in the eastern Pacific, cold anomalies in the western Pacific produce a La Niña–like response in the model circulation. Cold SST anomalies suppress convection over the western Pacific. Large-scale convergence shifts into the eastern Indian Ocean and modifies the summer monsoon circulation over India and Bangladesh. The probabilistic relationship between Bangladesh rainfall and SST is also explored using a nonparametric statistical technique. Decreased rainfall is strongly associated with cold SST in the western Pacific, while associations between SST and enhanced rainfall are substantially weaker. Also found are strong associations between rainfall and SST in the Indian Ocean in the absence of differences in forcing from the western Pacific. It thus appears that the Indian Ocean may represent an independent source of predictability for the monsoon and cholera risk. Likewise, under certain circumstances, the western Pacific may also exert a significant influence on Bangladesh rainfall and cholera risk.

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.

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