scholarly journals Indian Ocean Capacitor Effect on Indo–Western Pacific Climate during the Summer following El Niño

2009 ◽  
Vol 22 (3) ◽  
pp. 730-747 ◽  
Author(s):  
Shang-Ping Xie ◽  
Kaiming Hu ◽  
Jan Hafner ◽  
Hiroki Tokinaga ◽  
Yan Du ◽  
...  
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Western Pacific ◽  
Northwest Pacific ◽  
Tropospheric Temperature ◽  
Kelvin Wave ◽  
Climate Anomalies ◽  
Summer Climate ◽  
Anomalous Anticyclone

Abstract Significant climate anomalies persist through the summer (June–August) after El Niño dissipates in spring over the equatorial Pacific. They include the tropical Indian Ocean (TIO) sea surface temperature (SST) warming, increased tropical tropospheric temperature, an anomalous anticyclone over the subtropical northwest Pacific, and increased mei-yu–baiu rainfall over East Asia. The cause of these lingering El Niño effects during summer is investigated using observations and an atmospheric general circulation model (GCM). The results herein indicate that the TIO warming acts like a capacitor anchoring atmospheric anomalies over the Indo–western Pacific Oceans. It causes tropospheric temperature to increase by a moist-adiabatic adjustment in deep convection, emanating a baroclinic Kelvin wave into the Pacific. In the northwest Pacific, this equatorial Kelvin wave induces northeasterly surface wind anomalies, and the resultant divergence in the subtropics triggers suppressed convection and the anomalous anticyclone. The GCM results support this Kelvin wave–induced Ekman divergence mechanism. In response to a prescribed SST increase over the TIO, the model simulates the Kelvin wave with low pressure on the equator as well as suppressed convection and the anomalous anticyclone over the subtropical northwest Pacific. An additional experiment further indicates that the north Indian Ocean warming is most important for the Kelvin wave and northwest Pacific anticyclone, a result corroborated by observations. These results have important implications for the predictability of Indo–western Pacific summer climate: the spatial distribution and magnitude of the TIO warming, rather than simply whether there is an El Niño in the preceding winter, affect summer climate anomalies over the Indo–western Pacific and East Asia.

scholarly journals Tropical Indian Ocean Influence on Northwest Pacific Tropical Cyclones in Summer following Strong El Niño*

2011 ◽  
Vol 24 (1) ◽  
pp. 315-322 ◽  
Author(s):  
Yan Du ◽  
Lei Yang ◽  
Shang-Ping Xie
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Tropical Indian Ocean ◽  
Vertical Shear ◽  
Northwest Pacific ◽  
Kelvin Wave ◽  
Anomalous Anticyclone ◽  
The Western Pacific ◽  
Inducing Surface

Abstract In the summer following a strong El Niño, tropical cyclone (TC) number decreases over the Northwest (NW) Pacific despite little change in local sea surface temperature. The authors’ analysis suggests El Niño–induced tropical Indian Ocean (TIO) warming as the cause. The TIO warming forces a warm tropospheric Kelvin wave that propagates into the western Pacific. Inducing surface divergence off the equator, the tropospheric Kelvin wave suppresses convection and induces an anomalous anticyclone over the NW Pacific, both anomalies unfavorable for TCs. The westerly vertical shear associated with the warm Kelvin wave reduces the magnitude of vertical shear in the South China Sea and strengthens it in the NW Pacific, an east–west variation that causes TC activity to increase and decrease in respective regions. These results help improve seasonal TC prediction.

scholarly journals Interdecadal Variations in ENSO Influences on Northwest Pacific–East Asian Early Summertime Climate Simulated in CMIP5 Models

2014 ◽  
Vol 27 (15) ◽  
pp. 5982-5998 ◽  
Author(s):  
Kaiming Hu ◽  
Gang Huang ◽  
Xiao-Tong Zheng ◽  
Shang-Ping Xie ◽  
Xia Qu ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Early Summer ◽  
Specific Humidity ◽  
Cmip5 Models ◽  
Boreal Summer ◽  
Northwest Pacific ◽  
Tropospheric Temperature ◽  
Summer Climate ◽  
Anomalous Anticyclone

Abstract The present study investigates interdecadal modulations of the El Niño–Southern Oscillation (ENSO) influence on the climate of the northwest Pacific (NWP) and East Asia (EA) in early boreal summer following a winter ENSO event, based on 19 simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5). In the historical run, 8 out of 19 models capture a realistic relationship between ENSO and NWP early summer climate—an anomalous anticyclone develops over the NWP following a winter El Niño event—and the interdecadal modulations of this correlation. During periods when the association between ENSO and NWP early summer climate is strong, ENSO variance and ENSO-induced anomalies of summer sea surface temperature (SST) and tropospheric temperature over the tropical Indian Ocean (TIO) all strengthen relative to periods when the association is weak. In future projections with representative concentration pathways 4.5 and 8.5, the response of TIO SST, tropospheric temperature, and NWP anomalous anticyclone to ENSO all strengthen regardless of ENSO amplitude change. In a warmer climate, low-level specific humidity response to interannual SST variability strengthens following the Clausius–Clapeyron equation. The resultant intensification of tropospheric temperature response to interannual TIO warming is suggested as the mechanism for the strengthened ENSO effect on NWP–EA summer climate.

Interdecadal Variations in ENSO Teleconnection to the Indo–Western Pacific for 1870–2007

2012 ◽  
Vol 25 (5) ◽  
pp. 1722-1744 ◽  
Author(s):  
J. S. Chowdary ◽  
Shang-Ping Xie ◽  
Hiroki Tokinaga ◽  
Yuko M. Okumura ◽  
Hisayuki Kubota ◽  
...  
Keyword(s):  
Twentieth Century ◽  
Indian Ocean ◽  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Southern Oscillation ◽  
Western Pacific ◽  
Northwest Pacific ◽  
Early Twentieth Century ◽  
Late Nineteenth

Slow modulation of interannual variability and its relationship to El Niño–Southern Oscillation (ENSO) is investigated for the period of 1870–2007 using shipboard surface meteorological observations along a frequently traveled track across the north Indian Ocean (NIO; from the Gulf of Aden through Malacca Strait) and the South China Sea (to Luzon Strait). During the decades in the late nineteenth–early twentieth century and in the late twentieth century, the El Niño–induced NIO warming persists longer than during the 1910s–mid-1970s, well into the summer following the peak of El Niño. During the epochs of the prolonged NIO warming, rainfall drops and sea level pressure rises over the tropical northwest Pacific in summer following El Niño. Conversely, during the period when the NIO warming dissipates earlier, these atmospheric anomalies are not well developed. This supports the Indian Ocean capacitor concept as a mechanism prolonging El Niño influence into summer through the persistent Indian Ocean warming after El Niño itself has dissipated. The above centennial modulation of ENSO teleconnection to the Indo–northwest Pacific region is reproduced in an atmospheric general circulation model forced by observed SST. The modulation is correlated not with the Pacific decadal oscillation but rather with the ENSO variance itself. When ENSO is strong, its effect in the Indo–northwest Pacific strengthens and vice versa. The fact that enhanced ENSO teleconnections occurred 100 years ago during the late nineteenth–early twentieth century indicates that the recent strengthening of the ENSO correlation over the Indo–western Pacific may not entirely be due to global warming but reflect natural variability.

Strengthening of Tropical Indian Ocean Teleconnection to the Northwest Pacific since the Mid-1970s: An Atmospheric GCM Study*

2010 ◽  
Vol 23 (19) ◽  
pp. 5294-5304 ◽  
Author(s):  
Gang Huang ◽  
Kaiming Hu ◽  
Shang-Ping Xie
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Tropical Indian Ocean ◽  
Early Summer ◽  
Interdecadal Change ◽  
Northwest Pacific ◽  
Wind Pattern ◽  
Climate Anomalies

Abstract The correlation of northwest (NW) Pacific climate anomalies during summer with El Niño–Southern Oscillation (ENSO) in the preceding winter strengthens in the mid-1970s and remains high. This study investigates the hypothesis that the tropical Indian Ocean (TIO) response to ENSO is key to this interdecadal change, using a 21-member ensemble simulation with the Community Atmosphere Model, version 3 (CAM3) forced by the observed history of sea surface temperature (SST) for 1950–2000. In the model hindcast, the TIO influence on the summer NW Pacific strengthens in the mid-1970s, and the strengthened TIO teleconnection coincides with an intensification of summer SST variability over the TIO. This result is corroborated by the fact the model’s skills in simulating NW Pacific climate anomalies during summer increase after the 1970s shift. During late spring to early summer, El Niño–induced TIO warming decays rapidly for the epoch prior to the 1970s shift but grows and persists through summer for the epoch occurring after it. This difference in the evolution of the TIO warming determines the strength of the TIO teleconnection to the NW Pacific in the subsequent summer. An antisymmetric wind pattern develops in spring across the equator over the TIO, and the associated northeasterly anomalies aid the summer warming over the north Indian Ocean by opposing the prevailing southwest monsoon. In the model, this antisymmetric spring wind pattern is well developed after but absent before the 1970s shift.

scholarly journals Indian Ocean Variability in the CMIP5 Multimodel Ensemble: The Basin Mode

2013 ◽  
Vol 26 (18) ◽  
pp. 7240-7266 ◽  
Author(s):  
Yan Du ◽  
Shang-Ping Xie ◽  
Ya-Li Yang ◽  
Xiao-Tong Zheng ◽  
Lin Liu ◽  
...  
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Tropical Indian Ocean ◽  
Ocean Basin ◽  
North Indian Ocean ◽  
Cmip5 Models ◽  
Northwest Pacific ◽  
Kelvin Wave

Abstract This study evaluates the simulation of the Indian Ocean Basin (IOB) mode and relevant physical processes in models from phase 5 of the Coupled Model Intercomparison Project (CMIP5). Historical runs from 20 CMIP5 models are available for the analysis. They reproduce the IOB mode and its close relationship to El Niño–Southern Oscillation (ENSO). Half of the models capture key IOB processes: a downwelling oceanic Rossby wave in the southern tropical Indian Ocean (TIO) precedes the IOB development in boreal fall and triggers an antisymmetric wind anomaly pattern across the equator in the following spring. The anomalous wind pattern induces a second warming in the north Indian Ocean (NIO) through summer and sustains anticyclonic wind anomalies in the northwest Pacific by radiating a warm tropospheric Kelvin wave. The second warming in the NIO is indicative of ocean–atmosphere interaction in the interior TIO. More than half of the models display a double peak in NIO warming, as observed following El Niño, while the rest show only one winter peak. The intermodel diversity in the characteristics of the IOB mode seems related to the thermocline adjustment in the south TIO to ENSO-induced wind variations. Almost all the models show multidecadal variations in IOB variance, possibly modulated by ENSO.

scholarly journals Weakening of Northwest Pacific Anticyclone Anomalies during Post–El Niño Summers under Global Warming

2018 ◽  
Vol 31 (9) ◽  
pp. 3539-3555 ◽  
Author(s):  
Wenping Jiang ◽  
Gang Huang ◽  
Ping Huang ◽  
Kaiming Hu
Keyword(s):  
Global Warming ◽  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Northwest Pacific ◽  
Tropospheric Temperature ◽  
Coupled Models ◽  
Northwest Pacific Anticyclone ◽  
Sst Anomalies

The northwest Pacific anticyclone (NWPAC) anomalies during post–El Niño summers are a key predictor of the summer climate in East Asia and the northwestern Pacific (NWP). Understanding how this will change under global warming is crucial to project the changes in the variability of the northwest Pacific summer monsoon. Outputs from 18 selected coupled models from phase 5 of the Coupled Model Intercomparison Project show that the anomalous NWPAC response to El Niño will likely be weakened under global warming, which is attributed to the decreased zonal contrast between the tropical Indian Ocean (TIO) warming and the NWP cooling during post–El Niño summers. Under global warming, the NWPAC anomalies during the El Niño mature winter are weakened because of decreased atmospheric circulation in response to El Niño–Southern Oscillation (ENSO), which leads to the weakening of local air–sea interaction and then decreases the cold NWP SST anomalies. Furthermore, the decreased surface heat flux anomalies, the weakened anticyclone anomalies over the southeastern Indian Ocean, and the slackened anomalous easterlies over the north Indian Ocean weaken the warm TIO SST anomalies. However, the strengthened tropospheric temperature anomalies could enhance the anomalous TIO warming. Although the changes in TIO SST anomalies are indistinctive, the weakening of the SST anomaly gradient between the TIO and the NWP is robust to weaken the NWPAC anomalies during post–El Niño summers. Moreover, the positive feedback between the TIO–NWP SST anomalies and the NWPAC anomalies will enhance the weakening of NWPAC under global warming.

scholarly journals Indo-Western Pacific Climate Variability: ENSO Forcing and Internal Dynamics in a Tropical Pacific Pacemaker Simulation

2018 ◽  
Vol 31 (24) ◽  
pp. 10123-10139 ◽  
Author(s):  
Chuan-Yang Wang ◽  
Shang-Ping Xie ◽  
Yu Kosaka
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Southern Oscillation ◽  
Internal Variability ◽  
Tropical Pacific ◽  
Western Pacific ◽  
Ocean Atmosphere ◽  
Sst Anomalies

El Niño–Southern Oscillation (ENSO) peaks in boreal winter but its impact on Indo-western Pacific climate persists for another two seasons. Key ocean–atmosphere interaction processes for the ENSO effect are investigated using the Pacific Ocean–Global Atmosphere (POGA) experiment with a coupled general circulation model, where tropical Pacific sea surface temperature (SST) anomalies are restored to follow observations while the atmosphere and oceans are fully coupled elsewhere. The POGA shows skills in simulating the ENSO-forced warming of the tropical Indian Ocean and an anomalous anticyclonic circulation pattern over the northwestern tropical Pacific in the post–El Niño spring and summer. The 10-member POGA ensemble allows decomposing Indo-western Pacific variability into the ENSO forced and ENSO-unrelated (internal) components. Internal variability is comparable to the ENSO forcing in magnitude and independent of ENSO amplitude and phase. Random internal variability causes apparent decadal modulations of ENSO correlations over the Indo-western Pacific, which are high during epochs of high ENSO variance. This is broadly consistent with instrumental observations over the past 130 years as documented in recent studies. Internal variability features a sea level pressure pattern that extends into the north Indian Ocean and is associated with coherent SST anomalies from the Arabian Sea to the western Pacific, suggestive of ocean–atmosphere coupling.

scholarly journals Weakened Anomalous Western North Pacific Anticyclone during an El Niño–Decaying Summer under a Warmer Climate: Dominant Role of the Weakened Impact of the Tropical Indian Ocean on the Atmosphere

2018 ◽  
Vol 32 (1) ◽  
pp. 213-230 ◽  
Author(s):  
Chao He ◽  
Tianjun Zhou ◽  
Tim Li
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
North Pacific ◽  
Western North Pacific ◽  
El Nino ◽  
Tropical Indian Ocean ◽  
Tropospheric Temperature ◽  
Coupled Models ◽  
Subtropical Anticyclone ◽  
Mean State

Abstract The western North Pacific subtropical anticyclone (WNPAC) is the most prominent atmospheric circulation anomaly over the subtropical Northern Hemisphere during the decaying summer of an El Niño event. Based on a comparison between the RCP8.5 and the historical experiments of 30 coupled models from the CMIP5, we show evidence that the anomalous WNPAC during the El Niño–decaying summer is weaker in a warmer climate although the amplitude of the El Niño remains generally unchanged. The weakened impact of the sea surface temperature anomaly (SSTA) over the tropical Indian Ocean (TIO) on the atmosphere is essential for the weakened anomalous WNPAC. In a warmer climate, the warm tropospheric temperature (TT) anomaly in the tropical free troposphere stimulated by the El Niño–related SSTA is enhanced through stronger moist adiabatic adjustment in a warmer mean state, even if the SSTA of El Niño is unchanged. But the amplitude of the warm SSTA over TIO remains generally unchanged in an El Niño–decaying summer, the static stability of the boundary layer over TIO is increased, and the positive rainfall anomaly over TIO is weakened. As a result, the warm Kelvin wave emanating from TIO is weakened because of a weaker latent heating anomaly over TIO, which is responsible for the weakened WNPAC anomaly. Numerical experiments support the weakened sensitivity of precipitation anomaly over TIO to local SSTA under an increase of mean-state SST and its essential role in the weakened anomalous WNPAC, independent of any change in the SSTA.

scholarly journals Intensification and Northward Extension of Northwest Pacific Anomalous Anticyclone in El Niño Decaying Mid-Summer: An Energetic Perspective

2021 ◽  
Author(s):  
Haosu Tang ◽  
Kaiming Hu ◽  
Gang Huang ◽  
Ya Wang ◽  
Weichen Tao
Keyword(s):  
Energy Conversion ◽  
El Niño ◽  
El Nino ◽  
Dominant Role ◽  
North Indian Ocean ◽  
Northwest Pacific ◽  
Mean Flow ◽  
The North ◽  
Anomalous Anticyclone ◽  
Circulation Anomalies

Abstract The Northwest Pacific (NWP) anomalous anticyclone (AAC) intensifies and extends northward from El Niño decaying early to mid- summer despite the dissipating sea surface temperature anomalies in the North Indian Ocean, North Atlantic and tropical NWP. The present study investigates these two intraseasonal variations of AAC from the perspective of energetics. The efficiency of dry energy conversion from background mean flow to perturbations in the El Niño decaying mid-summer is high and well explains the intensification of El Niño-induced circulation anomalies over the East Asia (EA)-NWP. The baroclinic energy conversion plays a more dominant role in this process than barotropic energy conversion. Besides, mean state changes over the EA-NWP from early to mid- summer are found in favor of the northward shift of the preferred latitude of the circulation anomalies. Thus, the El Niño induced circulation anomalies over the EA-NWP are more northward-extended in the later period. Empirical orthogonal function analyses further confirm that the northward extension of El Niño-induced circulation anomalies over the EA-NWP stems from local optimal mode change from early to mid- summer.

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