scholarly journals Impact of the Indo-Pacific Warm Pool on the Hadley, Walker, and Monsoon Circulations

Atmosphere ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1030
Author(s):  
Hye-Ryeom Kim ◽  
Kyung-Ja Ha ◽  
Suyeon Moon ◽  
Hyoeun Oh ◽  
Sahil Sharma
Keyword(s):  
Dominant Role ◽  
Hadley Circulation ◽  
Walker Circulation ◽  
Warming Trend ◽  
Warm Pool ◽  
Vital Role ◽  
Natural Variability ◽  
Natural Mode ◽  
Monsoon Circulation ◽  
Pacific Warm Pool

The Indo-Pacific warm pool (IPWP) is enclosed by a 28 °C isotherm and plays a vital role in controlling atmospheric circulations. However, the effects of changes in regional warm pool sea surface temperatures (SSTs) remain unexplored. We divided the IPWP into the Indian and Pacific sectors and distinguished their responses to natural variability and global warming. Furthermore, we examined the impacts of the interannual variability (IAV) in warm pool SST on the tropical Hadley, Walker, and monsoon circulations. The Hadley circulation was affected by warm pool SST warming, i.e., warmer SSTs over the warm pool strengthened the upward branch of Hadley circulation, whereas the downward branch was respectively weakened and strengthened in the Northern and Southern Hemispheres. Walker circulation was strengthened (weakened) in the warming (natural) mode. Consequently, the Walker circulation is weakened since the natural variability of warm pool SST plays a more dominant role rather than the warming trend of SSTs over the warm pool. Furthermore, our analysis displays that warm pool warming has little impact on the monsoon circulation. Our findings highlight the different roles of the IAV of warm pool regions in each tropical circulation as part of the warming trend and natural variability.

scholarly journals Long-Term Variation of the Principal Mode of Boreal Spring Hadley Circulation Linked to SST over the Indo-Pacific Warm Pool

2013 ◽  
Vol 26 (2) ◽  
pp. 532-544 ◽  
Author(s):  
Juan Feng ◽  
Jianping Li ◽  
Fei Xie
Keyword(s):  
Meridional Circulation ◽  
Hadley Circulation ◽  
Warming Trend ◽  
Warm Pool ◽  
Asymmetric Mode ◽  
Principal Mode ◽  
Boreal Spring ◽  
Pacific Warm Pool ◽  
Term Variation

Abstract The variability of the boreal spring [March–May (MAM)] Hadley circulation (HC) is investigated, focusing on the long-term variation of the first principal mode for 1951–2008, which is an equatorially asymmetric mode (AM) with the rising branch located around 10°S. This mode explains about 70% of the variance of the MAM HC and shows an obvious upward trend and thus contributes to the strengthening of the MAM HC. The robust warming trends of sea surface temperature (SST) over the Indo-Pacific warm pool (IPWP) play an essential role in the variations of the MAM HC. When SST over the IPWP is warm, anomalous meridional circulation is induced with descending branches located in regions 30°–20°S and 5°–15°N and rising motion located near 10°S. The anomalous rising south of the equator is due to the inhomogeneous warming of SST over the IPWP. SST within the IPWP in the Southern Hemisphere shows a larger warming trend than that in the Northern Hemisphere. The position of the anomalous convergence associated with SST variations over the IPWP is aligned with the maximum meridional gradient of zonal mean SST, resulting in an equatorially asymmetric meridional circulation. This point is further established in theoretical analyses. However, the meridional SST gradient within the IPWP shows a decreasing trend, suggesting the associated anomalous meridional circulation intensifies, which in turn explains the strengthening of the MAM HC. Under this scenario, the accompanied descent in the regions of 30°–20°S and 5°–15°N is enhanced, implying a frequent drought in these regions during MAM.

Regime Change of the Boreal Summer Hadley Circulation and Its Connection with the Tropical SST

2011 ◽  
Vol 24 (15) ◽  
pp. 3867-3877 ◽  
Author(s):  
Ran Feng ◽  
Jianping Li ◽  
Jincheng Wang
Keyword(s):  
High Frequency ◽  
Regime Change ◽  
Hadley Circulation ◽  
Warm Pool ◽  
Boreal Summer ◽  
Tropical Atlantic ◽  
Asymmetric Mode ◽  
Pacific Warm Pool ◽  
Highly Correlated ◽  
Relationship Of

Abstract The year-to-year variability of the boreal summer [June–August (JJA)] Hadley circulation (HC) is dominated by an asymmetric mode centered in the Northern Hemisphere (AMN) and a quasi-symmetric mode centered at 5°N (QSM). The regime change of the JJA HC is revealed by the phase reversal of the time series of the AMN, showing significant weakening of the northern part of the JJA HC and a reversed seesaw relationship of the zonal-mean updraft over 10°–20°N and around the equator. This transition is accompanied by the southward retreat of the HC core and is well correlated with the weakening of tropical summer monsoons. The strong warming trends of the sea surface temperature over the tropical Atlantic and Indo–west Pacific warm pool play an important role in the regime change of the JJA HC. The high-frequency interannual variability of the JJA HC, however, is mainly featured by the QSM and is highly correlated with the Niño-3.4 index, implying that ENSO’s influence is mainly on the high-frequency interannual time scale.

scholarly journals Tropical Clouds and Circulation Changes during the 2006/07 and 2009/10 El Niños

2013 ◽  
Vol 26 (2) ◽  
pp. 399-413 ◽  
Author(s):  
Hui Su ◽  
Jonathan H. Jiang
Keyword(s):  
El Niño ◽  
Radiative Forcing ◽  
El Nino ◽  
Dominant Role ◽  
Hadley Circulation ◽  
Walker Circulation ◽  
Reanalysis Data ◽  
Tropical Circulation ◽  
Different Characteristics ◽  
Tropical Clouds

Abstract Changes in tropical cloud vertical structure, cloud radiative forcing (CRF), and circulation exhibit distinctly different characteristics during the 2006/07 and 2009/10 El Niños, revealed by CloudSat and Cloud–Aerosol Lidar and Infrared Pathfinder Satellite (CALIPSO) observations and reanalysis data. On the tropical average, the 2009/10 has a decrease of clouds from 2 to 14 km, an increase of clouds in the boundary layer, and an increase of cirrus clouds above 14 km. The tropical-mean cloud anomalies in the middle to upper troposphere (6–14 km) for the 2006/07 El Niño are nearly opposite to those in 2009/10 El Niño. The tropical averaged net CRF anomaly at the top of the atmosphere (TOA) is 0.6–0.7 W m−2 cooling (0.02–0.5 W m−2 warming) for the 2009/10 (2006/07) El Niño. The 2009/10 El Niño is associated with a strengthening of tropical circulation, increased high (low) clouds in extremely strong ascending (descending) regimes, and decreased clouds in the middle and high altitudes in a broad range of moderate circulation regimes. The strengthening of tropical circulation is primarily caused by the enhancement of the Hadley circulation. The 2006/07 El Niño is associated with a weakening of the tropical circulation, primarily caused by the reduction of the Walker circulation. The cloud anomalies in each circulation regime are approximately opposite for these two El Niños. The analysis herein suggests that both the magnitude and pattern of sea surface temperature anomalies in the two events contribute to the differences in clouds and circulation anomalies, with magnitude playing a dominant role. The contrasting behaviors of the two El Niños highlight the nonlinear response of tropical clouds and circulation to El Niño SST forcing.

The tropical atmospheric conveyor belt: a Lagrangian perspective of the large-scale tropical circulation

2020 ◽  
Author(s):  
Dana Raiter ◽  
Eli Galanti ◽  
Yohai Kaspi
Keyword(s):  
Large Scale ◽  
Meridional Circulation ◽  
Hadley Circulation ◽  
Warm Pool ◽  
Conveyor Belt ◽  
Jet Stream ◽  
Tropical Circulation ◽  
Pacific Warm Pool ◽  
Actual Movement ◽  
The Tropics

<div> <div>The Hadley circulation (HC) is a key element of the climate system. It is traditionally defined as the zonally averaged meridional circulation in the tropics, therefore treated as a zonally symmetric phenomenon. However, differences in temperature between land and sea cause zonal asymmetries on Earth, dramatically affecting the circulation. The longitudinal dependence of the HC evokes questions about where and when the actual large scale tropical circulation occurs. In this study, we look into the connection between the longitudinally dependent HC and the actual large scale movement of air in the tropics using a coupled Eulerian and Lagrangian approach. Decomposing the velocity field, we identify the components affecting the actual circulation. In addition, we calculate trajectories of air parcels to analyze the actual movement. We propose an alternative definition for the circulation, that describes the actual path of air parcels in the tropics, as a tropical conveyor belt. The Indo-Pacific warm pool is the driver of the circulation, where air converges and ascends, then moves westward and poleward before entering the jet stream, moving eastward with it, eventually beginning its descent near the Americas. Furthermore, using an idealized moist GCM, we explore how tropical asymmetries affect the circulation and discuss the possible mechanisms controlling the tropical conveyor belt.</div> </div>

scholarly journals Increased Chances of Drought in Southeastern Periphery of the Tibetan Plateau Induced by Anthropogenic Warming

2017 ◽  
Vol 30 (16) ◽  
pp. 6543-6560 ◽  
Author(s):  
Shuangmei Ma ◽  
Tianjun Zhou ◽  
Oliver Angélil ◽  
Hideo Shiogama
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
Climate Models ◽  
Hadley Circulation ◽  
Warm Pool ◽  
Severe Drought ◽  
The Tibetan Plateau ◽  
Ensemble Simulations ◽  
Pacific Warm Pool ◽  
Drought Conditions

The southeastern periphery of the Tibetan Plateau (SEPTP) was hit by an extraordinarily severe drought in the autumn of 2009. Overall, the SEPTP has been gripped by a sustained drought for six consecutive years. To better understand the physical causes of these types of severe and frequent droughts and thus to improve their prediction and enhance the ability to adapt, many research efforts have been devoted to the disastrous droughts in the SEPTP. Nonetheless, whether the likelihood and strength of the severe droughts in the SEPTP, such as that in the autumn of 2009, have been affected by anthropogenic climate change remains unknown. This study first identifies the atmospheric circulation regime responsible for the SEPTP droughts and then explores how human-induced climate change has affected the severe droughts in the SEPTP. It is found that the drought conditions in the SEPTP have been driven by the Indian–Pacific warm pool (IPWP) sea surface temperature (SST) through strengthening of the local Hadley circulation and anomalously cyclonic motion over the South China Sea. Ensemble simulations of climate models demonstrate a robust increase in the dry and warm meteorological conditions seen during the 2009 SEPTP autumn drought due to anthropogenic global warming. Given that warming is expected to continue into the future, these results suggest that it is likely that drought conditions will become more common in the SEPTP.

scholarly journals Glacial changes in tropical climate amplified by the Indian Ocean

2018 ◽  
Vol 4 (12) ◽  
pp. eaat9658 ◽  
Author(s):  
Pedro N. DiNezio ◽  
Jessica E. Tierney ◽  
Bette L. Otto-Bliesner ◽  
Axel Timmermann ◽  
Tripti Bhattacharya ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Climate Changes ◽  
Equatorial Indian Ocean ◽  
Walker Circulation ◽  
Warm Pool ◽  
Pacific Warm Pool ◽  
The Indian Ocean ◽  
The Tropics ◽  
The Last Glacial Maximum ◽  
The Last Glacial

The mechanisms driving glacial-interglacial changes in the climate of the Indo-Pacific warm pool are poorly understood. Here, we address this question by combining paleoclimate proxies with model simulations of the Last Glacial Maximum climate. We find evidence of two mechanisms explaining key patterns of ocean cooling and rainfall change interpreted from proxy data. Exposure of the Sahul shelf excites a positive ocean-atmosphere feedback involving a stronger surface temperature gradient along the equatorial Indian Ocean and a weaker Walker circulation—a response explaining the drier/wetter dipole across the basin. Northern Hemisphere cooling by ice sheet albedo drives a monsoonal retreat across Africa and the Arabian Peninsula—a response that triggers a weakening of the Indian monsoon via cooling of the Arabian Sea and associated reductions in moisture supply. These results demonstrate the importance of air-sea interactions in the Indian Ocean, amplifying externally forced climate changes over a large part of the tropics.

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