scholarly journals Timing of El Niño–Related Warming and Indian Summer Monsoon Rainfall

2008 ◽  
Vol 21 (11) ◽  
pp. 2711-2719 ◽  
Author(s):  
Chie Ihara ◽  
Yochanan Kushnir ◽  
Mark A. Cane ◽  
Alexey Kaplan
Keyword(s):  
Summer Monsoon ◽  
El Niño ◽  
Monsoon Rainfall ◽  
El Nino ◽  
Southern Oscillation ◽  
Monsoon Season ◽  
Summer Monsoon Rainfall ◽  
Equatorial Pacific ◽  
Central Pacific ◽  
Eastern Equatorial Pacific

Abstract The relationship between all-India summer monsoon rainfall (ISMR) and the timing of (El Niño–Southern Oscillation) ENSO-related warming/cooling is investigated, using observational data during the period from 1881 to 1998. The analysis of the evolutions of Indo-Pacific sea surface temperature (SST) anomalies suggests that when ISMR is not below normal despite the co-occurrence of an El Niño event, warming over the eastern equatorial Pacific starts from boreal winter and evolves early so that the western-central Pacific and Indian Ocean are warmer than normal during the summer monsoon season. In contrast, when the more usual El Niño–dry ISMR relationship holds, the eastern equatorial Pacific starts warming rapidly only about a season before the reference summer so that the western-central Pacific and Indian Oceans remain cold during the monsoon season.

scholarly journals El Nino, Southern Oscillation, equatorial eastern Pacific sea surface temperatures and summer monsoon rainfall in India

MAUSAM ◽  
2021 ◽  
Vol 49 (1) ◽  
pp. 103-114
Author(s):  
R. P. KANE
Keyword(s):  
Summer Monsoon ◽  
El Niño ◽  
Monsoon Rainfall ◽  
El Nino ◽  
Southern Oscillation ◽  
Summer Monsoon Rainfall ◽  
Stratospheric Wind ◽  
India Summer Monsoon ◽  
Cold Events ◽  
India Summer Monsoon Rainfall

For the 120 yean (1871-1990), every year was designated as an El Nino (EN), or Southern Oscillation (SO), minimum or a combination of these, or none. For all India summer monsoon rainfall (ISMR), unambiguous ENSOW [SO and W (warm events) in the middle of the calendar year] seemed to be best associated with droughts and events of type C (cold events) were best associated with floods. However, some droughts occurred without the presence of EN related events and some floods occurred even in the presence of EN related events. In these cases, other parameters such as Eurasian snow cover or stratospheric wind QBO might have had a larger influence.

scholarly journals A Three-Region Conceptual Model for Central Pacific El Niño Including Zonal Advective Feedback

2018 ◽  
Vol 31 (13) ◽  
pp. 4965-4979 ◽  
Author(s):  
Xiang-Hui Fang ◽  
Mu Mu
Keyword(s):  
Surface Temperature ◽  
Conceptual Model ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Equatorial Pacific ◽  
Sea Surface ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Eastern Equatorial Pacific

The simple zonal two-region framework of the recharge paradigm can accurately manifest the traditional eastern Pacific (EP) type of El Niño–Southern Oscillation (ENSO), as its major warming center is located in the EP and the anomalous sea surface temperature (SST) changes monotonically from west to east along the equatorial Pacific. However, it cannot fully depict the variations of the central Pacific (CP) type of ENSO, whose major warming center is mainly situated in the CP. Therefore, to better investigate the characteristics of the CP type of ENSO, the recharge paradigm is extended to a three-region conceptual model to describe the entire western, central, and eastern equatorial Pacific. The results show that the extended conceptual model can depict the different variations between the CP and EP well. Specifically, with increasing magnitude of the zonal advective feedback over the CP (i.e., imitating the situation for CP ENSO), the period of the system and SST magnitude over the CP and EP both decrease. However, the decreasing amplitude is more intense over the EP, indicating an enlargement of the SST differences between the CP and EP. These results are all consistent with the observational characteristics of CP ENSO.

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.

scholarly journals Evolutions of sea level high and warm pool in the southeastern Arabian Sea and their association with Asian monsoons : A study on cause-and-effect relationships

MAUSAM ◽  
2021 ◽  
Vol 59 (1) ◽  
pp. 87-94
Author(s):  
O. P. SINGH
Keyword(s):  
Sea Level ◽  
Summer Monsoon ◽  
El Niño ◽  
Arabian Sea ◽  
El Nino ◽  
Southern Oscillation ◽  
Monsoon Season ◽  
Warm Pool ◽  
Sea Surface ◽  
Southeastern Arabian Sea

The present study aims at gaining more insight into the evolution of warm pool and associated sea level dome in the southeastern Arabian Sea before the summer monsoon onset.  The results show that the Sea Surface Temperature (SST) maximum in the warm pool region is found during April close to the southwest coast of India.  The Sea Surface Height (SSH) maximum over the same region is observed during December. The collapse of sea level dome begins well in advance during the pre-monsoon whereas the warm pool collapses after the onset of summer monsoon during June.  Therefore, there is a lag of about three to four months between the collapses of the sea level high and the warm pool.  Most interesting aspect is the dramatic increase of SST from September and SSH from October which is continued throughout the post monsoon season (October - December). Therefore, both the collapse and evolution of warm pool are dramatic events before and after the summer monsoon.                    There are considerable variations in the intensity of warm pool and the height of sea level dome on interannual scale.  The variation during El-Nino Southern Oscillation (ENSO) epoch of 1987-88 has revealed many interesting features.  During El-Nino year 1987 the warm pool intensity reached its peak in June whereas during La Nina year 1988 the warm pool attained its maximum intensity much earlier, i.e., in April. 

scholarly journals Influence of Asian Summer Monsoon Anticyclone on the Trace gases and Aerosols over Indian region

2019 ◽  
Author(s):  
Ghouse Basha ◽  
M. Venkat Ratnam ◽  
Pangaluru Kishore ◽  
S. Ravindrababu ◽  
Isabella Velicogna
Keyword(s):  
Summer Monsoon ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Asian Summer Monsoon ◽  
Monsoon Season ◽  
Trace Gases ◽  
La Niña ◽  
La Nina ◽  
Asian Summer

Abstract. The Asian Summer Monsoon Anticyclone (ASMA) persisting during monsoon season in the upper troposphere and lower stratosphere (UTLS) region play an important role in confining the trace gases and aerosols for a longer period thus affects regional and global climate. Our understanding on these trace gases and aerosols variability in the ASMA is limited. In this study, the effect of the ASMA on the trace gases (Water Vapour (WV), Ozone (O3), Carbon Monoxide (CO)) and aerosols (Attenuated Scattering Ratio (ASR)) obtained from long-term (2006–2016) satellite measurements is investigated. Since the ASMA is present in the UTLS region, its influence on the tropopause characteristics is also explored. Higher tropopause altitude, WV, CO and ASR confining to the ASMA region is observed, whereas tropopause temperatures and O3 are found low. There exists large inter-annual variation in the ASMA and hence its effect on these trace gases and aerosols are also seen clearly. A significant relationship is also observed between the phases of Quasi-Biannual Oscillation (QBO) and El Niño Southern Oscillation (ENSO) on the trace gases and ASR, including the tropopause when measurements in the ASMA region are subject to multivariate regression analysis. Further, the influence of the Indian summer monsoon (ISM) activity on the ASMA trace gases and aerosols is studied with respect to active and break spells of monsoon, strong and weak monsoon years, strong La Niña, El Niño years. Results show a significant increase in WV, CO and decrease in O3 during the active phase of the ISM, strong monsoon years and strong La Niña years in the ASMA. Enhancement in the ASR values during the strong monsoon years and strong La Niña years is observed. Thus, it is prudent to conclude that the dynamics of the ASMA play an important role in the confinement of several trace gases and aerosols and suggested to consider the activity of summer monsoon while dealing with them at sub-seasonal scales.

The Termination of the 1997–98 El Niño. Part I: Mechanisms of Oceanic Change*

2006 ◽  
Vol 19 (12) ◽  
pp. 2633-2646 ◽  
Author(s):  
Gabriel A. Vecchi ◽  
D. E. Harrison
Keyword(s):  
El Niño ◽  
El Nino ◽  
Equatorial Pacific ◽  
Sea Surface ◽  
Central Pacific ◽  
Eastern Equatorial Pacific ◽  
Oceanic Response ◽  
Southward Shift ◽  
Sea Surface Temperature Anomalies ◽  
Subsurface Temperatures

Abstract The 1997–98 El Niño was both unusually strong and terminated unusually. Warm eastern equatorial Pacific (EEqP) sea surface temperature anomalies (SSTAs) exceeded 4°C at the event peak and lasted well into boreal spring of 1998, even though subsurface temperatures began cooling in December 1997. The oceanic processes that controlled this unusual termination are explored here and can be characterized by three features: (i) eastward propagating equatorial Pacific thermocline (Ztc) shoaling beginning in the central Pacific in November 1997; (ii) persistent warm EEqP SSTA between December 1997 and May 1998, despite strong EEqP Ztc shoaling (and subsurface cooling); and (iii) an abrupt cooling of EEqP SSTA in early May 1998 that exceeded 4°C within two weeks. It is shown here that these changes can be understood in terms of the oceanic response to changes to the meridional structure of the near-equatorial zonal wind field. Equatorial near-date-line westerly wind anomalies greatly decreased in late 1997, associated with a southward shift of convective and wind anomalies. In the EEqP, equatorial easterlies disappeared (reappeared) in late January (early May) 1998, driving the springtime extension (abrupt termination) of this El Niño event. The authors suggest that the wind changes arise from fundamentally meridional processes and are tied to the annual cycle of insolation.

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