scholarly journals Response of the Antarctic stratosphere to warm pool El Niño Events in the GEOS CCM

2011 ◽  
Vol 11 (3) ◽  
pp. 9743-9767 ◽  
Author(s):  
M. M. Hurwitz ◽  
I.-S. Song ◽  
L. D. Oman ◽  
P. A. Newman ◽  
A. M. Molod ◽  
...  
Keyword(s):  
El Niño ◽  
Planetary Wave ◽  
Lower Stratosphere ◽  
El Nino ◽  
Warm Pool ◽  
Wave Activity ◽  
Central Pacific ◽  
Quasi Biennial Oscillation ◽  
South Central ◽  
The Antarctic

Abstract. A new formulation of the Goddard Earth Observing System Chemistry-Climate Model, Version 2 (GEOS V2 CCM), with an improved general circulation model and an internally generated quasi-biennial oscillation (QBO), is used to investigate the response of the Antarctic stratosphere to (1) warm pool El Niño (WPEN) events and (2) the sensitivity of this response to the phase of the QBO. Two 50-yr time-slice simulations are forced by repeating annual cycles of sea surface temperatures and sea ice concentrations composited from observed WPEN and neutral ENSO (ENSON) events. In these simulations, greenhouse gas and ozone-depleting substance concentrations represent the present-day climate. The modelled responses to WPEN, and to the phase of the QBO during WPEN, are compared with NASA's Modern Era Retrospective-Analysis for Research and Applications (MERRA) reanalysis. WPEN events enhance poleward planetary wave activity in the central South Pacific during austral spring, leading to relative warming of the Antarctic lower stratosphere in November/December. During the easterly phase of the QBO (QBO-E), the GEOS V2 CCM reproduces the observed 3–5 K warming of the polar region at 50 hPa, in the WPEN simulation relative to ENSON. In the recent past, the response to WPEN events was sensitive to the phase of the QBO: the enhancement in planetary wave driving and the lower stratospheric warming signal were mainly associated with WPEN events coincident with QBO-E. In the GEOS V2 CCM, however, the Antarctic response to WPEN events is insensitive to the phase of the QBO: the modelled response is always easterly QBO-like. OLR, streamfunction and Rossby wave energy diagnostics are used to show that the modelled QBO does not extend far enough into the lower stratosphere and upper troposphere to modulate convection and thus planetary wave activity in the south central Pacific.

scholarly journals Response of the Antarctic stratosphere to warm pool El Niño Events in the GEOS CCM

2011 ◽  
Vol 11 (18) ◽  
pp. 9659-9669 ◽  
Author(s):  
M. M. Hurwitz ◽  
I.-S. Song ◽  
L. D. Oman ◽  
P. A. Newman ◽  
A. M. Molod ◽  
...  
Keyword(s):  
El Niño ◽  
Planetary Wave ◽  
Lower Stratosphere ◽  
El Nino ◽  
Warm Pool ◽  
Wave Activity ◽  
Central Pacific ◽  
Quasi Biennial Oscillation ◽  
South Central ◽  
The Antarctic

Abstract. The Goddard Earth Observing System Chemistry-Climate Model, Version 2 (GEOS V2 CCM) is used to investigate the response of the Antarctic stratosphere to (1) warm pool El Niño (WPEN) events and (2) the sensitivity of this response to the phase of the QBO. A new formulation of the GEOS V2 CCM includes an improved general circulation model and an internally generated quasi-biennial oscillation (QBO). Two 50-yr time-slice simulations are forced by repeating annual cycles of sea surface temperatures and sea ice concentrations composited from observed WPEN and neutral ENSO (ENSON) events. In these simulations, greenhouse gas and ozone-depleting substance concentrations represent the present-day climate. The modelled responses to WPEN, and to the phase of the QBO during WPEN, are compared with NASA's Modern Era Retrospective-Analysis for Research and Applications (MERRA) reanalysis. WPEN events enhance poleward tropospheric planetary wave activity in the central South Pacific region during austral spring, leading to relative warming of the Antarctic lower stratosphere in November/December. During the easterly phase of the QBO (QBO-E), the GEOS V2 CCM reproduces the observed 4–5 K warming of the polar region at 50 hPa, in the WPEN simulation relative to ENSON. In the recent past, the response to WPEN events was sensitive to the phase of the QBO: the enhancement in planetary wave driving and the lower stratospheric warming signal were mainly associated with WPEN events coincident with QBO-E. In the GEOS V2 CCM, however, the Antarctic response to WPEN events is insensitive to the phase of the QBO: the modelled response is always easterly QBO-like. The QBO signal does not extend far enough into the lower stratosphere and upper troposphere to modulate convection and thus planetary wave activity in the south central Pacific.

scholarly journals Response of the Antarctic Stratosphere to Two Types of El Niño Events

2011 ◽  
Vol 68 (4) ◽  
pp. 812-822 ◽  
Author(s):  
M. M. Hurwitz ◽  
P. A. Newman ◽  
L. D. Oman ◽  
A. M. Molod
Keyword(s):  
El Niño ◽  
Planetary Wave ◽  
El Nino ◽  
Warm Pool ◽  
Cold Tongue ◽  
Quasi Biennial Oscillation ◽  
El Niño Events ◽  
The Antarctic ◽  
Sst Anomalies ◽  
El Nino Events

Abstract This study is the first to identify a robust El Niño–Southern Oscillation (ENSO) signal in the Antarctic stratosphere. El Niño events between 1979 and 2009 are classified as either conventional “cold tongue” events (positive SST anomalies in the Niño-3 region) or “warm pool” events (positive SST anomalies in the Niño-4 region). The 40-yr ECMWF Re-Analysis (ERA-40), NCEP, and Modern Era Retrospective–Analysis for Research and Applications (MERRA) meteorological reanalyses are used to show that the Southern Hemisphere stratosphere responds differently to these two types of El Niño events. Consistent with previous studies, cold tongue events do not impact temperatures in the Antarctic stratosphere. During warm pool El Niño events, the poleward extension and increased strength of the South Pacific convergence zone favor an enhancement of planetary wave activity during September–November. On average, these conditions lead to higher polar stratospheric temperatures and a weakening of the Antarctic polar jet in November and December, as compared with neutral ENSO years. The phase of the quasi-biennial oscillation (QBO) modulates the stratospheric response to warm pool El Niño events; the strongest planetary wave driving events are coincident with the easterly phase of the QBO.

scholarly journals Ship- and island-based soundings from the 2016 El Niño Rapid Response (ENRR) field campaign

2018 ◽  
Author(s):  
Leslie M. Hartten ◽  
Christopher J. Cox ◽  
Paul E. Johnston ◽  
Daniel E. Wolfe ◽  
Scott Abbott ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Rapid Response ◽  
Public Access ◽  
Central Pacific ◽  
Quasi Biennial Oscillation ◽  
East Central ◽  
Field Campaign ◽  
Central Pacific Ocean ◽  
Christmas Island

Abstract. As the 2015/2016 El Niño was gathering strength in late 2015, scientists at the Earth System Research Laboratory's Physical Sciences Division proposed and led the implementation of NOAA's El Niño Rapid Response (ENRR) Field Campaign. ENRR observations included wind and thermodynamic profiles of the atmosphere over the near-equatorial east-central Pacific Ocean, many of which were collected from two field sites and transmitted in near-real time for inclusion in global forecasting models. From 26 January to 28 March 2016, twice-daily rawinsonde observations were made from Kiritimati (pronounced Christmas) Island (2.0°N, 157.4°E; call sign CXENRR). From 16 February to 16 March 2016, three to eight radiosondes were launched each day from the NOAA Ship Ronald H. Brown (allocated call sign WTEC) as it travelled southeast from Hawaii to service Tropical Atmosphere Ocean (TAO) buoys along longitudes 140°W and 125°W and then north to San Diego, California. Both the rapid and the remote nature of these deployments created particular difficulties in collecting and disseminating the soundings; these are described together with the methods used to reprocess the data after the field campaign finished. The reprocessed and lightly quality-controlled data have been put into an easy-to-read text format, qualifying them to be termed Level 2 soundings. They are archived and freely available for public access at NOAA's National Centers for Environmental Information (NCEI) in the form of two separate data sets: one consisting of 125 soundings from Kiritimati Island (doi:10.7289/V55Q4T5K), the other of 193 soundings from the NOAA Ship Ronald H. Brown (doi:10.7289/V5X63K15). Of the Kiritimati soundings, 94 % reached the tropopause and 88 % reached 40 hPa, while 89 % of the ship's soundings reached the tropopause and 87 % reached 40 hPa. The soundings captured the repeated advance and retreat of the ITCZ at Kiritimati, a variety of marine tropospheric environments encountered by the ship, and lower-stratospheric features of the 2015–2016 QBO (quasi-biennial oscillation), all providing a rich view of the local atmosphere's response to the east-central Pacific's extremely warm waters during the 2015/16 El Niño.

scholarly journals Intraseasonal Tropical Atmospheric Variability Associated with the Two Flavors of El Niño

2012 ◽  
Vol 140 (11) ◽  
pp. 3669-3681 ◽  
Author(s):  
Daria Gushchina ◽  
Boris Dewitte
Keyword(s):  
El Niño ◽  
El Nino ◽  
Wave Activity ◽  
Kelvin Wave ◽  
Atmospheric Variability ◽  
Central Pacific ◽  
Cp El Niño ◽  
Ocean Data Assimilation ◽  
Double Space ◽  
Ep El Niño

ABSTRACT The characteristics of intraseasonal tropical variability (ITV) associated with the two flavors of El Niño [i.e., the canonical or eastern Pacific (EP) El Niño and the Modoki or central Pacific (CP) El Niño] are documented using composite and regression analysis. Double space–time Fourier analysis is applied to the NCEP–NCAR zonal wind at 850 hPa (U850) to separate the different components of the ITV in the tropical troposphere, which is then used to define indices of wave activity, and document the spatial pattern of the waves. It is shown that the ITV characteristics are altered during CP El Niño compared to the typical seasonal dependence of the ITV–ENSO relationship. In particular, while EP El Niño is characterized by enhanced MJO and equatorial Rossby (ER) wave activity during spring–summer prior to the ENSO peak, during CP El Niño, the ITV activity is increased during the mature and decaying phases. It is suggested that ITV is more propitious to the triggering of the EP event; while during the CP event, it contributes mostly to the persistence of positive SST anomalies. The oceanic response of these ITV anomalous patterns is further investigated in the Simple Ocean Data Assimilation (SODA) reanalysis by documenting the seasonal evolution of the intraseasonal equatorial oceanic Kelvin wave (IEKW) activity during the two flavors of El Niño. It is shown that anomalous westerlies associated with ITV may generate the corresponding response in the ocean in the form of anomalous IEKW activity.

scholarly journals Ship- and island-based soundings from the 2016 El Niño Rapid Response (ENRR) field campaign

2018 ◽  
Vol 10 (2) ◽  
pp. 1165-1183 ◽  
Author(s):  
Leslie M. Hartten ◽  
Christopher J. Cox ◽  
Paul E. Johnston ◽  
Daniel E. Wolfe ◽  
Scott Abbott ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Rapid Response ◽  
Public Access ◽  
Data Sets ◽  
Central Pacific ◽  
Quasi Biennial Oscillation ◽  
Field Campaign ◽  
Central Pacific Ocean ◽  
Christmas Island

Abstract. As the 2015/2016 El Niño was gathering strength in late 2015, scientists at the Earth System Research Laboratory's Physical Sciences Division proposed and led the implementation of the National Oceanic and Atmospheric Administration's (NOAA's) El Niño Rapid Response (ENRR) Field Campaign. ENRR observations included wind and thermodynamic profiles of the atmosphere over the near-equatorial eastern central Pacific Ocean, many of which were collected from two field sites and transmitted in near-real time for inclusion in global forecasting models. From 26 January to 28 March 2016, twice-daily rawinsonde observations were made from Kiritimati (pronounced Christmas) Island (2.0° N, 157.4° E; call sign CXENRR). From 16 February to 16 March 2016, three to eight radiosondes were launched each day from NOAA Ship Ronald H. Brown (allocated call sign WTEC) as it travelled southeast from Hawaii to service Tropical Atmosphere Ocean (TAO) buoys along longitudes 140 and 125° W and then north to San Diego, California. Both the rapid and remote nature of these deployments created particular difficulties in collecting and disseminating the soundings; these are described together with the methods used to reprocess the data after the field campaign finished. The reprocessed and lightly quality-controlled data have been put into an easy-to-read text format, qualifying them to be termed Level 2 soundings. They are archived and freely available for public access at NOAA's National Centers for Environmental Information (NCEI) in the form of two separate data sets: one consisting of 125 soundings from Kiritimati (https://doi.org/10.7289/V55Q4T5K), the other of 193 soundings from NOAA Ship Ronald H. Brown (https://doi.org/10.7289/V5X63K15). Of the Kiritimati soundings, 94 % reached the tropopause and 88 % reached 40 hPa, while 89 % of the ship's soundings reached the tropopause and 87 % reached 40 hPa. The soundings captured the repeated advance and retreat of the Intertropical Convergence Zone (ITCZ) at Kiritimati, a variety of marine tropospheric environments encountered by the ship, and lower-stratospheric features of the 2015–2016 QBO (quasi-biennial oscillation), all providing a rich view of the local atmosphere's response to the eastern central Pacific's extremely warm waters during the 2015/16 El Niño.

scholarly journals Response of stratospheric water vapor and ozone to the unusual timing of El Niño and QBO disruption in 2015–2016

2018 ◽  
Author(s):  
Mohamadou Diallo ◽  
Martin Riese ◽  
Thomas Birner ◽  
Paul Konopka ◽  
Rolf Müller ◽  
...  
Keyword(s):  
Water Vapor ◽  
Greenhouse Gases ◽  
El Niño ◽  
Lower Stratosphere ◽  
El Nino ◽  
Enso Event ◽  
Quasi Biennial Oscillation ◽  
Stratospheric Water Vapor ◽  
Enso Events ◽  
The Impact

Abstract. The stratospheric circulation determines the transport and lifetime of key greenhouse gases, including water vapor and ozone, which radiatively impact surface climate. The unusually warm El Niño Southern Oscillation (ENSO) event aligned with a disrupted Quasi-Biennial Oscillation (QBO) caused an unprecedented perturbation to this circulation in 2015–2016. Here, we quantify the impact of the alignment of these two phenomena in 2015–2016 on lower stratospheric water vapor and ozone from satellite observations. We show that the warm ENSO event substantially increases water vapor and decreases ozone in the tropical lower stratosphere. The QBO disruption significantly decreases global lower stratospheric water vapor and tropical ozone from early spring to late autumn. Thus, this QBO disruption reverses the lower stratosphere moistening triggered by the alignment of the warm ENSO event with westerly QBO in early boreal winter. Our results suggest that the interplay of ENSO events and QBO phases will be crucial for the distributions of radiatively active greenhouse gases in a changing future climate, when increasing El Niño-like conditions and decreasing lower stratospheric QBO amplitude are expected.

scholarly journals Synchronized spatial shifts of Hadley and Walker circulations

2020 ◽  
Author(s):  
Kyung-Sook Yun ◽  
Axel Timmermann ◽  
Malte F. Stuecker
Keyword(s):  
El Niño ◽  
Climate Model ◽  
El Nino ◽  
Southern Oscillation ◽  
Walker Circulation ◽  
Warm Pool ◽  
Central Pacific ◽  
Spatial Shift ◽  
Southern Central ◽  
Spatio Temporal

Abstract. The El Niño-Southern Oscillation (ENSO) influences the most extensive tropospheric circulation cells on our planet, known as Hadley and Walker circulations. Previous studies have largely focused on the effect of ENSO on the strength of these cells. However, what has remained uncertain is whether interannual sea surface temperature anomalies can also cause synchronized spatial shifts of these circulations. Here, by examining the spatio-temporal relationship between Hadley and Walker cells in observations and climate model experiments, we demonstrate that the seasonally evolving warm pool SST anomalies in the decay phase of an El Niño event generate a meridionally asymmetric Walker circulation response, which couples the zonal and meridional atmospheric overturning circulations. This process, which can be characterized as a phase-synchronized spatial shift in Walker and Hadley cells, is accompanied by cross-equatorial northwesterly low-level flow that diverges from an area of anomalous drying in the western North Pacific and converges towards a region with anomalous moistening in the southern central Pacific. Our results show that the SST-induced concurrent spatial shifts of the two circulations are climatically relevant as they can further amplify extratropical precipitation variability on interannual timescales.

Dynamics Behind a Record-Breaking Trough over Mexico and Internal Atmospheric Variability during El Niño

2019 ◽  
Vol 100 (10) ◽  
pp. 1961-1978 ◽  
Author(s):  
Samuel P. Lillo ◽  
David B. Parsons ◽  
Malaquias Peña
Keyword(s):  
Rossby Wave ◽  
El Niño ◽  
El Nino ◽  
Weather Prediction ◽  
Wave Dispersion ◽  
Wave Activity ◽  
Central Pacific ◽  
Multiple Wave ◽  
Subtropical Anticyclone ◽  
The North

AbstractA major winter storm took place over Mexico during 7 to 11 March 2016, impacting 28 states and leaving four million families without power. Extensive agricultural damage and livestock deaths were also reported with widespread snow across central and northern Mexico. North of the border, this system resulted in record-breaking flooding and severe weather in Texas and Louisiana. The event was due to a trough that deepened and cut off over central Mexico with 500-hPa heights that were nine standard deviations below normal, well beyond previous records! Motivated by the societal impacts of this event, this study investigates factors that contributed to the extreme trough and influenced its predictability in forecast models. A strong El Niño provided the antecedent conditions, with enhanced tropical convection over the central Pacific, a strengthened subtropical anticyclone, and poleward Rossby wave dispersion. However, unlike past strong El Niños, the North Pacific preceding this event was characterized by significant synoptic-scale Rossby wave activity on the midlatitude jet stream including multiple wave packets tracking around the globe during February and March. The interaction of one of these packets with the subtropical anticyclone aloft resulted in a large anticyclonic wave break over the east Pacific, leading to the amplification of the downstream trough over Mexico. The ability of numerical weather prediction to capture this extreme trough is directly related to the predictability of the Rossby wave packet. These results are also discussed within the context of the relationship between El Niño, Rossby wave activity, and extreme events in western North America.

scholarly journals The Annual-Cycle Modulation of Meridional Asymmetry in ENSO’s Atmospheric Response and Its Dependence on ENSO Zonal Structure

2015 ◽  
Vol 28 (14) ◽  
pp. 5795-5812 ◽  
Author(s):  
Wenjun Zhang ◽  
Haiyan Li ◽  
Fei-Fei Jin ◽  
Malte F. Stuecker ◽  
Andrew G. Turner ◽  
...  
Keyword(s):  
Annual Cycle ◽  
El Niño ◽  
El Nino ◽  
Warm Pool ◽  
Atmospheric Response ◽  
Central Pacific ◽  
Cp El Niño ◽  
El Niño Events ◽  
Sst Anomalies ◽  
El Nino Events

Abstract Previous studies documented that a distinct southward shift of central Pacific low-level wind anomalies occurring during the ENSO decaying phase is caused by an interaction between the western Pacific annual cycle and El Niño–Southern Oscillation (ENSO) variability. The present study finds that the meridional movement of the central Pacific wind anomalies appears only during traditional eastern Pacific El Niño (EP El Niño) events rather than in central Pacific El Niño (CP El Niño) events in which sea surface temperature (SST) anomalies are confined to the central Pacific. The zonal structure of ENSO-related SST anomalies therefore has an important effect on meridional asymmetry in the associated atmospheric response and its modulation by the annual cycle. In contrast to EP El Niño events, the SST anomalies of CP El Niño events extend farther west toward the warm pool region with its climatological warm SSTs. In the warm pool region, relatively small SST anomalies are thus able to excite convection anomalies on both sides of the equator, even with a meridionally asymmetric SST background state. Therefore, almost meridionally symmetric precipitation and wind anomalies are observed over the central Pacific during the decaying phase of CP El Niño events. The SST anomaly pattern of La Niña events is similar to CP El Niño events with a reversed sign. Accordingly, no distinct southward displacement of the atmospheric response occurs over the central Pacific during the La Niña decaying phase. These results have important implications for ENSO climate impacts over East Asia, since the anomalous low-level anticyclone over the western North Pacific is an integral part of the annual cycle–modulated ENSO response.

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