scholarly journals Wintertime Northern Hemisphere Response in the Stratosphere to the Pacific Decadal Oscillation Using the Whole Atmosphere Community Climate Model

2016 ◽  
Vol 29 (3) ◽  
pp. 1031-1049 ◽  
Author(s):  
A. C. Kren ◽  
D. R. Marsh ◽  
A. K. Smith ◽  
P. Pilewskie
Keyword(s):  
Northern Hemisphere ◽  
Pacific Decadal Oscillation ◽  
El Niño ◽  
Climate Model ◽  
El Nino ◽  
Positive Phase ◽  
Late Winter ◽  
Community Climate Model ◽  
The Pacific ◽  
Community Climate

Abstract The response of the Northern Hemisphere winter stratosphere to the Pacific decadal oscillation (PDO) is examined using the Whole Atmosphere Community Climate Model. A 200-yr preindustrial control simulation that includes fully interactive chemistry, ocean and sea ice, constant solar forcing, and greenhouse gases fixed to 1850 levels is analyzed. Based on principal component analysis, the PDO spatial pattern, frequency, and amplitude agree well with the observed PDO over the period 1900–2014. Consistent with previous studies, the positive phase of the PDO is marked by a strengthened Aleutian low and a wave train of geopotential height anomalies reminiscent of the Pacific–North American pattern in the troposphere. In addition to a tropospheric signal, a zonal-mean warming of about 2 K in the northern polar stratosphere and a zonal-mean zonal wind decrease of about 4 m s−1 in the PDO positive phase are found. When compositing PDO positive or negative winters during neutral El Niño years, the magnitude is reduced and depicts an early winter forcing of the stratosphere compared to a late winter response from El Niño. Contamination between PDO and ENSO signals is also discussed. Stratospheric sudden warmings occur 63% of the time in the PDO positive phase compared to 40% in the negative phase. Although this sudden warming frequency is not statistically significant, it is quantitatively consistent with NCEP–NCAR reanalysis data and recent observational evidence linking the PDO positive phase to weak stratospheric vortex events.

scholarly journals The Hiatus in Global Warming and Interactions between the El Niño and the Pacific Decadal Oscillation: Comparing Observations and Modeling Results

Climate ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 72 ◽  
Author(s):  
Knut Seip ◽  
Hui Wang
Keyword(s):  
Global Warming ◽  
Pacific Decadal Oscillation ◽  
El Niño ◽  
Climate Model ◽  
El Nino ◽  
Global Climate ◽  
Global Climate Model ◽  
The Pacific ◽  
Common Cycles ◽  
Hadley Centre

Ocean oscillations interact across large regions and these interactions may explain cycles in global temperature anomaly, including hiatus periods. Here, we examine ocean interaction measures and compare results from model simulations to observations for El Niño and the Pacific decadal oscillation (PDO). We use the global climate model of the Met Office Hadley Centre. A relatively novel method for identifying running leading-agging LL-relations show that the observed El Niño generally leads the observed PDO and this pattern is strengthened in the simulations. However, LL-pattern in both observations and models shows that there are three periods, around 1910–1920, around 1960 and around 2000 where El Niño lags PDO, or the leading signature is weak. These periods correspond to hiatus periods in global warming. The power spectral density analysis, (PSD), identifies various ocean cycle lengths in El Niño and PDO, but the LL-algorithm picks out common cycles of 7–8 and 24 years that shows leading-lagging relations between them.

scholarly journals Climatology of migrating and non-migrating tides observed by three meteor radars in the southern equatorial region

2021 ◽  
Author(s):  
Jianyuan Wang ◽  
Wen Yi ◽  
Jianfei Wu ◽  
Tingdi Chen ◽  
Xianghui Xue ◽  
...  
Keyword(s):  
Harmonic Analysis ◽  
Northern Hemisphere ◽  
Climate Model ◽  
Equatorial Region ◽  
Stratospheric Sudden Warming ◽  
Tidal Model ◽  
Community Climate Model ◽  
Zonal Wavenumber ◽  
Climatic Features ◽  
Community Climate

Abstract. We present a study of migrating and non-migrating tidal winds observed simultaneously by three meteor radars situated in the southern equatorial region. The radars are located at Cariri (7.4° S, 36.5° W), Brazil, Kototabang (0.2° S, 100.3° E), Indonesia and Darwin (12.3° S, 130.8° E), Australia. Harmonic analysis was used to obtain amplitudes and phases for diurnal and semidiurnal solar migrating and non-migrating tides between 80 and 100 km altitude during the period 2005 to 2008. They include the important tidal components of diurnal westward-propagating zonal wavenumber 1 (DW1), diurnal eastward-propagating zonal wavenumber 3 (DE3), semidiurnal westward-propagating zonal wavenumber 2 (SW2), and semidiurnal eastward-propagating zonal wavenumber 2 (SE2). In addition, we also present a climatology of these wind tides and analyze the reliability of the fitting through the reference to Whole Atmosphere Community Climate Model (WACCM) winds. The analysis suggests that the migrating tides could be well fitted by the three different radars, but the non-migrating tides might be overestimated. The results based on observations were also compared with the Climatological Tidal Model of the Thermosphere (CTMT). In general, climatic features between observations and model migrating tides were satisfactory in both wind components. However, the features of the DW1, DE3 and SW2 amplitudes in both wind components were slightly different from the results of the CTMT models. This result is probably because tides could be enhanced by the 2006 northern hemisphere stratospheric sudden warming (NH-SSW) event.

Manifestation of the Pacific Decadal Oscillation in the stationary planetary waves activity

2021 ◽  
Author(s):  
Daria Sobaeva ◽  
Yulia Zyulyaeva ◽  
Sergey Gulev
Keyword(s):  
Pacific Decadal Oscillation ◽  
North American ◽  
Lower Stratosphere ◽  
El Nino ◽  
Planetary Waves ◽  
Positive Phase ◽  
Negative Phase ◽  
Middle Troposphere ◽  
The Pacific ◽  
The Tropics

<p>Strong quasi-decadal oscillations of the stratospheric polar vortex (SPV) intensity are in phase with the Pacific decadal oscillation (PDO). A stronger SPV is observed during the positive phase of the PDO, and during the negative phase, the intensity of the SPV is below the mean climate values. The SPV intensity anomalies, formed by the planetary waves and zonal mean flow interaction, lead to the weakening/intensification of the vortex.</p><p>This research aimed to obtain the differences in the characteristics and the spatial propagation pattern of the planetary waves in the middle troposphere and lower stratosphere during different PDO phases. We analyzed composite periods of years when the PDO index has extremely high and low values. Two periods were constructed for both positive and negative phases, the first consisting of years with El-Nino/La-Nina events and the second without prominent sea surface temperature anomalies in the tropics. </p><p>During the wintertime in the Northern Hemisphere (December-February), wave 2 with two ridges (Siberian and North American Highs) and two troughs (Icelandic and Aleutian Lows) dominates in the middle troposphere, along with wave 1 dominating in the lower stratosphere. In the middle troposphere, at the positive phase ​​of the PDO, the amplitude of wave 2 is higher than in years with negative values of the PDO index. The differences in the Aleutian Low and the North American High intensity between the two phases are significant at the 97.5% level. In the lower stratosphere, the wave amplitude is lower at the negative phase ​​of the PDO, but we can also talk about a slight shift of the wave phase to the east. The regions of the heavy rains in the tropics during El-Nino events are the planetary waves source. They propagate from low to high latitudes, which results in modifying the characteristics and locations of the intensification of the stationary planetary waves in mid-latitudes.</p>

scholarly journals Estudo da Influência da Oscilação Decadal do Pacífico no Nordeste do Brasil (Study of the Influence of Pacific Decadal Oscillation in Northeast of Brazil)

2011 ◽  
Vol 4 (4) ◽  
pp. 665 ◽  
Author(s):  
Djane Fonseca Da Silva ◽  
Josicleda Domiciano Galvíncio
Keyword(s):  
Pacific Decadal Oscillation ◽  
El Niño ◽  
Temporal Variability ◽  
El Nino ◽  
Rainfall Variability ◽  
Northeastern Brazil ◽  
Simultaneous Occurrence ◽  
Precipitation Data ◽  
The Pacific ◽  
Dominant Peak

 Pretende-se nesse trabalho investigar como a ODP exerce influência sobre a variabilidade pluviométrica da sub-bacia hidrográfica do Baixo São Francisco, situada na região Nordeste do Brasil. Foram utilizados dados de precipitação de 17 localidades para o período de dados de 1911-1993 obtidos através da Agência Nacional das Águas (ANA) pelo site www.ana.gov.br/hidroweb. O pico dominante para a variabilidade temporal do BSF é da escala de 20,2-22 anos e pico secundário, significativo, ocorre na escala de 11 anos. Durante a ocorrência simultânea de ENOS e ODP negativa, as anomalias positivas aumentaram consideravelmente. O que parece é que a ODP negativa incrementa os valores das anomalias de chuva, tanto durante El Niño, quanto La Niña.Palavras-chave: Oscilação Decadal do Pacífico, Baixo São Francisco, Análise de Ondeletas  Study of the Influence of the Pacific Decadal Oscillation in the Northeast of Brazil  ABSTRACT It is intended this work to investigate how the PDO influence on rainfall variability in the sub-basin of the Lower São Francisco, located in northeastern Brazil. We used precipitation data from 17 sites for the period 1911-1993 data obtained through the National Water Agency (ANA) by the site www.ana.gov.br / hidroweb. The dominant peak for the temporal variability of BSF is the range of 20.2 to 22 years and secondary peak, significantly, occurs in the range of 11 years. During the simultaneous occurrence of ENSO and PDO negative, the positive anomalies have increased considerably. It turns out that the PDO increases the negative values of abnormal rainfall, both during El Niño, and La Niña. Keywords: Pacific Decadal Oscillation, Low São Francisco, Wavelet Analysis

scholarly journals Influence of the Pacific Decadal Oscillation on the Relationship between El Niño and the Northeast Asian Summer Monsoon

2010 ◽  
Vol 23 (17) ◽  
pp. 4525-4537 ◽  
Author(s):  
Jinhee Yoon ◽  
Sang-Wook Yeh
Keyword(s):  
Pacific Decadal Oscillation ◽  
El Niño ◽  
El Nino ◽  
Asian Summer Monsoon ◽  
Northeast Asia ◽  
Summer Rainfall ◽  
The Pacific ◽  
Asian Summer ◽  
Northeast Asian ◽  
The Relationship

Abstract The influence of the Pacific decadal oscillation (PDO) on the relationship between El Niño and the northeast Asian summer monsoon (NEASM) is examined using observational datasets for the period of 1979–2007. When El Niño occurs during the boreal winter (December–February), the amount of rainfall over northeast Asia is usually above normal during the following summer (June–August). This relationship between El Niño and the NEASM is intensified when El Niño and the PDO are in phase during the previous winter. However, when El Niño and the PDO are out of phase, the relationship is weakened. The authors argue that the PDO can constructively or destructively interfere with the summer rainfall response over northeast Asia to El Niño. They follow the hypothesis that the summer rainfall over northeast Asia could be separated into two components, that is, the tropics-related component and the extratropics-related component. Then they argue that the PDO could modulate the relationship between El Niño and the NEASM through changes in the extratropics-related rainfall, which is associated with the atmospheric circulation, such as the Eurasian pattern. The conditional composites show that when El Niño and the PDO are in phase, the Eurasian-like pattern acts to enhance the extratropics-related rainfall over northeast Asia, resulting in the strengthening of the NEASM. In contrast, the Eurasian-like pattern acts to reduce the extratropics-related rainfall when El Niño and the PDO are out of phase, resulting in the weakening of the NEASM.

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