scholarly journals Relationships between the Antarctic Oscillation, the Madden–Julian Oscillation, and ENSO, and Consequences for Rainfall Analysis

2010 ◽  
Vol 23 (2) ◽  
pp. 238-254 ◽  
Author(s):  
B. Pohl ◽  
N. Fauchereau ◽  
C. J. C. Reason ◽  
M. Rouault
Keyword(s):  
Time Scales ◽  
Time Scale ◽  
Rainfall Variability ◽  
Austral Summer ◽  
La Niña ◽  
Madden Julian Oscillation ◽  
Antarctic Oscillation ◽  
Interannual Time Scale ◽  
La Nina ◽  
The Antarctic

Abstract The Antarctic Oscillation (AAO) is the leading mode of atmospheric variability in the Southern Hemisphere mid- and high latitudes (south of 20°S). In this paper, the authors examine its statistical relationships with the major tropical climate signals at the intraseasonal and interannual time scales and their consequences on its potential influence on rainfall variability at regional scales. At the intraseasonal time scale, although the AAO shows its most energetic fluctuations in the 30–60-day range, it is not unambiguously related to the global-scale Madden–Julian oscillation (MJO) activity, with in particular no coherent phase relationship with the MJO index. Moreover, in the high southern latitudes, the MJO-associated anomaly fields do not appear to project coherently on the well-known AAO patterns and are never of an annular nature. At the interannual time scale, a strong teleconnection with ENSO is found during the peak of the austral summer season, corroborating previous studies. El Niño (La Niña) tends to correspond to a negative (positive) AAO phase. The results are statistically significant only when the seasonal mean fields averaged for the November through February season are considered. Based on these results, the authors then isolate the specific influence of the AAO on rainfall variability at both intraseasonal and interannual time scales. The example taken here is southern Africa, a region under the influence of both the MJO and ENSO, experiencing its main rainy season in austral summer and containing a relatively dense network of rain gauge measurements. At the interannual time scale, the significance of the teleconnections between southern African rainfall and the AAO reveals itself to be a statistical artifact and becomes very weak once the influence of ENSO is removed. At the intraseasonal time scale, the AAO is seen to significantly affect the rainfall amounts over much of the country, without interference with other modes of variability. Its influence in modulating the rain appears to be strongest during La Niña years.

scholarly journals Análise Quantitativa da Variabilidade da Chuva em João Pessoa-PB, em Várias Escalas de Tempo (Quantitative Analysis of the Rain Variability in João Pessoa-PB, on Several Time Scales)

2016 ◽  
Vol 8 (6) ◽  
pp. 1748
Author(s):  
Biancca Correia de Medeiros ◽  
Aldinete Bezerra Barreto ◽  
José Diorgenes Alves de Oliveira ◽  
Regina Aragão Silva
Keyword(s):  
Time Scales ◽  
El Niño ◽  
El Nino ◽  
Rainfall Variability ◽  
La Niña ◽  
Land Breeze ◽  
Monthly Precipitation ◽  
Rainfall Events ◽  
Area Of Interest ◽  
La Nina

A área de interesse para este estudo foi João Pessoa, capital do Estado da Paraíba, localizada no litoral do Nordeste do Brasil. Neste estudo foram utilizados totais diários (1961 a 2012) da precipitação observada na estação climatológica do Instituto Nacional de Meteorologia (INMET), em João Pessoa-PB. Os dados foram usados para estudar a variabilidade da chuva em várias escalas de tempo, investigando as anomalias de precipitação em anos de El Niño e La Niña, como também identificar eventos de chuva intensa com ênfase em casos extremos. Os resultados destacam os meses de abril a julho como o período de picos máximos da precipitação média mensal e da frequência máxima do número de dias com chuva, bem como o período de número máximo de eventos extremos de chuva. Os desvios padronizados de precipitação (DPP) mensais apresentam valores negativos e positivos, entre -1,7 e 3,7. Observou-se que os DPP negativos predominam tanto na época de El Niño (62,04%) quanto de La Niña (56,37%), o que significa uma diminuição no volume de chuva, mas não representa uma evidência significativa da influência dos fenômenos El Niño e La Niña sobre a variabilidade da chuva. No ciclo diário, ficou evidente a importância da circulação de brisa terrestre no regime de precipitação da cidade de João Pessoa, já que favorece a chuva no final da noite até o inicio da manhã, com frequência máxima as 6 HL (Horário Local).   A B S T R A C T The area of interest for this study was João Pessoa, capital of Paraiba State, located on the coast of Northeast Brazil. In this study daily (1961-2012) rainfall totals observed at the meteorological station of the National Institute of Meteorology (INMET) in João Pessoa-PB were employed. The data were used to study the variability of rainfall on various time scales, investigating the precipitation anomalies in El Niño and La Niña years, as well as identifying heavy rainfall events with an emphasis on extreme cases. The results highlight the months from April to July as the period of maxima in the mean monthly precipitation, and in the frequency of rain days and extreme rainfall events. The monthly standardized precipitation deviation (DPP) shows negative and positive values ranging from -1.7 to 3.7. It was observed that negative DPP are more frequent both at the time of El Niño (62.04%) and La Niña (56.37%), which means a decrease in the volume of rainfall. But these results do not confirm a significant evidence of the influence of El Niño and La Niña phenomena on rainfall variability. In the daily cycle, it was evident the importance of the land breeze circulation in the precipitation regime of the city of João Pessoa, since it favors rainfall in late evening up to early morning, with maximum frequency at 6 LT (Local Time). Keywords: Urban Area. Precipitation. Extreme Event. Standard Deviation.   

scholarly journals Indo-Pacific Variability on Seasonal to Multidecadal Time Scales. Part II: Multiscale Atmosphere–Ocean Linkages

2018 ◽  
Vol 31 (2) ◽  
pp. 693-725 ◽  
Author(s):  
Dimitrios Giannakis ◽  
Joanna Slawinska
Keyword(s):  
Time Scales ◽  
El Niño ◽  
El Nino ◽  
Walker Circulation ◽  
La Niña ◽  
Central Pacific ◽  
Australian Monsoon ◽  
La Nina ◽  
Combination Modes ◽  
Sst Anomalies

The coupled atmosphere–ocean variability of the Indo-Pacific domain on seasonal to multidecadal time scales is investigated in CCSM4 and in observations through nonlinear Laplacian spectral analysis (NLSA). It is found that ENSO modes and combination modes of ENSO with the annual cycle exhibit a seasonally synchronized southward shift of equatorial surface zonal winds and thermocline adjustment consistent with terminating El Niño and La Niña events. The surface winds associated with these modes also generate teleconnections between the Pacific and Indian Oceans, leading to SST anomalies characteristic of the Indian Ocean dipole. The family of NLSA ENSO modes is used to study El Niño–La Niña asymmetries, and it is found that a group of secondary ENSO modes with more rapidly decorrelating temporal patterns contributes significantly to positively skewed SST and zonal wind statistics. Besides ENSO, fundamental and combination modes representing the tropospheric biennial oscillation (TBO) are found to be consistent with mechanisms for seasonally synchronized biennial variability of the Asian–Australian monsoon and Walker circulation. On longer time scales, a multidecadal pattern referred to as the west Pacific multidecadal mode (WPMM) is established to significantly modulate ENSO and TBO activity, with periods of negative SST anomalies in the western tropical Pacific favoring stronger ENSO and TBO variability. This behavior is attributed to the fact that cold WPMM phases feature anomalous decadal westerlies in the tropical central Pacific, as well as an anomalously flat zonal thermocline profile in the equatorial Pacific. Moreover, the WPMM is found to correlate significantly with decadal precipitation over Australia.

scholarly journals An Analysis of Anomalous Winter and Spring Tornado Frequency by Phase of the El Niño/Southern Oscillation, the Global Wind Oscillation, and the Madden-Julian Oscillation

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Todd W. Moore ◽  
Jennifer M. St. Clair ◽  
Tiffany A. DeBoer
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Madden Julian Oscillation ◽  
La Nina ◽  
Upper Level ◽  
Favorable Conditions

Winter and spring tornado activity tends to be heightened during the La Niña phase of the El Niño/Southern Oscillation and suppressed during the El Niño phase. Despite these tendencies, some La Niña seasons have fewer tornadoes than expected and some El Niño seasons have more than expected. To gain insight into such anomalous seasons, the two La Niña winters and springs with the fewest tornadoes and the two El Niño winters and springs with the most tornadoes between 1979 and 2016 are identified and analyzed in this study. The relationships between daily tornado count and the Global Wind Oscillation and Madden-Julian Oscillation in these anomalous seasons are also explored. Lastly, seasonal and daily composites of upper-level flow, low-level flow and humidity, and atmospheric instability are generated to describe the environmental conditions in the anomalous seasons. The results of this study highlight the potential for large numbers of tornadoes to occur in a season if favorable conditions emerge in association with individual synoptic-scale events, even during phases of the El Niño/Southern Oscillation, Global Wind Oscillation, and Madden-Julian Oscillation that seem to be unfavorable for tornadoes. They also highlight the potential for anomalously few tornadoes in a season even when the oscillations are in favorable phases.

scholarly journals Moist Thermodynamics of the Madden–Julian Oscillation in a Cloud-Resolving Simulation

2011 ◽  
Vol 24 (21) ◽  
pp. 5571-5583 ◽  
Author(s):  
Samson Hagos ◽  
L. Ruby Leung
Keyword(s):  
Time Scales ◽  
Time Scale ◽  
Deep Convection ◽  
Lower Troposphere ◽  
Active Phase ◽  
Vertical Transport ◽  
Madden Julian Oscillation ◽  
Boundary Layer Diffusion ◽  
Inactive Phase ◽  
Thermodynamic Processes

Abstract The moist thermodynamic processes that determine the time scale and energy of the Madden–Julian oscillation (MJO) are investigated using moisture and eddy available potential energy budget analyses on a cloud-resolving simulation. Two MJO episodes observed during the winter of 2007/08 are realistically simulated. During the inactive phase, moisture supplied by meridional moisture convergence and boundary layer diffusion generates shallow and congestus clouds that moisten the lower troposphere while horizontal mixing tends to dry it. As the lower troposphere is moistened, it becomes a source of moisture for the subsequent deep convection during the MJO active phase. As the active phase ends, the lower troposphere dries out primarily by condensation and horizontal divergence that dominates over the moisture supply by vertical transport. In the simulation, the characteristic time scales of convective vertical transport, mixing, and condensation of moisture in the midtroposphere are estimated to be about 2 days, 4 days, and 20 h respectively. The small differences among these time scales result in an effective time scale of MJO moistening of about 25 days, half the period of the simulated MJO. Furthermore, various cloud types have a destabilizing or damping effect on the amplitude of MJO temperature signals, depending on their characteristic latent heating profile and its temporal covariance with the temperature. The results are used to identify possible sources of the difficulties in simulating MJO in low-resolution models that rely on cumulus parameterizations.

scholarly journals State of the Climate in 2010

2011 ◽  
Vol 92 (6) ◽  
pp. S1-S236 ◽  
Author(s):  
J. Blunden ◽  
D. S. Arndt ◽  
M. O. Baringer
Keyword(s):  
Carbon Dioxide ◽  
Sea Ice ◽  
North Atlantic ◽  
El Niño ◽  
Arctic Oscillation ◽  
El Nino ◽  
La Niña ◽  
The Arctic ◽  
La Nina ◽  
The Antarctic

Several large-scale climate patterns influenced climate conditions and weather patterns across the globe during 2010. The transition from a warm El Niño phase at the beginning of the year to a cool La Niña phase by July contributed to many notable events, ranging from record wetness across much of Australia to historically low Eastern Pacific basin and near-record high North Atlantic basin hurricane activity. The remaining five main hurricane basins experienced below- to well-below-normal tropical cyclone activity. The negative phase of the Arctic Oscillation was a major driver of Northern Hemisphere temperature patterns during 2009/10 winter and again in late 2010. It contributed to record snowfall and unusually low temperatures over much of northern Eurasia and parts of the United States, while bringing above-normal temperatures to the high northern latitudes. The February Arctic Oscillation Index value was the most negative since records began in 1950. The 2010 average global land and ocean surface temperature was among the two warmest years on record. The Arctic continued to warm at about twice the rate of lower latitudes. The eastern and tropical Pacific Ocean cooled about 1°C from 2009 to 2010, reflecting the transition from the 2009/10 El Niño to the 2010/11 La Niña. Ocean heat fluxes contributed to warm sea surface temperature anomalies in the North Atlantic and the tropical Indian and western Pacific Oceans. Global integrals of upper ocean heat content for the past several years have reached values consistently higher than for all prior times in the record, demonstrating the dominant role of the ocean in the Earth's energy budget. Deep and abyssal waters of Antarctic origin have also trended warmer on average since the early 1990s. Lower tropospheric temperatures typically lag ENSO surface fluctuations by two to four months, thus the 2010 temperature was dominated by the warm phase El Niño conditions that occurred during the latter half of 2009 and early 2010 and was second warmest on record. The stratosphere continued to be anomalously cool. Annual global precipitation over land areas was about five percent above normal. Precipitation over the ocean was drier than normal after a wet year in 2009. Overall, saltier (higher evaporation) regions of the ocean surface continue to be anomalously salty, and fresher (higher precipitation) regions continue to be anomalously fresh. This salinity pattern, which has held since at least 2004, suggests an increase in the hydrological cycle. Sea ice conditions in the Arctic were significantly different than those in the Antarctic during the year. The annual minimum ice extent in the Arctic—reached in September—was the third lowest on record since 1979. In the Antarctic, zonally averaged sea ice extent reached an all-time record maximum from mid-June through late August and again from mid-November through early December. Corresponding record positive Southern Hemisphere Annular Mode Indices influenced the Antarctic sea ice extents. Greenland glaciers lost more mass than any other year in the decade-long record. The Greenland Ice Sheet lost a record amount of mass, as the melt rate was the highest since at least 1958, and the area and duration of the melting was greater than any year since at least 1978. High summer air temperatures and a longer melt season also caused a continued increase in the rate of ice mass loss from small glaciers and ice caps in the Canadian Arctic. Coastal sites in Alaska show continuous permafrost warming and sites in Alaska, Canada, and Russia indicate more significant warming in relatively cold permafrost than in warm permafrost in the same geographical area. With regional differences, permafrost temperatures are now up to 2°C warmer than they were 20 to 30 years ago. Preliminary data indicate there is a high probability that 2010 will be the 20th consecutive year that alpine glaciers have lost mass. Atmospheric greenhouse gas concentrations continued to rise and ozone depleting substances continued to decrease. Carbon dioxide increased by 2.60 ppm in 2010, a rate above both the 2009 and the 1980–2010 average rates. The global ocean carbon dioxide uptake for the 2009 transition period from La Niña to El Niño conditions, the most recent period for which analyzed data are available, is estimated to be similar to the long-term average. The 2010 Antarctic ozone hole was among the lowest 20% compared with other years since 1990, a result of warmer-than-average temperatures in the Antarctic stratosphere during austral winter between mid-July and early September.

scholarly journals Observed Changes in the Lifetime and Amplitude of the Madden–Julian Oscillation Associated with Interannual ENSO Sea Surface Temperature Anomalies

2007 ◽  
Vol 20 (11) ◽  
pp. 2659-2674 ◽  
Author(s):  
Benjamin Pohl ◽  
Adrian J. Matthews
Keyword(s):  
Zonal Wind ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
Average Lifetime ◽  
Wind Component ◽  
Madden Julian Oscillation ◽  
La Nina ◽  
Equatorial Wave

Abstract The Madden–Julian oscillation (MJO) is analyzed using the reanalysis zonal wind– and satellite outgoing longwave radiation–based indices of Wheeler and Hendon for the 1974–2005 period. The average lifetime of the MJO events varies with season (36 days for events whose central date occurs in December, and 48 days for events in September). The lifetime of the MJO in the equinoctial seasons (March–May and October–December) is also dependent on the state of El Niño–Southern Oscillation (ENSO). During October–December it is only 32 days under El Niño conditions, increasing to 48 days under La Niña conditions, with similar values in northern spring. This difference is due to faster eastward propagation of the MJO convective anomalies through the Maritime Continent and western Pacific during El Niño, consistent with theoretical arguments concerning equatorial wave speeds. The analysis is extended back to 1950 by using an alternative definition of the MJO based on just the zonal wind component of the Wheeler and Hendon indices. A rupture in the amplitude of the MJO is found in 1975, which is at the same time as the well-known rupture in the ENSO time series that has been associated with the Pacific decadal oscillation. The mean amplitude of the MJO is 16% larger in the postrupture (1976–2005) compared to the prerupture (1950–75) period. Before the 1975 rupture, the amplitude of the MJO is maximum (minimum) under El Niño (La Niña) conditions during northern winter, and minimum (maximum) under El Niño (La Niña) conditions during northern summer. After the rupture, this relationship disappears. When the MJO–ENSO relationship is analyzed using all-year-round data, or a shorter dataset (as in some previous studies), no relationship is found.

scholarly journals Simulated enhancement of ENSO-related rainfall variability due to Australian dust

2011 ◽  
Vol 11 (1) ◽  
pp. 1595-1639 ◽  
Author(s):  
L. D. Rotstayn ◽  
M. A. Collier ◽  
R. M. Mitchell ◽  
Y. Qin ◽  
S. K. Campbell
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Rainfall Variability ◽  
La Niña ◽  
Climate Feedback ◽  
Surface Cooling ◽  
Atmospheric Heating ◽  
La Nina ◽  
Eastern Australia

Abstract. Average dust emissions from Australia are small compared to those from the major sources in the Northern Hemisphere. However, they are highly episodic, and this may increase the importance of Australian dust as a climate feedback agent. We compare two 160-year coupled atmosphere-ocean simulations of modern-day climate using the CSIRO Mark 3.6 global climate model (GCM). The first run (DUST) includes an interactive treatment of mineral dust and its direct radiative effects. The second run (NODUST) is otherwise identical, but has the Australian dust source set to zero. We focus on the austral spring season, when the correlation between rainfall and the El Niño Southern Oscillation (ENSO) is strongest over Australia. We find that the ENSO-rainfall relationship over eastern Australia is stronger in the DUST run: dry (El Niño) years tend to be drier, and wet (La Niña) years wetter. The ENSO-rainfall relationship is also weaker over north-western Australia in the DUST run. The amplification of ENSO-related rainfall variability over eastern Australia and the weaker ENSO-rainfall relationship over the north-west both represent an improvement relative to observations. The suggested mechanism over eastern Australia involves stabilisation of the surface layer due to enhanced atmospheric heating and surface cooling in El Niño years, and enhanced ascent and moisture convergence driven by atmospheric heating in La Niña years. The results suggest that (1) a realistic treatment of Australian dust may be necessary for accurate simulation of the ENSO-rainfall relationship over Australia, and (2) radiative feedbacks involving dust may be important for understanding natural rainfall variability over Australia.

scholarly journals Simulação da Precipitação Sazonal com o Regcm4 sobre o Estado do Pará para Anos de El Niño e La Niña (Simulation of Seasonal Precipitation with Regcm4 about the State of Pará for Years of El Niño and La Niña)

2013 ◽  
Vol 6 (5) ◽  
pp. 1316
Author(s):  
Pâmela Lorena Ribeiro Ávila ◽  
Everaldo Barreiros de Souza ◽  
Amanda Nascimento Pinheiro
Keyword(s):  
Spatial Patterns ◽  
El Niño ◽  
Climate Modeling ◽  
El Nino ◽  
Rainfall Variability ◽  
Regional Distribution ◽  
The State ◽  
La Niña ◽  
Seasonal Rainfall ◽  
La Nina

Este trabalho apresenta uma contribuição aos estudos de modelagem climática com ênfase na variabilidade pluviométrica sazonal do estado do Pará, durante as estações de verão e outono (DJF e MAM). Baseado nos resultados das simulações regionais do RegCM4 para os anos de El Niño (1982/83) e Lã Niña (1988/89) usando domínio em alta resolução espacial (50 Km) e dois diferentes esquemas de convecção (Grell e MIT), foi investigado o desempenho do modelo em simular a distribuição regional de precipitação sazonal no estado do Pará. As análises quantitativas evidenciaram que o RegCM4 apresenta erros sistemáticos, sobretudo aqueles relacionados a uma subestimativa das chuvas nas três grades (G1, G2, G3) para os anos de El Niño e Lã Niña sendo representativo apenas em pequenas áreas na região sudeste do estado no período do verão para o esquema Grell, e mostrou-se mais representativo na grade G2 do para o ano de El Niño no esquema MIT. Além disso, através da técnica de composições, também foi investigado o desempenho do RegCM4 em reproduzir os padrões espaciais anômalos de precipitação sazonal em associação aos episódios ENOS, e as fases do gradiente térmico sobre o Atlântico intertropical. Os resultados demonstraram que o modelo conseguiu representar realisticamente bem o padrão espacial das anomalias pluviométricas acima (abaixo) do normal em grande parte da Amazônia oriental, durante os conhecidos cenários favoráveis, i.e., condições de La Niña e gradiente de aTSM para o Atlântico sul (desfavoráveis, i.e., El Niño e gradiente de aTSM para o Atlântico norte). A B S T R A C T This paper presents a contribution to studies of climate modeling with emphasis on seasonal rainfall variability in the state of Pará, during the summer and autumn (DJF and MAM). Based on the results of simulations of regional RegCM4 for El Niño years (1982/83) and La Niña (1988/89) using the field at high spatial resolution (40 km) and two different convection schemes (Grell and MIT), was investigated the performance of the model to simulate the regional distribution of seasonal rainfall in the state of Pará. The quantitative analysis showed that the RegCM4 presents systematic errors, especially those related to an underestimation of rain in three grades (G1, G2, G3) for the years of El Niño and La Niña are representative only in small areas in the southeastern state in summer period for the Grell scheme, and was more representative of the grid G2 for the year of El Niño in the MIT scheme. Moreover, using the technique of composition, was also investigated in the performance of RegCM4 reproduce the spatial patterns of anomalous seasonal rainfall in association with ENSO episodes and phases of the thermal gradient over the Atlantic intertropical. The results showed that the model represented realistically and spatial patterns of rainfall anomalies above (below) of normal in much of the eastern Amazon, during the known favorable scenarios, ie, La Niña and gradient SSTa South Atlantic (unfavorable, ie, El Niño and gradient SSTa North Atlantic). Keywords: seasonal rainfall, El Nino, La Nina, Amazon, ENSO, RegCM4.

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