scholarly journals Diurnal Cycle in Different Weather Regimes and Rainfall Variability over Borneo Associated with ENSO

2013 ◽  
Vol 26 (5) ◽  
pp. 1772-1790 ◽  
Author(s):  
Jian-Hua Qian ◽  
Andrew W. Robertson ◽  
Vincent Moron
Keyword(s):  
Diurnal Cycle ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Rainfall Variability ◽  
Austral Summer ◽  
Weather Types ◽  
Sea Breezes ◽  
Rainfall Anomalies ◽  
Dipolar Structure

Abstract The interannual variability of precipitation over the island of Borneo in association with El Niño–Southern Oscillation (ENSO) has been studied by using the Global Precipitation Climatology Centre (GPCC) gridded rain gauge precipitation, the NOAA Climate Prediction Center (CPC) Morphing Technique (CMORPH) satellite estimated precipitation, the Quick Scatterometer (QuikSCAT) satellite estimated sea winds, and the National Centers for Environmental Prediction (NCEP)–National Center for Atmospheric Research (NCAR) reanalysis data. Analysis of the GPCC precipitation shows a dipolar structure of wet southwest versus dry central and northeast in precipitation anomalies associated with El Niño over Borneo Island during the austral summer [December–February (DJF)]. By using the 0.25° and 3-hourly CMORPH precipitation, it is found that rainfall over Borneo is strongly affected by the diurnal cycle of land–sea breezes. The spatial distribution of rainfall over Borneo depends on the direction of monsoonal winds. Weather typing analysis indicates that the dipolar structure of rainfall anomalies associated with ENSO is caused by the variability in the frequency of occurrence of different weather types. Rainfall is enhanced in the coastal region where sea breezes head against off-shore synoptic-scale low-level winds (i.e., in the lee side or wake area of the island), which is referred to here as the “wake effect.” In DJF of El Niño years, the northwesterly austral summer monsoon in southern Borneo is weaker than normal over the Maritime Continent and easterly winds are more frequent than normal over Borneo, acting to enhance rainfall over the southwest coast of the island. This coastal rainfall generation mechanism in different weather types explains the dipole pattern of a wet southwest versus dry northeast in the rainfall anomalies over Borneo Island in the El Niño years.

scholarly journals Teleconnections between Monthly Rainfall Variability and Large-Scale Climate Indices in Southwestern Colombia

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1863 ◽  
Author(s):  
Teresita Canchala ◽  
Wilfredo Alfonso-Morales ◽  
Wilmar Loaiza Cerón ◽  
Yesid Carvajal-Escobar ◽  
Eduardo Caicedo-Bravo
Keyword(s):  
Water Resources ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Rainfall Variability ◽  
Monthly Rainfall ◽  
Wavelet Coherence ◽  
Climate Indices ◽  
Annual Scale ◽  
Wavelet Coherence Analysis

Given that the analysis of past monthly rainfall variability is highly relevant for the adequate management of water resources, the relationship between the climate-oceanographic indices, and the variability of monthly rainfall in Southwestern Colombia at different time scales was chosen as the research topic. It should also be noted that little-to-no research has been carried out on this topic before. For the purpose of conducting this research, we identified homogeneous rainfall regions while using Non-Linear Principal Component Analysis (NLPCA) and Self-Organizing Maps (SOM). The rainfall variability modes were obtained from the NLPCA, while their teleconnection in relation to the climate indices was obtained from Pearson’s Correlations and Wavelet Transform. The regionalization process clarified that Nariño has two regions: the Andean Region (AR) and the Pacific Region (PR). The NLPCA showed two modes for the AR, and one for the PR, with an explained variance of 75% and 48%, respectively. The correlation analyses between the first nonlinear components of AR and PR regarding climate indices showed AR high significant positive correlations with Southern Oscillation Index (SOI) index and negative correlations with El Niño/Southern Oscillation (ENSO) indices. PR showed positive ones with Niño1 + 2, and Niño3, and negative correlations with Niño3.4 and Niño4, although their synchronous relationships were not statistically significant. The Wavelet Coherence analysis showed that the variability of the AR rainfall was influenced principally by the Niño3.4 index on the 3–7-year inter-annual scale, while PR rainfall were influenced by the Niño3 index on the 1.5–3-year inter-annual scale. The El Niño (EN) events lead to a decrease and increase in the monthly rainfall on AR and PR, respectively, while, in the La Niña (LN) events, the opposite occurred. These results that are not documented in previous studies are useful for the forecasting of monthly rainfall and the planning of water resources in the area of study.

scholarly journals Variability in Severe Coastal Flooding, Associated Storms, and Death Tolls in Southeastern Australia since the Mid–Nineteenth Century

2016 ◽  
Vol 55 (5) ◽  
pp. 1139-1149 ◽  
Author(s):  
Scott B. Power ◽  
Jeff Callaghan
Keyword(s):  
Nineteenth Century ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Coastal Flooding ◽  
La Niña ◽  
Interdecadal Pacific Oscillation ◽  
Weather Types ◽  
Southeastern Australia ◽  
La Nina

AbstractThe variability in the number of severe floods that occurred in coastal catchments in southeastern Australia since the mid–nineteenth century, along with the variability in both the frequency of the weather types that triggered the floods and the associated death tolls, is analyzed. Previous research has shown that all of the severe floods identified were associated with one of two major weather types: east coast lows (ECLs) and tropical interactions (TIs). El Niño–Southern Oscillation (ENSO) is shown to strongly modulate the frequency of severe coastal flooding, weather types, and the number of associated deaths. The analysis presented herein, which examines links over more than a century, provides one of very few known statistically significant links between ENSO and death tolls anywhere in the world. Over the period 1876/77–2013/14 the average numbers of coastal floods, ECLs, TIs, and deaths associated with freshwater drowning in La Niña years are 92%, 55%, 150%, and 220% higher than the corresponding averages in El Niño years. The average number of deaths per flood in La Niña years is 3.2, which is 66% higher than the average in El Niño years. Death tolls of 10 or more occurred in only 5% of El Niño years, but in 27% of La Niña years. The interdecadal Pacific oscillation also modulates the frequency of severe floods, weather types, and death tolls. The results of this study are consistent with earlier research over shorter periods and broader regions, using less-complete datasets.

scholarly journals Influence of ENSO on the Diurnal Cycle of Rainfall over the Maritime Continent and Australia

2013 ◽  
Vol 26 (4) ◽  
pp. 1304-1321 ◽  
Author(s):  
Surendra P. Rauniyar ◽  
Kevin J. E. Walsh
Keyword(s):  
Diurnal Cycle ◽  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Walker Circulation ◽  
La Niña ◽  
Boreal Winter ◽  
Maritime Continent ◽  
La Nina ◽  
Rainfall Anomalies

Abstract This study examines the influence of ENSO on the diurnal cycle of rainfall during boreal winter for the period 1998–2010 over the Maritime Continent (MC) and Australia using Tropical Rainfall Measuring Mission (TRMM) and reanalysis data. The diurnal cycles are composited for the ENSO cold (La Niña) and warm (El Niño) phases. The k-means clustering technique is then applied to group the TRMM data into six clusters, each with a distinct diurnal cycle. Despite the alternating patterns of widespread large-scale subsidence and ascent associated with the Walker circulation, which dominates the climate over the MC during the opposing phases of ENSO, many of the islands of the MC show localized differences in rainfall anomalies that depend on the local geography and orography. While ocean regions mostly experience positive rainfall anomalies during La Niña, some local regions over the islands have more rainfall during El Niño. These local features are also associated with anomalies in the amplitude and characteristics of the diurnal cycle in these regions. These differences are also well depicted in large-scale dynamical fields derived from the interim ECMWF Re-Analysis (ERA-Interim).

Observed Relationships between the El Niño–Southern Oscillation and the Extratropical Zonal-Mean Circulation

2006 ◽  
Vol 19 (2) ◽  
pp. 276-287 ◽  
Author(s):  
Michelle L. L’Heureux ◽  
David W. J. Thompson
Keyword(s):  
Zonal Wind ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Austral Summer ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Annular Mode ◽  
Mean Circulation ◽  
The Impact

Abstract There is increasing evidence indicating that the climate response to variations in the El Niño–Southern Oscillation (ENSO) includes not only thermally forced zonal wind anomalies in the subtropics but also eddy-driven zonal wind anomalies that extend into the mid–high latitudes of both hemispheres. In this study, new insights into the observed seasonally varying signature of ENSO in the extratropical zonal-mean circulation are provided and the associated linkages with the dominant patterns of extratropical variability are examined. The zonal-mean extratropical atmospheric response to ENSO is characterized by two principal features: an equivalent barotropic dipole in the Southern Hemisphere (SH) zonal-mean zonal flow with centers of action located near ∼40° and ∼60° during austral summer, and a weaker, but analogous, dipole in the Northern Hemisphere (NH) with centers of action located near ∼25° and ∼45° during early and late boreal winter. Both structures are accompanied by eddy momentum flux anomalies that exhibit a remarkable degree of hemispheric symmetry. In the SH, the extratropical signature of ENSO projects strongly onto the primary mode of large-scale variability, the southern annular mode (SAM). During the austral summer, roughly 25% of the temporal variability in the SAM is linearly related to fluctuations in the ENSO cycle. An analogous relationship is not observed in association with the principal mode of climate variability in the NH, the northern annular mode (NAM). It is argued that the seasonally varying impact of ENSO on the extratropical circulation is consistent with the impact of the thermally forced subtropical wind anomalies on the dissipation of equatorward-propagating wave activity at subtropical latitudes.

scholarly journals The influence of El Niño–Southern Oscillation regimes on eastern African vegetation and its future implications under the RCP8.5 warming scenario

2017 ◽  
Vol 14 (18) ◽  
pp. 4355-4374 ◽  
Author(s):  
Istem Fer ◽  
Britta Tietjen ◽  
Florian Jeltsch ◽  
Christian Wolff
Keyword(s):  
Climate Change ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Rainfall Variability ◽  
Future Climate ◽  
Future Climate Change ◽  
El Nino Southern Oscillation ◽  
Vegetation Response ◽  
African Rainfall

Abstract. The El Niño–Southern Oscillation (ENSO) is the main driver of the interannual variability in eastern African rainfall, with a significant impact on vegetation and agriculture and dire consequences for food and social security. In this study, we identify and quantify the ENSO contribution to the eastern African rainfall variability to forecast future eastern African vegetation response to rainfall variability related to a predicted intensified ENSO. To differentiate the vegetation variability due to ENSO, we removed the ENSO signal from the climate data using empirical orthogonal teleconnection (EOT) analysis. Then, we simulated the ecosystem carbon and water fluxes under the historical climate without components related to ENSO teleconnections. We found ENSO-driven patterns in vegetation response and confirmed that EOT analysis can successfully produce coupled tropical Pacific sea surface temperature–eastern African rainfall teleconnection from observed datasets. We further simulated eastern African vegetation response under future climate change as it is projected by climate models and under future climate change combined with a predicted increased ENSO intensity. Our EOT analysis highlights that climate simulations are still not good at capturing rainfall variability due to ENSO, and as we show here the future vegetation would be different from what is simulated under these climate model outputs lacking accurate ENSO contribution. We simulated considerable differences in eastern African vegetation growth under the influence of an intensified ENSO regime which will bring further environmental stress to a region with a reduced capacity to adapt effects of global climate change and food security.

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