scholarly journals Regression-based season-ahead drought prediction for southern Peru conditioned on large-scale climate variables

2017 ◽  
Author(s):  
Eric Mortensen ◽  
Shu Wu ◽  
Michael Notaro ◽  
Steven Vavrus ◽  
Rob Montgomery ◽  
...  
Keyword(s):  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Local Level ◽  
Principal Component ◽  
Spatiotemporal Variability ◽  
Climate Indices ◽  
Southern Peru ◽  
Drought Prediction

Abstract. Located at a complex topographic, climatic, and hydrologic crossroads, southern Peru is a semi-arid region that exhibits high spatiotemporal variability in precipitation. The economic viability of the region hinges on this water, yet southern Peru is prone to water scarcity caused by seasonal drought. Droughts here are often triggered during El Niño episodes; however, other large-scale climate mechanisms also play a noteworthy role in controlling the region’s hydrologic cycle. An extensive season-ahead drought prediction model is developed to help bolster existing capacity of stakeholders to plan for and mitigate the deleterious impacts of this hydrologic extreme. In addition to existing climate indices, large-scale climatic variables, such as sea surface temperature, are investigated to identify potential drought predictors. A principal component regression framework is applied to eleven potential predictors to produce an ensemble forecast of January-March precipitation. Model hindcasts of 51 years, compared to climatology and another model conditioned solely on an El Niño-Southern Oscillation index, achieve notable skill and perform better for several metrics, including ranked probability skill score and a hit-miss statistic. Extending the lead time and spatially disaggregating precipitation predictions to the local level may further assist regional stakeholders and policymakers preparing for drought.

scholarly journals Regression-based season-ahead drought prediction for southern Peru conditioned on large-scale climate variables

2018 ◽  
Vol 22 (1) ◽  
pp. 287-303 ◽  
Author(s):  
Eric Mortensen ◽  
Shu Wu ◽  
Michael Notaro ◽  
Stephen Vavrus ◽  
Rob Montgomery ◽  
...  
Keyword(s):  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Local Level ◽  
Spatiotemporal Variability ◽  
Semiarid Region ◽  
Climate Indices ◽  
Southern Peru ◽  
Drought Prediction

Abstract. Located at a complex topographic, climatic, and hydrologic crossroads, southern Peru is a semiarid region that exhibits high spatiotemporal variability in precipitation. The economic viability of the region hinges on this water, yet southern Peru is prone to water scarcity caused by seasonal meteorological drought. Meteorological droughts in this region are often triggered during El Niño episodes; however, other large-scale climate mechanisms also play a noteworthy role in controlling the region's hydrologic cycle. An extensive season-ahead precipitation prediction model is developed to help bolster the existing capacity of stakeholders to plan for and mitigate deleterious impacts of drought. In addition to existing climate indices, large-scale climatic variables, such as sea surface temperature, are investigated to identify potential drought predictors. A principal component regression framework is applied to 11 potential predictors to produce an ensemble forecast of regional January–March precipitation totals. Model hindcasts of 51 years, compared to climatology and another model conditioned solely on an El Niño–Southern Oscillation index, achieve notable skill and perform better for several metrics, including ranked probability skill score and a hit–miss statistic. The information provided by the developed model and ancillary modeling efforts, such as extending the lead time of and spatially disaggregating precipitation predictions to the local level as well as forecasting the number of wet–dry days per rainy season, may further assist regional stakeholders and policymakers in preparing for drought.

scholarly journals Investigation of hydrological variability in the Korean Peninsula with the ENSO teleconnections

2016 ◽  
Vol 374 ◽  
pp. 165-173 ◽  
Author(s):  
Sunkwon Yoon ◽  
Taesam Lee
Keyword(s):  
El Niño ◽  
Korean Peninsula ◽  
El Nino ◽  
Southern Oscillation ◽  
Singular Spectrum Analysis ◽  
Warm Season ◽  
Principal Component ◽  
Lag Time ◽  
Climate Indices ◽  
Atmospheric Teleconnections

Abstract. This study analyzes nonlinear behavior links with atmospheric teleconnections between hydrologic variables and climate indices using statistical models during warm season (June to September) over the Korean Peninsula (KP). The ocean-related major climate factor, which is the El Niño-Southern Oscillation (ENSO) was used to analyze the atmospheric teleconnections by principal component analysis (PCA) and a singular spectrum analysis (SSA). The nonlinear lag time correlations between climate indices and hydrologic variables are calculated by Mutual Information (MI) technique. The nonlinear correlation coefficients (CCs) by MI were higher than linear CCs, and ENSO shows a few months of lag time correlation. The warm season hydrologic variables in KP shows a significant increasing tendency during the warm pool (WP), and the cold tongue (CT) El Niño decaying years shows a significant decreasing tendency, while the La Niña year shows slightly above normal conditions, respectively. A better understanding of the relationship between climate indices and streamflow, and their local impacts can help to prepare for the river discharge management by water managers and scientists. Furthermore, these results provide useful data for policy makers and end-users to support long-range water resources prediction and water-related policy.

scholarly journals Seasonal climate influences on the timing of the Australian monsoon onset

2021 ◽  
Vol 2 (2) ◽  
pp. 489-506
Author(s):  
Joel Lisonbee ◽  
Joachim Ribbe
Keyword(s):  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Monsoon Onset ◽  
Climate Indices ◽  
Australian Monsoon ◽  
Onset Timing ◽  
Climate Influences ◽  
The Impact

Abstract. The timing of the first monsoon burst of the season, or the monsoon onset, can be a critical piece of information for agriculture, fire management, water management, and emergency response in monsoon regions. Why do some monsoon seasons start earlier or later than others? Previous research has investigated the impact of climate influences such as the El Niño–Southern Oscillation (ENSO) on monsoon variability, but most studies have considered only the impact on rainfall and not the timing of the onset. While this question could be applied to any monsoon system, this research presented in this paper has focused on the Australian monsoon. Even with the wealth of research available on the variability of the Australian monsoon season, the timing of the monsoon onset is one aspect of seasonal variability that still lacks skilful seasonal prediction. To help us better understand the influence of large-scale climate drivers on monsoon onset timing, we recreated 11 previously published Australian monsoon onset datasets and extended these to all cover the same period from the 1950/1951 through the 2020/2021 Australian wet seasons. The extended datasets were then tested for correlations with several standard climate indices to identify which climate drivers could be used as predictors for monsoon onset timing. The results show that many of the relationships between monsoon onset dates and ENSO that were previously published are not as strong when considering the extended datasets. Only a strong La Niña pattern usually has an impact on monsoon onset timing, while ENSO-neutral and El Niño patterns lacked a similar relationship. Detrended Indian Ocean Dipole (IOD) data showed a weak relationship with monsoon onset dates, but when the trend in the IOD data is retained, the relationship with onset dates diminishes. Other patterns of climate variability showed little relationship with Australian monsoon onset dates. Since ENSO is a tropical climate process with global impacts, it is prudent to further re-examine its influences in other monsoon regions too, with the aim to evaluate and improve previously established prediction methodologies.

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 Analysis and quantification of ENSO-linked changes in the tropical Atlantic cloud vertical distribution using 14 years of MODIS observations

2019 ◽  
Vol 19 (21) ◽  
pp. 13535-13546
Author(s):  
Nils Madenach ◽  
Cintia Carbajal Henken ◽  
René Preusker ◽  
Odran Sourdeval ◽  
Jürgen Fischer
Keyword(s):  
Time Series ◽  
Vertical Distribution ◽  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Cloud Amount ◽  
Cloud Fraction ◽  
Tropical Atlantic ◽  
High Cloud

Abstract. A total of 14 years (September 2002 to September 2016) of Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) monthly mean cloud data are used to quantify possible changes in the cloud vertical distribution over the tropical Atlantic. For the analysis multiple linear regression techniques are used. For the investigated time period significant linear changes were found in the domain-averaged cloud-top height (CTH) (−178 m per decade), the high-cloud fraction (HCF) (−0.0006 per decade), and the low-cloud amount (0.001 per decade). The interannual variability of the time series (especially CTH and HCF) is highly influenced by the El Niño–Southern Oscillation (ENSO). Separating the time series into two phases, we quantified the linear change associated with the transition from more La Niña-like conditions to a phase with El Niño conditions (Phase 2) and vice versa (Phase 1). The transition from negative to positive ENSO conditions was related to a decrease in total cloud fraction (TCF) (−0.018 per decade; not significant) due to a reduction in the high-cloud amount (−0.024 per decade; significant). Observed anomalies in the mean CTH were found to be mainly caused by changes in HCF rather than by anomalies in the height of cloud tops themselves. Using the large-scale vertical motion ω at 500 hPa (from ERA-Interim ECMWF reanalysis data), the observed anomalies were linked to ENSO-induced changes in the atmospheric large-scale dynamics. The most significant and largest changes were found in regions with strong large-scale upward movements near the Equator. Despite the fact that with passive imagers such as MODIS it is not possible to vertically resolve clouds, this study shows the great potential for large-scale analysis of possible changes in the cloud vertical distribution due to the changing climate by using vertically resolved cloud cover and linking those changes to large-scale dynamics using other observations or model data.

scholarly journals Tropical Cyclone Activity in the Fiji Region: Spatial Patterns and Relationship to Large-Scale Circulation

2009 ◽  
Vol 22 (14) ◽  
pp. 3877-3893 ◽  
Author(s):  
Savin S. Chand ◽  
Kevin J. E. Walsh
Keyword(s):  
Tropical Cyclone ◽  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Vertical Wind Shear ◽  
Relative Vorticity ◽  
La Niña ◽  
Factors Affecting ◽  
La Nina

Abstract This study examines the variations in tropical cyclone (TC) genesis positions and their subsequent tracks for different phases of the El Niño–Southern Oscillation (ENSO) phenomenon in the Fiji, Samoa, and Tonga region (FST region) using Joint Typhoon Warning Center best-track data. Over the 36-yr period from 1970/71 to 2005/06, 122 cyclones are observed in the FST region. A large spread in the genesis positions is noted. During El Niño years, genesis is enhanced east of the date line, extending from north of Fiji to over Samoa, with the highest density centered around 10°S, 180°. During neutral years, maximum genesis occurs immediately north of Fiji with enhanced genesis south of Samoa. In La Niña years, there are fewer cyclones forming in the region than during El Niño and neutral years. During La Niña years, the genesis positions are displaced poleward of 12°S, with maximum density centered around 15°S, 170°E and south of Fiji. The cyclone tracks over the FST region are also investigated using cluster analysis. Tracks during the period 1970/71–2005/06 are conveniently described using three separate clusters, with distinct characteristics associated with different ENSO phases. Finally, the role of large-scale environmental factors affecting interannual variability of TC genesis positions and their subsequent tracks in the FST region are investigated. Favorable genesis positions are observed where large-scale environments have the following seasonal average thresholds: (i) 850-hPa cyclonic relative vorticity between −16 and −4 (×10−6 s−1), (ii) 200-hPa divergence between 2 and 8 (×10−6 s−1), and (iii) environmental vertical wind shear between 0 and 8 m s−1. The subsequent TC tracks are observed to be steered by mean 700–500-hPa winds.

The role of El Niño Southern Oscillation on the patterns of cycling rates observed over India during the monsoon season

2014 ◽  
Vol 5 (4) ◽  
pp. 696-706 ◽  
Author(s):  
T. V. Lakshmi Kumar ◽  
K. Koteswara Rao ◽  
R. Uma ◽  
K. Aruna
Keyword(s):  
Water Vapor ◽  
El Niño ◽  
Hydrological Cycle ◽  
El Nino ◽  
Southern Oscillation ◽  
Monsoon Season ◽  
Precipitable Water ◽  
Spatiotemporal Variability ◽  
Monsoon Period ◽  
Sw Monsoon

Trend and interannual variability of total integrated precipitable water vapor (PWV) has been studied over India for the period 1979–2004 using NCEP/National Centre for Atmospheric Research reanalysis data with 2.5° × 2.5° resolution. The spatiotemporal variability of cycling rates (CR; units: per day), obtained from the ratio of rainfall to the PWV were presented not only for the long term (1979–2004) but also during El Niño (EN) and La Niña (LN) years of the study period to understand the intensity of hydrological cycle. The paper then dwells on obtaining the monthly atmospheric residences times over India to infer the stay of water vapor before it precipitates. The results of the present study are: all India PWV shows decreasing trend in association with the increasing/decreasing trends of Niño 3 SST/Southern Oscillation Index (SOI) for the southwest (SW) monsoon period of 1979–2004; the spatial pattern of temporal correlations of CR with SOI and Niño 3 SST displayed the significant positive and negative values in peninsular and central Indian portions of India respectively; all India atmospheric residence times varied from 9 to 2 days from premonsoon/post monsoon to SW monsoon over India.

scholarly journals Interannual Variability of Summer Tropical Cyclone Rainfall in the Western North Pacific Depicted by CFSR and Associated Large-Scale Processes and ISO Modulations

2018 ◽  
Vol 31 (5) ◽  
pp. 1771-1787 ◽  
Author(s):  
Jau-Ming Chen ◽  
Pei-Hua Tan ◽  
Liang Wu ◽  
Hui-Shan Chen ◽  
Jin-Shuen Liu ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Interannual Variability ◽  
El Niño ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Monsoon Trough ◽  
Tropical Eastern Pacific

This study examines the interannual variability of summer tropical cyclone (TC) rainfall (TCR) in the western North Pacific (WNP) depicted by the Climate Forecast System Reanalysis (CFSR). This interannual variability exhibits a maximum region near Taiwan (19°–28°N, 120°–128°E). Significantly increased TCR in this region is modulated by El Niño–Southern Oscillation (ENSO)-related large-scale processes. They feature elongated sea surface temperature warming in the tropical eastern Pacific and a southeastward-intensified monsoon trough. Increased TC movements are facilitated by interannual southerly/southeasterly flows in the northeastern periphery of the intensified monsoon trough to move from the tropical WNP toward the region near Taiwan, resulting in increased TCR. The coherent dynamic relations between interannual variability of summer TCR and large-scale environmental processes justify CFSR as being able to reasonably depict interannual characteristics of summer TCR in the WNP. For intraseasonal oscillation (ISO) modulations, TCs tend to cluster around the center of a 10–24-day cyclonic anomaly and follow its northwestward propagation from the tropical WNP toward the region near Taiwan. The above TC movements are subject to favorable background conditions provided by a northwest–southeasterly extending 30–60-day cyclonic anomaly. Summer TCR tends to increase (decrease) during El Niño (La Niña) years and strong (weak) ISO years. By comparing composite TCR anomalies and correlations with TCR variability, it is found that ENSO is more influential than ISO in modulating the interannual variability of summer TCR in the WNP.

scholarly journals Large-Scale Mode Impacts on the Sea Level over the Red Sea and Gulf of Aden

2019 ◽  
Vol 11 (19) ◽  
pp. 2224 ◽  
Author(s):  
Kamal A. Alawad ◽  
Abdullah M. Al-Subhi ◽  
Mohammed A. Alsaafani ◽  
Turki M. Alraddadi ◽  
Monica Ionita ◽  
...  
Keyword(s):  
Sea Level ◽  
Red Sea ◽  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Positive Phase ◽  
El Nino Southern Oscillation ◽  
Gulf Of Aden ◽  
The Impact

Falling between seasonal cycle variability and the impact of local drivers, the sea level in the Red Sea and Gulf of Aden has been given less consideration, especially with large-scale modes. With multiple decades of satellite altimetry observations combined with good spatial resolution, the time has come for diagnosis of the impact of large-scale modes on the sea level in those important semi-enclosed basins. While the annual cycle of sea level appeared as a dominant cycle using spectral analysis, the semi-annual one was also found, although much weaker. The first empirical orthogonal function mode explained, on average, about 65% of the total variance throughout the seasons, while their principal components clearly captured the strong La Niña event (1999–2001) in all seasons. The sea level showed a strong positive relation with positive phase El Niño Southern Oscillation in all seasons and a strong negative relation with East Atlantic/West Russia during winter and spring over the study period (1993–2017). We show that the unusually stronger easterly winds that are displaced north of the equator generate an upwelling area near the Sumatra coast and they drive both warm surface and deep-water masses toward the West Indian Ocean and Arabian Sea, rising sea level over the Red Sea and Gulf of Aden. This process could explain the increase of sea level in the basin during the positive phase of El Niño Southern Oscillation events.

scholarly journals Cluster Analysis of Typhoon Tracks. Part II: Large-Scale Circulation and ENSO

2007 ◽  
Vol 20 (14) ◽  
pp. 3654-3676 ◽  
Author(s):  
Suzana J. Camargo ◽  
Andrew W. Robertson ◽  
Scott J. Gaffney ◽  
Padhraic Smyth ◽  
Michael Ghil
Keyword(s):  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Vertical Wind Shear ◽  
Longwave Radiation ◽  
Probabilistic Clustering ◽  
Consistent Picture ◽  
Regression Mixture ◽  
Typhoon Tracks

Abstract A new probabilistic clustering method, based on a regression mixture model, is used to describe tropical cyclone (TC) propagation in the western North Pacific (WNP). Seven clusters were obtained and described in Part I of this two-part study. In Part II, the present paper, the large-scale patterns of atmospheric circulation and sea surface temperature associated with each of the clusters are investigated, as well as associations with the phase of the El Niño–Southern Oscillation (ENSO). Composite wind field maps over the WNP provide a physically consistent picture of each TC type, and of its seasonality. Anomalous vorticity and outgoing longwave radiation indicate changes in the monsoon trough associated with different types of TC genesis and trajectory. The steering winds at 500 hPa are more zonal in the straight-moving clusters, with larger meridional components in the recurving ones. Higher values of vertical wind shear in the midlatitudes also accompany the straight-moving tracks, compared to the recurving ones. The influence of ENSO on TC activity over the WNP is clearly discerned in specific clusters. Two of the seven clusters are typical of El Niño events; their genesis locations are shifted southeastward and they are more intense. The largest cluster is recurving, located northwestward, and occurs more often during La Niña events. Two types of recurving and one of straight-moving tracks occur preferentially when the Madden–Julian oscillation is active over the WNP region.

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