scholarly journals Forecasting the Hydroclimatic Signature of the 2015/16 El Niño Event on the Western United States

2017 ◽  
Vol 18 (1) ◽  
pp. 177-186 ◽  
Author(s):  
N. Wanders ◽  
A. Bachas ◽  
X. G. He ◽  
H. Huang ◽  
A. Koppa ◽  
...  
Keyword(s):  
United States ◽  
Pacific Northwest ◽  
El Niño ◽  
El Nino ◽  
Western United States ◽  
Fire Season ◽  
Severe Drought ◽  
Forecast Performance ◽  
The North ◽  
El Niño Event

Abstract Dry conditions in 2013–16 in much of the western United States were responsible for severe drought and led to an exceptional fire season in the Pacific Northwest in 2015. Winter 2015/16 was forecasted to relieve drought in the southern portion of the region as a result of increased precipitation due to a very strong El Niño signal. A student forecasting challenge is summarized in which forecasts of winter hydroclimate across the western United States were made on 1 January 2016 for the winter hydroclimate using several dynamical and statistical forecast methods. They show that the precipitation forecasts had a large spread and none were skillful, while anomalously high observed temperatures were forecasted with a higher skill and precision. The poor forecast performance, particularly for precipitation, is traceable to high uncertainty in the North American Multi-Model Ensemble (NMME) forecast, which appears to be related to the inability of the models to predict an atmospheric blocking pattern over the region. It is found that strong El Niño sensitivities in dynamical models resulted in an overprediction of precipitation in the southern part of the domain. The results suggest the need for a more detailed attribution study of the anomalous meteorological patterns of the 2015/16 El Niño event compared to previous major events.

scholarly journals Drought in the Western United States: Its Connections with Large-Scale Oceanic Oscillations

Atmosphere ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 82 ◽  
Author(s):  
Peng Jiang ◽  
Zhongbo Yu ◽  
Kumud Acharya
Keyword(s):  
United States ◽  
Mississippi River ◽  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Southern Oscillation ◽  
Western United States ◽  
Spatiotemporal Pattern ◽  
Eof Analysis ◽  
The North

In this paper, we applied the Empirical Orthogonal Function (EOF) analysis on a drought index expressed as consecutive dry days (CDD) to identify the drought variability in western United States. Based on the EOF analysis, correlation maps were generated between the leading principle component (PC) of seasonal CDD and sea surface temperature (SST) anomalies to explore the dynamic context of the leading modes in CDD. The EOF analysis indicates that the spatiotemporal pattern of winter CDD is related to an integrated impact from El Niño–Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and Atlantic Multi-decadal Oscillation (AMO), while summer CDD is mainly controlled by PDO phases. We also calculated seasonal CDD anomalies during selected climatic phases to further evaluate the impacts of large-scale oceanic oscillation on the spatial pattern of droughts. We found that AMO+/PDO− will contribute to a consistent drought condition during the winter in the western United States. El Niño will bring a dry winter to the northern part of western United States while La Niña will bring a dry winter to the southern part. During El Niño years, the drought center changes with the type of El Niño events. Considering the future states of the examined ocean oscillations, we suggest possible drier than normal conditions in the western United States for upcoming decades, and moreover, an intensified drought for the coast areas of the north Pacific region and upper Mississippi River Basin.

scholarly journals The Impact of SST-Forced and Unforced Teleconnections on 2015/16 El Niño Winter Precipitation over the Western United States

2018 ◽  
Vol 31 (15) ◽  
pp. 5825-5844 ◽  
Author(s):  
Young-Kwon Lim ◽  
Siegfried D. Schubert ◽  
Yehui Chang ◽  
Andrea M. Molod ◽  
Steven Pawson
Keyword(s):  
United States ◽  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Winter Precipitation ◽  
Western United States ◽  
Southwestern United States ◽  
Atmospheric Variability ◽  
The North ◽  
The Impact

The factors impacting western U.S. winter precipitation during the 2015/16 El Niño are investigated using the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), data, and simulations with the Goddard Earth Observing System, version 5 (GEOS-5), atmospheric general circulation model forced with specified sea surface temperatures (SSTs). Results reveal that the simulated response to the tropical Pacific SST associated with the 2015/16 El Niño was to produce wetter than normal conditions over much of the North American west coast including California—a result at odds with the negative precipitation anomalies observed over much of the southwestern United States. It is shown that two factors acted to partly counter the canonical ENSO response in that region. First, a potentially predictable but modest response to the unusually strong and persistent warm SST in the northeastern Pacific decreased precipitation in the southwestern United States by increasing sea level pressure, driving anticyclonic circulation and atmospheric descent, and reducing moisture transport into that region. Second, large-scale unforced (by SST) components of atmospheric variability (consisting of the leading modes of unpredictable intraensemble variability) resembling the positive phase of the North Atlantic Oscillation and Arctic Oscillation are found to be an important contributor to the drying over the western United States. While a statistical reconstruction of the precipitation from our simulations that account for internal atmospheric variability does much to close the gap between the ensemble-mean and observed precipitation in the southwestern United States, some differences remain, indicating that model error is also playing a role.

scholarly journals Predictable and Unpredictable Aspects of U.S. West Coast Rainfall and El Niño: Understanding the 2015/16 Event

2019 ◽  
Vol 32 (10) ◽  
pp. 2843-2868 ◽  
Author(s):  
Benjamin A. Cash ◽  
Natalie J. Burls
Keyword(s):  
Pacific Northwest ◽  
West Coast ◽  
El Niño ◽  
El Nino ◽  
Rainfall Variability ◽  
Winter Season ◽  
Seasonal Forecasts ◽  
The North ◽  
Dry Conditions ◽  
The Individual

AbstractCalifornia experienced record-setting drought from 2012 to 2017. Based on both seasonal forecast models and historical associations, there was widespread expectation that the major El Niño event of 2015/16 would result in increased winter-season precipitation and break the drought. However, the 2015/16 winter rainy season ultimately resulted in slightly below-average precipitation and the drought continued. In this work we analyze data from both observations and seasonal forecasts made as part of the North American Multi-Model Ensemble (NMME) to better understand the general relationship between El Niño and U.S. West Coast rainfall, focusing on Southern California (SOCAL) rainfall, Pacific Northwest (PNW) rainfall, and the 2015/16 event. We find that while there is a statistically significant positive correlation between El Niño events and the SOCAL and PNW rainfall anomalies, this relationship explains at most one-third of the observed variance. Examination of hindcasts from the NMME demonstrates that the models are capable of accurately reproducing this observed correlation between tropical Pacific sea surface temperatures and California rainfall when information from the individual ensemble members is retained. However, focusing on the multimodel ensemble mean, which deliberately reduces the influence of unpredicted variability, drastically overestimates the strength of this relationship. Our analysis demonstrates that much of the winter rainfall variability along the U.S. West Coast is dominated by unpredicted variations in the 200-hPa height field and that this same unpredicted variability was largely responsible for the unexpectedly dry conditions in 2015/16.

scholarly journals The 1997-98 El Nino event and related wintertime lightning variations in the southeastern United States

2000 ◽  
Vol 27 (4) ◽  
pp. 541-544 ◽  
Author(s):  
S. J. Goodman ◽  
D. E. Buechler ◽  
K. Knupp ◽  
K. Driscoll ◽  
E. W. McCaul
Keyword(s):  
United States ◽  
El Niño ◽  
El Nino ◽  
Southeastern United States ◽  
El Niño Event

scholarly journals Stable isotopic evidence of El Niño-like atmospheric circulation in the Pliocene western United States

2013 ◽  
Vol 9 (2) ◽  
pp. 903-912 ◽  
Author(s):  
M. J. Winnick ◽  
J. M. Welker ◽  
C. P. Chamberlain
Keyword(s):  
United States ◽  
North America ◽  
El Niño ◽  
El Nino ◽  
Storm Track ◽  
Western United States ◽  
Western North America ◽  
Late Pliocene ◽  
Future Warming ◽  
Isotopic Anomalies

Abstract. Understanding how the hydrologic cycle has responded to warmer global temperatures in the past is especially important today as concentrations of CO2 in the atmosphere continue to increase due to human activities. The Pliocene offers an ideal window into a climate system that has equilibrated with current atmospheric pCO2. During the Pliocene the western United States was wetter than modern, an observation at odds with our current understanding of future warming scenarios, which involve the expansion and poleward migration of the subtropical dry zone. Here we compare Pliocene oxygen isotope profiles of pedogenic carbonates across the western US to modern isotopic anomalies in precipitation between phases of the El Niño–Southern Oscillation (ENSO). We find that when accounting for seasonality of carbonate formation, isotopic changes through the late Pliocene match modern precipitation isotopic anomalies in El Niño years. Furthermore, isotopic shifts through the late Pliocene mirror changes through the early Pleistocene, which likely represents the southward migration of the westerly storm track caused by growth of the Laurentide ice sheet. We propose that the westerly storm track migrated northward through the late Pliocene with the development of the modern cold tongue in the east equatorial Pacific, then returned southward with widespread glaciation in the Northern Hemisphere – a scenario supported by terrestrial climate proxies across the US. Together these data support the proposed existence of background El Niño-like conditions in western North America during the warm Pliocene. If the earth behaves similarly with future warming, this observation has important implications with regard to the amount and distribution of precipitation in western North America.

scholarly journals The Effect of El Niño on Flood Damages in the Western United States

2019 ◽  
Vol 11 (3) ◽  
pp. 489-504 ◽  
Author(s):  
Thomas W. Corringham ◽  
Daniel R. Cayan
Keyword(s):  
United States ◽  
Extreme Events ◽  
El Niño ◽  
Southern California ◽  
El Nino ◽  
Southern Oscillation ◽  
Western United States ◽  
Opposite Pattern ◽  
Flood Damages ◽  
Insured Losses

Abstract This paper quantifies insured flood losses across the western United States from 1978 to 2017, presenting a spatiotemporal analysis of National Flood Insurance Program (NFIP) daily claims and losses over this period. While considerably lower (only 3.3%) than broader measures of direct damages measured by a National Weather Service (NWS) dataset, NFIP insured losses are highly correlated to the annual damages in the NWS dataset, and the NFIP data provide flood impacts at a fine degree of spatial resolution. The NFIP data reveal that 1% of extreme events, covering wide spatial areas, caused over 66% of total insured losses. Connections between extreme events and El Niño–Southern Oscillation (ENSO) that have been documented in past research are borne out in the insurance data. In coastal Southern California and across the Southwest, El Niño conditions have had a strong effect in producing more frequent and higher magnitudes of insured losses, while La Niña conditions significantly reduce both the frequency and magnitude of losses. In the Pacific Northwest, the opposite pattern appears, although the effect is weaker and less spatially coherent. The persistent evolution of ENSO offers the possibility for property owners, policy makers, and emergency planners and responders that unusually high or low flood damages could be predicted in advance of the primary winter storm period along the West Coast. Within the 40-yr NFIP history, it is found that the multivariate ENSO index would have provided an 8-month look-ahead for heightened damages in Southern California.

scholarly journals Impact of Severe Drought during the Strong 2015/2016 El Nino on the Phenology and Survival of Secondary Dry Dipterocarp Species in Western Thailand

Forests ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 967
Author(s):  
Rungnapa Kaewthongrach ◽  
Yann Vitasse ◽  
Taninnuch Lamjiak ◽  
Amnat Chidthaisong
Keyword(s):  
El Niño ◽  
Tree Mortality ◽  
Secondary Forest ◽  
El Nino ◽  
Leaf Phenology ◽  
Severe Drought ◽  
Deciduous Species ◽  
El Niño Event ◽  
El Niño Events ◽  
El Nino Events

Secondary forest areas are increasing worldwide and understanding how these forests interact with climate change including frequent and extreme events becomes increasingly important. This study aims to investigate the effects of the strong 2015/2016 El Niño-induced drought on species-specific leaf phenology, dieback and tree mortality in a secondary dry dipterocarp forest (DDF) in western Thailand. During the 2015/2016 El Niño event, rainfall and soil water content were lower than 25 mm and 5% during 5–6 consecutive months. The dry season was 3–4 months longer during the El Niño than during non-El Niño events. We found that this prolonged drought induced the earlier shedding and a delay in leaf emergence of the DDF. The deciduousness period was also longer during the El Niño event (5 months instead of 2–3 months during non-El Niño event). We found that the DDF species showed different phenological responses and sensitivities to the El Niño-induced drought. The leaf phenology of stem succulent species Lannea coromandelica (Houtt.) Merr. and a complete deciduous species with low wood density. Sindora siamensis Teijsm. ex Miq. was only slightly affected by the El Niño-induced drought. Conversely, a semi-deciduous species such as Dipterocarpus obtusifolius Teijsm. ex Miq. showed a higher degree of deciduousness during the El Niño compared to non-El Niño events. Our results also highlight that dieback and mortality during El Niño were increased by 45 and 50%, respectively, compared to non-El Niño events, pointing at the importance of such events to shape DDF ecosystems.

Rain-on-Snow Events in the Western United States

2007 ◽  
Vol 88 (3) ◽  
pp. 319-328 ◽  
Author(s):  
Gregory J. McCabe ◽  
Martyn P. Clark ◽  
Lauren E. Hay
Keyword(s):  
United States ◽  
El Niño ◽  
Temporal Variability ◽  
El Nino ◽  
Flood Hazard ◽  
La Niña ◽  
Western United States ◽  
Spatial And Temporal Variability ◽  
Southwestern United States ◽  
La Nina

Rain-on-snow events pose a significant flood hazard in the western United States. This study provides a description of the spatial and temporal variability of the frequency of rain-on-snow events for 4318 sites in the western United States during water years (October through September) 1949–2003. Rain-on-snow events are found to be most common during the months of October through May; however, at sites in the interior western United States, rain-on-snow events can occur in substantial numbers as late as June and as early as September. An examination of the temporal variability of October through May rain-on-snow events indicates a mixture of increasing and decreasing trends in rain-on-snow events across the western United States. Decreasing trends in rain-on-snow events are most pronounced at lower elevations and are associated with trends toward fewer snowfall days and fewer precipitation days with snow on the ground. Rain-on-snow events are more (less) frequent in the northwestern (southwestern) United States during La Niña (El Niño) conditions. Additionally, increases in temperature in the western United States appear to be contributing to decreases in the number of rain-on-snow events for many sites through effects on the number of days with snowfall and the number of days with snow on the ground.

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