Three Recent Flavors of Drought in the Pacific Northwest

2010 ◽  
Vol 49 (9) ◽  
pp. 2058-2068 ◽  
Author(s):  
Karin A. Bumbaco ◽  
Philip W. Mote
Keyword(s):  
United States ◽  
Pacific Northwest ◽  
Summer Precipitation ◽  
Winter Precipitation ◽  
Western United States ◽  
Hydropower Generation ◽  
The Past ◽  
The Pacific ◽  
Hydrologic Impacts ◽  
Precipitation Events

Abstract In common with much of the western United States, the Pacific Northwest (defined in this paper as Washington and Oregon) has experienced an unusual number of droughts in the past decade. This paper describes three of these droughts in terms of the precipitation, temperature, and soil moisture anomalies, and discusses different drought impacts experienced in the Pacific Northwest (PNW). For the first drought, in 2001, low winter precipitation in the PNW produced very low streamflow that primarily affected farmers and hydropower generation. For the second, in 2003, low summer precipitation in Washington (WA), and low summer precipitation and a warm winter in Oregon (OR) primarily affected streamflow and forests. For the last, in 2005, a lack of snowpack due to warm temperatures during significant winter precipitation events in WA, and low winter precipitation in OR, had a variety of different agricultural and hydrologic impacts. Although the proximal causes of droughts are easily quantified, the ultimate causes are not as clear. Better precipitation observations in the PNW are required to provide timely monitoring of conditions leading to droughts to improve prediction in the future.

scholarly journals Seasonal Precipitation Influences Streamflow Vulnerability to the 2015 Drought in the Western United States

2019 ◽  
Vol 20 (7) ◽  
pp. 1261-1274
Author(s):  
Christopher P. Konrad
Keyword(s):  
United States ◽  
Pacific Northwest ◽  
Summer Precipitation ◽  
Western United States ◽  
Order Model ◽  
First Order ◽  
The Pacific ◽  
Critical Issues ◽  
Desert Southwest ◽  
Normative Models

Abstract Streamflow was exceptionally low in the spring and summer of 2015 across much of the western United States because of a regional drought that exploited the sensitivity of both snow- and rain-dominant rivers. Streamflow during 2015 was examined at 324 gauges in the region to assess its response to the amount, form, and seasonal timing of precipitation and the viability of using spatially aggregated, normative models to assess streamflow vulnerability to drought. Seasonal rain and spring snowmelt had the strongest effects on runoff during the same season, but their effects persisted into subsequent seasons as well. Below-normal runoff in the spring of 2015 was pervasive across the region, while distinct seasonal responses were evident in different hydroclimatic settings: January–March (winter) runoff was above normal in most snow-dominant rivers and runoff in all seasons was above normal for much of the desert Southwest. Summer precipitation contributed to summer runoff in both the Pacific Northwest and desert Southwest. A first-order model that presumes runoff is a constant fraction of precipitation (the precipitation elasticity of runoff, E = 1) could be used for assessing and forecasting runoff responses to precipitation deficits across the region, but runoff generally is more vulnerable to drought (E > 1) than predicted by a first-order model. Uncertainty in spring and summer precipitation forecasts remain critical issues for forecasting and predicting summer streamflow vulnerability to drought across much of the western United States.

Seasonal Cycle Shifts in Hydroclimatology over the Western United States

2005 ◽  
Vol 18 (2) ◽  
pp. 372-384 ◽  
Author(s):  
Satish Kumar Regonda ◽  
Balaji Rajagopalan ◽  
Martyn Clark ◽  
John Pitlick
Keyword(s):  
United States ◽  
Pacific Northwest ◽  
Snow Water Equivalent ◽  
Warming Trend ◽  
Winter Precipitation ◽  
Western United States ◽  
Temperature And Precipitation ◽  
The Pacific ◽  
Snow Water ◽  
Northwest Region

Abstract Analyses of streamflow, snow mass temperature, and precipitation in snowmelt-dominated river basins in the western United States indicate an advance in the timing of peak spring season flows over the past 50 years. Warm temperature spells in spring have occurred much earlier in recent years, which explains in part the trend in the timing of the spring peak flow. In addition, a decrease in snow water equivalent and a general increase in winter precipitation are evident for many stations in the western United States. It appears that in recent decades more of the precipitation is coming as rain rather than snow. The trends are strongest at lower elevations and in the Pacific Northwest region, where winter temperatures are closer to the melting point; it appears that in this region in particular, modest shifts in temperature are capable of forcing large shifts in basin hydrologic response. It is speculated that these trends could be potentially a manifestation of the general global warming trend in recent decades and also due to enhanced ENSO activity. The observed trends in hydroclimatology over the western United States can have significant impacts on water resources planning and management.

Interannual Variability of the Cyclonic Activity along the U.S. Pacific Coast: Influences on the Characteristics of Winter Precipitation in the Western United States

2009 ◽  
Vol 22 (21) ◽  
pp. 5732-5747 ◽  
Author(s):  
Boksoon Myoung ◽  
Yi Deng
Keyword(s):  
United States ◽  
Interannual Variability ◽  
Pacific Northwest ◽  
Pacific Coast ◽  
Storm Track ◽  
Winter Precipitation ◽  
Western United States ◽  
Cyclonic Activity ◽  
The Pacific ◽  
The U.S

Abstract This study examines the observed interannual variability of the cyclonic activity along the U.S. Pacific coast and quantifies its impact on the characteristics of both the winter total and extreme precipitation in the western United States. A cyclonic activity function (CAF) was derived from a dataset of objectively identified cyclone tracks in 27 winters (1979/80–2005/06). The leading empirical orthogonal function (EOF1) of the CAF was found to be responsible for the EOF1 of the winter precipitation in the western United States, which is a monopole mode centered over the Pacific Northwest and northern California. On the other hand, the EOF2 of the CAF contributes to the EOF2 of the winter precipitation, which indicates that above-normal precipitation in the Pacific Northwest and its immediate inland regions tends to be accompanied by below-normal precipitation in California and the southwestern United States and vice versa. The first two EOFs of CAF (precipitation) account for about 70% (78%) of the total interannual variance of CAF (precipitation). The second EOF modes of both the CAF and precipitation are significantly linked to the ENSO signal on interannual time scales. A composite analysis further reveals that the leading CAF modes increase (decrease) the winter total precipitation by increasing (decreasing) both the number of rainy days per winter and the extremeness of precipitation. The latter was quantified in terms of the 95th percentile of the daily rain rate and the probability of precipitation being heavy given a rainy day. The implications of the leading CAF modes for the water resources and the occurrence of extreme hydrologic events in the western United States, as well as their dynamical linkages to the Pacific storm track and various atmospheric low-frequency modes (i.e., teleconnection patterns), are also discussed.

scholarly journals Influence of the Pacific Decadal Oscillation on Winter Precipitation and Drought during Years of Neutral ENSO in the Western United States

2007 ◽  
Vol 22 (1) ◽  
pp. 116-124 ◽  
Author(s):  
Gregory B. Goodrich
Keyword(s):  
United States ◽  
Pacific Northwest ◽  
Pacific Decadal Oscillation ◽  
Severity Index ◽  
Winter Precipitation ◽  
Western United States ◽  
Drought Severity ◽  
The Pacific ◽  
Area Of Influence ◽  
Hydroclimatic Variables

Abstract The influence of the Pacific decadal oscillation (PDO) on important hydroclimatic variables during years of neutral ENSO for 84 climate divisions in the western United States is analyzed from 1925 to 1998. When the 34 neutral ENSO years are split by cold (12 yr) and warm (22 yr) PDOs, the resulting winter precipitation patterns are spatially similar to those that occur during years of La Niña–cold PDO and, to a lesser extent, years of El Niño–warm PDO, respectively, although the characteristic ENSO dipole is not evident. The PDO influence is similar when the winter Palmer drought severity index is analyzed, although the core area of influence moves from the Southwest to the northern Rockies. Correlations between Niño-3.4 SSTs and the hydroclimatic variables reverse sign when the neutral ENSO years are split by PDO phase. The greatest difference between correlations occurs in the characteristic dipole between the Pacific Northwest and the desert Southwest. Since seasonal forecast guidance based on ENSO conditions in the tropical Pacific often yields a forecast of “equal chances” during years of neutral ENSO, forecasters may be able to improve their forecasts for the southwestern United States depending on if the PDO is known to be in the cold (drier than normal) or warm (wetter than normal) phase. However, this can be difficult to implement considering the current uncertainty of the phase of the PDO.

Identification of Resistance to Powdery Mildew in Publicly Available Male Hop Germplasm

2018 ◽  
Vol 19 (3) ◽  
pp. 258-264
Author(s):  
David H. Gent ◽  
Briana J. Claassen ◽  
Megan C. Twomey ◽  
Sierra N. Wolfenbarger
Keyword(s):  
United States ◽  
Powdery Mildew ◽  
Pacific Northwest ◽  
Western United States ◽  
R Genes ◽  
Sources Of Resistance ◽  
Department Of Agriculture ◽  
Breeding Programs ◽  
The Pacific ◽  
The U.S

Powdery mildew (caused by Podosphaera macularis) is one of the most important diseases of hop in the western United States. Strains of the fungus virulent on cultivars possessing the resistance factor termed R6 and the cultivar Cascade have become widespread in the Pacific Northwestern United States, the primary hop producing region in the country, rendering most cultivars grown susceptible to the disease at some level. In an effort to identify potential sources of resistance in extant germplasm, 136 male accessions of hop contained in the U.S. Department of Agriculture collection were screened under controlled conditions. Iterative inoculations with three isolates of P. macularis with varying race identified 23 (16.9%) accessions with apparent resistance to all known races of the pathogen present in the Pacific Northwest. Of the 23 accessions, 12 were resistant when inoculated with three additional isolates obtained from Europe that possess novel virulences. The nature of resistance in these individuals is unclear but does not appear to be based on known R genes. Identification of possible novel sources of resistance to powdery mildew will be useful to hop breeding programs in the western United States and elsewhere.

The Windgrasses(AperaAdans., Poaceae) in North America

1992 ◽  
Vol 6 (2) ◽  
pp. 445-450 ◽  
Author(s):  
F. E. Northam ◽  
R. H. Callihan
Keyword(s):  
United States ◽  
North America ◽  
Pacific Northwest ◽  
Northeastern United States ◽  
Southern Ontario ◽  
Grass Seed ◽  
The Past ◽  
Winter Cereals ◽  
The Pacific ◽  
Additional Control

Two introduced windgrass species have become crop weeds in North America. Common windgrass is a major weed of winter cereals in Europe and was first documented in North America in the early 1800s. It is a weed of roadsides and waste areas in the northeastern United States and in winter grain fields of southern Ontario and Michigan. Interrupted windgrass was first reported in North America approximately 90 yr ago; it is adapted to more arid sites than common windgrass and is distributed predominantly in the northwestern U.S.A. During the past 10 to 15 yr, interrupted windgrass has adversely affected winter grain and grass seed producers in the Pacific Northwest due to additional control costs.

First Report of Powdery Mildew of Magnolia Caused by Microsphaera magnifica (Erysiphe magnifica) in the Pacific Northwest

2003 ◽  
Vol 4 (1) ◽  
pp. 37
Author(s):  
Dean A. Glawe
Keyword(s):  
United States ◽  
North America ◽  
Powdery Mildew ◽  
Pacific Northwest ◽  
Western United States ◽  
First Report ◽  
Landscape Plant ◽  
First Finding ◽  
The Pacific ◽  
First Time

Magnolia liliiflora Desrousseaux in Lamarck (orthographic variant: M. liliiflora), a species thought to have originated in China (3), is used as a landscape plant in North America. In August 2002, Microsphaera magnifica U. Braun was collected from three plants of M. liliiflora in the Magnolia collection at the Washington Park Arboretum, University of Washington, Seattle. This report documents for the first time a powdery mildew disease of a Magnolia species in the Pacific Northwest, and the first finding of M. magnifica in the western United States. Accepted for publication 14 April 2003. Published 12 May 2003.

scholarly journals Risk Assessment for Karnal Bunt Occurrence in the Pacific Northwest

Plant Disease ◽  
1997 ◽  
Vol 81 (6) ◽  
pp. 689-692 ◽  
Author(s):  
Richard W. Smiley
Keyword(s):  
United States ◽  
Risk Assessment ◽  
Pacific Northwest ◽  
The United States ◽  
Climatic Conditions ◽  
Karnal Bunt ◽  
Climate Data ◽  
Tilletia Indica ◽  
The Past ◽  
The Pacific

Tilletia indica, the causal agent of Karnal bunt of wheat, was first detected and reported in the United States in 1996. Karnal bunt occurred in the southwestern United States as early as 1992. Wheat contaminated with teliospores of T. indica is likely to have been transported from the Southwest to other regions, including the Pacific Northwest, before presence of the pathogen was discovered. Teliospore and sporidial germination and infection are highly dependent on climatic conditions. The potential for T. indica to infect wheat in the Pacific Northwest has not been reported. The objective of this study was to use published information on environmental factors favorable for infection and historical climate data for the Pacific Northwest to analyze the environmental risk for Karnal bunt to occur if wheat fields in the Pacific Northwest become contaminated by T. indica. Conditions during the past four decades appeared favorable for infection in nonirrigated wheat during 1 of every 3 years at two (Corvallis, OR, and Spokane, WA) of 13 Idaho, Oregon, and Washington locations examined, and every year at all locations where wheat is irrigated. If introduced to the area, it appears possible for T. indica to become established in selected regions of the Pacific Northwest.

scholarly journals Recent Changes in United States Extreme 3-Day Precipitation Using the R-CAT Scale

2020 ◽  
Vol 21 (6) ◽  
pp. 1207-1221 ◽  
Author(s):  
Maryam A. Lamjiri ◽  
F. Martin Ralph ◽  
Michael D. Dettinger
Keyword(s):  
United States ◽  
East Coast ◽  
The United States ◽  
Western United States ◽  
Eastern United States ◽  
Atmospheric Rivers ◽  
The Past ◽  
Extreme Precipitation Events ◽  
Precipitation Total ◽  
Precipitation Events

AbstractExtraordinary precipitation events have impacted the United States recently, including Hurricanes Harvey (2017) and Florence (2018), with 3-day precipitation totals larger than any others reported in the United States during the past 70 years. The rainfall category (R-CAT) scaling method is used here to document extreme precipitation events and test for trends nationally. The R-CAT scale uses thresholds of 3-day precipitation total in 100-mm increments (starting with 200 mm) that do not vary temporally or geographically, allowing for simple, intuitive comparisons of extremes over space and time. The paper that introduced the scale only required levels 1–4 to represent historical extremes, finding that R-CATs 3–4 strike the conterminous United States about as frequently as EF 4–5 tornadoes or category 3–5 hurricanes. Remarkably, Florence and Harvey require extending the scale to R-CAT 7 and 9, respectively. Trend analyses of annual maximum 3-day totals (1950–2019) here identify significant increases in the eastern United States, along with declines in Northern California and Oregon. Consistent with these results, R-CAT storms have been more frequent in the eastern, and less frequent in western, United States during the past decade compared to 1950–2008. Tropical storms dominate R-CAT events along the southeastern coast and East Coast with surprising contributions from atmospheric rivers, while atmospheric rivers completely dominate along the West Coast.

scholarly journals Utilizing Normalized Anomalies to Assess Synoptic-Scale Weather Events in the Western United States

2010 ◽  
Vol 25 (2) ◽  
pp. 428-445 ◽  
Author(s):  
Randall A. Graham ◽  
Richard H. Grumm
Keyword(s):  
United States ◽  
Pacific Northwest ◽  
Western United States ◽  
Return Periods ◽  
Synoptic Scale ◽  
Specific Level ◽  
Additional Information ◽  
Weather Events ◽  
The Pacific ◽  
Relative Rarity

Abstract Synoptic-scale weather events over the western United States are objectively ranked based on their associated tropospheric anomalies. Data from the NCEP 6-h reanalysis fields from 1948 to 2006 are compared to a 30-yr (1971–2000) reanalysis climatology. The relative rarity of an event is measured by the number of standard deviations that the 1000–200-hPa height, temperature, wind, and moisture fields depart from climatology. The top 20 synoptic-scale events were identified over the western United States, adjacent eastern Pacific Ocean, Mexico, and Canada. Events that composed the top 20 tended to be very anomalous in several, if not all four, of the atmospheric variables. The events included the northern Intermountain West region heavy rainfall and Yellowstone tornado of mid-July 1987 (ranked 5th), the Montana floods of September 1986 (ranked 4th), and the historic 1962 “Columbus Day” windstorm in the Pacific Northwest (ranked 10th). In addition, the top 10 most anomalous events were identified for each month and for each of the variables investigated revealing additional significant weather events. Finally, anomaly return periods were computed for each variable at a variety of levels. To place a given anomaly in perspective for a specific level or element, forecasters need information on the frequency with which that anomaly is observed. These return periods can be utilized by forecasters to compare forecast anomalies to the actual occurrence of similar anomalies for the element and level of interest to gauge the potential significance of the event. It is believed that this approach may allow forecasters to better understand the historical significance of an event and provide additional information to the user community.

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