scholarly journals A 431-Yr Reconstruction of Western Colorado Snowpack from Tree Rings

2003 ◽  
Vol 16 (10) ◽  
pp. 1551-1561 ◽  
Author(s):  
Connie A. Woodhouse
Keyword(s):  
Twentieth Century ◽  
River Basin ◽  
Tree Ring ◽  
Snow Water Equivalent ◽  
Southern Oscillation ◽  
Strong Relationship ◽  
Transitional Zone ◽  
Winter Precipitation ◽  
Winter Climate ◽  
Western Colorado

Abstract A tree-ring-based reconstruction for 1 April snow water equivalent (SWE) is generated for the Gunnison River basin region in western Colorado. The reconstruction explains 63% of the variance in the instrumental record and extends from 1569 to 1999. When the twentieth-century part of the record is compared to the full record, the variability and extremes in the twentieth century appear representative of the long-term record. However, years of extreme SWE (low and high) and persistent low SWE events are not evenly distributed throughout the record. The twentieth century is notable for several periods that lack extreme years, and along with the nineteenth century and the second half of the eighteenth century, contains many fewer persistent low SWE events than the first half of the reconstruction. Low SWE in the western United States is associated with several circulation patterns, including the Pacific–North American (PNA) pattern and those related to El Niño–Southern Oscillation (ENSO), but the Gunnison River basin is on the edge of the area with a strong relationship to the PNA and is generally in a transitional zone with respect to regional ENSO influences. Tree-ring chronologies from Oregon and New Mexico, regions impacted by ENSO, were used as rough proxies of northwestern and southwestern U.S. winter precipitation to explore possible associations between Gunnison SWE and winter climate in these two regions over the past four centuries.

scholarly journals Examining controls on peak annual streamflow and floods in the Fraser River Basin of British Columbia

2017 ◽  
Author(s):  
Charles L. Curry ◽  
Francis W. Zwiers
Keyword(s):  
British Columbia ◽  
Soil Moisture ◽  
River Basin ◽  
Snow Water Equivalent ◽  
Southern Oscillation ◽  
Snow Accumulation ◽  
Fraser River ◽  
Annual Maximum ◽  
Daily Streamflow ◽  
Annual Peak

Abstract. The Fraser River basin (FRB) of British Columbia is one of the largest and most important watersheds in Western North America, and is home to a rich diversity of biological species and economic assets that depend implicitly upon its extensive riverine habitats. The hydrology of the FRB is dominated by snow accumulation and melt processes, leading to a prominent annual peak streamflow invariably occurring in June–July. However, while annual peak daily streamflow (APF) during the spring freshet in the FRB is historically well correlated with basin-averaged, April 1 snow water equivalent (SWE), there are numerous occurrences of anomalously large APF in below- or near-normal SWE years, some of which have resulted in damaging floods in the region. An imperfect understanding of which other climatic factors contribute to these anomalously large APFs hinders robust projections of their magnitude and frequency. We employ the Variable Infiltration Capacity (VIC) process-based hydrological model driven by gridded observations to investigate the key controlling factors of anomalous APF events in the FRB and four of its subbasins that contribute more than 70 % of the annual flow at Fraser-Hope. The relative influence of a set of predictors characterizing the interannual variability of rainfall, snowfall, snowpack (characterized by the annual maximum value, SWEmax), soil moisture and temperature on simulated APF at Hope (the main outlet of the FRB) and at the subbasin outlets is examined within a regression framework. The influence of large-scale climate modes of variability (the Pacific Decadal Oscillation (PDO) and the El Niño-Southern Oscillation (ENSO)) on APF magnitude is also assessed, and placed in context with these more localized controls. The results indicate that next to SWEmax (which strongly controls the annual maximum of soil moisture), the snowmelt rate, the ENSO and PDO indices, and rate of warming subsequent to the date of SWEmax are the most influential predictors of APF magnitude in the FRB and its subbasins. The identification of these controls on annual peak flows in the region may be of use in the context of seasonal prediction or future projected streamflow behaviour.

scholarly journals Interdecadal Changes in the Relationship between ENSO, EAWM, and the Wintertime Precipitation over China at the End of the Twentieth Century

2017 ◽  
Vol 30 (6) ◽  
pp. 1923-1937 ◽  
Author(s):  
Xiaojing Jia ◽  
Jingwen Ge
Keyword(s):  
Twentieth Century ◽  
Southern Oscillation ◽  
Winter Precipitation ◽  
Interdecadal Change ◽  
Northwestern Pacific ◽  
Southeastern China ◽  
Precipitation Anomalies ◽  
The Impact ◽  
The Relationship ◽  
Interdecadal Changes

Abstract The current study investigates the interdecadal changes in the relationship between the winter precipitation anomalies in southeastern China, El Niño–Southern Oscillation (ENSO), and the East Asian winter monsoon (EAWM) at the end of the twentieth century. It appears that the relationships between the interannual variability of the southeastern China winter precipitation and ENSO as well as EAWM are obviously weakened after 1998/99. The possible mechanisms accounting for this interdecadal change in the relationship have been examined by dividing the data into two subperiods [1980–98 (P1) and 1999–2015 (P2)]. The results indicate that, without the linear contribution of EAWM, ENSO only play a limited role in the variability of winter precipitation in southeastern China in both subperiods. In contrast, in P1, corresponding to an ENSO-independent weaker-than-normal EAWM, anomalous southerlies along coastal southeastern China associated with an anticyclone over the northwestern Pacific transport water vapor to China. However, in P2 the impact of EAWM on winter precipitation in southeastern China is weakened because of the regime shift of EAWM. The EAWM-related positive SLP anomalies over the North Pacific move eastward in P2, causing an eastward migration of the associated anomalous southerlies along its western flank and therefore cannot significantly contribute to the positive winter precipitation anomalies in southeastern China.

scholarly journals Representation of Western Disturbances in CMIP5 Models

2019 ◽  
Vol 32 (7) ◽  
pp. 1997-2011 ◽  
Author(s):  
Kieran M. R. Hunt ◽  
Andrew G. Turner ◽  
Len C. Shaffrey
Keyword(s):  
Extreme Events ◽  
Strong Relationship ◽  
Winter Precipitation ◽  
Cmip5 Models ◽  
Western Himalayas ◽  
Winter Climate ◽  
Western Disturbances ◽  
Westerly Jet ◽  
High Fraction ◽  
Extratropical Disturbances

Abstract Western disturbances (WDs) are synoptic extratropical disturbances embedded in the subtropical westerly jet stream. They are an integral part of the South Asian winter climate, both for the agriculture-supporting precipitation they bring to the region and for the associated isolated extreme events that can induce devastating flash flooding. Here, WD behavior and impacts are characterized in 23 CMIP5 historical simulations and compared with reanalysis and observations. It is found that WD frequency has a strong relationship with model resolution: higher-resolution models produce significantly more WDs and a disproportionately high fraction of extreme events. Exploring metrics of jet strength and shape, we find that the most probable cause of this relationship is that the jet is wider in models with coarser resolution, and therefore the northern edge in which WDs are spun up sits too far north of India. The frequency of WDs in both winter and summer is found to be overestimated by most models, and thus the winter frequency of WDs estimated from the multimodel mean (30 per winter) is above the reanalysis mean (26 per winter). In this case, the error cannot be adequately explained by local jet position and strength. Instead, we show that it is linked with a positive bias in upstream midtropospheric baroclinicity. Despite a positive winter precipitation bias in CMIP5 models over most of India and Pakistan and a dry bias in the western Himalayas, the fraction of winter precipitation for which WDs are responsible is accurately represented. Using partial correlation, it is shown that the overestimation in WD frequency is the largest contributor to this bias, with a secondary, spatially heterogeneous contribution coming from the overestimation of WD intensity.

scholarly journals On the Changing Contribution of Snow to the Hydrology of the Fraser River Basin, Canada

2014 ◽  
Vol 15 (4) ◽  
pp. 1344-1365 ◽  
Author(s):  
Do Hyuk Kang ◽  
Xiaogang Shi ◽  
Huilin Gao ◽  
Stephen J. Déry
Keyword(s):  
Twentieth Century ◽  
River Basin ◽  
Snow Water Equivalent ◽  
Kendall Test ◽  
Fraser River ◽  
Infiltration Capacity ◽  
Time Step ◽  
Ecological Processes ◽  
Vic Model ◽  
Temperature And Precipitation

Abstract This paper presents an application of the Variable Infiltration Capacity (VIC) model to the Fraser River basin (FRB) of British Columbia (BC), Canada, over the latter half of the twentieth century. The Fraser River is the longest waterway in BC and supports the world’s most abundant Pacific Ocean salmon populations. Previous modeling and observational studies have demonstrated that the FRB is a snow-dominated system, but with climate change, it may evolve to a pluvial regime. Thus, the goal of this study is to evaluate the changing contribution of snow to the hydrology of the FRB over the latter half of the twentieth century. To this end, a 0.25° atmospheric forcing dataset is used to drive the VIC model from 1949 to 2006 (water years) at a daily time step over a domain covering the entire FRB. A model evaluation is first conducted over 11 major subwatersheds of the FRB to quantitatively assess the spatial variations of snow water equivalent (SWE) and runoff (R). The ratio of the spatially averaged maximum SWE to R (RSR) is used to quantify the contribution of snow to the runoff in the 11 subwatersheds of interest. From 1949 to 2006, RSR exhibits a significant decline in 9 of the 11 subwatersheds (with p < 0.05 according to the Mann–Kendall test statistics). To determine the sensitivity of RSR, the air temperature and precipitation in the forcing dataset are then perturbed. The ratio RSR decreases more significantly, especially during the 1990s and 2000s, when air temperatures have warmed considerably compared to the 1950s. On the other hand, increasing precipitation by a multiplicative factor of 1.1 causes RSR to decrease. As the climate continues to warm, ecological processes and human usage of natural resources in the FRB may be substantially affected by its transition from a snow to a hybrid (nival/pluvial) and even a rain-dominated system.

scholarly journals Long-Term Variability of Relationships between Potential Large-Scale Drivers and Summer Precipitation in North China in the CERA-20C Reanalysis

Atmosphere ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 81
Author(s):  
Lan Dai ◽  
Jonathon S. Wright
Keyword(s):  
Twentieth Century ◽  
Large Scale ◽  
North China ◽  
Southern Oscillation ◽  
Summer Precipitation ◽  
Strong Relationship ◽  
Atmospheric Model ◽  
Energy Budgets ◽  
Climate Projections ◽  
Seasonal Forecasts

Although much progress has been made in identifying the large-scale drivers of recent summer precipitation variability in North China, the evolution of these drivers over longer time scales remains unclear. We investigate multidecadal and interannual variability in North China summer precipitation in the 110-year Coupled ECMWF Reanalysis of the Twentieth Century (CERA-20C), considering changes in regional moisture and surface energy budgets along with nine circulation indices linked to anomalous precipitation in this region. The CERA-20C record is separated into three distinct periods according to the running climatology of summer precipitation: 1901–1944 (neutral), 1945–1979 (wet), and 1980–2010 (dry). CERA-20C reproduces expected relationships between large-scale drivers and regional summer precipitation anomalies well during 1980–2010, but these relationships generally do not extend to earlier periods. For example, a strong relationship with the Eurasian teleconnection pattern only emerges in the late 1970s, while correlations with the El Niño-Southern Oscillation and the Pacific–Japan pattern change sign in the mid-twentieth century. We evaluate two possible reasons for this nonstationarity: (1) the underlying atmospheric model may require strong data assimilation constraints to capture large-scale circulation influences on North China, or (2) large-scale drivers inferred from recent records may be less general than expected. Our analysis indicates that both factors contribute to the identified nonstationarity in CERA-20C, with implications for the reliability of seasonal forecasts and climate projections based on current models.

scholarly journals Recent Declines in Western U.S. Snowpack in the Context of Twentieth-Century Climate Variability

2009 ◽  
Vol 13 (12) ◽  
pp. 1-15 ◽  
Author(s):  
Gregory J. McCabe ◽  
David M. Wolock
Keyword(s):  
United States ◽  
Twentieth Century ◽  
Snow Water Equivalent ◽  
Winter Precipitation ◽  
Snow Accumulation ◽  
Western United States ◽  
Monthly Precipitation ◽  
Temperature And Precipitation ◽  
Decadal Scale

Abstract A monthly snow accumulation and melt model was used with monthly Precipitation-elevation Regressions on Independent Slopes Model (PRISM) temperature and precipitation data to generate time series of 1 April snow water equivalent (SWE) for 1900 through 2008 in the western United States. Averaged across the western United States, SWE generally was higher than long-term (1900–2008) average conditions during the periods 1900–25, 1944–55, and 1966–82; SWE was lower than long-term average conditions during the periods 1926–43, 1957–65, and 1984–2008. During the period 1900–2008, the temporal pattern in winter precipitation exhibited wetter-than-average and drier-than-average decadal-scale periods with no long-term increasing or decreasing trend. Winter temperature generally was below average from 1900 to the mid-1950s, close to average from the mid-1950s to the mid-1980s, and above average from the mid-1980s to 2008. In general, periods of higher-than-average SWE have been associated with higher precipitation and lower temperature. Since about 1980, western U.S. winter temperatures have been consistently higher than long-term average values, and the resultant lower-than-average SWE values have been only partially offset by periods of higher-than-average precipitation. The post-1980 lower-than-average SWE conditions in the western United States are unprecedented within the context of twentieth-century climate and estimated SWE.

scholarly journals Examining controls on peak annual streamflow and floods in the Fraser River Basin of British Columbia

2018 ◽  
Vol 22 (4) ◽  
pp. 2285-2309 ◽  
Author(s):  
Charles L. Curry ◽  
Francis W. Zwiers
Keyword(s):  
British Columbia ◽  
River Basin ◽  
Snow Water Equivalent ◽  
Climatic Factors ◽  
Southern Oscillation ◽  
Snow Accumulation ◽  
Fraser River ◽  
Daily Streamflow ◽  
Annual Peak ◽  
Rich Diversity

Abstract. The Fraser River Basin (FRB) of British Columbia is one of the largest and most important watersheds in western North America, and home to a rich diversity of biological species and economic assets that depend implicitly upon its extensive riverine habitats. The hydrology of the FRB is dominated by snow accumulation and melt processes, leading to a prominent annual peak streamflow invariably occurring in May–July. Nevertheless, while annual peak daily streamflow (APF) during the spring freshet in the FRB is historically well correlated with basin-averaged, 1 April snow water equivalent (SWE), there are numerous occurrences of anomalously large APF in below- or near-normal SWE years, some of which have resulted in damaging floods in the region. An imperfect understanding of which other climatic factors contribute to these anomalously large APFs hinders robust projections of their magnitude and frequency. We employ the Variable Infiltration Capacity (VIC) process-based hydrological model driven by gridded observations to investigate the key controlling factors of anomalous APF events in the FRB and four of its subbasins that contribute nearly 70 % of the annual flow at Fraser-Hope. The relative influence of a set of predictors characterizing the interannual variability of rainfall, snowfall, snowpack (characterized by the annual maximum value, SWEmax), soil moisture and temperature on simulated APF at Hope (the main outlet of the FRB) and at the subbasin outlets is examined within a regression framework. The influence of large-scale climate modes of variability (the Pacific Decadal Oscillation (PDO) and the El Niño–Southern Oscillation – ENSO) on APF magnitude is also assessed, and placed in context with these more localized controls. The results indicate that next to SWEmax (univariate Spearman correlation with APF of ρ^ = 0.64; 0.70 (observations; VIC simulation)), the snowmelt rate (ρ^ = 0.43 in VIC), the ENSO and PDO indices (ρ^ = −0.40; −0.41) and (ρ^ = −0.35; −0.38), respectively, and rate of warming subsequent to the date of SWEmax (ρ^ = 0.26; 0.38), are the most influential predictors of APF magnitude in the FRB and its subbasins. The identification of these controls on annual peak flows in the region may be of use in understanding seasonal predictions or future projected streamflow changes.

scholarly journals Incorporating Pacific Ocean climate information to enhance the tree-ring-based streamflow reconstruction skill

2020 ◽  
Author(s):  
Saria Bukhary ◽  
Ajay Kalra ◽  
Sajjad Ahmad
Keyword(s):  
Pacific Ocean ◽  
River Basin ◽  
Tree Ring ◽  
Cross Validation ◽  
Southern Oscillation ◽  
Low Flow ◽  
Tree Ring Chronology ◽  
Streamflow Reconstruction ◽  
Current Scenario ◽  
Instrumental Records

Abstract The Sacramento River Basin (SRB) and the San Joaquin River Basin (JRB) have a history of recurring droughts. Both are important for California, being the crucial source of water supply. The available instrumental records may not depict the long-term hydrologic variability encompassing the duration and frequency of the historic low flow events. Thus, streamflow reconstruction becomes important in the current scenario of climatic alteration, escalating population and growing water needs. Studies have shown that Pacific Decadal Oscillation (PDO), Southern Oscillation Index (SOI), and Pacific Ocean sea surface temperature (SST) influence the precipitation and streamflow volumes of southwestern United States, particularly California. The focus of this study is to enhance the traditional tree-ring chronology (TRC)-based streamflow reconstruction approach by incorporating the predictors of SST, PDO, and SOI together with TRC, in a stepwise linear regression (SLR) model. The methodology was successfully applied to selected gages located in the SRB and the JRB using five SLR models (SLR 1–5), and reconstructions were developed from 1801 to 1980 with an overlap period of 1933–1980. An improved reconstruction skill was demonstrated by using SST in combination with TRC (SLR-3 and SLR-5) (calibration r2 = 0.6–0.91 and cross-validation r² = 0.44–0.74) compared with using TRC only (SLR-1), or TRC along with SOI and PDO (SLR-2; calibration r2 = 0.51–0.78 and cross-validation r² = 0.41–0.68).

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