The Landfall and Inland Penetration of a Flood-Producing Atmospheric River in Arizona. Part I: Observed Synoptic-Scale, Orographic, and Hydrometeorological Characteristics

2013 ◽  
Vol 14 (2) ◽  
pp. 460-484 ◽  
Author(s):  
Paul J. Neiman ◽  
F. Martin Ralph ◽  
Benjamin J. Moore ◽  
Mimi Hughes ◽  
Kelly M. Mahoney ◽  
...  
Keyword(s):  
Sierra Nevada ◽  
Heat Fluxes ◽  
Back Trajectory ◽  
High Mountain ◽  
Wind Profiler ◽  
Plan View ◽  
Atmospheric Rivers ◽  
Tropical Water ◽  
Northeastern Pacific ◽  
The Impact

Abstract Atmospheric rivers (ARs) are a dominant mechanism for generating intense wintertime precipitation along the U.S. West Coast. While studies over the past 10 years have explored the impact of ARs in, and west of, California’s Sierra Nevada and the Pacific Northwest’s Cascade Mountains, their influence on the weather across the intermountain west remains an open question. This study utilizes gridded atmospheric datasets, satellite imagery, rawinsonde soundings, a 449-MHz wind profiler and global positioning system (GPS) receiver, and operational hydrometeorological observing networks to explore the dynamics and inland impacts of a landfalling, flood-producing AR across Arizona in January 2010. Plan-view, cross-section, and back-trajectory analyses quantify the synoptic and mesoscale forcing that led to widespread precipitation across the state. The analyses show that a strong AR formed in the lower midlatitudes over the northeastern Pacific Ocean via frontogenetic processes and sea surface latent-heat fluxes but without tapping into the adjacent tropical water vapor reservoir to the south. The wind profiler, GPS, and rawinsonde observations document strong orographic forcing in a moist neutral environment within the AR that led to extreme, orographically enhanced precipitation. The AR was oriented nearly orthogonal to the Mogollon Rim, a major escarpment crossing much of central Arizona, and was positioned between the high mountain ranges of northern Mexico. High melting levels during the heaviest precipitation contributed to region-wide flooding, while the high-altitude snowpack increased substantially. The characteristics of the AR that impacted Arizona in January 2010, and the resulting heavy orographic precipitation, are comparable to those of landfalling ARs and their impacts along the west coasts of midlatitude continents.

scholarly journals Influence of Atmospheric Rivers on Mountain Snowpack in the Western United States

2018 ◽  
Vol 31 (24) ◽  
pp. 9921-9940 ◽  
Author(s):  
N. Goldenson ◽  
L. R. Leung ◽  
C. M. Bitz ◽  
E. Blanchard-Wrigglesworth
Keyword(s):  
United States ◽  
Sierra Nevada ◽  
Snow Water Equivalent ◽  
Region Of Interest ◽  
Internal Variability ◽  
Western United States ◽  
Historical Period ◽  
Atmospheric Rivers ◽  
Atmospheric River ◽  
The Impact

In the coastal mountains of western North America, most extreme precipitation is associated with atmospheric rivers (ARs), narrow bands of moisture originating in the tropics. Here we quantify how interannual variability in atmospheric rivers influences snowpack in the western United States in observations and a model. We simulate the historical climate with the Model for Prediction Across Scales (MPAS) with physics from the Community Atmosphere Model, version 5 [CAM5 (MPAS-CAM5)], using prescribed sea surface temperatures. In the global variable-resolution domain, regional refinement (at ~30 km) is applied to our region of interest and upwind over the northeast Pacific. To better characterize internal variability, we conduct simulations with three ensemble members over 30 years of the historical period. In the Cascade Range, with some exceptions, winters with more atmospheric river days are associated with less snowpack. In California’s Sierra Nevada, winters with more ARs are associated with greater snowpack. The slope of the linear regression of observed snow water equivalent (SWE) on reanalysis-based AR count has the same sign as that arrived at using the model, but is statistically significant in observations only for California. In spring, internal variance plays an important role in determining whether atmospheric river days appear to be associated with greater or less snowpack. The cumulative (winter through spring) number of atmospheric river days, on the other hand, has a relationship with spring snowpack, which is consistent across ensemble members. Thus, the impact of atmospheric rivers on winter snowpack has a greater influence on spring snowpack than spring atmospheric rivers in the model for both regions and in California consistently in observations.

scholarly journals A WRF simulation of the impact of 3-D radiative transfer on surface hydrology over the Rocky–Sierra Mountains

2013 ◽  
Vol 13 (7) ◽  
pp. 19389-19419 ◽  
Author(s):  
K. N. Liou ◽  
Y. Gu ◽  
L. R. Leung ◽  
W. L. Lee ◽  
R. G. Fovell
Keyword(s):  
Water Resources ◽  
Solar Radiation ◽  
Radiative Transfer ◽  
Sierra Nevada ◽  
Snow Water Equivalent ◽  
Heat Fluxes ◽  
Solar Flux ◽  
Surface Hydrology ◽  
Elevation Range ◽  
The Impact

Abstract. Essentially all modern climate models utilize a plane-parallel (PP) radiative transfer approach in physics parameterizations; however, the potential errors that arise from neglecting three-dimensional (3-D) interactions between radiation and mountains/snow on climate simulations have not been studied and quantified. This paper is a continuation of our efforts to investigate 3-D mountains/snow effects on solar flux distributions and their impact on surface hydrology over the Western United States, specifically the Rocky and Sierra-Nevada Mountains. We use the Weather Research and Forecasting (WRF) model applied at a 30 km grid resolution with incorporation of a 3-D radiative transfer parameterization covering a time period from 1 November 2007 to 31 May 2008 during which abundant snowfall occurred. Comparison of the 3-D WRF simulation with the observed snow water equivalent (SWE) and precipitation from Snowpack Telemetry (SNOTEL) sites shows reasonable agreement in terms of spatial patterns and daily and seasonal variability, although the simulation generally has a positive precipitation bias. We show that 3-D mountain features have a profound impact on the diurnal and monthly variation of surface radiative and heat fluxes and on the consequent elevation-dependence of snowmelt and precipitation distributions. In particular, during the winter months, large deviations (3-D–PP) of the monthly mean surface solar flux are found in the morning and afternoon hours due to shading effects for elevations below 2.5 km. During spring, positive deviations shift to earlier morning. Over the mountain tops above 3 km, positive deviations are found throughout the day, with the largest values of 40–60 W m−2 occurring at noon during the snowmelt season of April to May. The monthly SWE deviations averaged over the entire domain show an increase in lower elevations due to reduced snowmelt, leading to a reduction in cumulative runoff. Over higher elevation areas, positive SWE deviations are found because of increased solar radiation available at the surface. Overall, this study shows that deviations of SWE due to 3-D radiation effects range from an increase of 18% at the lowest elevation range (1.5–2 km) to a decrease of 8% at the highest elevation range (above 3 km). Since lower elevation areas occupy larger fractions of the land surface, the net effect of 3-D radiative transfer is to extend snowmelt and snowmelt-driven runoff into the warm season. Additionally, because about 60–90% of water resources originate from mountains worldwide, the aforementioned differences in simulated hydrology due solely to 3-D interactions between solar radiation and mountains/snow merit further investigation in order to understand the implications to modeling mountain water resources and their vulnerability to climate change and air pollution.

scholarly journals A Seven-Year Wind Profiler–Based Climatology of the Windward Barrier Jet along California’s Northern Sierra Nevada

2010 ◽  
Vol 138 (4) ◽  
pp. 1206-1233 ◽  
Author(s):  
Paul J. Neiman ◽  
Ellen M. Sukovich ◽  
F. Martin Ralph ◽  
Mimi Hughes
Keyword(s):  
Sierra Nevada ◽  
Warm Season ◽  
Central Valley ◽  
Wind Profiler ◽  
Cool Season ◽  
Plan View ◽  
The North ◽  
Synoptic Conditions ◽  
Windward Slope ◽  
The Mean

Abstract This wind profiler–based study highlights key characteristics of the barrier jet along the windward slope of California’s Sierra Nevada. Between 2000 and 2007 roughly 10% of 100 000 hourly wind profiles, recorded at two sites, satisfied the sierra barrier jet (SBJ) threshold criteria described in the text. The mean magnitude of the terrain-parallel flow in the SBJ core (i.e., Vmax) was similar at both sites (∼17.5 m s−1) and at a comparable altitude, 500–1000 m above the surface. The cross-mountain wind speed was weak at the altitude of Vmax, consistent with blocked conditions. The seasonal cycle of SBJ occurrences showed a maximum during the cooler months and a minimum in summer. Additionally, the SBJ was stronger in winter than in summer. Because the warm-season (May–September) SBJs were different than their cool-season (October–April) counterparts and occurred during California’s dry season, they were not discussed in detail. An inventory of ∼250 cool-season SBJ cases from the two sites was generated (a case contains ≥8 consecutive SBJ profiles). Up to 60% of the nearby cool-season precipitation fell during SBJ cases, and these cases shifted the precipitation down the sierra’s windward slope and enhanced precipitation at the north end of the Central Valley (relative to non-SBJ conditions). The large number of cool-season SBJ cases was stratified by the mean strength and altitude of Vmax and by the case duration. Composite profiles of the along-barrier component for the top- and bottom-20 ranked cases in each of these three SBJ classes reveal stark differences in the magnitude and vertical positioning of the barrier jet. The three SBJ classes yielded uniquely different local precipitation characteristics in proximity to the wind profilers, with the strongest and longest-lived SBJs yielding the greatest precipitation. North American Regional Reanalysis plan-view composites were generated to explore the synoptic conditions responsible for, and to showcase the precipitation distributions associated with, the top- and bottom-20 ranked cases in each of the three classes of SBJs. The composite analyses yielded large contrasts between the SBJ classes that could prove useful in forecasting SBJs and their precipitation impacts. All SBJ classes occurred, on average, in the pre-cold-frontal environment of landfalling winter storms.

Focus on Thermokarst Lakes in Indian Himalaya: Inception and Implication under Warming Climate

2020 ◽  
Vol 6 (2) ◽  
pp. 59-69
Author(s):  
Pratima Pandey ◽  
S. Nawaz Ali ◽  
Vikram Sharma ◽  
Prashant K. Champati Ray
Keyword(s):  
Western Himalaya ◽  
High Mountain ◽  
Thermokarst Lakes ◽  
Glacial Environments ◽  
Global Warming Scenario ◽  
Scientific Attention ◽  
Topographic Depressions ◽  
Permafrost Thawing ◽  
The Impact ◽  
Thaw Lakes

Thermokarst (Thaw) lakes are landforms found in topographic depressions created by thawing ground ice in permafrost zones. They play an important role in the regulation of climatic functions. These lakes are a manifestation of warming surface temperatures that accelerates the ice-rich permafrost to degrade by creating marshy hollows/ponds. In the current global warming scenario, the thermokarst lakes in the high mountain regions (Himalaya) are expected to grow further. This accelerate permafrost thawing which will affect the carbon cycle, hydrology and local ecosystems. This phenomenon has attracted huge scientific attention because it has led to a rapid mass change of glaciers in the region, including extensive changes occurring on peri-glacial environments. The most striking fact is the release of an enormous amount of greenhouse gases, including methane, carbon dioxide and nitrous oxide that is locked in these lakes. The present study delves into the thermokarst lakes in the upper reaches of Chandra Valley and Western Himalaya. The study also aims at designating the impact of their changes on the ecosystem, particularly their influence on the atmospheric greenhouse gas concentrations.

scholarly journals Characterization of the subsurface urban heat island and its sources in the Milan city area, Italy

2021 ◽  
Author(s):  
Alberto Previati ◽  
Giovanni B. Crosta
Keyword(s):  
Urban Heat Island ◽  
Urban Areas ◽  
Heat Fluxes ◽  
Shallow Aquifer ◽  
Heat Island ◽  
Groundwater Temperature ◽  
City Area ◽  
Groundwater Environment ◽  
Urban Heat ◽  
The Impact

AbstractUrban areas are major contributors to the alteration of the local atmospheric and groundwater environment. The impact of such changes on the groundwater thermal regime is documented worldwide by elevated groundwater temperature in city centers with respect to the surrounding rural areas. This study investigates the subsurface urban heat island (SUHI) in the aquifers beneath the Milan city area in northern Italy, and assesses the natural and anthropogenic controls on groundwater temperatures within the urban area by analyzing groundwater head and temperature records acquired in the 2016–2020 period. This analysis demonstrates the occurrence of a SUHI with up to 3 °C intensity and reveals a correlation between the density of building/subsurface infrastructures and the mean annual groundwater temperature. Vertical heat fluxes to the aquifer are strongly related to the depth of the groundwater and the density of surface structures and infrastructures. The heat accumulation in the subsurface is reflected by a constant groundwater warming trend between +0.1 and + 0.4 °C/year that leads to a gain of 25 MJ/m2 of thermal energy per year in the shallow aquifer inside the SUHI area. Future monitoring of groundwater temperatures, combined with numerical modeling of coupled groundwater flow and heat transport, will be essential to reveal what this trend is controlled by and to make predictions on the lateral and vertical extent of the groundwater SUHI in the study area.

scholarly journals The Effect of Atmosphere–Ocean Coupling on the Structure and Intensity of Tropical Cyclone Bejisa in the Southwest Indian Ocean

Atmosphere ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 688
Author(s):  
Soline Bielli ◽  
Christelle Barthe ◽  
Olivier Bousquet ◽  
Pierre Tulet ◽  
Joris Pianezze
Keyword(s):  
Tropical Cyclone ◽  
Mixed Layer ◽  
Heat Fluxes ◽  
Sea Surface ◽  
Ocean Mixed Layer ◽  
Surface Cooling ◽  
Southwest Indian Ocean ◽  
Left Hand ◽  
Sea Surface Cooling ◽  
The Impact

A set of numerical simulations is relied upon to evaluate the impact of air-sea interactions on the behaviour of tropical cyclone (TC) Bejisa (2014), using various configurations of the coupled ocean-atmosphere numerical system Meso-NH-NEMO. Uncoupled (SST constant) as well as 1D (use of a 1D ocean mixed layer) and 3D (full 3D ocean) coupled experiments are conducted to evaluate the impact of the oceanic response and dynamic processes, with emphasis on the simulated structure and intensity of TC Bejisa. Although the three experiments are shown to properly capture the track of the tropical cyclone, the intensity and the spatial distribution of the sea surface cooling show strong differences from one coupled experiment to another. In the 1D experiment, sea surface cooling (∼1 ∘C) is reduced by a factor 2 with respect to observations and appears restricted to the depth of the ocean mixed layer. Cooling is maximized along the right-hand side of the TC track, in apparent disagreement with satellite-derived sea surface temperature observations. In the 3D experiment, surface cooling of up to 2.5 ∘C is simulated along the left hand side of the TC track, which shows more consistency with observations both in terms of intensity and spatial structure. In-depth cooling is also shown to extend to a much deeper depth, with a secondary maximum of nearly 1.5 ∘C simulated near 250 m. With respect to the uncoupled experiment, heat fluxes are reduced from about 20% in both 1D and 3D coupling configurations. The tropical cyclone intensity in terms of occurrence of 10-m TC wind is globally reduced in both cases by about 10%. 3D-coupling tends to asymmetrize winds aloft with little impact on intensity but rather a modification of the secondary circulation, resulting in a slight change in structure.

scholarly journals Formation Patterns of Mediterranean High-Mountain Water-Bodies in Sierra-Nevada, SE Spain

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 438
Author(s):  
Jose Luis Diaz-Hernandez ◽  
Antonio Jose Herrera-Martinez
Keyword(s):  
Sierra Nevada ◽  
Unknown Origin ◽  
Slope Instability ◽  
Water Bodies ◽  
High Mountain ◽  
Mountain Areas ◽  
Glacial Processes ◽  
The Mediterranean ◽  
Water Volumes

At present, there is a lack of detailed understanding on how the factors converging on water variables from mountain areas modify the quantity and quality of their watercourses, which are features determining these areas’ hydrological contribution to downstream regions. In order to remedy this situation to some extent, we studied the water-bodies of the western sector of the Sierra Nevada massif (Spain). Since thaw is a necessary but not sufficient contributor to the formation of these fragile water-bodies, we carried out field visits to identify their number, size and spatial distribution as well as their different modelling processes. The best-defined water-bodies were the result of glacial processes, such as overdeepening and moraine dams. These water-bodies are the highest in the massif (2918 m mean altitude), the largest and the deepest, making up 72% of the total. Another group is formed by hillside instability phenomena, which are very dynamic and are related to a variety of processes. The resulting water-bodies are irregular and located at lower altitudes (2842 m mean altitude), representing 25% of the total. The third group is the smallest (3%), with one subgroup formed by anthropic causes and another formed from unknown origin. It has recently been found that the Mediterranean and Atlantic watersheds of this massif are somewhat paradoxical in behaviour, since, despite its higher xericity, the Mediterranean watershed generally has higher water contents than the Atlantic. The overall cause of these discrepancies between watersheds is not connected to their formation processes. However, we found that the classification of water volumes by the manners of formation of their water-bodies is not coherent with the associated green fringes because of the anomalous behaviour of the water-bodies formed by moraine dams. This discrepancy is largely due to the passive role of the water retained in this type of water-body as it depends on the characteristics of its hollows. The water-bodies of Sierra Nevada close to the peak line (2918 m mean altitude) are therefore highly dependent on the glacial processes that created the hollows in which they are located. Slope instability created water-bodies mainly located at lower altitudes (2842 m mean altitude), representing tectonic weak zones or accumulation of debris, which are influenced by intense slope dynamics. These water-bodies are therefore more fragile, and their existence is probably more short-lived than that of bodies created under glacial conditions.

scholarly journals Influence of Land Cover and Soil Moisture on the Horizontal Distribution of Sensible and Latent Heat Fluxes in Southeast Kansas during IHOP_2002 and CASES-97

2007 ◽  
Vol 8 (1) ◽  
pp. 68-87 ◽  
Author(s):  
Margaret A. LeMone ◽  
Fei Chen ◽  
Joseph G. Alfieri ◽  
Mukul Tewari ◽  
Bart Geerts ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Latent Heat ◽  
Land Surface ◽  
Field Experiments ◽  
Time Of Day ◽  
Horizontal Distribution ◽  
Heat Fluxes ◽  
Surface Model ◽  
Green Vegetation ◽  
The Impact

Abstract Analyses of daytime fair-weather aircraft and surface-flux tower data from the May–June 2002 International H2O Project (IHOP_2002) and the April–May 1997 Cooperative Atmosphere Surface Exchange Study (CASES-97) are used to document the role of vegetation, soil moisture, and terrain in determining the horizontal variability of latent heat LE and sensible heat H along a 46-km flight track in southeast Kansas. Combining the two field experiments clearly reveals the strong influence of vegetation cover, with H maxima over sparse/dormant vegetation, and H minima over green vegetation; and, to a lesser extent, LE maxima over green vegetation, and LE minima over sparse/dormant vegetation. If the small number of cases is producing the correct trend, other effects of vegetation and the impact of soil moisture emerge through examining the slope ΔxyLE/ΔxyH for the best-fit straight line for plots of time-averaged LE as a function of time-averaged H over the area. Based on the surface energy balance, H + LE = Rnet − Gsfc, where Rnet is the net radiation and Gsfc is the flux into the soil; Rnet − Gsfc ∼ constant over the area implies an approximately −1 slope. Right after rainfall, H and LE vary too little horizontally to define a slope. After sufficient drying to produce enough horizontal variation to define a slope, a steep (∼−2) slope emerges. The slope becomes shallower and better defined with time as H and LE horizontal variability increases. Similarly, the slope becomes more negative with moister soils. In addition, the slope can change with time of day due to phase differences in H and LE. These trends are based on land surface model (LSM) runs and observations collected under nearly clear skies; the vegetation is unstressed for the days examined. LSM runs suggest terrain may also play a role, but observational support is weak.

scholarly journals Averaging-Related Biases in Monthly Latent Heat Fluxes

2012 ◽  
Vol 29 (7) ◽  
pp. 974-986 ◽  
Author(s):  
Paul J. Hughes ◽  
Mark A. Bourassa ◽  
Jeremy J. Rolph ◽  
Shawn R. Smith
Keyword(s):  
Latent Heat ◽  
Classical Method ◽  
Surface Flux ◽  
Heat Fluxes ◽  
Western Boundary ◽  
State University ◽  
Boundary Current ◽  
Surface Energy Fluxes ◽  
Temporal Averaging ◽  
The Impact

Abstract Seasonal-to-multidecadal applications that require ocean surface energy fluxes often require accuracies of surface turbulent fluxes to be 5 W m−2 or better. While there is little doubt that uncertainties in the flux algorithms and input data can cause considerable errors, the impact of temporal averaging has been more controversial. The biases resulting from using monthly averaged winds, temperatures, and humidities in the bulk aerodynamic formula (i.e., the so-called classical method) to estimate the monthly mean latent heat fluxes are shown to be substantial and spatially varying in a manner that is consistent with most prior work. These averaging-related biases are linked to nonnegligible submonthly covariances between the wind, temperature, and humidity. To provide additional insight into the averaging-related bias, the methodology behind the third-generation Florida State University monthly mean surface flux product (FSU3) is detailed to highlight additional sources of errors in gridded datasets. The FSU3 latent heat fluxes suffer from this averaging-related bias, which can be as large as 90 W m−2 in western boundary current regions during winter and can exceed 40 W m−2 in synoptically active portions of the tropics. The regional impacts of these biases on the mixed layer temperature tendency are shown to demonstrate that the error resulting from applying the classical method is physically substantial.

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