scholarly journals Controls on Streamflow Densities in Semiarid Rocky Mountain Catchments

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 521
Author(s):  
Caroline Martin ◽  
Stephanie K. Kampf ◽  
John C. Hammond ◽  
Codie Wilson ◽  
Suzanne P. Anderson
Keyword(s):  
Elevation Gradient ◽  
Rocky Mountain ◽  
Surface Flow ◽  
Colorado Front Range ◽  
Front Range ◽  
Channel Network ◽  
Stream Discharge ◽  
Geologic Maps ◽  
National Hydrography Dataset ◽  
Active Flow

Developing accurate stream maps requires both an improved understanding of the drivers of streamflow spatial patterns and field verification. This study examined streamflow locations in three semiarid catchments across an elevation gradient in the Colorado Front Range, USA. The locations of surface flow throughout each channel network were mapped in the field and used to compute active drainage densities. Field surveys of active flow were compared to National Hydrography Dataset High Resolution (NHD HR) flowlines, digital topographic data, and geologic maps. The length of active flow declined with stream discharge in each of the catchments, with the greatest decline in the driest catchment. Of the tributaries that did not dry completely, 60% had stable flow heads and the remaining tributaries had flow heads that moved downstream with drying. The flow heads were initiated at mean contributing areas of 0.1 km2 at the lowest elevation catchment and 0.5 km2 at the highest elevation catchment, leading to active drainage densities that declined with elevation and snow persistence. The field mapped drainage densities were less than half the drainage densities that were represented using NHD HR. Geologic structures influenced the flow locations, with multiple flow heads initiated along faults and some tributaries following either fault lines or lithologic contacts.

scholarly journals Changes in ozone and precursors during two aged wildfire smoke events in the Colorado Front Range in summer 2015

2017 ◽  
Vol 17 (17) ◽  
pp. 10691-10707 ◽  
Author(s):  
Jakob Lindaas ◽  
Delphine K. Farmer ◽  
Ilana B. Pollack ◽  
Andrew Abeleira ◽  
Frank Flocke ◽  
...  
Keyword(s):  
Pacific Northwest ◽  
Rocky Mountain ◽  
Colorado Front Range ◽  
Atmospheric Composition ◽  
Urban Site ◽  
Front Range ◽  
Wildfire Smoke ◽  
Mixing Ratios ◽  
The Pacific ◽  
Urban Rural

Abstract. The relative importance of wildfire smoke for air quality over the western US is expected to increase as the climate warms and anthropogenic emissions decline. We report on in situ measurements of ozone (O3), a suite of volatile organic compounds (VOCs), and reactive oxidized nitrogen species collected during summer 2015 at the Boulder Atmospheric Observatory (BAO) in Erie, CO. Aged wildfire smoke impacted BAO during two distinct time periods during summer 2015: 6–10 July and 16–30 August. The smoke was transported from the Pacific Northwest and Canada across much of the continental US. Carbon monoxide and particulate matter increased during the smoke-impacted periods, along with peroxyacyl nitrates and several VOCs that have atmospheric lifetimes longer than the transport timescale of the smoke. During the August smoke-impacted period, nitrogen dioxide was also elevated during the morning and evening compared to the smoke-free periods. There were nine empirically defined high-O3 days during our study period at BAO, and two of these days were smoke impacted. We examined the relationship between O3 and temperature at BAO and found that for a given temperature, O3 mixing ratios were greater (∼ 10 ppbv) during the smoke-impacted periods. Enhancements in O3 during the August smoke-impacted period were also observed at two long-term monitoring sites in Colorado: Rocky Mountain National Park and the Arapahoe National Wildlife Refuge near Walden, CO. Our data provide a new case study of how aged wildfire smoke can influence atmospheric composition at an urban site, and how smoke can contribute to increased O3 abundances across an urban–rural gradient.

Stand response to western spruce budworm and Douglas-fir bark beetle outbreaks, Colorado Front Range

1993 ◽  
Vol 23 (3) ◽  
pp. 479-491 ◽  
Author(s):  
Keith S. Hadley ◽  
Thomas T. Veblen
Keyword(s):  
Bark Beetle ◽  
Stand Structure ◽  
Fire Suppression ◽  
Rocky Mountain ◽  
Spruce Budworm ◽  
Douglas Fir ◽  
Colorado Front Range ◽  
Front Range ◽  
Western Spruce Budworm ◽  
Wide Range

The montane forests (i.e., below ca. 2900 m) of the Colorado Front Range have experienced repeated outbreaks of western spruce budworm (Choristoneuraoccidentalis Free.) and Douglas-fir bark beetle (Dendroctonuspseudotsugae Hopk.), both of which locally attack Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco). In this study we examine the effects of historically documented outbreaks of these insects on succession, stand structure, and radial growth of host and nonhost species in Rocky Mountain National Park. The most recent budworm (1974–1985) and bark beetle (1984–present) outbreaks resulted in the most severe and widespread disturbance of these forests since the late 1800s. Stand response to these outbreaks is primarily a function of stand structure and age characteristics of Douglas-fir prior to an outbreak. Young, vigorous postfire stands show minimal budworm defoliation, and in these stands only remnant trees from the prefire generation appear susceptible to beetle-caused mortality. Dense stands exhibit higher budworm-induced mortality, which hastens the natural thinning process and shifts dominance towards the nonhost species. The stands most severely disturbed by the combined insect agents are multistoried stands with high host densities and a wide range of stem sizes. The stand response to these disturbances include the growth release of shade-intolerant, seral species, and in some cases, a higher survivorship among midsized individuals of the host Douglas-fir. The net result of the combined insect outbreaks is the temporary slowing of the successional trend towards a steady-state Douglas-fir forest. Fire suppression, by increasing the density of suppressed Douglas-fir, has previously been shown to favor increased outbreak severity of western spruce budworm in the northern Rockies. However, in the Front Range, recent increases in outbreak severity and their synchroneity may also be the result of large areas of forest, burned during the late 19th century during European settlement, simultaneously entering structural stages susceptible to insect outbreak.

scholarly journals Observations of gas- and aerosol-phase organic nitrates at BEACHON-RoMBAS 2011

2013 ◽  
Vol 13 (1) ◽  
pp. 1979-2034 ◽  
Author(s):  
J. L. Fry ◽  
D. C. Draper ◽  
K. J. Zarzana ◽  
P. Campuzano-Jost ◽  
D. A. Day ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Rocky Mountain ◽  
Colorado Front Range ◽  
Temperature Cycle ◽  
Organic Nitrate ◽  
Organic Nitrates ◽  
Front Range ◽  
Aerosol Formation ◽  
Alkyl Nitrates

Abstract. At the Rocky Mountain Biogenic Aerosol Study (BEACHON-RoMBAS) field campaign in the Colorado front range, July–August 2011, measurements of gas- and aerosol-phase organic nitrates enabled a study of the role of NOx (NOx = NO + NO2) in oxidation of forest-emitted VOCs and subsequent aerosol formation. Substantial formation of peroxy- and alkyl-nitrates is observed every morning, with an apparent 2.9% yield of alkyl nitrates from daytime RO2 + NO reactions. Aerosol-phase organic nitrates, however, peak in concentration during the night, with concentrations up to 140 ppt as measured by both optical spectroscopic and mass spectrometric instruments. The diurnal cycle in aerosol fraction of organic nitrates shows an equilibrium-like response to the diurnal temperature cycle, suggesting some reversible absorptive partitioning, but the full dynamic range cannot be reproduced by thermodynamic repartitioning alone. Nighttime aerosol organic nitrate is observed to be positively correlated with [NO2] × [O3] but not with [O3]. These observations support the role of nighttime NO3-initiated oxidation of monoterpenes as a significant source of nighttime aerosol. Nighttime production of organic nitrates exceeds daytime photochemical production at this site, which we postulate to be representative of the Colorado front range forests.

scholarly journals Summertime Soil-Atmosphere Ammonia Exchange in the Colorado Rocky Mountain Front Range Pine Forest

Soil Systems ◽  
2019 ◽  
Vol 3 (1) ◽  
pp. 15 ◽  
Author(s):  
Amy Hrdina ◽  
Alexander Moravek ◽  
Heather Schwartz-Narbonne ◽  
Jennifer Murphy
Keyword(s):  
Forest Ecosystems ◽  
Rocky Mountain ◽  
Colorado Front Range ◽  
Front Range ◽  
Soil Extracts ◽  
Surface Atmosphere ◽  
Naturally Occurring ◽  
Direct Measurements ◽  
Mountain Front ◽  
Ammonia Exchange

Understanding the NH3 exchange between forest ecosystems and the atmosphere is important due to its role in the nitrogen cycle. However, NH3 exchange is dynamic and difficult to measure. The goal of this study was to characterize this exchange by measuring the atmosphere, soil, and vegetation. Compensation point modeling was used to evaluate the direction and magnitude of surface-atmosphere exchange. Measurements were performed at the Manitou Experimental Forest Observatory (MEFO) site in the Colorado Front Range by continuous online monitoring of gas and particle phase NH3-NH4+ with an ambient ion monitoring system coupled with ion chromatographs (AIM-IC), direct measurements of [NH4+] and pH in soil extracts to determine ground emission potential (Γg), and measurements of [NH4+]bulk in pine needles to derive leaf emission potential (Γst). Two different soil types were measured multiple times throughout the study, in which Γg ranged from 5 to 2122. Γst values ranged from 29 to 54. Inferred fluxes (Fg) from each soil type predicted intervals of emission and deposition. By accounting for the total [NH4+] pool in each compartment, the lifetime of NH3 with respect to the surface-atmosphere exchange in the soil is on the order of years compared to much faster naturally occurring processes, i.e., mineralization and nitrification.

scholarly journals The impact of aged wildfire smoke on atmospheric composition and ozone in the Colorado Front Range in summer 2015

2017 ◽  
Author(s):  
Jakob Lindaas ◽  
Delphine K. Farmer ◽  
Ilana B. Pollack ◽  
Andrew Abeleira ◽  
Frank Flocke ◽  
...  
Keyword(s):  
Pacific Northwest ◽  
Rocky Mountain ◽  
Colorado Front Range ◽  
Atmospheric Composition ◽  
Urban Site ◽  
Front Range ◽  
Wildfire Smoke ◽  
Mixing Ratios ◽  
Urban Rural ◽  
The Impact

Abstract. The relative importance of wildfire smoke for air quality over the western U.S. is expected to increase as the climate warms and anthropogenic emissions decline. We report on in situ measurements of ozone (O3), a suite of volatile organic compounds (VOCs), and reactive oxidized nitrogen species collected during summer 2015 at the Boulder Atmospheric Observatory (BAO) in Erie, CO. Aged wildfire smoke impacted BAO during two distinct time periods during summer 2015: 6–10 July and 16–30 August. The smoke was transported from the Pacific Northwest and Canada across much of the continental U.S. Carbon monoxide and particulate matter increased during the smoke-impacted periods, along with peroxyacyl nitrates and several VOCs that have atmospheric lifetimes longer than the transport timescale of the smoke. During the August smoke-impacted period, nitrogen dioxide was also elevated during the morning and evening compared to the smoke-free periods. There were six days during our study period where the maximum 8-hour average O3 at BAO was greater than 65 ppbv, and two of these days were smoke-impacted. We examined the relationship between O3 and temperature at BAO and found that for a given temperature, O3 mixing ratios were greater (~ 10 ppbv) during the smoke-impacted periods. Enhancements in O3 during the August smoke-impacted period were also observed at two long-term monitoring sites in Colorado: Rocky Mountain National Park and the Arapahoe National Wildlife Refuge near Walden, CO. Our data provide a new case study of how aged wildfire smoke can influence atmospheric composition at an urban site, and how smoke can contribute to increased O3 abundances across an urban-rural gradient.

Seasonal ozone behavior along an elevation gradient in the Colorado Front Range Mountains

2010 ◽  
Vol 44 (39) ◽  
pp. 5305-5315 ◽  
Author(s):  
Molly Brodin ◽  
Detlev Helmig ◽  
Samuel Oltmans
Keyword(s):  
Elevation Gradient ◽  
Colorado Front Range ◽  
Front Range

scholarly journals Observations of gas- and aerosol-phase organic nitrates at BEACHON-RoMBAS 2011

2013 ◽  
Vol 13 (17) ◽  
pp. 8585-8605 ◽  
Author(s):  
J. L. Fry ◽  
D. C. Draper ◽  
K. J. Zarzana ◽  
P. Campuzano-Jost ◽  
D. A. Day ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Rocky Mountain ◽  
Colorado Front Range ◽  
Temperature Cycle ◽  
Organic Nitrate ◽  
Organic Nitrates ◽  
Front Range ◽  
Aerosol Formation ◽  
Alkyl Nitrates

Abstract. At the Rocky Mountain Biogenic Aerosol Study (BEACHON-RoMBAS) field campaign in the Colorado front range, July–August 2011, measurements of gas- and aerosol-phase organic nitrates enabled a study of the role of NOx (NOx = NO + NO2) in oxidation of forest-emitted volatile organic compounds (VOCs) and subsequent aerosol formation. Substantial formation of peroxy- and alkyl-nitrates is observed every morning, with an apparent 2.9% yield of alkyl nitrates from daytime RO2 + NO reactions. Aerosol-phase organic nitrates, however, peak in concentration during the night, with concentrations up to 140 ppt as measured by both optical spectroscopic and mass spectrometric instruments. The diurnal cycle in aerosol fraction of organic nitrates shows an equilibrium-like response to the diurnal temperature cycle, suggesting some reversible absorptive partitioning, but the full dynamic range cannot be reproduced by thermodynamic repartitioning alone. Nighttime aerosol organic nitrate is observed to be positively correlated with [NO2] × [O3] but not with [O3]. These observations support the role of nighttime NO3-initiated oxidation of monoterpenes as a significant source of nighttime aerosol. Nighttime production of organic nitrates is comparable in magnitude to daytime photochemical production at this site, which we postulate to be representative of the Colorado front range forests.

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