Measurement of Incoming Radiation below Forest Canopies: A Comparison of Different Radiometer Configurations

Webster, Clare; Rutter, Nick; Zahner, Franziska; Jonas, Tobias

doi:10.1175/jhm-d-15-0125.1

Cited by 32 publications

(34 citation statements)

References 32 publications

(53 reference statements)

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“…Similarly, forests affect ablation rates by diminishing turbulent heat fluxes and reducing incoming solar radiation (Table 1; Link et al, 2004;Link & Marks, 1999;Musselman et al, 2008Musselman et al, , 2015Veatch et al, 2009). Simultaneously, snow receives enhanced longwave radiation from the forest, which increases the melt rate, but the enhancement of longwave radiation has a more localized effect (Table 1) and varies between sun-lit and shaded forest edges (Lawler & Link, 2011;Musselman & Pomeroy, 2017;Seyednasrollah & Kumar, 2014;Webster et al, 2016Webster et al, , 2017Woo & Giesbrecht, 2000).…”

Section: Forest and Topographic Processes Affecting Snow Depth Variabmentioning

confidence: 99%

“…Tuolumne had two sites classified as taiga (Dana Meadows and Dana Meadows South) and two sites classified as tundra, while sites at Jemez were all classified as warm forest. Warm forest was previously referred to as alpine in Sturm et al (1995) Golding and Swanson (1978), Lawler andLink (2011), Musselman et al (2015), and Seyednasrollah and Kumar (2014) Enhanced longwave radiation from the forest 1-2 m or 0.5 H Lawler and Link (2011), Musselman and Pomeroy (2017), Seyednasrollah and Kumar (2014), Webster et al (2016), and Woo and Giesbrecht (2000) Wind related deposition as a result of the forest 5-100 m or 3-10 H Brandle and Finch (1991), Hiemstra et al (2002Hiemstra et al ( , 2006, and Tabler (2003) 10.1029/2018WR022553…”

Section: Location and Datamentioning

confidence: 99%

See 1 more Smart Citation

Snow Depth Variability at the Forest Edge in Multiple Climates in the Western United States

Currier

Lundquist

2018

Water Resources Research

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Snow depth variability between different sides of the forest edge was analyzed using airborne lidar in the Olympic Mountains, WA; Tuolumne River Watershed, CA; Jemez Caldera, NM; and the Boulder Creek Watershed, CO. At Boulder Creek there were statistically significant snow depth differences between leeward and windward forest edges (mean: 38%), which were likely the result of cold winter temperatures (−5 to −10°C), substantial wind speeds (>10–12 m/s), and the forest architecture. In the Olympic Mountains, wind speeds were similar to Boulder Creek, but snow depth differences between forest edges were not significantly different, likely due to winter temperatures near 0°C and a more continuous forest distribution. At Jemez, forest shading likely caused significant snow depth differences between north and south facing forest edges (mean: 32%). Tuolumne had similar incoming solar radiation to Jemez, but only two of the four sites contained significant snow depth differences between north and south facing forest edges (14% and 31%). The Tuolumne sites without significant edge differences received less direct solar radiation due to shading by surrounding topography. At Jemez, Boulder Creek, and Tuolumne, snow depth differences between forest edges were greater than or equal to differences between exposed and under canopy areas. Furthermore, at Jemez and Tuolumne, forest‐edge snow depth differences were similar to snow depth differences between different aspects in exposed areas. Therefore, snow depth differences between forest‐edge classifications are of similar magnitude to classifications currently used to represent subelement heterogeneity within hydrologic models. Therefore, representation of forest‐edge variability within models should be explored.

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Section: Forest and Topographic Processes Affecting Snow Depth Variabmentioning

confidence: 99%

Section: Location and Datamentioning

confidence: 99%

Snow Depth Variability at the Forest Edge in Multiple Climates in the Western United States

Currier

Lundquist

2018

Water Resources Research

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“…Incoming shortwave and longwave radiation were measured simultaneously at 1 min (Alptal) and 15 s (Seehornwald) resolution. Details of the rail-mounted radiometers are described in Stähli et al [2009] and Webster et al [2015] and were replicated when the equipment was moved from Alptal to the Seehornwald site in 2007. The subcanopy CNR1 moved along a 10 m heated rail at 10 min intervals at a constant velocity and at a height of approximately 2 m above the forest floor, covering a range of V f (Alptal: 0.09-0.18; Seehornwald; 0.02-0.05).…”

Section: Alptal and Seehornwaldmentioning

confidence: 99%

Modeling subcanopy incoming longwave radiation to seasonal snow using air and tree trunk temperatures

et al. 2016

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Citation: Webster, Clare, Rutter, Nick, Zahner, Franziska and Jonas, Tobias (2016) Modelling sub-canopy incoming longwave radiation to seasonal snow using air and tree trunk temperatures. Journal of Geophysical 121 (3 Northumbria University has developed Northumbria Research Link (NRL) to enable users to access the University's research output. Copyright © and moral rights for items on NRL are retained by the individual author(s) and/or other copyright owners. Single copies of full items can be reproduced, displayed or performed, and given to third parties in any format or medium for personal research or study, educational, or not-for-profit purposes without prior permission or charge, provided the authors, title and full bibliographic details are given, as well as a hyperlink and/or URL to the original metadata page. The content must not be changed in any way. Full items must not be sold commercially in any format or medium without formal permission of the copyright holder. The full policy is available online: http://nrl.northumbria.ac.uk/policies.html This document may differ from the final, published version of the research and has been made available online in accordance with publisher policies. To read and/or cite from the published version of the research, please visit the publisher's website (a subscription may be required.)Modeling subcanopy incoming longwave radiation to seasonal snow using air and tree trunk temperatures Abstract Data collected at three Swiss alpine forested sites over a combined 11 year period were used to evaluate the role of air temperature in modeling subcanopy incoming longwave radiation to the snow surface. Simulated subcanopy incoming longwave radiation is traditionally partitioned into that from the sky and that from the canopy, i.e., a two-part model. Initial uncertainties in predicting longwave radiation using the two-part model resulted from vertical differences in measured air temperature. Above-canopy (35 m) air temperatures were higher than those within (10 m) and below (2 m) canopy throughout four snow seasons (December-April), demonstrating how the forest canopy can act as a cold sink for air. Lowest model root-mean-square error (RMSE) was using above-canopy air temperature. Further investigation of modeling subcanopy longwave radiation using above-canopy air temperature showed underestimations, particularly during periods of high insolation. In order to explicitly account for canopy temperatures in modeling longwave radiation, the two-part model was improved by incorporating a measured trunk view component and trunk temperature. Trunk temperature measurements were up to 25°C higher than locally measured air temperatures. This three-part model reduced the RMSE by up to 7.7 W m À2 from the two-part air temperature model at all sensor positions across the 2014 snowmelt season and performed particularly well during periods of high insolation when errors from the two-part model were up to 40 W m À2. A parameterization predicting tree trunk temperatures using measured air t...

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“…This process is called longwave enhancement and potentially contributes to ripening or melting of snow cover. Extensive observations of subcanopy longwave radiation in dense subalpine and alpine forests by Webster et al (2016a;2016b) revealed longwave enhancement values of up to 1.5, or 150%, and net longwave radiation fluxes into snow reaching 10-min averages of up to 40 W/m 2 during clear-sky days in spring. In contrast, net longwave radiation fluxes of about −100 W/m 2 are typical for snow under clear-sky conditions in unforested areas.…”

Section: Introductionmentioning

confidence: 99%

Simulation of Longwave Enhancement in Boreal and Montane Forests

et al. 2018

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Boreal forests cover about a fifth of seasonally snow‐covered land over the Northern Hemisphere. Enhancement of longwave radiation beneath coniferous forests has been found to impact the surface energy balance and rates of snowmelt. Although the skill of model‐simulated snowmelt has been shown to be lower for forests than for open areas, model intercomparisons and evaluations of model parameterizations have not yet focused on longwave enhancement. This study uses stand‐scale forcing for the simulation of subcanopy longwave radiation by Community Land Model version 4.5 (CLM4.5) and to drive SNOWPACK, a snow model featuring more complex canopy structure, as a benchmark model for CLM4.5. Simulated subcanopy longwave radiation and longwave enhancement are assessed using measurements from forest stands located within perennially snow‐covered regions. These forest stands, of varying canopy density, cover the range of boreal plant functional types in CLM4.5. CLM4.5 is found to overestimate the diurnal range of subcanopy longwave radiation and longwave enhancement, and simulation errors increase with decreasing cloudiness and increasing vegetation density. Implementation of a parameterization of heat storage by biomass reduces simulation errors but only marginally affects the amplitude of diurnal ranges. These results reaffirm previous findings that simulation of subcanopy longwave radiation can be improved by partitioning the vegetation canopy into two layers. Moreover, this study reveals the variations of simulation errors across meteorological conditions and vegetation density, the latter of which is the most important parameter for longwave enhancement independent of vegetation type.

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Measurement of Incoming Radiation below Forest Canopies: A Comparison of Different Radiometer Configurations

Cited by 32 publications

References 32 publications

Snow Depth Variability at the Forest Edge in Multiple Climates in the Western United States

Snow Depth Variability at the Forest Edge in Multiple Climates in the Western United States

Modeling subcanopy incoming longwave radiation to seasonal snow using air and tree trunk temperatures

Simulation of Longwave Enhancement in Boreal and Montane Forests

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