A Statistical Approach to Field Measurements of the Chemical Evolution of Cold (< 0 °C) Snow Cover

1991 ◽  
pp. 123-138
Author(s):  
Claude Laberge ◽  
Gerald Jones
Keyword(s):  
Snow Cover ◽  
Chemical Evolution ◽  
Statistical Approach ◽  
Field Measurements

scholarly journals Comparison of traditional and optical grain-size field measurements with SNOWPACK simulations in a taiga snowpack

2015 ◽  
Vol 61 (225) ◽  
pp. 151-162 ◽  
Author(s):  
L. Leppänen ◽  
A. Kontu ◽  
J. Vehviläinen ◽  
J. Lemmetyinen ◽  
J. Pulliainen
Keyword(s):  
Grain Size ◽  
Snow Cover ◽  
Electromagnetic Waves ◽  
Field Measurements ◽  
Scaling Factor ◽  
Field Conditions ◽  
Meteorological Forcing ◽  
Sensing Applications ◽  
Variable Nature ◽  
Snow Microstructure

AbstractKnowledge of snow microstructure is relevant for modelling the physical properties of snow cover and for simulating the propagation of electromagnetic waves in remote-sensing applications. Characterization of the microstructure in field conditions is, however, a challenging task due to the complex, sintered and variable nature of natural snow cover. A traditional measure applied as a proxy of snow microstructure, which can also be determined in field conditions, is the visually estimated snow grain size. Developing techniques also allow measurement, for example, of the specific surface area (SSA) of snow, from which the optical-equivalent grain size can be derived. The physical snow model SNOWPACK simulates evolution of snow parameters from meteorological forcing data. In this study we compare an extensive experimental dataset of measurements of traditional grain size and SSA-derived optical grain size with SNOWPACK simulations of grain-size parameters. On average, a scaling factor of 1.2 is required to match traditional grain-size observations with the corresponding SNOWPACK simulation; a scaling factor of 2.1 was required for the optical equivalent grain size. Standard deviations of scaling factors for the winters of 2011/12 and 2012/13 were 0.36 and 0.42, respectively. The largest scaling factor was needed in early winter and under melting conditions.

scholarly journals A new Snow-SVAT to simulate the accumulation and ablation of seasonal snow cover beneath a forest canopy

2004 ◽  
Vol 50 (169) ◽  
pp. 171-182 ◽  
Author(s):  
Melody J. Tribbeck ◽  
Robert J. Gurney ◽  
Elizabeth M. Morris ◽  
David W. C. Pearson
Keyword(s):  
Solar Radiation ◽  
Snow Cover ◽  
Forest Canopy ◽  
Correlation Coefficients ◽  
Field Measurements ◽  
Radiation Model ◽  
Physically Based ◽  
Boreal Ecosystem ◽  
Snow Model

AbstractA new snow—soil—vegetation—atmosphere transfer (Snow-SVAT) scheme, which simulates the accumulation and ablation of the snow cover beneath a forest canopy, is presented. The model was formulated by coupling a canopy optical and thermal radiation model to a physically based multi-layer snow model. This canopy radiation model is physically based yet requires few parameters, so can be used when extensive in situ field measurements are not available. Other forest effects such as the reduction of wind speed, interception of snow on the canopy and the deposition of litter were incorporated within this combined model, SNOWCAN, which was tested with data taken as part of the Boreal Ecosystem—Atmosphere Study (BOREAS) international collaborative experiment. Snow depths beneath four different canopy types and at an open site were simulated. Agreement between observed and simulated snow depths was generally good, with correlation coefficients ranging between r2 = 0.94 and r2 = 0.98 for all sites where automatic measurements were available. However, the simulated date of total snowpack ablation generally occurred later than the observed date. A comparison between simulated solar radiation and limited measurements of sub-canopy radiation at one site indicates that the model simulates the sub-canopy downwelling solar radiation early in the season to within measurement uncertainty.

scholarly journals An Integrated Shadow-Adjusted Snow-Aging Index for Alpine Regions

2020 ◽  
Vol 12 (8) ◽  
pp. 1249
Author(s):  
Haixing Li ◽  
Jinrong Liu ◽  
Xiangxu Bu ◽  
Xuezhi Feng ◽  
Pengfeng Xiao
Keyword(s):  
Snow Cover ◽  
Aging Process ◽  
Field Measurements ◽  
Northwest China ◽  
Analytic Hierarchy ◽  
Alpine Regions ◽  
Aging Index ◽  
Optical Images ◽  
Searching Method ◽  
Steep Slopes

Detecting the variations in snow cover aging over undulating alpine regions is challenging owing to the complex snow-aging process and shadow effect from steep slopes. This study proposes a novel snow-cover status index, namely shadow-adjusted snow-aging index (SASAI), portraying the integrated aging process within the Manas River Basin in northwest China. The Environment Satellites HJ-1A/B optical images and in-field measurements were used during the snow ablation and accumulation periods. The in-field measurements provide a reference for building a candidate library of snow-aging indicators. The representative aging samples for training and validation were obtained using the proposed time-gap searching method combined with the target zones established based on the altitude of snowline. An analytic hierarchy process was used to determine the snow-aging index (SAI) using multiple optimal snow-aging indicators. After correction by the extreme value optimization algorithm, the SASAI was finally corrected for the effects of shading and assessed. This study provides both a flexible algorithm that indicates the characteristics of snow aging and speculation on the causes of the aging process. The separability of the SAI/SASAI and adaptability of this algorithm on multiperiod remote sensing images further demonstrates the applicability of the SASAI to all the alpine regions.

scholarly journals Measurements of mass balance in dense snow avalanche events

2001 ◽  
Vol 32 ◽  
pp. 230-236 ◽  
Author(s):  
Betty Sovilla ◽  
Francesco Sommavilla ◽  
Alvise Tomaselli
Keyword(s):  
Mass Balance ◽  
Snow Cover ◽  
Field Measurements ◽  
Test Site ◽  
Small Dimension ◽  
Deceleration Phase ◽  
Mass Entrainment ◽  
Speed Flow ◽  
Avalanche Dynamics ◽  
Deposition Processes

AbstractSince 1993 the Avalanche Centre of Arabba has managed a test site to determine avalanche-dynamics parameters (Sommavilla and others, 1997; Sommavilla and Sovilla, 1998). The system is located on an avalanche track which is representative for the Dolomites, northern Italy It monitors avalanche pressures, speed, flow height and variations of the avalanche shape and extent. In winter 1997/98, together with the standard measurements, a series of new field measurements and observations of the snow cover on the avalanche path were conducted for the first time in order to accurately determine the avalanche mass balance. The information collected is typical for dense flow avalanches which have small dimension and develop mainly along a channelled path. In winter 1997/98, four events were studied. For each event, in several sections from the starting zone to the deposition zone, manual measurements were carried out in order to investigate mass entrainment and deposition processes. The mass evolution of the avalanche has been determined. It is shown that the avalanche mass increases by up to 720% with respect to the initial release mass. This entrainment process is related to the speed reached by the avalanche front. In addition, it has been determined that during the acceleration phase of the avalanche front the underlying snow cover is mostly eroded and there is no deposition of snow. In the deceleration phase, by contrast, erosion decreases progressively, reaching the value zero, while deposition becomes progressively larger. These results underscore the importance of the mass balance as a fundamental component in avalanche-dynamics research.

scholarly journals Vertical variability in the position of the zero isochion in geomorphologic regions of Czechia

Geografie ◽  
2014 ◽  
Vol 119 (2) ◽  
pp. 145-160
Author(s):  
Libor Ducháček
Keyword(s):  
Snow Cover ◽  
Large Scale ◽  
Snow Water Equivalent ◽  
Field Measurements ◽  
Mountainous Areas ◽  
Snow Cover Area ◽  
Interconnected System ◽  
Central Highland ◽  
Snow Water ◽  
Source Of Information

Knowledge of the volume of water retained in mountainous areas serves as an important source of information for the anticipation of spring floods, as well as for other purposes, such as those related to agricultural management. Similarly, the extent and distribution of snow coverage (snow cover area – SCA) in lowlands are factors influencing the threat of large-scale floods caused by the melting of even a thin layer of snow cover. Every week during the winter months, the Czech Hydrometeorological Institute (CHMI) provides up to date information on the snow water equivalent present in Czech regions and especially within important hydrological basins. This information comes predominantly from an observation of net and field measurements. The position of the zero isohione, determined through remote sensing, helps to increase the accuracy of the calculations of such spatial distribution in Czechia. As a consequence of this practical use, changes in the accumulation and distribution of snow cover can be readily observed via remote senzing. This is further made easier by Czechia’s orographic disposition, specifically its interconnected system of border mountains and a central highland. As a result, the position of the zero isohione can be determined with an accuracy of 50 m a.s.l. If we compare selected geomorphological regions, we can find statistically substantiated differences in the position of the zero isohione of more than 200 m.

scholarly journals Event-driven deposition of snow on the Antarctic Plateau: analyzing field measurements with SNOWPACK

2013 ◽  
Vol 7 (1) ◽  
pp. 333-347 ◽  
Author(s):  
C. D. Groot Zwaaftink ◽  
A. Cagnati ◽  
A. Crepaz ◽  
C. Fierz ◽  
G. Macelloni ◽  
...  
Keyword(s):  
Snow Cover ◽  
Meteorological Data ◽  
Lower Boundary ◽  
Field Measurements ◽  
Antarctic Plateau ◽  
Event Driven ◽  
Total Magnitude ◽  
Strong Winds ◽  
The Antarctic ◽  
Snow Deposition

Abstract. Antarctic surface snow has been studied by means of continuous measurements and observations over a period of 3 yr at Dome C. Snow observations include solid deposits in form of precipitation, diamond dust, or hoar, snow temperatures at several depths, records of deposition and erosion on the surface, and snow profiles. Together with meteorological data from automatic weather stations, this forms a unique dataset of snow conditions on the Antarctic Plateau. Large differences in snow amounts and density exist between solid deposits measured 1 m above the surface and deposition at the surface. We used the snow-cover model SNOWPACK to simulate the snow-cover evolution for different deposition parameterizations. The main adaptation of the model described here is a new event-driven deposition scheme. The scheme assumes that snow is added to the snow cover permanently only during periods of strong winds. This assumption followed from the comparison between observations of solid deposits and daily records of changes in snow height: solid deposits could be observed on tables 1 m above the surface on 94 out of 235 days (40%) while deposition at the surface occurred on 59 days (25%) during the same period, but both happened concurrently on 33 days (14%) only. This confirms that precipitation is not necessarily the driving force behind non-temporary snow height changes. A comparison of simulated snow height to stake farm measurements over 3 yr showed that we underestimate the total accumulation by at least 33%, when the total snow deposition is constrained by the measurements of solid deposits on tables 1 m above the surface. During shorter time periods, however, we may miss over 50% of the deposited mass. This suggests that the solid deposits measured above the surface and used to drive the model, even though comparable to ECMWF forecasts in its total magnitude, should be seen as a lower boundary. As a result of the new deposition mechanism, we found a good agreement between model results and measurements of snow temperatures and recorded snow profiles. In spite of the underestimated deposition, the results thus suggest that we can obtain quite realistic simulations of the Antarctic snow cover by the introduction of event-driven snow deposition.

scholarly journals A statistical approach for estimating representative emission rates of biogenic volatile organic compounds and their determination for 192 plant species/genera in China

2017 ◽  
Author(s):  
Lingyu Li ◽  
Yaqi Li ◽  
Shaodong Xie
Keyword(s):  
Plant Species ◽  
Statistical Approach ◽  
Emission Rate ◽  
Field Measurements ◽  
Gas Chromatography Mass Spectrometry ◽  
Emission Rates ◽  
Crop Species ◽  
Volatile Organic ◽  
Monoterpene Emission ◽  
High Emission

Abstract. To obtain more and accurate biogenic volatile organic compound (BVOC) emission rates for more plant species in China and further improve the accuracy of emission rates used in BVOC emission inventories, we conducted field measurements and developed a statistical approach for estimating representative emission rates. We performed field measurements of BVOC emissions from 50 plant species at nine locations in China using our established semi-static enclosure system. The emissions of 102 VOCs, including isoprene, α-pinene, β-pinene, and other VOC species, were analyzed with a custom-built online gas chromatography-mass spectrometry/flame ionization detector system. From the results, broadleaf trees were the greatest potential emitters of isoprene, while needle-leaf trees emitted more pinene. Shrubs had lower isoprene and pinene emission potentials, but higher emission potentials for other VOCs. Methyl methacrylate, isopropylbenzene, isopentane, acetone, ethane, propane, toluene, and xylene were the dominant species among other VOCs, probably with high emission intensities. Therefore, their emissions should be considered in future global and regional BVOC estimation studies. Next, we summarized our field measurements along with reported emission rates from China and abroad. The emission intensity categories were produced based on statistics, with more detailed categories, accurate emission rate intervals and representative rates compared to previous studies. The results showed that the BVOC emission intensities of plants displayed different categories, such as lowest, lower, low, moderate, high, higher, and highest. The isoprene emission rate intervals and representative rates were: lowest, 0.08–0.11 and 0.1 μg C gdw−1 h−1; lower, 0.9–1.3 and 1.0 μg C gdw−1 h−1; low, 5.2–6.5 and 5.8 μg C gdw−1 h−1; moderate, 13.1–15.3 and 14.4 μg C gdw−1 h−1; high, 31.1–37.0 and 33.6 μg C gdw−1 h−1; higher, 67.2–75.1 and 70.1 μg C gdw−1 h−1; and highest, 135.1–157.6 and 142.5 μg C gdw−1 h−1. The monoterpene emission rate intervals and representative rates were: lowest, 0.08–0.11 and 0.1 μg C gdw−1 h−1; lower, 0.17–0.22 and 0.2 μg C gdw−1 h−1; low, 0.5–0.7 and 0.6 μg C gdw−1 h−1; moderate, 1.2–1.5 and 1.4 μg C gdw−1 h−1; high, 2.8–3.3 and 3.0 μg C gdw−1 h−1; and higher, 11.1–14.9 and 12.6 μg C gdw−1 h−1. Using these established emission intervals, we determined the isoprene and monoterpene emission rates for 192 plant species/genera in China, including 30 dominant tree species, 149 shrub and grass genera, and 13 crop species. These estimations would be further improved by integrating larger quantities of rigorous field measurements from China in the future.

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