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The collection efficiency of a typical precipitation gauge-shield configuration decreases with increasing wind speed, with a high scatter for a given wind speed. The high scatter in the collection efficiency for a given wind speed arises in part from the variability in the characteristics of falling snow and atmospheric turbulence. This study uses weighing gauge data collected at the Marshall Field Site near Boulder, Colorado, during the WMO Solid Precipitation Intercomparison Experiment (SPICE). Particle diameter and fall speed data from a laser disdrometer were used to show that the scatter in the collection efficiency can be reduced by considering the fall speed of solid precipitation particles. The collection efficiency was divided into two classes depending on the measured mean-event particle fall speed during precipitation events. Slower-falling particles were associated with a lower collection efficiency. A new transfer function (i.e., the relationship between collection efficiency and other meteorological variables, such as wind speed or air temperature) that includes the fall speed of the hydrometeors was developed. The root-mean-square error of the adjusted precipitation with the new transfer function with respect to a weighing gauge placed in a double fence intercomparison reference was lower than using previously developed transfer functions that only consider wind speed and air temperature. This shows that the measured fall speed of solid precipitation with a laser disdrometer accounts for a large amount of the observed scatter in weighing gauge collection efficiency.

We investigated the influence of post-collection changes and snow gauge undercatch on the stable isotopic compositions of winter precipitation. Post-collection changes by evaporation or sublimation can be severe, and may be minimized, but not eliminated, by emptying collection gauges immediately after snowfall. Snow gauge undercatch caused two main effects: a small direct effect caused by preferential separation of snow particles during snowfall, and a much larger effect on the measured stable isotopic compositions of average annual precipitation as a result of under representation of winter precipitation. Despite these effects, however, we found little change to calculated local meteoric water lines (LMWL) for Saskatoon, SK, Canada. A comprehensive 27-year LMWL for Saskatoon which incorporates these effects can be described by

Accurate snowfall measurements are critical for a wide variety of research fields, including snowpack monitoring, climate variability, and hydrological applications. It has been recognized that systematic errors in snowfall measurements are often observed as a result of the gauge geometry and the weather conditions. The goal of this study is to understand better the scatter in the snowfall precipitation rate measured by a gauge. To address this issue, field observations and numerical simulations were carried out. First, a theoretical study using finite-element modeling was used to simulate the flow around the gauge. The snowflake trajectories were investigated using a Lagrangian model, and the derived flow field was used to compute a theoretical collection efficiency for different types of snowflakes. Second, field observations were undertaken to determine how different types, shapes, and sizes of snowflakes are collected inside a Geonor, Inc., precipitation gauge. The results show that the collection efficiency is influenced by the type of snowflakes as well as by their size distribution. Different types of snowflakes, which fall at different terminal velocities, interact differently with the airflow around the gauge. Fast-falling snowflakes are more efficiently collected by the gauge than slow-falling ones. The correction factor used to correct the data for the wind speed is improved by adding a parameter for each type of snowflake. The results show that accurate measure of snow depends on the wind speed as well as the type of snowflake observed during a snowstorm.

Rainfall-induced failures of natural and artificial slopes such as cut slopes, which are subjected to freezing and thawing, have been frequently reported in Hokkaido, Japan. In particular, many failures occur intensively from spring to summer seasons. Despite numerous field studies, explanation of their mechanical behavior based on in situ data has not yet been completely achieved due to the difficulty in grasping failure conditions. This study aims at clarifying the aspects of in-situ volcanic slopes subjected to rainfall and freeze-thaw action. The changes in soil moisture, pore pressure, deformations, and temperatures in the slope were investigated using soil moisture meters, tensiometers, thermocouple sensors, clinometers, settlement gauges, an anemovane, a snow gauge, and a rainfall gauge. The data generated from these measures indicated deformation in the slope examined mainly proceeded during the drainage process according to changes in soil moisture. Based on this data, a prediction method for failures is discussed in detail.

This paper provides an updated fresh snowfall water equivalent adjustment factor (ρswe) map for Canada to allow the estimation of solid precipitation amount from ruler measurements of the depth of freshly fallen snow, which has been the standard method for measuring snowfall since Canadian climate measurements began in the middle of the nineteenth century. The ρswe map is created based on the comparison of corrected solid Nipher gauge precipitation to snowfall ruler depth measurements at 175 stations with more than 20 years of concurrent observations. The Nipher gauge correction process involved a careful analysis of station metadata to obtain precise information on anemometer heights and the dates that Nipher gauges were activated. The updated fresh snowfall water equivalent adjustment factor map allows estimates of ρswe to be obtained for all long‐term climate stations in Canada. The spatial pattern is consistent with processes influencing the density of fresh snowfall and its initial settling ...

To develop a more reliable means for measuring precipitation in the Arctic, daily solid precipitation in Barrow, Alaska, was measured from October 24, 2002 to January 14, 2003 using a Double-Fence Intercomparison Reference (DFIR), which is the World Meteorological Organization (WMO) reference standard for solid precipitation measurements. Furthermore, a new approach using a snow particle counter (SPC) that outputs the number flux of snow particles without directly catching them was introduced. The correction procedures for wind, wetting, evaporation losses, and trace amounts were applied on a daily basis to the DFIR precipitation. The total corrected DFIR precipitation (61.35 mm) was found to be 1.47 times the uncorrected measurement (41.65 mm). The SPC-estimated precipitation measurements correlate well (r2 = 0.72) with the corrected DFIR measurements, suggesting that precipitation gauges that do not directly catch snow particles are effective in low-precipitation areas such as the polar regions.

We need water equivalent unit data of snowfall for the purpose of forecast and hydrology related research area. This study developed new method of automatic recording snowfall as weight unit. The instrument designed for measuring weight of snowfall by stain-gauge loadcell. Field test of instrument carried out at Daegwallyeong Obs. Station from 22 Jan. to 22 Feb. 2007. During observation period there is 15.3 cm snow depth and 16.0 mm of accumulated water equivalent depth at Daegwallyeong Obs. Station on 13 to 14 Feb. 2007. But the instrument of this study recorded 22.1 mm of water equivalent depth. It is not easy to explain difference between Daegwallyeong and this study. Because this study is only one case of comparison of snow measurement and there is very little amount of snow observation research. The density of snowfall calculated from 0.09 to from the observation data of 13 to 14 Feb. 2007. There is high relation between radar echo and snowfall amount measured by weight unit. It can supports forecast of snowfall and development of numerical model for forecast.

This paper describes and evaluates an algorithm for nowcasting snow water equivalent (SWE) at a point on the surface based on a real-time correlation of equivalent radar reflectivity (Ze) with snow gauge rate (S). It is shown from both theory and previous results that Ze–S relationships vary significantly during a storm and from storm to storm, requiring a real-time correlation of Ze and S. A key element of the algorithm is taking into account snow drift and distance of the radar volume from the snow gauge. The algorithm was applied to a number of New York City snowstorms and was shown to have skill in nowcasting SWE out to at least 1 h when compared with persistence. The algorithm is currently being used in a real-time winter weather nowcasting system, called Weather Support to Deicing Decision Making (WSDDM), to improve decision making regarding the deicing of aircraft and runway clearing. The algorithm can also be used to provide a real-time Z–S relationship for Weather Surveillance Radar-1988...

The goal of this project was to develop adjustment procedures to use daily resolution data to generate high quality time series of precipitation and to perform regional trend analyses on the resulting datasets. A total of 69 locations, most with data covering the period 1900–96 were used. Data availability in much of the Canadian Arctic was restricted to 1948–96. By using daily data, improved corrections to precipitation data, not practical with monthly data, could be implemented. For each of three rain gauge types, corrections to account for wind undercatch and evaporation were implemented. Gauge specific wetting loss corrections were applied for each rainfall event. For snowfall, ruler measurements were used throughout the time series, to minimize potential discontinuities introduced by the adoption of Nipher shielded snow gauge measurements in the mid‐1960s. Density corrections based upon coincident ruler and Nipher measurements were applied to all ruler measurements. Where necessary, records ...

Routine snow survey and snow gauge data provided by weather stations establish snow-on-the-ground and snowfall time series but they lack a spatial dimension. Of particular importance to arctic hydrology is the end-of-winter snow conditions. For micro-scale investigations of spring breakup, slope runoff generation or gully sediment production, detailed mapping of the late winter snow cover is required. On a meso-scale, terrain exerts the principal control on snow distribution so that for catchment snowmelt and water balance studies, terrain units should be distinguished and the snow water equivalent for various terrain types obtained through ground survey. Regional dispositon of the snowline or early melt zones can be mapped from satellite but ground truthing is necessary if the quantity of snow needs to be known. Passive microwave sensor offers the potential of mapping the snow water equivalent after the signals are calibrated by ground snow data. Spatially distributed but areally integrated rather than point snow data are appropriate for macro-scale hydrological investigations. Field studies carried out in the Canadian Arctic Islands over the past decades provide the database and the experience needed to recommend appropriate methods for acquiring snow cover information compatible with the scale and the subject of enquiry.

Rainfall-induced failures of natural and artificial slopes, such as cut slopes or embankments subjected to freezing and thawing, have been frequently reported in Hokkaido, Japan. Despite of numerous field studies, mechanical behavior based on in-situ data has not been completely clarified yet. This study aims at clarifying mechanical behavior and failure mechanism of slopes using a full-scale embankment constructed by volcanic soils. Firstly, a series of model test was performed on smallscale volcanic slopes to reveal failure mechanism. Thereafter, a trial embankment of 5 m in height, 12 m in length, 2 m in width and the angle of 45° was constructed using the same volcanic soil as that of the small-scale slope. The changes in soil moisture, temperatures in the embankment were investigated using soil moisture meters, a thermometer, a snow gauge and a rainfall gauge. On the basis of those data, in this paper, a prediction method on slope failure is discussed in detail.

The Advanced Microwave Scanning Radiometer-EOS (AMSR-E) launched in 2002 aboard NASA's Aqua satellite, has improved spatial resolution capabilities compared with previous passive microwave instruments. Snow depth retrievals from AMSR-E are tested with GEWEX (Global Energy and Water Experiment) Asian Monsoon Experiment (GAME) and Coordinated Enhanced Observing Period (CEOP) data. Level 1B AMSR-E brightness temperatures are used in the study. Seven acoustic snow gauge sites recorded daily snow depth within a 100 km times 100 km domain located near Yakutsk in Siberia. These point snow depth measurements span a period between October 2002 and February 2003 and are used to test AMSR-E ascending and descending retrievals. The paper describes the accuracy of the snow depth estimates compared with the GAME/CEOP Siberia sites. It also assesses how World Meteorological Organization/Global Telecommunication System meteorological snow data from a station at Yakutsk compare with the GAME/CEOP site snow depth data and AMSR-E estimates

A large mass of water is stored in snowpack on mountains during winter and it is very important to estimate its volume before the melting season begins. The authors describe a way to estimate snowpack water equivalent combining satellite images and point observations. Snow covered area extension is obtained by remote sensing techniques; snow gauges give measurements of snow thickness and density at monitoring stations. Soft classifications are performed in order to have careful infonnation about snow presence on the ground. In fact soft classification of satellite images supplies pixels membership degrees to snow class that are good evaluations of the snow presence inside pixels. Simultaneous local measures of snow thickness are then used to calibrate a statistical model describing snow thickness as a function of terrain altitude and aspect. A calibrated model allows estimation of the snow thickness pixel by pixel and so estimation of pixel by pixel snow volume too. Snow density information is added to transform snow volume into water volume. The described method is applied to estimate water equivalent on the Adda river basin for April 1996.

Snow, as one form of precipitation, plays a very significant role in the water cycle and in water resource management. However, the spatial and temporal variations in snow cover complicate the monitoring of this role. Field measurements, especially in mountainous areas, are often impossible without the use of new technologies. In this study, moderate resolution imaging spectroradiometer (MODIS) at 500-m resolution has been used to provide a map of snow cover area (SCA) using the normalized difference snow index in the central Zab basin in West Azerbaijan, Iran. Eight-day composite data are used to minimize the effect of cloud cover and maximize the amount of useable SCA images. The importance of snow in this basin was simulated using a snowmelt runoff model (SRM) as one of the major applications of daily MODIS-8 images based on various algorithms. The location of snow gauge stations on digital elevation model (DEM) of central Zab basin extracted from advanced space borne thermal emission and reflection radiometer images by using bilinear interpolation method. The SCA index, along with spectral threshold on bands 2 and 4, provided a stable relationship for extraction of the snow cover map in the study area. The simulated flow in the water year 2010 to 2011 had a coefficient of determination (R2) of 0.8953 and a volume difference (Dv) of 0.1498%, which shows a good correlation between the measured and computed runoff by using the SRM in the central Zab basin. The first results of the modeling process show that MODIS snow covered area product can be used for simulation and measuring value of snowmelt runoff in central Zab basin. The studies found that the SCA results were more reliable in the study area.

During the period from December 1977 to May 1978, continuous observations of water equivalent of snow were carried out at four different sites distributed between sea level and 1440 m elevation, using the attenuation of cosmic-ray-produced neutrons through snow cover. Day-to-day variations of the snow water equivalent, thus determined, demonstrate an excellent agreement with those obtained by snow core sampler and other methods. For this cosmic-ray snow gauge, the counting statistics are the predominant source of experimental error, which is found to be a few percent of the total value of snow water equivalent. It is emphasized that the cosmic-ray snow gauge is very useful to determine the absolute value of snow water equivalent in place of the existing snow sampler or other methods. Some uncertainties in determination due to primary cosmic-ray modulations and soil moisture content are discussed.

During the period from December 1977 to May 1978, continuous observations of water-equivalents of snow depths using cosmic-ray snow gauges were carried out at three locations : Mt. Iwakisan, Takada and Mt. Arimine. It is shown that day-to-day variations of water-equivalent thus obtained are in good agreement with those measured by conventional instruments such as a snow sampler or a gamma-ray snow gauge. Discussions are given of the snow melting rate and the snow density, and it is suggested that this new snow gauge may attain an importance equivalent to that of the snow sampler method.

A new technique for the determination of the water-equivalent of snow using cosmic ray neutrons is described on the basis of a definite relation between snow-water depths and neutron fluxes measured under snow covers. Several environmental and geographical effects on cosmic ray neutrons, including galactic cosmic ray changes, are discussed quantitatively with respect to the experimental accuracy of water-equivalent snow-water depths determined by this technique. It is shown that most of these effects introduce no serious and fundamental errors on the water-equivalent determination, except for the possible influence of soil moisture content upon neutron fluxes on the ground level where the snow gauge sensor is installed.

Application of the water absorption character of cosmic-ray neutrons to the determination of the water equivalent depth of a snow cover is shown. We call this device the cosmic-ray snow gauge. The attenuation curves of the cosmic-ray snow gauge set under or in water or snow are experimentally obtained. Continuous field observations of the snow depths during four snow seasons demonstrate the effectiveness of the present device even for a snow cover of more than 1 m water equivalent, where the relative accuracy is found to be a few percent of the water depth. Possible effects of primary cosmic rays, barometric pressure and water content of soil upon the determination of snow depths are discussed.

Continous refinement and improvement were applied on the established basic design of cosmic-ray snow gauge. The following technical problems have been improved.1) Minimized power consumption which is essential when the snow gauge is used at remote or mountain sites where no commercial electric power is obtainable.2) Automatic correction for the barometric pressure effect on cosmic rays.3) A system for the real-time indication of the water-equivalent of snow depth to round of the statistical fluctuation inherent to cosmic rays.As a result, the power supply necessary for a sensor part of the instrument is less than 30 mW, and a digital printer can give hourly values of the water-equivalent of snow depths in units of centimeters.

For hydroelectric power generation it is necessary to estimate the quantity of melt water flowing into the reservoir during the snow-thawing season. Up to this time the estimation was made with the snow gauge using radioactive isotope Co60, but this method required strict control over the preservation and handling of the radioactive substance. Therefore, a new method for snow detection, using photoelectric effect instead of Co60, was developed, and has been tested since 1973 in the area around Lake Towada. In the new method, cadmium sulfide photoelectric cells are placed in a transparent polymethyl-methacrylate pipe, and the depth of snow is estimated by the amplitide of light detected. The weight of the snow must be converted into the corresponding amount of water, and a little error may be caused by the conditions of snow. Nevertheless, this method has advantages in that the equipment is simpler, the reliability is higher, and it is free of troublesome maintenance or handling. The method can be applied to various types of robot snow gauge.

This partly bibliographical study starts with a review of satellites transmitting useful data for snow surveys and draws attention to difficulties experienced in converting raw data into usable information (e.g. extent of snow-covered areas). Examples are then described of reports published by mostly North American authors, in which satellite data are related to hydrological variables. Most of the information originates from a NASA seminar at South Lake Tahoe in August 1975 and a WMO seminar in Geneva in October 1976, on the subject of "Satellite surveys of snow cover for hydrological forecasting". This study ends with a discussion of present use of ground-based measurements by "Electricite de France" for forecasting seasonal precipitation supplies and the types of additional service teledetection could provide. It seems unlikely that teledetection from satellites will ever replace ground-based measurements as a means of evaluating the water equivalent of the snow burden in the Alps or Pyrenees while it is accumulating in winter, i.e. calculating probable snow melt inflows sufficiently far ahead. Satellite pictures of snow-covered areas do not become representative of the actual storage volume until several weeks after the snow starts to melt, i.e. not before the 15th May in the Alps, whereas Electricite de France forescasts from ground-based measurements become effective as from the 1st February. The economic importance of such advance notice for water power storage management is the reason why such considerable efforts are being made to automate daily snow depth telemeasurements (the remote-indicating snow gauge with a moving horizontal beam provides a complete decimetre-by-decimetre density profile). In future, and on the assumption that the frequency and accuracy of satellite pictures will substantially improve, teledetection should provide an effective means of improving short-term forecasts by analysis in the visible and infra-red ranges of the fringe areas of the seasonal snow cover while it is melting : contours, albedo, surface temperature. Hyperfrequency teledetection at wavelengths from 1 mm to 300 mm also seems to offer reasonably hopeful prospects; such frequencies pass through clouds and can provide information on the depth of dry snow, but are reflected by wet snow. With existing satellites the only application of teledetection capable of providing useful information, for observation of the short-term behaviour of floods originating from snow and/or rain, is the daily picture of snow-covered areas without pronounced relief features between altitudes of 800 m and 1200 m in the Massif Central and Jura mountains from NOAA satellites on a polar orbit, and perhaps also METEOSAT.

電子天秤とマイクロコンピューターを使って重量測定から降雪強度を求める雪量計を試作し, 二冬間札幌で使用した. この装置の特徴として, 1) 雪を水に変換して測定する従来の溢水式や温水式の雪量計に比べ, 雪の重量を直接測定するタイプであるから, 時間の遅れ, 加熱による蒸発の誤差がない.2) 任意の時間間隔でデータの収録ができる.3) 天秤の最小感度0.1g, 受雪部の直径35Cmで, 0.062mm/hrの微小な降雪強度を測定できる.4) 集計時間間隔を一分間にした場合, 24時間まで連続してデータの収録ができる.5) データをデジタルで収録しているので平均化, グラフ化など解析処理が容易である.6) 防風ネット二枚, 防風板一枚で三重に雪量計を囲ったので, 風の影響を受けにくく, 降雪の補足率が高い.などが挙げられる.他の測定値と比べた結果, 数分の時間スケールで細かく変動する降雪現象を, この雪量計の降雪強度の変化からみることが出来た.従ってこの雪量計を使うことによって水平的に微細な構造をもった降雪雲からの降水強度の時間変化を詳しく調べることができる.

In the past decade there have been several research efforts in the United States to develop a method of measuring the water equivalent (total water content) of a snow pack that will allow the automatic recording and transmission of the record from remote mountain locations. The methods include: (1) an electrical method utilizing capacitance properties of the snow between two electrically-insulated electrodes projecting up through the snow pack; (2) a radioisotope snow gauge that utilizes the attenuation of gamma rays between a source positioned above the snow pack and a counting system at the snow-ground interface; and (3) a pressure pillow in which the change in pressure within a fluid-filled flat pillow reflects the weight of the snow directly above the pillow. The accuracy of the gauges is discussed as well as the location of use and experimentation, and the method of recording and transmitting the record. The object has been to improve on the system of manual snow-tube measurements hitherto employed.

The study of the radioactive snow gauge has been undertaken in Grenoble in 1962 with the objective to develop, up to the routine operation, an automatic solid state electronic snow gauge, radio transmitting every day. 4 units of a first design, with steady vertical radioactive beam have been operated from 1964, but the limitation of the measurable depth to 4 meters of snow, 1,2 meter of water, was soon found too low in the French Alps. A new type of gauge, with moving horizontal beam, profiling the snow pack, was designed in 1965, and evaluated through the last two years—During the measuring cycle, the source (30 millicuries of Cesium 137) and the G.H. detector are moving up at the same level inside two vertical pipes whose distance is 60 cm and height 6 meters; their speed is related to the pulse rate of the detector. One radio signal is emitted each decimeter during the motion. As soon as the team energes from the snow, it stops and returns back to its starting position under the ground level—t...

THE meteorologist of my expedition has unfortunately given a somewhat incorrect idea about the snow conditions at Cape Adare. He reports, namely, that there is a very small snow fall at the sea-level. This is, in my opinion, not the case. But his mistake is excusable and easily explicable; of course, being a young Tasmanian and not previously having seen ice and snow, a devotee to his instrument, took down in his note book the evidence of a usual snow gauge. Snow seldom or never fell in the Antarctic except during heavy gales, and it must be clear to anybody familiar with snow that a snow gauge of the ordinary type is worse than useless during heavy gales. Although Cape Adare itself and the peninsula on which we lived were almost free of snow in the open, we had more than ten feet of snow to the leeward of our hut at Camp Ridley, and undoubtedly there would have been still more had the huts been higher. This indicates, of course, that much snow fell, but it was blown away as well from the promontory at Cape Adare as from the unfortunate snow gauge. In my opinion a very heavy snow fall takes place within the Antarctic circle. And I believe that the strong gales within the Antarctic circle generally are local and that these snow bared dark pronmontories are the very homes of the Antarctic gales, while those places where no dark land is to be seen probably are unmolested by great atmospheric disturbances and are therefore covered in heavy snow. From time to time in the pack ice I have passed through distances where the ice was covered in several yards of loose snow. This I noticed as well on my first voyage in 1894 as during my last expedition. I will therefore use the opportiffiity to warn the coming expeditions from not providing against the difficulties which a very heavy snow fall incurs for sledge parties within the Antarctic circle.