Konosuke Sugiura

Measurements of snow mass flux and transport rate at different particle diameters in drifting snow

Abstract Wind tunnel experiments were carried out to investigate the snow mass flux and the snow transport rate as functions of friction velocity and particle diameter. Friction velocities obtained with an ultra sonic anemometer was from u*=0.15 to 0.39 m/s. The number flux and the particle size of drifting snow were measured with a new snow particle counter at heights of 16 to 61 mm above the snow surface. The horizontal snow mass flux at each particle diameter d, qd, decreased exponentially with height qd∝exp(−λdz/(u*2/g)), where z is the height, g is the acceleration due to gravity and λd is a dimensionless parameter. The constant λd was independent of friction velocity, and at larger particle diameters, approached to 0.3. The total snow transport rate increased with the power (3.96) of friction velocity, but the total snow transport rate at each particle diameter showed that the power decreased with increasing particle diameter, and approached to 3.

Wind-Tunnel Measurements Of Restitution Coefficients And Ejection Number Of Snow Particles In Drifting Snow: Determination Of Splash Functions

Wind-tunnel experiments of drifting snow were carried out andsplash functions were formulated to describe probability distributions of vertical restitution coefficient, horizontal restitution coefficient and ejection number when a natural snow particle collided at a natural snow surface. The following results were obtained:(1) The vertical restitution coefficient was usually larger than unity and decreased sharply with impact angle. At smaller impact angles around 5 degrees the vertical restitution coefficient exceeded a magnitude of ten.(2) The horizontal restitution coefficient, ranging from -1 to 1.5, decreased with impact velocity, but was not clearly dependent on impact angle.(3) The ejection number amounted to five per impact and increasedwith impact velocity.(4) Three splash functions to express the probability distributions of the vertical restitution coefficient, horizontal restitution coefficient and ejection number were formulated, which will be used in future computer simulations of the snow drifting process.

Variations of the snow physical parameters and their effects on albedo in Sapporo, Japan

Abstract Continuous measurements of the radiation budget and meteorological components, along with frequent snow-pit work, were performed in Sapporo, Hokkaido, Japan, during two winters from 2003 to 2005. The measured relationships between broadband albedos and the mass concentration of snow impurities were compared with theoretically predicted relationships calculated using a radiative transfer model for the atmosphere–snow system in which different types (in light absorption) of impurity models based on mineral dust and soot were assumed. The result suggests that the snow in Sapporo was contaminated not only with mineral dust but also with more absorptive soot. A comparison of the measured relationships between broadband albedos and snow grain size for two different layers with the theoretically predicted relationships revealed that the visible albedo contains information about the snow grain size in deeper snow layers (10 cm), and the near-infrared albedo contains only surface information. This is due to the difference in penetration depth of solar radiation into snow between the visible and the near-infrared wavelengths.

Catch Characteristics of Precipitation Gauges in High-Latitude Regions with High Winds

Abstract Intercomparison of solid precipitation measurement at Barrow, Alaska, has been carried out to examine the catch characteristics of various precipitation gauges in high-latitude regions with high winds and to evaluate the applicability of the WMO precipitation correction procedures. Five manual precipitation gauges (Canadian Nipher, Hellmann, Russian Tretyakov, U.S. 8-in., and Wyoming gauges) and a double fence intercomparison reference (DFIR) as an international reference standard have been installed. The data collected in the last three winters indicates that the amount of solid precipitation is characteristically low, and the zero-catch frequency of the nonshielded gauges is considerably high, 60%–80% of precipitation occurrences. The zero catch in high-latitude high-wind regions becomes a significant fraction of the total precipitation. At low wind speeds, the catch characteristics of the gauges are roughly similar to the DFIR, although it is noteworthy that the daily catch ratios decreased mo...

Grain size dependence of eolian saltation lengths during snow drifting

Eolian saltation, a primary process in the transport of fine granular material by wind, produces a variety of geophysical effects on Earth and other planetary surfaces. Wind-tunnel experiments were carried out to investigate the dependence of saltation on grain size. The saltation length of snow particles was estimated at size intervals of 0.05 mm in diameter by measuring local vertical mass fluxes in 17 snow collectors arrayed at the lee end of the snow surface. The measured mean saltation length of snow particles of 0.01–1 mm in diameter ranged from 0.1 to 1.0 m at wind velocities of 5–10 m/s. Mean saltation length decreased with increasing diameter and decreasing wind speed. We suggest that the probability of the saltation length of a particle at each diameter is described by a monotonically decreasing distribution function, that is, the shorter the saltation length, the higher the frequency of its occurrence. One ramification of this distribution is that the mean saltation length does not imply the dominance of saltating particles of this length.

Response of glaciers in the Suntar―Khayata range, eastern Siberia, to climate change

Abstarct Following an International Geophysical Year project, we conducted meteorological observations during 2004–07 around the Suntar–Khayata range in eastern Siberia, where a strong temperature inversion exists throughout the winter. The temperature on the flat plain around Oymyakon (~700ma.s.l.) was ~20°C lower than that in a glaciated area located at ~2000ma.s.l. The inversion remained stable from October to April due to the Siberian high. Snowfall was limited to the beginning and end of winter. The stable conditions prevented atmospheric disturbances and inhibited snowfall during midwinter. From 1945 to 2003, glaciers in the Suntar–Khayata range retreated, with an area reduction of 19.3%. To assess this retreat, we estimated the response of the glaciers to climate change. According to US National Centers for Environmental Prediction (NCEP) data, the temperature in this region increased by ~1.9°C over 60 years. By calculating snow accumulation and ablation, the sensitivity of the equilibrium-line altitude (ELA) to the temperature shift was evaluated. We estimated snow precipitation based on precipitation at <0°C and ablation using the degree-day method. By these estimates, the ELA of Glacier No. 31, assumed 2350 m at present, could rise ~150m if temperature rises an average of 1°C. Furthermore, a 1.8°C temperature rise could cause the ELA to rise to 2600ma.s.l., removing the accumulation zone. With no accumulation zone, the glacier body would decrease, roughly halving in volume after ~400 years.

The Splash Function for Snow From Wind-Tunnel Measurements

Abstract In wind transport of snow, horizontal momentum is extracted from the mean wind flow and transferred to the snow grains. Upon colliding with the surface the grains can bounce and eject further grains in a process known as splashing. How efficiently the horizontal momentum is converted to vertical momentum in the splash process is the determining factor for mass-transport rates. This paper discusses wind-tunnel experiments performed to calculate the splash function for snow particles. The data are used to develop a new splash function. Particular care is taken to include correlations in the data such as between ejection velocity and ejection angle. The new splash function includes these correlations, and its parameters are related to physical properties of the bed and snow.

Large-scale characteristics of the distribution of blowing-snow sublimation

Abstract To consider the large-scale characteristics of blowing-snow sublimation and its importance in the hydrological cycle in the cryosphere, we investigated the sublimation of blowing snow particles on a global scale using the global datasets of the European Centre for Medium-RangeWeather Forecasts (ECMWF) re-analysis data and the International Satellite Land Surface Climatology Project (ISLSCP) Initiative I data for 1987. The sublimation fluxes of blowing snow particles were estimated globally with 2.5˚ resolution at 6 hour intervals. We found that the sublimation of blowing snow particles occurs more widely in the Northern Hemisphere than in the Southern Hemisphere, does not increase monotonously with latitude, and becomes more active in the polar coast regions and highlands, although the annual mean sublimation fluxes of the Northern and Southern Hemispheres are almost equal. In addition, we confirmed the characteristic seasonal changes in the area of sublimation in the Northern Hemisphere. Although we need to incorporate continuous parameters from systematic ground-based studies of the structure of blowing snow in specific fields to reduce uncertainty regarding the characteristics of blowing snow, our results point to a need to review the current understanding of the hydrological cycle.

Validation results of ADEOS-II/GLI snow products

Two types of snow grain sizes and mass concentration of snow impurities were made with ADEOS-II/GLI data from April to October in 2004. In general, both of retrieved snow parameters took lower values in the high latitudinal areas and low temperature areas. For the calibration of the sensor and the validation of the algorithms, several field campaigns were carried out in Alaska and eastern Hokkaido, Japan. Based on snow pit work, the retrieved snow grain size using the channel combination at 0.46μm and 0.865μm agreed with the measured values averaged over a snow layers from surface to several-cm depth. However, the satellitederived grain sizes from 1.64μm-channel, which is expected to be sensitive to surface snow grain size, were generally smaller than those measured at the ground. Possible reason of this underestimate is sun crust (thin ice layer created by solar radiation under clear sky) at snow surface, which increases the snow reflectance by additional specular reflection, in the case of granular (wet) snow during melting reason. The mass concentration of snow impurities retrieved from the satellite data was lower than the measured one. This is because snow impurities are assumed to be soot in the remote sensing algorithm, whereas the main composition of in situ measured impurities was generally found to be mineral dust in our sites.

Spatial Characteristics of Rainfall at Sparsely Distributed Station Network over the High-Latitude Mountainous Regions in Eastern Siberia

To describe the spatial characteristics of rainfall at sparsely distributed measurement network over the high-latitude mountainous regions in eastern Siberia through ground-based observation, rainfall observations were performed using non-recording standard rain gauges. Such standard rain gauges have been used over the years to measure annual rainfall at six sites from the Suntar Khayata Range to Oymyakon and 12 sites along the Kolyma Highway from Magadan to Agayakan. Relational expressions of rainfall were obtained and observation data from these gauges clearly showed that the corrected rainfall in these areas depends on altitude, that the rainfall increased slightly with an increase in altitude, and that the increased ratio of rainfall due to altitude decreased with an increase in the distance from the nearby coast.