Lateral flow refers to the flow of water moving parallel to the slope in a snowpack. This process causes nonuniform infiltration and local concentration of water from the snow base into the ground. Consequently, this affects the occurrence of snowmelt disasters and the timing of river runoffs. Studies of lateral flow in snowpacks have been performed through observations and experiments in the field. Recently, there has also been progress in the numerical modeling of water infiltration in slope snow. In this paper, the knowledge of field experiments, observations, and measurement technics for the process of water infiltration in slope snow are summarized to understand the relationship of their process to the modeling.

We applied several fast-imaging sequences on the water distribution in wet snow using Cryospheric Magnetic Resonance Imager/Imaging (C-MRI). Most of the fast-imaging sequences used for other objects require extremely detailed optimization to obtain high quality images suitable for analysis. However, it is difficult to apply them to C-MRI. Therefore, we have shortened the scanning time by 30 % by applying the standard MRI sequences with compressed sensing that reduces scanning time with Nuclear Magnetic Resonance signal under sampling. Moreover, we have shortened the scanning time by setting an MRI sequence repetition time shorter than the T1 relaxation time of water. As a result, the imaging time to acquire a 3D image of a 51.2 mm cube with a spatial resolution of 0.4 mm was 3.3 min. A guideline for selecting the optimum MRI sequences for measuring the water distribution in wet snow was provided by comparing the imaging time, signal to noise ratio, and area ratio for MRI phantom of each image using various MRI sequences.

Methods for measuring the water content of snow containing salt, which contains liquid water at subzero temperatures, were investigated. Since the temperature of wet snow containing salt is below freezing, a conventional method using a calorimeter underestimates the water content. Two methods were devised: one was to use a calorimeter and add a process of correction for the specific heat from the subzero temperature to 0 °C，and the other was to calculate the water content from the theory of freezing-point depression using only the temperature and salinity of the sample without using a calorimeter. The dataset of water content of snow obtained by both methods agreed well with an error of 3 % for the natural snow samples and artificially salted snow samples. While the former method is rather complex, it is rigorous and applicable for all the salt-contained samples. On the other hand, the latter method is useful because of its simplicity, but it is not applicable when the temperature is above －1 °C．These methods were applied to the measurement of the water content of snow on the Arctic sea ice and on the ice of Saroma-ko lagoon, and it was confirmed that they can be applied to a wide range of conditions.

When it snows in the Maibara / Sekigahara area，the Tokaido Shinkansen performs “driving speed down” and “wetting snow by sprinkler” to prevent snow accretion on the car body due to the soaring snow.

Although these snow accretion preventive measures are effective during the daytime when the temperature rises，there is a problem that the snow accretion preventive effect is reduced at minus air temperatures in the early morning.

The reason for this was presumed to be due to the reduction in the effect of wetting snow by water sprinkling at minus air temperatures.

In this study, we confirmed this through laboratory tests and outdoor observations, and developed a sprinkler that effectively wets and turns the snow surface into wet snow at minus air temperatures.

On-site verification was also conducted along the Tokaido Shinkansen, and its effectiveness was confirmed to some extent.

The prism faces of a new snow crystal as a thin plate have been found to grow not only by direct injection of water molecules in the diffusion field but also by adjoining surface transference of water molecules from basal faces. The paper investigates the adjoining surface transference of water molecules from a basal face to prism faces in the growth of dendrites photographed in two experiments. The investigation reveals the following: one of the two basal faces of a growing dendrite is always observable because it has an important role in transferring surface water molecules to prism faces; in a supercooled cloud of about －15 °C，a dendrite typically grows from one of thin plates protruding from a frozen water droplet; the tips of a growing dendrite can remain thin when the growth conditions are kept almost constant; rimed cloud droplets interrupt the growth of prism faces of a dendrite; and generation of ridges on a dendrite is also explicable. These results conclude that the adjoining surface transference of water molecules from a basal face to prism faces is an important factor for the growth of prism faces of a dendrite.