The Lena river is one of the four largest rivers flowing into the Arctic Ocean. It has a complicated hydrological system that is affected not only by the amount of precipitation but also by the timing of ice break-up. To determine the mechanisms of runoff formation, a numerical analysis based on modeling was carried out for the period 1986–2000. The results show that (1) the timing of flood rise and peak can be modeled at Tabaga, which represents the upper and central portions of the Lena river; (2) river-freeze processes delay the spring, snowmelt-dominated flood by about 23 days; and (3) the difference between the break-up dates at Tabaga and Kirensk has ranged from several days to >2 months, and a maximum value of 69 days was recorded in spring 1998.

To understand the formation of hard snow in the field and its relationship to the physical parameters of snow surfaces, we carried out snowpack observations at a flat and snow-covered field in Barrow, Alaska. These observations were performed in the middle of winter and included two drifting snow events. After the end of each drifting snow event, the minimum snow surface density increased slightly with time and there was a rapid increase in the minimum snow surface hardness. There was no rain during our observations. Therefore, the strong bonds among the snow surface particles were not due to melting and refreezing; they formed because of hardening during water-vapor transport under a temperature gradient and also by exposure of the inner snow layer through erosion. As a consequence, the snow formed a hard surface following the drifting snow events.

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.

Variation of the microparticle concentration in an ice core from Mizuho station, East Antarctica, does not show the annual cycle that has been demonstrated for ice cores from Antarctica and Greenland by other authors. Possible reasons for the lack of a annual cycle are considered and two causes are suggested. (1) Semi-annual variation of microparticle concentration as observed in drift-snow. The low particle concentration in March and in August to October is not due to minor particle transport, but to the dilution of microparticles transported mainly from arid regions in the southern hemisphere through the troposphere by falling snow. (2) Discontinuous surface-layer formation. A seasonal or an annual sequence of the variation in microparticle concentration in surface snow layers may be interrupted by the absence of surface snow-layer formation.

Quite high amounts of evaporation observed on glaciers in dry Central Asia are one important component in the mass balance of glaciers. During glaciological research at West Kunlun Mountains on the northwestern Tibetan plateau in 1987, high evaporation of more than 2 mm of water per day was observed near the equilibrium line (5800–5900 m a.s.l.) in mid-summer due to dry and windy climate. Annual evaporation is estimated by a semi-empirical method using the full year meteorological data taken by an automatic meteorological station. This value shows that evaporation occupies quite a high percentage within the mass balance near the equilibrium line and on the whole glacier. Discussions will centre on comparison with evaporation data obtained on other glaciers and on the effect of such evaporation in the climate-glacier relation.

Each component of the heat balance equation was obtained independently for 24 days in winter and 8 days in summer in 1980 at Mizuho station, East Antarctica. In winter, net radiation QNR was -37.6W/m-2 , QS; +36.7W/m-2 and QC; +2.5W/m2 QL was three orders less than QS. In the summer, QNR; +l9.9W/m-2 QC;-7.4W/m’, QL ; -.SW/m-2 and Q C; .2W/m-2. In the winter cloud amount was an important factor determining the variation in heat balance components, but also variation in the strength of the katabatic wind had effect. Condensation of water vapor occurred in winter and sublimation in summer: summer sublimation had a significant effect on the heat balance. The small condensation may be due to the structure of the temperature inversion at Mizuho which is related to the katabatic wind. The present results show that at Mizuho, the radiation loss Q NR and Q S which compensate it is larger than at any other site on the continent excluding the coastal stations.

This paper describes the results of snow drift measurements made on a strong katabatic wind slope at Mizuho Station (70°42.6’S, 44°18.9’E; 2230 m above mean sea level) in East Antarctica. From the vertical profile of the mass flux of blowing snow up to 28 m above the snow surface under conditions of snow fall, the snow fall densitities have been estimated as asymptotes of the profile (Fohn 1980). Snow fall densities as asymptotes were estimated between 8x10-6 and 8xl0-5 kg/m3. Assuming a fall velocity of blowing snow particles as 0.5 m/s, above values correspond to values of the vertical flux of snow fall between 2x10-3 and 1.5xl0-1 mm/h.

Solar radiation is one of the most important meteorological components in the heat balance of the glaciers and other snow and ice masses. Observed solar radiation values are generally discussed in relation to altitude, landform, geographical position of the observation point and cloud. However, as surface of snow and ice masses possess high albedo, the surface global solar radiation on snow and ice masses usually shows higher value than surrounding ground which is low albedo, due to multiple reflection between surface and cloud. This is an important factor in determination of solar radiation on snow and ice masses. When this process is prominent, surface global solar radiation will depend on the size of the snow and ice masses. This process will be investigated in two parts. One is the presentation of radiation data taken on an ice cap and surrounding ground in the northwestern Tibetan plateau. Observations show that mean daily global solar radiation was 26% higher on the ice cap than on the ground: especially on cloudy days this value exceeded 50%. The second is collaboration of radiation data on snow and ice masses of previous studies: those data will be discussed from the above point of view. The size effect of snow and ice masses on surface solar radiation will be stressed.

Scale-dependent atmosphere-glacier interactions operate over a glacier surface as the surface has different thermal and radiative characteristics from those of the surrounding ground. In order to evaluate heat supply to the glacier surface in the main ablation period, three main interaction processes are considered: advection, glacier wind, and multiple reflection of solar radiation. The amount of heat supply was calculated for the equilibrium line altitude (ELA) by assuming a simple rectangular-shaped glacier, and by applying meteorological and glaciological data for four different glaciated regions (Tien Shan, Patagonia, west Kunlun and Nepal Himalaya). The total heat supply due to the above three processes had the common tendency of being smallest for glaciers of 1 to several kilometres in length, and largest at 16 km, which was the maximum length considered in this study. Among the cases, the Tien Shan showed a daytime heat supply higher by 2.3 MJ m−2 for a 16km-long glacier compared with a small glacier 2 km in length. Relating this difference directly to ELA, an ELA approximately 300 m higher might be expected for a long glacier than a short one, assuming the same amount of solid precipitation. Glacier inventory data for China support this tendency, but the calculated value is slightly larger than that observed. The results show that there is a possibility that responses in glacier variation to climate change may be modified considerably through scale-dependent atmosphere-glacier interactions.

A mass-balance model based on the energy balance at the snow or ice surface is formulated, with particular attention paid to processes affecting absorption of radiation. The model is applied to a small glacier, Glacier AX010 in the Nepalese Himalaya, and tests of its mass-balance sensitivity to input and climatic parameters are carried out. Calculated and observed area-averaged mass balances of the glacier during summer 1978 (June-September) show good agreement, namely -0.44 and -0.46 m w.e., respectively.

Results show the mass balance is strongly sensitive to snow or ice albedo, to the effects of screening by surrounding mountain walls, to areal variations in multiple reflection between clouds and the glacier surface, and to thin snow covers which alter the surface albedo. In tests of the sensitivity of the mass balance to seasonal values of climatic parameters, the mass balance is found to be strongly sensitive to summer air temperature and precipitation but only weakly sensitive to relative humidity.

The annual evaporation of a continental-type glacier (43°05’ Ν, 86°48’ E) in the Chinese Tien Shan is estimated, based on data derived from four field observations carried out between summer 1987 and spring 1988, and data from a permanent weather station near the glacier. The evaporation during the melting and non-melting seasons is estimated as 81 mm and negligible, respectively. Assuming that the ablation is equivalent to the annual precipitation (650 mm) in 1987, estimated annual evaporation of 81 mm is 12% of the ablation and consumes 54% of the energy which causes the ablation. It can be said that evaporation suppresses ablation by 50% in comparison with the condition in which there is no evaporation.

The influence of fluctuations of air temperature and humidity on the ablation of the glacier were evaluated. Changes in temperature and humidity cause larger changes in ablation of glaciers in a cold and dry climate. The influence of humidity change is very important to glaciers located in a relatively warm environment.