Analysis and Estimation of Snowpack Properties Using CLPX Data

An analysis of snow grain size behavior with respect to other snow parameters such as snow depth, density, and temperature was performed. From this analysis, a pattern was derived which can be used to approximate the range of grain size variations. Data used in this research are from NASA Cold Land Processes Field Experiment (CLPX) in Colorado. This intensive field survey was conducted in February and March of 2002 and 2003. The measurements include the grain size, density, and temperature in different layers of snowpack profiles. The analysis of snowpack profiles showed that the snow density usually tends to increase towards the bottom of the snow. Snow density is about 0.1 kg/m for fresh snow and increase up to 0.4 kg/m for the old snow, bottom layers. Snowpack temperature increases towards the snow-ground interface ranging between -1 C to 0 C. The very top layer temperature is usually very dependent to the air temperature in the area (-6 to -8 C for our measurements). The grain size profile generally shows an increase in the snowpack profile. Fresh snow grains are around 0.1 mm which their size increases toward the lower layers of snow up to 2.5mm. It needs to be mentioned that the changes in grain size profile are not linear. In addition, there are cases where a layer of dense snow with large grain size is located between snow layers with smaller grain sizes which can be explained by melt and refreeze during the season. Overall, the snow grain size variation is highly correlated with both snow density, and temperature. The correlation is generally higher between snow grain size and snowpack temperature as compared with grain size and density. In order to better re-analyze evolution of snowpack properties, we excluded the very top layer of the fresh snow from the analysis. The results showed an increase in correlation between snowpack temperature and grain size. On the other hand, the snowpack temperature profile might be estimated by a function (possibly linear) by using the top and bottom temperature. The slope of the regression line indicates the dependency of the regression slope to the snow depth. The surface and body temperature of the snowpack can be obtained from NCDC and microwave channels. Using snowpack temperature, the grain size evolution can be approximated.