The Cold Land Processes Field Experiment (CLPX): Field Data Collection

Field measurements for the NASA Cold Land Processes Experiment (CLPX) included a broad spectrum of snowpack properties, soil conditions and site characterizations over a broad range of physiographies at the Colorado study sites. A regional study area encompassing an area 215-km x 170-km in north-central Colorado was divided into three 25-km x 25-km Meso-Cell Study Areas (MSA). The MSA sites were selected to represent a forested area with moderate snow depths and significant topographic variability (Fraser), deep snow with mixed forest types (Rabbit Ears) and low snow accumulation with minor topography and vegetation (North Park). Three 1-km x 1-km Intensive Study Areas (ISA) were chosen in each MSA to represent a wide range of topographic, vegetative, meteorologic and hydrologic conditions within each MSA. The three basic environments found in each MSA, along with the additional variation found within the ISAs, represent a large portion of mid- to high-latitude seasonally snow-covered regions of the Earth. In order to characterize these sites for research related to the CLPX, an intensive sampling program was designed and carried out during two field experiments with concurrent airborne data collection. Sample design for all parameters was carried out with future modeling efforts and validation of remotely sensed data in mind. Field data collection occurred during two Intensive Observing Periods (IOP) from February 19-25 and March 25-April 1, 2002. Snow depth was sampled at 500 locations in each ISA in a stratified random sampling approach that included transects of variable resolution and orientation. Additional measurements collected at depth transects included snow surface roughness and snow surface wetness. Snow density was measured in snow pits excavated at 16 locations in each ISA selected by a stratified random sample. The same relative sample locations were used in all nine ISAs. Additional measurements collected at each snow pit site included basic stratigraphy (grain size and type), snow temperature, snow/soil interface temperature, soil moisture in the top 20 cm, canopy cover, snow surface roughness and snow surface wetness. A small number of sample locations were not measured due to avalanche danger in the Fraser MSA. Preliminary results suggest that the sites were well chosen to characterize the hydrologic variability. The 2002 water year was characterized by low snowfall, with subsequent meteorology that led to one of the lowest stream flow years on record for the region. Snow depth and density showed high spatial variability both within ISAs and between ISAs and MSAs. The spatial distribution of water equivalent reflected these high variances. The desired temporal change was reflected in the data where the first IOP showed a cold snowpack and the second IOP showed a transitional snowpack with dry snow in some areas and the onset of melt in other areas. Sampling in the 2003 water year will follow the same protocol established in 2002 with two more IOPS at approximately the same dates. In addition, each ISA has been instrumented with a full suite of meteorological instruments at the center of the 1-km study areas.