DOI: 10.5061/dryad.qv9s4mwr2
title: Fresh snow, peak accumulation, and ablation-Sun Cup snow surface datasets for evaluation of geometry aerodynamic roughness code

description: These three datasets have been prepared to assess a computer code for the
 computation of the geometric-based aerodynamic roughness length z0. using
 the Lettau (1969;
 https://doi.org/10.1175/1520-0450(1969)008%3C0828:NOARPE%3E2.0.CO;2)
 formulation. They are at an extend of 1000 by 1000 pixels and in units of
 meters. They are in ASCIIGRID fomat ingestable by GIS software. 
 The fresh snow surface is at a 0.001 m (1 mm) resolution and the data were
 collected on 2021-04-19 in Fort Collins, Colorado USA. The ablation-sun
 cup surface is at a 0.005 m (5 mm) resolution and the data were collected
 on 2017-06-13 in the headwaters of the Poudre River, near Milner Pass,
 Colorado USA. Both datasets were collected with a Faro Focus3D X 130 model
 Terrestrial lidar Scanner. The raw point cloud data were interpolated to
 the stated resolution using kriging with the SURFER software. The peak
 accumulation dataset is at a 1 m resolution for the Niwot Saddle near
 Niwot Ridge, Colorado and were collected on 2010-05-20 using airborne
 lidar (see Harpold et al., 2014 https://doi.org/10.1002/2013WR013935 and
 Sexstone et al., 2022; https://doi.org/10.18172/cig.4951 for the raw
 data). The data were in gridded format, but linearly and then non-linearly
 detrended.
description: Two datasets (fresh snow and sun cups) were collected
 with a Faro Focus3D X 130 model Terrestrial lidar Scanner.
 The fresh snow (FS-FC) dataset was collected during a new
 snowfall event on 2021-04-19 in Fort Collins Colorado with snow snowcover
 existing on the ground. The FS-FC raw point cloud was at a resolution
 finer than 1 mm. The ablation-sun cup (SC-PH) dataset
 were collected when substantial sun cups were present during snowmelt on
 2017-06-13 in the headwaters of the Poudre River, near Milner Pass,
 Colorado. The SC-PH raw point cloud was at a resolution of about 3 mm. The
 ablation-sun cup data were collected as three separate scans due to the
 nature of the surface, i.e., sun cups. The three point cloud were sewn
 together with Cloud Compare, an open-source software for 3D point cloud
 and mesh analysis. Each of the raw point
 cloud (FS-FC and SC-PH) (three sewn together for SC-PH) was processed
 using Cloud Compare. The scans were cropped to the area of interest,
 ensuring that the dataset was limited to the preferred geographic region
 or feature under study. Any rogue points, such as noise or erroneous data
 points often caused by environmental, were identified and removed to
 enhance the accuracy and clarity of the dataset. 
 The cropped point cloud was interpolated using kriging in Golden
 Software’s Surfer program. Each gridded dataset was
 detrended in the X and Y directions to reduce bias from sloping
 surfaces. The original data for the third dataset
 (peak accumulation at Niwot Saddle, PA-NS) was already in the public
 domain (see Harpold et al., 2014 https://doi.org/10.1002/2013WR013935 and
 Sexstone et al., 2022; https://doi.org/10.18172/cig.4951 for the raw
 data). Those data are at a 1 m resolution. The data herein were linearly
 detrended, then detrended using a third order polynominal, and then
 linearly detrended again. The third order polynomial detrending remove the
 influence of the hillslope.
description: # Fresh Snow and Ablation-Sun Cup Snow Surface Datasets for Evaluation of
 Geometry Aerodynamic Roughness Code
 [https://doi.org/10.5061/dryad.qv9s4mwr2](https://doi.org/10.5061/dryad.qv9s4mwr2) ## Description of the data and file structure Snow surfaces gridded to 1001 by 1001 pixels: fresh snow (`FC2021_ARC_data_001m1.csv`) at 0.001-m (1-mm) resolution, peak accumulation (`NS2010_ARC_data_1m.csv`) at 1-m resolution, and ablation-sun cups (PR2017_ARC_data_005m1.csv) at 0.005-m (5-mm) resolution. The datasets represent three phases of the snowpack (accumulation, peak and melt) with varying surface characteristics, and at different resolutions. When the fresh snow (`FC2021_ARC_data_001m1.csv`) was accumulating, there was about 0.1 meters of snow on the ground. For the peak accumulation (NS2010_ARC_data_1m.csv), there was about 1.5 meters of snow on the ground. For the ablation-sun cups (PR2017_ARC_data_005m1.csv), there was about 1 meter of snow on the ground. ### Files and variables #### File: FC2021\_ARC\_data\_001m1.csv **Description:** files as ASCII grids, suitable for GIS upload. The header includes the number of columns (NCOLS = 1001), the number of rows (NROWS = 1001), the X and Y location of the lower left hand corner (XLLCORNER = 0, YLLCORNER = 0), the grid size in meters (CELLSIZE = 0.001), the no-data identifier (NODATA_VALUE = -9999), and the cell values are elevation in meters. ##### Variables * the 1001 by 1001 grid is the snow surface elevation (that has been linearly detrended). The cell values are in meters. #### File: PR2017\_ARC\_data\_005m1.csv **Description:** files as ASCII grids, suitable for GIS upload. The header includes the number of columns (NCOLS = 1001), the number of rows (NROWS = 1001), the X and Y location of the lower left hand corner (XLLCORNER = 0, YLLCORNER = 0), the grid size in meters (CELLSIZE = 0.005), the no-data identifier (NODATA_VALUE = -9999), and the cell values are elevation in meters. ##### Variables * the 1001 by 1001 grid is the snow surface elevation (that has been linearly detrended). The cell values are in meters. #### File: NS2010\_ARC\_data\_1m.csv **Description:** files as ASCII grids, suitable for GIS upload. The header includes the number of columns (NCOLS = 1001), the number of rows (NROWS = 1001), the X and Y location of the lower left hand corner (XLLCORNER = 0, YLLCORNER = 0), the grid size in meters (CELLSIZE = 0.001), the no-data identifier (NODATA_VALUE = -9999), and the cell values are elevation in meters. ##### Variables * the 1001 by 1001 grid is the snow surface elevation (that has been linearly detrended). The cell values are in meters. ## Code/software The data are in ASCII (csv) format and can be viewed as data in EXCEL or any Spreadsheet, or any text editor. The data can be view as a surface in most GIS packages, such as QGIS. The data are in ESRI ARC ASCIIGRID format. ## Access information Other publicly accessible locations of the data: * N/A The Fresh Snow and Sun Cups data were derived from the following sources: * Scans using a Faro Focus3D X 130 model Terrestrial lidar Scanner * Initial data assessment using Cloud Compare * Area of Interest cropping using Cloud Compare * Point Cloud interpolation to a grid using SURFER * Surface detrending in EXCEL The Peak Accumulation data were modified from an existing dataset: Harpold et al. (2014; [https://doi.org/10.1002/2013WR013935](https://doi.org/10.1002/2013WR013935)) and Sexstone et al. (2022; [https://doi.org/10.18172/cig.4951](https://doi.org/10.18172/cig.4951)) * The surface was detrending linearly, then with a third order polynomial, and then linearly again, all in EXCEL