SnowSTAR 2002 Transect Reconstruction Using SNTHERM Model July 19, 2006 Xiaogang Shi and Dennis P. Lettenmaier

Contents   SnowSTAR2002   Objective  Data Sets and Model   Results and Problems   Future Work

SnowSTAR2002 U. S. Army Corps of Engineers Cold Regions Research and Engineering Lab (CRREL) Matthew Sturm

ALASKA Nome Barrow The traverse: From Nome, Alaska on the Seward Peninsula to the most northern point in U.S., Barrow in Alaska. Route Length: about 700 miles Period: March 30 - April 26, 2002 SnowSTAR2002 Transect Domain

Measurement sites: 83 Snow Pits: 415 Snow Water Equivalent:830 SnowSTAR2002

Objective The objective of this project is to apply the one- dimensional energy balance snow model SNTHERM (Jordan, 1991) to simulate snow properties along SnowSTAR2002 route throughout the winter/spring of The objective of this project is to apply the one- dimensional energy balance snow model SNTHERM (Jordan, 1991) to simulate snow properties along SnowSTAR2002 route throughout the winter/spring of Especially, the main purpose is to simulate the vertical distribution and temporal change of snow properties in the point mode, and further investigate the regional trends in the snow properties in Alaska. Especially, the main purpose is to simulate the vertical distribution and temporal change of snow properties in the point mode, and further investigate the regional trends in the snow properties in Alaska.

Data Sets and Model

ALASKA Nome Barrow Meteorological stations: 293 Data length: Resolution: 1/16 degree Time Step: Daily 1/16-degree Gridded Meteorological Data Set Data Set 1

1Download the raw data of Alaska (P,Tmax,Tmin) from the NCDC web site and use the Control package (Alan Hamlet,2004) to reformat the data. 2Scale the precipitation data with PRISM monthly mean in Alaska from 1961 through PRISM was developed by Dr. Daly of Oregon State University. It is a statistical-geographic approach to mapping climate. PRISM uses point precipitation measurements and DEM, to generate estimates of monthly mean precipitation in Alaska. 3Get the 1/16 degree VIC input format data using regridding package which is based on the interpolation routine called SYMAP (Shepard, D.S., 1984). [GRID_2000, UW Hydro ] 4. Combine the 10-meter daily wind data, which was obtained from the NCEP Reanalysis, and gridded linearly interpolated to 1/16 degree. 1/16-degree Gridded Meteorological Data Set in Alaska Data Set 1

1.ERA-40 dataset from European Centre for Medium- Range Weather Forecasts (ECMWF) (Reanalysis ) 2.Period: Time step: daily 4. Resolution:0.5 degree (Downscaled from 2.5 degree by Nathalie) 5. VIC input format data ERA-40 DATA Data Set 2

Using VIC model to get the hourly data Purpose: 1. Get Radiation data and Relative Humidity (by modifying the write_data.c ) 2. Disaggregate the daily Meteorological and Radiation data to hourly data

Using VIC model to get the hourly data Precipitation Maximum Temperature Minimum Temperature Wind Speed Precipitation Air Temperature Wind speed Incoming solar radiation Reflected solar radiation Incoming longwave radiation Relative humidity Input (Daily) Output (hourly)

Schematic diagram of SNTHERM model (CRREL,2004) Developed by Dr. Rachel Jordan from Cold Regions Research and Engineering Lab (CRREL). Physically-based 1-D snow model Solves energy and mass balance equations Accounts for densification, metamorphosis, freeze/melt, liquid water percolation SNTHERM Model

Snow depth Snow density Snow temperature Snow grain size Snow water equivalent Precipitation Air Temperature Wind speed Incoming solar radiation Reflected solar radiation Incoming longwave radiation Relative humidity Input (hourly) Output (hourly) SNTHERM Model Initial conditions of snow and soil The initial condition starts from no snow.

Model Validation Station: Ivotuk Station: Ivotuk Location: N, W Location: N, W Slope: Flat Slope: Flat Vegetation type: tundra Vegetation type: tundra ALASKA Barrow Nome Ivotuk

Model Validation Observed Data: Observed Data: snow depth data Net Radiation Soil Temperature and Moisture Relative Humidity Meteorological data ( winter precipitation is not measured)

Validation Experimental Design Meteorological inputs from: 1. 1/16 Degree Data Set Pseudo Station ( N, W) 2. ERA Degree Data Set Pseudo Station (68.75 N, W) VIC SNTHERM Snow depth data validation with observed site ivotuk- Met1 (68.49 N, W)

Results and Problems

Snow depth comparison between 1/16 Degree and ERA Degree data sets Snow Depth Precipitation

Comparison between 1/16 Degree and ERA Degree data sets Snowpack T Air T Air T

ALASKA Nome Barrow

Comparison between 1/16 Degree and ERA Degree data sets SWE Snow Grain Size

Future Work Future Work   Run SNTHERM at 83 sites along the SnowSTAR2002 using the two data sets.   Get SnowSTAR2002 snow properties measured data from Matthew Sturm of Cold Regions Research and Engineering Lab (CRREL).   Compare SNTHERM outputs with the field measurements and further investigate the regional trends in the snow properties for Alaska.

Thank You Question?