SnowSTAR 2002 TransectSnowSTAR 2002 Transect Reconstruction Using Reconstruction Using SNTHERM ModelSNTHERM Model

July 19, 2006

Xiaogang Shi and Dennis P. Lettenmaier

ContentsContents

SnowSTAR2002

Objective

Data Sets and ModelData Sets and Model

Results and Problems

Future Work

SnowSTAR2002SnowSTAR2002

U. S. Army Corps of EngineersCold Regions Research and Engineering Lab (CRREL)

Matthew Sturm

ALASKANome

BarrowThe traverse: From The traverse: From Nome, Alaska on the Nome, Alaska on the Seward Peninsula to the Seward Peninsula to the most northern point in most northern point in U.S., Barrow in Alaska.U.S., Barrow in Alaska.

Route Length: about 700 Route Length: about 700 milesmiles

Period: March 30 - April Period: March 30 - April 26 , 200226 , 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-The objective of this project is to apply the one-dimensional energy balance snow model SNTHERM dimensional energy balance snow model SNTHERM (Jordan, 1991) to simulate snow properties along (Jordan, 1991) to simulate snow properties along SnowSTAR2002 route throughout the winter/spring of SnowSTAR2002 route throughout the winter/spring of 2002. 2002.

Especially, the main purpose is to simulate the Especially, the main purpose is to simulate the vertical distribution and temporal change of snow vertical distribution and temporal change of snow properties in the point mode, and further investigate properties in the point mode, and further investigate the regional trends in the snow properties in Alaska . the regional trends in the snow properties in Alaska .

Data Sets and ModelData Sets and Model

ALASKANome

BarrowMeteorological stations: 293

Data length: 1950 -2005

Resolution: 1/16 degree

Time Step: Daily

1/16-degree Gridded Meteorological Data SetData Set 1

11 Download the raw data of Alaska (P,Tmax,Tmin) from the Download the raw data of Alaska (P,Tmax,Tmin) from the NCDC web site and use the Control package (Alan NCDC web site and use the Control package (Alan Hamlet,2004) to reformat the data.Hamlet,2004) to reformat the data.

22 Scale the precipitation data with PRISM monthly mean in Scale the precipitation data with PRISM monthly mean in Alaska from 1961 through 1990. PRISM was developed by Dr. Alaska from 1961 through 1990. PRISM was developed by Dr. Daly of Oregon State University. It is a statistical-geographic Daly of Oregon State University. It is a statistical-geographic approach to mapping climate. PRISM uses point precipitation approach to mapping climate. PRISM uses point precipitation measurements and DEM, to generate estimates of monthly measurements and DEM, to generate estimates of monthly mean precipitation in Alaska.mean precipitation in Alaska.

33 Get the 1/16 degree VIC input format data using regridding Get the 1/16 degree VIC input format data using regridding package which is based on the interpolation routine called package which is based on the interpolation routine called SYMAP (Shepard, D.S., 1984). [GRID_2000, UW Hydro ]SYMAP (Shepard, D.S., 1984). [GRID_2000, UW Hydro ]

4. Combine the 10-meter daily wind data, which was obtained 4. Combine the 10-meter daily wind data, which was obtained from the NCEP Reanalysis, and gridded linearly interpolated to from the NCEP Reanalysis, and gridded linearly interpolated to 1/16 degree. 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: 1979-2002.

3. Time step: daily

4. Resolution:0.5 degree (Downscaled from 2.5 degree by Nathalie)

5. VIC input format data

ERA-40 DATAData 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

PrecipitationPrecipitationMaximum TemperatureMaximum TemperatureMinimum TemperatureMinimum TemperatureWind SpeedWind Speed

Precipitation Precipitation

Air TemperatureAir Temperature

Wind speedWind speed

Incoming solar radiationIncoming solar radiation

Reflected solar radiationReflected solar radiation

Incoming longwave radiationIncoming longwave radiation

Relative humidityRelative 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

SSnow depthnow depthSnow densitySnow densitySnow temperatureSnow temperatureSnow grain sizeSnow grain sizeSnow water equivalentSnow water equivalent

Precipitation Precipitation

Air TemperatureAir Temperature

Wind speedWind speed

Incoming solar radiationIncoming solar radiation

Reflected solar radiationReflected solar radiation

Incoming longwave radiationIncoming longwave radiation

Relative humidityRelative humidity

Input (hourly)

Output (hourly)

SNTHERM Model

Initial conditions of snow and soilThe initial condition

starts from no snow.

Model Validation

Station: IvotukStation: Ivotuk

Location: 68.49 Location: 68.49 N,155.74 W N,155.74 W

Slope: FlatSlope: Flat

Vegetation type: tundraVegetation type: tundraALASKA

Barrow

Nome

Ivotuk

Model Validation

Observed Data:Observed Data:

snow depth datasnow depth data

Net RadiationNet Radiation

Soil Temperature and MoistureSoil Temperature and Moisture

Relative HumidityRelative Humidity

Meteorological data ( winter Meteorological data ( winter precipitation is not measured)precipitation is not measured)

Validation Experimental Design

Meteorological inputs from:

1. 1/16 Degree Data Set Pseudo Station (68.46875 N,155.78125W)

2. ERA-40 0.5 Degree Data Set Pseudo Station (68.75 N, 155.75 W)

VICVIC

SNTHERMSNTHERM Snow depth data validation

with observed site ivotuk-Met1 (68.49 N,155.74 W)

Results Results and Problemsand Problems

Snow depth comparison between 1/16 Degree Snow depth comparison between 1/16 Degree and and ERA-40 0.5 Degree data setsERA-40 0.5 Degree data sets

Snow DepthSnow Depth PrecipitationPrecipitation

Comparison between 1/16 Degree Comparison between 1/16 Degree and ERA-40 0.5 and ERA-40 0.5 Degree data setsDegree data sets

Snowpack TSnowpack T Air TAir T

ALASKA

Nome

Barrow

Comparison between 1/16 Degree Comparison between 1/16 Degree and ERA-40 0.5 and ERA-40 0.5 Degree data setsDegree data sets

SWESWE Snow Grain SizeSnow Grain Size

Future WorkFuture 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 YouThank You

Question?Question?