Transcript Snow formation in the atmosphere: properties of snow and

Snowpack Hydrologic Modelling
Modelling Topics
• Modelling Strategies
• Data Requirements
– Basin Characteristics
– Parameters
– Meteorological Data
• Validation / Evaluation
Modelling Strategies
• Model Domain
– Point models
– Watershed models
• Small in the order of hectares
• Very large, eg. Mississippi and Mackenzie Basin (106 km2)
– Continental or Global
• Weather, Climate or Circulation Models
Model Types
• Conceptual Index
– Empirical relationships to approximate mass
balance
• Physical
– Mass and energy balance
Point Energy Balance Model
water balance
energy balance
met data
groundwater
• Only vertical process
representation
• Multiple snow and
soil layers
• Often used to model
a specific variable,
such as snowmelt
Index Model
• Vertical Processes
met data
– Index models, usually
using temperature
• Horizontal processes
water balance
- index methods
– Physical mass
relationships
hydraulics
- internal slope
streamflow
routing
groundwater
• Hydrologic/Hydraulic
Routing
– Index or Physical
streamflow
Physically-based Hydrologic Model
water balance
energy balance
met data
hydraulics
- internal slope
streamflow
routing
groundwater
Physical Data for Models
• Topographic data
– Derived from DEM
• Basin boundaries from a specific streamflow gauge
• Elevation, slope, aspect
• Data used directly or parameters derived
– Land cover / land use (vegetation type, etc.)
– Cover density for vegetation
– Soils maps (hydraulic conductivity, etc.)
Modelling Dataset
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Precipitation
Air Temperature
Wind Speed (and direction)
Pressure
Specific Humidity
Radiation (Shortwave and Longwave)
Hydrologic Cycle:
movement, phase change and storage
Snow-cover Depletion
Areal Distribution Curve
Snow-cover Profile
Melt
depth
1
2
3
1
Melt
4
2
3
5
4
0
5
100
Percent <= depth indicated
Frequency Distribution
2
Snow-cover Depletion Curve
1
frequency
3
Melt
5
depth
1
2
Mean snow depth
4
3
4
5
0
100
Snowcovered Area (%)
Sample Index Models
• HBV - Sweden
• SRM (snow runoff model) - USDA
• PRMS (precipitation runoff modelling system)
- USGS
• SLURP (simple lumped reservoir) - Env. Can.
• UBC Watershed Model
• TOPMODEL - Keith Beven
Sample Physical Models
• SNTHERM - US Army Corps CRREL
• LSM (land surface model) and other SVATs
• VIC (variable infiltration capacity) - U
Washington
• WATCLASS (Watflood/CLASS) - Env. Can.
• SHE (systeme hydrologique european)
Sample Process Representation
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Snow-covered vs. Snow-free
Mixed precipitation (rain and snow)
Density of fresh snow
Maximum attainable snowpack density
Canopy snowfall interception
Snow redistribution
Snow-covered vs. Snow-free
decoupling
Snow Covered Area
Bare Area
Mixed Cover Type
Constant Soil Properties
Separate Cover Types
Differing Soil Properties
Snow–covered vs. Snow-free
water content
Snow–covered vs. Snow-free
water content
Snow–covered vs. Snow-free
hydrograph
flow (m3/s)
400
average snow-covered + snow-free
separate snow-covered/snow-free
observed
300
200
100
0
Mar 21
Mar 26
Mar 31
(1993 for the Grand River at Galt)
Apr 5
percent probability of snow
Mixed Precipitation
100
80
60
40
20
0
-2
0
2
4
temperature (degrees Celsius)
6
Mixed Precipitation Formulation:
snow depth (1993)
0.5
observed
0 deg. division
2.2 deg. division
snow depth (m)
0.4
Auer's curve
DAVOS curve
0.3
USACE's curve
0.2
0.1
0
Jan 01
Jan 29
Feb 26
Mar 25
Apr 22
Mixed Precipitation Formulation:
soil temperature
soil temperature ( degrees C)
10
5
0 deg. division
2.2 deg. division
Auer's curve
DAVOS curve
USACE's curve
0
-5
-10
Jan 01
Jan 29
Feb 26
Mar 25
Apr 22
60
0 deg division
60
2.2 deg division
40
Auer curve
Davos curve
20
60
40
USACE curve
2
ground heat flux (W/m )
latent h eat flux (W/m 2)
Mixed Precipitation Formulation:
heat fluxes (Apr 4/93)
0
40
sensible heat
-20
20
-40
0
20
0
-20
-40
-60
-20
0
6
12
18
time (h)
-60
-40
0
-60
0
6
12
18
time (h)
6
12
18
time (h)
Mixed Precipitation Formulation:
hydrograph
350
observed
300
0 deg. division
2.2 deg. division
flow (m3/s)
250
Auer's curve
DAVOS curve
200
USACE's curve
150
100
50
0
Mar 20
Mar 27
Apr 03
Fresh Snow Density
3
fresh snow density (kg/m )
150
constant of 100
100
particle shape
Hedstrom & Pomeroy
50
Alta function
0
-21
-16
-11
-6
temperature (degrees C)
-1
Fresh Snow Density Measurements
-3
fresh snow density (kg.m
)
200
Diamond & Lowry data (1953)
Schmidt & Gluns (1991)
Alta function (La Chapelle, 1961)
Hedstrom & Pomeroy (1998)
particle shape fit
Fassnacht 1999
160
120
80
40
0
-21
-16
-11
temperature (degrees C)
-6
-1
Fresh Snow Density Variations:
snow depth (1993)
0.5
snow depth (m)
0.4
observed
constant of 100 kg/m 3
Hedstrom and Pom eroy
Alta function
particle shape curve
0.3
0.2
0.1
0
Jan 01
Jan 29
Feb 26
Mar 25
Apr 22
Fresh Snow Density Variations:
soil temperature
soil temperature ( degrees C)
10
5
constant of 100 kg/m 3
Hedstrom and Pom eroy
Alta function
particle shape curve
0
-5
-10
Jan 01
Jan 29
Feb 26
Mar 25
Apr 22
Fresh Snow Density Variations:
heat fluxes (Apr 1)
35
30
constant of 100 kg/m 3
Hedstrom & Pom eroy
Alta function
particle shape curve
2
20
10
15
5
10
0
-5
30
20
2
sensible heat flux (W/m )
-10
25
0
2
5
ground heat flux (W/m )
latent heat flux (W/m )
25
0
6
12
18
time (h)
-5
-10
-15
-20
-25
15
-30
10
-35
5
0
-5
-10
-15
0
6
12
18
time (h)
Fresh Snow Density Variations:
hydrograph
350
300
flow (m3/s)
250
observed
constant of 100 kg/m 3
Hedstrom and Pom eroy
Alta function
particle shape curve
200
150
100
50
0
Mar 20
Mar 27
Apr 03
Apr 10
Maximum Snowpack Density
Differences among land classes
rs(max) =
300
350
kg/m3
250/350
Maximum Snowpack Density Variations:
snow depth
0.5
snow depth (m)
0.4
observed
250 kg/m3
300 kg/m3
350 kg/m3
0.3
0.2
0.1
0
Jan 01
Jan 29
Feb 26
Mar 25
Apr 22
Maximum Snowpack Density Variations:
soil temperature
0
-5
0.5
-10
0.4
-15
Jan 01
Jan 29
Feb 26
snow depth (m)
soil temperature ( degrees C)
5
observed
250 kg/m3
300 kg/m3
350 kg/m3
0.3
Mar 25
0.2
Apr 22
Maximum Snowpack Density Variations:
snow water equivalent
snow snow
water depth
equivalent
(m) (mm)
120
0.5
100
0.4
80
0.3
observed
250 kg/m3
300 kg/m3
350 kg/m3
60
0.2
40
0.1
20
00
Jan 01
01
Jan
Jan
Jan 29
29
Feb
Feb26
26
Mar
Mar2525
Apr
2222
Apr
Maximum Snowpack Density Variations
120
0.5
snow water equivalent (mm)
snow depth (m)
0.4
observed
250 kg/m3
300 kg/m3
350 kg/m3
0.3
0.2
0.1
100
80
60
40
20
0
0
Jan 01
Jan 29
Feb 26
Mar 25
Jan 01
Apr 22
Feb 26
Mar 25
Apr 22
350
5
300
0
250
flow (m3/s)
soil temperature ( degrees C)
Jan 29
-5
200
150
100
-10
50
-15
Jan 01
Jan 29
Feb 26
Mar 25
Apr 22
0
Mar 20
Mar 27
Apr 03
Apr 10
Maximum Snowpack Density Variations:
heat fluxes (Mar 30)
max at 250 kg/m3
max at 300 kg/m3
max at 350 kg/m3
100
100
80
80
2
ground heat flux (W/m )
2
latent h eat flux (W/m )
120
60
40
20
2
sensible heat flux (W/m )
0
0
-20
-20
-40
-60
-80
-100
60
40
20
0
-20
0
6
12
18
time (h)
-40
0
6
12
18
time (h)
Snowfall Canopy Interception
20% of LAI
Max = 50% of LAI
50% + Hedstrom & Pomeroy
Canopy Snowfall Interception Processes
120
snow water equivalent (mm)
observed (crop)
100
rain interception
holding capacity = 0.5
80
Hedstrom and Pom eroy
60
40
20
0
Jan 01
Jan 29
Feb 26
Mar 25
Apr 22
Snowfall Interception: Canopy Type
snow water equivalent (mm)
120
100% deciduous
snow water equivalent (mm)
120
100
observed (crop)
rain interception
100
holding capacity = 0.5
Hedstrom and Pom eroy
80
60
40
20
0
Jan 01
Jan 29
Feb 26
Mar 25
Apr 22
80
60
100% coniferous
40
20
0
Jan 01
Jan 29
Feb 26
Mar 25
Apr 22
Redistribution
None
Between land classes
Within land class
Redistribution (between land classes)
- snow movement
observed
no redistribution
bare class 150mm max
low veg class 250mm max
low veg class 150mm max
low veg class 5mm max
flow (cms)
300
200
100
0
Mar 24
Mar 29
Apr 3
Apr 8
Redistribution (within land class)
- 100% SCA capacity
350
300
observed
D100 = 0.10
D100 = 0.15
3
flow (m /s)
250
0.15 except
0.06 forest
200
150
100
50
0
Mar 20
Mar 27
Apr 03
Apr 10
Apr 17
Influence of Cloud Cover Fraction on
Streamflow (via longwave radiation)
100% CC
variable CC
300
50% CC
flow (cms)
30% CC
observed
0% CC
200
100
0
Mar 24
Mar 29
Apr 3
Apr 8
Meteorological Forcing Data
streamflow (m 3/s)
200
observed
old met data
new met data
150
100
50
cumulative flow (m3/s)
0
1990
20000
1991
1992
1993
1994
1995
1996
1997
1998
1993
1994
1995
1996
1997
1998
observed
old met data
new met data
10000
0
1990
1991
1992
Vegetation Maps
Forest Type
mixed forest
(oak-pine)
USFS
conifer
(Ponderosa Pine)
fir-spruce
IGBP
chaparral
Pinyon Juniper
non-forest
Landsat TM
Brown & Lowe
field maps
Simulated Streamflow
- different land cover maps
cumulative streamf low (m3/s)
25000
20000
USGS
IGBP
Brown & Lowe
Landsat TM
Observed
15000
10000
5000
0
1990
1991
1992
1993
1994
1995
1996
1997
1998