GSWP-2 Input Data

The input data for models in GSWP-2 are divided into three categories:
The soil and vegetation data are parameter data sets that are used to specify characteristics of the land surface. The meteorological data provide the forcing at the upper boundary of the land surface.

Soils data

The soils data include more information that will be needed for any one model, in order to accomodate some of the variations in soil specification used by different LSSs. Three overlapping data sets for specifying soil hydraulic properties are given: Sand, silt, clay and organic fractions; a soil texture map and look-up table based on USDA categories; and calculated gridded soil parameters. This should accomodate the major methods employed by current LSSs. The parameter tables and gridded parameters are based on the Cosby et al. (1984) approach - if another methodology is prefered (e.g., van Genuchten 1980), the modelers will have to derive their own parameters. We will gladly post any other data sets that modeling groups derive, so that they may be shared with others.

The table below lists the soil parameters that are provided for GSWP-2. All are time-invariant global fields at 1° resolution (land points only 60°S-90°N). The final field, initital soil temperature, is computed from the mean June air temperature, and should be used as the initial soil temperature at the beginning of the model spin-up (1 July 1982).

Name

Description

Units

Range

Source

Time scale

SoilClass

Soil texture class

-

Max = 12

Min = 0

ISLSCP-II

fixed

SoilDepth

Depth of active soil column

m

Max = 30.0

Min = 0.0

ISLSCP-I

fixed

Clay

Clay fraction

-

Max = 1.0

Min = 0.0

ISLSCP-II

fixed

Sand

Sand fraction

-

Max = 1.0

Min = 0.0

ISLSCP-II

fixed

Silt

Silt fraction

-

Max = 1.0

Min = 0.0

ISLSCP-II

fixed

Organic

Organic fraction

-

Max = 1.0

Min = 0.0

ISLSCP-II

fixed

Elevation

Mean grid elevation

m

Max = 9000.0

Min = -400.0

ISLSCP-II

fixed

Slope

Mean slope

m m-1

Max = 1.0

Min = 0.01

ISLSCP-II

fixed

W_fieldcap

Field capacity

m3 m-3

Max = 1.0

Min = 0.0

ISLSCP-II

fixed

W_wilt

Wilting point

m3 m-3

Max = 1.0

Min = 0.0

ISLSCP-II

fixed

W_sat

Saturated water content

m3 m-3

Max = 1.0

Min = 0.0

ISLSCP-II

CEA84

fixed

W_bpower

B exponent

-

Max = 15.0

Min = 1.0

CEA84

fixed

W_sat_hydc

Saturated hydraulic conductivity

m s-1

Max = 0.0001

Min = 0.0

ISLSCP-II

CEA84

fixed

W_sat_matp

Saturated matric potential

m

Max = -0.0001

Min = -3.0

CEA84

fixed

Albedo_vi

Visible albedo of soil (snow free)

-

Max = 1.0

Min = 0.0

ISLSCP-I

fixed

Albedo_ir

Near-infrared albedo of soil (snow free)

-

Max = 1.0

Min = 0.0

ISLSCP-I

fixed

Albedo_soil

Total albedo of soil (snow free)

-

Max = 1.0

Min = 0.0

ISLSCP-I

fixed

Cti

Compound topographic index

-

Max = 13.5

Min = 0.0

ISLSCP-II

fixed

SoilTemp_init

Initial soil temperature

-

Max = 350.0

Min = 190.0

NCEP

fixed


The SoilClass data set is a global map of texture classes, based on the USGS soil texture classifications. The table below gives the relevant texture data. Cosby values for silt are estimated, as they were not provided in the original RhoneAGG data set from which the parameters are taken. The quartz content data come from Peters-Lidard et al. (1998).

Texture

USDA

Cosby (RhoneAGG) USDA

Class

Sand

Silt

Clay

 Quartz

Wfc

Wwilt

Wsat

b

PHIsat

Ksat

1

Sand

92%

5%

3%

 0.92

0.132

0.033

0.373

3.30

-0.05

2.45E-05

2

Loamy Sand

82%

12%

6%

 0.82

0.156

0.051

0.386

3.80

-0.07

1.75E-05

3

Sandy Loam

58%

32%

10%

 0.60

0.196

0.086

0.419

4.34

-0.16

8.35E-06

4

Loam

17%

70%

13%

 0.40

0.270

0.169

0.476

5.25

-0.65

2.36E-06

5

Silt Loam

10%

85%

5%

 0.25

0.361

0.045

0.471

3.63

-0.84

1.10E-06

6

Silt

43%

39%

18%

 0.10

0.250

0.148

0.437

5.96

-0.24

4.66E-06

7

Sandy Clay Loam

58%

15%

27%

 0.60

0.253

0.156

0.412

7.32

-0.12

6.31E-06

8

Clay Loam

10%

56%

34%

 0.35

0.334

0.249

0.478

8.41

-0.63

1.44E-06

9

Silty Clay Loam

32%

34%

34%

 0.10

0.301

0.211

0.447

8.34

-0.28

2.72E-06

10

Sandy Clay

52%

6%

42%

 0.52

0.288

0.199

0.415

9.70

-0.12

4.25E-06

11

Silty Clay

6%

47%

47%

 0.10

0.363

0.286

0.478

10.78

-0.58

1.02E-06

12

Clay

22%

20%

58%

 0.25

0.353

0.276

0.450

12.93

-0.27

1.33E-06


Vegetation Data

Both NDVI and phenology data are provided as monthly mean values that can be used for specifying the time-varying vegetation properties as each modeler sees fit. For models that simulate vegetation phenology, these data may be used for initialization, validation, etc.

Monthly-varying and static vegetation parameters are listed below. For models that using a mosaic or tilig structure, data on the fractional coverage of each grid box by each vegetation type for the IGBP and U. Maryland vegetation data classFrac are provided.

Name

Description

Units

Range

Source

Time scale

Period

VegClass

Vegetation class

-

Max = 21

Min = 0

IGBP, U. Maryland

fixed

-

LAI

Leaf area index

m2 m-2

Max = 8.08

Min = 0.0

UK

Univ. of Wales

monthly

1982-1995

vegFrac

Fraction of vegetation cover

-

Max = 1.0

Min = 0.0

UK

fixed

-

grnFrac

Greenness fraction

(green LAI / Total LAI)

-

Max = 1.0

Min = 0.0

Calculated from Univ. of Wales data

monthly

1982-1995

classFrac

Fraction of each VegClass

(not in ALMA variable list)

-

Max = 1.0

Min = 0.0

IGBP; U. Maryland

fixed

-

NDVI

Normalized difference vegetation index

-

Max = 1.0

Min = 0.0

UK