Cycle 32r3 of the ECMWF forecast and analysis system includes a change in the soil hydrology which affects soil moisture. The land surface scheme has been improved by the introduction of a global distribution of soil type (based on the FAO soil texture data set) and new soil drainage and runoff schemes.
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An example MARS compute script together with the table below are provided for users that need to compute the SMI. The soil texture type (MARS parameter SLT, GRIB Code 43) as well as the soil moisture at different layers (MARS parameters SWVL1, SWVL2, SWVL3 and SWVL4, GRIB Codes 39, 40, 41 and 42, respectively) are needed as input.
Old | Soil | PWP [m³/m³] | FC [m³/m³] |
|---|---|---|---|
1 | Loamy | 0.171 | 0.323 |
New | Soil | PWP [m³/m³] | FC [m³/m³] |
1 | Coarse | 0.059 | 0.242 |
2 | Medium | 0.151 | 0.346 |
3 | Medium-fine | 0.133 | 0.382 |
4 | Fine | 0.279 | 0.448 |
5 | Very fine | 0.335 | 0.541 |
6 | Organic | 0.267 | 0.662 |
Example MARS script for computing the Soil Moisture Index
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For further information about mathematical computations in MARS please see the MARS User Guide.