Algorithm Theoretical Based Document (ATBD) - CESBIO

SO-TN-ESL-SM-GS-0001
Issue 1.a
Date: 31/08/2006
SMOS level 2 processor
Soil moisture ATBD
Selected models for fractions FM
4 Soft topo pollution MWP0 MWS0 MDd MDd MDd MDd MDd MDd MDd MDd
5 All wet snow MWP0 MWS0 MD MD0 MN0 MN0 MWP0 MD0 MD0 MD0
6 All mixed snow MWP0 MWS0 MDd MDd MDd MDd MDd MDd MDd MDd
7 Wet snow pollution MWP0 MWS0 MDd MDd MDd MDd MDd MDd MDd MDd
8 Mixed snow pollution MWP0 MWS0 MDd MDd MDd MDd MDd MDd MDd MDd
9 All frost MWP0 MWS0 MD0 MD MN0 MN0 MWP0 MD0 MD0 MD0
10 Frost pollution MWP0 MWS0 MDd MDd MDd MDd MDd MDd MDd MDd
11 Forest cover MWP0 MWS0 MD0 MD0 MN MN MWP0 MD0 MD0 MD0
13 Soil cover MWP0 MWS0 MD0 MD0 MN MN MWP0 MD0 MD0 MD0
14 All wetlands MWP0 MWS0 MD0 MD0 MN0 MN0 MWP MD0 MD0 MD0
15 All barren MWP0 MWS0 MD0 MD0 MN0 MN0 MWP0 MD MD0 MD0
16 All ice MWP0 MWS0 MD0 MD0 MN0 MN0 MWP0 MD0 MD MD0
18 All urban MWP0 MWS0 MD0 MD0 MN0 MN0 MWP0 MD0 MD0 MD
19 Heterogeneous MWP0 MWS0 MDd MDd MDd MDd MDd MDd MDd MDd
Notes:
• The forwards models for each fraction FM and decision tree branch are referred to as defined in Table 17. A
"0" suffix have been added for default contributions.
• The models used for retrieval are printed in bold.
• The aggregate of fractions used for retrieval define an overall aggregated fraction FRE.
• For frozen conditions, an option is to override the tests on lines 6 and 7 and to process with MN (see section
3.1.4.2)
• As long as the dedicated SNOW cover model MS is not defined for wet or mixed snow, it is replaced by the
cardioid model. This model is applied to different fractions depending if the snow is characterized as "mixed"
or "wet"
• The cardioid model MD is used for either some prevailing cover cases, or highly inhomogeneous situations. In
the second case it is referred to as MDd in the table.
• Inasmuch as the cardioid retrieval is requested systematically, an additional MD retrieval must be performed
for cases # 1, 11, 13 and 14, applied to the same aggregated fractions.
• In multiple model retrieval, either different models (e.g. case 1) or same models (e.g. case 2), the free
parameters are the same for all concerned fractions i.e. in case 1, for example, if T PHYS is retrieved then T PHYS
is the same for both FWP and FWS. Fixed parameters values are always fractions model dependent.
• For branches 11 and 13, the retrieving option is introduced to retrieve SM on both the FNO and FFO fraction
simultaneously, using the same MN model. For branch 11, every other FNO parameter is fixed; for branch 13,
every other FFO parameter is fixed. This option of course only to be considered when a FNO (branch 11) or a
FFO (branch 13) is present. The option is to be chosen when the reference TAU_nadir for FFO is smaller than
a specified threshold TH_TAU_FN.
3.2.3.4.3 Default versus retrieval models
It must be stressed that formally the direct models may be slightly different depending whether they are used for
building default contribution of for retrieving floating parameters. This feature has been indicated above for the MD
model. This will also have to be specified for the other models concerning effective temperature and some vegetation
parameters; see Table 19.
Table 19: Default models vs. retrieval models
Default
Retrieval
Dielectric constant formulation
MD Complex dielectric constant (A,U) cardioid with U frozen
MN Check case of sand Check case of sand
MW
Vegetation layer litter component (forest TBC) in TAU single TAU
Physical temperature distinct Tg and Tc (not for forest) single Tgc = T_PHYS
3.2.3.5 Computing reference values for parameters
.
80