At present the surface scheme prognostic or boundary conditions variables that are updated along forecasts are summarized in the following table:

VariableGrib code.tableDescriptionUnits
STL1,2,3,4139.128, 170,128,
183.128, 236.128		Soil TemperatureK
SWVL1,2,3,439.128, 40,128,
41.128, 42.128		Soil Moisture-
SRC198.128Skin reservoir contentm
SKT235.128Skin temperatureK
SD141.128Snow Depth (water eq.)m
TSN238.128Snow TemperatureK
ASN32.128Snow Albedo-
RSN33.128Snow Densitykg/m3
ISTL1,2,3,435.128, 36.128
37.128, 38.128		Ice TemperatureK
LMLT8.228Lake Mix-Layer TemperatureK
LBLT10.228Lake Bottom Layer TemperatureK
LICT13.228Lake Ice TemperatureK
LTLT11.228Lake Total Layer TemperatureK
LMLD9.228Lake Mix-Layer Depthm
LICD14.228Lake Ice Depthm
LSHF12.228Lake Shape Factor-
SST34.128Sea-Surface TemperatureK
CI31.128Ice Cover-
LAI_LV66.128Leaf Area Index Low Vegetation-
LAI_LH67.128Leaf Area Index High Vegetation-
ALUVP15.128UV/Vis Albedo Direct Radiation-
ALUVD16.128UV/Vis Albedo Diffuse Radiation-
ALNIP17.128NIR Albedo Direct Radiation-
ALNID18.128NIR Albedo Diffuse Radiation-
Further reading...

For more detailed information about the surface model, please see Chapter 8 in the IFS technical manual Part IV: Physical processes.

The technical manuals for IFS cycles can be found here:

https://www.ecmwf.int/en/forecasts/documentation-and-support/changes-ecmwf-model/ifs-documentation