Rhône AGG Description/Documentation
Output Variables
The requested output variables are listed in Tables 5.1 and 5.2.
They are to be reported using the netCDF format.
The variable naming and sign conventions, definitions, whether they
are to be averaged over the time step of interest or
reported instantaneously,
and units use the ALMA convention. Please see
http://www.lmd.jussieu.fr/ALMA/
for more details on the ALMA
conventions and for links related to
the netCDF format.
In addition to the output variables listed in Tables
5.1 and 5.2,
we would like the modelers to report their
aggregated or effective parameters for Experiments 2 (20 and 60 points) and 3 (3 points).
If a mosaic or tile approach was used, we ask that the
parameters for each tile within each grid box
be reported. We also request a short summary of the methods used
by each group to aggregate their parameters (this is not necessary
if the parameters provided in the distribution for Experiments 2 and 3
were used).
Data Format
The output variables shown in Tables 5.1 and 5.2
are to be written using the netCDF format (ALMA convention).
The * symbol is used to indicate variables which are to be reported
at a time step of 3 hours, while all other variables are to be
reported at a time step of one day.
Some Notes on Output Variables
In this section, we clarify the definitions of certain output variables for
this experiment. Please note
we request that multi-layer snow schemes report up to a maximum of
5 snow layers. If a model has more than this maximum, we ask that they
average their sub-surface layers in an appropriate fashion down to at most 4 layers
(while reporting the 5th or uppermost layer without averaging).
- Qfz This is average liquid water converted from liquid water
within the snowpack to ice
(using the convention positive from liquid to solid). This can include both
frozen canopy drip or rainwater, and re-frozen snowmelt.
- Qst Snowpack through-fall: this is defined as all liquid water
flowing out of the snowpack (at it's base) over the prescribed time interval. Note that
for models which have no liquid water retention (or re-freezing of liquid) within
their snowpacks, this variable is equivalent to Qsm.
- Qf This is to include only the energy which directly influences
the surface energy budget: the surface snow layer, snow or ice in the
canopy interception reservoir, and any surface soil ice or frost
phase change energy.
- DelColdCont The total snow cold content (J m-2) is defined as
|
(4.1)
|
where the subscript s represents snow, i represents the layer index
(i > 1 for multi-layer snow schemes), and Ns is the number of
snow layers. The other symbols are:
snow heat capacity (cs: J m-3 K-1)
snow layer thickness (Ds: m), snow layer-average temperature
(Ts: K), triple point (Tf: K),
latent heat of fusion (Lf: J kg-1), SWE (Ws: kg m-2) and
snow liquid water content (Wl: kg m-2). We assume that
cs is either a constant or is parameterized in terms
of other snowpack variables (eg. snow density or temperature).
- SliqFrac The liquid water fraction of each snow layer.
Total liquid water content of the snowpack (kg m-2) is the product
of this variable and the SWE. For schemes which
do not model liquid water retention within the snow cover,
this variable is zero.
- RainfSnowFrac This is defined as the fraction of the total grid box rainfall which is
intercepted by the snowpack. Schemes which have no liquid water retention
within the snow can report this variable as zero (it will
be used to close the snowpack mass budget for schemes which intercept
rainfall).
- SnowfSnowFrac We assume that most schemes assume that all snowfall
is intercepted by the snow-covered fraction of the grid
box. Nonetheless, we request this variable in order to be as general
as possible.
- Water Budget
We will calculate the water budget in terms of the listed
variables as in PILPS-2e:
DelSWE + DelIntercept + DelSoilMoist +
DelSurfStor =
tstep ( Rainf + Snowf + Evap + Qs + Qsb)
where the definition of Evap is slightly different
from PILPS-2e (due to the addition of SubSurf):
Evap = ECanop + TVeg +
ESoil + EWater + SubSnow +
EvapSnow + SubSurf
- Energy Budget
We will calculate the energy budget in terms of the listed
variables as:
DelSurfHeat + DelColdCont = SWnet +
LWnet + Qle + Qh + Qa + Qg
+ Qv + Qf
which is similar to the definition used in PILPS-2e, except
for the variable DelSurfHeat which includes
the heat storage of both the surface soil layer (for schemes which
consider surface soil layer heat storage in the surface energy budget)
and the bulk-canopy layer (for schemes which consider
the heat storage by the canopy).