Table 1. Modeled processes.
Snow
Solar radiation
Flow
interception
through
Snowpack
Cold
Water
Rain
through
Multilayer
by canopy
canopy
temperature
Albedo
content
retention
on snow
snow
snow
HEC-1-T
SSARR-T
x
x
x
x
NWSRFS
x
x
x
x
x
PRMS
x
x
x
x
x
x
x
x
2
SRM
SRM-RAD
HEC-1-E
50%
x
SSARR-E
x
x
x
x
x
SNTHERM
x
x
x
x
x
x
many
SNAP
x
x
x
x
x
x
Notes:
NWSRFS and SSARR-E may run on 3- to 24-hr intervals.
PRMS runs on a 12-hr interval.
HEC-1-T and SSARR-T are temperature-based methods; HEC-1-E and SSARR-E are energy balance methods.
tions. SNAP is an energy balance approach using
These algorithms provide approximations of
a one-layer snowpack, and offers a new math-
snowmelt that are best suited for forested basins
ematical approach to flow routing through the
(rather than open areas), without topographic
pack, aimed at saving computation time.
variation (slope and aspect variability), but have
predictive capability in all cases where tempera-
Data requirements
ture is a good predictor of snowmelt. The second
The reviewed snowmelt algorithms break into
group requires the additional use of satellite
three groups based on input requirements (Table
derived snow-covered area information, or radia-
2). The first group are temperature index methods
tion data. Net radiation is considered a better
that require only temperature and precipitation.
single predictor of snowmelt than temperature,
Table 2. Meteorological data requirements.
Wind
Wind
Snow
Air
RH
Dewpoint
speed
speed
cover
Is↓
Is↑
Iir↓
temperature
(%)
temperature
2m
50 ft
Q*
area
HEC-1-T
x
x
SSARR-T
x
x
NWSRFS
x
x
PRMS
x
x
x*
SRM
x
x
x**
SRM-RAD
x
x
x
x**
HEC-1-E
x
x
x
x
x
SSARR-E
x
x
x
x
x
x†
x†
x†
SNTHERM
x
x
x
x
SNAP
x
x
x
x
x
x
x
Notes:
* PRMS can substitute cloud cover information for incoming solar radiation.
† SNTHERM can substitute cloud cover, solar aspect, and slope for radiation observations.
** SRM requires snow-covered area maps derived from satellite data.
13
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