With the increasing use of numerical models predicting the snow cover statu
s, the need for a simple and standardized evaluation procedure arises. We p
resent such a method that compares numerical model profiles with snow pit p
rofiles and provides a quantitative statistical agreement-disagreement meas
ure. The method can also be used to compare several model profiles with eac
h other.
The first step of the method is the mapping of the model profile layers ont
o the layers of the observed profile. This mapping is necessary to adjust f
or deviating total snow depth and shifted positions of the layers. Followin
g the mapping, the individual profile parameters such as grain type, grain
size, liquid water content, temperature and density are compared. The resul
t of the comparison is a score between 0 (profiles show no agreement) and 1
(profiles are identical) for each parameter. The parameter scores can be c
ombined to give an overall profile score between 0 and 1. The method facili
tates evaluation studies and allows to quantify improvements made in the mo
deling of processes in the snow cover.
This is illustrated by analyzing a simulated profile at an IMIS (German: In
terkantonales Mess-und Informations System) automatic snow and weather stat
ion with an observed, detailed snow pit profiles from the Swiss Alps. The a
greement score for the parameter grain type increased from 0.3 to 0.7 after
introducing an additional grain type in the simulation. In addition, the s
cores were calculated for two observation stations in the Swiss Alps for a
whole winter season and it was detected that for most of the winter an over
all agreement score between SNOWPACK simulation and snow pit profile of app
roximately 0.8 is reached. The temperature regime is modeled best and most
difficulties are encountered with grain type. An important result is furthe
r that the energy balance processes at the beginning of the spring melt sea
son has to be improved. (C) 2001 Elsevier Science B.V. All rights reserved.