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Table 12.3. RMSE (degree centigrade) for the reanalysis of the Iowa MDSS bridge surface temperatures
Table 13.4. Results of chemical concentration sampling
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12.5
Road
Temperature
Analysis
Summary
In an
earlier
study
conducted
under
controlled
conditions
at
the
CRREL
road
test
site
SNTHERM-RT
exhibited
considerable
skill
in
predicting
the
road
surface
and
sub-
surface
temperature
information.
This
level
of
skill
was
only
achieved
after
using
SNTHERM_RT
and
measured
field
data
to
`back
out'
the
optical,
and
thermal
properties
of
the
road and
underlying
gravel
and
soil
layers.
We
feel
that
this
same
level
of
skill
can
be
achieved
using
SNTERM-RT
for
`real
world
situation'
if a
similar
procedure
is
used
to
`back
out'
the
road
thermal
and
optical
properties.
The
physical
properties
(road
layer
thickness,
etc)
should
be
available
from
DOT
information.
To
implement
this
approach it
would
entail
collecting
data
before
the
winter
season
for
the
desired
road
sites
and
tuning
SNTHERM-RT
for
each
site
by
`backing
out'
the
desired
road
surface
properties.
The
ensemble
forecast
meteorological
information
used
in
conjunction
with
SNTHERM-RT
provided
high
quality
prognostic
road
surface
temperature
information
for
Maintenance
Decision
Support
to
the
Iowa
DOT.
The
limited
reanalysis
presented
here
should
be
extended
since an
extensive
data
set
was
collected
for
the
Iowa
MDSS
field
program.
Its
completeness
makes it an
ideal
data
set
for
future
research
and
road
surface
energy
budget
model
development.
Since
SNTHERM-RT
does
not
model
the
impact
of
chemicals
on
the
road
surface
energy
budget,
snow
removal
by
plowing,
or
the
influence
of
traffic,
future
modeling
efforts
should
focus
on
developing
procedures to
handle
these
situations.
13 CHEMICAL
CONCENTRATION
SAMPLING
In
order
to
verify
the
chemical
concentration
algorithms,
which
have
been
implemented
in
the
RCTM,
CRREL
developed
techniques
to sample
the
on-road
chemical
concentration.
A
method
was
sought
that
would
offer
laboratory
quality
concentration
results
while
being
acceptable
for
collecting
samples
under
open and
operating
roadways
during
winter
storm
conditions.
The
approach we
evaluated
during
the
2004
MDSS
demonstration
involved
using
an absorbent
glass
wool
to
collect
a sample
directly
from
the
road
surface.
Small
sections of
the
glass
wool
absorbing
medium
where
each
pre-
weighted
along
with
a
numbered
plastic
bag.
For
the
field
sampling
we
used
forceps
to
remove
the
glass
wool
from
the
bag
and
wipe
it
around
in
the
solution
on
the
road
until
it
became
saturated.
Once
the
glass
wool
was saturated to
the
maximum
extent
possible it
was replaced in
the
bag
from
which
it was
removed
and
the
bag
was
sealed.
The
bag
number,
time,
date
and
location
of
the
sample
were
then
recorded in a
log
sheet.
All
samples
were
returned
to
CRREL
where
they
were
analyzed
in
our
chemistry
laboratories.
The
results
from
a
portion
of
the
chemical
concentration
sampling
are
presented
in
Table
13.4.
The
concentrations
observed
appear
to be
low
based
on
expected
concentrations
.
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