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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