Department of Geosciences
Committee Members: A J Kimerling
HJ Andrews Temperature Mapping Project
The goal of this project is to create the most accurate possible maps depicting
spatial variation in mean monthly maximum and minimum temperatures throughout
the year in the HJ Andrews Experimental Forest. This Long Term Ecological
Research (LTER) site has a wealth of reliable long-term temperature data
providing a solid 30-year dataset at an unusually high spatial resolution that
is ideally suited for this. However, the effects of topography and varying
forest canopy cover on these datasets are problematic and must be accounted for
when using them for spatial analysis. Climate studies have been done in the HJ
Andrews but at this time a detailed temperature study taking into account the
area's complex terrain and varying forest cover has not been undertaken.
The primary product of the project will be a set of maximum and minimum
temperature maps for each month in the HJ Andrews. In order to maximize the
project's potential most fully, we propose to model temperatures in the
absence of vegetation. After correcting 'short-term' sites to the 30-year
dataset by correcting them with their highest correlated counterparts, we will
determine a function that best relates temperature to canopy cover. Our premise
is that solar radiation plays a major role in determining temperature patterns.
We will take fisheye photographs at each site and use HemiView software to
determine the percentage of solar radiation blocked by both the canopy and
surrounding topography for each month. Since insolation measurements are only
taken at a few sites in the HJ Andrews, we will have to determine the
theoretical radiation values for each month at each site taking into account
all possible sources of attenuation including seasonal cloudiness, topography,
canopy cover, normal atmospheric attenuation, and elevational differences.
The Image Processing Workbench (IPW) software will be used to determine the
amount of radiation blocked by topography and clouds throughout the year.
Using both of these software packages together will allow us to separate the
attenuation due to canopy from that due to topography, and obtain a correction
factor to 'bring the sites out into the open'. Once this final correction is
made to the dataset, the PRISM (Parameter-elevation Regressions on Independent
Slopes Model) software will be used to interpolate temperatures at all points
in the HJ Andrews by taking into account wide array of climatic variables.
The usefulness and applications of such a product are numerous. Being an LTER
site, various national and international research projects are constantly being
conducted at the HJ Andrews that would benefit from a spatial representation of
temperature variation. Depicting temperature variations in the absence of
canopy cover increases the applicability of the project. For example, such a
product would allow Forestry researchers the ability to apply their own canopy
models to an existing dataset. Studies of flora, fauna, watersheds, and stream
flow could also benefit greatly from an accurate temperature model.
Additionally, accurate radiation maps of the HJ Andrews accounting for
cloudiness, canopy cover, topographic shading, or any combination of these will
likely be valued by researchers from various fields.