- The objective of this study was to compile, validate, and map minimum and maximum mean monthly temperature and temperature ranges for periods of 10 to 14 months between July 2009 and June 2012, measured using 16 to 182 sensors distributed over the HJ Andrews Forest, a mountain landscape of 64 km². Maps were created using inverse distance weighting (IDW) as an extrapolation method in Arc GIS 10.1.
We found that temperature was dominated by lapse-rate, topographic shading, and cold air pooling effects, depending on the time of year. Both minimum and maximum monthly temperature in spring (some Mar, April, May, and even June) and fall (Oct, Nov) tends to be lapse-rate dominated. Late summer (Aug, Sep, Oct) maximum temperature tends to be dominated by topographic shading, despite interannual variation in precipitation. Cold air pooling appeared in July, August, and September minimum temperature, but in maximum temperature only for a dry December (2011).
Additional sensors (from 16 to 40 or even 56) increase the ability to identify topographic shading patterns and the associated heterogeneity in temperature, with weak indications of cold air pooling. Even more sensors (from 40/56 to 166/182) increase the ability to identify very small scale variability, including cool air pooling in the main-stem valley of the Andrews Forest.
For a given month, temperature spatial patterns were fairly consistent from one year to another. For a given month, temperature values between years vary with interannual variation in precipitation.
Some sites in the Andrews Forest have a very large diurnal temperature range (mean monthly min to mean monthly max) while other sites have very small ranges. Sites close to each other may have very different mean monthly temperature, due to the effect of topography. Sites with the largest temperature ranges were on the south-facing slopes of Carpenter Mountain, and those with the smallest ranges were along the north-facing slope of the south side of Andrews Forest (Lookout Ridge) and northwest of the upper end of Lookout Creek. North-facing slopes on Lookout Mountain and Roswell Ridge may also have very small temperature ranges, but these areas were not instrumented. Sites with small temperature ranges may serve as refugia for organisms in response to climate change.
For mountain environments subjected to climate change, these findings imply that different parts of the landscape experience climate change differently. There may be "refugia" from climate change in mountain landscapes, defined as locations with small diurnal and seasonal temperature ranges.