1. Mapping the Thermal Climate of the HJ Andrews Experimental Forest, Oregon Jonathan Smith Spatial Climate Analysis Service Oregon State University Corvallis, Oregon PHOTOS COURTESY OF AL LEVNO

3. Project goal To create 1971-2000 mean monthly maximum and minimum temperature maps of the HJ Andrews… … accounting for several environmental factors affecting microclimates in forested, mountainous terrain - Elevation*** - Forest Canopy** - Cloudiness** - Topography*

4. Landscape-scale influences on HJ Andrews temperatures Elevationadiabatic heating/cooling (Tmax Tmin) Heterogeneous landscape at the HJ Andrews  complex thermal climates Temperatures modeled to minimize effects of forest canopy Forest Canopylimits incoming shortwave radiation (Tmax) limits longwave radiation loss – sky view factor (Tmin) Topography slope/aspect:determines shortwave radiation regime (Tmax) terrain configuration:cold air drainage patterns  inversions  thermal belts (Tmax Tmin) Cloudinesslimits incoming shortwave radiation (Tmax) limits longwave radiation loss (Tmin)

5. Open thermistors shielded above with PVC Digital data loggers MET sites: relatively open, (sometimes) flat terrain thermister towers (1.5, 2.5, 3.5, 4.5m), many other sensors Other sites:highly variable canopies, slopes, aspects air temperature sensor (~1.5m), other sensors Climate station instrumentation and siting

6. Initial adjustments to datasets Any site not having at least 3 years of data eliminated (62-19=43) 13 sites >= 22.5 years (long-term), 30 sites < 22.5 years (short-term) Monthly means computed from daily TMAX, TMIN To eliminate temporal biases, short-term sites adjusted to full period using highest correlated long-term site 71819101

7. Determined monthly cloud factors using UPLMET radiation data 1 – [UPLMET observed rad’n / IPW clear-sky rad’n] Used Image Processing Workbench (IPW) to create clear-sky radiation grids, using 50-meter DEM Radiation adjustments to datasets STEP 1: Determine monthly topo/cloud-sensitive radiation at each temperature site JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 0.49 0.45 0.40 0.35 0.34 0.26 0.19 0.17 0.19 0.34 0.47 0.48

8. Explicitly accounted for cloudiness on topographic shading by adjusting ratio of direct to diffuse radiation: - Used Bristow & Campbell’s (1985) equation relating direct and diffuse proportions of solar radiation to transmissivity - Necessary to produce ‘sharp’ radiation regimes on clear days (  direct,  diffuse), ‘flat’ radiation regimes on cloudy days (  direct,  diffuse) STEP 1: (continued) Obtained topo/cloud-sensitive radiation by rerunning IPW radiation routines with radiation lowered and direct/diffuse ratio modified by transmissivity ‘SHARP’ REGIME‘FLAT’ REGIME

9. At each site, separated out proportion of radiation blocked by topography only: Used HemiView to calculate proportions of direct and diffuse radiation blocked by canopy and topography Took fisheye photos at each site STEP 2: Determine monthly topo/cloud/canopy-sensitive radiation at each temperature site At each site, determined proportion of radiation blocked by canopy only: Reduced each sites’ topo/cloud-sensitive radiation by its proportion of radiation blocked by canopy only 1 - IPW topo/cloud-sensitive rad’n = IPW proportion of rad’n blocked IPW flat, open cloud-sensitive rad’n by topography only HemiView proportion blocked _ IPW proportion blocked = proportion of rad’n blocked by canopy and topography by topography by canopy only RS10UPLMETOPEN

10. TMIN slopes varied because of variations in cloudiness: STEP 3: Calculate regression functions to adjust temperatures to flat, open siting conditions JAN: y = -1.00x(R² = 0.49) APR: y = -1.01x(R² = 0.31) JUL: y = -3.41x(R² = 0.81) OCT: y = -2.07x(R² = 0.66) (y = difference in TMIN, x = difference in sky view factors) JAN: y = 1.17x(R² = 0.91) APR: y = 0.33x(R² = 0.99) JUL: y = 0.20x(R² = 0.74) OCT: y = 0.52x(R² = 0.91) (y = difference in TMAX, x = difference in radiation) TMIN/SVF regression functions:TMAX/radn regression functions: TMAX slopes varied because of variations in radiation:

11. ‘Parameter-elevation Regressions on Independent Slopes Model’ (PRISM) used to spatially interpolate TMAX, TMIN Uses a combination of geographic and statistical methods Elevation-based interpolator, using linear temperature-elevation regression functions, DEM, and point (station) data Accounts for elevation, inversion layers (2-layer atmosphere model) Spatially interpolating temperatures across the HJ Andrews * Results of adjustment procedures removed effects of everything but elevation – PRISM’s strength is the elevation-temperature relationship

12. PRISM temperature-elevation plots showed inversions throughout the year TMAX-Elevation Plot for JanuaryTMAX-Elevation Plot for July TMIN-Elevation Plot for JanuaryTMIN-Elevation Plot for July

13. a) PRISM September TMAX map showing no radiation effects b) IPW September radiation map c) PRISM September TMAX map showing radiation effects d) Difference between a) and c)

14. a) PRISM September TMIN map showing no SVF effects b) IPW SVF map c) PRISM September TMIN map showing SVF effects d) Difference between a) and c)

16. Study quantified some of the effects of elevation, cloudiness, topography, and canopy on radiation/temperature regimes Temperatures were modeled to simulate open canopy conditions Temperature patterns most sensitive to elevation and topographic position (year-round valley inversions) TMAX was sensitive to shortwave radiation variations, especially in winter (due to low solar radiation load) TMIN was sensitive to sky view factor variations, especially during clear summer months (fewer clouds enhance radiative nighttime cooling) Summary and conclusions

17. Maps incorporate only large-scale effects of cold-air drainage in the HJ Andrews (elevation relationships) Edge effects not quantified (homogeneity of forest cover) Scale effects not investigated (radiation at points) Stream effects on temperatures not quantified Some Study Weaknesses

18. More data! (stations and remotely-sensed) Some vegetation modification around climate stations seems justified to bring them up to NWS standards Development of historical database of vegetation changes at each site Test TMAX/radiation, TMIN/sky view factor functions elsewhere Recommendations