Deep Valley Radiation and Surface Energy Budget Microclimates. Part I: Radiation

Whiteman, C. David; Allwine, K.J.; Fritschen, Leo J.; Orgill, M.M.; Simpson, James

doi:10.1175/1520-0450(1989)028<0414:dvrase>2.0.co;2

Cited by 70 publications

(50 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…If such an approximation is to be performed reliably, not only net radiometers but also pyranometers should be installed to distinguish the total, direct and diffuse shortwave radiation components. In such a way, direct shortwave radiation can be easily corrected for slope effects knowing the azimuthal and elevation angles, latitude and surface inclination (Garnier and Ohmura 1968;Whiteman et al 1989). Since direct shortwave radiation represents 60 to 80 % of R n for mid-latitudes, and is the component most affected by slope effects (Holst et al 2005), such post-processing correction typically yields acceptable results.…”

Section: Discussionmentioning

confidence: 99%

Surface-Parallel Sensor Orientation for Assessing Energy Balance Components on Mountain Slopes

Serrano-Ortiz

Sánchez‐Cañete

Olmo

et al. 2015

Boundary-Layer Meteorol

View full text Add to dashboard Cite

The consistency of eddy-covariance measurements is often evaluated in terms of the degree of energy balance closure. Even over sloping terrain, instrumentation for measuring energy balance components is commonly installed horizontally, i.e. perpendicular to the geo-potential gradient. Subsequently, turbulent fluxes of sensible and latent heat are rotated perpendicular to the mean streamlines using tilt-correction algorithms. However, net radiation (Rn) and soil heat fluxes (G) are treated differently, and typically only Rn is corrected to account for slope. With an applied case study, we show and argue several advantages of installing sensors surface-parallel to measure surface-normal Rn and G. For a 17 % south-west-facing slope, our results show that horizontal installation results in hysteresis in the energy balance closure and errors of up to 25 %. Finally, we propose an approximation to estimate the surface-normal Rn, when only vertical Rn measurements are available

show abstract

Section: Discussionmentioning

confidence: 99%

Surface-Parallel Sensor Orientation for Assessing Energy Balance Components on Mountain Slopes

Serrano-Ortiz

Sánchez‐Cañete

Olmo

et al. 2015

Boundary-Layer Meteorol

View full text Add to dashboard Cite

show abstract

“…not only depends on the inclination of the slope as the solar declination also modifies this parameter as well as the slope azimuth angle. can be defined as the difference between β and Z , where β is the angle between the solar beam and the normal to the slope, whereas Z is the solar zenith angle (Whiteman et al 1989). Matzinger et al (2003) presented an empiric relationship between the horizontally measured net radiation Q * and the slope parallel measured Q * .…”

Section: Surface Radiation On An Inclined Surfacementioning

confidence: 99%

Eddy-Covariance Flux Measurements in the Complex Terrain of an Alpine Valley in Switzerland

Hiller

Zeeman

Eugster

2008

Boundary-Layer Meteorol

View full text Add to dashboard Cite

We measured the surface energy budget of an Alpine grassland in highly complex terrain to explore possibilities and limitations for application of the eddy-covariance technique, also for CO 2 flux measurements, at such non-ideal locations. This paper focuses on the influence of complex terrain on the turbulent energy measurements of a characteristic high Alpine grassland on Crap Alv (Alp Weissenstein) in the Swiss Alps during the growing season 2006. Measurements were carried out on a topographic terrace with a slope of 25 • inclination. Flux data quality is assessed via the closure of the energy budget and the quality flag method used within the CarboEurope project. During 93% of the time the wind direction was along the main valley axis (43% upvalley and 50% downvalley directions). During the transition times of the typical twice daily wind direction changes in a mountain valley the fraction of high and good quality flux data reached a minimum of ≈50%, whereas during the early afternoon ≈70% of all records yielded good to highest quality (CarboEurope flags 0 and 1). The overall energy budget closure was 74 ± 2%. An angular correction for the shortwave energy input to the slope improved the energy budget closure slightly to 82 ± 2% for afternoon conditions. In the daily total, the measured turbulent energy fluxes are only underestimated by around 8% of net radiation. In summary, our results suggest that it is possible to yield realistic energy flux measurements under such conditions. We thus argue that the Crap Alv site and similar topographically complex locations with short-statured vegetation should be well suited also for CO 2 flux measurements.

show abstract

“…The REBS instrument was intercalibrated with the Swissteco reference instrument in the field at Happy Valley (69°07 0 N, 148°50 0 W) on 18 -19 June 1995, and new calibration factors for the REBS instrument were derived and used throughout the study. Because of unequal response to shortwave and long-wave radiation of the REBS instruments [Field et al, 1992;Whiteman et al, 1989], different calibration coefficients were used for R n ! 0 and R n < 0.…”

Section: Additional Measurements From Toolik Lakementioning

confidence: 99%

CO₂ exchange between air and water in an Arctic Alaskan and midlatitude Swiss lake: Importance of convective mixing

et al. 2003

View full text Add to dashboard Cite

[1] CO 2 exchange between lake water and the atmosphere was investigated at Toolik Lake (Alaska) and Soppensee (Switzerland) employing the eddy covariance (EC) method. The results obtained from three field campaigns at the two sites indicate the importance of convection in the lake in driving gas flux across the water-air interface. Measurements were performed during short (1-3 day) periods with observed diurnal changes between stratified and convective conditions in the lakes. Over Toolik Lake the EC net CO 2 efflux was 114 ± 33 mg C m À2 d À1 , which compares well with the 131 ± 2 mg C m À2 d À1 estimated by a boundary layer model (BLM) and the 153 ± 3 mg C m À2 d À1 obtained with a surface renewal model (SRM). Floating chamber measurements, however, indicated a net efflux of 365 ± 61 mg C m À2 d À1 , which is more than double the EC fluxes measured at the corresponding times (150 ± 78 mg C m À2 d À1 ). The differences between continous (EC, SRM, and BLM) and episodic (chamber) flux determination indicate that the chamber measurements might be biased depending on the chosen sampling interval. Significantly smaller fluxes ( p < 0.06) were found during stratified periods (51 ± 42 mg C m À2 d À1 ) than were found during convective periods (150 ± 45 mg C m À2 d À1 ) by the EC method, but not by the BLM. However, the congruence between average values obtained by the models and EC supports the use of both methods, but EC measurements and the SRM provide more insight into the physical-biological processes affecting gas flux. Over Soppensee, the daily net efflux from the lake was 289 ± 153 mg C m À2 d À1 during the measuring period. Flux differences were significant ( p < 0.002) between stratified periods (240 ± 82 mg C m À2 d À1 ) and periods with penetrative convection (1117 ± 236 mg C m À2 d À1 ) but insignificant if convection in the lake was weak and nonpenetrative. Our data indicate the importance of periods of heat loss and convective mixing to the process of gas exchange across the water surface, and calculations of gas transfer velocity using the surface renewal model support our observations. Future studies should employ the EC method in order to obtain essential data for process-scale investigations. Measurements should be extended to cover the full season from thaw to freeze, thereby integrating data over stratified and convective periods. Thus the statistical confidence in the seasonal budgets of CO 2 and other trace gases that are exchanged across lake surfaces could be increased considerably.

show abstract

Deep Valley Radiation and Surface Energy Budget Microclimates. Part I: Radiation

Cited by 70 publications

References 0 publications

Surface-Parallel Sensor Orientation for Assessing Energy Balance Components on Mountain Slopes

Surface-Parallel Sensor Orientation for Assessing Energy Balance Components on Mountain Slopes

Eddy-Covariance Flux Measurements in the Complex Terrain of an Alpine Valley in Switzerland

CO₂ exchange between air and water in an Arctic Alaskan and midlatitude Swiss lake: Importance of convective mixing

Contact Info

Product

Resources

About

Deep Valley Radiation and Surface Energy Budget Microclimates. Part I: Radiation

Cited by 70 publications

References 0 publications

Surface-Parallel Sensor Orientation for Assessing Energy Balance Components on Mountain Slopes

Surface-Parallel Sensor Orientation for Assessing Energy Balance Components on Mountain Slopes

Eddy-Covariance Flux Measurements in the Complex Terrain of an Alpine Valley in Switzerland

CO2 exchange between air and water in an Arctic Alaskan and midlatitude Swiss lake: Importance of convective mixing

Contact Info

Product

Resources

About

CO₂ exchange between air and water in an Arctic Alaskan and midlatitude Swiss lake: Importance of convective mixing