Estimating the atmospheric boundary layer height over sloped, forested terrain from surface spectral analysis during BEARPEX

Abstract

Abstract.The atmospheric boundary layer (ABL) height (z i ) over complex, forested terrain is estimated based on the power spectra and the integral length scale of cross-stream winds obtained from a three-axis sonic anemometer during the two summers of the BEARPEX (Biosphere Effects on Aerosol and Photochemistry) Experiment. The z i values estimated with this technique show very good agreement with observations obtained from balloon tether sondes (2007) and rawinsondes (2009) under unstable conditions (z/L < 0) at the coniferous forest in the California Sierra Nevada. On the other hand, the low frequency behavior of the streamwise upslope winds did not exhibit significant variations and was therefore not useful in predicting boundary layer height. The behavior of the nocturnal boundary layer height (h) with respect to the power spectra of the v-wind component and temperature under stable conditions (z/L > 0) is also presented. The nocturnal boundary layer height is found to be fairly well predicted by a recent interpolation formula proposed by Zilitinkevich et al. (2007), although it was observed to only vary from 60-80 m during the 2009 experiment in which it was measured. Finally, significant directional wind shear was observed during both day and night soundings. The winds were found to be consistently backing from the prevailing westsouthwesterlies within the ABL (the anabatic cross-valley circulation) to southerlies in a layer ∼1-2 km thick just above the ABL before veering to the prevailing westerlies further aloft. This shear pattern is shown to be consistent with the forcing of a thermal wind driven by the regional temperature gradient directed east-southeast in the lower troposphere.

Eddy covariance fluxes and vertical concentration gradient measurements of NO and NO&lt;sub&gt;2&lt;/sub&gt; over a ponderosa pine ecosystem: observational evidence for within-canopy chemical removal of NO&lt;sub&gt;x&lt;/sub&gt;

“…Analysis of the local meteorology by Choi et al (2011) and Dillon et al (2002) indicate that in the summer (May-September), winds at the BEARPEX site are characterized by daytime southwesterlies (210-240 • ) and nighttime northeasterlies (30 • ) with little variability. The major source of anthropogenic emissions in the region is the city of Sacramento and its suburbs.…”

Observations of atmosphere-biosphere exchange of total and speciated peroxynitrates: nitrogen fluxes and biogenic sources of peroxynitrates

“…In the summer (May to September), wind patterns at the site are controlled by the topography and are characterized by southwesterlies (210-240 • ) during daytime and northeasterlies (30 • ) at night. More detailed descriptions of the local and regional meteorology are available elsewhere (Dillon et al, 2002;Cahill et al, 2006;Choi et al, 2011;Bianco et al, 2011). The forest at this site is dominantly Pinus ponderosa L., planted in 1990, with some Douglas fir, white fir, and incense cedar.…”

Biogenic volatile organic compound emissions during BEARPEX 2009 measured by eddy covariance and flux–gradient similarity methods

“…Defining source strengths of biogenic volatile organic compounds (BVOC; e.g., isoprene and monoterpenes) and understanding their role in ozone (O 3 ) and secondary organic aerosol (SOA) formation are critical issues in atmospheric chemistry and climate science (Chameides et al, 1988;Andreae and Crutzen, 1997;Fuentes et al, 2000;Jang et al, 2002). On the global scale, VOC emissions from terrestrial vegetation are estimated to be an order of magnitude greater than those from fossil fuel combustion (Guenther et al, 1995).…”