A comparison of optical and microwave scintillometers with eddy covariance derived surface heat fluxes
Type
ArticleAuthors
Yee, Mei SunPauwels, Valentijn R N
Daly, Edoardo
Beringer, Jason
Rüdiger, Christoph
McCabe, Matthew

Walker, Jeffrey P.
KAUST Department
Biological and Environmental Sciences and Engineering (BESE) DivisionEnvironmental Science and Engineering Program
Water Desalination and Reuse Research Center (WDRC)
Date
2015-11Permanent link to this record
http://hdl.handle.net/10754/594087
Metadata
Show full item recordAbstract
Accurate measurements of energy fluxes between land and atmosphere are important for understanding and modeling climatic patterns. Several methods are available to measure heat fluxes, and scintillometers are becoming increasingly popular because of their ability to measure sensible (. H) and latent (. LvE) heat fluxes over large spatial scales. The main motivation of this study was to test the use of different methods and technologies to derive surface heat fluxes.Measurements of H and LvE were carried out with an eddy covariance (EC) system, two different makes of optical large aperture scintillometers (LAS) and two microwave scintillometers (MWS) with different frequencies at a pasture site in a semi-arid environment of New South Wales, Australia. We used the EC measurements as a benchmark. Fluxes derived from the EC system and LAS systems agreed (R2>0.94), whereas the MWS systems measured lower H (bias ~60Wm-2) and larger LvE (bias ~65Wm-2) than EC. When the scintillometers were compared against each other, the two LASs showed good agreement of H (R2=0.98), while MWS with different frequencies and polarizations led to different results. Combination of LAS and MWS measurements (i.e., two wavelength method) resulted in performance that fell in between those estimated using either LAS or MWS alone when compared with the EC system. The cause for discrepancies between surface heat fluxes derived from the EC system and those from the MWS systems and the two-wavelength method are possibly related to inaccurate assignment of the structure parameter of temperature and humidity. Additionally, measurements from MWSs can be associated with two values of the Bowen ratio, thereby leading to uncertainties in the estimation of the fluxes. While only one solution has been considered in this study, when LvE was approximately less than 200Wm-2, the alternate solution may be more accurate. Therefore, for measurements of surface heat fluxes in a semi-arid or dry environment, the optical scintillometer is recommended, whereas further work will be required to improve the estimation of surface heat fluxes from microwave systems. © 2015 Elsevier B.V.Citation
Yee MS, Pauwels VRN, Daly E, Beringer J, Rüdiger C, et al. (2015) A comparison of optical and microwave scintillometers with eddy covariance derived surface heat fluxes. Agricultural and Forest Meteorology 213: 226–239. Available: http://dx.doi.org/10.1016/j.agrformet.2015.07.004.Sponsors
Japan Aerospace Exploration AgencyPublisher
Elsevier BVae974a485f413a2113503eed53cd6c53
10.1016/j.agrformet.2015.07.004