Infrared and millimetre-wave scintillometry in the suburban environment – Part 2: Large-area sensible and latent heat fluxes

摘要

A millimetre-wave scintillometer was paired with an infrared scintillometer,enabling estimation of large-area evapotranspiration across northernSwindon, a suburban area in the UK. Both sensible and latent heat fluxes canbe obtained using this "two-wavelength" technique, as it is able to provideboth temperature and humidity structure parameters, offering a majoradvantage over conventional single-wavelength scintillometry. The firstpaper of this two-part series presented the measurement theory andstructure parameters. In this second paper, heat fluxes are obtainedand analysed. These fluxes, estimated using two-wavelength scintillometryover an urban area, are the first of their kind. Source area modellingsuggests the scintillometric fluxes are representative of 5–10 km2. Forcomparison, local-scale (0.05–0.5 km2) fluxes were measured by an eddycovariance station. Similar responses to seasonal changes are evident at thedifferent scales but the energy partitioning varies between source areas.The response to moisture availability is explored using data from 2 consecutive years with contrasting rainfall patterns (2011–2012). Thisextensive data set offers insight into urban surface-atmosphere interactionsand demonstrates the potential for two-wavelength scintillometry to deliverfluxes over mixed land cover, typically representative of an area 1–2 ordersof magnitude greater than for eddy covariance measurements. Fluxes at thisscale are extremely valuable for hydro-meteorological model evaluation andassessment of satellite data products.