Surface Temperature and Surface-Layer Turbulence in a Convective Boundary Layer
- 874 Downloads
Previous laboratory and atmospheric experiments have shown that turbulence influences the surface temperature in a convective boundary layer. The main objective of this study is to examine land-atmosphere coupled heat transport mechanism for different stability conditions. High frequency infrared imagery and sonic anemometer measurements were obtained during the boundary layer late afternoon and sunset turbulence (BLLAST) experimental campaign. Temporal turbulence data in the surface-layer are then analyzed jointly with spatial surface-temperature imagery. The surface-temperature structures (identified using surface-temperature fluctuations) are strongly linked to atmospheric turbulence as manifested in several findings. The surface-temperature coherent structures move at an advection speed similar to the upper surface-layer or mixed-layer wind speed, with a decreasing trend with increase in stability. Also, with increasing instability the streamwise surface-temperature structure size decreases and the structures become more circular. The sequencing of surface- and air-temperature patterns is further examined through conditional averaging. Surface heating causes the initiation of warm ejection events followed by cold sweep events that result in surface cooling. The ejection events occur about 25 % of the time, but account for 60–70 % of the total sensible heat flux and cause fluctuations of up to 30 % in the ground heat flux. Cross-correlation analysis between air and surface temperature confirms the validity of a scalar footprint model.
KeywordsAtmospheric surface layer Convective boundary layer Infra-red imagery Surface-layer plumes Surface temperature
We thank (i) Daniel Alexander from University of Utah, USA; Dr. Marie Lothon, Dr. Fabienne Lohou, Solene Derrien from Laboratoire d’Aérologie, Université de Toulouse, France; Dr. Arnold Moene, Dr. Oscar Hartogensis, Anneke Van de Boer from Wageningen University, Netherlands for field assistance, data sharing and discussion; (ii) Peter Cottle and Anders Nottrott from University of California, San Diego for pre-experimental laboratory assistance and discussion about the data analysis respectively; (iii) BLLAST organizers for their hospitality during the experiment; (iv) funding from a NASA New Investigator Program award for AG and JK, and from INSU-CNRS (Institut National des Sciences de l’Univers, Centre national de la Recherche Scientifique, LEFE-IDAO program), Météo-France, Observatoire Midi-Pyrénées (University of Toulouse), EUFAR (EUropean Facility for Airborne Research) and COST ES0802 (European Cooperation in the field of Scientific and Technical) for the BLLAST field experiment.
- Campbell GS, Norman JM (1998) An introduction to environmental biophysics. Springer, New York, 286 ppGoogle Scholar
- Carslaw HS, Jaeger JC (1959) Conduction of heat in solids. Oxford University Press, London, 510 ppGoogle Scholar
- Christen A, Voogt JA (2009) Linking atmospheric turbulence and surface temperature fluctuations in a street canyon. Paper no. A3–6. The 7th international conference on urban climate, YokohomaGoogle Scholar
- Christen A, Voogt JA (2010) Inferring turbulent exchange process in an urban street canyon from high-frequency thermography. Paper no. J3A.3. 9th symposium on the urban environment, KeystoneGoogle Scholar
- Derksen DS (1974) Thermal infrared pictures and the mapping of microclimate. Neth J Agric Sci 22:119–132Google Scholar
- Howard LN (1966) Convection at high Rayleigh number. In: Görtler H (ed) Proceedings of the 11th international congress on applied mechanics. Springer, San Diego, pp 1109–1115Google Scholar
- Lothon M, Lohou F, Durand P, Couvreux Sr. F, Hartogensis OK, Legain D, Pardyjak E, Pino D, Reuder J, Vilà Guerau de Arellano J, Alexander D, Augustin P, Bazile E, Bezombes Y, Blay E, van de Boer A, Boichard JL, de Coster O, Cuxart J, Dabas A, Darbieu C, Deboudt K, Delbarre H, Derrien S, Faloona I, Flament P, Fourmentin M, Garai A, Gibert F, Gioli B, Graf A, Groebner J, Guichard F, Jonassen M, van de Kroonenberg A, Lenschow D, Martin S, Martinez D, Mastrorillo L, Moene A, Moulin E, Pietersen H, Piguet B, Pique E, Román-Cascón C, Said F, Sastre M, Seity Y, Steeneveld GJ, Toscano P, Traullé O, Tzanos D, Wacker S, Yagüe C (2012) The boundary layer late afternoon and sunset turbulence 2011 filed experiment. Paper no. 14B.1. 20th symposium on boundary layers and turbulence, BostonGoogle Scholar
- Oke TR (1987) Boundary layer climates. Methuen, London, 435 ppGoogle Scholar
- Vogt R (2008) Visualisation of turbulent exchange using a thermal camera. Paper no. 8B.1. 18th symposium on boundary layer and turbulence, StockholmGoogle Scholar
- Wilczak JM, Businger JA (1983) Thermally indirect motions in the convective atmospheric boundary layer. J Atmos Sci 40:343–358Google Scholar