Climate of the Past Discussions www.clim-past-discuss.net 1814-9340 1814-9359 3 2 2007 10.5194/cpd-3-469-2007 http://www.clim-past-discuss.net/3/469/2007/ http://www.clim-past-discuss.net/3/469/2007/cpd-3-469-2007.html http://www.clim-past-discuss.net/3/469/2007/cpd-3-469-2007.pdf 469 500 2007-03-08 Thermal signal propagation in soils in Romania: conductive and non-conductive processes C. Demetrescu crisan@geodin.ro D. Nitoiu C. BoroneanÅ£ A. Marica B. Lucaschi Institute of Geodynamics, Bucharest, Romania National Meteorological Administration, Bucharest, Romania Temperature data recorded in 2002 and 2003 at 10 stations out of the 70 of the Romanian automatic weather stations network are presented and analyzed in terms of the heat transfer from air to underground. The air temperature at 2 m, the soil temperatures at 0, 5, 10, 20, 50 and 100 cm below soil surface as well as precipitation and snow thickness have been monitored. The selected locations sample various climate environments in Romania. First order modelling confirm that at certain locations and for certain time intervals soil temperatures track air temperature variations and consequently the heat transfer is by conduction, while at others, processes such as soil freezing and/or solar radiation heating play an important part in the heat flux balance at the air/soil interface. However, the propagation of the annual thermal signal in the first meter of soil is through conduction; the effective thermal diffusivity for 8 stations with continuous time series at all depth levels ranges from 3 to 10×10^–6m²s^–1. Barlett, M. G., Chapman, D. S., and Harris, R. N.: Snow and the ground temperature record of climate change, J. Geophys. Res., 109, F04008, doi:10.1029/2004JF000224, 2004. Beltrami, H.: Active layer distortion of annual air/soil thermal orbits, Permafrost Periglacial Processes, 27, 101–110, 1996. Beltrami, H.: On the relationship between ground temperature histories and meteorological records: a report on the Pomquet station, Global Planet. Change, 29, 327–349, 2001. Beltrami, H. and Kellman, L.: An examination of short-and long-term air-ground temperature coupling, Global Planet. Change, 38, 291–303, 2003. Boronean\ct, C., Ioni\ctã, M., and Dumitrescu, A.: Trends and shifts in the seasonal temperature mean in Romania during the period 1961–2000, International Workshop "Significant Scientific Research on Global Environmental Change in Central and Eastern Europe ", Sinaia, 6–8 October, 2004. Carslaw, H. S. and Jaeger, J. C.: Conduction of Heat in Solids, 2nd ed., Oxford Univ. Press, New York, 1959. Demetrescu, C., Nitoiu, D., Boronean\ct, C., Marica, A., and Lucaschi, B.: Preliminary analysis of two-year long records of air and underground temperatures as measured at automatic weather stations in Romania, Rev. Rom. Geophys., 50, 21–31, 2006. Esper, J., Cook, E. R., and Schweingruber, F. H.: Low-frequency signals in long tree-ring chronologies for reconstructing past temperature variability, Science, 295, 2250–2253, 2002. González-Rouco, J. F., Beltrami, H., Zorita, E., and Von Storch, H.: Simulation and inversion of borehole temperature profiles in surrogate climates: Spatial distribution and surface coupling, Geophys. Res. Lett., 33, L01703, doi:10.1029/2005GL024693, 2006. Goodrich, L. E.: The influence of snow cover on the ground thermal regime, Can. Geotech. J., 19, 421–432, 1982. Grundstein, A., Todhunter, P., and Mote, T.: Snowpack control over the thermal offset of air and soil temperatures in eastern North Dakota, Geophys, Res. Lett., 32, L08503, doi:10.1029/2005GL022532, 2005. Harris, R. and Chapman, D.: Geothermics and climate change 1.Analysis of borehole temperatures with emphasis on resolving power, J. Geophys. Res., 103, B4, 7363–7360, 1998. Hurley, S. and Wiltshire, R. J.: Computing thermal diffusivity from soil temperature measurements, Computers and Geosciences, 19, 475–477, 1993. Kane, D., Hinkel, K., Goering, D., Hinzman, L., and Outcalt, S.: Non-conductive heat transfer associated with frozen soils, Global Planet. Change, 29, 275–292, 2001. Ling, F. and Zhang, T.: Impact of the Timing and Duration of Seasonal Snow Cover on the Active Layer and Permafrost in the Alaskan Arctic, Permafrost Periglac. Process, 14, 141-150, 2003. Mareschal, J. C. and Beltrami, H.: Evidence for recent warming from perturbed geothermal gradients: Examples from eastern Canada, Clim. Dyn., 6, 135–143, 1992. McIntyre, S. and McKitrick, R.: Hockey sticks, principal components, and spurious significance, Geophys. Res. Lett., 32, L03710, doi:10.1029/2004GL021750, 2005. Nitoiu, D. and Beltrami, H.: Subsurface thermal effects of land use changes, J. Geophys. Res., 110, F01005, doi:10.1029/2004JF000151, 2005. Nitoiu, D.: Ground surface temperature history reconstruction from geothermal data and the influence of land disruptions on the subsurface temperature profiles, MSc Thesis, St. Francis Xavier University, 2005. Oke, T. R.: Boundary Layer Climates, Second Edition, Cambridge University Press, 1987. Pollack, H. N. and Smerdon, J. E.: Borehole climate reconstructions: Spatial structure and hemispheric averages, J. Geophys. Res., 109, D11106, doi:10.1029/2003JD004163, 2004. Pollack, H. N., Smerdon, J. E., and van Keken, P. E.: Variable seasonal coupling between air and ground temperatures: A simple representation in terms of subsurface thermal diffusivity., Geophys. Res. Lett., 32, L15405, doi:10.1029/2005GL023869, 2005. Romanovsky, V. E. and Osterkamp, T. E.: Effects of unfrozen water on heat and mass transport processes in the active layer and permafrost, Permafrost and Periglac. Process., 11, 219–239, 2000. Schmidt, W. L., Gosnold, W. D., and Enz, J. W.: A decade of air–ground temperature exchange from Fargo, North Dakota, Global Planet. Change, 29, 311-325, 2001. Smerdon, J. E., Pollack, H. N., Enz, J. W., and Lewis, M. J.: Conduction dominated heat transport of the annual temperature signal in soil, J. Geophys. Res., 108(B9), 2431, doi:10.1029/2002JB002351, 2003. Şerban, D., Nielsen , S., and Demetrescu, C.: Long wavelength ground surface temperature history from continuous temperature logs in the Transylvanian Basin, Global Planet. Change, 29, 201–217, 2001. Trenberth, K. E. and Shea, D. J.: Relationships between precipitation and surface temperature, Geophys. Res. Lett., 32, L14703, doi:10.1029/2005GL022760, 2005. \cT\^i\cstea, D., Dincă, I., Cazacu, G., S\^irbu, V., Călinescu, N., Neamu, G., and Teodoreanu, E. : Air temperature map, in Atlas Republica Socialistă România, Romanian Academy Publishing House, 1979.