Climate of the Past www.clim-past.net 1814-9324 1814-9332 3 4 2007 10.5194/cp-3-637-2007 http://www.clim-past.net/3/637/2007/ http://www.clim-past.net/3/637/2007/cp-3-637-2007.html http://www.clim-past.net/3/637/2007/cp-3-637-2007.pdf 637 645 2007-11-02 Thermal signal propagation in soils in Romania: conductive and non-conductive processes C. Demetrescu crisan@geodin.ro D. Nitoiu C. Boroneant 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 available in 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 the surface as well as rain fall and snow cover thickness have been monitored. The selected locations sample various climate environments in Romania. Preliminary analytical modelling shows that soil temperatures track air temperature variations at certain locations and, consequently, the heat transfer is by conduction, while at other stations 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 uppermost one meter of soil is mainly by conduction; the inferred thermal diffusivity for 8 stations with continuous time series at all depth levels ranges from 3 to 10×10^−7 m² s^−1. Bartlett, 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. Bartlett, M. G., Chapman, D. S., and Harris, R. N.: Snow effect on North American ground temperatures, 1950–2002, J. Geophys. Res., 110, F03008, doi:10.1029/2005JF000293, 2005. 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.: Climate from borehole data: Energy fluxes and temperatures since 1500, Geophys. Res. Lett., 29, 2111, doi:10.1029/2002GL015702, 2002. 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. Briffa, K. R. and Osborn, T. J.: Blowing hot and cold, Science, 295, 2227–2228, 2002. Carslaw, H. S. and Jaeger, J. C.: Conduction of Heat in Solids, 2nd ed., Oxford Univ. Press, New York, 1959. Chapman, D. S., Bartlett, M. G., and Harris, R. N.: Comment on "Ground vs. surface air temperature trends: Implications for borehole surface temperature reconstructions" by Mann M. E. and Schmidt G., Geophys. Res. Lett., 31, L07205, doi:10.1029/2003GL019054, 2004. 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, 99–106, 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, doi:10.1126/science.1066208, 2002. Esper, J., Frank, D. C., and Wilson, R. J. S.: Climate reconstructions: low-frequency ambition and high-frequency ratification, EOS, 85, 113, p. 120, 2004. González-Rouco, J. F., von Storch, H., and Zorita, E.: Deep soil temperature as proxy for surface air-temperature in a coupled model simulation of the last thousand years, Geophys. Res. Lett., 30, 2116–2119, 2003. 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. 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. Hegerl, G. C., Crowley, T. J., Allen, M., Hyde, W. T., Pollack, H. N., Smerdon, J. E., and Zorita, E.: Detection of human influence on a new, validated 1500-year temperature reconstruction, J. Climate, 20, 650–666, 2007. Huang, S., Pollack, H. N., and Shen, P. Y.: Temperature trends over the last five centuries reconstructed from borehole temperatures, Nature, 403, 756–758, 2000. 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. Mann, M. E., Rutherford, S., Bradley, R. S., Hughes, M. K., and Keiming, F. T.: Optimal surface temperature reconstructions using terrestrial borehole data, J. Geophys. Res., 108(D7), 4203, doi:10.1029/2002JD002532, 2003. Mann, M. E. and Schmidt, G. A.: Ground vs. surface air temperature trends: Implications for borehole surface temperature reconstructions, Geophys. Res. Lett., 30, 1607, doi:10.1029/2003GL017170, 2003. 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. Putnam, S. N. and Chapman, D. S.: A geothermal climate change observatory: First year results from Emigrant Pass in northwest Utah, J. Geophys. Res., 101, 21 877–21 890, 1996. Romanovsky, V. E. and Osterkamp, T. E.: Effects of unfrozen water on heat and mass transport processes in the active layer and permafrost, Permafrost 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. Smerdon, J. E., Pollack, H. N., Cermak, V., Enz, J. W., Kresl, M., Safanda, J., and Wehmiller, J. F.: Air-ground temperature coupling and subsurface propagation of annual temperature signals, J. Geophys. Res., 109, D21107, doi:10.1029/2004JD005056, 2004. Smerdon, J. E., Pollack, H. N., Cermak, V., Enz, J. W., Kresl, M., Safanda, J., and Wehmiller, J. F.: Daily, seasonal and annual relationships between air and subsurface temperatures, J. Geophys. Res.-Atmos., 111, D07191, doi:10.1029/2004JD005578, 2006. Sokratov, S. A. and Barry, R. G.: Intraseasonal variation in the thermoinsulation effect of snow cover on soil temperature and energy balance, J. Geophys. Res., 107(D10), doi:10.1029/2001JD000489, 2002. Stevens, M. B., González-Rouco, J. F., and Beltrami, H.: North American climate of the last millennium: Underground temperatures and model comparison, J. Geophys. Res., 2006JF000705, in press, 2007. Stieglitz, M., Dery, S. J., Romanovsky, V. E., and Osterkamp, T. E.: The role of snow cover in the warming of arctic permafrost, Geophys. Res. Lett., 30, 1721, doi:10.1029/2003GL017337, 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. Yoshikawa, K., Bolton, W. R., Romanovsky, V. E., Fukunda, M., and Hinzman, L. D.: Impacts of wildfire on the permafrost in the boreal forests of Interior Alaska, J. Geophys. Res., 108, 8148, doi:10.1029/2001JD000438, 2003.