Variations in air and ground temperature and the POM-SAT model: results from the Northern Hemisphere

Abstract

Abstract. The POM-SAT model for comparing air and ground temperatures is based on the supposition that surface air temperature (SAT) records provide a good prediction of thermal transients in the shallow subsurface of the Earth. This model consists of two components, the forcing function and an initial condition, termed the pre-observational mean (POM). I explore the sensitivity of this model as a function of forcing periods at time scales appropriate for climate reconstructions. Synthetic models are designed to replicate comparisons between borehole temperatures contained in the global database of temperature profiles for climate reconstructions and gridded SAT data. I find that the root mean square (RMS) misfit between forcing functions and transient temperature profiles in the subsurface are sensitive to periods longer than about 50 years, are a maximum when the period and the 150-year time series are equal and then decreases for longer periods. The magnitude of the POM is a robust parameter for periods equal to or shorter than the length of this time series. At longer periods there is a tradeoff between the amplitude of the forcing function and the POM. These tests provide guidelines for assessing comparisons between air and ground temperatures at periods appropriate for climate reconstructions. The sensitivity of comparisons between the average Northern Hemisphere gridded SAT record and subsurface temperature-depth profile as a function of forcing period is assessed. This analysis indicates that the Northern Hemisphere extratropical average SAT and reduced temperature-depth profile are in good agreement. By adding modest heat to the subsurface at intermediate periods some improvement in misfit can be made, but this extra heat has negligible influence on the POM. The joint analysis of borehole temperatures and SAT records indicate warming of about 1.1 • C over the last 500 years, consistent with previous studies.

Borehole climatology: a discussion based on contributions from climate modeling

“…8 can be related to that of comparing instrumental time series and observed BTPs (Harris and Gosnold, 1999;Harris and Chapman, 2001;Harris, 2007). Also in this case the selection of a mean temperature reference is not self-evident because boreholes integrate a much larger climate history that the approximately twocentury-long instrumental period or even the 1000 year GCM paleoclimatic simulations considered here.…”

Pre-Observational Evolution of Surface Temperature in Romania as Inferred from Borehole Temperature Measurements

“…1, were used either as forcing functions in the POM-SAT model or for a direct comparison with reconstructed surface temperatures by inversion of borehole data. An important issue for such comparisons, as discussed by Gonzáles-Rouco et al (2009), HARRIS (2007, and references therein, is whether the ground surface temperature tracks the air temperature. According to that discussion, variations Meteorological Administration.…”

“…Therefore, climate change studies based on borehole temperature profiles are adequate to determine long-term changes of surface temperature. Attempts to reduce these disadvantages were made by combining borehole data with proxy or meteorological data (e.g., BELTRAMI et al, 1992, 1995, BELTRAMI and TAYLOR, 1995, CHAPMAN et al, 1992, BODRI and Č ERMÁ K, 1995, HARRIS and CHAPMAN, 1995, 1998PASQUALE et al, 2005;HARRIS, 2007). The latter gives a comprehensive review of the so-called POM-SAT model that allows, by combining meteorological and borehole data, to infer information on the mean temperature before the instrumental record.…”

Mathematical modelling of soil temperature depend on two dimensional heat conductivity equation

“…Isı iletkenliği denklemine dayanarak yapılan bir çok sıcaklık modellerinde (Mahrer ve Katan, 1981;Dardo ve ark., 2001;Elias ve ark., 2004;Haris, 2007) girdi parametrelerinin fazlalığı, modelin zor ve karmaşık olmasına neden olarak, modelin hassasiyetine olumsuz etki yapmaktadır. Mahrer ve Katan (1981) tarafından, toprak sıcaklığının uzaysal dağılımını tahmin etmek için, albedo, radyasyon, hava yoğunluğu vb.…”