Least-squares optimum-order regional geothermal gradient determination from deep borehole temperature data with application to the Western Desert of Egypt

1993 ◽  
Vol 37 (3) ◽  
pp. 302-314
Author(s):  
E. M. Abdelrahman ◽  
H. M. El-Araby ◽  
B. El-Hakim ◽  
A. I. Bayoumi ◽  
A. M. Ismail
Keyword(s):  
Least Squares ◽  
Geothermal Gradient ◽  
Temperature Data ◽  
Western Desert ◽  
Deep Borehole ◽  
Optimum Order ◽  
Borehole Temperature

On the least‐squares residual anomaly determination

Geophysics ◽  
1985 ◽  
Vol 50 (3) ◽  
pp. 473-480 ◽  
Author(s):  
E. M. Abdelrahman ◽  
S. Riad ◽  
E. Refai ◽  
Y. Amin
Keyword(s):  
Least Squares ◽  
Least Squares Method ◽  
Vertical Cylinder ◽  
Correlation Factor ◽  
Western Desert ◽  
Bouguer Gravity ◽  
Residual Component ◽  
Optimum Order ◽  
Gravity Interpretation ◽  
Residual Maps

This paper discusses an approach to determine the least‐squares optimum order of the regional surface which, when subtracted from the Bouguer gravity anomaly data, minimizes distortion of the residual component of the field. The least‐squares method was applied to theoretical composite gravity fields each consisting of a constant residual component (sphere or vertical cylinder) and a regional component of different order using successively increasing orders of polynomial regionals for residual determination. The overall similarity between each two successive residual maps was determined by computing the correlation factor between the mapped variables. Similarity between residual maps of the lowest orders, verified by good correlation, may generally be considered a criterion for determining the optimum order of the regional surface and consequently the least distorted residual component. The residual map of the lower order in this well‐correlated doublet is considered the most plausible one and may be used for gravity interpretation. This approach was successfully applied to the Bouguer gravity of Abu Roash dome, located west of Cairo in the Western Desert of Egypt.

scholarly journals Impact of postglacial warming on borehole reconstructions of last millennium temperatures

2012 ◽  
Vol 8 (3) ◽  
pp. 1059-1066 ◽  
Author(s):  
V. Rath ◽  
J. F. González Rouco ◽  
H. Goosse
Keyword(s):  
Climate Models ◽  
Ground Surface ◽  
Geothermal Gradient ◽  
Temperature Profiles ◽  
Temperature Changes ◽  
Open Questions ◽  
Temperature Signal ◽  
Borehole Temperatures ◽  
Borehole Temperature ◽  
The Impact

Abstract. The investigation of observed borehole temperatures has proved to be a valuable tool for the reconstruction of ground surface temperature histories. However, there are still many open questions concerning the significance and accuracy of the reconstructions from these data. In particular, the temperature signal of the warming after the Last Glacial Maximum is still present in borehole temperature profiles. It is shown here that this signal also influences the relatively shallow boreholes used in current paleoclimate inversions to estimate temperature changes in the last centuries by producing errors in the determination of the steady state geothermal gradient. However, the impact on estimates of past temperature changes is weaker. For deeper boreholes, the curvature of the long-term signal is significant. A correction based on simple assumptions about glacial–interglacial temperature changes shows promising results, improving the extraction of millennial scale signals. The same procedure may help when comparing observed borehole temperature profiles with the results from numerical climate models.

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