Analysis of soil temperatures in the arid zone of India by fourier techniques

✍ Scribed by A. Krishnan; R.S. Kushwaha

• Publisher: Elsevier Science
• Year: 1972
• Weight: 448 KB
• Volume: 10
• Category: Article
• ISSN: 0002-1571
• DOI: 10.1016/0002-1571(72)90007-6

✦ Synopsis

Harmonic analyses of weekly means of soil temperatures were made at Jodhpur, India with sandy to loamy sand soil (clay content 6-8%). The amplitudes and phase angles corresponding to various depths in respect of different harmonics are presented. The amplitudes for various depths vary between 4.8°C and 9.1°C for first harmonic and decrease sharply with higher order harmonics. The values for fourth harmonic range from 0.12-0.64°C only. The warmest soil near the soil surface occurs on June 28 while at 120 cm depth, the highest temperature maximum occurs on July 29, a delay of one month.

Though many workers have reported that the annual soil temperature cycle is well represented by the first harmonic alone, it has not been found true under Jodhpur conditions mostly due to occurrence of the southwest monsoon is well reflected, if the third harmonic is superimposed on the sum compared to 96-98% reported by other workers. The second and third harmonics represent 8-22 and 0.6-4% of total variance respectively. This effect of monsoon period on soil temperature profile at Jodhpur is due to infiltration of rainfall. The change in soil temperature pattern after July due to occurrence of the southwest monsoon is well reflected, if the third harmonic is superimposed on the sum of the first two harmonics. The thermal diffusivity computed from amplitude variation and from phase displacement do not agree-showing the non-applicability of the theory of heat conduction in a semi-infinite homogeneous medium for Jodhpur soil. The mass movement of moisture during the monsoon and flow of moisture in the vapour phase probably invalidate the application of this simple theory.