ALMA Memo #369
Seasonal and Diurnal Variation of Upper Soil Resistivity in the Cerro Chasc´on Science Preserve

Seiichi Sakamoto
May 2001

We monitored seasonal and diurnal variation of upper soil resistivity in the Cerro Chasc ´on Science Preserve in the Wenner method with a .xed electrode spacing of 2 m.The resistivity shows a factor ~3 seasonal variation with the lowest values during austral summer.The resistivity in summer is ~300 .m in the Pampa La Bola area while it is ~1000 .m in the Llano de Chajnantor area.Throughout the year,the resistivity at Pampa La Bola is systematically a factor ~3 lower than at Llano de Chajnantor.This means that worked area needed to realize a certain ground resistance will be a factor ~10smaller at Pampa La Bola than at Llano de Chajnantor.Although diurnal variation also exists with the lowest values near the sunsets,the peak-to-peak variation is less than 3%of the mean value of the day.

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