Heat balance studies at the Chilton Valley, Cass in the New Zealand Southern Alps
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
This study shows that a knowledge of the values of the heat balance at the earth's surface gives an increased understanding of the character of the climate of an alpine valley. Daily, monthly, and annual values of net radiation, soil heat flow, sensible heat flow and evaporative heat loss are measured, or estimated, for the period 15 August, 1969 to 14 August, 1970 at the Chilton Valley in the New Zealand Southern Alps (altitude 780 m.a.s.l.). In the estimation of these values use is made of a regression equation between net radiation and incoming shortwave radiation, non-weighing lysimeter measurements, and a modified form of the Penman formula for calculating daily values of evapotranspiration. Also reported are subsidiary studies of related phenomena such as the incident shortwave radiation on slopes, ice needle growth, the wetting and drying of soils, and advection. The average values of the energy flows during the study year were:- net radiation, 136 ly day-¹, soil heat flow, 2 ly day-¹ ,sensible heat flow, -58 ly day -¹,and evaporative heat loss, -82 ly day-¹. Spectral and harmonic analysis showed the daily values of the heat balance components to contain periodicities. The application of Lettau’s theory of climatonomy illuminated other features of the climate. The daily energy flow values are shown to be interrelated, and to be associated with major synoptic weather types. In comparison with the heat balances of other mid-latitude stations, near the west coasts of land masses, the heat balance of the Chilton Valley during the study year was noteworthy for (a) a positive mean monthly value of net radiation in winter, (b) a net mean monthly flow of sensible heat away from the surface in winter, and (c) the possibility of high monthly mean and daily values of the Bowen ratio, owing to soil moisture deficits in months of consistently high net radiation.