An estimate of the heat balance in an alpine valley in the New Zealand southern Alps

Abstract

Daily, monthly and annual values of net radiation, soil heat flow, sensible heat flow and evaporative heat loss were 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 was made of a regression equation between net radiation and incoming shortwave radiation, drainage lysimeter measurements, and a modified form of the Penman formula for estimating daily values of evapotranspiration. 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. 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 and daily mean values of Bowen ratio, owing to soil moisture deficits in months of consistently high net radiation.