Patterns of deviation from linearity in the relationship between lake surface water temperature and altitude above sea level in the Swiss Alps

摘要

From July to September in 1997 and 2000, "Minilog" thermistors with integrated data loggers were deployed to measure lake surface water temperature (LSWT; actually the temperature 5 cm below the surface) of 10 lakes in the Swiss Alps, spanning a range of altitudes from 613 to 2339m a.s.l. (Fig. 1, Table 1). Details of the measurement method used in 1997 have been given by Livingstone et al. (1999); the method used in 2000 was identical. The sampling interval was 30 min in 1997 and 1 hour in 2000. For the purposes of the current paper, the original sampled data were used to compute daily mean LSWTs. Based on the 1997 measurements, Livingstone et al. (1999) showed that LSWTs in the Swiss Alps decreased approximately linearly with altitude, allowing the computation of an LSWT "lapse rate" analogous to an air temperature lapse rate. Here, the measurements made in 1997 and 2000 are compared, and conclusions are drawn with respect to the pattern of deviations from the linear relationship between LSWT and altitude shown by the 10 lakes.