Fine-scale variations of near-surface-temperature lapse rates in the high drakensberg escarpment, South Africa: Environmental implications

Abstract

The objective of this study is to determine fine-scale spatial and temporal trends in screen temperature, lapse rates, and inversions associated with the Great African Escarpment wall. Particular attention is focused on the characteristics of near-surface-temperature lapse rates, their variability associated with particular synoptic conditions, and environmental implications such as for modeling climate projections in topographic- and climatic-specific high mountain regions. Hourly temperature data were logged on northeast- and southeast-facing slopes over 12 months in 2001, in the high Drakensberg Escarpment of southern Africa, at a range of elevations including: 2650, 2900, and 3200 m a.s.l. High spatial and temporal variations in lapse rates are recorded and illustrated. A relatively low mean annual lapse rate of -0.42 C 100 m-1 between 2650 and 2900 m a.s.l. doubles to -0.84 C 100 m -1 between 2900 and 3200 m a.s.l. The frequent westerlies and tropical temperate troughs provide for high lapse rates (-0.91 C 100 m -1), which are likely responsible for the relatively high annual average lapse rate of -0.63 C 100 m-1. Quantifying the fine-scale temperature trends has important implications for better understanding site-specific paleoenvironmental signatures and for projecting future climate scenarios and associated bio- and geosystem responses.