Cave climate: Assessment of heat and moisture exchange

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Abstract

Earlier work on the role of airflow and ventilation in cave climate is extended to include the processes of heat and mass transfer. The study site is Glowworm Cave in New Zealand which is of special interest because of the existence of climate sensitive cave fauna on which the value of a cave as a tourist resource depends. However, the purpose is to provide greater insight into processes governing cave climate generally. Detailed measurements of temperature, humidity and evaporation were made over a 12-month period and a thermodynamic advection model calibrated to help explain climatic patterns observed and processes operating. The results show that the spatial and temporal distribution of cave air temperature and humidity, as well as direction of airflow, can be determined from external air temperature and humidity. The dominant processes are the vapour and sensible and latent heat fluxes to and from both the air moving through the cave and the cave surfaces. Tn winter there is strong drying and cooling of the cave environment as external air entering the cave is warmed. In summer, humidity levels in the cave rise substantially and result in condensation (wetting) through the cave despite general warming of the cave air.

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