An Overview of Parameterezations of Heat Transfer over Moss-Covered Surfaces in the Earth System Models

Moss cover plays an important role in shaping the thermodynamic and biogeochemical functioning of ecosystems at high latitudes, where it is the dominant vegetation type. It reduces the heat transfer through the soil-atmosphere interface and between deep levels of the active layer, which leads to a decrease in the thickness of the seasonally thawed layer, and regulates the soil moisture. At the same time, in Earth system models, the heat and moisture exchange in the moss cover is represented by simplified approaches. The purpose of this paper is to summarize up-to-date knowledge on heat-transfer mechanisms acting in moss cover and methods for their quantitative description; we also aim to identify the data missing for constructing physically justified parameterizations and formulate tasks for the future theoretical and experimental work. This paper provides a brief overview of the heat-transfer parameterizations for the moss-lichen cover used in modern Earth system models; presents the results of experimental and theoretical studies of the thermal conductivity of soils and mosses; and strives to encompass available information on the dynamic and thermal roughness of plant communities, including mosses. In conclusion, recommendations are given on the development of parameterizations of thermodynamic processes in the moss cover and design of desirable model and field experiments.