Connections between the low-level airflow and the increase of precipitation with altitude

A topographic precipitation gradient is established from 6 years of observations in the Reykjanes peninsula, SW-Iceland. The precipitation gradient is compared to temperature, humidity and the speed of the flow impinging the mountain range. A clear positive correlation is found between the wind speed perpendicular to the mountain ridge and the precipitation gradient, while the connection between temperature, humidity and the precipitation gradient is more complex and related to the vertical profile below and above mountain top level. Knowledge of the link between key factors of the mesoscale airflow and the precipitation gradient in mountains is very important for mapping precipitation in mountainous regions of sparse and non-continuous observations and the results from the present study will be applied in such regions.