Determination of the mixing layer height from ceilometer backscatter profiles

The mixing layer height (MLH) is a key parameter in studies of many atmospheric boundary layer processes, including air quality. It primarily determines the volume in which turbulence is active and into which constituents, which are emitted near the surface, are dispersed. The height of the mixing layer typically varies between 50 and 2500 m for the Netherlands, depending on, for example, the season, time of day, the synoptic situation and local conditions as orography, land use and surface roughness.

The research presented here is performed as part of the project Integrated observations and modelling of Greenhouse Gas budgets at the national level in the Netherlands1), (hereafter ME2 project). This project is executed in the frame of the programme Besluit Subsidies Investeringen Kennisinfrastructuur – Klimaat voor Ruimte (BSIK-KvR)2). The overall goal of the ME2 project is to improve the description of the temporal and spatial distribution of greenhouse gases in the Netherlands. One of the work packages focuses on the influence of the dynamics and mixing processes in the Planetary Boundary Layer (PBL) on greenhouse gas concentrations that are observed in the PBL. An important task within this work package is the continuous monitoring of PBL height and the driving variables for PBL growth (e.g., sensible heat flux) at several locations in the Netherlands. KNMI actively participates in the ME2 project, together with a number of other Dutch research institutes and universities.