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Atmospheric boundary‐layer characteristics from ceilometer measurements. Part 2: Application to London's urban boundary layer
Author(s) -
Kotthaus Simone,
Grimmond C. Sue B.
Publication year - 2018
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.3298
Subject(s) - ceilometer , planetary boundary layer , boundary layer , environmental science , cloud cover , meteorology , convective boundary layer , diurnal cycle , lidar , boundary (topology) , atmospheric sciences , cloud top , cloud computing , potential temperature , remote sensing , geology , computer science , mathematics , geography , physics , mechanics , mathematical analysis , operating system
Long‐term measurements of mixed layer height (Z ML ) are possible with advances in detecting Z ML based on Automatic Lidars and Ceilometers (ALC) observations. Six years of ALC measurements in central London are analysed using the CABAM (“Characterising the Atmospheric Boundary layer (ABL) based on ALC Measurements”) algorithm which provides Z ML and an ABL classification by cloud cover and type. The boundary‐layer dynamics are shown to respond to day‐length, cloud cover and cloud type. Seasonal median daily maxima range from 707 m (stratiform clouds) to 1704 m (days with convective boundary‐layer clouds following a clear night). A common approach to ABL classification and clear definition of key Z ML ‐indicators can facilitate inter‐city comparison. A simple parametrisation based on empirical coefficients derived from the London measurements is proposed to generalise the description of diurnal and seasonal variations in Z ML , including cloud conditions. This has the potential to aid improved understanding of the complex relations between surface air quality and boundary‐layer dynamics.