Universität zu Köln

Gierens, Rosa T., Henriksson, Svante, Josipovic, Micky, Vakkari, Ville, van Zyl, Pieter G., Beukes, Johan P., Wood, Curtis R. and O'Connor, Ewan J. (2019). Observing continental boundary-layer structure and evolution over the South African savannah using a ceilometer. Theor. Appl. Climatol., 136 (1-2). S. 333 - 347. WIEN: SPRINGER WIEN. ISSN 1434-4483

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Abstract

The atmospheric boundary layer (BL) is the atmospheric layer coupled to the Earth's surface at relatively short timescales. A key quantity is the BL depth, which is important in many applied areas of weather and climate such as air-quality forecasting. Studying BLs in climates and biomes across the globe is important, particularly in the under-sampled southern hemisphere. The present study is based on a grazed grassland-savannah area in northwestern South Africa during October 2012-August 2014. Ceilometers are probably the cheapest method for measuring continuous aerosol profiles up to several kilometers above ground and are thus an ideal tool for long-term studies of BLs. A ceilometer-estimated BL depth is based on profiles of attenuated backscattering coefficients from atmospheric aerosols; the sharpest drop often occurs at BL top. Based on this, we developed a new method for layer detection that we call the signal-limited layer method. The new algorithm was applied to ceilometer profiles which thus classified BL into classic regime types: daytime convective mixing, and a double layer at night of surface-based stable with a residual layer above it. We employed wavelet fitting to increase successful BL estimation for noisy profiles. The layer-detection algorithm was supported by an eddy-flux station, rain gauges, and manual inspection. Diurnal cycles were often clear, with BL depth detected for 50% of the daytime typically being 1-3 km, and for 80% of the night-time typically being a few hundred meters. Variability was also analyzed with respect to seasons and years. Finally, BL depths were compared with ERA-Interim estimates of BL depth to show reassuring agreement.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Gierens, Rosa T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Henriksson, Svante UNSPECIFIED UNSPECIFIED UNSPECIFIED Josipovic, Micky UNSPECIFIED UNSPECIFIED UNSPECIFIED Vakkari, Ville UNSPECIFIED UNSPECIFIED UNSPECIFIED van Zyl, Pieter G. UNSPECIFIED UNSPECIFIED UNSPECIFIED Beukes, Johan P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Wood, Curtis R. UNSPECIFIED UNSPECIFIED UNSPECIFIED O'Connor, Ewan J. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-151814
DOI:	10.1007/s00704-018-2484-7
Journal or Publication Title:	Theor. Appl. Climatol.
Volume:	136
Number:	1-2
Page Range:	S. 333 - 347
Date:	2019
Publisher:	SPRINGER WIEN
Place of Publication:	WIEN
ISSN:	1434-4483
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language MIXING-HEIGHT; DOPPLER LIDAR; RETRIEVAL; PROFILES; AEROSOLS; VARIABILITY; PARTICLES; POLLUTION; TRENDS; CLOUD Multiple languages Meteorology & Atmospheric Sciences Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/15181