A Ceilometer-Derived Climatology of the Convective Boundary Layer Over a Southern Hemisphere Subtropical City
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A Ceilometer-Derived Climatology of the Convective Boundary Layer Over a Southern Hemisphere Subtropical City Hannah G. Marley1 · Kim N. Dirks2 · Ian McKendry3 · Lena F. Weissert4 · Jennifer A. Salmond1 Received: 26 March 2020 / Accepted: 9 October 2020 © Springer Nature B.V. 2020
Abstract Accurate measurements of the depth of the convective boundary layer (CBL) are fundamental for understanding and forecasting weather, air quality, and climate. However, the CBL depth (BLD) shows significant spatial and temporal variability, which is challenging to measure and model. Ceilometer instruments, which estimate the CBL depth from aerosol layers, are relatively cheap, have high temporal resolution, and have the potential for increased spatial coverage. Nevertheless, their performance in subtropical environments with low aerosol concentrations is unknown. Furthermore, climatological studies of the variability in the urban CBL depth are scarce, especially in the Southern Hemisphere, and very few studies have examined the relationship between BLD variability and synoptic conditions. Using three years of continuous ceilometer data, we present a novel climatology of the temporal variability in CBL depth over the Southern Hemisphere subtropical, coastal city of Auckland, New Zealand. The results indicate that the median daytime maximum CBL depth (BLDMAX ) over the Auckland CBD is 1100 m a.g.l. (above ground level) during summer and 700 m a.g.l. during winter. Strong relationships are found between the maximum CBL depth and both solar radiation and soil moisture; however, no relationship is found between the maximum CBL depth and the synoptic conditions as determined by the New Zealand Kidson weather types synoptic classification. The absence of a relationship between the maximum CBL depth and Kidson weather types may explain the poor correlation previously observed between synoptic class and air pollution events in Auckland. Keywords Boundary-layer depth · Ceilometer · Convective boundary layer · Kidson weather types · Urban climatology
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Hannah G. Marley [email protected]
1
School of Environment, The University of Auckland, Auckland 1010, New Zealand
2
School of Population Health, The University of Auckland, Auckland 1023, New Zealand
3
Department of Geography, University of British Columbia, Vancouver, BC V6T 1Z2, Canada
4
School of Chemical Sciences, The University of Auckland, Auckland 1010, New Zealand
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H. G. Marley et al.
1 Introduction The convective boundary layer (CBL) plays an important role in the transfer of energy and atmospheric constituents, including water vapour and pollutants, between the surface and the free atmosphere (Tang et al. 2016). When CBL growth is inhibited through unfavourable meteorological conditions, the build-up of pollutants can lead to prolonged episodes of poor air quality (Herrera-Mejía and Hoyos 2019). Furthermore, the depth and characteristics of the CBL are linked via complex feedback loops with processes which regulate surface meteorological and climatic variab
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