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.

中文翻译：

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南半球亚热带城市对流边界层的云高仪衍生气候学

对流边界层 (CBL) 深度的准确测量是了解和预测天气、空气质量和气候的基础。然而，CBL 深度 (BLD) 显示出显着的空间和时间可变性，这对测量和建模具有挑战性。从气溶胶层估计 CBL 深度的云高仪仪器相对便宜，具有较高的时间分辨率，并具有增加空间覆盖的潜力。然而，它们在气溶胶浓度低的亚热带环境中的性能尚不清楚。此外，关于城市 CBL 深度变异的气候学研究很少，尤其是在南半球，而且很少有研究检查 BLD 变异与天气条件之间的关系。使用三年的连续云高仪数据，我们提出了新西兰奥克兰南半球亚热带沿海城市 CBL 深度随时间变化的新气候学。结果表明，夏季奥克兰中央商务区白天最大 CBL 深度 (BLDMAX) 的中位数为 1100 m agl（高于地面），冬季为 700 m agl。发现最大 CBL 深度与太阳辐射和土壤湿度之间有很强的关系；然而，在新西兰基德森天气类型天气分类确定的最大 CBL 深度和天气条件之间没有发现任何关系。最大 CBL 深度与 Kidson 天气类型之间没有关系，这可能解释了先前观察到的奥克兰天气等级与空气污染事件之间的相关性较差。