Ceilometer-Based Analysis of Shanghai’s Boundary Layer Height (under Rain- and Fog-Free Conditions)

Abstract

To investigate the boundary layer dynamics of the coastal megacity Shanghai, China, backscatter data measured by a Vaisala CL51 ceilometer are analyzed with a modified ideal curve fitting algorithm. The boundary layer height zi retrieved by this method and from radiosondes compare reasonably overall. Analyses of mobile and stationary ceilometer data provide spatial and temporal characteristics of Shanghai’s boundary layer height. The consistency between when the ceilometer is moving and stationary highlights the potential of mobile observations of transects across cities. An analysis of 16 months of zi measured at the Fengxian site in Shanghai reveals that the diurnal variation of zi in the four seasons follows the expected pattern; for all seasons zi starts to increase at sunrise, reflecting the influence of solar radiation. However, the boundary layer height is generally higher in autumn and winter than in summer and spring (mean hourly averaged zi for days with low cloud fraction at 1100–1200 local time are 900, 654, 934, and 768 m for spring, summer, autumn, and winter, respectively). This is attributed to seasonal differences in the dominant meteorological conditions, including the effects of a sea breeze at the near-coastal Fengxian site. Given the success of the retrieval method, other ceilometers installed across Shanghai are now being analyzed to understand more about the spatial dynamics of zi and to investigate in more detail the effects of prevailing mesoscale circulations and their seasonal dynamics.

Long-term trends of global maximum atmospheric mixed layer heights derived from radiosonde measurements

“…Qualitatively, these patterns agree well with regional BLH climatology reported by Seidel et al (2012) for Europe and Guo et al (2016) for China. The seasonal patterns of MMLH also qualitatively agree with those derived using ceilometers over Shanghai (Peng et al 2017), London (Kotthaus and Grimmond 2018), Vienna (Lotteraner and Piringer 2016), and Vancouver (van der Kamp and McKendry 2010), and with that derived using micro-pulse lidar derived MMLH over Hong Kong (Yang et al 2013) and Beijing (Chu et al 2019). These studies suggest higher MMLH in the local summer and fall and lowest MMLH is found in winter.…”

Atmospheric boundary‐layer characteristics from ceilometer measurements. Part 2: Application to London's urban boundary layer

“…Uncertainty of ALC‐derived Z ML is pronounced as aerosols may remain dispersed within the ABL even if turbulent mixing is reduced. This leads to the emerging residual layer often associated with Z ML (Haeffelin et al, ; Peng et al, ). Atmospheric stability (e.g.…”

Atmospheric boundary‐layer characteristics from ceilometer measurements. Part 1: A new method to track mixed layer height and classify clouds

“…The idealised profile method (Steyn et al, ) fits a theoretical profile to the observed attenuated backscatter (e.g. Eresmaa et al, ; ; Peng et al, ).…”

“…Peng et al . () classify by cloud cover and then manually group days by relation to detected Z ML and potential residual layer to determine if the nocturnal detection results could be interpreted as the layer connected to the surface or the residual layer above. Harvey et al .…”