ALI, ZEESHAN (2026) Planetary Boundary Layer Height (PBLH) retrieval and analysis over two ACTRIS Stations by Active Remote Sensing Techniques. [Tesi di dottorato]

Documento PDF ALI_ZEESHAN_38.pdf Download (7MB)

Abstract

Planetary boundary-layer height (PBLH) is a key parameter for characterising the depth of turbulent vertical mixing in the lower atmosphere and for interpreting near-surface aerosol variability. The objective of this study is to investigate the diurnal and seasonal variability of PBLH using active remote sensing observations within the ACTRIS framework, with the main multi-instrument analysis carried out at the Potenza station, where aerosol lidar, ceilometer, and wind Doppler lidar measurements are simultaneously available. A complementary land-sea comparison is then performed using ceilometer observations at Potenza and at the marine site of Lampedusa to examine how boundary-layer development differs between continental and marine environments under different seasonal conditions. At Potenza, multi-wavelength aerosol lidar range-corrected signal (RCS) profiles are analysed using a consistent set of lidar-based retrieval techniques, including gradient-based approaches (GM, IPM, LGM, CRGM) and the wavelet covariance transform (WCT), applied at wavelengths of 355, 532, and 1064 nm. Ceilometer backscatter profiles are processed using the error-function fitting method (ERF-fit). Wind Doppler lidar observations are used to estimate PBLH using the vertical-velocity variance method applied to vertical-stare measurements and the wind-shear method applied to DBS (Doppler beam swinging) scans, supported by wind-speed and wind-direction estimates. The aerosol-lidar results at Potenza show that method-to-method differences occur under stratified conditions and in multi-layer situations, where the retrieved PBLH can vary between algorithms. A small wavelength dependence is also observed, with 1064 nm generally yielding slightly higher PBLH peaks than 532 and 355 nm, while the 355 nm estimates tend to be slightly lower. Overall, a coherent seasonal cycle is observed across wavelengths, with the deepest daytime development in summer, intermediate growth in spring, reduced amplitude in autumn, and the shallowest and most stable conditions in winter. For the wind Doppler lidar, variance and shear-based estimates agree well during peak convective hours, while differences occur during the late-afternoon transition, when turbulence weakens but shear aloft can remain pronounced. The ceilometer-based land-sea comparison highlights a clearer seasonal amplitude and stronger daytime growth at Potenza, whereas Lampedusa shows a weaker seasonal amplitude and a different annual pattern, consistent with the distinct controls acting over marine environments.

Downloads

Actions (login required)

Modifica documento