Evaluation of retrieval methods for planetary boundary layer height based on radiosonde data

Hui Li,Yuefeng Zhao,Boming Liu,Xin Ma,Shikuan Jin,Wei Gong,Yingying Ma

doi:10.5194/amt-14-5977-2021

Abstract

Abstract. Radiosonde (RS) is widely used to detect the vertical structures of the planetary boundary layer (PBL), and numerous methods have been proposed for retrieving PBL height (PBLH) from RS data. However, an algorithm that is suitable under all atmospheric conditions does not exist. This study evaluates the performance of four common PBLH algorithms under different thermodynamic stability conditions based on RS data collected from nine sites in January–December 2019. The four RS algorithms are the potential temperature gradient method (GMθ), relative humidity (RH) gradient method (GMRH), parcel method (PM) and Richardson number method (RM). Atmospheric conditions are divided into convective boundary layer (CBL), neutral boundary layer (NBL) and stable boundary layer (SBL) on the basis of the potential temperature profile. Results indicate that SBL is dominant at nighttime, whilst CBL dominates at daytime. Under all and SBL classifications, PBLH retrieved by RM is typically higher than those retrieved using the other methods. On the contrary, the PBLH result retrieved by PM is the lowest. Under CBL and NBL classifications, PBLH retrieved by PM is the highest. PBLH retrieved by GMθ and GMRH is relatively low under all classifications. Moreover, the uncertainty analysis shows that the consistency of PBLH retrieved by different algorithms is more than 80 % under CBL and NBL classifications. By contrast, the consistency of PBLH is less than 60 % under SBL classification. The average profiles and standard deviations of wind speed and potential temperature under consistent and inconsistent conditions are also investigated. The results indicate that consistent cases are typically accompanied by evident atmospheric stratification, such as a large gradient in the potential temperature profile or a low-level jet in the wind speed profile. These results indicate that the reliability of the PBLH results retrieved from RS data is affected by the structure of the boundary layer. Overall, GMθ and RM are appropriate for CBL condition. GMθ and PM are recommended for NBL condition. GMθ and GMRH are robust for SBL condition. This comprehensive comparison provides a reference for selecting the appropriate algorithm when retrieving PBLH from RS data.

Highlights

The planetary boundary layer (PBL) is the lowest layer of the atmosphere
GMθ and GMRH are robust for stable boundary layer (SBL) condition
The proportion of invalid values for Richardson number method (RM) is 18.30 % and 63.47 % under neutral boundary layer (NBL) and SBL classifications, respectively. This finding indicates that GMθ, GMRH and parcel method (PM) are more effective than RM under NBL and SBL conditions

Summary

Introduction

The planetary boundary layer (PBL) is the lowest layer of the atmosphere. Its vertical structure is highly significant in the study of the environment and climate (Stull, 1988; Garratt et al, 1982; Guo et al, 2016; Wang et al, 2021). The structure of PBL is greatly affected by topography, season and weather (Eresmaa et al, 2006; Guo et al, 2016). The PBL height (PBLH) is directly related to the accumulation and diffusion of pollutants, and it can be used as the input parameter of atmospheric chemical models and weather forecast systems (Liu et al, 2020a; Shi et al, 2020; Zhang et al, 2021). Monitoring PBLH is important (Seidel et al, 2010)

Methods

Results

Conclusion