An ensemble method for improving the estimation of planetary boundary layer height from radiosonde data
Abstract. The planetary boundary layer (PBL) height (PBLH) is an important parameter for both weather, climate and air quality models. Radiosonde is one of the commonly used instruments for PBLH determination and is generally accepted as a standard for other methods. However, mainstream approaches for the estimation of PBLH from radiosonde present some uncertainties and even show disadvantages under some circumstances and the results need to be visually verified, especially during the transition period of different PBL regimes. To avoid the limitations of individual methods and provide a benchmark estimation of PBLH, we propose an ensemble method based on high-resolution radiosonde data collected in Beijing in 2017. Seven existing methods including four gradient-based methods are combined along with statistical modification. The ensemble method is verified during afternoon, morning, and evening transition periods, respectively. The overestimation of PBLH can be effectively eliminated by setting threshold for gradient-based methods and the inconsistency between individual methods can be reduced by clustering. Based on the statistics of one-year observational analysis, the effectiveness of the ensemble method reaches up to 70.8 %, an increase of 14.7 % ~ 61.2 % compared with the existing methods. Nevertheless, the ensemble method suffers to some extent from uncertainties caused by the removal of truly high PBLH, the profiles with a multi-layer structure, and the intermittent turbulence in the stable boundary layer (SBL). Finally, this method has been applied to characterize the diurnal and seasonal variations of different PBL regimes. Particularly, the average CBL height is found to be the highest in spring and the SBL is lowest in summer with about 200 m. The average PBLH at transition stage lies around 900 m and there is no obvious seasonal variation. The findings imply the effectiveness of the ensemble method.
Xi Chen et al.
Status: open (until 05 Jul 2023)
- RC1: 'Comment on amt-2023-78', Anonymous Referee #1, 21 May 2023 reply
Xi Chen et al.
Xi Chen et al.
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It has been well recognized that the estimate of planetary boundary-layer height (PBLH) from radiosonde varies dramatically by the methods used, especially at the morning and evening transitional period. To reduce the inconsistency between existing methods, this manuscript by Chen et al. proposed an ensemble method to confront this challenge based on one year worth of high-resolution radiosonde measurement at Beijing weather station. This algorithm has solid physical basis. The analysis methods are scientifically sound and the results are reasonalbe from my point of view. The manuscript is well organized and figures and tables are presented in a succint way and easy to follow. Nevertheless, the effectiveness of this method seems elusive to me and thus further clarification is neeed. Therefore, I recomment this manuscript be accepted after a minor revision. The specific comments are as follows:
L19: “during afternoon, morning, and evening transition periods, respectively.” can be reprased as “at 0800, 1400 and 2000 Beijing time”
L25: what does CBL stands for? For its first appearance, the acronym is supposed to be given a full name.
L27: It is better to use an adjective to describe the EFFECTIVENESS of the ensemble method developed in the present study.
L36: “with the free troposphere” can be revised to “between the free troposphere and groun surface”.
L47: the dash line in “wind-profiler” can be dropped.
L73: “As the routine radiosonde generally operates” -> “As the routine radiosonde measurements are generally taken”
L77: “further understanding of the transition period” -> “further understanding of the PBL structure and evolution during the transition period”.
L238 and 245: “the integrated method” is used instead of “the ensemble method” that appear in the title of this manuscript. Are there any differences between them? If not, I suggest the authors use one term through the whole manuscript.
L334: “an accuracy estimation” -> “a reliable estimation”
L336: “first” can be removed.
L367-368: “and that results in some shortcomings of these methods being retained” can be rephrased.