Estimation of planetary boundary layer height from radiosonde profiles over West Africa during the AMMA field campaign: Intercomparison of different methods
Estimation of planetary boundary layer height from radiosonde profiles over West Africa during the AMMA field campaign: Intercomparison of different methods
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DOI：
10.1016/j.sciaf.2019.e00228
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发表时间：
2020-03
影响因子：
2.9
通讯作者：
J. N. Aryee;L. Amekudzi;K. Preko;W. A. Atiah;S. Danuor
中科院分区：
文献类型：
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作者：
J. N. Aryee;L. Amekudzi;K. Preko;W. A. Atiah;S. Danuor
推导真实的行星边界层高度（PBLH）对于天气、气候和空气质量模式至关重要，尽管其性质模棱两可。在本文中，7 PBLH估计方法进行了比较评估，在非洲季风多学科分析（AMMA）项目活动期间，2006年6月至2007年7月，在西非的18个地点的无线电探空仪配置文件。首先，PBLH从无线电探空仪廓线中被识别为混合比（q）、相对湿度（RH）和水汽活动（N）的最小梯度和位温（θ）的最大梯度的位置。用于识别PBL顶部的其他方法是在0.25的临界阈值下的AkticalNS方法和批量Richardson（Rib）方法。接下来，将参考方法（ho）确定为PBL比较的基准。目视检查的个人档案允许评估的homethod产生可靠的PBLH估计。此后，对流和稳定的情况下，PBLH进行比较，与稳定的边界层（SBL）的高度一般低于700米A.G.L的所有方法，而对流边界层（CBL）的高度范围在300米A.G.L和1400米A.G.L的研究区域的不同区域。同样，NS方法由于不能识别露点或虚位温不连续性而未能检测到SBL。此外，肋方法，特别是在稳定的情况下，产生的PBL顶部与参考方法（ho）一致时，NLLJ是明确定义的，由于急流核心下方的风切变湍流动能（TKE）的生产。然后，将研究领域分为三个区域，并根据每个区域评估每种方法的性能。在空间上，CBL的高度被观察到增长厚的东北方向上的干燥，干旱地区，感热的积分值迅速转换的表面净辐射，有显着的影响CBL整个白天的增长。其他可能的原因是平流，地形和机械湍流的生产。然而，在夜间观察到了逆转，SBL在干燥，干旱地区较薄，而在沿海地区相对较高。最后，统计评估，再加上目视检查的个人档案，表明梯度方法（特别是N）优于RibandNS方法，产生非常低的偏差，以及，高和统计上显着的相关系数。这些结果是有用的，以提高该地区的PBL模式的性能。本研究结果的可能局限性是不同地点之间的不同上升时间，以及每个地点的上升次数，这对结果有潜在的影响。目前正在根据西非动力学-气溶胶-化学-云相互作用实地活动的观测结果开展进一步工作，以充分证实辐射和能量收支在PBL发展中的作用，同时进一步评估其对PBL探测方法性能的重大影响。
Deducing realistic planetary boundary layer heights (PBLH) is crucial for weather, climate and air quality models, despite its equivocal nature. In this paper, a comparative assessment of seven PBLH estimation methods has been performed, with radiosonde profiles taken during the African Monsoon Multidisciplinary Analyses (AMMA) project campaign from June, 2006 to July, 2007 over 18 locations in West Africa. First, PBLH was identified from the radiosonde profiles as the location of minimum gradients in mixing ratio (q), relative humidity (RH) and refractivity (N), and maximum gradient in potential temperature (θ). Other methods used to identify PBL tops were the statisticalNSmethod and bulk Richardson (Rib) method at a critical threshold of 0.25. Next, a reference method (ho) was identified as the benchmark for PBL comparison. Visual inspection of the individual profiles allowed for assessing the homethod to yield reliable PBLH estimates. Thereafter, comparisons of the PBLH were performed for both convective and stable cases, with the stable boundary layer (SBL) height being generally below 700 m a.g.l for all methods, whereas, convective boundary layer (CBL) heights ranged between 300 m a.g.l and 1400 m a.g.l across different regions of the study area. Contrarily, the NS method failed to detect the SBL due to its inability to identify a dewpoint or virtual potential temperature discontinuity. Additionally, the Ribmethod, particularly in stable cases, yielded PBL tops consistent with the reference method (ho) whenever the NLLJ was clearly defined due to contribution of wind shear beneath the jet core to turbulent kinetic energy (TKE) production. Afterwards, the study domain was split into three zones and the performance of each method was assessed per each zone. Spatially, the CBL height was observed to grow thicker in the north-east direction over the dry, arid regions, where integral values of sensible heat rapidly converted by surface net radiation, has significant influence on the growth of CBL throughout daytime. Other likely reasons for this observation are advection, orography and mechanical turbulence production. However, a reversal was observed at night with the SBL being thinner in the dry, arid regions and rather relatively, higher in the coastal regions. Finally, the statistical assessment, coupled with visual inspection of the individual profiles, showed that the gradient methods (particularlyN) outperformed theRibandNSmethods, yielding very low biases as well as, high and statistically significant correlation co-efficients. These results are useful for enhancing the performance of PBL models over the region. Possible limitations to the findings of this study are the different ascent times between the sites, as well as the number of ascents per site, which have potential implications for the results. Further work, based on observations from the DACCIWA (Dynamics-aerosol-chemistry-cloud interactions in West Africa) field campaign, is currently ongoing to also fully substantiate the role of radiation and energy budgets in PBL development, while further assessing their significant effect on the performance of the PBL-detection methods.