Knepp Travis N, Szykman James J, Long Russell, Duvall Rachelle M, Krug Jonathan, Beaver Melinda, Cavender Kevin, Kronmiller Keith, Wheeler Michael, Delgado Ruben, Hoff Raymond, Berkoff Timothy, Olson Erik, Clark Richard, Wolfe Daniel, Van Gilst David, Neil Doreen
Science Systems and Applications Inc., Hampton, Virginia 23666, USA.
NASA Langley Research Center, Hampton, Virginia 23681, USA.
Atmos Meas Tech. 2017;10:3963-3983. doi: 10.5194/amt-10-3963-2017.
Differing boundary/mixed-layer height measurement methods were assessed in moderately-polluted and clean environments, with a focus on the Vaisala CL51 ceilometer. This intercomparison was performed as part of ongoing measurements at the Chemistry And Physics of the Atmospheric Boundary Layer Experiment (CAPABLE) site in Hampton, Virginia and during the 2014 Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) field campaign that took place in and around Denver, Colorado. We analyzed CL51 data that were collected via two different methods (BLView software, which applied correction factors, and simple terminal emulation logging) to determine the impact of data collection methodology. Further, we evaluated the STRucture of the ATmosphere (STRAT) algorithm as an open-source alternative to BLView (note that the current work presents an evaluation of the BLView and STRAT algorithms and does not intend to act as a validation of either). Filtering criteria were defined according to the change in mixed-layer height (MLH) distributions for each instrument and algorithm and were applied throughout the analysis to remove high-frequency fluctuations from the MLH retrievals. Of primary interest was determining how the different data-collection methodologies and algorithms compare to each other and to radiosonde-derived boundary-layer heights when deployed as part of a larger instrument network. We determined that data-collection methodology is not as important as the processing algorithm and that much of the algorithm differences might be driven by impacts of local meteorology and precipitation events that pose algorithm difficulties. The results of this study show that a common processing algorithm is necessary for LIght Detection And Ranging (LIDAR)-based MLH intercomparisons, and ceilometer-network operation and that sonde-derived boundary layer heights are higher (10-15% at mid-day) than LIDAR-derived mixed-layer heights. We show that averaging the retrieved MLH to 1-hour resolution (an appropriate time scale for a priori data model initialization) significantly improved correlation between differing instruments and differing algorithms.
在中度污染和清洁环境中对不同的边界层/混合层高度测量方法进行了评估，重点是维萨拉CL51云高仪。此次比对是弗吉尼亚州汉普顿大气边界层化学与物理实验（CAPABLE）站点正在进行的测量的一部分，也是2014年在科罗拉多州丹佛市及其周边开展的从与空气质量相关的柱面和垂直解析观测中获取地表状况信息（DISCOVER - AQ）野外考察的一部分。我们分析了通过两种不同方法收集的CL51数据（应用校正因子的BLView软件和简单终端仿真记录），以确定数据收集方法的影响。此外，我们评估了大气结构（STRAT）算法，将其作为BLView的开源替代方案（请注意，当前工作是对BLView和STRAT算法的评估，并非对二者进行验证）。根据每种仪器和算法的混合层高度（MLH）分布变化定义了滤波标准，并在整个分析过程中应用该标准，以去除MLH反演中的高频波动。主要关注点是确定不同的数据收集方法和算法在作为更大仪器网络的一部分进行部署时，相互之间以及与无线电探空仪得出的边界层高度相比情况如何。我们确定数据收集方法不如处理算法重要，并且算法的许多差异可能是由当地气象和降水事件的影响导致的，这些事件给算法带来了困难。本研究结果表明，对于基于光探测和测距（LIDAR）的MLH比对以及云高仪网络运行而言，通用的处理算法是必要的，并且探空仪得出的边界层高度比LIDAR得出的混合层高度更高（中午时高10 - 15%）。我们表明，将反演得到的MLH平均到1小时分辨率（这是先验数据模型初始化的合适时间尺度），显著提高了不同仪器和不同算法之间的相关性。
