Sunday, 22 January 2017
4E (Washington State Convention Center )
The primary objective was to gain a better understanding of the mechanisms that play important roles in the maintenance and vitality of nocturnal precipitation systems. One of PECAN’s scientific objectives was to better understand the relationship between the stable boundary layer (SBL), nocturnal low-level jet (NLLJ), and the high values of convectively available potential energy (CAPE) above the SBL on the initiation of nocturnal convection. The original PECAN domain spanned from northern Oklahoma, central Kansas and south-central Nebraska, but expanded throughout the project. Measurements were obtained by the Millersville University Atmospheric Research and Aerostat Facility (MARAF) located in Ellis, KS at Fixed PECAN Integrated Sounding Array 3 (FP3). Instrumentation used to capture this phenomenon included an acoustic SODAR with a RASS extension, a micropulse LiDAR, radiosondes, and ground-based sensors. A Scintec MFAS SODAR (1650 – 2750 sequential and polyphonic multi-frequency) w/RASS operated nearly continuously at 1290 MHz. Data were collected and averaged over 30 minute intervals and assimilated over 120 minute intervals. Parameters measured by SODAR with RASS included 3-component wind and virtual temperature and their variability to produce a suite of derived turbulence statistics. A full list of all variables measured can be found on the PECAN EOL data catalog. A case study of the strong LLJ (30 m/s) of 22 June 2015 is presented. SODAR data provided information about the evolution, duration, and dissipation of the low level jet (LLJ). Differences in the strength of the LLJ core influenced the height of the residual layer and the mixing within the boundary layer, which were also evident in MARAF MPL-111 Lidar data. These SODAR w/RASS data are supported by Lidar and surface flux measurements obtained at FP3 (see posters by K. Pozsonyi and J. Hane). Using data collected at FP3 in support of the data collected across the entire PECAN domain, we can advance the understanding of nocturnal precipitation.
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