Scientific Program Overview (SPO): Plains Elevated Convection at Night (PECAN)

PECAN活动被设想为一个多机构项目（NSF，NOAA，NASA，DOE），旨在促进对大陆夜间暖季降水的理解。PECAN将集中在夜间对流的条件下，低空急流和稳定的边界层与最大的对流可用位能位于高处。研究结果应适用于夜间雷暴最大的其他大陆地区。PECAN有四个研究重点：i）夜间对流的启动; ii）孔扰动; iii）夜间中尺度对流系统（MCS）; iv）夜间对流的预测。PECAN将于2015年6月1日至7月15日在北方俄克拉荷马州、堪萨斯中部和内布拉斯加州中南部进行。PECAN活动需要三架飞机，其中NSF-怀俄明州大学空中国王号和NASA DC-8探测对流前环境，NOAA P-3观察MCS的动力学和微物理特征。该项目设计包括NCAR S-POL雷达和几个移动的和固定扫描多普勒雷达。实验设计的一个独特方面是将各种各样的剖面系统集成到固定和移动的PECAN集成探测阵列（比萨）中，包括差分吸收激光雷达、多普勒激光雷达和拉曼激光雷达、多通道微波辐射计、红外光谱仪和声学系统。10个拟议的比萨单元中的每一个都将在风、温度、水蒸气和气溶胶的剖面能力方面具有高度的互补性。PECAN建议从国家气象局和能源部与他们的南部大平原测量facility.Intellectual优点：这是建立良好的对流是最常见的日落后，整个大平原在夏季，和大部分由此产生的降水福尔斯从MCS的补充无线电探空仪soundings。然而，在文献中存在相当大的科学争论，以启动，组织和维持这种夜间对流的动力机制。最近的模拟和观测个例研究表明，在这种稳定的低空急流环境中，夜间对流经常触发钻孔、波状钻孔和孤立波[以下简称钻孔]。这些钻孔与强烈的向上净地块位移（例如，0.5-1.0公里），最低的~3公里，这使夜间环境不稳定。虽然理想化的模拟研究表明，孔提升可以维持对流的存在下，夜间稳定层，很少有观测证据存在任何反馈之间的这种提升和组织，强度，启动和维护夜间系统。PECAN将是第一个旨在检查孔结构和这些潜在反馈的现代活动，这使其与其他研究美国中部深对流的活动不同。由于这些扰动的产生和结构取决于MCS冷池和风暴相关流型的细节，PECAN将解决夜间MCS的动力学和微物理学以及夜间对流的启动和预测。更广泛的影响：比萨测量方法使PECAN特别适合于测试“从地面观测天气和气候：全国网络网络”（NRC 2009年）、“当天气重要时：满足关键社会需求的科学和服务”（NRC 2010年）以及在美国、热力学剖面技术（Carbone等人，2012年）和加拿大举办的后续讲习班。该项目有相当大的教育参与，通过研究生和潜在的链接到REU计划。PECAN的更广泛影响在很大程度上也是由于对夜间对流的预测不佳，加上它们对水文，能源和农业的重要性以及MCS严重和危险天气的公共安全风险。PECAN研究将通过学术界和NOAA国家严重风暴实验室之间的合作，影响国家的预报和数值天气预报能力。这项工作与NOAA的目标高度相关，即评估风暴尺度预测对数值模拟的依赖程度，如在预测预警倡议中。该项目将通过美国航天局的参与，协助开发和应用天基遥感、天气预测和气候建模。

The PECAN campaign is envisioned as a multi-agency project (NSF, NOAA, NASA, DOE) designed to advance the understanding of continental nocturnal warm-season precipitation. PECAN will focus on nocturnal convection in conditions with a low-level jet and a stable boundary layer with the largest Convectively Available Potential Energy located aloft. The findings should be applicable to other continental regions with nocturnal thunderstorm maxima. PECAN has four research foci: i) Nocturnal convective initiation; ii) Bore disturbances; iii) Nocturnal mesoscale convective systems (MCSs); iv) Prediction of nocturnal convection. PECAN will be conducted across northern Oklahoma, central Kansas and into south-central Nebraska from 1 June to 15 July 2015. The PECAN campaign calls for three aircraft with the NSF-University of Wyoming King Air and the NASA DC-8 probing the pre-convective environment and the NOAA P-3 observing the dynamical and microphysical characteristics of MCSs. The project design includes the NCAR S-POL radar and several mobile and fixed scanning Doppler radars. A unique aspect of the experimental design is the integration of a wide variety of profiling systems into a fixed and mobile PECAN Integrated Sounding Array (PISA) including Differential Absorption Lidars, Doppler lidars, and Raman lidars, multi-channel microwave radiometers, infrared spectrometers, and acoustic systems. Each of the 10 proposed PISA units will be highly complementary in their capability to profile wind, temperature, water vapor, and aerosols. PECAN proposes supplemental radiosonde soundings from National Weather Service and DOE sites associated with their Southern Great Plains measurement facility.Intellectual Merit :It is well established convection is most common after sunset across the Great Plains in summer, and much of the resulting precipitation falls from MCSs. Considerable scientific debate, however, exists in the literature as to the dynamical mechanisms that initiate, organize and maintain this nocturnal convection. Recent modeling and observational case studies have shown that nocturnal convection in this stable, low-level jet environment frequently triggers bores, undular bores and solitary waves [hereafter referred to as bores]. These bores are associated with intense upward net parcel displacements (e.g., 0.5-1.0 km) in the lowest ~3 km, which destabilizes the nocturnal environment. While idealized modeling studies suggest that bore lifting can maintain convection in the presence of a nocturnal stable layer, little observational evidence exists for any feedbacks between this lifting and the organization, intensity, initiation and maintenance of nocturnal systems. PECAN will be the first modern campaign designed to examine bore structure and these potential feedbacks, which distinguishes it from other campaigns that have studied deep convection in the central USA. Since the generation and structure of these disturbances depends on the details of the MCS cold pool and storm-relative flow patterns, PECAN will address the dynamics and microphysics of nocturnal MCSs as well as the initiation and prediction of nocturnal convection.Broader Impacts :The PISA measurement approach makes PECAN particularly well suited to testing the national goals outlined in "Observing Weather and Climate from the Ground Up: A Nationwide Network of Networks" (NRC 2009), "When Weather Matters: Science and Service to Meet Critical Societal Needs" (NRC 2010) and the follow-up workshop on in the US, Thermodynamic Profiling Technologies (Carbone et al. 2012) and Canada. The project has considerable educational involvement through graduate students and potential links to REU programs. The broader impact of PECAN is also driven in large part by poor prediction of nocturnal convection coupled with their importance to hydrology, energy and agriculture and the public safety risk of MCS severe and hazardous weather. PECAN research will impact the nation's forecasting and numerical weather prediction capabilities through collaborative efforts between the academic community and NOAA's National Severe Storms Laboratory. The effort is highly relevant to NOAA's goal to assess the increasing dependence of storm-scale prediction on numerical modeling, as in the Warn on Forecast Initiative. The project will assist in developing and applying space-based remote sensing, weather prediction and climate modeling through NASA participation.