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

山核桃运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了解。山核桃将集中在低层急流和稳定边界层条件下的夜间对流，最大对流可用势能位于高空。这一发现应该适用于其他夜间雷暴最大的大陆地区。山核桃有四个研究重点：1)夜间对流启动；2)钻孔扰动；3)夜间中尺度对流系统(MCSs)；4)夜间对流预报。山核桃将于2015年6月1日至7月15日在俄克拉荷马州北部、堪萨斯州中部和内布拉斯加州中南部进行。山核桃活动需要三架飞机，美国国家科学基金会-怀俄明大学国王航空公司和美国国家航空航天局DC-8探测对流前环境，NOAA P-3观察MCSs的动力学和微物理特征。项目设计包括NCAR S-POL雷达和几部移动和固定扫描多普勒雷达。实验设计的一个独特之处是将各种不同的剖面分析系统集成到一个固定和移动的山核桃综合探测阵列(PISA)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。拟议的10个PISA单元中的每一个都将在风、温度、水蒸气和气溶胶轮廓方面具有很强的互补性。山核桃建议从国家气象局和美国能源部与其南部大平原测量设施相关的地点进行补充无线电探空探测。明智的优点：众所周知，夏季大平原的日落后最常见的对流，以及由此产生的大部分降水来自MCSs。然而，关于启动、组织和维持这种夜间对流的动力机制，文献中存在着相当大的科学争论。最近的模拟和观测案例研究表明，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[下称钻孔]。这些钻孔与最低3公里处强烈向上的地块净位移(例如，0.5-1.0公里)有关，这破坏了夜间环境的稳定。虽然理想化的模拟研究表明，钻孔提升可以在夜间稳定层存在的情况下保持对流，但很少有观测证据表明这种提升与夜间系统的组织、强度、启动和维持之间存在任何反馈。山核桃将是第一个旨在研究钻孔结构和这些潜在反馈的现代活动，这使它有别于其他研究美国中部深对流的活动。由于这些扰动的产生和结构取决于MCS冷池和与风暴相关的气流模式的细节，山核桃将研究夜间MCS的动力学和微物理，以及夜间对流的发起和预测。广泛的影响：PISA测量方法使山核桃特别适合测试在“从地面上观察天气和气候：全国网络网络”(NRC 2009)、“当天气很重要：满足关键社会需求的科学和服务”(NRC 2010)和后续研讨会(Carbone等人)中概述的国家目标。2012年)和加拿大。该项目通过研究生和与REU项目的潜在联系，有相当大的教育参与度。山核桃的更广泛影响也在很大程度上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。通过学术界和NOAA国家严重风暴实验室的合作，山核桃的研究将影响国家的预报和数值天气预报能力。这一努力与NOAA的目标高度相关，即评估风暴规模预测对数值模拟日益增长的依赖，就像在警告预报倡议中所述。该项目将通过美国宇航局的参与，协助开发和应用天基遥感、天气预报和气候建模。

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.