SGER: Origin and Consequences of 'Dry Lightning' in a Dry Desert Environment

SGER：干燥沙漠环境中“干燥闪电”的起源和后果

• 批准号: 0849396
• 负责人: John Hallett
• 金额: $ 2.6万
• 依托单位: Nevada System of Higher Education, Desert Research Institute
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2009-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0849396&HistoricalAwards=false
• 关键词: SGER; Origin; Consequences; Dry; Lightning

Intellectual Merit: High level thunderstorms (sometimes called 'dry thunderstorms') originate from advection of mid level moisture with cloud condensation level near 0°C. Below the moist level lies dry air so that any precipitation particularly, in the form of smaller particles readily evaporates and fails to reach the surface. Charge separation may occur from convection in the moist region, aided by local orographic and local convergence effects, leading to strikes to ground, with the ability to initiate fires under the dry surface conditions. Such events are in contrast to deeper instability thunderstorms, formed in moist air and having cloud base temperatures above 20°C, leading not only to charge generation through the mixed phase regions aloft but giving rise to significant rain at the surface, discouraging any fire starts under the previously dry conditions. In collaboration with wildfire experts, the Principle Investigator will perform a preliminary investigation into the characteristics of these dry thunderstorms which appear to have a significant influence on the initiation of some wildfires. This investigation will include ascertaining the antecedent conditions that might lead to the formation of electrically active dry thunderstorms. Broader Impact: The ultimate purpose of the study is to assemble aspects of the events important for anticipating and forecasting similar future scenarios and to examine the frequency of the particular meteorological and midlevel cloud forming condition and the associated charge generation. There are further ramifications of the project since the large amount of smoke produced by the fires may lead to health problems extending many miles downwind. The ability to predict such events may have implications for public health as well implications for early deployment of fire fighting capabilities.

智力优势：高空雷暴（有时称为“干雷暴”）源于中层水汽的平流，云凝结水平接近0°C。 在潮湿的水平线之下是干燥的空气，因此任何降水，特别是较小颗粒形式的降水，都很容易蒸发，无法到达地表。 电荷分离可能发生在潮湿地区的对流中，并受到局部地形和局部会聚效应的帮助，导致对地面的撞击，并有能力在干燥的表面条件下引发火灾。 这类事件与更深层的不稳定性雷暴形成对比，后者形成于潮湿空气中，云底温度超过20°C，不仅导致高空混合相区产生电荷，而且在地表产生大量降雨，阻止了在先前干燥条件下发生的任何火灾。在野火专家的合作下，首席调查员将对这些干雷暴的特征进行初步调查，这些干雷暴似乎对一些野火的发生有重大影响。 这项研究将包括确定可能导致电活跃干雷暴形成的先决条件。 更广泛的影响：这项研究的最终目的是收集事件的重要方面，预测和预报类似的未来情景，并检查特定的气象和中层云形成条件和相关的电荷产生的频率。该项目还有进一步的后果，因为火灾产生的大量烟雾可能导致顺风延伸数英里的健康问题。预测此类事件的能力可能对公共卫生以及早期部署消防能力产生影响。