Downbursts are strong downdrafts of negatively buoyant air associated with convective storms and are capable of producing severe near-surface winds. Microbursts and macrobursts are subcategories of downbursts with the horizontal extent of damaging winds smaller or larger than 4 km, respectively. From January 2000 to June 2020, the Severe Weather Event Reports provided by the National Centers for Environmental Information (hereafter: Storm Events Database) contained 927 downburst, 914 microburst, and only 27 macroburst entries. We found a spatial variability of reported downbursts that is unlikely to be a result of natural processes, but rather artificially caused by the population density. An example of this bias is the abrupt decline in the number of reported events between southern and northern Arizona. Combining the Storm Events Database, ERA5 reanalysis and lightning data from the National Lightning Detection Network, we showed that cold pool strength, low-level lapse rates, WINDEX, lifted condensation level, DCAPE, WMAXSHEAR, derecho composite parameter, 2-m temperature, delta theta-e and mean low-level relative humidity demonstrate some value in downburst prediction. By combining the best predictor (cold pool strength) with the least correlated WMAXSHEAR, we created a downburst environment index (DEI) and used it to model climatological frequency of favorable downburst environments. Our analysis has shown that favorable downburst environments conditioned on lightning are the most frequent during summer over Southwest and Southeast with the most extreme environments across Great Plains. The vertical profiles of theta-e for the downburst events from reanalysis are further compared against nonsevere thunderstorms and rawinsonde data from four downburst field measurement campaigns. The results show that changes in theta-e over the lowest 200 hPa are the most important for downburst formation.

下暴流是与对流风暴相关的负浮力空气的强烈下沉气流，能够产生强烈的近地表风。微暴和大暴是下暴的子类别，破坏性风的水平范围分别小于或大于 4 公里。从 2000 年 1 月到 2020 年 6 月，国家环境信息中心（以下简称：风暴事件数据库）提供的恶劣天气事件报告包含 927 次下暴、914 次微暴和仅 27 次大暴条目。我们发现报告的暴雨的空间变异性不太可能是自然过程的结果，而是人口密度人为造成的。这种偏差的一个例子是亚利桑那州南部和北部之间报告的事件数量突然下降。结合风暴事件数据库，ERA5 再分析和来自国家闪电探测网络的闪电数据，我们显示了冷池强度、低层递减率、WINDEX、提升凝结水位、DCAPE、WMAXSHEAR、derecho 复合参数、2 米温度、delta theta-e 和平均值低水平相对湿度在下暴雨预测中显示出一些价值。通过将最佳预测因子（冷池强度）与相关性最小的 WMAXSHEAR 相结合，我们创建了一个下暴环境指数 (DEI)，并用它来模拟有利下暴环境的气候频率。我们的分析表明，以闪电为条件的有利下暴环境在夏季在西南和东南部最为频繁，在大平原地区最为极端。来自再分析的下暴事件的 theta-e 垂直剖面进一步与来自四个下暴现场测量活动的非严重雷暴和 rawinsonde 数据进行比较。结果表明，最低 200 hPa 上的 theta-e 变化对下暴形成最重要。