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This study introduces a recent field experiment investigating multiscale terrain–circulation–precipitation interactions. When a synoptic‐scale northeasterly wind prevails under the active East Asian winter monsoon, stratocumulus cloud decks with severe rainfall exceeding 100 mm·day−1 frequently occur in the northeastern plain area and adjacent mountains in Yilan, Taiwan. The Yilan Experiment of Severe Rainfall (YESR2020) is a field campaign from November 20, 2020, to November 24, 2020, to survey the physical processes leading to severe wintertime rainfall. The three‐dimensional structure of the wind field and the atmospheric environment can be identified through high temporal and spatial resolution sounding observations, which is empowered by the novel Storm Tracker mini‐radiosonde. During YESR2020, the continuously collected meteorological data of two northeasterly episodes captured the variability of local‐scale wind patterns and the features of the severe rainfall induced by stratocumulus. A preliminary analysis indicated that a local‐scale convergence line could appear over the plain area of Yilan under the northeasterly environmental condition. The precipitation hotspot was located in the mountain region of southern Yilan, where the local winds signified turbulence features. Moreover, the severe rainfall of the two northeasterly episodes spotlighted shallow cumulus under stratus with pure warm rain processes. The results of YESR2020 inspire the arrangement of future field observations to explore detailed mechanisms of heavily precipitating stratocumulus over complex topography. [ABSTRACT FROM AUTHOR]

Coordinated TLE (transient luminous event) optical observations in Taiwan have been held since 2011, with an aim to achieve triangulation. Currently, there are four observation stations with baselines varying from 100 to 400 km between them. The system recorded eight gigantic jets (GJs) that were recorded by at least two stations on the night of 20 August 2014. The weather radar data indicate that these GJs occurred around the troposphere overshooting tops of a vigorous cumulonimbus cloud. A leader‐to‐streamer transition was discerned as the appearance of these GJs changed from jet‐like (leader) to fan‐like (streamer) at ~40 km altitude. Most of these GJs terminated at the lower ionosphere boundary (80–90 km), but one GJ topped with a 10 km thick diffuse region extended higher than 100 km. Moreover, three sets of the GJs occurred within 0.5–100 s in the same general region. The residual plasma patches from the preceding GJs appear to cause the subsequent GJs to contain more bead structures and to be brighter. Also, three streamer columns of a subsequent GJ that occurred more than 100 s after the preceding GJ were identified to have rebrightened at 55 to 70 km altitudes. The rebrightened streamers and the bead structure increments in the subsequent GJs suggest that there were GJ‐produced long‐lasting plasma patches in the mesosphere. Key Points: The radar reflectivity profile showed that most of the GJs occurred around the overshooting tops of the troposphereA gigantic jet with a diffuse region on the top extended above 100 kmThe rebrightened streamers and brighter beads in the follow‐up GJ indicate that there are long‐lasting residual electron patches [ABSTRACT FROM AUTHOR]