Analysis of Cumulus Cloud Updrafts as Observed with 1-Min Resolution Super Rapid Scan GOES Imagery

Abstract

A study was undertaken to examine growing cumulus clouds using 1-min time resolution Super Rapid Scan Operations for Geostationary Operational Environmental Satellite-R (GOES-R) (SRSOR) imagery to diagnose in-cloud processes from cloud-top information. SRSOR data were collected using GOES-14 for events in 2012–14. Use of 1-min resolution SRSOR observations of rapidly changing scenes provides far more insights into cloud processes as compared to when present-day 5–15-min time resolution GOES data are used. For midday times on five days, cloud-top temperatures were cataloged for 71 cumulus clouds as they grew to possess anvils and often overshooting cloud tops, which occurred over 33–152-min time periods. Characteristics of the SRSOR-observed updrafts were examined individually, on a per day basis, and collectively, to reveal unique aspects of updraft behavior, strength, and acceleration as related to the ambient stability profile and cloud-top glaciation. A conclusion is that the 1-min observations capture two specific cumulus cloud growth periods, less rapid cloud growth between the level of free convection and the 0°C isotherm level, followed by more rapid growth shortly after the time of cloud-top glaciation. High correlation is found between estimated vertical motion (w) and the amount of convective available potential energy (CAPE) realized to the cloud-top level as clouds grew, which suggests that updrafts were responding to the local buoyancy quite strongly. Influences of the environmental buoyancy profile shape and evidence of entrainment on cloud growth are also found through these SRSOR data analyses.

Electrical discharges in the overshooting tops of thunderstorms

“…The short pulsing variations we observed in the maximum height and in the upper density of VHF sources in the overshooting top are consistent with the oscillations in cloud top height observed by Mecikalski et al . [] and with the constantly evolving cellular structures comprising quasi‐steady updrafts noted by Doswell and Burgess [].…”

“…Even relatively small cumulus clouds typically contain multiple updrafts overlapping in time as they grow [e.g., Blyth et al, 1988;Blyth and Latham, 1997]. Furthermore, in rapid-scan satellite imagery of cloud tops, Mecikalski et al [2016] observed oscillations of cloud top temperature and height above the LNB lasting < 10 min; they also suggested that cases in which sequential oscillations of the cloud top rising above and falling below the height of glaciation over a period of a few minutes were caused by the rise and fall of successive turrets. The short pulsing variations we observed in the maximum height and in the upper density of VHF sources in the overshooting top are consistent with the oscillations in cloud top height observed by Mecikalski et al [2016] and with the constantly evolving cellular structures comprising quasisteady updrafts noted by Doswell and Burgess [1993].…”

Detection of Mixed‐Phase Convective Clouds by a Binary Phase Information From the Passive Geostationary Instrument SEVIRI

“…In the present study, we refer to the phase of the cloud coldest pixel: This method has already been used in previous studies (Mecikalski et al, 2016;Schröder et al, 2009), and we can therefore observe the beginning of the cloud glaciation. Several techniques can be used to define a cloud as liquid or ice.…”

“…Several techniques can be used to define a cloud as liquid or ice. In the present study, we refer to the phase of the cloud coldest pixel: This method has already been used in previous studies (Mecikalski et al, 2016;Schröder et al, 2009), and we can therefore observe the beginning of the cloud glaciation. We require that each tracked cloud has its coldest pixel at least 30 min in the liquid phase and ice phase to be able to observe the phase transition.…”

“…We require that each tracked cloud has its coldest pixel at least 30 min in the liquid phase and ice phase to be able to observe the phase transition. We define a reference time as the time for which the coldest pixel changes from liquid to ice, the process that all tracked clouds have in common, and is taken for synchronization (Mecikalski et al, 2016;Senf & Deneke, 2017).…”