Topic
Convective available potential energy
About: Convective available potential energy is a research topic. Over the lifetime, 936 publications have been published within this topic receiving 43773 citations. The topic is also known as: CAPE.
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TL;DR: In this article, the electrical processes active in ordinary (nonsevere) thunderstorms are also present in severe storms, which are defined by exceedence criteria for surface wind speed [50 knots (26 m s−1), hailstone diameter [3/4″ (19 mm), and the occurrence of a tornado.
Abstract: This review is concerned with electrification and lightning in severe weather. Based on substantial evidence that the electrical processes active in ordinary (nonsevere) thunderstorms are also present in severe storms, the initial discussion here is focused on ordinary thunderstorms. This material forms a physical basis for understanding the often marked departures in electrical behavior in severe storms, which are defined by exceedence criteria for surface wind speed [50 knots (26 m s−1)], hailstone diameter [3/4″ (19 mm)], and/or the occurrence of a tornado.
159 citations
TL;DR: In this paper, the two major tropical continental zones of active convection (Africa and South America) are compared from the standpoint of lightning activity, rainfall, thermodynamics, hydrology and aerosol-influenced cloud microphysics.
154 citations
TL;DR: In this article, the authors compared the mean-layer and surface-based parcels (SBLCL and MLLCL) using mean temperature and dewpoint in lowest 100 hPa.
Abstract: Approximately 400 Automated Surface Observing System (ASOS) observations of convective cloud-base heights at 2300 UTC were collected from April through August of 2001. These observations were compared with lifting condensation level (LCL) heights above ground level determined by 0000 UTC rawinsonde soundings from collocated upper-air sites. The LCL heights were calculated using both surface-based parcels (SBLCL) and mean-layer parcels (MLLCL—using mean temperature and dewpoint in lowest 100 hPa). The results show that the mean error for the MLLCL heights was substantially less than for SBLCL heights, with SBLCL heights consistently lower than observed cloud bases. These findings suggest that the mean-layer parcel is likely more representative of the actual parcel associated with convective cloud development, which has implications for calculations of thermodynamic parameters such as convective available potential energy (CAPE) and convective inhibition. In addition, the median value of surface-based CAPE (SBCAPE) was more than 2 times that of the mean-layer CAPE (MLCAPE). Thus, caution is advised when considering surface-based thermodynamic indices, despite the assumed presence of a well-mixed afternoon boundary layer.
153 citations
TL;DR: It is demonstrated that the atmospheric boundary layer over the forested areas is more unstable and characterized by larger values of the convective available potential energy (CAPE) due to greater humidity than that which is found over the deforested area.
Abstract: Shallow clouds are prone to appear over deforested surfaces whereas deep clouds, much less frequent than shallow clouds, favor forested surfaces Simultaneous atmospheric soundings at forest and pasture sites during the Rondonian Boundary Layer Experiment (RBLE-3) elucidate the physical mechanisms responsible for the observed correlation between clouds and land cover We demonstrate that the atmospheric boundary layer over the forested areas is more unstable and characterized by larger values of the convective available potential energy (CAPE) due to greater humidity than that which is found over the deforested area The shallow convection over the deforested areas is relatively more active than the deep convection over the forested areas This greater activity results from a stronger lifting mechanism caused by mesoscale circulations driven by deforestation-induced heterogeneities in land cover
152 citations
TL;DR: In this paper, a new cumulus parameterization is developed for which an entraining plume model is adopted, and the lateral entrainment rate varies vertically depending on the surrounding environment.
Abstract: A new cumulus parameterization is developed for which an entraining plume model is adopted. The lateral entrainment rate varies vertically depending on the surrounding environment. Two different formulations are examined for the rate. The cumulus ensemble is spectrally represented according to the updraft velocity at cloud base. Cloud-base mass flux is determined with prognostic convective kinetic energy closure. The entrainment rate tends to be large near cloud base because of the small updraft velocity near that level. Deep convection tends to be suppressed when convective available potential energy is small because of upward reduction of in-cloud moist static energy. Dry environmental air significantly reduces in-cloud humidity mainly because of the large entrainment rate in the lower troposphere, which leads to suppression of deep convection, consistent with observations and previous results of cloud-resolving models. The change in entrainment rate has the potential to influence cumulus conve...
147 citations