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.

Water and Climate

Abstract: The vertical profiles and temperature and moisture in convective regimes were investigated, using moist available energy as a guide. The generalized convective available potential energy observed during the Global Atmosphere Research Program's Atlantic Tropical Experiment (GATE) phase 3 was analyzed. Ice effects were included. The results have been used to develop an improved cumulus parameterization. Several reprints from the Journal of Atmospheric Sciences are appended.

Crucial Role of Mesoscale Convective Systems in the Vertical Mass, Water, and Energy Transports of the South Asian Summer Monsoon

Abstract: Abstract Convective vertical transport is critical in the monsoonal overturning, but the relative roles of different convective systems are not well understood. This study used a cloud classification and tracking technique to decompose a convection-permitting simulation of the South Asian summer monsoon (SASM) into subregimes of mesoscale convective systems (MCSs), non-MCS deep convection (non-MCS), congestus, and shallow convection/clear sky. Isentropic analysis is adopted to quantify the contributions of different convective systems to the total SASM vertical mass, water, and energy transports. The results underscore the crucial roles of MCSs in the SASM vertical transports. Compared to non-MCSs, the total mass and energy transports by MCSs are at least 1.5 times stronger throughout the troposphere, with a larger contributing fraction from convective updrafts compared to upward motion in stratiform regions. Occurrence frequency of non-MCSs is around 40 times higher than that of MCSs. However, per instantaneous convection features, the vertical transports and net moist static energy (MSE) exported by MCSs are about 70–100 and 58 times stronger than that of non-MCSs. While these differences are dominantly contributed by differences in the per-feature MCS and non-MCS area coverage, MCSs also show stronger transport intensities than non-MCSs over both ocean and land. Oceanic MCSs and non-MCSs show more obvious top-heavy structures than their inland counterparts, which are closely related to the widespread stratiform over ocean. Compared to the monsoon break phase, MCSs occur more frequently (~1.6 times) but their vertical transport intensity slightly weakens (by ~10%) during the active phases. These results are useful for understanding the SASM and advancing the energetic framework.

Environmental controls on convective-scale perturbation growth

Abstract: Flooding from intense rainfall, resulting from convection, causes millions of pounds of damage each year. However, convection has limited predictability, often resulting in short lead times for warnings of such events. This research aims to determine the spatial scales of perturbation growth in convective-scale forecasts for different environmental conditions over the British Isles. The convective adjustment timescale identifies whether cases are in equilibrium with the large-scale forcing, so can be used to quantitatively classify convection into the regimes of quasi-equilibrium and non-equilibrium. A method is found to calculate the timescale based on criteria considering its variability and the environment in which it is calculated. The most appropriate method uses a Gaussian kernel to spatially smooth convective available potential energy and precipitation accumulation fields before the calculation. A model climatology is created over the summers of 2012-2014 (due to limited operational data from the United Kingdom Variable resolution, UKV, configuration of the Met Office United Model) to understand the characteristics of the regimes over the British Isles. In summer 85% of convection is in convective quasi-equilibrium, with more nonequilibrium events in the south and west of the British Isles. The UKV is perturbed with Gaussian buoyancy perturbations to create an ensemble. These perturbations represent unresolved processes within the boundary layer. The perturbation growth is examined across a spectrum of cases and it is shown that events at the non-equilibrium end of the spectrum have higher spatial predictability than those at the equilibrium end (O(1 km) vs. O(10 km)), implying more localised growth in nonequilibrium, than quasi-equilibrium, environments. This research has implications in the interpretation of forecasts for defining regions when issuing weather warnings associated with convection. The research also has implications for adaptive forecasting, in which high-resolution forecasts are used for nonequilibrium convection and large-member ensembles are used for events in convective quasi-equilibrium

Effect of Spatial Variation of Convective Adjustment Time on the Madden–Julian Oscillation: A Theoretical Model Analysis

Abstract: The observed convective adjustment time (CAT) associated with Madden–Julian Oscillation (MJO) precipitation is found to vary significantly in space. Here, we investigate the effect of different spatial distributions of CAT on MJO precipitation based on the frictional coupled dynamics moisture (FCDM) model. The results show that a large value of CAT tends to decrease the frequency and growth rate of eastward-propagating MJO-like mode in the FCDM model, delaying the occurrence of MJO deep convection and slowing down its eastward propagation. A large phase lag between circulation and convection decreases convective available potential energy (CAPE). In the observations, a small background vertical moisture gradient (BVMG) tends to increase the frequency associated with cold sea surface temperature (SST), while a large value of CAT tends to decrease the frequency. Due to their competing effect, the simulated frequency and phase speed remain the same when the convection moves from a warm to a cold SST region. The convection is heavily suppressed over the cold SST region due to the decreasing growth rate of unstable wavenumber-one mode with smaller BVMG and longer CAT. This theoretical finding should improve our understanding of MJO dynamics and simulation.

Analyses of Formation Mechanisms of a Rainstorm during the Declining Phase of a Northeast Cold Vortex

Abstract: The rainstorm usually occurs in the developing stage of northeast cold vortex,not in the declining phaseSo people are apt to miss the rainstorm that appears during the declining phase of cold vortexBased on the observed data and the numerical simulation results,the process of the rainstorm which occurs during the declining phase of one northeast cold vortex is analyzed in middle and eastern Jilin Province on 21 Jun 2005The results show that there is one instable layer at the center of the rainstorm,with a little convective available potential energy(CAPE)The coupling and fluctuation of low levels jet in different layers present the "relay shape" in time and space,which leads to the especial water-vapor configuration and the right instability condition,which further lead to the intense development of moist potential vorticity in the heavy rain areaUnder the condition of convective instability(CI) and conditional symmetric instability(CSI),the mesoscale convective system(MCS) forms and the convection develops in the stratiformis cloud,which directly bring the precipitationGravity wave is the possible trigger mechanism of rainstorm