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.

Diurnal variation of radar reflectivity factor during intense convective clouds over Indonesia

Abstract: Intense convective clouds is represented by very high of clouds tops that produce heavy rainfall/intense convective precipitation. The vertical structure of intense convective clouds over Indonesia was investigated using radar reflectivity factor (dBZ) data from Tropical Rainfall Measuring Mission (TRMM) satellite-Precipitation Radar (PR) 2A25 product during 1998-2014. The vertical distribution of dBZ was classified into two convective cells following the classification proposed by some previous studies. The first type, Comulonimbus Tower (CbT) that contains Z threshold of 20 dBZ in 12 km altitude with at least 9 km depth and Intense Convective Clouds (ICC) that contains Z threshold of 30 and 41 dBZ at 8 and 3 km, respectively. The distribution of intense convective clouds is more frequently observed over land such as Sumatra, Kalimantan, Java and Irian Jaya than over ocean areas. To observe the pattern of vertical structure of intense convective clouds, the vertical profile of dBZ for several locations that represent land, coastal and ocean areas were analyzed. The land and coastal areas show similar vertical structure of intense convective. On seasonal basis, intense convective clouds are more frequently found during March, April and May (MAM) which coincided with the maximum of convective available potential energy (CAPE) value. Furthermore, on diurnal basis, intense convective clouds are significantly observed during 16-18 LT (local time) and 04-09 LT over mainland and ocean areas, respectively

Potential Relationship Between Aerosols and Positive Cloud-to-Ground Lightning During the Warm Season in Sichuan, Southwest China

Abstract: This study discussed the influence of aerosols on the relative frequency of positive cloud-to-ground (CG) lightning and its dependence on thermodynamic and cloud-related factors in Sichuan during the warm season from 2005 to 2017. The relative frequency of positive CG lightning is defined as the proportion of positive CG lightning flashes to total CG lightning flashes. Although the total CG lightning density in the Western Sichuan Plateau is significantly lower than that in the Sichuan Basin, the relative frequency of positive CG lightning is higher than that in the basin. Convective available potential energy (CAPE) and vertical wind shear in the low-to-mid level of the troposphere (SHEAR-5 km) are the controlling factors of positive CG lightning frequency. A small CAPE and a large SHEAR-5 km represent weak convection, which is more conducive to the generation of positive CG lightning. The upper main positive charge region in a thriving thunderstorm is higher from the ground, which is not conducive to the transport of positive charge to the ground, so it is not conducive to the generation of positive CG lightning. In the basin, the relationship between aerosols and positive lightning is not significant, which may be due to the strong total CG lightning and the low proportion of positive CG lightning. In the plateau, both sulfate aerosol and black carbon (BC) aerosol have a significant inhibition effect on the positive CG lightning relative frequency. Sulfate aerosol stimulates the ice-phase process through a microphysical effect and promotes the development of convection. The distribution of the main positive charge center is higher, which is not conducive to the transport of positive charge to the ground and the generation of positive CG lightning. The significant heating effect of BC aerosol on the lower troposphere makes the convective development more vigorous and is not conducive to the occurrence of positive CG lightning.

The Connection between Carnot and CAPE Formulations of TC Potential Intensity

Abstract: Abstract Tropical cyclone (TC) potential intensity (PI) theory has a well-known form, consistent with a Carnot cycle interpretation of TC energetics, which relates PI to mean environmental conditions: the difference between surface and TC outflow temperatures and the air–sea enthalpy disequilibrium. PI has also been defined as a difference in convective available potential energy (CAPE) between two parcels, and quantitative assessments of future changes make use of a numerical algorithm based on this definition. Here, an analysis shows the conditions under which these Carnot and CAPE-based PI definitions are equivalent. There are multiple conditions, not previously enumerated, which in particular reveal a role for irreversible entropy production from surface evaporation. This mathematical analysis is verified by numerical calculations of PI’s sensitivity to large changes in surface-air relative humidity. To gain physical insight into the connection between the CAPE and Carnot formulations of PI, we use a recently developed analytic theory for CAPE to derive, starting from the CAPE-based definition, a new approximate formula for PI that nearly recovers the previous Carnot PI formula. The derivation shows that the difference in undilute buoyancies of saturated and environmental parcels that determines CAPE PI can in fact be expressed as a difference in the parcels’ surface moist static energy, providing a physical link between the Carnot and CAPE formulations of PI. This combination of analysis and physical interpretation builds confidence in previous numerical CAPE-based PI calculations that use climate model projections of the future tropical environment.

Genesis of severe local storms: A genetic algorithm approach

Abstract: Soft computing as Genetic Algorithm (GA) is employed In this study to discern the role of Convective Available Potential Energy (CAPE) and Convective Inhibition Energy (CINE) In the genesis of severe thunderstorms of pre-monsoon season over Northeasterm part of India. Result evinces that the population string with low CINE have higher fitness In the genesis of pre-monsoon thunderstorms than the strings with low or high CAPE. The convergence of the algorithm to a population string having low CINE and high CAPE reveals the existence of a negative correlation between CAPE and CINE during the occurrence of such storms.

Intensive Radiosonde Measurements of Summertime Convection over the Inner Mongolia Grassland in 2014: Difference between Shallow Cumulus and Other Conditions

Abstract: Using radiosonde measurements from 26 July to 30 July 2014 at Baiqi over the Inner Mongolia grassland of China, the vertical structure of shallow cumulus (SCu) clouds and associated environmental conditions were investigated. The cloud base height and the cloud top height of SCu was 3.4 km and 5 km, respectively. The temperature of the SCu layer was less than 0°C. The horizontal advection of specific humidity was smaller than the vertical transport in the atmosphere below 5 km. Above 5 km, the thermodynamic structure of the atmosphere remained stable. At the interface of the cloud layer and free air atmosphere, there was obvious wind shear and a temperature inversion (~2.9°C). Comparisons of environmental parameters associated with cumulus congestus, rain and clear days, showed that the formation of SCu was characterized by a higher Bowen ratio (high sensible heat flux and low latent heat flux), which indicated intensive turbulence in the boundary layer. The formation of SCu was associated with the boundary layer height exceeding the lifting condensation level. The maintenance of SCu was likely associated with the lower convective available potential energy, weak wind shear, and weak subsidence of the synoptic system, which did not favor the dramatic vertical development of SCu and thereby the transformation of SCu to cumulus congestus.