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.

Analysis of Convective-Symmetric Instabilities and Frontogenesis in a Convective Rain Band on the Northwest Edge of WPSH

Abstract: The cloud characteristics of a convective rain band that occurred on the northwest edge of the western Pacific subtropical high(WPSH) on August 25, 2009 are analyzed using infrared cloud images. Using the ARW-WRF V3.3 model, the occurrence and development of the convective rain band are simulated. Based on the success of the simulation, the symmetric, convective, inertial instabilities, and frontogenesis of the convective rain band are studied using the model output. The results show that the convective rain band on the northwest edge of the WPSH consists of a number of mesoscale convective cells, which develop and die out when moving with the middle troposphere environmental flow and often bring heavy rain in their passing-by region. There is a broad baroclinic cloud band on the northwest side of the band and a cloudless sky controlled by WPSH on the southeast side. The convective band occurs in the symmetric unstable area below 700 hPa and there are convective and weak inertial instabilities between 700 and 500 hPa. With the development of the convection, the convective instability becomes weak, but the inertial instability becomes intensified between 700 and 500 hPa. The convective body is an obvious mixture of slanted convection and vertical convection, with slanted upward flow in the low troposphere, vertical upward flow in the mid–high troposphere, and downward flow on the left side of the body, reflecting the energy release of convective-symmetric instabilities. The frontogenesis below 750 hPa provides an advantage for energy release of convective-symmetric instabilities. The band is nearly parallel to 800–500 hPa constant thickness lines, which deviates from 500 hPa contour lines. The convective body in the rain band moves with environmental flow, showing that the rain band is in accordance with banded precipitation characteristics, which is associated with symmetric instability. The above conclusions can be used for operational forecast on the location and orientation of the convective rain band on the northwest edge of WPSH.

The intensity of turbulence in convective clouds

Abstract: Calculations of collision rates between cloud droplets in turbulent air show that this would be an effective precipitation mechanism in cumulus if the r.m.s. turbulent acceleration were about 3 times that due to gravity. An estimated value, based on published records of flights through thunderstorms, is about one-sixth of gravity. In the absence of more direct evidence, it seems that turbulence is not an important factor in convective precipitation.

Controls on Boundary-Layer Thermodynamics and Dynamics in Coastal West Africa During the Rainy Season of 2006

Abstract: We investigate dominant processes modulating the coastal West African atmospheric boundary layer during August and September 2006. We evaluated boundary-layer attributes using upper air soundings, tower-based observations, and information from the European Centre for Medium-Range Weather Forecasts reanalyses. Boundary-layer thermodynamics exhibited continental and maritime attributes in response to influences from regional onshore (sea to land) flows and local land–atmosphere exchanges of energy and moisture. Onshore flows transported maritime air inland and gave rise to deep (>1 km) nighttime mixed layers whose heat and moisture content resulted in maximum virtual potential temperatures of 306 K and specific humidities up to 20 g kg−1. The presence of the Saharan Air Layer corresponded with capping inversions greater than 4 K and lapse rates exceeding 7 K km−1 above the mixed layer. Mixed layers at these times became deeper than expected (≈1 km) because dust layer events were often concurrent with strong onshore flows. Despite diurnally variable land–atmosphere fluxes of sensible and latent heat that reached maximum values of 200 and 400 W m−2, respectively, the mixed-layer depth exhibited little diurnal variation due to the influences of onshore flows. Daytime heating of the land, the upward transport of moisture, and onshore flows produced boundary layers with high convective available potential energy that often exceeded 3,000 J kg−1. These results demonstrate that the atmospheric boundary-layer thermodynamics in western Senegal can be favorable for storm development during both day and night. Mesoscale and regional models applied in this region should include several processes controlling the boundary-layer attributes to realistically estimate the energy available for storm development.

Thunderstorms: Thermodynamics and Organization

Abstract: Thunderstorm research is strongly motivated by the wish to reduce the harm they do to people and their property Thunderstorms are a global phenomenon, although some areas in the mid-latitudes and tropics are particularly at risk They form where and whenever the ingredients for their formation come together: instability, moisture and lift Especially upon interaction with vertical wind shear, they may develop into well-organized systems that produce hazards such as large hail, severe winds, heavy precipitation, and tornadoes