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.

The Sensitivity of Simulated Storm Structure and Intensity to the Temperature at the Lifted Condensation Level

Abstract: Prior parameter space studies of simulated deep convection are extended to embrace variations in the ambient temperature at the Lifted Condensation Level (LCL) Within the context of the parameter space study design, changes in LCL temperature are roughly equivalent to changes in the ambient precipitable water Two series of simulations are conducted, one with a warm LCL that is associated with approximately 60 mm of precipitable water, and another with LCL temperatures 8 C cooler, so that PW is reduced to roughly 30 mm The sets of simulations include tests of the impact of changes in the buoyancy and shear profile shapes and of changes in mixed and moist layer depths, all of which have been shown to be important in prior work Simulations discussed here feature values of bulk convective available potential energy (CAPE) of 800, 2000, or 3200 Joules per kilogram, and a single semicircular hodograph having radius of 12 meters per second, but with variable vertical shear The simulations reveal a consistent trend toward stronger peak updraft speeds for the cooler LCL temperature (reduced PW) cases, if all other environmental parameters are held constant Roughly comparable increases in updraft speeds are noted for all combinations of LCL and level of free convection heights These increases in updraft strength are evidently the result of both the reduction of condensate loading aloft and the lower altitudes at which the latent heat release by freezing and deposition commences in the cooler, low-PW environments Because the latent heat of fusion adds relatively more energy to the updrafts at low CAPE, those storms show more strengthening at low PW than do the larger CAPE storms As expected, maximum storm precipitation rates tend to diminish as PW is decreased, but only slightly, and by amounts not proportionate to the decrease in PW The low-PW cases thus actually feature larger environment-relative precipitation efficiency than do the high-PW cases In addition, more hail reaches the surface in the low-PW cases because of reduced melting in the cooler environments

A Numerical Study of Intense ConvectionThat Caused the Tornado in Blagoveshchensk on July 31, 2011

Abstract: The results of the numerical simulation of intense convection that caused the tornado in the city of Blagoveshchensk on July 31, 2011 are presented. The WRF-ARW nonhydrostatic mesoscale model on the nested grids with the spacing to 500 m is used for simulations. It is found that the tornado was initiated by the meso-γ vortex associated with a quasilinear convective system at the height of 700–900 m. The mesovortex was generated when the wind shear in the lower 2-km layer was 21–27 m/s and convective available potential energy was to 1800 J/kg. The position and center of the mesovortex were specified by the values of vorticity and the Okubo–Weiss number. The simulated tornado was formed close to this mesovortex. The main contribution to the intensification of vertical velocity in the tornado was made by the perturbations of pressure and buoyancy and that to vorticity was made by the horizontal advection. The simulated time of occurrence, location, and duration of the event slightly differ from the real ones.

A tornado with anticyclonic rotation at clooncan, co. mayo

Abstract: On 31 July 2004 a tornado that was unusual in several ways occurred in the west of Ireland. It had an anticyclonic, rather than the more normal cyclonic, rotation, and it occurred under relatively unpromising synoptic conditions, where there was a slack surface-pressure gradient close to the centre of a ridge of high pressure over north-west Europe. However, regional low-level wind shear and strong convergence are shown to have created a favourable environment over Co. Mayo, aided by a limited amount of convective available potential energy (CAPE) that accumulated beneath an inversion at 816hPa and by a strong vertical moisture profile. The role of the contrasting thermal properties between Lough Carra and the adjacent land surface in producing an anticyclonically rotating tornado from a horizontal vortex that developed within the sheared environment is considered. All of these features are found to be strongly localised. Comparisons are made with the non-mesocyclonic tornado environments documented in US research, and a number of contrasts are noted. The tornado track was only partially traceable due to the terrain, and it reached its widest point of 18m where it entered bogland after 0.75km. John Tyrrell (email: j.tyrrell@ucc.ie), Department of Geography, UCC, Cork.

Studies of Evolution Features and Persistent Development Mechanism of Mesoscale Convective Clouds over the Northern South China Sea

Abstract: By using data of Precipitation Radar(PR) and Microwave Imager(TMI) sensors on the Tropical Rainfall Measuring Missions(TRMM),and intensive observational sounding data,the evolution characteristics and long-lasting development mechanism of mesoscale convective clouds over the northern South China Sea(15°N-25°N,108°E-122°E) in the South China Sea Monsoon Experiment(SCSMEX) are studied.The results show that the cold frontal cloud band from southern China coastal region started to weaken and dissipate as it entered the South China Sea before onset of the monsoon,and intensified and developed into deeper and long-lasting convective clouds with heavy precipitation after onset of the monsoon.The convective available potential energy(CAPE),wind shear and latent heat were found to play very important roles in maintaining and developing of the intense convective clouds.Before the monsoon onset,though the atmosphere over the northern South China Sea had higher CAPE,the wind shear was too weak,thus,the convective cloud band could not last longer.During the monsoon period,the monsoon circulation maintained the high CAPE and wind shear,and led to a long-lasting development of intense convective cloud system.The heating rate due to latent heat release also increased more than two times during the monsoon period,which provided the favorable condition for upward transportation of energy and water vapor from the ocean.

Observation of Temperature Profiles of Kototabang (Bukittinggi-West Sumatera Indonesia) Using Radiosonde and Rain Event Identification

Abstract: We recorded temperature profiles of Kototabang (West Sumatera-Indonesia) in a four days observation using Radio Acoustic Sounding System (RASS) and Radiosonde. The activity was carried out in August 2016, on a research cooperation framework of National Institute of Aeronautics and Space (LAPAN), Indonesia and Research Institute for Sustainable Humanosphere (RISH), Kyoto University, Japan. The current article discussed the temperature profile based on 12 times launch of Radiosonde, Convective Available Potential Energy (CAPE) estimation and its relationship with rain events, while the temperature profile based on RASS was discussed in another report. CAPE is the amount of energy an air parcel would have if lifted to a certain distance vertically through the atmosphere. CAPE is effectively the positive buoyancy of an air parcel and is an indicator of atmospheric instability, related to convection clouds. If there is not enough water vapour present, there is no ability for condensation, and therefore, storms, clouds, and rain will not form. CAPE is calculated as the area of positive region in the thermodynamic diagram or through relationships with virtual temperature. On August 30, 2016, at 08 LT, the range of temperatures based on Radiosonde measurements was recorded from 294.9°K at ground level to 186.5°K at an altitude of 26.8 km. The temperature range varied with time. CAPE based on Radiosonde data ranged from 0 to 5075.2 Jkg-1 within 30 August 2016 until 2 September 2016. The maximum CAPE value occurred on August 30, 2016 at 15.34 LT. Large CAPE (> 2000 Jkg-1) was coincident with rain events.