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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 authors investigated the mechanisms responsible for the development and maintenance of long-lived squall lines in dry environments through two-dimensional numerical experiments by using a nonhydrostatic cloud model.
Abstract: The mechanisms responsible for the development and maintenance of long-lived squall lines in dry environments are investigated through two-dimensional numerical experiments by using a nonhydrostatic cloud model. The squall line environments are characterized by a low convective available potential energy (CAPE), low moisture content, and a high level of free convection (LFC), which are based on observations of a squall line over an arid region in China. Although these environments seem to be unfavorable for the development of convective systems, a long-lived squall line is simulated in the environment of a well-mixed moisture profile within a deep, mixed boundary layer. During the mature stage of this simulated squall line, the air parcels originating in the upper part of the mixed layer ahead of a surface cold-air pool are lifted to the upper troposphere. On the other hand, the air parcels originating in the lower part of the mixed layer are forced to go rearward, never reaching the upper levels...

35 citations

Journal ArticleDOI
TL;DR: In the Tropics, the variation of rainfall with sea surface temperature (SST) is highly nonlinear as mentioned in this paper, and the tendency for temperatures above the boundary layer to be homogeneous plays an important role in the rapid increase in rainfall near the convective threshold SST.
Abstract: In the Tropics, the variation of rainfall with sea surface temperature (SST) is highly nonlinear. Rainfall shows no dependence on SST for SST increases from 198 to 268C, abruptly increases by a factor of 5 as SSTs increase from 268 to 298C, and then rapidly declines. It is argued that this nonlinear dependence is a response to the nonlinear dependence of convective mass on SST. Convective mass is a measure of the mass in the convective boundary layer thermodynamically able to participate in deep convection by virtue of its positive convective available potential energy (CAPE). Monthly mean estimates of convective mass were obtained at various islands in the tropical Pacific and Caribbean from the NOAA/National Climatic Data Center highresolution radiosonde database. In the inner Tropics, the tendency for temperatures above the boundary layer to be homogeneous plays an important role in the rapid increase in rainfall near the convective threshold SST. At SSTs below the convective threshold, near-surface winds are generally directed from cold to warmer SSTs, so that horizontal advection of equivalent potential temperature (u e) will tend to suppress moist entropy, and rainfall, in these regions. In areas of the ocean with SSTs larger than the convective threshold, the mean frequency distribution of u e in the boundary layer becomes independent of SST. This occurs both as a response to the homogeneity of temperatures in the inner Tropics, and to the tendency for wind speeds in the boundary layer to decrease with SST for SSTs larger than the convective threshold. In the subtropics, temperature fluctuations are much larger than in the inner Tropics, and can be expected to play a much greater role in determining precipitation patterns.

35 citations

Journal ArticleDOI
TL;DR: In this article, a transilient matrix for moist convection is introduced, which quantifies the nonlocal transport of air by convective eddies: for every height z, it gives the distribution of starting heightsz9fortheeddiesthatarriveatz.
Abstract: A method is introduced for diagnosing a transilient matrix for moist convection. This transilient matrix quantifies the nonlocal transport of air by convective eddies: for every height z, it gives the distribution of starting heightsz9fortheeddiesthatarriveatz.Inacloud-resolvingsimulationofdeepconvection,thetransilient matrix shows that two-thirds of the subcloud air convecting into the free troposphere originates from within 100 m of the surface. This finding clarifies which initial height to use when calculating convective available potential energy from soundings of the tropical troposphere.

35 citations

Journal ArticleDOI
TL;DR: In this paper, the role played by planetary boundary layer (PBL) in the development and evolution of a severe convective storm is studied by means of meso-scale modeling and surface and upper air observations.
Abstract: . The role played by planetary boundary layer (PBL) in the development and evolution of a severe convective storm is studied by means of meso-scale modeling and surface and upper air observations. The severe convective precipitation event that occurred on 14 September 1999 in the northeast of the Iberian Peninsula was simulated by means of the mesoscale model MM5 (version 3) using three different PBL schemes. The numerical results show a large impact of the PBL schemes on the precipitation fields associated to the convective storm. The schemes are based on different physical assumptions: the nonlocal first order Medium-Range Forecast (MRF) and Blackadar (BLA) scheme and the local, one-and-a-half order ETA scheme. Surface and radar observations are used to validate the model results. The comparison focuses on three aspects: the evolution, the spatial distribution and the 24-h accumulated precipitation. The comparison with rain gauge observations shows that the MRF, BLA and ETA schemes predicted most of the precipitation during the morning, whereas the rain gauge stations recorded rainfall during the evening. The evaluation performed with the radar data shows that all three numerical simulations produced a realistic spatial accumulated precipitation distribution. According to the quantity distribution, all three numerical simulations were able to predict precipitation quantities comparable to the rain gauge measurements. The MRF scheme predicted the largest average accumulated precipitation and the largest average precipitation rate, whereas the ETA scheme predicted the smallest accumulated precipitation and average precipitation rate. However, the ETA scheme yielded the highest extreme precipitation rates. The performance of the three schemes is analyzed in terms of the vertical distribution of potential temperature, specific humidity and conserved variables, like equivalent potential temperature and total water content. The MRF scheme showed more evidence of enhanced mixing than did the other schemes. Due to this process, more moisture was more efficiently transported to the free atmosphere. Consequently, the MRF scheme predicts more widespread precipitation. Furthermore, the enhanced mixing led to a less sharp capping inversion. However, the stronger inversion resulting from suppressed mixing processes in the case of the ETA scheme yielded higher values of convective available potential energy (CAPE) than did the other two schemes. Consequently, the more extreme precipitation rates are simulated by MM5 when the ETA scheme is used.

35 citations

Journal ArticleDOI
TL;DR: In this paper, an analysis of the latest satellite rainfall and reanalysis datasets from 1998 to 2012 demonstrates that eastward-propagating rainfall episodes, which typically occur in late night and early morning, are determinant factors for the rainfall diurnal cycle and climate anomalies over eastern China.
Abstract: Analysis of the latest satellite rainfall and reanalysis datasets from 1998 to 2012 demonstrates that eastward-propagating rainfall episodes, which typically occur in late night and morning, are determinant factors for the rainfall diurnal cycle and climate anomalies over eastern China. The episode growth and propagation are facilitated by an elevated layer of conditionally unstable air in a mesoscale zone at their eastern leading edge. The convective available potential energy (CAPE), despite convection consumption and nocturnal cooling, decreases only from a high value to a moderate one during episode duration. An estimate of the CAPE generation budget suggests that low-level horizontal advection and vertical lifting of the warm moist air can produce sufficient CAPE to balance other stabilization effects, sustaining the mesoscale maximum of convective instability ahead of rainfall episodes. These instability geneses are pronounced at the convection growth stage and linked closely to a mesoscale ...

35 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202365
202291
202151
202038
201932
201827