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 basic features of the severe convection at the background of cold vortex over north china

Abstract: The risk weather data in Beijing,Tianjin and Hebei are used to analyze the temporal-spatial distribution as well as the dynamic-thermal characteristics of the severe convection associated with cold vortex over North China during 2001—2008 from May to August.The results indicate that:(1) Short-term heavy precipitation had the largest occurrence probability in coastal areas,especially during the afternoon to evening.The strong wind and hail had the largest probability during morning in the mountain of Northwest Hebei,and the region of large probability expanded southward and eastward from the afternoon to evening.The largest occurrence probability of tornado was in the morning,the center was in Beijing.(2) There were northwest wind mostly,and gale mainly;most hail diameter were 5～20 mm;short-term heavy precipitation occurred mainly lasting less than 20 minutes,and the precipitation were 20～23 mm mostly.The large convection intensity was located in the leeward of Taihang and Yanshan Mountains and the coastal areas.(3) Before the occurrence of short-term heavy precipitation,the vapor was the most favorable,the Convective Available Potential Energy(CAPE) and Best Lifting Index(BLI) were the largest,but the Lifting Condensation Level(LCL) was the highest.(4) Before the occurrence of strong wind,the vertical wind shear was the strongest,the LCL was the lowest.(5) Before the occurrence of hail,the height of 0 ℃ was about 3 400 m,the height of-20 ℃ was about 6 400 m,the Storm Relative Helicity(SRH)150 m2/s2.

A Modeling Study of the Impacts of Pearl River Delta Urban Environment on Convective Precipitation

Abstract: Using a 2-km-resolution WRF model,along with its single-layer urban canopy model and Thompson bulk-parameterization microphysics scheme,numerical simulation of a convective rainstorm is executed over Guangzhou city in the Pear River Delta(PRD) to investigate the impacts of urban environments(including urban land use changes and urban air pollution-enhanced cloud droplet number concentration) on the convective precipitationResults indicate that urban heat island and dry island effect produced by the land surface can lead to an enhanced urban boundary layer,which is conducive to air confluence and unstable energy increase in the areas near the citySimulation shows that to the north and south of Guangzhou city,caused by the urban land surface,there exists respectively a convergence zone with enhanced CAPE(Convective Available Potential Energy) valuesThe simulated radar echoes being initiated within these zones and consistent well with observations reflect that the urban land surface plays a more direct role in convection initiation and developmentOnce convection develops,sensitive experiments show that enhanced cloud droplet number concentration might lead to more precipitationIn case with high concentration(polluted cases),precipitation is increased by up to 20%Diagnostic analysis suggests that the increased precipitation results from that more rain water and supercooled cloud water produce in the convective cloudsThese rain and cloud water,carried upward by strong upward motion intensified by more latent heat release during this process,can be transported to higher altitudes,where ice formation is enhanced through freezing or through interaction with other already existing ice species,and that finally results in surface precipitation increase

A model for the relationship between rainfall, GNSS-derived integrated water vapour, and CAPE in the eastern central Andes

Abstract: Atmospheric water vapour content is a key variable that controls the development of deep convective storms and rainfall extremes over the central Andes. Direct measurements of water vapour are challenging; however, recent developments in microwave processing allow the use of phase delays from L-band radar to measure the water vapour content throughout the atmosphere: Global Navigation Satellite System (GNSS)-based integrated water vapour (IWV) monitoring shows promising results to measure vertically integrated water vapour at high temporal resolutions. Previous works also identified convective available potential energy (CAPE) as a key climatic variable for the formation of deep convective storms and rainfall in the central Andes. Our analysis relies on GNSS data from the Argentine Continuous Satellite Monitoring Network, Red Argentina de Monitoreo Satelital Continuo (RAMSAC) network from 1999 to 2013. CAPE is derived from version 2.0 of the ECMWF’s (European Centre for Medium-Range Weather Forecasts) Re-Analysis (ERA-interim) and rainfall from the TRMM (Tropical Rainfall Measuring Mission) product. In this study, we first analyse the rainfall characteristics of two GNSS-IWV stations by comparing their complementary cumulative distribution function (CCDF). Second, we separately derive the relation between rainfall vs. CAPE and GNSS-IWV. Based on our distribution fitting analysis, we observe an exponential relation of rainfall to GNSS-IWV. In contrast, we report a power-law relationship between the daily mean value of rainfall and CAPE at the GNSS-IWV station locations in the eastern central Andes that is close to the theoretical relationship based on parcel theory. Third, we generate a joint regression model through a multivariable regression analysis using CAPE and GNSS-IWV to explain the contribution of both variables in the presence of each other to extreme rainfall during the austral summer season. We found that rainfall can be characterised with a higher statistical significance for higher rainfall quantiles, e.g., the 0.9 quantile based on goodness-of-fit criterion for quantile regression. We observed different contributions of CAPE and GNSS-IWV to rainfall for each station for the 0.9 quantile. Fourth, we identify the temporal relation between extreme rainfall (the 90th, 95th, and 99th percentiles) and both GNSS-IWV and CAPE at 6 h time steps. We observed an increase before the rainfall event and at the time of peak rainfall—both for GNSS-integrated water vapour and CAPE. We show higher values of CAPE and GNSS-IWV for higher rainfall percentiles (99th and 95th percentiles) compared to the 90th percentile at a 6-h temporal scale. Based on our correlation analyses and the dynamics of the time series, we show that both GNSS-IWV and CAPE had comparable magnitudes, and we argue to consider both climatic variables when investigating their effect on rainfall extremes.

Climatic Background of Warm-Season Convective Weather in North China Based on the NCEP Analysis

Abstract: Due to the demand of nowcasting of convective weather in North China(including Beijing,Tianjin,and Hebei Province),the authors use the averaged fields of NCEP 1°× 1° final analyses during May to August of 2000-2005 to analyze the climatic background of convective weather in warm season in north China.The averaged fields include mean circulation of the lower and upper troposphere,mean humidity,temperature,pseudo-equivalent potential temperature,convective available potential energy(CAPE),convective inhibition(CIN),and so on.The results show that the climatic background in May and June is different to that in July and August.In May and June,cold air mass from north is more active,and North China is mainly influenced by disturbances of westerly wind systems in mid-latitudes,in contrast,in July and August this area is influenced by both disturbances of westerly wind systems in mid-latitudes and disturbances in lower latitudes.There are more hailstorms and thunderstorms in May and June,but more heavy rains in July and August.The mean daily variation of relative humidity of lower troposphere reveals that there is one dry line(dew point front)in the afternoon to the east of Beijing,and the averaged streamlines of 850 hPa indicate that there exists a large-scale convergence line in boundary layer at the north of Beijing.The above results provide nowcasting of convective weather in north China with a climatic background.