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.

Characteristics of Pre-summer Daytime Cloud Regimes over Coastal South China from the Himawari-8 Satellite

Abstract: Using the high spatiotemporal resolution (2 km-and-10 min) data from the Advanced Himawari Imager onboard the Himawari-8 satellite, this study documents the fine-scale characteristics of daytime cloud regimes (CRs) over coastal South China during the pre-summer rainy season (April–June). Six CRs (CR1–CR6) are identified based on the joint frequency distribution of cloud top brightness temperature and cloud optical thickness, namely, the optically thin-to-moderate cloud mixture, optically thin warm clouds with cirrus, optically thick warm clouds, weak convective cloud mixture, strong convective clouds, and extreme, deep convective clouds. The optically thick warm clouds are the major CR during April and May, with higher frequencies over land, especially along the urban agglomeration, rather than the offshore which may be an indicator of the higher aerosol concentrations being a contributing factor over the cities. The CRs with weak convective cloud mixtures and strong convective clouds appear more frequently over the land, while the two CRs with optically thinner clouds occur mainly offshore. Synoptic flow patterns (SPs) are objectively identified and examined focusing on those favoring the two major rain-producing CRs (CR5 and CR6) and the highly reflective CR with optically thick warm clouds (CR3). The two SPs favoring CR5 and CR6 are characterized by abundant moisture with low-level jets after monsoon onset, and a northwest high-southeast low pattern with strong dynamic convergence along the coastline, respectively. The non-convective CR3 with high reflectance is related to a SP that features the western North Pacific subtropical high extending more westward, leading to a moderate moisture supply and a wide range of convective available potential energy, but also, large convective inhibition.

Mesoscale characteristics of a rare severe hailstorm event

Abstract: This study analyzed the environmental field, physical quantify fields, convection parameters and radar echo characteristics of a severe hailstorm that occurred on June 18, 2013, due to a mesoscale convective system. The analysis was performed using ground meteorological data, sounding data and GFS-ANL (gfs 0.5° × 0.5°) reanalysis data in combination with satellite cloud imagery and Doppler radar observations. The results showed that this rare hailstorm event was generated under the influence of a weakening and eastwardly moving low vortex over Lake Balkhash; and a distinct shear line in the middle and lower troposphere over the western South Xinjiang. Strong vertical wind shears, deep conditionally unstable stratification, ample water vapor in the lower troposphere and suitable wet-bulb zero heights are important contributors to the formation of severe hailstorms. An increase in convective available potential energy (CAPE) and a decrease in the lifting index are strong indicators of a severe hailstorm. For the studied hailstorm event, the time corresponding to the maximum value of the normalized CAPE was close to the timing of the actual hailstorm. The severe hailstorm, consisting of multiple supercells, exhibited notable characteristics of hail clouds and supercells. The formation, disappearance and replacement of strong convection cells occurred while the supercells were sustained. The tracking and forecasting results obtained using the Thunderstorm Identification, Tracking, Analysis and Nowcasting system are found to be, to a certain extent, able to indicate of the direction of the supercell storms during this severe hailstorm event.

Observations of a Heavy Rainfall Event in Shanghai on 5 August 2001

Abstract: An extremely heavy rainfall event was observed in Shanghai on 5 August 2001. It had the maximum 24-h accumulated precipitation of 275.2 mm and caused serious floods. This paper documents the detailed evolution of this event by using a suite of observational data, including Geostationary Meteorological Satellite (GMS)-5 satellite images, Weather Surveillance Radar 88 Doppler (WSR-88D) radar data, automatic rain-gauge and sounding data, and objective reanalysis. The synoptic situation prior to the heavy rainfall was characterized with a north-south oriented trough at 500 hPa and a surface meso-scale low with a surface cyclonical circulation at 00 UTC 5 August 2001. A lower-level southerly jet on the eastern flank of this meso-scale low supplied humid air to fuel the heavy rainfall. The soundings indicated that the atmosphere was most unstable before and during the rainfall, with large convective available potential energy. The clockwise rotation of wind direction with height suggested the warm advection over Shanghai. WSR-88D radar reflectivity of convective systems exceeding 50 dBZ, with large vertical integrated liquid value of 23-32 kg m - 2 , suggested that rainfall was very intense.

Determination of the Type of Flood-producing Thunderstorms by Some Convection-related Parameters and Radar Images in Northwestern Iran

Abstract: The structure of five flood-producing storms was analyzed in northwestern Iran. The storms contained several coexisting convective cells during analysis period. We tried to obtain knowledge of Intensity, Duration and Type (IDT) of the storms by radar images and verify some convection-related parameters such as K, Showalter, Total- Total, Helicity and Energy-Helicity (EHI) indices; Convective available potential energy (CAPE) and Bulk Richardson number (BRN) in the area. The surface and upper air data were taken from General Forecast System (GFS) with spatial resolution of 0.5°×0.5° and a temporal resolution of 6 h. Results show, the CAPE values for thunderstorms are equal zero or less than 1000 Jkg-1 even for super and multi cells in the area. The most flood producing thunderstorms was single or multi cell and those merges together and makes Complex cell. One of the cases was twin squall lines that accompanied with cold front. Super-cell without Tornado sign was very infrequent. The growth of vertical cell in radar images has the direct relationships with convective available potential energy.