scholarly journals Objective Classification of Tropical Mesoscale Convective Systems

2009 ◽  
Vol 22 (22) ◽  
pp. 5797-5808 ◽  
Author(s):  
Mick Pope ◽  
Christian Jakob ◽  
Michael J. Reeder
Keyword(s):  
Mesoscale Convective Systems ◽  
Wet Season ◽  
Convective Systems ◽  
Eastern Australia ◽  
Class 1 ◽  
Mesoscale Convective ◽  
Westerly Flow ◽  
Geostationary Meteorological Satellite ◽  
Objective Classification ◽  
Number Of Classes

Abstract A cluster analysis is applied to the mesoscale convective systems (MCSs) that developed in northern Australia and the surrounding oceans during six wet seasons (September–April) from 1995/96 to 2000/01. During this period, 13 585 MCSs were identified and tracked using an infrared channel (IR1) on the Japanese Meteorological Agency Geostationary Meteorological Satellite 5 (GMS5). Based on the lifetimes of the MCSs, the area covered by cloud, the expansion rate of the cloud, the minimum cloud-top temperature, and their zonal direction of propagation, the MCSs are grouped objectively into four classes. One of the strengths of the analysis is that it objectively condenses a large dataset into a small number of classes, each with its own physical characteristics. MCSs in class 1 (short) are relatively short lived, with 95% having lifetimes less than 5 h, and they are found most frequently over the oceans during the early and late parts of the wet season. MCSs in classes 2 and 3 [long and intermediate west (Int-West)] are longer lived and propagate to the west, developing over continental northwest Australia in deep easterly flow during breaks in the monsoon. These two classes are distinguished principally by their lifetime, with 95% of MCSs in the long class having lifetimes exceeding 4 h. Class 4 (Int-East) comprises MCSs that form over the subtropical latitudes of eastern Australia and in the deep westerly flow over northern parts of the continent during the monsoon and active phases of the MJO.

Numerical Investigations on the Formation of Tropical Storm Debby during NAMMA-06

2010 ◽  
Vol 25 (3) ◽  
pp. 866-884 ◽  
Author(s):  
Sen Chiao ◽  
Gregory S. Jenkins
Keyword(s):  
Mesoscale Model ◽  
Vortex Formation ◽  
Tropical Storm ◽  
Mesoscale Convective Systems ◽  
Weather Research And Forecasting ◽  
Grid Spacing ◽  
Convective Systems ◽  
Sensitivity Tests ◽  
Mesoscale Convective ◽  
Westerly Flow

Abstract Mesoscale model forecasts were carried out beginning at 0000 UTC 19 August for simulating Tropical Disturbance 4, which was named Tropical Storm Debby on 22 August 2006. The Weather Research and Forecasting model, with 25-km grid spacing and an inner nested domain of 5-km grid spacing, was used. The development of a small closed vortex at approximately 0600 UTC 20 August 2006 at 850 hPa was found off the coast of Guinea in agreement with satellite images in the 5-km simulation. Intense convection offshore and over the Guinea Highlands during the morning of 20 August 2006 led to the production of a vortex formation by 1400 UTC at 700 hPa. Sensitivity tests show that the Guinea Highlands play an important role in modulating the impinging westerly flow, in which low-level flow deflections (i.e., northward turning) enhance the cyclonic circulation of the vortex formation. Yet, the moist air can be transported by the northward deflection flow from lower latitudes to support the development of mesoscale convective systems (MCSs). Although the model forecast is not perfect, it demonstrates the predictability of the formation and development of the tropical disturbance associated with the Guinea Highlands.

scholarly journals Chemical properties of rain events during the AMMA campaign: an evidence of dust and biogenic influence in the convective systems

2010 ◽  
Vol 10 (6) ◽  
pp. 15263-15293 ◽  
Author(s):  
K. Desboeufs ◽  
E. Journet ◽  
J.-L. Rajot ◽  
S. Chevaillier ◽  
S. Triquet ◽  
...  
Keyword(s):  
Elemental Composition ◽  
Chemical Properties ◽  
Convective Cloud ◽  
Mesoscale Convective Systems ◽  
Biogenic Emissions ◽  
Rain Event ◽  
Wet Season ◽  
Convective Systems ◽  
Mesoscale Convective ◽  
Rain Events

Abstract. This paper documents the chemical composition of 7 rain events associated with mesoscale convective systems sampled at the supersite of Banizoumbou, Niger, during the first special observation periods (June–July 2006) of the African Monsoon Multidisciplinary Analyses (AMMA) experiment. Time-resolved rain sampling was performed in order to discriminate the local dust scavenged at the beginning of rain event from the aerosol particles incorporated in the cloud at the end of the rain. The total elemental composition is dominated by Al, Si, Fe and Ca, indicating a high influence of dust and limited marine or anthropogenic contribution. After the aerosol wash-out, the elemental concentrations normalized to Al and the microscopic observations of diatoms, a tracer of the Bodélé depression, both indicate that the total elemental composition of rainwater is controlled by dust originating from North-Eastern Saharan sources and probably incorporated in the convective cloud from the Harmattan layer. The low variability of the rain composition over the measurement period indicates a regional and temporal homogeneity of dust composition in the Harmattan layer. In the dissolved phase, the dominant anions are nitrate (NO3−), sulphate (SO42−) and chloride (Cl−). However, between June and July we observe an increasing contribution of the organic anions (formate, acetate, oxalate) associated with biogenic emissions to the total ion composition. These results confirm the large influence of biogenic emissions on the rain composition over Sahel during the wet season. The paper concludes on the capacity of mesoscale convective systems to carry simultaneously dust and biogenic compounds originating from different locations and depose them jointly. It also discusses the potential biogeochemical impact of such a phenomenon.

scholarly journals Chemistry of rain events in West Africa: evidence of dust and biogenic influence in convective systems

2010 ◽  
Vol 10 (19) ◽  
pp. 9283-9293 ◽  
Author(s):  
K. Desboeufs ◽  
E. Journet ◽  
J.-L. Rajot ◽  
S. Chevaillier ◽  
S. Triquet ◽  
...  
Keyword(s):  
Elemental Composition ◽  
Convective Cloud ◽  
Mesoscale Convective Systems ◽  
Biogenic Emissions ◽  
Rain Event ◽  
Wet Season ◽  
Time Resolved ◽  
Convective Systems ◽  
Mesoscale Convective ◽  
Rain Events

Abstract. This paper documents the chemical composition of 7 rain events associated with mesoscale convective systems sampled at the supersite of Banizoumbou, Niger, during the first special observation periods (June–July 2006) of the African Monsoon Multidisciplinary Analyses (AMMA) experiment. Time-resolved rain sampling was performed in order to discriminate the local dust scavenged at the beginning of rain event from the aerosol particles incorporated in the cloud at the end of the rain. The total elemental composition is dominated by Al, Si, Fe and Ca, indicating a high influence of dust and limited marine or anthropogenic contribution. After the aerosol wash-out, the elemental concentrations normalized to Al and the microscopic observations of diatoms, a tracer of the Bodélé depression, both indicate that the total elemental composition of rainwater is controlled by dust originating from North-eastern Saharan sources and probably incorporated in the convective cloud from the Harmattan layer. The low variability of the rain composition over the measurement period indicates a regional and temporal homogeneity of dust composition in the Harmattan layer. In the dissolved phase, the dominant anions are nitrate (NO3−), sulphate (SO42−) and chloride (Cl−). However, between June and July we observe an increasing contribution of the organic anions (formate, acetate, oxalate) associated with biogenic emissions to the total ion composition. These results confirm the large influence of biogenic emissions on the rain composition over Sahel during the wet season. The paper concludes on the capacity of mesoscale convective systems to carry simultaneously dust and biogenic compounds originating from different locations and depose them jointly. It also discusses the potential biogeochemical impact of such a phenomenon.

A five-year climatological lightning characteristics of linear mesoscale convective systems over North China

2021 ◽  
Vol 256 ◽  
pp. 105580
Author(s):  
Dongxia Liu ◽  
Mengyu Sun ◽  
Debin Su ◽  
Wenjing Xu ◽  
Han Yu ◽  
...  
Keyword(s):  
North China ◽  
Mesoscale Convective Systems ◽  
Convective Systems ◽  
Mesoscale Convective

scholarly journals An Observational Study of Mesoscale Convective Systems with Heavy Rainfall over the Korean Peninsula

2006 ◽  
Vol 21 (2) ◽  
pp. 125-148 ◽  
Author(s):  
Hyung Woo Kim ◽  
Dong Kyou Lee
Keyword(s):  
Observational Study ◽  
Korean Peninsula ◽  
Wind Shear ◽  
Heavy Rainfall ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Mesoscale Convective Systems ◽  
Low Level ◽  
Convective Systems ◽  
Mesoscale Convective

Abstract A heavy rainfall event induced by mesoscale convective systems (MCSs) occurred over the middle Korean Peninsula from 25 to 27 July 1996. This heavy rainfall caused a large loss of life and property damage as a result of flash floods and landslides. An observational study was conducted using Weather Surveillance Radar-1988 Doppler (WSR-88D) data from 0930 UTC 26 July to 0303 UTC 27 July 1996. Dominant synoptic features in this case had many similarities to those in previous studies, such as the presence of a quasi-stationary frontal system, a weak upper-level trough, sufficient moisture transportation by a low-level jet from a tropical storm landfall, strong potential and convective instability, and strong vertical wind shear. The thermodynamic characteristics and wind shear presented favorable conditions for a heavy rainfall occurrence. The early convective cells in the MCSs initiated over the coastal area, facilitated by the mesoscale boundaries of the land–sea contrast, rain–no rain regions, saturated–unsaturated soils, and steep horizontal pressure and thermal gradients. Two MCSs passed through the heavy rainfall regions during the investigation period. The first MCS initiated at 1000 UTC 26 July and had the characteristics of a supercell storm with small amounts of precipitation, the appearance of a mesocyclone with tilting storm, a rear-inflow jet at the midlevel of the storm, and fast forward propagation. The second MCS initiated over the upstream area of the first MCS at 1800 UTC 26 July and had the characteristics of a multicell storm, such as a broken areal-type squall line, slow or quasi-stationary backward propagation, heavy rainfall in a concentrated area due to the merging of the convective storms, and a stagnated cluster system. These systems merged and stagnated because their movement was blocked by the Taebaek Mountain Range, and they continued to develop because of the vertical wind shear resulting from a low-level easterly inflow.

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