Study of Mesoscale Convective Complex (MCC) and its impact over the Makassar Strait (case study: 9 December 2014)

Abstract A mesoscale Convective System (MCS) is a system consisting of groups of convective cells in the mesoscale. One of the largest types of MCS subclass is Mesoscale Convective Complex (MCC) occurred in the eastern part of the Makassar Strait near the Madjene and Polewali Mandar regions on 9 December 2014, morning to evening (09.00-15.00 LT). Using MTSAT-2 Satellite Imagery data, reanalysis of the European Centre for Medium-Range Weather Forecasts (ECMWF) interim era, the Global Satellite Mapping of Precipitation (GsMap) rainfall, sea surface temperature, surface air observation, and upper air observation, the author will examine the existence of MCC in the Makassar Strait in terms of atmospheric conditions when MCC enters the initial until extinct and the accompanying effects of precipitation. In general, it is known that the MCC formed in the waters of the Makassar Strait in the morning, and then it moved westward. The mechanism of its formation was through a process of convergence of the lower layers in the waters of the Makassar Strait and its surroundings to trigger the process of cloud formation. Warm thermal conditions also gave a big influence on the lower layers to the top and activate convective in the study area. Meanwhile, the MCC occurrence region also has high relative humidity, negative divergence values, and maximum vorticity values. The impact of the emergence of MCC on that date resulted in areas with very large humidity and cloud formation and produced rain in the surrounding area, in this case using rainfall data from Hasanuddin Meteorological Station, Makassar, South Sulawesi. With a duration of up to seven hours extinct, MCC in the Makassar Strait produces heavy rainfall in the Makassar Strait waters.

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Dynamics of the Stratiform Sector of a Tropical Cyclone Rainband

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-12-0245.1 ◽

2013 ◽

Vol 70 (7) ◽

pp. 1891-1911 ◽

Cited By ~ 38

Author(s):

Anthony C. Didlake ◽

Robert A. Houze

Keyword(s):

Boundary Layer ◽

Doppler Radar ◽

Mesoscale Convective System ◽

Convective System ◽

Stratiform Region ◽

Mesoscale Convective ◽

Upward Transport ◽

Radial Outflow ◽

Convective Cells ◽

Low Entropy

Abstract Airborne Doppler radar documented the stratiform sector of a rainband within the stationary rainband complex of Hurricane Rita. The stratiform rainband sector is a mesoscale feature consisting of nearly uniform precipitation and weak vertical velocities from collapsing convective cells. Upward transport and associated latent heating occur within the stratiform cloud layer in the form of rising radial outflow. Beneath, downward transport is organized into descending radial inflow in response to two regions of latent cooling. In the outer, upper regions of the rainband, sublimational cooling introduces horizontal buoyancy gradients, which produce horizontal vorticity and descending inflow similar to that of the trailing-stratiform region of a mesoscale convective system. Within the zone of heavier stratiform precipitation, melting cooling along the outer rainband edge creates a midlevel horizontal buoyancy gradient across the rainband that drives air farther inward beneath the brightband. The organization of this transport initially is robust but fades downwind as the convection dissipates. The stratiform-induced secondary circulation results in convergence of angular momentum above the boundary layer and broadening of the storm's rotational wind field. At the radial location where inflow suddenly converges, a midlevel tangential jet develops and extends into the downwind end of the rainband complex. This circulation may contribute to ventilation of the eyewall as inflow of low-entropy air continues past the rainband in both the boundary layer and midlevels. Given the expanse of the stratiform rainband region, its thermodynamic and kinematic impacts likely help to modify the structure and intensity of the total vortex.

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Prediction of Graupel Density in a Bulk Microphysics Scheme

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-12-0204.1 ◽

2013 ◽

Vol 70 (2) ◽

pp. 410-429 ◽

Cited By ~ 42

Author(s):

Jason A. Milbrandt ◽

Hugh Morrison

Keyword(s):

A Priori ◽

Kinematic Model ◽

Mesoscale Convective System ◽

Convective System ◽

Atmospheric Conditions ◽

Microphysics Scheme ◽

Surface Precipitation ◽

Convective Region ◽

Wide Range ◽

Mesoscale Convective

Abstract A method to predict the bulk density of graupel ρg has been added to the two-moment Milbrandt–Yau bulk microphysics scheme. The simulation of graupel using the modified scheme is illustrated through idealized simulations of a mesoscale convective system using a 2D kinematic model with a prescribed flow field and different peak updraft speeds. To examine the relative impact of the various approaches to represent rimed ice, simulations were run for various graupel-only and graupel-plus-hail configurations. Because of the direct feedback of ρg to terminal fall speeds, the modified scheme produces a much different spatial distribution of graupel, with more mass concentrated in the convective region resulting in changes to the surface precipitation at all locations. With a strong updraft, the model can now produce solid precipitation at the surface in the convective region without a separate hail category. It is shown that a single rimed-ice category is capable of representing a realistically wide range of graupel characteristics in various atmospheric conditions without the need for a priori parameter settings. Sensitivity tests were conducted to examine various aspects of the scheme that affect the simulated ρg. Specific parameterizations pertaining to other hydrometeor categories now have a direct impact on the simulation of graupel, including the assumed aerosol distribution for droplet nucleation, which affects the drop sizes of both cloud and rain, and the mass–size relation for snow, which affects its density and hence the embryo density of graupel converted from snow due to riming.

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Seven-Doppler Radar and In Situ Analysis of the 25–26 June 2015 Kansas MCS during PECAN

Monthly Weather Review ◽

10.1175/mwr-d-19-0151.1 ◽

2019 ◽

Vol 148 (1) ◽

pp. 211-240 ◽

Cited By ~ 2

Author(s):

Rachel L. Miller ◽

Conrad L. Ziegler ◽

Michael I. Biggerstaff

Keyword(s):

Doppler Radar ◽

Mesoscale Convective System ◽

Cold Pool ◽

Convective System ◽

Stable Layer ◽

Kinematic Evolution ◽

Stratiform Region ◽

Stationary Front ◽

Mesoscale Convective ◽

Convective Cells

Abstract This case study analyzes a nocturnal mesoscale convective system (MCS) that was observed on 25–26 June 2015 in northeastern Kansas during the Plains Elevated Convection At Night (PECAN) project. Over the course of the observational period, a broken line of elevated nocturnal convective cells initiated around 0230 UTC on the cool side of a stationary front and subsequently merged to form a quasi-linear MCS that later developed strong, surface-based outflow and a trailing stratiform region. This study combines radar observations with mobile and fixed mesonet and sounding data taken during PECAN to analyze the kinematics and thermodynamics of the MCS from 0300 to 0630 UTC. This study is unique in that 38 consecutive multi-Doppler wind analyses are examined over the 3.5 h observation period, facilitating a long-duration analysis of the kinematic evolution of the nocturnal MCS. Radar analyses reveal that the initial convective cells and linear MCS are elevated and sustained by an elevated residual layer formed via weak ascent over the stationary front. During upscale growth, individual convective cells develop storm-scale cold pools due to pockets of descending rear-to-front flow that are measured by mobile mesonets. By 0500 UTC, kinematic analysis and mesonet observations show that the MCS has a surface-based cold pool and that convective line updrafts are ingesting parcels from below the stable layer. In this environment, the elevated system has become surface based since the cold pool lifting is sufficient for surface-based parcels to overcome the CIN associated with the frontal stable layer.

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A Numerical Study of the Beijing Extreme Rainfall of 21 July 2012 and the Impact of Topography

Advances in Meteorology ◽

10.1155/2015/980747 ◽

2015 ◽

Vol 2015 ◽

pp. 1-12 ◽

Cited By ~ 3

Author(s):

Hongxiong Xu ◽

Wenqing Yao

Keyword(s):

Numerical Study ◽

Deep Convection ◽

Mesoscale Convective System ◽

Extreme Rainfall ◽

Convective System ◽

Stratiform Region ◽

Moist Environment ◽

The Right ◽

Convective Cells ◽

The Impact

The extreme rainfall on 21 July 2012 is the heaviest rainfall that has occurred in Beijing since 1961. Observations and WRF (Weather Research and Forecasting) model are used to study the effect of MCS (mesoscale convective system) and topography on the rainfall. In this high-impact event, a quasi-stationary MCS developed in a favorable moist environment. The numerical simulation successfully reproduced the amount, location, and time evolution of the rainfall despite 4–6 h delay. In particular, the model reproduced the repeat passage of convective cells at the leading convergence line region along Taihang Mountains and the trailing stratiform region, producing the rainfall at nearly the right position. Results indicate the important roles of mesolow and low-level jet in maintaining the conditional instability that lifted the moist air to trigger deep convection and the repeated initiation and movement of the line shaped convective cells that produced the rainfall. The sensitive experiment was then further carried out to examine the effect of topography on this heavy rainfall. The reduction in model elevation field significantly influenced the above mesoscale systems, which lead to convective cells becoming less organized, and the peak rainfall amount in Beijing decreased by roughly 50%.

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Multiscale Characteristics and Evolution of Perturbations for Warm Season Convection-Allowing Precipitation Forecasts: Dependence on Background Flow and Method of Perturbation

Monthly Weather Review ◽

10.1175/mwr-d-13-00204.1 ◽

2014 ◽

Vol 142 (3) ◽

pp. 1053-1073 ◽

Cited By ~ 34

Author(s):

Aaron Johnson ◽

Xuguang Wang ◽

Ming Xue ◽

Fanyou Kong ◽

Gang Zhao ◽

...

Keyword(s):

Warm Season ◽

Mesoscale Convective System ◽

Haar Wavelet ◽

Precipitation Forecast ◽

Initial Time ◽

Small Scale ◽

Convective System ◽

Mesoscale Convective ◽

Perturbation Energy ◽

The Impact

Abstract Multiscale convection-allowing precipitation forecast perturbations are examined for two forecasts and systematically over 34 forecasts out to 30-h lead time using Haar Wavelet decomposition. Two small-scale initial condition (IC) perturbation methods are compared to the larger-scale IC and physics perturbations in an experimental convection-allowing ensemble. For a precipitation forecast driven primarily by a synoptic-scale baroclinic disturbance, small-scale IC perturbations resulted in little precipitation forecast perturbation energy on medium and large scales, compared to larger-scale IC and physics (LGPH) perturbations after the first few forecast hours. However, for a case where forecast convection at the initial time grew upscale into a mesoscale convective system (MCS), small-scale IC and LGPH perturbations resulted in similar forecast perturbation energy on all scales after about 12 h. Small-scale IC perturbations added to LGPH increased total forecast perturbation energy for this case. Averaged over 34 forecasts, the small-scale IC perturbations had little impact on large forecast scales while LGPH accounted for about half of the error energy on such scales. The impact of small-scale IC perturbations was also less than, but comparable to, the impact of LGPH perturbations on medium scales. On small scales, the impact of small-scale IC perturbations was at least as large as the LGPH perturbations. The spatial structure of small-scale IC perturbations affected the evolution of forecast perturbations, especially at medium scales. There was little systematic impact of the small-scale IC perturbations when added to LGPH. These results motivate further studies on properly sampling multiscale IC errors.

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The Impact of Low-Level Moisture Errors on Model Forecasts of an MCS Observed during PECAN

Monthly Weather Review ◽

10.1175/mwr-d-16-0296.1 ◽

2017 ◽

Vol 145 (9) ◽

pp. 3599-3624 ◽

Cited By ~ 17

Author(s):

John M. Peters ◽

Erik R. Nielsen ◽

Matthew D. Parker ◽

Stacey M. Hitchcock ◽

Russ S. Schumacher

Keyword(s):

Convective Available Potential Energy ◽

Mesoscale Convective System ◽

Squall Line ◽

Convective System ◽

Low Level ◽

Eastern Flank ◽

Western Flank ◽

Mesoscale Convective ◽

Outflow Boundary ◽

The Impact

This article investigates errors in forecasts of the environment near an elevated mesoscale convective system (MCS) in Iowa on 24–25 June 2015 during the Plains Elevated Convection at Night (PECAN) field campaign. The eastern flank of this MCS produced an outflow boundary (OFB) and moved southeastward along this OFB as a squall line. The western flank of the MCS remained quasi stationary approximately 100 km north of the system’s OFB and produced localized flooding. A total of 16 radiosondes were launched near the MCS’s eastern flank and 4 were launched near the MCS’s western flank. Convective available potential energy (CAPE) increased and convective inhibition (CIN) decreased substantially in observations during the 4 h prior to the arrival of the squall line. In contrast, the model analyses and forecasts substantially underpredicted CAPE and overpredicted CIN owing to their underrepresentation of moisture. Numerical simulations that placed the MCS at varying distances too far to the northeast were analyzed. MCS displacement error was strongly correlated with models’ underrepresentation of low-level moisture and their associated overrepresentation of the vertical distance between a parcel’s initial height and its level of free convection ([Formula: see text], which is correlated with CIN). The overpredicted [Formula: see text] in models resulted in air parcels requiring unrealistically far northeastward travel in a region of gradual meso- α-scale lift before these parcels initiated convection. These results suggest that erroneous MCS predictions by NWP models may sometimes result from poorly analyzed low-level moisture fields.

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Relationships between Lightning Location and Polarimetric Radar Signatures in a Small Mesoscale Convective System

Monthly Weather Review ◽

10.1175/2009mwr2860.1 ◽

2009 ◽

Vol 137 (12) ◽

pp. 4151-4170 ◽

Cited By ~ 65

Author(s):

Nicole R. Lund ◽

Donald R. MacGorman ◽

Terry J. Schuur ◽

Michael I. Biggerstaff ◽

W. David Rust

Keyword(s):

Mesoscale Convective System ◽

Convective System ◽

Polarimetric Radar ◽

Mature Phase ◽

Mesoscale Convective ◽

Mapping Array ◽

Lightning Initiation ◽

Convective Cells ◽

Differential Reflectivity ◽

Kinematic Properties

Abstract On 19 June 2004, the Thunderstorm Electrification and Lightning Experiment observed electrical, microphysical, and kinematic properties of a small mesoscale convective system (MCS). The primary observing systems were the Oklahoma Lightning Mapping Array, the KOUN S-band polarimetric radar, two mobile C-band Doppler radars, and balloonborne electric field meters. During its mature phase, this MCS had a normal tripolar charge structure (lightning involved a midlevel negative charge between an upper and a lower positive charge), and flash rates fluctuated between 80 and 100 flashes per minute. Most lightning was initiated within one of two altitude ranges (3–6 or 7–10 km MSL) and within the 35-dBZ contours of convective cells embedded within the convective line. The properties of two such cells were investigated in detail, with the first lasting approximately 40 min and producing only 12 flashes and the second lasting over an hour and producing 105 flashes. In both, lightning was initiated in or near regions containing graupel. The upper lightning initiation region (7–10 km MSL) was near 35–47.5-dBZ contours, with graupel inferred below and ice crystals inferred above. The lower lightning initiation region (3–6 km MSL) was in the upper part of melting or freezing layers, often near differential reflectivity columns extending above the 0°C isotherm, which is suggestive of graupel formation. Both lightning initiation regions are consistent with what is expected from the noninductive graupel–ice thunderstorm electrification mechanism, though inductive processes may also have contributed to initiations in the lower region.

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Increase of the aerosol hygroscopicity by cloud processing in a mesoscale convective system: a case study from the AMMA campaign

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-6907-2008 ◽

2008 ◽

Vol 8 (23) ◽

pp. 6907-6924 ◽

Cited By ~ 60

Author(s):

S. Crumeyrolle ◽

L. Gomes ◽

P. Tulet ◽

A. Matsuki ◽

A. Schwarzenboeck ◽

...

Keyword(s):

Cloud Condensation Nuclei ◽

Mesoscale Convective System ◽

Atmospheric Model ◽

Dust Particles ◽

Convective System ◽

Cloud Processing ◽

Before And After ◽

Mesoscale Convective ◽

The Impact ◽

Aerosol Properties

Abstract. Aerosol properties were measured during an airborne campaign experiment that took place in July 2006 in West Africa within the framework of the African Monsoon Multidisciplinary Analyses (AMMA). The goal of the present study was to determine the main microphysical processes that affect the aerosols during the passage of a mesoscale convective system (MCS) over the region of Niamey in Niger. A significant change in the aerosol profiles measured before and after the passage of the MCS was found in a layer located between 1300 and 3000 m, where the aerosol concentration drastically decreased after the passage of the MCS. Concurrently, a significant increase in the cloud condensation nuclei (CCN) fraction was also observed during the post-MCS period in the same layer. Moreover, the results of the elemental composition analyses of individual particles collected in this layer after the MCS passage have shown higher contributions of sulfate, nitrate and chloride to the total aerosol mass. A mesoscale atmospheric model with on-line dust parameterization and Lagrangian backtrajectories was used to interpret the impact of the MCS on the aerosol properties. The results of the simulation show that the MCS 1) generates dust particles at the surface in the gust front of the system and washout of particles during the system precipitation, 2) modifies the aerosol mixing state (intensive aerosol property) through cloud processing, and 3) enhances CCN activity of particles through coating by soluble material.

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Impacts of Dust–Radiation versus Dust–Cloud Interactions on the Development of a Modeled Mesoscale Convective System over North Africa

Monthly Weather Review ◽

10.1175/mwr-d-18-0459.1 ◽

2019 ◽

Vol 147 (9) ◽

pp. 3301-3326 ◽

Cited By ~ 3

Author(s):

Chu-Chun Huang ◽

Shu-Hua Chen ◽

Yi-Chiu Lin ◽

Kenneth Earl ◽

Toshihisa Matsui ◽

...

Keyword(s):

North Africa ◽

Dust Cloud ◽

Mesoscale Convective System ◽

Model Verification ◽

Convective System ◽

Mesoscale Convective ◽

Cloud Development ◽

Radiation Induced ◽

Cloud Effect ◽

The Impact

AbstractThis study evaluates the impact of dust–radiation–cloud interactions on the development of a mesoscale convective system (MCS) by comparing numerical experiments run with and without dust–radiation and/or dust–cloud interactions. An MCS that developed over North Africa on 4–6 July 2010 is used as a case study. The CloudSat and Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellites passed over the center of the MCS after it reached maturity, providing valuable profiles of aerosol backscatter and cloud information for model verification. The model best reproduces the MCS’s observed cloud structure and morphology when both dust–radiation and dust–cloud interactions are included. Our results indicate that the dust–radiation effect has a far greater influence on the MCS’s development than the dust-cloud effect. Results show that the dust-radiative effect, both with and without the dust–cloud interaction, briefly delays the MCS’s formation but ultimately produces a stronger storm with a more extensive anvil cloud. This is caused by dust–radiation-induced changes to the MCS’s environment. The impact of the dust–cloud effect on the MCS, on the other hand, is greatly affected by the presence of the dust–radiation interaction. The dust–cloud effect alone slows initial cloud development but enhances heterogeneous ice nucleation and extends cloud lifetime. When the dust–radiation interaction is added, increased transport of dust into the upper portions of the storm—due to a dust–radiation-driven increase in convective intensity—allows dust–cloud processes to more significantly enhance heterogeneous freezing activity earlier in the storm’s development, increasing updraft strength, hydrometeor growth (particularly for ice particles), and rainfall.

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A Diagnostic Study of a Retreating Mei-Yu Front and the Accompanying Low-Level Jet Formation and Intensification

Monthly Weather Review ◽

10.1175/mwr3099.1 ◽

2006 ◽

Vol 134 (3) ◽

pp. 874-896 ◽

Cited By ~ 32

Author(s):

George Tai-Jen Chen ◽

Chung-Chieh Wang ◽

Li-Fen Lin

Keyword(s):

Mesoscale Convective System ◽

Heavy Rain ◽

Meridional Wind ◽

Convective System ◽

Diagnostic Study ◽

Cloud Band ◽

Weather Forecasts ◽

Low Level ◽

Mesoscale Convective ◽

Low Level Jet

Abstract During 7–8 June 1998, an organized mesoscale convective system (MCS) formed within the mei-yu frontal cloud band and moved northeastward to produce heavy rain over the island of Taiwan. During this period, the section of the mei-yu front east of Taiwan moved northward, most significantly for about 300 km over 12 h. Meanwhile, a low-level jet (LLJ) developed within the environmental southwesterly flow to the south of the mei-yu front and the MCS. Observations revealed that the front retreated as low-level meridional wind components over the postfrontal region shifted from northerly to southerly. Using European Centre for Medium-Range Weather Forecasts (ECMWF) analyses with piecewise potential vorticity (PV) inversion technique and other methods, a diagnostic study was carried out to investigate the northward frontal movement and the formation of the LLJ. Results indicated that diabatic latent heating from the MCS, large enough in scale, generated positive PV and height fall at low levels. The enhanced height gradient induced northwestward-directed ageostrophic winds and the LLJ formed southeast of the MCS through Coriolis torque. The southwesterly flow associated with this diabatic PV perturbation led to rapid retreat of the frontal segment east of Taiwan at a speed of about 25 m s−1, while the movement was dominated by horizontal advection in the present case. During this process of readjustment toward geostrophy, a thermally indirect circulation also appeared over and south of the front, and the LLJ formed within its lower branch at 850 hPa. The enhanced southwesterly winds reached LLJ strength because they were superimposed upon a background monsoon flow at the same direction. To the lee of Taiwan, the topography also played the role in enhancing local wind speed at lower levels and contributed toward the frontal retreat at nearby regions.

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