Methods for mesoscale convective systems detection and tracking:a survey
01 Jul 2019-pp 1-7
TL;DR: Various MCS detection and tracking methods are surveyed and discussed citing their benefits, limitations and research directions to help new researchers to understand current ongoing research related to MCS in combination with other weather phenomenon such as precipitation, storms and atmospheric circulations.
Abstract: Mesoscale Convective Systems are group of convective clouds extending over hundreds of kilometers in one direction. These cloud systems are responsible for most of the precipitation and severe weather conditions causing significant damage to property and loss of life. Therefore it is essential to study patterns of MCS occurrence. Global warming and increasing pollution also varies MCS patterns resulting in extreme weather conditions causing heavy rain and floods. MCS detection and tracking are important steps for studying its characteristics pattern. MCS are detected based on cloud temperature and its size thresholds. In this paper various MCS detection and tracking methods are surveyed and discussed citing their benefits, limitations and research directions. Presented work will help new researchers to understand current ongoing research related to MCS in combination with other weather phenomenon such as precipitation, storms and atmospheric circulations. Methods surveyed in this paper are based on satellite IR image dataset.
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TL;DR: In this article , a convolutional neural network (CNN) was used to detect bow echoes from French kilometer-scale model outputs in order to facilitate and accelerate the operational forecasting of BEs.
Abstract:
Bow echoes (BEs) are bow-shaped lines of convective cells that are often associated with swaths of damaging straight-line winds and small tornadoes. This paper describes a convolutional neural network (CNN) able to detect BEs directly from French kilometer-scale model outputs in order to facilitate and accelerate the operational forecasting of BEs. The detections are only based on the maximum pseudoreflectivity field predictor (“pseudo” because it is expressed in mm h−1 and not in dBZ). A preprocessing of the training database is carried out in order to reduce imbalance issues between the two classes (inside or outside bow echoes). A CNN sensitivity analysis against a set of hyperparameters is done. The selected CNN configuration has a hit rate of 86% and a false alarm rate of 39%. The strengths and weaknesses of this CNN are then emphasized with an object-oriented evaluation. The BE largest pseudoreflectivities are correctly detected by the CNN, which tends to underestimate the size of BEs. Detected BE objects have wind gusts similar to the hand-labeled BE. Most of the time, false alarm objects and missed objects are rather small (e.g., <1500 km2). Based on a cooperation with forecasters, synthesis plots are proposed that summarize the BE detections in French kilometer-scale models. A subjective evaluation of the CNN performances is also reported. The overall positive feedback from forecasters is in good agreement with the object-oriented evaluation. Forecasters perceive these products as relevant and potentially useful to handle the large amount of available data from numerical weather prediction models.
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References
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TL;DR: A global set of 714 mesoscale convective complexes is compiled and some of the common properties of the convective systems are identified and examined from a global perspective as discussed by the authors.
Abstract: A global set of 714 mesoscale convective complexes is compiled and some of the common properties of the convective systems are identified and examined from a global perspective. the data set includes date of occurrence, time of first storms, initiation, maximum extent, termination, duration, cold-cloud shield areas, and tracks from initiation to termination.
It is found that the typical convective complex is nocturnal, generates a cold-cloud shield area of approximately 350 000 km2, and persists for about 10 h. the largest systems and most persistent systems tend to occur near the summer solstices. For the globe, about 400 systems occur each year, primarily over land areas. Most systems develop in favoured zones, although some activity occurs over every continent (except Antarctica) and all major oceans. the concentration of activity into favoured zones indicates that there must be special dynamic and/or thermodynamic conditions necessary for convection to organize into convective complexes.
Activity is strongly tied to the solar day, and shifts from 35°S in early January to about 50°N during the boreal summer and back to 35°S by December. Within the northern hemisphere there is a pronounced poleward migration as the jet stream shifts northward. Relatively little migration occurs in the ocean-dominated southern hemisphere where the subtropical jet remains quasi-stationary over the convective-complex regions.
The nocturnal life cycles, copious rainfall, large cloud shields, and great frequency of mesoscale convective complexes suggest that they may be significant contributors to the global hydrologic cycle and earth-system energy budget.
339 citations
TL;DR: In this article, the authors developed and validated an algorithm for tracking and forecasting radiative and morphological characteristics of mesoscale convective systems (MCSs) through their entire life cycle using geostationary satellite thermal channel information (10.8 μm).
Abstract: The purpose of this study is to develop and validate an algorithm for tracking and forecasting radiative and morphological characteristics of mesoscale convective systems (MCSs) through their entire life cycles using geostationary satellite thermal channel information (10.8 μm). The main features of this system are the following: 1) a cloud cluster detection method based on a threshold temperature (235 K), 2) a tracking technique based on MCS overlapping areas in successive images, and 3) a forecast module based on the evolution of each particular MCS in previous steps. This feature is based on the MCS’s possible displacement (considering the center of the mass position of the cloud cluster in previous time steps) and its size evolution. Statistical information about MCS evolution during the Wet Season Atmospheric Mesoscale Campaign (WETAMC) of the Large-Scale Biosphere–Atmosphere Experiment in Amazonia (LBA) was used to obtain area expansion mean rates for different MCSs according to their lifet...
168 citations
"Methods for mesoscale convective sy..." refers background or methods in this paper
...There is a near-linear relation between the cloud size area and a given temperature threshold below 245 K in the range of 10–20 K [9]....
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...vulnerability towards damage due to extreme weather conditions [9]....
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...[9] performed scale analysis to get minimum area size threshold value of 2400 km(2) for 4 km x 4 km image resolution using Geostationary Operational Environmental Satellite (GOES) images taken after every 30 min time interval....
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...There are many methods used for MCS tracking such as forward and backward tracking, adaptive temperature threshold [14], spatial correlation technique[9] [14], and area overlapping techniques [9] [14] [16]....
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...geostationary satellites is used in many studies [2] – [7] [9] [11] [13]-[19] as it directly gives us cloud top temperature values....
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TL;DR: In this article, an investigation of several hundred mesoscale convective systems (MCSs) during the warm seasons (April-August) of 1996-1998 is presented.
Abstract: An investigation of several hundred mesoscale convective systems (MCSs) during the warm seasons (April–August) of 1996–98 is presented. Circular and elongated MCSs on both the large and small scales were classified and analyzed in this study using satellite and radar data. The satellite classification scheme used for this study includes two previously defined categories and two new categories: mesoscale convective complexes (MCCs), persistent elongated convective systems (PECSs), meso-β circular convective systems (MβCCSs), and meso-β elongated convective systems (MβECSs). Around two-thirds of the MCSs in the study fell into the larger satellite-defined categories (MCCs and PECSs). These larger systems produced more severe weather, generated much more precipitation, and reached a peak frequency earlier in the convective season than the smaller, meso-β systems. Overall, PECSs were found to be the dominant satellite-defined MCS, as they were the largest, most common, most severe, and most prolific ...
135 citations
TL;DR: In this article, an automated method for producing a significant European mesoscale convective system (MCS) climatology is presented, which is composed of two main tools: an automated cloud-shield tracking method and a robust method of discriminating between convective and non-convective cloud shields.
Abstract: An automated method aimed at producing a significant European mesoscale convective system (MCS) climatology is presented. It uses Meteosat infrared window channel images and is composed of two main tools: an automated cloud-shield tracking method and a robust method of discriminating between convective and nonconvective cloud shields.
The automated cloud-tracking method defines cloud systems as connected sets of pixels, named ‘cells’, after temperature and area thresholding and it is based on the overlapping between cells in successive images. It handles splits and merges of cells and takes cell movement into account. It has three parameters: the temperature and area thresholds and a minimum overlapping threshold. It is concluded that it performs a correct tracking at any temperature threshold between −30°C and −55°C and for an area threshold greater than 1000 km2, so that it allows the tracking of MCSs during most of their life cycle.
The automated discrimination between convective and non-convective cloud shields uses a discrimination parameter based on brightness-temperature gradients on the edges of cells, because strong values of this gradient are observed at the beginning of the life cycle of MCSs when cold anvils develop. A seasonal study, and the sensitivity of the method to the temperature threshold, are presented. The method shows significant quality during the entire warm season (from April to September): it correctly discriminates 80% of MCSs and more than 90% of the most electrically active ones, while showing a low false-alarm rate around 8%; therefore the method seems to be useful for climatological purposes. Copyright © 2002 Royal Meteorological Society
125 citations
"Methods for mesoscale convective sy..." refers background in this paper
...geostationary satellites is used in many studies [2] – [7] [9] [11] [13]-[19] as it directly gives us cloud top temperature values....
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...Later Laing and Fritsch [1] [19], Morel and Senesi [11] also contributed for MCS detection by utilizing satellite images....
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...Later Laing and Fritsch [1] [19], Morel and Senesi [11] also contributed for MCS detection by utilizing satellite images....
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TL;DR: A new algorithm called Tracking Of Organized Convection Algorithm through a 3-D segmentatioN has been developed and is presented in this paper, which reveals that MCSs are detected earlier in life cycle and later in their dissipation stages.
Abstract: This paper focuses on the tracking of mesoscale convective systems (MCS) from geostationary satellite infrared data in the tropical regions. In the past, several automatic tracking algorithms have been elaborated to tackle this problem. However, these techniques suffer from limitations in describing convection at the “true” scale and in depicting coherent MCS life cycles (split and merge artifacts). To overcome these issues, a new algorithm called Tracking Of Organized Convection Algorithm through a 3-D segmentatioN has been developed and is presented in this paper. This method operates in a time sequence of infrared images to identify and track MCS and is based on an iterative process of 3-D segmentation of the volume of infrared images. The objective of the new tracking algorithm is to associate the convective core of an MCS to its anvil cloud in the spatiotemporal domain. The technique is applied on various case studies over West Africa, Bay of Bengal, and South America. The efficiency of the new algorithm is established from an analysis of the case studies and via a statistical analysis showing that the cold cloud shield defined by a 235-K threshold in the spatiotemporal domain is decomposed into realistic MCSs. In comparison with an overlap-based tracking algorithm, the analysis reveals that MCSs are detected earlier in life cycle and later in their dissipation stages. Moreover, MCSs identified are not anymore affected by split and merge events along their life cycles, allowing a better characterization of their morphological parameters along their life cycles.
119 citations
"Methods for mesoscale convective sy..." refers background or methods in this paper
...Fiolleau and Roca in [13] developed a method for MCS detection and its tracking....
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...195 K temperature threshold value to identify relatively smaller systems [5] [7] [13]....
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...The TOOCAN algorithm addresses the limiting issues of earlier MCSs tracking methods [13]....
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...Fiolleau and Roca [13] used multiple brightness temperature thresholds (190 K, 200 K, 210 K, 220 K, and 235 K) for detection of all convective clouds having IR temperature below 235K.Three-dimensional clusters are defined by considering contiguous area of pixels having a brightness temperature lower than the threshold value in the spatiotemporal domain....
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...geostationary satellites is used in many studies [2] – [7] [9] [11] [13]-[19] as it directly gives us cloud top temperature values....
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