Assessment of mesoscale convective systems using IR brightness temperature in the southwest of Iran

Rafati, Somayeh; Karimi, Mostafa

doi:10.1007/s00704-016-1797-7

Cited by 12 publications

(5 citation statements)

References 39 publications

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“…Due to the good correspondence between brightness temperature (BT) of infrared channel (at around 11 μm) from satellite and gauge-based rain rate (Vicente et al, 1998), the BT at this infrared channel has been widely used to identify pMCSs from satellite images in numerous previous works (e.g., Laing et al, 2008;Mathon et al, 2002;Mathon & Laurent, 2001). Interestingly, the BT threshold varies substantially, ranging from 208 to 258 K (Ai et al, 2016;Hodges & Thorncroft, 1997;Machado et al, 1998;Rafati & Karimi, 2017). As suggested by Arkin and Meisner (1987), cold cloud tops with BT lower than 235 K present the best correlations with tropical rainfall.…”

Section: Identifying Potential Mcssmentioning

confidence: 99%

“…Given that, some criteria in terms of the areas and durations of MCSs are applied as constrains. Generally, the ultimate MCS is required to meet the following criteria: The pMCS at least reaches the area extent of 10,000 km 2 during its life cycle (Rafati & Karimi, ), and the duration of the convective system larger than or equal to 3 hr (Ai et al, ; Jirak et al, ; Rafati & Karimi, ). The pMCSs that do not meet these two criteria will be excluded for further analyses.…”

Section: Algorithmsmentioning

confidence: 99%

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Mesoscale Convective Systems in the Asian Monsoon Region From Advanced Himawari Imager: Algorithms and Preliminary Results

et al. 2019

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The knowledge of mesoscale convective system (MCS) in the Asian monsoon region remains still deficient due to the limited available data and less powerful algorithms. Here, using the data from Advanced Himawari Imager onboard Himawari‐8 (HW8), an improved algorithm combining the area overlapping with the Kalman filter is developed, which captures much smaller MCSs that are unavailable otherwise. Several influential factors like the overlapping rate and splitting/merging in the area overlapping method, and the initial state variable in the Kalman filter method, all of which were less appreciated, are handled explicitly. The occurrence frequency, and moving trajectory of two types of MCS, including the ordinary MCS and superconvective system, has been comprehensively examined in the Asian monsoon region for the warm season (April to September) of 2016. Comparison analyses with ground precipitation and radar measurements confirm the good performance of our algorithm. In particular, the moving direction of MCS strongly depends on latitudes, so does the horizontal velocity. Compared with over ocean, the frequency of MCSs dominates over land or along coasts in the tropics, where strong moisture flux convergence is frequently observed in the low troposphere. In addition, the MCSs detected in eastern China can roughly capture the meridional propagation over time, which corresponds well to the precipitation belts linked to Meiyu front systems. The superconvective systems dominate over the Bay of Bengal and South China Sea due to the large‐scale circulation. Our findings provide new insights to spatiotemporal patterns of MCSs during warm season in the Asian monsoon region.

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Section: Identifying Potential Mcssmentioning

confidence: 99%

Section: Algorithmsmentioning

confidence: 99%

Mesoscale Convective Systems in the Asian Monsoon Region From Advanced Himawari Imager: Algorithms and Preliminary Results

et al. 2019

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“…The brightness temperature (BT) threshold used to define points inside MCSs has varied substantially in prior studies, ranging from 208 to 258 K (e.g., Hodges and Thorncroft 1997;Machado et al 1998;Ai et al 2016;Rafati and Karimi 2017). Arkin and Meisner (1987) found that cloud tops with BT , 235 K were associated with tropical rainfall so that a threshold of 235 K has since been used to identify points contained within MCSs (Laurent et al 2002;Vila et al 2008).…”

Section: ) Methods Of Identifying Mcs and Age Of Mcsmentioning

confidence: 99%

Dependence of Ice Microphysical Properties On Environmental Parameters: Results from HAIC-HIWC Cayenne Field Campaign

McFarquhar

et al. 2021

Journal of the Atmospheric Sciences

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High Ice Water Content (HIWC) regions above tropical mesoscale convective systems are investigated using data from the second collaboration of the High Altitude Ice Crystals and High Ice Water Content projects (HAIC-HIWC) based in Cayenne, French Guiana in 2015. Observations from in-situ cloud probes on the French Falcon 20 determine the microphysical and thermodynamic properties of such regions. Data from a 2-D stereo probe and precipitation imaging probe show how statistical distributions of ice crystal mass median diameter (MMD), ice water content (IWC), and total number concentration (Nt) for particles with maximum dimension (Dmax) > 55 μm vary with environmental conditions, temperature (T), and convective properties such as vertical velocity (w), MCS age, distance away from convective peak (L), and surface characteristics. IWC is significantly correlated with w, whereas MMD decreases and Nt increases with decreasing T consistent with aggregation, sedimentation and vapor deposition processes at lower altitudes. MMD typically increases with IWC when IWC < 0.5 g m-3, but decreases with IWC when IWC > 0.5 g m-3 for -15 °C ≤ T ≤ -5 °C. Trends also depend on environmental conditions, such as presence of convective updrafts that are the ice crystal source, MMD being larger in older MCSs consistent with aggregation and less injection of small crystals into anvils, and IWCs decrease with increasing L at lower T. The relationship between IWC and MMD depends on environmental conditions, with correlations decreasing with decreasing T. The strength of correlation between IWC and Nt increases as T decreases.

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“…This more constrained BT threshold is similar to that applied to MCSs in the Americas (e.g., Maddox, 1980;Cotton et al 1989;Arritt, 1998, 2001;Cheeks et al 2020) and has previously been applied to MCCs in South Africa (Blamey and Reason, 2012). The 10,000 km 2 size threshold has previously been used in the literature (e.g., García-Herrera et al 2005;Rafati and Karimi, 2017). Various size thresholds are used in the literature ranging from 100 km 2 through to 100,000 km 2 (Hitchens et al, 2012).…”

Section: Mcs Databasementioning

confidence: 98%

Long-Lived Mesoscale Convective Systems over Eastern South Africa

2021

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A climatology of large, long-lived mesoscale convective systems (MCSs) over eastern South Africa for the extended austral summer (September-April) from 1985-2008 is presented. On average, 63 MCSs occur here in summer, but with considerable interannual variability in frequency. The systems mainly occur between November and March, with a December peak. This seasonal cycle in MCS activity is shown to coincide with favorable CAPE and vertical shear profiles across the domain. Most systems tend to occur along the eastern escarpment and adjacent warm waters of the northern Agulhas Current with a nocturnal life cycle. Typically, initiation begins in the early afternoon, MCS status is reached mid-afternoon, maximum extent early in the night and termination around midnight or shortly thereafter. It is found that most MCSs initiate over land, but systems that initiate over the ocean tend to last longer than those that develop over land. The results also show that there are differences in the seasonal cycle between continental and oceanic MCSs, with oceanic systems containing two intraseasonal peaks (December and April). There is a relatively strong positive relationship between the Southern Annular Mode (SAM) and early summer MCSs frequency. For the late summer, the frequency of MCSs appears related to the strength of the Mascarene High and Mozambique Channel Trough which modulate the inflow of moisture into eastern South Africa and the stability of the lower atmosphere over the region.

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Assessment of mesoscale convective systems using IR brightness temperature in the southwest of Iran

Cited by 12 publications

References 39 publications

Mesoscale Convective Systems in the Asian Monsoon Region From Advanced Himawari Imager: Algorithms and Preliminary Results

Mesoscale Convective Systems in the Asian Monsoon Region From Advanced Himawari Imager: Algorithms and Preliminary Results

Dependence of Ice Microphysical Properties On Environmental Parameters: Results from HAIC-HIWC Cayenne Field Campaign

Long-Lived Mesoscale Convective Systems over Eastern South Africa

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