The Role of Environmental Shear and Thermodynamic Conditions in Determining the Structure and Evolution of Mesoscale Convective Systems during TOGA COARE

LeMone, Margaret A.; Zipser, Edward J.; Trier, Stanley B.

doi:10.1175/1520-0469(1998)055<3493:troesa>2.0.co;2

Cited by 211 publications

(234 citation statements)

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“…Bluestein, 1993;Emanuel, 1994). Using the thermodynamic parameters and stability indices, a number of studies examine the thermodynamic environments for MCSs and rainstorms that occur in various climate regions: the United Stated (Bluestein and Jain, 1985;Houze et al, 1990;Cohen et al, 2007); the Tropics (Barnes and Sieckman, 1984;LeMone et al, 1998); and the subtropical regions (Wang et al, 1990). However, it is very difficult to determine a universal standard for the diagnosis of the development of MCSs by use of a single stability index or some combination of the indices.…”

Section: Introductionmentioning

confidence: 99%

Dependence of the precipitation intensity in mesoscale convective systems to temperature lapse rate

Takemi

2010

Atmospheric Research

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The dependence of the structure and intensity of precipitation generated within squall lines to environmental temperature lapse rate is investigated by the use of a large set of numerical experiments under idealized model configurations. The lapse rate in a convectively unstable layer is used for the present analysis. The mean precipitation intensity during the simulated period generally increases with the increase in lapse rate, while the maximum precipitation intensity increases with the decrease in lapse rate. The precipitation mean is dependent on the intensity of cold pool resulting from organized convective clouds. In contrast, the precipitation maxima is regulated by relative humidity within the tropospheric lower layer. In an environment with higher lapse rate, a larger amount of CAPE is distributed in a deeper layer of the lower troposphere, which is beneficial for the development and intensification of convection and precipitation. Lapse rate in the troposphere is useful in comparing the characteristics of precipitation produced by mesoscale convective systems that occur in various climate regions of the world and also produced in a future climate under global warming.

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Section: Introductionmentioning

confidence: 99%

Dependence of the precipitation intensity in mesoscale convective systems to temperature lapse rate

Takemi

2010

Atmospheric Research

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“…In the real world, squall lines are observed frequently, and in agreement with many studies, are often associated with moderate or greater low-level wind shear. LeMone et al [1998] summarized the convective lines during TOGA-COARE finding that convection prefers orientation parallel to the low level wind shear if it is sufficiently strong, but otherwise may line up parallel to midlevel shear. Johnson et al's [2005] results added the factor of humidity in the mid troposphere with the more complicated structures observed in South China Sea Monsoon Experiment [Lau et al, 2000].…”

Section: Convective Linesmentioning

confidence: 99%

“…Although in general MCSs consist of regions with convective and stratiform precipitation and nonprecipitating regions with anvil cloud, they have a large variety of precipitation and cloud structures [e.g., McAnelly and Cotton, 1989;Johnson et al, 2005]. Different organizations of MCSs can occur under different environments [e.g., Hodges and Thorncroft, 1997;Lemone et al, 1998;Carbone et al, 2002;Johnson et al, 2004]. As a result, they may appear with different morphologies, sometimes as a near-circular shaped, long lasting mesoscale convective complex [e.g., Maddox, 1980], or as a convective line, often with a typical leading line of convection and a trailing area with stratiform precipitation [e.g., Houze, 1977;Zipser, 1977].…”

Section: Introductionmentioning

confidence: 99%

“…This organized convection is dominant in the life cycle of an MCS. Focusing on the mechanism of leading line/trailing stratiform type of MCSs, many studies have shown that organization of the convection is related to vertical wind shear and convective available potential energy [e.g., Moncrieff and Green, 1972;Houze, 1977;Rotunno et al, 1988;LeMone et al, 1998;Johnson et al, 2004]. If there is significant vertical wind shear at low (middle) levels, convection is usually aligned normal (parallel) to the wind shear direction [LeMone et al, 1998;Johnson et al, 2004;Cetrone and Houze, 2006], and this difference may affect how much stratiform precipitation is generated.…”

Section: Introductionmentioning

confidence: 99%

“…[4] Many studies of organized convection are based upon observations from field campaigns, such as the GARP Atlantic Tropical Experiment (GATE) [Cheng and Houze, 1979;Szoke and Zipser, 1986], Equatorial Mesoscale Experiment [Alexander and Young, 1992], The Tropical Ocean Global Atmosphere Coupled Atmosphere-Ocean Response Experiment (TOGA-COARE) [LeMone et al, 1998], and the South China Sea Monsoon Experiment [Lau et al, 2000] whereas some are based on model simulations [Moncrieff and Green, 1972;Rotunno et al, 1988]. In recent years, an increasing quantity of satellite observations provides opportunities to describe MCSs from a global perspective [Laing and Fritsch, 1997;Nesbitt et al, 2000;Schumacher et al, 2004].…”

Section: Introductionmentioning

confidence: 99%

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Regional variation of morphology of organized convection in the tropics and subtropics

Liu

Zipser

2013

JGR Atmospheres

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[1] Properties of organized convection with large horizontal area (> 1000 km 2 ) and with different horizontal structures in the tropics and subtropics are investigated by using 14 years of Tropical Rainfall Measuring Mission observations. First, the convective features (CFs) are defined as contiguous areas of convective precipitation detected by the Tropical Rainfall Measuring Mission precipitation radar. Using the minor and major axes of fitted ellipses, the morphology of the CFs are described as closer to a circular or a line shape. Regional variations and the properties of organized convection are examined with CFs with area > 1000 km 2 after categorizing them by their shapes. Organized convection tends to have larger extent and a higher fraction of near-circular shapes over land than over ocean. Shallow organized convection with maximum radar echo top height below 4.5 km is found mainly over ocean and some coastal regions. Of all tropical oceans, most shallow organized convection is found over the east Pacific. The fraction of line shaped organized convection is higher over the ocean than over land, and is higher in the subtropics than in the tropics. More convective lines are found in winter than in summer over oceans, but more in summer over land. Organized convective lines are slightly less convectively intense indicated by lower 30 dBZ echo top heights and warmer 37 GHz brightness temperatures than those with near-circular shapes. Orientations of organized convective lines are often aligned with fronts, dry lines, warm ocean currents, coastlines, and mountain slopes. Over the subtropics, organized convective lines are tilted more east-west over land, and more north-south over oceans. The largest and the most intense convective lines are found over central Africa, Argentina, and southeast U.S. over land, and over several warm currents in subtropical oceans.

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An explosive convective cloud system and its environmental conditions in MJO initiation observed during DYNAMO

Judt

Chen

2014

J. Geophys. Res. Atmos.

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An unusually large, explosive convective cloud system was observed over the equatorial Indian Ocean on 28 November 2011 during the DYNAMO (Dynamics of the Madden-Julian Oscillation (MJO)) field campaign. The significance of this mesoscale convective system (MCS) is its size and explosive development of cold cloud tops (À96°C) during the initiation of a strong MJO event. Observations from the DYNAMO show that the large MCS developed within a well-defined synoptic-scale cyclonic circulation associated with an equatorial low-pressure system with characteristics of a mixed Rossby-gravity wave that dominated the flow in the DYNAMO array. Prior to the development of the MCS, the equatorial flow was characterized by strong vertical wind shear with low-level westerlies and upper level easterlies. A region of decreased wind shear and enhanced upper level divergence emerged concurrently with the passage of the westward moving mixed Rossby-gravity wave-related low-pressure system and convective activity. In situ sounding observations suggest that widespread deep convection upstream of the large MCS may have contributed to the reduction of the upper level easterlies through vertical momentum transport and convective outflow. Both the reduction in vertical wind shear and enhanced low-level convergence induced by the equatorial low-pressure system created a favorable environment for the rapid development of the MCS. This study examines the development of the MCS and the associated synoptic-scale equatorial low-pressure system within the large-scale MJO circulation using in situ sounding observations from DYNAMO, which provide new insights into the interaction between convection and environmental flow during MJO initiation over the equatorial Indian Ocean.

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The Role of Environmental Shear and Thermodynamic Conditions in Determining the Structure and Evolution of Mesoscale Convective Systems during TOGA COARE

Cited by 211 publications

References 74 publications

Dependence of the precipitation intensity in mesoscale convective systems to temperature lapse rate

Dependence of the precipitation intensity in mesoscale convective systems to temperature lapse rate

Regional variation of morphology of organized convection in the tropics and subtropics

An explosive convective cloud system and its environmental conditions in MJO initiation observed during DYNAMO

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