Characteristics of a Subtropical Squall Line Determined from TAMEX Dual-Doppler Data. Part I: Kinematic Structure

Wang, Tai-Chi Chen; Lin, Yeong-Jer; Shen, Hsi; Pasken, Robert W.

doi:10.1175/1520-0469(1990)047<2357:coassl>2.0.co;2

Cited by 43 publications

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“…Since the surface temperature in the southwesterly-wind area was 27 or 28 C, as shown in Fig. 11c, the temperature drop from the southwesterly low-level inflow is estimated to have been about 3 C. Such a small decrease of less than 5 C was also observed in past studies on a convective system during the Baiu seasons (Ishihara et al 1992;Ishihara et al 1995;Takahashi et al 1996;Wang et al 1990). This value is similar to that associated with a tropical squall line (@4 C, Chong et al 1987), and smaller than that associated with a midlatitude squall line (@8 C, Ogura and Liou 1980).…”

Section: Comparison With Baiu-frontal Macss In the Past Studies A Cosupporting

confidence: 70%

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Three-Dimensional Structure of a Mesoscale Convective System in a Baiu-Frontal Depression Generated in the Downstream Region of the Yangtze River

Yamada¹,

Geng²,

Reddy³

et al. 2003

Journal of the Meteorological Society of Japan

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A Baiu-frontal meso-a-scale depression was generated on 18 June 2001 in the mesoscale observational region, which was located in the downstream region of the Yangtze River. Based mainly on the data collected in this observation, we analyze the three-dimensional structure of a meso-a-scale convective system. We describe this structure and discuss the evolution of Baiu-frontal convective systems near the east coast of the continent.This convective system was composed of several meso-b-scale convective groups, which were bandshaped echoes located near the depression center, cellular echoes formed one after another ahead of the center, and a band-shaped echo extending more than 500 km in the rearward of the depression. There were three flows toward the convective system in the lower troposphere: moist southwesterly jet, dry west-to-northwesterly wind, and cold shallow easterly wind, which appeared near the coast. These convective groups were formed where the southwesterly wind, with convectively-unstable air, was lifted up to the free-convection level. This lifting resulted from low-level convergence, which was formed both by easterly and west-to-northwesterly wind in the central portion of the depression, by easterly wind at the forward portion, and by west-to-northwesterly wind at the rear portion.The system-relative speed of the southwesterly wind in the forward portion was larger than that in the rear. It is suggested that this strong inflow caused the formation of a deep convective structure in the forward portion, which reached the tropopause. The easterly wind played an important role in lifting such a strong inflow, and forming the deep convective groups in the meso-a-scale convective system, and then contributed to evolving the depression through the extension of the convective-updraft area. The Corresponding author: Hiroyuki Yamada, Frontier Observational Research System for Global Change, 3173-25, Shouwa-machi, Kanazawa-ku, Yokohama, 236-0001, Japan. E-mail: yamada@jamstec.go.jp ( 2003, Meteorological Society of Japan mechanism that the easterly wind was formed locally near the coastline is discussed. The enhancement of low-level convergence, due to the formation of such a local wind system, is suggested to be one of the causes for the development of a mesoscale convective system, near the east coast of the continent during Baiu seasons.

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Section: Comparison With Baiu-frontal Macss In the Past Studies A Cosupporting

confidence: 70%

“…The internal kinematic structure of frontal mesoscale rainbands was revealed in several studies (Trier et al 1990;Wang et al 1990;Lin et al 1992). The thermodynamic structure of the rainbands was examined in Lin et al (1990) and Ray et al (1991).…”

Section: Introductionmentioning

confidence: 99%

Three-Dimensional Structure of a Mesoscale Convective System in a Baiu-Frontal Depression Generated in the Downstream Region of the Yangtze River

Yamada¹,

Geng²,

Reddy³

et al. 2003

Journal of the Meteorological Society of Japan

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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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“…The dual-Doppler synthesis was performed using the CEDRIC (Custom Editing and Display of Reduced Information in Cartesian space) software developed by NCAR (Mohr et al 1986). According to Wang et al (1990), this squall line moved from 250 at a nearly constant speed of 16.5 ms À1 . After removing the system motion, the dual-Doppler derived storm-relative horizontal wind field, and the radar reflectivity (>30 dBZ) at the height of 2 km AGL (Above Ground Level) are plotted in Fig.…”

Section: Verification With a Real Casementioning

confidence: 99%

Single-Doppler Retrieval of the Three-Dimensional Wind in a Deep Convective System Based on an Optimal Moving Frame of Reference

Liou

2007

Journal of the Meteorological Society of Japan

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A single-Doppler radar velocity retrieval method, based on an optimally determined moving frame of reference, is developed. This method enables the recovery of the complete three-dimensional wind field using reflectivity, and radial wind observations, detected by a single Doppler radar over multiple volume scans. This method first computes a set of optimal moving speeds ðU; V; WÞ, which can be functions of the height. It is considered optimal in the sense that when a reference frame is traveling at this speed, as much of the radar reflectivity, interpolated onto this frame can be conserved as possible. The perturbation velocities ðu 0 ; v 0 ; w 0 Þ are then solved simultaneously, with respect to the moving speeds, by minimizing a cost function through the three-dimensional variational (3D-Var) approach. This cost function consists of a set of weak constraints, mainly the equation for radar reflectivity conservation, the continuity equation, the geometric relationship between the radar-observed radial wind and the Cartesian winds, and a smoothness filter. Finally, by adding the optimal moving speed to the perturbation velocities, a complete three-dimensional wind field is obtained.The performance of this method is tested under different scenarios, including cases with deep convections, embedded in an environment without mean wind, with constant mean wind, with vertical wind shear of the horizontal mean wind, and with differences in the radar observational time at each grid point within one volume scan are considered.This method is demonstrated to be feasible by applying it to recover the three-dimensional wind structure of a subtropical squall line from Doppler radar data, collected during the 1987 Taiwan Area Mesoscale Experiment (TAMEX).

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Characteristics of a Subtropical Squall Line Determined from TAMEX Dual-Doppler Data. Part I: Kinematic Structure

Cited by 43 publications

References 0 publications

Three-Dimensional Structure of a Mesoscale Convective System in a Baiu-Frontal Depression Generated in the Downstream Region of the Yangtze River

Three-Dimensional Structure of a Mesoscale Convective System in a Baiu-Frontal Depression Generated in the Downstream Region of the Yangtze River

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

Single-Doppler Retrieval of the Three-Dimensional Wind in a Deep Convective System Based on an Optimal Moving Frame of Reference

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