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- Author or Editor: K. R. Knupp x
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Abstract
A detailed, multisensor case study of mesoscale convective storms occurring in summer over the central and eastern Colorado Rockies is presented. This case study uses data obtained during the 1977 South Park Area Cumulus Experiment (SPACE) from surface meteorological stations, rawinsondes and tethered balloons, conventional and Doppler radars, powered aircraft and satellites.
On 19 July 1977, a north–south oriented line of intense convective cells formed and remained within South Park, an elevated plain 2.8 km above sea level located within the Rocky Mountains. Elevated surface heating in South Park created a region of low-level convergence which imported Pacific moisture from west of the Rockies into South Park. The mososcale thunderstorm line formed over this convergence zone. Subsequently, northerly surface flow, having the appearance of a “density current”, penetrated into South Park late in the afternoon, enhancing the intensity of convective storms. Various interactions of the storm system with the mesoscale environment were observed. A single large convective cell was then observed to grow on the southern end of the mesoscale line, exhibiting supercell characteristics and substantial modification of the environmental flow. A detailed description of this quasi-steady storm is given in Parts II and III (Knupp and Cotton, 1982a,b).
Abstract
A detailed, multisensor case study of mesoscale convective storms occurring in summer over the central and eastern Colorado Rockies is presented. This case study uses data obtained during the 1977 South Park Area Cumulus Experiment (SPACE) from surface meteorological stations, rawinsondes and tethered balloons, conventional and Doppler radars, powered aircraft and satellites.
On 19 July 1977, a north–south oriented line of intense convective cells formed and remained within South Park, an elevated plain 2.8 km above sea level located within the Rocky Mountains. Elevated surface heating in South Park created a region of low-level convergence which imported Pacific moisture from west of the Rockies into South Park. The mososcale thunderstorm line formed over this convergence zone. Subsequently, northerly surface flow, having the appearance of a “density current”, penetrated into South Park late in the afternoon, enhancing the intensity of convective storms. Various interactions of the storm system with the mesoscale environment were observed. A single large convective cell was then observed to grow on the southern end of the mesoscale line, exhibiting supercell characteristics and substantial modification of the environmental flow. A detailed description of this quasi-steady storm is given in Parts II and III (Knupp and Cotton, 1982a,b).
Abstract
One advantage of dual-polarization radars is the ability to differentiate between water and ice phases in storms. The application of difference reflectivity (Z DP) in the analysis of mixed-phase precipitation is presented. Here, Z DP analysis is used to obtain the fraction of water and ice in mixed-phase precipitation. The techniques developed are applied to data collected on 9 August 1991 during the Convection and Precipitation Electrification experiment. Time series of storm total liquid and ice water contents are computed. The liquid and ice water contents are used in a water budget equation to obtain the net latent heating of the convective storm. It is shown that the latent heating profile shows good correlation with the updraft and electric field increases in the time evolution of the storm.
Abstract
One advantage of dual-polarization radars is the ability to differentiate between water and ice phases in storms. The application of difference reflectivity (Z DP) in the analysis of mixed-phase precipitation is presented. Here, Z DP analysis is used to obtain the fraction of water and ice in mixed-phase precipitation. The techniques developed are applied to data collected on 9 August 1991 during the Convection and Precipitation Electrification experiment. Time series of storm total liquid and ice water contents are computed. The liquid and ice water contents are used in a water budget equation to obtain the net latent heating of the convective storm. It is shown that the latent heating profile shows good correlation with the updraft and electric field increases in the time evolution of the storm.
Abstract
The relationships among kinematic, microphysical, and electric field properties within a multicell Florida thunderstorm are investigated using observations from three Doppler radars (one with multiple wavelength and polarization diversity capabilities), four instrumented penetrating aircraft, a surface-based electric field mill network, and other observation facilities. The storm was convectively active for about 1 h and at least five primary cells developed within the storm during this time, one of which went through three consecutive development cycles. The updrafts in this storm were 2–4 km wide, exhibited bubble-like evolution, and had lifetimes of 10–20 min. The maximum updraft determined by the multiple Doppler analysis was about 20 m s−1. A differential reflectivity (Z DR) “column,” indicating regions containing millimeter-size raindrops, extending above the freezing level, was associated with each cell during its developing stages. This column reached altitudes exceeding 6 km (−8°C) in the stronger updrafts. As the Z DR columns reached maximum altitude, a “cap” of enhanced linear depolarization ratio (LDR) and enhanced 3-cm wavelength attenuation (A 3) formed, overlapping the upper regions of the Z DR column. These parameters indicate rapid development of mixed-phase conditions initiated by freezing of supercooled raindrops.
Lightning was observed only in the central and strongest convective cell. Electric fields exceeding 10 kV m−1 were noted during aircraft penetrations in this as well as several other cells that did not produce lightning. Fields exceeding 1 kV m−1 were noted by the instrumented aircraft at midcloud levels within a few minutes of development of mixed-phase conditions at these levels or aloft. The first intracloud lightning was detected by the surface field mill network within 5 min of development of mixed-phase conditions aloft in the first cycle of development in the central cell, and the first cloud-to-ground event was noted within 9 min of this development. Lightning continued through two additional cycles of updraft growth in this central region and diminished as the convection subsided after about 30 min. Aircraft-measured electric fields and lightning retrievals from the surface field meter network are consistent with a tendency for negative charge to accumulate above the 6.5 km(−12°C) level within regions of radar reflectivity maxima and for positive charge to accumulate in the anvil region well above 9 km (−30°C).
Abstract
The relationships among kinematic, microphysical, and electric field properties within a multicell Florida thunderstorm are investigated using observations from three Doppler radars (one with multiple wavelength and polarization diversity capabilities), four instrumented penetrating aircraft, a surface-based electric field mill network, and other observation facilities. The storm was convectively active for about 1 h and at least five primary cells developed within the storm during this time, one of which went through three consecutive development cycles. The updrafts in this storm were 2–4 km wide, exhibited bubble-like evolution, and had lifetimes of 10–20 min. The maximum updraft determined by the multiple Doppler analysis was about 20 m s−1. A differential reflectivity (Z DR) “column,” indicating regions containing millimeter-size raindrops, extending above the freezing level, was associated with each cell during its developing stages. This column reached altitudes exceeding 6 km (−8°C) in the stronger updrafts. As the Z DR columns reached maximum altitude, a “cap” of enhanced linear depolarization ratio (LDR) and enhanced 3-cm wavelength attenuation (A 3) formed, overlapping the upper regions of the Z DR column. These parameters indicate rapid development of mixed-phase conditions initiated by freezing of supercooled raindrops.
Lightning was observed only in the central and strongest convective cell. Electric fields exceeding 10 kV m−1 were noted during aircraft penetrations in this as well as several other cells that did not produce lightning. Fields exceeding 1 kV m−1 were noted by the instrumented aircraft at midcloud levels within a few minutes of development of mixed-phase conditions at these levels or aloft. The first intracloud lightning was detected by the surface field mill network within 5 min of development of mixed-phase conditions aloft in the first cycle of development in the central cell, and the first cloud-to-ground event was noted within 9 min of this development. Lightning continued through two additional cycles of updraft growth in this central region and diminished as the convection subsided after about 30 min. Aircraft-measured electric fields and lightning retrievals from the surface field meter network are consistent with a tendency for negative charge to accumulate above the 6.5 km(−12°C) level within regions of radar reflectivity maxima and for positive charge to accumulate in the anvil region well above 9 km (−30°C).
Abstract
Short-period (1–5 min) temperature and humidity soundings up to 10-km height are retrieved from ground-based 12-channel microwave radiometer profiler (MWRP) observations. In contrast to radiosondes, the radiometric retrievals provide very high temporal resolution (1 min or less) of thermodynamic profiles, but the vertical resolution, which declines in proportion to the height above ground level, is lower. The high temporal resolution is able to resolve detailed meso-γ-scale thermodynamic and limited microphysical features of various rapidly changing mesoscale and/or hazardous weather phenomena. To illustrate the MWRP capabilities and potential benefits to research and operational activities, the authors present example radiometric retrievals from a variety of dynamic weather phenomena including upslope supercooled fog, snowfall, a complex cold front, a nocturnal bore, and a squall line accompanied by a wake low and other rapid variations in low-level water vapor and temperature.
Abstract
Short-period (1–5 min) temperature and humidity soundings up to 10-km height are retrieved from ground-based 12-channel microwave radiometer profiler (MWRP) observations. In contrast to radiosondes, the radiometric retrievals provide very high temporal resolution (1 min or less) of thermodynamic profiles, but the vertical resolution, which declines in proportion to the height above ground level, is lower. The high temporal resolution is able to resolve detailed meso-γ-scale thermodynamic and limited microphysical features of various rapidly changing mesoscale and/or hazardous weather phenomena. To illustrate the MWRP capabilities and potential benefits to research and operational activities, the authors present example radiometric retrievals from a variety of dynamic weather phenomena including upslope supercooled fog, snowfall, a complex cold front, a nocturnal bore, and a squall line accompanied by a wake low and other rapid variations in low-level water vapor and temperature.
