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Abstract
Two X-hand Doppler radars observed a hailstorm that passed directly over one of the radars during the 1973 National Hail Research Experiment (NHRE). While one of the radars scanned the storm at low elevation angles the other radar, which operated simultaneously in a zenith–pointing mode, measured part of an updraft. Observations by other NHRE participants assisted in interpreting the radial velocity fields so that inflow and outflow could be identified from the scanning radar measurements. The peak updrafts occurred just ahead of. the highest reflectivity while the strongest downdrafts were found only 6 km behind the updraft. Strong turbulence was generated in the transition region between updraft and downdraft as evidenced by large velocity variances. A substantial part of the downdraft appeared to have been led by air that had ascended in the updraft. Low–level velocity fields were in general agreement with surface measurements and showed the outflow toward the front of the storm in the gust front as well as outflow opposite the echo motion behind the storm. There was strong outflow opposite the direction of echo motion at the top of the storm which agreed with photographs of the anvil overhang.
Abstract
Two X-hand Doppler radars observed a hailstorm that passed directly over one of the radars during the 1973 National Hail Research Experiment (NHRE). While one of the radars scanned the storm at low elevation angles the other radar, which operated simultaneously in a zenith–pointing mode, measured part of an updraft. Observations by other NHRE participants assisted in interpreting the radial velocity fields so that inflow and outflow could be identified from the scanning radar measurements. The peak updrafts occurred just ahead of. the highest reflectivity while the strongest downdrafts were found only 6 km behind the updraft. Strong turbulence was generated in the transition region between updraft and downdraft as evidenced by large velocity variances. A substantial part of the downdraft appeared to have been led by air that had ascended in the updraft. Low–level velocity fields were in general agreement with surface measurements and showed the outflow toward the front of the storm in the gust front as well as outflow opposite the echo motion behind the storm. There was strong outflow opposite the direction of echo motion at the top of the storm which agreed with photographs of the anvil overhang.
Abstract
A model of an evolving hailstorm is synthesized from data presented in four related papers in this issue. The storm model, which is applicable to a class of ordinary multicell hailstorms and similar to earlier models derived by workers in South Dakota and Alberta, is discussed in terms of the growth of hail and its implications for hail suppression. Hail is grown in time–evolving updrafts that begin as discrete new clouds on the flank of the storm. Low concentrations of embryos develop rapidly within each of these clouds. The embryos subsequently grow into small hailstones while suspended near or above, the −20°C level as each new cloud grows and becomes the main updraft. Recycling is not a feature of this model as it is in supercell models. To improve the chance of silver iodide seeding being effective in suppressing the growth of hall in multicell storms, it is proposed that the seeding should be carried out not in the main updraft as is often the practice, but, rather, in the regions of weaker updraft associated with the early stages of developing clouds an the flank of the storm.
Abstract
A model of an evolving hailstorm is synthesized from data presented in four related papers in this issue. The storm model, which is applicable to a class of ordinary multicell hailstorms and similar to earlier models derived by workers in South Dakota and Alberta, is discussed in terms of the growth of hail and its implications for hail suppression. Hail is grown in time–evolving updrafts that begin as discrete new clouds on the flank of the storm. Low concentrations of embryos develop rapidly within each of these clouds. The embryos subsequently grow into small hailstones while suspended near or above, the −20°C level as each new cloud grows and becomes the main updraft. Recycling is not a feature of this model as it is in supercell models. To improve the chance of silver iodide seeding being effective in suppressing the growth of hall in multicell storms, it is proposed that the seeding should be carried out not in the main updraft as is often the practice, but, rather, in the regions of weaker updraft associated with the early stages of developing clouds an the flank of the storm.
