Search Results

You are looking at 1 - 4 of 4 items for

  • Author or Editor: J. F. Mezeix x
  • Refine by Access: All Content x
Clear All Modify Search
J. F. Mezeix

Abstract

In a recent article, Dessens uses economic data to evaluate a nonrandomized hail suppression project involving seeding from the ground. Given the far-reaching repercussions of such an evaluation within both the scientific and agricultural communities the control method used and the results must be irrefutable. These comments have received the agreement of the scientific committee of the French Hail Program attributed to G.N.E.F.A. by the Ministry of Agriculture, the insurance company, and the agricultural organizations.

Full access
A. Waldvogel
,
H. H. Schiesser
,
W. Schmid
, and
J. F. Mezeix

Abstract

Full access
A. Waldvogel
,
B. Federer
,
W. Schmid
, and
J. F. Mezeix

Abstract

The kinetic energy of hailfalls is measured with a 10 cm radar. For comparison of the results a total of 204 hailpad stations was used covering an area of 780 km2, i.e., one pad per 3.8 km2. The experimental setup is such that the largest distance between any hailpad and the radar is less than 30 km. The radar is accurately calibrated with raindrop disdrometers and hailstone spectrometers. The radar data consist of PPI pictures obtained at a constant elevation angle of 5.5° with a time resolution of 1 min and a reflectivity resolution of 5 dBZ. The radar reflectivity values are transformed into kinetic energies by means of empirical Z–Ė relations obtained from measured time-resolved hailstone spectra.

The data of six severe hailstorms are studied and the following results are obtained: 1) The correlation coefficient of corresponding hailpad and radar derived kinetic energies at single points of a hailstorm is 0.7, a value which can be increased to 0.8 if four-point averages are taken; 2) the global kinetic energy Eg (Z) of a hailfall calculated from radar data agrees to better than 20% with the corresponding value Eg deduced from hailpad information; and 3) the agreement between Eg (Z) and Eg of a hailstorm is better than a few percent for the two cases for which individual Z–Ė relations are available.

Full access
B. Federer
,
A. Waldvogel
,
W. Schmid
,
H. H. Schiesser
,
F. Hampel
,
Marianne Schweingruber
,
W. Stahel
,
J. Bader
,
J. F. Mezeix
,
Nadie Doras
,
G. D'Aubigny
,
G. DerMegreditchian
, and
D. Vento

Abstract

The main results of a randomized hail suppression experiment, Grossversuch IV, are presented in this paper. Grossversuch IV tested the “Soviet” hail prevention method during five years (1977–81). The field experiment took place in central Switzerland with the participation of research groups from France, Italy and Switzerland.

A very dense hailpad network (330 hailpads over 1300 km2) and a carefully calibrated 10-cm radar were used to measure in two independent ways the hail kinetic energy of seeded and unseeded hail cells. The total sample included 216 cells. The main result of the confirmatory as well as most of the exploratory analyses is that there is no statistically significant difference between seeded and unseeded hail cells. A detailed discussion of the reliability of the measurements, tests and methods is given together with a discussion about possibilities of future evaluations of the Grossversuch IV data and other cloud seeding experiments.

Full access