Hail climate datasets

A selection of datasets from the project "Hail Climate Switzerland" is available for use in climate research and practice.

DOI:

10.18751/Climate/Griddata/CHHC/1.0

Name:

CHHC: Swiss Hail Climatology

Version and year of publication:

1.0 / 2021

Citation:

Technical Report: Hail Climate Switzerland (will be made available).

Datasets: Hail Climatology Switzerland Project Team (2021): Swiss Hail Climatology. National Centre for Climate Services. doi: 10.18751/Climate/Griddata/CHHC/1.0

Licence:

CC BY 4.0

Description and Data Access

The datasets fall into three categories:

Number of hail days

The data contain the monthly and yearly number of hail days and the long-term average number of hail days per year or per month of the summer half-year (April to September), per km2. Hail cannot be measured on the ground over a wide area. The size is derived from radar measurements. A hail day is defined as a day on which a high probability of hail on the ground was concluded from the radar measurements (based on radar parameter POH). The 24 hours between 06 UTC and 06 UTC of the following day are considered.


Maximum expected hailstone sizes (radar)


The data contain the largest hailstone size by month and year, respectively, as well as the average number of days with hailstone sizes from 2 cm and 4 cm, respectively. Hailstone sizes cannot be measured on the ground over a large areas. The size is derived from radar measurements and describes the maximum expected hail size on one square kilometer based on the radar parameter MESHS (Maximum Expected Severe Hail Size).
Due to the infrequent occurrence of hail, averaging of hailstone sizes over many years is not meaningful. The number of days from hailstone sizes of at least 2 cm and 4 cm is provided as climatology. These data allow a robust statement about the frequency of events of certain hailstone sizes.
Hailstone sizes are given in classes from 2 cm to greater than 6 cm in 0.5 cm increments, with the lower end being inclusive and the upper end exclusive: the grid value 2 represents values from 2 cm (incl.) to 2.5 cm (excl.).


Return values of the maximum hailstone size (MESHS)

The data contain the return values of the hailstone sizes MESHS as a function of the return period T. They describe the hailstone size that is exceeded with a probability of 1/T per year under today's climate conditions, at a fixed location. The return values were determined using a resampling approach and describe the maximum hailstone size to be expected on a square kilometre (based on the radar parameter MESHS).


Hail hazard maps for buildnig protection: return periods for hailstone size LEHA on reference area of 100 m2

The hail hazard maps show statistically estimated return values of the hailstone size LEHA-100. LEHA-100 describes the largest hailstone size to be expected on a reference area of 100 m2. It is derived from the radar algorithm MESHS, which is the size of the maximum expected hailstone per square kilometre (radar data from MeteoSwiss for 2002 to 2020).


Radar Hail Data

In addition to the freely accessible climatological hail information described above (number of hail days and maximum expected hail size (radar) per month or year), the radar hail products Probability of Hail POH and Maximum Expected Severe Hail Size MESHS are available as a 5-minute grid and as daily maxima at 00 and 06 UTC for a fee. The radar hail data, like the other radar measurements, are subject to the Ordinance on Fees.

Last modification 11.05.2021

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