Rainfall regimes in a Mountainous Mediterranean Region: Statistical analysis at short time steps.
Abstract
This paper presents an analysis of the rainfall regime of a Mediterranean mountainous region of south-
eastern France. The rainfall regime is studied on temporal scales from hourly to yearly using daily and hourly
rain gauge data of 43 and 16 years, respectively. The domain is 200 3 200 km2 with spatial resolution of hourly
and daily rain gauges of about 8 and 5 km, respectively. On average, yearly rainfall increases from about
0.5 m yr21 in the large river plain close to the Mediterranean Sea to up to 2 m yr21 over the surrounding
mountain ridges. The seasonal distribution is also uneven: one-third of the cumulative rainfall occurs during
the autumn season and one-fourth during the spring. At finer time scales, rainfall is studied in terms of rain–
no-rain intermittency and nonzero intensity. The monthly intermittency (proportion of dry days per month)
and the daily intermittency (proportion of dry hours per day) is fairly well correlated with the relief. The
higher the rain gauges are, the lower the monthly and daily intermittencies are. The hourly and daily rainfall
intensities are analyzed in terms of seasonal variability, diurnal cycle, and spatial pattern. The difference
between regular and heavy-rainfall event is depicted by using both central parameters and maximum values of
intensity distributions. The relationship between rain gauge altitudes and rainfall intensity is grossly inverted
relative to intermittency and is also far more complex. The spatial and temporal rainfall patterns depicted
from rain gauge data are discussed in the light of known meteorological processes affecting the study region
Domains
Geomorphology
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