The tenth IMSC, Beijing, China, 2007 - International Meetings on ...

Homogenization of daily meteorological series is a difficult task. Several kinds of
problems have to be taken into consideration in the course of homogenization: selection of a
proper homogenization method with regard to the data used, creation of reference series,
completion of missing values, annual course of adjustments and others. We present an
attempt to create a homogeneous series of daily air pressure, temperature and precipitation
readings in the area of Southern Moravia (Czech Republic) from 1848 to 2006. Tools for
converting daily precipitation series to be normally distributed were adopted. In case of air
temperature and precipitation, other characteristics such as monthly and annual number of
days above given thresholds (0°C, 5°C, 10°C, 15°C for temperature, ≥ 0.1, 1.0, 5.0, 10.0 mm
for precipitation) were investigated and mutually compared.
Because of presence of a noise in the series, statistical homogeneity tests give their
results with some portion of uncertainty. Using various statistical tests along with various types
of reference series made it possible to increase considerably the number of homogeneity tests
results for each tested series and thus to assess homogeneity more reliably. Two basic
approaches were adopted: (i) homogenization of monthly series and projection of estimated
smoothed monthly adjustments in annual variation of daily adjustments and (ii)
homogenization of daily values in individual months and direct estimation of daily adjustments,
again smoothed by low-pass filter. Differences in results obtained from these two approaches
are further discussed.
<strong>The</strong> series were prepared, quality checked and homogenized by means of AnClim and
ProClimDB software (www.climahom.eu).
Basic methodological questions of homogenization and the MASH procedure
Speaker: Tamas Szentimrey
Tamas Szentimrey
Hungarian Meteorological Service
szentimrey.t@met.hu
<strong>The</strong> MASH (Multiple Analysis of Series for Homogenization) iterative procedure is a
relative method and depending on the distribution of examined climate element additive or
multiplicative model can be applied. In the earlier program system the following subjects were
elaborated for monthly series: series comparison, break point (changepoint) and outlier
detection, correction of series, missing data complementing, automatic usage of meta data
and a verification procedure to evaluate the homogenization results. <strong>The</strong> new version was
developed further for daily data: homogenization, quality control and missing data
complementing.
As we see it, the basic methodological questions of homogenization are as follows:
comparison of series, break point detection and correction of shifts. In general the relative
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