evalHomogeneity: Quality labels for temperature and precipitation observation...

Description Usage Arguments Details Value Author(s) References See Also Examples

Description

This function classifies time series as "useful", "doubtful" or "suspect", based on 4 homogeneity tests (see below). It follows the Algorithm Theoretical Basis Document (ATBD) of the European Climate Assessment & Dataset project (ECA&D), hosted by the Dutch meteorological service KNMI.

Usage

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Arguments

X

A dataclim object or a data.frame.

Details

If X is an object of dataclim, the function calls the 4 homogeneity tests Standard Normal Homogeneity test (SNHtest), the BuisHand Range test (BHRtest), the PETtitt test (PETtest) and the VON Neumann ratio (VONtest) and, for temperature, applies them to annual means of daily temperature ranges (Tmax-Tmin) and the day-to-day difference of the daily temperature ranges. For precipitation, the annual counts of days with more than 1mm of rain are evaluated.

If no more than one test indicates a break at the 1% level of significance, the temperature or precipitation observations are considered as "useful". If two tests indicate a break at the 1% level, the respective observations are considered as "doubtful". With three or more tests indicating breaks at the 1% level, the respective observations are considered as "suspect". The two derived temperature characteristics are aggregated by using the maximum number of 1%-significant breaks.

Note that the four tests cannot handle NAs. If X is a dataclim object and the derived annual means have missing values, the function checks whether there are at least 20 valid years and at least 70% of the years are valid for all variables. In this case, the missing values are linearly interpolated.

If X is a data.frame, the function assumes the data.frame to contain equidistant non-NA observations. The series are tested directly, without any processing of derived quantities as in the case of the dataclim object.

Value

A list of

tests

A data.frame with the significance levels (Not Significant, NS - 5% significance level, p5 - 1% significance level, p1) for each test for the (derived annual) variables.

breaks

A data.frame with the approximate locations of the break for each test for the (derived annual) variables (except for the VONtest). For the dataclim method, the years are returned. For the data.frame method, a row-index is returned.

classes

A named vector containing the resulting classification of temperature and precipitation as "useful", "doubtful" or "suspect".

Author(s)

Boris Orlowsky <boris@climate-babel.org>

References

The ATBD: http://www.ecad.eu/documents/atbd.pdf

See Also

SNHtest, BHRtest, PETtest, VONtest

Examples

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data(potsdam)
date <- as.Date(potsdam$date)
myDataclim <- createDataclim(date=date, tmin=potsdam$tmin, tmax=potsdam$tmax,
                          prec=potsdam$prec, basePeriod=1981:2010)
evalHomogeneity(myDataclim)


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