Double mass analysis

Double mass analysis

Double mass analysis [1] is a commonly used data analysis approach for investigating the behaviour of records made of hydrological or meteorological data at a number of locations. It is used to determine whether there is a need for corrections to the data to account for changes in data collection procedures or other local conditions. Such changes may result from a variety of things including changes in instrumentation, changes in observation procedures, or changes in gauge location or surrounding conditions. Double mass analysis for checking consistency of a hydrological or meteorological record is considered to be an essential tool before taking it for analysis purpose.

An example of a double mass analysis is a "double mass plot", or "double mass curve"[2]. For this, points and/or a joining line are plotted where the x- and y- coordinates are determined by the running totals of the values observed at two stations. If both stations are affected to the same extent by the same trends then a double mass curve should follow a straight line. A break in the slope of the curve would indicate that conditions have changed at one location but not at another.

Notes

  1. ^ Searcy, J.K. and C.H. Hardison (1960). Double-mass curves. U.S. Geological Survey Water-Supply Paper 1541-B'
  2. ^ Wilson, E.M. (1983) Engineering Hydrology, 3rd edition. Macmillan Press, London. p.27

Further reading

  • Dubreuil P. (1974). "Initiation à l'analyse hydrologique". Masson& Cie et ORSTOM, Paris.

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