The divide between decadal and interannual scales corresponds to a period of 10 years, so that variability due to the El Niño-Southern Oscillation (ENSO) falls into the interannual category, while variability on time scales of 10 years or longer is classified as decadal. The procedures used to separate these signal components, as well as some cautionary notes regarding their interpretation, are discussed in an accompanying EOS article and in a more detailed reference document.
Beyond the choice of temperature or precipitation, a range of analysis and display options is available: The user may define a season of interest, in which case the decomposition will be performed on the corresponding seasonally-averaged data. Results may be displayed either as a map, or as time series, in the latter case at an individual gridpoint or averaged over a user-selectable area. Maps may display either the standard deviation or the percent of variance in the raw data explained by variability on the selected time scale.
At particular locations, data may include "filled" values, where instrumental measurements are lacking. Since the presence of many filled values may degrade analysis results, a screening procedure has been implemented, whereby individual gridpoints are rejected if their records contain too many such values. Since the imposition of such a requirement results in removal of gridpoints from consideration, stricter screening results in fewer available points, especially in the case of precipitation. The user is therefore given a choice in the Precipitation Maproom, between a high level of temporal coverage (strict screening), a high level of spatial coverage (no screening) and a compromise between these two extremes. It is recommended that the high temporal coverage option be chosen if possible, the compromise option being a fallback. The high spatial coverage option may yield less reliable results, and is provided primarily so that the user can see the full geographic range of dataset coverage. Please refer to the documentation page for further details on the screening procedures, as well as the analysis, employed.
To get started click on either "Temperature" or "Precipitation" below.
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