Empirical Mode Decomposition on the sphere: application to the spatial scales of surface temperature variations

摘要

Empirical Mode Decomposition (EMD) is applied here in two dimensionsover the sphere to demonstrate its potential as a data-adaptivemethod of separating the different scales of spatial variability ina geophysical (climatological/meteorological) field. After a briefdescription of the basics of the EMD in 1 then 2 dimensions, theprinciples of its application on the sphere are explained, inparticular via the use of a zonal equal area partitioning. EMD isfirst applied to an artificial dataset, demonstrating its capabilityin extracting the different (known) scales embedded in the field.The decomposition is then applied to a global mean surfacetemperature dataset, and we show qualitatively that it extractssuccessively larger scales of temperature variations related, forexample, to topographic and large-scale, solar radiation forcing. Wepropose that EMD can be used as a global data-adaptive filter,which will be useful in analysing geophysical phenomena that ariseas the result of forcings at multiple spatial scales.