Dynamic models for Icelandic meteorological data sets

Dynamic models are derived from pairs of time series of daily surface and 500 hPa height observations in the Icelandic region in order to interpret these data. The models describe the motion of data points in the phase plane spanned by a pair of variables. For each pair, a regression model of first order (R-model) is derived, which assumes linear motion in the phase plane. The coefficients of the corresponding Fokker–Planck equation (FP) are also derived from the data. This equation describes changes of the probability density distribution of the data pair and takes nonlinear aspects into account. The data are interpreted in the light of both models. The R-model yields a mean rotation and convergence which characterize the basic type of motion inherent in a data set. It is found in all cases that the timescale of contraction is shorter than the ‘‘dynamic’’ timescale linked to the rotation. The FP equation yields a mean motion which resembles quite often that in the R-model as well as a diffusive part. The R-model is not satisfactory in some cases which involve the meridional surface winds. For example, southerlies (northerlies) and temperature rotate clockwise (anticlockwise).Meridional and zonal surface winds rotate anticlockwise in a southerly flow, but clockwise in a northerly one. Therefore, new aspects of the Icelandic meteorology can be extracted form the data by use of the FP equation