Bundesamt für Seeschifffahrt und Hydrographie

Monthly Maps

BSH has published weekly composite SST analyses since 1968. Until November 1994 the mapping technique consisted in plotting ship and station data onto a map for each week. The maps were hand contoured subjectively and grid point values extracted on a 20nm equal area grid. Since December 1994 objective statistical interpolation has been used to estimate grid point SSTs on a 20km Lambert equal area grid. In data sparse regions the analysis employs a blending algorithm for AVHRR SSTs. The monthly mean maps presented here were computed from these weekly SST maps.


A monthly SST climatology for the period 1971-1993 was computed from BSH's weekly SST grids. This climatology was used to identify the presented anomalies in the spatiotemporal SST distribution.


The interannual variability of the spatiotemporal SST distribution undergoes seasonal fluctuations. The rating of the departures of monthly SST fields from the monthly climatology (1971-1993), i.e. the plain anomalies, may be based on the interannual standard deviations of the monthly climatology. Percentiles give the area under the unit normal distribution between -infinity and the standardized departures. P-values in excess of 90% or below 10% suggest that the expected average occurrence of such strong or stronger a warm/cold anomaly is less than 10%.

BSH M5402, P. Loewe, 1. Feb. 1999