Geostrophic winds are derived from six-hourly synoptic and monthly mean surface atmospheric pressure fields. Tom Nickelson of ODFW forwarded the data to us. The layer in which an appreciable amount of this offshore transport occurs is termed the surface Ekman layer, and is generally 20 to 50 meters deep. Ekman transports are resolved into components parallel and normal to the local coastline orientation. The magnitude of the offshore component is considered to be an index of the amount of deep water upwelled from depths below the base of the Ekman layer.
Positive values are, in general, the result of equatorward wind stress.
Negative values imply downwelling, the onshore advection of surface waters accompanied by a downward displacement of water. The figure below shows upwelling anomalies at 42 and 45 degrees N since 1997. The last two springs have seen strong spring transitions, reflected in the sudden upsurge in upwelling anomalies, especially at 42 degrees. OCS predicts cooler than normal temperatures, above-normal precipitation, and a good chance of snow in January and February, followed by another wet, cool spring.