On April 19, 2018, a workshop on the “Northern Annular Mode” (NAM) was held at IMAU. The NAM represents an irregular oscillation in the strength of the westerly winds in the middle latitudes, both at the earth’s surface and near the tropopause. A complete understanding of the physical origin or cause of this oscillation is still lacking. The NAM is an important factor in determining the temperature- and precipitation-anomalies both in Eurasia and in North America, especially in winter. For example, in the negative phase of the NAM, surface temperatures in Northern Eurasia and Eastern United States are well below normal.
About 20 researchers from IMAU, KNMI and Reading University attended the workshop, which was unfortunately too short to agree on many issues concerning the physics of the NAM. Nevertheless, the workshop was a big success; it is good to go back to the basics and discuss a fundamental problem in meteorology. The complete report of the workshop can be found here.