Differences from average atmospheric thickness (standardized geopotential height anomalies) in the column of air over the Arctic from the troposphere to the stratosphere since late October 2023. The two layers of the atmosphere appear to have been weakly connected in late October, and more strongly connected in mid-November, when the low thickness anomalies (purple areas, suggesting a stronger-than-average polar vortex) extended from mid-stratosphere to the surface. Since then, there’s been little connection between them. It seems the stratosphere may be trying to connect with the troposphere (via downward spreading positive anomalies), who, so far, hasn’t been answering. The models predict that, on average, the ghosting may continue.
Geopotential height means "the altitude where a given pressure exists." A geopotential height anomaly means that a given pressure level is occurring at higher or lower altitudes than average, usually a sign that the air in the column is warmer or cooler than average. Anomalies are based on departures from the 1991-2020 average, and have been divided by the standard deviation to create a standardized (unitless) index. Daily data are from the Global Forecast System observational analysis and forecast, and climatologies are from the Climate Forecast System Reanalysis. NOAA Climate.gov image, adapted from analysis by Laura Ciasto.