I just submitted a paper that I wrote with co-authors Elizabeth Barnes and Stefan Sobolowski. It’s about trying to understand why the weather from one month to the next sometimes stays the same. For example, if January is really cold, it’s quite likely that February will be cold as well. Here’s the abstract for the paper:
Persistence of large cold and warm surface temperature anomalies beyond typical weather time scales of about 10 days can be detrimental for human and natural systems. The physical mechanisms that drive this persistence are a combination of advection of anomalously cold or warm air masses from neighboring regions and local feedbacks with the land surface, such as dry soils during heat waves. In Northern Europe the level of persistence varies throughout the year; it is strong in winter and summer and weaker but still non-negligible in spring and fall. Here the role of advection in dictating this annual cycle is investigated by means of centuries-long simulations by climate models with radiative forcing kept constant at pre-industrial levels. The main finding is that, with regard to advection, the minima in persistence during the shoulder seasons are due to two factors: 1) A reversal in the sign of the east/west temperature gradient in spring and fall (because Eastern Europe is warmer than the North Atlantic in summer but colder in winter); and 2) A reversal in the sign of the meridional wind during the same seasons, from southerlies in winter to northerlies in summer. These reversals are accompanied by reductions of the month-to-month persistence of temperature advection over Northern Europe during the shoulder seasons, and thereby influence the persistence of the near-surface temperature in the same region.
The background for this is found in a paper that has already been published: Erik W. Kolstad, Stefan P. Sobolowski, and Adam A. Scaife, 2015: Intraseasonal Persistence of European Surface Temperatures. Journal of Climate, 28, 5365–5374.
That’s where we identified the persistence in temperature, and also the annual cycle of it. It’s stronger in winter and summer than in spring and fall. Here’s the abstract for that paper:
Recent periods of extreme weather in Europe, such as the cold winter of 2009/10, have caused widespread impacts and were remarkable because of their persistence. It is therefore of great interest to improve the ability to forecast such events. Weather forecasts at midlatitudes generally show low skill beyond 5–10 days, but long-range forecast skill may increase during extended tropospheric blocking episodes or perturbations of the stratospheric polar vortex, which can affect midlatitude weather for several weeks at a time. Here a simple, linear approach is used to identify previously undocumented persistence in northern European summer and winter temperature anomalies in climate model simulations, corroborated by observations and reanalysis data. For instance, temperature anomalies of at least one standard deviation above or below climatology in March were found to be about 20%–120% more likely than normal if the preceding February was anomalous by 0.5–1.5 standard deviations (with the same sign). The corresponding range for April (i.e., persistence over two months) is between 20% and 80%. The persistence is observed irrespective of the data source or driving mechanisms, and the temperature itself is a more skillful predictor of the temperatures one month ahead than the stratospheric polar vortex or the NAO and even than both factors together. The results suggest potential to conditionally improve the skill of long-range forecasts and enhance recent advancements in dynamical seasonal prediction.