Sensitivity of tropospheric forecasts to stratospheric initial conditions

Abstract

SUMMARYA number of recent papers in the atmospheric science literature have suggested that a dynamical link exists between the stratosphere and troposphere. Numerical modelling studies have shown that the troposphere has a time-mean response to changes to the stratospheric climatological state. In this study the response of the troposphere to an imposed transient stratospheric change is examined.The study uses a high horizontal and vertical resolution numerical weather-prediction model. Experiments compare the tropospheric forecasts of two medium-range forecast ensembles which have identical tropospheric initial conditions and different stratospheric initial conditions. In three case studies described here, stratospheric initial conditions have a statistically significant impact on the tropospheric flow. The mechanism for this change involves, in its most basic step, a change to tropospheric synoptic-scale systems. A consistent change to the tropospheric synoptic-scale systems occurs in response to the stratospheric initial conditions. The aggregated impact of changes to individual synoptic systems maps strongly onto the structure of the Arctic Oscillation, particularly over the North Atlantic storm track. The relationship between the stratosphere and troposphere, while apparent in Arctic Oscillation diagnostics, does not occur on coherent, hemispheric scales.

Regional Arctic sea ice variations as predictor for winter climate conditions

“…A number of studies (Christiansen 2001;Baldwin et al 2003;Charlton et al 2004) indicate an impact of the stratospheric circulation on the troposphere at lead times of a few weeks. Figure 11 shows that the early winter (November, December, January average, NDJ) Polar Vortex, which we defined here as zonal mean at 65°N of the zonal wind in 10 hPa height, is significantly correlated with the winter (DJF) SLP in the detrended ERA-interim data.…”

Comparison of co‐located independent ground‐based middle atmospheric wind and temperature measurements with numerical weather prediction models

“…In recent years, general circulation models (GCMs) have been progressively extended higher to cover the whole stratosphere and in some cases the mesosphere, because it is now recognized that stratospheric circulation anomalies, often formed in the mesosphere and the lower thermosphere (MLT) [Coy et al, 2011;Angot et al, 2012], may affect tropospheric weather on time scales from weeks to months [e.g., Baldwin et al, 2003;Charlton-Perez et al, 2004]. The MLT is a dynamic medium with variability over time scales ranging from minutes to days.…”

Evaluation of wind and temperature profiles from ECMWF analysis on two hemispheres using volcanic infrasound

“…While the influence of the troposphere on the stratosphere is well known, recent observational and modeling studies [Baldwin and Dunkerton, 2001;Baldwin et al, 2003;Charlton et al, 2004;Shaw and Shepherd, 2008] have demonstrated that the stratosphere has an impact on the troposphere as well. One example is the influence of the onset and duration of Sudden Stratospheric Warmings (SSWs) on the latitude of the tropospheric jet stream, as this has a strong impact on near-term weather forecasting [Gerber et al, 2009].…”