Contribution of stratospheric warmings to temperature trends in the middle atmosphere from the lidar series obtained at Haute‐Provence Observatory (44°N)

Abstract

[1] This study describes a method to calculate long-term temperature trends, as an alternative to the ones based on monthly mean temperatures, which are highly impacted by the high winter variability partially due to wave-mean flow interactions like Sudden Stratospheric Warmings (SSW). This method avoids the strong influence of SSWs and provides "background" temperature trend estimates which are in better agreement with expected direct radiative effects. The data set used results from lidar measurements -performed above southern France continuously since late 1978 -combined with radiosonde profiles. With this new methodology, the long-term trends during winter at 40 km shows a larger cooling per decade (À2 AE 0.4 K) than when the mean temperature is used (À0.4 AE 0.4 K). The background temperature trend is closer to the summer trend estimates which are similar whatever the temperature proxy used, due to the absence of SSWs (À2.9 AE 0.3 K per decade with the mean-based method and À3.4 AE 0.3 K per decade with the background-based calculation). Based on this background temperature, composite evolutions of winter anomalies for both vortex-displacement and vortex-splitting major SSWs have been displayed: in both cases the largest warming occurs at the time of the SSW in the upper stratosphere, with mean amplitudes of more than 10 K. A warm signal in the upper mesosphere could suggest a potential precursory role of gravity waves. Displacement-type events present an 18-day periodicity, which is a clear sign of the wave number one Rossby wave. Colder tropospheric temperatures are noticed before and during the SSW, and warmer ones after the event, with a stronger signal for split-type events.Citation: Angot, G., P. Keckhut, A. Hauchecorne, and C. Claud (2012), Contribution of stratospheric warmings to temperature trends in the middle atmosphere from the lidar series obtained at

Satellite observations of middle atmosphere gravity wave absolute momentum flux and of its vertical gradient during recent stratospheric warmings

“…SSWs have effect on the average temperature of the stratosphere at high northern latitudes. Changes in the frequency of SSWs will therefore result in temperature trends (Angot et al, 2012). In addition, the warming of the lower stratosphere induced by SSWs can lead to temperatures too warm for polar stratospheric clouds to form, which has a strong influence on ozone depletion in the Arctic.…”

Middle-atmospheric zonal and meridional wind profiles from polar, tropical and midlatitudes with the ground-based microwave Doppler wind radiometer WIRA

“…6. The dual peak regime might be related to sudden stratospheric warming events as analogously proposed by Angot et al (2012) for the temperature distribution. Therefore the non-Gaussicity is expected to be even stronger when considering only the winter months.…”

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.…”

“…It has been running since 1979, measuring temperature in the 30-90 km altitude range [Keckhut et al, 1993]. The long-term highquality measurements of this network allow monitoring trends in the MA dynamics and composition [Angot et al, 2012]. 2.…”