Temperature trends in the midlatitude summer mesosphere

Abstract

Here we analyze the contribution of varying concentrations of CO 2 and O 3 to the temperature trend in the mesosphere. It is important to distinguish between trends on pressure altitudes, z p , and geometrical altitudes, z geo , where the latter includes the effect of shrinking due to cooling at lower heights. For the period 1961-2009, temperature trends on geometrical and pressure altitudes can differ by as much as -0.9 K/dec in the mesosphere. Temperature trends reach approximately -1.3˙0.11 K/dec at z p 60 km and -1.8˙0.18 K/dec at z geo 70 km, respectively. CO 2 is the main driver of these trends in the mesosphere, whereas O 3 contributes approximately one third, both on geometrical and pressure heights. Depending on the time period chosen, linear temperature trends can vary substantially. Altitudes of pressure levels in the mesosphere decrease by up to several hundred meters. We have performed long-term runs with LIMA applying twentieth century reanalysis dating back to 1871. Again, trends are nonuniform with time. Since the late nineteenth century, temperatures in the mesosphere have dropped by approximately 5-7 K on pressure altitudes and up to 10-12 K on geometrical altitudes.

Neutral atmosphere temperature trends and variability at 90 km, 70 °N, 19 °E, 2003–2014

“…altered concentrations of CO 2 and O 3 , the atmosphere has been shrinking, leading to a lowering of pressure surfaces at various altitudes. It is important to distinguish between trends on fixed pressure altitudes and fixed geometric altitudes, since trends on geometric altitudes include the effect of a shrinking atmosphere (Lübken et al, 2013). In this study, we have obtained Aura MLS temperature data (version 3.3) for latitude 69.7 • N ± 5.0 • and longitude 19.0 • E ± 10.0 • at 90 km geometric altitude.…”

Hydroxyl layer: trend of number density and intra-annual variability

“…Figure 8 displays the pressure height of the OH * peak over the OH * ν=6 density for different seasons. We show correlations in so-called pressure heights (e.g., Lübken et al, 2013) because expression Eq. (4) shows dependence of concentration on pressure.…”

“…These results are based on calculations made by the chemical transport model (CTM) using dynamical parameters (wind components, pressure, and temperatures) from the LIMA (Leibniz Institute Middle Atmosphere) model (e.g., chemistry and dynamics in Sonnemann et al, 1994Sonnemann et al, , 1998Sonnemann et al, , 2006aSonnemann et al, , 2006bSonnemann et al, , 2007Sonnemann et al, , 2008; Grygalashvyly and Sonnemann, 2006;dynamics only in Berger, 2008;Lübken et al, 2009Lübken et al, , 2013. The dynamical part of the model LIMA employs for all model runs the real increase in CO 2 and ozone concentration (Lübken et al, 2013). The most important difference to the precursor model COMMA-IAP (COlogne Model of the Middle Atmosphere of the Institute of Atmospheric Physics) is that LIMA assimilates ECMWF (European Centre for Medium-Range Weather Forecasts) data (Uppala et al, 2005) for temperature and horizontal wind components below 35 km, dating back to 1961.…”

“…"Realistic input data" from LIMA are based on observations of GHGs (CO 2 and O 3 in particular), Lyman-α flux, and ECMWF data assimilated in the dynamical part of the model (see also Berger 2008; Lübken et al, 2013). In the chemical part, the growth of GHGs (CH 4 , CO 2 , N 2 O) at the lower border and Lyman-α flux are parameterized by data of measurements (see Grygalashvyly et al, 2014).…”

Local Time Dependence of Polar Mesospheric Clouds: A model study

“…More precisely, we have used relative anomalies at 0.5 hPa from 1979 to 2013 as measured by SBUV satellite instruments (from http://acd-ext.gsfc.nasa.gov/Data-services/merged/), for more details see Lübken et al (2013). Before 1979 ozone data are taken from the World Meteorological Organization (WMO) report.…”