Hamburg Model Of The Neutral And Ionized Atmosphere Research Articles

Nighttime Mesospheric/Lower Thermospheric Tropical Ozone Response to the 27‐Day Solar Rotational Cycle: ENVISAT‐GOMOS Satellite Observations Versus HAMMONIA Idealized Chemistry‐Climate Model Simulations

AbstractGlobal Ozone Monitoring by Occultation of Stars (GOMOS) satellite data are analyzed to estimate the first observation‐based nighttime (22:00 median local time) ozone response to the 27‐day solar rotational cycle in the tropical mesosphere/lower thermosphere (50–110 km altitude). The ozone response to solar rotational variability is derived from linear correlation and regressions using Lyman‐α line (121.6 nm) as solar index that varies by about 10–15% over solar rotational cycles. In the lower mesosphere (50–70 km), the GOMOS ozone is found to be correlated with the solar fluctuations and exhibits a sensitivity of ~0.1 (expressed in percent change of ozone for 1% change in Lyman‐α). In the upper mesosphere/lower thermosphere (above 80 km), ozone variations become anticorrelated with solar rotational variations. In this region, the vertical profile of ozone sensitivity to the 27‐day solar cycle exhibits a maximum of 1.8 at 81 km, a minimum of 0.3 at 100 km, and a sharp increase above. Such high ozone sensitivities are observed for the first time. The observed ozone response is compared with chemistry‐climate simulations from the Hamburg model of the neutral and ionized atmosphere (HAMMONIA) that is forced with an idealized 27‐day solar spectral irradiance time series. Although observational and model results share some common features, substantial discrepancies are found. Namely, the altitude of transition from positive to negative solar ozone correlation signal in the model simulation is found about 10 km below the altitude of the observations and the amplitude of the ozone sensitivity is generally vastly underestimated by the model.

Semidiurnal solar tide differences between fall and spring transition times in the Northern Hemisphere

Abstract. We present a study of the semidiurnal solar tide (S2) during the fall and spring transition times in the Northern Hemisphere. The tides have been obtained from wind measurements provided by three meteor radars located at Andenes (69∘ N, 16∘ E), Juliusruh (54∘ N, 13∘ E) and Tavistock (42∘ N, 81∘ W). During the fall, S2 is characterized by a sudden and pronounced decrease occurring every year and at all height levels. The spring transition also shows a decrease in S2, but not sudden and that ascends from lower to higher altitudes during an interval of ∼ 15 to 40 days. To assess contributions of different semidiurnal tidal components, we have examined a 20-year free-run simulation by the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA). We found that the differences exhibited by the S2 tide between equinox times are mainly due to distinct behaviors of the migrating semidiurnal and the non-migrating westward-propagating wave number 1 tidal components (SW2 and SW1, respectively). Specifically, during the fall both SW2 and SW1 decrease, while during the springtime SW2 decreases but SW1 remains approximately constant or decreases only slightly. The decrease shown by SW1 during the fall occurs later than that of SW2 and S2, which indicates that the behavior of S2 is mainly driven by the migrating component. Nonetheless, the influence of SW1 is necessary to explain the behavior of S2 during the spring. In addition, a strong shift in the phase of S2 (of SW2 in the simulations) is also observed during the fall. Our meteor radar wind measurements show more gravity wave activity in the fall than during the spring, which might be indicating that the fall decrease is partly due to interactions between SW2 and gravity waves.

Coupling of Stratospheric Warmings with Mesospheric Coolings in Observations and Simulations

Abstract The vertical coupling between the stratosphere and the mesosphere is diagnosed from polar cap temperatures averaged over 60°–90°N with a new method: the joint occurrence of a warm stratosphere at 10 hPa and a cold mesosphere at 0.01 hPa. The investigation of an 11-yr-long dataset (2004–15) from Aura-MLS observations shows that such mesospheric coupling days appear in 7% of the winter. During major sudden stratospheric warming events mesospheric couplings are present with an enhanced average daily frequency of 22%. This daily frequency changes from event to event but broadly results in five of seven major warmings being classified as mesospheric couplings (2006, 2008, 2009, 2010, and 2013). The observed fraction of mesospheric coupling events (71%) is compared with simulations of the Kühlungsborn Mechanistic Circulation Model (KMCM), the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA), and the Whole Atmosphere Community Climate Model (WACCM). The simulated fraction of mesospheric coupling events ranges between 57% and 94%, which fits the observations. In searching for causal relations weak evidence is found that major warming events with strong intensity or split vortices favor their coupling with the upper mesosphere. More evidence is found with a conceptual model: an effective vertical coupling between 10 and 0.01 hPa is provided by deep zonal-mean easterlies at 60°N, which are acting as a gravity-wave guide. The explained variance is above 40% in the four datasets, which indicates a near-realistic simulation of this process.

HEPPA-II model–measurement intercomparison project: EPP indirect effects during the dynamically perturbed NH winter 2008–2009

Abstract. We compare simulations from three high-top (with upper lid above 120 km) and five medium-top (with upper lid around 80 km) atmospheric models with observations of odd nitrogen (NOx = NO + NO2), temperature, and carbon monoxide from seven satellite instruments (ACE-FTS on SciSat, GOMOS, MIPAS, and SCIAMACHY on Envisat, MLS on Aura, SABER on TIMED, and SMR on Odin) during the Northern Hemisphere (NH) polar winter 2008/2009. The models included in the comparison are the 3-D chemistry transport model 3dCTM, the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model, FinROSE, the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA), the Karlsruhe Simulation Model of the Middle Atmosphere (KASIMA), the modelling tools for SOlar Climate Ozone Links studies (SOCOL and CAO-SOCOL), and the Whole Atmosphere Community Climate Model (WACCM4). The comparison focuses on the energetic particle precipitation (EPP) indirect effect, that is, the polar winter descent of NOx largely produced by EPP in the mesosphere and lower thermosphere. A particular emphasis is given to the impact of the sudden stratospheric warming (SSW) in January 2009 and the subsequent elevated stratopause (ES) event associated with enhanced descent of mesospheric air. The chemistry climate model simulations have been nudged toward reanalysis data in the troposphere and stratosphere while being unconstrained above. An odd nitrogen upper boundary condition obtained from MIPAS observations has further been applied to medium-top models. Most models provide a good representation of the mesospheric tracer descent in general, and the EPP indirect effect in particular, during the unperturbed (pre-SSW) period of the NH winter 2008/2009. The observed NOx descent into the lower mesosphere and stratosphere is generally reproduced within 20 %. Larger discrepancies of a few model simulations could be traced back either to the impact of the models' gravity wave drag scheme on the polar wintertime meridional circulation or to a combination of prescribed NOx mixing ratio at the uppermost model layer and low vertical resolution. In March–April, after the ES event, however, modelled mesospheric and stratospheric NOx distributions deviate significantly from the observations. The too-fast and early downward propagation of the NOx tongue, encountered in most simulations, coincides with a temperature high bias in the lower mesosphere (0.2–0.05 hPa), likely caused by an overestimation of descent velocities. In contrast, upper-mesospheric temperatures (at 0.05–0.001 hPa) are generally underestimated by the high-top models after the onset of the ES event, being indicative for too-slow descent and hence too-low NOx fluxes. As a consequence, the magnitude of the simulated NOx tongue is generally underestimated by these models. Descending NOx amounts simulated with medium-top models are on average closer to the observations but show a large spread of up to several hundred percent. This is primarily attributed to the different vertical model domains in which the NOx upper boundary condition is applied. In general, the intercomparison demonstrates the ability of state-of-the-art atmospheric models to reproduce the EPP indirect effect in dynamically and geomagnetically quiescent NH winter conditions. The encountered differences between observed and simulated NOx, CO, and temperature distributions during the perturbed phase of the 2009 NH winter, however, emphasize the need for model improvements in the dynamical representation of elevated stratopause events in order to allow for a better description of the EPP indirect effect under these particular conditions.

Multimodel comparison of the ionosphere variability during the 2009 sudden stratosphere warming

AbstractA comparison of different model simulations of the ionosphere variability during the 2009 sudden stratosphere warming (SSW) is presented. The focus is on the equatorial and low‐latitude ionosphere simulated by the Ground‐to‐topside model of the Atmosphere and Ionosphere for Aeronomy (GAIA), Whole Atmosphere Model plus Global Ionosphere Plasmasphere (WAM+GIP), and Whole Atmosphere Community Climate Model eXtended version plus Thermosphere‐Ionosphere‐Mesosphere‐Electrodynamics General Circulation Model (WACCMX+TIMEGCM). The simulations are compared with observations of the equatorial vertical plasma drift in the American and Indian longitude sectors, zonal mean F region peak density (NmF2) from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites, and ground‐based Global Positioning System (GPS) total electron content (TEC) at 75°W. The model simulations all reproduce the observed morning enhancement and afternoon decrease in the vertical plasma drift, as well as the progression of the anomalies toward later local times over the course of several days. However, notable discrepancies among the simulations are seen in terms of the magnitude of the drift perturbations, and rate of the local time shift. Comparison of the electron densities further reveals that although many of the broad features of the ionosphere variability are captured by the simulations, there are significant differences among the different model simulations, as well as between the simulations and observations. Additional simulations are performed where the neutral atmospheres from four different whole atmosphere models (GAIA, HAMMONIA (Hamburg Model of the Neutral and Ionized Atmosphere), WAM, and WACCMX) provide the lower atmospheric forcing in the TIME‐GCM. These simulations demonstrate that different neutral atmospheres, in particular, differences in the solar migrating semidiurnal tide, are partly responsible for the differences in the simulated ionosphere variability in GAIA, WAM+GIP, and WACCMX+TIMEGCM.

Diurnal tides at low latitudes: Radar, satellite, and model results

Mean winds and tidal signatures in the mesosphere and lower thermosphere (MLT) region are derived from meteor radar observations at three sites around 22°S acquired in 2005. The observed differences of mean winds and tides are discussed in relation to the meteorological situation in the lower atmosphere and the possible generation of non-migrating tides. The longitudinally well separated radar sites allowed the evaluation of the migrating tidal component. The seasonal variation of signatures of the diurnal tide derived from ground-based radar observations, TIDI measurements aboard TIMED satellite, and model results obtained with HAMMONIA (Hamburg Model of the Neutral and Ionized Atmosphere) are compared. The ground-based, satellite, and model results of the total diurnal tide are in good agreement. The same is true for the migrating diurnal tide obtained from the radar observations, TIDI observations and from the model studies of HAMMONIA and GSWM00 (Global Scale Wave Model).

Composition changes after the "Halloween" solar proton event: the High Energy Particle Precipitation in the Atmosphere (HEPPA) model versus MIPAS data intercomparison study

Abstract. We have compared composition changes of NO, NO2, H2O2, O3, N2O, HNO3, N2O5, HNO4, ClO, HOCl, and ClONO2 as observed by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat in the aftermath of the "Halloween" solar proton event (SPE) in late October 2003 at 25–0.01 hPa in the Northern Hemisphere (40–90° N) and simulations performed by the following atmospheric models: the Bremen 2-D model (B2dM) and Bremen 3-D Chemical Transport Model (B3dCTM), the Central Aerological Observatory (CAO) model, FinROSE, the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA), the Karlsruhe Simulation Model of the Middle Atmosphere (KASIMA), the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model, the modeling tool for SOlar Climate Ozone Links studies (SOCOL and SOCOLi), and the Whole Atmosphere Community Climate Model (WACCM4). The large number of participating models allowed for an evaluation of the overall ability of atmospheric models to reproduce observed atmospheric perturbations generated by SPEs, particularly with respect to NOy and ozone changes. We have further assessed the meteorological conditions and their implications for the chemical response to the SPE in both the models and observations by comparing temperature and tracer (CH4 and CO) fields. Simulated SPE-induced ozone losses agree on average within 5 % with the observations. Simulated NOy enhancements around 1 hPa, however, are typically 30 % higher than indicated by the observations which are likely to be related to deficiencies in the used ionization rates, though other error sources related to the models' atmospheric background state and/or transport schemes cannot be excluded. The analysis of the observed and modeled NOy partitioning in the aftermath of the SPE has demonstrated the need to implement additional ion chemistry (HNO3 formation via ion-ion recombination and water cluster ions) into the chemical schemes. An overestimation of observed H2O2 enhancements by all models hints at an underestimation of the OH/HO2 ratio in the upper polar stratosphere during the SPE. The analysis of chlorine species perturbations has shown that the encountered differences between models and observations, particularly the underestimation of observed ClONO2 enhancements, are related to a smaller availability of ClO in the polar night region already before the SPE. In general, the intercomparison has demonstrated that differences in the meteorology and/or initial state of the atmosphere in the simulations cause a relevant variability of the model results, even on a short timescale of only a few days.

Atmospheric Ionization Module Osnabrück (AIMOS): 3. Comparison of electron density simulations by AIMOS-HAMMONIA and incoherent scatter radar measurements

[1] Ionization of the atmosphere due to precipitating solar energetic particles as well as magnetospheric particles is a major source of thermospheric electron density. In this paper we evaluate numerical simulations of the 3-D spatial and temporal electron densities produced by these particle populations through a comparison with incoherent scatter radar observations. The 3-D precipitation patterns are determined with the Atmospheric Ionization Module Osnabruck (AIMOS). We use a version of the general circulation and chemistry model Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA) enhanced by ion chemistry to calculate the impact of particle ionization on the electron density. These modeled data are compared to radar observations from European Incoherent Scatter Svalbard and Tromso as well as the incoherent scatter radar stations at Millstone Hill and Sondrestrom. Particle precipitation is severely affected by geomagnetic disturbance and latitude. Therefore, different locations (inside the polar cap and at auroral latitudes) and geomagnetic conditions are included in the comparison. The main results of the paper can be summarized as follows: (1) as expected, particle forcing will significantly improve modeled electron density in comparison to results of the radar measurements; (2) in particular nighttime comparisons of the electron density are affected; here the particle forcing will account for a boost of 2 to 3 orders of magnitude.

Daytime ozone and temperature variations in the mesosphere: a comparison between SABER observations and HAMMONIA model

Abstract. This paper investigates the latest version 1.07 SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) tropical ozone from the 1.27 μm as well as from the 9.6 μm retrieval and temperature data with respect to day time variations in the upper mesosphere. The processes involved are compared to day time variations of the three-dimensional general circulation and chemistry model HAMMONIA (Hamburg Model of the Neutral and Ionized Atmosphere). The results show a good qualitative agreement for ozone. The amplitude of daytime variations is in both cases approximately 60% of the daytime mean. During equinox the daytime maximum ozone abundance is for both, the observations and the model, higher than during solstice, especially above 0.01 hPa (approx. 80 km). The influence of tidal signatures either directly in ozone or indirectly via a temperature response above 0.01 hPa can not be fully eliminated. Below 0.01 hPa (photo-)chemistry is the main driver for variations. We also use the HAMMONIA output of daytime variation patterns of several other different trace gas species, e.g., water vapor and atomic oxygen, to discuss the daytime pattern in ozone. In contrast to ozone, temperature data show little daytime variations between 65 and 90 km and their amplitudes are on the order of less than 1.5%. In addition, SABER and HAMMONIA temperatures show significant differences above 80 km.

Wintertime water vapor in the polar upper mesosphere and lower thermosphere: First satellite observations by Odin submillimeter radiometer

In this paper we present Odin submillimeter radiometer (Odin/SMR) water vapor measurements in the upper mesosphere and lower thermosphere with focus on the polar latitudes in winter. Measurements since 2003 have been compiled to provide a first overview of the water vapor distribution in this altitude range. Our observations show a distinct seasonal increase of the water vapor concentration during winter at a given altitude above 90 km. Above 95 km the observations exhibit the annual water vapor maximum during wintertime. Model simulations from the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA) and the Whole Atmosphere Community Climate Model version 3 (WACCM3) show results that are very similar to the observations. We suggest that the observed increase in water vapor during winter is mainly caused by a combination of upwelling of moister air from lower altitudes and diffusion processes. Distinct interhemispheric differences in the winter water vapor distribution in the upper mesosphere and lower thermosphere can be observed, both in the observations and the model results. The seasonal water vapor increase in the polar regions is much more pronounced in the Southern Hemisphere winter where higher concentrations can be observed. This observation is most likely due to interhemispheric differences in the underlying dynamics and diffusion processes.

Long-term variability in mesopause region temperatures over Fort Collins, Colorado (41°N, 105°W) based on lidar observations from 1990 through 2007

During 1990–2007, there were 894 lidar observations of nocturnal mesopause region temperatures over Fort Collins, Colorado. In an earlier analysis with data to April 1997, an unexpected episodic warming, peaking in 1993 with a maximum value over 10 K, was reported and attributed to the Mount Pinatubo eruption in June 1991. With all data, long-term temperature trends from a 7-parameter linear regression analysis including solar cycle effect and long-term trends leads to a cooling of as much as 6.8 K/decade at ∼100 km, consistent with some reported observations but larger than model predictions. Including the observed episodic warming response in an 11-parameter nonlinear regression analysis reduces the maximum long-term cooling trends to ∼1.5 K/decade at 91 km, with magnitude and altitude dependences consistent with the prediction of two models, Spectral Mesosphere/Lower Thermosphere Model (SMLTM) and Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA). In addition, the mid-latitude middle-atmospheric response to solar flux variability in Thermosphere–Ionosphere-Energetics and Dynamics (TIMED)/Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperatures is presented.

Seasonal variations of semidiurnal tidal perturbations in mesopause region temperature and zonal and meridional winds above Fort Collins, Colorado (40.6°N, 105.1°W)

On the basis of Colorado State University (CSU) Na lidar observations over full diurnal cycles from May 2002 to April 2006, a harmonic analysis was performed to extract semidiurnal perturbations in mesopause region temperature and zonal and meridional winds over Fort Collins, Colorado (40.6°N, 105.1°W). The observed monthly results are in good agreement with MF radar tidal climatology for Urbana, Illinois, and with predictions of the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA), sampled at the CSU Na lidar coordinates. The observed semidiurnal tidal period perturbation within the mesopause region is found to be dominated by propagating modes in winter and equinoctial months with a combined vertical wavelength varying from 50 km to almost 90 km and by a mode with evanescent behavior and longer vertical wavelength (100–150 km) in summer months, most likely due to dominance of (2, 2) and (2, 3) tidal (Hough) modes. The observed semidiurnal tidal amplitude shows strong seasonal variation, with a large amplitude during the winter months, with a higher growth rate above ∼85–90 km, and minimal amplitudes during the summer months. Maximum tidal amplitudes over 50 m/s for wind and 12 K for temperature occur during fall equinox. A detailed comparison with HAMMONIA predictions shows excellent agreement in semidiurnal phases. HAMMONIA‐predicted semidiurnal amplitudes generally agree well with observations; however, HOMMONIA underestimates temperature amplitudes in some of the nonsummer months as well as zonal wind and meridional wind amplitudes in April and September but overestimates them in February. To reveal the effects of the atmospheric background on vertical propagation of tidal modes and their relative importance in the composite semidiurnal tide during different seasons, we use the lidar‐observed monthly mean temperature and zonal wind from the same data set as well as HAMMONIA output to calculate the vertical wave number seasonal variations of the major tidal modes of the migrating semidiurnal tide. This leads to a qualitative understanding of the lidar‐observed and HAMMONIA‐predicted seasonal variation of the semidiurnal tidal perturbation.

Climatology of mesopause region temperature, zonal wind, and meridional wind over Fort Collins, Colorado (41°N, 105°W), and comparison with model simulations

Between May 2002 and April 2006, many continuous observations of mesopause region temperature and horizontal wind, each lasting longer than 24 h (termed full‐diurnal‐cycle observations), were completed at the Colorado State University Na Lidar Facility in Fort Collins, Colorado (41°N, 105°W). The combined data set consists of 120 full‐diurnal‐cycle observations binned on a monthly basis, with a minimum of 7 cycles in April and a maximum of 18 cycles in August. Each monthly data set was analyzed to deduce mean values and tidal period perturbations. After removal of tidal signals, monthly mean values are used for the study of seasonal variations in mesopause region temperature, zonal and meridional winds. The results are in qualitative agreement with our current understanding of mean temperature and wind structures in the midlatitude mesopause region with an observed summer mesopause of 167 K at 84 km, summer peak eastward zonal wind of 48 m/s at 94 km, winter zonal wind reversal at ∼95 km, and peak summer (pole) to winter (pole) meridional flow of 17 m/s at 86 km. The observed mean state in temperature, zonal and meridional winds are compared with the predictions of three current general circulation models, i.e., the Whole Atmosphere Community Climate Model version 3 (WACCM3) with two different simulations of gravity wavefields, the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA), and the 2003 simulation of the Thermosphere‐Ionosphere‐Mesosphere‐Electrodynamics General Circulation Model (TIME‐GCM). While general agreement is found between observation and model predictions, there exist discrepancies between model prediction and observation, as well as among predictions from different models. Specifically, the predicted summer mesopause altitude is lower by 3 km, 8 km, 3 km, and 1 km for WACCM3 the two WACCM runs, HAMMONIA, and TIME‐GCM, respectively, and the corresponding temperatures are 169 K, 170 K, 158 K, and 161 K. The model predicted summer eastward zonal wind peaks to 71 m/s at 102 km, to 48 m/s at 84 km, to 75 m/s at 93 km, and to 29 m/s at 94 km, in the same order. The altitude of the winter zonal wind reversal and seasonal asymmetry of the pole‐to‐pole meridional flow are also compared, and the importance of full‐diurnal‐cycle observations for the determination of mean states is discussed.

The Response of the Middle Atmosphere to Solar Cycle Forcing in the Hamburg Model of the Neutral and Ionized Atmosphere

This paper studies the response of the middle atmosphere to the 11-year solar cycle. The study is based on numerical simulations with the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA), a chemistry climate model that resolves the atmosphere from the Earth’s surface up to about 250 km. Results presented here are obtained in two multi-year time-slice runs for solar maximum and minimum conditions, respectively. The magnitude of the simulated annual and zonal mean stratospheric response in temperature and ozone corresponds well to observations. The dynamical model response is studied for northern hemisphere winter. Here, the zonal mean wind change differs substantially from observations. The statistical significance of the model’s dynamical response is, however, poor for most regions of the atmosphere. Finally, we discuss several issues that render the evaluation of model results with available analyses of observational data of the stratosphere and mesosphere difficult. This includes the possibility that the atmospheric response to solar variability may depend strongly on longitude.

The HAMMONIA Chemistry Climate Model: Sensitivity of the Mesopause Region to the 11-Year Solar Cycle and CO2 Doubling

Abstract This paper introduces the three-dimensional Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA), which treats atmospheric dynamics, radiation, and chemistry interactively for the height range from the earth’s surface to the thermosphere (approximately 250 km). It is based on the latest version of the ECHAM atmospheric general circulation model of the Max Planck Institute for Meteorology in Hamburg, Germany, which is extended to include important radiative and dynamical processes of the upper atmosphere and is coupled to a chemistry module containing 48 compounds. The model is applied to study the effects of natural and anthropogenic climate forcing on the atmosphere, represented, on the one hand, by the 11-yr solar cycle and, on the other hand, by a doubling of the present-day concentration of carbon dioxide. The numerical experiments are analyzed with the focus on the effects on temperature and chemical composition in the mesopause region. Results include a temperature response to the solar cycle by 2 to 10 K in the mesopause region with the largest values occurring slightly above the summer mesopause. Ozone in the secondary maximum increases by up to 20% for solar maximum conditions. Changes in winds are in general small. In the case of a doubling of carbon dioxide the simulation indicates a cooling of the atmosphere everywhere above the tropopause but by the smallest values around the mesopause. It is shown that the temperature response up to the mesopause is strongly influenced by changes in dynamics. During Northern Hemisphere summer, dynamical processes alone would lead to an almost global warming of up to 3 K in the uppermost mesosphere.