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The consequences of different quasi-biennial oscillation (QBO) nudging widths on stratospheric dynamics and chemistry are analyzed by comparing two model simulations with the National Center for Atmospheric Research's Whole Atmosphere Community Climate Model (WACCM) where the width of the QBO is varied between 22° and 8.5° north and south. The sensitivity to the nudging width is strongest in Northern Hemisphere (NH) winter where the Holton-Tan effect in the polar stratosphere, i.e., stronger zonal mean winds during QBO west phases, is enhanced for the wider compared to the narrower nudging case. The differences between QBO west and east conditions for the two model experiments can be explained with differences in wave propagation, wave-mean flow interaction, and the residual circulation. In the wider nudging case, a divergence anomaly in the midlatitude upper stratosphere/lower mesosphere occurs together with an equatorward anomaly of the residual circulation. This seems to result in a strengthening of the meridional temperature gradient and hence a significant strengthening of the polar night jet (PNJ). In the narrower nudging case, these circulation changes are weaker and not statistically significant, consistent with a weaker and less significant impact on the PNJ. Chemical tracers like ozone, water vapor, and methane react accordingly. From a comparison of westerly minus easterly phase composite differences in the model to reanalysis and satellite data, we conclude that the standard WACCM configuration (QBO22) generates more realistic QBO effects in stratospheric dynamics and chemistry during NH winter. Our study also confirms the importance of the secondary mean meridional circulation associated with the QBO for the Holton-Tan effect. Key Points The sensitivity to QBO nudging width is strongest in NH winterHolton-Tan effect in the polar stratosphere is enhanced for the wider nudgingWave-mean flow interactions explain differences between QBO west and east ©2013. American Geophysical Union. All Rights Reserved.

Global Positioning System (GPS) radio occultation (RO) temperature data are used to validate MPI-ESM (Max Planck Institute – Earth System Model) decadal hindcast experiments in the upper troposphere and lower stratosphere (UTLS) region between 300 hPa and 10 hPa (8 km and 32 km) for the time period between 2002 and 2011. The GPSRO dataset is unique since it is very precise, calibration independent and covers the globe better than the usual radiosonde dataset. In addition it is vertically finer resolved than any of the existing satellite temperature measurements available for the UTLS and provides now a unique one decade long temperature validation dataset. The initialization of the MPI-ESM decadal hindcast runs mostly increases the skill of the atmospheric temperatures when compared to uninitialized climate projections with very high skill scores for lead-year one, and gradually decreases for the later lead-years. A comparison between two different initialization sets (b0, b1) of the low-resolution (LR) MPI-ESM shows increased skills in b1-LR in most parts of the UTLS in particular in the tropics. The medium resolution (MR) MPI-ESM initializations are characterized by reduced temperature biases in the uninitialized runs as compared to observations and a better capturing of the high latitude northern hemisphere interannual polar vortex variability as compared to the LR model version. Negative skills are found for the b1-MR hindcasts however in the regions around the mid-latitude tropospheric jets on both hemispheres and in the vicinity of the tropical tropopause in comparison to the b1-LR variant. It is interesting to highlight that none of the model experiments can reproduce the observed positive temperature trend in the tropical tropopause region since 2001 as seen by GPSRO data.

Heparin was administered subcutaneously by a jet injector and a disposable syringe in a cross-over trial of ten subjects. Thrombin time, activated partial thromboplastin time, prothrombin time and factor Xa activity were measured. Complete absorption of heparin was demonstrated after injector administration. It saved time and effort. Use of a jet injector for the subcutaneous administration of low heparin doses is thus a sensible and safe alternative in the prevention of thrombo-embolism.

International audience; Recent observational and modeling transport studies of Arctic stratospheric final warming have shown that tropical/subtropical air masses can be transported to high latitudes and remain confined within a long-lived “frozen- in” anticyclone (FriaC), embedded in the summer easterlies for several months.We first present a climatology of these sporadic events over the period 1960-2011 using era-40 and era interim reanalyses. this study highlights stratospheric favorable preconditioning for FrIACs occurrence, that is: i) early and abrupt final warming, ii) no stratospheric major warming during the previous winter, and iii) east phase of the Quasi-Biennial Oscillation. We will present in detail the FriaC in spring 2011, which was the largest ever recorded. Our climatology further suggests that the frequency of occurrence of FriaCs has increased over the last decade (among the nine cases detected over the period 1960- 2011, five occurred between 2002 and 2011).A chemistry climate model is then used for the first time to investigate FriaCs characteristics and variability. simulations were performed with the nCar’s Community earth system Model (CesM, version 1.0.2), a coupled model system including the Whole Atmosphere Community Climate Model (WACCM). FrIACs characteristics (i.e. spatial extent and duration), are overall consistent by comparing with FriaCs detected era-40 meteorological reanalyses. Dynamical analysis reveals that FriaCs are associated with an abrupt and early winter-to-summer stratospheric circulation transition, characterized by an amplification of planetary wave activity. Furthermore, our model results confirm that FrIACs occur preferentially under the easterly phase of the QBO and in absence of MSW during the preceding winter. Finally, we notice that extreme climate change conditions (RCP8.5 scenario) do not influence FriaCs frequency.

The 11 year solar‐cycle component of climate variability is assessed in historical simulations of models taken from the Coupled Model Intercomparison Project, phase 5 (CMIP‐5). Multiple linear regression is applied to estimate the zonal temperature, wind and annular mode responses to a typical solar cycle, with a focus on both the stratosphere and the stratospheric influence on the surface over the period ∼1850–2005. The analysis is performed on all CMIP‐5 models but focuses on the 13 CMIP‐5 models that resolve the stratosphere (high‐top models) and compares the simulated solar cycle signature with reanalysis data. The 11 year solar cycle component of climate variability is found to be weaker in terms of magnitude and latitudinal gradient around the stratopause in the models than in the reanalysis. The peak in temperature in the lower equatorial stratosphere (∼70 hPa) reported in some studies is found in the models to depend on the length of the analysis period, with the last 30 years yielding the strongest response. A modification of the Polar Jet Oscillation (PJO) in response to the 11 year solar cycle is not robust across all models, but is more apparent in models with high spectral resolution in the short‐wave region. The PJO evolution is slower in these models, leading to a stronger response during February, whereas observations indicate it to be weaker. In early winter, the magnitude of the modelled response is more consistent with observations when only data from 1979–2005 are considered. The observed North Pacific high‐pressure surface response during the solar maximum is only simulated in some models, for which there are no distinguishing model characteristics. The lagged North Atlantic surface response is reproduced in both high‐ and low‐top models, but is more prevalent in the former. In both cases, the magnitude of the response is generally lower than in observations. ISSN:0035-9009 ISSN:1477-870X

Paleo-simulations of atmosphere-ocean circulation are not only an indispensable tool for understanding former climate conditions. It also impacts on other research areas, such as the investigation of the development of shelf areas or the reconstruction of topography.We model the dynamical state of atmosphere and oceans both separately and in a coupled mode for the Pliocene and pre-industrial times, using the atmosphere model ECHAM5 and the ocean model MPIOM. In comparison, the Pliocene has a globally warmer (2.2C) and slightly drier (1.4 cm/yr) climate than today. South America and Africa are both colder (4C) and drier (6 cm/yr), evoked mainly by changes in vegetation type and density. This explanation is supported by the fact that the composition of the atmosphere, the solar radiance and the land-sea distribution are similar in both time-slices for these regions. Changes in oceanic currents are strongly influenced by the opening of the Straight of Panama and a decreased meridional temperature gradient. This leads to a weakening of the Atlantic Meridional Overturning Circulation (AMOC) and the Antarctic Circumpolar Current (ACC) during the Pliocene in comparison to nowadays.