Abstract. During the MaCWAVE winter campaign in January 2003, layers of enhanced echo power known as PMWE (Polar Mesosphere Winter Echoes) were detected by the ESRAD 52 MHz radar on several occasions. The cause of these echoes is unclear and here we use observations by meteorological and sounding rockets and by lidar to test whether neutral turbulence or aerosol layers might be responsible. PMWE were detected within 30 min of meteorological rocket soundings (falling spheres) on 5 separate days. The observations from the meteorological rockets show that, in most cases, conditions likely to be associated with neutral atmospheric turbulence are not observed at the heights of the PMWE. Observations by instrumented sounding rockets confirm low levels of turbulence and indicate considerable small-scale structure in charge density profiles. Comparison of falling sphere and lidar data, on the other hand, show that any contribution of aerosol scatter to the lidar signal at PMWE heights is less than the detection threshold of about 10%.

[1] Extreme pyrocumulonimbus (pyroCb) blowups that pollute the stratosphere have been documented on at least five occasions. However, the frequency of these events is still uncertain. One published pyroCb case study, the Chisholm Fire in May 2001, was restricted to the convective phase and its immediate aftermath. Here and in a companion paper we describe the stratospheric impact of the Chisholm pyroCb. The companion paper focuses on nadir satellite views of the plume. This paper synthesizes a broad array of space-, balloon-, and ground-based profile measurements. The Chisholm pyroCb, which we identify as the singular cause of stratospheric aerosol increase in northern spring/ summer of 2001, created a doubling of the zonal average aerosol optical depth in the lowermost stratosphere. The meridional spread of the plume was from the tropics (20°N) to the high Arctic (79°N) within the first month. The stratospheric Chisholm smoke became a hemispheric phenomenon in midlatitudes and northern tropics and persisted for at least 3 months. A size-resolved particle concentration profile over Laramie, Wyoming, indicated a lower stratospheric aerosol with a twofold to threefold increase in volume of particles with radii between 0.3 and 0.6 mm. We also find evidence of localized warming in the air masses of four of the lidar-measured smoke layers. This work contains the first reported stratospheric smoke layers measured by lidar at Ny Å lesund, Esrange, Kühlungsborn, Garmisch-Partenkirchen, Boulder, and Mauna Loa. In addition, the first detection of smoke-enhanced aerosol extinction at near IR wavelengths by the Halogen Occultation Experiment (HALOE) is introduced.

No abstract

Abstract. The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) has been operating since March 2002 onboard of the ENVIronmental SATellite of the European Space Agency (ESA). The high resolution (0.035 cm −1 full width half maximum, unapodized) limb-emission measurements acquired by MIPAS in the first two years of operation have very good geographical and temporal coverage and have been re-processed by ESA with the most recent versions (4.61 and 4.62) of the inversion algorithms. The products of this processing chain are pressures at the tangent points and geolocated profiles of temperature and of the volume mixing ratios of six key atmospheric constituents: H 2 O, O 3 , HNO 3 , CH 4 , N 2 O and NO 2 . As for all the measurements made with innovative instruments and techniques, this data set requires a thorough validation. In this paper we present a geophysical validation of the temperature profiles derived from MIPAS measurements by the ESA retrieval algorithm. The validation is carried-out by comparing MIPAS temperature with Correspondence to: M.Ridolfi (Marco.Ridolfi@unibo.it) correlative measurements made by radiosondes, lidars, insitu and remote sensors operated either from the ground or stratospheric balloons.The results of the intercomparison indicate that the bias of the MIPAS profiles is generally smaller than 1 or 2 K depending on altitude. Furthermore we find that, especially at the edges of the altitude range covered by the MIPAS scan, the random error estimated from the intercomparison is larger (typically by a factor of two to three) than the corresponding estimate derived on the basis of error propagation.In this work we also characterize the discrepancies between MIPAS temperature and the temperature fields resulting from the analyses of the European Centre for Mediumrange Weather Forecasts (ECMWF). The bias and the standard deviation of these discrepancies are consistent with those obtained when comparing MIPAS to correlative measurements; however, in this case the detected bias has a peculiar behavior as a function of altitude. This behavior is very similar to that observed in previous studies and is suspected to be due to vertical oscillations in the ECMWF temperature.Published by Copernicus Publications on behalf of the European Geosciences Union. M.Ridolfi et al.: MIPAS temperature validationThe current understanding is that, at least in the upper stratosphere (above ≈10 hPa), these oscillations are caused by a discrepancy between model biases and biases of assimilated radiances from primarily nadir sounders.

Abstract. The importance of polar stratospheric clouds (PSC) for polar ozone depletion is well established. Lidar experiments are well suited to observe and classify polar stratospheric clouds. On 5 January 2005 a PSC was observed simultaneously on the east and west sides of the Scandinavian mountains by ground-based lidars. This cloud was composed of liquid particles with a mixture of solid particles in the upper part of the cloud. Multi-colour measurements revealed that the liquid particles had a mode radius of r≈300 nm, a distribution width of σ ≈1.04 and an altitude dependent number density of N≈2-20 cm −3 . Simulations with a microphysical box model show that the cloud had formed about 20 h before observation. High HNO 3 concentrations in the PSC of 40-50 weight percent were simulated in the altitude regions where the liquid particles were observed, while this concentration was reduced to about 10 weight percent in that part of the cloud where a mixture between solid and liquid particles was observed by the lidar. The model simulations also revealed a very narrow particle size distribution with values similar to the lidar observations. Below and above the cloud almost no HNO 3 uptake was simulated. Although the PSC shows distinct wave signatures, no gravity wave activity was observed in the temperature profiles measured by the lidars and meteorological analyses support this observation. The observed cloud must have formed in a wave field above Iceland about 20 h prior to the measurements and the cloud wave pattern was advected by the background wind to Scandinavia. In this wave field above Iceland temperatures potentially dropped below the ice formation temperature, so that ice clouds may have formed which can act as condensation nuclei for the nitric acid trihydrate (NAT) particles observed at the cloud top above Esrange.