[1] We report on in situ and remote sensing measurements of ice particles in the tropical stratosphere found during the Geophysica campaigns TROCCINOX and SCOUT-O3. We show that the deep convective systems penetrated the stratosphere and deposited ice particles at altitudes reaching 420 K potential temperature. These convective events had a hydrating effect on the lower tropical stratosphere due to evaporation of the ice particles. In contrast, there were no signs of convectively induced dehydration in the stratosphere. Citation: Corti, T., et al. (2008), Unprecedented evidence for deep convection hydrating the tropical stratosphere, Geophys. Res. Lett., 35, L10810,

The Basel UrBan Boundary Layer Experiment (BUBBLE) was a year-long experimental effort to investigate in detail the boundary layer structure in the City of Basel, Switzerland. At several sites over different surface types (urban, suburban and rural reference) towers up to at least twice the main obstacle height provided turbulence observations at many levels. In addition, a Wind Profiler and a Lidar near the city center were profiling the entire lower troposphere. During an intensive observation period (IOP) of one month duration, several sub-studies on street canyon energetics and satellite ground truth, as well as on urban turbulence and profiling (sodar, RASS, tethered balloon) were performed. Also tracer experiments with near-roof-level release and sampling were performed. In parallel to the experimental activities within BUBBLE, a meso-scale numerical atmospheric model, which contains a surface exchange parameterization, especially designed for urban areas was evaluated and further developed. Finally, the area of the full-scale tracer experiment which also contains several sites of other special projects during the IOP (street canyon energetics, satellite ground truth) is modeled using a very detailed physical scale-model in a wind tunnel. In the present paper details of all these activities are presented together with first results.

The determination of the depth of daytime and nighttime mixing layers must be known very accurately to relate boundary-layer concentrations of gases or particles to upstream fluxes. The mixing-height is parametrized in numerical weather prediction models, so improving the determination of the mixing height will improve the quality of the estimated gas and particle budgets. Datasets of mixing-height diurnal cycles with high temporal and spatial resolutions are sought by various end users. Lidars and ceilometers provide vertical profiles of backscatter from aerosol particles. As aerosols are predominantly concentrated in the mixing layer, lidar backscatter profiles can be used to trace the depth of the mixing layer. Large numbers of automatic profiling lidars and ceilometers are deployed by meteorological services and other agencies in several European countries providing systems to monito

[1] A High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS) was evaluated for its ability to quantify submicron sea salt mass concentrations. The evaluation included both laboratory and field studies. Quantification of the sea salt signal in the HR-ToF-AMS was achieved by taking the 23 Na 35 Cl + ion as a surrogate for sea salt and then identifying a calibration scaling factor through a comparison with mono-disperse laboratory generated sea salt aerosol. Ambient sea salt concentrations calculated using this method agreed well with those obtained by ion chromatography of filter samples, following a 1:1 regression slope and a correlation coefficient R = 0.93. A key advantage of this AMS-based method is that it allows for high time resolution measurements of sea salt (5 min) along with the speciation of other chemical compounds, including primary organics contributing to sea spray. The high-time resolution sea salt measurement capability enabled the quantification of sea salt mass in both increasing and decreasing wind speed regimes up to 26 m s À1 . A mass flux source function was also derived and found to have a power law wind speed dependency with an exponent of 3.1 for increasing winds and 2.3 for decreasing winds. Comparison of the mass flux relationship in this study suggests that previous schemes based on the Monahan whitecap-wind speed approach significantly over-estimate the submicron mass flux. Both the whitecap-wind speed component and the differential whitecap-aerosol productivity component of the source flux function contribute toward the over-estimation.

[1] High-time resolution measurements of primary marine organic sea-spray physico-chemical properties reveal an apparent dichotomous behavior in terms of water uptake: specifically sea-spray aerosol enriched in organic matter possesses a low hydroscopic Growth Factor (GF∼1.25) while simultaneously having a cloud condensation nucleus/ condensation nuclei (CCN/CN) activation efficiency of between 83% at 0.25% supersaturation and 100% at 0.75%. In contrast, the activation efficiency of particles dominated by non-sea-salt (nss)-sulfate ranged between 48-100% over supersaturation range of 0.25%-1%. Simultaneous retrieval of Cloud Droplet Number Concentration (CDNC) during primary organic aerosol plumes reveals CDNC concentrations of 350 cm −3 for organic mass concentrations 3-4 mg m −3 . It is demonstrated that the retrieved high CDNCs under clean marine conditions can only be explained by organic seaspray and corroborates the high CCN activation efficiency associated with primary organics. It is postulated that marine hydrogels are responsible for this dichotomous behavior.