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The Jungfraujoch Research Station (46.55[degrees]N, 7.98[degrees]E, 3580 m above sea level) for decades has contributed in a significant manner to the systematic observation of the Earth's atmosphere both with in situ measurements and with trace gas column detection. We report on the development of a lidar system that improves the measurement potential of highly resolved atmospheric parameters in both time and space, with the goal of achieving long-term monitoring of atmospheric aerosol optical properties and water-vapor content. From the simultaneously detected elastic-backscatter signals at 355, 532, and 1064 nm, Raman signals from nitrogen at 387 and 607 nm, and water vapor at 408 nm, the aerosol extinction and backscatter coefficients at three wavelengths and a water-vapor mixing ratio are derived. Additional information about particle shape is obtained by depolarization measurements at 532 nm. Water-vapor measurements by use of both nitrogen and water-vapor Raman returns from the 355-nm laser beam are demonstrated with a vertical range resolution of 75 m and an integration time of 2 h. The comparison to the water-vapor profile derived from balloon measurements (Snow White technique) showed excellent agreement. The system design and the results obtained by its operation are reported. OCIS codes: 010.3640, 010.1100, 010.7030.

Numerical simulations compared with field measurements are used to explain the effect of sea breezes on photochemical smog episodes in Athens during the Mediterranean Campaign of Photochemical Tracers on 1214 September 1994. The numerical simulations, performed using a nonhydrostatic vorticity mesoscale model coupled to the Lurmann-Carter-Coyner photochemical module, are compared with ground-based lidar and aircraft measurements. The current analysis shows that the three selected days include the two main summertime flow patterns characteristic of the Athens peninsula, each of which lead to significantly different pollution amounts. On 12 and 13 September, a strong, northerly synoptic wind reduces the inland penetration of the sea breeze so that ozone concentrations within the greater Athens area remained low. In contrast, the weaker synoptic forcing on 14 September allowed the development of sea breezes over the whole peninsula and high ozone concentrations were found north and east of the city. An analysis based on pollution amounts and wind patterns is carried out to divide the peninsula into regions, each of which corresponds to a specific pollutant behavior.

Measurements of the spatial uniformity of Hamamatsu H5783-06 photosensor modules were performed by the flying spot method. The results were used to simulate the influence of the photomultiplier tube on a lidar signal. A simple method for improving the spatial uniformity is proposed.

Mixtures of methane, hydrogen, and argon ([CH.sub.4]:[H.sub.2]:Ar) were studied as UV Raman shifters for ozone differential absorption lidar application. They have higher photochemical stability than pure [CH.sub.4] and the capability to produce, with high enough efficiency, either first [CH.sub.4] Stokes or, simultaneously, [CH.sub.4] and [H.sub.2] first Stokes with equal energies. These mixtures can be used as an inexpensive replacement for [D.sub.2] or a more stable substitute for pure [CH.sub.4] in single-pass high-power Raman shifters.

From lidar signals detected with a shot per shot differential absorption lidar instrument tuned for tropospheric ozone measurements and recording each individual return, we reconstruct histograms of their sampled values for each channel of our digitizers. The analysis of their shape permits the correction of our measurements for experimental biases. In particular, a negative correlation is found between the skew of the histograms and the intensity of the backscattered light. The skew comes from a tail at high sampled values, interpreted as due to a raise of the relative contribution to the signal of a signal-induced noise when this intensity diminishes. By fitting a Gaussian function to the histograms without considering their tails, we calculate average signals unbiased by the corresponding noise. This approach allows us to increase the range of our ozone profiles, up to as much as double it in some cases. Key words: Lidar, ozone, troposphere, atmospheric fluctuations, signal-induced bias.

Single-pass Raman cells pumped by either a quadrupled Nd:YAG (266-nm) laser or a KrF excimer laser are studied. The Raman-active gases comprise [H.sub.2], [D.sub.2], or [CH.sub.4], as well as a mixture of them, with the addition of He, Ne, or Ar. A parametric study, in which the Stokes conversion efficiency and the beam quality ([M.sup.2]) were measured, was made. The first Stokes efficiency increases and all the Stokes thresholds decrease with an increase in the lens focal length or the [M.sup.2] parameter of the pump beam. The quality of the Stokes beams deteriorates when the active-gas pressure increases but is improved by the addition of an inert gas. Laser-induced breakdown is shown to be a factor that limits the conversion efficiency and the quality of the Stokes beams. With a mixture of [D.sub.2], [H.sub.2], and Ar, a 10-15-mJ pulse energy is obtained (depending on the pump [M.sup.2] parameter) in the first Stokes beam of [D.sub.2] (289 nm) and [H.sub.2] (299 nm), with a full-angle divergence of 0.5 mrad (at 86% power). Key words: Stimulated Raman scattering, four-wave mixing, UV Raman shifter, beam quality, differential absorption lidar in the UV.

We present the first validation of the Swisens Poleno, currently the only operational automatic pollen monitoring system based on digital holography. The device provides in-flight images of all coarse aerosols and here we develop a two-step classification algorithm that uses these images to identify a range of pollen taxa. Deterministic criteria based on the shape of the particle are applied to initially distinguish between intact pollen grains and other coarse particulate matter. This first level of discrimination identifies pollen with an accuracy of 96 %. Thereafter, individual pollen taxa are recognised using supervised learning techniques. The algorithm is trained using data obtained by inserting known pollen types into the device and out of eight pollen taxa six can be identified with an accuracy of above 90 %. In addition to the ability to correctly identify aerosols, an automatic pollen monitoring system needs to be able to correctly determine particle concentrations. To further verify the device, controlled chamber experiments using polystyrene latex beads were performed. This provided reference aerosols with traceable particle size and number concentrations to ensure particle size and sampling volume were correctly characterised. [ABSTRACT FROM AUTHOR]

A new lidar instrument has been developed to measure tropospheric ozone and water vapor at low altitude. The lidar uses Raman scattering of an UV beam from atmospheric nitrogen, oxygen, and water vapor to retrieve ozone and water-vapor vertical profiles. By numerical simulation we investigate the sensitivity of the method to both atmospheric and device perturbations. The aerosol optical effect in the planetary boundary layer, ozone interference in water-vapor retrieval, statistical error, optical cross talk between Raman-shifted channels, and optical cross talk between an elastically backscattered signal in Raman-shifted signals and an afterpulse effect are studied in detail. In support of the main conclusions of this model study, time series of ozone and water vapor obtained at the Swiss Federal Institute of Technology in Lausanne and during a field campaign in Crete are presented. They are compared with point monitor and balloon sounding measurements for daytime and nighttime conditions.

We validate the Ozone Monitoring Instrument (OMI) Ozone Profile (PROFOZ) product from October 2004 through December 2014 retrieved by the Smithsonian Astrophysical Observatory (SAO) algorithm against ozonesonde observations. We also evaluate the effects of OMI row anomaly (RA) on the retrieval by dividing the dataset into before and after the occurrence of serious OMI RA, i.e., pre-RA (2004-2008) and post-RA (2009-2014). The retrieval shows good agreement with ozonesondes in the tropics and midlatitudes and for pressure <~50 hPa in the high latitudes. It demonstrates clear improvement over the a priori down to the lower troposphere in the tropics and down to an average of ~550 (300) hPa at middle (high) latitudes. In the tropics and midlatitudes, the profile mean biases (MBs) are less than 6%, and the standard deviations (SDs) range from 5 to 10% for pressure <~50 hPa to less than 18% (27%) in the tropics (midlatitudes) for pressure >~50 hPa after applying OMI averaging kernels to ozonesonde data. The MBs of the stratospheric ozone column (SOC, the ozone column from the tropopause pressure to the ozonesonde burst pressure) are within 2% with SDs of <5% and the MBs of the tropospheric ozone column (TOC) are within 6% with SDs of 15%. In the high latitudes, the profile MBs are within 10% with SDs of 5-15% for pressure <~50 hPa but increase to 30% with SDs as great as 40% for pressure >~50 hPa. The SOC MBs increase up to 3% with SDs as great as 6% and the TOC SDs increase up to 30%. The comparison generally degrades at larger solar zenith angles (SZA) due to weaker signals and additional sources of error, leading to worse performance at high latitudes and during the midlatitude winter. Agreement also degrades with increasing cloudiness for pressure>~100 hPa and varies with cross-track position, especially with large MBs and SDs at extreme off-nadir positions. In the tropics and midlatitudes, the post-RA comparison is considerably worse with larger SDs reaching 2% in the stratosphere and 8% in the troposphere and up to 6% in TOC. There are systematic differences that vary with latitude compared to the pre-RA comparison. The retrieval comparison demonstrates good long-term stability during the pre-RA period but exhibits a statistically significant trend of 0.14-0.7%year-1 for pressure<~80 hPa, 0.7DUyear-1 in SOC, and -0.33DUyear-1 in TOC during the post-RA period. The spatiotemporal variation of retrieval performance suggests the need to improve OMI's radiometric calibration especially during the post-RA period to maintain the long-term stability and reduce the latitude/season/SZA and cross-track dependency of retrieval quality. [ABSTRACT FROM AUTHOR]

A large-scale comparison of water-vapour vertical-sounding instruments took place over Central Europe on 17 October 2008, during a rather homogeneous deep stratospheric intrusion event (LUAMI, Lindenberg Upper-Air Methods Intercomparison). The measurements were carried out at four observational sites, Payerne (Switzerland), Bilthoven (The Netherlands), Lindenberg (North-East Germany) and the Zugspitze mountain (Garmisch-Partenkichen, German Alps), and by an air-borne water-vapour lidar system creating a transect of humidity profiles between all four stations. A high data quality was verified that strongly underlines the scientific findings. The intrusion layer was very dry with minimum mixing ratios of 0 to 65 ppm on its lower west side, but did not drop below 120 ppm on the higher-lying east side (Lindenberg). The dryness hardens the findings of a preceding study ("Part 1") that, e.g., 73% of deep intrusions reaching the German Alps and travelling six days and less exhibit minimum mixing ratios of 50 ppm and less. These low values reflect values found in the lowermost stratosphere and indicate very slow mixing with tropospheric air during the downward transport to the lower troposphere. The peak ozone values were around 70 ppb, confirming the idea that intrusion layers depart from the lowermost edge of the stratosphere. The data suggest an increase of ozone from the lower to the higher edge of the intrusion layer. This behaviour is also confirmed by stratospheric aerosol caught in the layer. Both observations are in agreement with the idea that sections of the vertical distributions of these constituents in the the source region were transferred to Central Europe without major change. LAGRANTO trajectory calculations demonstrated a rather shallow outflow the stratosphere from just above the dynamical tropopause, for the first time confirming the conclusions in "Part 1" from the Zugspitze CO observations. The trajectories qualitatively explain the temporal evolution of the intrusion layers above the four stations participating in the campaign. [ABSTRACT FROM AUTHOR]

We validate the Ozone Monitoring Instrument (OMI) ozone-profile (PROFOZ) product from October 2004 through December 2014 retrieved by the Smithsonian Astrophysical Observatory (SAO) algorithm against ozonesonde observations. We also evaluate the effects of OMI Row anomaly (RA) on the retrieval by dividing the data set into before and after the occurrence of serious OMI RA, i.e., pre-RA (2004-2008) and post-RA (2009-2014). The retrieval shows good agreement with ozonesondes in the tropics and mid-latitudes and for pressure < ~50 hPa in the high latitudes. It demonstrates clear improvement over the a priori down to the lower troposphere in the tropics and down to an average of ~550 (300) hPa at middle (high latitudes). In the tropics and mid-latitudes, the profile mean biases (MBs) are less than 6%, and the standard deviations (SDs) range from 5-10% for pressure < ~50 hPa to less than 18% (27%) in the tropics (midlatitudes) for pressure > ~50 hPa after applying OMI averaging kernels to ozonesonde data. The MBs of the stratospheric ozone column (SOC) are within 2% with SDs of < 5% and the MBs of the tropospheric ozone column (TOC) are within 6% with SDs of 15%. In the high latitudes, the profile MBs are within 10% with SDs of 5-15% for pressure < ~50 hPa, but increase to 30% with SDs as great as 40% for pressure > ~50 hPa. The SOC MBs increase up to 3% with SDs as great as 6% and the TOC SDs increase up to 30%. The comparison generally degrades at larger solarzenith angles (SZA) due to weaker signals and additional sources of error, leading to worse performance at high latitudes and during the mid-latitude winter. Agreement also degrades with increasing cloudiness for pressure > ~100 hPa and varies with cross-track position, especially with large MBs and SDs at extreme off-nadir positions. In the tropics and mid-latitudes, the post-RA comparison is considerably worse with larger SDs reaching 2% in the stratosphere and 8% in the troposphere and up to 6% in TOC. There are systematic differences that vary with latitude compared to the pre-RA comparison. The retrieval comparison demonstrates good long-term stability during the pre-RA period, but exhibits a statistically significant trend of 0.14-0.7%/year for pressure < ~ 80 hPa, 0.7 DU/year in SOC and -0.33 DU/year in TOC during the post-RA period. The spatiotemporal variation of retrieval performance suggests the need to improve OMI’s radiometric calibration especially during the post-RA period to maintain the long-term stability and reduce the latitude/season/SZA and cross-track dependence of retrieval quality., Astronomy