An introduction to the SCOUT-AMMA stratospheric aircraft, balloons and sondes campaign in West Africa, August 2006: rationale and roadmap

A multi-platform field measurement campaign involving aircraft and balloons took place over West Africa between 26 July and 25 August 2006, in the frame of the concomitant AMMA Special Observing Period and SCOUT-O3 African tropical activities. Specifically aiming at sampling the upper troposphere and lower stratosphere, the high-altitude research aircraft M55 Geophysica was deployed in Ouagadougou (12.3° N, 1.7° W), Burkina Faso, in conjunction with the German D-20 Falcon, while a series of stratospheric balloon and sonde flights were conducted from Niamey (13.5° N, 2.0° E), Niger. The stratospheric aircraft and balloon flights intended to gather experimental evidence for a better understanding of large scale transport, assessing the effect of lightning on NOx production, and studying the impact of intense mesoscale convective systems on water, aerosol, dust and chemical species in the upper troposphere and lower stratosphere. The M55 Geophysica carried out five local and four transfer flights between southern Europe and the Sahel and back, while eight stratospheric balloons and twenty-nine sondes were flown from Niamey. These experiments allowed a characterization of the tropopause and lower stratosphere of the region. We provide here an overview of the campaign activities together with a description of the general meteorological situation during the flights and a summary of the observations accomplished

An introduction to the SCOUT-AMMA stratospheric aircraft, balloons and sondes campaign inWest Africa, August 2006: rationale and roadmap

A multi-platform field measurement campaign involving aircraft and balloons took place overWest Africa between 26 July and 25 August 2006, in the frame of the concomitant AMMA Special Observing Period and SCOUT-O3 African tropical activities. Specifically aiming at sampling the upper troposphere and lower stratosphere, the high-altitude research aircraft M55 Geophysica was deployed in Ouagadougou (12.3 N, 1.7 W), Burkina Faso, in conjunction with the German D- 20 Falcon, while a series of stratospheric balloons and sonde flights were conducted from Niamey (13.5 N, 2.0 E), Niger. Altogether, these measurements were intended to provide experimental evidence for a better understanding of large scale transport, assessing the effect of lightning on NOx production, and studying the impact of intense mesoscale convective systems on water, aerosol, dust and chemical species in the upper troposphere and lower stratosphere. The M55 Geophysica carried out five local and four transfer flights between southern Europe and the Sahel and back, while eight stratospheric balloons and twenty-nine sondes were flown from Niamey. These experiments allowed a characterization of the tropopause and lower stratosphere of the region. The paper provides an overview of SCOUT-AMMA campaign activities together with a description of the meteorology of the African monsoon and the situation prevailing during the flights and a brief summary of the observations accomplished

Intermolecular potentials for the metastable neon*-rare gas and neon*-molecule systems

The absolute value and the velocity dependence of the total cross section Q(g) has been measured in a crossed beam machine for the Ne*-Ar, Kr, Xe and Ne*-O2, N2, CH2 and CO2 systems, using a mixed beam containing Ne*(3P(0) and Ne * (3P2) fine structure states in a 1:5 ratio. The range of velocities is typically 1000 g 8000 m s-1, always including the interesting N = 1 glory oscillation. The results for the Ne* -rare gas systems are in excellent agreement with the predictions of the ion-atom Morse-Morse-spline-van der Waals potentials of Gregor and Siska, both with regard to the absolute value (1.5%), position of the N = 1 glory maximum (2.7%) and the amplitude of the N = 1 glory maximum (4.3%). The predictions of the potentials proposed by Hausamann are less satisfactory, most likely due to the specific switchover function used to connect the well area at R/RM ˜ 1.1 to the van der Waals long-range attractive branch at R/RM ˜ 2 (RM is the well position). By using a semiclassical scaling method the potential parameters e (well depth), RM (well position) and C6 (van der Waals constant) have been determined for the Ne*-molecule systems, using the Gregor and Siska IAMMSV potential for the Ne*-Xe system as a reference. The well parameters are (e (meV), RM (Å)) = (3.21, 5.43), (4.24, 5.17), (13.55, 4.74) and (7.08, 5.44) for the Ne*-N2, O2, CO2 and CH4, systems, respectively. For the C6 values we observe a fair scaling with the polarisibility a of the molecule. For the Ne*-CO2 system we observe a damping of the amplitude of the glory oscillations, which increases rapidly with decreasing velocity. This damping is interpreted in terms of the probability for ionisation along the glory trajectory, providing useful information for determining a complex potential for this system

The endothermic excitation transfer process krypton*(3PJ) + molecular nitrogen(X) -> Kr(1S0) + N2((C): a sensitive probe for the 3P2:3P0 population ratio

The excitation transfer cross section of the Kr*-N2 system has been measured in a crossed-beam experiment in the energy range 0.5 E(eV) 2.7, using a mixed beam of metastable Kr* atoms. The strongly different threshold energies (0.47 and 1.12 eV for the values J = 0 and J = 2, respectively, of total electronic angular momentum of Kr*) allow for an analysis in terms of fine-structure-dependent cross sections QJ(E), resulting in Q0 (0.94 eV) = 3.38 Å2 and Q2(2.24 eV) = 2.46 Å2 at twice the threshold energy. The slightly larger cross section for J = 0 can be explained qualitatively in terms of diabatic initial- and final-state potentials, coupled by two curve crossings with the ionic Kr+-N-2 Coulomb potential. The large difference with the experiments of Tabayashi and Shobatake, resulting in Q0 ˜ 10-2 Q2, is most likely due to a population ratio 3P0:3P2 = 1:146 in their atmospheric-arc beam source which is far from the assumed ratio 1:5 of statistical weights

Long-range intermolecular potentials for the metastable rare gas-rare gas systems argon*, krypton* (3P0,2) + argon, krypton, xenon

In a crossed beam experiment with a calibrated supersonic secondary beam the absolute value (rms accuracy 2.5%) and the velocity dependence of the total cross section Q have been measured in a wide range of relative velocities 50

Validation of the DLW method in Japanese quail at different water fluxes using laser and IRMS

In Japanese quail (Coturnix c. japonica; n = 9), the doubly labeled water (DLW) method (2H, 18O) for estimation of CO2 production (l/day) was validated. To evaluate its sensitivity to water efflux levels (rH2Oe; g/day) and to assumptions of fractional evaporative water loss (x; dimensionless), animals were repeatedly fed a dry pellet diet (average rH2Oe of 34.8 g/day) or a wet mash diet (95.8 g/day). We simultaneously compared the novel infrared laser spectrometry (LS) with isotope ratio mass spectrometry. At low rH2Oe, calculated CO2 production rate exhibited little sensitivity to assumptions concerning x, with the best fit being found at 0.51, and only little error was made employing an x value of 0.25. In contrast, at high rH2Oe, sensitivities were much higher with the best fit at x = 0.32. Conclusions derived from isotope ratio mass spectrometry and LS were similar, proving the usefulness of LS. Within a threefold range of rH2Oe, little error in the DLW method is made when assuming one single x value of 0.25, indicating its robustness in comparative studies.