Ground-based FTIR water vapour profile analyses

Due to a large vertical gradient and strong variability of water vapour, algorithms that are effectively applied for ground-based remote sensing of many different atmospheric trace gases can be insufficient for the retrieval of tropospheric water vapour profiles. We review the most important features of the retrieval and of the radiative transfer modelling required for accurate monitoring of tropospheric water vapour profiles by ground-based FTIR (Fourier Transform Infrared) experiments. These are: a fit of a variety of different water vapour lines with different strength, a logarithmic scale inversion, a speed dependent Voigt line shape model, and a joint temperature profile retrieval. Furthermore, the introduction of an interspecies constraint allows for a monitoring of HDO/H<sub>2</sub>O ratio profiles

Technical Note: Recipe for monitoring of total ozone with a precision of around 1 DU applying mid-infrared solar absorption spectra

International audienceMid-infrared solar absorption spectra recorded by a state-of-the-art ground-based FTIR system have the potential to provide precise total O3 amounts. The currently best-performing retrieval approaches use a combination of small and broad spectral O3 windows between 780 and 1015 cm?1. We show that for these approaches the uncertainties of the temperature profile are by far the major error sources. We demonstrate that a joint optimal estimation of temperature and O3 profiles widely eliminates this error. The improvements are documented by an extensive theoretical error estimation. Our results suggest that mid-infrared FTIR measurements can provide total O3 amounts with a precision of around 1 DU, placing this method among the most precise ground-based O3 monitoring techniques. We recapitulate the requirements on the instrumental hardware and on the retrieval that are needed to achieve this high precision

Recipe for continuous monitoring of total ozone with a precision of around 1 DU applying mid-infrared solar absorption spectra

International audienceMid-infrared solar absorption spectra recorded by a state-of-the-art ground-based FTIR system have the potential to provide precise total O3 amounts. The currently best-performing retrieval approaches use a combination of small and broad spectral O3 windows between 780 and 1015 cm?1. We show that for these approaches uncertainties in the temperature profile are by far the major error sources. We demonstrate that a joint optimal estimation of temperature and O3 profiles widely eliminates this error. The improvements are documented by an extensive theoretical error estimation. Our results suggest that mid-infrared FTIR measurements can provide total O3 amounts with a precision of around 1 DU, placing this method among the most precise ground-based O3 monitoring techniques. We recapitulate the requirements on instrumental hardware and retrieval necessary to achieve this high precision

Growing and In-Situ Processing of Cells on BEEM Capsule Caps for Scanning Electron Microscopy

A simple technique for processing cells grown on BEEM capsule caps for scanning electron microscopic (SEM) observation is described. The cells adhere to a substratum on the inner surface of caps coated with either an egg white-polyvinylpyrrolidone solution or a polylysine solution in the case of eukaryotic cells and an agar solution in the case of bacteria. The adhering cells are cultured and then processed in situ for SEM observation. Electron micrographs revealed details of the shape of the cells growing on the surface of the substrate. The technique seems to be particularly well suited for observing sequential morphological changes of cells, bacteria, and protozoa cultured under a specified experimental condition as well as of interactions between cells and parasitic microorganisms

Confirmation of a one-dimensional spin-1/2 Heisenberg system with ferromagnetic first-nearest-neighbor and antiferromagnetic second-nearest-neighbor interactions in Rb2{}_{2}Cu2{}_{2}Mo3{}_{3}O12{}_{12}

We have investigated magnetic properties of Rb$_2$Cu$_2$Mo$_3$O$_{12}$ powder. Temperature dependence of magnetic susceptibility and magnetic-field dependence of magnetization have shown that this cuprate is a model compound of a one-dimensional spin-1/2 Heisenberg system with ferromagnetic first-nearest-neighbor (1NN) and antiferromagnetic second-nearest-neighbor (2NN) competing interactions (competing system). Values of the 1NN and 2NN interactions are estimated as $J_1 = -138$ K and $J_2 = 51$ K ($\alpha \equiv J_2 / J_1 = -0.37$). This value of $\alpha$ suggests that the ground state is a spin-singlet incommensurate state. In spite of relatively large $J_1$ and $J_2$, no magnetic phase transition appears down to 2 K, while an antiferromagnetic transition occurs in other model compounds of the competing system with ferromagnetic 1NN interaction. For that reason, Rb$_2$Cu$_2$Mo$_3$O$_{12}$ is an ideal model compound to study properties of the incommensurate ground state that are unconfirmed experimentally.Comment: 6 pages, 4 figure

Observations of precipitable water vapour over complex topography of Ethiopia from ground-based GPS, FTIR, radiosonde and ERA-Interim reanalysis

Water vapour is one of the most important greenhouse gases. Long-term changes in the amount of water vapour in the atmosphere need to be monitored not only for its direct role as a greenhouse gas but also because of its role in amplifying other feedbacks such as clouds and albedo. In recent decades, monitoring of water vapour on a regular and continuous basis has become possible as a result of the steady increase in the number of deployed global positioning satellite (GPS) ground-based receivers. However, the Horn of Africa remained a data-void region in this regard until recently, when some GPS ground-receiver stations were deployed to monitor tectonic movements in the Great Rift Valley. This study seizes this opportunity and the installation of a Fourier transform infrared spectrometer (FTIR) at Addis Ababa to assess the quality and comparability of precipitable water vapour (PWV) from GPS, FTIR, radiosonde and interim ECMWF Re-Analysis (ERA-Interim) over Ethiopia. The PWV from the three instruments and the reanalysis show good correlation, with correlation coefficients in the range from 0.83 to 0.92. On average, GPS shows the highest PWV followed by FTIR and radiosonde observations. ERA-Interim is higher than all measurements with a bias of 4.6 mm compared to GPS. The intercomparison between GPS and ERA-Interim was extended to seven other GPS stations in the country. Only four out of eight GPS stations included simultaneous surface pressure observations. Uncertainty in the model surface pressure of 1 hPa can cause up to 0.35 mm error in GPS PWV. The gain obtained from using observed surface pressure in terms of reducing bias and strengthening correlation is significant but shows some variations among the GPS sites. The comparison between GPS and ERA-Interim PWV over the seven other GPS stations shows differences in the magnitude and sign of bias of ERA-Interim with respect to GPS PWV from station to station. This feature is also prevalent in diurnal and seasonal variabilities. The spatial variation in the relationship between the two data sets is partly linked to variation in the skill of the European Centre for Medium-Range Weather Forecasts (ECMWF) model over different regions and seasons. This weakness in the model is related to poor observational constraints from this part of the globe and sensitivity of its convection scheme to orography and land surface features. This is consistent with observed wet bias over some highland stations and dry bias over few lowland stations. The skill of ECMWF in reproducing realistic PWV varies with time of the day and season, showing large positive bias during warm and wet summer at most of the GPS site

Spin Defects in Spin-Peierls Systems

We examine spin-Peierls systems in the presence of spin defects which are introduced by replacing magnetic ions $Cu^{2+}$ with non-magnetic ones $Zn^{2+}$ in $CuGeO_3$. By using the action for the bosonized Hamiltonian, it is shown directly that the antiferromagnetic state induced by the spin defects coexists with the spin-Peierls states. Further the doping dependences of both transition temperature of spin-Peierls state and the spin gap have been calculated. The transition temperature of the present estimation shows good agreement quantitatively with that observed in Cu_{1-\de} Zn_\de O_3 for the region of the doping rate, \de<0.02.Comment: jpsj style, 11 pages, 2 figure

The ground-based FTIR network's potential for investigating the atmospheric water cycle

We present tropospheric H&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;16&lt;/sup&gt;O and HD&lt;sup&gt;16&lt;/sup&gt;O/H&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;16&lt;/sup&gt;O vapour profiles measured by ground-based FTIR (Fourier Transform Infrared) spectrometers between 1996 and 2008 at a northern hemispheric subarctic and subtropical site (Kiruna, Northern Sweden, 68&amp;deg; N and Izaña, Tenerife Island, 28&amp;deg; N, respectively). We compare these measurements to an isotope incorporated atmospheric general circulation model (AGCM). If the model is nudged towards meteorological fields of reanalysis data the agreement is very satisfactory on time scales ranging from daily to inter-annual. Taking the Izaña and Kiruna measurements as an example we document the FTIR network's unique potential for investigating the atmospheric water cycle. At the subarctic site we find strong correlations between the FTIR data, on the one hand, and the Arctic Oscillation index and the northern Atlantic sea surface temperature, on the other hand. The Izaña FTIR measurements reveal the importance of the Hadley circulation and the Northern Atlantic Oscillation index for the subtropical middle/upper tropospheric water balance. We document where the AGCM is able to capture these complexities of the water cycle and where it fails