Emission spectrum of hot HDO below 4000 cm-1

Fourier transform emission spectra were recorded using a mixture of H2O and D2O at a temperature of 1500 °C. The spectra were recorded in three overlapping sections and cover the wavenumber range 1800–3932 cm−1. This spectrum is analyzed together with a previously reported one spanning the 380–2190 cm−1 range [Parekunnel et al., J. Mol. Spectrosc. 2001 (28) 101]. This analysis leads to 4409 newly assigned HDO emission lines. This work particularly extends data on the (200) and (120) states of HDO for which newly determined energy levels are presented

Greenhouse Gas Measurements Over a 144 km Open Path in the Canary Islands

A new technique for the satellite remote sensing of greenhouse gases in the atmosphere via the absorption of short-wave infrared laser signals transmitted between counter-rotating satellites in low Earth orbit has recently been proposed; this would enable the acquisition of a long-term, stable, global set of altitude-resolved concentration measurements. We present the first ground-based experimental demonstration of this new infrared-laser occultation method, in which the atmospheric absorption of CO2 near 2.1µm was measured over a ∼144km path length between two peaks in the Canary Islands (at an altitude of ∼2.4 km), using relatively low power diode lasers (∼4 to 10mW). The retrieved CO2 volume mixing ratio of 400 ppm (±15 ppm) is consistent within experimental uncertainty with simultaneously recorded in situ validation measurements. We conclude that the new method has a sound basis for monitoring CO2 in the free atmosphere; other greenhouse gases such as methane, nitrous oxide and water vapour can be monitored in the same way

Retrieval and Validation of Carbon Dioxide, Methane, and Water Vapor for the Canary Islands IR-Laser Occultation Experiment

The first ground-based experiment to prove the concept of a novel space-based observation technique for microwave and infrared-laser occultation between low-Earthorbit satellites was performed in the Canary Islands between La Palma and Tenerife. For two nights from 21 to 22 July 2011 the experiment delivered the infrared-laser differential transmission principle for the measurement of greenhouse gases (GHGs) in the free atmosphere. Such global and long-term stable measurements of GHGs, accompanied also by measurements of thermodynamic parameters and line-of-sight wind in a self-calibrating way, have become very important for climate change monitoring. The experiment delivered promising initial data for demonstrating the new observation concept by retrieving volume mixing ratios of GHGs along a ~ 144 km signal path at altitudes of ~ 2.4 km. Here, we present a detailed analysis of the measurements, following a recent publication that introduced the experiment\u27s technical setup and first results for an example retrieval of CO2. We present the observational and validation data sets, the latter simultaneously measured at the transmitter and receiver sites; the measurement data handling; and the differential transmission retrieval procedure. We also determine the individual and combined uncertainties influencing the results and present the retrieval results for 12CO2, 13CO2, C18OO, H2O and CH4. The new method is found to have a reliable basis for monitoring of greenhouse gases such as CO2, CH4, and H2O in the free atmosphere

Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites (BORTAS) experiment: design, execution and science overview

We describe the design and execution of the BORTAS (Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites) experiment, which has the overarching objective of understanding the chemical aging of air masses that contain the emission products from seasonal boreal wildfires and how these air masses subsequently impact downwind atmospheric composition. The central focus of the experiment was a two-week deployment of the UK BAe-146-301 Atmospheric Research Aircraft (ARA) over eastern Canada, based out of Halifax, Nova Scotia. Atmospheric ground-based and sonde measurements over Canada and the Azores associated with the planned July 2010 deployment of the ARA, which was postponed by 12 months due to UK-based flights related to the dispersal of material emitted by the Eyjafjallajökull volcano, went ahead and constituted phase A of the experiment. Phase B of BORTAS in July 2011 involved the same atmospheric measurements, but included the ARA, special satellite observations and a more comprehensive ground-based measurement suite. The high-frequency aircraft data provided a comprehensive chemical snapshot of pyrogenic plumes from wildfires, corresponding to photochemical (and physical) ages ranging from 45 sr 10 days, largely by virtue of widespread fires over Northwestern Ontario. Airborne measurements reported a large number of emitted gases including semi-volatile species, some of which have not been been previously reported in pyrogenic plumes, with the corresponding emission ratios agreeing with previous work for common gases. Analysis of the NOy data shows evidence of net ozone production in pyrogenic plumes, controlled by aerosol abundance, which increases as a function of photochemical age. The coordinated ground-based and sonde data provided detailed but spatially limited information that put the aircraft data into context of the longer burning season in the boundary layer. Ground-based measurements of particulate matter smaller than 2.5 μm (PM2.5) over Halifax show that forest fires can on an episodic basis represent a substantial contribution to total surface PM2.5

Investigation of CO, C2H6 and aerosols in a boreal fire plume over eastern Canada during BORTAS 2011 using ground- and satellite-based observations, and model simulations

We present the results of total column measurements of CO, C2H6 and fine mode aerosol optical depth (AOD) during the "Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites" (BORTAS-B) campaign over Eastern Canada. Ground-based observations, using Fourier transform spectrometers (FTSs) and sun photometers, were carried out in July and August 2011. These measurements were taken in Halifax, Nova Scotia, which is an ideal location to monitor the outflow of boreal fires from North America, and also in Toronto, Ontario. Measurements of fine mode AOD enhancements were highly correlated with enhancements in coincident trace gas (CO and C2H6) observations between 19 and 21 July 2011, which is typical for a smoke plume event. In this paper, we focus on the identification of the origin and the transport of this smoke plume. We use back-trajectories calculated by the Canadian Meteorological Centre as well as FLEXPART forward-trajectories to demonstrate that the enhanced CO, C2H6 and fine mode AOD seen near Halifax and Toronto originated from forest fires in Northwestern Ontario that occurred between 17 and 19 July 2011. In addition, total column measurements of CO from the satellite-borne Infrared Atmospheric Sounding Interferometer (IASI) have been used to trace the smoke plume and to confirm the origin of the CO enhancement. Furthermore, the emission ratio (ERC2H6/CO) and the emission factor (EFC2H6) of C2H6 (with respect to the CO emission) were estimated from these ground-based observations. These C2H6 emission results from boreal fires in Northwestern Ontario agree well with C2H6 emission measurements from other boreal regions, and are relatively high compared to fires from other geographical regions. The ground-based CO and C2H6 observations were compared with outputs from the 3-D global chemical transport model GEOS-Chem, using the Fire Locating And Monitoring of Burning Emissions (FLAMBE) inventory. Agreement within the stated measurement uncertainty was found for the magnitude of the enhancement of the total columns of CO (~3%) and C2H6 (~8%) between the measured and modelled results. However, there is a small shift in time (of approximately 6 h) of arrival of the plume over Halifax between the results

FOURIER TRANSFORM EMISSION SPECTROSCOPY OF THE B′2Σ+−X2Σ+B^{\prime} {^{2}}\Sigma^{+} - X {^{2}}\Sigma^{+} TRANSITIONS OF MgH AND MgD

Author Institution: Department of Chemistry, University of WaterlooEmission spectra of MgH and MgD have been investigated in the $8000 - 22000 cm^{-1}$ region using a high resolution Fourier transform spectrometer. These molecules were generated in a furnace-discharge source, at about 900 K and 333 mA discharge current with magnesium and a mixture of Ar and $H_{2}$ or $D_{2}$ gases. The recorded spectra contain not only the well-known $A {^{2}}\pi - X {^{2}}\Sigma^{+}$ transitions, but also the $B^{\prime} {^{2}}\Sigma^{+} - X {^{2}}\Sigma^{+}$ transitions of MgH and MgD. We obtained data for $v^{\prime \prime} = 2$ to 9 for the ground state of MgH and $v^{\prime \prime} = 3$ to 13 for MgD. Analyses of the data is in progress, and will lead to improved potential energy curves for the $X {^{2}}\Sigma^{+}$ states of MgH and MgD. These results will be presented at the time of symposium

Vibration-rotation emission spectrum of free BeH2

The gaseous BeH2 molecule has been synthesized by means of an electrical discharge inside a high-temperature furnace and identified with infrared emission spectroscopy. The antisymmetric stretching mode 3 has been detected near 2179 reciprocal centimeters. The BeH2 molecule has a linear, symmetric structure with an r0 BeH bond length of 1.333761(2) angstroms

FOURIER TRANSFORM EMISSION SPECTROSCOPY OF THE E2^{2}Π\Pi--X2^{2}Σ\Sigma+^{+} TRANSITIONS OF SrH, SrD AND BaH.

Author Institution: Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK; Department of Chemistry, University of Arizona, Tucson, AZ 85721, USA; Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK; Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA 23529 USA; Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK; Department of Physics, University of Toronto, Toronto, Ont., M5S 1A7, CanadaEmission spectra of SrH, SrD and BaH have been studied at high resolution using a Fourier transform spectrometer. The SrH and SrD molecules have been produced in a high temperature furnace by the reaction of strontium metal vapor with H$_{2}$/D$_{2}$ in the presence of a slow flow of Ar gas. The spectra observed in the 18000--19000 cm$^{-1}$ region consist of the 0--0 and 1--1 bands of the E$^{2}$$\Pi$--X$^{2}$$\Sigma$$^{+}$ transition of the two isotopologues. A rotational analysis of these bands has been obtained by combining the present measurements with previously available pure rotation and vibration-rotation measurements for the ground state, and improved spectroscopic constants have been obtained for the E$^{2}$$\Pi$ state.\newline The high resolution spectrum of the E$^{2}$$\Pi$--X$^{2}$$\Sigma$$^{+}$ transition of BaH has been observed using a Ba hollow cathode lamp operated with 150 V and 300 mA current with a slow flow of 700 mTorr of Ar and 40 mTorr of H$_{2}$ gases. The spectrum in the 14000--15600 cm$^{-1}$ region was recorded at a resolution of 0.015 cm$^{-1}$ with the 1-m Fourier transform spectrometer associated with the McMath-Pierce Telescope of the National Solar Observatory at Kitt Peak. A rotational analysis of the 0--0, 1--1 and 2--2 bands has been performed and improved spectroscopic constants were determined for the E$^{2}$$\Pi$ state by combining the data with existing vibration-rotation measurements of the ground state

Optimizing UV Index determination from broadband irradiances

A study was undertaken to improve upon the prognosticative capability of Environment and Climate Change Canada's (ECCC) UV Index forecast model. An aspect of that work, and the topic of this communication, was to investigate the use of the four UV broadband surface irradiance fields generated by ECCC's Global Environmental Multiscale (GEM) numerical prediction model to determine the UV Index. The basis of the investigation involves the creation of a suite of routines which employ high-spectral-resolution radiative transfer code developed to calculate UV Index fields from GEM forecasts. These routines employ a modified version of the Cloud-J v7.4 radiative transfer model, which integrates GEM output to produce high-spectral-resolution surface irradiance fields. The output generated using the high-resolution radiative transfer code served to verify and calibrate GEM broadband surface irradiances under clear-sky conditions and their use in providing the UV Index. A subsequent comparison of irradiances and UV Index under cloudy conditions was also performed. Linear correlation agreement of surface irradiances from the two models for each of the two higher UV bands covering 310.70–330.0 and 330.03–400.00 nm is typically greater than 95 % for clear-sky conditions with associated root-mean-square relative errors of 6.4 and 4.0 %. However, underestimations of clear-sky GEM irradiances were found on the order of  ∼  30–50 % for the 294.12–310.70 nm band and by a factor of  ∼  30 for the 280.11–294.12 nm band. This underestimation can be significant for UV Index determination but would not impact weather forecasting. Corresponding empirical adjustments were applied to the broadband irradiances now giving a correlation coefficient of unity. From these, a least-squares fitting was derived for the calculation of the UV Index. The resultant differences in UV indices from the high-spectral-resolution irradiances and the resultant GEM broadband irradiances are typically within 0.2–0.3 with a root-mean-square relative error in the scatter of  ∼  6.6 % for clear-sky conditions. Similar results are reproduced under cloudy conditions with light to moderate clouds, with a relative error comparable to the clear-sky counterpart; under strong attenuation due to clouds, a substantial increase in the root-mean-square relative error of up to 35 % is observed due to differing cloud radiative transfer models