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Ground-based observations of 11.072 GHz atmospheric ozone (O3) emission have been made using the Ny-Ålesund Ozone in the Mesosphere Instrument (NAOMI) at the UK Arctic Research Station (latitude 78 ∘ 55 ′ 0 ′′ N, longitude 11 ∘ 55 ′ 59 ′′ E), Spitsbergen. Seasonally averaged O3 vertical profiles in the Arctic polar mesosphere–lower thermosphere region for night-time and twilight conditions in the period 15 August 2017 to 15 March 2020 have been retrieved over the altitude range 62–98 km. NAOMI measurements are compared with corresponding, overlapping observations by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite instrument. The NAOMI and SABER version 2.0 data are binned according to the SABER instrument 60 d yaw cycles into nominal 3-month "winter" (15 December–15 March), "autumn" (15 August–15 November), and "summer" (15 April–15 July) periods. The NAOMI observations show the same year-to-year and seasonal variabilities as the SABER 9.6 µm O3 data. The winter night-time (solar zenith angle, SZA ≥ 110 ∘) and twilight (75 ∘ ≤ SZA ≤ 110 ∘) NAOMI and SABER 9.6 µm O3 volume mixing ratio (VMR) profiles agree to within the measurement uncertainties. However, for autumn twilight conditions the SABER 9.6 µm O3 secondary maximum VMR values are higher than NAOMI over altitudes 88–97 km by 47 % and 59 %, respectively in 2017 and 2018. Comparing the two SABER channels which measure O3 at different wavelengths and use different processing schemes, the 9.6 µm O3 autumn twilight VMR data for the three years 2017–2019 are higher than the corresponding 1.27 µm measurements with the largest difference (58 %) in the 65–95 km altitude range similar to the NAOMI observation. The SABER 9.6 µm O3 summer daytime (SZA < 75 ∘) mesospheric O3 VMR is also consistently higher than the 1.27 µm measurement, confirming previously reported differences between the SABER 9.6 µm channel and measurements of mesospheric O3 by other satellite instruments. [ABSTRACT FROM AUTHOR]

Ground-based observations of 11.072 GHz atmospheric ozone (O3) emission have been made using the Ny-Ã…lesund Ozone in the Mesosphere Instrument (NAOMI) at the UK Arctic Research Station (latitude 78°55’0” N, longitude 11°55’59” E), Spitsbergen. Seasonally-averaged O3 vertical profiles in the Arctic polar mesosphere-lower thermosphere region for night-time and twilight conditions in the period 15 August 2017 to 15 March 2020 have been retrieved over the altitude range 62– 98 km. NAOMI measurements are compared with corresponding, overlapping observations by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite instrument. The NAOMI and SABER data are binned according to the SABER instrument 60-day yaw cycles into 3-month ‘winter’ (15 December–15 March), ‘autumn’ (15 August– 15 November), and ‘summer’ (15 April–15 July) periods. The NAOMI observations show the same year-to-year and seasonal variabilities as the SABER 9.6 μm O3 data. The winter night-time (solar zenith angle, SZA = 110°) and twilight (75° = SZA = 110°) NAOMI and SABER 9.6 &#956m O3 volume mixing ratio (VMR) profiles agree to within the measurement uncertainties. However, for autumn twilight conditions the SABER 9.6 µm O3 secondary maximum VMR values are higher than NAOMI over altitudes 88–97 km by 47% and 59% respectively in 2017 and 2018. Comparing the two SABER channels which measure O3 at different wavelengths and use different processing schemes, the 9.6 &#956m O3 autumn twilight VMR data for the three years 2017–19 are higher than the corresponding 1.27 µm measurements with the largest difference (58%) in the 65–95 km altitude range similar to the NAOMI observation. The SABER 9.6 &#956m O3 summer daytime (SZA < 75°) mesospheric O3 VMR is also consistently higher than the 1.27 µm measurement, confirming previously reported differences between the SABER 9.6 µm channel and measurements of mesospheric O3 by other satellite instruments. [ABSTRACT FROM AUTHOR]

The Ku-band microwave frequencies (10.70–14.25 GHz) overlap emissions from ozone (O3) at 11.072 GHz and hydroxyl radical (OH) at 13.441 GHz. These important chemical species in the polar middle atmosphere respond strongly to high-latitude geomagnetic activity associated with space weather. Atmospheric model calculations predict that energetic electron precipitation (EEP) driven by magnetospheric substorms produces large changes in polar mesospheric O3 and OH. The EEP typically peaks at geomagnetic latitudes of ∼65 ∘ and evolves rapidly with time longitudinally and over the geomagnetic latitude range 60–80 ∘. Previous atmospheric modelling studies have shown that during substorms OH abundance can increase by more than an order of magnitude at 64–84 km and mesospheric O3 losses can exceed 50 %. In this work, an atmospheric simulation and retrieval study has been performed to determine the requirements for passive microwave radiometers capable of measuring diurnal variations in O3 and OH profiles from high-latitude Northern Hemisphere and Antarctic locations to verify model predictions. We show that, for a 11.072 GHz radiometer making 6 h spectral measurements with 10 kHz frequency resolution and root-mean-square baseline noise of 1 mK, O3 could be profiled over 8×10-4 –0.22 hPa (∼98 –58 km) with 10–17 km height resolution and ∼1 ppmv uncertainty. For the equivalent 13.441 GHz measurements with vertical sensor polarisation, OH could be profiled over 3×10-3 –0.29 hPa (∼90 –56 km) with 10–17 km height resolution and ∼3 ppbv uncertainty. The proposed observations would be highly applicable to studies of EEP, atmospheric dynamics, planetary-scale circulation, chemical transport, and the representation of these processes in polar and global climate models. Such observations would provide a relatively low-cost alternative to increasingly sparse satellite measurements of the polar middle atmosphere, extending long-term data records and also providing "ground truth" calibration data. [ABSTRACT FROM AUTHOR]

The Ku-band microwave frequencies (10.70–14.25GHz) overlap emissions from ozone (O3) at 11.072 GHz and hydroxyl radical (OH) at 13.441GHz. These important chemical species in the polar middle atmosphere respond strongly to high latitude geomagnetic activity associated with space weather. Atmospheric model calculations predict that energetic electron precipitation (EEP) driven by magnetospheric sub storms produces large changes in polar mesospheric O3 and OH. The EEP typically peaks at geomagnetic latitudes ~65° and evolves rapidly with time longitudinally and over the geomagnetic latitude range 60°–80°. Previous atmospheric modelling studies have shown that during sub storms OH abundance can increase by more than an order of magnitude at 64–84km and mesospheric O3 losses can exceed 50%. In this work, an atmospheric simulation and retrieval study has been performed to determine the requirements for passive microwave radiometers capable of measuring diurnal variations in O3 and OH profiles from high latitude northern hemisphere and Antarctic locations to verify model predictions. We show that, for a 11.072GHz radiometer making 6h spectral measurements with 10kHz frequency resolution and root mean square baseline noise of 1mK, O3 could be profiled over 8×10−4–0.22hPa (~98–58km) with 10–17km height resolution and ~1ppmv uncertainty. For the equivalent 13.441GHz measurements with vertical sensor polarisation, OH could be profiled over 3×10−3–0.29hPa (~90–56km) with 10–17km height resolution and ~3ppbv uncertainty. The proposed observations would be highly applicable to studies of EEP, atmospheric dynamics, planetary scale circulation, chemical transport, and the representation of these processes in polar and global climate models. Such observations would provide a relatively low cost alternative to increasingly sparse satellite measurements of the polar middle atmosphere, extending long-term data records and also providing ground truth calibration data. [ABSTRACT FROM AUTHOR]

Meteorological and atmospheric models are being extended up to 80 km altitude but there are very few observing techniques that can measure stratospheric–mesospheric winds at altitudes between 20 and 80 km to verify model datasets. Here we demonstrate the feasibility of horizontal wind profile measurements using ground-based passive millimetre-wave spectroradiometric observations of ozone lines centred at 231.28, 249.79, and 249.96 GHz. Vertical profiles of horizontal winds are retrieved from forward and inverse modelling simulations of the line-of-sight Doppler-shifted atmospheric emission lines above Halley station (75°37′ S, 26°14′ W), Antarctica. For a radiometer with a system temperature of 1400 K and 30 kHz spectral resolution observing the ozone 231.28 GHz line we estimate that 12 h zonal and meridional wind profiles could be determined over the altitude range 25–74 km in winter, and 28–66 km in summer. Height-dependent measurement uncertainties are in the range 3–8 m s−1 and vertical resolution  ∼  8–16 km. Under optimum observing conditions at Halley a temporal resolution of 1.5 h for measuring either zonal or meridional winds is possible, reducing to 0.5 h for a radiometer with a 700 K system temperature. Combining observations of the 231.28 GHz ozone line and the 230.54 GHz carbon monoxide line gives additional altitude coverage at 85 ± 12 km. The effects of clear-sky seasonal mean winter/summer conditions, zenith angle of the received atmospheric emission, and spectrometer frequency resolution on the altitude coverage, measurement uncertainty, and height and time resolution of the retrieved wind profiles have been determined. [ABSTRACT FROM AUTHOR]

The far-infrared properties of all five known polymorphic forms of the drug sulfathiazole have been studied by terahertz pulsed spectroscopy and low-frequency Raman spectroscopy. The observed spectra of the different polymorphs are distinctly different. Terahertz pulsed spectroscopy proves to be a rapid and complementary alternative to other physical characterization techniques reported in the literature for distinguishing between the five forms. Variable-temperature measurements (293–473 K) of all polymorphic forms have been performed. The phase transitions observed have been related to thermal analysis data. Form I is the form stable at high temperature of sulfathiazole with a melting point of about 475 K. Form II melts at around 470 K and recrystallizes at higher temperatures to form I. Forms III, IV, and V all convert to form I via a solid–solid phase transition at temperatures below 450 K. The phase transitions can be monitored by terahertz pulsed spectroscopy. Polymorphic impurities of the samples can be detected in the room temperature spectra and their effect on the phase transition behavior can be studied. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95:2486–2498, 2006 [ABSTRACT FROM AUTHOR]

Abstract: In this study for the first time temperature dependent terahertz pulsed spectroscopy was performed on a pharmaceutical drug. The polymorphic conversion process of carbamazepine form III to I was studied at varying temperatures. Furthermore, the solid-state transformation at isothermal conditions below the melting point of carbamazepine was investigated. The ability to study solid-state reactions with terahertz pulsed spectroscopy could be demonstrated. [Copyright &y& Elsevier]

The pressure shifts, δ, of the (0–0) band of the b1Σg+–X3Σg− electronic transition of oxygen (the so-called ‘A-band’) have been measured at room temperature using high-resolution Fourier transform spectroscopy. The rotational dependence of δ has been measured and characterised; the average value of the shift over the whole band is −0.009±0.001 cm−1 atm−1. No significant variation in δ is found for different O2 mixing ratios in N2, and the results presented here are therefore appropriate for high-resolution atmospheric applications using the O2 A-band. [Copyright &y& Elsevier]