Toward High Precision XCO2 Retrievals From TanSat Observations: Retrieval Improvement and Validation Against TCCON Measurements.

TanSat is the 1st Chinese carbon dioxide (CO2) measurement satellite, launched in 2016. In this study, the University of Leicester Full Physics (UoL-FP) algorithm is implemented for TanSat nadir mode XCO2 retrievals. We develop a spectrum correction method to reduce the retrieval errors by the online fitting of an 8th order Fourier series. The spectrum-correction model and its a priori parameters are developed by analyzing the solar calibration measurement. This correction provides a significant improvement to the O2 A band retrieval. Accordingly, we extend the previous TanSat single CO2 weak band retrieval to a combined O2 A and CO2 weak band retrieval. A Genetic Algorithm (GA) has been applied to determine the threshold values of post-screening filters. In total, 18.3% of the retrieved data is identified as high quality compared to the original measurements. The same quality control parameters have been used in a footprint independent multiple linear regression bias correction due to the strong correlation with the XCO2 retrieval error. Twenty sites of the Total Column Carbon Observing Network (TCCON) have been selected to validate our new approach for the TanSat XCO2 retrieval. We show that our new approach produces a significant improvement on the XCO2 retrieval accuracy and precision when compared to TCCON with an average bias and RMSE of -0.08 ppm and 1.47 ppm, respectively. The methods used in this study can help to improve the XCO2 retrieval from TanSat and subsequently the Level-2 data production, and hence will be applied in the TanSat operational XCO2 processing.

Recent Northern Hemisphere stratospheric HCl increase due to atmospheric circulation changes.

The abundance of chlorine in the Earth's atmosphere increased considerably during the 1970s to 1990s, following large emissions of anthropogenic long-lived chlorine-containing source gases, notably the chlorofluorocarbons. The chemical inertness of chlorofluorocarbons allows their transport and mixing throughout the troposphere on a global scale, before they reach the stratosphere where they release chlorine atoms that cause ozone depletion. The large ozone loss over Antarctica was the key observation that stimulated the definition and signing in 1987 of the Montreal Protocol, an international treaty establishing a schedule to reduce the production of the major chlorine- and bromine-containing halocarbons. Owing to its implementation, the near-surface total chlorine concentration showed a maximum in 1993, followed by a decrease of half a per cent to one per cent per year, in line with expectations. Remote-sensing data have revealed a peak in stratospheric chlorine after 1996, then a decrease of close to one per cent per year, in agreement with the surface observations of the chlorine source gases and model calculations. Here we present ground-based and satellite data that show a recent and significant increase, at the 2σ level, in hydrogen chloride (HCl), the main stratospheric chlorine reservoir, starting around 2007 in the lower stratosphere of the Northern Hemisphere, in contrast with the ongoing monotonic decrease of near-surface source gases. Using model simulations, we attribute this trend anomaly to a slowdown in the Northern Hemisphere atmospheric circulation, occurring over several consecutive years, transporting more aged air to the lower stratosphere, and characterized by a larger relative conversion of source gases to HCl. This short-term dynamical variability will also affect other stratospheric tracers and needs to be accounted for when studying the evolution of the stratospheric ozone layer.

FTIR spectroscopy of three fundamental bands of H2F+.

The ν1, ν2, and ν3 bands of H2F(+) were observed with a Fourier transform absorption spectroscopic technique in the 3 and 7 µm regions. The ion was produced with a hollow cathode discharge in a F2, He, and H2 gas mixture. A simultaneous analysis of FT data combined with laser spectroscopic data was carried out using the Watson's A-reduced Hamiltonian to determine molecular constants in vibrationally excited states. The effect of the vibration-rotation interaction between the ν1 and ν3 states was found to be small compared with the case of H2O. The vibration-rotation transitions of the ν2 band were first identified and analyzed to obtain molecular constants in the ν2 state, and the band origin was determined to be 1370.5236 (7) cm(-1) with one standard deviation in parentheses. Determined molecular constants can be used to derive the re structure of H2F(+) as re(H-F) = 0.9608(6) Å, ∠e(H-F-H) = 112.2(2)° with the error corresponding to the uncertainty of the assumed vibration rotation constant γ2(a) and the range of the values derived from three pairs of rotational constants.

Effective interaction energy of water dimer at room temperature: an experimental and theoretical study.

Buffer-gas pressure broadening for the nu(1)+nu(3) band of H(2)O at 1.34-1.44 mum for a variety of buffer gases was investigated at room temperature using continuous-wave cavity ring-down spectroscopy. The effective interaction energy of water dimer under room temperature conditions was evaluated from the pressure broadening coefficients for rare gases using Permenter-Seaver's relation. Monte Carlo simulations were performed using ab initio molecular orbital calculations to evaluate the interaction energies for the water dimer at 300 K. In this theoretical calculation, the orientations of the two water molecules were statistically treated.

Terahertz Measurements of Rotational Transitions in Vibrationally Excited States of N2O.

We have measured and analyzed rotational transitions of N2O in the following vibrational states, 01(1e,f)0, 02(0,2e,f)0, 03(1,3e,f)0, 00(0)1, 01(1e,f)1, and 10(0)0. The NAIR terahertz spectrometer was used to measure the frequencies of transitions in the range J = 25 <-- 24 to J = 31 <-- 30 with accuracies of +/-0.020 MHz in most cases. These measurements were fit, along with other microwave and infrared measurements involving the same states, to obtain improved rovibrational term values for those vibrational states. It is shown that the measurements can be fit with fewer constants if both l-type resonance and the Fermi resonance among the levels 00(0)1 and 02(0,2)0 or 01(1)1 and 03(1,3)0 are included in the least-squares fit. These measurements also contribute to improving the N2O wavenumber calibration standards for the infrared region. Copyright 1999 Academic Press.

Terahertz Spectroscopy of the Amidogen Radical, NH2.

The rotational spectrum of the NH2 radical in its &Xtilde;2B1 ground vibronic state was investigated between 614 and 1003 GHz. One hundred fifty-nine newly observed lines (188 hyperfine components) of six rotational transitions with 0

Analysis of the Line Profiles of CH3CN for the J = 5 <-- 4 and J = 6 <-- 5 Rotational Transitions.

The pressure broadening, pressure shift coefficients, and absolute intensities have been obtained for the J = 6 <-- 5 and the J = 5 <-- 4 absorption lines of acetonitrile CH3CN at 110 and 92 GHz, respectively. The absorption line shapes have been directly recorded modulating the radiation beam by an optical chopper. In addition to the self-effects, the foreign-broadening coefficients have also been measured for N2, O2, and Ar. Copyright 1998 Academic Press.

High-J Rotational Transitions of NNO Measured with the NAIR Terahertz Spectrometer

A BWO-based terahertz spectrometer has been constructed and tested by measuring some high-J rotational transitions of NNO in the frequency region from 620 to 730 GHz. The observed line center frequencies confirm the previously reported ones obtained by FTIR spectroscopy. The high sensitivity of the present spectrometer allowed us to record spectra of singly substituted isotopomers, 15NNO, N15NO, NN18O, and NN17O, in natural abundance. The rotational and centrifugal distortion constants have been revised. Copyright 1997 Academic Press. Copyright 1997Academic Press

Fourier Transform Far-Infrared Spectroscopy of the NH2, NHD, and ND2 Radicals

The gas-phase far-infrared absorption spectra of the NH2, NHD, and ND2 radicals have been observed in the 51-366 cm-1 region with a high-resolution Fourier transform spectrometer. The NH2 radical was generated in a multiple-traversal absorption cell by a dc discharge in an NH3 and Ar mixture. A discharge in an NH3, D2, and Ar mixture was used for production of NHD and ND2. The observed spectra with a resolved fine structure were analyzed by Watson's A-reduced Hamiltonian including a spin-rotation interaction term. The rotational and spin-rotation constants were determined to higher order. In the same experiment of NH2, the rotational spectrum of the NH radical was also observed. From the rotational constants, inertia defect Delta and r0 structure were determined, as follows, with one standard deviation in parentheses:NH2ND2r0 (A)1.0245(37)1.0239(19)theta0 (degree)103.34(51)103.33(27)Deltaobs (amuA2)0.049561(4)0.06770(4);Dgr;calc (amuA2)0.0476530.066566 Copyright 1997Academic Press

[Findings from slit lamp and histological examination of the anterior capsule in patients with severe anterior capsular shrinkage and opacities after implantation of intraocular lenses].

Seven pseudophakic patients with severe anterior capsular shrinkage and opacities after continuous curvilinear capsulorhexis as a severe anterior capsular shrinkage group and seven pseudophakic patients without the complication as control group were studied in a slit lamp examination of zonular fibers and anterior vitreus body with an indentation mirror. A light and electron microscopic study of the shrunken anterior capsular edge was performed in one case of the severe anterior capsular shrinkage group. No morphological findings suggesting weakness of zonular fibers such as cleavage or scarceness were observed, but reduction in elasticity of the zonular fibers was surmised and degeneration and liquefacation of the anterior vitreus body was observed in the severe anterior capsular shrinkage group. Histological study revealed several layers of proliferated spindle cells and also abundant extracellular matrix, consisting of collagen types I, III and IV, under the monolayer of lens epithelium attached to the anterior capsule. Spindle cells were epithelial cells and considered to be derived from lens epithelium, because the spindle cells were connected by junctional apparatus, which is a feature of epithelium. Severe anterior capsular shrinkage and opacities were due to low ability of the lens supporting system of zonular fibers and anterior vitreus and severe scarring and shrinkage at the anterior capsular edge.

[A case of primary orbital T-cell lymphoma].

A 46-year-old man presented with eyelid swelling and choroidal folds in the right eye. These symptoms were rapidly exacerbated, but inflammatory findings were not observed. MRI tomography confirmed the presence of an orbital tumor compressing the eyeball. In 67Ga scintigram, a hot spot was recognized only at the right orbital region. This orbital tumor was removed subtotally. It was diagnosed histologically as non-Hodgkin malignant lymphoma (diffuse medium cell-type) and stained on paraffin sections, using monoclonal antibodies immunohistochemically. Anti-LCA, anti-MT-1, anti-UCHL-1 antibodies were positive, and anti-MB-1 antibody was negative. The clinical stage was IE in the Ann-Arbor classification. He was treated by radiation and chemotherapy, but died because of opportunistic infection after 6 months. This is, so far as we know, the first case in Japan diagnosed as primary orbital T-cell type malignant lymphoma immunohistochemically.

Fibronectin synthesis in subretinal membranes of proliferative vitreoretinopathy.

In situ hybridisation and immunohistochemical studies were conducted on six surgically excised subretinal membranes of proliferative vitreoretinopathy to investigate whether displacement of retinal pigment epithelial and glial cells to subretinal membranes was associated with fibronectin production by the subretinal membrane cells. Fibronectin messenger RNA (mRNA) and fibronectin immunoreactivity were observed in some cells in all of the subretinal membranes studied and up to 30% of the cells in individual specimens showed intense labelling for fibronectin mRNA. The results support the concept that the cells in subretinal membranes produce fibronectin. Locally produced fibronectin may play a role in subretinal membrane cohesion, and displacement of retinal pigment epithelial and glial cells from their normal location may induce the cells to manufacture fibronectin. Fibronectin production may be more prominent in migrating subretinal cells.

Variation in epiretinal membrane components with clinical duration of the proliferative tissue.

Immunohistochemical investigations were conducted on surgically excised epiretinal membranes to determine how cellular and extracellular components of proliferative vitreoretinopathy membranes change with time. Specimens of less than four months' duration contained a significantly higher proportion of retinal pigment epithelial cells than later membranes. No association was found between membrane duration and the content of collagen subtypes I to IV and laminin, but 'early' specimens contained significantly more fibronectin than did 'late' membranes. Fibronectin and collagens I, III, and IV showed a variable relationship with glial cells and were most consistently associated with retinal pigment epithelial and fibroblast-like cells. These observations may explain some of the surgical features of epiretinal membranes.

[A case of orbital hemangiopericytoma].

A 38-year old woman presented with severe proptosis in the left eye which had been developing for more than ten years. CT scan revealed a large mass in the left orbit, therefore lateral orbitotomy was performed. The histopathology of this tumor consisted of ovoid to spindle-shaped cells tumor around a sinusoidal vascular component forming staghorn channels. This tumor was diagnosed as a hemangiopericytoma. The prognosis of orbital hemangiopericytoma including clinicopathological aspects are discussed with reference to recent reports.

Cellular components of subretinal membranes in proliferative vitreoretinopathy.

To determine the cellular composition of subretinal membranes in proliferative vitreoretinopathy, surgically excised membranes were studied using electron microscopic and immunohistochemical procedures. Light microscopic immunohistochemistry was found to be superior to conventional electron microscopy as a means of evaluating the relative contributions of retinal pigment epithelium and glia to subretinal membranes. The cells of subretinal membranes chiefly comprised retinal pigment epithelium while glial cells were either absent or contributed only a minor component. It is proposed that the clinical properties of subretinal membranes in proliferative vitreoretinopathy derive from their retinal pigment epithelial cell element.