High-resolution Atmospheric Spectra Research Articles

Retrieval of Carbon Monoxide Total Column in the Atmosphere from High Resolution Atmospheric Spectra

Carbon monoxide (CO) is a marker of the atmospheric pollution caused by fires and combustion engine emissions. The regular monitoring of the CO content in the atmosphere is needed to control air quality. In this work, the results of CO atmospheric total column retrievals from the solar spectra recorded by Fourier -transform spectrometers at the St. Petersburg (59.88° N, 29.83° E) and Kourovka (57.038° N, 59.545° E) stations are presented. The impact of differences in CO absorption line parameters in modern spectroscopic databases on the accuracy of the CO atmospheric total column retrieved from high resolution spectra is estimated.

Retrieval of carbon monoxide content in the atmosphere from high resolution atmospheric spectra

Retrieval of carbon monoxide content in the atmosphere from high resolution atmospheric spectra

Revision of spectral parameters for the B- and γ-bands of oxygen and their validation against atmospheric spectra

Until recently the B ( b 1Σ g + ( v=1)− X 3Σ g − ( v=0)) and γ ( b 1Σ g + ( v=2)− X 3Σ g − ( v=0)) bands of oxygen in the visible region had not been used extensively in satellite remote sensing of the atmosphere. These bands roughly cover the regions around 14,527 and 15,904 cm −1, respectively (0.69 and 0.63 μm). However, these bands (in particular the B-band) are now being increasingly considered for future satellite missions. In this light, it is important to make sure that the reference spectroscopic parameters allow accurate retrieval of important physical characteristics from the atmospheric spectra. The spectroscopic parameters currently given for these bands in the HITRAN2008 spectroscopic database were tested against high-resolution atmospheric spectra measured with solar-pointing Fourier transform spectrometers at Park Falls, Wisconsin (B-band) and Kitt Peak, Arizona ( γ-band). It was found that the current HITRAN parameters cannot produce satisfactory fits of the observed spectra. In order to improve the database we have collected the best available measured line positions that involve the b 1Σ g + ( v=1 and v=2) states for the three most abundant isotopologues of oxygen and performed a combined fit to obtain a consistent set of spectroscopic constants. These constants were then used to calculate the line positions. A careful review of the available intensity and line-shape measurements was also carried out, and new parameters were derived based on that review. In particular, line shift parameters, that were not previously available, were introduced. The new data have been validated using the high-resolution atmospheric spectra measured with the Fourier transform spectrometers at Park Falls, Wisconsin (B-band) and Kitt Peak, Arizona ( γ-band) and have yielded substantial improvement. In addition, we report the first direct observation and analysis of the 16O 18O lines in the γ-band.

Study of molecular line parameters down to very low temperature

The impact of precise spectroscopic measurements on the P(9) multiplet in the ν3 band of 12CH4, obtained using a newly developed cold Herriott cell coupled with a tunable diode laser spectrometer, is examined in the context of remote sensing of methane in the atmosphere. More specifically, the influence of the air-broadening temperature dependence, of line narrowing and of line-mixing effects is assessed when fitting high resolution atmospheric spectra recorded from a balloon in the solar occultation mode. This is achieved by considering residuals and retrieved methane volume mixing ratio profiles. By combining data from previous studies together with new measurements, the expression for the temperature dependence of the broadening coefficient has been revisited. It is shown that a correcting factor applied to the usual law gives better results, when considering all the available measurements from room temperature down to about 10–20 K, as compared to the usual expression of the width versus temperature. These results clearly demonstrate that collision broadening is more sensitive to long-range attractive forces when the temperature is decreased.

Operational trace gas retrieval algorithm for the Infrared Atmospheric Sounding Interferometer

The Infrared Atmospheric Sounding Interferometer (IASI) is a nadir‐viewing remote sensor due for launch on board the European Metop satellites (to be launched in 2005, 2010, and 2015). It is dedicated to the study of the troposphere and the lower stratosphere to support operational meteorology as well as atmospheric chemistry and climate studies. For this purpose, it will record high resolution atmospheric spectra in the thermal infrared, allowing the measurement of several infrared absorbing species. This paper describes the clear‐sky retrieval scheme developed in the framework of the preparation of the IASI mission for the operational, near real time, retrieval of O3, CH4, and CO concentrations. It includes the inversion module, based on a neural network approach, as well as an error analysis module. The studies undertaken on test simulations have shown that a performance of the order of 1.5%, 2%, and 5% for the retrieval of total columns of O3, CH4, and CO, respectively, can be achieved, and of the order of 28%, 15%, and 9% for the retrieval of partial columns of O3 between the surface and 6, 12, and 16 km high, respectively. The efficiency of the algorithm is demonstrated on the atmospheric measurements provided by the Interferometric Monitor for Greenhouse Gases (IMG)/ADEOS, allowing to obtain the first remote‐sensing simultaneous distributions of ozone and its two precursors, CO and CH4.

First satellite ozone distributions retrieved from nadir high‐resolution infrared spectra

The Interferometric Monitor for Greenhouse Gases (IMG) on board the Japanese ADEOS platform provided the first high resolution atmospheric spectra allowing the simultaneous measurement of several IR absorbing species, including ozone. The paper describes the retrieval of total column ozone fields from nadir radiances, using an inversion algorithm developed for the Infrared Atmospheric Sounding Interferometer (IASI). The accuracy and sensitivity of the retrieved concentrations are assessed. The global distributions obtained from the available IMG/ADEOS Level 1C data are shown to be in good agreement with the TOMS/ADEOS (Total Ozone Mapping Spectrometer) Level 2 measurements.

Retrieval of CO columns from IMG/ADEOS spectra

The high-resolution atmospheric spectra recorded by the Interferometric Monitor for Greenhouse gases instrument on the ADvanced Earth Observing System (IMG/ADEOS) in June, 1997, were analyzed by two different and complementary inversion algorithms to retrieve CO total columns. Spectral fits of high quality were obtained using a global fit algorithm on selected cloud-free measurements. Global distribution maps of CO obtained using a fast neural network retrieval algorithm are compared to the results provided by current chemistry-transport models. These studies highlight the need for complementary information (temperature, emissivity, instrumental function, and cloud content) to retrieve accurate CO vertical columns.

Nighttime and daytime variation of atmospheric NO2 from ground‐based infrared measurements

During the period February 28 to March 2, 1986, 19 high resolution atmospheric spectra have been recorded during the night using the moon or during the day using the sun as a source with the Fourier transform spectrometer at the McMath Solar telescope on Kitt Peak. The NO2 absorption peak located at 2914.65 cm−1 has been used to derive from the spectra the total vertical column densities of atmospheric NO2. A rather rapid decrease of the NO2 amount during the night has been observed and its daytime increase from sunrise to sunset has been confirmed. A comparison with the predictions of a photochemical model is given.

Daytime variation of atmospheric NO2 from ground based infrared measurements

During the day of September 20, 1982 16 high resolution atmospheric spectra were recorded at regularly spaced time intervals from sunrise to sunset using the Fourier transform spectrometer of the McMath solar telescope of Kitt Peak National Observatory. Using well isolated NO2 absorption peaks appearing in the 2850‐2950 cm−1 region, it has been possible to measure precisely the daytime variation of the NO2 vertical column density. A rapid increase from sunrise to noon is observed followed by a slower increase in the afternoon. A comparison with the predictions of a photochemical model is given.

Airborne infra-red measurements at the Royal Aircraft Establishment∗

Infra-red radiometric and spectroscopic equipment fitted in a Comet aircraft for use up to 14,000 m altitude is described. Typical results are given as examples of the use of this installation. These include emission from towed pyrotechnic targets, infra-red reflection of sunlight from cloud tops, horizontal transmission measurements and high resolution atmospheric spectra out to 25μ using liquid helium cooled detectors.