21 research outputs found
A geostationary thermal infrared sensor to monitor the lowermost troposphere: O₃ and CO retrieval studies
This paper describes the capabilities of a nadir thermal infrared (TIR) sensor proposed for deployment onboard a geostationary platform to monitor ozone (O3) and carbon monoxide (CO) for air quality (AQ) purposes. To assess the capabilities of this sensor we perform idealized retrieval studies considering typical atmospheric profiles of O3 and CO over Europe with different instrument configuration (signal to noise ratio, SNR, and spectral sampling interval, SSI) using the KOPRA forward model and the KOPRA-fit retrieval scheme. We then select a configuration, referred to as GEO-TIR, optimized for providing information in the lowermost troposphere (LmT; 0–3 km in height). For the GEO-TIR configuration we obtain ~1.5 degrees of freedom for O3 and ~2 for CO at altitudes between 0 and 15 km. The error budget of GEO-TIR, calculated using the principal contributions to the error (namely, temperature, measurement error, smoothing error) shows that information in the LmT can be achieved by GEO-TIR. We also retrieve analogous profiles from another geostationary infrared instrument with SNR and SSI similar to the Meteosat Third Generation Infrared Sounder (MTG-IRS) which is dedicated to numerical weather prediction, referred to as GEO-TIR2. We quantify the added value of GEO-TIR over GEO-TIR2 for a realistic atmosphere, simulated using the chemistry transport model MOCAGE (MOd`ele de Chimie Atmospherique `a Grande Echelle). Results show that GEO-TIR is able to capture well the spatial and temporal variability in the LmT for both O3 and CO. These results also provide evidence of the significant added value in the LmT of GEO-TIR compared to GEO-TIR2 by showing GEO-TIR is closer to MOCAGE than GEO-TIR2 for various statistical parameters (correlation, bias, standard deviation)
The added value of a visible channel to a geostationary thermal infrared instrument to monitor ozone for air quality
Ozone is a tropospheric pollutant and plays a key role in
determining the air quality that affects human wellbeing. In this
study, we compare the capability of two hypothetical grating
spectrometers onboard a geostationary (GEO) satellite to sense ozone
in the lowermost troposphere (surface and the 0–1 km
column). We consider 1 week during the Northern Hemisphere summer
simulated by a chemical transport model, and use the two GEO
instrument configurations to measure ozone concentration (1) in the
thermal infrared (GEO TIR) and (2) in the thermal infrared and the
visible (GEO TIR+VIS). These configurations are compared against
each other, and also against an ozone reference state and a priori
ozone information. In a first approximation, we assume clear sky
conditions neglecting the influence of aerosols and clouds. A number
of statistical tests are used to assess the performance of the two
GEO configurations. We consider land and sea pixels and whether
differences between the two in the performance are
significant. Results show that the GEO TIR+VIS configuration
provides a better representation of the ozone field both for surface
ozone and the 0–1 km ozone column during the daytime
especially over land
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