A feasibility study for the monitoring of diurnal variations of the tropospheric NO2 over Tokyo from a geostationary satellite
Abstract
The long-term evolution of tropospheric NO2 has been observed by space-borne sensors such as GOME, SCIAMACHY, OMI and GOME-2 since the mid-1990s. However, these measurements were always taken at fixed local times as the sun-synchronous orbits are used. Because tropospheric NO2 shows substantial diurnal variations due to variations in the photochemistry, meteorology and surface emissions, measurements at various local times are needed to understand the NO2 distribution and its related chemistry and sources. Measurements from a geostationary orbit provide observations of the diurnal variation, because this orbit enables continuous measurements throughout the day. On the other hand, the requirements for sensor specification in a geostationary orbit become much more severe than for low-earth orbit sensors due to the weaker intensity of light coming from the Earth's atmosphere. In this context, we have conducted a feasibility study for the geostationary monitoring of diurnal variations of the tropospheric NO2 over Tokyo. Using NO2 fields from a chemical transport model, synthetic spectra were created by a radiative transfer model, SCIATRAN, for various geometric and seasonal scenarios. We then performed a Differential Optical Absorption Spectroscopy analysis to retrieve NO2 slant column densities (SCDs) and to estimate the precision of the retrieved SCDs. The results of the retrieval simulation showed that we need signal-to-noise ratios (SNR) better than 500 to detect the diurnal variation of the NO2 SCD (~1E16 /cm2). The simulation also showed that the precision of the SCDs would be 2-6% with the sensor specification (spatial resolution of 5km and time resolution of 1hr) as currently discussed for geostationary instruments of GMAP-ASIA (Geostationary Mission for Meteorology and Air Pollution) in Japan. We also discuss the effect of uncertainties in surface reflectivity (albedo) on the retrieval.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.A53D0268N
- Keywords:
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- 0345 ATMOSPHERIC COMPOSITION AND STRUCTURE / Pollution: urban and regional;
- 0365 ATMOSPHERIC COMPOSITION AND STRUCTURE / Troposphere: composition and chemistry;
- 0368 ATMOSPHERIC COMPOSITION AND STRUCTURE / Troposphere: constituent transport and chemistry;
- 0394 ATMOSPHERIC COMPOSITION AND STRUCTURE / Instruments and techniques