J. Pepijn Veefkind

Retrieval of aerosol optical depth over land using two‐angle view satellite radiometry during TARFOX

A new aerosol optical depth retrieval algorithm is presented that uses the two-angle view capability of the Along Track Scanning Radiometer 2 (ATSR-2). By combining the two-angle view and the spectral information this so-called dual view algorithm separates between aerosol and surface contributions to the top of the atmosphere radiance. First validation of the dual view algorithm was performed during the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX), which was conducted at the mid-Atlantic coast of the United States in July 1996. The satellite retrieved spectral aerosol optical depth is in good agreement with the aerosol optical depth from ground-based Sun/sky radiometers in three out of four cases. This shows the potential of aerosol retrieval over land using two-angle view satellite radiometry. Copyright 1998 by the American Geophysical Union.

Regional Distribution of Aerosol over Land, Derived from ATSR-2 and GOME

Abstract Two aerosol optical depth retrieval algorithms, using different instruments and different methods, are compared. The first method uses both the directional and the spectral information of the Along Track Scanning Radiometer 2 (ATSR-2) to compute the aerosol optical depth in the visible and near-infrared ranges. The second algorithm uses data in the wavelength range between 0.340 μm and 0.400 μm from the Global Ozone Monitoring Experiment (GOME) to determine the aerosol optical depth in the ultraviolet. Both ATSR-2 and GOME are onboard the ERS-2 satellite. The two methods are applied to data from the ERS-2 overpass over northwestern Europe on 25 July 1995. The retrieved aerosol optical depths compare favorably. Also, there is good comparison between satellite retrievals and ground-based measurements. Optical depth images show a large aerosol plume over Belgium and northern France. Back-trajectories indicate that the sources for this aerosol plume are the industrialized regions in Germany and Belgium.

Testing and improving OMI DOMINO tropospheric NO2 using observations from the DANDELIONS and INTEX‐B validation campaigns

We present a sensitivity analysis of the tropospheric NO2 retrieval from the Ozone Monitoring Instrument (OMI) using measurements from the Dutch Aerosol and Nitrogen Dioxide Experiments for Validation of OMI and SCIAMACHY (DANDELIONS) and Intercontinental Chemical Transport Experiment-B (INTEX-B) campaigns held in 2006. These unique campaigns covered a wide range of pollution conditions and provided detailed information on the vertical distribution of NO2. During the DANDELIONS campaign, tropospheric NO2 profiles were measured with a lidar in a highly polluted region of the Netherlands. During the INTEX-B campaign, NO2 profiles were measured using laser-induced fluorescence onboard an aircraft in a range of meteorological and polluted conditions over the Gulf of Mexico and the east Pacific. We present a comparison of measured profiles with a priori profiles used in the OMI tropospheric NO2 retrieval algorithm. We examine how improvements in surface albedo estimates improve the OMI NO2 retrieval. From these comparisons we find that the absolute average change in tropospheric columns retrieved with measured profiles and improved surface albedos is 23% with a standard deviation of 27% and no trend in the improved being larger or smaller than the original. We show that these changes occur in case studies related to pollution in the southeastern United States and pollution outflow in the Gulf of Mexico. We also examine the effects of using improved Mexico City terrain heights on the OMI NO2 product.

Aerosol optical depth retrieval using ATSR‐2 and AVHRR data during TARFOX

Satellite retrieved aerosol optical properties are compared to aircraft measurements for a case study during the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX). Two satellite instruments are used: the Along Track Scanning Radiometer 2 (ATSR-2) and the advanced very high resolution radiometer (AVHRR). The aerosol optical depth in the mid-visible (0.555 μm) retrieved from the ATSR-2 data agrees within 0.03 with colocated sunphotometer measurements. Also, the spectral behavior of the aerosol optical depth is retrieved accurately. Good correlation is found between aerosol optical depths for AVHRR channel 1 (0.64 μm) and sunphotometer derived values, but the satellite retrieved values are 0.05 to 0.15 lower. The Angstrom wavelength exponent is determined both from the ATSR-2 and the AVHRR data. The ATSR-2 derived Angstrom exponents are in good agreement with the values computed from the sunphotometer data. The Angstrom exponents determined from AVHRR data show very large variations. Both the ATSR-2 and the AVHRR aerosol optical depth images show a large gradient. Vertical profile data of temperature, relative humidity, and particle scattering indicate that this gradient is probably caused by changes in the dry aerosol properties, rather than a change in the relative humidity. Copyright 1999 by the American Geophysical Union.

Technology evolution of the TROPOMI instrument

TROPOMI is the sun backscatter trace gas instrument on ESAs Sentinel-5 precursor satellite. TROPOMI builds upon a rich heritage from similar instruments, the main ones being SCIAMACHY on ESAs ENVISAT and OMI on NASAs AURA satellite. This paper explains how the technology from the heritage instruments evolved, considering high level design aspects such as geometry for Earth and sun viewing, polarization treatment, spectral calibration and whisk- or push-broom concept and leading to the TROPOMI concept. Netherlands parties have played and continue to play an important role in the relevant instruments. TROPOMI is the single payload on the Sentinel-5 precursor mission. The launch in 2015 is meant to bridge the data gap between OMI and SCIAMACHY and the upcoming Sentinel 5 mission. The instrument is funded jointly by the Netherlands Space Office and by ESA1. Dutch Space acts as overall instrument prime.