Teruo Aoki

Cross-calibration of satellite sensors over snow fields

Besides pre-launch and on-board calibration, the method of vicariously calibrating space sensors became a reliable tool for space sensor calibration. One possibility of vicarious calibration is to inter-calibrate sensors aboard different satellite platforms directly. This leads to a better understanding of differences in global data sets produced these sensors. Recently, ADEOS-2 was launched (14 Dec 2002) successfully and the optical sensor GLI onboard the ADEOS-2 satellite became operational from April 2003. In a first calibration check-up, the radiometric performance of GLI was compared relatively to that of other sensors on different satellites with different calibration backgrounds. As calibration site a large snowfield near Barrow (Alaska, USA) was used, where space sensors in polar orbits view the same ground target on the same day with small differences in the local crossing times. This is why GLI, MODIS (terra, aqua), SeaWiFS, AHVRR (N16, N17) and MERIS data sets were selected for the following clear-sky condition days: April 14th and 26th 2003. At the same time ground-truth experiments, e.g., measurements of ground reflectance, BRDF, aerosol optical thickness (AOT), were carried out. Thereinafter, top-of-atmosphere (TOA) radiance/reflectance was forward calculated by means of radiative transfer code (RTC) for each sensor, each band and each day. Finally, the vicariously retrieved TOA reflectance was compared to TOA sensor L1B data. As a result GLI’s performance is encouraging at this early time of the mission. GLI and the other 6 sensors deliver similar sensor output in the range of about 5-7% around the expected vicariously calculated TOA signal.

The International Radiation Symposium 2016

The 2016 International Radiation Symposium, a joint venture between the IRC (International Radiation Commission) and IAMAS (International Association of Meteorology and Atmospheric Sciences), took place at the University of Auckland from April 16th to 22nd. The wide scope of atmospheric radiation research was apparent, with focuses ranging from the planetary to the particulate, and from the hourly to the millennial. The symposium, which was attended by 268 scientists from 28 countries, provided an excellent forum for the exchange of knowledge between modelers and experimentalists. (Fig. 1) Two awards were presented by the IRC: the Young Scientist Award, to Zhibo ZHANG (Fig. 2), and the Gold Medal Award, to Teruyuki NAKAJIMA (Fig. 3). Both gave wellreceived keynote talks after accepting their awards at the conference dinner at the Auckland Museum.