Abstract
Passive microwave sensor AMSR2 was successfully launched by JAXA in May 2012 onboard GCOM-W1 satellite. The antenna diameter of AMSR2 is 2.0 m which provide highest spatial resolution as a passive microwave sensor in space. This paper describes about the outline of sea ice monitoring with AMSR2 and introduces some of the initial result acquired from AMSR2 observation. The sea ice concentration images derived from AMSR2 data allow us to see more detailed sea ice distributions compared with those of SSM/I. The sea ice concentration estimated from AMSR2 data were evaluated using MODIS data observed from Aqua satellite within few minutes after AMSR2 observation from GCOM-W1. The procedures of the evaluation are as follows. Firstly, MODIS ch2 data were binarized to discriminate sea ice from open water and sea ice concentration of each pixel size of AMSR2 were calculated. Then the AMSR2 sea ice concentration of each pixel was compared with the sea ice concentration calculated from MODIS data. The result suggested the possibility of estimating sea ice concentration from AMSR2 data with less than 10 % error under good weather condition. On 16 September 2012, the minimum sea ice extent in Northern Hemisphere was recorded by AMSR2 in the history of passive microwave sensor observation from space. The annual sea ice extent graph produced from the historical passive microwave sensor data strongly suggested the trend of sea ice extent reduction in the Northern Hemisphere. The importance of sea ice monitoring with AMSR2 is increasing.
