Heli-borne passive microwave radiometer / camera observations

 


Takeshi Tamura, Kazuki Nakata, and Kay I. Ohshima

(National Institute of Polar Research NiPR and Institute of Low Temperature Science ILTS, Japan)

We will try to acquire helicopter-borne passive-microwave brightness temperatures and thermal infrared (IR) measurements of ice/snow surface temperature by the potable microwave radiometer, and will process them to obtain thin ice thickness distributions (in conjunction with satellite passive microwave polarization ratio data).

Tamura et al. (2006) estimates sea-ice thickness through the heat flux calculation using sea-ice surface temperature estimates from Advanced Very High Resolution Radiometer (AVHRR) data combined with European Centre for Medium-Range Weather Forecasts (ECMWF) data in an Antarctic coastal polynya, and confirms the validity of this method by comparing with independent ice-surface temperature and ice-thickness data obtained during Antarctic Remote Ice Sensing Experiment (ARISE) 2003. Tamura et al. (2007) presents an algorithm that estimates thin ice thickness using Special Sensor Microwave/Imager (SSM/I) data in the Southern Ocean, through a comparison with sea ice thicknesses estimated from the AVHRR data. Although marginal ice zones are also identified as thin ice regions in this algorithm, this paper cannot determine whether these regions are really areas of new ice or whether they result from the reduced ice concentration in the marginal ice zones.

The main object of this study is in-situ validation of ice thickness distribution for thin ice algorithm of satellite passive-microwave and visible/thermal-infrared data (SSM/I, Advanced Microwave Scanning Radiometer 2 (AMSR2), AVHRR, and Moderate Resolution Imaging Spectroradiometer (MODIS)). Results will be validated by the comparison with independent ice surface temperature and ice-thickness data obtained during the cruise.

Portable microwave radiometer (36GHz Horizontal/Vertical), IR sensor (Heitronics KT-19.85-II thermal infrared radiometer), video camera, and portable GPS will be used. The portable microwave radiometer needs to be installed outside under the helicopter. The primary target area is the coastal polynya. The secondary one is the marginal ice zone.

We tried similar heli-borne observation in the SIPEX 2007, but there were three potential problems as follows. First, sensor zenith angle was 45 degrees, i.e. not the same as that of AMSR-E. Second, there was peripheral contamination from the helicopter fuselage. Third, the sensor was single channel only (36 GHz-H). In the SIPEX-2 voyage, we need to overcome these problems. (The third one has been already overcome).

Takeshi TAMURA: tamura.takeshi@nipr.ac.jp.

Kazuki NAKATA: kazuki-nakata@ees.hokudai.ac.jp