Extraction of the sea - ice information from NOAA Satellite Imagery
Huang Runheng, Wang Qiang, Jin Zhengang
National Research center For Marine Environment Forecasts
Dahuisi 8 Beijing 100081, PRCC
Abstract
This paper introduces a method to derive the ses-ice information and some remote sensing products from NOAA operational meteorological imagery According to the difference in albedo the criterion to identify sea ice and water was deduced .The sea ice was classified on the basis of the relationship between the thickness of sea-ice and its albedo The concept of distinguishing interval was introduced to overcome the difficulty in concentration calculation of sea-ice and water mixed pixels which results from low resolution of NOAA satellite imagery And the concentration and thickness distributions averaged in the grid was derived .In addition , the apparent displacement of sea-ice was obtained by using of the maximum cross correlation method these quantitative data are useful to monitoring and analysis of sea ice and the initial data of numerical prediction model of sea-ice.
Introduction
The Bohai Sea of China is located between 37
0-41
O N icing takes place region three months every year The sea ice makes a great impact to marine transportations and engineering facilities Mean while the sea ice has an influence on the global energy budget of atmospheric system. Therefore it is necessary that we know the situation of sea ice in the Bohai sea for both economic developing and study of east Asia weather.
The satellite technique is a new useful means for large scale monitoring of sea-ice The study have shown that the Synthetic Aperture Radar is the most ideal instrument for monitoring sea-ice [1] But it is difficult to use it operationally because of the complex technique and large capacity information Taking the advantage of continuous observations, VIS and IR scanning radiometers mounted on the operational meteorological satellites can be used to detect earth surface characteristics though they have low resolution and are influenced from this kind of satellite data. Based on our work of monitoring the sea ice this paper introduces the method to derive sea ice quantitative information from NOAA satellite data Some results have been given.
Orginal satellite data.
Before application of NOAA satellite data the following steps must to be done real time ingesting of AVHRR data pre-processing (it consists of data separations radiance calibration geographical location and solar zenith angle calculation ) Mercator projection transformation and land mark rectification . Then we can get a digital remote sensing image of bohai sea north Huanghai Sea.
There arefive channels on satellite AVHRR (advanced very high resolution radiometer) of which channel 1 and 2 are VIS and near IR channel respectively . They are used to detect solar reflective characteristics of underlying surface. By using these two channel data after calibration and solar angle correction we can get the albedo is possible to distinguish between sea ice and water and to classify the sea ice according to the magnitude of its albedo.
