Paddy rice is a tropical crop that can now be cultivated in areas as far north as Hokkaido that have cool climates, as human beings have succeeded in improving rice varieties.

Because rice was originally a tropical crop, however, in areas such as Hokkaido and Tohoku where climatic conditions are sometimes severe, rice will suffer cold weather damage. In 1993, Japan was hit with cold weather damage that far exceeded that of any year in recent memory, and the damage to yields including total loss of crops was extensive along the Pacific side of the Tohoku Region and in Hokkaido. Because the previous year's crop had also suffered cold weather damage, Japan's rice stocks fell to low levels. The government responded with emergency rice imports, resulting in a sharp rise in the price of rice on international markets.

While it is possible to understand the level of harm from cold weather damage from statistics complied by municipal government units, it is difficult to obtain area data at a more detailed level. This situation makes it critical to develop technology to understand cold damage by the use of remote sensing data.

Years with cold weather damage are periods of unseasonable weather, making the prospects for gathering sufficient optical sensor data somewhat limited. Therefore the development of a technique that does not involve the types of optical data used - in other words, a technique for using data that is not always highly accurate - is required.

For 1993, the year hit by cold weather damage, there is very little satellite optical data for Hokkaido's paddy rice zone during the rice-growing period because clouds interrupted observations.

The sole existing data is MOS-1/MESSR data from the observation on September 14, 1993. Compared to LANDSAT/TM data, this MESSR data with four bands and 50m ground resolution is inferior in both the number of bands and in ground resolution. Moreover the recorded digital numbers are distributed in low range, and the signal-to-noise ratio also is not good.

We attempted to extract paddy fields from the September 14, 1993 MESSR data and use the mean value of each municipality to discover a high correlation between the MESSR band 2 (red) data and crop yields; by creating a paddy rice yield distribution map for central Hokkaido in 1993, we sought to clarify the unique characteristics of the cold weather damage.

For 1993, a year in which crops failed to ripen, the brightness value of MESSR band 2 corresponding to chlorophyll absorption wavelengths showed a high correlation with yield. it is possible to use a logistic function to show the relationship between the MESSR band-2 brightness value and the yield.

We used this function to create a yield distribution map with a 500m mesh of the paddy rice zone in the central region of Hokkaido.

The analysis showed the effectiveness of satellite data during period of extensive cold weather damage that had a significant social impact.

In addition, the usefulness of Japan's domestically manufactured satellite MOS-1 was reconfirmed.