We developed a method for determining nationwide 1 km-grid square values of daily mean, maximum and minimum air temperature, and daily precipitation in Japan. The data were obtained using the JMA's nationwide observations, numerical forecasts, and climatic normal values. RMSE values for these elements in the past were 0.66 ℃, 0.98 ℃, 1.10 ℃, and 5.9 mm/day, while those for one-day future were 1.18 ℃, 1.65 ℃, 2.00 ℃, and 11.0 mm/day, respectively. The improvement in accuracy by introducing the forecasts was recognized even for values six-day future, though errors tended to increase with forecast range. The data are intended for use in the management of currently growing crops with a combination of crop models.
We designed an inter-latitudinal temperature gradient chamber (TGC) experiment to obtain data for analyzing the effects of global warming on paddy rice production in Japan. TGC experiments were carried out at three sites of different latitudes: Sapporo, Morioka and Kumamoto. The TGCs at each site were controlled to maintain an air temperature gradient of 2 with water temperature treatment (heated 2 and unheated, except for Kumamoto) to grow eight rice varieties: Nikomaru, Reiho, Nipponbare, Koshihikari, Hitomebore, Sasanishiki, Akitakomachi and Kirara397. The higher temperature accelerated the heading date of all varieties in Sapporo and Morioka, but not Kumamoto. The relationship between the cumulative air temperature from the 5th leaf stage to the heading stage (CAT5H) and the temperature gradient in the TGC at each site suggested that the difference in CAT5H among the regions was attributable to day length, and the fact that Kirara397, Akitakomachi, Sasanishiki and Hitomebore have little sensitivity to the photoperiod, whereas Reiho, Nikomaru and Koshihikari exhibit a greater sensitivity to the photoperiod, although the critical day length of Koshihikari was longer than that of the other two varieties. The development of the rice plant depends on both air and water temperatures and the degree of dependency is based on the type of maturity. These results confirm that the effect of global warming on the development of the rice plant and paddy rice production will differ by region (latitude) and variety. Thus, inter-latitudinal TGC experiments are useful for gathering data to estimate the effects of global warming on paddy rice production.
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