Table 2. Basic statistics for climatic variables.

	Annual mean temperature (°C)	Annual mean solar radiation (MJ/day)	Annual total sunshine duration (h)	Annual meaneffective daylength at 1000 lx(h/day)	Annual meaneffective daylength at 4000 lx(h/day)	Annual meaneffective daylength at 10000 lx(h/day)
Maximum	22.3(Okinawa)	14.00(Kochi)	2104(Kochi)	11.70(Kochi)	10.80(Kochi)	9.03(Kochi)
Minimum	7.1(Hokkaido)	11.70(Niigata)	1570(Niigata)	11.60(Niigata)	10.42(Akita)	8.05(Akita)
Mean	14.1	12.78	1861	11.65	10.63	8.57
Median	14.6	12.80	1883	11.65	10.63	8.60