Abstract
There occurred two field fires near Aerological Observatory, Tateno, Ibaraki Prefecture, in January, 1944. The first grass fire occurred at about 13h 40m and stopped spreading at about 14h. The shape of the burned area resembles to that of the spindle. Its length reaches to 150m, directs from northwest to southeast, and its breadth is abont 20m. The relative humidity was nearly 100% in the morning on that day but diminished rather rapidly from 9h and reached 36% at 13h and 30% at 14h The wind was calm in the morning but it became strong gradually and exceeded 5m at 14h. The burning velocity is 450 metre per hour.
The second field fire spread from northnorthwest to southsoutheast. The burned area reached 450m in length and 140m in breadth. The area was covered with a kind of pampas grass or small pine. The burning occurred at about 14n 50m and ended at about 15h 50m. The burning veloci ty is 540 metre per hour. On this day, relative humidity was more than 90% in the morning but also diminished rather rapidly from 9h and reached 28% at 14h and 27% at 15h. The wind was calm in the morning but gradually became strong and reached to 9.3m at 14h, 11.6m at 15h and 12.3m at 16h.
