Studies on the micrometeorology in the sloping orchards. 1

Abstract

1. The curve for daily variation of the amount of insolation on the southern and northern slopes is symmetrical to the noon line, regardless of inclination and month. The largest of the amont of insolation appears at noon. But in June, its amount on the northern slope is smallest at noon, taking the form of a concave in the case of inclinations more than 55. if the inclination of the slope becomes steeper, the sunshine exists only in the early morning and in the late evening. On the southern slope, in the warm season, the duration of sunshine decreases as the slope inclination increases; in the cold season, the times of sunrise and sunset become similar for all slope inclinations as it is on the flat surface. 2. On each slope situated in southwest, west and northwest (southeast, east and northeast), the times of sunset (sunrise) is the same as it is on the flat surface, while, as the slope inclination increases, that of sunrise (sunset) comes to be later (earlier) than that on the flat surface. The time when the amount of insolation becomes greatest, comes to be later (earlier) than on the flat surface, as the slope inclination increases. Therefore, these slopes are favoured with the amount of insolation in the afternoon (in the morning). 3. The relation between the inclination of the slope and the amount of insolation is as follows: In the cold season: The amount of insolation on the northern and northwestern (northeastern) slopes is smaller than on the flat surface, and decreases as the slope inclination increases. On the southern and southwestern (southeastern) slopes, its amount is greater than on the flat surface, the greatest amount is on that slope which is perpendicular to the sun. So it is greatest at the inclination near 60°. The amount of insolation on the western (eastern) slope lies about halfway between northwest (northeast) and southwest (southeast) slopes. In the warm season: The amount of insolation is less on every inclination in all directions than on the flat surface and decreases as the inclination of the slope increases. 4. As to the yearly variation of the amount of insolation, the amount on the northern, northwestern (northeastern) and western (eastern) slopes is greatest at the summer solstice and least at the winter solstice throughout every inclination in all directions. Its amount on the southern slope is largest at the summer solstice and least at the winter solstice when the slope inclination is small; as the slope inclination increases, two maxima come to appear before and after the summer solstice. As the slope inclination increases still more, the amount of insolation becomes largest at the winter solstice and least at the summer solstice as seen at 90° inclination. 5. In the cold season, the daily total amount of insolation, is largest on the southern slope throughout every inclination in all directions, the amount of insolation becomes less in the following order, southwestern (southeastern), western (eastern) and northwestern (northeastern) slopes, and the northern slope takes the least. In the warm season the southern slope takes the least and the western (eastern) slope takes the largest. 6. The yearly total amount of insolation, is least on the northern slope, throughout each inclination of the slope. The southern slope takes the largest amount up to 70° inclination, but over the degrees, the largest amount appears towards the southwestern and southeastern slopes. Thus, as the inclination of the slope increases, the distribution of the amount of insolation takes the form of a heart, and it becomes gradually flat as the inclination increases further. 7. The amount of insolation received by a trunk of a plant is larger on its northern side than on its southern one, in the warm season about June or July. In the cold season, the northern side of a trunk takes no sunshine all the day