Investigation and Analysis on Surface Air Temperature of Sloping Fields of Lianjiang County in 2004/2005 Winter

The technique of inverse temperature of sloping fields as an effective method to prevent the frozen loss is applied to protect these fruit trees in practice. Comparison of results from the traditional methods which are laborious and costly in protecting fruit trees shows that the maximal increasing temperature effect of inverse temperature of sloping fields is excellent. By analyzing the characters of inverse temperature of sloping fields, to select appropriate regions for planting these fruit trees is significant in avoiding or mitigating the freezing harm to them. According to the investigation statistics data of low temperature of 2004 and 2005 in Lianjiang, the effect of low temperatures in sloping fields is studied. The results reveal that the temperature gap (Δt_d), which denotes difference between the low temperature of observation spot in sunlight days (t_d) and the temperature at the bottom of sloping fields, is increasing with the increase of altitude where the hills with relative total altitude gaps (ΔH) are 49 m. Along with the distance close to the top of the sloping fields, Δt_d and t_d are larger and larger. Furthermore, t_d is the highest, and the inverse temperature is prominent where the middle or upper parts of the hills with ΔH are 100 m and relative altitudes ratios, which is the ratio (G) between the relative altitudes gaps of observation spot and ΔH are 0.90 approximately. As a result, based on the investigation in the study, a conclusion can be drawn that the inverse temperature of sloping fields has three characters as follows: in unclouded nights, the inverse temperature phenomenon that the temperature at the top or middle of the sloping fields is higher than at the bottom of the sloping fields exists at the hills. If ΔH≤60 m, the formula can be acquired: Δt_d=b₀+b₁×G (b₁ > 0), which means t_d at the top of the sloping fields is the highest, and the maximum of inverse temperature (ΔT_d) can be calculated from the formula: ΔT_d=b₀+b₁. Else if 300 m > ΔH≥80 m, they reveal that Δt_d can be calculated from the formula: ΔT_d=b₀-b₁×(G-b₂)² (b₁ > 0, b₂ > 0), when G equals b₂, t_d is the highest and ΔT_d equals b₀; considering the hills where the relative altitude gaps are less than 300 m, the location of the ratio (G) where the maximum inverse temperature exists is opposite to ΔH, and with the increase of ΔH, G is descending; ΔT_d is correlated with the amount of push-join (B) (which denotes the ratio between the azimuth of the push-join and 360°) and ΔH of hills. When the B are identical, with the increase of ΔH, ΔT_d is increasing acco rdingly. When ΔH are identical, because of the restrictive condition 1≥B > 0, with the decrease of B, ΔT_d is increasing contrarily.