The Effects on Micrometeorology of Dense Vegetation at High Temperature with Sprinkling

Studies of effects on micrometeorology with sprinkling (II)

Abstract

The effects on micrometeorology of dense vegetation sprinkling at high temperature in summer are discussed on the basis of field experimental results.
The effects were expressed in terms of differences or rates based on values of a control field.
Generally the values of the sprinkling field differed from those of the control field before the first sprinkling in a day, because of the remaining water in the soil from the day before.
The effects were compared with those in the case of sparse vegetation described in the previous paper.
The main results obtained are as follows:
1) The effects on air temperature at heights of 1.5, 1, 0.3m were-0.1, -0. 1, -0.9°C before sprinkling, -2.7, -3.4, -3. 6°C during sprinkling and-0.4, -0.6, -1.8°C after sprinkling respectively. In comparison-with the effects in the case of sparse vegetation, the effects are much the same at a height of 1 m above the ground, slight at a height of 0.1m above the canopy top and small inside the canopy.
2) The effect on canopy surface temperature was noted only during sprinkling and was-2.3°C. This is nearly equal to that in the case of sparse vegetation.
3) The effects on relative humidity at height of 1.5, 1, 0.3m were+1.6, +2.3, +5. 8% before sprinkling, +13.0, +17.2, +20.4% during sprinkling and+2.4, +3.6, +12.8% after sprinkling respectively. In comparison with the effects in the case of sparse vegetation, the effects are much the same at a height of 1m above the ground, slight at a height of 0.1m above the canopy top and small inside the canopy.
4) The effects on upward longwave radiation were?0. 6% before sprinkling, -3.5% during sprinkling and-0.4% after sprinkling. These are smaller than the effects in the case of sparse vegetation.
5) The effects on net radiation were-1.8% before sprinkling, +8.9% during sprinkling and +2.7% after sprinkling. The effects during sprinkling were greater than those in the case of sparse vegetation.
6) The effects on latent heat flux were +1% before sprinkling, +48% during sprinkling and +11% after sprinkling. The effects during sprinkling were somewhat larger than those in the case of sparse vegetation.
7) On regard to dense and sparse vegetations, the ratio of biomass derived from variation in the canopy surface temperature, was equal to the ratio of vegetation indices.
8) Canopy surface temperature excess induced theoretically was equal to the value observed. Thus the constant difference between theory and observation in sparse vegetation is due to the bare ground between canopies.