| This research explored the heat fluxes and soil thermal regime (solar spectrum, net radiation, soil heat flux et al) over the Changwu Tableland by Eddy Covariance, Large Aperture and the meteorological data. The objective of this research gave meaningfull suggestion with energy balance and water circle. The result of this study is as follows:(1) The value of sensible heat flux in summer is higher than that of in any other seasons; the value of potential heat flux in spring and summer is a little higher than that in fall season, and much higher than that in the winter. In the short time, the daily change of potential heat flux in the winter is relatively smooth when comparing to that in the spring and winter. Further, In the summer that is most violent. Under cloudy days, the daily change of the sensible heat flux and potential heat flux was the same . Under the sunny day, When nearby 13:00, the value of sensible heat flux was higher than that of the potential heat flux, but it was also similar in other stages.(2) In the growing season of winter wheat, the footprint in the wintering period and green stage was much larger, it was decreased in the jointing stage. Under the P=50%, P=70%, P=90%, the sensor can catch the most distance respectively was: 76.7, 67.4, 12.68, 11.44, 10.53m;95.9, 85.4, 16.76, 15.6,14.94m;130, 118.6, 26.12, 26.4, 27.81m。(3) The value of sensible heat flux measured by LAS is less than that measured by EC. Daily changes appeared as a single-peak curve and the maximum value was 230w/m2. The transformation of net radiation into heat needed about 2 hours.(4) The solar radiation in Changwu Tableland was nuch stronger between 450 and 650nm. The strongest radiation was in 476nm, up to 1900Mw/m2. In 875nm, there was very deep trough. Daily changes appeared as a single-peak curve at 13:30, the solar radiation showed the maximum value.(5) The results showed that the range of soil temperature reduced with the depth of wheat field on the Tableland of Loess Plateau. The change of soil temperature gradient showed a singular-peak curve. Soil temperature gradient, soil heat flux, and soil albedo showed a strong daily regime;There was no linear relationship between net radiation and soil heat flux .The radiation intensity of one day was consistent with difference heat flux, and the delay of soil heat flux was not obvious. When radiation increasing, the modeling curve between net radiation and heat flux, R12=0.766 less than R22=0.799 when radiation continuously reduced. The correlation coefficient of farmland ecosystem between net radiation and soil heat flux is much higher than that of forest land, and which is lower than that of grassland and sparse shrubs.(6) The minimum temperature of every layer presented on Feb. the maximum temperature of 2, 10 and 20 cm appeared on Jul. and that of 40, 80 cm appeared on Aug. The frozen layer in the winter can come to 30 cm; The temperature gratitude changed its transmission direction between Feb. and Mar. and that between Aug. and Sept. The mean temperature gratitude of 2-10 cm layer was more higher than that of 2-80 cm when the heat conducted into the deeper layer, it was up to the maximum value ranging from May to Jun, however, when the heat conducted to top layer, the mean temperature gratitude of 2-10 cm layer was more lower than that of 2-80 cm, both layers were up to the maximum on end of Nov. The soil albedo was up to the maximum 0.66 on Jan. there were not significant differences between Mar. and Aug. It declined to the minimum value 0.14 on Sept. and increased significantly from Oct. to Dec. |
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