Dynamic characteristics and influencing factors of actual evapotranspiration in cold wetland
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Abstract:
In order to understand the actual evapotranspiration ( ETa ) process in cold wetland and to make effective management of water resources, we analyzed the variation of ETa in Harbin Jinhewan wetland and its influencing factors under different time scales based on the measured dat a of eddy covariance system from August 2015 to July 2016. The annual ETa was 660mm during the study period, and the maximum daily ETa was up to 8. 1mm/ d. The ETa was the highest in summer ( 3.4 mm/ d) , second highest in spring ( 2.3 mm/ d) and autumn ( 1.4 mm/ d) , and was the lowest and stable in winter ( 0.1 mm/ d) . The crop coefficient(Kc) increased from 0.95 to about 1.18 in May ( plantg rowing period) .The Kc was between 1.05-1. 18 from June to the middle of August (plant stabilizing period), and it decreased from 1.05 to 0.85 during late August to September (plant withering period) . The main meteorological factors affecting the ETa were net radiation and vapor pressure deficit. The correlations between ETa and meteorological factors were different at differenttime scales. The correlations of net radiation and water vaporpr essure deficit with ETa were significant at both scales, but net radiation was more correlated to ETa at the 30min scale. The correlation between temperature and ETa was basically consistent at both scales. High temperature would promote ETa and low temperature would suppress ETa. At the daily scale, the correlation between air humidity and ETa was obvious in autumn and winter; at the 30 min scale, the correlation was o bvious in spring and winter. The correlation between wind speed and ETa was only obvio us in summer and autumn at the 30 min scale.