Publication Date:
2015-01-21
Description:
The complementary relationship (CR) of evapotranspiration allows the estimation of the actual evapotranspiration rate ( ET a ) of the land surface using only routine meteorological data, which is of great importance in the Tibetan Plateau (TP) due to its sparse observation network. With the highest in-situ automatic climate observation system in a typical semi-arid alpine steppe region of the TP, the wind function of Penman was replaced by one based on the Monin-Obukhov Similarity theory for calculating the potential evapotranspiration rate ( ET p ); the Priestley-Taylor coefficient, α , was estimated using observations in wet days; and the slope of the saturation vapor pressure curve was evaluated at an estimate of the wet surface temperature, provided the latter was smaller than the actual air temperature. A symmetric CR was obtained between the observed daily actual and potential evapotranspiration. Local calibration of the parameter value (in this order) is key to obtaining a symmetric CR: α , wet environment air temperature ( T wea ), and wind function. Also, present symmetric CR contradicts previous research that used default parameter values for claiming an asymmetric CR in arid and semi-arid regions of the TP. The effectiveness of estimating the daily ET a via symmetric CR was greatly improved when local calibrations were implemented. At the same time, an asymmetric CR was found between the observed daily ET a and pan evaporation rates ( E pan ), both for D20 above-ground and E601B sunken pans. The daily ET a could also be estimated by coupling the E pan of D20 above-ground and/or E601B sunken pan through CR. The former provided good descriptors for observed ET a , while the latter still tended to overestimate it to some extent. This article is protected by copyright. All rights reserved.
Print ISSN:
0043-1397
Electronic ISSN:
1944-7973
Topics:
Architecture, Civil Engineering, Surveying
,
Geography
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