Calibration‐free complementary relationship estimates terrestrial evapotranspiration globally

2021 ◽  
Author(s):  
Ning Ma ◽  
Jozsef Szilagyi ◽  
Yongqiang Zhang
Keyword(s):  
Complementary Relationship ◽  
Calibration Free

scholarly journals Water Balance Backward: Estimation of Annual Watershed Precipitation and Its Long-Term Trend with the Help of the Calibration-Free Generalized Complementary Relationship of Evaporation

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1775
Author(s):  
Jozsef Szilagyi
Keyword(s):  
Water Balance ◽  
Mean Squared Error ◽  
Linear Trend ◽  
Free Water ◽  
The United States ◽  
Discharge Data ◽  
Complementary Relationship ◽  
Stream Discharge ◽  
Calibration Free

Watershed-scale annual evapotranspiration (ET) is routinely estimated by a simplified water balance as the difference in catchment precipitation (P) and stream discharge (Q). With recent developments in ET estimation by the calibration-free generalized complementary relationship, the water balance equation is employed to estimate watershed/basin P at an annual scale as ET + Q on the United States (US) Geological Survey’s Hydrologic Unit Code (HUC) 2- and 6-level watersheds over the 1979–2015 period. On the HUC2 level, mean annual PRISM P was estimated with a correlation coefficient (R) of 0.99, relative bias (RB) of zero, root-mean-squared-error (RMSE) of 54 mm yr−1, ratio of standard deviations (RS) of 1.08, and Nash–Sutcliffe efficiency (NSE) of 0.98. On the HUC6 level, R, RS, and NSE hardly changed, RB remained zero, while RMSE increased to 90 mm yr−1. Even the long-term linear trend values were found to be fairly consistent between observed and estimated values with R = 0.97 (0.81), RMSE = 0.63 (1.63) mm yr−1, RS = 0.99 (1.05), NSE = 0.92 (0.59) on the HUC2 and HUC6 (in parentheses) levels. This calibration-free water-balance method demonstrates that annual watershed precipitation can be estimated with an acceptable accuracy from standard atmospheric/radiation and stream discharge data.

The calibration-free complementary relationship (CR) approach aids large-scale ET estimation

2020 ◽  
Author(s):  
Ning Ma ◽  
Jozsef Szilagyi ◽  
Yinsheng Zhang
Keyword(s):  
Remote Sensing ◽  
Water Balance ◽  
Eddy Covariance ◽  
Land Surface ◽  
Large Scale ◽  
Relative Bias ◽  
Dew Point ◽  
Surface Model ◽  
Complementary Relationship ◽  
Calibration Free

<p>Having recognized the limitations in spatial representativeness and/or temporal coverage of (i) current ground evapotranspiration (ET<sub>a</sub>) observations, and; (ii) land surface model (LSM) and remote sensing (RS) based ET<sub>a</sub> estimates due to uncertainties in soil and vegetation parameters, a calibration-free nonlinear complementary relationship (CR) model is employed with inputs of air and dew-point temperature, wind speed, and net radiation to estimate monthly ET<sub>a</sub> over conterminous United States during 1979–2015. Similar estimates of three land surface models (Noah, VIC, Mosaic), two reanalysis products (NCEP-II, ERA-Interim), two remote-sensing-based (GLEAM, PML) algorithms, and the spatially upscaled eddy-covariance ET<sub>a</sub> measurements of FLUXNET-MTE plus this new result from CR were validated against water-balance-derived results. We found that the CR outperforms all other methods in the multiyear mean annual HUC2-averaged ET<sub>a</sub> estimates with RMSE = 51 mm yr<sup>−1</sup>, R = 0.98, relative bias of −1 %, and NSE = 0.94, respectively. Inclusion of the GRACE data into the annual water balances for the considerably shorter 2003–2015 period does not have much effect on model performance. Besides, the CR outperforms all other models for the linear trends in annual ET rates over the HUC2 basins. Over the significantly smaller HUC6 basins where the water-balance validation is more uncertain, the CR still outperforms all other models except FLUXNET-MTE, which has the advantage of possible local ET<sub>a</sub> measurements, a benefit that clearly diminishes at the HUC2 scale.</p><p>   Because the employed CR method is calibration-free and requires only very few meteorological inputs, yet it yields superior ET performance at the regional scale, we further employed this method to develop a new 34-year (1982-2015) ET<sub>a</sub> product for China. The new Chinese ET<sub>a</sub> product was first validated against 13 eddy-covariance measurements in China, producing NSE values in the range of 0.72–0.95. On the basin scale, the modeled ET<sub>a</sub> values yielded a relative bias of 6%, and an NSE value of 0.80 in comparison with water-balance-derived evapotranspiration rates across ten major river basins in China, indicating the CR-simulated ET<sub>a</sub> rates reliable over China. Further evaluations suggest that the CR-based ET<sub>a</sub> product is more accurate than seven other mainstream ET<sub>a</sub> products. During last three decades, our new ET<sub>a</sub> product showed that annual ET<sub>a</sub> increased significantly over most parts of western and northeastern China, but decreased significantly in many regions of the North China Plain as well as in the eastern and southern coastal regions of China. This new CR-derived ET<sub>a</sub> product would benefit the community for long-term large-scale hydroclimatological studies.</p>

scholarly journals A calibration-free evapotranspiration mapping technique for spatially-distributed regional-scale hydrologic modeling

2011 ◽  
Vol 59 (2) ◽  
pp. 118-130 ◽  
Author(s):  
Jozsef Szilagyi ◽  
Akos Kovacs
Keyword(s):  
Surface Temperature ◽  
Land Surface Temperature ◽  
Land Surface ◽  
Hydrologic Modeling ◽  
Regional Scale ◽  
Mapping Technique ◽  
Monthly Basis ◽  
Complementary Relationship ◽  
Spatially Distributed ◽  
Calibration Free

A calibration-free evapotranspiration mapping technique for spatially-distributed regional-scale hydrologic modelingMonthly evapotranspiration (ET) rates over Hungary for 2000-2008 are mapped at a spatial scale of about 1 km with the help of MODIS daytime land surface temperature as well as sunshine duration, air temperature and humidity data. Mapping is achieved by a linear transformation of MODIS daytime land surface temperature values employing the complementary relationship of evaporation. Validation of the ET rates has been performed at spatial scales spanning almost three magnitudes from a few hundred meters to about a hundred kilometers employing eddy-covariance (EC) measurements and catchment water balance closures. Typically the unbiased ET estimates are within 15% of EC values at a monthly basis, within 7% at an annual, and within only a few percent at a multi-year basis. The ET estimates yield an especially remarkable match (relative error of 0.2%, R2= 0.95) with high-tower EC measurements at a monthly basis. The spatial distribution of the ET estimates confirm earlier, complex regional hydrologic model results and observations as well as yields a perfect estimate of the country's precipitation recycling index (the ratio of the multi-year mean ET and precipitation rates spatially aggregated for the whole country) of 89.2% vs an observed value of 89.6%. The CREMAP method is very simple, easy to implement, requires minimal data, calibration-free, and works accurately when conditions for the complementary relationship are met.

scholarly journals A continental-scale evaluation of the calibration-free complementary relationship with physical, machine-learning, and land-surface models

2021 ◽  
Author(s):  
Daeha Kim ◽  
Minha Choi ◽  
Jong Ahn Chun
Keyword(s):  
Machine Learning ◽  
Water Balance ◽  
Land Surface ◽  
The Other ◽  
Land Surface Models ◽  
Complementary Relationship ◽  
Physical Machine ◽  
Surface Models ◽  
The Mean ◽  
Calibration Free

Abstract. The widespread negative correlation between the atmospheric vapor pressure deficit and soil moisture lends strong support to the complementary relationship (CR) of evapotranspiration. While it has showed outstanding performance in predicting actual evapotranspiration (ETa) over land surfaces, the calibration-free CR formulation has not been tested in the Australian continent dominantly under (semi-)arid climates. In this work, we comparatively evaluated its predictive performance with seven physical, machine-learning, and land surface models for the continent at a 0.5° × 0.5° grid resolution. Results showed that the calibration-free CR that forces a single parameter to everywhere produced considerable biases when comparing to water-balance ETa (ETwb). The CR method was unlikely to outperform the other physical, machine-learning, and land surface models, overrating ETa in (semi-)humid coastal areas for 2002–2012 while underestimating in arid inland locations. By calibrating the parameter against water-balance ETa independent of the simulation period, the CR method became able to outperform the other models in reproducing the spatial variation of the mean annual ETwb and the interannual variation of the continental means of ETwb. However, interannual the grid-scale variability and trends were captured unacceptably even after the calibration. The calibrated parameters for the CR method were significantly correlated with the mean net radiation, temperature, and wind speed, implying that (multi-)decadal climatic variability could diversify the optimal parameters for the CR method. The other physical, machine-learning, and land surface models provided a consistent indication with the prior global-scale assessments. We also argued that at least some surface information is necessary for the CR method to describe long-term hydrologic cycles at the grid scale.

The Equality of Women: The Bahá’í Principle of Complementarity

1990 ◽  
Vol 2 (3) ◽  
pp. 55-66
Author(s):  
John S. Hatcher
Keyword(s):  
Careful Consideration ◽  
Careful Study ◽  
Men And Women ◽  
Complementary Relationship ◽  
Baha'i Faith ◽  
Religious Convictions ◽  
Role Of Women ◽  
Principle Of Complementarity

The Bahá’í teachings simultaneously assert the equality of men and women while advocating in some cases distinct duties according to gender. Since the Bahá’í Faith also teaches that religious convictions should be examined by the “standards of science,” this ostensible paradox invites careful study. At the heart of the response to this query is the Universal House of Justice statement that “equality between men and women does not, indeed physiologically it cannot, mean identity of functions.” To appreciate and to accept this thesis that there can be gender distinction, even insofar as the assignment of fundamental tasks is concerned, without any attendant diminution in the role of women, we must turn to statements in the Bahá’í writings about the complementary relationship between men and women. Through a careful consideration of this principle, we can discover how there can indeed be gender distinction without inequality in status or function.

La lettre et la figure dans Calligrammes de Guillaume Apollinaire

2015 ◽  
pp. 109-118
Author(s):  
Moucherif Abdelhakim
Keyword(s):  
Complementary Relationship ◽  
Guillaume Apollinaire ◽  
Semiotic Systems ◽  
Poetic Text

This article is devoted to Guillaume Apollinaire original poetic experience’s who tried to found a synthetic art combining heterogeneous semiotic systems such as painting and poetry. We propose, then, to study the various complementary relationship, polysemy or counterpoint established between the letters, poetic text and pictorial images.

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