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Journal of Geophysical Research: Atmospheres

Diagnostic analysis of interannual variation of global land evapotranspiration over 1982–2011: Assessing the impact of ENSO

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Abstract

[1] Global land evapotranspiration (E) between 1982 and 2011 was estimated by using a canopy conductance-based process E model (Air Relative Humidity-Based Two-Source model) [Yan et al., 2012]. To analyze the impact of precipitation forcing on E, an ensemble of six E data sets was derived from a driving ensemble of six precipitation data sets (i.e., Global Historical Climatology Network, Global Precipitation Climatology Centre, Climate Research Unit, Global Dataset of Meteorological Forcings, Global Precipitation Climatology Project, and Delaware). The result shows that ensemble average E over global land had an annual mean of 64.8 ± 0.8 × 103 km3 yr−1 and a significant linear trend of 4.6 mm per decade (p < 0.01). Significant partial correlations were found between the ensemble average E and its three controlling variables (i.e., precipitation (Pr), vegetation leaf area index (Lai), and potential evaporation (Ep)). These correlations explained 95% of the interannual variation of global land E with Pr as the dominant forcing contributing 37% variation of E; i.e., global land E was slightly sensitive to Pr than Lai and Ep. Pr, Lai, and Ep all showed increases of 8.8 mm (p < 0.01), 0.4 m2 m−2 (p < 0.01), and 2.0 mm (p < 0.1) per decade, respectively, which characterized a favorable environment for the increase of E over past 30 years. Both negative Multivariate El Niño–Southern Oscillation (ENSO) Index (MEI) and Southern Oscillation Index (SOI) displayed an increasing trend. The La Niña phase tended to be dominant from 1982 to 2011 and caused a significant increase of land Pr and further enhanced land E. Impacts of ENSO and corresponding Pr variation require attention to increase the understanding of the interannual variation of global land E.

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