Abstract. Accurate global terrestrial evapotranspiration (ET)
estimation is essential to better understand Earth's energy and water
cycles. Although several global ET products exist, recent studies indicate
that ET estimates exhibit high uncertainty. With the increasing trend of
extreme climate hazards (e.g., droughts and heat waves), accurate ET
estimation under extreme conditions remains challenging. To overcome these
challenges, we used 3 h and 0.25∘ Global Land Data Assimilation
System (GLDAS) datasets (net radiation, land surface temperature (LST), and
air temperature) and a three-temperature (3T) model, without resistance and
parameter calibration, in global terrestrial ET product development. The
results demonstrated that the 3T model-based ET product agreed well with
both global eddy covariance (EC) observations at daily (root mean square
error (RMSE) = 1.1 mm d−1, N=294 058) and monthly (RMSE = 24.9 mm month−1, N=9632) scales and basin-scale water balance observations (RMSE = 116.0 mm yr−1, N=34). The 3T model-based global terrestrial
ET product was comparable to other common ET products, i.e., MOD16, P-LSH,
PML, GLEAM, GLDAS, and Fluxcom, retrieved from various models, but the 3T
model performed better under extreme weather conditions in croplands than
did the GLDAS, attaining 9.0 %–20 % RMSE reduction. The proposed daily and
0.25∘ ET product covering the period of 2001–2020 could provide periodic and large-scale information to support water-cycle-related studies.
The dataset is freely available at the Science Data Bank
(https://doi.org/10.57760/sciencedb.o00014.00001, Xiong et al., 2022).
Urban evapotranspiration (ET) is an effective way to mitigate ecological challenges resulting from rapid urbanization. However, the characteristics of urban vegetation ET, especially how they respond to meteorological factors and soil water, remains unclear, which is crucial for urban ET regulation. Therefore, this study measured the actual ET rate of an urban lawn (ETlawn) using the Bowen ratio system and an urban tree (Ttree) by a sap flow system in the hot summer of a subtropical megacity, Shenzhen. The results showed that the daily ETlawn was more restricted by energy (Rs) and diffusion conditions (vapor pressure deficit, VPD), while the daily Ttree was more restricted by VPD and relative extractable water (REW) in the urban area. The daily Ttree decreased when the REW was lower than 0.18, while the daily ETlawn started to decrease when it was lower than 0.14. When REW was lower than 0.11, the Ttree stayed at a relatively low level. The impacts of VPD was more evident on the diurnal Ttree than on the diurnal ETlawn. Wind speed had a scarce impact as it was relatively low in urban areas. This study clarifies the different responses of ETlawn and Ttree to meteorological factors and soil water based on actual ET. The results are of great significance for the knowledge of urban forestry and urban hydrology.
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