Print Email Facebook Twitter Phenophase-based comparison of field observations to satellite-based actual evaporation estimates of a natural woodland: miombo woodland, southern Africa Title Phenophase-based comparison of field observations to satellite-based actual evaporation estimates of a natural woodland: miombo woodland, southern Africa Author Zimba, H.M. (TU Delft Water Resources; Ministry of Agriculture and Livestock, Zambia) Coenders-Gerrits, Miriam (TU Delft Water Resources) Kawawa, Banda (University of Zambia) Schilperoort, B. (TU Delft Atmospheric Remote Sensing) van de Giesen, N.C. (TU Delft Water Resources) Nyambe, Imasiku (University of Zambia) Savenije, Hubert (TU Delft Water Resources) Date 2023 Abstract The trend and magnitude of actual evaporation across the phenophases of miombo woodlands are unknown. This is because estimating evaporation in African woodland ecosystems continues to be a challenge, as flux observation towers are scant if not completely lacking in most ecosystems. Furthermore, significant phenophase-based discrepancies in both trend and magnitude exist among the satellitebased evaporation estimates (i.e. Global Land Evaporation Amsterdam Model (GLEAM), moderate resolution imaging spectroradiometer (MODIS), operational simplified surface energy balance (SSEBop), and water productivity through open-access remotely sensed derived data (WaPOR)), making it difficult to ascertain which of the estimates are close to field conditions. Despite the many limitations with estimation of evaporation in woodlands, the development and application of the distributed temperature system (DTS) is providing deepened insights and improved accuracy in woodland energy partitioning for evaporation assessment. In this study, the Bowen ratio distributed temperature sensing (BRDTS) approach is used to partition available energy and estimate actual evaporation across three canopy phenophases of the miombo woodland, covering the entire 2021 dry season (May–October) and early rain season (November– December) at a representative site in Mpika in Zambia, southern Africa. To complement the field experiment, four satellite-based evaporation estimates are compared to the field observations. Our results show that actual evaporation of the miombo woodland appears to follow the trend of the net radiation, with the lowest values observed during the phenophase with the lowest net radiation in the cool dry season and the highest values during the phenophase with peak net radiation in the early rainy season. It appears the continued transpiration during the driest period in the dormant phenophase (with lowest canopy cover and photosynthetic activities) may be influenced by the species-dependent adapted physiological attributes such as access to moisture in deep soils (i.e. due to deep rooting), plant water storage, and the simultaneous leaf fall and leaf flush among miombo plants. Of the four satellite-based evaporation estimates, only the WaPOR has a similar trend to the field observations across the three phenophases. However, all four satellitebased estimates underestimate the actual evaporation during the dormant and green-up phenophases. Large coefficients of variation in actual evaporation estimates among the satellite-based estimates exist in the dormant and green-up phenophases and are indicative of the difficulty in estimating actual evaporation in these phenophases. The differences between field observations and satellite-based evaporation estimates can be attributed to the model structure, processes, and inputs. To reference this document use: http://resolver.tudelft.nl/uuid:8ad5b1ef-be19-41db-986f-c78b31327986 DOI https://doi.org/10.5194/hess-27-1695-2023 ISSN 1027-5606 Source Hydrology and Earth System Sciences, 27 (8), 1695-1722 Part of collection Institutional Repository Document type journal article Rights © 2023 H.M. Zimba, Miriam Coenders-Gerrits, Banda Kawawa, B. Schilperoort, N.C. van de Giesen, Imasiku Nyambe, Hubert Savenije Files PDF hess_27_1695_2023.pdf 15.39 MB Close viewer /islandora/object/uuid:8ad5b1ef-be19-41db-986f-c78b31327986/datastream/OBJ/view