Assessment and Validation of FAPAR, a Satellite-Based Plant Health and Water Stress Indicator, over Uganda
Abstract
Highlights
- Monthly photosynthetic activity (FAPAR) over Uganda has been increasing, becoming highly variable and dominated by a moderate activity of 0.35–0.45 units.
- The Standardized FAPAR Index (SFI) had strong positive and negative correlations with the scale 3 Standardized Precipitation and Evapotranspiration Index (SPEI-03) and crop water stress index (CWSI), respectively.
- The observed distribution and patterns of photosynthetic activity are jointly governed by precipitation, evapotranspiration, LULC, and teleconnections.
- Satellite-based FAPAR products can suitably track ecosystem functionality over Uganda, with an emphasis on water stress.
Abstract
1. Introduction
- (i)
- Explore the spatiotemporal variability of FAPAR of Uganda;
- (ii)
- Determine trends in FAPAR and FAPAR-centered stress indices (SFI > −1);
- (iii)
- Compare and indirectly validate FAPAR using the Standardized Precipitation and Evapotranspiration Index at scale 3 (SPEI-03) and crop water stress index (CWSI) over Uganda at high spatial resolutions to facilitate their smooth adoption in Uganda.
2. Description of Study Area
3. Data and Methods
3.1. Data Sources and Preprocessing
3.1.1. Data Acquisition
3.1.2. Computation of Standardized FAPAR Index (SFI), Scale-03 Standardized Precipitation and Evapotranspiration Index (SPEI-03), and Crop Water Stress Index (CWSI)
3.2. Data Analysis
3.2.1. Climatology and Variability Analysis
3.2.2. Non-Parametric Statistical Test for Trends in FAPAR and FAPAR-Centered Stress (SFI < −1)
3.2.3. Spatiotemporal Correlation Analysis
4. Results
4.1. FAPAR Climatology over Uganda (1983–2013)
4.2. Trend in FAPAR and FAPAR-Centered Stress Indices (SFI < −1) over Uganda (1983–2013)
4.3. Correlation Between Standardized FAPAR Index and Agricultural Drought Indicators
5. Discussions
5.1. Spatiotemporal Variability of FAPAR and FAPAR-Centered Stress Indices over Uganda
5.2. Performance of FAPAR in Drought and Plant Water Stress Monitoring
6. Conclusions
Supplementary Materials
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Variable | Temporal | Spatial | Period | Notes | Reference |
---|---|---|---|---|---|
FAPAR | Daily | ~5 km | 1983–2013 | Directly sourced from NOAA-CDR | [11] |
SPEI-03 | Monthly | ~4 km | 1983–2013 | Computed from precipitation and potential evapotranspiration data | [22,34] |
CWSI | Monthly | ~4 km | 1983–2013 | Computed from actual and potential evapotranspiration data | [22,34] |
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Ssembajwe, R.; Twah, A.; Kagezi, G.H.; Löytty, T.; Kobusinge, J.; Gidudu, A.; Arinaitwe, G.; Du, Q.; Voda, M. Assessment and Validation of FAPAR, a Satellite-Based Plant Health and Water Stress Indicator, over Uganda. Remote Sens. 2025, 17, 3501. https://doi.org/10.3390/rs17203501
Ssembajwe R, Twah A, Kagezi GH, Löytty T, Kobusinge J, Gidudu A, Arinaitwe G, Du Q, Voda M. Assessment and Validation of FAPAR, a Satellite-Based Plant Health and Water Stress Indicator, over Uganda. Remote Sensing. 2025; 17(20):3501. https://doi.org/10.3390/rs17203501
Chicago/Turabian StyleSsembajwe, Ronald, Amina Twah, Godfrey H. Kagezi, Tuula Löytty, Judith Kobusinge, Anthony Gidudu, Geoffrey Arinaitwe, Qingyun Du, and Mihai Voda. 2025. "Assessment and Validation of FAPAR, a Satellite-Based Plant Health and Water Stress Indicator, over Uganda" Remote Sensing 17, no. 20: 3501. https://doi.org/10.3390/rs17203501
APA StyleSsembajwe, R., Twah, A., Kagezi, G. H., Löytty, T., Kobusinge, J., Gidudu, A., Arinaitwe, G., Du, Q., & Voda, M. (2025). Assessment and Validation of FAPAR, a Satellite-Based Plant Health and Water Stress Indicator, over Uganda. Remote Sensing, 17(20), 3501. https://doi.org/10.3390/rs17203501