Department of Environmental Studies
https://karuspace.karu.ac.ke/handle/20.500.12092/1935
2024-03-29T11:41:48ZAnalysis of Short-Term Drought Episodes Using Sentinel-3 SLSTR Data under a Semi-Arid Climate in Lower Eastern Kenya.
https://karuspace.karu.ac.ke/handle/20.500.12092/2995
Analysis of Short-Term Drought Episodes Using Sentinel-3 SLSTR Data under a Semi-Arid Climate in Lower Eastern Kenya.
Musyimi, Peter K.; Sahbeni, Ghada; Timár, Gábor; Weidinger, Tamas
This study uses Sentinel-3 SLSTR data to analyze short-term drought events between
2019 and 2021. It investigates the crucial role of vegetation cover, land surface temperature, and
water vapor amount associated with drought over Kenya’s lower eastern counties. Therefore, three
essential climate variables (ECVs) of interest were derived, namely Land Surface Temperature (LST),
Fractional Vegetation Cover (FVC), and Total Column Water Vapor (TCWV). These features were
analyzed for four counties between the wettest and driest episodes in 2019 and 2021. The study
showed that Makueni and Taita Taveta counties had the highest density of FVC values (60–80%)
in April 2019 and 2021. Machakos and Kitui counties had the lowest FVC estimates of 0% to 20%
in September for both periods and between 40% and 60% during wet seasons. As FVC is a crucial
land parameter for sequestering carbon and detecting soil moisture and vegetation density losses,
its variation is strongly related to drought magnitude. The land surface temperature has drastically
changed over time, with Kitui and Taita Taveta counties having the highest estimates above 20 ◦C in
2019. A significant spatial variation of TCWV was observed across different counties, with values
less than 26 mm in Machakos county during the dry season of 2019, while Kitui and Taita Taveta
counties had the highest estimates, greater than 36 mm during the wet season in 2021. Land surface
temperature variation is negatively proportional to vegetation density and soil moisture content, as
non-vegetated areas are expected to have lower moisture content. Overall, Sentinel-3 SLSTR products
provide an efficient and promising data source for short-term drought monitoring, especially in
cases where in situ measurement data are scarce. ECVs-produced maps will assist decision-makers
with a better understanding of short-term drought events as well as soil moisture loss episodes that
influence agriculture under arid and semi-arid climates. Furthermore, Sentinel-3 data can be used to
interpret hydrological, ecological, and environmental changes and their implications under different
environmental conditions.
Analysis of Short-Term Drought Episodes Using
Sentinel-3 SLSTR Data under a Semi-Arid Climate
2023-06-01T00:00:00ZHourly reference evapotranspiration analysis using synoptic meteorological measurements and ERA5 reanalysis data from Kenyan Counties
https://karuspace.karu.ac.ke/handle/20.500.12092/2994
Hourly reference evapotranspiration analysis using synoptic meteorological measurements and ERA5 reanalysis data from Kenyan Counties
Musyimi, Peter K.; Mendyl, Abderrahmane; Agustiyara, Agustiyara; Székely, Balázs
Kenya has had five failed rain seasons for the last three years. In this context, there was a mass recurrent crop failure, death of livestock and wildlife, persistent water scarcity, and droughts of varying intensities. There have been a lot of challenges in assessing climate change and variability impacts in Kenya due to limited data sources. Further, assessing the local and regional effects on the hydrological cycle, food security, and available water resources remains a great regional threat. Reference evapotranspiration, is the evaporative power climatic parameter of the atmosphere, vital for water budgets on the land surface. The study’s main goal was to analyze hourly reference evapotranspiration, from two climatic regions using single levels ERA5 hourly dataset from 2000 to 2022. The dataset was sought from three stations from, arid, and semi-arid savannah tropical conditions regions (Voi Garissa, and Mombasa) with elevations between 57 m to 579 m, and three (Trans-Nzoia, Nyeri, and Embu) sought from humid Kenya highlands (>1350 m). Reference Evapotranspiration was calculated using Penman-Monteith (FAO56), the standard methodology developed by Food and Agriculture Organization. Results from 5 years (2018 to 2022) in Taita-Taveta County indicated that ranged from 0.17±0.2 mm/hour in 2020 to 0.22±0.2 mm/hour in 2022. Daily averages were 4.17±1.2 mm./day to 5.2±1.1 mm/day in 2020 and 2022 respectively. The mean monthly and was highest in March with an estimated value of 159.7±53.7 mm/month while the lowest was 120±15 mm/month in December. This is because March falls at the onset of the long rainy season in Kenya where precipitation is high while December is the last month of the short rainy season when precipitation reduces significantly. These results are vital because they enhance comparisons of the spatial climatological patterns and variability of seasonal precipitation about the evaporative power and demand variation across regions. Further, it will necessitate investigations of uncertainties from the datasets for better decision-making after comparisons with analysis from field meteorological datasets and soil moisture data measurements currently being carried out in Kenya. Further comparison of the results with reference evapotranspiration from the original station and the Global Land Evaporation Amsterdam Model dataset will also be investigated.
Hourly reference evapotranspiration analysis using synoptic meteorological measurements and ERA5 reanalysis data
2023-09-01T00:00:00ZFine‐scale variation in soil and topography influences herbaceous vegetation and the distribution of large mammalian herbivores
https://karuspace.karu.ac.ke/handle/20.500.12092/2961
Fine‐scale variation in soil and topography influences herbaceous vegetation and the distribution of large mammalian herbivores
Ang'ila, Robert O.; Kimuyu, Duncan M.; Wambugu, Geoffrey M.; Kenfack, David; Musil, Paul M.; Kartzinel, Tyler R.
Current understanding of the distribution of vegetation and large mammalian herbivores (LMH) is based
on a combination of biogeographic studies and highly controlled field experiments, but a more complete
understanding of these patterns requires study of their natural co-occurrence patterns at intermediate
spatial scales. The study was conducted in the 120-ha Mpala Forest Global Earth Observatory (ForestGEO)
plot, Kenya. We examined differences in herbaceous plant communities and habitat use by LMH among
three topographic habitats with distinct soil types, namely steep slopes, valley and plateau. Each pair of
habitats differed in plant and animal com position. The steep slopes and plateau respectively had ≥1-fold
higher percentage herbaceous cover than the valley, whereas the steep slopes and valley had >1.5-fold
greater grass species richness and diversity than the plateau. The activity of LMH was ≥1.7-fold higher in
the valley than the steep slopes and plateau, reflecting a positive relationship between LMH activity index
and richness and diversity of grass species. Results indicate that fine-scale variation in topography and soil
are associated with both the distribution of herbaceous vegetation and LMH, suggesting a need to account
for local habitat characteristics when examining the distributions of plants, animals, and plant-herbivore
interactions in natural systems
Distribution of large mammalian
herbivores
2023-04-01T00:00:00Z5. Absentee owners and overlapping home ranges in a territorial species
https://karuspace.karu.ac.ke/handle/20.500.12092/2857
5. Absentee owners and overlapping home ranges in a territorial species
Isbell, Lynne A.; Bidner, Laura R.; Loftus, Carter; Kimuyu, Duncan M.; Young, Truman P.
Abstract Understanding animals’ use of space can shed valuable light on multiple other aspects of behavioral ecology, including social organization, dispersal, and foraging efficiency. Home ranges, territories, core areas, and home range overlaps have been widely studied, but unless animals are directly observed or are tracked remotely on a fine temporal scale, how they actually use the space available to them and how they share (or partition) this space with a community of conspecifics over time cannot be fully understood. Using GPS technology, we tracked three adjacent groups of vervet monkeys (Chlorocebus pygerythrus) in Laikipia, Kenya, for 1 year to better understand the processes involved in territoriality and home range overlaps. Home ranges overlapped with any one neighboring group by 12.7–34.7%, but intergroup encounters only occurred in restricted areas within these zones, which defined territorial boundaries. The resources closest to the territorial boundaries were nocturnal core areas with preferred sleeping sites adjacent to shortgrass areas offering fewer hiding places for ambush predators and greater visibility for predator detection. Home range overlaps were not neutral zones, the result of shifting home range boundaries over time, or based on intergroup encounters at boundaries, but resulted when groups made incursions beyond their territorial boundaries while the neighbor was far away and likely unaware of the intruders. Thus, territories can be non-exclusive but may still be perceived by the animals themselves as sole-owned, as neighbors only intrude when territory owners are absent from that area.
Absentee owners and overlapping home ranges
2021-01-07T00:00:00Z