Browsing by Subject "global warming"

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    Investigating Dew Trends and Drivers Using Ground-Based Metreological Observations at the Namib Desert
    (2024-08) Javanmardi, Sara; Wang, Lixin; Li, Lin; Jacinthe, Pierre-André
    In arid environments such as the Namib Desert, sources of non-rainfall waters such as dew and fog are crucial for sustaining ecosystem functions such as vegetation dynamics and biogeochemical processes, yet they remain among the least studied features of the water cycle. There is a concern that dew may become increasingly scarce because of climate warming, a trend not yet documented in the Namib Desert. This study aims to examine how dew formation trends in this region are evolving, drawing on field observations and assessing the factors influencing these trends. Our analysis involved processing meteorological data gathered from SASSCAL (Southern African Science Service Center for Climate and Adaptive Land Management) between 2015 and 2022, supplemented by direct dew observations to estimate dew occurrence in Gobabeb, a research station in Namib Desert. We developed an empirical equation to calculate dew formation based on the meteorological data. We used field-based dew records to validate the empirical equation and applied this equation to calculate dew formation between 2015 and 2022. We found dew formation concentrated in December to May (wet season). We evaluated the trends of dew formation at both monthly and annual scales. The findings showed a decline in dew formation (13.74% in the annual dew days count), a trend that could significantly impact the ecosystems in the Namib Desert. We found that soil temperature, air temperature, and humidity are the major contributors of the observed dew trends. The inverse relationship observed between increasing temperatures and dew formation supports the notion that elevated temperatures accelerate evaporation rates and diminish the chances of dew formation. This association underscores the susceptibility of dew formation to the impacts of climate change, as rising temperatures and shifting precipitation patterns are anticipated outcomes.
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    Satellite Solar-Induced Chlorophyll Fluorescence Reveals Heat Stress Impacts on Wheat Yield in India
    (MDPI, 2020) Song, Yang; Wang, Jing; Wang, Lixin; Earth Sciences, School of Science
    With continued global warming, the frequency and severity of heat wave events increased over the past decades, threatening both regional and global food security in the future. There are growing interests to study the impacts of drought on crop. However, studies on the impacts of heat stress on crop photosynthesis and yield are still lacking. To fill this knowledge gap, we used both statistical models and satellite solar-induced chlorophyll fluorescence (SIF) data to assess the impacts of heat stress on wheat yield in a major wheat growing region, the Indo-Gangetic Plains (IGP), India. The statistical model showed that the relationships between different accumulated degree days (ADD) and reported wheat yield were significantly negative. The results confirmed that heat stress affected wheat yield across this region. Building on such information, satellite SIF observations were used to further explore the physiological basis of heat stress impacts on wheat yield. Our results showed that SIF had strong negative correlations with ADDs and was capable of monitoring heat stress. The SIF results also indicated that heat stress caused yield loss by directly impacting the photosynthetic capacity in wheat. Overall, our findings demonstrated that SIF as an effective proxy for photosynthetic activity would improve our understanding of the impacts of heat stress on wheat yield.