The non-stationary and spatially varying associations between hand,foot and mouth disease and multiple environmental factors:A Bayesian spatiotemporal mapping model study

The transmission and prevalence of Hand,Foot and Mouth Disease(HFMD)are affected by a variety of natural and socio-economic environmental factors.This study aims to quantitatively investigate the non-stationary and spatially varying associations between various environmental factors and HFMD risk.We collected HFMD surveillance cases and a series of relevant environmental data from 2013 to 2021 in Xi'an,Northwest China.By controlling the spatial and temporal mixture effects of HFMD,we constructed a Bayesian spatiotemporal mapping model and characterized the impacts of different driving factors into global linear,non-stationary and spatially varying effects.The results showed that the impact of meteorological conditions on HFMD risk varies in both type and magnitude above certain thresholds(temperature:30°C,precipitation:70 mm,solar radiation:13000 kJ/m^(2),pressure:945 hPa,humidity:69%).Air pollutants(PM_(2.5),PM_(10),NO_(2))showed an inverted U-shaped relationship with the risk of HFMD,while other air pollutants(O_(3),SO_(2))showed nonlinear fluctuations.Moreover,the driving effect of increasing temperature on HFMD was significant in the 3-year period,while the inhibitory effect of increasing precipitation appeared evident in the 5-year period.In addition,the proportion of urban/suburban/rural area had a strong influence on HFMD,indicating that the incidence of HFMD firstly increased and then decreased during the rapid urbanization process.The influence of population density on HFMD was not only limited by spatial location,but also varied between high and low intervals.Higher road density inhibited the risk of HFMD,but higher night light index promoted the occurrence of HFMD.Our findings further demonstrated that both ecological and socioeconomic environmental factors can pose multiple driving effects on increasing the spatiotemporal risk of HFMD,which is of great significance for effectively responding to the changes in HFMD epidemic outbreaks.

Area,lake-level and volume variations of typical lakes on the Tibetan Plateau and their response to climate change,1972-2019

Most lakes have undergone significant changes on the Tibetan Plateau in recent decades,affecting water resources on the Tibetan Plateau and its surrounding areas.In this paper,we investigated the variations of 25 lakes in five sub-regions on the Tibetan Plateau from 1972 to 2019 based on SRTM DEM data and Landsat imagery.We used a method to derive lake-levels based on DEM and lake boundaries delineated from Landsat imagery,and then calculated the changes in lake area,level,and volume in 1972 to 2019.We also analyzed the potential impacts of temperature,precipitation,glacial and permafrost melting in lake changes during this period.The results show that the lakes tended to shrink until 2010 in southern and western plateau,after which they began to expand gradually but the overall trend is still shrinking.Limited meltwater from glaciers and permafrost and low precipitation are the main reasons for their shrinkage.The lakes in the central plateau,northwest plateau and northeast plateau tend to expand overall.The reason for the expansion of the lakes is not only precipitation but also the melting of glaciers and permafrost.Overall,the lake changes have gone through 3 phases,namely a slight decrease during 1972-2000,a rapid increase during 2000-2010,and a slowdown in the last decade(2010-2019).Multiple factors such as temperature,precipitation,the state of glaciers and permafrost have contributed to the changes in the lake.

The effect of grid size on the quantification of erosion,deposition,and rill network

Hillslope rill/interrill erosion has been investigated from the perspective of runoff transport of sediment.Recent advances in terrestrial laser scanning can provide high-resolution elevation data up to centimeter levels,and temporal digital elevation models(DEMs)enabled the detection and quantification of sediment redistribution.Erosion and deposition are spatially heterogeneous across hillslopes,and the choice of resolution is critical when using a DEM to study the spatial pattern of the processes.This study investigates the influence of grid size on the sediment change calculation and rill network delineation based on two surveys using a terrestrial laser scanner on a hillslope with well-developed rills in 2014 and 2015.Temporal DEMs were used to quantify elevation changes and used to delineate rill networks.We produced DEM pairs of incremental grid sizes(1-cm,2-cm,5-cm,8-cm,10-cm,15-cm,20-cm,and 30-cm)for DEM difference and rill network delineation.We used the 1-cm DEM as the reference to compare the results produced from other DEMs.Our results suggest that erosion mainly occurs on the rill sidewalls,and deposition on the rill floors,with patches of erosion/deposition within the interrill areas.Both the area and volume of detectable change decrease as the grid size increases,while the area and volume of erosion are less sensitive compared to those of deposition.The total length and number of rills decrease with the increased grid size,whereas the average length of rills increases.The mean offset between delineated rill network and the reference increases with larger grid sizes.In contrast to the erosion and deposition detected within rills,minor changes are detected on the interrill areas,indicating that either no topographic changes occurred or the changes were too small to be detected on the interill areas by our finest 1-cm DEMs.We recommend to use the finest possible grid size that can be achieved for future studies.