Effects Of Interannual Variability Research Articles

Temperature variability and long-run economic development

This study examines the effects of temperature variability on long-run economic development. To identify causal effects, a novel econometric strategy is employed, based on spatial first-differences. Economic activity is proxied by satellite data on nightlights. Drawing on climate science, the study distinguishes between temperature variability on three time scales: day-to-day, seasonal, and interannual variability. The results indicate that day-to-day temperature variability has a statistically significant, negative effect on economic activity, while seasonal variability has a smaller but also negative effect. The effect of interannual variability is positive at low temperatures, but negative at high temperatures. Furthermore, the results suggest that daily temperature levels have a non-linear effect on economic activity with an optimal temperature around 15 degrees Celsius. However, most of the estimated effects of variability cannot be explained with this non-linearity and instead seem to be due to larger uncertainty about future temperature realisations. The empirical effects can be found in both urban and rural areas, and they cannot be explained by the distribution of agriculture. The results indicate that projected changes of temperature variability might add to the costs of anthropogenic climate change especially in relatively warm and currently relatively poor regions.

Cover crops control nitrogen and phosphorus transport from two agricultural watersheds at multiple measurement scales

Environmental impacts on freshwater ecosystems persist due to inputs of excess fertilizer to agricultural landscapes. Conservation efforts, such as cover crops, are being encouraged to reduce nitrogen (N) and phosphorus (P) runoff from fields, but their effects on working lands are rarely documented. We quantified reductions of nitrate-N and soluble reactive phosphorus (SRP) losses from cropland in response to widespread planting of cover crops in two agricultural watersheds (Indiana, USA) over four water years (2016–2019). We collected water samples bimonthly from tile drains and stream sites to measure nitrate-N and SRP losses across scales. Cover crops consistently reduced tile drain nitrate-N loss by 27–72%, while SRP reductions were more variable, ranging from 7%–58%. Subwatershed nitrate-N yields were consistent across each watershed, while headwaters disproportionately contributed SRP to the stream, suggesting targeted cover crop implementation may be required to reduce SRP export. Finally, watershed-scale nitrate-N export was reduced by 2–67% (5/8 site-years) and SRP export by 31–88% (7/8 site-years) in spring. However, given the effect of interannual variability in runoff and spatial heterogeneity in N and P loading, regional-scale planting of cover crops may be needed to confer consistent reductions in annual export, with meaningful impacts on downstream water quality.

Spatio-temporal rainfall variability of equatorial small island: case study Bintan Island, Indonesia

The water resources of Bintan Island depend much on rainfall since the impervious granitic basement that bears a low water storage capacity dominates the geology of Bintan Island. Water demand in Bintan is increasing due to both population and economic growth. This paper aims to determine the spatial and temporal rainfall variability over Bintan Island using the daily corrected-CHIRPS (Climate Hazards Group InfraRed Precipitation with Station data) version two (v2.0) dataset to a ground-based observation dataset (Kijang station) using quantile-base bias correction for period 1 January 1981–31 August 2018. For the analysis process, we used monthly corrected-CHIRPS, NINO 3.4 anomaly index, the DMI (dipole mode index), zonal and meridional wind, and specific humidity from January 1981 to December 2017. Semi-annual, annual, and interannual variations influence monthly rainfall amounts over the island. Two peaks representing equatorial and monsoonal patterns characterize the temporal variability of rainfall. Spatially, the southern part of the island receives more rainfall than the northern part especially in MAM and SON related to the more convergence of moisture. The effects of interannual variation, ENSO (El Nino-Southern Oscillation) and IOD (Indian Ocean dipole), vary with season. ENSO contributes more to rainfall variability than IOD during the period of study.

Importance of snowmelt contribution to seasonal runoff and summer low flows in Czechia

Abstract. The streamflow seasonality in mountain catchments is often influenced by snow. However, a shift from snowfall to rain is expected in the future. Consequently, a decrease in snow storage and earlier snowmelt is predicted, which will cause changes not only in seasonal runoff distribution in snow-dominated catchments, but it may also affect the total annual runoff. The objectives of this study were to quantify (1) how inter-annual variations in snow storages affect spring and summer runoff, including summer low flows, and (2) the importance of snowmelt in generating runoff compared to rainfall. The snow storage, groundwater recharge and streamflow were simulated for 59 mountain catchments in Czechia in the period from 1980 to 2014 using a bucket-type catchment model. The model output was evaluated against observed daily runoff and snow water equivalent. Hypothetical scenarios were performed, which allowed for analysing the effect of inter-annual variations in snow storage on seasonal runoff separately from other components of the water balance. The results showed that 17 %–42 % (26 % on average) of the total runoff in the study catchments originates as snowmelt, despite the fact that only 12 %–37 % (20 % on average) of the precipitation falls as snow. This means that snow is more effective in generating catchment runoff compared to liquid precipitation. This was demonstrated by modelling experiments which showed that total annual runoff and groundwater recharge decrease in the case of a precipitation shift from snow to rain. In general, snow-poor years were clearly characterized by a lower snowmelt runoff contribution compared to snow-rich years in the analysed period. Additionally, snowmelt started earlier in these snow-poor years and caused lower groundwater recharge. This also affected summer baseflow. For most of the catchments, the lowest summer baseflow was reached in years with both relatively low summer precipitation and snow storage. This showed that summer low flows (directly related to baseflow) in our study catchments are not only a function of low precipitation and high evapotranspiration, but they are significantly affected by the previous winter snowpack. This effect might intensify drought periods in the future when generally less snow is expected.

Living near the limits: Effects of interannual variation in food availability on diet and reproduction in a temperate primate, the Taihangshan macaque (Macaca mulatta tcheliensis).

Nutrient intake of animals is influenced by an interplay of external and internal factors, such as food availability and reproductive state, respectively. We used the nutritional geometry framework to analyze individual-based data on energy and nutrient intake in relation to reproductive state in a population of rhesus macaques (Macaca mulatta tcheliensis), which live in a harsh high-latitude habitat, the Taihangshan mountains of China, and exhibit strong reproductive seasonality. We combined data over a 3-year period on food availability, diets, reproductive output, and components of maternal investment to understand how Taihangshan macaques respond to variation in food availability and nutrition in reproduction. Our results show there was high interannual variation in availability of an important staple source of fat and carbohydrates (nonprotein energy), seeds of oak (Quercus spp). Despite this variability in seed availability skewing the dietary macronutrient ratios considerably (from 12.96% to 30.12% dietary energy from protein), total metabolizable energy intake was maintained across years during pregnancy. Lactating females had higher mean daily energy intakes than pregnant females. As in pregnant females, energy intake was maintained constant across years, but only when seed availability enabled the contribution of available protein to energy intake to be maintained between 15.32% (2013) and 17.97% (2015). In 2014, when seeds were scarce, lactating females had a shortfall in energy intake compared with 2013 and 2015. This corresponded with a reduction in the number of females giving birth (11 out of 23), but there was no interannual difference in survival rates. Compared to 2013 and 2015, in 2014 females had greater weight loss (drew on body reserves), moved less, and spent more time nursing their offspring. We discuss implications of these results for range limitation in Taihangshan macaques.

Genetic and environmental factors influencing the contents of essential oil compounds in Atractylodes lancea.

Rhizomes of Atractylodes lancea are used in traditional Japanese medicine (Kampo) and Chinese medicine to treat numerous diseases and disorders because they contain many pharmacologically active compounds. The major active compounds in A. lancea are essential oil compounds such as β-eudesmol, hinesol, atractylon, and atractylodin. The contents of the compounds in A. lancea exhibit high variability depending on their habitat. We cultivated clonal lines of A. lancea in different years (2016, 2017) and different locations (Hokkaido, Ibaraki) to investigate the influence of genetic and environmental factors on the contents of major compounds, namely, β-eudesmol, hinesol, atractylon, and atractylodin. Broad sense heritability of β-eudesmol, hinesol, atractylon, and atractylodin contents were 0.84, 0.77, 0.86, and 0.87, respectively. The effects of interannual variability on the contents of the compounds were lower than those of genotype. In addition, the cultivated environmental factors were assessed by different locations, and the correlations between Hokkaido and Ibaraki grown plants based on β-eudesmol, hinesol, atractylon, and atractylodin contents were 0.94, 0.94, 1.00, and 0.83, respectively. The results suggest that the contents of β-eudesmol, hinesol, atractylon, and atractylodin in A. lancea are largely influenced by genetic factors, and clonal propagation could be an effective strategy for obtaining populations with high contents of essential oil compounds. Furthermore, the contents of β-eudesmol, hinesol, atractylon, and atractylodin in A. lancea exhibited few correlations with rhizome yields. A. lancea cultivars with not only high contents of essential oil compounds but also high rhizome yield could be developed through selective breeding.

The Effect of Interannual Variations in Water Temperature on the Yellowtail Catch, Seriola Quinqueradiata, in the Eastern Part of the Korean Peninsula

The Effect of Interannual Variations in Water Temperature on the Yellowtail Catch, Seriola Quinqueradiata, in the Eastern Part of the Korean Peninsula

Environmental heterogeneity and biotic interactions mediate climate impacts on tropical forest regeneration.

Predicting the fate of tropical forests under a changing climate requires understanding species responses to climatic variability and extremes. Seedlings may be particularly vulnerable to climatic stress given low stored resources and undeveloped roots; they also portend the potential effects of climate change on future forest composition. Here we use data for ca. 50,000 tropical seedlings representing 25 woody species to assess (i) the effects of interannual variation in rainfall and solar radiation between 2007 and 2016 on seedling survival over 9years in a subtropical forest; and (ii) how spatial heterogeneity in three environmental factors-soil moisture, understory light, and conspecific neighborhood density-modulate these responses. Community-wide seedling survival was not sensitive to interannual rainfall variability but interspecific variation in these responses was large, overwhelming the average community response. In contrast, community-wide responses to solar radiation were predominantly positive. Spatial heterogeneity in soil moisture and conspecific density were the predominant and most consistent drivers of seedling survival, with the majority of species exhibiting greater survival at low conspecific densities and positive or nonlinear responses to soil moisture. This environmental heterogeneity modulated impacts of rainfall and solar radiation. Negative conspecific effects were amplified during rainy years and at dry sites, whereas the positive effects of radiation on survival were more pronounced for seedlings existing at high understory light levels. These results demonstrate that environmental heterogeneity is not only the main driver of seedling survival in this forest but also plays a central role in buffering or exacerbating impacts of climate fluctuations on forest regeneration. Since seedlings represent a key bottleneck in the demographic cycle of trees, efforts to predict the long-term effects of a changing climate on tropical forests must take into account this environmental heterogeneity and how its effects on regeneration dynamics play out in long-term stand dynamics.

Hysteresis in simulations of malaria transmission

Malaria transmission is a complex system and in many parts of the world is closely related to climate conditions. However, studies on environmental determinants of malaria generally consider only concurrent climate conditions and ignore the historical or initial conditions of the system. Here, we demonstrate the concept of hysteresis in malaria transmission, defined as non-uniqueness of the relationship between malaria prevalence and concurrent climate conditions. We show the dependence of simulated malaria transmission on initial prevalence and the initial level of human immunity in the population. Using realistic time series of environmental variables, we quantify the effect of hysteresis in a modeled population. In a set of numerical experiments using HYDREMATS, a field-tested mechanistic model of malaria transmission, the simulated maximum malaria prevalence depends on both the initial prevalence and the initial level of human immunity in the population. We found the effects of initial conditions to be of comparable magnitude to the effects of interannual variability in environmental conditions in determining malaria prevalence. The memory associated with this hysteresis effect is longer in high transmission settings than in low transmission settings. Our results show that efforts to simulate and forecast malaria transmission must consider the exposure history of a location as well as the concurrent environmental drivers.

Effect of inter-annual variability in pasture growth and irrigation response on farm productivity and profitability based on biophysical and farm systems modelling

Farm system and nutrient budget models are increasingly being used in analysis to inform on farm decision making and evaluate land use policy options at regional scales. These analyses are generally based on the use of average annual pasture yields. In New Zealand (NZ), like in many countries, there is considerable inter-annual variation in pasture growth rates, due to climate. In this study a modelling approach was used to (i) include inter-annual variability as an integral part of the analysis and (ii) test the approach in an economic analysis of irrigation in a case study within the Hawkes Bay Region of New Zealand.The Agricultural Production Systems Simulator (APSIM) was used to generate pasture dry matter yields (DMY) for 20 different years and under both dryland and irrigation. The generated DMY were linked to outputs from farm-scale modelling for both Sheep and Beef Systems (Farmaxx Pro) and Dairy Systems (Farmax® Dairy Pro) to calculate farm production over 20 different years. Variation in DMY and associated livestock production due to inter-annual variation in climate was large, with a coefficient of variations up to 20%. Irrigation decreased this inter-annual variation. On average irrigation, with unlimited available water, increased income by $831 to 1195/ha, but when irrigation was limited to 250mm/ha/year income only increased by $525 to 883/ha. Using pasture responses in individual years to capturing the inter-annual variation, rather than the pasture response averaged over 20years resulted in lower financial benefits. In the case study income from irrigation based on an average year were 10 to >20% higher compared with those obtained from individual years.

Interacting effects of soil degradation and precipitation on plant productivity in NE Patagonia, Argentina

ABSTRACTOur objective was to examine the effects of inter-annual variation of precipitation on productivity of two dominant species (Chuquiraga avellanedae, an evergreen shrub, and Nassella tenuis, a perennial grass) in two communities of contrasting soil degradation: a herbaceous steppe with shrubs (HSS) and a degraded shrub steppe (SS). Data were collected during two consecutive years with different annual precipitation. Aboveground productivity was determined nondestructively using a double sampling approach. The number of inflorescences per plant was recorded too. Perennial grass productivity was lower in SS than in HSS in both years, while shrub productivity was lower in SS only during the year of below average precipitation. With rising precipitation the perennial grass increased the number of inflorescences while the evergreen shrub augmented vegetative biomass. In summary, the effects of precipitation on plant productivity are community dependent; abiotic factors, such as superficial and sub-superficial soil characteristics, and biotic factors, such as leaf area index (LAI) or tussock sizes, may interact to influence the responses of species to precipitation. Our results suggest that if precipitation increased, this would favor the dominance of shrubs over grasses.

Effects of the interannual variability in chlorophyll concentrations on sea surface temperatures in the east tropical Indian Ocean

AbstractThe effects of interannual variability in chlorophyll concentrations on sea surface temperatures in the east tropical Indian Ocean (ETIO) during two positive Indian Ocean Dipole (IOD) events (in the boreal fall of 1997 and 2006) are investigated; this is done through two ocean model experiments, one with and one without the interannual variability of chlorophyll concentrations. A comparison of the two chlorophyll perturbation experiments reveals that, in contrast to the cooling effects at the seasonal time scale, increased chlorophyll concentrations during positive IOD events lead to an increase in the sea surface temperatures within the ETIO. Although upward velocity is enhanced (with a cooling effect), this does not counterbalance the increase in solar heating caused by the increased chlorophyll concentrations. This interannual variability of chlorophyll concentrations in the ETIO could reduce the amplitude of the IOD by about 6%.

Forage nutritional characteristics and yield dynamics in a grazed semiarid steppe ecosystem of Inner Mongolia, China

In the steppe of Inner Mongolia, forage is the only source of feed for sheep. The forage intake of sheep can be characterized in both quantity and quality terms, which are determined by environmental and anthropogenic factors and grazing has a strong effect on steppe productivity and the grassland ecosystem. Evaluation of forage quality and quantity is therefore of critical importance. The effects of grazing intensity, interannual variability effects, and species composition on aboveground net primary productivity (ANPP) and forage nutritional characteristics were investigated in a controlled grazing experiment along a gradient of 7 grazing intensities (from non-grazed to very heavily grazed) over six years (2005–2010) on typical steppe in Inner Mongolia. Forage nutritional characteristics were defined by the nutritional value (concentrations of crude protein (CP), cellulase digestible organic matter (CDOM), metabolizable energy (ME) and neutral detergent fibre (NDF)) and the nutritional yield. The forage nutritional yield is a function of ANPP and the forage nutritional value. Forage nutritional value increased but ANPP and nutritional yields decreased with increasing grazing intensity. The inter-annual variation of ANPP, forage nutritional value and yield were weakly linked to the inter-annual variability of precipitation. However, ANPP and nutritional value also varied during the growing season, depending on the seasonal distribution of precipitation and temperature, which influence forage digestibility (CDOM) and metabolizable energy (ME), with higher CDOM and ME under high seasonal precipitation and low seasonal mean temperature. Forage nutritional value and yield, as well as ANPP, were predominantly determined by the dominant species rather than by species diversity. The results suggest that forage nutritional yield in the Inner Mongolian steppe is predominantly determined by the ANPP and only to a minor extent by forage nutritional value, and is predominantly determined by the dominant species and only to a minor extent by species diversity. Therefore, herbage productivity seems to be the most limiting factor in managing this steppe ecosystem as a feeding resource for livestock and to be the best ecological and environmental indicator for grassland management practices.

Effect of interannual variation in winter vertical mixing on CH4 dynamics in a subtropical reservoir

AbstractAlthough freshwaters are considered to be substantial natural sources of atmospheric methane (CH4), in situ processes of CH4 production and consumption in freshwater ecosystems are poorly understood, especially in subtropical areas, leading to uncertainties in the estimation of global CH4 emissions. To improve our understanding of physical and biogeochemical factors affecting CH4 dynamics in subtropical lakes, we examined vertical and seasonal profiles of dissolved CH4 and its carbon isotope ratio (δ13C) and conducted incubation experiments to assess CH4 production and oxidation in the deep subtropical Fei‐Tsui Reservoir (FTR; Taiwan). The mixing pattern of the FTR is essentially monomixis, but the intensity of winter vertical mixing changes with climatic conditions. In years with incomplete vertical mixing (does not reach the bottom) and subsequent strong thermal stratification resulting in profundal hypoxia, we observed increases in sedimentary CH4 production and thus profundal CH4 storage with the development of reducing conditions. In contrast, in years with strong winter vertical mixing to the bottom of the reservoir, CH4 production was suppressed under NO3−‐rich conditions, during which denitrifiers have the competitive advantage over methanogens. Diffusive emission from profundal CH4 storage appeared to be negligible due to the efficiency of CH4 oxidation during ascent through methane‐oxidizing bacteria (MOB) activity. Most of the profundal CH4 was rapidly oxidized by MOB in both oxic and anoxic layers, as characterized by its carbon isotope signature. In contrast, aerobic CH4 production in the subsurface layer, which may be enhanced under high temperatures in summer, may account for a large portion of atmospheric CH4 emissions from this reservoir. Our CH4 profiling results provide valuable information for future studies predicting CH4 emissions from subtropical lakes with the progress of global warming.

Managing cattle grazing intensity: effects on soil organic matter and soil nitrogen

Extensive cattle grazing is the dominant land use in northern Australia. It has been suggested that grazing intensity and rainfall have profound effects on the dynamics of soil nutrients in northern Australia’s semi-arid rangelands. Previous studies have found positive, neutral and negative effects of grazing pressure on soil nutrients. These inconsistencies could be due to short-term experiments that do not capture the slow dynamics of some soil nutrients and the effects of interannual variability in rainfall. In a long-term cattle grazing trial in northern Australia on Brown Sodosol–Yellow Kandosol complex, we analysed soil organic matter and mineral nitrogen in surface soils (0–10 cm depth) 11, 12 and 16 years after trial establishment on experimental plots representing moderate stocking (stocked at the long-term carrying capacity for the region) and heavy stocking (stocked at twice the long-term carrying capacity). Higher soil organic matter was found under heavy stocking, although grazing treatment had little effect on mineral and total soil nitrogen. Interannual variability had a large effect on soil mineral nitrogen, but not on soil organic matter, suggesting that soil nitrogen levels observed in this soil complex may be affected by other indirect pathways, such as climate. The effect of interannual variability in rainfall and the effects of other soil types need to be explored further.

Site-specific factors influence the richness and phenology of snowbed plants in the Pyrenees

Although the timing of snowmelt and growth temperatures appear to be the main factors that influence the species richness and phenology of snowbed plants, site-specific characteristics may also play a role in modifying the effects of the timing of snowmelt and temperature. In this study, the effects of site-specific factors (microtopography and snow origin) on species richness and plant phenology were evaluated in 72 plots in two snowbeds in the Andorran Pyrenees. Snowmelt patterns influenced the spatial distribution of species richness and abundance. Site-specific factors had significant effects on the responses of species (shortening or lengthening the duration of the phenophase) and on the extent to which the timing of snowmelt influenced leaf expansion and flowering. Notably, the highest rates of leaf expansion occurred on late snowmelt isoclines, where, nevertheless, the time taken to reach peak flowering was significantly longer than on the early snowmelt isoclines. The results of this study highlight the fact that, in addition to the effects of interannual variability in climate, site-specific factors have a significant effect on the phenology and reproductive success of the commonest plants in the snowbed communities of the Pyrenees.

Trend detection in seasonal data: from hydrology to water resources

Summary In this paper we investigate the relationship between hydro-climatic trends and their impacts on water resources at the basin scale, focusing on a catchment on the Italian and Swiss Alps in the period 1974–2010. More generally, we address the topic of trend detection in environmental time series combining novel and traditional tools in order to simultaneously tackle the issue of seasonality and interannual variability, which usually characterize natural processes. The paper’s contribution is twofold. First, we propose a novel tool to be applied in Exploratory Data Analysis, named MASH (Moving Average over Shifting Horizon). It allows to simultaneously investigate the seasonality in the data and filter out the effects of interannual variability, thus facilitating trend detection. We describe how to combine the MASH with statistical trend detection tests, like the Mann–Kendall test, the Seasonal Kendall test, and the Linear Regression test, and Sen’s method, to quantify the trends occurring in different seasons. Second, we estimate the impacts of hydrological changes in terms of water resources and we discuss their relevance from the water resources management perspective. We define and simulate a set of indicators of performances, resilience, reliability, and vulnerability, so to assess the ability of the water resources systems to absorb changes in the hydrological patterns. The analysis reveals that, in the case study area, statistically significant trends in hydro-climatic records have been undergoing in the last decades, although they have had limited impacts on water resources.

A long-term assessment of the effect of winter severity on the food habits of white-tailed deer

Nutrition is a critical link between environmental and population variation in northern populations of free-ranging white-tailed deer (Odocoileus virginianus). Yet, few studies have investigated winter food habits of northern free-ranging deer and all of these were short-term studies (1–2 winters). Consequently, little information is available on the effect of inter-annual variation in winter severity on browse availability and diet composition of free-ranging deer. We describe winter browse use by white-tailed deer on 4 study sites in northern Minnesota during 1991–2005. We also tested several a priori predictions about how browse use and availability would change as a function of winter severity. We collected browse data from 1,028 feeding trails and recorded 38 available browse species or species groups. The 4 most common browse species (beaked hazel [Corylus cornuta], mountain maple [Acer spicatum], trembling aspen [Populus tremuloides], and speckled alder [Alnus incana]) accounted for 76% of total available stems, and beaked hazel and mountain maple accounted for 68% of total used stems. As expected, browse use and availability distributions were very similar (i.e., deer used many of the available browse resources). Mean number of browse species used did not increase (decreased selection) with snow depth. However, mean browse rate (functional response) increased with increasing snow depth, and use of speckled alder (starvation food) increased when snow depth exceeded 40 cm. In addition, the number of browse species along feeding trails declined and stem abundance increased, on average, with increasing snow depth. Deep snow and increased use of dense conifer cover in northern Minnesota may restrict deer to greater use of lower quality feeding sites. In landscapes where this may occur, habitat management should attempt to minimize over-browsing on feeding sites in proximity to dense conifer cover by maximizing browse abundance and availability, particularly for beaked hazel and mountain maple. Managers also should consider enhancing alternative early-winter feeding sites. © 2013 The Wildlife Society. © The Wildlife Society, 2013

The effect of vaccination coverage and climate on Japanese encephalitis in Sarawak, Malaysia.

BackgroundJapanese encephalitis (JE) is the leading cause of viral encephalitis across Asia with approximately 70,000 cases a year and 10,000 to 15,000 deaths. Because JE incidence varies widely over time, partly due to inter-annual climate variability effects on mosquito vector abundance, it becomes more complex to assess the effects of a vaccination programme since more or less climatically favourable years could also contribute to a change in incidence post-vaccination. Therefore, the objective of this study was to quantify vaccination effect on confirmed Japanese encephalitis (JE) cases in Sarawak, Malaysia after controlling for climate variability to better understand temporal dynamics of JE virus transmission and control.Methodology/principal findingsMonthly data on serologically confirmed JE cases were acquired from Sibu Hospital in Sarawak from 1997 to 2006. JE vaccine coverage (non-vaccine years vs. vaccine years) and meteorological predictor variables, including temperature, rainfall and the Southern Oscillation index (SOI) were tested for their association with JE cases using Poisson time series analysis and controlling for seasonality and long-term trend. Over the 10-years surveillance period, 133 confirmed JE cases were identified. There was an estimated 61% reduction in JE risk after the introduction of vaccination, when no account is taken of the effects of climate. This reduction is only approximately 45% when the effects of inter-annual variability in climate are controlled for in the model. The Poisson model indicated that rainfall (lag 1-month), minimum temperature (lag 6-months) and SOI (lag 6-months) were positively associated with JE cases.Conclusions/significanceThis study provides the first improved estimate of JE reduction through vaccination by taking account of climate inter-annual variability. Our analysis confirms that vaccination has substantially reduced JE risk in Sarawak but this benefit may be overestimated if climate effects are ignored.

Trend Change Detection in NDVI Time Series: Effects of Inter-Annual Variability and Methodology

Changing trends in ecosystem productivity can be quantified using satellite observations of Normalized Difference Vegetation Index (NDVI). However, the estimation of trends from NDVI time series differs substantially depending on analyzed satellite dataset, the corresponding spatiotemporal resolution, and the applied statistical method. Here we compare the performance of a wide range of trend estimation methods and demonstrate that performance decreases with increasing inter-annual variability in the NDVI time series. Trend slope estimates based on annual aggregated time series or based on a seasonal-trend model show better performances than methods that remove the seasonal cycle of the time series. A breakpoint detection analysis reveals that an overestimation of breakpoints in NDVI trends can result in wrong or even opposite trend estimates. Based on our results, we give practical recommendations for the application of trend methods on long-term NDVI time series. Particularly, we apply and compare different methods on NDVI time series in Alaska, where both greening and browning trends have been previously observed. Here, the multi-method uncertainty of NDVI trends is quantified through the application of the different trend estimation methods. Our results indicate that greening NDVI trends in Alaska are more spatially and temporally prevalent than browning trends. We also show that detected breakpoints in NDVI trends tend to coincide with large fires. Overall, our analyses demonstrate that seasonal trend methods need to be improved against inter-annual variability to quantify changing trends in ecosystem productivity with higher accuracy.