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Seasonal climate and topography influence C3 and C4 grass species aboveground biomass (AGB). Climate change further threatens these grasses AGB, thereby compromising their ability to provide ecosystem goods and services. This emphasises the need to monitor their AGB for well‐informed management. New‐generation sensors, with improved resolution capabilities present an opportunity to explore C3 and C4 AGB. This study therefore investigated the response of remotely sensed C3 and C4 grasses AGB to seasonal climate and topography. Overall, the spatial and temporal responses of AGB due to seasonal climate and topography were observed across the study area. For example, in March, a marked increase in C4 AGB was associated with an increase in rainfall, with the highest significant positive relationship (R2 = 0.82, p < 0.005). Elevation had very significant positive relationship (R2 = 0.84; p < 0.005) with C3 and highest negative (R2 = −0.77; p < 0.005) with C4 AGB. During the winter fall, AGB significantly decreased from averages of 2.592 and 1.101 kg/m2 in winter (May), to 0.718 and 0.469 kg/m2 in August, for C3 and C4 grasses, respectively. These findings provide a key step in monitoring rangelands and assessing management practices to boost productivity. [ABSTRACT FROM AUTHOR]

In the present study, two districts of North-East region of Bangladesh; a flood prone area with high temperature and maximum precipitation, respectively, were selected along-with two widely cultivated Boro rice varieties in Bangladesh. Reference evapotranspiration (ETO) during the study period from 1994 to 2010 was estimated with the daily meteorological data utilizing the FAO Penman-Monteith method. A MAKESENS trend model was adopted for the assessment of both Mann-Kendall test and Sen's rate of change over the study period. During the study period, the potential crop water requirement of Bangladesh Rice Research Institute dhan 28 (B28) and BRRI dhan 29 (B29) in Moulvibazar has been declined by -3.953 mm year-1 and -5.182 mm year-1, respectively; whereas it has been raised by 2.483 mm year-1 and 2.387 mm year-1, respectively in Sylhet. The climatic parameters affecting the observed and projected trends in Potential water requirement differed both significantly and insignificantly over the months of the year. For both varieties, maximum water demand was observed in mid-season stage; whereas the development stage, the water demand was found to be minimum. [ABSTRACT FROM AUTHOR]

Anthropogenic heat release (AHR) is the heat generated in global energy consumption, which has not been considered in global climate models generally. The global high-resolution AHR from 1992 to 2013, which is estimated by using the Defense Meteorological Satellite Program (DMSP)/Operational Linescan System (OLS) satellite data, is implemented into the Community Atmosphere Model version 5 (CAM5). The seasonal climatic effects and possible feedbacks of AHR are examined in this study. The modeling results show that AHR increases the global annual mean surface temperature and land surface temperature by 0.02 ± 0.01 K (1σ uncertainty) and 0.05 ± 0.02 K (1σ uncertainty), respectively. The global climatic effect of AHR varies with season: with a stronger climatic effect in the boreal winter leading to global mean land surface temperature increases by 0.10 ± 0.01 K (1σ uncertainty). In the selected regions (40°N–60°N, 0°E–45°E) of Central and Western Europe the average surface temperature increases by 0.46 K in the boreal summer, and in the selected regions (45°N–75°N, 30°E–140°E) of northern Eurasia the average surface temperature increases by 0.83 K in the boreal winter. AHR changes the height and thermodynamic structure of the global planetary boundary layer, as well as the stability of the lower troposphere, which affects the global atmospheric circulation and low cloud fraction. In addition, at the surface both the shortwave radiation flux in the boreal summer and the down-welling longwave flux in the boreal winter change significantly, as a result of the change in low clouds caused by the effect of AHR. This study suggests a possible new mechanism of AHR effect on global climate through changing the global low-cloud fraction, which is crucial for global energy balance, by modifying the thermodynamic structure and stability of the lower troposphere. Thus this study improves our understanding of the global climate change caused by human activities. [ABSTRACT FROM AUTHOR]

Indications suggest that anthropic activities have altered the atmospheric composition, causing alterations in elements generating extreme weather events and contributing to what we know today as global warming, through global and local changes in the rain regime and other climatic variables that interact in the hydrological cycle, causing extreme events with greater frequency. It is necessary to know the trends and extreme events of rains in order to have a basis for the adaptation and prevention of natural disasters caused by these macroclimatic phenomena. Through non-parametric tests, we found an increasing trend in rainfall between 5% to 20% average, in comparison with the behavior in the period of 1980 to 1990. Similarly, the influence of the macroclimatic variables in rainfall behavior is null. [ABSTRACT FROM AUTHOR]

Interannual variability (IAV, represented by standard deviation) in net ecosystem exchange of CO 2 (NEE) is mainly driven by climatic drivers and biotic variations (i.e., the changes in photosynthetic and respiratory responses to climate), the effects of which are referred to as climatic (CE) and biotic effects (BE), respectively. Evaluating the relative contributions of CE and BE to the IAV in carbon (C) fluxes and understanding their controlling mechanisms are critical in projecting ecosystem changes in the future climate. In this study, we applied statistical methods with flux data from 65 sites located in the Northern Hemisphere to address this issue. Our results showed that the relative contribution of BE (CnBE) and CE (CnCE) to the IAV in NEE was 57% ± 14% and 43% ± 14%, respectively. The discrepancy in the CnBE among sites could be largely explained by water balance index (WBI). Across water-stressed ecosystems, the CnBE decreased with increasing aridity (slope = 0.18% mm −1 ). In addition, the CnBE tended to increase and the uncertainty reduced as timespan of available data increased from 5 to 15 years . Inter-site variation of the IAV in NEE mainly resulted from the IAV in BE (72%) compared to that in CE (37%). Interestingly, positive correlations between BE and CE occurred in grasslands and dry ecosystems ( r > 0.45, P < 0.05) but not in other ecosystems. These results highlighted the importance of BE in determining the IAV in NEE and the ability of ecosystems to regulate C fluxes under climate change might decline when the ecosystems experience more severe water stress in the future. [ABSTRACT FROM AUTHOR]

Dengue fever is one of the most widespread vector-borne diseases and has caused more than 50 million infections annually over the world. For the purposes of disease prevention and climate change health impact assessment, it is crucial to understand the weather-disease associations for dengue fever. This study investigated the nonlinear delayed impact of meteorological conditions on the spatiotemporal variations of dengue fever in southern Taiwan during 1998–2011. We present a novel integration of a distributed lag nonlinear model and Markov random fields to assess the nonlinear lagged effects of weather variables on temporal dynamics of dengue fever and to account for the geographical heterogeneity. This study identified the most significant meteorological measures to dengue fever variations, i.e., weekly minimum temperature, and the weekly maximum 24-hour rainfall, by obtaining the relative risk (RR) with respect to disease counts and a continuous 20-week lagged time. Results show that RR increased as minimum temperature increased, especially for the lagged period 5–18 weeks, and also suggest that the time to high disease risks can be decreased. Once the occurrence of maximum 24-hour rainfall is > 50 mm, an associated increased RR lasted for up to 15 weeks. A temporary one-month decrease in the RR of dengue fever is noted following the extreme rain. In addition, the elevated incidence risk is identified in highly populated areas. Our results highlight the high nonlinearity of temporal lagged effects and magnitudes of temperature and rainfall on dengue fever epidemics. The results can be a practical reference for the early warning of dengue fever. [ABSTRACT FROM AUTHOR]

Abstract: A natural water hydrochemical investigation was carried out on three watersheds in northern Xinjiang, China to evaluate the climatic, geological and anthropogenic influence on aqueous major element chemistry in an arid environment. Wide spatial variations are observed in the dissolved solids (TDS) and water chemistry. The hydrochemistry is typically carbonate and alkaline in nature, with Ca2+, HCO3 − and SO4 2− dominating the major ion composition. Four major water types, Ca–HCO3, Ca–NDA (non-dominant anion), Ca–SO4 and NDC (non-dominant cation)–NDA or Na–NDA type, are identified in terms of the Piper model. The water chemistry agrees well with the “rock dominance” mechanism, with a TDS value of 80–600mg/L and a Na+/(Na+ +Ca2+) ratio of 0.1–0.6. Correlation analysis suggests that most of the ions derive from multiple sources. Stoichiometric analyses indicate that carbonate weathering is the primary source of dissolved ions, followed by silicate weathering and evaporite dissolution. The effects of local pollution have somewhat greater contribution on the oases and central areas of the Zhungarer watershed. Most parts of the rivers show an increasing trend in the dissolved load toward the lower reaches, which is primarily attributed to an evaporation process control along the water course. Variations in water chemistry show clear correlation with the regional lithological distribution, topography and atmospheric precipitation. Using rainwater as a baseline, contributions from atmospheric precipitation and rock weathering to the tributary chemistry are roughly evaluated to be in the range of 2–39% (average 13%) and 59–98% (average 86%), respectively, implying a high effective control of regional geology on stream chemistry compared with that of atmospheric input. [Copyright &y& Elsevier]