scholarly journals Effect of Elevation on Variation in Reference Evapotranspiration under Climate Change in Northwest China

2021 ◽  
Vol 13 (18) ◽  
pp. 10151
Author(s):  
Wei Liu ◽  
Linshan Yang ◽  
Meng Zhu ◽  
Jan F. Adamowski ◽  
Rahim Barzegar ◽  
...  
Keyword(s):  
Climate Change ◽  
Land Surface ◽  
Reference Evapotranspiration ◽  
Sunshine Duration ◽  
Northwest China ◽  
Temporal Variations ◽  
Climatic Conditions ◽  
Dominant Factor ◽  
Mountainous Regions ◽  
Meteorological Observations

Through its effects on water and energy cycles, elevation plays an important role in modulating the spatial distribution of climatic changes in mountainous regions. A key hydrological indicator, reference evapotranspiration (ET0) reflects the maximum amount of water transferred to the atmosphere from the land surface. The current scarcity of information regarding elevation’s impact on variation in ET0 under climate change limits our understanding of the extent to which elevation modulates interactions between ET0 and climate change and of the attendant processes involved. Drawing upon long-term (1960–2017) meteorological observations from 84 stations in Northwest China (NWC), we examined (i) spatial and temporal variations in ET0; (ii) the sensitivity and contribution of air temperature (T), sunshine duration (SD), relative humidity (RH), and wind speed (WS) to ET0; (iii) the existence of a relationship between elevation and ET0 trends; and (iv) the major factor in controlling this relationship by using attribution analysis. Overall, annual ET0 in NWC showed a declining trend between 1960 and 2017, though at a change point in 1993, the trend shifted from a decline to a rise. A significant correlation between temporal change in ET0 and elevation confirmed the existence of a relationship between elevation and ET0 variation. The effect of elevation on changes in ET0 depended mainly on the elevation-based tradeoff between the contributions of T and WS: WS was the primary factor contributing to the decrease in ET0 below 2000 m, and T was the dominant factor contributing to the increase of ET0 above 2000 m. The rate of reduction in WS declined as elevation increased, thereby diminishing its contribution to variation in ET0. The present study’s results can serve to guide agricultural irrigation in different elevation zones under NWC’s evolving climatic conditions.

scholarly journals Spatiotemporal Variations of Reference Evapotranspiration and Its Determining Climatic Factors in the Taihang Mountains, China

Water ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 3145
Author(s):  
Tingting Kang ◽  
Zeng Li ◽  
Yanchun Gao
Keyword(s):  
Climate Change ◽  
Land Surface ◽  
Reference Evapotranspiration ◽  
Climatic Factors ◽  
Sunshine Duration ◽  
High Elevation ◽  
Lower Sensitivity ◽  
Effective Measure ◽  
The Impact ◽  
The Relationship

Reference evapotranspiration (ETo) is an effective measure of atmospheric water demand of the land surface. In-depth investigations of the relationship between ETo and primary climatic factors can facilitate the adaptable agriculture and optimize water management, especially in the ecologically fragile Taihang Mountains (THM). This work assessed the spatiotemporal dynamics of ETo and its driving climatic factors from 1973 to 2016 in THM. Results showed: (1) Annual ETo slightly increased during 1973–2016; relative humidity (RH) decreased more slowly, the temperature increased more rapidly, and wind speed (WS) decreased more rapidly at higher elevation than those at lower elevations; (2) two breakpoints occurred in ETo series at 1990 and 1997, and an “evaporation paradox” existed in 1973–1990; (3) ETo at higher elevations had greater sensitivity to changes in RH and lower sensitivity to changes in Tmax and WS. Sensitivity of ETo to minimum air temperature (Tmin) at middle elevations was lowest among three elevation bands; (4) RH and sunshine duration (SD) were the dominant climatic factors of ETo for most periods and stations. This study helps us understand the impact of climate change on ETo in mountainous areas and confirms reference evapotranspiration in high-elevation areas is particularly sensitive to climate change.

scholarly journals The effects of ENSO, climate change and human activities on the water level of Lake Toba, Indonesia: a critical literature review

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Hendri Irwandi ◽  
Mohammad Syamsu Rosid ◽  
Terry Mart
Keyword(s):  
Climate Change ◽  
Water Level ◽  
Human Activities ◽  
Southern Oscillation ◽  
Climatic Conditions ◽  
Water Levels ◽  
Dominant Factor ◽  
Climate Projections ◽  
Continuous Increase ◽  
The Future

AbstractThis research quantitatively and qualitatively analyzes the factors responsible for the water level variations in Lake Toba, North Sumatra Province, Indonesia. According to several studies carried out from 1993 to 2020, changes in the water level were associated with climate variability, climate change, and human activities. Furthermore, these studies stated that reduced rainfall during the rainy season due to the El Niño Southern Oscillation (ENSO) and the continuous increase in the maximum and average temperatures were some of the effects of climate change in the Lake Toba catchment area. Additionally, human interventions such as industrial activities, population growth, and damage to the surrounding environment of the Lake Toba watershed had significant impacts in terms of decreasing the water level. However, these studies were unable to determine the factor that had the most significant effect, although studies on other lakes worldwide have shown these factors are the main causes of fluctuations or decreases in water levels. A simulation study of Lake Toba's water balance showed the possibility of having a water surplus until the mid-twenty-first century. The input discharge was predicted to be greater than the output; therefore, Lake Toba could be optimized without affecting the future water level. However, the climate projections depicted a different situation, with scenarios predicting the possibility of extreme climate anomalies, demonstrating drier climatic conditions in the future. This review concludes that it is necessary to conduct an in-depth, comprehensive, and systematic study to identify the most dominant factor among the three that is causing the decrease in the Lake Toba water level and to describe the future projected water level.

scholarly journals Impact of global dimming on reference evapotranspiration in Hai River basin, China

2015 ◽  
Vol 368 ◽  
pp. 287-292 ◽  
Author(s):  
N. Zhao ◽  
X. Zeng ◽  
H. Sun
Keyword(s):  
River Basin ◽  
Surface Energy Balance ◽  
Hydrological Cycle ◽  
Reference Evapotranspiration ◽  
Sunshine Duration ◽  
Global Radiation ◽  
Dominant Factor ◽  
Upward Trend ◽  
Temporal And Spatial ◽  
Global Dimming

Abstract. Global radiation can impact the surface energy balance and hydrological cycle. This study analysed changes in global radiation in Hai River basin, China during 1960 to 2012. Global radiation decreased significantly from 1960 to 1989 and increased from 1990 to 2012, which has been described as “from dimming to brightening”. Sunshine duration was used as a proxy index where radiation records were unavailable. Results showed that sunshine duration (for 45 stations) show a significant decreasing trend from 1960 to 2012, which was a little different to global radiation (for 6 stations) during the brightening phase. Penman-Monteith model was used for estimating trends of reference evapotranspiration. The consistency of temporal and spatial variations in sunshine duration and reference evapotranspiration was examined during the periods 1960−1989 and 1990−2012. The results showed that the annual reference evapotranspiration trend was consistent with the sunshine duration trend (both were decreasing for 37 of the 45 stations) during 1960 to 1989, followed by an upward trend (for 26 of the 45 stations) from 1990, while the annual sunshine duration indicated a downward trend (for all 45 stations) during the whole period 1960−2012. Overall, global dimming could be the dominant factor for the decreased reference evapotranspiration from 1960 to 1989, while the increased reference evapotranspiration from 1990 to 2012 could be driven by other meteorological variables, especially global warming.

Terrestrial Processes and Their Roles in Climate Change

2021 ◽  
Author(s):  
Nathalie de Noblet-Ducoudré ◽  
Andrew J. Pitman
Keyword(s):  
Climate Change ◽  
Greenhouse Gases ◽  
Land Surface ◽  
Seasonal Cycle ◽  
Spatial Scales ◽  
Climatic Conditions ◽  
Surface Processes ◽  
Climate Modelling ◽  
Climate Simulations

The land surface is where humans live and where they source their water and food. The land surface plays an important role in climate and anthropogenic climate change both as a driver of change and as a system that responds to change. Soils and vegetation influence the exchanges of water, energy and carbon between the land and the overlying atmosphere and thus contribute to the variability and the evolution of climate. But the role of the land in climate is scale dependent which means different processes matter on different timescales and over different spatial scales. Climate change alters the functioning of the land with changes in the seasonal cycle of ecosystem growth, in the extent of forests, the melt of permafrost, the magnitude and frequency of disturbances such as fire, drought, … Those changes feedback into climate at both the global and the regional scales. In addition, humans perturb the land conditions via deforestation, irrigation, urbanization, … and this directly affects climatic conditions at the local to regional scales with also sometimes global consequences via the release of greenhouse gases. Not accounting for land surface processes in climate modelling, whatever the spatial scale, will result in biases in the climate simulations.

scholarly journals Variations in the Simulation of Climate Change Impact Indices due to Different Land Surface Schemes over the Mediterranean, Middle East and Northern Africa

Atmosphere ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 26 ◽  
Author(s):  
Katiana Constantinidou ◽  
George Zittis ◽  
Panos Hadjinicolaou
Keyword(s):  
Climate Change ◽  
Middle East ◽  
Land Surface ◽  
Climate Change Impact ◽  
Climate Model ◽  
Eastern Mediterranean ◽  
Regional Climate ◽  
Climatic Conditions ◽  
Relative Dispersion ◽  
Change Impact

The Eastern Mediterranean (EM) and the Middle East and North Africa (MENA) are projected to be exposed to extreme climatic conditions in the 21st century, which will likely induce adverse impacts in various sectors. Relevant climate change impact assessments utilise data from climate model projections and process-based impact models or simpler, index-based approaches. In this study, we explore the implied uncertainty from variations of climate change impact-related indices as induced by the modelled climate (WRF regional climate model) from different land surface schemes (Noah, NoahMP, CLM and RUC). The three climate change impact-related indicators examined here are the Radiative Index of Dryness (RID), the Fuel Dryness Index (Fd) and the Water-limited Yield (Yw). Our findings indicate that Noah simulates the highest values for both RID and Fd, while CLM gives the highest estimations for winter wheat Yw. The relative dispersion in the three indices derived by the different land schemes is not negligible, amounting, for the overall geographical domain of 25% for RID and Fd, and 10% for Yw. The dispersion is even larger for specific sub-regions.

scholarly journals Changes in Reference Evapotranspiration over Southwest China during 1960–2018: Attributions and Implications for Drought

Atmosphere ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 705 ◽  
Author(s):  
Zhaoqi Zeng ◽  
Wenxiang Wu ◽  
Yang Zhou ◽  
Zhaolei Li ◽  
Mei Hou ◽  
...  
Keyword(s):  
Linear Regression ◽  
Multiple Linear Regression ◽  
Southwest China ◽  
Reference Evapotranspiration ◽  
Sunshine Duration ◽  
Dominant Role ◽  
Driving Factors ◽  
Dominant Factor ◽  
Drought Duration ◽  
Entire Study

Reference evapotranspiration (ET0) is important to the global energy balance and to hydrological cycling. However, the extent to which ET0 changes, the main driving factors, and especially the implications of its shift for drought in Southwest China are not clear. In this study, trends in Penman–Monteith ET0 and other climatic parameters at 79 stations in Southwest China from 1960 to 2018 were investigated by using the Mann–Kendall test. Furthermore, partial correlation analysis and multiple linear regression were used to determine the dominant climate driving factors in changes in ET0. The relative contribution of precipitation and ET0 to drought duration was also quantified based on spatial multiple linear regression. Results revealed that annual ET0 decreased significantly (p < 0.01) at a rate of 14.1 mm per decade from 1960 to 2000, and this decrease disappeared around 2000. For the entire study period, the sunshine duration (Tsun) was the most closely correlated with and played a dominant role in the variations in ET0 at both annual and seasonal (summer and autumn) timescales, whereas the relative humidity was the most dominant factor in the spring and winter. Trends in the Standardized Precipitation Evapotranspiration Index revealed that drought has become more serious in Southwest China, and ET0 has made a greater contribution to the duration of drought than precipitation. Our findings highlight that more attention should be paid to the impacts of ET0 changes on drought in Southwest China. Furthermore, these results can provide a reference for the allocation of water resources and the implementation of countermeasures to climate change.

scholarly journals Quantifying the Contributions of Environmental Factors to Wind Characteristics over 2000–2019 in China

2021 ◽  
Vol 10 (8) ◽  
pp. 515
Author(s):  
Yuming Lu ◽  
Bingfang Wu ◽  
Nana Yan ◽  
Weiwei Zhu ◽  
Hongwei Zeng ◽  
...  
Keyword(s):  
Climate Change ◽  
Wind Speed ◽  
Environmental Factors ◽  
Human Activities ◽  
Land Surface ◽  
Power Plants ◽  
Sunshine Duration ◽  
Central Area ◽  
Eastern Region ◽  
Human Beings

Global climate change and human activities have resulted in immense changes in the Earth’s ecosystem, and the interaction between the land surface and the atmosphere is one of the most important processes. Wind is a reference for studying atmospheric dynamics and climate change, analyzing the wind speed change characteristics in historical periods, and studying the influence of wind on the Earth-atmosphere interaction; additionally, studying the wind, contributes to analyzing and alleviating a series of problems, such as the energy crisis, environmental pollution, and ecological deterioration facing human beings. In this study, data from 697 meteorological stations in China from 2000 to 2019 were used to study the distribution and trend of wind speed over the past two decades. The relationships between wind speed and climate factors were explored using statistical methods; furthermore, combined with terrain, climate change, and human activities, we quantified the contribution of environmental factors to wind speed. The results show that a downward trend was recorded before 2011, but overall, there was an increasing trend that was not significant; moreover, the wind speed changes showed obvious seasonality and were more complicated on the monthly scale. The wind speed trend mainly increased in the western region, decreased in the eastern region, was higher in the northeastern, northwestern, and coastal areas, and was lower in the central area. Temperature, bright sunshine duration, evaporation, and precipitation had a strong influence, in which wind speed showed a significant negative correlation with temperature and precipitation and vice versa for sunshine and evapotranspiration. The influence of environmental factors is diverse, and these results could help to develop environmental management strategies across ecologically fragile areas and improve the design of wind power plants to make better use of wind energy.

Variations and Sensitivity Analysis of Reference Evapotranspiration During 2010-2019 in the Zhangye Farmland Oasis, Northwest China

2021 ◽  
Author(s):  
Miao Fang
Keyword(s):  
Sensitivity Analysis ◽  
Reference Evapotranspiration ◽  
Sunshine Duration ◽  
Northwest China ◽  
Meteorological Factor ◽  
Maximum Temperature ◽  
Regression Equations ◽  
Significance Level ◽  
Hargreaves Equation ◽  
Increasing Trends

Abstract Reference evapotranspiration (ET0) is an important parameter for agricultural water management in the arid Zhangye farmland oasis. However, the ET0 variations in this oasis over the last decade and meteorological forcings of these variations are unknown. This study investigated the ET0 variations during 2010-2019 in this oasis using the FAO-56 Penman-Monteith (PM) and Hargreaves equations. Results showed that the ET0 features daily and monthly variations with peak values in mid-July and an annual cycle. Although the estimated ET0 series based on the two equations have high correlations in the time domain, the Hargreaves equation always underestimates the ET0 compared to the PM equation. The yearly ET0 showed statistically significant increasing trends (90% significance level) during 2010-2019, while statistically significant increasing trends in monthly ET0 are found only in March and November. Increasing trends reflected in monthly and yearly ET0 are mainly attributed to the increasing maximum temperature and sunshine duration and decreasing relative humidity. Sensitivity analysis demonstrated that the meteorological factor to which the ET0 is most sensitive varies with time scale and equation. Moreover, regression equations used to correct the underestimation associated with the Hargreaves equation for estimating ET0 in the Zhangye farmland oasis also were constructed.

scholarly journals Spatial and temporal variation of reference evapotranspiration under climate change: a case study in the Sanjiang Plain, Northeast China

2017 ◽  
Vol 49 (1) ◽  
pp. 251-265 ◽  
Author(s):  
Xinyi Song ◽  
Kui Zhu ◽  
Fan Lu ◽  
Weihua Xiao
Keyword(s):  
Sensitivity Analysis ◽  
Wind Speed ◽  
Reference Evapotranspiration ◽  
Sunshine Duration ◽  
Meteorological Data ◽  
Negative Influence ◽  
Sanjiang Plain ◽  
Spatial And Temporal Variation ◽  
The Sanjiang Plain ◽  
Mountainous Regions

Abstract It is essential to understand the changing patterns in reference evapotranspiration (ET0) and its relation to climate variables. In this study, meteorological data obtained from the Sanjiang Plain (SJP) between 1959 and 2013 are used to calculate ET0 via the Penman–Monteith method. This study analyses the spatial and temporal changes of ET0 and determines which meteorological variables have an impact on this. The Mann–Kendall test, moving t-test, sensitivity analysis and simulated results have been used to conduct these analyses. The results demonstrate the following. (1) Spatially, there is an increasing trend in the annual ET0 values in agricultural areas. However, significant decreasing trends (P &lt; 0.05) can be found in mountainous regions. (2) Temporally, two abrupt changes can be detected in the early 1980s and the late 1990s for the entire SJP, leading to large inter-annual differences. (3) Sensitivity analysis shows that relative humidity (RH) is the most sensitive climate variable and has a negative influence on ET0, followed by temperature, sunshine duration and wind speed, all of which exert positive impacts. (4) The simulated result shows that ET0 is most sensitive to RH. However, significant reductions in wind speed can exert large influences on the ET0 values.

scholarly journals Estimation of Soil Respiration by Its Driving Factors Based on Multi-Source Data in a Sub-Alpine Meadow in North China

2019 ◽  
Vol 11 (12) ◽  
pp. 3274 ◽  
Author(s):  
Yanan Liang ◽  
Yanpeng Cai ◽  
Junxia Yan ◽  
Hongjian Li
Keyword(s):  
Remote Sensing ◽  
Soil Respiration ◽  
Seasonal Variations ◽  
Land Surface ◽  
North China ◽  
Alpine Meadow ◽  
Temporal Variations ◽  
Exponential Model ◽  
Climatic Conditions ◽  
Significant Difference

Soil respiration (Rs) in high-altitude areas are normally sensitive to varying climatic conditions. The objective of this research was mainly to explore temporal variations in Rs rates and the corresponding controlling factors for the establishment of appropriate fitting models in a sub-alpine meadow of north China. The data was obtained through field measuring and extraction of the Moderate Resolution Imaging Spectroradiometer (MODIS) in the geographical unit of the study site over the period of 2007 to 2015. The main results were as follows: (1) seasonal variations in Rs rates, soil temperature (Ts), land surface temperature (LST), and normalized difference vegetation index (NDVI) all produced symmetrical bell type patterns, while soil moisture (Ms) showed a fluctuating pattern, (2) a Ts-exponential model could greatly capture seasonal variations of Rs rates in the study site, reflecting the role of temperature as a dominant driving factor in determining Rs temporal variations in alpine meadow areas, (3) there was no significant difference between the performing indicators evaluating the proposed Ts-exponential model and the LST-exponential model. This indicated great potential for applying remote sensing products to estimate seasonal Rs rates and 4) seasonal variations in Rs rates towards temperature sensitivity (Q10) showed a concave curve and dramatically decreased as the temperature increased from −1 to 11 °C. Overall, the results indicated that attention to significant effects of climatic conditions on Rs, particularly in areas of low temperature, should be warranted. Also, applicability of remote sensing products for estimating Rs was reflected and demonstrated.

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