Significant Decrease In Wind Speed Research Articles

On the Pattern and Attribution of Pan Evaporation over China (1951–2021)

Abstract Pan evaporation (Epan) serves as a monitorable method for estimating potential evaporation, evapotranspiration, and reference crop evapotranspiration, providing crucial data and information for fields such as water resource management and agricultural irrigation. Based on the PenPan model, the monthly Epan was calculated over China during 1951–2021, resulting in an average R2 of 0.93 ± 0.045 and an RMSE of 21.48 ± 6.06 mm month−1. The trend of Epan over time was characterized by an initial increase before 1961, followed by a decrease from 1961 to 1993, and a subsequent increase from 1994 to 2021. However, the sustained duration and magnitude of the decreasing trend led to an overall decreasing trend in the long-term dataset. To better understand the drivers of Epan trends, the Epan process was decomposed into radiative and aerodynamic components. While radiation was found to be the dominant component, its trend remained relatively stable over time. In contrast, the aerodynamic component, although smaller in proportion, exhibited larger fluctuations and played a crucial role in the trend of Epan. The primary influencing factors of the aerodynamic component were found to be wind speed and vapor pressure deficit (VPD). Wind speed and VPD jointly promoted Epan before 1961, and the significant decrease in wind speed from 1961 to 1993 led to a decrease in Epan. From 1994 to 2021, the increase in VPD was found to be the main driver of the observed increase in Epan. These results show the complex and dynamic nature of Epan and underscore the need for continued monitoring and in-depth analysis of its drivers. Significance Statement The primary objective of this study is to explore the spatiotemporal patterns and potential driving factors of pan evaporation in China based on constructing a comprehensive dataset of pan evaporation. This is important because pan evaporation is an important indicator of the water cycle, which is currently undergoing modifications and is expected to become more pronounced as the climate continues to warm. Our findings showed that the patterns of pan evaporation were characterized by its drivers. As the drivers are numerous and continuously changing under climate change, it is necessary to pay attention to the pattern and attribution of pan evaporation.

ИЗМЕНЕНИЯ ИСПАРЕНИЯ ПО ДАННЫМ ИНСТРУМЕНТАЛЬНЫХ НАБЛЮДЕНИЙ И ЕГО РЕАКЦИЯ НА ИЗМЕНЕНИЕ КЛИМАТА В ПРОВИНЦИИ ХЭЙЛУНЦЗЯН

In this study, instrument-measured evaporation and conventional meteorological observations from 80 stations in Heilongjiang Province from 1961 to 2020 were collected. Using these data, methods such as linear trend estimation, cumulative anomaly, multiple linear regression, and Morlet wavelet analysis were employed to analyze the changes of instrument-measured evaporation annually and seasonally in Heilongjiang Province. Additionally, we analyzed its response to climate change. The results showed that from 1961 to 2020, annual pan evaporation in Heilongjiang Province showed a significant downward trend, decreasing at 10.5 mm per decade. Evaporation decreased significantly in spring, while the magnitude of this decrease in summer and autumn was relatively small, and evaporation increased significantly in winter. In the periodic change, annual and seasonal evaporation have significant periods on short time scales. Among them, PE y and PE Su mainly have a short period of 3-4 years, PE Sp has short periods of about 3 years and 6 years, PE A mainly has short periods of 2 years and 3 years, and PE W mainly has short periods of about 4 years. The geographical correlation of evaporation was significant, with evaporation decreasing as latitude, longitude and altitude increased. Additionally, we found that changes in annual and seasonal pan evaporation were positively correlated to changes in average temperature, hours of sunshine, and wind speed, and negatively correlated to changes relative humidity. Our analysis indicates that a significant decrease in wind speed and hours of sunshine is the dominant factor leading to the decrease in evaporation throughout the year as well as in spring, summer, and autumn, while higher temperatures and lower relative humidity may lead to a significant increase in evaporation in winter.

Impacts of meteorological factors and crop area changes on the variations in winter wheat water requirements in the lower reaches of the Yellow River Basin

Meteorological factors and human activities (such as changes in crop area) have exerted great impacts on the agricultural water resources. A thorough understanding of the changes in crop water requirements (CWR) and irrigation water requirements (IR) is crucial for effective agricultural water management. In the present study, the unit area and total volume of winter wheat CWR and IR were estimated based on meteorological and crop area data, and spatiotemporal variations were analyzed from 2001 to 2018 in the lower reaches of the Yellow River Basin. The impacts of meteorological factors and crop area changes on the CWR and IR variations were explored using sensitivity analysis and the logarithmic mean Divisia index method along with the identification of the main driving factors. The results revealed that both the unit area CWR and IR exhibited a decreasing trend with a multi-year average value of 540 mm and 488 mm, respectively, and increased gradually from south to northwest in the spatial distribution. The significant decrease in wind speed exerted the greatest impact on the unit area CWR and IR changes with the highest sensitivity among considered meteorological factors. The total volume of CWR and IR increased by 56.5 × 108 m3 and 32.3 × 108 m3 from 2001 to 2018, respectively. The crop area change of winter wheat was a major contributor to the variations in total volume of CWR and IR rather than meteorological factors during the study period, and evident spatial and temporal differences were observed. The results of this study provide valuable insights for developing adaptive strategies considering the impacts of meteorological factors and planted crop area changes and can therefore contribute to the sustainable utilization and management of agricultural water resources.

FORMATION OF THE STRUCTURE OF PAYMENTS FOR THE USE OF THE FOREST ECOSYSTEM SERVICES

The formed structure of payments for the use of resources and functions of forest ecosystems is presented in the form of a matrix, which was the purpose of the scientific article. The practical experience of implementing ecosystem payments in the field of forest use abroad was evaluated. It is well-founded that many countries have already implemented such payments, and in particular, in Costa Rica, these financial instruments have been operating effectively for 30 years. A mechanism was developed and a description of the process of forming the matrix of ecosystem payments and the algorithm of its creation was carried out. The structure of payments for the use of resources and functions of forest ecosystems has been developed in the form of a matrix, which is the most significant result and scientific novelty of this research. The "Matrix of payments for the use of resources and functions of forest ecosystems" lists various services or functions of forest ecosystems: regulation of the water regime; stabilization of the composition of the atmosphere, waste assimilation; significant decrease in wind speed, absorption of noise by the forest; provision of recreational services by forest ecosystems and others. The matrix highlights various conditions under which payments are differentiated: depending on the type of documentation, on the scale or size of the forest area, on the level of management or type of ownership; as well as the obligation of ecosystem payments, their regularity, or voluntariness, or their combination. A structure of ecosystem payments has been developed, which includes: ecological payments for regulating the water regime, regulating the climate regime, regulating the intensity of snowmelt and the water level in rivers; for stabilization of the composition of the atmosphere, assimilation of waste, improvement of the environment with the help of the release of phytoncides for bioremediation by plants; for a significant decrease in wind speed, for keeping under the tent the crowns of fauna and flora, absorbing noise by the forest; for the provision of recreational services by forest ecosystems. Ecosystem payments for compensation of economic losses caused to forest ecosystems are separately allocated. This scientific work was carried out on the basis of many years of research, analysis of domestic and foreign legislative and regulatory documents, economic literature, constructive consultations of well-known scientists in the field of environmental economics, and own conclusions.

Identifying the dominant local factors of 2000–2019 changes in dust loading over East Asia

East Asian dust aerosols play a vital role in the local and regional climate through its direct, indirect, and semidirect effects, but the dominant factors affecting the interannual variation of dust aerosols over East Asia and their regional differences remain unclear. This study verified the accuracy of MEERA-2 dust data in East Asia, analyzed the interannual trends of dust in East Asia from 2000 to 2019 using the MERRA-2 dust column mass density (DCMD) and identified the dominant factors affecting the interannual variation during the dusty season (March–July) by developing the regional multiple linear regression models, combined with correlation and partial correlation analysis. The comparison with the dust index (DI) calculated from ground-based observations of dust events frequency indicated that MERRA-2 DCMD exhibited high spatial agreement ( R > 0.8) with ground-based observations in most regions (especially in the dust source region of North China). The trend analysis revealed that DCMD in East Asia decreased significantly after 2000, particularly in the dusty season (March–July). These significant decreases were generally highly correlated with increases in normalized differential vegetation index (NDVI), volumetric soil moisture (VSM), and precipitation (PPT) and with decreases in wind speed (WS). Furthermore, WS dominated the interannual variation in the dust concentration over the East Asian dust source regions and their downstream. By contrast, PPT, through its wet deposition effect, dominated the variation in the rest of the regions away from the dust source regions. The study findings may help clarify the associations between local meteorological and surface factors and long-term variations in dust aerosols over East Asia. • MERRA-2 DCMD has a high accuracy in East Asia in 2000-2018. • Significant increases in NDVI, SM and PPT and significant decrease in WS all contributed to the decrease in DCMD. • WS dominated the variation of dust over the East Asian dust source regions and their downstream. • PPT dominated the variation of dust in the rest of the regions away from the dust source regions.

Trend and Sensitivity Analysis of Reference Evapotranspiration in the Senegal River Basin Using NASA Meteorological Data

Understanding evapotranspiration and its long-term trends is essential for water cycle studies, modeling and for water uses. Spatial and temporal analysis of evapotranspiration is therefore important for the management of water resources, particularly in the context of climate change. The objective of this study is to analyze the trend of reference evapotranspiration (ET0) as well as its sensitivity to climatic variables in the Senegal River basin. Mann-Kendall’s test and Sen’s slope were used to detect trends and amplitude changes in ET0 and climatic variables that most influence ET0. Results show a significant increase in annual ET0 for 32% of the watershed area over the 1984–2017 period. A significant decrease in annual ET0 is observed for less than 1% of the basin area, mainly in the Sahelian zone. On a seasonal scale, ET0 increases significantly for 32% of the basin area during the dry season and decreases significantly for 4% of the basin during the rainy season. Annual maximum, minimum temperatures and relative humidity increase significantly for 68%, 81% and 37% of the basin, respectively. However, a significant decrease in wind speed is noted in the Sahelian part of the basin. The wind speed decrease and relative humidity increase lead to the decrease in ET0 and highlight a “paradox of evaporation” in the Sahelian part of the Senegal River basin. Sensitivity analysis reveals that, in the Senegal River basin, ET0 is more sensitive to relative humidity, maximum temperature and solar radiation.

Trends in reference evapotranspiration and their causative factors in the West Liao River basin, China

In this study the daily reference evapotranspiration (ETref) was estimated through the Penman-Monteith method at 15 meteorological stations in the arid and semi-arid area of the West Liao River basin of China from 1960 to 2012. The characteristics of the seasonal and annual variation and the spatial distribution of ETref through the Cokriging (spherical) interpolation methods were analyzed. The trends of seasonal and annual ETref and meteorological factors were investigated using the Mann-Kendall test after eliminating the effect of significant lag-1 serial correlation by trend-free pre-whitening. Moreover, the major meteorological factors affecting ETref using stepwise regression and partial correlation analysis were investigated. Results showed that: (1) The decreasing degree of ETref at 46.7% stations is larger than the increasing degree of ETref at 53.3% stations, which resulted in the decreasing trends of ETref during the study period. The magnitude of the negative trend in annual average ETref was 0.28mmyr−1; (2) a significant overall increase in air temperature, a significant decrease in wind speed, solar radiation, sunshine duration, and relative humidity was observed; (3) ETref was larger for the plain area and gradually decreased toward the surrounding areas. It was smaller for the mountain area. ETref has obvious zonal effect; (4) There was a significant negative correlation between ETref and relative humidity while ETref has a significant positive correlation with other factors (p<0.05). In annual time scale, solar radiation was found to be the most dominant variable influencing ETref, however, in seasonal time scale, average air temperature, maximum air temperature, relative humidity were the most dominant factors in spring, summer and winter, and autumn, respectively. Wind speed was the second most significant factor in all seasons. The results of this study support the conclusion that the evapotranspiration decreases over the West Liao River basin are controlled mainly by trends in the radiative component.

Spatiotemporal variation of temperature, precipitation and wind trends in a desertification prone region of China from 1960 to 2013

Spatial and temporal distributions of temperature, precipitation and wind speed from 1960 to 2013 at 179 meteorological stations situated in the desertification prone region (DPR) of China are analysed using the Mann–Kendall test and the Theil–Sen's slope estimator on monthly, seasonal and annual timescales. The results indicate that annual mean temperature has increased at a rate of 0.33 °C (10 year)−1 over the DPR. Tmin generally increased at a higher rate than Tmax in the majority of the months and seasons over the past 54 years; this has resulted in a decrease in the diurnal temperature range. Precipitation increased for the majority of the meteorological stations in the western area of the DPR, and decreased in the eastern area, but few of these trends are statistically significant on all timescales. The majority of meteorological stations recorded a significant decrease in wind speed at the majority of timescales. Results from this investigation show that the climate is becoming warmer and wetter in the western area of the DPR, and warmer and drier in eastern area of the DPR. A greater understanding of how the historical climate has been changing enables scientific support for the adaption of mitigation policies for land desertification/degradation, water resources, ecological projects and agricultural production. These policies will aid in combating the desertification processes, maintaining ecological security and promoting sustainable development in the DPR.

Spatiotemporal variation and driving forces of reference evapotranspiration in Jing River Basin, northwest China

AbstractEvapotranspiration is an important component of the hydrological cycle, which integrates atmospheric demands and surface conditions. Research on spatial and temporal variations of reference evapotranspiration (ETo) enables understanding of climate change and its effects on hydrological processes and water resources. In this study, ETo was estimated by the FAO‐56 Penman–Monteith method in the Jing River Basin in China, based on daily data from 37 meteorological stations from 1960 to 2005. ETo trends were detected by the Mann–Kendall test in annual, seasonal, and monthly timescales. Sensitivity coefficients were used to examine the contribution of important meteorological variables to ETo. The influence of agricultural activities, especially irrigation on ETo was also analyzed. We found that ETo showed a decreasing trend in most of the basin in all seasons, except for autumn, which showed an increasing trend. Mean maximum temperature was generally the most sensitive parameter for ETo, followed by relative humidity, solar radiation, mean minimum temperature, and wind speed. Wind speed was the most dominant factor for the declining trend in ETo. The more significant decrease in ETo for agricultural and irrigation stations was mainly because of the more significant decrease in wind speed and sunshine hours, a mitigation in climate warming, and more significant increase in relative humidity compared with natural stations and non‐irrigation stations. Changes in ETo and the sensitivity coefficient of meteorological variables in relation to ETo were also affected by topography. Better understanding of ETo response to climate change will enable efficient use of agricultural production and water resources, which could improve the ecological environment in Jing River Basin. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Sensitivity study of reference crop evapotranspiration during growing season in the West Liao River basin, China

We have analyzed the trends of reference crop evapotranspiration (ET0) through the Penman–Monteith model and climate factors in the West Liao River basin using the Mann–Kendall test after removing the effect of significant lag-1 serial correlation from the time series of the data by trend-free pre-whitening. The changing characteristics of the sensitivity coefficients and the spatial distribution during growing season are investigated, and the correlation between the sensitivity coefficients with elevation and the key climate factors by relative contribution and stepwise regression methods are evaluated. A significant overall increase in air temperature, and a significant decrease in wind speed, solar radiation, sunshine duration, relative humidity, and a slight decrease in ET0 are observed. Sensitivity analysis shows that ET0 is most sensitive to solar radiation, followed by relative humidity. In contrast, ET0 is least sensitive to the average air temperature. The sensitivity coefficients for the maximum and minimum air temperature and relative humidity have a significant negative correlation with elevation, while the coefficients for other variables are not strongly correlated with elevation. The spatial distribution of the sensitivity coefficients for wind speed and solar radiation is opposite, i.e., in regions where the sensitivity coefficients for wind speed are high; the sensitivity coefficients for solar radiation are low and vice versa. The sensitivity for relative humidity and average air temperature is region specific in the plain area. However, ET0 is most sensitive to the climate change in regions of high elevation. Wind speed is the most dominant contributor followed by solar radiation. Average air temperature contributes the least. The stepwise regression analysis indicates that wind speed is the foremost dominant variable influencing ET0. Relative contribution and stepwise regression analysis can be used to determine the main variables affecting ET0, and it also strongly supports that the aerodynamic component is the dominant factor.

Impact of climate change on the water requirement of summer maize in the Huang-Huai-Hai farming region

Crop water requirement and the temporal and spatial changes of this important characteristic provide key information for irrigation scheduling, water resource planning, and future decision-making. In the Huang-Huai-Hai (HHH) farming region in north China, both crop evapotranspiration (ETc) and evapotranspiration of the applied water (ETaw) in the growing season of summer maize during 1960–2009 were calculated using the SIMETAW (simulation of evapotranspiration of applied water) model and the daily weather data. Inverse distance weighted interpolation (IDW) was used to interpret spatial distribution of ETc and ETaw. Results showed that: (1) During 1960–2009 in the HHH farming region, ETc of summer maize during the growing season showed a significant downward trend; the average ETc decreased from 335.6mm/decade in the period 1960–1969 to 311.4mm/decade in the period 2000–2009. The variation of ETaw of summer maize during the growing season did not drop significantly due to yearly fluctuation of the effective rainfall (Re) in the growing season, and the improvement of irrigation efficiency and cultivation management measures. Although the descent of ETc might mitigate the agricultural water stress in this area to some extent, the variation of ETaw still depended on the effective rainfall. (2) The average ETc values per decade presented higher in the eastern and lower in the western regions; inter-regional differences were observed for ETaw, and the highest ETaw value of about 109.6mm was found in the western regions of the Shandong and Hebei Provinces. Adjusting irrigation system and adopting the different irrigation systems in different region should be taken into consideration to guarantee the maize yield in this area. (3) During 1960–2009, a significant overall increase in temperature, a significant decrease in wind speed, humidity, and solar radiation, and a slight decrease in precipitation were observed. The solar radiation decrease contributed most to the summer maize ETc decrease, while relative humidity and precipitation were negatively correlated with ETc.

Trend analysis of reference evapotranspiration in Northwest China: The roles of changing wind speed and surface air temperature

AbstractReference evapotranspiration (ET0) is an important element in the water cycle that integrates atmospheric demands and surface conditions, and analysis of changes in ET0 is of great significance for understanding climate change and its impacts on hydrology. As ET0 is an integrated effect of climate variables, increases in air temperature should lead to increases in ET0. However, this effect could be offset by decreases in vapor pressure deficit, wind speed, and solar radiation which lead to the decrease in ET0. In this study, trends in the Penman–Monteith ET0 at 80 meteorological stations during 1960–2010 in the driest region of China (Northwest China) were examined. The results show that there was a change point for ET0 series around the year 1993 based on the Pettitt's test. For the region average, ET0 decreased from 1960 to 1993 by −2.34 mm yr−2, while ET0 began to increase since 1994 by 4.80 mm yr−2. A differential equation method based on the Food and Agriculture Organization Penman–Monteith formula was used to attribute the change in ET0. The attribution results show that the significant decrease in wind speed dominated the change in ET0, which offset the effect of increasing air temperature and led to the decrease in ET0 from 1960 to 1993. However, wind speed began to increase, and the amplitude of increase in air temperature also rose significantly since the mid‐1990s. Increases in air temperature and wind speed together reversed the trend in ET0 and led to the increase in ET0 since 1994. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Decreasing potential evaporation trends in China from 1956 to 2005: Accelerated in regions with significant agricultural influence?

The potential evaporation trends in stations in China with varying agricultural influences from 1956 to 2005 were evaluated. The decreasing trends in potential evaporation are accelerated for stations in regions with significant agricultural influences. A total of 244 stations, whose cultivated land area ratio within a 5 km radius is larger than 50%, are categorized as having significant agricultural influence and designated as agricultural stations, whereas 195 stations, whose sum of cultivated, residential, industrial, and traffic land area ratio within a 5 km radius is smaller than 30%, are categorized as having little anthropogenic influence and designated as natural stations. The decreasing trends in potential evaporation are more significant in agricultural stations with a more significant decrease in the aerodynamic term in the arid/semi-arid region and a more significant decrease in the radiation term in the humid region. In the arid/semi-arid region, the significant decrease in potential evaporation in the agricultural stations is attributed to the significant decrease in wind speed, significant increase in relative humidity, and smaller increase in air temperature compared with those in the natural stations. In the semi-humid and humid regions, the more significant decrease in potential evaporation in the agricultural stations is attributed to the significant decrease in solar radiation and wind speed compared with those in the natural stations. According to the analysis of the complementary relationship between actual and potential evaporation, the decrease in potential evaporation is accelerated in the agricultural stations with a more significant increase in water availability induced by irrigation in the arid/semi-arid region and a more significant decrease in solar radiation in the humid region.

Causes of decreased reference evapotranspiration and pan evaporation in the Jinghe River catchment, northern China

This study focused on the changes of reference evapotranspiration (ET0) and pan evaporation (ETpan) to study the impacts of climate change on the hydrological cycle in the Jinghe River catchment. Based on the Penman–Monteith equation, the ET0 was calculated. The temporal trend and spatial distribution of ET0 and Epan measured with a 20-cm pan were examined at the 14 stations during 1957–2005. The effects of meteorological factors on the variation of ET0 were determined by analyzing the trends in themselves with comparison between original climate and detrended climate scenarios and then their sensitivity to ET0. Both the ET0 and Epan showed remarkable decreasing trends from 1957 to 2005 and their decreasing rate was 40.9 and 17.7 mm per 10 years, respectively. Trend analysis of meteorological factors exhibited that the reduction in ET0 and ETpan was principally caused by both significant decreases in wind speed and sunshine hours. Furthermore, the decreasing trend of ET0 was mainly dominated by the significant decrease in wind speed with high sensitivity, to a less extent, by the decrease in net radiation. Although relative humidity is one of the most sensitive variables, its effect on ET0 was negligible because of its temporal constancy. The contribution of wind speed reduction to decreased ET0 has increased from 50 to 76.1%, but net radiation, by contrast, decreased from 50 to 23.9%.

Spatial distribution and temporal variation of reference evapotranspiration in arid and semi‐arid regions of Iran

AbstractAnalysis of spatial and temporal variations of reference evapotranspiration (ETo) is important in arid and semi‐arid regions where water resources are limited. The main aim of this study was to analyse the spatial distribution and the annual, seasonal and monthly trends of the Penman–Monteith ETo for 21 stations in the arid and semi‐arid regions of Iran. Three statistical tests the Mann‐Kendall, Sen's slope estimator and linear regression were used for the analysis. The analysis revealed that ETo increased from January to July and deceased from July to December at almost all stations. Additionally, higher annual ETo values were found in the southeast of the study region and lower values in the northwest of the region. Although the results showed both positive and negative trends in annual ETo series, ETo generally increased, significantly so in six (∼30%) of the stations. Analysis of the impacts of meteorological variables on the temporal trends of ETo indicated that the increasing trend of ETo was most likely due to a significant increase in minimum air temperature, while decreasing trend of ETo was mainly caused by a significant decrease in wind speed. At the sites where increasing ETo trends were statistically significant, the rate of increase varied from (+)8·36 mm/year at Mashhad station to (+)31·68 mm/year at Iranshahr station. On average, an increasing trend of (+)4·42 mm/year was obtained for the whole study area during the last four decades. Seasonal and monthly ETo have also tended to increase at the majority of the stations. The greatest numbers of significant trends were observed in winter on the seasonal time‐scale and in September on the monthly time‐scale. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Recent trends in surface sensible heat flux on the Tibetan Plateau

Over the last three decades, the Tibetan Plateau has exhibited a significant increase in air temperature and a significant decrease in wind speed. How the surface heat source has changed is an important issue in monsoon research. Based on routine meteorological data, this study investigates the differences between methods for estimating trends in surface sensible heat flux on the Tibetan Plateau for the period 1984–2006. One is a physical method based on micro-meteorological theory and experiments, and takes into account both atmospheric stability and thermal roughness length. The other approach includes conventional empirical methods that assume the heat transfer coefficient is a constant value or a simple function of wind speed. The latter method is used widely in climatologic studies. Results from the physical method show that annual mean sensible heat flux has weakened by 2% per decade, and flux seasonal mean has weakened by ∼2%–4% except in winter. The two commonly used empirical methods showed high uncertainties in heat flux trend estimates, although they produced similar climatologies. Annual mean heat flux has weakened by 7% per decade when a fixed transfer coefficient is used, whereas the trend is negligible when the transfer coefficient is assumed a function of wind speed. Conventional empirical methods may therefore misrepresent the trend in sensible heat flux.