scholarly journals Formation and dynamics of sandy dunes in the inland areas of the Hexi Corridor

2020 ◽  
Author(s):  
Bing-Qi Zhu
Keyword(s):  
Climate Change ◽  
Wind Speed ◽  
Human Activities ◽  
Hexi Corridor ◽  
Strong Wind ◽  
Fluvial Sediments ◽  
Dynamic Changes ◽  
The North ◽  
Sand Particles ◽  
Moving Speed

Abstract. Dynamic changes of aeolian landforms and desertification under global warming in a middle-latitude desert belt, the Hexi Corridor in China, considered to be one of the source and engine area of sandstorms in China and Northern Hemisphere (NH), is a typical problem of climate change and landscape response, which need a comprehensive understanding of the history and forcing mechanisms of recent landform and environmental changes in the region. Based on the existing high-resolution satellite image interpretations, field investigations and observations, comprehensive evidences from geomorphological, aeolian-physical, granulometrical and geochemical analysis, this study discussed the formation of dune landforms, the mechanism of desertification and their environmental implications in the Hexi Corridor. The analytical results show that 80 % of the sand particles flow within a height of 20–30 cm near the surface, and about half of the sand particles flow within a height of 0.3–0.5 cm near the surface in the Hexi Corridor. The average height of the typical crescent-shaped dunes is about 6.75 m, and the minimum and maximum values are between 2.6 and 11.2 m. On the inter-annual and multi-year time scales, only the crescent-shaped dunes and chains of barchan dunes are moving or wigwagging in the study area, while the parabolic and longitudinal dunes did not move. Under the influence of wind speed, strong wind days and other factors, the dunes at the edge of the Minqin Oasis move the fastest, with a moving speed of about 6.2 m/a. Affected by the main wind direction and other factors, the dunes at the edge of the Dunhuang Oasis move the slowest, with a moving speed of about 0.8 m/a. The main factors affecting the dynamic changes of sandy dunes in the Hexi Corridor are the annual precipitation, the annual average wind speed and the number of annual strong wind days, of which the annual precipitation contributes the largest, indicating that the climate factors have a most important impact on the dynamic change of sand dunes. The cumulative curve of particle size frequency of dune sediments in the Hexi Corridor basically presents a three-segment model, indicating a saltation mode dominated under the action of wind, but superimposed with a small amount of coarser and finer particles dominated by the creeping and suspension models, which is obviously different from that of the Gobi sediments with a dominant two-segment mode. The palaeo-geographical, sedimentological and geochemical evidences indicate that dune sediments in the Hexi Corridor are mainly derived from locally or in-situ raised sandy sediments, which are mainly come from alluvial plains and ancient fluvial sediments, as well as ancient lake plains and lacustrine deposits, aeolian deposits in the piedmont denudation zones of the north and south mountains and modern fluvial sediments in the corridor. In geochemical compositions of major and trace elements, the dunes in the Hexi Corridor have certain similarities and differences to other sandy dunes in the northwest and northern deserts of China or aeolian loess in the Loess Plateau. Sandy dunes in the Hexi Corridor are relatively rich in iron and Co. Considering the proportion of fine particles on the surface, the coverage rate of surface salt crust, and the potential migration of erodible sandy materials, it can be concluded that the Gobi area in the west Hexi Corridor is not the main source area of sandstorms in the middle and east of the corridor, but the north probably is. In the past half century, the warming and humidification of local climate is the main cause of the reduction of sandstorms in the study area, and the Hexi Corridor has a potential trend of anti-desertification, which is mainly controlled by climate change but not human activities. For the oasis areas of the corridor, however, the effective measures to restrict desertification depend on human activities. Restriction of the decline of groundwater is the key to preventing desertification in oases, rather than water transfer from outer river basins.

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.

scholarly journals Quantifying Early Indicators of Global Climate Change

2006 ◽  
Vol 30 ◽  
pp. 97-99
Author(s):  
Diane Debinski
Keyword(s):  
Climate Change ◽  
Global Climate Change ◽  
Human Activities ◽  
Global Climate ◽  
Warning System ◽  
Ecological Communities ◽  
The North ◽  
Ecological Changes ◽  
Montane Meadows ◽  
Associated Species

One of the more significant voids remaining in our scientific understanding of global climate change is the relationship between climate change and the resulting changes expected in ecological communities. Because a large proportion of the North American landscape has been modified by human activities, it is difficult to assess whether ecological changes are being caused by human activities or climate change. Thus, we must look to landscapes where the modification has been less severe. One of the most pristine landscapes in North America where scientists can study natural processes is that of the Greater Yellowstone Ecosystem. Within this system some of the more sensitive habitats are the montane meadows. These habitats exist along a continuum from very dry (xeric) sagebrush meadows, to flowering (mesic) meadows, to wet (hydric) sedge meadows. Because of the relatively short growing season, species in these meadows can exhibit quick changes in distribution and abundance relative to climatic changes. My research uses satellite images and field surveys to evaluate how meadow habitats and their associated species respond to interannual changes in precipitation and soil moisture. I am examining the plant and butterfly communities to measure the response. Over 100 species of butterflies occur in this area and many are closely associated with specific types of meadows. This research is significant because it will provide an early warning system for assessing the effects of climate change. Documenting changes in montane meadows will assist in understanding how climate change may affect more highly managed areas of the globe.

scholarly journals Circulation conditions of strong and elemental wind over southwestern Ukraine

2017 ◽  
pp. 38-48 ◽  
Author(s):  
Н.P. Ivus ◽  
E.V. Agayar ◽  
L.M. Hurska ◽  
А.В. Semergei-Chumachenko
Keyword(s):  
Wind Speed ◽  
Atmospheric Circulation ◽  
Black Sea ◽  
The Black Sea ◽  
Strong Wind ◽  
The South ◽  
The North ◽  
Strong Winds ◽  
The Impact ◽  
North Western

Introduction. Nowadays the problem of storm winds appears to be a very relevant one in those spheres of human activities related to safety of human living, coastal infrastructure, seafaring, aviation etc. One of the conditions for successful forecasting of strong winds is familiarization with wind characteristics of the study area and with synoptic conditions causing them. The below listed results of research form continuation of previous works for search of a better synoptic classification reflecting completeness of macroscale baric processes causing formation of winds, including strong winds, over the South of Ukraine and also providing an opportunity to forecast winds in a more accurate manner. The purpose of this publication consists in analysis of interaction of large-scale atmospheric circulation with formation of unfavorable weather conditions (strong and very strong winds) on the north-west coast of the Black Sea. Methods and results. The impact of storm winds is significant for functioning of the national economic complex of the North-Western Black Sea region. In order to investigate this effect there were fifty seven cases of wind amplification up to criterion of strong ≥ 15 m·s-1 and very strong ≥ 25 m·s-1 selected within the Odessa region during the period from October to March in 2011 – 2014. Indexes of Katz circulation for isobaric surface of 500 hPa were calculated as per the data of synoptic archive for the cases with wind speed of ≥ 15 m·s-1. A more detailed study of the structure of macrocirculation processes under strong winds, except for Katz indexes, is provided by means of classification and calendar of successive change of elementary circulation mechanisms (ECM) in the Northern hemisphere according to Dzerdzeyevskyi B.L. and typification of synoptic processes developed at the Department of Theoretical Meteorology and Meteorological Forecasts of OSENU. It was determined that strong and very strong winds often occur in southern and central regions, particularly at the stations located on the shores of seas and estuaries (Bilgorod-Dnistrovskyi, Ust-Dunaysk, Pivdennyi port). Meridional type of atmospheric circulation (77.2%) creates favourable conditions for wind amplification in the North-Western part of the Black Sea up to the criterion of strong and very strong one, zonal type of circulation constitutes 22.8% from the total number of cases. Meridional type of circulation is mainly represented by mixed and western forms – (24.6%) and (22.8%) respectively. Main types of synoptic situations (5, 6) of Katz typification that used to cause strong winds were revealed. Most frequently strong wind was observed while moving of cyclonic vortexes from the South (ECM type – 12a, 13z) and in the area of cyclones and anticyclones interaction. Conclusion. It was found that wind speed amplification in the South of Ukraine up to the criteria of strong and very strong one mainly occurs due to the meridional type of atmospheric circulation which is dominated by mixed or western forms of circulation as per Katz typification, ECM type 12a and 13z according to Dzerdzeyevskyi B.L. and types 5 (subtype 5.2) and 6 (all subtypes depending on ECM) as per synoptic typification of OSENU. Directions for further research should include the following. The conclusions have preliminary character and need confirmation on the basis of bigger scope of statistical data.

scholarly journals Analysis of the Dynamic Changes of the Baiyangdian Lake Surface Based on a Complex Water Extraction Method

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1616 ◽  
Author(s):  
Xiaoya Wang ◽  
Wenjie Wang ◽  
Weiguo Jiang ◽  
Kai Jia ◽  
Pinzeng Rao ◽  
...  
Keyword(s):  
Climate Change ◽  
Economic Development ◽  
Human Activities ◽  
Water Surface ◽  
Human Life ◽  
Water Area ◽  
Ecological Environment ◽  
Landsat Images ◽  
Dynamic Changes ◽  
Baiyangdian Lake

Lakes have an important role in human life and the ecological environment, but they are easily affected by human activity and climate change, especially around urban areas. Hence, it is critical to extract water with a high precision method and monitor long-term sequence dynamic changes in lakes. As the greatest natural lake of the Beijing-Tianjin-Hebei region, Baiyangdian Lake has a significant function in human life, socio-economic development, and regional ecological balance. This lake area has shown large changes due to human activity and climate change. The change monitoring process of the water surface is of great significance in providing support for the management and protection of the lake. The Spectrum Matching based on Discrete Particle Swarm Optimization (SMDPSO) method is a new, robust, and low-cost method for water extraction, that has obvious advantages in extracting complex water surfaces. In this paper, the SMDPSO method was used to extract the water surface of Baiyangdian Lake by Landsat images from 1984 to 2018. This method has a good effect on complex water surface extraction with vegetation, shadows, and so forth, and the Landsat images have higher resolution and longer time series. The main contents and results of this paper are as follows: (1) We verified the applicability of the SMDPSO method in the Baiyangdian Lake using visual interpretation and correlation analysis. The relative errors between observed and extracted results were all less than 5% in spring, summer, and fall, and the correlation coefficient between the water area and water level was 0.96. (2) According to seasonal verification and comparison of the extraction results, the SMDPSO method was used to extract the water surface area of Baiyangdian Lake during spring of the years 1984–2018. Water area changes of Baiyangdian Lake can be divided into four periods: Dry period (1984–1988), degraded period (1989–2000), stable period (2000–2008), and recovery period (2008–2018). The water area reached a maximum of 280 km2 in 1989 and a minimum of 44 km2 in 2002. (3) The possible causes of the changes in the water area of Baiyangdian Lake were also analyzed. The changes were caused by climate and human activities during the first and second periods, but mainly human activities during the third and fourth periods. In fact, effective policies combined with water conservancy projects were directly conducive to improving or even recovering the water and ecological environment of Baiyangdian Lake. Considering its importance for the benign development of the Beijing-Tianjin-Hebei Region and the construction of the Xiong’an New Area, a policy is necessary to ensure that the lake’s ecological environment will not be destroyed under the premise of economic development.

scholarly journals Stilling and Recovery of the Surface Wind Speed Based on Observation, Reanalysis, and Geostrophic Wind Theory over China from 1960 to 2017

2020 ◽  
Vol 33 (10) ◽  
pp. 3989-4008 ◽  
Author(s):  
Zhengtai Zhang ◽  
Kaicun Wang
Keyword(s):  
Wind Speed ◽  
Decadal Variability ◽  
Surface Wind ◽  
Geostrophic Wind ◽  
Surface Wind Speed ◽  
Strong Wind ◽  
Wind Speeds ◽  
The North ◽  
Wind Theory ◽  
Weak Winds

AbstractSurface wind speed (SWS) from meteorological observation, global atmospheric reanalysis, and geostrophic wind speed (GWS) calculated from surface pressure were used to study the stilling and recovery of SWS over China from 1960 to 2017. China experienced anemometer changes and automatic observation transitions in approximately 1969 and 2004, resulting in SWS inhomogeneity. Therefore, we divided the entire period into three sections to study the SWS trend, and found a near-zero annual trend in the SWS in China from 1960 to 1969, a significant decrease of −0.24 m s−1 decade−1 from 1970 to 2004, and a weak recovery from 2005 to 2017. By defining the 95th and 5th percentiles of daily mean wind speeds as strong and weak winds, respectively, we found that the SWS decrease was primarily caused by a strong wind decrease of −8% decade−1 from 1960 to 2017, but weak wind showed an insignificant decreasing trend of −2% decade−1. GWS decreased with a significant trend of −3% decade−1 before the 1990s; during the 1990s, GWS increased with a trend of 3% decade−1 whereas SWS continued to decrease with a trend of 10% decade−1. Consistent with SWS, GWS demonstrated a weak increase after the 2000s. After detrending, both SWS and GWS showed synchronous decadal variability, which is related to the intensity of Aleutian low pressure over the North Pacific. However, current reanalyses cannot reproduce the decadal variability and cannot capture the decreasing trend of SWS either.

Application of Cluster Analysis and Trend Extraction in Wind Speed Series Consistency Correction

2011 ◽  
Vol 130-134 ◽  
pp. 3425-3429
Author(s):  
Yang Zhang ◽  
Li Ming Wu ◽  
Zuo Min Wang
Keyword(s):  
Climate Change ◽  
Cluster Analysis ◽  
Wind Speed ◽  
Human Activities ◽  
Practical Application ◽  
Trend Extraction ◽  
Consistency Requirement ◽  
Frequency Calculation ◽  
Mean Equality ◽  
Correction Result

In recent years, as affected by climate change and human activities, wind speed shows an obvious downward trend. According to the following three correction methods : correction of the cluster analysis and mean equality, correction of the trend extraction, and the combination of the aforementioned two methods, the wind speed series which meets the consistency requirement of frequency calculation is obtained in this paper. Practical application shows that the correction methods have good adaptability, correction result and great practical value.

Stilling and Recovery of the Surface Wind Speed Based on Observation, Reanalysis, and Geostrophic Wind Theory over China from 1960 to 2017

2020 ◽  
Author(s):  
Zhengtai Zhang ◽  
Kaicun Wang
Keyword(s):  
Wind Speed ◽  
Decadal Variability ◽  
Surface Wind ◽  
Geostrophic Wind ◽  
Surface Wind Speed ◽  
Strong Wind ◽  
Wind Speeds ◽  
The North ◽  
Wind Theory ◽  
Weak Winds

<p>Surface wind speed (SWS) from meteorological observation, global atmospheric reanalysis, and geostrophic wind speed (GWS) calculated from surface pressure were used to study the stilling and recovery of SWS over China from 1960 to 2017. China experienced anemometer changes and automatic observation transitions in approximately 1969 and 2004, resulting in SWS inhomogeneity. Therefore, we divided the entire period into three sections to study the SWS trend, and found a near zero annual trend in the SWS in China from 1960 to 1969, a significant decrease of -0.24 m/s decade<sup>-1 </sup>from 1970 to 2004, and a weak recovery from 2005 to 2017. By defining the 95<sup>th</sup> and 5<sup>th</sup> percentiles of monthly mean wind speeds as strong and weak winds, respectively, we found that the SWS decrease was primarily caused by a strong wind decrease of -8 % decade<sup>-1</sup> from 1960 to 2017, but weak wind showed an insignificant decreasing trend of -2 % decade<sup>-1</sup>. GWS decreased with a significant trend of -3 % decade<sup>-1 </sup>before the 1990s, during the 1990s, GWS increased with a trend of 3 % decade<sup>-1 </sup>whereas SWS continued to decrease with a trend of 10 % decade<sup>-1</sup>. Consistent with SWS, GWS demonstrated a weak increase after the 2000s. After detrended, both of SWS and GWS showed synchronous decadal variability, which is related to the intensity of Aleutian low pressure over the North Pacific. However, current reanalyses cannot reproduce the decadal variability, and can not capture the decreasing trend of SWS either.</p>

scholarly journals European climate change at global mean temperature increases of 1.5 and 2 °C above pre-industrial conditions as simulated by the EURO-CORDEX regional climate models

2018 ◽  
Vol 9 (2) ◽  
pp. 459-478 ◽  
Author(s):  
Erik Kjellström ◽  
Grigory Nikulin ◽  
Gustav Strandberg ◽  
Ole Bøssing Christensen ◽  
Daniela Jacob ◽  
...  
Keyword(s):  
Climate Change ◽  
Wind Speed ◽  
Climate Models ◽  
Regional Climate ◽  
Surface Wind ◽  
Near Surface ◽  
The North ◽  
Global Mean Temperature ◽  
Mean Temperature ◽  
Global Mean

Abstract. We investigate European regional climate change for time periods when the global mean temperature has increased by 1.5 and 2 °C compared to pre-industrial conditions. Results are based on regional downscaling of transient climate change simulations for the 21st century with global climate models (GCMs) from the fifth-phase Coupled Model Intercomparison Project (CMIP5). We use an ensemble of EURO-CORDEX high-resolution regional climate model (RCM) simulations undertaken at a computational grid of 12.5 km horizontal resolution covering Europe. The ensemble consists of a range of RCMs that have been used for downscaling different GCMs under the RCP8.5 forcing scenario. The results indicate considerable near-surface warming already at the lower 1.5 °C of warming. Regional warming exceeds that of the global mean in most parts of Europe, being the strongest in the northernmost parts of Europe in winter and in the southernmost parts of Europe together with parts of Scandinavia in summer. Changes in precipitation, which are less robust than the ones in temperature, include increases in the north and decreases in the south with a borderline that migrates from a northerly position in summer to a southerly one in winter. Some of these changes are already seen at 1.5 °C of warming but are larger and more robust at 2 °C. Changes in near-surface wind speed are associated with a large spread among individual ensemble members at both warming levels. Relatively large areas over the North Atlantic and some parts of the continent show decreasing wind speed while some ocean areas in the far north show increasing wind speed. The changes in temperature, precipitation and wind speed are shown to be modified by changes in mean sea level pressure, indicating a strong relationship with the large-scale circulation and its internal variability on decade-long timescales. By comparing to a larger ensemble of CMIP5 GCMs we find that the RCMs can alter the results, leading either to attenuation or amplification of the climate change signal in the underlying GCMs. We find that the RCMs tend to produce less warming and more precipitation (or less drying) in many areas in both winter and summer.

scholarly journals European climate change at global mean temperature increases of 1.5 and 2 °C above pre-industrial conditions as simulated by the EURO-CORDEX regional climate models

2017 ◽  
Author(s):  
Erik Kjellström ◽  
Grigory Nikulin ◽  
Gustav Strandberg ◽  
Ole Bøssing Christensen ◽  
Daniela Jacob ◽  
...  
Keyword(s):  
Climate Change ◽  
Wind Speed ◽  
Climate Models ◽  
Regional Climate ◽  
Surface Wind ◽  
Near Surface ◽  
The North ◽  
Global Mean Temperature ◽  
Mean Temperature ◽  
Global Mean

Abstract. We investigate European regional climate change for time periods when the global mean temperature has increased by respectively 1.5 °C and 2 °C compared to preindustrial conditions. Results are based on regional downscaling of transient climate change simulations for the 21st century with global climate models (GCMs) from the fifth phase Coupled Model Intercomparison Project (CMIP5). We use an ensemble of EURO-CORDEX high-resolution regional climate model (RCM) simulations undertaken at a computational grid of 12.5 km horizontal resolution covering Europe. The ensemble consists of a range of RCMs that have been used for downscaling different GCMs under different forcing scenarios. The results indicate considerable near-surface warming already at the lower 1.5 °C warming. Regional warming exceeds that of the global mean in most parts of Europe, strongest in northernmost parts of Europe in winter and in southernmost parts of Europe together with parts of Scandinavia in summer. Changes in precipitation, that are less robust than the ones in temperature, include increases in the north and decreases in the south with a borderline that migrates from a northerly position in summer to a southerly one in winter. Some of these changes are seen already at 1.5 °C warming but larger and more robust at 2 °C. Changes in near-surface wind speed are associated with a large spread between individual ensemble members at both warming levels. Relatively large areas over the North Atlantic and some parts of the continent shows decreasing wind speed while some ocean areas in the far north show increasing wind speed. The changes in temperature, precipitation and wind speed are shown to be modified by changes in mean sea level pressure indicating a strong relationship with the large-scale circulation and its internal variability on decade-long timescales. By comparing to a larger ensemble of CMIP5 GCMs we find that the RCMs can alter the results leading either to attenuation of amplification of the climate change signal in the underlying GCMs. We find that the RCMs tend to produce less warming and more precipitation (or less drying) in many areas in both winter and summer.

Sign in / Sign up

Export Citation Format

Share Document