scholarly journals Observed Key Surface Parameters for Characterizing Land–Atmospheric Interactions in the Northern Marginal Zone of the Taklimakan Desert, China

Atmosphere ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 458 ◽  
Author(s):  
Lili Jin ◽  
Zhenjie Li ◽  
Qing He ◽  
Yongqiang Liu ◽  
Ali Mamtimin ◽  
...  

An observational data set of the year 2010 at a site in the northern marginal zone of the Taklimakan Desert (TD) was used to analyse the key surface parameters in land–atmospheric interactions in the desert climate of northwest China. We found that the surface albedo (α) and emissivity (ε) were 0.27 and 0.91, respectively, which were consistent with the values obtained based on observations in the hinterland of the TD as well as being similar to the dry parts of the Great Basin desert in North America, where they were comparable to the α and ε values retrieved from remote sensing products. Peak frequency value of z0m was 5.858 × 10−3 m, which was similar to the Mojave Desert, Peruvian desert, Sonoran Desert, HEIFE (Heihe region) Desert, and Badain Jaran Desert. The peak frequency value of z0h was 1.965 × 10−4 m, which was different from those obtained in the hinterland of the TD. The average annual value of excess resistance to heat transfer (kB−1) was 2.5, which was different from those obtained in the HEIFE Gobi and desert, but they were similar to those determined for the Qinghai–Tibetan Plateau and HAPEX-Sahel. Both z0m and z0h varied less diurnally but notably seasonally, and kB−1 exhibited weak diurnal and seasonal variations. We also found that z0m was strongly influenced by the local wind direction. There were many undulating sand dunes in the prevailing wind and opposite to the prevailing wind, which were consistent with the directions of the peak z0m value. The mean values calculated over 24 h for Cd and Ch were 6.34 × 10−3 and 5.96 × 10−3, respectively, which were larger than in the Gobi area, hinterland of the TD and semiarid areas, but similar to HEIFE desert. Under the normal prevailing (NNE–ESE) wind, the mean bulk transfer coefficient Cd and Ch were of the same order of magnitude as expected based on similarity theory. Using the data obtained under different wind directions, we determined the relationships between Cd, Ch, the wind speed U, and stability parameter z/L, and the results were different. Cd and Ch decreased rapidly as the wind speed dropped below 3.0 m s−1 and their minimum values reached around 1–2 m s−1. It should also be noted that the ε values estimated using the sensible heat flux (H) were better compared with those produced using other estimation methods.

2020 ◽  
Vol 12 (2) ◽  
pp. 739 ◽  
Author(s):  
Cheng Liu ◽  
Qinglan Li ◽  
Wei Zhao ◽  
Yuqing Wang ◽  
Riaz Ali ◽  
...  

The spatiotemporal characteristics of near-surface wind in Shenzhen were investigated in this study by using hourly observations at 92 automatic weather stations (AWSs) from 2009 to 2018. The results show that during the past 10 years, most of the stations showed a decreasing trend in the annual mean of the 10 min average wind speed (avg-wind) and the mean of the 3 s average wind speed (gust wind). Over half of the decreasing trends at the stations were statistically significant (p < 0.05). Seasonally, the decrease in wind speed was the most severe in spring, followed by autumn, winter, and summer. The distribution of wind speed tends to be greater in the east and coastal areas for both avg-wind and gust wind. From September to March of the following year, the prevailing wind direction in Shenzhen was northerly, and from April to August, the prevailing wind direction was southerly. The seasonal wind speed distribution exhibited two different types, spring–summer type and autumn–winter type, which may be induced by their different prevailing wind directions. The analysis by the empirical orthogonal function (EOF) method confirmed the previous findings that the mean wind speed was decreasing in Shenzhen and that two different seasonal wind speed spatial distribution patterns existed. Such a study could provide references for wind forecasting and risk assessment in the study area.


2020 ◽  
Vol 61 (12) ◽  
pp. 162-165
Author(s):  
Ulker Faig Bayramova ◽  

The article reviews wind conditions at Ganja International Airport and specifies the maximum winds observed during the month and the direction of the winds. The direction of the mean, maximum wind speed of the prevailing wind was analyzed. Based on our analysis, we can see that the prevailing wind direction isnortheast and the maximum speed was recorded in March. Key words: wind, temperature, aviation, wind rose, visibility


2021 ◽  
Author(s):  
Liu Xinchun ◽  
kang yongde ◽  
Chen Hongna ◽  
Lu Hui

Abstract Near-surface (10 m) wind speed (NWS) plays a crucial role in many areas, including the hydrological cycle, wind energy production, and the dispersion of air pollution. Based on wind speed data from Tazhong and the northern margins of the Taklimakan Desert in Xiaotang in spring, summer, autumn, and winter of 2014 and 2015, statistical methods were applied to determine the characteristics of the diurnal changes in wind speed near the ground and the differences in the wind speed profiles between the two sites. The average wind speed on a sunny day increased slowly with height during the day and rapidly at night. At heights below 4 m the wind speed during the day was higher than at night, whereas at 10 m the wind speed was lower during the day than at night. The semi-empirical theory and Monin-Obukhov (M-O) similarity theory were used to fit the NWS profile in the hinterland of the Tazhong Desert. A logarithmic law was applied to the neutral stratification wind speed profile, and an exponential fitting correlation was used for non-neutral stratification. The more unstable the stratification, the smaller the n. Using M-O similarity theory, the “linear to tens of” law was applied to the near-neutral stratification. According to the measured data, the distribution of φM with stability was obtained. The γm was obtained when the near-surface stratum was stable in the hinterland of Tazhong Desert and the βm was obtained when it was unstable. In summer, γm and βm were 5.84 and 15.1, respectively, while in winter, γm and βm were 1.9 and 27.1, respectively.


2018 ◽  
Vol 137 (1-2) ◽  
pp. 1449-1456 ◽  
Author(s):  
Chenglong Zhou ◽  
Ali Mamtimin ◽  
Fan Yang ◽  
Wen Huo ◽  
Minzhong Wang ◽  
...  

2019 ◽  
Vol 97 (3) ◽  
pp. 1069-1081
Author(s):  
Xinghua Yang ◽  
Chenglong Zhou ◽  
Wen Huo ◽  
Fan Yang ◽  
Xinchun Liu ◽  
...  

Symmetry ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 679
Author(s):  
Jimmy Reyes ◽  
Emilio Gómez-Déniz ◽  
Héctor W. Gómez ◽  
Enrique Calderín-Ojeda

There are some generalizations of the classical exponential distribution in the statistical literature that have proven to be helpful in numerous scenarios. Some of these distributions are the families of distributions that were proposed by Marshall and Olkin and Gupta. The disadvantage of these models is the impossibility of fitting data of a bimodal nature of incorporating covariates in the model in a simple way. Some empirical datasets with positive support, such as losses in insurance portfolios, show an excess of zero values and bimodality. For these cases, classical distributions, such as exponential, gamma, Weibull, or inverse Gaussian, to name a few, are unable to explain data of this nature. This paper attempts to fill this gap in the literature by introducing a family of distributions that can be unimodal or bimodal and nests the exponential distribution. Some of its more relevant properties, including moments, kurtosis, Fisher’s asymmetric coefficient, and several estimation methods, are illustrated. Different results that are related to finance and insurance, such as hazard rate function, limited expected value, and the integrated tail distribution, among other measures, are derived. Because of the simplicity of the mean of this distribution, a regression model is also derived. Finally, examples that are based on actuarial data are used to compare this new family with the exponential distribution.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hiroto Yamashita ◽  
Rei Sonobe ◽  
Yuhei Hirono ◽  
Akio Morita ◽  
Takashi Ikka

AbstractSpectroscopic sensing provides physical and chemical information in a non-destructive and rapid manner. To develop non-destructive estimation methods of tea quality-related metabolites in fresh leaves, we estimated the contents of free amino acids, catechins, and caffeine in fresh tea leaves using visible to short-wave infrared hyperspectral reflectance data and machine learning algorithms. We acquired these data from approximately 200 new leaves with various status and then constructed the regression model in the combination of six spectral patterns with pre-processing and five algorithms. In most phenotypes, the combination of de-trending pre-processing and Cubist algorithms was robustly selected as the best combination in each round over 100 repetitions that were evaluated based on the ratio of performance to deviation (RPD) values. The mean RPD values were ranged from 1.1 to 2.7 and most of them were above the acceptable or accurate threshold (RPD = 1.4 or 2.0, respectively). Data-based sensitivity analysis identified the important hyperspectral regions around 1500 and 2000 nm. Present spectroscopic approaches indicate that most tea quality-related metabolites can be estimated non-destructively, and pre-processing techniques help to improve its accuracy.


2004 ◽  
Vol 57 (3) ◽  
pp. 329-344 ◽  
Author(s):  
Zhibao Dong ◽  
Guangting Chen ◽  
Xingdong He ◽  
Zhiwen Han ◽  
Xunming Wang

1985 ◽  
Vol 107 (3) ◽  
pp. 237-239
Author(s):  
R. W. Baker

The hourly wind speed data collected over a six-year period at four wind power measurement locations are used to estimate the annual energy output of a large wind turbine generator. The interannual energy and wind speed variations are discussed. The estimated interannual energy output at each location is related to the mean annual wind speed variation. The data indicate that at three of the four locations the estimated interannual energy variation varied as the square of the mean annual wind speed variation. That is, a 10 percent increase in the mean annual wind speed resulted in a 20 percent increase in the annual energy output. At the fourth location there was an approximate linear relationship.


Geomorphology ◽  
2008 ◽  
Vol 96 (1-2) ◽  
pp. 39-47 ◽  
Author(s):  
Ruiping Zu ◽  
Xian Xue ◽  
Mingrui Qiang ◽  
Bao Yang ◽  
Jianjun Qu ◽  
...  

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