Near-surface sand-dust horizontal flux in Tazhong-the hinterland of the Taklimakan Desert

Tazhong is the hinterland and a sandstorm high-frequency area of the Taklimakan Desert. However, little is known about the detailed time-series of aeolian sand transport in this area. An experiment to study the sand-dust horizontal flux of near-surface was carried out in Tazhong from January to December 2009. By measur- ing the sand-dust horizontal flux throughout sixteen sand-dust weather processes with a 200-cm tall Big Spring Number Eight （BSNE） sampler tower, we quantitatively analyzed the vertical variation of the sand-dust horizontal flux. And the total sand-dust horizontal flux of different time-series that passed through a section of 100 cm in width and 200 cm in height was estimated combining the data of saltation movement continuously recorded by piezo- electric saltation sensors （Sensit）. The results indicated that, in the surface layer ranging from 0-200 cm, the inten- sity of sand-dust horizontal flux decreased with the increase of the height, and the physical quantities obeyed power function well. The total sand-dust horizontal flux of the sixteen sand-dust weather processes that passed through a section of 100 cm in width and 200 cm in height was about 2,144.9 kg, the maximum of one sand-dust weather event was about 396.3 kg, and the annual total sand-dust horizontal flux was about 3,903.2 kg. The high levels of aeolian sand transport occurred during daytime, especially from 13：00 to 16：00 in the afternoon. We try to develop a new method for estimation of the detailed time-series of aeolian sand transport.

Relationship between thermal anomalies in Tibetan Plateau and summer dust storm frequency over Tarim Basin,China

The dust storm is the most important and frequent meteorological disaster over Tarim Basin, which causes huge damages on local social economics. How to predict the springtime and summertime dust storm oc- currence has become a hot issue for meteorologists. This paper employed the data of dust storm frequency and 10-m wind velocity at 35 stations over Tarim Basin and the reanalysis data from the National Center for Environ- mental Prediction and the National Center for Atmospheric Research （NCEP/NCAR） during 1961-2007 to study the relationship between dust storm frequency （DSF） in summer over Tarim Basin and the thermal anomalies in Tibetan Plateau in May by using the statistical methods, such as Empirical Orthogonal Function （EOF）, correlation and binomial moving average. The results show when negative anomalies in Tibetan Plateau and positive anomalies in its southern region are present along 30~N （the second mode of surface temperature anomalies by EOF decomposition） in May, the time coefficient （PC2） plays an important role in summer DSF variation and has a close relation with the summer DSF at both inter-annual and decadal time scales. When negative anomalies in Tibetan Plateau and positive anomalies are present in its southern region （PC2 in positive phase）, there is an anomalous anticyclone in North China, which weakens the northwest wind and is not beneficial for cold air moving from high latitude to the Tarim Basin, and the circulation pattern is hard to result in dust storm weather. Furthermore, the sea level pressure （SLP） increased over Tarim Basin and the direction of SLP gradient reversed, which resulted in the 10-m wind velocity slowing down, so the DSF decreased. From above all, it can be conclude that the thermal anomalies in Tibetan Plateau in May has important effects on the summertime dust storm frequency over Tarim Basin and the PC2 can be used as a prediction factor for the summertime dust storm occurrence.

Trends and abrupt changes in surface vapor content over Tarim Basin during the last 50 years

The surface vapor content has a close correlation with the generation of precipitation. Based on the atmospheric circulation data and surface vapor content data from 37 weather stations across the Tarim Basin dur- ing 1961-2010, the paper analyzed the vapor variation trend, period, abrupt changes and their causes. The results show that the increase trend of surface vapor content over the Tarim Basin mostly conforms with the average trend coefficient of 0.48. There were 3 centers displaying a trend of high vapor increase and 3 centers displaying a low vapor increase. These centers were distributed in strips and blocks across the basin from northeast to southwest. Notable inter-decadal variations in annual and seasonal vapor contents occurred in the Tarim Basin during the 50 years of the study period, with more vapor after the mid-1980s and less vapor in the 1960s and the 1970s. The significant increase in vapor content in the 50 year period occurred mostly in the 1980s and the 1990s. The in- creasing trend across the four seasons was strongest in summer, reaching 0.43, and weakest in spring. Great variations existed between the spring trend and the annual, summer, autumn and winter trends. During the 50-year study period, there are distinguishable periods of 4-6 years and 8-10 years in which the annual and seasonal vapor contents varied alternately between low and high concentrations. The annual vapor content and that of the four individual seasons all changed abruptly in about the mid-1980s （a〈0.05）. The west wind circulation, Tibetan Plateau circulation and the annual mean temperatures of the Tarim Basin are the main factors that influenced the surface vapor content over the study area, of which the Tibetan Plateau circulation may be the most important one.

Vertical distribution characteristics of dust aerosol mass concentration in the Taklimakan Desert hinterland

The different height mass concentrations of dust aerosol data from the atmosphere environment observation station （Ta- zhong Station） was continuously observed by instruments of Grimm 1.108, Thermo RP 1400a and TSP from January of 2009 to February of 2010 in the Taklimakan Desert hinterland. Results show that： （1） The mass concentration value of 80 m PMl0 was higher, but PM2.5 and PM1.0 concentrations at 80 m was obviously lower than 4 m PMl0, and the value of 80 m PM1.0 mass concentration was the lowest. （2） The PM mass concentrations gradually decreased from night to sunrise, with the lowest concentration at 08：00, with the mass concentration gradually increased, up to the highest concentration around 18：00, and then decreased again. It was exactly the same with the changes of wind speed. （3） The high monthly average mass concentration of TSP mainly appeared from March to September, and the highest concentration was in April and May, subsequently gradually decreased. Also, March-September was a period with high value area of PM monthly average mass concentration, with the highest monthly average mass concentration of 846.0 p.g/m3 for 4 m PM^0 appeared in May. The concentration of PM10 was much higher than those of PM2.5 and PM1.0 at 80 m. There is a small difference between the concentration of PM2.5 and PM~ 0. Dust weather was the main factor which influenced the concentration content of the different diameter dust aerosol, and the more dust weather days, the higher content of coarse particle, conversely, fine particle was more. （4） The mass concentration of different diameter aerosols had the following sequence during dust weather： clear day 〈 blowing dust 〈 floating and blowing dust 〈 sandstorm. In different dust weather, the value of PM^o/TSP in fine weather was higher than that in floating weather, and much higher than those in blowing dust and sandstorm weather. （5） During the dust weather process, dust aerosol concentration gradually decreased with particle size decreasing. The dust aerosol mass concentration at different heights and diameter would have a peak value area every 3-4 days according to the strengthening process of dust weather.

The atmospheric circulation patterns influencing the frequency of spring sand-dust storms in the Tarim Basin

Using NCEP/NCAR reanalysis data and the sand-storm frequency data fi＇om 37 weather stations in the Tarim Basin for the period 1961-2009, the relationship between the frequency of spring sandstorms in the Tafim Basin and the associated atmospheric circu- lation pattems is analyzed in this study. We found significantly negative correlations between sandstorm frequency and the 500-hPa geopotential height over the Paris Basin and midwestem Mongolia, while there were positive correlations over the Ural River region. The rising of the 500-hPa geopotential height in midwestem Mongolia and its falling over the Ural region corre- spond to a weakening of the large-scale wave patterns in the Eurasian region, which directly causes the frequency of the sand-dust storms in the Tarim Basin to decline. Also, the abrupt decline in the spring sandstorm frequency in the Tarim Basin observed in the last half-century is associated with profound changes in the atmospheric circulation in these key regions. At the interannual scale, the strengthened cyclonic atmospheric circulation patterns in the western part of Mongolia and the anticyclonic patterns over the East European plains at 500-hPa geopotential height, are responsible for frequent sandstorm occurrences in the Tarim Basin.

The characteristics of grain size from the Kumtag Desert and its environmental significance

The Kumtag Desert is located in the arid northwestern portion of China,and is considered China’s sixth-largest desert.Grain-size analysis of the sand plays a very important role in differentiating sedimentary environments,determining the ways that sediments are transported,estimating hydrodynamic conditions,and analyzing grain-size trends.The analysis of the grain size of 20 sand samples that were taken from mid-northern,north margin,western,middle,southern,and southeast margins of the Kumtag Desert shows that grain sizes are vastly different.The grain-size parameters fall in the following range:the median diameter Mz = 1.55Φ-2.92Φ,the standard deviation σI= 0.41-1.11,the skewness SKI = ?0.11-0.31,kurtosis KG = 0.77-1.23.The frequency curves of grain size have characteristics with single peaks and multi-peaks,and most of the sand samples’ skewness appears close to asymmetric.The analytical results reveal that the sediments of the Kumtag Desert are complex and diverse,which affected by such forces as wind deposition,lacustrine sediment,and alluvial and proluvial river deposits.

Analysis of mass concentration of atmospheric particulate matter in a sandstorm course and its affecting factors in the Taklimakan Desert

During the course of a major sandstorm from April 17 to April 23, 2008 in the Taklimakan Desert, data pertaining to the mass concentrations of different-sized atmospheric particulate matter were observed continuously with Grimm 1.108, Thermo RP 1400a, TSP, and CAWS-600 instruments. The results showed that： （1） during the entire sandstorm process there were some dif- ferences between the daily mean particle concentration peaks and the hourly mean particle concentration peaks because the actual sandstorm lasted for only about 4 hr, whereas more particles were accumulated in the floating dust days before and after the actual sandstorm; （2） the intensity of the sandstorm was enhanced with the increase of wind speed, and this was related to the peak mass concentrations of atmospheric particulate matter; the wind speed directly affected the concentration of atmospheric particulate matter： the higher the wind speed, the higher the mass concentration （〉0.23 μm was 39,496.5 μg/m^3, and 〉20.0 μm was 5,390.7μg/m^3）; （3） the concentration changes of PM10 and TSP were also related to the course and intensity of the sandstorm; and （4） the mass concentration of atmospheric particulate matter had the following sequence during the dust weather： clear day 〈 floating dust 〈 floating and blowing dust 〈 sandstorm. Temperature, relative humidity, and barometric pressure are important factors affecting the strength of storms, which could also indirectly affect the concentration change of atmospheric particulate matter.

The variation characteristics and effect factors of surface ozone concentration in the Taklimakan Desert hinterland

Based on automatic continuous surface ozone concentration observation data from June 10, 2010 to March 20, 2012 in the Taklimakan Desert hinterland, combined with corresponding meteorological data, the temporal, seasonal and daily variation characteristics of surface ozone concentrations under different weather conditions were analyzed. At the same time, the main fac- tors affecting ozone variation are discussed. Results show that： （1） Daily variation of ozone concentration was characterized by one obvious peak, with gentle changes during the night and dramatic changes during the day. The lowest concentration was at 09：00 and the highest was at 18：00. Compared to urban areas, there was a slight time delay. （2） Ozone concentration variation had a weekend effect phenomenon. Weekly variation of ozone concentration decreased from Monday to Wednesday with the lowest in Wednesday, and increased after Thursday with the highest in Sunday. （3） The highest monthly average concentration was 89.6 I.tg/m3 in June 2010, and the lowest was 32.0 ~g/m3 in January 2012. Ozone concentration reduced month by month from June to December in 2010. （4） Ozone concentration in spring and summer was higher than in autumn and winter. The variation trend agreed with those in other large and medium-sized cities. （5） Under four different types of weather, daily ozone concentration var- ied most dramatically in sunny days, followed by slight variation in rain days, and varied gently in cloudy days. Ozone concentra- tion varied inconspicuously before a sandstorm appearance, and dropped rapidly at the onset of a sandstorm. （6） Daily variation of radiation was also characterized by a single peak, and the variation was significantly earlier than ozone concentration variation. Sun radiation intensity had a direct influence on the photochemical reaction speed, leading to variation of ozone concentration. （7） Daily average ozone concentration in dust weather was higher than in slight rain and clear days. The variation of near surface ozone concentration could also be affected by meteorological factors such as relative humidity, wind speed, wind direction and sunshine hours. Thus, numerous factors working together led to ozone pollution.

安全壳环形空间设计压力限值的计算方法及应用研究

安全壳环形空间设计压力限值的确定是安全壳环形空间通风系统设计的关键。以空气动力学和污染物传输动力学为基础,提出了复杂环境下安全壳环形空间设计压力限值的确定方法。结合实际案例,介绍了核电机组安全壳环形空间设计压力限值确定方法的应用。

Analysis of atmospheric boundary ozone profiles in winter in hinterland of Taklimakan Desert

In order to reveal the variation characteristics of ozone （03） concentration in the atmosphere boundary layer over a desert in winter, an observation experiment was carried out in the Tazhong area by means of a tethered balloon during January 18-25, 2008. The vertical distribution of O3 concentration and its correlation with temperature and humidity were analyzed based on experimental observation data and related data. Results show that： （1） The concentration of O3 mainly ranges from 10 to 50 μg/L, with a maximum of 56.1 μg/L, minimum of 2.6 μg/L, and a daily average concentration of 34.4 μg/L. （2） O3 profiles can be divided into three types： peak, uniform, and growth, where uniform accounts for the majority. （3） Temperature and moisture are influential on O3 concentrations in atmospheric boundary layer. Temperature inversion and water vapor increase in an atmospheric boundary layer leads to a decrease of O3. （4） O3 concentration has an obvious daily change in Tazhong. It is lower at night, begins to increase after sunrise, and reaches a maximum at noon. The maximum appears at 17：00 BJT （Beijing Time）, and the minimum appears at 08：00 BJT.

随气候变化塔克拉玛干沙漠碳汇能力逐渐衰弱

全球碳循环中被长期忽视的沙漠生态系统,可能会封存大量CO2发挥碳汇作用.塔克拉玛干沙漠是世界第二大流动沙漠,其碳汇作用的内部过程以及气候变化下碳汇的长期趋势仍不明确.研究发现,流沙的热量波动引起含CO2的土壤空气的膨胀/收缩和盐碱的化学作用共同控制了塔克拉玛干沙漠流沙CO2交换作用.这些过程的相互作用使得该沙漠流沙表现出明显的碳汇作用(速率为1.60×106 t a-1).如果以塔克拉玛干沙漠流沙的CO2吸收量为平均状态,那么全球流动沙漠每年可吸收CO2约2.125×108 t.但是,随气候变化,流沙温差的增大会刺激流沙中空气膨胀,向大气中注入更多的CO2,导致未来流沙碳汇能力逐渐减少.该发现对于评估全球碳循环、缩小碳失汇差额和重新认识沙漠生态系统在碳循环中的地位具有重要作用.