Li X.,Institute of Desert Meteorology |
Xia X.,CAS Institute of Atmospheric Physics |
Xia X.,Nanjing University of Information Science and Technology |
Wang L.,Urumqi Meteorological Bureau |
And 5 more authors.
Journal of Geophysical Research D: Atmospheres | Year: 2015
The impact of sandwich foehn on air pollution in Urumqi, a gap town located on the northern lee side of the Tianshan Mountains of China, is analyzed. The results show that during days with high pollution, the boundary layer over the city and the down-valley area can be divided into a three-layer structure, with the southeasterly foehn sandwiched between the northwesterly winds on top and the cold air surface pool beneath. The southeasterly foehn at heights between 480 and 2100 m results in a very stable boundary layer structure. In combination with the decoupling between the foehn flow and cold air pool, such boundary layer structure prevents vertical mixing of atmospheric pollutants. In the up-valley area from the northern lee side flank to the southern urban area, the ground-based foehn confronts the thermally driven valley breeze and forms a "minifront," which moves northward in the morning and retreats southward in the afternoon. Although the minifront disappears in the early evening, the wind shear of the mountain breeze between the southern suburb and downtown areas is still remarkable, which is favorable for a convergence line to persist around the city all day long. In this case, air pollutants emitted from the up-valley and down-valley areas are transported toward the urban area. Therefore, the air pollutants accumulate daily, leading to the frequent occurrence of heavy pollution events in Urumqi. This indicates that the sandwich foehn plays a critical role in the formation of heavy air pollution events in Urumqi. Key Points The winter boundary layer is characterized by the presence of a sandwich foehn The boundary layer with a sandwich foehn is very stable on HPDs in winter The interaction between cold air pool and foehn causes the convergence in town. © 2015 American Geophysical Union. All Rights Reserved.
Zhang G.,Institute of Desert Meteorology |
Sun S.,Urumqi Meteorological Bureau |
Ma Y.,Institute of Desert Meteorology |
Zhao L.,Institute of Desert Meteorology
Journal of Geographical Sciences | Year: 2010
According to climate features and river runoff conditions, Xinjiang could be divided into three research areas: The Altay-Tacheng region, the Tianshan Mountain region and the northern slope of the Kunlun Mountains. Utilizing daily observations from 12 sounding stations and the annual runoff dataset from 34 hydrographical stations in Xinjiang for the period 1960-2002, the variance of the summertime 0°C level height and the changing trends of river runoff are analyzed both qualitatively and quantitatively, through trend contrast of curves processed by a 5-point smoothing procedure and linear correlation. The variance of the summertime 0°C level height in Xinjiang correlates well with that of the annual river runoff, especially since the early 1990s, but it differs from region to region, with both the average height of the 0°C level and runoff quantity significantly increasing over time in the Altay-Tacheng and Tianshan Mountain regions but decreasing on the northern slope of the Kunlun Mountains. The correlation holds for the whole of Xinjiang as well as the three individual regions, with a 0. 01 significance level. This indicates that in recent years, climate change in Xinjiang has affected not only the surface layer but also the upper levels of the atmosphere, and this raising and lowering of the summertime 0°C level has a direct impact on the warming and wetting process in Xinjiang and the amount of river runoff. Warming due to climate change increases the height of the 0°C level, but also speeds up, ice-snow melting in mountain regions, which in turn increases river runoff, leading to a season of plentiful water instead of the more normal low flow period. © 2010 Science in China Press and Springer-Verlag Berlin Heidelberg.
Wang M.,Lanzhou University |
Wei W.,Lanzhou University |
He Q.,Urumqi Institute of Desert Meteorology |
Wang S.,Lanzhou University |
And 3 more authors.
Meteorology and Atmospheric Physics | Year: 2014
Using the multi-source observation data from wind-profiling radar, microwave radiometer, Doppler weather radar, etc. during the blizzard event in 19-20 March 2012 in Urumqi, this paper analyzed the detailed characteristics of the atmospheric dynamics, thermodynamics, intensity and water vapor during the process of this blizzard weather. The findings suggest: (1) in the course of the blizzard weather, the near-surface atmosphere is mainly dominated by northwest airflows, the wind speed and relative humidity increase rapidly, temperature drops and air pressure ascends; (2) the blizzard weather this time is accompanied by cold front system whose entering time is about 16:00 BT 19 March; the shear line that develops from low to high is the position height of the frontal zone, and the variation of the high-level frontal zone directly reflects the altitude and layers where cold and warm air masses interact; (3) the radar equivalent reflectivity factor of the snowstorm process changes within the range 8-25 dBZe and its large-value zone is correlated well with the blizzard duration, the height for the formation of rain (snow) particles and the snow intensity; (4) before the occurrence of the blizzard, atmosphere is in the state of high temperature and high humidity, the maximum vapor density is around 6 g m-3, water vapor mainly stays under the height of 5,000 m; affected by cold front system, cold airs gradually lift warm and moist airs so that the vapor condenses and deposits into water drops and snow particles, forming the snowstorm in the end. © 2014 Springer-Verlag Wien.
Li X.,Institute of Desert Meteorology |
Guo Y.-H.,Xinjiang Environmental Monitor Center |
Lu X.-Y.,Xinjiang Meteorological Observatory |
Gulgina H.,Xinjiang Meteorological Information Center |
And 7 more authors.
Zhongguo Huanjing Kexue/China Environmental Science | Year: 2016
Measures mainly based on the Coal to Gas Engineering (CTGE) for heating between 2012 and 2013 were taken to improve the air quality in Urumqi. In this paper, a comprehensive study was conducted to evaluate the effects of these measures on atmospheric environment in Urumqi by using the data of the concentrations of major air pollutants during wintertime of 2009~2014, the direct radiation, visibility, hazy days between 1993~2014. The results show that the concentrations of PM10, SO2 and NO2 in Urumqi during the wintertime of 2013~2014 decline by 26.1%, 80.2% and 11.6% respectively compared to those in the wintertime of 2009~2011 which represent the concentrations before CTGE. The ratio of total water-soluble matter to PM2.5 also decreases by 20.57%. The top three ions' concentrations in PM2.5 are SO4 2, NH4 + and NO3 -before and after the CTGE. However, there is 50% decrease of the mass fractions of SO4 2-and NH4 + in PM2.5 after the CTGE, and the mass fraction of NO3 -in PM2.5 remains unchanged. In the view of atmospheric physics, the total direct radiations during the wintertime in Urumqi increase after the CTGE and the value of 2013~2014 reaches up to the second peak for the past 23 years. There is a 5.7 km increase for the wintertime visibility of 2013~2014 which is the maximum value since 1997. At the same time, there are 15days less for the wintertime hazy days of 2012~2013 compared to that of previous year which is a decrease of 50%. The results and analysis indicate that the CTGE for heating improved the atmospheric environment in Urumqi to a certain extent. © 2016, Chinese Society for Environmental Sciences. All right reserved.
Jiang Y.-A.,Xinjiang Climatic Center |
Chen Y.,Xinjiang Climatic Center |
Zhao Y.-Z.,Urumqi Meteorological Bureau |
Chen P.-X.,Xinjiang Climatic Center |
And 3 more authors.
Advances in Climate Change Research | Year: 2014
By using the observation data from 89 weather stations in Xinjiang during 1961-2010, this paper analyzed the basic climatic elements including temperature, precipitation, wind speed, sunshine duration, water vapor pressure, and dust storm in the entire Xinjiang and the sub areas: North Xinjiang, Tianshan Mountains, and South Xinjiang. The results indicate that from 1961 to 2010 the annual and seasonal mean temperatures in the entire Xinjiang show an increasing trend with the increasing rate rising from south to north. The increasing rate of annual mean minimum temperature is over twice more than that of the annual mean maximum temperature, contributing much to the increase in the annual averages. The magnitude of the decrease rate of low-temperature days is larger than the increase rate of high-temperature days. The increase of warm days and warm nights and the decrease of cold days and cold nights further reveal that the temperature increasing in Xinjiang is higher. In addition, annual and seasonal rainfalls have been increasing. South Xinjiang experiences higher increase in rainfall amounts than North Xinjiang and Tianshan Mountains. Annual rainy days, longest consecutive rainy days, the daily maximum precipitation and extreme precipitation events, annual torrential rain days and amount, annual blizzard days and amount, all show an increasing trend, corresponding to the increasing in annual mean water vapor pressure. This result shows that the humidity has increased with temperature increasing in the past 50 years. The decrease in annual mean wind speed and gale days lessen the impact of dust storm, sandstorm, and floating dust events. The increase in annual rainy days is the cause of the decrease in annual sunshine duration, while the increase in spring sunshine duration corresponds with the decrease in dust weather. Therefore, the increase in precipitation indicators, the decrease in gales and dust weather, and the increasing in sunshine duration in spring will be beneficial to crops growth.