60-year changes and mechanisms of Urumqi Glacier No.1 in the eastern Tianshan of China,Central Asia

Worldwide examination of glacier change is based on detailed observations from only a small number of glaciers.The ground-based detailed individual glacier monitoring is of strong need and extremely important in both regional and global scales.A long-term integrated multi-level monitoring has been carried out on Urumqi Glacier No.1(UG1)at the headwaters of the Urumqi River in the eastern Tianshan Mountains of Central Asia since 1959 by the Tianshan Glaciological Station,Chinese Acamedey of Sciences(CAS),and the glaciological datasets promise to be the best in China.The boundaries of all glacier zones moved up,resulting in a shrunk accumulation area.The stratigraphy features of the snowpack on the glacier were found to be significantly altered by climate warming.Mass balances of UG1 show accelerated mass loss since 1960,which were attributed to three mechanisms.The glacier has been contracting at an accelerated rate since 1962,resulting in a total reduction of 0.37 km2 or 19.3%from 1962 to 2018.Glacier runoff measured at the UG1 hydrometeorological station demonstrates a significant increase from 1959 to 2018 with a large interannual fluctuation,which is inversely correlated with the glacier's mass balance.This study analyzes on the changes in glacier zones,mass balance,area and length,and streamflow in the nival glacial catchment over the past 60 years.It provides critical insight into the processes and mechanisms of glacier recession in response to climate change.The results are not only representative of those glaciers in the Tianshan mountains,but also for the continental-type throughout the world.The direct observation data form an essential basis for evaluating mountain glacier changes and the impact of glacier shrinkage on water resources in the interior drainage rivers within the vast arid and semi-arid land in northwestern China as well as Central Asia.

Spatiotemporal variations in surface albedo during the ablation season and linkages with the annual mass balance on Muz Taw Glacier,Altai Mountains

Melt-albedo feedback on glaciers is recognized as important processes for understanding glacier behavior and its sensitivity to climate change.This study selected the Muz Taw Glacier in the Altai Mountains to investigate the spatiotemporal variations in albedo and their linkages with mass balance,which will improve our knowledge of the recent acceleration of regional glacier shrinkage.Based on the Landsat-derived albedo,the spatial distribution of ablation-period albedo was characterized by a general increase with elevation,and significant east–west differences at the same elevation.The gap-filling MODIS values captured a nonsignificant negative trend of mean ablation-period albedo since 2000,with a total decrease of approximately 4.2%.From May to September,glacier-wide albedo exhibited pronounced V-shaped seasonal variability.A significant decrease in annual minimum albedo was found from 2000 to 2021,with the rate of approximately−0.30%yr−1 at the 99%confidence level.The bivariate relationship demonstrated that the change of ablation-period albedo explained 82%of the annual mass-balance variability.We applied the albedo method to estimate annual mass balance over the period 2000–2015.Combined with observed values,the average mass balance was−0.82±0.32 m w.e.yr−1 between 2000 and 2020,with accelerated mass loss.

Online monitoring of water-soluble ionic composition of PM_(10)during early summer over Lanzhou City

Lanzhou is one of the most aerosol-polluted cities in China. In this study, an online analyzer for Monitoring for AeRosols and GAses was deployed to measure major water-soluble inorganic ions in PM10 at 1-hour time resolution, and 923 samples were obtained from Apr 1 to May 24, 2011. During the field campaign, air pollution days were encountered with Air Quality Index more than 100 and daily average concentration of PM10 exceeding 150 itg/m3. Based on the variation of water-soluble ions and results of Positive Matrix Factorization 3.0 model execution, the air pollution days were classified as crustal species- or secondary aerosol-induced, and the different formation mechanisms of these two air pollution types were studied. During the crustal species pollution days, the content of Ca2＋ increased and was about 2.3 times higher than the average on clear days, and the air parcel back trajectory was used to analyze the sources of crustal species. Data on sulfate, trace gases and meteorological factors were used to reveal the formation mechanism of secondary aerosol pollution. The sulfur oxidation ratio （SOR） was derived from the 923 samples, and the SOR had high positive correlation with relative humidity in early summer in Lanzhou.

Case study of dust event sources from the Gobi and Taklamakan deserts:An investigation of the horizontal evolution and topographical effect using numerical modeling and remote sensing

A severe dust event occurred from April 23 to April 27, 2014, in East Asia. A state-of-the-art online atmospheric chemistry model, WRF/Chem, was combined with a dust model, GOCART, to better understand the entire process of this event. The natural color images and aerosol optical depth （AOD） over the dust source region are derived from datasets of moderate resolution imaging spectroradiometer （MODIS） loaded on a NASA Aqua satellite to trace the dust variation and to verify the model results. Several meteorological conditions, such as pressure, temperature, wind vectors and relative humidity, are used to analyze meteorological dynamic. The results suggest that the dust emission occurred only on April 23 and 24, although this event lasted for 5 days. The Gobi Desert was the main source for this event, and the Taklamakan Desert played no important role. This study also suggested that the landform of the source region could remarkably interfere with a dust event. The Tarim Basin has a topographical effect as a ＂dust reservoir＂ and can store unsettled dust, which can be released again as a second source, making a dust event longer and heavier.