The Taklimakan Desert, the world's second largest desert, plays an important role in regional climate change. Previousstudies on its spatial temperature features suffered from sparse conventional detection data, b...The Taklimakan Desert, the world's second largest desert, plays an important role in regional climate change. Previousstudies on its spatial temperature features suffered from sparse conventional detection data, but the Atmospheric InfraredSounder (AIRS) provides excellent temperature retrievals with high spatiotemporal resolution. Validation of AIRS temperatureretrievals over desert regions with high land-surface emissivity, the key contributor to inversion error, is essential beforeusing these data in regional weather/climate modeling. This paper examines the correlation coefficients, root meansquare error (RMSE) and mean BIAS between AIRS-retrieved atmospheric temperature data and radiosonde observations(RAOBs) in the Taklimakan Desert hinterland and oases in the morning and at dusk. Firstly, the AIRS retrievals are consistentwith RAOBs and are more consistent in the morning than at dusk. The consistency is better over a small-scale desert oasisthan over a large-scale oasis in the morning and exhibits the opposite trend at dusk. The correlation coefficient over thehinterland is high in the morning but negative at dusk due to high desert-surface emissivity. Second, the RMSEs, which areall smaller than 3 K, are generally higher over desert sites than over oasis sites and slightly lower over a small-scale oasisthan over a large-scale oasis in the morning. At dusk, the RMSEs are higher over desert sites than over oases and slightlyhigher over a small-scale oasis than over a large-scale oasis. Furthermore, the RMSEs are generally higher in the morningthan at dusk over a large-scale oasis and lower in the morning than at dusk over a small-scale oasis. Third, the absolutemean BIAS values are mostly lower than 1 K. In the morning, relative to RAOB temperatures, the retrieval temperaturesare higher over desert sites but lower over oasis sites. At dusk, the retrieval temperatures are lower than RAOB temperaturesover both desert and oasis sites. The retrieval temperatures are higher than RAOB temperatures over desert sites inthe morning but slightly lower at dusk. Most absolute mean BIAS values are higher in the morning than at dusk overboth oasis and desert sites. Finally, the consistency between the AIRS and RAOB temperature data is high from 700 hPato 100 hPa in the morning and from 700 hPa to 300 hPa at dusk. The difference between the AIRS and RAOB temperaturedata is generally higher in the morning than that at dusk. The RMSE differences between the AIRS and RAOB data areslightly lower in the morning than at dusk and are lower in the middle layers between 700 hPa and 150 hPa than in the layersabove 150 hPa during both the morning and night. The BIAS is lower in the morning than at dusk below 300 hPabut higher in the upper layers. Moreover, the BIAS value is positive in the middle layers between 500 hPa and 150 hPaand negative at other levels at both times. Generally, the AIRS retrieval temperatures are reliable and can be used in furtherstudies in the Taklimakan Desert.展开更多
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-d...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.展开更多
The size distribution of airborne dust particles is an important parameter in the measurement of dust emissions due to wind erosion,and a quantitative and accurate description is necessary.Observations regarding the s...The size distribution of airborne dust particles is an important parameter in the measurement of dust emissions due to wind erosion,and a quantitative and accurate description is necessary.Observations regarding the size distribution of airborne dust particles are currently lacking in Tibetan Plateau(TP).This study aims to obtain a dust particle size distribution and compare the difference in spatial distribution at a field site(FS)and two urban observation sites(Minfeng and Hetian),in the north of the TP,under the condition of the dust-days and clear-days.The observation data was collected from 5 July to 4 August,2019.The mass concentration of dust(PM20)was measured with a 10-stage quartz crystal microbalance cascade impactor.The results suggested that 91.9%of the particles were less than 1.4μm on clear-days,and particles of d≥1.4μm increased to 27.2%with the occurrence of the dust events.More than 80%of the airborne dust particles were less than 1.4μm for each friction velocity.The proportion of d<0.7μm was the greatest at 3.0 m(above the surface,similarly hereinafter)on dust-days,while the proportion of d>0.7μm was the greatest at 0.5 m on clear-days.During urban observation,with the occurrence of dust events,the concentration of a particle size greater than 2.5μm increased most significantly in Minfeng,while the concentration of a particle size less than 0.7μm increased most significantly in Hetian.Moreover,the proportion of particles with d<0.7μm had the smallest difference,while the proportion of particles with d>1.4μm had the most obvious difference among these three sites.展开更多
The global carbon balance is a core issue in climate change research and a focus of in ternational policy concern[1-3].The"missing carbon sink"caused by approximately 1.6-2.0 Pg Ca-1(1 Pg=1015 g)that is curr...The global carbon balance is a core issue in climate change research and a focus of in ternational policy concern[1-3].The"missing carbon sink"caused by approximately 1.6-2.0 Pg Ca-1(1 Pg=1015 g)that is currently unaccounted for,has long plagued researchers[4,5].Evidence is mounting those seemingly lifeless desert ecosystems,whose roles in the global carbon-cycle have long been neglected,exhib让the unconventional phenomenon of absorption of atmospheric CO2,sequestering enonnous amounts of CO2 and thereby creating a significant carbon-sink[6-9].展开更多
文摘The Taklimakan Desert, the world's second largest desert, plays an important role in regional climate change. Previousstudies on its spatial temperature features suffered from sparse conventional detection data, but the Atmospheric InfraredSounder (AIRS) provides excellent temperature retrievals with high spatiotemporal resolution. Validation of AIRS temperatureretrievals over desert regions with high land-surface emissivity, the key contributor to inversion error, is essential beforeusing these data in regional weather/climate modeling. This paper examines the correlation coefficients, root meansquare error (RMSE) and mean BIAS between AIRS-retrieved atmospheric temperature data and radiosonde observations(RAOBs) in the Taklimakan Desert hinterland and oases in the morning and at dusk. Firstly, the AIRS retrievals are consistentwith RAOBs and are more consistent in the morning than at dusk. The consistency is better over a small-scale desert oasisthan over a large-scale oasis in the morning and exhibits the opposite trend at dusk. The correlation coefficient over thehinterland is high in the morning but negative at dusk due to high desert-surface emissivity. Second, the RMSEs, which areall smaller than 3 K, are generally higher over desert sites than over oasis sites and slightly lower over a small-scale oasisthan over a large-scale oasis in the morning. At dusk, the RMSEs are higher over desert sites than over oases and slightlyhigher over a small-scale oasis than over a large-scale oasis. Furthermore, the RMSEs are generally higher in the morningthan at dusk over a large-scale oasis and lower in the morning than at dusk over a small-scale oasis. Third, the absolutemean BIAS values are mostly lower than 1 K. In the morning, relative to RAOB temperatures, the retrieval temperaturesare higher over desert sites but lower over oasis sites. At dusk, the retrieval temperatures are lower than RAOB temperaturesover both desert and oasis sites. The retrieval temperatures are higher than RAOB temperatures over desert sites inthe morning but slightly lower at dusk. Most absolute mean BIAS values are higher in the morning than at dusk overboth oasis and desert sites. Finally, the consistency between the AIRS and RAOB temperature data is high from 700 hPato 100 hPa in the morning and from 700 hPa to 300 hPa at dusk. The difference between the AIRS and RAOB temperaturedata is generally higher in the morning than that at dusk. The RMSE differences between the AIRS and RAOB data areslightly lower in the morning than at dusk and are lower in the middle layers between 700 hPa and 150 hPa than in the layersabove 150 hPa during both the morning and night. The BIAS is lower in the morning than at dusk below 300 hPabut higher in the upper layers. Moreover, the BIAS value is positive in the middle layers between 500 hPa and 150 hPaand negative at other levels at both times. Generally, the AIRS retrieval temperatures are reliable and can be used in furtherstudies in the Taklimakan Desert.
基金funded by the National Natural Science Foundation of China (41175017)the Central Scientific Research Institute of the public basic scientific research business professional ( IDM201103)the R&D Special Fund for Public Welfare Industry (Meteorology)(GYHY201106025)
文摘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.
基金funded by the National Natural Science Foundation of China(41875019&41905009)Basic Business Expenses(IDM2019002&IDM2016005)+1 种基金Chinese Desert Meteorological Science Research Found(Sqj2018019)Flexible Talents Introducing Project of Xinjiang(2018)。
文摘The size distribution of airborne dust particles is an important parameter in the measurement of dust emissions due to wind erosion,and a quantitative and accurate description is necessary.Observations regarding the size distribution of airborne dust particles are currently lacking in Tibetan Plateau(TP).This study aims to obtain a dust particle size distribution and compare the difference in spatial distribution at a field site(FS)and two urban observation sites(Minfeng and Hetian),in the north of the TP,under the condition of the dust-days and clear-days.The observation data was collected from 5 July to 4 August,2019.The mass concentration of dust(PM20)was measured with a 10-stage quartz crystal microbalance cascade impactor.The results suggested that 91.9%of the particles were less than 1.4μm on clear-days,and particles of d≥1.4μm increased to 27.2%with the occurrence of the dust events.More than 80%of the airborne dust particles were less than 1.4μm for each friction velocity.The proportion of d<0.7μm was the greatest at 3.0 m(above the surface,similarly hereinafter)on dust-days,while the proportion of d>0.7μm was the greatest at 0.5 m on clear-days.During urban observation,with the occurrence of dust events,the concentration of a particle size greater than 2.5μm increased most significantly in Minfeng,while the concentration of a particle size less than 0.7μm increased most significantly in Hetian.Moreover,the proportion of particles with d<0.7μm had the smallest difference,while the proportion of particles with d>1.4μm had the most obvious difference among these three sites.
基金the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0602)the National Natural Science Foundation of China(41521004,41975010 and 41175140)the China University Research Talents Recruitment Program(B13045).
文摘The global carbon balance is a core issue in climate change research and a focus of in ternational policy concern[1-3].The"missing carbon sink"caused by approximately 1.6-2.0 Pg Ca-1(1 Pg=1015 g)that is currently unaccounted for,has long plagued researchers[4,5].Evidence is mounting those seemingly lifeless desert ecosystems,whose roles in the global carbon-cycle have long been neglected,exhib让the unconventional phenomenon of absorption of atmospheric CO2,sequestering enonnous amounts of CO2 and thereby creating a significant carbon-sink[6-9].
