Based on NCEP reanalysis data,EDAS data and ground observation data,the causes of a strong sandstorm process in Ulanqab City from March 14 to 15,2021 were analyzed.The analysis shows that"3.15"sandstorm,a sa...Based on NCEP reanalysis data,EDAS data and ground observation data,the causes of a strong sandstorm process in Ulanqab City from March 14 to 15,2021 were analyzed.The analysis shows that"3.15"sandstorm,a sandstorm process accompanied by northwest gale behind the front,was caused by strong cold air in the north.In the early stage,the Mongolian cyclone resulted in the increase of temperature and decrease of pressure on the ground.When a strong surface cold high pressure at the rear of the cyclone invaded the city,a strong pressure gradient between high and low pressure provided dynamic conditions for the sandstorm outbreak.The transit of the surface cold front was the sign of the sandstorm outbreak,and the downward transmission of momentum at high altitudes increased the wind speed near the surface.展开更多
The Weather Research and Forecasting (WRF) model was used to investigate the role of downward momentum transport in the formation of severe surface winds for a squall line on 3-4 June 2009 across regions of the Henan ...The Weather Research and Forecasting (WRF) model was used to investigate the role of downward momentum transport in the formation of severe surface winds for a squall line on 3-4 June 2009 across regions of the Henan and Shandong Provinces of China. The results show that there was a strong westerly jet belt with a wind speed greater than 30 m s 1 and a thickness of 5 km at an altitude of 11-16 km. The jet belt was accelerated, and it descended while the squall line convective system occurred. It was found that the appearance of strong negative perturbation pressure accompanied by the squall line caused the acceleration of the upper-level westerly jet and increased the horizontal wind speed by a maximum of 18%. Meanwhile, the negative buoyancy due to the loading, melting, and evaporation of cloud hydrometeors induced the downward momentum transport from the upper levels. The downward momentum transport contributed approximately 70% and the surface cold pool 30% to the formation of severe surface winds.展开更多
The weekly averages of near-surface ^7Be, ^210pb, 03, and CO2 concentrations at the Global Atmospheric Watch Observatory, Mt. Waliguan （101.98°E, 36.287°N, 3810 m a.s.l.）, from October 2002 to January 2004...The weekly averages of near-surface ^7Be, ^210pb, 03, and CO2 concentrations at the Global Atmospheric Watch Observatory, Mt. Waliguan （101.98°E, 36.287°N, 3810 m a.s.l.）, from October 2002 to January 2004 are presented. With the establishment of the new datasets of DCCW （Differential Concentrations in Contiguous Weeks） of ^7Be,^210pb, and O3, CO2 （△^7Be, △^210pb, △O3, △CO2, respectively, the impacts of upper-level downward transports and land-surface emissions on O3 and CO2 concentrations are implied by ^7Be and ^210pb being as independent tracers. The relations among △^7Be, △^210pb, and △O3, △CO2 are examined statistically and compared. The results indicate that with the DCCWs, the interferences with the tracing significance of ^7Be and ^210Pb from the seasonal wet scavenging of atmospheric aerosol are greatly reduced, and the weighting sources of O3 or CO2 variations are more pronounced. Basically, the variability of surface O3 is controlled predominately by air mass transported from the upper atmosphere levels while the emission from the Continent Boundary Layer （CBL） has an obvious input for CO2. The relation between △^210pb and △O3 reflects that influences of CBL emission are generally positive/negative for surface O3 budget in summer/winter, and the relation of △^7Be and △CO2 also reveals that upper level downward transport has positive/negative inputs for CO2 in summer/winter. With the highly correlated relations between ^7Be and O3, a quantitative estimation is made of the stratospheric contributions to the budget of surface O3 at WLG： the monthly averages of stratospheric O3 range from 6 ×10^-9 to 8 ×10^-9 （volume mixing ratio） in April and from June to August, and 2 ×10^-9 to 4 ×10^-9 in the remaining months. For the ultimate sources of the baseline concentration of surface 03, which consist of only stratospheric transport and tropospheric photochemistry production, the contribution from stratospheric transport is estimated to be about 20 ×10^-9 from May to July, and （12-15） ×10^-9 in the remaining months, and the total relative contribution rate is about 35% to 40%.展开更多
文摘Based on NCEP reanalysis data,EDAS data and ground observation data,the causes of a strong sandstorm process in Ulanqab City from March 14 to 15,2021 were analyzed.The analysis shows that"3.15"sandstorm,a sandstorm process accompanied by northwest gale behind the front,was caused by strong cold air in the north.In the early stage,the Mongolian cyclone resulted in the increase of temperature and decrease of pressure on the ground.When a strong surface cold high pressure at the rear of the cyclone invaded the city,a strong pressure gradient between high and low pressure provided dynamic conditions for the sandstorm outbreak.The transit of the surface cold front was the sign of the sandstorm outbreak,and the downward transmission of momentum at high altitudes increased the wind speed near the surface.
基金supported by the National Meteorology Public Welfare Industry Research Project(GYHY200806001)the National Science and Technology Support Program (2006BAC12B03)
文摘The Weather Research and Forecasting (WRF) model was used to investigate the role of downward momentum transport in the formation of severe surface winds for a squall line on 3-4 June 2009 across regions of the Henan and Shandong Provinces of China. The results show that there was a strong westerly jet belt with a wind speed greater than 30 m s 1 and a thickness of 5 km at an altitude of 11-16 km. The jet belt was accelerated, and it descended while the squall line convective system occurred. It was found that the appearance of strong negative perturbation pressure accompanied by the squall line caused the acceleration of the upper-level westerly jet and increased the horizontal wind speed by a maximum of 18%. Meanwhile, the negative buoyancy due to the loading, melting, and evaporation of cloud hydrometeors induced the downward momentum transport from the upper levels. The downward momentum transport contributed approximately 70% and the surface cold pool 30% to the formation of severe surface winds.
基金supported by National Natural Science Foundation of China (Grant Nos.40575013,40175032 and 40830102)
文摘The weekly averages of near-surface ^7Be, ^210pb, 03, and CO2 concentrations at the Global Atmospheric Watch Observatory, Mt. Waliguan （101.98°E, 36.287°N, 3810 m a.s.l.）, from October 2002 to January 2004 are presented. With the establishment of the new datasets of DCCW （Differential Concentrations in Contiguous Weeks） of ^7Be,^210pb, and O3, CO2 （△^7Be, △^210pb, △O3, △CO2, respectively, the impacts of upper-level downward transports and land-surface emissions on O3 and CO2 concentrations are implied by ^7Be and ^210pb being as independent tracers. The relations among △^7Be, △^210pb, and △O3, △CO2 are examined statistically and compared. The results indicate that with the DCCWs, the interferences with the tracing significance of ^7Be and ^210Pb from the seasonal wet scavenging of atmospheric aerosol are greatly reduced, and the weighting sources of O3 or CO2 variations are more pronounced. Basically, the variability of surface O3 is controlled predominately by air mass transported from the upper atmosphere levels while the emission from the Continent Boundary Layer （CBL） has an obvious input for CO2. The relation between △^210pb and △O3 reflects that influences of CBL emission are generally positive/negative for surface O3 budget in summer/winter, and the relation of △^7Be and △CO2 also reveals that upper level downward transport has positive/negative inputs for CO2 in summer/winter. With the highly correlated relations between ^7Be and O3, a quantitative estimation is made of the stratospheric contributions to the budget of surface O3 at WLG： the monthly averages of stratospheric O3 range from 6 ×10^-9 to 8 ×10^-9 （volume mixing ratio） in April and from June to August, and 2 ×10^-9 to 4 ×10^-9 in the remaining months. For the ultimate sources of the baseline concentration of surface 03, which consist of only stratospheric transport and tropospheric photochemistry production, the contribution from stratospheric transport is estimated to be about 20 ×10^-9 from May to July, and （12-15） ×10^-9 in the remaining months, and the total relative contribution rate is about 35% to 40%.
