Thin film methods and X ray energy dispersive technique were applied to analyze sulfate-containing particles inBeijing in order to examine their features and sources. Atmospheric aerosol particles were collected on el...Thin film methods and X ray energy dispersive technique were applied to analyze sulfate-containing particles inBeijing in order to examine their features and sources. Atmospheric aerosol particles were collected on electron microscope meshes according to two size ranges: coarse particles (r>0.5μm) and fine particles (0.5μm>r>0. 1μm) by using a two-stage impactor. It was found that more than seventy percent of the fine particles and about twenty percentof the coarse particles were sulfate-containing particles. These particles were formed mainly through heterogeneousnucleation. The element composition analyses revealed that the atmospheric aerosol particles in Beijing were domi-nated by crustal particles and construction dust.展开更多
The vertical and horizontal propagation of internal gravity waves forced by a local thermal source at the lowerboundary is examined using the irrotational two-dimensional model developed by Zhang et al. (1995).The sou...The vertical and horizontal propagation of internal gravity waves forced by a local thermal source at the lowerboundary is examined using the irrotational two-dimensional model developed by Zhang et al. (1995).The sourcegenerates waves with the same absolute frequency 1/15 d-1 but different wavenumber.Internal gravity waves withwide spreading frequencies and wavenumbers appear due to wave-wave interactions. The foreced waves iW (westward-propagating with wavenumber 1)and iE (eastward-propagating with wavenumber 1),whose absolute phasespeeds are 31 m s-1,are predominant. Other forced waves with smaller phase speeds are relatively weaker.Thesewaves interact with the zonal mean flow,causing the flow to alternate with easterly and westerly with a 32-month period. The absolute maximum wind speeds of easterly and westerly are 35 m s-l which is larger than the largest phasespeed of forced waves. The forced waves iE and iW may accelerate easterly and westerly up to i 31 m s',respectively.The excessive accelerations are due to the self--acceleration of waves iE and iW or newly generated highfrequency waves iE and IW.The horizontal propagation of the waves are mainly affected by the forcing and wave--flow interactions whichlead to fast-slow variations of wave phase speed and amplitude.展开更多
A zonalwetiCal two-dimensional equatorial model is used to study the PO￣ty that the long Period oSCillation of the zonal mean now occurring in the lower equatorial stratosphere(QBO) is cause by local thermal activihe...A zonalwetiCal two-dimensional equatorial model is used to study the PO￣ty that the long Period oSCillation of the zonal mean now occurring in the lower equatorial stratosphere(QBO) is cause by local thermal activihes at the tropiCal tropopause.The model sumesfully reproduces Q￣like o￣tions of the zonal mean now,suggeshng that the lOCal heating or cooling at the trOPical trOPOpose is Probably the main ￣n of QBO,s generahon. The analysis of the dependence of the oedllahon on the wave foeing iudicatw that the o￣hon is not areaible to the forCing scale.The model can reproduce QBO--like oscillahons with any forCing￣if the forcing Period and amplitude take appropriate valuex, proving that the inaneal cavity waves ge￣od by lOCal thermal sough take much important roles in QBO.展开更多
文摘Thin film methods and X ray energy dispersive technique were applied to analyze sulfate-containing particles inBeijing in order to examine their features and sources. Atmospheric aerosol particles were collected on electron microscope meshes according to two size ranges: coarse particles (r>0.5μm) and fine particles (0.5μm>r>0. 1μm) by using a two-stage impactor. It was found that more than seventy percent of the fine particles and about twenty percentof the coarse particles were sulfate-containing particles. These particles were formed mainly through heterogeneousnucleation. The element composition analyses revealed that the atmospheric aerosol particles in Beijing were domi-nated by crustal particles and construction dust.
文摘The vertical and horizontal propagation of internal gravity waves forced by a local thermal source at the lowerboundary is examined using the irrotational two-dimensional model developed by Zhang et al. (1995).The sourcegenerates waves with the same absolute frequency 1/15 d-1 but different wavenumber.Internal gravity waves withwide spreading frequencies and wavenumbers appear due to wave-wave interactions. The foreced waves iW (westward-propagating with wavenumber 1)and iE (eastward-propagating with wavenumber 1),whose absolute phasespeeds are 31 m s-1,are predominant. Other forced waves with smaller phase speeds are relatively weaker.Thesewaves interact with the zonal mean flow,causing the flow to alternate with easterly and westerly with a 32-month period. The absolute maximum wind speeds of easterly and westerly are 35 m s-l which is larger than the largest phasespeed of forced waves. The forced waves iE and iW may accelerate easterly and westerly up to i 31 m s',respectively.The excessive accelerations are due to the self--acceleration of waves iE and iW or newly generated highfrequency waves iE and IW.The horizontal propagation of the waves are mainly affected by the forcing and wave--flow interactions whichlead to fast-slow variations of wave phase speed and amplitude.
文摘A zonalwetiCal two-dimensional equatorial model is used to study the PO￣ty that the long Period oSCillation of the zonal mean now occurring in the lower equatorial stratosphere(QBO) is cause by local thermal activihes at the tropiCal tropopause.The model sumesfully reproduces Q￣like o￣tions of the zonal mean now,suggeshng that the lOCal heating or cooling at the trOPical trOPOpose is Probably the main ￣n of QBO,s generahon. The analysis of the dependence of the oedllahon on the wave foeing iudicatw that the o￣hon is not areaible to the forCing scale.The model can reproduce QBO--like oscillahons with any forCing￣if the forcing Period and amplitude take appropriate valuex, proving that the inaneal cavity waves ge￣od by lOCal thermal sough take much important roles in QBO.
