A state-of-the art Rayleigh and Mie backscattering lidar was set up at Gadanki （13.5°N, 79.2°E） in the Tropics in India. Using this system, regular observations of upper tropospheric clouds, aerosols at st...A state-of-the art Rayleigh and Mie backscattering lidar was set up at Gadanki （13.5°N, 79.2°E） in the Tropics in India. Using this system, regular observations of upper tropospheric clouds, aerosols at stratospheric heights and atmospheric temperatures in the range from 30 to 80 km were made. In this paper, the data collected during the period of 1998-99 were selected for systematic investigation and presentation. The Mie scattering lidar system is capable of measuring the degree of depolarization in the laser backscattering. Several tropical cirrus cloud structures have been identified with low to moderate ice content. Occasionally, thin sub-visible cirrus clouds in the vicinity of the tropical tropopause have also been detected. The aerosol measurements in the upper troposphere and lower stratosphere show low aerosol content with a vertical distribution up to 35 km altitude. Rayleigh-scattering lidar observations reveal that at the tropical site, temperature inversion occurs at mesospheric heights. Atmospheric waves have induced perturbations in the temperatures for several times at the upper stratospheric heights. A significant warming in the lower mesosphere associated with a consistent cooling in the upper stratospheric heights is observed particularly in the winter season during the events of sudden stratospheric warming （ssw）.展开更多
The present study describes variation of peak linear depolarization ratio (LDR) with wind around the cloud altitude using simultaneous observation of winds and cirrus cloud for the first time using Indian MST radar an...The present study describes variation of peak linear depolarization ratio (LDR) with wind around the cloud altitude using simultaneous observation of winds and cirrus cloud for the first time using Indian MST radar and polarization lidar co-located over a low latitude station Gadanki (13.7°N and 79.2°E). Three different cases of passage of the cirrus at different altitudes are noticed, one during a North-East monsoon day and other two during South-West monsoon days. The zonal wind below the cloud height has shown similar variation with LDR during 02 November 2006 and the meridional wind within the cloud height during 25 July 2007 and 08 June 2006 has shown opposite variation with LDR. Even though there is a significant increase in zonal wind due to the existence of tropical easterly jet (TEJ) above cloud height during 25 July 2007 and 08 June 2006, also, the vertical wind is found to be continuously varying during 25 July 2007 and it is upward dominant in the initial stage and is mostly downward in the later stage of observation on 08 June 2006, there is a slight descent in cloud altitude only during 25 July 2007. Thus, the wind above the cloud height alone may not affect the ascent/descent of the cloud top altitude. The potential temperature gradient is high within the cloud heights when the cirrus present near the cold point tropopause indicates the maximum air-mass mixing near the tropopause.展开更多
文摘A state-of-the art Rayleigh and Mie backscattering lidar was set up at Gadanki （13.5°N, 79.2°E） in the Tropics in India. Using this system, regular observations of upper tropospheric clouds, aerosols at stratospheric heights and atmospheric temperatures in the range from 30 to 80 km were made. In this paper, the data collected during the period of 1998-99 were selected for systematic investigation and presentation. The Mie scattering lidar system is capable of measuring the degree of depolarization in the laser backscattering. Several tropical cirrus cloud structures have been identified with low to moderate ice content. Occasionally, thin sub-visible cirrus clouds in the vicinity of the tropical tropopause have also been detected. The aerosol measurements in the upper troposphere and lower stratosphere show low aerosol content with a vertical distribution up to 35 km altitude. Rayleigh-scattering lidar observations reveal that at the tropical site, temperature inversion occurs at mesospheric heights. Atmospheric waves have induced perturbations in the temperatures for several times at the upper stratospheric heights. A significant warming in the lower mesosphere associated with a consistent cooling in the upper stratospheric heights is observed particularly in the winter season during the events of sudden stratospheric warming （ssw）.
文摘The present study describes variation of peak linear depolarization ratio (LDR) with wind around the cloud altitude using simultaneous observation of winds and cirrus cloud for the first time using Indian MST radar and polarization lidar co-located over a low latitude station Gadanki (13.7°N and 79.2°E). Three different cases of passage of the cirrus at different altitudes are noticed, one during a North-East monsoon day and other two during South-West monsoon days. The zonal wind below the cloud height has shown similar variation with LDR during 02 November 2006 and the meridional wind within the cloud height during 25 July 2007 and 08 June 2006 has shown opposite variation with LDR. Even though there is a significant increase in zonal wind due to the existence of tropical easterly jet (TEJ) above cloud height during 25 July 2007 and 08 June 2006, also, the vertical wind is found to be continuously varying during 25 July 2007 and it is upward dominant in the initial stage and is mostly downward in the later stage of observation on 08 June 2006, there is a slight descent in cloud altitude only during 25 July 2007. Thus, the wind above the cloud height alone may not affect the ascent/descent of the cloud top altitude. The potential temperature gradient is high within the cloud heights when the cirrus present near the cold point tropopause indicates the maximum air-mass mixing near the tropopause.
