First Ground Observations of OI5577 Green Line Emission over the Taiwan Area

Worldwide ground observations of upper atmospheric airglow with particular emphasis on the OI 557.7 and 630 nm emissions have been conducted since 1960s. This study reports the first ground observations of OI 557.7 nm green line emission over the Taiwan area. For comparison, the background continuum at 530 nm was also measured by the same system. The experiments were conducted during the period of Aug - Dec, 2004 at various locations in Taiwan using a self-developed photometer instrument. Daily height integrated intensity of the night-time green line emission may vary in the range of 80 - 210 Rayleighs and twilight enhancement is also identified. The observational results may serve as a useful reference for follow-up sounding rocket measurements of OI 557.7 nm airglow emission over the Taiwan area

Multichannel Polarization Lidar Measurements of Aerosols and Cirrus Clouds

In this paper we report using a 6-channel polarization detector to measure optical properties of aerosols and clouds. The polarization lidar system is designed to measure Stokes vectors and Mueller matrices from back-scatterings of air, aerosols and clouds by using several polarizers of setting at different angles, and a retarder to measure circular polarization. The 4 components Stokes vectors of the scattering media are constructed and a case of tropopause cirrus cloud and stratospheric aerosols are measured with the Mueller matrix derived

Vacuum Ultraviolet Photofragmentation of Water and Nitrogen Dioxide: Laboratory Studies and Atmospheric Applications.

Vacuum ultraviolet photodissociation of H(,2)O and NO(,2) in a flow system is discussed with emphasis on the electronic energy deposited in the fragments. Quantum yields for producing the excited OH(A('2)(SIGMA)('+)), NO(A('2)(SIGMA)('+)), and NO(B('2)(PI)) systems were measured at wavelengths 1216, 1236, 1302 A by observing the photofragmentation fluorescence of the electronic transitions from these excited states to the ground state. Moreover, quenching and pressure induced transitions between different excited states were studied for NO; results were found to be consistent with theoretical prediction. Quantum yields are generally low with values less than 10%. Our laboratory investigations can be applied as an analytical tool for atmospheric measurements in the earth's stratosphere. Since water vapor generates the most important hydrogen radical, OH, in the stratosphere, the accurate measurement of water is of significant value. The feasibility of using the VUV photofragmentation technique to measure stratospheric water is discussed, and the design of the flight instrument using a cryogenically cooled flow tube to eliminate the instrumental outgassing is given. This flight instrument has a sensitivity at ppb level and will be used in conjunction with OH and HO(,2) measurements to underst and the chemistry of hydrogen-oxygen compounds in the stratosphere. Perturbations to stratospheric ozone caused by the water is also discussed with a simple photochemical steady state model. This study can help us interpret the simultaneous measurements of stratospheric water and other species, which is important in testing our knowledge about stratospheric chemistry.Ph.D.Physics, Atmospheric ScienceUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/159615/1/8324253.pd

A method for determination of cirrus extinction-to-backscatter ratio from CALIOP data

We are presenting an empirical equation to retrieve cirrus lidar ratio by using CALIOP 532 nm level 1 data for nighttime cases. Retrieval results have non-relationship with cirrus multiple scattering effects and not affected by the error of transmission. The average CALIPSO 532 nm cirrus lidar ratio over Longitude 120+/- 10 and Latitude 25+/-10 for whole year of 2008 are 21.66±0.06sr for the year of 2008 respectively, with the maximum bias of 9.25% for the year 2008, the results is fairly stable and reasonable

Measurements of Terminal Velocities of Cirrus Clouds in the Upper Trosphere

Cirrus clouds are composed of ice crystals condensed from humidity due to low temperature condition in the upper atmosphere. The microphysics of cirrus clouds including sizes and shapes of ice particles are not well understood but are important in climate modeling. Ice crystal will fall under gravitational sedimentation to reach terminal velocities which depend on the size, mass, and ice habit. We studied here the terminal velocity of cirrus clouds by using lidar observations at Chungli (25N, 121E). The terminal velocities for a few cases of stable cirrus clouds are measured to determine the ice particle sizes and processes in the upper atmosphere

Measurements of Terminal Velocities of Cirrus Clouds in the Upper Trosphere

Cirrus clouds are composed of ice crystals condensed from humidity due to low temperature condition in the upper atmosphere. The microphysics of cirrus clouds including sizes and shapes of ice particles are not well understood but are important in climate modeling. Ice crystal will fall under gravitational sedimentation to reach terminal velocities which depend on the size, mass, and ice habit. We studied here the terminal velocity of cirrus clouds by using lidar observations at Chungli (25N, 121E). The terminal velocities for a few cases of stable cirrus clouds are measured to determine the ice particle sizes and processes in the upper atmosphere

Measurements of Terminal Velocities of Cirrus Clouds in the Upper Trosphere

Cirrus clouds are composed of ice crystals condensed from humidity due to low temperature condition in the upper atmosphere. The microphysics of cirrus clouds including sizes and shapes of ice particles are not well understood but are important in climate modeling. Ice crystal will fall under gravitational sedimentation to reach terminal velocities which depend on the size, mass, and ice habit. We studied here the terminal velocity of cirrus clouds by using lidar observations at Chungli (25N, 121E). The terminal velocities for a few cases of stable cirrus clouds are measured to determine the ice particle sizes and processes in the upper atmosphere

Real-Time Observations of Dust–Cloud Interactions Based on Polarization and Raman Lidar Measurements

Dust aerosols have significant impact on the environment and climate through long-range transport. We report, in this paper, a case of dust–cloud interaction process using combined measurements of a ground-based polarization and Raman (PR) lidar systems, and implemented by the spaceborne Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) lidar observations. The dust event occurred on 14 March 2009 over East Asia. During the two hours of observing time, the ground-based lidar observed an ongoing process of decreasing of the depolarization ratio (DR) accompanied by the increase of the water vapor simultaneously, indicating a dust–cloud interaction and particle transformation. CALIPSO measurements also found similar layers of dusts and clouds over lands and oceans with properties similar to the ground based lidar measurements. Our observation was a real-time dust–cloud process with the observation of occurrence of particle transformation. The depolarization reduced from 0.2 to 0.1 corresponding to a change of aspect ratio from 1.2 to 1.1. A discussion of a dust–cloud interaction in terms of three-stage cloud processes is made based on back-trajectory analyses and lidar observations. The result shows that dust aerosols decrease the cloud extinction coefficient by 41% but increase the cloud optical depth (COD) of water cloud by 12.79%, compared with that of pure water clouds. Furthermore, if dust aerosols participate as cloud condensation nuclei (CCN) in cloud physical processes, then they significantly reduce the size of the cloud droplet by 44–79%. Finally, based on three-year collocated CALIPSO and CloudSat measurements from 2007 to 2010, we found approximately one-third of clouds are originally dusty in the spring over the Pacific Coast areas

OH Airglow and Equatorial Variations Observed by ISUAL Instrument on Board the FORMOSAT 2 Satellite

OH airglow observed by the ISUAL (Imager of Sprites and Upper Atmospheric Lightning) instrument on board the FORMOSAT 2 satellite is reported in this paper. The satellite is sun-synchronous and it returns to the same orbit at the same local time daily. By using this property, we can study the upper atmosphere in detail. With a CCD camera, ISUAL has measured the emission layers of OH Meinel band at 630 nm for several two-week periods in 2004 and 2007 in equatorial regions. ISUAL images are snapshots of the atmosphere 250 km (height) ¡_ 1200 km (horizontal distance). These images of OH airglow are analyzed to derive its peak height and latitudinal variations. ISUAL observation is unique in its capability of continuous observation of the upper atmosphere as the satellite travels from south to north along a specific orbit. However, 630 nm filter also measured O(1D) at 200 km, and there are interferences between O(1D) and OH airglows as as observed from a distance in space. We have studied the overlap of two airglows by simulations, and our final analyses show that OH airglow can be correctly derived with its average peak height of 89 ¡_ 2.1 km usually lying within ¡_10¢X latitude about the equator. ISUAL data reveal detailed structures of equatorial OH airglow such as the existences of a few secondary maxima within the equatorial regions, and the oscillations of the peak latitudes. These results are discussed and compared with previous reports