DISTRIBUTION OF AEROSOL EXTINCTION IN THE LOWER TROPOSPHERE BY MICRO-PULSE LIDAR OBSERVATION

The profiles of aerosol extinction coefficients are investigated by micro-pulse lidar(MPL) combined with the meteorological data in the lower troposphere at Meteorological Research Institute(MRI).Japan.Larger extinction values of aerosol are demonstrated in the nocturnal stable air layer with larger Richardson number,and light wind velocities are favorable for aerosol concentrating in the planetary boundary layer(PBL).But aerosol extinction coefficients show larger values over the altitudes of 2.0 to 5.0km where correspond to higher relative humidity (RH).The tops of PBL identified by the aerosol extinction profiles almost agree with ones by radiosonde data.The diurnal variations of aerosol extinction profiles are clearly displayed, intensive aerosol layers usually are formed over the period of mid-morning to 1400 Loeal Time (LT).then elapse in the cloudless late afternoon and nighttime.Thermal eonvection or turbulent transport from the surfaee probably dominates these temporal and spatial changes of aerosol distribution.

Study on Horizontal Relative Diffusion in theTroposphere and Lower Stratosphere

The behaviour of relative diffusion theory and Gifford’s random-force theory for long-range atmospheric diffusion is examined. When a puff scale is smaller than the Lagrangian length scale, √2KTL, an accelerative relative diffusion region exists, i.e., σy∝ t 3/2. While the puff diffusion enters a two-dimensional turbulence region, in which the diffusion scale is larger than 500 km, or time scale is larger than 1 day, divergence and convergence are main cause of horizontal diffusion. Between the two above-mentioned regimes, diffusion deviation is given by σy = √2KT. The large-scale horizontal relative diffusion parameters were obtained by analyzing the data of radioactive cloud width collected in air nuclear tests. Key words Tropospheric and lower stratospheric diffusion - Relative diffusion - Large scale turbulence - Nuclear explosion clouds This work is sponsored by the National Natural Science Foundation of China under Grant No. 49505064.The author would like to thank Prof. Chen Jiayi Department of Geophysics of Peking University and Dr. Cai Xiaoming School of Geography and Environmental Sciences of Birmingham University for their helpful discussions.

Variation of Zonal Winds in the Upper Troposphere and Lower Stratosphere in Association with Deficient and Excess Indian Summer Monsoon Scenario

The Indian summer monsoon is one of the most dominant tropical circulation systems in the general circulation of the atmosphere. The country receives more than 80% of the annual rainfall during a short span of four months (June to September) of the southwest monsoon season. Variability in the quantum of rainfall during the monsoon season has profound impacts on water resources, power generation, agriculture, economics and ecosystems in the country. The inter annual variability of Indian Summer Monsoon Rainfall (ISMR) depends on atmospheric and oceanic conditions prevailed during the season. In this study we have made an attempt to understand the variation of the of zonal winds in the tropical Upper Troposphere and Lower Stratosphere (UT/LS) region during deficient and Excess rainfall years of Indian summer monsoon and its relation to Indian Summer Monsoon Rainfall (ISMR). It is found that in the equatorial Upper Troposphere zonal winds have westerly anomalies during deficient rainfall year’s and easterly anomaly during excess rainfall years of Indian summer monsoon and opposite zonal wind anomaly is noted in the equatorial Lower Stratosphere during the deficient and excess rainfall years of Indian summer monsoon. It is also found that the June to September upper troposphere zonal winds averaged between 15°N and 15°S latitudes have a long-term trend during 1960 to 1998. Over this period the tropical easterlies and the tropical jet stream have weakened with time.

Features of Ozone Mini-Hole Events over the Tibetan Plateau

Based on TOMS total ozone data and SCIAMACHY ozone profile data, climatology of the ozone minihole events over the Tibetan Plateau and ozone vertical structure variations during an ozone mini-hole event in December 2003 are analyzed. The analyses show that before 1990 ozone mini-hole events only occurred in November-December of 1987 but that the number of events increases after 1990. These events only occur from October through February, with maximum occurrence frequency in December. During the event in December 2003, the decrease in total ozone of over 20% is mainly caused by the ozone loss in the upper troposphere and lower stratosphere region due to the horizontal transport of low ozone from the lower latitude subtropics and the uplift of low ozone from the lower troposphere over the Tibetan Plateau.

Role of a Meso-γ Vortex in Meiyu Torrential Rainfall over the Hangzhou Bay,China:An Observational Study

A mesoscale torrential rainfall event that occurred over eastern China in June 2013 is analyzed by using observational data.The results show that a mesoscale convergence line and a weak convective cloud line formed over the northern part of the Hangzhou Bay during the onset of the torrential rainfall event.A meso-vortex appeared over the confluence point of northeasterly flow associated with the Yellow-Sea high,easterly flow from rainfall area,and southeasterly flow from the Hangzhou Bay.The meso-vortex with a horizontal scale of 10-20 km lasted for about 1 h for stable surface circulations.The analysis of radar retrieval reveals that the meso-vortex in the boundary layer occurred at the south of strong radar echo.The formation of the meso-vortex turned to enhance convergence and cyclonic vorticity in the lower troposphere,which strengthened updrafts that are tilted into convective clouds and caused torrential rainfall.Thus,the occurrence of the meso-vortex in boundary layer is one of the mechanisms that are responsible for the enhancement of convective development.