Gravity Wave Activity and Stratosphere-Troposphere Exchange During Typhoon Molave(2020)

To investigate the stratosphere-troposphere exchange(STE)process induced by the gravity waves(GWs)caused by Typhoon Molave(2020)in the upper troposphere and lower stratosphere,we analyzed the ERA5 reanalysis data provided by the European Centre for Medium-Range Weather Forecasts and the CMA Tropical Cyclone Best Track Dataset.We also adopted the mesoscale forecast model Weather Research and Forecasting model V4.3 for numerical simulation.Most of the previous studies were about typhoon-induced STE and typhoon-induced GWs,while our research focused on the STE caused by typhoon-induced gravity waves.Our analysis shows that most of the time,the gravity wave signal of Typhoon Molave appeared below the tropopause.It was stronger on the east side of the typhoon center(10°-20°N,110°-120°E)than on the west side,suggesting an eastward tilted structure with height increase.When the GWs in the upper troposphere and lower stratosphere region on the west side of the typhoon center broke up,it produced strong turbulence,resulting in stratosphere-troposphere exchange.At this time,the average potential vorticity vertical flux increased with the average ozone mass mixing ratio.The gravity wave events and STE process simulated by the WRF model were basically consistent with the results of ERA5 reanalysis data,but the time of gravity wave breaking was different.This study indicates that after the breaking of the GWs induced by typhoons,turbulent mixing will also be generated,and thus the STE.

The Impact of Cut-off Lows on Ozone in the Upper Troposphere and Lower Stratosphere over Changchun from Ozonesonde Observations

In situ measurements of the vertical structure of ozone were made in Changchun （43.53°N, 125.13°E）, China, by the Institute of Atmosphere Physics, in the summers of 2010-13. Analysis of the 89 validated ozone profiles shows the vari- ation of ozone concentration in the upper troposphere and lower stratosphere （UTLS） caused by cut-off lows （COLs） over Changchun. During the COL events, an increase of the ozone concentration and a lower height of the tropopause are observed. Backward simulations with a trajectory model show that the ozone-rich airmass brought by the COL is from Siberia. A case study proves that stratosphere-troposphere exchange （STE） occurs in the COL. The ozone-rich air mass transported from the stratosphere to the troposphere first becomes unstable, then loses its high ozone concentration. This process usually happens during the decay stage of COLs. In order to understand the influence of COLs on the ozone in the UTLS, statistical analysis of the ozone profiles within COLs, and other profiles, are employed. The results indicate that the ozone concentrations of the in-COL profiles are significantly higher than those of the other profiles between ±4 km around the tropopause. The COLs induce an increase in UTLS column ozone by 32% on average. Meanwhile, the COLs depress the lapse-rate tropopause （LRT）/dynamical tropopause height by 1.4/1.7 km and cause the atmosphere above the tropopause to be less stable. The influence of COLs is durable because the increased ozone concentration lasts at least one day after the COL has passed over Changchun. Furthermore, the relative coefficient between LRT height and lower stratosphere （LS） column ozone is -0.62, which implies a positive correlation between COL strength and LS ozone concentration.

A multi-location joint field observation of the stratosphere and troposphere over the Tibetan Plateau

The unique geographical location and high altitude of the Tibetan Plateau can greatly influence regional weather and climate.In particular, the Asian summer monsoon(ASM) anticyclone circulation system over the Tibetan Plateau is recognized to be a significant transport pathway for water vapor and pollutants to enter the stratosphere. To improve understanding of these physical processes, a multi-location joint atmospheric experiment was performed over the Tibetan Plateau from late July to August in 2018, funded by the fiveyear(2018–2022) STEAM(stratosphere and troposphere exchange experiment during ASM) project, during which multiple platforms/instruments—including long-duration stratospheric balloons, dropsondes, unmanned aerial vehicles, special sounding systems, and ground-based and satellite-borne instruments—will be deployed. These complementary methods of data acquisition are expected to provide comprehensive atmospheric parameters(aerosol, ozone, water vapor, CO_2, CH_4, CO, temperature, pressure,turbulence, radiation, lightning and wind); the richness of this approach is expected to advance our comprehension of key mechanisms associated with thermal, dynamical, radiative, and chemical transports over the Tibetan Plateau during ASM activity.

Research on variety characteristics of China's Mainland troposphere based on CMONOC

In this research, we processed the GPS and meteorological data from about 220 stations of Crustal Movement Observation Network of China(CMONOC) observed in 2014 and derived the Zenith Total Delay(ZTD) map in both spatial and temporal dimension. The results of ZTD have high accurate and reliable as IGS and all sites with varying locations show obvious variety characteristics of Chinese mainland. Meanwhile, the precipitable water vapor(PWV) correlation coefficients between GPS observation and upper air sounding is close to 1, and the comparison of GPS-derived PWV and observed PWV from meteorological sites indicating GPS observation data generated in CMONOC project applied to the weather forecast research is feasible. In addition, based on all stations covered the whole Chinese land area and using interpolation algorithms, we make contour plots of PWV distribution per hour. We observe obvious feature that the precipitable water in north and western area is less than south and east area all over this year. High latitudes area may be dry and low latitudes area is wet.

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.

Direct Observations of Atmospheric Transport and Stratosphere-Troposphere Exchange from High-Precision Carbon Dioxide and Carbon Monoxide Profile Measurements

The balloon-borne Aircore campaign was conducted in Inner Mongolia,China,on June 13 and 142018,which detected carbon dioxide(CO2)and carbon monoxide(CO)profiles from surface to 24 km,showing strong positive and negative correlations between 8 km and 10 km on 13 and 14 June,respectively.Backward trajectories,meteorological analyses,and CO2 horizontal distributions were combined to interpret this phenomenon.The results indicated that the source region experienced a stratospheric intrusion and exhibited a large horizontal CO2 gradient;namely,lower CO concentrations corresponded to higher CO2 concentrations and vice versa.The laminar structure with multiple origins resulted in the highly negative correlation between CO2 and CO in the upper troposphere on 14 June.The contribution of stratospheric air mass to the upper troposphere and that of tropospheric air mass to the lower stratosphere were 26.7%and24.3%,respectively,based on a mass balance approach.Another interesting phenomenon is that CO2 and CO concentrations increased substantially at approximately 8 km on 13 June.An analysis based on the backward trajectory implied that the air mass possibly came from anthropogenic sources.The slope of CO2/CO representing the anthropogenic sources was 87.3 ppm ppm-1.In addition,the CO2 profile showed that there was a large CO2 gradient of 4 ppm km-1 within the boundary layer on 13 June,and this gradient disappeared on 14 June.

Modeling and Analysis of the Impacts of Temporal-Spatial Variant Troposphere on Ground-Based SAR Imaging of Asteroids

The near-Earth asteroid collisions could cause catastrophic disasters to humanity and the Earth,so it is crucial to monitor asteroids.Ground-based synthetic aperture radar(SAR)is an observation technique for high resolution imaging of asteroids.The ground-based SAR requires a long integration time to achieve a large synthetic aperture,and the echo signal will be seriously affected by temporal-spatial variant troposphere.Traditional spatiotemporal freezing tropospheric models are ineffective.To cope with this,this paper models and analyses the impacts of temporal-spatial variant troposphere on ground-based SAR imaging of asteroids.For the background tropo-sphere,a temporal-spatial variant ray tracing method is proposed to trace the 4D(3D spatial+temporal)refractive index network provided by the numerical weather model,and calculate the error of the background troposphere.For the tropospheric turbulence,the Andrew power spectral model is used in conjunction with multiphase screen theory,and varying errors are obtained by tracking the changing position of the pierce point on the phase screen.Through simulation,the impact of temporal-spatial variant tropospheric errors on image quality is analyzed,and the simulation results show that the X-band echo signal is seriously affected by the troposphere and the echo signal must be compensated.

Calculation of stratosphere–troposphere exchange in East Asia cut-off lows:cases from the Lagrangian perspective

In this study,the authors focus on the cut-off low pressure systems（COLs）lingering over East Asia in late spring and early summer and quantify the two-way stratosphere–troposphere exchange（STE）by 3D trajectory integrations,achieved using a revised version of the UK Universities Global Atmospheric Modelling Programme Offline Trajectory Code（Version 3）.By selecting 10 typical COLs and calculating the cross-tropopause air mass fluxes,it is found that stratosphere-to-troposphere transport（STT）fluxes exist in the center of COLs;and in the periphery of the COL center,troposphereto-stratosphere transport（TST）fluxes and STT fluxes are distributed alternately.Net transport fluxes in COLs are from stratosphere to troposphere,and the magnitude is about 10-4 kg m-2 s-1.The ratio between the area-averaged STT and TST fluxes increases with increasing strength of the COLs.By adopting appropriate residence time,the spurious transports are effectively excluded.Finally,the authors compare the results with previous studies,and find that the cross-tropopause fluxes（CTFs）induced by COLs are about one to two orders of magnitude larger than global CTFs.COLs play a significant role in local,rapid air mass exchanges,although they may only be responsible for a fraction of the total STE.

CCN Concentration in Troposphere over China

CCN concentration in the middle-lower troposphere over northern China was observed using a cloud condensation nucleus counter, MEE-130, installed on an IL-14 aircraft in the summer of 1983 and 1984. More than 60 sets of data (each flight as one set) were collected.The main results are: (1) in northern China, CCN concentration is 102-104/ cm3 near ground, decreases with increasing height and follows exponential distribution; (2) the local CCN concentration and its distribution with altitude are influenced by some meteorological factors: such as inversion, cloud and precipitation, wind and land-sea brce/.e etc. The inversion makes CCN significantly accumulate just below the inversion level; CCN concentration is lower inside clouds than outside clouds at same level; wind plays an important role of transporting CCN horizontally; (3) the CCN concentration is higher above the land than above the sea at same level; CCN concentration is one order of magnitude lower over the coastal cities like Qingdao than over the continental cities like Zhengzhou: (4) all these suggest that CCN in northern China comes mainly from continental surface layer. Densely-populated areas and industrial areas may produce more CCN.

RELATIONSHIPS BETWEEN ZONAL WIND ANOMALIES IN HIGH AND LOW TROPOSPHERE AND ANNUAL FREQUENCY OF NW PACIFIC TROPICAL CYCLONES

Relationships between large-scale zonal wind anomalies and annual frequency of NW Pacific tropical cyclones and possible mechanisms are investigated with the methods of correlation and composition. It is indicated that when A U2oo- A U850 〉0 in the eastern tropical Pacific and A U2oo- A U850 〈0 in western tropical Pacific, the Walker cell is stronger in the Pacific tropical region and the annual frequency of NW Pacific tropical cyclone are above normal. In the years with zonal wind anomalies, the circulation of high and low troposphere and the vertical motions in the troposphere have significant characteristics. In the time scale of short-range climate prediction, zonal wind anomalies in high and low troposphere are useful as a preliminary signal of the annual frequency prediction of NW Pacific tropical cyclones.

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.

A Two-step Estimation Method of Troposphere Delay with Consideration of Mapping Function Errors

Mapping function errors are usually not taken into consideration, when space geodetic data observed by VLBI, GNSS and some other techniques are utilized to estimate troposphere delay, which could, however, probably bring non-ignorable errors to solutions. After analyzing the variation of mapping function errors with elevation angles based on several-year meteorological data, this paper constructed a model of this error and then proposed a two-step estimation method of troposphere delay with consideration of mapping function errors. The experimental results indicate that the method put forward by this paper could reduce the slant path delay residuals efficiently and improve the estimation accuracy of wet tropospheric delay to some extent.

Recent Enhanced Deep Troposphere-to-Stratosphere Air Mass Transport Accompanying the Weakening Asian Monsoon

The Asian monsoon(AM) region is a well-known region with prevailing stratosphere–troposphere exchange(STE).However,how the STE across this region changes with the weakening AM remains unclear.Here,we particularly diagnose the air mass transport between the planetary boundary layer(PBL) and the stratosphere over the AM region during 1992–2017 using the Lagrangian particle dispersion model FLEXPART based on the ERA-Interim reanalysis data.The results show that both the downward and upward deep STEs exhibit a detectable increasing trend,while the latter,namely,the deep troposphere-to-stratosphere transport(DTST),is relatively more significant.Further analysis reveals that the long-term trend of DTST over the AM region could be partly attributed to changes in the Pacific Walker circulation and the air temperature(especially at upper levels).Additionally,it is found that DTST increases markedly over the tropical oceanic regions,while the increasing DTST into the stratosphere can be attributed to the enhanced air masses originated from the PBL over the terrestrial regions,where large amounts of pollutant emissions occur.The results imply that the influence of the DTST on the chemical composition and the climate of the stratosphere over the AM region is expected to become increasingly important,and is thereby of relevance to climate projection in an evolving climate.

Characteristics of vertical ozone distribution in the lower troposphere in the Yangtze River Delta at Lin'an in the spring of 2001

We analyzed vertical distributions of ozone (O3) in the lower troposphere (< 5 km above ground) at Lin’an (119.75°E, 30.30°N), Zhejiang Province using electrochemical concen- tration cell (ECC) ozonesonde data obtained from February 21 to April 13, 2001. The results showed that the vertical O3 distributions are controlled by metrological conditions and the char- acteristics of O3 profiles are related to those of wet bulb potential temperature and wind field. O3 below 2 km showed that the strongest variability and enhanced O3 mixing ratios were associated with easterly winds that blow pollutants from the upwind source region of the Yangtze River Delta (YRD) region. Vertical O3 profiles below 5 km can be grouped into 5 categories: (1) peak mixing ratio type, (2) well-mixed type, (3) layered-structure type, (4) episodic pollution type and (5) alti- tudinal increasing type. Vertical distributions of O3 affected by regional transport of polluted air masses were investigated. Transport of polluted air from high latitudes of northern China, ac- companying subsiding motion of air and stagnant atmospheric conditions are important factors that lead to high mixing ratios of O3 at Lin’an. The stagnant atmospheric conditions associated with a continental high pressure system and pollution plume transported from the YRD and cen- tral-eastern China also lead to regional accumulation of O3 and high O3 mixing ratio at Lin’an. Long-range transport of O3 and pollutants from the Pearl River Delta in South China and in-situ O3 formation also resulted in elevated O3 mixing ratios at around 1 km altitudes and layered O3 distribution in the lower troposphere.

Hydroxyl,hydroperoxyl free radicals determination methods in atmosphere and troposphere

The hydroxyl radical(·OH)has a crucial function in the oxidation and removal of many atmospheric compounds that are harmful to health.Nevertheless,high reactivity,low atmospheric abundance,determination of hydroxyl,and hydroperoxyl radical’s quantity is very difficult.In the atmosphere and troposphere,hydroperoxyl radicals(HO_(2))are closely demanded in the chemical oxidation of the troposphere.But advances in technology have allowed researchers to improve the determination methods on the research of free radicals through some spectroscopic techniques.So far,several methods such as laser-induced fluorescence(LIF),high-performance liquid chromatography(HPLC),and chemical ionization mass spectroscopy have been identified and mostly used in determining the quantity of hydroxyl and hydroperoxyl radicals.In this systematic review,we have advised the use of scavenger as an advance for further researchers to circumvent some of these problems caused by free radicals.The primary goal of this review is to deepen our understanding of the functions of the most critical free radical(·OH,HO_(2))and also understand the currently used methods to quantify them in the atmosphere and troposphere.

ZONAL MEAN STRUCTURES OF THE EXTRATROPICAL TROPOSPHERE

The study of mean circulation fields requires evaluation of eddy foreings in the atmosphere.Due to the difficulty in calculating the eddy forcings on theory,the mean state equations including the eddy forcings were used mostly for diagnostic studies only.Using the geostrophic perturbation solutions obtained by McHall (1991a),we may deal with theoretically the eddy fluxes and their convergence.This allows us to employ the mean state equations for the study of mean circulation fields.It will be found that the time averaged zonal mean structure and circulation of the troposphere at middle and high latitudes can be reproduced basically in terms of the mass and momentum balances in geostrophic wave circulations.

Diurnal variations of turbulence parameters over the tropical oceanic upper troposphere during SCSMEX

Using the method of Thorpe analysis, the TKE （turbulence kinematic energy） dissipation rate （e） and turbulence diffusivity （K） were derived from the RS （radiosounding） measurements in the tropical oceanic upper troposphere. The measurements were performed four times per day during two intense observation periods （May 5-25, and June 5-25） on the Kexue #1 scientific observation ship of SCSMEX （South China Sea Monsoon EXperiment） in 1998. There are three new features obtained from our analysis. First, the responses of e and K to the onset of monsoon are negligible over the ocean at least for the data used here Second, the temporal variations of e and K are in a similar manner and exhibit strong diurnal variations. The diurnal variations achieve their maxima in the morning （08 LT） and early afternoon （14 LT）, and achieve their minima in the evening （20 LT） and early morning hours （02 LT）. The diurnal variations of turbulence parameters （e and K） and their responses to the onset of monsoon are entirely different from those derived over land at similar latitudes. Finally, although the correlations between the variations of e and MCSs （mesoscale convective systems）, which were derived from TRMM （tropical rainfall measuring mis- sion） satellite, are not very well in only few days, the diurnal variations of e averaged over May and June are strongly correlat- ed with the diurnal variations of MCSs with correlation factors of 0.79 and 0.94, respectively. This indicates that the turbulence and its diurnal variations over the tropic oceanic upper stratosphere region are highly related to the MCSs.

A large impact of tropical biomass burning on CO and CO_2 in the upper troposphere

A large interannual variation of biomass burning emissions from Southeast Asia is associated with the ENSO events. During 1997/98 and 1994 El Nino years, uncontrolled wildfires of tropical rainforests and peat lands in Indonesia were enlarged due to a long drought. Enhanced CO injection into the upper troposphere from the intense Indonesian fires was clearly observed in the 8-year measurements from a regular flask sampling over the western Pacific using a JAL airliner between Australia and Japan. This airliner observation also revealed that upper tropospheric CO2 cycle largely changed during the 1997 El Nino year due partly to the biomass burning emissions. Widespread pollution from the biomass burnings in Southeast Asia was simulated using a CO tracer driven by a 3D global chemical transport model. This simulation indicates that tropical deep convections connected to rapid advection by the subtropical jet play a significant role in dispersing biomass-burning emissions from Southeast Asia on a global scale.

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 OF OBSERVATION FOR CH_4 CONCENTRATION IN TROPOSPHERE

Recently evidence shows that the global concentration of CH4 is increasing by about 1% per year. The average worldwide tropospheric mixing ratio of CH4 has increased from 1.52 parts per million by volume （ppmv）in January 1978 to 1. 684 ppmv in September 1988.