Search

Over the past three decades, China has seen aerosol levels substantially surpass the global average, significantly impacting regional climate. This study investigates the long-term and seasonal variations of aerosols in the Huai River Basin (HRB) using MODIS, CALIOP observations from 2007 to 2021, and ground-based measurements. A notable finding is a significant decline in the annual mean Aerosol Optical Depth (AOD) across the HRB, with MODIS showing a decrease of approximately 0.023 to 0.027 per year, while CALIOP, which misses thin aerosol layers, recorded a decrease of about 0.016 per year. This downward trend is corroborated by improvements in air quality, as evidenced by PM2.5 measurements and visibility-based aerosol extinction coefficients. Aerosol decreases occurred at all heights, but for aerosols below 800 m, with an annual AOD decrease of 0.011. The study also quantifies the long-term trends of five major aerosol types, identifying Polluted Dust (PD) as the predominant frequency type (46%), which has significantly decreased, contributing to about 68% of the total AOD reduction observed by CALIOP (0.011 per year). Despite this, Dust and Polluted Continental (PC) aerosols persist, with PC showing no clear trend of decrease. Seasonal analysis reveals aerosol peaks in summer, contrary to surface measurements, attributed to variations in the Boundary Layer (BL) depth, affecting aerosol distribution and extinction. Furthermore, the study explores the influence of seasonal wind patterns on aerosol type variation, noting that shifts in wind direction contribute to the observed changes in aerosol types, particularly affecting Dust and PD occurrences. The integration of satellite and ground measurements provides a comprehensive view of regional aerosol properties, highlighting the effectiveness of China's environmental policies in aerosol reduction. Nonetheless, the persistence of high PD and PC levels underscores the need for continued efforts to reduce both primary and secondary aerosol production to further enhance regional air quality. [ABSTRACT FROM AUTHOR]

To provide references for the design of the lab's upcoming prototype of the compact spaceborne lidar with a high-repetition-rate laser (CSLHRL), in this paper, the detection signal of spaceborne lidar was simulated by the measured signal of ground-based lidar, and then, the detection capability of spaceborne lidar under different atmospheric conditions was evaluated by means of the signal-to-noise ratio (SNR), volume depolarization ratio (VDR) and attenuated color ratio (ACR). Firstly, the Fernald method was used to invert the optical parameters of cloud and aerosol with the measured signal of ground-based lidar. Secondly, the effective signal of the spaceborne lidar was simulated according to the known atmospheric optical parameters and the parameters of the spaceborne lidar system. Finally, by changing the cumulative laser pulse number and atmospheric conditions, a simulation was carried out to further evaluate the detection performance of the spaceborne lidar, and some suggestions for the development of the system are given. The experimental results showed that the cloud layer and aerosol layer with an extinction coefficient above 0.3 km−1 could be easily obtained when the laser cumulative pulse number was 1000 and the vertical resolution was 15 m at night; the identification of moderate pollution aerosols and thick clouds could be easily identified in the daytime when the laser cumulative pulse number was 10,000 and the vertical resolution was 120 m. [ABSTRACT FROM AUTHOR]

This paper investigates the transmitter and receiver performance of an active rotating tropospheric stratospheric Doppler wind Lidar. A 532 nm laser was determined as the detection wavelength based on transmission and scattering aspects. A ten-fold Galileo beam expander consisting of spherical and aspherical mirrors was designed and produced to compress the outgoing laser's divergence angle using ZEMAX simulation optimization and optical-mechanical mounting means. The structure and support of the 800 mm Cassegrain telescope was redesigned. Additionally, the structure of the receiver was optimized, and the size was reduced. Meanwhile, the detectors and fiber mountings were changed to improve the stability of the received optical path. A single-channel atmospheric echo signal test was used to select the best-performing photomultiplier tube (PMT). Finally, the atmospheric wind field detection results of the original and upgraded systems were compared. The results show that after optimizing the transmitter and receiver, the detection altitude of the system is increased to about 47 km, and the wind speed and wind direction profiles match better with radiosonde measurements. [ABSTRACT FROM AUTHOR]

A Doppler lidar mounted on a rotary platform has been developed for measuring wind fields in the upper troposphere and stratosphere. The rotating platform was used to support a large system for the detection of wind velocities of sight (VOS) in four directions. The principle, structure, and parameters of the lidar system are introduced. The Fabry-Perot interferometer (FPI), the core component of the wind measurement system, was designed after comprehensively considering the measurement uncertainty and the influence of Mie scattering. Its dual-edge channel bandwidth is 1.05 GHz with 3.48 GHz spacing. In operation, the FPI channels are locked to the laser frequency with a stability of 14.8 MHz. Compared with the local radiosonde, it was found that the deviation in wind speed below 28 km was generally less than 10 m/s, and the deviation in wind direction below 19 km was less than 10 degrees. The 42-day profile comparison between lidar in Hefei and radiosondes in Anqing and Fuyang was analyzed. The statistical results show that the wind speed and wind direction deviations between lidar and radiosondes below 20 km were approximately 10 m/s and 20 degrees, respectively, which are comparable to the regional differences in the wind field. However, as altitudes exceed 20 km, the deviations increased rapidly with height. The experiments indicate that the Doppler lidar could measure wind fields from 7 km to 30 km, with better detection accuracy below 20 km. [ABSTRACT FROM AUTHOR]

For ground-based lidars in atmospheric observation, their data acquisition unit and control unit usually work independently. They usually require the cooperation of large-volume, high-power-consumption Industrial Personal Computer (IPC). However, the space-borne lidar has high requirements on the stability and integration of the acquisition control system. In this paper, a new data acquisition and lidar control system (DALCS) was developed based on System-on-Chip Field-Programmable Gate Array (SoC FPGA) technology. It can be used in lidar systems with high repetition rate and photon-counting mode and has functions such as data storage, laser control, automatic collimation, wireless communication, and fault self-test. DALCS has two working modes: in online mode, the echo data collected by DALCS are transmitted to the computer for display in real-time and then stored with the current time as the file name; in offline mode, the data are stored in local non-volatile memory, which can be read remotely and can work autonomously when there is no IPC. The test results showed that in the frequency range of 0–70 M, the counting linearity of DALCS reached 0.9999, and the maximum relative error between the DALCS card and the standard signal source was 0.211%. The comparison results showed that the correlation coefficient between DALCS and MCS-PCI was as high as 0.99768. The DALCS was placed in a self-developed lidar sensor system for continuous observation, and the system worked stably under different weather conditions. The range-squared-corrected signal profiles obtained from the observations reflect the spatial and temporal distribution characteristics of aerosols and clouds well. This provides scheme verification and experimental support for the development of space-borne lidar data acquisition and control system. [ABSTRACT FROM AUTHOR]

• A novel Rayleigh Doppler lidar technology based on a quadruple dual-pass Fabry–Perot interferometer (FPI) that can accurately measure wind field, temperature and aerosol backscatter ratio from the troposphere to lower stratosphere is proposed. This technology significantly inhibits the influence of the Mie scattering signal on wind speed and temperature measurement, and can take into account the temperature and aerosol backscatter ratio detection, thus greatly reducing the wind speed measurement errors caused by the inconsistency between the mode temperature and the actual temperature and the contamination of the Mie scattering signal in the traditional Rayleigh Doppler lidar. • The structure of quadruple two-pass FPI-based Rayleigh Doppler lidar is designed. The quadruple two-pass FPI consists of two edge channels FPI-1 and FPI-2, aerosol channel FPI-M and locking channel FPI-L. FPI-1, FPI-2 and FPI-M use dual-pass optical path, and FPI-L uses single-pass optical path. The parameters of FPI are optimized. • The detection performance of the designed Rayleigh Doppler lidar is simulated. The results show that the measurement errors of aerosol backscatter ratio, temperature and radial wind speed of the lidar system in the daytime and night-time are less than 4.36 × 10−3 and 3.32 × 10−3 (excluding cirrus cloud area), 4.0 K and 3.0 K, 3.8 m/s and 1.9 m/s, respectively from an altitude of 0.06 to 35 km. A novel Rayleigh Doppler lidar technology based on a quadruple dual-pass Fabry–Perot interferometer (FPI) that can accurately measure wind field, temperature and aerosol backscatter ratio from the troposphere to lower stratosphere is proposed. This study aims to analyse the detection principle of wind speed, temperature and aerosol backscatter ratio in detail and obtain their measurement error formulas. The structure of this type of lidar is studied and designed. The FPI consists of two edge channels FPI-1 and FPI-2, aerosol channel FPI-M and locking channel FPI-L. FPI-1, FPI-2 and FPI-M use a dual-pass optical path, whereas FPI-L uses a single-pass optical path. The parameters of FPI are optimised as follows: the free spectral spacing (FSR) is 12 GHz, the FWHM of FPI-1 and FPI-2 are both 2.2 GHz, the peak-to-peak interval of FPI-1 and FPI-2 is 5.8 GHz, the FWHM of FPI-M and FPI-L are both 1.2 GHz, the peak-to-peak interval of FPI-M and FPI-1 is 2.9 GHz and the peak-to-peak interval of FPI-L and FPI-1 is 2.3 GHz. Under simulated atmospheric conditions, for a daytime sky background brightness of 0.3 Wsr−1m−2nm−1 at 355 nm, using a laser with a pulse energy of 350 mJ and a repetition frequency of 50 Hz and a telescope with a 0.45-m aperture, with a vertical range resolution of 30 m at 0–10 km, 100 m at 10–20 km and 500 m at 20–35km, temporal resolution of 30 min, zenith angle of 0° for temperature and aerosol backscatter ratio detection and temporal resolution of 3 min and zenith angle of 30° for radial wind speed detection, the detection performance of the designed Rayleigh Doppler lidar is determined. The simulation results show that the measurement errors of aerosol backscatter ratio, temperature and radial wind speed of the lidar system in the daytime and night-time are less than 4.36 × 10−3 and 3.32 × 10−3 (excluding cirrus cloud area), 4.0 K and 3.0 K and 3.8 m/s and 1.9 m/s, respectively, from an altitude of 0.06 to 35km. [ABSTRACT FROM AUTHOR]

The detection principle of a multi-longitudinal-mode (MLM) Doppler lidar based on a quadri-channel Mach–Zehnder interferometer (QMZI) was analysed. The measurement error formulas for the radial wind speed and backscatter ratio of this type of Doppler lidar system were derived. The advantages of this detection technology were thoroughly analysed based on the principle. The optical path difference (OPD) ' l ' between the two interference arms of the QMZI was optimised. For a detection height of 0–20 km, ' l ' was selected as 50 cm to balance the detection of radial wind speed and backscatter ratio. The overall structure of the MLM Doppler lidar based on QMZI was designed, and detailed design parameters of the system were provided. Further simulation was conducted to evaluate the detection performance of the designed QMZI- based MLM Doppler lidar system. The simulation results showed that when using a pulse laser with a power of 17.5 W@355 nm and a telescope with an aperture of 25 cm, a detection zenith angle of 30°, a vertical resolution of 26 m@0–10 km and 52 m@10–20 km and a pulse accumulation time of 1 min, the radial wind speed measurement errors of the system during the day and night were less than 2.1 m/s and 2.5 m/s; the backscatter ratio relative measurement errors were less than 0.81% and 0.97%. • The detection principle of QMZI based MLM Doppler lidar is analysed. • The lidar measurement error formulas for radial wind speed and backscatter ratio are derived. • The optimised OPD of QMZI two arms is 50 cm for both wind speed and backscatter ratio measurements at height of 0–20 km. • The detailed design parameters of the lidar system are provided. • The performance simulation and error analysis of the designed lidar system are performed. [ABSTRACT FROM AUTHOR]

The Fabry–Perot interferometer (FPI) plays a crucial role as the frequency discriminator in the incoherent Doppler wind lidar. However, in the practical receiver system, reflections occurring between optical elements introduce non-normal incident components in the light beams passing through the FPI. This phenomenon results in the deformation of the FPI transmission spectral lines. Based on that, a theoretical model has been developed to describe the transmission spectrum of the FPI when subjected to obliquely incident light beams with a divergence angle. By appropriately adjusting the model parameters, the simulated transmission spectrum of the FPI edge channels can coincide with the experimentally measured FPI spectral line. Subsequently, the impact of deformations in the transmission spectrum of the two edge channels on wind measurements is evaluated. The first implication is a systematic shift of 30.7 m/s in line-of-sight (LOS) wind velocities. This shift is based on the assumption that the lidar echo is solely backscattered from atmospheric molecules. The second consequence is the inconsistency in the response sensitivities of Doppler frequency shift between Rayleigh signals and Mie signals. As a result, the lidar system fails to fully achieve its initial design objectives, particularly in effectively suppressing interference from Mie signals. The presence of aerosols can introduce a significant error of several meters per second in the measurement of LOS wind velocity. [ABSTRACT FROM AUTHOR]

Space-borne lidar is preferred for observing different characteristic aerosols that should be distributed vertically in every corner of the world. Therefore, a compact space-borne lidar (CSBL) with a high repetition rate laser and photon counting mode is developed to meet the detection requirements in this paper. The detection principle is described in detail, and the design parameters of the CSBL are simulated. The CSBL is assembled and calibrated in its entirety after the development of a long-life, high-beam quality laser and a highly sensitive, quantum-efficient single-photon counting core component. Moreover, after ground and flight tests, the CSBL completed the integrated inversion of atmospheric aerosols and clouds, and it can remotely detect global atmospheric aerosols and cloud spatial distribution structures. • A compact space-borne Lidar (CSBL) for global different characteristic aerosols study. • The single-photon counting technique is adopted by the CSBL. • Ground and flight echo signals of CSBL were simulated and calculated. • Ground and flight tests have verified the possibility of the CSBL becoming a payload. [ABSTRACT FROM AUTHOR]

The scanning polarization Mie lidar (SPML) system has been developed and is described. The lidar system has two detection channels to receive the parallel and perpendicular polarization components at the laser wavelength of 532 nm, which indicates the nonsphericity of aerosol and cloud particles. It can take the horizontal, vertical and conical scans of the atmosphere with the elevation and azimuth motors. This paper discusses the current capability of the SPML lidar and its results. The observation shows that the SPML lidar can provide the multi-dimensional views of the atmosphere which is impossible to achieve with other ground-based vertically pointing lidars. It is helpful to track and monitor aerosol plumes in urban area, to determinate the planetary boundary layer height and to enhance the measurement of atmosphere in the lower height where the geometrical form factor of lidar system affects. [ABSTRACT FROM AUTHOR]

Through the observation of ground-based LIDAR and satellite sensors, the weather conditions of continuous foggy-hazy alternations in the Huainan region from 26 December 2016 to 5 January 2017 were analyzed and observed. In this study, the formation and influence of this event were discussed by analyzing pollutant concentrations, meteorological factors and aerosol optical characteristics. The concentrations of PM10 and PM2.5 increased significantly. The maximum value of PM10 was 412 μg/m3, and the maximum value of PM2.5 was 258 μg/m3. The transportation of pollutants and the production of man-made pollutants promote the accumulation of pollutants. In this weather process, meteorological factors such as the surface wind speed, humidity, surface temperature, and inversion also promote the accumulation of pollutants, which is the main reason for the formation of this weather process. Furthermore, the near surface air mass mainly came from the cities near the Huainan region and the heavily polluted areas in the north, while the upper air mass came from Inner Mongolia. In this paper, piecewise inversion was adopted to achieve accurate all-weather extinction coefficient profile inversion by reasonably selecting a cloud LIDAR ratio through a backscatter ratio, and the LIDAR ratio of cloud in this period was 22.57–34.14 Sr. By means of extinction coefficient inversion and correlation analysis, the correlation index of PM2.5 and the aerosol optical depth (AOD) was 0.7368, indicating that there was a positive correlation between PM2.5 and AOD, and AOD can also reflect the pollution condition of this region. The formation process of foggy-hazy weather in the Huainan region studied in this paper can provide a research basis for foggy-hazy pollution in this region. [ABSTRACT FROM AUTHOR]

A dual-frequency, ground-based microwave radiometer (WVR-1100) is used to investigate the behavior of the atmosphere in terms of zenith brightness temperature ( T B ) at 23.8 and 31.4 GHz respectively. Some experimental findings in SKYNET Hefei site from September 2002 to August 2012 are presented. The cumulative distributions of T B at both frequencies for all sky conditions show four different regions, while only two regions can be identified for clear, lightly cloudy and cloudy condition. Annual cycle of T B at 23.8 GHz is apparently remarkable, indicating the large annual cycle of atmospheric water vapor. Regular seasonal variations of T B are observed with the strongest value in summer and the weakest in winter. [ABSTRACT FROM AUTHOR]

Dust storms pose a serious threat to air quality and public health through large‐scale, long‐distance transport. In early April 2018, two severe dust storm events occurred in the Taklimakan and Gobi Deserts in northwestern China. The advected air‐masses containing dust traveled eastward over long distances reaching the western Yangtze River Delta region (WYRDR) with local PM10 peak concentrations of 190 and 410 μg/m3 on April 6 and April 11, 2018, respectively. Satellite remote sensing and ground‐based lidar observations showed that the first dust event was transported to WYRDR at an altitude of <5 km, while the second transport height was at an altitude of <3 km. The first one was accompanied with the dry‐cold air mass in the northwest moving eastward and southward. By comparison, in the second event, the dust aerosols were mixed with anthropogenic aerosols from southwestern China. Meanwhile, as southerly warm‐humid air flows prevailed at near‐surface layer over the WYRDR in the second event, the associated higher relative humidity potentially induced hygroscopic growth of polluted dust aerosols, resulting in explosive growth of PM10. In addition, the average depolarization ratio of aerosols over WYRDR on April 6 was 0.3, while on April 11 it was 0.2, indicating that the previous pollution event featured more obvious nonspherical characteristics of aerosols. Our findings provide scientific evidence that transboundary dust events and resultant local PM10 pollution are closely related to various transport trajectories of dust aerosols as well as the local vertical wind profiles and surface humidity conditions. Key Points: The magnitudes of local PM10 pollutions depend on various transport trajectories of dust aerosols as well as local meteorological conditionsDifferent dust transported heights are revealed by integrated observations of satellite remote sensing and ground‐based lidarThe spherical characteristics of dust‐related aerosols are identified by depolarization ratio of aerosols from lidar observation [ABSTRACT FROM AUTHOR]

Abstract Successive images of a scene are captured and then further processed to achieve the moving object tracking. However, due to modulation rate limitations of the spatial light modulator in single-pixel imaging (SPI) system, the imaging frame rate cannot meet the high-resolution and real-time requirements for object tracking. In this paper, we demonstrate a fast object tracking technique based on SPI with an ultra-low sampling rate that is independent of imaging. We construct modulation information that satisfies the projection conditions and can transform 2D images into 1D projection curves. The 1D projection curves, which provide the location information of the moving object, can be obtained with high resolution in real-time, and then the tracking of the moving object is realized. A background subtraction technique for tracking moving objects that removes static components from a scene is also proposed. The proposed technique is verified by computational simulations and laboratory experiments. In the laboratory experiments, we demonstrate that the proposed method can be used to track moving objects with less than 0.2% of the measurements established by the Nyquist criterion, and it presents 256 × 256 pixels at ∼ 177 fps. The reported technique accelerates the tracking speed of SPI and provides an efficient strategy for remote sensing and biomedical applications. [ABSTRACT FROM AUTHOR]

Highlights • The influence of the fluctuation of CO 2 concentration in the lower atmosphere is discussed in the measurement of XCO 2. • A weighting function optimized method is provided considering the actual CO 2 concentration profile and the proportion of the lower weighting function. • The method corrects the bias in the measurement and relaxes the atmosphere sensitivity to pressure. • More appropriate wavelengths have been provided for the further reference of development of an IPDA lidar. Abstract Weighting function can affect the retrieval of the column gas mixing ratio of integrated path differential absorption (IPDA) lidar because it contains the vertical distribution information of the target gas. In order to optimize the wavelengths within the 1.57 um spectral band for IPDA lidar for CO 2 measurement. The temperature, pressure and water vapor (TPH) sensitivity and the proportion of the weight function integration in the lower layer part to the total atmosphere layer (R) of each wavelength are calculated. The measurement errors of each wavelength are simulated with CO 2 fluctuation in the lower layer. The specific wavelength with the R value of 0.6 has been found to be a stable measurement bias which does not change with fluctuations, so the R value of 0.6 is used to optimize the wavelength for measurement CO 2. The simulation results show that the measurement error via wavelength is smaller than 0.05 ppm, when the TPH sensitivity is smaller than 0.95 and when R is about 0.6. This proposed method can be applicable for the further airborne or space-borne lidar development. [ABSTRACT FROM AUTHOR]

A two-stage Fabry-Perot interferometer (FPI)-based high-spectral-resolution (HSR) Rayleigh temperature lidar technology is proposed that is capable of simultaneously detecting tropospheric temperature and aerosol optical properties with high-precision. The system structure is designed and the measurement principle is analysed. A two-channel integrated FPI used forming a two-stage FPI ensures the relative stability of the two FPI spectrums. The first-stage FPI with high spectral resolution can effectively separate Mie and Rayleigh signals to derive the signal components. Two adjacent-order transmission spectrums of the second-stage FPI are just located in the two wings of Rayleigh-Brillouin (R-B) scattering spectrum to measure temperature. Two multimode polarization insensitive optical circulators used in receiver system can achieve high-efficiency utilization of  signals. A narrow linewidth semiconductor laser at 852 nm is used as light source. Using the selected and optimized system parameters, the lidar performance simulation results show that in the sunny weather conditions for 0.15WSr-1 m-2 nm-1 sky brightness, with 0.3 W laser power, a 30 cm diameter telescope, 60 m range resolution and 30 min observation time, the temperature measurement errors are below 0.4 K in night-time and below 1.6 K in daytime; the relative measurement errors of backscatter ratio are below 0.04% in night-time and below 0.13% in daytime respectively up to 6 km height. Compared with the traditional FPI-based HSR technique, the technique we proposed can improve the detection accuracy of temperature by 2.5 times and can also significantly improve the detection accuracy of backscatter ratio. [ABSTRACT FROM AUTHOR]

A novel design of the 532 nm Rayleigh–Mie Doppler lidar receiving system is carried out. The use of polarization isolation technology to effectively improve the receiving system optical reception efficiency, suppress the background noise, not only improves the system wind field detection accuracy, while achieving a high-accuracy temperature measurement. The wind speed and temperature measurement principle of the system are discussed in detail, and the triple Fabry–Perot etalon parameters are optimized. Utilizing the overall design parameters of the system, the system detection performance is simulated. The simulation results show that from 5 to 50 km altitude with vertical resolution of 0.1 km@5 ∼ 20 km, 0.5 km@20 ∼ 40 km, 1 km@40 ∼ 50 km, by using the laser with single pulse energy of 600 mJ, repetition frequency of 50 Hz and the receiving telescope with aperture of 0.8 m, with 2min integration time and in ± 50 m/s radial wind speed range, the radial wind speed measurement accuracies of our designed lidar in the day and night are better than 2.6 m/s and 0.9 m/s respectively, and its performance is obviously superior to that of traditional system 5.6 m/s and 1.4 m/s wind speed accuracies; with 10min integration time and in 210 ∼ 280 K temperature range, the temperature measurement accuracies of the system in the day and night are better than 3.4 K and 1.2 K respectively; since the wind speed sensitivities of the Mie and Rayleigh scattering signals are not exactly the same, in ± 50 m/s radial wind speed range, the wind speed bias induced by Mie signal is less than 1 m/s in the temperature range of 210–290 K and in the backscatter ratio range of 1–1.5 for pair measurement. [ABSTRACT FROM AUTHOR]

Lidar, radiosonde, and ground-based in situ nephelometer measurements made during an intensive field campaign carried out from July to September 2014 at the Xinzhou meteorological station were used to determine the aerosol hygroscopic growth effect in a cloud-capped, well-mixed boundary layer. Aerosol hygroscopic properties at 355 and 532 nm were examined for two cases with distinct aerosol layers. Lidar-derived maximum enhancement factors in terms of aerosol backscatter coefficient derived using a relative humidity ( RH ) reference value of 85% were 1.19 at 532 nm and 1.10 at 355 nm for Case I and 2.32 at 532 nm and 1.94 at 355 nm for Case II. To derive the aerosol particle hygroscopic growth factor at specific RH values, the Kasten and Hänel models were used. A comparison of the goodness of fit for the two models showed that the Kasten model performed better. The hygroscopic growth curve for RH >90% was much steeper than that for RH in the range of 85–90%. The slopes of the lidar-derived enhancement factor curve (measured from 85% to 95% RH ) and the nephelometer-derived enhancement factor curve (measured from 40% to 62% RH ) in Case I show similar trends, which lends confidence to using lidar measurements for studying aerosol particle hygroscopic growth. Data from a ground aerosol chemical speciation monitor showed that the larger values of aerosol hygroscopic enhancement factor in Case II corresponded to greater mass concentrations of sulfate and nitrate in the atmosphere. [ABSTRACT FROM AUTHOR]

The near-ground aerosols have the most impact on the human beings. Its fine spatial and temporal distribution, with which the environmental and meteorological departments concern themselves most, has not been elaborated very well due to the unavailable measurement tools. We present the continuous observations of the vertical profile of near-ground aerosol backscattering coefficients by employing our self-developed side-scattering lidar system based on charge-coupled device camera. During the experimental period from April 2013 to August 2014, four catalogs of aerosol backscattering coefficient profiles are found in the near ground. The continuous measurement is revealed by the contour plots measured during the whole night. These experimental results indicate that the aerosol backscattering coefficients in near ground are inhomogeneous and vary with altitude and time, which are very useful for the model researchers to study the regional air pollution and its climate impact. [ABSTRACT FROM AUTHOR]

The optical properties, time-height distribution and impact on the local air quality from a heavy Asian dust transport episode are investigated with a synergistic ground-based, satellite sensors and transport model on 1 May, 2011 at Nanjing (32.05° N, 118.78° E, and 94 m ASL) in southeast China. Two dust layers located in the planetary-boundary-layer (PBL, <2.5 km) and free troposphere (3–6 km) are observed by a Polarization Raman-Mie Lidar, with the lower one originating from the Gobi deserts and the higher one from the Taklimakan deserts. The dust aerosol layer shows the depolarization ratios at 0.1–0.2 and strong extinction coefficients of 1.0 km −1 at 532-nm, while the extinction-to-backscatter ratios (e.g. lidar ratios) of dust are 47.3–55 sr below 2.5 km. During this dust intrusion period, the aerosol optical depths (AOD) dramatically increase from 0.7 to 1.6 at 500-nm whereas the Angstrom exponents decrease from 1.2 to 0.2. Meanwhile, surface PM 10 and PM 2.5 concentrations show a significant and coincident increase with the peak value reaching 767 μg/m 3 and 222 μg/m 3 , respectively, indicating the mixture of dust with the anthropogenic aerosols. Regional influences of the transported dust in east China are further illustrated by the AERONET-sunphotometer at Taihu and Xianghe sites (downwind and upwind from Nanjing), satellites MODIS, CALIPSO and model products. Furthermore, the model product of dust profile and surface concentration are evaluated with the ground-based and CALISPO observation. The results indicate the model is capable of simulating the right timing of dust transport event and most loading below 3-km altitude; normalization of model dust with the PM 10 near the Gobi deserts improves modeling surface dust concentration in Nanjing. [ABSTRACT FROM AUTHOR]

Aerosol extinction coefficient profile is an essential parameter for atmospheric radiation model. It is difficult to get higher signal to noise ratio (SNR) of backscattering lidar from the ground to the tropopause especially in near range. Higher SNR problem can be solved by combining side-scattering and backscattering lidar. Using Raman-scattering lidar, aerosol extinction to backscatter ratio (lidar ratio) can be got. Based on side-scattering, backscattering and Raman-scattering lidar system, aerosol extinction coefficient is retrieved precisely from the earth’s surface to the tropopause. Case studies show this method is reasonable and feasible. [ABSTRACT FROM AUTHOR]

To explore the vertical distribution of the aerosol optical parameters over Jinhua City, southeast China, a Dual-wavelength Mie Polarization Raman Lidar (DMPRL) system was operated to obtain the atmospheric backscattering signals from June 2013 to May 2014. Profiles of aerosol occurrence frequency and aerosol optical parameters, including backscattering ratio, particle depolarization ratio, and color ratio, were retrieved from the lidar signals. The cases with a cloud base below 6 km and profiles on rainy days were eliminated. The multi-layer vertical aerosol structure was found in Jinhua area and the altitude-resolved optical properties varies with seasons. In autumn, winter and spring, the aerosol layer occurrence frequencies were higher than summer at 3–6 km, especially in spring. The mean particle depolarization ratio at 4–6 km exceeded 0.1 in autumn, winter, and spring, whereas it was <0.05 in summer. Aerosol with high color ratios appeared at 0–2 km in autumn. The analysis of one-year backward trajectories exhibits a dust dominating aerosol layer at 4–6 km in autumn, winter, and spring, a partially sea salt dominating aerosol layer at 0–2 km in autumn and a partially dust aerosol layer at 0–2 km in winter. Six cases were used to study the influence of aerosol advection and local sources vertical aerosol properties distribution. Through our analysis, aerosols at different altitudes are influenced by different sources, which are important for understanding the spatiotemporal characteristics of aerosol layers over Jinhua. The vertical distribution of aerosol properties in Jinhua area is affected by locally emitted aerosol , transported dust and ocean aerosol. • Multi-layer aerosol with corresponding properties observed by lidar over Jinhua. • High occurrences of aerosol layers were found at 3–6 km except summer. • Source-related aerosol vertical distribution dominated especially at 4–6 km. • Larger particles with high color ratios appeared at 0–2 km in autumn. • Regional and transported source aerosols affected the vertical aerosol properties. [ABSTRACT FROM AUTHOR]

The new side‐scattering lidar using two charge‐coupled device cameras and one CW laser is developed to measure the near‐ground aerosol profiles in haze day, which is a powerful tool and is most interested for the environmental and meteorological agencies. A new inversion method for the side‐scattering lidar to retrieve the aerosol backscattering coefficient is proposed for the first time, which is based on the aerosol backscattering coefficient measured by itself at the ground as a constrained condition. Numerical simulation is carried out to analyze the convergence of this new method. Case studies indicate that this method is reasonable and feasible. The method is especially suitable for the measurement in the foggy and hazy weathers even during the daytime, and it does not need a simultaneous backscattering lidar as the reference any more. Plain Language Summary: The CCD lidar is a new technique for aerosol observation in haze day; it is different from traditional backscattering lidar. For one thing, the detecting of aerosol profiles near the ground is really improved by this CCD lidar because there is no overlap function, instead of the traditional lidar. For another thing, we use two CCD in this system, and the calibration problem will be easily solved by itself. So, the CCD lidar will be a very useful tool with its low cost in the future. Key Points: A new low‐cost CCD lidar is developed for haze measurement in day and night time, and it is quite useful tool the environmental and meteorological fieldsA new inversion method for this CCD lidar to retrieve the aerosol backscattering coefficient is proposed, and it does not need another simultaneous instrument as the reference any moreThe system and its inversion method have been proved by numerical simulation and experimental study [ABSTRACT FROM AUTHOR]

The 355-nm ultraviolet high-spectral-resolution technique based on a triple Fabry-Perot etalon (FPE) for simultaneous high-accuracy measurement of tropospheric temperature and aerosol is proposed. The detection principle is analyzed and the whole structure of lidar system is designed. The parameters of the triple FPE-labeled FPE-1, FPE-2 and FPE-L are optimized in detail. FPE-1, FPE-2 and FPE-L are used for measuring aerosol and separating Rayleigh signal from Mie signal, for measuring temperature and for frequency locking, respectively. The performance simulation of the proposed lidar system showed that the measurement errors of temperature and backscatter ratio are below 2 K and 0.17% at 8 km and below 4 K and 0.39% at 12 km with 30-m range resolution and 1-min integration time using a 48 mJ pulse energy and 20 Hz repetition rate laser and a 25-cm telescope. The influence of Mie signal contamination on temperature measurement mainly depends on the relative Mie rejection factors of the two channels for temperature measurement, which are 4.2 and 10.4% of our proposed system at 270 K and the corresponding temperature deviation is 1 K with backscatter ratio of 10 and Rayleigh photoelectrons of 105. Assuming the same number of total photoelectrons received, the backscatter ratio and temperature measurement accuracies of our proposed lidar are 4.16-22.58 and 2.07-2.76 times, respectively, that of the traditional dual-pass multi-cavity-FPE-based HSRL at temperature of 220-290 K and backscatter ratio of 1-10. [ABSTRACT FROM AUTHOR]