Polarized Micro Pulse Lidar Research Articles

Transboundary transport of non-east and East Asian dust observed at Dunhuang, northwest China

Long-range transport of North African and Middle Eastern dust has been frequently observed in East Asia. However, understanding of their characteristics and effects in this region is insufficient. In this study, the transboundary transport of multi-source dust was captured by a polarized micro-pulse lidar from April 5 to 10, 2012, during a field campaign in Dunhuang, northwest China. Six dust plumes (DN1-DN6) were selected based on the spatiotemporal evolution of the depolarization ratio. Furthermore, the source, vertical characteristics of the coarse and fine components and their contributions were investigated by combining lidar observation with the WRF-Chem model simulation. The results indicated that DN1 was from Central Asia and it took approximately 4–5 days. DN2 originated from sources in North Africa and the Middle East and took approximately 6–7 days to reach Dunhuang. Samples DN3-DN6 originated from the Taklimakan and Gobi deserts in East Asia. A noticeable contrast was observed in the vertical distribution of the coarse and fine components between the long-range transported (DN1∼DN2) and fresh (DN3∼DN6) dust plumes. DN1 and DN2 presented comparable dust components (DD = Dc + Df, where Dc and Df are coarse- and fine-mode dust, respectively) and non-dust (ND) component contributions and a high predominance of Dc particles was present with at least 40% of total components in DN3-DN4. The contribution of ND particles was nearly negligible in DN5 and DN6. Lidar observations and model simulation both indicated that the maximum contribution of North African and Middle Eastern dust to the local aerosol loading exceeded 58%. However, the model simulation underestimated the contribution of DN1 by an average of 18% compared to lidar observations because DN1 was not reproduced well. This implies that the vertical distribution of dust should be carefully considered when dust impacts (e.g., radiation effects and air quality) are finely assessed using a model on a regional scale.

Fresh volcanic aerosols injected in the atmosphere during the volcano eruptive activity at the Cumbre Vieja area (La Palma, Canary Islands): Temporal evolution and vertical impact

For the first time in fifty years, the Cumbre Vieja volcanic area (La Palma, Canary Islands, Spain) erupted on September 19, 2021, giving birth to a new volcano. Fresh volcanic aerosols were continuously injected into the troposphere at different height levels, decreasing with time until the end of December 2021 (15 weeks duration). A wide set of different instrumentation was deployed all over the Island in order to evaluate the effects of the volcanic plumes on the atmosphere and the air quality. For the first time, a long-term study of the relative mass contribution and vertical impact of the volcanic components, ash and non-ash particles separately, during the eruptive activity was carried out in this work. In particular, a polarized Micro-Pulse Lidar (P-MPL) was deployed at Tazacorte (at around 8 km west from the volcano) in 24/7 operation from October 17, 2021 until the end of the volcano activity (11 weeks) for vertical monitoring of the volcanic particles. First, a statistical study of the mass conversion factors for mass concentration estimation of the volcanic (ash and non-ash) particles was performed by using the AERONET sun/sky-photometer dataset at Fuencaliente (at around 18 km south from the volcano). A representative mass conversion factor was obtained for ash and non-ash particles: 1.89 ± 0.53 and 0.31 ± 0.06 g m−2, respectively, with no dependence on time and optical depth. Second, these factors were used to calculate the ash and non-ash mass concentrations from P-MPL observations. Ash particles dominated 11% of the time and mostly until week 3 (i.e. week 7 from the volcanic eruption). Their mass concentration decreased by one order of magnitude: the relative ash mass contribution was 73 ± 18% with a total mass loading of 566 ± 281 mg m−2 at week 1, reducing gradually down to 38 ± 32% and 120 ± 49 mg m−2, respectively, at week 11. Layer-to-layer, it decreased with increasing layer-height; no ash was detected above 4 km at the end of the volcanic period. Third, in order to analyse the potential AERONET underestimation of the coarse mass conversion factor due to the 15 μm cutoff effect in the AERONET retrieval, two worst-case-scenarios (WCS) were examined, representing aged-like ash particles (WCS1, 4-μm radius) and fresh-like (WCS2, 10-μm radius). For both scenarios, the mass concentration of the volcanic plumes exceeded the first contamination level (>200 μg m−3, as defined by the UK Meteorological Office) up to 5–6 km height mostly during week 1 and up to 1–2 km until week 9. The extreme contamination level (>2000 μg m−3, aircraft flight limitations) was only exceeded from week 1 to week 6 under WCS2 conditions. This work infers a new long-term insight on the volcanic matter injected in the atmosphere with relevance for Air Quality issues and air traffic safety policies.

Seasonal Variation of Dust Aerosol Vertical Distribution in Arctic Based on Polarized Micropulse Lidar Measurement

This study investigates the seasonal variation of dust aerosol vertical distribution using polarized Micropulse lidar (MPL) measurements at the Atmospheric Radiation Measurement (ARM) North Slope of Alaska (NSA) observatory from January 2013 to September 2017. For the first time, multi-year aerosol backscatter coefficients are retrieved at the ARM NSA site from MPL measurements and are consistent with co-located high spectral resolution lidar (HSRL) measurements. The high-quality aerosol backscatter coefficient retrievals are used to derive the particle depolarization ratio (PDR) at the wavelength of 532 nm, which is used to identify the presence of dust aerosols. The annual cycles of the vertical distributions of dust backscatter coefficient and PDR and dust aerosol optical depth (DAOD) show that aerosol loading has a maximum in late winter and early spring but a minimum in late summer and early autumn. Vertically, dust aerosol occurs in the entire troposphere in spring and winter and in the low and middle troposphere in summer and autumn. Because dust aerosols are effective ice nuclei, the seasonality of dust aerosol vertical distribution has important implications for the Arctic climate through aerosol–cloud–radiation interactions, primarily through impacting mixed-phase cloud processes.

Retrieval of Aged Biomass-Burning Aerosol Properties by Using GRASP Code in Synergy with Polarized Micro-Pulse Lidar and Sun/Sky Photometer

The aim of this study was to analyze the potential of the GRASP code to retrieve optical and microphysical properties vertically-resolved using a synergy of polarized Micro-Pulse Lidar and Sun/sky photometer observations. The focus was on the long-range transport of Canadian aged-smoke plumes observed at El Arenosillo/Huelva (Spain) from 7 to 8 September 2017. Both the columnar and height-resolved microphysical and optical properties were assessed in comparison with AERONET data and vertical lidar-retrieved profiles, respectively. In particular, the vertical properties were also derived using the POLIPHON approach, which serves as a comparison for GRASP retrievals. The retrieved columnar aerosol microphysical properties (volume concentration and effective radius) showed an excellent agreement, with negligible differences, and were within the uncertainties. Nevertheless, for the retrieved columnar optical properties, we could only perform an individual comparison, due to the strong AERONET limitations, and although the agreements were generally good, no conclusions were obtained, due to differences in the real refractive index and due to the large uncertainties obtained in the retrievals. For the vertical profiles, however, we present a large advance that permits obtaining aerosol backscatter and extinction coefficients, plus volume concentrations, without the need for internal assumptions (extinction-to-backscatter ratios and depolarization measurements), due to the very good agreement observed between GRASP and the lidar-derived methodologies. However, the separation of the properties into their fine and coarse modes was not feasible using the one-wavelength elastic lidar measurements with the GRASP retrieval configuration used in this work. Therefore, current studies are being addressed to assessing the introduction of lidar depolarization in the GRASP code as an encouraged added-value, for the improvement of the retrieval of vertical aerosol properties.

Volcanic Eruption of Cumbre Vieja, La Palma, Spain: A First Insight to the Particulate Matter Injected in the Troposphere

The volcanic eruption of Cumbre Vieja (La Palma Island, Spain), started on 19 September 2021 and was declared terminated on 25 December 2021. A complete set of aerosol measurements were deployed around the volcano within the first month of the eruptive activity. This paper describes the results of the observations made at Tazacorte on the west bank of the island where a polarized micro-pulse lidar was deployed. The analyzed two-and-a-half months (16 October–31 December) reveal that the peak height of the lowermost and strongest volcanic plume did not exceed 3 km (the mean of the hourly values is 1.43 ± 0.45 km over the whole period) and was highly variable. The peak height of the lowermost volcanic plume steadily increased until week 11 after the eruption started (and 3 weeks before its end) and started decreasing afterward. The ash mass concentration was assessed with a method based on the polarization capability of the instrument. Two days with a high ash load were selected: The ash backscatter coefficient, aerosol optical depth, and the volume and particle depolarization ratios were, respectively, 3.6 (2.4) Mm−1sr−1, 0.52 (0.19), 0.13 (0.07) and 0.23 (0.13) on 18 October (15 November). Considering the limitation of current remote sensing techniques to detect large-to-giant particles, the ash mass concentration on the day with the highest ash load (18 October) was estimated to have peaked in the range of 800–3200 μg m−3 in the lowermost layer below 2.5 km.

Vertical assessment of the mineral dust optical and microphysical properties as retrieved from the synergy between polarized micro-pulse lidar and sun/sky photometer observations using GRASP code

The potential of the synergetic use of both polarized Micro-Pulse Lidar (P-MPL) and Sun/sky photometer observations by using the GRASP (Generalized Retrieval of Atmosphere and Surface Properties) code for retrieving dust properties has been analysed in this work. Both the columnar and height-resolved variables have been evaluated in comparison, respectively, with AERONET data and vertical P-MPL-derived profiles of the dust optical and microphysical properties over a mid-latitude site. The linear regression analysis together with the mean fractional bias values and relative differences between datasets have been used as the statistical proxies for assessing the degree of agreement by examining 24 selected dust cases. Regarding columnar variables, the microphysical properties (both the particle volume concentration and effective radius) presented a high confidence level between GRASP and AERONET retrievals by taking into account all the proxies. In addition, the single scattering albedo and the real refractive index presented a good confidence level at all the wavelengths, as well, unlike the imaginary refractive index, which was confident at 440 nm only. By analysing the height-resolved properties of the total particle backscatter coefficient and the total volume concentration, the degree of agreement shows a high confidence between GRASP retrievals and P-MPL-derived variables, which were retrieved by using an alternative, well-validated, polarization-based methodology. Indeed, these results can be essential for application with no-polarized systems (e.g., ceilometers, lidars …). Overall, the synergy between P-MPL and Sun/sky photometer measurements regarding the usual co-location of both MPLNET and AERONET networks in combination with GRASP code represent an improved approach to derive the height-resolved optical and microphysical properties for mineral dust particles with a high degree of confidence.

Experimental assessment of a micro-pulse lidar system in comparison with reference lidar measurements for aerosol optical properties retrieval

Abstract. Simultaneous observations of a polarized micro-pulse lidar (P-MPL) system and two reference European Aerosol Research Lidar Network lidars running at the Leipzig site Germany, 51.4∘ N, 12.4∘ E; 125 m a.s.l.) were performed during a comprehensive 2-month field intercomparison campaign in summer 2019. An experimental assessment regarding both the overlap (OVP) correction of the P-MPL signal profiles and the volume linear depolarization ratio (VLDR) analysis, together with its impact on the retrieval of the aerosol optical properties, is achieved; the experimental procedure used is also described. The optimal lidar-specific OVP function is experimentally determined, highlighting that the one delivered by the P-MPL manufacturer cannot be used long. Among the OVP functions examined, the averaged function between those obtained from the comparison of the P-MPL observations with those of the other two reference lidars seems to be the best proxy at both near- and far-field ranges. In addition, the impact of the OVP function on the accuracy of the retrieved profiles of the total particle backscatter coefficient (PBC) and the particle linear depolarization ratio (PLDR) is examined. The VLDR profile is obtained and compared with that derived from the reference lidar, showing that it needs to be corrected by a small offset value with good accuracy. Once P-MPL measurements are optimally (OVP, VLDR) corrected, both the PBC and PLDR profiles can be accurately derived and are in good agreement with reference aerosol retrievals. Overall, as a systematic requirement for lidar systems, an adequate OVP function determination and VLDR testing analysis needs to be performed on a regular basis to correct the P-MPL measurements in order to derive suitable aerosol products. A dust event observed in Leipzig in June 2019 is used for illustration.

Observations of Atmospheric Aerosol and Cloud Using a Polarized Micropulse Lidar in Xi’an, China

A polarized micropulse lidar (P-MPL) employing a pulsed laser at 532 nm was developed by the Institute of Oceanographic Instrumentation, Qilu University of Technology (Shandong Academy of Sciences). The optomechanical structure, technical parameters, detection principle, overlap factor calculation method, and inversion methods of the atmospheric boundary layer (ABL) depth and depolarization ratio (DR) were introduced. Continuous observations using the P-MPL were carried out at Xi’an Meteorological Bureau, and the observation data were analyzed. In this study, we gleaned much information on aerosols and clouds, including the temporal and spatial variation of aerosols and clouds, aerosol extinction coefficient, DR, and the structure of ABL were obtained by the P-MPL. The variation of aerosols and clouds before and after a short rainfall was analyzed by combining time-height-indication (THI) of range corrected signal (RCS) and DR was obtained by the P-MPL with profiles of potential temperature (PT) and relative humidity (RH) detected by GTS1 Digital Radiosonde. Then, the characteristics of tropopause cirrus cloud were discussed using the data of DR, PT, and RH. Finally, a haze process from January 1st to January 5th was studied by using aerosol extinction coefficients obtained by the P-MPL, PT, and RH profiles measured by GTS1 Digital Radiosonde and the time-varying of PM2.5 and PM10 observed by ambient air quality monitor. The source of the haze was simulated by using the NOAA HYSPLIT Trajectory Model.

Comprehensive observation and analysis of aerosol optical properties and vertical distribution in Nanjing, China

Abstract Comprehensive observational experiments on atmospheric aerosol particles were conducted over Nanjing. Aerosol particles were detected vertically in real time by polarization micro pulse lidar (PMPL). To improve the accuracy of the lidar ratio, we combined observational data from ground-based polarization lidar and a sun photometer. Furthermore, the influence of meteorological conditions on vertically-resolved aerosol optical properties was analyzed. On the other hand, sources of aerosol pollution were analyzed using backward air mass trajectory, the potential and source contribution function (PSCF) and concentration weighted trajectory (CWT) models. Aerosol types were identified from PMPL data, sun photometer and cloud-aerosol lidar and infrared pathfinder satellite observations (CALIPSO). Accordingly, a large number of coarse-mode aerosol particles (pure sand-dust particles predominate) from North China appeared in spring, and smoke aerosol particles were generated from biomass combustion in autumn. The study shows that the local emission and regional transport are both important contributors to aerosol pollution events.

Cirrus-induced shortwave radiative effects depending on their optical and physical properties: Case studies using simulations and measurements

Cirrus (Ci) clouds play an important role in the atmospheric radiative balance, and hence in Climate Change. In this work, a polarized Micro-Pulse Lidar (P-MPL), standard NASA/Micro Pulse NETwork (MPLNET) system, deployed at the INTA/El Arenosillo station in Huelva (SW Iberian Peninsula) is used for Ci detection and characterization for the first time at this site. Three days were selected on the basis of the predominantly detected Ci clouds in dependence on their cloud optical depth (COD). Hence, three Ci cloud categories were examined at day-times for comparison with solar radiation issues: 19 cases of sub-visuals (svCi, COD: 0.01–0.03) on 1 October 2016, 7 cases of semitransparents (stCi, COD: 0.03–0.30) on 8 May 2017, and 17 cases of opaques (opCi, COD: 0.3–3.0) on 28 October 2016. Their radiative-relevant optical, macro- and micro-physical properties were retrieved. The mean COD for the svCi, stCi and opCi groups was 0.02 ± 0.01, 0.22 ± 0.08 and 0.93 ± 0.40, respectively; in overall, their lidar ratio ranged between 25 and 35 sr. Ci clouds were detected at 11–13 km height (top boundaries) with geometrical thicknesses of 1.7–2.0 km. Temperatures reported at those altitudes corresponded to lower values than the thermal threshold for homogenous ice formation. Volume linear depolarization ratios of 0.3–0.4 (and normalized backscattering ratios higher than 0.9) also confirmed Ci clouds purely composed of ice particles. Their effective radius was within the interval of 9–15 μm size, and the ice water path ranged from 0.02 (svCi) to 9.9 (opCi) g m−2. The Cirrus Cloud Radiative Effect (CCRE) was estimated using a Radiative Transfer (RT) model for Ci-free conditions and Ci-mode (Ci presence) scenarios. RT simulations were performed for deriving the CCRE at the top-of-atmosphere (TOA) and on surface (SRF), and also the atmospheric CCRE, for the overall shortwave (SW) range and their spectral sub-intervals (UV, VIS and NIR). A good agreement was first obtained for the RT simulations as validated against solar radiation measurements under clean conditions for solar zenith angles less than 75° (differences were mainly within ±20 W m−2 and correlation coefficients close to 1). By considering all the Ci clouds, independently on their COD, the mean SW CCRE values at TOA and SRF were, respectively, −30 ± 26 and − 24 ± 19 W m−2, being the mean atmospheric CCRE of −7 ± 7 W m−2; these values are in good agreement with global annual estimates found for Ci clouds. By using linear regression analysis, a Ci-induced enhancing cooling radiative effect was observed as COD increased for all the spectral ranges, with high correlations. In particular, the SW CCRE at TOA and SRF, and the atmospheric CCRE, presented COD-dependent rates of −74 ± 4, −55 ± 5, −19 ± 2 W m−2τ−1, respectively. Additionally, increasing negative rates are found from UV to NIR for each Ci category, reflecting a higher cooling NIR contribution w.r.t. UV and VIS ranges to the SW CCRE, and being also more pronounced at the TOA w.r.t. on SRF, as expected. The contribution of the SW CCRE to the net (SW + LW) radiative balance can be also potentially relevant. These results are especially significant for space-borne photometric/radiometric instrumentation and can contribute to validation purposes of the next ESA's EarthCARE mission, whose principal scientific goal is focused on radiation-aerosol-cloud interaction research.

Separation of the optical and mass features of particle components in different aerosol mixtures by using POLIPHON retrievals in synergy with continuous polarized Micro-Pulse Lidar (P-MPL) measurements

Abstract. The application of the POLIPHON (POlarization-LIdar PHOtometer Networking) method is presented for the first time in synergy with continuous 24/7 polarized Micro-Pulse Lidar (P-MPL) measurements to derive the vertical separation of two or three particle components in different aerosol mixtures, and the retrieval of their particular optical properties. The procedure of extinction-to-mass conversion, together with an analysis of the mass extinction efficiency (MEE) parameter, is described, and the relative mass contribution of each aerosol component is also derived in a further step. The general POLIPHON algorithm is based on the specific particle linear depolarization ratio given for different types of aerosols and can be run in either 1-step (POL-1) or 2 steps (POL-2) versions with dependence on either the 2- or 3-component separation. In order to illustrate this procedure, aerosol mixing cases observed over Barcelona (NE Spain) are selected: a dust event on 5 July 2016, smoke plumes detected on 23 May 2016 and a pollination episode observed on 23 March 2016. In particular, the 3-component separation is just applied for the dust case: a combined POL-1 with POL-2 procedure (POL-1/2) is used, and additionally the fine-dust contribution to the total fine mode (fine dust plus non-dust aerosols) is estimated. The high dust impact before 12:00 UTC yields a mean mass loading of 0.6±0.1 g m−2 due to the prevalence of Saharan coarse-dust particles. After that time, the mean mass loading is reduced by two-thirds, showing a rather weak dust incidence. In the smoke case, the arrival of fine biomass-burning particles is detected at altitudes as high as 7 km. The smoke particles, probably mixed with less depolarizing non-smoke aerosols, are observed in air masses, having their origin from either North American fires or the Arctic area, as reported by HYSPLIT back-trajectory analysis. The particle linear depolarization ratio for smoke shows values in the 0.10–0.15 range and even higher at given times, and the daily mean smoke mass loading is 0.017±0.008 g m−2, around 3 % of that found for the dust event. Pollen particles are detected up to 1.5 km in height from 10:00 UTC during an intense pollination event with a particle linear depolarization ratio ranging between 0.10 and 0.15. The maximal mass loading of Platanus pollen particles is 0.011±0.003 g m−2, representing around 2 % of the dust loading during the higher dust incidence. Regarding the MEE derived for each aerosol component, their values are in agreement with others referenced in the literature for the specific aerosol types examined in this work: 0.5±0.1 and 1.7±0.2 m2 g−1 are found for coarse and fine dust particles, 4.5±1.4 m2 g−1 is derived for smoke and 2.4±0.5 m2 g−1 for non-smoke aerosols with Arctic origin, and a MEE of 2.4±0.8 m2 g−1 is obtained for pollen particles, though it can reach higher or lower values depending on predominantly smaller or larger pollen grain sizes. Results reveal the high potential of the P-MPL system, a simple polarization-sensitive elastic backscatter lidar working in a 24/7 operation mode, to retrieve the relative optical and mass contributions of each aerosol component throughout the day, reflecting the daily variability of their properties. In fact, this procedure can be simply implemented in other P-MPLs that also operate within the worldwide Micro-Pulse Lidar Network (MPLNET), thus extending the aerosol discrimination at a global scale. Moreover, the method has the advantage of also being relatively easily applicable to space-borne lidars with an equivalent configuration such as the ongoing Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) on board NASA CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) and the forthcoming Atmospheric Lidar (ATLID) on board the ESA EarthCARE mission.

Cirrus clouds properties derived from polarized micro pulse lidar (p-mpl) observations at the atmospheric observatory ‘el arenosillo’ (sw iberian peninsula): a case study for radiative implications

Cirrus (Ci) clouds are involved in Climate Change concerns since they affect the radiative balance of the atmosphere. Recently, a polarized Micro Pulse Lidar (P-MPL), standard system within NASA/MPLNET has been deployed at the INTA/Atmospheric Observatory ‘El Arenosillo’ (ARN), located in the SW Iberian Peninsula. Hence, the INTA/P-MPL system is used for Ci detection over that station for the first time. Radiative effects of a Ci case observed over ARN are examined, as reference for future long-term Ci observations. Optical and macrophysical properties are retrieved, and used for radiative transfer simulations. Data are compared to the measured surface radiation levels and all-sky images simultaneously performed at the ARN station.

Vertical separation of the atmospheric aerosol components by using poliphon retrieval in polarized micro pulse lidar (P-MPL) measurements: case studies of specific climate-relevant aerosol types

POLIPHON (POlarization-LIdar PHOtometer Networking) retrieval consists in the vertical separation of two/three particle components in aerosol mixtures, highlighting their relative contributions in terms of the optical properties and mass concentrations. This method is based on the specific particle linear depolarization ratio given for different types of aerosols, and is applied to the new polarized Micro-Pulse Lidar (P-MPL). Case studies of specific climate-relevant aerosols (dust particles, fire smoke, and pollen aerosols, including a clean case as reference) observed over Barcelona (Spain) are presented in order to evaluate firstly the potential of P-MPLs measurements in combination with POLIPHON for retrieving the vertical separation of those particle components forming aerosol mixtures and their properties.

Depolarization ratio measurement using single photomultiplier tube in micropulse lidar

The conventional dual polarization micropulse lidar uses two separate photomultiplier tubes (PMT) to detect both the copolarized and cross-polarized beam. The prominent sources of error in the depolarization ratio measurement are mismatch in PMT, improper selection of discriminator threshold and unequal PMT high voltage. In the present work a technique for the measurement of lidar depolarization ratio using only one PMT sensor has been developed. The same PMT detects both copolarized and cross-polarized lidar backscatter. A stepper motor is used along with the mirrors to bring both the received polarization signals over the PMT window. Application of the same PMT minimizes the error caused in the depolarization ratio measurement due to error in photon counting of an individual channel. The design description of this technique along with the preliminary results depicting its functionality has been mentioned in this article.

Mobile Lidar Profiling of Tropical Aerosols and Clouds

Abstract Lidar profiling of atmospheric aerosols and clouds in the lower atmosphere has been in progress at the Indian Institute of Tropical Meteorology (IITM), Pune (18°32′N, 73°52′E, 559 m MSL), India, for more than two decades. To enlarge the scope of these studies, an eye-safe new portable dual polarization micropulse lidar (DPMPL) has been developed and installed at this station. The system utilizes a diode-pumped solid-state (DPSS) neodymium–yttrium–aluminum–garnet (Nd:YAG) laser second harmonic, with either parallel polarization or alternate parallel and perpendicular polarization, as a transmitter and a Schmidt–Cassegrain telescope, with a high-speed detection and data acquisition and processing system, as a receiver. This online system in real-time mode provides backscatter intensity profiles up to about 75 km at every minute in both parallel and perpendicular polarization channels, corresponding to each state of polarization of the transmitted laser radiation. Thus, this versatile lidar system is expected to play a vital role not only in atmospheric aerosol and cloud physics research and environmental monitoring but also in weather and climate modeling studies of the impact of radiative forcing on the earth–atmosphere radiation balance and hydrological cycle. This paper provides a detailed description of Asia’s only lidar facility and presents initial observations of space–time variations of boundary layer structure from experiments carried out during winter 2005/06.