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PollyXT Raman polarization lidar observations were performed at the Remote Sensing Laboratory (RS-Lab) in Warsaw (52.2109∘ N, 20.9826∘ E), Poland, in the framework of the European Aerosol Research Lidar Network (EARLINET) and the Aerosol, Clouds, and Trace gases Research Infrastructure (ACTRIS) projects. Data collected in July, August, and September of 2013, 2015, and 2016 were analysed using the classical Raman approach. In total, 246 sets of intact profiles, each set comprising particle extinction (α) and backscatter coefficients (β) as well as linear particle depolarization ratios (δ) at 355 nm and 532 nm, were derived for statistical investigations and stored in the EARLINET/ACTRIS database. The main analysis was focused on intensive optical properties obtained within the atmospheric boundary layer (ABL). Their interrelations were discussed for different periods: the entire day; nighttime, with respect to the nocturnal boundary layer (NL) and the residual boundary layer (RL); at sunrise, with respect to the morning transition boundary layer (MTL); and from late afternoon until sunset, with respect to the well-mixed boundary layer (WML). Within the boundary layer, the lidar-derived optical properties (entire day, 246 sets) revealed a mean aerosol optical depth (AODABL) of 0.20±0.10 at 355 nm and 0.11±0.06 at 532 nm; a mean Ångström exponent (ÅEABL) of 1.54±0.37; a mean lidar ratio (LRABL) of 48±17 sr at 355 nm and 41±15 sr at 532 nm; a mean linear particle depolarization ratio (δABL) of 0.02±0.01 at 355 nm and 0.05±0.01 at 532 nm; and a mean water vapour mixing ratio (WVABL) of 8.28±2.46 g kg−1. In addition, the lidar-derived daytime boundary layer optical properties (for the MTL and WML) were compared with the corresponding daytime columnar aerosol properties derived from the multi-filter rotating shadowband radiometer (MFR-7) measuring within the National Aerosol Research Network (PolandAOD-NET) and the CE318 sun photometer of the Aerosol Robotic NETwork (AERONET). A high linear correlation of the columnar aerosol optical depth values from the two latter instruments was obtained in Warsaw (a correlation coefficient of 0.98 with a standard deviation of 0.02). The contribution of the aerosol load in the summer and early-autumn free troposphere can result in an AODCL value that is twice as high as the AODABL over Warsaw. The occurrence of a turbulence-driven aerosol burst from the boundary layer into the free troposphere can further increase this difference. Aerosol within the ABL and in the free troposphere was interpreted based on comparisons of the properties derived at different altitudes with values reported in the literature, which were characteristic for different aerosol types, in combination with backward trajectory calculations, satellite data, and model outputs. Within the boundary layer, the aerosol consisted of either urban anthropogenic pollution (∼ 61 %) or mixtures of anthropogenic aerosol with biomass-burning aerosol (< 14 %), local pollen (< 7 %), or Arctic marine particles (< 5 %). No significant contribution of mineral dust was found in the boundary layer. The lidar-derived atmospheric boundary layer height (ABLH) and the AODABL exhibited a positive correlation (R of 0.76), associated with the local anthropogenic pollution (most pronounced for the RL and WML). A positive correlation of the AODABL and LRABL and a negative correlation of the ÅEABL and LRABL, as well as the expected negative trends for the WVABL (and surface relative humidity, RH) and δABL, were observed. Relations of the lidar-derived aerosol properties within the ABL and the surface in situ measurements of particulate matter with an aerodynamic diameter less than 10 µm (PM10) and less than 2.5 µm (PM2.5) measured by the Warsaw Regional Inspectorate for Environmental Protection (WIOS) network, and the fine-to-coarse mass ratio (FCMR) were investigated. The FCMR and surface RH showed a positive correlation even at nighttime (R of 0.71 for the MTL, 0.63 for the WML, and 0.6 for the NL), which generally lacked statistically significant relations. A weak negative correlation of the FCMR and δABL (more pronounced at 532 nm at nighttime) and no casual relation between the FCMR and ÅEABL were found. Most interestingly, distinct differences were observed for the morning transition layer (MTL) and the well-mixed layer (WML). The MTL ranged up to 0.6–1 km, and was characterized by a lower AODABL(), wetter conditions (RH 50–80 %), smaller particles (ÅEABL of 1–2.2; FCMR from 0.5 to 3), and a low LRABL of between 20 and 40 sr. The WML ranged up to 1–2.5 km and exhibited a higher AODABL (reaching up to 0.45), drier conditions (RH 25–60  %), larger particles (ÅEABL of 0.8–1.7; FCMR of 0.2–1.5), and a higher LRABL of up to 90 sr.

Отмечается, что основным методом для калибровки солнечных фотометров до сих остается метод Ленгли. Основным недостатком метода Ленгли является временная нестабильность составляемых графических диаграмм, вызванная нестабильностью оптической толщины атмосферного аэрозоля. Временная нестабильность оптической толщины атмосферного аэрозоля приводит к изменению крутизны построенной диаграммы и, в конечном счете, к случайным смещениям графически вычисляемой калибровочной величины. Другой немаловажный недостаток метода Ленгли заключается в отсутствии полностью аналитического выражения для вычисления калибровочной величины и в необходимости осуществления графических построений. Для устранения первого из вышеизложенных недостатков были предложены ряд усовершенствований. В частности известен метод, позволяющий аналитически вычислить калибровочную величину при двух оптических массах, где нестабильность исходного метода сохраняется. Хорошо известно, что оптические массы различных газовых составляющих атмосферы значительно различаются при малых углах высоты Солнца. Следовательно, измерения, проведенные в широком диапазоне изменения угла высоты Солнца, точно не могут быть расценены как изменение общей оптической массы в таком же диапазоне. Это обстоятельство значительно ограничивает возможности известного метода. В настоящей статье излагается предлагаемый двухволновой метод калибровки солнечных фотометров при двух оптических воздушных массах. Показано, что переход от одноволнового метода к двухволновому позволяет существенно уменьшить аэрозольную погрешность метода калибровки при двух оптических массах. Предлагаемый в настоящей статье двухволновой метод калибровки солнечных фотометров при двух оптических массах позволяет исключить влияние изменчивых атмосферных условий на результат калибровки, имеющее место в известном одноволновом методе, реализуемым при двух значениях оптической массы, что создает потенциальную возможность повышение точности солнечнофотометрических исследований атмосферных газов и аэрозоля., It is noted that the major method used for calibration of the Sun photometers is still the Langley method. The major weakness of the Langley method is temporal instability of drawn graphical diagrams, caused by instability of optical depth of atmospheric aerosol. The temporal instability of atmospheric aerosols optical depth leads to change in the steepness of drawn up diagrams and, as a result, to random shifts of graphically calculated calibration quantity. Another significant limitation of the Langley method is the lack of fully analytical formula for calculating calibration quantity and the necessity to draw the graphics. There are some modifications of the Langley method, for example, there is an analytical method making it possible to calculate the calibration quantity analytically upon two optical masses, where the instability of basic method remains. It is well known that optical masses of different atmospheric gas components significantly differ upon low height angle of the Sun. Thus, the measurements carried out in broadband of the Sun elevation angles variation cannot be estimated as variation of common optical mass in the same band. This fact significantly limits the possibilities of the known method. The article describes the suggested twowavelength method for calibration of the Sun photometers in two optical air masses. It is shown that transition from the onewavelength method to the twowavelength method make it possible to decrease significantly the aerosol error of calibration method applied upon two air masses. The twowavelength method for calibration of the Sun photometers upon two optical masses suggested in this article make it possible to remove the impact of atmospheric conditions on results of calibration inherent for the onewavelength method realized upon two optical masses. The suggested method makes it possible to increase the accuracy of sunphotometric measurements of atmospheric trace gases and aerosol., №3(15) (2019)

A comprehensive uncertainty analysis validates a Solar Spectral Irradiance Meter (SolarSIM) for accurately resolving the spectral and broadband direct normal irradiances (DNI), spectral aerosol optical depth (AOD), precipitable water vapour and atmospheric total column ozone amounts. The derivation of these parameters from four SolarSIMs were compared to reference instrumentation at the Physikalisch-Meteorologisches Observatorium Davos and World Radiation Center (PMOD/WRC) in Davos, Switzerland in September 2015. The SolarSIMs are the first instruments to ever simultaneously participate in the 12th WMO International Pyrheliometer Comparison, Fourth Filter Radiometer Comparison, and First Spectroradiometer Comparison. The SolarSIMs’ DNI data were compared to the World Standard Group’s PMO2 absolute cavity radiometer, with World Radiometric Reference factors ranging from 0.999674 to 0.994610 for the best and the worst performing devices, respectively. In addition, the SolarSIMs’ spectral DNI data was compared against PMOD’s Precision Spectral Radiometer. The mean difference of the spectral DNI was found to be less than 5% for wavelengths above 400 nm. The SolarSIMs’ measurements of AOD data were compared against PMOD’s Precision Filter Radiometer triad. The median AOD differences and their standard deviations were found to be 0.0046 ± 0.0044, 0.0016 ± 0.0034, 0.0018 ± 0.0026, and 0.0041 ± 0.0022 for 368 nm, 412 nm, 500 nm, and 865 nm, respectively. The SolarSIMs’ measurements of precipitable water vapour were compared against PMOD’s Cimel CE318 sun photometer. The median difference and the corresponding standard deviation averaged 1 ± 0.2 mm for all SolarSIMs. Furthermore, the SolarSIMs’ measurements of total column atmospheric ozone were compared against PMOD’s Brewer MkIII spectrophotometer. The median difference and the corresponding standard deviation averaged 6 ± 7 DU for all SolarSIMs.

In the present study, we report the first comparison between the aerosol optical depth (AOD) and Ångström exponent (AE) of the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on the Terra (AODt) and Aqua (AODa) satellites and those measured using a sun photometer (AODSP) at Camagüey, Cuba, for the period 2008 to 2014. The comparison of Terra and Aqua data includes AOD derived with both deep blue (DB) and dark target (DT) algorithms from MODIS Collection 6. Combined Terra and Aqua (AODta) data were also considered. Assuming an interval of ±30 min around the overpass time and an area of 25 km around the sun photometer site, two coincidence criteria were considered: individual pairs of observations and both spatial and temporal mean values, which we call collocated daily means. The usual statistics (root mean square error, RMSE; mean absolute error, MAE; median bias, BIAS), together with linear regression analysis, are used for this comparison. Results show very similar values for both coincidence criteria: the DT algorithm generally displays better statistics and higher homogeneity than the DB algorithm in the behaviour of AODt, AODa, AODta compared to AODSP. For collocated daily means, (a) RMSEs of 0.060 and 0.062 were obtained for Terra and Aqua with the DT algorithm and 0.084 and 0.065 for the DB algorithm, (b) MAE follows the same patterns, (c) BIAS for both Terra and Aqua presents positive and negative values but its absolute values are lower for the DT algorithm; (d) combined AODta data also give lower values of these three statistical indicators for the DT algorithm; (e) both algorithms present good correlations for comparing AODt, AODa, AODta vs. AODSP, with a slight overestimation of satellite data compared to AODSP, (f). The DT algorithm yields better figures with slopes of 0.96 (Terra), 0.96 (Aqua) and 0.96 (Terra + Aqua) compared to the DB algorithm (1.07, 0.90, 0.99), which displays greater variability. Multi-annual monthly means of AODta establish a first climatology that is more comparable to that given by the sun photometer and their statistical evaluation reveals better agreement with AODSP for the DT algorithm. Results of the AE comparison showed similar results to those reported in the literature concerning the two algorithms' capacity for retrieval. A comparison between broadband aerosol optical depth (BAOD), derived from broadband pyrheliometer observations at the Camagüey site and three other meteorological stations in Cuba, and AOD observations from MODIS on board Terra and Aqua show a poor correlation with slopes below 0.4 for both algorithms. Aqua (Terra) showed RMSE values of 0.073 (0.080) and 0.088 (0.087) for the DB and DT algorithms. As expected, RMSE values are higher than those from the MODIS–sun photometer comparison, but within the same order of magnitude. Results from the BAOD derived from solar radiation measurements demonstrate its reliability in describing climatological AOD series estimates.

In this paper, we present long term observations of atmospheric aerosols and nitrogen dioxide (NO2) in Hong Kong using a Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) instrument. Ground based MAX-DOAS measurements were performed over 5years from December 2010 to November 2015. Vertical distribution profiles of aerosols and NO2 were derived from MAX-DOAS O4 and NO2 observations by applying the optimal estimation method. Retrieved MAX-DOAS measurements of aerosols and NO2 show good agreement with sun photometer observation of aerosol optical depths (AODs) and long path DOAS measurement of ground level NO2 mixing ratios. Tropospheric vertical column densities (VCDs) of NO2 derived from MAX-DOAS measurements are used to validate OMI satellite NO2 observations. Daily data show reasonably good agreement with each other with Pearson correlation coefficient R=0.7. However, MAX-DOAS NO2 VCDs are on average higher than OMI observations by a factor of 2. Introducing aerosols in the air mass factor calculation would enhance the OMI VCDs by 7-13%, the remaining discrepancy is mainly due to the differences in spatial coverage between the two instruments. Diurnal variation patterns of aerosols and NO2 indicated significant contributions from local anthropogenic emissions. Analysis of air mass transport shows that the enhancement of surface aerosols and NO2 concentrations mainly results from accumulation of local emissions under low wind speed conditions.

This work presents the results of observation and the numerical simulation relationship between columnar and surface aerosol optical properties. The presented data include sun photometer nephelometer, aethalometer, and ceilometer observation, as well as the Navy Aerosol Analysis and Prediction System (NAAPS) re-analysis obtained between 2013 and 2016. Measurements were made in Strzyzow station (south-eastern part of Poland), which belongs to the AERONET and Poland-AOD network. Observation and simulation data show that the correlation coefficient between aerosol optical depth and surface aerosol scattering coefficient depends on the averaging period. For the monthly mean both parameters are negatively correlated as a result of the seasonal variability of anthropogenic emission in Central Europe and long-range transport of natural aerosol, as well as the change of the meteorological conditions. Reduction of the averaging time leads to an increase in the correlation coefficient, which is almost zero for a 10-day period and 0.4 ± 0.05 when the six-hour data are selected. In addition, the correlation between columnar and surface aerosol optical properties shows significant variation with surface temperature gradient. During convective conditions the correlation coefficient between aerosol optical depth and aerosol scattering coefficient is as much as 0.89 ± 0.03 while during inversion it is approximately 0.48 ± 0.08.

Satellite-based aerosol products are routinely validated against ground-based reference data, usually obtained from sun photometer networks such as AERONET (AEROsol RObotic NETwork). In a typical validation exercise a spatial sample of the instantaneous satellite data is compared against a temporal sample of the point-like ground-based data. The observations do not correspond to exactly the same column of the atmosphere at the same time, and the representativeness of the reference data depends on the spatiotemporal variability of the aerosol properties in the samples. The associated uncertainty is known as the collocation mismatch uncertainty (CMU). The validation results depend on the sampling parameters. While small samples involve less variability, they are more sensitive to the inevitable noise in the measurement data. In this paper we study systematically the effect of the sampling parameters in the validation of AATSR (Advanced Along-Track Scanning Radiometer) aerosol optical depth (AOD) product against AERONET data and the associated collocation mismatch uncertainty. To this end, we study the spatial AOD variability in the satellite data, compare it against the corresponding values obtained from densely located AERONET sites, and assess the possible reasons for observed differences. We find that the spatial AOD variability in the satellite data is approximately 2 times larger than in the ground-based data, and the spatial variability correlates only weakly with that of AERONET for short distances. We interpreted that only half of the variability in the satellite data is due to the natural variability in the AOD, and the rest is noise due to retrieval errors. However, for larger distances (∼ 0.5∘) the correlation is improved as the noise is averaged out, and the day-to-day changes in regional AOD variability are well captured. Furthermore, we assess the usefulness of the spatial variability of the satellite AOD data as an estimate of CMU by comparing the retrieval errors to the total uncertainty estimates including the CMU in the validation. We find that accounting for CMU increases the fraction of consistent observations.

The optical and physical properties as well as the direct radiative forcings (DRFs) of fractionated aerosols in the urban area of the western Yangtze River Delta (YRD) are investigated with measurements from a Cimel sun photometer combined with a radiation transfer model. Ground-based observations of aerosols have much higher temporal resolutions than satellite retrievals. An initial analysis reveals the characteristics of the optical properties of different types of fractionated aerosols in the western YRD. The total aerosols, mostly composed of scattering components (93.8 %), have mean optical depths of 0.65 at 550 nm and refractive index of 1.44 + 0.0084i at 440 nm. The fine aerosols are approximately four times more abundant and have very different compositions from coarse aerosols. The absorbing components account for only ∼ 4.6 % of fine aerosols and 15.5 % of coarse aerosols and have smaller sizes than the scattering aerosols within the same mode. Therefore, fine particles have stronger scattering than coarse ones, simultaneously reflecting the different size distributions between the absorbing and scattering aerosols. The relationships among the optical properties quantify the aerosol mixing and imply that approximately 15 and 27.5 % of the total occurrences result in dust- and black-carbon-dominating mixing aerosols, respectively, in the western YRD. Unlike the optical properties, the size distributions of aerosols in the western YRD are similar to those found at other sites over eastern China on a climatological scale, peaking at radii of 0.148 and 2.94 µm. However, further analysis reveals that the coarse-dominated particles can also lead to severe haze pollution over the YRD. Observation-based estimations indicate that both fine and coarse aerosols in the western YRD exert negative DRFs, and this is especially true for fine aerosols (−11.17 W m−2 at the top of atmosphere, TOA). A higher absorption fraction leads directly to the negative DRF being further offset for coarse aerosols (−0.33 W m−2) at the TOA. Similarly, the coarse-mode DRF contributes to only 13.3 % of the total scattering aerosols but > 33.7 % to the total absorbing aerosols. A sensitivity analysis states that aerosol DRFs are not highly sensitive to their profiles in clear-sky conditions. Most of the aerosol properties and DRFs have substantial seasonality in the western YRD. The results further reveal the contributions of each component of the different size particles to the total aerosol optical depths (AODs) and DRFs. Additionally, these results can be used to improve aerosol modelling performance and the modelling of aerosol effects in the eastern regions of China.

A new method for quantifying the total ozone column (TOC) using a smartphone image sensor has been developed and validated. The TOC has been evaluated for relatively cloud free days at high air masses for solar zenith angles between 49.7o and 76.7o at a sub-tropical site. The method is based on the evaluation of the direct solar irradiances at 305 nm and 312 nm using the red colour pixel values of the solar disc recorded at these wavelengths by a smartphone camera. Narrow bandpass filters of 2 nm FWHM at each of the two wavelengths were used in turn placed over the camera sensor to directly image the solar disc. The calibration of the pixel values of the solar disc to provide the direct solar irradiances at each of these two wavelengths allowed evaluation of the total ozone column calibrated to a portable sun photometer. The RMSE for the smartphone derived ozone values calibrated to corresponding values from a portable sun photometer was 4.3 DU. The validation measurements for the smartphone derived ozone values provided an average residual of 3.5% (up to a maximum of 11%) compared to the corresponding portable sun photometer values, with an RMSE of 8.4 DU during days of intermittent inclement weather conditions. The evaluation of the total ozone column based on a widely available device such as a smartphone has the potential to increase current citizen science initiatives valued by the general public and school aged learners by enhancing knowledge and awareness of ozone and the resulting influences on the solar UV environment.

We propose a new application of inexpensive LED-based Sun photometers, consisting of measuring the Aerosol Optical Thickness (AOT) with high resolution within metropolitan scales. Previously, these instruments have been used at continental scales by the GLOBE program, but this extension is already covered by more expensive and higher precision instruments of the AERONET global network. For this we built an open source two channeled LED based sun photometer based on previous developments, with improvements in the hardware, software and modifications on the calibration procedure. Among these we highlight the use of MODTRAN to characterize the effect introduced by using LED sensors in the AOT retrieval, an open design available for the scientific community and a calibration procedure that takes advantage of a CIMEL sun photometer located within the city, enables the inter-comparison of several LED sun photometers with a common reference. We estimated the root mean square error in the AOT retrieved by the prototypes as 0.006 at the 564 nm and 0.009 at the 408 nm. This error is way under the magnitude of the AOT daily cycle variability measured by us in our campaigns, even for distances closer than 15 km. In addition to inner city campaigns, we also show aerosol tracing applications by measuring AOT variations from the city of Santiago to the Andes glaciers. Measuring AOT at high spatial resolution in urban areas can improve our understanding of urban scale aerosol circulation, providing information for solar energy planning, health policies and climatological studies, among others.

In the present work a hybrid approach is implemented to retrieve aerosol optical depth (AOD) from ocean colour monitor sensor on board Oceansat-2. The retrieved AOD (490 nm) has been validated with the ground observed AOD (500 nm) made at different locations of the study area for different months observed by AERONET sites and hand held sun photometer. The Oceasat 2 retrieved AOD (490 nm) is also compared with the MODIS retrieved AOD (470 nm). It is observed that Oceansat 2 retrieved AOD is in good agreement with ground observed AOD with a significant correlation of 0.839 and with a RMSE value of 0.273. The comparison between Oceansat 2 retrieved AOD and MODIS retried AOD are also found to be encouraging with a correlation coefficient of 0.852 with RMSE 0.1243.

The current understanding of the climate effects of mixed-type aerosols is an open question. The optical and radiative properties of the anthropogenic, mixed-type, and dust aerosols were studied using simultaneous observations of a sun photometer and a depolarization lidar over the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL), northwestern China. The aerosol radiative effect was calculated using the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model and was in good agreement with the Aerosol Robotic Network (AERONET) product. The anthropogenic, mixed-type, and dust aerosols were identified mainly based on the lidar-measured depolarization ratio, which was supported by the airmass back trajectories. The mixed-type aerosols exhibit lower (higher) extinctions below (above) 1.5 km above the ground, indicating anthropogenic pollution from the atmospheric boundary layer and dust aerosols above. The dust aerosols exhibit the highest absolute radiative effect because of the highest aerosol loading. However, the mixed-type aerosols are effective in both scattering and absorbing solar radiation, leading to the highest cooling efficiency at the bottom of the atmosphere (BOA), 7.4% and 6.5% higher than those of the anthropogenic and dust aerosols, respectively. The mixed-type aerosols exhibit the highest warming efficiency in the atmosphere (ATM), 20.8% and 28.2% higher than the anthropogenic and dust aerosols, respectively. The mixed-type aerosols also show the lowest cooling efficiency at the top of the atmosphere (TOA). The results suggest the necessity of carefully characterizing the mixed-type aerosols in atmospheric numerical models to more precisely assess the energy budget of the Earth–atmosphere system.

In the tropics, Langley calibration is often complicated by abundant cloud cover. The lack of an objective and robust cloud screening algorithm in Langley calibration is often problematic, especially for tropical climate sites where short, thin cirrus clouds are regular and abundant. Errors in this case could be misleading and undetectable unless one scrutinizes the performance of the best fitted line on the Langley regression individually. In this work, we introduce a new method to improve the sun photometer calibration past the Langley uncertainty over a tropical climate. A total of 20 Langley plots were collected using a portable spectrometer over a mid-altitude (1,574 m a.s.l.) tropical site at Kinabalu Park, Sabah. Data collected were daily added to Langley plots, and the characteristics of each Langley plot were carefully examined. Our results show that a gradual evolution pattern of the calculated Perez index in a time-series was observable for a good Langley plot, but days with poor Langley data basically demonstrated the opposite behavior. Taking advantage of this fact, the possibly contaminated data points were filtered by calculating the Perez derivative of each distinct air mass until a negative value was obtained. Any points that exhibited a negative derivative were considered bad data and discarded from the Langley regression. The implementation was completely automated and objective, rendering qualitative observation no longer necessary. The improved Langley plot exhibits significant improvement in addressing higher values for correlation, R, and lower values for aerosol optical depth, τa. The proposed method is sensitive enough to identify the occurrence of very short and thin cirrus clouds and is particularly useful for sun-photometer calibration over a tropical climate.

We explore how the microstructure parameters of atmospheric aerosol can be estimated from regression equations that describe their relationships with spectral measurements of the aerosol optical depth (AOD). Special attention is paid to the problem of estimating the volume concentration, total cross section, and mean radius of coarse aerosol particles. This problem is topical because of large errors arising when an insufficiently wide spectral range of measurements is available to retrieve these parameters using directly the AOD inversion. Estimates of the coefficients of simple and multiple linear regressions are presented together with the results of their use to retrieve the parameters of coarse-mode aerosol from data of sun photometer measurements in Tomsk.

The transparency of the atmosphere over the central part of Yakutia is classified using ground-based observations of aerosol optical depth (AOD) for the period of 2004-2014. The annual variations in monthly mean values of AOD are compared with satellite monitoring data. It is revealed that every year the days with the values of AOD corresponding to the class III of atmospheric transparency (turbid atmosphere) made up 25-30% of the total number of AOD measurement days.

Results of studying the time variations in aerosol microstructure parameters retrieved by inverting the spectral measurements of the aerosol optical depth are presented. The input data were obtained at the Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences using SP-type sun photometers during periods of observations in 2003–2006 and 2011–2014. During the first period, aerosol optical depth was measured at 13 wavelengths in the range 0.37–4 μm. In the second period, the upper boundary of the wavelength range of measurements was 2.14 μm. The total amount of data processed had been more than 7000 hourly average spectra. The aerosol microstructure parameters, such as the geometric cross section, volume concentration, and average particle radius, were analyzed.

The interest in the use of ceilometers for optical aerosol characterization has increased in the last few years. They operate continuously almost unattended and are also much less expensive than lidars; hence, they can be distributed in dense networks over large areas. However, due to the low signal-to-noise ratio it is not always possible to obtain particle backscatter coefficient profiles, and the vast number of data generated require an automated and unsupervised method that ensures the quality of the profiles inversions. In this work we describe a method that uses aerosol optical depth (AOD) measurements from the AERONET network that it is applied for the calibration and automated quality assurance of inversion of ceilometer profiles. The method is compared with independent inversions obtained by co-located multiwavelength lidar measurements. A difference smaller than 15ĝ in backscatter is found between both instruments. This method is continuously and automatically applied to the Iberian Ceilometer Network (ICENET) and a case example during an unusually intense dust outbreak affecting the Iberian Peninsula between 20 and 24 February 2016 is shown. Results reveal that it is possible to obtain quantitative optical aerosol properties (particle backscatter coefficient) and discriminate the quality of these retrievals with ceilometers over large areas. This information has a great potential for alert systems and model assimilation and evaluation. © 2017 Author(s)., Acknowledgements. This work was supported by the Spanish Ministry of Economy and Competitiveness through projects CGL2012-39623-C02-01, CGL2013-45410-R, CGL2014-56255-C2-1-R, CMT2015-66742-R, CGL2015-70741-R, CGL2015-73250-JIN and CGL2016-81092-R; by the regional government of Andalusia through project P12-RNM-2409; by the regional government of Castilla y Leon through project VA100U14; by the Junta de Extremadura (Ayuda a Grupos de Investigación GR15137); and by the European Union’s Horizon 2020 research and innovation program through project ACTRIS-2 (grant agreement no. 654109). The authors thankfully acknowledge the FEDER program for the instrumentation used in this work. This work was also partially funded by the University of Granada through the contract “Plan Propio. Programa 9. Convocatoria 2013”. Marco Pandolfi is funded by a Ramón y Cajal Fellowship (RYC-2013-14036) awarded by the Spanish Ministry of Economy and Competitiveness. The authors would like to acknowledge the valuable contribution through the discussions in the working group meetings organized by COST Action ES1303 (TOPROF).

We investigate the uncertainty introduced to the optical and microphysical properties estimated with the lidar radiometer inversion code (LIRIC) by user-defined input parameters based on measurements carried out with a multi-wavelength Raman lidar and a sun photometer located at Thessaloniki, Greece (40.6° N, 22.9° E, 60 m above sea level). The sensitivity study involves three tests. We first evaluate the selection of the regularization parameters needed for the algorithm to initialize the iteration process. The latter two tests consider the impact of the boundary limits at the top/bottom (upper/lower limit) of the signal to the derived concentration profiles. The aforementioned tests were applied to two different cases, a Saharan dust event and a continental pollution case. We concluded that the largest uncertainties are introduced when varying the lower limit (more than 35%) regardless of the aerosol type or mode (fine/coarse). Varying the regularization parameters resulted in an uncertainty of ...

In this paper, we present a quantitative estimation of the impacts of biomass burning emissions from different source regions to the local air quality in Hong Kong in 2014 using global chemistry transport model simulations, sun photometer measurements, satellite observations and local monitoring network data. This study focuses on two major biomass burning pollutants, black carbon aerosols and carbon monoxide (CO). The model simulations of atmospheric black carbon and CO show excellent agreement with sun photometer aerosol optical depth (AOD) measurements, satellite CO columns observations and local monitoring stations data. From the model simulation results, we estimated that biomass burning contributes 12% of total black carbon and 16% of atmospheric CO in Hong Kong on annual average. South East Asia shows the largest influence to the black carbon and CO levels in Hong Kong, accounts for 11% of the total atmospheric black carbon and 8% of CO. Biomass burning in North East Asia and Africa also show significant impacts to Hong Kong. Elevated levels of atmospheric black carbon aerosols and CO were observed during springtime (March and April) which is mainly due to the enhancement of biomass burning contributions. Black carbon and CO originating from biomass burning sources are estimated to contribute 40% of atmospheric black carbon and 28% of CO in Hong Kong during March 2014. An investigation focusing on the biomass burning pollution episode during springtime suggests the intensified biomass burning activities in the Indochinese Peninsula are the major sources of black carbon and CO in Hong Kong during the time.

We use two cloud screening methods—the clustering method and the multiplet method—to process the measurements of a sun photometer from March 2020 to April 2021 in Shouxian. The aerosol optical depth (AOD) and Angström parameters α and β are retrieved, variation characteristics and single scattering albedo are studied. The results show that: (1) The fitting coefficient of AOD retrieved by the two methods is 0.921, and the changing trend is consistent. The clustering method has fewer effective data points and days, reducing the overall average of AOD by 0.0542 (500 nm). (2) Diurnal variation of AOD can be divided into flat type, convex type, and concave type. Concave type and convex type occurred the most frequently, whereas flat type the least. (3) During observation, the overall average of AOD is 0.48, which is relatively high. Among them, AOD had a winter maximum (0.70), autumn and spring next (0.54 and 0.40), and a summer minimum (0.26). The variation trend of AOD and β is highly consistent, and the monthly mean of α is between 0.69 and 1.61, concerning mainly continental and urban aerosols. (4) Compared with others, the single scattering albedo in Shouxian is higher, reflecting strong scattering and weak aerosol absorption.

The polarization–Raman Lidar combined sun photometer is a powerful method for separating dust and urban haze backscatter, extinction, and mass concentrations. The observation was performed in Beijing during the 2019 National Day parade, the particle depolarization ratio at 532 nm and Lidar ratio at 355 nm are 0.13 ± 0.05 and 52 ± 9 sr, respectively. It is the typical value of a mixture of dust and urban haze. Here we quantify the contributions of cross-regional transported natural dust and urban haze mass concentrations to Beijing’s air quality. There is a significant correlation between urban haze mass concentrations and surface PM2.5 (R = 0.74, p < 0.01). The contributions of local emissions to air pollution during the 2019 National Day parade were insignificant, mainly affected by regional transport, including urban haze in North China plain and Guanzhong Plain (Hebei, Tianjin, Shandong, and Shanxi), and dust aerosol in Mongolia regions and Xinjiang. Moreover, the trans-regional transmission of natural dust dominated the air pollution during the 2019 National Day parade, with a relative contribution to particulate matter mass concentrations exceeding 74% below 4 km. Our results highlight that controlling anthropogenic emissions over regional scales and focusing on the effects of natural dust is crucial and effective to improve Beijing’s air quality.

The direct and indirect radiation forcing of aerosol particles deeply affect the energy budget and the atmospheric chemical and physical processes. To retrieve the vertical aerosol mass fluxes and to investigate the vertical transport process of aerosol by a coherent Doppler lidar (CDL), a practical method for instrumental calibration and aerosol optical properties retrieval based on CDL and sun photometer synchronization observations has been developed. A conversion of aerosol optical properties to aerosol microphysical properties is achieved by applying a well-developed algorithm. Furthermore, combining the vertical velocity measured simultaneously with a CDL, we use the eddy covariance (EC) method to retrieve the vertical turbulent aerosol mass fluxes by a CDL and sun photometer with a spatial resolution of 15 m and a temporal resolution of 1 s throughout the planetary boundary layer (PBL). In this paper, we present a measurement case of 24-h continuous fluxes observations and analyze the diurnal variation of the vertical velocity, the aerosol backscatter coefficient at 1550 nm, the mean aerosol mass concentration, and the vertical aerosol mass fluxes on 13 April 2020. Finally, the main relative errors in aerosol mass flux retrieval, including sample error σF,S, aerosol optical properties retrieval error σF,R, and error introduced from aerosol microphysical properties retrieval algorithm σF,I, are evaluated. The sample error σF,S is the dominating error which increases with height except during 12:00–13:12 LST. The aerosol optical properties retrieval error σF,R is 21% and the error introduced from the aerosol microphysical properties retrieval algorithm σF,I is less than 50%.

We examine the impact of atmospheric aerosols and clouds on the surface solar radiation and solar energy at Nainital, a high-altitude remote location in the central Gangetic Himalayan region (CGHR). For this purpose, we exploited the synergy of remote-sensed data in terms of ground-based AERONET Sun Photometer and satellite observations from the MODerate Resolution Imaging Spectroradiometer (MODIS) and the Meteosat Second Generation (MSG), with radiative transfer model (RTM) simulations and 1 day forecasts from the Copernicus Atmosphere Monitoring Service (CAMS). Clouds and aerosols are one of the most common sources of solar irradiance attenuation and hence causing performance issues in the photovoltaic (PV) and concentrated solar power (CSP) plant installations. The outputs of RTM results presented with high accuracy under clear, cloudy sky and dust conditions for global horizontal (GHI) and beam horizontal irradiance (BHI). On an annual basis the total aerosol attenuation was found to be up to 105 kWh m−2 for the GHI and 266 kWh m−2 for BHI, respectively, while the cloud effect is much stronger with an attenuation of 245 and 271 kWh m−2 on GHI and BHI. The results of this study will support the Indian solar energy producers and electricity handling entities in order to quantify the energy and financial losses due to cloud and aerosol presence.

In the morning of 21 July 2019, a dense forest fire smoke plume was detected over Evora (Portugal) in the lower troposphere. Around 13:00 UTC, a Sahara dust layer was detected by lidar between 3000 and 4000 m height above sea level. In this work results of these events using an EARLINET Raman lidar and AERONET Sun-photometer measurements are reported and discussed: the dense smoke layer, the mixing of smoke with dust and the lofted dust layer that crossed Evora. During the morning, in-situ hourly mean black carbon concentration reached a maximum of 6.28 ± 0.73 μgm−3. The AERONET fine mode aerosol optical depth at 500 nm reached 0.77 and the Angstrom exponent at 440–870 nm varied between 1.45 and 1.82, indicating the presence of fine smoke particles in the atmospheric column. In the beginning of the afternoon, the lidar profiles indicated the presence of a smoke layer followed by two thin layers of pollution mixed with dust and a lofted dust layer. The smoke particles caused low particle linear depolarization ratios at 532 nm with mean value of 0.059 ± 0.002 in the smoke layer. In contrast, the lofted dust layer caused mean particle linear depolarization ratio at 532 nm of 0.26 ± 0.01. Mass concentrations were in the order of 22–29 μg m−3 in the smoke layer and 60–178 μg m−3 in the lofted dust layer. During the afternoon and at night, mixing dust layers were identified by using lidar data. In the afternoon, two aerosol layers exhibited mean particle linear depolarization ratios at 532 nm of 0.23 ± 0.01 and 0.25 ± 0.01 with the dust dominating the extinction and mass concentration in both aerosol layers. Mass concentrations of dust were in the order of 101–266 μg m−3 and 159–195 μg m−3. At night, the particle linear depolarization ratio presented low variability across the identified layer with mean value of 0.20 ± 0.01. The Angstrom exponents were low, the mean lidar ratios were 50 ± 6 sr (355 nm) and 42 ± 4 sr (532 nm) and the aerosol optical depth was 0.32 (355 nm) and 0.30 (532 nm). Mass concentrations ranged in 10–28 μg m−3 for non-dust and in 77–186 μg m−3 for dust.

Accurate detection of solar irradiance has important application value for theoretical research on climate change and atmospheric analysis, so this paper proposes the integrated spectral sun-photometer to enrich methods of obtaining the solar irradiance and entire atmospheric transmittance. With the ARM microprocessor as central processing unit and Linux OS as the software platform, the two-dimensional turntable and grating spectrometer are combined to construct sun-photometer which can measure continuous wavebands. This article advances the solution scheme to realize data transmission between microcontroller and turntable through CANopen communication. Meanwhile, the spectrometer based on USB communication protocol is used to obtain spectrum from visible to near-infrared band. In addition, both the multiple task operating system Linux and application framework Qt are employed to design friendly user-interface and display real-time process images, which would simplify and integrate the solar radiometer. After Langley calibration is used to calculate the constants to achieve calibration of instrument in spectral band, measured data of the radiometer and results of the DTF solar radiometer are compared and analysed, which confirms the reliability of integrated sun-photometer.