Figure 1.
The schematic diagram of the lidar ratio regional transfer method and the spatial distribution of the lidar network. (a) The schematic diagram of the lidar ratio regional transfer method. The blue circle in the figure represents the combination of HSRL and the sun photometer (SP) at the same position, and the orange circle represents the combination of ML and the sun photometer (SP) at the same position. The direction of the arrow represents the lidar ratio transfer from HSRL to different MLs using the LR-AFNR. No. 0-n represents the instrument number (n ≥ 1); (b) Schematic of the spatial distribution of the lidar network of HSRL combined with MLs. The blue and orange pentagons correspond to the two combinations of the lidar and sun photometer mentioned in figure (a).
Figure 1.
The schematic diagram of the lidar ratio regional transfer method and the spatial distribution of the lidar network. (a) The schematic diagram of the lidar ratio regional transfer method. The blue circle in the figure represents the combination of HSRL and the sun photometer (SP) at the same position, and the orange circle represents the combination of ML and the sun photometer (SP) at the same position. The direction of the arrow represents the lidar ratio transfer from HSRL to different MLs using the LR-AFNR. No. 0-n represents the instrument number (n ≥ 1); (b) Schematic of the spatial distribution of the lidar network of HSRL combined with MLs. The blue and orange pentagons correspond to the two combinations of the lidar and sun photometer mentioned in figure (a).
Figure 2.
Flowchart of the lidar ratio regional transfer method. The flowchart consists of six steps: data acquisition, data retrieval, data screening, developing the LR-AFNR model, determining the conditions for using the LR-AFNR, and completing the lidar ratio regional transfer.
Figure 2.
Flowchart of the lidar ratio regional transfer method. The flowchart consists of six steps: data acquisition, data retrieval, data screening, developing the LR-AFNR model, determining the conditions for using the LR-AFNR, and completing the lidar ratio regional transfer.
Figure 3.
The screening results of dust-dominated observations with the lidar ratio at the KORUS site based on HSRL on 21 April 2017. (a) Aerosol extinction coefficient; (b) Scattering ratio; (c) Aerosol depolarization ratio; (d) Selection of dust-dominated lidar ratio result by screening criteria (grey represents the screened part).
Figure 3.
The screening results of dust-dominated observations with the lidar ratio at the KORUS site based on HSRL on 21 April 2017. (a) Aerosol extinction coefficient; (b) Scattering ratio; (c) Aerosol depolarization ratio; (d) Selection of dust-dominated lidar ratio result by screening criteria (grey represents the screened part).
Figure 4.
Statistics of the monthly average fraction of relevant absorbing aerosols at the three sites in the selected period. (a) The monthly average fraction distribution of dust, carbonaceous aerosol, and other aerosols at the Yonsei University site in March and April each year from 2016 to 2018; (b) The monthly average fraction distribution of dust, carbonaceous aerosol, and other aerosols at the Cart site from July to October of each year from 2016 to 2018.
Figure 4.
Statistics of the monthly average fraction of relevant absorbing aerosols at the three sites in the selected period. (a) The monthly average fraction distribution of dust, carbonaceous aerosol, and other aerosols at the Yonsei University site in March and April each year from 2016 to 2018; (b) The monthly average fraction distribution of dust, carbonaceous aerosol, and other aerosols at the Cart site from July to October of each year from 2016 to 2018.
Figure 5.
Scatter plot of the absorbing aerosol lidar ratio retrieved by HSRL and fraction retrieval by the sun photometer. N and R2 represent the number of fitting points and coefficient of determination, respectively. (a–c) represent the fitting relationship of the lidar ratio and dust fraction at the SGP, KORUS, and Madison sites, respectively. The solid red line represents the fitting results, and the color bar represents the dust absorbing mixing ratio; (d–f) represent the fitting relationship of the lidar ratio and carbonaceous aerosol fraction at the SGP, KORUS, and Madison site, respectively. The solid black line represents the fitting results, and the color bar represents the carbonaceous aerosol absorbing mixing ratio. The top of the subplot represents the equation of the fitted curve.
Figure 5.
Scatter plot of the absorbing aerosol lidar ratio retrieved by HSRL and fraction retrieval by the sun photometer. N and R2 represent the number of fitting points and coefficient of determination, respectively. (a–c) represent the fitting relationship of the lidar ratio and dust fraction at the SGP, KORUS, and Madison sites, respectively. The solid red line represents the fitting results, and the color bar represents the dust absorbing mixing ratio; (d–f) represent the fitting relationship of the lidar ratio and carbonaceous aerosol fraction at the SGP, KORUS, and Madison site, respectively. The solid black line represents the fitting results, and the color bar represents the carbonaceous aerosol absorbing mixing ratio. The top of the subplot represents the equation of the fitted curve.
Figure 6.
The probability distribution of dust and carbonaceous aerosol fractions in six regions (eastern U.S., central Europe, southern Europe, northern China, eastern China, and South Korea). (a–f) represent the probability distribution of the dust fraction in the six respective regions; (g–l) represent the probability distribution of the carbonaceous aerosol fraction in the six respective regions, where the horizontal coordinate (10–20% of the scale) actually includes only 15–20% of the fraction.
Figure 6.
The probability distribution of dust and carbonaceous aerosol fractions in six regions (eastern U.S., central Europe, southern Europe, northern China, eastern China, and South Korea). (a–f) represent the probability distribution of the dust fraction in the six respective regions; (g–l) represent the probability distribution of the carbonaceous aerosol fraction in the six respective regions, where the horizontal coordinate (10–20% of the scale) actually includes only 15–20% of the fraction.
Figure 7.
The scatter-fitting relationship between the relative distance and the relative error of the lidar ratio under different aerosol absorbing conditions. The six different scatter colors represent the lidar ratio average relative error between any two sites in the six regions of the eastern US, northern Europe, northern Europe, northern China, eastern China, and South Korea. The solid black line represents the fitting curve, and N and R2 represent the total number of fitting points and the coefficient of determination for the six regions, respectively. (a) Under the condition of heavy dust, point A represents the intersection of the lidar ratio relative error of 23.7% and the relative distance of 108 km; (b) Under the condition of light dust; (c) Under the condition of heavy carbonaceous aerosols, point B represents the intersection of the lidar ratio relative error of 22.9% and the relative distance of 85 km; (d) Under the condition of light carbonaceous aerosols. The dashed line in the subplot points to the equation of the fitted curve.
Figure 7.
The scatter-fitting relationship between the relative distance and the relative error of the lidar ratio under different aerosol absorbing conditions. The six different scatter colors represent the lidar ratio average relative error between any two sites in the six regions of the eastern US, northern Europe, northern Europe, northern China, eastern China, and South Korea. The solid black line represents the fitting curve, and N and R2 represent the total number of fitting points and the coefficient of determination for the six regions, respectively. (a) Under the condition of heavy dust, point A represents the intersection of the lidar ratio relative error of 23.7% and the relative distance of 108 km; (b) Under the condition of light dust; (c) Under the condition of heavy carbonaceous aerosols, point B represents the intersection of the lidar ratio relative error of 22.9% and the relative distance of 85 km; (d) Under the condition of light carbonaceous aerosols. The dashed line in the subplot points to the equation of the fitted curve.
Figure 8.
Take dust as an example, the Klett–Fernald method was used to retrieve the , as well as the relative error distribution of . (a) The results of retrieval using 50 simulated signal profiles in the 3 km boundary layer. The dotted black line (①), the solid blue line (②), the solid purple line (③), and the solid orange line (④) represent the simulated actual (the lidar ratio was 56.8 Sr) and the average of retrieval after substituting three reference lidar ratios (lidar ratios of 60, 45, and 30 Sr). The three error bars represent the standard deviation of retrieval using the three reference lidar ratios (b) Relative error profile of retrieval using three reference lidar ratios.
Figure 8.
Take dust as an example, the Klett–Fernald method was used to retrieve the , as well as the relative error distribution of . (a) The results of retrieval using 50 simulated signal profiles in the 3 km boundary layer. The dotted black line (①), the solid blue line (②), the solid purple line (③), and the solid orange line (④) represent the simulated actual (the lidar ratio was 56.8 Sr) and the average of retrieval after substituting three reference lidar ratios (lidar ratios of 60, 45, and 30 Sr). The three error bars represent the standard deviation of retrieval using the three reference lidar ratios (b) Relative error profile of retrieval using three reference lidar ratios.
Figure 9.
The relationship between the relative error of and the lidar ratio, as well as the actual lidar ratio and the reference lidar ratio. (a,b) represent the relative error of and the lidar ratio under the dust condition; (c,d) represent the relative error of and the lidar ratio under the carbonaceous aerosol condition. The pink dotted line represents the position where the relative error of was 20%, and the black dotted line represents the relative error of the lidar ratio at the same position (same horizontal and vertical coordinates) as the pink dotted line in the figure. The grey area represents the part that exceeded the upper limit of the color bar.
Figure 9.
The relationship between the relative error of and the lidar ratio, as well as the actual lidar ratio and the reference lidar ratio. (a,b) represent the relative error of and the lidar ratio under the dust condition; (c,d) represent the relative error of and the lidar ratio under the carbonaceous aerosol condition. The pink dotted line represents the position where the relative error of was 20%, and the black dotted line represents the relative error of the lidar ratio at the same position (same horizontal and vertical coordinates) as the pink dotted line in the figure. The grey area represents the part that exceeded the upper limit of the color bar.
Figure 10.
The relationship between the two absorbing aerosol fractions and the lidar ratio relative error. The horizontal and vertical coordinates represent the actual value of the two absorbing aerosol fractions and the absolute error of the reference value, respectively. The color bar represents the relative error of the lidar ratio calculated after the two absorbing aerosol fractions were input into the LR-AFNR. The white part in the figure represents no data. (a) Under the condition of dust, the sky blue, black, and white dotted lines represent the positions where the relative error of the lidar ratio was 30%, 20%, and 10%, respectively; (b) Under the condition of carbonaceous aerosol, the sky blue, black and white dotted lines represent the positions where the relative error of the lidar ratio was 40%, 20%, and 10%, respectively.
Figure 10.
The relationship between the two absorbing aerosol fractions and the lidar ratio relative error. The horizontal and vertical coordinates represent the actual value of the two absorbing aerosol fractions and the absolute error of the reference value, respectively. The color bar represents the relative error of the lidar ratio calculated after the two absorbing aerosol fractions were input into the LR-AFNR. The white part in the figure represents no data. (a) Under the condition of dust, the sky blue, black, and white dotted lines represent the positions where the relative error of the lidar ratio was 30%, 20%, and 10%, respectively; (b) Under the condition of carbonaceous aerosol, the sky blue, black and white dotted lines represent the positions where the relative error of the lidar ratio was 40%, 20%, and 10%, respectively.
Figure 11.
The influence of different types of carbonaceous aerosols (different AAEs and SSAs) on the fitting results of the LR-AFNR model. (
a,
b) represent the results of the fitting curves for different types of carbonaceous aerosols (fresh and aged) under dust-dominated conditions compared with the original fitting curve in
Figure 5b. The solid red line represents the original fitting curve, and the black dotted lines represent the fitting curves of fresh and aged smoke; (
c,
d) represent the results of the fitting curves for different types of carbonaceous aerosols (fresh and aged) under carbonaceous aerosol-dominated conditions compared with the original fitting curve in
Figure 5f. The solid black line represents the original fitting curve, and the blue dotted lines represent the fitting curves of fresh and aged smoke. N and R
2 represent the number of fitting points and the coefficient of determination, respectively. It should be noted that the solid red line corresponds to the dust fraction range of 20–100% in
Figure 5b, and the solid black line corresponds to the carbonaceous aerosol fraction range of 15–60% in
Figure 5f, so only part of the curve is shown in this Figure.
Figure 11.
The influence of different types of carbonaceous aerosols (different AAEs and SSAs) on the fitting results of the LR-AFNR model. (
a,
b) represent the results of the fitting curves for different types of carbonaceous aerosols (fresh and aged) under dust-dominated conditions compared with the original fitting curve in
Figure 5b. The solid red line represents the original fitting curve, and the black dotted lines represent the fitting curves of fresh and aged smoke; (
c,
d) represent the results of the fitting curves for different types of carbonaceous aerosols (fresh and aged) under carbonaceous aerosol-dominated conditions compared with the original fitting curve in
Figure 5f. The solid black line represents the original fitting curve, and the blue dotted lines represent the fitting curves of fresh and aged smoke. N and R
2 represent the number of fitting points and the coefficient of determination, respectively. It should be noted that the solid red line corresponds to the dust fraction range of 20–100% in
Figure 5b, and the solid black line corresponds to the carbonaceous aerosol fraction range of 15–60% in
Figure 5f, so only part of the curve is shown in this Figure.
Table 1.
The information of UW-HSRL sites, which includes the site name, system name, longitude, latitude, and data selection period.
Table 1.
The information of UW-HSRL sites, which includes the site name, system name, longitude, latitude, and data selection period.
Site Name | System Name | Latitude (°) | Longitude (°) | Selection Period |
---|
SGP | BagoHSRL | 36.62 N | 97.49 W | January 2015–October 2017 |
KORUS | AHSRL | 37.56 N | 126.95 E | January 2016–December 2018 |
Madison | BagoHSRL | 43.01 N | 89.41 W | November 2012–June 2019 |
Table 2.
The screening criteria for the lidar ratio data when dust or carbonaceous aerosols are the dominant type.
Table 2.
The screening criteria for the lidar ratio data when dust or carbonaceous aerosols are the dominant type.
| Dust-Dominated Data | Carbonaceous Aerosol-Dominated Data |
---|
Height (km) | 0.5–4 | 0.5–4 |
Aerosol depolarization ratio (unit) | 0.15–0.3 | 0.05–0.15 |
Scattering ratio (unit) | 1.2–10 | 1.2–10 |
Lidar ratio (Sr) | 30–60 | 40–100 |
Absorbing mixing ratio (%) | 50–100 (dust) | 50–100 (carbonaceous aerosol) |
Scattering ratio above 4 km (unit) | | |
Table 3.
The information of AERONET sites, which includes the site name, location, longitude, latitude, and data selection period.
Table 3.
The information of AERONET sites, which includes the site name, location, longitude, latitude, and data selection period.
Site Name | Location | Latitude (°) | Longitude (°) | Selection Period |
---|
Cart | Oklahoma, United States | 36.61 N | 97.49 W | January 2015–December 2018 |
Yonsei University | Seoul, South Korea | 37.56 N | 126.94 E | January 2016–December 2018 |
U of Wisconsin SSEC | Wisconsin, United States | 43.01 N | 89.41 W | November 2012–June 2019 |
Table 4.
The values of AAE and SSA used for fresh and aged smoke conditions for BC and BrC.
Table 4.
The values of AAE and SSA used for fresh and aged smoke conditions for BC and BrC.
| BC | BrC |
---|
Fresh smoke dominated | | |
AAE1 | 0.495 | 4.095 |
AAE2 | 0.765 | 0 |
SSA | 0.15 | 0.85 |
Aged smoke dominated | | |
AAE1 | 0.605 | 5.005 |
AAE2 | 0.935 | 0 |
SSA | 0.3 | 0.95 |