# Vertical Measurement of Equivalent Black Carbon Concentration at Low Altitude
## 3 Results and Discussion  
### eBC Concentrations and Temperatures in Winter, Spring, Summer and Early Autumn  
Data shown in Figure 3 are examples of typical characteristics of diurnal evolution of eBC concentrations measured at various altitudes in April 30 th, 2017. The eBC concentrations were measured to be noisy in the morning and noon though less noisy in the evening. Most of high spikes around 9:35, 9:50, 10:45, 10:50, 11: 45, 11:55, 12:25, 12:40 and 12:55, as shown in the morning (Figure 3a,b), turned out to be measured on the ground level while batteries were manually being changed. In this case, the peak concentrations were similar to the eBC concentration on the ground. In the morning, the eBC concentration was observed highest at the ground level. In the evening, however, the eBC concentration at the ground level was similar to or less than the eBC concentrations at altitudes from 10 m to 130 m.  
Figure 3: Examples of vertical eBC concentration measurements. The short horizontal black bars in figures indicate the duration of eBC concentration measurements at each altitudes: (**a**) Measurement in the morning; (**b**) Measurement in the late morning; (**c**) Measurement in the evening; (**d**) Measurement at night. Figure 2: Measurement at a mountain: (**a**) Photo of a tomb near the top of Eun Seok Mountain; (**b**) The altitude of the tomb from the ground is approximately 400 m. The vertical profile of eBC from the tomb up to 100 m higher than the tomb has been measured. We measured eBC concentrations on 28 February 2017 to represent the BC situation in winter at KOREATECH campus as shown in Figure 4a. The average eBC concentrations alongside the vertical altitude for 3 cases was 2.9 \(\pm\) 1.6 \(\upmu\)g/m\({}^{3}\), which is higher than usual eBC concentrations (~1.5 \(\upmu\)g/m\({}^{3}\)) at this area through spring to autumn [20]. In terms of the measurement timing, eBC concentrations measured in the morning were highest among other eBC concentrations measured in the evening or in the late morning. More specifically, eBC concentrations measured in the late morning is the lowest. The eBC concentration decreased as the altitude increased up to around 60 m, and then it increased up to 90 m. It seems that the temperature change around at 60 m high influenced the movement of air mass so that BC has been trapped between 60 m and 90 m high. In other words, high BC concentrations at h = 70-90 m could be related to the temperature inversion (at h = 50-60 m), which blocked transfer from midair to the ground as can be seen in Figure 4b. Average wind speed and direction during the measurements on 28 February 2017 were 2.5 m/s and 294\({}^{\circ}\), respectively. Moderate wind speed seems to partly affect the high eBC concentration on the ground level. Figure 4: _Cont._  
Figure 4c shows eBC concentrations measured on April 30 th to reflect the BC situation in spring. Similar to the result in winter, eBC concentrations were highest on the ground, especially in the morning. Average eBC concentrations from 10 m to 130 m, however, were \(1.89\pm 0.48\)\(\mathrm{\SIUnitSymbolMicro g}\)/m\({}^{3}\), showing less fluctuated than the vertical eBC concentrations measured in winter. The eBC concentrations measured in the morning were higher than those measured in the late morning, which is similar to the situation of the eBC concentration in winter. Note that the temperature scale ranges from 10 to 35 \({}^{\circ}\)C, which is 5 \({}^{\circ}\)C higher than the temperature scale range in winter as shown in Figure 4d. Average wind speed and direction during the measurements on 30 April 2017 were 7.3 m/s and 224\({}^{\circ}\), respectively. We measured eBC concentrations on 27 May to represent the BC situation in early summer as shown in Figure 4e. The level of eBC concentrations were mostly low. As opposed to the results in winter and spring (Figure 4a,c), eBC concentrations on the ground were highest when measured in the late morning.