Boundary layer analysis - BLVIEW - CL61

BL-View for CL61 User Guide

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A ceilometer sends out short, powerful laser pulses in a vertical or near-vertical direction. The light reflection caused by haze, fog, mist, virga, precipitation, aerosols, and clouds, known as backscatter, is measured as the laser pulses traverse the sky.

The backscatter profile, that is, the signal strength versus the height, is stored and processed, and the data is used to calculate the cloud bases and the planetary boundary layer structure.

The planetary boundary layer is the portion of the lower atmosphere where wind, temperature, and moisture are strongly influenced by the Earth’s surface. The depth of this layer, also known as the mixing height layer, is important for analyzing the state of the atmosphere, for example, for air quality evaluation and aviation.

The backscatter signal is typically stronger in the planetary boundary layer where particle concentration is higher, but weaker in the free atmosphere where the atmosphere typically has fewer particles. BL-View detects the backscatter gradient between the planetary boundary layer and free atmosphere (the mixing height), as well as other atmospheric structures, such as residual boundary layers and elevated smoke or aerosol plumes that may produce strong backscatter gradients.

To reduce sensitivity to noise and transient details in atmospheric structure, BL-View performs vertical and temporal averaging on the ceilometer data.

Figure 1. Backscatter profile from convective boundary layer