Nephelometer (NEPH)

The Nephelometer is an instrument used for measuring light scattering properties of aerosols at multiple wavelengths.

Data Format

• File format: Raw data file (.dat)
• Sampling frequency: 5 minutes
• File naming pattern: *.dat
• Record types:
  • T records: Timestamp information
  • D records: Scattering measurements
  • Y records: Status and RH information

Measurement Parameters

The Nephelometer provides measurements at three wavelengths:

• B, G, R: Total scattering coefficients at blue, green, and red wavelengths (Mm⁻¹)
• BB, BG, BR: Backscattering coefficients at blue, green, and red wavelengths (Mm⁻¹)
• RH: Relative humidity inside the nephelometer (%)

Data Processing

Data Reading

• Processes different record types (T, D, Y)
• Extracts timestamp from T records
• Extracts scattering measurements from D records
• Extracts status and RH from Y records
• Converts raw scattering values to Mm⁻¹
• Handles both normal (NBXX) and total (NTXX) scattering modes

Quality Control

• Removes physically impossible values (negative or > 2000 Mm⁻¹)
• Ensures physical consistency:
  • Backscattering must be less than total scattering
  • Blue > Green > Red (Rayleigh scattering principle)
• Applies time-aware IQR filtering with 1-hour windows
• Ensures data completeness across all channels
• Filters data based on instrument status codes

Output Data

The processed data contains the following columns:

• Time index: Data acquisition time
• B, G, R: Total scattering coefficients (Mm⁻¹)
• BB, BG, BR: Backscattering coefficients (Mm⁻¹)
• RH: Relative humidity (%)

Notes

• Provides information about aerosol optical properties and size distribution
• Supports both normal and total scattering modes
• Maintains physical consistency between measurements
• Automatically handles different record types and data formats