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Nephelometer (NEPH)

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

AeroViz.rawDataReader.script.NEPH.Reader 

Reader(*args, **kwargs)

Bases: AbstractReader

Nephelometer (NEPH) Data Reader

A specialized reader for integrating nephelometer data files, which measure light scattering properties of aerosols at multiple wavelengths.

See full documentation at docs/source/instruments/NEPH.md for detailed information on supported formats and QC procedures.

Attributes

nam class-attribute instance-attribute 

nam = 'NEPH'

SCAT_COLUMNS class-attribute instance-attribute 

SCAT_COLUMNS = ['B', 'G', 'R', 'BB', 'BG', 'BR']

CAL_COLUMNS class-attribute instance-attribute 

CAL_COLUMNS = ['sca_550', 'SAE']

MIN_SCAT_VALUE class-attribute instance-attribute 

MIN_SCAT_VALUE = 0

MAX_SCAT_VALUE class-attribute instance-attribute 

MAX_SCAT_VALUE = 2000

STATUS_COLUMN class-attribute instance-attribute 

STATUS_COLUMN = 'status'

STATUS_OK class-attribute instance-attribute 

STATUS_OK = 0

_status_data instance-attribute 

_status_data = None

Functions

_raw_reader 

_raw_reader(file)

Read and parse raw Nephelometer data files.

Parameters:

Name Type Description Default
file Path or str

Path to the Nephelometer data file.

 required

Returns:

Type Description
DataFrame

Processed Nephelometer data with datetime index and scattering coefficient columns.

_QC 

_QC(_df)

Perform quality control on Nephelometer raw data.

QC Rules Applied (raw data only)
  1. Status Error : Non-zero status code indicates instrument error
  2. No Data : All scattering columns are NaN
  3. Invalid Scat Value: Scattering coefficient outside 0-2000 Mm^-1
  4. Invalid Scat Rel. : Wavelength dependence violation (B < G < R)
  5. Insufficient : Less than 50% hourly data completeness

Note: SAE calculation is done in _process() after QC.

_process 

_process(_df)

Calculate scattering coefficients and SAE.

Processing Steps
  1. Calculate scattering coefficient at 550nm
  2. Calculate SAE (Scattering Ångström Exponent)

Parameters:

Name Type Description Default
_df DataFrame

Quality-controlled DataFrame with scattering columns and QC_Flag

 required

Returns:

Type Description
DataFrame

DataFrame with sca_550, SAE, and updated QC_Flag

Data Format

Time Record Format T YYYY MM DD HH NN SS
Example T 2022 05 08 13 29 22
Data Record Format D mode time B G R BB GB RB
Example D NBXX 2258 7.527e-5 6.984e-5 4.275e-5 6.821e-6 1.070e-5 5.130e-6
Auxiliary Record Format Y x pressure Sample Temp Inlet Temp RH lamp voltage lamp current BNC voltage Status
Example Y 348 973 302.8 300 91.2 12.5 5.7 2 0000
  • 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:

Column Wavelength Description
B 450 nm Total scattering (blue)
G 550 nm Total scattering (green)
R 700 nm Total scattering (red)
BB 450 nm Backscattering (blue)
BG 550 nm Backscattering (green)
BR 700 nm Backscattering (red)

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

The NEPH reader uses the declarative QCFlagBuilder system with the following rules:

+-----------------------------------------------------------------------+
|                         QC Thresholds                                 |
+-----------------------------------------------------------------------+
| MIN_SCAT_VALUE = 0       Mm⁻¹                                         |
| MAX_SCAT_VALUE = 2000    Mm⁻¹                                         |
| STATUS_OK      = 0       (numeric status code)                        |
+-----------------------------------------------------------------------+

+-----------------------------------------------------------------------+
|                            _QC() Pipeline                             |
+-----------------------------------------------------------------------+
|                                                                       |
|  [Pre-process] Calculate scattering Angstrom exponent (SAE)           |
|       |                                                               |
|       v                                                               |
|  +---------------------------+                                        |
|  | Rule: Status Error        |                                        |
|  +---------------------------+                                        |
|  | Status code != 0          |                                        |
|  | (from Y record col 9)     |                                        |
|  +---------------------------+                                        |
|           |                                                           |
|           v                                                           |
|  +---------------------------+    +---------------------------+       |
|  | Rule: No Data             |    | Rule: Invalid Scat Value  |       |
|  +---------------------------+    +---------------------------+       |
|  | All columns are NaN       |    | Value <= 0 OR             |       |
|  +---------------------------+    | Value > 2000 Mm⁻¹         |       |
|           |                       +---------------------------+       |
|           v                                |                          |
|  +---------------------------+             v                          |
|  | Rule: Invalid Scat Rel    |    +---------------------------+       |
|  +---------------------------+    | Rule: Insufficient        |       |
|  | Blue < Green < Red        |    +---------------------------+       |
|  | (violates physics)        |    | < 50% hourly data         |       |
|  +---------------------------+    +---------------------------+       |
|                                                                       |
+-----------------------------------------------------------------------+

QC Rules Applied

Rule Condition Description
Status Error Status ≠ 0 Non-zero status code indicates instrument error
No Data All columns NaN All scattering columns are missing
Invalid Scat Value Value ≤ 0 OR > 2000 Mm⁻¹ Scattering outside valid range
Invalid Scat Rel B < G < R Wavelength dependence violation
Insufficient < 50% hourly data Less than 50% hourly data completeness

Wavelength Dependence Check

    Scattering (Mm⁻¹)
       ^
       |     Expected: Blue > Green > Red
       |
       |  B *
       |      \
       |       G *
       |           \
       |            R *
       +----+----+----+-----> Wavelength
           450  550  700

Output Data

The processed data contains the following columns:

Column Unit Description
B, G, R Mm⁻¹ Total scattering coefficients
BB, BG, BR Mm⁻¹ Backscattering coefficients
sca_550 Mm⁻¹ Scattering at 550nm
SAE - Scattering Angstrom Exponent

QC_Flag Handling

  • The intermediate file (_read_neph_qc.pkl/csv) contains the QC_Flag column
  • The final output has invalid data set to NaN and QC_Flag column removed

Notes

  • Provides information about aerosol optical properties and size distribution
  • Supports both normal and total scattering modes
  • Wavelength dependence follows Rayleigh scattering principle