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AE33 Aethalometer

The AE33 is a multi-wavelength aethalometer used for measuring black carbon aerosol concentrations in the atmosphere.

AeroViz.rawDataReader.script.AE33.Reader 

Reader(path: Path | str, reset: bool | str = False, qc: bool | str = True, **kwargs)

Bases: AbstractReader

AE33 Aethalometer Data Reader.

A specialized reader for AE33 Aethalometer data files, which measure black carbon concentrations at seven wavelengths.

See full documentation at docs/source/instruments/AE33.md for detailed information on supported formats and QC procedures.

Attributes

nam class-attribute instance-attribute 

nam = 'AE33'

BC_COLUMNS class-attribute instance-attribute 

BC_COLUMNS = ['BC1', 'BC2', 'BC3', 'BC4', 'BC5', 'BC6', 'BC7']

ABS_COLUMNS class-attribute instance-attribute 

ABS_COLUMNS = ['abs_370', 'abs_470', 'abs_520', 'abs_590', 'abs_660', 'abs_880', 'abs_950']

CAL_COLUMNS class-attribute instance-attribute 

CAL_COLUMNS = ['abs_550', 'AAE', 'eBC']

MIN_BC class-attribute instance-attribute 

MIN_BC = 0

MAX_BC class-attribute instance-attribute 

MAX_BC = 20000

MIN_AAE class-attribute instance-attribute 

MIN_AAE = 0.7

MAX_AAE class-attribute instance-attribute 

MAX_AAE = 2.0

ERROR_STATES class-attribute instance-attribute 

ERROR_STATES = [1, 2, 3, 4, 16, 32, 384, 1024, 2048, 4096]

Functions

_raw_reader 

_raw_reader(file)

Read and parse raw AE33 Aethalometer data files.

_QC 

_QC(_df)

Perform quality control on AE33 Aethalometer raw data.

QC Rules Applied (raw data only)
  1. Status Error : Invalid instrument status codes
  2. Invalid BC : BC concentration outside 0-20000 ng/m³
  3. Insufficient : Less than 50% hourly data completeness

Note: AAE validation is done in _process() after calculation.

_process 

_process(_df)

Calculate absorption coefficients and validate derived parameters.

Processing Steps
  1. Calculate absorption coefficients at each wavelength
  2. Calculate AAE (Absorption Ångström Exponent)
  3. Calculate eBC (equivalent Black Carbon)
  4. Validate AAE range and update QC_Flag

Parameters:

Name Type Description Default
_df DataFrame

Quality-controlled DataFrame with BC columns and QC_Flag

 required

Returns:

Type Description
DataFrame

DataFrame with absorption coefficients, AAE, eBC, and updated QC_Flag

Data Format

  • File format: Tab-delimited text file (.dat)
  • Sampling frequency: 1 minute
  • File naming pattern: [!ST|!CT|!FV]*[!log]_AE33*.dat
    • log file is not included ex. AE33_log_AE33-S05-00494_20220401.dat
  • Header: 5 rows of header information
  • Data columns: 67 columns including timestamp and measurements

Measurement Parameters

The AE33 provides black carbon concentration measurements at seven wavelengths:

Column Wavelength Description
BC1 370 nm UV channel
BC2 470 nm Blue channel
BC3 520 nm Green channel
BC4 590 nm Yellow channel
BC5 660 nm Red channel
BC6 880 nm Near-IR channel (reference)
BC7 950 nm IR channel

Data Processing

Data Reading

  • Automatically skips the first 5 rows of header information
  • Parses timestamps from date and time columns (columns 0 and 1)
  • Extracts black carbon concentration data for seven wavelengths
  • Strips semicolons from column names
  • Validates file size (warns if < 550KB)

Quality Control

The AE33 reader uses the declarative QCFlagBuilder system with the following rules:

+-----------------------------------------------------------------------+
|                            _QC() Pipeline                             |
+-----------------------------------------------------------------------+
|                                                                       |
|  [Pre-process] Calculate absorption coefficients, AAE, eBC            |
|       |                                                               |
|       v                                                               |
|  +---------------------+    +---------------------+                   |
|  | Rule: Status Error  |    | Rule: Invalid BC    |                   |
|  +---------------------+    +---------------------+                   |
|  | Bitwise status      |    | BC <= 0 OR          |                   |
|  | code filtering      |    | BC > 20000 ng/m³    |                   |
|  +---------------------+    +---------------------+                   |
|           |                          |                                |
|           v                          v                                |
|  +---------------------+    +---------------------+                   |
|  | Rule: Invalid AAE   |    | Rule: Insufficient  |                   |
|  +---------------------+    +---------------------+                   |
|  | AAE < -2.0 OR       |    | < 50% hourly data   |                   |
|  | AAE > -0.7          |    | completeness        |                   |
|  +---------------------+    +---------------------+                   |
|                                                                       |
+-----------------------------------------------------------------------+

QC Rules Applied

Rule Condition Description
Status Error Bitwise status code check Invalid instrument status codes detected
Invalid BC BC ≤ 0 OR BC > 20000 ng/m³ BC concentration outside valid range
Invalid AAE AAE < -2.0 OR AAE > -0.7 Angstrom exponent outside valid range
Insufficient < 50% hourly data Less than 50% hourly data completeness

Error Status Codes

Code Description
1 Tape advance, fast calibration, warm-up
2 First measurement – obtaining ATN0
3 Stopped
4 Flow low/high by more than 0.5 LPM
16 Calibrating LED
32 Calibration error (at least one channel OK)
384 Tape error (tape not moving, end of tape)
1024 Stability test
2048 Clean air test
4096 Optical test

Output Data

The final output (output_ae33.csv) contains the following columns:

Column Unit Description
BC1-BC7 ng/m³ Black carbon at 7 wavelengths
abs_370-950 Mm⁻¹ Absorption coefficients
abs_550 Mm⁻¹ Interpolated absorption at 550nm
AAE - Absorption Angstrom Exponent
eBC ng/m³ Equivalent black carbon

QC_Flag Handling

  • The intermediate file (_read_ae33_qc.pkl/csv) contains the QC_Flag column
  • The final output has invalid data set to NaN and QC_Flag column removed

Notes

  • The AE33 provides real-time black carbon concentration measurements
  • Useful for distinguishing between biomass burning and fossil fuel combustion
  • Files smaller than 550KB may indicate incomplete data