MERRA2AODANAProcessor
Overview
The MERRA2AODANAProcessor module is designed to extract and convert aerosol optical depth data (AODANA) from NASA’s MERRA-2 atmospheric reanalysis dataset. Specifically, it focuses on transforming .nc4 files (NetCDF format) into structured .csv outputs for downstream dust storm fusion analysis and visualization.
Unlike DUSMASS, which measures surface-level dust mass concentration, AODANA represents the total column aerosol optical depth—a key variable for estimating aerosol load in the atmosphere. Including this variable provides a second dimension to storm confidence assessments, especially in dusty but optically active regions.
Functionality
This module performs the following tasks:
Iterates through a directory of .nc4 files containing daily MERRA-2 AODANA data.
Extracts metadata such as: - Time (hourly UTC timestamps) - Latitude and longitude grid - AODANA values for each grid point
Filters out invalid or missing values (e.g., fill values)
Writes the processed data into .csv files, one per day, preserving temporal and spatial resolution.
Scientific Motivation
AODANA is a critical metric in remote sensing and atmospheric science as it:
Provides insight into how optically thick the atmosphere is due to aerosols
Helps distinguish between fine particulate pollution, sea salt, and dust
Complements DUSMASS by adding a vertical optical measurement over surface-based mass estimation
This dual perspective is particularly useful when fusing datasets in modules like FusionStormDetector, which require strong evidence from both mass and optical profiles to confirm a dust storm.
Integration with Other Modules
Used in conjunction with MERRA2DUSMASSProcessor for fusion-based blob detection in FusionStormDetector.
May also be compared with satellite instruments or METARs for cross-validation.
CSVs generated here are expected in the same format as DUSMASS files to allow seamless pairing and temporal matching.
File Structure
Each generated .csv file contains the following fields:
latitude: Grid latitude in degrees
longitude: Grid longitude in degrees
datetime: UTC time (with hourly resolution)
AODANA: Aerosol Optical Depth at 550 nm
The filename format is standardized as:YYYYMMDD.csv
where YYYYMMDD corresponds to the date of the original .nc4 file.
Usage Considerations
This processor assumes a consistent grid and variable name (AODANA) in the MERRA-2 files.
Missing data (e.g., due to quality filtering or oceanic regions) are excluded from the CSV output.
The output folder is automatically created if it doesn’t exist.
Dependencies
netCDF4
pandas
numpy
os and glob for file handling
tqdm for progress bars