Sentinel-5P NRTI AER AI: Near Real-Time UV Aerosol Index

Dataset Availability: 2018-07-10T11:17:44Z–2024-12-20T09:35:07Z
Dataset Provider: European Union/ESA/Copernicus
Earth Engine Snippet: ee.ImageCollection("COPERNICUS/S5P/NRTI/L3_AER_AI")

Revisit Interval: 2 Days
Tags: aai aerosol air-quality copernicus esa eu knmi pollution s5p sentinel tropomi uvai

Description

NRTI/L3_AER_AI

This dataset provides near real-time high-resolution imagery of the UV Aerosol Index (UVAI), also called the Absorbing Aerosol Index (AAI).

The AAI is based on wavelength-dependent changes in Rayleigh scattering in the UV spectral range for a pair of wavelengths. The difference between observed and modelled reflectance results in the AAI. When the AAI is positive, it indicates the presence of UV-absorbing aerosols like dust and smoke. It is useful for tracking the evolution of episodic aerosol plumes from dust outbreaks, volcanic ash, and biomass burning.

The wavelengths used have very low ozone absorption, so unlike aerosol optical thickness measurements, AAI can be calculated in the presence of clouds. Daily global coverage is therefore possible.

For this L3 AER_AI product, the absorbing_aerosol_index is calculated with a pair of measurements at the 354 nm and 388 nm wavelengths.

NRTI L3 Product

To make our NRTI L3 products, we use harpconvert to grid the data.

Example harpconvert invocation for one tile: harpconvert --format hdf5 --hdf5-compression 9 -a 'absorbing_aerosol_index_validity>50;derive(datetime_stop {time}); bin_spatial(2001, 50.000000, 0.01, 2001, -120.000000, 0.01); keep(absorbing_aerosol_index,sensor_altitude,sensor_azimuth_angle, sensor_zenith_angle,solar_azimuth_angle,solar_zenith_angle)' S5P_NRTI_L2__AER_AI_20181113T080042_20181113T080542_05618_01_010200_20181113T083707.nc output.h5

Sentinel-5 Precursor

Sentinel-5 Precursor is a satellite launched on 13 October 2017 by the European Space Agency to monitor air pollution. The onboard sensor is frequently referred to as Tropomi (TROPOspheric Monitoring Instrument).

All of the S5P datasets, except CH₄, have two versions: Near Real-Time (NRTI) and Offline (OFFL). CH₄ is available as OFFL only. The NRTI assets cover a smaller area than the OFFL assets, but appear more quickly after acquisition. The OFFL assets contain data from a single orbit (which, due to half the earth being dark, contains data only for a single hemisphere).

Because of noise on the data, negative vertical column values are often observed in particular over clean regions or for low SO2 emissions. It is recommended not to filter these values except for outliers, i.e. for vertical columns lower than -0.001 mol/m^2.

The original Sentinel 5P Level 2 (L2) data is binned by time, not by latitude/longitude. To make it possible to ingest the data into Earth Engine, each Sentinel 5P L2 product is converted to L3, keeping a single grid per orbit (that is, no aggregation across products is performed).

Source products spanning the antimeridian are ingested as two Earth Engine assets, with suffixes _1 and _2.

The conversion to L3 is done by the harpconvert tool using the bin_spatial operation. The source data is filtered to remove pixels with QA values less than:

80% for AER_AI
75% for the tropospheric_NO2_column_number_density band of NO2
50% for all other datasets except for O3 and SO2

The O3_TCL product is ingested directly (without running harpconvert).

Bands

Resolution
1113.2 meters

Bands

Name	Units	Min	Max	Description
`absorbing_aerosol_index`		-25*	39*	A measure of the prevalence of aerosols in the atmosphere. The UVAI index is based on spectral contrast in the ultraviolet (UV) spectral range for a given wavelength pair, where the difference between observed and modeled reflectance results in a residual value. When this residual is positive it indicates the presence of UV-absorbing aerosols, like dust and smoke, and is often referred to as the Absorbing Aerosol Index (AAI). Clouds yield near-zero residual values and strongly negative residual values can be indicative of the presence of non-absorbing aerosols including sulfate aerosols. Unlike satellite-based aerosol optical thickness measurements, AAI can also be calculated in the presence of clouds so that daily, global coverage is possible. This is ideal for tracking the evolution of episodic aerosol plumes consisting of desert dust, ash from volcanic eruptions, and smoke from biomass burning. See further details in the ATBD.
`sensor_altitude`	m	828543*	856078*	Altitude of the satellite with respect to the geodetic sub-satellite point (WGS84).
`sensor_azimuth_angle`	deg	-180*	180*	Azimuth angle of the satellite at the ground pixel location (WGS84); angle measured East-of-North.
`sensor_zenith_angle`	deg	0.09*	67*	Zenith angle of the satellite at the ground pixel location (WGS84); angle measured away from the vertical.
`solar_azimuth_angle`	deg	-180*	180*	Azimuth angle of the Sun at the ground pixel location (WGS84); angle measured East-of-North.
`solar_zenith_angle`	deg	8*	88*	Zenith angle of the satellite at the ground pixel location (WGS84); angle measured away from the vertical.

* estimated min or max value

Image Properties

Image Properties

Name	Type	Description
ALGORITHM_VERSION	STRING	The algorithm version used in L2 processing. It is separate from the processor (framework) version, to accommodate different release schedules for different products.
BUILD_DATE	STRING	The date, expressed as milliseconds since 1 Jan 1970, when the software used to perform L2 processing was built.
HARP_VERSION	INT	The version of the HARP tool used to grid the L2 data into an L3 product.
INSTITUTION	STRING	The institution where data processing from L1 to L2 was performed.
L3_PROCESSING_TIME	INT	The date, expressed as milliseconds since 1 Jan 1970, when Google processed the L2 data into L3 using harpconvert.
LAT_MAX	DOUBLE	The maximum latitude of the asset (degrees).
LAT_MIN	DOUBLE	The minimum latitude of the asset (degrees).
LON_MAX	DOUBLE	The maximum longitude of the asset (degrees).
LON_MIN	DOUBLE	The minimum longitude of the asset (degrees).
ORBIT	INT	The orbit number of the satellite when the data was acquired.
PLATFORM	STRING	Name of the platform which acquired the data.
PROCESSING_STATUS	STRING	The processing status of the product on a global level, mainly based on the availability of auxiliary input data. Possible values are "Nominal" and "Degraded".
PROCESSOR_VERSION	STRING	The version of the software used for L2 processing, as a string of the form "major.minor.patch".
PRODUCT_ID	STRING	Id of the L2 product used to generate this asset.
PRODUCT_QUALITY	STRING	Indicator that specifies whether the product quality is degraded or not. Allowed values are "Degraded" and "Nominal".
SENSOR	STRING	Name of the sensor which acquired the data.
SPATIAL_RESOLUTION	STRING	Spatial resolution at nadir. For most products this is `3.5x7km2`, except for `L2__O3__PR`, which uses `28x21km2`, and `L2__CO____` and `L2__CH4___`, which both use `7x7km2`. This attribute originates from the CCI standard.
TIME_REFERENCE_DAYS_SINCE_1950	INT	Days from 1 Jan 1950 to when the data was acquired.
TIME_REFERENCE_JULIAN_DAY	DOUBLE	The Julian day number when the data was acquired.
TRACKING_ID	STRING	UUID for the L2 product file.

Terms of Use

Terms of Use

The use of Sentinel data is governed by the Copernicus Sentinel Data Terms and Conditions.

Explore with Earth Engine

Code Editor (JavaScript)

var collection = ee.ImageCollection('COPERNICUS/S5P/NRTI/L3_AER_AI')
  .select('absorbing_aerosol_index')
  .filterDate('2019-06-01', '2019-06-06');

var band_viz = {
  min: -1,
  max: 2.0,
  palette: ['black', 'blue', 'purple', 'cyan', 'green', 'yellow', 'red']
};

Map.addLayer(collection.mean(), band_viz, 'S5P Aerosol');
Map.setCenter(-118.82, 36.1, 5);

Open in Code Editor

Sentinel-5P NRTI AER AI: Near Real-Time UV Aerosol Index

NRTI/L3_AER_AI This dataset provides near real-time high-resolution imagery of the UV Aerosol Index (UVAI), also called the Absorbing Aerosol Index (AAI). The AAI is based on wavelength-dependent changes in Rayleigh scattering in the UV spectral range for a pair of wavelengths. The difference between observed and modelled reflectance results in …

COPERNICUS/S5P/NRTI/L3_AER_AI, aai,aerosol,air-quality,copernicus,esa,eu,knmi,pollution,s5p,sentinel,tropomi,uvai

2018-07-10T11:17:44Z/2024-12-20T09:35:07Z

Google Earth Engine

https://developers.google.com/earth-engine/datasets