Sentinel-5P OFFL CH4: Offline Methane

Dataset Availability

2019-02-08T08:13:16Z–2024-12-16T20:35:10Z

Dataset Provider

European Union/ESA/Copernicus

Earth Engine Snippet

ee.ImageCollection("COPERNICUS/S5P/OFFL/L3_CH4")

Revisit Interval

2 Days

Tags

climate copernicus esa eu knmi methane s5p sentinel sron tropomi

Description

OFFL/L3_CH4

This dataset provides offline high-resolution imagery of methane concentrations.

Methane (CH₄) is, after carbon dioxide (CO₂), the most important contributor to the anthropogenically enhanced greenhouse effect. Roughly three-quarters of methane emissions are anthropogenic and as such it is important to continue the record of satellite based measurements. TROPOMI aims at providing CH₄ column concentrations with high sensitivity to the Earth's surface, good spatiotemporal coverage, and sufficient accuracy to facilitate inverse modeling of sources and sinks. TROPOMI uses absorption information from the Oxygen-A Band (760nm) and the SWIR spectral range to monitor CH₄ abundances in the Earth's atmosphere. More information.

Currently, the following data quality issues are known, are not covered by the quality flags, and should be kept in mind when looking at the methane product and also at preliminary validation results. For more details, see the MPC VDAF website.

Filtering on qa_value < 0.5 does not remove all pixels considered bad. Some pixels with too low methane concentrations are still present:

• Single TROPOMI overpasses show stripes of erroneous CH₄ values in the flight direction.

• Not all pixels above inland water are filtered.

• Uncertainties for the XCH₄ is only based on the single sounding precision due to measurement noise. For applications requiring an overall uncertainty estimate, we propose to multiply the provided error by a factor 2, which reflects the scatter of single sounding errors in the TCCON validation.

• Data prior to November 2021 only provides XCH₄ over land, after which glint ocean observations were added.

• No data are present between 2022-07-26 and 2022-08-31 due to a provider outage.

OFFL L3 Product

To make our OFFL L3 products, we find which areas within the product's bounding box contain data by using a command like this:

harpconvert --format hdf5 --hdf5-compression 9
-a 'CH4_column_volume_mixing_ratio_dry_air_validity>50;derive(datetime_stop {time})'
S5P_OFFL_L2__CH4____20190223T202409_20190223T220540_07072_01_010202_20190301T221106.nc
grid_info.h5

We then merge all the data into one large mosaic (area-averaging values for pixels that may have different values for different times). From the mosaic, we create a set of tiles containing orthorectified raster data.

Example harpconvert invocation for one tile: harpconvert --format hdf5 --hdf5-compression 9 -a 'CH4_column_volume_mixing_ratio_dry_air_validity>50; derive(datetime_stop {time}); bin_spatial(2001, 50.000000, 0.01, 2001, -120.000000, 0.01); keep(CH4_column_volume_mixing_ratio_dry_air, aerosol_height, aerosol_optical_depth, sensor_azimuth_angle, sensor_zenith_angle, solar_azimuth_angle, solar_zenith_angle)' S5P_OFFL_L2__CH4____20190223T202409_20190223T220540_07072_01_010202_20190301T221106.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
CH4_column_volume_mixing_ratio_dry_air	Mol fraction	1285*	2405*	Column-averaged dry air mixing ratio of methane, as parts-per-billion
aerosol_height	m	906*	11251*	Aerosol height parameter in the CH4 retrieval
aerosol_optical_depth		0.00032*	0.2405*	aerosol optical thickness in the SWIR band
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	1*	60*	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	6*	70*	Zenith angle of the satellite at the ground pixel location (WGS84); angle measured away from the vertical.
CH4_column_volume_mixing_ratio_dry_air_bias_corrected	Mol fraction	1295*	2432*	Column-averaged dry air mixing ratio of methane, as parts-per-billion, corrected for surface albedo
CH4_column_volume_mixing_ratio_dry_air_uncertainty	Mol fraction	0*	10*	Uncertainty of the column averaged dry air mixing ratio of methane (1 sigma error)

* 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.

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Code Editor (JavaScript)

var collection = ee.ImageCollection('COPERNICUS/S5P/OFFL/L3_CH4')
  .select('CH4_column_volume_mixing_ratio_dry_air')
  .filterDate('2019-06-01', '2019-07-16');

var band_viz = {
  min: 1750,
  max: 1900,
  palette: ['black', 'blue', 'purple', 'cyan', 'green', 'yellow', 'red']
};

Map.addLayer(collection.mean(), band_viz, 'S5P CH4');
Map.setCenter(0.0, 0.0, 2);

Open in Code Editor

Sentinel-5P OFFL CH4: Offline Methane

OFFL/L3_CH4 This dataset provides offline high-resolution imagery of methane concentrations. Methane (CH4) is, after carbon dioxide (CO2), the most important contributor to the anthropogenically enhanced greenhouse effect. Roughly three-quarters of methane emissions are anthropogenic and as such it is important to continue the record of satellite based measurements. TROPOMI aims …

COPERNICUS/S5P/OFFL/L3_CH4, climate,copernicus,esa,eu,knmi,methane,s5p,sentinel,sron,tropomi

2019-02-08T08:13:16Z/2024-12-16T20:35:10Z

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