Google Earth Engine ——数据全解析专辑（COPERNICUS/S5P/OFFL/L3_AER_AI和LH）气溶胶指数数据集

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发布于 2024-02-02 11:13:14

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发布于 2024-02-02 11:13:14

OFFL/L3_AER_AI

This dataset provides offline 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. The COPERNICUS/S5P/OFFL/L3_SO2 product has the absorbing_aerosol_index calculated using the 340 nm and 380 nm wavelengths.

OFFL/L3_AER_AI
该数据集提供了紫外线气溶胶指数 (UVAI) 的离线高分辨率图像，也称为吸收气溶胶指数 (AAI)。

AAI 基于一对波长的 UV 光谱范围内瑞利散射的波长相关变化。观察到的和模拟的反射率之间的差异导致了 AAI。当 AAI 为正值时，表明存在吸收紫外线的气溶胶，如灰尘和烟雾。它可用于跟踪粉尘爆发、火山灰和生物质燃烧引起的偶发气溶胶羽流的演变。

所使用的波长对臭氧的吸收非常低，因此与气溶胶光学厚度测量不同，AAI 可以在有云的情况下计算。因此，每日全球报道是可能的。

对于此 L3 AER_AI 产品，吸收气溶胶指数是通过在 354 nm 和 388 nm 波长处进行的一对测量计算得出的。 COPERNICUS/S5P/OFFL/L3_SO2 产品具有使用 340 nm 和 380 nm 波长计算的吸收气溶胶指数。

OFFL L3 Product

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

harpconvert --format hdf5 --hdf5-compression 9
-a 'absorbing_aerosol_index_validity>50;derive(datetime_stop {time})'
S5P_OFFL_L2__AER_AI_20181030T213916_20181030T232046_05427_01_010200_20181105T210529.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 '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_OFFL_L2__AER_AI_20181030T213916_20181030T232046_05427_01_010200_20181105T210529.nc
output.h5

Dataset Availability

2018-07-04T13:34:21 - 2021-09-04T00:00:00

Dataset Provider

European Union/ESA/Copernicus

Collection Snippet

ee.ImageCollection("COPERNICUS/S5P/OFFL/L3_AER_AI")

Resolution

0.01 degrees

Bands Table

Name	Description	Min*	Max*	Units
absorbing_aerosol_index	A measure of the prevalence of aerosols in the atmosphere, calculated by [this equation](https://earth.esa.int/web/sentinel/technical-guides/sentinel-5p/level-2/aerosol-index) using the 354/388 wavelength pair.	-21	39
sensor_altitude	Altitude of the satellite with respect to the geodetic sub-satellite point (WGS84).	828543	856078	m
sensor_azimuth_angle	Azimuth angle of the satellite at the ground pixel location (WGS84); angle measured East-of-North.	-180	180	degrees
sensor_zenith_angle	Zenith angle of the satellite at the ground pixel location (WGS84); angle measured away from the vertical.	0.098	66.87	degrees
solar_azimuth_angle	Azimuth angle of the Sun at the ground pixel location (WGS84); angle measured East-of-North.	-180	180	degrees
solar_zenith_angle	Zenith angle of the satellite at the ground pixel location (WGS84); angle measured away from the vertical.	8	88	degrees

* = Values are estimated

影像属性：

Name	Type	Description
ALGORITHM_VERSION	String	The algorithm version used in L2 processing. It's 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.

代码：

var collection = ee.ImageCollection('COPERNICUS/S5P/OFFL/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);