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This formaldehyde (HCHO) image service provides information on the amount of formaldehyde (molecules per square centimeter) in the atmosphere, available as approximately one-hour scans for daylight hours over North America, from August 2023 to present. These data are collected by the Tropospheric Emissions: Monitoring of Pollution (TEMPO). These data should be considered as provisional products, which are potentially ready for testing by operational users and may be suitable for scientific publication.
Formaldehyde Overview
Multiple sources contribute to ambient formaldehyde including but not limited to wildfire emissions, industrial activities, and secondary production resulting from the oxidation of other compounds emitted by industries and vegetations. Formaldehyde is a carcinogenic, hazardous air pollutant. While ambient formaldehyde concentrations are usually below U.S. federal recommendations, ambient exposure can cause health issues in people. In addition to measuring formaldehyde for its impacts on human health, satellite formaldehyde observations are also extremely valuable in understanding atmospheric chemistry and production of ground-level ozone.
Layer Overview
The Tropospheric Emissions: Monitoring of Pollution (TEMPO) Formaldehyde Vertical Column layer provides information on the amount of formaldehyde in the atmosphere as a vertical column density, calculated in molecules per square centimeter (molecules/cm^2). In other words, the total number of formaldehyde molecules present in the atmosphere from the Earth's surface to the top of the atmosphere over an area of one square centimeter. Typical values range from 0 to 6e16 molecules/cm^2, though certain events like wildfires may cause these limits to be exceeded. Formaldehyde Level 3 files provide trace gas information on a regular grid consisting of 0.02° x 0.02° grid points across the TEMPO field of regard covering the continental United States (CONUS), much of Mexico, Canada, and the Caribbean. Level 3 files are derived by combining information from all Level 2 files constituting a TEMPO East-West scan cycle, using an area-weighted re-gridding approach. The data have been converted from their native file format (netCDF4) to Cloud Raster Format (CRF).
Note: The information shown here is total column density (molecules per unit area for the whole vertical column of the atmosphere), not a concentration. Atmospheric concentration refers to the amount of trace gas (e.g., formaldehyde) in a specific point (in this case altitude). Conversion from total column density to atmospheric concentration requires additional information, such as the state of the atmosphere and the vertical distribution of the column, which are not provided in this layer. The use of this layer to derive atmospheric concentrations of formaldehyde is discouraged for the non-specialist.
Temporal Coverage
The temporal resolution of a nominal scan is approximately one hour during daylight hours, with more frequent scans in the morning over the eastern portion of the field of regard and in the evenings over the western portion of the field of regard. Each image is presented with the starting timestamp of the corresponding TEMPO scan. Due to the nature of the TEMPO instrument's east to west scanning pattern, each image is a composite of measurements taken over a period of 40-60 minutes, depending on the spatial coverage of the scan. Data are available from August 2023 to present and updated daily with the previous day's data.Geographic Coverage
Imagery is available for the TEMPO field of regard covering the continental United States (CONUS), much of Mexico, Canada, and the Caribbean. This layer is presented in its native geographic coordinate system (WGS 1984) and resolution. The sensor's native spatial resolution is ~2 km x 4.75 km at the center of TEMPO's field of regard (33.7°N, 91.7°W) and the Level 3 product resolution is 0.02 x 0.02 degrees.
Data Filtering
The layer is filtered to remove low-quality pixels using the main data quality flag (removing low confidence measurements), solar zenith angle (removing data retrieved at high solar zenith angles), and effective cloud fraction (removing where clouds obscure the column) variables. The filters applied are set to remove pixels based on the following: main_data_quality_flag > 1,eff_cloud_fraction > 0.5, and solar_zenith_angle > 80.
Data Validation
These data should be considered as provisional products per the Provisional Product Maturity level defined in the TEMPO validation plan. These data are at provisional maturity, which means that product performance has been demonstrated through a large, but still (seasonally or otherwise) limited number of independent measurements. The analysis is sufficient for limited qualitative determinations of product fitness-for-purpose, and the product is potentially ready for testing by operational users and may be suitable for scientific publication. Users may consult the TEMPO User Guide for descriptions of the data and associated known issues.
Recommended Usage Notes
When viewing the image service in the ESRI online map viewer, it is recommended to use the multidimensional slider rather than the default time slider. The multidimensional slider can be accessed via the multidimensional icon in the right-hand menu.
Mission Overview
The TEMPO instrument is a grating spectrometer, sensitive to visible (VIS) and ultraviolet (UV) wavelengths of light with a spectral range of 290-490 + 540-740 nm and 0.6 nm spectral resolution. The TEMPO instrument is attached to the Earth-facing side of a commercial telecommunications satellite (Intelsat 40e) in geostationary orbit over 91° W longitude (about 22,000 miles above Earth's equator). This allows TEMPO to maintain a continuous view of North America so that the instrument's light-collecting mirror can make a complete east-to-west scan of the field of regard hourly during daylight hours. By measuring sunlight reflected and scattered from the Earth's surface and atmosphere back to the instrument's detectors, TEMPO's ultraviolet and visible light sensors provide measurements of ozone, nitrogen dioxide, formaldehyde, and other constituents involved in the chemical dynamics of Earth's atmosphere.The primary mission objectives of TEMPO involve understanding the dynamics of air quality, pollution sources, and their impact on climate change. By providing near real-time data and comprehensive atmospheric composition measurements, TEMPO will assist scientists in studying pollution patterns, evaluating the efficacy of environmental policies, and predicting future trends in air quality.
Contact
For inquiries about this service, please contact larc-dl-asdc-tempo@mail.nasa.gov or post/view questions on the Earthdata Forum