The Hyper-Angular Rainbow Polarimeter #2 (HARP2) instrument, flying aboard the PACE spacecraft, is a wide-angle imaging polarimeter designed to measure aerosol particles and clouds, as well as properties of land and water surfaces. HARP2 will combine data from multiple along-track viewing angles (up to 60), four spectral bands in the visible and near infrared ranges, and three angles of linear polarization to measure the microphysical properties of the atmospheric particles including their size distribution, amount, refractive indices and particle shape.

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OB_CLOUD Short Name: PACE_HARP2_L1B_AST4 Version ID: 3 Unique ID: C3555841895-OB_CLOUD

The Hyper-Angular Rainbow Polarimeter #2 (HARP2) instrument, flying aboard the PACE spacecraft, is a wide-angle imaging polarimeter designed to measure aerosol particles and clouds, as well as properties of land and water surfaces. HARP2 will combine data from multiple along-track viewing angles (up to 60), four spectral bands in the visible and near infrared ranges, and three angles of linear polarization to measure the microphysical properties of the atmospheric particles including their size distribution, amount, refractive indices and particle shape.

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OB_CLOUD Short Name: PACE_HARP2_L1C_AST4 Version ID: 3 Unique ID: C3555841907-OB_CLOUD

MAPOL_OCEAN provides simultaneous aerosol and ocean color products using the Fast Multi-Angle Polarimetric Ocean and Land algorithm (FastMAPOL). The retrievals jointly solve for aerosol and ocean parameters with a coupled atmosphere and ocean vector radiative-transfer model, accelerated by deep neural networks to improve speed and accuracy. The retrieved aerosol properties are then used to derive angular water leaving signals through multi-angle atmospheric corrections. Use these products for advanced aerosol and ocean color studies, cross-sensor and cross-algorithm data product analysis. Core geophysical variables in this suite include: • Rrs1/Rrs2 — Angular remote sensing reflectance before and after BRDF correction (sr⁻¹) • chla_mapol — Chlorophyll-a concentration (mg m⁻³) • aot / aot_fine / aot_coarse — Aerosol optical thickness for total/fine/coarse mode (unitless) • ssa / ssa_fine / ssa_coarse — Aerosol single scattering albedo for total/fine/coarse mode (unitless) • fmf / fvf — Aerosol fine mode fraction and fine mode volume fraction (unitless) • angstrom — Aerosol Ångström exponent (unitless; reported for 440–670 nm and 440–870 nm) • alh — Aerosol layer height (km) • reff_fine / reff_coarse — Aerosol effective radius for fine/coarse mode (µm) • veff_fine / veff_coarse — Aerosol effective variance for fine/coarse mode (unitless) • sph / sph_fine / sph_coarse — Aerosol spherical fraction for total/fine/coarse mode (unitless) • mr / mi — Real and imaginary parts of aerosol refractive index (unitless; total/fine/coarse modes available) • vd — Aerosol volume density (µm³ µm⁻²; fine/coarse modes and submodes also available) • wind_speed — Ocean surface wind speed (m s⁻¹)

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OB_CLOUD Short Name: PACE_HARP2_L2_MAPOL_OCEAN_NRT Version ID: 3.0 Unique ID: C3652817338-OB_CLOUD

The CLOUD_GPC suite provides cloud properties derived from the GISS Polarimetric Cloud (GPC) algorithm, along with additional variables obtained through combination with the OCI CLOUD suite. Given the novelty of implementing a polarimetric algorithm on a global scale, note that several experimental variables—particularly those intended for diagnostic purposes and future refinement—are included and may change in subsequent, more mature versions. Core geophysical variables in this suite include: • cloud_droplet_effective_radius / variance - Cloud droplet effective radius and variance (µm, unitless) • cloud_droplet_number_concentration - Droplet number concentration (combining with OCI CLOUD) (cm⁻³) • cloud_liquid_water_path - Cloud liquid water path (combining with OCI CLOUD) (g m⁻²) • cloud_liquid_index - Index measuring polarized primary bow strength (unitless) • cloud_optical_thickness - Cloud optical thickness (from OCI CLOUD) (unitless) • cloud_bow_extinction_cross_section_Xnm – 355/532 nm extinction cross section based on Cloud Bow retrievals • cloud_bow_lidar_ratio_Xnm – 355/532 lidar ratios based on Cloud Bow retrievals • cloud_rft_* - Retrievals from Rainbow Fourier Transform (experimental and exploratory, intended for future substantial refinements) • cloud_top_properties - Cloud top altitude (m), pressure (hPa), and temperature (K) (from OCI CLOUD)

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OB_CLOUD Short Name: PACE_HARP2_L2_CLOUD_GPC_NRT Version ID: 3.0 Unique ID: C3600169974-OB_CLOUD

MAPOL_OCEAN provides simultaneous aerosol and ocean color products using the Fast Multi-Angle Polarimetric Ocean and Land algorithm (FastMAPOL). The retrievals jointly solve for aerosol and ocean parameters with a coupled atmosphere and ocean vector radiative-transfer model, accelerated by deep neural networks to improve speed and accuracy. The retrieved aerosol properties are then used to derive angular water leaving signals through multi-angle atmospheric corrections. Use these products for advanced aerosol and ocean color studies, cross-sensor and cross-algorithm data product analysis. Core geophysical variables in this suite include: • Rrs1/Rrs2 — Angular remote sensing reflectance before and after BRDF correction (sr⁻¹) • chla_mapol — Chlorophyll-a concentration (mg m⁻³) • aot / aot_fine / aot_coarse — Aerosol optical thickness for total/fine/coarse mode (unitless) • ssa / ssa_fine / ssa_coarse — Aerosol single scattering albedo for total/fine/coarse mode (unitless) • fmf / fvf — Aerosol fine mode fraction and fine mode volume fraction (unitless) • angstrom — Aerosol Ångström exponent (unitless; reported for 440–670 nm and 440–870 nm) • alh — Aerosol layer height (km) • reff_fine / reff_coarse — Aerosol effective radius for fine/coarse mode (µm) • veff_fine / veff_coarse — Aerosol effective variance for fine/coarse mode (unitless) • sph / sph_fine / sph_coarse — Aerosol spherical fraction for total/fine/coarse mode (unitless) • mr / mi — Real and imaginary parts of aerosol refractive index (unitless; total/fine/coarse modes available) • vd — Aerosol volume density (µm³ µm⁻²; fine/coarse modes and submodes also available) • wind_speed — Ocean surface wind speed (m s⁻¹)

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OB_CLOUD Short Name: PACE_HARP2_L3M_MAPOL_OCEAN_NRT Version ID: 3.0 Unique ID: C3974353160-OB_CLOUD