CALIPSO¶

Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) CALIOP Level 2 and Level 3 aerosol and cloud profiles

Discontinued

At a glance¶

Note on period: L1 and L2 V5.00 cover 2006-06-12 to 2023-06-30, and the L3 monthly products June 2006 to June 2023. Science observations paused while the orbit was lowered from 705 km to 688 km on 13 September 2018 and resumed on 25 September. The earlier L3 tropospheric aerosol versions (V4.20, V4.21) only run to December 2021.

Overview¶

CALIPSO, launched by NASA and CNES in 2006, carried the CALIOP lidar, which sliced vertically through the atmosphere at 532 and 1064 nm for 17 years to observe the height, thickness, type and extinction of clouds and aerosols. Its flagship products are the Level 2 layer and profile data, which give a curtain beneath the ground track, and the Level 3 tropospheric and stratospheric aerosol products, which aggregate them on a monthly 2° × 5° grid. It became a reference for aerosol vertical distribution, dust and smoke transport, polar stratospheric clouds and evaluation of model vertical structure; V5.00, a reprocessing of the full record released in 2025 after the mission ended, is the current version.

What changes with the successor¶

CALIOP V4.51 → CALIOP V5.00¶

Transition: 2025-10

A reprocessing of the full 2006–2023 record that strengthens the handling of low-energy laser shots (LEM) and revises the Level 3 screening. The screening changes alone can shift the global mean Level 3 tropospheric aerosol optical depth (AOD) by more than 10%, so the two versions must not be mixed.

Sources: CALIOP Level 2 Profile Data Description and Quality Summary (V5.00, 2026-01-30) · CALIOP Level 3 Tropospheric Aerosol Profile Data Description and Quality Summary (V5.00) · CALIOP Level 2 Layer Data Description and Quality Summary (V5.00)

CALIPSO CALIOP → EarthCARE ATLID¶

Transition: 2024-08

The record moves from an elastic-backscatter lidar at 532 and 1064 nm (CALIOP) to a 355 nm high-spectral-resolution lidar (ATLID). ATLID separates particle (Mie) and molecular (Rayleigh) returns, so it retrieves extinction and backscatter independently, whereas CALIOP had to assume a lidar ratio for each aerosol type.

Sources: Wehr et al. (2023) The EarthCARE mission – science and system overview, AMT · ESA Earth Online — ATLID instrument description · CALIPSO Data User's Guide FAQ · CALIPSO Final Report (NASA/TP-20260000771)

Compare the two side by side

Available variables¶

HDF4 SDS names as given in the V5.00 quality summaries and the V4.20 data description. Most fill values are -9999, with special values such as -333 (extinction retrieval failed) and -111 (low-energy shots). Aerosol subtype has no variable of its own; it is in bits 9–11 of Atmospheric_Volume_Description (profiles) and Feature_Classification_Flags (layers).

instantaneous mean accumulated maximum minimum static — instantaneous: value at the time stamp · mean/accumulated/maximum/minimum: over the indicated interval · static: does not change with time

L2 aerosol profile (CAL_LID_L2_05kmAPro, 5 km)¶

L2 aerosol layer (CAL_LID_L2_05kmALay, 5 km)¶

L3 tropospheric aerosol (CAL_LID_L3_Tropospheric_APro_*, 2° × 5° monthly)¶

The full variable list is in the official documentation.

How to get the data¶

• NASA ASDC — CALIPSO data holdings — Web (product pages → Earthdata Search, direct download)
  • As checked in 2026-10, the project page list shows versions only up to V4.51. Find the V5.00 collections in Earthdata Search or CMR.
• NASA Earthdata Search — CAL_LID_L2_05kmAPro-Standard-V5-00 — Earthdata Search / earthaccess (HDF4)
  • A free Earthdata Login is required. The layer product is CAL_LID_L2_05kmALay-Standard-V5-00 and Level 3 includes CAL_LID_L3_Tropospheric_APro_AllSky-Standard-V5-00.
• CMR virtual directory (L2 aerosol profile V5.00) — HTTPS directory (wget/curl, Earthdata Login)
• CALIPSO browse images (per-orbit curtain previews) — Web
  • Useful for picking cases from orbit curtains before downloading (V4.51 based).

Example code¶

Downloads a V5.00 Level 2 aerosol profile file with earthaccess and reads it with pyhdf. The first run asks for your Earthdata credentials. CALIPSO files are HDF4, which xarray cannot open directly.

# pip install earthaccess pyhdf numpy
import earthaccess
import numpy as np
from pyhdf.SD import SD, SDC

earthaccess.login()
results = earthaccess.search_data(
    short_name="CAL_LID_L2_05kmAPro-Standard-V5-00", version="V5-00",
    temporal=("2021-03-15", "2021-03-16"),
    bounding_box=(115, 30, 135, 45),          # (west, south, east, north) — East Asia
)
files = earthaccess.download(results[:1], "./calipso")

f = SD(files[0], SDC.READ)
ext = f.select("Extinction_Coefficient_532")[:].astype(float)   # (profiles, 399 altitudes), km-1
qc = f.select("Extinction_QC_Flag_532")[:]
cad = f.select("CAD_Score")[:]
alt = f.select("Lidar_Data_Altitudes")[:]                       # a dataset from V5.00 on (km)
ext[ext < 0] = np.nan                                          # drop -9999, -333, -111 and other special values
print(ext.shape, alt[:3], np.nanmax(ext))

Practical tips¶

• Do not average extinction as is. First remove special values such as -9999 (no particulates), -333 (retrieval failed), -111 (low energy) and -444 (suspect cloud clearing), low-confidence features with CAD_Score between −20 and 0, and rejected Extinction_QC_Flag_532 values.
• CAD_Score is negative for aerosol and positive for cloud. A magnitude of 20 or less means low confidence.
• Below fully attenuating cloud or dust layers there is no signal, so the column optical depth only reaches the base of the lowest visible layer. Ignoring opacity leads to underestimated AOD.
• CALIOP AOD is at 532 nm and depends on the assumed lidar ratio. When comparing with MODIS or AERONET (550 or 500 nm), consider both the wavelength difference and the lidar-ratio uncertainty.
• Daytime data are noisy and easily miss tenuous aerosol layers. Climatologies and trends are often checked against night-time data first.
• In the South Atlantic Anomaly, radiation noise and low-energy shots cut V5.00 Level 3 samples by 80–100%, leaving many fill cells.
• The V4.20 data description lists the tropospheric AOD as Column_Optical_Depth_Aerosols_532. If you also use older files, check the SDS names for each version.
• After the orbit was lowered from 705 km to 688 km in September 2018 to form the C-Train with CloudSat, CALIPSO no longer followed the A-Train (Aqua, Aura) track. Re-check space-time collocation distances for MODIS or OMI matchups after that date.

Notices and change history¶

References for your paper¶

Dataset citation¶

L2 aerosol profile V5-00 — DOI 10.5067/CALIOP/CALIPSO/CAL_LID_L2_05kmAPro-Standard-V5-00

@misc{calipso_l2_apro_v500,
  author    = {Winker, David},
  title     = {{CALIPSO} Lidar Level 2 Aerosol Profile, {V5-00}},
  year      = {2026},
  publisher = {NASA Langley Atmospheric Science Data Center Distributed Active Archive Center},
  doi       = {10.5067/CALIOP/CALIPSO/CAL_LID_L2_05kmAPro-Standard-V5-00}
}

L2 5 km aerosol layer V5-00 — DOI 10.5067/CALIOP/CALIPSO/CAL_LID_L2_05kmALay-Standard-V5-00

@misc{calipso_l2_alay_v500,
  author    = {Winker, David},
  title     = {{CALIPSO} Lidar Level 2 5 km Aerosol Layer Data, {V5-00}},
  year      = {2026},
  publisher = {NASA Langley Atmospheric Science Data Center Distributed Active Archive Center},
  doi       = {10.5067/CALIOP/CALIPSO/CAL_LID_L2_05kmALay-Standard-V5-00}
}

L3 tropospheric aerosol profiles (all-sky) V5-00 — DOI 10.5067/CALIOP/CALIPSO/LID_L3_Tropospheric_APro_AllSky-Standard-V5-00

@misc{calipso_l3_tropo_allsky_v500,
  author    = {Winker, David},
  title     = {{CALIPSO} Lidar Level 3 Tropospheric Aerosol Profiles, All Sky Data, Standard {V5-00}},
  year      = {2026},
  publisher = {NASA Langley Atmospheric Science Data Center Distributed Active Archive Center},
  doi       = {10.5067/CALIOP/CALIPSO/LID_L3_Tropospheric_APro_AllSky-Standard-V5-00}
}

Reference papers¶

CALIPSO mission and CALIOP processing algorithms overview — DOI 10.1175/2009JTECHA1281.1

@article{winker2009calipso,
  author  = {Winker, David M. and Vaughan, Mark A. and Omar, Ali and Hu, Yongxiang and Powell, Kathleen A. and Liu, Zhaoyan and Hunt, William H. and Young, Stuart A.},
  title   = {Overview of the {CALIPSO} Mission and {CALIOP} Data Processing Algorithms},
  journal = {Journal of Atmospheric and Oceanic Technology},
  volume  = {26},
  number  = {11},
  pages   = {2310--2323},
  year    = {2009},
  doi     = {10.1175/2009JTECHA1281.1}
}

Version 4 aerosol classification and lidar ratio selection — DOI 10.5194/amt-11-6107-2018

@article{kim2018caliopv4,
  author  = {Kim, Man-Hae and Omar, Ali H. and Tackett, Jason L. and Vaughan, Mark A. and Winker, David M. and Trepte, Charles R. and Hu, Yongxiang and Liu, Zhaoyan and Poole, Lamont R. and Pitts, Michael C. and Kar, Jayanta and Magill, Brian E.},
  title   = {The {CALIPSO} version 4 automated aerosol classification and lidar ratio selection algorithm},
  journal = {Atmospheric Measurement Techniques},
  volume  = {11},
  pages   = {6107--6135},
  year    = {2018},
  doi     = {10.5194/amt-11-6107-2018}
}

Acknowledgements¶

The ASDC recommends the acknowledgement "These data were obtained from the NASA Langley Research Center Atmospheric Science Data Center." and points to the citation generator on each collection's DOI landing page for the exact citation format. The citations above are built from the DataCite metadata (creator, year, title). State every product and version (such as V5-00) you used.

Information on the datasets used in this study was compiled with the help of the Korean Climate Data Navigator (KCDN) (Sim, 2026; https://doi.org/10.5281/zenodo.23300923).

Links¶

• NASA ASDC — CALIPSO
• NASA Science — CALIPSO mission
• CALIPSO Data Products Catalog (Release 5.00)
• CALIPSO Data User's Guide FAQ
• CALIPSO Final Report (NASA NTRS)
• CNES — CALIPSO