Earthdata Forum

Dear CALIPSO Science Team, I am a graduate student investigating the long-term vertical evolution of global aerosol distributions. My study utilizes the CALIPSO Level 3 (V4.2) monthly tropospheric aerosol product to analyze interannual AOD trends at different altitudes. During my research, my advisor has raised critical concerns regarding the reliability of CALIPSO upper-tropospheric data, specifically for the 8–12 km layer. Specifically, he points out that accurate discrimination between smoke, dust, and thin cirrus remains challenging in the upper troposphere, which may lead to misclassification between clouds and aerosols. The dataset also contains a substantial noise floor that is not fully accounted for in the standard L3 product. These inherent limitations could introduce systematic biases—particularly systematic negative biases—that distort the estimation of long-term aerosol trends in the 8–12 km layer. I have not yet found clear documentation addressing the following questions: 1. Whether the L3 product accounts for the noise floor issue; 2. Whether official trend evaluation reports have explicitly identified trend biases caused by the noise floor; 3. Whether publicly available correction strategies or empirical coefficients exist to mitigate such systematic negative biases in upper-tropospheric trend analysis. Any relevant technical reports, uncertainty assessment results, or practical correction suggestions would greatly help me quantify and improve the reliability of trend estimates in my research. I would be deeply grateful for any feedback or support you could kindly provide. Thank you very much for your generosity and guidance. Best regards

Dear Qia Ye,
Thank you for contacting us with an interest in CALIPSO data.
The Subject Matter Expert will contact you shortly to assist with your question.

Warm Regards,
Atmospheric Science Datat Center
User Services

Hello @yq20221014,

May I suggest using version 5.00 of the Level 3 Tropospheric Aerosol Data. Below is the data description and quality summary for this data where it highlights the most significant changes that were made from version 4.2:
https://asdc.larc.nasa.gov/documents/calipso/quality_summaries/cal_lid_l3_tropoaero_V5-00_desc_qs.pdf

Please let us know if you have any further questions.

Thanks,

Thank you very much for your detailed response. I have carefully reviewed the documentation for the Version 5 dataset and have a clarification to confirm with your team.
While the Level 3 Version 5 product has significantly reduced the underlying negative bias of weak aerosols through a series of improvements and corrected the previous global underestimation of AOD, I would like to verify whether residual baseline noise still inevitably impacts the accuracy of Level 3 AOD, particularly in mid-to-upper atmospheric regions with low signal-to-noise ratios.