An overview of the CATS level 1 processing algorithms and data products

Abstract

The Cloud‐Aerosol Transport System (CATS) is an elastic backscatter lidar that was launched on 10 January 2015 to the International Space Station (ISS). CATS provides both space‐based technology demonstrations for future Earth Science missions and operational science measurements. This paper outlines the CATS Level 1 data products and processing algorithms. Initial results and validation data demonstrate the ability to accurately detect optically thin atmospheric layers with 1064 nm nighttime backscatter as low as 5.0E−5 km−1 sr−1. This sensitivity, along with the orbital characteristics of the ISS, enables the use of CATS data for cloud and aerosol climate studies. The near‐real‐time downlinking and processing of CATS data are unprecedented capabilities and provide data that have applications such as forecasting of volcanic plume transport for aviation safety and aerosol vertical structure that will improve air quality health alerts globally.

Radiative Forcing and Stratospheric Warming of Pyrocumulonimbus Smoke Aerosols: First Modeling Results With Multisensor (EPIC, CALIPSO, and CATS) Views from Space

“…Where CATS observed a persistent and somewhat defined plume, GEOS‐Chem had spread the pyroCb aerosols throughout the Northern Hemisphere stratosphere. In these August and September 2017 cases, the CATS V2‐01 aerosol typing algorithm suggests these aerosols are volcanic in origin; however, this is merely a result of the algorithm categorizing any UTLS aerosols as volcanic (Yorks et al, ). In the CATS V3‐00 data products, which will be released shortly, this aerosol classification name has been changed to “UTLS” as a result of the observations discussed in this paper (Yorks, ).…”

Seasonally transported aerosol layers over southeast Atlantic are closer to underlying clouds than previously reported

“…The CATS layer detection algorithm is a threshold‐based layer detection method that is nearly identical to the CALIOP‐SIBYL technique with four distinct differences, namely, the use of 60 m vertical resolution, a single horizontal spatial resolution (5 km), the use of the 1064 nm wavelength rather than 532 nm, and a technique to identify clouds embedded within aerosol layers [ Yorks et al , ]. The CATS L2 Operational (L2O) CAD algorithm is a multidimensional PDF technique like the CALIOP one [ Yorks et al , ] but uses the layer‐integrated attenuated backscatter at 1064 nm and other variables such as layer midtemperature and layer thickness instead of the layer‐integrated backscatter color ratio due to the unreliable 532 nm data in Mode 7.2. The use of a single horizontal spatial resolution in the CATS algorithm misses optically thin cirrus clouds and aerosols during the daytime in the CATS L2O Version 1‐05 data products, though it performs well during nighttime observations.…”

“…The current CALIOP‐SIBYL primarily uses 532 nm because it has higher signal‐to‐noise ratios and lower minimum detectable backscatter (MDB,weakest aerosol backscatter coefficient that can be detected) than the CALIOP 1064 nm data resulting in more accurate uniform cloud and aerosol layer detection [ Vaughan et al , ]. The CATS layer detection algorithm uses the 1064 nm attenuated scattering ratio because the CATS 532 nm data in Mode 7.2 are extremely noisy and the 1064 nm MDB is orders of magnitude lower [ Yorks et al , ]. For ACA detection specifically, the 1064 nm wavelength is preferred over the 532 nm wavelength for layer detection.…”

The Mineral Aerosol Profiling from Infrared Radiances (MAPIR) algorithm: version 4.1 description and evaluation

“…CATS is a lidar instrument on board the International Space Station (ISS) which provided vertically resolved cloud and aerosol properties at 1064 nm from March 2015 until October 2017 (Yorks et al, 2016). CATS orbited between 375 and 435 km above Earth's surface at a 51.6 • inclination with nearly a 3-day repeat cycle (McGill et al, 2015).…”