1
|
Toth TD, Campbell JR, Reid JS, Tackett JL, Vaughan MA, Zhang J, Marquis JW. Minimum aerosol layer detection sensitivities and their subsequent impacts on aerosol optical thickness retrievals in CALIPSO level 2 data products. ATMOSPHERIC MEASUREMENT TECHNIQUES 2018; 11:499-514. [PMID: 33868502 PMCID: PMC8051137 DOI: 10.5194/amt-11-499-2018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Due to instrument sensitivities and algorithm detection limits, level 2 (L2) Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) 532nm aerosol extinction profile retrievals are often populated with retrieval fill values (RFVs), which indicate the absence of detectable levels of aerosol within the profile. In this study, using 4 years (2007-2008 and 2010-2011) of CALIOP version 3 L2 aerosol data, the occurrence frequency of daytime CALIOP profiles containing all RFVs (all-RFV profiles) is studied. In the CALIOP data products, the aerosol optical thickness (AOT) of any all-RFV profile is reported as being zero, which may introduce a bias in CALIOP-based AOT climatologies. For this study, we derive revised estimates of AOT for all-RFV profiles using collocated Moderate Resolution Imaging Spectroradiometer (MODIS) Dark Target (DT) and, where available, AErosol RObotic NEtwork (AERONET) data. Globally, all-RFV profiles comprise roughly 71% of all daytime CALIOP L2 aerosol profiles (i.e., including completely attenuated profiles), accounting for nearly half (45 %) of all daytime cloud-free L2 aerosol profiles. The mean collocated MODIS DT (AERONET) 550 nm AOT is found to be near 0.06 (0.08) for CALIOP all-RFV profiles. We further estimate a global mean aerosol extinction profile, a so-called "noise floor", for CALIOP all-RFV profiles. The global mean CALIOP AOT is then recomputed by replacing RFV values with the derived noise-floor values for both all-RFV and non-all-RFV profiles. This process yields an improvement in the agreement of CALIOP and MODIS over-ocean AOT.
Collapse
Affiliation(s)
- Travis D Toth
- Dept. of Atmospheric Sciences, University of North Dakota, Grand Forks, ND, USA
| | - James R Campbell
- Aerosol and Radiation Sciences Section, Marine Meteorology Division, Naval Research Laboratory, Monterey, CA, USA
| | - Jeffrey S Reid
- Aerosol and Radiation Sciences Section, Marine Meteorology Division, Naval Research Laboratory, Monterey, CA, USA
| | | | | | - Jianglong Zhang
- Dept. of Atmospheric Sciences, University of North Dakota, Grand Forks, ND, USA
| | - Jared W Marquis
- Dept. of Atmospheric Sciences, University of North Dakota, Grand Forks, ND, USA
| |
Collapse
|
2
|
Lewis JR, Campbell JR, Welton EJ. Overview of MPLNET Version 3 Cloud Detection. JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2016; Volume 33:2113-2134. [PMID: 32440037 PMCID: PMC7241671 DOI: 10.1175/jtech-d-15-0190.1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The National Aeronautics and Space Administration Micropulse Lidar Network Version 3 cloud detection algorithm is described and its differences relative to the previous version highlighted. Clouds are identified from normalized Level 1 signal profiles using two complementary methods. The first considers signal derivatives vertically for resolving low-level clouds. The second, which resolves high-level clouds like cirrus, is based on signal uncertainties given the relatively low signal-to-noise ratio exhibited in the upper troposphere by eye-safe network instruments, especially during daytime. Furthermore, a multi-temporal averaging scheme is used to improve cloud detection under conditions of weak signal-to-noise. Diurnal and seasonal cycles of cloud occurrence frequency based on one year of measurements at the Goddard Space Flight Center (Greenbelt, MD) site are compared for the new and previous versions. The largest differences, and perceived improvement, in detection occurs for high clouds (above 5-km, mean sea level) which increase in occurrence by nearly 6%. There is also an increase in the detection of multi-layered cloud profiles from 9% to 20%. Macrophysical properties and estimates of cloud optical depth are presented for a transparent cirrus dataset. However, the limit to which molecular signal can be reliably retrieved above cirrus clouds occurs between cloud optical depths of 0.5 and 0.8.
Collapse
Affiliation(s)
- Jasper R. Lewis
- Corresponding author address: NASA GSFC, Code 612, Greenbelt, MD 20771.
| | | | | |
Collapse
|
3
|
Lin NH, Sayer AM, Wang SH, Loftus AM, Hsiao TC, Sheu GR, Hsu NC, Tsay SC, Chantara S. Interactions between biomass-burning aerosols and clouds over Southeast Asia: current status, challenges, and perspectives. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2014; 195:292-307. [PMID: 25085565 DOI: 10.1016/j.envpol.2014.06.036] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2014] [Revised: 06/08/2014] [Accepted: 06/28/2014] [Indexed: 06/03/2023]
Abstract
The interactions between aerosols, clouds, and precipitation remain among the largest sources of uncertainty in the Earth's energy budget. Biomass-burning aerosols are a key feature of the global aerosol system, with significant annually-repeating fires in several parts of the world, including Southeast Asia (SEA). SEA in particular provides a "natural laboratory" for these studies, as smoke travels from source regions downwind in which it is coupled to persistent stratocumulus decks. However, SEA has been under-exploited for these studies. This review summarizes previous related field campaigns in SEA, with a focus on the ongoing Seven South East Asian Studies (7-SEAS) and results from the most recent BASELInE deployment. Progress from remote sensing and modeling studies, along with the challenges faced for these studies, are also discussed. We suggest that improvements to our knowledge of these aerosol/cloud effects require the synergistic use of field measurements with remote sensing and modeling tools.
Collapse
Affiliation(s)
- Neng-Huei Lin
- Department of Atmospheric Sciences, National Central University, Chung-Li, Taiwan; Chemistry Department and Environmental Science Program, Faculty of Science, Chiang Mai University, Chiang Mai, 50200, Thailand.
| | - Andrew M Sayer
- Goddard Space Flight Center, NASA, Greenbelt, MD, USA; Universities Space Research Association, Columbia, MD, USA
| | - Sheng-Hsiang Wang
- Department of Atmospheric Sciences, National Central University, Chung-Li, Taiwan
| | - Adrian M Loftus
- Goddard Space Flight Center, NASA, Greenbelt, MD, USA; Oak Ridge Associated Universities, Oak Ridge, TN, USA
| | - Ta-Chih Hsiao
- Graduate Institute of Environmental Engineering, National Central University, Chung-Li, Taiwan
| | - Guey-Rong Sheu
- Department of Atmospheric Sciences, National Central University, Chung-Li, Taiwan
| | | | - Si-Chee Tsay
- Goddard Space Flight Center, NASA, Greenbelt, MD, USA
| | - Somporn Chantara
- Chemistry Department and Environmental Science Program, Faculty of Science, Chiang Mai University, Chiang Mai, 50200, Thailand
| |
Collapse
|