scholarly journals Investigation of CATS aerosol products and application toward global diurnal variation of aerosols

2018 ◽  
Author(s):  
Logan Lee ◽  
Jianglong Zhang ◽  
Jeffrey S. Reid ◽  
John E. Yorks
Keyword(s):  
Local Time ◽  
North Africa ◽  
Early Morning ◽  
Orthogonal Polarization ◽  
Aerosol Extinction ◽  
Dust Generation ◽  
Time Variations ◽  
First Time ◽  
Level 2 ◽  
Local Noon

Abstract. We present a comparison of 1064 nm aerosol optical depth (AOD) and aerosol extinction profiles from the Cloud-Aerosol Transport System (CATS) Level 2 aerosol product with collocated Aerosol Robotic Network (AERONET) AOD, Aqua and Terra Moderate Imaging Spectroradiometer (MODIS) Dark Target (AOD) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) AOD and extinction data for the period of Feb. 2015–Oct. 2017. Upon quality assurance checks of CATS data, reasonable agreements are found between aerosol data from CATS and other sensors. Using quality assured CATS aerosol data, for the first time, variations in AODs and aerosol extinction profiles are evaluated at 00, 06, 12, and 18 UTC (and/or 0:00 am, 6:00 am, 12:00 pm and 6:00 pm local solar times) on both regional and global scales. This study suggests that marginal variations are found in AOD from a global mean perspective, with the maximum and minimum aerosol vertical profiles found at local noon and 6:00 pm local time respectively, for both the June–November and December–May seasons. Strong diurnal variations are found over North Africa and India for the December–May season, and over North Africa, Middle East, and India for the June–November season. In particular, over North Africa, during the June-November season, a diurnal peak in aerosol extinction profile of 20 % larger than daily mean is found at 6:00 am (early morning local time), which may possibly be associated with dust generation through the breaking down of low level jet during morning hours.

scholarly journals Investigation of CATS aerosol products and application toward global diurnal variation of aerosols

2019 ◽  
Vol 19 (19) ◽  
pp. 12687-12707 ◽  
Author(s):  
Logan Lee ◽  
Jianglong Zhang ◽  
Jeffrey S. Reid ◽  
John E. Yorks
Keyword(s):  
Middle East ◽  
North Africa ◽  
Orthogonal Polarization ◽  
Aerosol Extinction ◽  
Extinction Data ◽  
Time Variations ◽  
First Time ◽  
Global Oceans ◽  
Level 2 ◽  
Global Mean

Abstract. We present a comparison of 1064 nm aerosol optical depth (AOD) and aerosol extinction profiles from the Cloud-Aerosol Transport System (CATS) level 2 aerosol product with collocated Aerosol Robotic Network (AERONET) AOD, Moderate Imaging Spectroradiometer (MODIS) Aqua and Terra Dark Target AOD and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) AOD and extinction data for the period of March 2015–October 2017. Upon quality-assurance checks of CATS data, reasonable agreement is found between aerosol data from CATS and other sensors. Using quality-assured CATS aerosol data, for the first time, variations in AODs and aerosol extinction profiles are evaluated at 00:00, 06:00, 12:00 and 18:00 UTC (and/or 00:00, 06:00, 12:00 and 18:00 local time or LT) on both regional and global scales. This study suggests that marginal variations are found in AOD from a global mean perspective, with the minimum aerosol extinction values found at 18:00 LT near the surface layer for global oceans, for both the June–November and December–May seasons. Over land, below 500 m, the daily minimum and maximum aerosol extinction values are found at 12:00 and 00:00/06:00 LT, respectively. Strong diurnal variations are also found over north Africa, the Middle East and India for the December–May season, and over north Africa, south Africa, the Middle East and India for the June–November season.

scholarly journals Minimum aerosol layer detection sensitivities and their subsequent impacts on aerosol optical thickness retrievals in CALIPSO level 2 data products

2018 ◽  
Vol 11 (1) ◽  
pp. 499-514 ◽  
Author(s):  
Travis D. Toth ◽  
James R. Campbell ◽  
Jeffrey S. Reid ◽  
Jason L. Tackett ◽  
Mark A. Vaughan ◽  
...  
Keyword(s):  
Optical Thickness ◽  
Aerosol Optical Thickness ◽  
Orthogonal Polarization ◽  
Aerosol Layer ◽  
Aerosol Extinction ◽  
Noise Floor ◽  
Data Products ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Level 2 ◽  
Global Mean

Abstract. Due to instrument sensitivities and algorithm detection limits, level 2 (L2) Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) 532 nm 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.

scholarly journals CALIPSO lidar level 3 aerosol profile product: version 3 algorithm design

2018 ◽  
Vol 11 (7) ◽  
pp. 4129-4152 ◽  
Author(s):  
Jason L. Tackett ◽  
David M. Winker ◽  
Brian J. Getzewich ◽  
Mark A. Vaughan ◽  
Stuart A. Young ◽  
...  
Keyword(s):  
Algorithm Design ◽  
Global Ocean ◽  
Orthogonal Polarization ◽  
Aerosol Extinction ◽  
Averaging Methods ◽  
Global Land ◽  
Level 3 ◽  
Classification Information ◽  
The Impact ◽  
Level 2

Abstract. The CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) level 3 aerosol profile product reports globally gridded, quality-screened, monthly mean aerosol extinction profiles retrieved by CALIOP (the Cloud-Aerosol Lidar with Orthogonal Polarization). This paper describes the quality screening and averaging methods used to generate the version 3 product. The fundamental input data are CALIOP level 2 aerosol extinction profiles and layer classification information (aerosol, cloud, and clear-air). Prior to aggregation, the extinction profiles are quality-screened by a series of filters to reduce the impact of layer detection errors, layer classification errors, extinction retrieval errors, and biases due to an intermittent signal anomaly at the surface. The relative influence of these filters are compared in terms of sample rejection frequency, mean extinction, and mean aerosol optical depth (AOD). The “extinction QC flag” filter is the most influential in preventing high-biases in level 3 mean extinction, while the “misclassified cirrus fringe” filter is most aggressive at rejecting cirrus misclassified as aerosol. The impact of quality screening on monthly mean aerosol extinction is investigated globally and regionally. After applying quality filters, the level 3 algorithm calculates monthly mean AOD by vertically integrating the monthly mean quality-screened aerosol extinction profile. Calculating monthly mean AOD by integrating the monthly mean extinction profile prevents a low bias that would result from alternately integrating the set of extinction profiles first and then averaging the resultant AOD values together. Ultimately, the quality filters reduce level 3 mean AOD by −24 and −31 % for global ocean and global land, respectively, indicating the importance of quality screening.

scholarly journals Synergy between CALIOP and MODIS instruments for aerosol monitoring: application to the Po Valley

2010 ◽  
Vol 3 (2) ◽  
pp. 1323-1359 ◽  
Author(s):  
P. Royer ◽  
J.-C. Raut ◽  
G. Ajello ◽  
S. Berthier ◽  
P. Chazette
Keyword(s):  
Signal To Noise Ratio ◽  
Extinction Ratio ◽  
Orthogonal Polarization ◽  
Aerosol Extinction ◽  
Large Area ◽  
Total Uncertainty ◽  
Aerosol Model ◽  
Po Valley ◽  
The Mean ◽  
Level 2

Abstract. We propose here a synergy between Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations/Cloud-Aerosol LIdar with Orthogonal Polarization (CALIPSO/CALIOP) and Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Aqua and Terra in order to retrieve aerosol optical properties over the Po Valley from June 2006 to February 2009. Such an approach gives simultaneously access to the aerosol extinction vertical profile and to the equivalent backscatter-to-extinction ratio at 532 nm (BER, inverse of the lidar ratio). The choice of the Po valley has been driven by the great occurrences of pollutant events leading to a mean MODIS-derived aerosol optical thickness of 0.27(±0.17) at 550 nm over a large area of ~120 000 km2. In such area, a significant number of CALIOP level-1 vertical profiles can be averaged (~200 individual laser shots) leading to a signal-to-noise ratio greater than 10 in the planetary boundary layer (PBL) sufficient to perform a homemade inversion of the mean lidar profiles. The mean BER (together with the associated variabilities) over the Po Valley retrieved from the coupling between CALIOP/MODIS-Aqua and CALIOP/MODIS-Terra are ~0.014(±0.003) sr−1 and ~0.013(±0.004) sr−1, respectively. The total uncertainty on BER retrieval has been assessed to be ~0.003 sr−1 using a Monte Carlo approach. These mean BER values retrieved have been compared with those given by the level-2 operational products of CALIOP ~0.016(±0.003) sr−1. The values we assessed appear close to what is expected above urban area. A seasonal cycle has been observed with higher BER values in spring, summer and fall, which can be associated to dust event occurring during this period. In most of cases, the mean aerosol extinction coefficient in the PBL diverges significantly between the level-2 operational products and the result of our own inversion procedure. Indeed, mean differences of 0.10 km−1 (~50%) and 0.13 km−1 (~60%) have been calculated using MODIS-Aqua/CALIOP and MODIS-Terra/CALIOP synergies, respectively. Such differences may be due to the identification of the aerosol model by the operational algorithm and thus to the choice of the BER.

scholarly journals Minimum Aerosol Layer Detection Sensitivities and their Subsequent Impacts on Aerosol Optical Thickness Retrievals in CALIPSO Level 2 Data Products

2017 ◽  
Author(s):  
Travis D. Toth ◽  
James R. Campbell ◽  
Jeffrey S. Reid ◽  
Jason L. Tackett ◽  
Mark A. Vaughan ◽  
...  
Keyword(s):  
Optical Thickness ◽  
Aerosol Optical Thickness ◽  
Orthogonal Polarization ◽  
Aerosol Layer ◽  
Aerosol Extinction ◽  
Noise Floor ◽  
Data Products ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Level 2 ◽  
Global Mean

Abstract. Due to instrument sensitivities and algorithm detection limits, Level 2 (L2) Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) 532 nm 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 four 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.

scholarly journals An accuracy assessment of the CALIOP/CALIPSO version 2/version 3 daytime aerosol extinction product based on a detailed multi-sensor, multi-platform case study

2011 ◽  
Vol 11 (8) ◽  
pp. 3981-4000 ◽  
Author(s):  
M. Kacenelenbogen ◽  
M. A. Vaughan ◽  
J. Redemann ◽  
R. M. Hoff ◽  
R. R. Rogers ◽  
...  
Keyword(s):  
Accuracy Assessment ◽  
High Spectral Resolution ◽  
Calibration Coefficient ◽  
Orthogonal Polarization ◽  
Aerosol Layer ◽  
Aerosol Extinction ◽  
Backscatter Coefficient ◽  
Aerosol Backscatter ◽  
Level 2

Abstract. The Cloud Aerosol LIdar with Orthogonal Polarization (CALIOP), on board the CALIPSO platform, has measured profiles of total attenuated backscatter coefficient (level 1 products) since June 2006. CALIOP's level 2 products, such as the aerosol backscatter and extinction coefficient profiles, are retrieved using a complex succession of automated algorithms. The goal of this study is to help identify potential shortcomings in the CALIOP version 2 level 2 aerosol extinction product and to illustrate some of the motivation for the changes that have been introduced in the next version of CALIOP data (version 3, released in June 2010). To help illustrate the potential factors contributing to the uncertainty of the CALIOP aerosol extinction retrieval, we focus on a one-day, multi-instrument, multiplatform comparison study during the CALIPSO and Twilight Zone (CATZ) validation campaign on 4 August 2007. On that day, we observe a consistency in the Aerosol Optical Depth (AOD) values recorded by four different instruments (i.e. space-borne MODerate Imaging Spectroradiometer, MODIS: 0.67 and POLarization and Directionality of Earth's Reflectances, POLDER: 0.58, airborne High Spectral Resolution Lidar, HSRL: 0.52 and ground-based AErosol RObotic NETwork, AERONET: 0.48 to 0.73) while CALIOP AOD is a factor of two lower (0.32 at 532 nm). This case study illustrates the following potential sources of uncertainty in the CALIOP AOD: (i) CALIOP's low signal-to-noise ratio (SNR) leading to the misclassification and/or lack of aerosol layer identification, especially close to the Earth's surface; (ii) the cloud contamination of CALIOP version 2 aerosol backscatter and extinction profiles; (iii) potentially erroneous assumptions of the aerosol extinction-to-backscatter ratio (Sa) used in CALIOP's extinction retrievals; and (iv) calibration coefficient biases in the CALIOP daytime attenuated backscatter coefficient profiles. The use of version 3 CALIOP extinction retrieval for our case study seems to partially fix factor (i) although the aerosol retrieved by CALIOP is still somewhat lower than the profile measured by HSRL; the cloud contamination (ii) appears to be corrected; no particular change is apparent in the observation-based CALIOP Sa value (iii). Our case study also showed very little difference in version 2 and version 3 CALIOP attenuated backscatter coefficient profiles, illustrating a minor change in the calibration scheme (iv).

scholarly journals CALIPSO lidar level 3 aerosol profile product: version 3 algorithm design

2018 ◽  
Author(s):  
Jason L. Tackett ◽  
David M. Winker ◽  
Brian J. Getzewich ◽  
Mark A. Vaughan ◽  
Stuart A. Young ◽  
...  
Keyword(s):  
Algorithm Design ◽  
Global Ocean ◽  
Orthogonal Polarization ◽  
Aerosol Extinction ◽  
Averaging Methods ◽  
Global Land ◽  
Level 3 ◽  
Classification Information ◽  
The Impact ◽  
Level 2

Abstract. The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) level 3 aerosol profile product reports globally-gridded, quality-screened monthly mean aerosol extinction profiles retrieved by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). This paper describes the quality screening and averaging methods used to generate the version 3 product. The fundamental input data are CALIOP level 2 aerosol extinction profiles and layer classification information (aerosol, cloud, and clear-air). Prior to aggregation, the extinction profiles are quality-screened by a series of filters to reduce the impact of layer detection errors, layer classification errors, extinction retrieval errors, and biases due to an intermittent signal anomaly at the surface. The relative influence of these filters are compared in terms of sample rejection frequency, mean extinction, and mean AOD. The extinction QC flag filter is the most influential in preventing high-biases in level 3 mean extinction, while the misclassified cirrus fringe filter is most aggressive at rejecting cirrus misclassified as aerosol. The impact of quality screening on monthly mean aerosol extinction is investigated globally and regionally. After applying quality filters, monthly mean AOD is reduced by −24 and −31 % for global ocean and global land, respectively, thus indicating the importance of quality screening.

scholarly journals Daytime aerosol extinction profiles from the combination of CALIOP profiles and AERONET products

2013 ◽  
Vol 6 (2) ◽  
pp. 3983-4038 ◽  
Author(s):  
C. Marcos ◽  
R. Pedrós ◽  
J. L. Gómez-Amo ◽  
M. Sicard ◽  
M. P. Utrillas ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Mediterranean Coast ◽  
Saharan Dust ◽  
Orthogonal Polarization ◽  
Aerosol Extinction ◽  
Lidar Measurements ◽  
Level 1 ◽  
The Vertical Distribution ◽  
Level 2 ◽  
Good Agreement

Abstract. The solar background illumination has a strong effect on CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) measurements, leading to a decrease in the signal-to-noise ratio of the lidar signal. Because of this, CALIOP level 2 data algorithms might be limited in the retrieval of the properties of the aerosols in the atmosphere. In this work, we present a methodology that combines CALIOP level 1 data with AERONET (Aerosol RObotic NETwork) measurements to retrieve aerosol extinction profiles and lidar ratios in daytime conditions. In this way, we fulfill a two-fold objective: first, we obtain more accurate daytime aerosol information; second, we supplement column integrated measurements from AERONET sun photometers with information about the vertical distribution of aerosols. The methodology has been applied to Burjassot (39.30° N, 0.25° W) and Barcelona (41.39° N, 2.11° E) AERONET stations in the Mediterranean coast of Spain in the period from June 2006 to September 2011. We have found good agreement for the extinction profiles in several study cases of ground lidar measurements in Barcelona, coincident with CALIOP overpasses. Finally, the methodology has proved to be useful for the study of special episodes such as Saharan dust outbreaks.

Sourcebook in the Mathematics of Medieval Europe and North Africa

2016 ◽  
Keyword(s):  
North Africa ◽  
Cultural Influences ◽  
Mathematical Induction ◽  
Cross Cultural ◽  
General Introduction ◽  
Extensive Survey ◽  
Medieval Europe ◽  
Ceva’S Theorem ◽  
Arabic Speaking ◽  
First Time

Medieval Europe was a meeting place for the Christian, Jewish, and Islamic civilizations, and the fertile intellectual exchange of these cultures can be seen in the mathematical developments of the time. This book presents original Latin, Hebrew, and Arabic sources of medieval mathematics, and shows their cross-cultural influences. Most of the Hebrew and Arabic sources appear here in translation for the first time. Readers will discover key mathematical revelations, foundational texts, and sophisticated writings by Latin, Hebrew, and Arabic-speaking mathematicians, including Abner of Burgos's elegant arguments proving results on the conchoid—a curve previously unknown in medieval Europe; Levi ben Gershon's use of mathematical induction in combinatorial proofs; Al-Muʾtaman Ibn Hūd's extensive survey of mathematics, which included proofs of Heron's Theorem and Ceva's Theorem; and Muhyī al-Dīn al-Maghribī's interesting proof of Euclid's parallel postulate. The book includes a general introduction, section introductions, footnotes, and references.

scholarly journals A review of the Sarcophaga (Heteronychia) (Diptera: Sarcophagidae) of Sardinia

Zootaxa ◽  
2009 ◽  
Vol 2318 (1) ◽  
pp. 566-588 ◽  
Author(s):  
DANIEL WHITMORE
Keyword(s):  
Canary Islands ◽  
North Africa ◽  
Junior Synonym ◽  
Arthropod Diversity ◽  
Italian Regions ◽  
Males And Females ◽  
First Time

An account is given of the species of Sarcophaga Meigen, 1826 subgenus Heteronychia Brauer & Bergenstamm, 1889 known from the island of Sardinia (Italy). Most of the nearly 1,400 specimens examined were collected in the SW part of the island during 2003–2006 as part of a project investigating the arthropod diversity of the Monti Marganai and Montimannu areas (respectively Carbonia-Iglesias and Medio Campidano provinces). The study resulted in the finding of eight species of Heteronychia, six of which are recorded from Sardinia for the first time. Sarcophaga (Heteronychia) penicillata Villeneuve, 1907, previously mentioned in the literature, is excluded from the fauna of the island. Sarcophaga (Heteronychia) thirionae (Lehrer, 1976) is recorded for the first time from Europe and North Africa (Algeria). One species, Sarcophaga (Heteronychia) gabrielei sp. nov., from various sites in the limestone massif of Marganai, is described as new. Previously unpublished records from other Italian regions and from other countries (Algeria, Canary Islands, Greece) are also given for several species. Sarcophaga (Heteronychia) schnabli Villeneuve, 1911 is recognized as a junior synonym of S. (H.) consanguinea Rondani, 1860 syn. nov. The possible synanthropy of Sarcophaga (Heteronychia) pandellei (Rohdendorf, 1937) is briefly discussed. A key to males and females of all known Sardinian and Corsican species of Sarcophaga (Heteronychia) is provided.

Sign in / Sign up

Export Citation Format

Share Document