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Charles R. Trepte - One of the best experts on this subject based on the ideXlab platform.
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Overview of the CALIPSO Version 4 Lidar Data Products
2016Co-Authors: Mark A Vaughan, Zhaoyan Liu, Charles R. Trepte, David M. Winker, Jacques Pelon, Anne Garnier, Melody A. Avery, Jason L. Tackett, Jayanta Kar, Ali OmarAbstract:NASA’s Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission is scheduled to release version 4 of their level 2 data products in the fall of 2016. This presentation will highlight some of the many significant improvements delivered by the version 4 CALIPSO lidar cloud and aerosol data products, with a particular focus on the retrieval of extinction-to-backscatter ratios for both ice clouds and water clouds.
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Detection of pollution outflow from Mexico City using CALIPSO lidar measurements
Remote Sensing of Environment, 2015Co-Authors: Jayanta Kar, Ali Omar, Mark A Vaughan, Charles R. Trepte, Jason L. Tackett, Z. Liu, Thomas Duncan Fairlie, R. KowchAbstract:Abstract We present the evidence of regional scale outflow of particulate pollution from Mexico City using measurements from the space borne CALIPSO lidar. The vertically resolved results are presented for winter months when the large scale biomass burning from nearby areas is minimized, and the aerosol loading is dominated by anthropogenic outflow from the city. The particulate depolarization ratio in the outflowing plume has high values and reflects the influence of mixing of the urban pollution with the ubiquitous dust around the city. This is consistent with the results from previous field campaigns in the city and leads to polluted dust being the dominant aerosol subtype as identified by the CALIPSO algorithm. A first order estimate of the mass flux on two episodes using the aerosol extinction profiles from CALIPSO indicates outflow of several hundred tons per day.
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Ocean subsurface studies with the CALIPSO spaceborne lidar
Journal of Geophysical Research: Oceans, 2014Co-Authors: Charles R. Trepte, S. Zeng, James H. ChurnsideAbstract:The primary objective of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission is to study the climate impact of clouds and aerosols in the atmosphere. However, recent studies have demonstrated that CALIPSO also collects information about the ocean subsurface. The objective of this study is to estimate the ocean subsurface backscatter from CALIPSO lidar measurements. The effects of the lidar receiver's transient response on the attenuated backscatter were first removed in order to obtain the correct attenuated backscatter profile. The empirical relationship between sea surface lidar backscatter and wind speed was used to estimate the theoretical ocean surface backscatter. Then the two-way atmospheric transmittance was estimated as the ratio between the corrected ocean surface backscatter and the theoretical one. The ocean subsurface backscatter was finally derived from the subsurface attenuated backscatter divided by the two-way atmospheric transmittance. Significant relationships between integrated subsurface backscatter and chlorophyll-a concentration and between integrated subsurface backscatter and particulate organic carbon were found, which indicate a potential use of CALIPSO lidar to estimate global chlorophyll-a and particulate organic carbon concentrations.
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A Super-Resolution Laser Altimetry Concept
IEEE Geoscience and Remote Sensing Letters, 2014Co-Authors: Charles R. Trepte, Zhaoyan LiuAbstract:A super-resolution laser altimetry technique has been proposed to provide improved lidar altimetry from Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation(CALIPSO) lidar data, and it is applicable to other similar atmospheric profiling lidar with low-pass filters. To achieve high altimetry resolution, the new technique relies on an empirical relationship between the peak signal ratio and the distance between land surface and the peak signal range bin center, which is directly derived from the CALIPSO lidar measurements and does not require the CALIPSO's transient response. The CALIPSO surface elevation results in Northern America retrieved by the new technique agree with the National Elevation Database high resolution elevation maps, and the comparisons suggest that the precision of the technique is much better than 1.4 m. The preliminary data product of land surface elevation retrieved by the new technique from CALIPSO lidar measurements is available to the altimetry community for evaluation.
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comparison of CALIPSO aerosol optical depth retrievals to aeronet measurements and a climatology for the lidar ratio of dust
Atmospheric Chemistry and Physics, 2012Co-Authors: Gregory L Schuster, Mark A Vaughan, D. M. Winker, David G. Macdonnell, Oleg Dubovik, Tatyana Lapyonok, Charles R. TrepteAbstract:Abstract. We compared CALIPSO column aerosol optical depths at 0.532 μm to measurements at 147 AERONET sites, synchronized to within 30 min of satellite overpass times during a 3-yr period. We found 677 suitable overpasses, and a CALIPSO bias of −13% relative to AERONET for the entire data set; the corresponding absolute bias is −0.029, and the standard deviation of the mean (SDOM) is 0.014. Consequently, the null hypothesis is rejected at the 97% confidence level, indicating a statistically significant difference between the datasets. However, if we omit CALIPSO columns that contain dust from our analysis, the relative and absolute biases are reduced to −3% and −0.005 with a standard error of 0.016 for 449 overpasses, and the statistical confidence level for the null hypothesis rejection is reduced to 27%. We also analyzed the results according to the six CALIPSO aerosol subtypes and found relative and absolute biases of −29% and −0.1 for atmospheric columns that contain the dust subtype exclusively, but with a relatively high correlation coefficient of R = 0.58; this indicates the possibility that the assumed lidar ratio (40 sr) for the CALIPSO dust retrievals is too low. Hence, we used the AERONET size distributions, refractive indices, percent spheres, and forward optics code for spheres and spheroids to compute a lidar ratio climatology for AERONET sites located in the dust belt. The highest lidar ratios of our analysis occur in the non-Sahel regions of Northern Africa, where the median lidar ratio at 0.532 μm is 55.4 sr for 229 retrievals. Lidar ratios are somewhat lower in the African Sahel (49.7 sr for 929 retrievals), the Middle East (42.6 sr for 489 retrievals), and Kanpur, India (43.8 sr for 67 retrievals). We attribute this regional variability in the lidar ratio to the regional variability of the real refractive index of dust, as these two parameters are highly anti-correlated (correlation coefficients range from −0.51 to −0.85 for the various regions). The AERONET refractive index variability is consistent with the variability of illite concentration in dust across the dust belt.
David M. Winker - One of the best experts on this subject based on the ideXlab platform.
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Using in situ airborne measurements to evaluate three cloud phase products derived from CALIPSO
Journal of Geophysical Research: Atmospheres, 2016Co-Authors: Gregory Cesana, Hélène Chepfer, Brian Getzewich, David M. Winker, Yuichiro Hagihara, Hajime Okamoto, X. Cai, Olivier Jourdan, Guillaume Mioche, Vincent NoëlAbstract:We compare the cloud detection and cloud phase determination of three independent climatologies based on Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) to airborne in situ measurements. Our analysis of the cloud detection shows that the differences between the satellite and in situ measurements mainly arise from three factors. First, averaging CALIPSO Level l data along track before cloud detection increases the estimate of high-and low-level cloud fractions. Second, the vertical averaging of Level 1 data before cloud detection tends to artificially increase the cloud vertical extent. Third, the differences in classification of fully attenuated pixels among the CALIPSO climatologies lead to differences in the low-level Arctic cloud fractions. In another section, we compare the cloudy pixels detected by colocated in situ and satellite observations to study the cloud phase determination. At midlatitudes, retrievals of homogeneous high ice clouds by CALIPSO data sets are very robust (more than 94.6% of agreement with in situ). In the Arctic, where the cloud phase vertical variability is larger within a 480 m pixel, all climatologies show disagreements with the in situ measurements and CALIPSO-General Circulation Models-Oriented Cloud Product (GOCCP) report significant undefined-phase clouds, which likely correspond to mixed-phase clouds. In all CALIPSO products, the phase determination is dominated by the cloud top phase. Finally, we use global statistics to demonstrate that main differences between the CALIPSO cloud phase products stem from the cloud detection (horizontal averaging, fully attenuated pixels) rather than the cloud phase determination procedures.
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Overview of the CALIPSO Version 4 Lidar Data Products
2016Co-Authors: Mark A Vaughan, Zhaoyan Liu, Charles R. Trepte, David M. Winker, Jacques Pelon, Anne Garnier, Melody A. Avery, Jason L. Tackett, Jayanta Kar, Ali OmarAbstract:NASA’s Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission is scheduled to release version 4 of their level 2 data products in the fall of 2016. This presentation will highlight some of the many significant improvements delivered by the version 4 CALIPSO lidar cloud and aerosol data products, with a particular focus on the retrieval of extinction-to-backscatter ratios for both ice clouds and water clouds.
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Far-Reaching Impacts of African Dust- A CALIPSO Perspective
2014Co-Authors: Mian Chin, Ali Omar, David M. Winker, Tianle Yuan, Huisheng Bian, Joseph M. Prospero, Lorraine A. Remer, Yuekui Yang, Yan ZhangAbstract:African dust can transport across the tropical Atlantic and reach the Amazon basin, exerting far-reaching impacts on climate in downwind regions. The transported dust influences the surface-atmosphere interactions and cloud and precipitation processes through perturbing the surface radiative budget and atmospheric radiative heating and acting as cloud condensation nuclei and ice nuclei. Dust also influences biogeochemical cycle and climate through providing nutrients vital to the productivity of ocean biomass and Amazon forests. Assessing these climate impacts relies on an accurate quantification of dust transport and deposition. Currently model simulations show extremely large diversity, which calls for a need of observational constraints. Kaufman et al. (2005) estimated from MODIS aerosol measurements that about 144 Tg of dust is deposited into the tropical Atlantic and 50 Tg of dust into the Amazon in 2001. This estimated dust import to Amazon is a factor of 3-4 higher than other observations and models. However, several studies have argued that the oversimplified characterization of dust vertical profile in the study would have introduced large uncertainty and very likely a high bias. In this study we quantify the trans-Atlantic dust transport and deposition by using 7 years (2007-2013) observations from CALIPSO lidar. CALIPSO acquires high-resolution aerosol extinction and depolarization profiles in both cloud-free and above-cloud conditions. The unique CALIPSO capability of profiling aerosols above clouds offers an unprecedented opportunity of examining uncertainties associated with the use of MODIS clear-sky data. Dust is separated from other types of aerosols using the depolarization measurements. We estimated that on the basis of 7-year average, 118142 Tg of dust is deposited into the tropical Atlantic and 3860 Tg of dust into the Amazon basin. Substantial interannual variations are observed during the period, with the maximum to minimum ratio of about 1.6 and 2.5 for the deposition to the tropical Atlantic and Amazon, respectively. The MODIS-based estimates appear to fall within the range of CALIPSO-based estimates; and the difference between MODIS and CALIPSO estimates can be largely attributed to the interannual variability, which is corroborated by long-term surface dust concentration observations in the tropical Atlantic. Considering that CALIPSO generally tends to underestimate the aerosol loading, our estimate is likely to represent a low bound for the dust transport and deposition estimate. The finding suggests that models have substantial biases and considerable effort is needed to improve model simulations of dust cycle.
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Macrophysical properties of tropical cirrus clouds from the CALIPSO satellite and from ground‐based micropulse and Raman lidars
Journal of Geophysical Research: Atmospheres, 2013Co-Authors: Tyler J. Thorsen, Mark A Vaughan, David M. Winker, Jennifer M. Comstock, Chitra Sivaraman, David D. TurnerAbstract:Lidar observations of cirrus cloud macrophysical properties over the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) program Darwin, Australia site are compared from the Cloud-Aerosol Lidar and In- frared Pathfinder Satellite Observation (CALIPSO) satellite, the ground-based ARM micropulse lidar (MPL), and the ARM Raman lidar (RL). Comparisons are made using the subset of profiles where the lidar beam is not fully attenuated. Daytime measurements using the RL are shown to be relatively unaffected by the solar background and are therefore suited for checking the validity of diurnal cycles. RL and CALIPSO cloud fraction profiles show good agreement while the MPL detects significantly less cirrus, particularly during the daytime. Both MPL and CALIPSO observations show that cirrus clouds occur less frequently during the day than at night at all altitudes. In contrast, the RL diurnal cy- cle is significantly different than zero only below about 11 km; where it is the opposite sign (i.e. more clouds during the daytime). For cirrus geomet- rical thickness, the MPL and CALIPSO observations agree well and both datasets have signficantly thinner clouds during the daytime than the RL. From the examination of hourly MPL and RL cirrus cloud thickness and through the application ofmore » daytime detection limits to all CALIPSO data we find that the decreased MPL and CALIPSO cloud thickness during the daytime is very likely a result of increased daytime noise. This study highlights the vast im- provement the RL provides (compared to the MPL) in the ARM program's ability to observe tropical cirrus clouds as well as a valuable ground-based lidar dataset for the validation of CALIPSO observations and to help im- prove our understanding of tropical cirrus clouds.« less
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macrophysical properties of tropical cirrus clouds from the CALIPSO satellite and from ground based micropulse and raman lidars
Journal of Geophysical Research, 2013Co-Authors: Tyler J. Thorsen, Mark A Vaughan, David M. Winker, Jennifer M. Comstock, Chitra Sivaraman, David D. TurnerAbstract:Lidar observations of cirrus cloud macrophysical properties over the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) program Darwin, Australia site are compared from the Cloud-Aerosol Lidar and In- frared Pathfinder Satellite Observation (CALIPSO) satellite, the ground-based ARM micropulse lidar (MPL), and the ARM Raman lidar (RL). Comparisons are made using the subset of profiles where the lidar beam is not fully attenuated. Daytime measurements using the RL are shown to be relatively unaffected by the solar background and are therefore suited for checking the validity of diurnal cycles. RL and CALIPSO cloud fraction profiles show good agreement while the MPL detects significantly less cirrus, particularly during the daytime. Both MPL and CALIPSO observations show that cirrus clouds occur less frequently during the day than at night at all altitudes. In contrast, the RL diurnal cy- cle is significantly different than zero only below about 11 km; where it is the opposite sign (i.e. more clouds during the daytime). For cirrus geomet- rical thickness, the MPL and CALIPSO observations agree well and both datasets have signficantly thinner clouds during the daytime than the RL. From the examination of hourly MPL and RL cirrus cloud thickness and through the application ofmore » daytime detection limits to all CALIPSO data we find that the decreased MPL and CALIPSO cloud thickness during the daytime is very likely a result of increased daytime noise. This study highlights the vast im- provement the RL provides (compared to the MPL) in the ARM program's ability to observe tropical cirrus clouds as well as a valuable ground-based lidar dataset for the validation of CALIPSO observations and to help im- prove our understanding of tropical cirrus clouds.« less
Zhaoyan Liu - One of the best experts on this subject based on the ideXlab platform.
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Overview of the CALIPSO Version 4 Lidar Data Products
2016Co-Authors: Mark A Vaughan, Zhaoyan Liu, Charles R. Trepte, David M. Winker, Jacques Pelon, Anne Garnier, Melody A. Avery, Jason L. Tackett, Jayanta Kar, Ali OmarAbstract:NASA’s Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission is scheduled to release version 4 of their level 2 data products in the fall of 2016. This presentation will highlight some of the many significant improvements delivered by the version 4 CALIPSO lidar cloud and aerosol data products, with a particular focus on the retrieval of extinction-to-backscatter ratios for both ice clouds and water clouds.
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A Super-Resolution Laser Altimetry Concept
IEEE Geoscience and Remote Sensing Letters, 2014Co-Authors: Charles R. Trepte, Zhaoyan LiuAbstract:A super-resolution laser altimetry technique has been proposed to provide improved lidar altimetry from Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation(CALIPSO) lidar data, and it is applicable to other similar atmospheric profiling lidar with low-pass filters. To achieve high altimetry resolution, the new technique relies on an empirical relationship between the peak signal ratio and the distance between land surface and the peak signal range bin center, which is directly derived from the CALIPSO lidar measurements and does not require the CALIPSO's transient response. The CALIPSO surface elevation results in Northern America retrieved by the new technique agree with the National Elevation Database high resolution elevation maps, and the comparisons suggest that the precision of the technique is much better than 1.4 m. The preliminary data product of land surface elevation retrieved by the new technique from CALIPSO lidar measurements is available to the altimetry community for evaluation.
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Comparison of Two Different Cloud Climatologies Derived from CALIOP-Attenuated Backscattered Measurements (Level 1): The CALIPSO-ST and the CALIPSO-GOCCP
Journal of Atmospheric and Oceanic Technology, 2013Co-Authors: Hélène Chepfer, Brian Getzewich, Mark A Vaughan, Dave Winker, G. Cesana, Zhaoyan LiuAbstract:AbstractTwo different cloud climatologies have been derived from the same NASA–Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP)-measured attenuated backscattered profile (level 1, version 3 dataset). The first climatology, named Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations–Science Team (CALIPSO-ST), is based on the standard CALIOP cloud mask (level 2 product, version 3), with the aim to document clouds with the highest possible spatiotemporal resolution, taking full advantage of the CALIOP capabilities and sensitivity for a wide range of cloud scientific studies. The second climatology, named GCM-Oriented CALIPSO Cloud Product (CALIPSO-GOCCP), is aimed at a single goal: evaluating GCM prediction of cloudiness. For this specific purpose, it has been designed to be fully consistent with the CALIPSO simulator included in the Cloud Feedback Model Intercomparison Project (CFMIP) Observation Simulator Package (COSP) used within version 2 of the CFMIP (CFMIP-2) experiment and phase...
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The CALIPSO Mission: results and progress
Lidar Technologies Techniques and Measurements for Atmospheric Remote Sensing VI, 2010Co-Authors: Dave Winker, Zhaoyan Liu, Chieko Kittaka, Brian Getzewich, Michael C. Pitts, Melody A. Avery, Jason L. Tackett, Mark A VaughanAbstract:Aerosols and clouds play important roles in Earth's climate system but uncertainties over their interactions and their effects on the Earth energy budget limit our understanding of the climate system and our ability to model it. The CALIPSO satellite was developed to provide new capabilities to observe aerosol and cloud from space and to reduce these uncertainties. CALIPSO carries the first polarization-sensitive lidar to fly in space, which has now provided a four-year record of global aerosol and cloud profiles. This paper briefly summarizes the status of the CALIPSO mission, describes some of the results from CALIPSO, and presents highlights of recent improvements in data products.
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Global view of aerosol vertical distributions from CALIPSO lidar measurements and GOCART simulations: Regional and seasonal variations
Journal of Geophysical Research, 2010Co-Authors: Mian Chin, Zhaoyan Liu, Chieko Kittaka, Ali Omar, David M. Winker, Thomas DiehlAbstract:This study examines seasonal variations of the vertical distribution of aerosols through a statistical analysis of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) lidar observations from June 2006 to November 2007. A data-screening scheme is developed to attain good quality data in cloud-free conditions, and the polarization measurement is used to separate dust from non-dust aerosol. The CALIPSO aerosol observations are compared with aerosol simulations from the Goddard Chemistry Aerosol Radiation Transport (GOCART) model and aerosol optical depth (AOD) measurements from the MODerate resolution Imaging Spectroradiometer (MODIS). The CALIPSO observations of geographical patterns and seasonal variations of AOD are generally consistent with GOCART simulations and MODIS retrievals especially near source regions, while the magnitude of AOD shows large discrepancies in most regions. Both the CALIPSO observation and GOCART model show that the aerosol extinction scale heights in major dust and smoke source regions are generally higher than that in industrial pollution source regions. The CALIPSO aerosol lidar ratio also generally agrees with GOCART model within 30% on regional scales. Major differences between satellite observations and GOCART model are identified, including (1) an underestimate of aerosol extinction by GOCART over the Indian sub-continent, (2) much larger aerosol extinction calculated by GOCART than observed by CALIPSO in dust source regions, (3) much weaker in magnitude and more concentrated aerosol in the lower atmosphere in CALIPSO observation than GOCART model over transported areas in midlatitudes, and (4) consistently lower aerosol scale height by CALIPSO observation than GOCART model. Possible factors contributing to these differences are discussed.
Mark A Vaughan - One of the best experts on this subject based on the ideXlab platform.
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Overview of the CALIPSO Version 4 Lidar Data Products
2016Co-Authors: Mark A Vaughan, Zhaoyan Liu, Charles R. Trepte, David M. Winker, Jacques Pelon, Anne Garnier, Melody A. Avery, Jason L. Tackett, Jayanta Kar, Ali OmarAbstract:NASA’s Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission is scheduled to release version 4 of their level 2 data products in the fall of 2016. This presentation will highlight some of the many significant improvements delivered by the version 4 CALIPSO lidar cloud and aerosol data products, with a particular focus on the retrieval of extinction-to-backscatter ratios for both ice clouds and water clouds.
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Detection of pollution outflow from Mexico City using CALIPSO lidar measurements
Remote Sensing of Environment, 2015Co-Authors: Jayanta Kar, Ali Omar, Mark A Vaughan, Charles R. Trepte, Jason L. Tackett, Z. Liu, Thomas Duncan Fairlie, R. KowchAbstract:Abstract We present the evidence of regional scale outflow of particulate pollution from Mexico City using measurements from the space borne CALIPSO lidar. The vertically resolved results are presented for winter months when the large scale biomass burning from nearby areas is minimized, and the aerosol loading is dominated by anthropogenic outflow from the city. The particulate depolarization ratio in the outflowing plume has high values and reflects the influence of mixing of the urban pollution with the ubiquitous dust around the city. This is consistent with the results from previous field campaigns in the city and leads to polluted dust being the dominant aerosol subtype as identified by the CALIPSO algorithm. A first order estimate of the mass flux on two episodes using the aerosol extinction profiles from CALIPSO indicates outflow of several hundred tons per day.
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Macrophysical properties of tropical cirrus clouds from the CALIPSO satellite and from ground‐based micropulse and Raman lidars
Journal of Geophysical Research: Atmospheres, 2013Co-Authors: Tyler J. Thorsen, Mark A Vaughan, David M. Winker, Jennifer M. Comstock, Chitra Sivaraman, David D. TurnerAbstract:Lidar observations of cirrus cloud macrophysical properties over the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) program Darwin, Australia site are compared from the Cloud-Aerosol Lidar and In- frared Pathfinder Satellite Observation (CALIPSO) satellite, the ground-based ARM micropulse lidar (MPL), and the ARM Raman lidar (RL). Comparisons are made using the subset of profiles where the lidar beam is not fully attenuated. Daytime measurements using the RL are shown to be relatively unaffected by the solar background and are therefore suited for checking the validity of diurnal cycles. RL and CALIPSO cloud fraction profiles show good agreement while the MPL detects significantly less cirrus, particularly during the daytime. Both MPL and CALIPSO observations show that cirrus clouds occur less frequently during the day than at night at all altitudes. In contrast, the RL diurnal cy- cle is significantly different than zero only below about 11 km; where it is the opposite sign (i.e. more clouds during the daytime). For cirrus geomet- rical thickness, the MPL and CALIPSO observations agree well and both datasets have signficantly thinner clouds during the daytime than the RL. From the examination of hourly MPL and RL cirrus cloud thickness and through the application ofmore » daytime detection limits to all CALIPSO data we find that the decreased MPL and CALIPSO cloud thickness during the daytime is very likely a result of increased daytime noise. This study highlights the vast im- provement the RL provides (compared to the MPL) in the ARM program's ability to observe tropical cirrus clouds as well as a valuable ground-based lidar dataset for the validation of CALIPSO observations and to help im- prove our understanding of tropical cirrus clouds.« less
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macrophysical properties of tropical cirrus clouds from the CALIPSO satellite and from ground based micropulse and raman lidars
Journal of Geophysical Research, 2013Co-Authors: Tyler J. Thorsen, Mark A Vaughan, David M. Winker, Jennifer M. Comstock, Chitra Sivaraman, David D. TurnerAbstract:Lidar observations of cirrus cloud macrophysical properties over the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) program Darwin, Australia site are compared from the Cloud-Aerosol Lidar and In- frared Pathfinder Satellite Observation (CALIPSO) satellite, the ground-based ARM micropulse lidar (MPL), and the ARM Raman lidar (RL). Comparisons are made using the subset of profiles where the lidar beam is not fully attenuated. Daytime measurements using the RL are shown to be relatively unaffected by the solar background and are therefore suited for checking the validity of diurnal cycles. RL and CALIPSO cloud fraction profiles show good agreement while the MPL detects significantly less cirrus, particularly during the daytime. Both MPL and CALIPSO observations show that cirrus clouds occur less frequently during the day than at night at all altitudes. In contrast, the RL diurnal cy- cle is significantly different than zero only below about 11 km; where it is the opposite sign (i.e. more clouds during the daytime). For cirrus geomet- rical thickness, the MPL and CALIPSO observations agree well and both datasets have signficantly thinner clouds during the daytime than the RL. From the examination of hourly MPL and RL cirrus cloud thickness and through the application ofmore » daytime detection limits to all CALIPSO data we find that the decreased MPL and CALIPSO cloud thickness during the daytime is very likely a result of increased daytime noise. This study highlights the vast im- provement the RL provides (compared to the MPL) in the ARM program's ability to observe tropical cirrus clouds as well as a valuable ground-based lidar dataset for the validation of CALIPSO observations and to help im- prove our understanding of tropical cirrus clouds.« less
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Comparison of Two Different Cloud Climatologies Derived from CALIOP-Attenuated Backscattered Measurements (Level 1): The CALIPSO-ST and the CALIPSO-GOCCP
Journal of Atmospheric and Oceanic Technology, 2013Co-Authors: Hélène Chepfer, Brian Getzewich, Mark A Vaughan, Dave Winker, G. Cesana, Zhaoyan LiuAbstract:AbstractTwo different cloud climatologies have been derived from the same NASA–Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP)-measured attenuated backscattered profile (level 1, version 3 dataset). The first climatology, named Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations–Science Team (CALIPSO-ST), is based on the standard CALIOP cloud mask (level 2 product, version 3), with the aim to document clouds with the highest possible spatiotemporal resolution, taking full advantage of the CALIOP capabilities and sensitivity for a wide range of cloud scientific studies. The second climatology, named GCM-Oriented CALIPSO Cloud Product (CALIPSO-GOCCP), is aimed at a single goal: evaluating GCM prediction of cloudiness. For this specific purpose, it has been designed to be fully consistent with the CALIPSO simulator included in the Cloud Feedback Model Intercomparison Project (CFMIP) Observation Simulator Package (COSP) used within version 2 of the CFMIP (CFMIP-2) experiment and phase...
Chieko Kittaka - One of the best experts on this subject based on the ideXlab platform.
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The CALIPSO Mission: results and progress
Lidar Technologies Techniques and Measurements for Atmospheric Remote Sensing VI, 2010Co-Authors: Dave Winker, Zhaoyan Liu, Chieko Kittaka, Brian Getzewich, Michael C. Pitts, Melody A. Avery, Jason L. Tackett, Mark A VaughanAbstract:Aerosols and clouds play important roles in Earth's climate system but uncertainties over their interactions and their effects on the Earth energy budget limit our understanding of the climate system and our ability to model it. The CALIPSO satellite was developed to provide new capabilities to observe aerosol and cloud from space and to reduce these uncertainties. CALIPSO carries the first polarization-sensitive lidar to fly in space, which has now provided a four-year record of global aerosol and cloud profiles. This paper briefly summarizes the status of the CALIPSO mission, describes some of the results from CALIPSO, and presents highlights of recent improvements in data products.
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THE CALIPSO MISSION: A Global 3D View of Aerosols and Clouds
Bulletin of the American Meteorological Society, 2010Co-Authors: David M. Winker, Jacques Pelon, Raymond M. Hoff, James A. Coakley, Steven A. Ackerman, Robert J. Charlson, Peter R. Colarco, Pierre H. Flamant, Chieko KittakaAbstract:Aerosols and clouds have important effects on Earth's climate through their effects on the radiation budget and the cycling of water between the atmosphere and Earth's surface. Limitations in our understanding of the global distribution and properties of aerosols and clouds are partly responsible for the current uncertainties in modeling the global climate system and predicting climate change. The CALIPSO satellite was developed as a joint project between NASA and the French space agency CNES to provide needed capabilities to observe aerosols and clouds from space. CALIPSO carries CALIOP, a two-wavelength, polarization-sensitive lidar, along with two passive sensors operating in the visible and thermal infrared spectral regions. CALIOP is the first lidar to provide long-term atmospheric measurements from Earth's orbit. Its profiling and polarization capabilities offer unique measurement capabilities. Launched together with the CloudSat satellite in April 2006 and now flying in formation with the A-train satellite constellation, CALIPSO is now providing information on the distribution and properties of aerosols and clouds, which is fundamental to advancing our understanding and prediction of climate. This paper provides an overview of the CALIPSO mission and instruments, the data produced, and early results.
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Global view of aerosol vertical distributions from CALIPSO lidar measurements and GOCART simulations: Regional and seasonal variations
Journal of Geophysical Research, 2010Co-Authors: Mian Chin, Zhaoyan Liu, Chieko Kittaka, Ali Omar, David M. Winker, Thomas DiehlAbstract:This study examines seasonal variations of the vertical distribution of aerosols through a statistical analysis of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) lidar observations from June 2006 to November 2007. A data-screening scheme is developed to attain good quality data in cloud-free conditions, and the polarization measurement is used to separate dust from non-dust aerosol. The CALIPSO aerosol observations are compared with aerosol simulations from the Goddard Chemistry Aerosol Radiation Transport (GOCART) model and aerosol optical depth (AOD) measurements from the MODerate resolution Imaging Spectroradiometer (MODIS). The CALIPSO observations of geographical patterns and seasonal variations of AOD are generally consistent with GOCART simulations and MODIS retrievals especially near source regions, while the magnitude of AOD shows large discrepancies in most regions. Both the CALIPSO observation and GOCART model show that the aerosol extinction scale heights in major dust and smoke source regions are generally higher than that in industrial pollution source regions. The CALIPSO aerosol lidar ratio also generally agrees with GOCART model within 30% on regional scales. Major differences between satellite observations and GOCART model are identified, including (1) an underestimate of aerosol extinction by GOCART over the Indian sub-continent, (2) much larger aerosol extinction calculated by GOCART than observed by CALIPSO in dust source regions, (3) much weaker in magnitude and more concentrated aerosol in the lower atmosphere in CALIPSO observation than GOCART model over transported areas in midlatitudes, and (4) consistently lower aerosol scale height by CALIPSO observation than GOCART model. Possible factors contributing to these differences are discussed.
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CALIPSO at Four: Results and Progress
2010Co-Authors: Dave Winker, Chieko Kittaka, Michael C. Pitts, Jason L. Tackett, Z. Liu, Mark VaughanAbstract:Aerosols and clouds play important roles in Earth?s climate system, but limitations in our ability to observe them globally limit our understanding of the climate system and our ability to model it. The CALIPSO satellite was developed to provide new capabilities to observe aerosol and cloud from space. CALIPSO carries the first polarization-sensitive lidar to fly in space, which has now provided a four-year record of global aerosol and cloud profiles. This paper briefly summarizes the status of the CALIPSO mission, describes some of the results from CALIPSO, and presents highlights of recent improvements in data products.
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The CALIPSO Automated Aerosol Classification and Lidar Ratio Selection Algorithm
Journal of Atmospheric and Oceanic Technology, 2009Co-Authors: Ali Omar, Chieko Kittaka, Chris A. Hostetler, Mark A Vaughan, Charles R. Trepte, David M. Winker, Richard A. Ferrare, Kam-pui Lee, Raymond R. RogersAbstract:Abstract Descriptions are provided of the aerosol classification algorithms and the extinction-to-backscatter ratio (lidar ratio) selection schemes for the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) aerosol products. One year of CALIPSO level 2 version 2 data are analyzed to assess the veracity of the CALIPSO aerosol-type identification algorithm and generate vertically resolved distributions of aerosol types and their respective optical characteristics. To assess the robustness of the algorithm, the interannual variability is analyzed by using a fixed season (June–August) and aerosol type (polluted dust) over two consecutive years (2006 and 2007). The CALIPSO models define six aerosol types: clean continental, clean marine, dust, polluted continental, polluted dust, and smoke, with 532-nm (1064 nm) extinction-to-backscatter ratios Sa of 35 (30), 20 (45), 40 (55), 70 (30), 65 (30), and 70 (40) sr, respectively. This paper presents the global distributions of the CALIPSO aerosol types, the complementary distributions of integrated attenuated backscatter, and the volume depolarization ratio for each type. The aerosol-type distributions are further partitioned according to surface type (land/ocean) and detection resolution (5, 20, and 80 km) for optical and spatial context, because the optically thick layers are found most often at the smallest spatial resolution. Except for clean marine and polluted continental, all the aerosol types are found preferentially at the 80-km resolution. Nearly 80% of the smoke cases and 60% of the polluted dust cases are found over water, whereas dust and polluted continental cases are found over both land and water at comparable frequencies. Because the CALIPSO observables do not sufficiently constrain the determination of the aerosol, the surface type is used to augment the selection criteria. Distributions of the total attenuated color ratios show that the use of surface type in the typing algorithm does not result in abrupt and artificial changes in aerosol type or extinction.