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1

The Retrieval of Ice-Cloud Properties from Cloud Radar and Lidar Synergy.  

NASA Astrophysics Data System (ADS)

Clouds are an important component of the earth's climate system. A better description of their microphysical properties is needed to improve radiative transfer calculations. In the framework of the Earth, Clouds, Aerosols, and Radiation Explorer (EarthCARE) mission preparation, the radar-lidar (RALI) airborne system, developed at L'Institut Pierre Simon Laplace (France), can be used as an airborne demonstrator. This paper presents an original method that combines cloud radar (94-95 GHz) and lidar data to derive the radiative and microphysical properties of clouds. It combines the apparent backscatter reflectivity from the radar and the apparent backscatter coefficient from the lidar. The principle of this algorithm relies on the use of a relationship between the extinction coefficient and the radar specific attenuation, derived from airborne microphysical data and Mie scattering calculations. To solve radar and lidar equations in the cloud region where signals can be obtained from both instruments, the extinction coefficients at some reference range z0 must be known. Because the algorithms are stable for inversion performed from range z0 toward the emitter, z0 is chosen at the farther cloud boundary as observed by the lidar. Then, making an assumption of a relationship between extinction coefficient and backscattering coefficient, the whole extinction coefficient, the apparent reflectivity, cloud physical parameters, the effective radius, and ice water content profiles are derived. This algorithm is applied to a blind test for downward-looking instruments where the original profiles are derived from in situ measurements. It is also applied to real lidar and radar data, obtained during the 1998 Cloud Lidar and Radar Experiment (CLARE'98) field project when a prototype airborne RALI system was flown pointing at nadir. The results from the synergetic algorithm agree reasonably well with the in situ measurements.

Tinel, Claire; Testud, Jacques; Pelon, Jacques; Hogan, Robin J.; Protat, Alain; Delanoë, Julien; Bouniol, Dominique

2005-06-01

2

Investigating cloud radar sensitivity to optically thin cirrus using collocated Raman lidar observations  

NASA Astrophysics Data System (ADS)

The sensitivity of the millimeter cloud radar (MMCR) to optically thin single-layer cirrus at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site is investigated using collocated Raman lidar observations. The sensitivity is characterized in terms of cloud optical depth (OD) and infrared (IR) radiative flux using over three years of coincident Raman lidar and MMCR observations. For cases when the Raman lidar is not fully attenuated (OD < 2.0) the MMCR detects approximately 70% of the total cloud OD with the majority of missed cloud OD occurring near cloud top. If only MMCR observations are used for computing cloudy top-of-the-atmosphere (TOA) IR flux, the missed cloud OD results in TOA flux biases from 0 to over 100 W/m2; however, the most frequently occurring bias is approximately 16 W/m2. This result highlights the importance of combining Raman lidar, or other sensitive cloud lidars that are able to measure cloud extinction directly, with the MMCR in order to accurately characterize the cloud radiative forcing for thin cirrus cases.

Borg, Lori A.; Holz, Robert E.; Turner, David D.

2011-03-01

3

Validation of SCIAMACHY O2 A band cloud heights using Cloudnet radar/lidar measurements  

NASA Astrophysics Data System (ADS)

For the first time two SCIAMACHY O2 A band cloud height products are validated using ground-based radar/lidar measurements between January 2003 and December 2011. The products are the ESA Level 2 (L2) version 5.02 cloud top height and the FRESCO (Fast Retrieval Scheme for Clouds from the Oxygen A band) version 6 cloud height. The radar/lidar profiles are obtained at the Cloudnet sites of Cabauw and Lindenberg, and are averaged for one hour centered at the SCIAMACHY overpass time to achieve an optimal temporal and spatial match. In total we have about 220 cases of single layer clouds and 200 cases of multi-layer clouds. The FRESCO cloud height and ESA L2 cloud top height are compared with the Cloudnet cloud top height and Cloudnet cloud middle height. We find that the ESA L2 cloud top height has a better agreement with the Cloudnet cloud top height than the Cloudnet cloud middle height. The ESA L2 cloud top height is on average 0.44 km higher than the Cloudnet cloud top height, with a standard deviation of 3.07 km. The FRESCO cloud height is closer to the Cloudnet cloud middle height than the Cloudnet cloud top height. The mean difference between the FRESCO cloud height and the Cloudnet cloud middle height is -0.14 km with a standard deviation of 1.88 km. The SCIAMACHY cloud height products are further compared to the Cloudnet cloud top height and the Cloudnet cloud middle height in 1 km bins. For single layer clouds, the difference between the ESA L2 cloud top height and the Cloudnet cloud top height is less than 1 km for each cloud bin at 3-7 km, which is 24 % percent of the data. The difference between the FRESCO cloud height and the Cloudnet cloud middle height is less than 1 km for each cloud bin at 0-6 km, which is 85 % percent of the data. The results are similar for multi-layer clouds, but the percentage of cases having a bias within 1 km is smaller than for single layer clouds. Since globally about 60 % of all clouds are low clouds and 42 % are single-layer low clouds, we expect that globally for a large percentage of cases the FRESCO cloud height would be close to the cloud middle height.

Wang, P.; Stammes, P.

2013-10-01

4

Characteristics of mixed-phase clouds. I: Lidar, radar and aircraft observations from CLARE'98  

NASA Astrophysics Data System (ADS)

Results are presented from two case-studies during the 1998 Cloud Lidar And Radar Experiment (CLARE'98) in which mixed-phase clouds were observed by a multitude of ground-based and airborne instruments. In both cases supercooled liquid water was present in the form of highly reflective layers in lidar imagery, while the radar echo was dominated by the contribution from the much larger ice particles. In the first case-study, four individual liquid-water layers were observed by an airborne nadir-pointing polarimetric lidar at temperatures between -7 °C and -15 °C, embedded within a warm-frontal ice cloud. Their phase was confirmed by the in situ measurements and by their very low depolarization of the lidar signal. The effective droplet radius ranged from 2 to 5 m. Simultaneous temperature and vertical-wind measurements by the aircraft demonstrated that they were generated by a gravity wave with a wavelength of around 15 km. Thin sector plates grew rapidly in the high-supersaturation conditions and were responsible for the high values of differential reflectivity measured by the ground-based radar in the vicinity of the layers. In the second case-study a liquid-water altocumulus layer was observed at -23 °C, which was slowly glaciating. Profiles of liquid and ice extinction coefficient, water content and effective radius were derived from the remote measurements taken in both cases, using radar-lidar and dual-wavelength radar techniques to size the ice particles; where in situ validation was available, agreement was good. Radiative-transfer calculations were then performed on these profiles to ascertain the radiative effect of the supercooled water. It was found that, despite their low liquid-water path (generally less than 10-20 g m-2), these clouds caused a significant increase in the reflection of solar radiation to space, even when cirrus was present, above which the long-wave signal dominated. In the cases considered, their capacity to decrease the net absorbed radiation was at least twice as large as that of the ice. The layers were typically 100-200 m thick, suggesting that they are unlikely to be adequately represented by the resolutions of current forecast and climate models. These results suggest that a spaceborne lidar and radar would be ideally suited to characterizing the occurrence and climatological importance of mixed-phase clouds on a global scale.

Hogan, R. J.; Francis, P. N.; Flentje, H.; Illingworth, A. J.; Quante, M.; Pelon, J.

2003-07-01

5

Cirrus Cloud Microphysical Property Retrieval Using Lidar and Radar Measurements. Part I: Algorithm Description and Comparison with In Situ Data  

Microsoft Academic Search

A retrieval algorithm is described to estimate vertical profiles of cirrus-cloud ice water content (IWC) and general effective size Dge from combined lidar and radar measurements. In the algorithm, the lidar extinction coefficient is parameterized as = IWC[a0 + (a1\\/Dge)] and water equivalent radar reflectivity factor Ze is parameterized as Ze = C(IWC\\/i)Dbge, where a0, a1, C, and b are

Zhien Wang; Kenneth Sassen

2002-01-01

6

Cloud effective particle size and water content profile retrievals using combined lidar and radar observations, 2, Comparison with IR radiometer and in situ measurements of ice clouds  

NASA Astrophysics Data System (ADS)

A new combined iidar/radar inversion procedure has been developed for cloud effective radius and water content retrievals. The algorithm treats the lidar extinction, derived effective particle size, and multiple-scattering effects together in a consistent fashion. This procedure has been applied to data taken during the Netherlands Cloud and Radiation (CLARA) campaign and the Cloud Lidar and Radar Experiment (CLARE'98) multisensor cloud measurement campaign. The results of the algorithm compare well with simultaneous IR radiometer cloud measurements as well as with measurements made by using aircraft-mounted two-dimensional probe particle-sizing instruments.

Donovan, D. P.; van Lammeren, A. C. A. P.; Hogan, R. J.; Russchenberg, H. W. J.; Apituley, A.; Francis, P.; Testud, J.; Pelon, J.; Quante, M.; Goddard, J.

2001-11-01

7

An assessment of Multiangle Imaging Spectroradiometer (MISR) stereo-derived cloud top heights and cloud top winds using ground-based radar, lidar, and microwave radiometers  

Microsoft Academic Search

(1) In this article stereoscopically derived cloud top heights and cloud winds estimated from the Multiangle Imaging Spectroradiometer (MISR) are assessed. MISR is one of five instruments on board the NASATerra satellite. The cloud top height assessment is based on a comparison of more than 4 years of MISR retrievals with that derived from ground-based radar and lidar systems operated

Roger T. Marchand; Thomas P. Ackerman; Catherine Moroney

2007-01-01

8

An assessment of Multiangle Imaging Spectroradiometer (MISR) stereo-derived cloud top heights and cloud top winds using ground-based radar, lidar, and microwave radiometers  

Microsoft Academic Search

In this article stereoscopically derived cloud top heights and cloud winds estimated from the Multiangle Imaging Spectroradiometer (MISR) are assessed. MISR is one of five instruments on board the NASA Terra satellite. The cloud top height assessment is based on a comparison of more than 4 years of MISR retrievals with that derived from ground-based radar and lidar systems operated

Roger T. Marchand; Thomas P. Ackerman; Catherine Moroney

2007-01-01

9

ATLID: atmospheric lidar four clouds and aerolsol observations combined with radar sounding  

NASA Astrophysics Data System (ADS)

The atmospheric lidar ATLID is part of the payload of the joint collaborative satellite mission Earth Cloud and Aerosol Explorer (EarthCARE) conducted by the European Space Agency (ESA) and the National Space Development Agency of Japan (JAXA). In December 2002, ESA granted Alcatel Space with a phase A study of the EarthCARE mission in which Alcatel Space is also in charge to define ATLID. The primary objective of ATLID at the horizon 2011 is to provide global observation of clouds in synergy with a cloud profiling radar (CPR) mounted on the same platform. The planned spaceborne mission also embarks an imager and a radiometer and shall fly for 3 years. The lidar design is based on a novel concept that maximises the scientific return and fosters a cost-effective approach. This improved capability results from a better understanding of the way optical characteristics of aerosol and clouds affect the performance budget. For that purpose, an end to end performance model has been developed utilising a versatile data retrieval method suitable for new and more conventional approaches. A synthesis of the achievable performance will be presented to illustrate the potential of the system together with a description of the design.

Pain, Th.; Martimort, Ph.; Tanguy, Ph.; Leibrandt, W.; Hélière, A.

2004-06-01

10

On the relationship among cloud turbulence, droplet formation and drizzle as viewed by Doppler radar, microwave radiometer and lidar  

SciTech Connect

Cloud radar, microwave radiometer, and lidar remote sensing data acquired during the Atlantic Stratocumulus Transition Experiment (ASTEX) are analyzed to address the relationship between (1) drop number concentration and cloud turbulence as represented by vertical velocity and vertical velocity variance and (2) drizzle formation and cloud turbulence. Six cases, each of about 12 hours duration, are examined; three of these cases are characteristic of nondrizzling boundary layers and three of drizzling boundary layers. In all cases, microphysical retrievals are only performed when drizzle is negligible (radar reflectivity{lt}{minus}17dBZ). It is shown that for the cases examined, there is, in general, no correlation between drop concentration and cloud base updraft strength, although for two of the nondrizzling cases exhibiting more classical stratocumulus features, these two parameters are correlated. On drizzling days, drop concentration and cloud-base vertical velocity were either not correlated or negatively correlated. There is a significant positive correlation between drop concentration and mean in-cloud vertical velocity variance for both nondrizzling boundary layers (correlation coefficient r=0.45) and boundary layers that have experienced drizzle (r=0.38). In general, there is a high correlation (r{gt}0.5) between radar reflectivity and in-cloud vertical velocity variance, although one of the boundary layers that experienced drizzle exhibited a negative correlation between these parameters. However, in the subcloud region, all boundary layers that experienced drizzle exhibit a negative correlation between radar reflectivity and vertical velocity variance. {copyright} 1999 American Geophysical Union

Feingold, G.; Frisch, A.S. [Cooperative Institute for Research in the Atmosphere/NOAA, Environmental Technology Laboratory Boulder, Colorado (United States); Stevens, B. [Department of Atmospheric Sciences, University of California, Los Angeles (United States); Cotton, W.R. [Department of Atmospheric Science, Colorado State University, Fort Collins (United States)

1999-09-01

11

Vertical cloud properties in the tropical western Pacific Ocean: Validation of the CCSR\\/NIES\\/FRCGC GCM by shipborne radar and lidar  

Microsoft Academic Search

This study examined the vertical cloud structure over the tropical western Pacific Ocean using 95-GHz radar and lidar data observed from September to December 2001 during the MR01-K05 cruise of the research vessel Mirai. The cloud vertical structure was homogeneous between 6 and 10 km, and the maximum cloud occurrence was 20% and located at 12 km. The mean precipitation

Hajime Okamoto; Tomoaki Nishizawa; Toshihiko Takemura; Kaori Sato; Hiroshi Kumagai; Yuichi Ohno; Nobuo Sugimoto; Atsushi Shimizu; Ichiro Matsui; Teruyuki Nakajima

2008-01-01

12

Development of radar and lidar simulator and its application to the evaluation of the cloud and aerosol microphysics in the AGCM  

NASA Astrophysics Data System (ADS)

The radar and lidar simulator is presented for the evaluation of the cloud and aerosol microphysical properties reproduced in the models such as the AGCM and the NHM. There are two possible ways to evaluate the macro-scale and microphysical properties of clouds and aerosols simulated in the models; one is the comparison of the simulated microphysics with the retrieved ones by the algorithms. The other is the direct comparisons of the observed and simulated radar and lidar signals. The simulator is designed to use the outputs about the cloud and aerosol microphysical properties from the models to simulate the observables obtained by the radar and the lidar. It can treat ice and water clouds as well as aerosols. Particle shapes and orientations of ice particles are also taken into account in the estimation of the backscattering and extinction properties of ice clouds in the radar and lidar wavelengths. Four aerosol types are also considered; sulfate, carbonaceous, sea-salt and dust particles, in the lidar simulations. The simulator has a function to generate both of the ground-based and space-borne radar and lidar signals from the output parameters. It is worth to note that the same cloud and aerosol particle models and their scattering properties are also used in the retrieval algorithms for cloud and aerosol microphysics from the space-borne or ground-based radar and lidar observations. This consistency assures the further investigation of the information content obtained in the comparisons of observed and simulated signals. Some application of the radar and lidar simulator is demonstrated for the comparison of the shipborne measurements and the AGCM. We also present the comparisons of the radar reflectivity observed in CloudSat and the lidar backscattering coefficients at 532nm and 1064nm and depolarization ratio in CALIPSO with the simulated signals in the GCM. Extension of the simulator for the EarthCARE CPR and ATLID lidar is also introduced. Information content in the comparisons of the observed and simulated signals is discussed together with the analysis of the comparisons of retrieved and simulated microphysics of clouds and aerosols. The essential parts of the radar and lidar simulator have been incorporated into the Joint Simulator for Satellite Sensors(J-simulator).

Okamoto, H.; Sato, K.; Takemura, T.; Hagihara, Y.; Nishizawa, T.

2011-12-01

13

Mapping tropical forest biomass with radar and spaceborne LiDAR: overcoming problems of high biomass and persistent cloud  

NASA Astrophysics Data System (ADS)

Spatially-explicit maps of aboveground biomass are essential for calculating the losses and gains in forest carbon at a regional to national level. The production of such maps across wide areas will become increasingly necessary as international efforts to protect primary forests, such as the REDD+ (Reducing Emissions from Deforestation and forest Degradation) mechanism, come into effect, alongside their use for management and research more generally. However, mapping biomass over high-biomass tropical forest is challenging as (1) direct regressions with optical and radar data saturate, (2) much of the tropics is persistently cloud-covered, reducing the availability of optical data, (3) many regions include steep topography, making the use of radar data complex, (4) while LiDAR data does not suffer from saturation, expensive aircraft-derived data are necessary for complete coverage. We present a solution to the problems, using a combination of terrain-corrected L-band radar data (ALOS PALSAR), spaceborne LiDAR data (ICESat GLAS) and ground-based data. We map Gabon's Lopé National Park (5000 km2) because it includes a range of vegetation types from savanna to closed-canopy tropical forest, is topographically complex, has no recent cloud-free high-resolution optical data, and the dense forest is above the saturation point for radar. Our 100 m resolution biomass map is derived from fusing spaceborne LiDAR (7142 ICESat GLAS footprints), 96 ground-based plots (average size 0.8 ha) and an unsupervised classification of terrain-corrected ALOS PALSAR radar data, from which we derive the aboveground biomass stocks of the park to be 78 Tg C (173 Mg C ha-1). This value is consistent with our field data average of 181 Mg C ha-1, from the field plots measured in 2009 covering a total of 78 ha, and which are independent as they were not used for the GLAS-biomass estimation. We estimate an uncertainty of ± 25 % on our carbon stock value for the park. This error term includes uncertainties resulting from the use of a generic tropical allometric equation, the use of GLAS data to estimate Lorey's height, and the necessity of separating the landscape into distinct classes. As there is currently no spaceborne LiDAR satellite in operation (GLAS data is available for 2003-2007 only), this methodology is not suitable for change-detection. This research underlines the need for new satellite LiDAR data to provide the potential for biomass-change estimates, although this need will not be met before 2015.

Mitchard, E. T. A.; Saatchi, S. S.; White, L. J. T.; Abernethy, K. A.; Jeffery, K. J.; Lewis, S. L.; Collins, M.; Lefsky, M. A.; Leal, M. E.; Woodhouse, I. H.; Meir, P.

2011-08-01

14

Evaluating the Potential of Retrieving Vertically-Resolved Cloud Drop Microphysical Properties From APS/RSP Polarization Measurements Combined With Lidar and Radar Using Large-Eddy Simulations  

NASA Astrophysics Data System (ADS)

Multi-spectral, multi-directional polarimetric measurements, such as those made by the Aerosol Polarimetry Sensor (APS) on the forthcoming Glory satellite mission, coupled with co-located CALIPSO/CLOUDSAT lidar and radar measurements have great potential in retrieving accurate information about cloud droplet number concentrations and the vertical distribution of cloud liquid water content, which are crucial quantities for studies on, e.g., indirect aerosol effects. A cloud retrieval algorithm making use of such a combination of measurements has been developed and tested on measurements of an aircraft-mounted version of APS, the Research Scanning Polarimeter (RSP),in combination with aircraft-based lidar and radar measurements. However, validating the retrieval results can be challenging due to lack of validation data or the difficulty of interpreting and comparing retrieval results from different instruments. In this presentation we present an additional validation approach in which APS/RSP, lidar and radar measurements are simulated based on large-eddy simulations of marine stratocumulus fields in various atmospheric conditions. By comparing the quantities retrieved from these simulated measurement with the true values from the large-eddy simulations, we will demonstrate the potential and limitations of this retrieval approach.

Cairns, B.; van Diedenhoven, B.; Ackerman, A. S.

2009-12-01

15

Characterization of ice cloud properties obtained by shipborne radar/lidar over the tropical western Pacific Ocean for evaluation of an atmospheric general circulation model  

NASA Astrophysics Data System (ADS)

This study analyzed 95-GHz radar/lidar data collected from the R/V Mirai over the tropical western Pacific to characterize the vertical distribution of ice cloud effective radius reff, ice water content IWC, and in-cloud vertical velocity of the region in conjunction with weather regimes classified by International Satellite Cloud Climatology Project (ISCCP) cluster analysis. Ice clouds observed from the Mirai were roughly consistent with the ISCCP weather regimes; more convectively active regimes had larger amounts of high cloud consisting of deeper cloud with larger ice water path (IWP) and precipitating ice fraction. Ice cloud microphysics of the Center for Climate System Research, National Institute for Environmental Studies, Frontier Research Center for Global Change atmospheric general circulation model (AGCM) was then evaluated using the radar-lidar simulator and ISCCP weather regimes for comparison of the statistics at different scales. The model tended to produce a high cloud fraction that was two times larger in the cirrus regimes but 50% lower in the deepest convective regime. The simulated IWP could only weakly reproduce the observed variety and generally underestimated the observed values despite the weather regimes. Cutoff in the simulated grid mean IWC around 0.1 g-3 was too small, especially above 11 km. The AGCM successfully predicted the observed frequency distribution for reff above 11 km, but produced large overestimation in the peak value below 11 km due to the excessively large fraction of reff ˜100 ?m. Establishing a cutoff for cloud ice at reff > 120 ?m was found to be quite reasonable, although it would miss some of the larger particles that were observed.

Sato, Kaori; Okamoto, Hajime; Takemura, Toshihiko; Kumagai, Hiroshi; Sugimoto, Nobuo

2010-08-01

16

The Ability of MM5 to Simulate Ice Clouds: Systematic Comparison between Simulated and Measured Fluxes and Lidar/Radar Profiles at SIRTA Atmospheric Observatory  

SciTech Connect

Ice clouds play a major role in the radiative energy budget of the Earth-atmosphere system (Liou 1986). Their radiative effect is governed primarily by the equilibrium between their albedo and greenhouse effects. Both macrophysical and microphysical properties of ice clouds regulate this equilibrium. For quantifying the effect of these clouds onto climate and weather systems, they must be properly characterized in atmospheric models. In this paper we use remote-sensing measurements from the SIRTA ground based atmospheric observatory (Site Instrumental de Recherche par Teledetection Atmospherique, http://sirta.lmd.polytechnique.fr). Lidar and radar observations taken over 18 months are used, in order to gain statistical confidence in the model evaluation. Along this period of time, 62 days are selected for study because they contain parts of ice clouds. We use the ''model to observations'' approach by simulating lidar and radar signals from MM5 outputs. Other more classical variables such as shortwave and longwave radiative fluxes are also used. Four microphysical schemes, among which that proposed by Reisner et al. (1998) with original or modified parameterizations of particle terminal fall velocities (Zurovac-Jevtic and Zhang 2003, Heymsfield and Donner 1990), and the simplified Dudhia (1989) scheme are evaluated in this study.

Chiriaco, M.; Vautard, R.; Chepfer, H.; Haeffelin, M.; Wanherdrick, Y.; Morille, Y.; Protat, A.; Dudhia, J.

2005-03-18

17

Mapping tropical forest biomass with radar and spaceborne LiDAR in Lopé National Park, Gabon: overcoming problems of high biomass and persistent cloud  

NASA Astrophysics Data System (ADS)

Spatially-explicit maps of aboveground biomass are essential for calculating the losses and gains in forest carbon at a regional to national level. The production of such maps across wide areas will become increasingly necessary as international efforts to protect primary forests, such as the REDD+ (Reducing Emissions from Deforestation and forest Degradation) mechanism, come into effect, alongside their use for management and research more generally. However, mapping biomass over high-biomass tropical forest is challenging as (1) direct regressions with optical and radar data saturate, (2) much of the tropics is persistently cloud-covered, reducing the availability of optical data, (3) many regions include steep topography, making the use of radar data complex, (5) while LiDAR data does not suffer from saturation, expensive aircraft-derived data are necessary for complete coverage. We present a solution to the problems, using a combination of terrain-corrected L-band radar data (ALOS PALSAR), spaceborne LiDAR data (ICESat GLAS) and ground-based data. We map Gabon's Lopé National Park (5000 km2) because it includes a range of vegetation types from savanna to closed-canopy tropical forest, is topographically complex, has no recent contiguous cloud-free high-resolution optical data, and the dense forest is above the saturation point for radar. Our 100 m resolution biomass map is derived from fusing spaceborne LiDAR (7142 ICESat GLAS footprints), 96 ground-based plots (average size 0.8 ha) and an unsupervised classification of terrain-corrected ALOS PALSAR radar data, from which we derive the aboveground biomass stocks of the park to be 78 Tg C (173 Mg C ha-1). This value is consistent with our field data average of 181 Mg C ha-1, from the field plots measured in 2009 covering a total of 78 ha, and which are independent as they were not used for the GLAS-biomass estimation. We estimate an uncertainty of ±25% on our carbon stock value for the park. This error term includes uncertainties resulting from the use of a generic tropical allometric equation, the use of GLAS data to estimate Lorey's height, and the necessity of separating the landscape into distinct classes. As there is currently no spaceborne LiDAR satellite in operation (GLAS data is available for 2003-2009 only), this methodology is not suitable for change-detection. This research underlines the need for new satellite LiDAR data to provide the potential for biomass-change estimates, although this need will not be met before 2015.

Mitchard, E. T. A.; Saatchi, S. S.; White, L. J. T.; Abernethy, K. A.; Jeffery, K. J.; Lewis, S. L.; Collins, M.; Lefsky, M. A.; Leal, M. E.; Woodhouse, I. H.; Meir, P.

2012-01-01

18

Lidar-Radar Lower Atmospheric Observations.  

National Technical Information Service (NTIS)

Daytime observations of the vertical temperature and humidity structure in the atmosphere below 1000 meters made with a Cricketsonde rocket system are compared with simultaneous observations from a ruby lidar (laser radar) and a microwave K-band radar. Ob...

W. Viezee J. Oblanas

1968-01-01

19

Cloud and Precipitation Radar  

NASA Astrophysics Data System (ADS)

Precipitation or weather radar is an essential tool for research, diagnosis, and nowcasting of precipitation events like fronts or thunderstorms. Only with weather radar is it possible to gain insights into the three-dimensional structure of thunderstorms and to investigate processes like hail formation or tornado genesis. A number of different radar products are available to analyze the structure, dynamics and microphysics of precipitation systems. Cloud radars use short wavelengths to enable detection of small ice particles or cloud droplets. Their applications differ from weather radar as they are mostly orientated vertically, where different retrieval techniques can be applied.

Hagen, Martin; Höller, Hartmut; Schmidt, Kersten

20

Comparison of Cloud Boundaries Measured with 8.6 mm Radar and 10.6 Micrometer Lidar.  

National Technical Information Service (NTIS)

One of the most basic cloud properties is location; the height of cloud base and the height of cloud top. The glossary of meteorology defines cloud base (top) as follows: 'For a given cloud or cloud layer, that lowest (highest) level in the atmosphere at ...

T. Uttal J. M. Intrieri

1993-01-01

21

CloudSat spaceborne 94 GHz radar bright bands in the melting layer: An attenuation-driven upside-down lidar analog  

Microsoft Academic Search

The CloudSat satellite supports a W-band (94 GHz) cloud profiling radar. At this 3.2 mm wavelength, ground-based measurements of rainfall associated with melting snowflakes do not show the radar reflectivity peak that is characteristic of bright band measurements at longer (Rayleigh scattering-dominated) wavelengths. Nonetheless, examination of downward-looking CloudSat returns in precipitation often indicate an obvious signal peak in the melting

Kenneth Sassen; Sergey Matrosov; James Campbell

2007-01-01

22

Combined lidar-radar remote sensing: Initial results from CRYSTAL-FACE  

Microsoft Academic Search

In the near future, NASA plans to fly satellites carrying a two-wavelength polarization lidar and a 94-GHz cloud profiling radar in formation to provide complete global profiling of cloud and aerosol properties. The Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE) field campaign, conducted during July 2002, provided the first high-altitude collocated measurements from lidar

M. J. McGill; L. Li; W. D. Hart; G. M. Heymsfield; D. L. Hlavka; P. E. Racette; L. Tian; M. A. Vaughan; D. M. Winker

2004-01-01

23

Project Pre-Gondola I: Lidar Observations of the Pre-Gondola I Clouds.  

National Technical Information Service (NTIS)

The report describes lidar (laser radar) observations of the dust and steam clouds that resulted from the Pre-GONDOLA I series of four chemical explosions made near Fort Peck Reservoir, Montana, during October-November 1966. The neodymium lidar was well a...

J. W. Oblanas R. T. H. Collis

1967-01-01

24

Scanning ARM Cloud Radar Handbook.  

National Technical Information Service (NTIS)

The scanning ARM cloud radar (SACR) is a polarimetric Doppler radar consisting of three different radar designs based on operating frequency. These are designated as follows: (1) X-band SACR (X-SACR); (2) Ka-band SACR (Ka-SACR); and (3) W-band SACR (W-SAC...

K. Johnson K. Widener N. Bharadwaj

2012-01-01

25

Millimeter Wave Cloud Radar (MMCR) Handbook  

SciTech Connect

The millimeter cloud radar (MMCR) systems probe the extent and composition of clouds at millimeter wavelengths. The MMCR is a zenith-pointing radar that operates at a frequency of 35 GHz. The main purpose of this radar is to determine cloud boundaries (e.g., cloud bottoms and tops). This radar will also report radar reflectivity (dBZ) of the atmosphere up to 20 km. The radar possesses a doppler capability that will allow the measurement of cloud constituent vertical velocities.

KB Widener; K Johnson

2005-01-30

26

Modification of Lidar Point Cloud Processing Methodology  

Microsoft Academic Search

Airborne Laser Scanning (ALS), often called LiDAR (Light Detection And Raging), delivers a point cloud as a survey result. This point cloud consist of topographic surface data and coating elements (e.g. vegetation, buildings) is used to build a Digital Surface Model (DSM). The point cloud processing can be represented in following steps: OBTAINING DATA ? PRE-PROCESSING ? MAIN PROCESSING ?

Artur JANOWSKI

27

An Atmospheric Radiation Measurement Value-Added Product to Retrieve Optically Thin Cloud Visible Optical Depth using Micropulse Lidar  

SciTech Connect

The purpose of the Micropulse Lidar (MPL) Cloud Optical Depth (MPLCOD) Value-Added Product (VAP) is to retrieve the visible (short-wave) cloud optical depth for optically thin clouds using MPL. The advantage of using the MPL to derive optical depth is that lidar is able to detect optically thin cloud layers that may not be detected by millimeter cloud radar or radiometric techniques. The disadvantage of using lidar to derive optical depth is that the lidar signal becomes attenuation limited when ? approaches 3 (this value can vary depending on instrument specifications). As a result, the lidar will not detect optically thin clouds if an optically thick cloud obstructs the lidar beam.

Lo, C; Comstock, JM; Flynn, C

2006-10-01

28

Lidar and Radar Measurements of the melting layer in the frame of the Convective and Orographically-induced Precipitation Study  

NASA Astrophysics Data System (ADS)

During the Convective and Orographically-induced Precipitation Study (COPS), lidar dark bands were observed by the Univ. of BASILicata Raman lidar system (BASIL) on several IOPs and SOPs (among others, 23 July, 15 August, 17 August). Dark band signatures appear in the lidar measurements of particle backscattering at 355, 532 and 1064 nm and particle extinction at 355 and 532 nm, as well as in particle depolarization measurements. Lidar data are supported by measurements from the University of Hamburg cloud radar MIRA 36 (36 GHz), the University of Hamburg dual-polarization micro rain radars (24.1 GHz) and the University of Manchester Radio UHF clear air wind profiler (1.29 GHz). Results from BASIL and the radars are illustrated and discussed to support in the comprehension of the microphysical and scattering processes responsible for the appearance of the lidar dark band and radar bright band.

di Girolamo, Paolo; Summa, Donato; Bhawar, Rohini; di Iorio, Tatiana; Vaughan, Geraint; Norton, Emily; Peters, Gerhard

2009-03-01

29

Detecting trails in lidar point cloud data  

NASA Astrophysics Data System (ADS)

The goal of this work is to determine methods for detecting trails using statistics of LiDAR point cloud data, while avoiding reliance on a Digital Elevation Model (DEM). Creation of a DEM is a subjective process that requires assumptions be made about the density of the data points, the curvature of the ground, and other factors which can lead to very dierent results in the nal DEM product, with no single correct" result. Exploitation of point cloud data also lends itself well to automation. A LiDAR point cloud based trail detection scheme has been designed in which statistical measures of local neighborhoods of LiDAR points are calculated, image processing techniques employed to mask non-trail areas, and a constrained region growing scheme used to determine a nal trails map. Results of the LiDAR point cloud based trail detection scheme are presented and compared to a DEM-based trail detection scheme. Large trails are detected fairly reliably with some missing gaps, while smaller trails are detected less reliably. Overall results of the LiDAR point cloud based methods are comparable to the DEM-based results, with fewer false alarms.

Kim, Angela M.; Olsen, Richard C.

2012-05-01

30

Lidar and radar measurements of the melting layer: observations of dark and bright band phenomena  

NASA Astrophysics Data System (ADS)

Multi-wavelength lidar measurements in the melting layer revealing the presence of dark and bright bands have been performed by the University of BASILicata Raman lidar system (BASIL) during a stratiform rain event. Simultaneously radar measurements have been also performed from the same site by the University of Hamburg cloud radar MIRA 36 (35.5 GHz), the University of Hamburg dual-polarization micro rain radar (24.15 GHz) and the University of Manchester UHF wind profiler (1.29 GHz). Measurements from BASIL and the radars are illustrated and discussed in this paper for a specific case study on 23 July 2007 during the Convective and Orographically-induced Precipitation Study (COPS). Simulations of the lidar dark and bright band based on the application of concentric/eccentric sphere Lorentz-Mie codes and a melting layer model are also provided. Lidar and radar measurements and model results are also compared with measurements from a disdrometer on ground and a two-dimensional cloud (2DC) probe on-board the ATR42 SAFIRE. Measurements and model results are found to confirm and support the conceptual microphysical/scattering model elaborated by Sassen et al. (2005).

Di Girolamo, P.; Summa, D.; Cacciani, M.; Norton, E. G.; Peters, G.; Dufournet, Y.

2012-05-01

31

Lidar observation of PBL clouds: part of the Experimental Cloud Lidar Pilot Study (ECLIPS) phase II  

NASA Astrophysics Data System (ADS)

The clouds play a significant role in the atmosphere particularly in the determination of the radiant balance. Since their type, structure and height considerable influence the transmission, absorption and re-radiation of the IR radiation they are of great importance for the local meteorology and the global climatology. In small spatial scales (micro- and meso- ones) the clouds considerable change in space and time. The ECLIPS (Experimental Cloud Lidar Pilot Study) program in which our lidar group also takes part is well described. In general, the main purpose is a ground-based lidar observation of the clouds simultaneously with the NOAA 10 and NOAA 11 meteorological satellites overpassing the same areas to be performed. Essential lidar data are the recorded profiles from which the information about the clouds height, optical depth and vertical extinction can be derived. The experimental data required for the ECLIPS Phase II measurements were recorded during the period from 21 May to O9 July 1991 at 30 observations by 3 hours each i.e. 1 hour before and 1 hour after the NOAA 10 and NOAA 11 satellites overpasses. The lidar data are completed with certain meteorological information obtained by the conventional means. The presented experiment was conducted using triple- beam aerosol meteorological lidar developed at the Institute of Electronics of Bulgarian Academy of Sciences, which are well described previously.

Kolev, Ivan N.; Parvanov, Orlin; Kaprielov, Boiko; Grigorov, Ivan; Gospodinova, Nadia

1994-12-01

32

Application of Doppler radar and lidar to diagnose atmospheric phenomena  

Microsoft Academic Search

Observations and comparison of measurements of wind, waves, and turbulence, made with Doppler radar, lidar, and in-situ sensors, are presented. Applications to the detection of weather hazards to safe flight are discussed. A method to estimate rainfall with a polarization diversity Doppler radar is shown to be less sensitive to drop size distribution variations than commonly used Z-R relations. The

R. J. Doviak; M. Eilts; V. Mazur; M. Sachidananda; D. S. Zrnic

1986-01-01

33

Scanning ARM Cloud Radar Handbook  

SciTech Connect

The scanning ARM cloud radar (SACR) is a polarimetric Doppler radar consisting of three different radar designs based on operating frequency. These are designated as follows: (1) X-band SACR (X-SACR); (2) Ka-band SACR (Ka-SACR); and (3) W-band SACR (W-SACR). There are two SACRs on a single pedestal at each site where SACRs are deployed. The selection of the operating frequencies at each deployed site is predominantly determined by atmospheric attenuation at the site. Because RF attenuation increases with atmospheric water vapor content, ARM's Tropical Western Pacific (TWP) sites use the X-/Ka-band frequency pair. The Southern Great Plains (SGP) and North Slope of Alaska (NSA) sites field the Ka-/W-band frequency pair. One ARM Mobile Facility (AMF1) has a Ka/W-SACR and the other (AMF2) has a X/Ka-SACR.

Widener, K; Bharadwaj, N; Johnson, K

2012-06-18

34

Using an Airborne Doppler Lidar to Evaluate QuikSCAT and RadarSat Derived Winds  

NASA Astrophysics Data System (ADS)

While near surface winds derived from space-based remote sensing have proven very useful, both operationally and for research, there remain several issues not fully resolved. Besides the persistent wind direction uncertainty, high wind speeds (> 25 m/s) and organized circulations such as those associated with large marine atmospheric boundary layer eddies continue to introduce magnitude and representativeness errors in the data products. The US Navy and the Integrated Program Office of NPOESS have jointly sponsored the installation and use of a scanning Doppler wind lidar on a Navy Twin Otter aircraft. The lidar is a 2 micron coherent system with a side door mounted hemispherical scanner. Returns from aerosols are processed to obtain wind profiles (above and below flight level). The measurement accuracy is on the order of a few cm/sec in speed and a degree or two in direction. The footprint of the lidar beam is < 1 meter and the full profiles are constructed with wind observations over a one l kilometer flight segment. The vertical resolution is usually < 50 meters. In the nadir looking mode, the Doppler lidar can resolve wave structures with < 5 cm/sec vertical motion accuracy and with .5 meter horizontal resolution. In the Spring of 2002, the lidar was flown over Monterey Bay (CA)during QuikSCAT and RadarSat overpasses. Cloud streets were observed from the aircraft and with the lidar in the vicinity of organized patterns in the RadarSAT returns. The lidar data offer detailed insight into the velocity and aerosol structures within the larger footprints of the space-based sensors. Detailed analyses of the collocated lidar, QuikScat and RadarSat data will be presented along with plans for the future use of this new research facility.

Emmitt, G. D.; O'Handley, C.; Brown, R. A.; Foster, R.

2002-12-01

35

Cloud properties derived from two lidars over the ARM SGP site  

SciTech Connect

[1] Active remote sensors such as lidars or radars can be used with other data to quantify the cloud properties at regional scale and at global scale (Dupont et al., 2009). Relative to radar, lidar remote sensing is sensitive to very thin and high clouds but has a significant limitation due to signal attenuation in the ability to precisely quantify the properties of clouds with a 20 cloud optical thickness larger than 3. In this study, 10-years of backscatter lidar signal data are analysed by a unique algorithm called STRucture of ATmosphere (STRAT, Morille et al., 2007). We apply the STRAT algorithm to data from both the collocated Micropulse lidar (MPL) and a Raman lidar (RL) at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site between 1998 and 2009. Raw backscatter lidar signal is processed and 25 corrections for detector deadtime, afterpulse, and overlap are applied. (Campbell et al.) The cloud properties for all levels of clouds are derived and distributions of cloud base height (CBH), top height (CTH), physical cloud thickness (CT), and optical thickness (COT) from local statistics are compared. The goal of this study is (1) to establish a climatology of macrophysical and optical properties for all levels of clouds observed over the ARM SGP site 30 and (2) to estimate the discrepancies induced by the two remote sensing systems (pulse energy, sampling, resolution, etc.). Our first results tend to show that the MPLs, which are the primary ARM lidars, have a distinctly limited range where all of these cloud properties are detectable, especially cloud top and cloud thickness, but even actual cloud base especially during summer daytime period. According to the comparisons between RL and MPL, almost 50% of situations show a signal to noise ratio too low (smaller than 3) for the MPL in order to detect clouds higher than 7km during daytime period in summer. Consequently, the MPLderived annual cycle of cirrus cloud base (top) altitude is biased low, especially for daylight periods, compared with those derived from the RL data, which detects 5 cloud base ranging from 7.5 km in winter to 9.5 km in summer (and tops ranging from 8.6 to 10.5 km). The optically thickest cirrus clouds (COT>0.3) reach 50% of the total population for the Raman lidar and only 20% for the Micropulse lidar due to the difference of pulse energy and the effect of solar irradiance contamination. A complementary study using the cloud fraction 10 derived from the Micropulse lidar for clouds below 5 km and from the Raman lidar for cloud above 5 km allows for better estimation of the total cloud fraction between the ground and the top of the atmosphere. This study presents the diurnal cycle of cloud fraction for each season in comparisons with the Long et al. (2006) cloud fraction calculation derived from radiative flux analysis.

Dupont, Jean-Charles; Haeffelin, Martial; Morille, Y.; Comstock, Jennifer M.; Flynn, Connor J.; Long, Charles N.; Sivaraman, Chitra; Newsom, Rob K.

2011-02-16

36

MU radar and lidar observations of clear-air turbulence and mammatus underneath cirrus  

Microsoft Academic Search

Mammatus are smooth hanging protuberances on the undersurface of a cloud (Glossary of Meteorology). Their mechanisms for formation and their role in the atmosphere are still not well-known. We obtained Rayleigh\\/Mie\\/Raman (RMR) lidar measurements of cirrus mammatus in the night of 07-08 June 2006 at Shigaraki Observatory (34.85°N, 136.10°E, Japan). Coincident observations from the VHF (46.5 MHz) MU radar in

H. Luce; T. Nakamura; M. Yamamoto; S. Fukao

2009-01-01

37

Polarization Lidar Liquid Cloud Detection Algorithm for Winter Mountain Storms.  

National Technical Information Service (NTIS)

We have collected an extensive polarization lidar dataset from elevated sites in the Tushar Mountains of Utah in support of winter storm cloud seeding research and experiments. Our truck-mounted ruby lidar collected zenith, dual-polarization lidar data th...

K. Sassen H. Zhao

1992-01-01

38

Airborne Lidar Studies of Arctic Polar Stratospheric Clouds.  

National Technical Information Service (NTIS)

Airborne lidar measurements of Arctic polar stratospheric clouds (PSC) in January 1984 and January 1986 are reported. The locales and altitudes of the clouds coincided in both years with very cold ambient temperatures. Enhancements in aerosol backscatteri...

L. R. Poole

1987-01-01

39

Next-generation spaceborne Cloud Profiling Radars  

Microsoft Academic Search

One of the instruments recommended for deployment on the Aerosol\\/Cloud\\/Echosystems (ACE) mission is a new advanced Cloud Profiling Radar (ACE-CPR). The atmospheric sciences community has initiated the effort to define the scientific requirements for this instrument. Initial studies focusing on system configuration, performance and feasibility start from the successful experience of the Cloud Profiling Radar on CloudSat Mission (CS-CPR), the

Simone Tanelli; Stephen L. Durden; Eastwood Im; Gerald M. Heymsfield; Paul Racette; D. O. Starr

2009-01-01

40

A 2-year climatology of Arctic clouds for Eureka, Canada prepared from High Spectral Resolution Lidar data.  

NASA Astrophysics Data System (ADS)

Measurements show that Arctic is warming faster than the rest of the globe. Warming is also predicted by climate models. However, there is more disagreement between the predictions of individual models in the Arctic then at lower latitudes. Differences in cloud parametrization are the likely to be the main source of the model-to-model variations. Unfortunately, it is difficult to evaluate model predictions of Arctic cloudiness because of a lack of reliable cloud observations. The Canadian Network for the Detection of Atmospheric Change (CANDAC) and the NOAA Study of Environmental Arctic Change (SEARCH) have installed an instrumentation suite at Eureka(80 deg N, 86 deg W) in the Nunavut territory of Northern Canada. These instruments include the University of Wisconsin Arctic High Spectral Resolution Lidar(AHSRL) and the NOAA 8.6 mm wavelength cloud radar (MCR). Both instruments have operated nearly continuously since Sept 2005. This paper presents a record of cloud cover, cloud altitude and cloud phase derived from the lidar. It also presents comparisons between lidar, radar, and convention meteorological observations of cloudiness. It is shown that optically thin clouds are frequently observed at this site. As a result, the observed fractional cloud cover depends strongly on the optical depth threshold used to define the presence of cloud. The lidar data indicates that Eureka has fewer clouds than DOE Atmospheric Radiation Measurement (ARM) site in Barrow, Alaska and fewer clouds than were observed during the Surface Heat Budget of the Arctic Ocean(SHEBA) experiment.

Eloranta, E. W.; Shupe, M. D.; Uttal, T.

2007-12-01

41

Micropulse lidar for aerosol and cloud measurement  

NASA Astrophysics Data System (ADS)

A lidar system employing a diode laser pumped Nd:YLF laser and photon counting technique is described for use in automated cloud and aerosol measurements. A Nd:YLF laser provides 523 nm 10 (mu) J/pulse energy at 2500 Hz repetition rate. A coaxial configuration is used for transmitting laser pulse and receiving the signal with a 0.2 m Schmidt-Cassegrain telescope. An avalanche photodiode is used for back scattered photon counting in Geiger mode. This micro pulse lidar (MPL) is capable to detect subvisible cirrus and boundary layer within 10 second averaging time. Also the MPL takes back scattered signal at four different spatial resolutions of 30 m, 75 m, 150 m, and 300 m to meet various user requirements. The detected signal is processed and displayed on a personal computer. The 32 bit data processing software is running on the Window 95 platform.

Hwang, In H.; Lokos, Sandor; Kim, Jin

1997-05-01

42

Radar, lidar, and optical observations in the polar summer mesosphere shortly after a space shuttle launch  

NASA Astrophysics Data System (ADS)

In the summer of 2007, a noctilucent cloud (NLC) campaign was organized in Alaska. Radar, lidar, and photographic methods were used. Due to lighting conditions, the campaign was carried out near the end of the NLC season. Sporadic radar and lidar echoes were obtained until the very end of the campaign, when an exceptionally intense event occurred on the local time night of 10-11 August. This late-season event followed the launch of the space shuttle on 8 August. At least twice before, solstice launches of the shuttle have been followed by unique observations of NLC and sporadic iron layers in the polar regions. This was the case here as well. The iron layer increased in altitude and density, the latter by a factor of 20, compared to the previous night. And, for the first time, (1) polar mesospheric summer echoes (PMSE) were recorded by a radar in an event of this nature and (2) an intense sporadic E layer was collocated with the iron atom layer. At the UHF radar frequency used, very large Schmidt numbers are required for PMSE. Indeed, the PMSE was found at and just above the particles responsible for Mie scatter. Such large particles are likely needed to yield large Schmidt numbers. Additionally, similar lidar and sporadic E layers were detected over Greenland on the previous night. Here we consider the ion chemistry that could lead to the collocated atom and iron layers and conclude that considerably enhanced water vapor content was required.

Kelley, M. C.; Nicolls, M. J.; Varney, R. H.; Collins, R. L.; Doe, R.; Plane, J. M. C.; Thayer, J.; Taylor, M.; Thurairajah, B.; Mizutani, K.

2010-05-01

43

Lidar observations of high-altitude aerosol layers (cirrus clouds)  

NASA Astrophysics Data System (ADS)

Aerosols, clouds and aerosol-cloud interactions are recognized as the key factors influencing the climate. Clouds are the primary modulators of the Earth's radiative budget. This paper focuses on the detection of high-altitude aerosol layers in the troposphere over mid-latitude lidar station in Sofia, Bulgaria. They are situated in the height-region 6 km÷16 km, with thickness in the range 0.2 km÷5 km and have varying optical characteristics. On the basis of the general utilized classification of the Cirrus clouds, high values of the calculated atmospheric backscatter coefficient and Angströmexponent estimation results we conclude that the registered strongly scattered aerosol layers are Cirrus clouds. Lidar measurements are performed with an aerosol lidar, equipped with Nd:YAG laser at wavelengths 532 nm and 1064 nm. Mainly, lidar data are presented in terms of vertical atmospheric backscatter coefficient profiles. We also include 2Dcolormap in height-time coordinates build on the basis of so called range corrected signals. It shows in general changes of the aerosol stratification over the lidar station during the measurement period. We employed HYSPLIT backward trajectories and DREAM forecasts to analyze the lidar profile outlines and characterize the events during which Cirrus cloud samples were observed. So was remarked that most of the results were obtained during Saharan dust long-way transport over the city of Sofia. Reported experimental examples are extracted from regular lidar investigations of the atmosphere within the frame of European project EARLINET.

Deleva, Atanaska D.; Grigorov, Ivan V.

2013-03-01

44

Hybrid Lidar-Radar for Enhanced Underwater Detection.  

NASA Astrophysics Data System (ADS)

Conventional air-to-underwater lidar systems are contrast limited in the detection of small, shallow underwater targets. This is due to the backscatter of the transmitted optical beam from water particles within the receiver field of view. In response to this shortcoming, a hybrid lidar -radar detection scheme has been developed by combining the sophisticated detection and signal processing techniques of radar with the underwater transmission capability of lidar. The work in this thesis focuses on evaluating the ability of this new technique to reduce backscatter clutter and to improve the detection sensitivity of underwater targets. The feasibility of this novel detection scheme was investigated through laboratory experiments. An ocean mass simulator was designed and constructed to test the effect of the water on a modulated optical pulse. An analytical model based on the ocean mass simulator was developed to predict experimental outcomes. The results of the theoretical study and corresponding laboratory experiments confirmed the ability of the hybrid detection scheme to reduce backscatter clutter and improve the contrast of underwater targets. Due to the limitations of the laboratory environment in determining the effects of lidar system variables on the hybrid system performance, an ocean experiment was designed and conducted. A theoretical model was developed to predict experimental results, and a hybrid lidar-radar system was designed and fabricated for ocean experimentation. The field test results established the merits of the hybrid system in improving the contrast of small, shallow underwater targets which remain contrast limited in conventional lidar systems. Significantly, the observance of microwave interference effects verified that the microwave signal integrity was preserved and provided confidence that the implementation of more sophisticated modulation and detection schemes may further improve the system performance.

Mullen, Linda Jeanne

45

Relation of Cloud Occurrence Frequency, Overlap, and Effective Thickness Derived from CALIPSO and CloudSat Merged Cloud Vertical Profiles.  

National Technical Information Service (NTIS)

A cloud frequency of occurrence matrix is generated using merged cloud vertical profile derived from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Cloud Profiling Radar (CPR). The matrix contains vertical profiles of cloud occurrence frequ...

B. A. Wielicki F. G. Rose P. Minnis S. Kato S. Sun-Mack W. F. Miller Y. Chen

2009-01-01

46

Scanning lidar with a coupled radar safety system.  

PubMed

A small scanning three-wavelength lidar system at NASA Langley Research Center in Hampton, Virginia, has been used since 1992 to make atmospheric measurements on stratospheric and upper tropospheric aerosols and on the evolution of aircraft exhaust plumes. Many of these measurements have been made away from the zenith, and, to reduce the hazard to air traffic produced by the laser beam, a radar safety device has been installed. The radar application is original in that the radar beam is made collinear with the laser beam by use of a dichroic mirror that transmits the laser radiation and reflects the microwaves. This mirror is inserted into the outgoing optical path prior to the radiation from both the radar and the laser passing through the independent scanning unit. Tests of the complete system show that the lidar and radar beams remain collocated as they are scanned and that the radar can be used to inhibit the laser prior to an aircraft passing through the beam. PMID:18324168

Kent, G S; Hansen, G M

1999-10-20

47

Two optronic identification techniques: lidar-radar and multispectral polarimetric imaging  

Microsoft Academic Search

We propose to review two concepts that can be used for target detection and identification in optronic systems: lidar-radar and multipectral polarimetric active imaging. The lidar-radar concept uses an optically pre-amplified intensity modulated lidar, where the modulation frequency is in the microwave domain (1-10 GHz). Such a system permits to combine directivity of laser beams with mature radar processing. As

Loic Morvan; Mehdi Alouini; Arnaud Grisard; Eric Lallier; Daniel Dolfi; Xavier Normandin; Anne M. Bouchardy; Gerard Berginc; G. Granger; Jean Chazelas

2004-01-01

48

Lidar and radar measurements of the melting layer in the frame of the Convective and Orographically-induced Precipitation Study: observations of dark and bright band phenomena  

NASA Astrophysics Data System (ADS)

During the Convective and Orographically-induced Precipitation Study (COPS), lidar dark and bright bands were observed by the University of BASILicata Raman lidar system (BASIL) during several intensive (IOPs) and special (SOPs) observation periods (among others, 23 July, 15 August, and 17 August 2007). Lidar data were supported by measurements from the University of Hamburg cloud radar MIRA 36 (36 GHz), the University of Hamburg dual-polarization micro rain radars (24.1 GHz) and the University of Manchester UHF wind profiler (1.29 GHz). Results from BASIL and the radars for 23 July 2007 are illustrated and discussed to support the comprehension of the microphysical and scattering processes responsible for the appearance of the lidar and radar dark and bright bands. Simulations of the lidar dark and bright band based on the application of concentric/eccentric sphere Lorentz-Mie codes and a melting layer model are also provided. Lidar and radar measurements and model results are also compared with measurements from a disdrometer on ground and a two-dimensional cloud (2DC) probe on-board the ATR42 SAFIRE.

di Girolamo, P.; Summa, D.; Bhawar, R.; di Iorio, T.; Norton, E. G.; Peters, G.; Dufournet, Y.

2011-11-01

49

Amplification of radar and lidar signatures using quantum sensors  

NASA Astrophysics Data System (ADS)

One of the major scientific thrusts from recent years has been to try to harness quantum phenomena to dramat­ ically increase the performance of a wide variety of classical devices. These advances in quantum information science have had a considerable impact on the development of photonic-based quantum sensors. Even though quantum radar and quantum lidar remain theoretical proposals, preliminary results suggest that these sensors have the potential of becoming disruptive technologies able to revolutionize reconnaissance systems. In this paper we will discuss how quantum entanglement can be exploited to increase the radar and lidar signature of rectangular targets. In particular, we will show how the effective visibility of the target is increased if observed with an entangled multi-photon quantum sensor.

Lanzagorta, Marco

2013-05-01

50

Ground-based microwave radar and optical lidar signatures of volcanic ash plumes: models, observations and retrievals  

NASA Astrophysics Data System (ADS)

The detection and quantitative retrieval of volcanic ash clouds is of significant interest due to its environmental, climatic and socio-economic effects. Real-time monitoring of such phenomena is crucial, also for the initialization of dispersion models. Satellite visible-infrared radiometric observations from geostationary platforms are usually exploited for long-range trajectory tracking and for measuring low level eruptions. Their imagery is available every 15-30 minutes and suffers from a relatively poor spatial resolution. Moreover, the field-of-view of geostationary radiometric measurements may be blocked by water and ice clouds at higher levels and their overall utility is reduced at night. Ground-based microwave radars may represent an important tool to detect and, to a certain extent, mitigate the hazard from the ash clouds. Ground-based weather radar systems can provide data for determining the ash volume, total mass and height of eruption clouds. Methodological studies have recently investigated the possibility of using ground-based single-polarization and dual-polarization radar system for the remote sensing of volcanic ash cloud. A microphysical characterization of volcanic ash was carried out in terms of dielectric properties, size distribution and terminal fall speed, assuming spherically-shaped particles. A prototype of volcanic ash radar retrieval (VARR) algorithm for single-polarization systems was proposed and applied to S-band and C-band weather radar data. The sensitivity of the ground-based radar measurements decreases as the ash cloud is farther so that for distances greater than about 50 kilometers fine ash might be not detected anymore by microwave radars. In this respect, radar observations can be complementary to satellite, lidar and aircraft observations. Active remote sensing retrieval from ground, in terms of detection, estimation and sensitivity, of volcanic ash plumes is not only dependent on the sensor specifications, but also on the range and ash cloud distribution. The minimum detectable signal can be increased, for a given system and ash plume scenario, by decreasing the observation range and increasing the operational frequency using a multi-sensor approach, but also exploiting possible polarimetric capabilities. In particular, multi-wavelengths lidars can be complementary systems useful to integrate radar-based ash particle measurement. This work, starting from the results of a previous study and from above mentioned issues, is aimed at quantitatively assessing the optimal choices for microwave and millimeter-wave radar systems with a dual-polarization capability for real-time ash cloud remote sensing to be used in combination with an optical lidar. The physical-electromagnetic model of ash particle distributions is systematically reviewed and extended to include non-spherical particle shapes, vesicular composition, silicate content and orientation phenomena. The radar and lidar scattering and absorption response is simulated and analyzed in terms of self-consistent polarimetric signatures for ash classification purposes and correlation with ash concentration and mean diameter for quantitative retrieval aims. A sensitivity analysis to ash concentration, as a function of sensor specifications, range and ash category, is carried out trying to assess the expected multi-sensor multi-spectral system performances and limitations. The multi-sensor multi-wavelength polarimetric model-based approach can be used within a particle classification and estimation scheme, based on the VARR Bayesian metrics. As an application, the ground-based observation of the Eyjafjallajökull volcanic ash plume on 15-16 May 2010, carried out at the Atmospheric Research Station at Mace Head, Carna (Ireland) with MIRA36 35-GHz Ka-Band Doppler cloud radar and CHM15K lidar/ceilometer at 1064-nm wavelength, has been considered. Results are discussed in terms of retrievals and intercomparison with other ground-based and satellite-based sensors.

Mereu, Luigi; Marzano, Frank; Mori, Saverio; Montopoli, Mario; Cimini, Domenico; Martucci, Giovanni

2013-04-01

51

Investigation of cloud properties using a Raman lidar  

NASA Astrophysics Data System (ADS)

Raman lidar is well known to be a useful tool for charting the evolution of water vapor and aerosols in the atmosphere. The goal of this dissertation is to use the Raman lidar technique to study cloud properties that are important in understanding atmospheric radiation and dynamics. The lidar system used here is the NASA/GSFC Scanning Raman Lidar. A detailed description of this state of the art Raman lidar is given. The system configuration and several important optical design considerations are described fully. Following this, a detailed derivation of the basic equations pertaining to the Raman lidar measurement of aerosol backscattering ratio, aerosol backscatter coefficient, aerosol extinction, aerosol optical depth and water vapor mixing ratio are given. In the process, a new formulation of the lidar equations is presented that accounts for the temperature sensitivity of the backscattered spectra. A detailed analysis of the method of computing aerosol extinction is presented. Analysis of Raman lidar data using these equations is shown. Then, a new technique is developed that allows droplet radius and number density to be retrieved from liquid clouds. The technique is demonstrated using Raman lidar data. In support of this new atmospheric technique, laboratory measurements of the Raman scattering of liquid water were performed demonstrating that aspects of the backscattered spectrum of liquid water agree with theory. The influence of multiple scattering on optical depth is studied resulting in a technique that allows the bulk extinction to backscatter ratio of the cirrus clouds to be determined. It also allows information about the particle size to be determined. A 6-night sequence of cirrus cloud optical depth measurements acquired on Andros Island, Bahamas is presented. They were acquired during the nearby passage of hurricane Bonnie. The radiative significance of cirrus clouds is studied for one of these nights. The study reveals that cirrus clouds dominate the radiance seen by satellite and that cirrus clouds with optical depths as low as 0.005 can influence satellite radiances. Using the International Satellite Cloud Climatology Project cirrus cloud detection thresholds implies up to a 40% high bias in retrieved total precipitable water due to undetected cirrus clouds. This result has potentially important consequences for the global database of precipitable water determined using IR satellite measurements.

Whiteman, David Neil

52

Measurement of cloud solar reflected radiance and extinction from space lidar  

Microsoft Academic Search

A method of obtaining the reflected solar radiance from clouds with space lidar is described. The lidar telescope and detector are used effectively together as a visible radiometer at the lidar wavelength, the background signal on a lidar backscatter profile being proportional to the observed radiance in the lidar field of view. A DC-coupled output from the telescope detector is

C. Martin R. Platt; William H. Hunt; David M. Winker; Mark A. Vaughan

1998-01-01

53

Fractal properties and denoising of lidar signals from cirrus clouds  

NASA Astrophysics Data System (ADS)

Airborne lidar signals of cirrus clouds are analyzed to determine the cloud structure. Climate modeling and numerical weather prediction benefit from accurate modeling of cirrus clouds. Airborne lidar measurements of the European Lidar in Space Technology Experiment (ELITE) campaign were analyzed by combining shots to obtain the backscatter at constant altitude. The signal at high altitude was analyzed for horizontal structure of cirrus clouds. The power spectrum and the structure function show straight lines on a double logarithmic plot. This behavior is characteristic for a Brownian fractal. Wavelet analysis using the Haar wavelet confirms the fractal aspects. It is shown that the horizontal structure of cirrus can be described by a fractal with a dimension of 1.8 over length scales that vary 4 orders of magnitude. We use the fractal properties in a new denoising method. Denoising is required for future lidar measurements from space that have a low signal to noise ratio. Our wavelet denoising is based on the Haar wavelet and uses the statistical fractal properties of cirrus clouds in a method based on the maximum a posteriori (MAP) probability. This denoising based on wavelets is tested on airborne lidar signals from ELITE using added Gaussian noise. Superior results with respect to averaging are obtained.

van den Heuvel, J. C.; Driesenaar, M. L.; Lerou, R. J. L.

2000-02-01

54

W-band ARM Cloud Radar (WACR) Handbook.  

National Technical Information Service (NTIS)

The W-band Atmospheric Radiation Measurement (ARM) Program Cloud Radar (WACR) systems are zenith pointing Doppler radars that probe the extent and composition of clouds at 95.04 GHz. The main purpose of this radar is to determine cloud boundaries (e.g., c...

K. Johnson K. B. Widener

2006-01-01

55

CloudSat as a Global Radar Calibrator  

Microsoft Academic Search

The calibration of the CloudSat spaceborne cloud radar has been thoroughly assessed using very accurate internal link budgets before launch, comparisons with predicted ocean surface backscatter at 94 GHz, direct comparisons with airborne cloud radars, and statistical comparisons with ground-based cloud radars at different locations of the world. It is believed that the calibration of CloudSat is accurate to within

Alain Protat; Dominique Bouniol; E. J. OConnor; H. Klein Baltink; J. Verlinde; Kevin B. Widener

2011-01-01

56

Noctilucent cloud in the western Arctic in 2005: Simultaneous lidar and camera observations and analysis  

NASA Astrophysics Data System (ADS)

We report observations of a noctilucent cloud (NLC) over central Alaska by a ground-based lidar and camera on the night of 9-10 August 2005. The lidar at Poker Flat Research Range (PFRR), Chatanika (65°N, 147°W) measured a maximum integrated backscatter coefficient of 2.4×10-6 sr-1 with a peak backscatter coefficient of 2.6×10-9 m-1 sr-1 corresponding to an aerosol backscatter ratio of 120 at an altitude of 82.1 km. The camera at Donnelly Dome, 168 km southeast of PFRR, recorded an extensive NLC display across the sky with distinct filamentary features corresponding to wave structures measured by the lidar. The occurrence of the maximum integrated backscatter coefficient corresponded to the passage of a bright cloud band to the southwest over PFRR. The camera observations indicate that the cloud band had a horizontal width of 50 km and a length of 150 km. The horizontal scale of the cloud band was confirmed by medium-frequency radar wind measurements that reported mesopause region winds of 30 m/s to the southwest during the period when the cloud band passed over PFRR. Comparison of these measurements with current NLC microphysical models suggests a lower bound on the water vapor mixing ratio at 83 km of 7-9 ppmv and a cloud ice mass of 1.5-1.8×103 kg. Satellite measurements show that this NLC display occurred during a burst of cloud activity that began on 5 August and lasted for 10 days. This cloud appeared 10 days after a launch of the space shuttle. We discuss the appearance of NLCs in August over several years at this lower polar latitude site in terms of planetary wave activity and space shuttle launches.

Collins, R. L.; Taylor, M. J.; Nielsen, K.; Mizutani, K.; Murayama, Y.; Sakanoi, K.; Deland, M. T.

2009-03-01

57

CloudSat as a Global Radar Calibrator  

SciTech Connect

The calibration of the CloudSat spaceborne cloud radar has been thoroughly assessed using very accurate internal link budgets before launch, comparisons with predicted ocean surface backscatter at 94 GHz, direct comparisons with airborne cloud radars, and statistical comparisons with ground-based cloud radars at different locations of the world. It is believed that the calibration of CloudSat is accurate to within 0.5 to 1 dB. In the present paper it is shown that an approach similar to that used for the statistical comparisons with ground-based radars can now be adopted the other way around to calibrate other ground-based or airborne radars against CloudSat and / or detect anomalies in long time series of ground-based radar measurements, provided that the calibration of CloudSat is followed up closely (which is the case). The power of using CloudSat as a Global Radar Calibrator is demonstrated using the Atmospheric Radiation Measurement cloud radar data taken at Barrow, Alaska, the cloud radar data from the Cabauw site, The Netherlands, and airborne Doppler cloud radar measurements taken along the CloudSat track in the Arctic by the RASTA (Radar SysTem Airborne) cloud radar installed in the French ATR-42 aircraft for the first time. It is found that the Barrow radar data in 2008 are calibrated too high by 9.8 dB, while the Cabauw radar data in 2008 are calibrated too low by 8.0 dB. The calibration of the RASTA airborne cloud radar using direct comparisons with CloudSat agrees well with the expected gains and losses due to the change in configuration which required verification of the RASTA calibration.

Protat, Alain; Bouniol, Dominique; O'Connor, E. J.; Baltink, Henk K.; Verlinde, J.; Widener, Kevin B.

2011-03-01

58

Lidar-radar synergy for characterizing properties of ultragiant volcanic aerosol  

NASA Astrophysics Data System (ADS)

The atmospheric aerosol has a relevant effect on our life influencing climate, aviation safety, air quality and natural hazards. The identification of aerosol layers through inspection of continuous measurements is strongly recommended for quantifying their contribution to natural hazards and air quality and to establish suitable alerting systems. In particular, the study of ultragiant aerosols may improve the knowledge of physical-chemical processes underlying the aerosol-cloud interactions and the effect of giant nuclei as a potential element to expedite the warm-rain process. Moreover, the identification and the characterization of ultragiant aerosols may strongly contribute to quantify their impact on human health and their role in airplane engine damages or in visibility problems, especially in case of extreme events as explosive volcanic eruptions. During spring 2010, volcanic aerosol layers coming from Eyjafjallajökull volcano were observed over most of the European countries, using lidar technique. From 19 April to 19 May 2010, they were also observed at CNR-IMAA Atmospheric Observatory (CIAO) with the multi-wavelength Raman lidar systems of the Potenza EARLINET station (40.60N, 15.72E, 760 m a.s.l), Southern Italy. During this period, ultragiant aerosol were also observed at CIAO using a co-located Ka-band MIRA-36 Doppler microwave radar operating at 8.45 mm (35.5 GHz). The Ka-band radar observed in four separate days (19 April, 7, 10, 13 May) signatures consistent with the observations of non-spherical ultragiant aerosol characterized by anomalous values of linear depolarization ratio higher than -4 dB, probably related to the occurrence of multiple effects as particle alignment and presence of an ice coating. 7-days backward trajectory analysis shows that the air masses corresponding to the ultragiant aerosol observed by the radar were coming from the Eyjafjallajökull volcano area. Only in one case the trajectories do not come directly from Iceland, but from Central Europe where many lidar observations confirm the presence of volcanic aerosol in the previous days. Therefore, both CIAO lidar observations and the backtrajectory analysis suggests a volcanic origin of the ultragiant aerosol observed by the radar, revealing that these particles might have travelled for more than 4000 km after their injection into the atmosphere. The reported observation fostered a study, reported in this work, about the performances of multi-wavelength Raman lidars in the identification and the characterization of ultragiant aerosols layers in the troposphere. Results from simulations using Mie, T-Matrix and ray-tracing codes will be presented and compared with the observations performed in April-May 2010 during the Eyjafjallajökull eruption. Sensitivity ranges in detection of aerosol layer are pointed out in terms of experimental limits of both lidar and radar techniques and of aerosol optical depth. Moreover, recommendations for use of a combined lidar-radar approach for the aerosol typing and for the retrieval of their microphysical properties are reported.

Madonna, F.; Amodeo, A.; D'Amico, G.; Giunta, A.; Mona, L.; Pappalardo, G.

2011-12-01

59

Towards an automatic Lidar cirrus cloud retrieval for climate studies  

NASA Astrophysics Data System (ADS)

In the present study, a methodology to calculate lidar ratios for distinct cirrus clouds has been implemented for a site located in the Southern Hemisphere. The cirrus cloud lidar data processing has been developed to consider a large cloud variability with the final aim of cirrus cloud monitoring through a robust retrieval process. Among the many features lidar systems can extract for cirrus detection, we highlight: cloud geometrical information and extinction-to-backscatter ratio (also called lidar ratio - LR). LR's can, in general, provide important information on cirrus cloud microphysics due to the presence of ice crystals and their properties such as shape, size, composition and orientation of particles and their effect on LR values. Conditions for LR calculations and their resulting uncertainty have been improved as their analysis requires identifying cirrus cloud stationary periods through the use of a specific statistical approach well-established in the literature and employed here with good results, allowing for the study of specific cases with multi-layer cirrus cloud occurrence. The results from the measurements taken in the region of the Metropolitan City of São Paulo - MSP have been used to implement and test the methodology developed herein. In addition to the geometrical parameters extracted, improved values of LR's were calculated and showed significantly different values for the different layers inspected, varying between 19 ± 01 sr and 74 ± 13 sr. This large value interval allowed us to indirectly verify the presence of different ice crystal sizes and shapes and those associated with different air mass sources for the cirrus cloud formation.

Larroza, E. G.; Nakaema, W. M.; Bourayou, R.; Hoareau, C.; Landulfo, E.; Keckhut, P.

2013-04-01

60

Radar and radiation properties of ice clouds  

SciTech Connect

The authors derive relations of the equivalent radar reflectivity Z{sub e} and extinction coefficient a of ice clouds and confirm the theory by in situ aircraft observations during the First International Satellite Cloud Climatology Project Regional Experiment. Equivalent radar reflectivity Z{sub e} is a function of ice water content Wand a moment of the size distribution such as the median volume diameter D{sub 0}. Stratification of the data by D{sub 0} provides a set of W-Z{sub e} relations from which one may deduce the dependence of particle density on size. This relation is close to that of Brown and Francis and provides confidence in the methodology of estimating particle size and mass. The authors find that there is no universal W-Z{sub e} relation, due both to large scatter and systematic shifts in particle size from day to day and cloud to cloud. These variations manifest the normal changes in ice crystal growth. The result is that, with the exception of temperatures less than -40{degrees}C, temperature cannot be used to reliably parameterize the particle size as has been previously suggested. To do so is to risk large possible systematic errors in retrievals. Even if one could measure monthly averages of ice water content, this is inadequate to estimate the monthly radiative effect because of the nonlinearity between the two. The authors show that a sizable fraction of radiatively significant clouds would be missed at a radar threshold of -30 dBZ, the value proposed for a spaceborne cloud-profiling radar. 29 refs., 13 figs., 3 tabs.

Atlas, D. [NASA/Goddard Space Flight Center, Greenbelt, MD (United States); Matrosov, S.Y. [Univ. of Colorado, Boulder CO (United States); Heymsfield, A.J. [National Center for Atmospheric Research, Boulder, CO (United States)] [and others

1995-11-01

61

ALOMAR: atmospheric science using lidars, radars and ground based instruments.  

NASA Astrophysics Data System (ADS)

On top of the 379-m high Ramnan mountain on the island of Andøya (69°30'N, 16°01'E) in northern Norway, the ALOMAR (The Arctic Lidar Observatory for Middle Atmospheric Research) will soon be in operation. Through measurements of different atmospheric parameters, ALOMAR will provide information on the dynamics of the middle and upper atmosphere using ground-based instrumentation. Routine measurements, including ozone observations, can be carried out more efficiently than currently possible. The observatory is currently using three lidar instruments, one radar and several ground-based instruments to measure density, temperature, wind profiles and aerosol densities over a height range of approximately 10 to 100 km. ALOMAR will provide scientists worldwide with the opportunity for year-round, in-depth studies of the polar middle atmosphere, concentrating on physics, chemistry and meteorology. The observatory will offer unique research opportunities, and its activities can be correlated using the Andøya Rocket Range, who operate the facility, and with other important research facilities such as the EISCAT radar, and the University of Tromsø observatories which are located nearby. There are many opportunities for additional cooperative scientific experiments using ground-based measurements and instruments carried by aircraft, balloons and sounding rockets.

Skatteboe, R.

1996-12-01

62

CloudSat's Cloud Profiling Radar After Two Years in Orbit: Performance, Calibration, and Processing  

Microsoft Academic Search

The Cloud Profiling Radar, the sole science instrument of the CloudSat Mission, is a 94-GHz nadir-looking radar that measures the power backscattered by hydrometeors (clouds and precipitation) as a function of distance from the radar. This instrument has been acquiring global time series of vertical cloud structures since June 2, 2006. In this paper, an overview of the radar performance

Simone Tanelli; Stephen L. Durden; Eastwood Im; Kyung S. Pak; Dale G. Reinke; Philip Partain; John M. Haynes; Roger T. Marchand

2008-01-01

63

Leveraging LIDAR-derived Point Clouds for Topographic Characterization  

NASA Astrophysics Data System (ADS)

Velásquez, C. F., Glenn, N. F., Ames, D. P. Acquisition of accurate x, y and z coordinates of terrain information throughout large geographic areas is possible with Light Detection and Ranging (LiDAR) technology. The mass of points (or point cloud) remotely acquired with airborne LiDAR sensors, for instance, are used for the creation of quality digital models of terrain. Extraction of hydrological features such as channel networks from digital terrain models is a common task. This task is generally conducted by means of implementing software tools that analyze raster structures for representation of terrain surfaces. Exploring the feasibility of directly and effectively extracting land cover features from a point cloud deserves due attention given both the proliferation of LiDAR data availability and the potential for the information to overcome some disadvantages that are intrinsic to the raster structure. Pursuing an alternative mode to leveraging LiDAR data for hydrologic applications is, therefore, the subject motivating the current research. A methodology for extraction of concave-shaped terrain surfaces is proposed. These features, relevant to hydrological applications, are extracted by means of implementing a convolution operation that is conducted on the x, y, and z coordinates of the point cloud and with an adapted construct for a zero-sum kernel function. The mass of points that are topographically lower of what is referred to as a zero-crossing level appear to reasonably well delineate concave-shaped landforms. The proposed method is, therefore, of merit to further investigation.

Velasquez, C.; Glenn, N. F.; Ames, D. P.

2010-12-01

64

Dust-cloud density estimation using a single wavelength lidar  

NASA Astrophysics Data System (ADS)

The passage of commercial and military aircraft through invisible fresh volcanic ash clouds has caused damage to many airplanes. On December 15, 1989 all four engines of a KLM Boeing 747 were temporarily extinguished in a flight over Alaska resulting in $DOL80 million for repair. Similar aircraft damage to control systems, FLIR/EO windows, wind screens, radomes, aircraft leading edges, and aircraft data systems were reported in Operation Desert Storm during combat flights through high-explosive and naturally occurring desert dusts. The Defense Nuclear Agency is currently developing a compact and rugged lidar under the Aircraft Sensors Program to detect and estimate the mass density of nuclear-explosion produced dust clouds, high-explosive produced dust clouds, and fresh volcanic dust clouds at horizontal distances of up to 40 km from an aircraft. Given this mass density information, the pilot has an option of avoiding or flying through the upcoming cloud.

Youmans, Douglas G.; Garner, Richard; Petersen, Kent R.

1994-09-01

65

A dual frequency millimetre wave radar for cloud characterization  

NASA Astrophysics Data System (ADS)

For a long period of time FHR is developing millimetre wave radars for airborne remote sensing applications, namely at 35 GHz and 94 GHz. While for these applications generally a high bandwidth is used to allow an adequate range resolution, the requirements for cloud radars are more directed towards an ultimate sensitivity and long range. Based upon this expertise investigations were done to develop a cloud radar at 220 GHz, which should be used simultaneously with respective radars at 35 GHz and 94 GHz. To gain experience with this topic, a 94 GHz-radar, which was formerly used for propagation experiments over long range, was modified and measurements on clouds were conducted. The radar to be developed shall mainly be used for investigations on snow clouds over relatively short range, and is not intended to be able to characterize Cirrus type clouds at high altitude.

Essen, H.; Sieger, S.

2010-10-01

66

Global estimation of above-cloud aerosols using spaceborne LIDAR  

NASA Astrophysics Data System (ADS)

Estimates of global mean direct climate forcing by absorbing aerosols located above boundary layer clouds are large, uncertain, and almost entirely unconstrained by observations. Spaceborne lidar offers a new opportunity of estimating the aerosols at global scale. Here we use two recently available techniques quantifying the above-cloud aerosols using liquid water clouds as lidar targets from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) [Chand et al., 2008]. Both methods can quantify aerosols above clouds and are based on their self-calibrating techniques. We used one year of global data between 70N-70S to show that day time calibration constants are different than night time calibrations constants. A clear latitudinal dependence is observed in the calibrations constants in CALIPSO observations. Using these 'self-calibration' constants, aerosol optical depth (AOD) and angstrom exponent (AE) of 'above- cloud' aerosols are quantified. Biomass burning is a major source of fine mode aerosols in different regions of world. For example, it is observed that June is the onset of the biomass burning fires in Southern Africa, peaking in August and September and then slowly decreasing until November, with a corresponding signature in aerosol optical depth. Layers with aerosol optical depth greater than 0.3 are commonly observed up to several thousand kilometers away from Africa over the Atlantic Ocean. The 'above-cloud' AOD as high as 1.5 is observed in the peak months. Despite of large variations is AOD, mean AE of these aerosols is about 1.6, without any systematic variability away from the source region. The results estimating the aerosols above clouds, including other regions at global scale, will be presented in the AGU meeting. Chand, D., T. L. Anderson, R. Wood, R. J. Charlson, Y. Hu, Z. Liu, and M. Vaughan (2008), Quantifying above-cloud aerosol using spaceborne lidar for improved understanding of cloudy-sky direct climate forcing, J. Geophys. Res., 113, D13206, doi:10.1029/2007JD009433.

Chand, D.; Wood, R.; Anderson, T. L.; Satheesh, S. K.; Leahy, L.

2008-12-01

67

ESTIMATION OF TROPICAL FOREST STRUCTURE AND BIOMASS FROM FUSION OF RADAR AND LIDAR MEASUREMENTS (Invited)  

NASA Astrophysics Data System (ADS)

Radar and Lidar instruments are active remote sensing sensors with the potential of measuring forest vertical and horizontal structure and the aboveground biomass (AGB). In this paper, we present the analysis of radar and lidar data acquired over the La Selva Biological Station in Costa Rica. Radar polarimetry at L-band (25 cm wavelength), P-band (70 cm wavelength) and interferometry at C-band (6 cm wavelength) and VV polarization were acquired by the NASA/JPL airborne synthetic aperture radar (AIRSAR) system. Lidar images were provided by a large footprint airborne scanning Lidar known as the Laser Vegetation Imaging Sensor (LVIS). By including field measurements of structure and biomass over a variety of forest types, we examined: 1) sensitivity of radar and lidar measurements to forest structure and biomass, 2) accuracy of individual sensors for AGB estimation, and 3) synergism of radar imaging measurements with lidar imaging and sampling measurements for improving the estimation of 3-dimensional forest structure and AGB. The results showed that P-band radar combined with any interformteric measurement of forest height can capture approximately 85% of the variation of biomass in La Selva at spatial scales larger than 1 hectare. Similar analysis at L-band frequency captured only 70% of the variation. However, combination of lidar and radar measurements improved estimates of forest three-dimensional structure and biomass to above 90% for all forest types. We present a novel data fusion approach based on a Baysian estimation model with the capability of incorporating lidar samples and radar imagery. The model was used to simulate the potential of data fusion in future satellite mission scenarios as in BIOMASS (planned by ESA) at P-band and DESDynl (planned by NASA) at L-band. The estimation model was also able to quantify errors and uncertainties associated with the scale of measurements, spatial variability of forest structure, and differences in radar and lidar geometry and pixel locations. Keywords: Amazon, Biomass, Carbon, Forest Structure, Tropical forests, Radar, Polarimetry, Interferometry, Lidar This work is performed partially at the Jet Propulsion Laboratory, California Institute of Technology, under contract from National Aeronautic and Space Administration.

Saatchi, S. S.; Dubayah, R.; Clark, D. B.; Chazdon, R.

2009-12-01

68

Coordinated optical and radar image measurements of noctilucent clouds and polar mesospheric summer echoes  

NASA Astrophysics Data System (ADS)

Novel coincident 3-D radar, lidar and optical image measurements of dynamical structures in polar mesosphere summer echoes (PMSE) and noctilucent clouds (NLC) are presented. Common volume mesospheric measurements were made over central Alaska using the new Poker Flat Incoherent Scatter Radar (PFISR), a co-located Rayleigh lidar and remote, two-station digital image observations, enabling the first detailed investigation of the horizontal and vertical structures of NLC and PMSE. Coincident measurements were made of an unusual NLC display recorded on 10-11 August 2007, characterized by a broad luminous band that contained several prominent wave forms. Concurrent lidar and image measurements established the presence of NLC within the radar volume from ~09:00 UT (01:00 LT), when the solar depression angle was 10.4°, until dawn. Strong but intermittent PMSE were detected by PFISR, with distinct patchy structures that exhibited a similar southward motion as the NLC. Detailed comparison of the 3-D PMSE structures and the NLC lidar and image data have revealed striking similarities when account was taken of the NLC layer altitude, suggesting a direct link between their small-scale spatial signatures (within the current resolution of the radar measurements). At the same time, the lidar detected a sustained increase in the backscatter signal, while the imagers revealed the development of copious short horizontal wavelength (4.9 km) billow waves. We conclude that strong wind shears associated with the Kelvin-Helmholtz billow instabilities played a key role in the development of a neutral turbulence layer in close proximity to the NLC layer resulting in the strong but intermittent PMSE detected at 450 MHz on this occasion.

Taylor, M. J.; Zhao, Y.; Pautet, P.-D.; Nicolls, M. J.; Collins, R. L.; Barker-Tvedtnes, J.; Burton, C. D.; Thurairajah, B.; Reimuller, J.; Varney, R. H.; Heinselman, C. J.; Mizutani, K.

2009-05-01

69

A High Resolution Hydrometer Phase Classifier Based on Analysis of Cloud Radar Doppler Spectra.  

SciTech Connect

The lifecycle and radiative properties of clouds are highly sensitive to the phase of their hydrometeors (i.e., liquid or ice). Knowledge of cloud phase is essential for specifying the optical properties of clouds, or else, large errors can be introduced in the calculation of the cloud radiative fluxes. Current parameterizations of cloud water partition in liquid and ice based on temperature are characterized by large uncertainty (Curry et al., 1996; Hobbs and Rangno, 1998; Intriery et al., 2002). This is particularly important in high geographical latitudes and temperature ranges where both liquid droplets and ice crystal phases can exist (mixed-phase cloud). The mixture of phases has a large effect on cloud radiative properties, and the parameterization of mixed-phase clouds has a large impact on climate simulations (e.g., Gregory and Morris, 1996). Furthermore, the presence of both ice and liquid affects the macroscopic properties of clouds, including their propensity to precipitate. Despite their importance, mixed-phase clouds are severely understudied compared to the arguably simpler single-phase clouds. In-situ measurements in mixed-phase clouds are hindered due to aircraft icing, difficulties distinguishing hydrometeor phase, and discrepancies in methods for deriving physical quantities (Wendisch et al. 1996, Lawson et al. 2001). Satellite-based retrievals of cloud phase in high latitudes are often hindered by the highly reflecting ice-covered ground and persistent temperature inversions. From the ground, the retrieval of mixed-phase cloud properties has been the subject of extensive research over the past 20 years using polarization lidars (e.g., Sassen et al. 1990), dual radar wavelengths (e.g., Gosset and Sauvageot 1992; Sekelsky and McIntosh, 1996), and recently radar Doppler spectra (Shupe et al. 2004). Millimeter-wavelength radars have substantially improved our ability to observe non-precipitating clouds (Kollias et al., 2007) due to their excellent sensitivity that enables the detection of thin cloud layers and their ability to penetrate several non-precipitating cloud layers. However, in mixed-phase clouds conditions, the observed Doppler moments are dominated by the highly reflecting ice crystals and thus can not be used to identify the cloud phase. This limits our ability to identify the spatial distribution of cloud phase and our ability to identify the conditions under which mixed-phase clouds form.

Luke,E.; Kollias, P.

2007-08-06

70

Turbulent characteristics of cirrus clouds as observed by 35/94-GHz Doppler radars  

NASA Astrophysics Data System (ADS)

The turbulent features and the internal structure of a convectively-generated cirrus cloud are studied using profiling observations from two surface-based millimeter cloud Doppler radars. The University of Miami W-band observations provided 30-m sampling in the vertical with temporal resolution of 1.7-s and the NOAA/ET operated a K-band with 4 different operational modes. It provided 10-s temporal resolution vertical profiles. The Doppler spectra measurements were made during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers Florida Area Cirrus Experiment (CRYSTAL FACE) conducted in the summer of 2002 in South Florida to study cumulus generated cirrus clouds and were further supported by lidar measurements of cloud-base height as well as observations from a third radar (NOAA S-band) deployed at the site. A thick non- precipitating cirrus was observed for approximately 3 hours. Three different areas within the same cloud are analyzed. Horizontal gradients of the vertical velocity and power density spectrum are calculated and compared using both radars and confirm the importance or turbulence on the observed Doppler spectrum width in low reflectivity non precipitating clouds. This study further illustrates the importance of the sampling strategy needed to retrieve turbulence characteristics using Doppler spectra.

Jo, I.; Albrecht, B. A.; Kollias, P.

2006-12-01

71

A 94GHz Doppler radar for cloud observations  

Microsoft Academic Search

A Doppler radar operating at 3.2 mm wavelength was designed and assembled primarily for observation of clouds and precipitation. Phase detection of the radar signals which is required for Doppler operation is implemented through the use of a coherent oscillator phase locked on the transmitter pulse and used as a reference in the phase detector. The radar and associated signal

Roger Lhermitte

1987-01-01

72

W-band ARM Cloud Radar (WACR) Handbook  

SciTech Connect

The W-band Atmospheric Radiation Measurement (ARM) Program Cloud Radar (WACR) systems are zenith pointing Doppler radars that probe the extent and composition of clouds at 95.04 GHz. The main purpose of this radar is to determine cloud boundaries (e.g., cloud bottoms and tops). This radar reports estimates for the first three spectra moments for each range gate up to 15 km. The 0th moment is reflectivity, the 1st moment is radial velocity, and the 2nd moment is spectral width. Also available are the raw spectra files. Unlike the millimeter wavelength cloud radar (MMCR), the WACR does not use pulse coding and operates in only copolarization and cross-polarization modes.

Widener, KB; Johnson, K

2005-01-05

73

On cloud radar and microwave radiometer measurements of stratus cloud liquid water profiles  

Microsoft Academic Search

We show a method for determining stratus cloud liquid water profiles using a microwave radiometer and cloud radar. This method is independent of the radar calibration and the cloud-droplet size distribution provided that the sixth moment of the size distribution can be related to the square of the third moment. We have calculated these moments with a wide variety of

A. S. Frisch; G. Feingold; C. W. Fairall; T. Uttal; J. B. Snider

1998-01-01

74

Balloonborne lidar for cloud physics studies.  

PubMed

An innovative balloonborne microjoule lidar (MULID) has been developed within the framework of the HIBISCUS project to provide nighttime measurements of visible and subvisible cirrus and aerosols. MULID has been designed to be a low-cost and an ultralow consumption instrument, due to the remote possibilities of payload recovery and the necessity of a low-weight battery power supply. Ground tests have been performed at the Observatory of Haute Provence (France), and the first technical flight has been made from Trapani, Italy, on a stratospheric balloon; finally, the instrument has been scientifically deployed during the pre-HIBISCUS and HIBISCUS tropical campaigns in Bauru, Brazil, in February 2003 and February 2004, respectively. A description of the instrument is provided together with the results of the ground-based and flight tests as well as an overview and discussion of the first results. PMID:16855669

Di Donfrancesco, Guido; Cairo, Francesco; Buontempo, Carlo; Adriani, Alberto; Viterbini, Maurizio; Snels, Marcel; Morbidini, Roberto; Piccolo, Francesco; Cardillo, Francesco; Pommereau, Jean-Pierre; Garnier, Anne

2006-08-01

75

Segmentation and Reconstruction of Polyhedral Building Roofs From Aerial Lidar Point Clouds  

Microsoft Academic Search

This paper presents a solution framework for the segmentation and reconstruction of polyhedral building roofs from aerial LIght Detection And Ranging (lidar) point clouds. The eigenanalysis is first carried out for each roof point of a building within its Voronoi neighborhood. Such analysis not only yields the surface normal for each lidar point but also separates the lidar points into

Aparajithan Sampath; Jie Shan

2010-01-01

76

Studies of Polar Stratospheric Cloud Composition using CALIPSO Lidar Data  

NASA Astrophysics Data System (ADS)

The CALIOP (Cloud-Aerosol LIdar with Orthogonal Polarization) lidar system onboard the CALIPSO spacecraft has been operating nearly continuously since mid-June 2006. Measurements are made at latitudes up to about 82 degrees, resulting in a wealth of polar stratospheric cloud (PSC) observations over two complete PSC "seasons" in both the Antarctic and Arctic. CALIOP backscatter data are collected in three receiver channels - 532-nm parallel-polarized, 532-nm perpendicular-polarized, and 1064-nm total, which together provide information on PSC particle shape and size, and hence composition. Our second-generation CALIOP PSC detection algorithm uses both the 532-nm scattering ratio (ratio of total-to-molecular backscatter) and 532-nm perpendicular backscatter coefficient, as well as a successive horizontal averaging scheme that enhances the detection of very tenuous PSCs. The PSCs are then separated into composition classes based on their ensemble optical properties in a manner analogous to that used in previous ground-based and airborne lidar PSC studies. This paper will discuss the new algorithm and provide an overview of the first two years of CALIOP PSC observations, highlighting interhemispheric differences and interannual variability.

Pitts, M. C.; Poole, L. R.; Thomason, L. W.

2008-05-01

77

A self-directing elastic backscatter lidar system for debris cloud tracking and characterization  

SciTech Connect

An elastic backscatter lidar that utilizes the lidar signal itself to direct the system towards fast moving isolated aerosol clouds has been developed. However, detecting and tracking invisible transient effluents from unknown locations, though conceptually straightforward, has still remained experimentally challenging. Accurate cloud volume, cloud density distribution, and track information have been obtained on small, fast moving, subvisible debris clouds resulting from above ground tests in which conventional explosives were detonated.

Clark, D.A.; Dighe, K.A. [Los Alamos National Lab., NM (United States); Tunnell, T.W. [Bechtel Nevada, Los Alamos, NM (United States). Los Alamos Operations

1996-06-01

78

Simulation of Spaceborne Doppler Radar Observations of Clouds  

Microsoft Academic Search

Space-borne Doppler radar observations of clouds are scientifically very interesting, but the correct interpretation of the measurements is challenging. Global observations of vertical velocity in cloud systems in many different climate zones will improve our understanding of large-scale convective motions and cloud microphysics. Unfortunately, observed Doppler speeds are a complex weighted average over all line-of-sight velocities within the radar's field-of-view.

N. Schutgens

2006-01-01

79

Comparison of CloudSat and TRMM radar reflectivities  

NASA Astrophysics Data System (ADS)

Comparison of reflectivity data of radars onboard CloudSat and TRMM is performed using coincident overpasses. The contoured frequency by altitude diagrams (CFADs) are constructed for two cases: (a) only include collocated vertical profiles that are most likely to be raining and (b) include all collocated profiles along with cloudy pixels falling within a distance of about 50 km from the centre point of coincidence. Our analysis shows that for both cases, CloudSat underestimates the radar reflectivity by about 10 dBZ compared to that of TRMM radar below 15 km altitude. The difference is well outside the uncertainty value of ~2 dBZ of each radar. Further, CloudSat reflectivity shows a decreasing trend while that of TRMM radar an increasing trend below 4 km height. Basically W-band radar that CloudSat flies suffers strong attenuation in precipitating clouds and its reflectivity value rarely exceeds 20 dBZ though its technical specification indicates the upper measurement limit to be 40 dBZ. TRMM radar, on the other hand, cannot measure values below 17 dBZ. In fact combining data from these two radars seems to give a better overall spatial structure of convective clouds.

Sindhu, K. D.; Bhat, G. S.

2013-08-01

80

Cloud radar Doppler spectra in drizzling stratiform clouds: 1. Forward modeling and remote sensing applications  

NASA Astrophysics Data System (ADS)

Several aspects of spectral broadening and drizzle growth in shallow liquid clouds remain not well understood. Detailed, cloud-scale observations of microphysics and dynamics are essential to guide and evaluate corresponding modeling efforts. Profiling, millimeter-wavelength (cloud) radars can provide such observations. In particular, the first three moments of the recorded cloud radar Doppler spectra, the radar reflectivity, mean Doppler velocity, and spectrum width, are often used to retrieve cloud microphysical and dynamical properties. Such retrievals are subject to errors introduced by the assumptions made in the inversion process. Here, we introduce two additional morphological parameters of the radar Doppler spectrum, the skewness and kurtosis, in an effort to reduce the retrieval uncertainties. A forward model that emulates observed radar Doppler spectra is constructed and used to investigate these relationships. General, analytical relationships that relate the five radar observables to cloud and drizzle microphysical parameters and cloud turbulence are presented. The relationships are valid for cloud-only, cloud mixed with drizzle, and drizzle-only particles in the radar sampling volume and provide a seamless link between observations and cloud microphysics and dynamics. The sensitivity of the five observed parameters to the radar operational parameters such as signal-to-noise ratio and Doppler spectra velocity resolution are presented. The predicted values of the five observed radar parameters agree well with the output of the forward model. The novel use of the skewness of the radar Doppler spectrum as an early qualitative predictor of drizzle onset in clouds is introduced. It is found that skewness is a parameter very sensitive to early drizzle generation. In addition, the significance of the five parameters of the cloud radar Doppler spectrum for constraining drizzle microphysical retrievals is discussed.

Kollias, Pavlos; RéMillard, Jasmine; Luke, Edward; Szyrmer, Wanda

2011-07-01

81

Ice Crystal Size Retrivals using High Spectral Resolution Lidar and Millimeter Wave Radar Data  

Microsoft Academic Search

The University of Wisconsin Arctic High Spectral Resolution Lidar(AHSRL) and the NOAA 8.6 mm radar(MMCR) are collecting data in the high Arctic at Eureka, Canada (79.94N, 85.56W). They have been deployed as part of the NOAA SEARCH program since August of 2005. AHSRL and MMCR data are distributed at http:\\/\\/lidar.ssec.wisc.edu. This web site allows visual scans of available data, composition

E. Eloranta

2006-01-01

82

Lidar measurements of Asian dust storms and dust cloud interactions  

NASA Astrophysics Data System (ADS)

Long-range transport of Asian dust storms has been investigated by using lidar at Chungli (24.6°N, 121.1°E) in 2002-2004. One of the dust storms that occurred in the period of 27-31 March 2002 was also observed by lidar at Hefei (31.9°N, 117.16°E). The lidar height distributions of dust extinction were compared with back trajectory calculation and atmospheric data including First Global GARP Experiment (FGGE)-type ground observations and National Center for Environment Prediction/Atmospheric Research (NCEP/NCAR) reanalysis. Dust layers had an average total (aerosol and molecular) depolarization ratio (DR) about 0.2; however, formation of droplets with near-zero depolarization ratio (0.02) was also measured. The cloud condensation nuclei (CCN) activities of dust particles were considered based on chemical properties observed from the ground. We observed that dust transport to the south may interact strongly with the moisture from the active weather system in the region producing significant climate effects.

Nee, Jan B.; Chiang, Chih-Wei; Hu, Huan-Ling; Hu, Shun-Xing; Yu, Jia-Yuh

2007-08-01

83

Fusing ultra-wideband radar and lidar for small UGV navigation in all-weather conditions  

NASA Astrophysics Data System (ADS)

Autonomous small UGVs have the potential to greatly increase force multiplication capabilities for infantry units. In order for these UGVs to be useful on the battlefield, they must be able to operate under all-weather conditions. For the Daredevil Project, we have explored the use of ultra-wideband (UWB) radar, LIDAR, and stereo vision for all-weather navigation capabilities. UWB radar provides the capability to see through rain, snow, smoke, and fog. LIDAR and stereo vision provide greater accuracy and resolution in clear weather but has difficulty with precipitation and obscurants. We investigate the ways in which the sensor data from UWB radar, LIDAR, and stereo vision can be combined to provide improved performance over the use of a single sensor modality. Our research includes both traditional sensor fusion, where data from multiple sensors is combined in a single representation, and behavior-based sensor fusion, where the data from one sensor is used to activate and deactivate behaviors using other sensor modalities. We use traditional sensor fusion to combine LIDAR and stereo vision for improved obstacle avoidance in clear air, and we use behavior-based sensor fusion to select between radar-based and LIDAR/vision-based obstacle avoidance based on current environmental conditions.

Yamauchi, Brian

2010-04-01

84

On the horizontal and temporal structure of noctilucent clouds as observed by satellite and lidar at ALOMAR (69N)  

NASA Astrophysics Data System (ADS)

Simultaneous and common volume observations of Noctilucent Clouds (NLC) and Polar Mesospheric Clouds (PMC) have been performed above the ALOMAR research station in Northern Norway (69°N, 16°E) from ground and space, respectively. A detailed case study on August 5, 2008 shows that the measured particle sizes and T-matrix simulations of the optical properties allow to combine the two observation techniques. From the ground, the observations were performed by lidar sounding of the temporal evolution of the cloud at two locations separated by about 40 km, before, during and after the coincidence. From space, the CIPS instrument onboard the AIM satellite observed the horizontal structure of the cloud. Using mesospheric radar wind measurements at ALOMAR the advection of the cloud particles is calculated and the temporal evolution of the cloud as seen from ground is compared with the horizontal structure observed from satellite. This comparison allows estimation of the timescales during which the clouds behave as passive tracers. We find that during this case study cloud structures larger than about 5 km × 5 km and oscillations slower than about one minute behaved like a passive tracer for up to one hour corresponding to horizontal scales of about 300 km. However, if the cloud shows wave structures with brightness modulations of 20% microphysical changes might take place on scales of minutes and kilometers.

Baumgarten, G.; Chandran, A.; Fiedler, J.; Hoffmann, P.; Kaifler, N.; Lumpe, J.; Merkel, A.; Randall, C. E.; Rusch, D.; Thomas, G.

2012-01-01

85

Space-borne clear air lidar measurements in the presence of broken cloud  

NASA Astrophysics Data System (ADS)

A number of proposed lidar systems, such as ESA’s AEOLUS (formerly ADM) and DIAL missions (e.g. WALES) are to make use of lidar returns in clear air. However, on average, two-thirds of the globe is covered in cloud. Hence, there is a strong likelihood that data from these instruments may be contaminated by cloud. Similarly, optically thick cloud may not be penetrated by a lidar pulse, resulting in unobservable regions that are overshadowed by the cloud. To address this, it is suggested, for example, in AEOLUS, that a number of consecutive short sections of lidar data (between 1 and 3.5 km in length) be tested for cloud contamination or for overshadowing and only those that are unaffected by cloud be used to derive atmospheric profiles. The prob-ability of obtaining profiles to near ground level using this technique is investigated both analytically and using UV air-borne lidar data recorded during the CLARE’98 campaign. These data were measured in the presence of broken cloud on a number of flights over southern England over a four-day period and were chosen because the lidar used has the same wavelength, footprint and could match the along-track spacing of the proposed AEOLUS lidar.

Astin, I.; Kiemle, C.

2003-03-01

86

Fusing ultra-wideband radar and lidar for small UGV navigation in all-weather conditions  

Microsoft Academic Search

Autonomous small UGVs have the potential to greatly increase force multiplication capabilities for infantry units. In order for these UGVs to be useful on the battlefield, they must be able to operate under all-weather conditions. For the Daredevil Project, we have explored the use of ultra-wideband (UWB) radar, LIDAR, and stereo vision for all-weather navigation capabilities. UWB radar provides the

Brian Yamauchi

2010-01-01

87

Preliminary results of cloud observation with millimeter wave multi-parameter cloud profiling radar (SPIDER)  

Microsoft Academic Search

Cloud plays one of the biggest unknown factors in global warming prediction. To observe the 3-dimensional profiles of clouds, a mm-wave multi-parameter airborne cloud profiling radar (nickname: SPIDER) has been developed by the Communications Research Laboratory (CRL). SPIDER was designed for airborne as well as ground-based use. The frequency of the radar is in the W-band (95 GHz) giving it

Hiroaki HORIE; Hiroshi HANADO; Yuji OHSAKI; T. Iguchi; Hiroshi KUMAGAI

1998-01-01

88

Airborne validation of cirrus cloud properties derived from CALIPSO lidar measurements: Optical properties  

NASA Astrophysics Data System (ADS)

The Cloud-Aerosol Lidar Infrared Pathfinder Satellite Observations (CALIPSO) satellite was successfully launched in April 2006 to study cloud and aerosol layers using range-resolved laser remote sensing. Dedicated flights were conducted from July 26 to August 14, 2006 using the airborne Cloud Physics Lidar (CPL) to validate the CALIPSO lidar (CALIOP) data products. This paper presents results from coincident ice cloud measurements of lidar ratio, extinction coefficient, and optical depth. Flight segment case studies are shown as well as statistics for all coincident measurements during this CALIPSO-CloudSat Validation Experiment (CC-VEX). For the penetrated portion of opaque layers, CALIOP estimates of lidar ratio and extinction are substantially lower than the corresponding CPL values. Significant differences were also found for measurements of horizontally aligned ice, where different instrument viewing geometries precluded meaningful comparisons. After filtering the data set to exclude these discrepancies, overall CALIOP lidar ratio and extinction averages compared favorably to within 1% of overall CPL averages. When restricting the data further to exact coincident in-cloud point-pairs, CALIOP lidar ratios remained close to CPL values, averaging 2.1% below CPL, and the retrieved extinction and optical depth averaged 14.7% above CPL values, a result partially of higher average CALIOP attenuated backscatter but still a respectably close match.

Hlavka, Dennis L.; Yorks, John E.; Young, Stuart A.; Vaughan, Mark A.; Kuehn, Ralph E.; McGill, Matthew J.; Rodier, Sharon D.

2012-05-01

89

Coupling of Land and Atmosphere Over Complex Terrain as Observed by Lidar and Wind Profiler Radar  

Microsoft Academic Search

The Marshall-2001 experiment was conducted south of Boulder\\/Colorado to study the dynamics of the atmospheric boundary layer (ABL) over hilly terrain. Two remote sensing techniques, an elastic backscatter lidar and a multiple antenna profiling radar, were used to observe the mixing in the ABL. In addition, fluxes of sensible and latent heat, soil heat flux and net radiation were recorded

M. Pahlow; M. B. Parlange; W. O. Brown; E. Bou-Zeid; V. Kumar; T. You-Yu

2001-01-01

90

Comparison of radar polarimetric and lidar scattering matrix measurements and systems calibration methods  

Microsoft Academic Search

A systematic approach to the measurements of the four basic scattering matrices used in radar and also recently more frequently in lidar metrology of isolated scatterers and distributed scatter ensembles is considered. The pertinent scattering matrices in use are the 2×2 complex JONES propagation matrix [T] or the 2×2 complex Sinclair scattering matrix [S] for the coherent point scatter case;

H. Mott; Y. Yamaguchi; W.-M. Boerner

1993-01-01

91

Radar based remote sensing of cloud liquid water—application of various techniques—a case study  

NASA Astrophysics Data System (ADS)

During the BALTEX BRIDGE Campaign (BBC) of CLIWA-NET, conducted at Cabauw, The Netherlands, from 1 August through 31 September 2001, cloud radar parameters like reflectivity, linear depolarization ratio and Doppler velocities have been observed using a 95 GHz cloud radar. These observations along with other remotely sensed parameters from the ground, have been used to derive the liquid water content of clouds which is one of the most important parameters to be known when the radiative transfer of clouds needs to be calculated. Simultaneously a multi-channel passive microwave radiometer and a lidar ceilometer have been operated close to the radar. While drizzle could be ruled out to have a significant impact on the return signal, corrections due to atmospheric absorption (gaseous) and attenuation due to clouds (mainly loss of signal due to absorption) had to be applied to the radar data. The corrections will be discussed in detail and have been applied to the radar reflectivity profiles before estimating cloud liquid water profiles. After the liquid water content profile has been calculated (for a fixed integrated liquid water path) the maximum in liquid water content of the cloud increased by about 14% and shifted upward within the cloud. The applied corrections bring the liquid water profile closer to adiabatic in the middle and upper part of the cloud. Examples of time series of corrected vertical profiles and average profiles are shown and are discussed. The ground based remotely sensed liquid water profiles show, on average, excellent agreement with simultaneously in situ measured liquid water content from aircraft measurements.

Meywerk, J.; Quante, M.; Sievers, O.

2005-05-01

92

Convective clouds modelling and tracking by an airborne radar  

Microsoft Academic Search

A method for modelling and tracking convective clouds within radar images is described. Clouds are non-rigid heterogeneous objects; a good representation of the weather scene is performed by extracting skeletal lines of the 2-dimensional grayscale pictures. Skeletons are reduced to sets of segments within a graph structure and tracked among successive pictures by means of relaxation labelling processes. We present

Clementine Costes; Rene Garello; Gregoire Mercier; Jean-Paul Artis; Nicolas Bon

2008-01-01

93

A millimeter-wave Cloud Profiling Radar System (CPRS)  

Microsoft Academic Search

The Microwave Remote Sensing Laboratory (MIRSL) at the University of Massachusetts has developed a unique dual-frequency polarimetric Cloud Profiling Radar System (CPRS). This system, whose development was funded by the Atmospheric Radiation Measurement (ARM) program, was intended to fill the need for remote sensors capable of remotely sensing cloud properties such as partical phase and size. CPRS polarimetric and dual-wavelength

S. M. Sekelsky; R. E. McIntosh

1994-01-01

94

Cloud Liquid Water and Ice Content Retrieval by Multiwavelength Radar  

Microsoft Academic Search

Cloud liquid water and ice content retrieval in precipitating clouds by the differential attenuation method using a dual-wavelength radar, as a function of the wavelength pair, is first discussed. In the presence of non- Rayleigh scatterers, drizzle, or large ice crystals, an ambiguity appears between attenuation and non-Rayleigh scattering. The liquid water estimate is thus biased regardless of which pair

Nicolas Gaussiat; Henri Sauvageot; Anthony J. Illingworth

2003-01-01

95

Phoenix Lidar Observations of the Cloud Topped Boundary Layer on Mars  

Microsoft Academic Search

The NASA Phoenix mission to Mars landed on 25 May 2008 and operated for five months. The LIDAR instrument on Phoenix observed water ice clouds in the atmosphere of Mars that were similar to cirrus clouds on Earth. Fall streaks in the cloud structure traced the precipitation of ice crystals toward the ground. Measurements of atmospheric dust indicated that the

J. A. Whiteway; L. Komguem; C. Dickinson; C. Cook; M. Illnicki; J. Seabrook; V. Popovici; T. Duck; R. Davy; P. Taylor; J. Pathak; D. Fisher; A. Carswell; M. Daly; V. Hipkin; L. Tamppari; N. Renno; J. Moores; M. Lemmon; F. Daerden; P. H. Smith

2009-01-01

96

Model interpretation of cloud observations by the LIDAR on the Phoenix Mars lander  

Microsoft Academic Search

Phoenix LIDAR observations [Whiteway et al. 2009] of clouds and precipitation in the planetary boundary layer (PBL) on Mars have been interpreted by a microphysical model for Mars ice clouds in combination with a coupled PBL-Aeolian dust model [Davy et al. 2009, Daerden et al. 2010]. The model simulates nighttime clouds and fall streaks within the PBL that are similar

Frank Daerden; J. A. Whiteway; R. Davy; L. Komguem; C. Dickinson; P. A. Taylor

2010-01-01

97

Dual-polarization cloud lidar using a liquid crystal variable retarder  

NASA Astrophysics Data System (ADS)

Information on local cloud coverage, with high spatial and temporal resolution, is useful for studying how the radiative properties of clouds affect the climate. The resolution of a lidar allows for detection of subvisual cloud and aerosol layers, and for determining particle sizes of the scatterers. A cloud lidar sensitive to polarization can distinguish between ice and water in clouds, since ice crystals are more depolarizing than water droplets. Cloud lidars complement either ground-based or space-based cloud imagers by supplying the missing vertical dimension. This paper describes the design and characterization of a lidar system for the direct detection of clouds, using a liquid crystal to discriminate between backscattered polarization states on alternate laser pulses (at 30 Hz). The source is a Nd:YAG laser at a wavelength of 532 nm and with pulse energies of 118 mJ. The system is designed to be compact and robust enough for transport and deployment. Data presented show the lidar system is capable of detecting clouds up to 9.5 km above ground level (the normal operating range is 15 km) with a 1.5 m range resolution. The receiver field of view is conveniently variable up to 8.8 mrad. Daytime operation is possible, thanks to laser-line interference filters and a gated photomultiplier tube. Polarization discrimination is sufficient to measure depolarization ratios with an additive error of less than 0.4%.

Seldomridge, Nathan L.; Shaw, Joseph A.; Repasky, Kevin S.

2005-08-01

98

Three-Dimensional Spatial Structure of Cirrus Clouds Determined from Lidar Satellite Observations.  

National Technical Information Service (NTIS)

Simultaneous imagery from the University of Wisconsin Volume Imaging Lidar (VIL) and meteorological satellites were used to quantify the spatial structure of cirrus clouds with 60 m resolution. This data was used to determine the spatial distributions of ...

E. W. Eloranta D. Wylie W. Wolf

1996-01-01

99

Error analysis of Raman differential absorption lidar ozone measurements in ice clouds.  

PubMed

A formalism for the error treatment of lidar ozone measurements with the Raman differential absorption lidar technique is presented. In the presence of clouds wavelength-dependent multiple scattering and cloud-particle extinction are the main sources of systematic errors in ozone measurements and necessitate a correction of the measured ozone profiles. Model calculations are performed to describe the influence of cirrus and polar stratospheric clouds on the ozone. It is found that it is sufficient to account for cloud-particle scattering and Rayleigh scattering in and above the cloud; boundary-layer aerosols and the atmospheric column below the cloud can be neglected for the ozone correction. Furthermore, if the extinction coefficient of the cloud is ?0.1 km(-1), the effect in the cloud is proportional to the effective particle extinction and to a particle correction function determined in the limit of negligible molecular scattering. The particle correction function depends on the scattering behavior of the cloud particles, the cloud geometric structure, and the lidar system parameters. Because of the differential extinction of light that has undergone one or more small-angle scattering processes within the cloud, the cloud effect on ozone extends to altitudes above the cloud. The various influencing parameters imply that the particle-related ozone correction has to be calculated for each individual measurement. Examples of ozone measurements in cirrus clouds are discussed. PMID:18354611

Reichardt, J

2000-11-20

100

First observations of noctilucent clouds by lidar at Svalbard  

NASA Astrophysics Data System (ADS)

In summer 2001 a potassium lidar was installed near Longyearbyen (78° N) on the north polar island of Spitsbergen which is part of the archipelago Svalbard. At the same place a series of meteorological rockets ("falling spheres", FS) were launched which gave temperatures from the lower thermosphere to the stratosphere. The potassium lidar is capable of detecting noctilucent clouds (NLCs) and of measuring temperatures in the lower thermosphere, both under daylight conditions. In this paper we give an overview on the NLC measurements (the first at this latitude) and compare the results with temperatures from meteorological rockets which have been published recently (Lübken and Müllemann, 2003).. NLCs were observed from 12 June (the first day of operation) until 12 August when a period of bad weather started. When the lidar was switched on again on 26 August, no NLC was observed. The mean occurrence frequency in the period 12 June-12 August ("lidar NLC period") is 77%. The mean of all individual NLC peak altitudes is 83.6 km (variability: 1.1 km). The mean peak NLC altitude does not show a significant variation with season. The average top and bottom altitude of the NLC layer is 85.1 and 82.5 km, respectively, with a variability of ~1.2 km. The mean of the maximum volume backscatter coefficient ßmax at our wavelength of 770 nm is 3.9×10-10/m/sr with a large variability of +/-3.8×10-10/m/sr. Comparison of NLC characteristics with measurements at ALOMAR (69° N) shows that the peak altitude and the maximum volume backscatter coefficient are similar at both locations but NLCs occur more frequently at higher latitudes. Simultaneous temperature and NLC measurements are available for 3 flights and show that the NLC layer occurs in the lower part of the height range with super-saturation. The NLC peak occurs over a large range of degree of saturation (S) whereas most models predict the peak at S=1. This demonstrates that steady-state considerations may not be applicable when relating individual NLC properties to background conditions. On the other hand, the mean variation of the NLC appearance with height and season is in agreement with the climatological variation of super-saturation derived from the FS temperature measurements.

Höffner, J.; Fricke-Begemann, C.; Lübken, F.-J.

2003-02-01

101

Validation of Cloud Radar Retrievals of Ice Cloud Microphysics in TWP-ICE and CC VEx  

Microsoft Academic Search

The Tropical Warm Pool International Cloud Experiment (TWP-ICE) and the CALIPSO-CloudSat Validation Experiment (CC-VEx) have both provided valuable data sets for the validation of ice cloud microphysical retrievals (among other purposes). TWP-ICE was conducted in the region around Darwin and the Tiwi Islands in Australia's Northern Territory in January and February 2006. The Jet Propulsion Laboratory Airborne Cloud Radar (ACR)

R. T. Austin; G. L. Stephens

2006-01-01

102

Lidar and Triple-Wavelength Doppler Radar Measurements of the Melting Layer: A Revised Model for Dark and Brightband Phenomena  

Microsoft Academic Search

During the recent Cirrus Regional Study of Tropical Anvils and Cirrus Layers (CRYSTAL) Florida Area Cirrus Experiment (FACE) field campaign in southern Florida, rain showers were probed by a 0.523-mum lidar and three (0.32-, 0.86-, and 10.6-cm wavelength) Doppler radars. The full repertoire of backscattering phenomena was observed in the melting region, that is, the various lidar and radar dark

Kenneth Sassen; James R. Campbell; Jiang Zhu; Pavlos Kollias; Matthew Shupe; Christopher Williams

2005-01-01

103

Arctic Mixed-Phase Cloud Properties from AERI Lidar Observations: Algorithm and Results from SHEBA  

Microsoft Academic Search

A new approach to retrieve microphysical properties from mixed-phase Arctic clouds is presented. This mixed-phase cloud property retrieval algorithm (MIXCRA) retrieves cloud optical depth, ice fraction, and the effective radius of the water and ice particles from ground-based, high-resolution infrared radiance and lidar cloud boundary observations. The theoretical basis for this technique is that the absorption coefficient of ice is

D. D. Turner; David D

2005-01-01

104

Subtropical cirrus cloud extinction to backscatter ratios measured by Raman Lidar during CAMEX-3  

NASA Astrophysics Data System (ADS)

The NASA/GSFC Scanning Raman Lidar was stationed on Andros Island, Bahamas for the third Convection and Moisture Experiment (CAMEX 3) held in August-September, 1998 and acquired an extensive set of cirrus cloud measurements [Whiteman et al., 2001]. Distinct differences in the optical properties of the clouds are found when the cirrus are hurricane-induced versus non-hurricane-induced. Hurricane-induced cirrus clouds are found to generally possess lower values of extinction-to-backscatter ratio (S) than non-hurricane-induced clouds. Comparison of the S measurements made here with those of other studies reveal at times large differences. Given that S is often a required parameter for space-based retrievals of cloud optical depth using backscatter lidar, these large differences in S measurements imply difficulties in developing a parameterization of S for use in space-based lidar retrievals.

Whiteman, D. N.; Demoz, B.; Wang, Z.

2004-06-01

105

Global distribution of instantaneous daytime radiative effects of high thin clouds observed by the cloud profiling radar  

Microsoft Academic Search

The instantaneous daytime geographical distribution and radiative effects of high thin clouds (optical thickness < 5) are investigated on the basis of the CloudSat Cloud Profiling Radar (CPR) radiative flux and cloud classification products. The regional features of the fraction and radiative effects of high thin clouds are associated with ITCZ, SPCZ and mid-latitude storm track regions. High thin clouds

Yong-Keun Lee; Thomas J. Greenwald; Ping Yang; Steve Ackerman; Hung-Lung Huang

2010-01-01

106

Smoke-Column Observations from Two Forest Fires Using Doppler Lidar and Doppler Radar.  

NASA Astrophysics Data System (ADS)

To demonstrate the usefulness of active remote-sensing systems in observing forest fire plume behavior, we studied two fires, one using a 3.2-cm-wavelength Doppler radar, and one more extensively, using Doppler lidar. Both instruments observed the kinematics of the convection column, including the presence of two different types of rotation in the columns, and monitored the behavior of the smoke plume.The first fire, a forest fire that burned out of control, was observed by the Doppler radar during late-morning and afternoon hours. Strong horizontal ambient winds produced a bent-over convection column, which the radar observed to have strong horizontal flow at its edges and weaker flow along the centerline of the plume. This velocity pattern implies that the column consisted of a pair of counterrotating horizontal vortices (rolls), with rising motion along the centerline and sinking along the edges. The radar tracked the smoke plume for over 30 km. It also provided circular depolarization ratio measurements, which gave information that the scattering particles were mostly flat or needle shaped as viewed by the radar, perhaps pine needles or possibly flat ash platelets being viewed edge on.The second fire, observed over a 5-h period by Doppler lidar, was a prescribed forest fire ignited in the afternoon. During the first hour of the fire the lidar observed many kinematic quantities of the convection column, including flow convergence and anticyclonic whole-column, rotation of the nearly vertical column, with a vorticity of approximately 102 s1 and an estimated peak vertical velocity w of 1 5 m s1. After the first hour ambient meteorological conditions changed, the whole-column rotation ceased, and the convection column and smoke plume bent over toward the lidar in stronger horizontal flow. At two times during this later stage, w was estimated to be 24 and 10 m s1. Lidar observations show that the smoke plume of this second fire initially went straight up in the convection column to heights of over 2 km, so most of the smoke was injected into the atmosphere above the unstable, afternoon, convective boundary layer, or mixed layer. Later, as the horizontal winds increased, a larger friction of the smoke remained in the mixed layer. Finally, very late in the afternoon, after ignitions had ceased and the fire was smoldering, almost all of the smoke remained within the mixed layer.These analyses show that lidar and radar can provide valuable three-dimensional datasets on kinematic quantities and smoke distribution in the vicinity of fires. This kind of information should be of great value in understanding and modeling convection-column dynamics and smoke-plume behavior.

Banta, R. M.; Olivier, L. D.; Holloway, E. T.; Kropfli, R. A.; Bartram, B. W.; Cupp, R. E.; Post, M. J.

1992-11-01

107

The Cloud-Aerosol Transport System (CATS): a new lidar for aerosol and cloud profiling from the International Space Station  

NASA Astrophysics Data System (ADS)

Spaceborne lidar profiling of aerosol and cloud layers has been successfully implemented during a number of prior missions, including LITE, ICESat, and CALIPSO. Each successive mission has added increased capability and further expanded the role of these unique measurements in wide variety of applications ranging from climate, to air quality, to special event monitoring (ie, volcanic plumes). Many researchers have come to rely on the availability of profile data from CALIPSO, especially data coincident with measurements from other A-Train sensors. The CALIOP lidar on CALIPSO continues to operate well as it enters its fifth year of operations. However, active instruments have more limited lifetimes than their passive counterparts, and we are faced with a potential gap in lidar profiling from space if the CALIOP lidar fails before a new mission is operational. The ATLID lidar on EarthCARE is not expected to launch until 2015 or later, and the lidar component of NASA's proposed Aerosols, Clouds, and Ecosystems (ACE) mission would not be until after 2020. Here we present a new aerosol and cloud lidar that was recently selected to provide profiling data from the International Space Station (ISS) starting in 2013. The Cloud-Aerosol Transport System (CATS) is a three wavelength (1064, 532, 355 nm) elastic backscatter lidar with HSRL capability at 532 nm. Depolarization measurements will be made at all wavelengths. The primary objective of CATS is to continue the CALIPSO aerosol and cloud profile data record, ideally with overlap between both missions and EarthCARE. In addition, the near real time data capability of the ISS will enable CATS to support operational applications such as air quality and special event monitoring. The HSRL channel will provide a demonstration of technology and a data testbed for direct extinction retrievals in support of ACE mission development. An overview of the instrument and mission will be provided, along with a summary of the science objectives and simulated data.

Welton, E. J.; McGill, M. J.; Yorks, J. E.; Hlavka, D. L.; Hart, W. D.; Palm, S. P.; Colarco, P. R.

2011-12-01

108

Initial Results of the Cloud, Aerosol Polarization and Backscatter Lidar at Summit, Greenland  

NASA Astrophysics Data System (ADS)

Measurements of cloud properties over Summit, Greenland are necessary to document the full range of cloud conditions and characteristics throughout the Arctic. A new lidar system has been developed to measure depolarization and backscatter of clouds in the lower troposphere and aerosols in the upper troposphere and lower stratosphere. This lidar uses recent developments in optical methods to characterize system polarization effects in order to compensate for systematic phase shifts. The lidar utilizes the detection of three polarization planes to determine the depolarization ratio and diattenuation of clouds and aerosols below 2.5% error. The ability to measure diattenuation allows for a qualitative assessment of particle orientation and analysis of the data that can forego the assumption of randomly oriented particles. The lidar is located at Summit, Greenland as part of the Integrated Characterization of Energy, Clouds, Atmospheric State, and Precipitation at Summit project and NOAA’s Global Monitoring Division’s stratospheric lidar network. Initial results from the first six months of operation suggest cloud formation similar to other Arctic sites. Here we particularly look at the persistence of mixed phase clouds and new results suggesting possible ice crystal alignment under certain atmospheric conditions.

Neely, R. R.; Hayman, M.; Thayer, J.; Hardesty, R.; O'Neill, M.; Shupe, M.

2010-12-01

109

Methods for LiDAR point cloud classification using local neighborhood statistics  

NASA Astrophysics Data System (ADS)

LiDAR data are available in a variety of publicly-accessible forums, providing high-resolution, accurate 3- dimensional information about objects at the Earth's surface. Automatic extraction of information from LiDAR point clouds, however, remains a challenging problem. The focus of this research is to develop methods for point cloud classification and object detection which can be customized for specific applications. The methods presented rely on analysis of statistics of local neighborhoods of LiDAR points. A multi-dimensional vector composed of these statistics can be classified using traditional data classification routines. Local neighborhood statistics are defined, and examples are given of the methods for specific applications such as building extraction and vegetation classification. Results indicate the feasibility of the local neighborhood statistics approach and provide a framework for the design of customized classification or object detection routines for LiDAR point clouds.

Kim, Angela M.; Olsen, Richard C.; Kruse, Fred A.

2013-05-01

110

Model of Lidar Return in Marine Stratus Cloud Layers.  

National Technical Information Service (NTIS)

Various types of lidars have been used in attempts to obtain quantitative information about the nearby atmosphere. This report investigates the use of a handheld visioceilometer lidar to determine the extinction coefficient sigma as a function of range r ...

V. R. Noonkester

1986-01-01

111

Transport of noctilucent clouds by tidal winds observed in the western Arctic  

Microsoft Academic Search

The NICT Rayleigh lidar, MF radar and a digital camera were installed at Poker Flat Research Range (PFRR), Chatanika, Alaska (65° N, 147° W). The NICT Rayleigh lidar measures scattered light from noctilucent clouds (NLCs) during Arctic summer (late July to August). The raw lidar measurements yield profiles at 20 s and 75 m resolution. The NICT MF radar measures

Kazuyo Sakanoi; Yasuhiro Murayama; Richard Collins; Kohei Mizutani

2008-01-01

112

Comparison of precipitation observations from a prototype space-based cloud radar and ground-based radars  

NASA Astrophysics Data System (ADS)

A prototype space-based cloud radar has been developed and was installed on an airplane to observe a precipitation system over Tianjin, China in July 2010. Ground-based S-band and Ka-band radars were used to examine the observational capability of the prototype. A cross-comparison algorithm between different wavelengths, spatial resolutions and platform radars is presented. The reflectivity biases, correlation coefficients and standard deviations between the radars are analyzed. The equivalent reflectivity bias between the S- and Ka-band radars were simulated with a given raindrop size distribution. The results indicated that reflectivity bias between the S- and Ka-band radars due to scattering properties was less than 5 dB, and for weak precipitation the bias was negligible. The prototype space-based cloud radar was able to measure a reasonable vertical profile of reflectivity, but the reflectivity below an altitude of 1.5 km above ground level was obscured by ground clutter. The measured reflectivity by the prototype space-based cloud radar was approximately 10.9 dB stronger than that by the S-band Doppler radar (SA radar), and 13.7 dB stronger than that by the ground-based cloud radar. The reflectivity measured by the SA radar was 0.4 dB stronger than that by the ground-based cloud radar. This study could provide a method for the quantitative examination of the observation ability for space-based radars.

Liu, Liping; Zhang, Zhiqiang; Yu, Danru; Yang, Hu; Zhao, Chonghui; Zhong, Lingzhi

2012-11-01

113

Accuracy of biomass estimates from radar and lidar over temperate forests  

NASA Astrophysics Data System (ADS)

A better understanding of ecosystem processes requires accurate estimates of forest biomass and structure on global scales. Recently, there have been demonstrations of the ability of remote sensing instruments, such as radar and lidar, for the estimation of forest parameters from spaceborne platforms in a consistent manner. These advances can be exploited for global forest biomass accounting and structure characterization, leading to a better understanding of the global carbon cycle. The popular techniques for estimation of forest parameters from radar instruments in particular, use backscatter intensity, interferometry and polarimetric interferometry. In this paper we analyze the accuracy of biomass estimates over temperate forests of the North-Eastern United States from lidar and radar backscatter. We adopt an empirical approach, relying on ground truth data collected during DESDynI field campaigns over the Harvard and Howland Forests in 2009 and remote sensing data from LVIS, the GSFC full-waveform lidar and NASA JPL's L-band UAVSAR. UAVSAR collected data over the Harvard and Howland Forests during a deployment in 2009 where it was flown in a repeat-pass configuration collecting several fully polarimetric scenes. In a concurrent deployment of the GSFC LVIS instrument, full waveform lidar data was collected over the same region. Diameter and species information from fifteen hectares at the Harvard Forest and twenty three hectares at the Howland forest was collected during the July 2009 DESDynI field campaigns as well. We assess the accuracy of biomass estimates based on diameter measurements by using a classic statistical approach to characterize the impact of the diameter-biomass allometry at both field sites. Using a lidar error model and estimates of error in field biomass, we attempt to characterize the error in biomass estimates from common full waveform lidar metrics from LVIS data over the Harvard and Howland forests. Similarly, using a radar backscatter error model and data from UAVSAR, we analyze the accuracy of the backscatter-biomass relationship and characterize the uncertainty in biomass estimates from radar in a non-linear regression setting with measurement error. A discussion will be provided on the implications of this analysis on the design and science outcomes of the proposed DESDynI mission.

Ahmed, R.; Siqueira, P. R.; Hensley, S.

2011-12-01

114

UV Raman lidar measurements of relative humidity for the characterization of cirrus cloud microphysical properties  

NASA Astrophysics Data System (ADS)

Raman lidar measurements performed in Potenza by the Raman lidar system BASIL in the presence of cirrus clouds are discussed. Measurements were performed on 6 September 2004 in the frame of Italian phase of the EAQUATE Experiment. The major feature of BASIL is represented by its capability to perform high-resolution and accurate measurements of atmospheric temperature and water vapour, and consequently relative humidity, both in daytime and night-time, based on the application of the rotational and vibrational Raman lidar techniques in the UV. BASIL is also capable to provide measurements of the particle backscatter and extinction coefficient, and consequently lidar ratio (at the time of these measurements only at one wavelength), which are fundamental to infer geometrical and microphysical properties of clouds. A case study is discussed in order to assess the capability of Raman lidars to measure humidity in presence of cirrus clouds, both below and inside the cloud. While air inside the cloud layers is observed to be always under-saturated with respect to water, both ice super-saturation and under-saturation conditions are found inside these clouds. Upper tropospheric moistening is observed below the lower cloud layer. The synergic use of the data derived from the ground based Raman Lidar and of spectral radiances measured by the NAST-I Airborne Spectrometer allows to determine the temporal evolution of the atmospheric cooling/heating rates due to the presence of the cirrus cloud anvil. Lidar measurements beneath the cirrus cloud layer have been interpreted using a 1-D cirrus cloud model with explicit microphysics. The 1-D simulations indicates that sedimentation-moistening has contributed significantly to the moist anomaly, but other mechanisms are also contributing. This result supports the hypothesis that the observed mid-tropospheric humidification is a real feature which is strongly influenced by the sublimation of precipitating ice crystals. Results illustrated in this study demonstrate that Raman lidars, like the one used in this study, can resolve the spatial and temporal scales required for the study of cirrus cloud microphysical processes and appears sensitive enough to reveal and quantify upper tropospheric humidification associated with cirrus cloud sublimation.

di Girolamo, P.; Summa, D.; Lin, R.-F.; Maestri, T.; Rizzi, R.; Masiello, G.

2009-07-01

115

UV Raman lidar measurements of relative humidity for the characterization of cirrus cloud microphysical properties  

NASA Astrophysics Data System (ADS)

Raman lidar measurements performed in Potenza by the Raman lidar system BASIL in the presence of cirrus clouds are discussed. Measurements were performed on 6 September 2004 in the frame of the Italian phase of the EAQUATE Experiment. The major feature of BASIL is represented by its capability to perform high-resolution and accurate measurements of atmospheric temperature and water vapour, and consequently relative humidity, both in daytime and night-time, based on the application of the rotational and vibrational Raman lidar techniques in the UV. BASIL is also capable to provide measurements of the particle backscatter and extinction coefficient, and consequently lidar ratio (at the time of these measurements, only at one wavelength), which are fundamental to infer geometrical and microphysical properties of clouds. A case study is discussed in order to assess the capability of Raman lidars to measure humidity in presence of cirrus clouds, both below and inside the cloud. While air inside the cloud layers is observed to be always under-saturated with respect to water, both ice super-saturation and under-saturation conditions are found inside these clouds. Upper tropospheric moistening is observed below the lower cloud layer. The synergic use of the data derived from the ground based Raman Lidar and of spectral radiances measured by the NAST-I Airborne Spectrometer allows the determination of the temporal evolution of the atmospheric cooling/heating rates due to the presence of the cirrus cloud. Lidar measurements beneath the cirrus cloud layer have been interpreted using a 1-D cirrus cloud model with explicit microphysics. The 1-D simulations indicate that sedimentation-moistening has contributed significantly to the moist anomaly, but other mechanisms are also contributing. This result supports the hypothesis that the observed mid-tropospheric humidification is a real feature which is strongly influenced by the sublimation of precipitating ice crystals. Results illustrated in this study demonstrate that Raman lidars, like the one used in this study, can resolve the spatial and temporal scales required for the study of cirrus cloud microphysical processes and appear sensitive enough to reveal and quantify upper tropospheric humidification associated with cirrus cloud sublimation.

di Girolamo, P.; Summa, D.; Lin, R.-F.; Maestri, T.; Rizzi, R.; Masiello, G.

2009-11-01

116

A study of equatorial wave characteristics using rockets, balloons, lidar and radar  

Microsoft Academic Search

A co-ordmated experimental campaign was conducted for 40 consecutive days from 21 February to 01 April 2000 using RH-200 rockets, balloons, Rayleigh lidar and MST radar, with the objective of delineating the equatorial waves and estimating momentum fluxes associated with them. Winds and temperatures in the troposphere, stratosphere and mesosphere over two low latitude stations Gadanki (13.5°N, 79.2°E) and SHAR

M. N. Sasi; B. V. Krishna Murthy; Geetha Ramkumar; K. Satheesan; K. Parameswaran; K. Rajeev; S. V. Sunilkumar; Prabha R. Nair; K. Krishna Moorthy; Y. Bhavanikumar; K. Raghunath; A. R. Jain; P. B. Rao; M. Krishnaiah; S. R. Prabhakaran Nayars; K. Revathy; S. Devanarayanan

2003-01-01

117

ALOMAR: atmospheric science using lidars, radars and ground based instruments  

Microsoft Academic Search

On top of the 379 m high Ramnan mountain on the island of Andøya (69°30?N, 16°01?E) in Northern Norway, the ALOMAR (The Arctic Lidar Observatory for Middle Atmospheric Research) will soon be in operation. Through measurements of different atmospheric parameters, ALOMAR will provide information on the dynamics of the middle and upper atmosphere using ground-based instrumentation. Routine measurements, including ozone

Rolf Skatteboe

1996-01-01

118

Advanced clouds tracking for airborne weather radar & ground primary surveillance radar  

Microsoft Academic Search

A method for modeling and tracking convective clouds within radar images is presented. An object modeling approach is used, based on the extraction of either morphological or grayscale skeletons from 2-dimensionnal cross-section of 3-dimensional radar data. Grayscale skeletons are appropriate shape descriptors for non-rigid and heterogeneous objects, in which gray-level local maxima correspond to regions of interest. The modeling scheme

C. Costes; J.-P. Artis; F. Barbaresco

2010-01-01

119

Cloud radar Doppler spectra in drizzling stratiform clouds: 2. Observations and microphysical modeling of drizzle evolution  

SciTech Connect

In part I, the influence of cloud microphysics and dynamics on the shape of cloud radar Doppler spectra in warm stratiform clouds was discussed. The traditional analysis of radar Doppler moments was extended to include skewness and kurtosis as additional descriptors of the Doppler spectrum. Here, a short climatology of observed Doppler spectra moments as a function of the radar reflectivity at continental and maritime ARM sites is presented. The evolution of the Doppler spectra moments is consistent with the onset and growth of drizzle particles and can be used to assist modeling studies of drizzle onset and growth. Time-height radar observations are used to exhibit the coherency of the Doppler spectra shape parameters and demonstrate their potential to improve the interpretation and use of radar observations. In addition, a simplified microphysical approach to modeling the vertical evolution of the drizzle particle size distribution in warm stratiform clouds is described and used to analyze the observations. The formation rate of embryonic drizzle droplets due to the autoconversion process is not calculated explicitly; however, accretion and evaporation processes are explicitly modeled. The microphysical model is used as input to a radar Doppler spectrum forward model, and synthetic radar Doppler spectra moments are generated. Three areas of interest are studied in detail: early drizzle growth near the cloud top, growth by accretion of the well-developed drizzle, and drizzle depletion below the cloud base due to evaporation. The modeling results are in good agreement with the continental and maritime observations. This demonstrates that steady state one-dimensional explicit microphysical models coupled with a forward model and comprehensive radar Doppler spectra observations offer a powerful method to explore the vertical evolution of the drizzle particle size distribution.

Kollias, P.; Luke, E.; Szyrmer, W.; Rémillard, J.

2011-07-02

120

Cloud radar Doppler spectra in drizzling stratiform clouds: 2. Observations and microphysical modeling of drizzle evolution  

NASA Astrophysics Data System (ADS)

In part I, the influence of cloud microphysics and dynamics on the shape of cloud radar Doppler spectra in warm stratiform clouds was discussed. The traditional analysis of radar Doppler moments was extended to include skewness and kurtosis as additional descriptors of the Doppler spectrum. Here, a short climatology of observed Doppler spectra moments as a function of the radar reflectivity at continental and maritime ARM sites is presented. The evolution of the Doppler spectra moments is consistent with the onset and growth of drizzle particles and can be used to assist modeling studies of drizzle onset and growth. Time-height radar observations are used to exhibit the coherency of the Doppler spectra shape parameters and demonstrate their potential to improve the interpretation and use of radar observations. In addition, a simplified microphysical approach to modeling the vertical evolution of the drizzle particle size distribution in warm stratiform clouds is described and used to analyze the observations. The formation rate of embryonic drizzle droplets due to the autoconversion process is not calculated explicitly; however, accretion and evaporation processes are explicitly modeled. The microphysical model is used as input to a radar Doppler spectrum forward model, and synthetic radar Doppler spectra moments are generated. Three areas of interest are studied in detail: early drizzle growth near the cloud top, growth by accretion of the well-developed drizzle, and drizzle depletion below the cloud base due to evaporation. The modeling results are in good agreement with the continental and maritime observations. This demonstrates that steady state one-dimensional explicit microphysical models coupled with a forward model and comprehensive radar Doppler spectra observations offer a powerful method to explore the vertical evolution of the drizzle particle size distribution.

Kollias, Pavlos; Szyrmer, Wanda; RéMillard, Jasmine; Luke, Edward

2011-07-01

121

A study on the use of radar and lidar for characterizing ultragiant aerosol  

NASA Astrophysics Data System (ADS)

19 April to 19 May 2010, volcanic aerosol layers originating from the Eyjafjallajökull volcano were observed at the Institute of Methodologies for Environmental Analysis of the National Research Council of Italy Atmospheric Observatory, named CIAO (40.60°N, 15.72°E, 760 m above sea level), in Southern Italy with a multiwavelength Raman lidar. During this period, ultragiant aerosols were also observed at CIAO using a colocated 8.45 mm wavelength Doppler radar. The Ka-band radar signatures observed in four separate days (19 April and 7, 10, and 13 May) are consistent with the observation of nonspherical ultragiant aerosols characterized by values of linear depolarization ratio (LDR) higher than -4 dB. Air mass back trajectory analysis suggests a volcanic origin of the ultragiant aerosols observed by the radar. The observed values of the radar reflectivity (Ze) are consistent with a particle effective radius (r) larger than 50-75 µm. Scattering simulations based on the T-matrix approach show that the high LDR values can be explained if the observed particles have an absolute aspect ratio larger than 3.0 and consist of an internal aerosol core and external ice shell, with a variable radius ratio ranging between 0.2 and 0.7 depending on the shape and aspect ratio. Comparisons between daytime vertical profiles of aerosol backscatter coefficient (?) as measured by lidar and radar LDR reveal a decrease of ? where ultragiant particles are observed. Scattering simulations based on Mie theory show how the lidar capability in typing ultragiant aerosols could be limited by low number concentrations or by the presence of an external ice shell covering the aerosol particles. Preferential vertical alignment of the particles is discussed as another possible reason for the decrease of ?.

Madonna, F.; Amodeo, A.; D'Amico, G.; Pappalardo, G.

2013-09-01

122

Active probing of cloud thickness and optical depth using wide-angle imaging LIDAR.  

SciTech Connect

At most optical wavelengths, laser light in a cloud lidar experiment is not absorbed but merely scattered out of the beam, eventually escaping the cloud via multiple scattering. There is much information available in this light scattered far from the input beam, information ignored by traditional 'on-beam' lidar. Monitoring these off-beam returns in a fully space- and time-resolved manner is the essence of our unique instrument, Wide Angle Imaging Lidar (WAIL). In effect, WAIL produces wide-field (60{sup o} full-angle) 'movies' of the scattering process and records the cloud's radiative Green functions. A direct data product of WAIL is the distribution of photon path lengths resulting from multiple scattering in the cloud. Following insights from diffusion theory, we can use the measured Green functions to infer the physical thickness and optical depth of the cloud layer. WAIL is notable in that it is applicable to optically thick clouds, a regime in which traditional lidar is reduced to ceilometry. Section 2 covers the up-to-date evolution of the nighttime WAIL instrument at LANL. Section 3 reports our progress towards daytime capability for WAIL, an important extension to full diurnal cycle monitoring by means of an ultra-narrow magneto-optic atomic line filter. Section 4 describes briefly how the important cloud properties can be inferred from WAIL signals.

Love, Steven P.; Davis, A. B. (Anthony B.); Rohde, C. A. (Charles A.); Tellier, L. L. (Larry L.); Ho, Cheng,

2002-01-01

123

Categorizing precipitating clouds by using radar and geostationary satellite  

NASA Astrophysics Data System (ADS)

The classification of precipitating cloud systems over Thailand was attempted by using radar reflectivity and Multifunctional Transport Satellites (MTSAT) infrared brightness temperature (TBB) data. The proposed method can classify the convective rain (CR) area, stratiform rain (SR) area and non-precipitation area such as cumulus and cirrus cloud by applying an integrating analysis of rain gauge, ground-based radar and geostationary satellite data. Since the present study focuses on precipitation, the classified results of precipitation area are used to estimate quantitative precipitation amount. To merge different rainfall products, the bias between the products should be removed. The bias correction method is used to estimate spatially varying multiplicative biases in hourly radar and satellite rainfall using a gauge and radar rainfall product, respectively. An extreme rain event was selected to obtain the multiplicative bias correction and to merge data set. Correlation coefficient (CC), root mean square error (RMSE) and mean bias are used to evaluate the performance of bias correction method. The combined radar-MTSAT method is a simple and useful method. This method has been successfully applied to merge radar and gauge rainfall for hydrological purpose.

Wetchayont, P.; Hayasaka, T.; Katagiri, S.; Satomura, T.

2012-11-01

124

Ice crystal properties retrieval using radar spectral polarimetric measurements within ice\\/mixed-phase clouds  

Microsoft Academic Search

In the field of atmospheric research, ground-based radar systems are often employed to study ice\\/mixed-phase cloud properties based on retrieval techniques. These techniques convert the radar signal backscattered by each bulk of ice crystals being probed within the same radar resolution volume to cloud’s microphysical characteristics. However, the size of a radar resolution volume is often too large compared to

Y. Dufournet

2010-01-01

125

Ice-cloud depolarization of backscatter for CO2 and other infrared lidars  

NASA Astrophysics Data System (ADS)

The depolarization of backscatter from ice particles at the CO2 lidar wavelength of 10.59 microns was investigated through field measurements, with simultanous depolarization measurements taken at 0.6943 micron for comparison. The depolarization ratio at the infrared wavelength was usually at or below the lidar's sensitivity limit of 0.01, which is dramatically smaller than the typical 0.5 linear depolarization ratio for short-wave lidars. This behavior is explained by the strong absorption of ice at the infrared wavelength. Depolarization measurements at a 10.59-micron wavelength cannot discriminate between ice and water clouds in the manner of short-wave lidars. A possibility exists for more prominent depolarization at shorter CO2 lidar wavelengths, but additional research is required. Depolarization at the 2.09-micron wavelength is predicted to be substantial and useful for hydrometeor observations.

Eberhard, Wynn L.

1992-10-01

126

Lidar measurements of Asian dust storms and dust cloud interactions  

Microsoft Academic Search

Long-range transport of Asian dust storms has been investigated by using lidar at Chungli (24.6°N, 121.1°E) in 2002–2004. One of the dust storms that occurred in the period of 27–31 March 2002 was also observed by lidar at Hefei (31.9°N, 117.16°E). The lidar height distributions of dust extinction were compared with back trajectory calculation and atmospheric data including First Global

Jan B. Nee; Chih-Wei Chiang; Huan-ling Hu; Shun-xing Hu; Jia-Yuh Yu

2007-01-01

127

Physical State and Composition of Polar Stratospheric Clouds Inferred from Airborne Lidar Measurements During SESAME  

Microsoft Academic Search

The airborne lidar LEANDRE was deployed from Kiruna (Sweden) in January1995, during Phase III of the Second European Stratospheric Arctic andMid-latitude Experiment (SESAME). Polar Stratospheric Clouds (PSC) weredetected on several flights. Four lidar retrievals, on two different days, arepresented together with the thermal history of air masses, derived from 5-daybackward trajectories calculated from the TOPCAT model, using ECMWF analyses.The first

C. DAVID; S. GODIN; G. MEGIE; Y. EMERY; C. FLESIA

1997-01-01

128

A comparison of simulated cloud radar output from the multiscale modeling framework global climate model with CloudSat cloud radar observations  

Microsoft Academic Search

Over the last few years a new type of global climate model (GCM) has emerged in which a cloud-resolving model is embedded into each grid cell of a GCM. This new approach is frequently called a multiscale modeling framework (MMF) or superparameterization. In this article we present a comparison of MMF output with radar observations from the NASA CloudSat mission,

Roger Marchand; John Haynes; Gerald G. Mace; Thomas Ackerman; Graeme Stephens

2009-01-01

129

Observation of clouds with the newly developed cloud profiling FM-CW radar at 95 GHz  

NASA Astrophysics Data System (ADS)

We developed a low-power and high-sensitivity cloud profiling radar transmitting frequency modulated continuous wave (FM-CW) at 95 GHz for ground-based observations. Millimeter wave at 95 GHz is used to realize much higher sensitivity than lower frequencies to small cloud particles. An FM-CW type radar realizes similar sensitivity with much smaller output power to a pulse type radar. Two 1m-diameter parabolic antennas separated by 1.4m each other are used for transmitting and receiving the wave. The direction of the antennas is fixed at the zenith. The radar is designed to observe clouds between 0.3 and 20 km in height with a resolution of 15 m. Using the developed millimeter-wave FM-CW radar at 95 GHz, we observed clouds in a campaign observation in Amami Island in March 2003, and on a sail on Mirai, a Japanese scientific research vessel, in September 2004 to January 2005 in the Arctic Ocean and the southwest of the Pacific Ocean. The radar provided good and sensitive data in these long-term observations.

Takano, Toshiaki; Akita, Ken-ichi; Kubo, Hiroshi; Kawamura, Youhei; Kumagai, Hiroshi; Takamura, Tamio; Nakanishi, Yuji; Nakajima, Teruyuki

2005-10-01

130

Development status of the cloud profiling radar for the cloudsat mission  

Microsoft Academic Search

The Cloud Profiling Radar, the primary science instrument of the CloudSat Mission, is a 94-GHz nadir-looking radar that measures the power backscattered by clouds as a function of distance from the radar. Shortly after the scheduled launch in November 2004, this instrument will acquire a global time series of vertical atmospheric cloud structure at 500-m vertical resolution and 1.4-km horizontal

Eastwood Im; Stephen L. Durden; Chialin Wu

2003-01-01

131

Process virtualization of large-scale lidar data in a cloud computing environment  

NASA Astrophysics Data System (ADS)

Light detection and ranging (lidar) technologies have proven to be the most powerful tools to collect, within a short time, three-dimensional (3-D) point clouds with high-density, high-accuracy and significantly detailed surface information pertaining to terrain and objects. However, in terms of feature extraction and 3-D reconstruction in a computer-aided drawing (CAD) format, most of the existing stand-alone lidar data processing software packages are unable to process a large volume of lidar data in an effective and efficient fashion. To break this technical bottleneck, through the design of a Condor-based process virtualization platform, we presented in this paper a novel strategy that uses network-related computational resources to process, manage, and distribute vast quantities of lidar data in a cloud computing environment. Three extensive experiments with and without a cloud computing environment were compared. The experiment results demonstrated that the proposed process virtualization approach is promisingly applicable and effective in the management of large-scale lidar point clouds.

Guan, Haiyan; Li, Jonathan; Zhong, Liang; Yongtao, Yu; Chapman, Michael

2013-10-01

132

Assessment of variability in continental low stratiform clouds based on observations of radar reflectivity  

Microsoft Academic Search

The variability of overcast low stratiform clouds observed over the ARM Climate Research Facility Southern Great Plains (ACRF SGP) site is analyzed, and an approach to characterizing subgrid variability based on assumed statistical distributions is evaluated. The analysis is based on a vast (>1000 hours) radar reflectivity database collected by the Millimeter-Wave Cloud Radar at ACRF SGP site. The radar

Zena N. Kogan; David B. Mechem; Yefim L. Kogan

2005-01-01

133

Validation of Cloud Radar Retrievals of Ice Cloud Microphysics in TWP-ICE and CC- VEx  

NASA Astrophysics Data System (ADS)

The Tropical Warm Pool International Cloud Experiment (TWP-ICE) and the CALIPSO-CloudSat Validation Experiment (CC-VEx) have both provided valuable data sets for the validation of ice cloud microphysical retrievals (among other purposes). TWP-ICE was conducted in the region around Darwin and the Tiwi Islands in Australia's Northern Territory in January and February 2006. The Jet Propulsion Laboratory Airborne Cloud Radar (ACR) was mounted on a Twin Otter aircraft, observing cirrus cloud layers and anvils from an altitude of 10,000 feet. In-cloud sampling of ice water content and ice particle microphysical properties was performed by various cloud probes carried on the DoE Proteus and the ARA Egrett aircraft. CC-VEx was conducted over the southeastern United States and adjacent regions of the Atlantic Ocean and the Gulf of Mexico in July and August 2006. CC-VEx flights were planned to observe cirrus clouds and associated convection to provide validation data for CloudSat observations and algorithms; flight tracks were selected to coincide with satellite overpasses. The NASA ER-2 airplane carried the Cloud Radar System (CRS) and the MODIS Airborne Simulator, observing the cloud systems from an altitude of 65,000 feet, while the WMI Learjet flew within the cloud layers, making microphysical measurements with several cloud probes. In this presentation, we compare statistics of recent retrievals of ice microphysical properties to direct measurements of those properties as collected by cloud probes during both of these campaigns. We comment on the effect of recent variations on the retrieval and how the retrievals perform under varying cloud conditions.

Austin, R. T.; Stephens, G. L.

2006-12-01

134

Feeder-Cell Ingestion of Seeding Aerosol from Cloud Base Determined by Tracking Radar Chaff  

Microsoft Academic Search

Questions of delivery, transport, and dispersion of cloud seeding aerosol in a convective feeder cloud are addressed by using radar chaff as a surrogate for aerosol and tracking it with circular-polarization radar. In a case study, a line source of chaff was released by an aircraft at the roots of a growing cloud flanking and feeding into a thunderstorm line.

Roger F. Reinking; Brooks E. Martner

1996-01-01

135

Polar winter cloud depolarization measurements with the CANDAC Rayleigh-Mie-Raman Lidar  

NASA Astrophysics Data System (ADS)

Clouds introduce a significant positive forcing to the Arctic radiation budget and this is strongest during the polar winter when shortwave radiation is absent (Intrieri et al., 2002). The amount of forcing depends on the occurrence probability and optical depth of the clouds as well as the cloud particle phase (Ebert and Curry 1992). Mixed-phase clouds are particularly complex as they involve interactions between three phases of water (vapour, liquid and ice) coexisting in the same cloud. Although significant progress has been made in characterizing wintertime Arctic clouds (de Boer et al., 2009 and 2011), there is considerable variability in the relative abundance of particles of each phase, in the morphology of solid particles, and in precipitation rates depending on the meteorology at the time. The Canadian Network for the Detection of Atmospheric Change (CANDAC) Rayleigh-Mie-Raman Lidar (CRL) was installed in the Canadian High Arctic at Eureka, Nunavut (80°N, 86°W) in 2008-2009. The remotely-operated system began with measurement capabilities for multi-wavelength aerosol extinction, water vapour mixing ratio, and tropospheric temperature profiles, as well as backscatter cross section coefficient and colour ratio. In 2010, a new depolarization channel was added. The capability to measure the polarization state of the return signal allows the characterization of the cloud in terms of liquid and ice water content, enabling the lidar to probe all three phases of water in these clouds. Lidar depolarization results from 2010 and 2011 winter clouds at Eureka will be presented, with a focus on differences in downwelling radiation between mixed phase clouds and ice clouds. de Boer, G., E.W. Eloranta, and M.D. Shupe (2009), Arctic mixed-phase stratiform cloud properties from multiple years of surface-based measurements at two high-latitude locations, Journal of Atmospheric Sciences, 66 (9), 2874-2887. de Boer, G., H. Morrison, M. D. Shupe, and R. Hildner (2011), Evidence of liquid dependent ice nucleation in high-latitude stratiform clouds from surface remote sensors, Geophysical Research Letters, 38, L01803. Ebert, EE and J.A .Curry (1992), A parameterization of ice cloud optical properties for climate models, Journal of Geophysical Research 97:3831-3836. Intrieri JM, Fairall CW, Shupe MD, Persson POG, Andreas EL, Guest PS, Moritz RE. 2002. An annual cycle of Arctic surface cloud forcing at SHEBA. Journal of Geophysical Research 107 NO. C10, 8039 . Noel, V., H. Chepfer, M. Haeffelin, and Y. Morille (2006), Classification of ice crystal shapes in midlatitude ice clouds from three years of lidar observations over the SIRTA observatory. Journal of the Atmospheric Sciences, 63:2978 - 2991.

McCullough, E. M.; Nott, G. J.; Duck, T. J.; Sica, R. J.; Doyle, J. G.; Pike-thackray, C.; Drummond, J. R.

2011-12-01

136

Lidar and All-Sky IR Camera Cloud Measurements for LSST Scheduling  

NASA Astrophysics Data System (ADS)

LSST has acquired an all-sky thermal IR imager to evaluate its cloud detection performances to inform the automatic scheduling process during night operations. Observations in the 10micron window have long been used at observatories to detect the presence of thick clouds and recent progresses in IR detector performances should enable the detection of thin cirrus at high altitudes. Lidar is quite effective at measuring the altitude and the optical depth of thin cirrus clouds well below 1% transmission losses and is therefore a perfectly suited instrument to help evaluating the detection performance of the all-sky IR imager. For that purpose, the IR imager has been deployed at the UNM Campus Observatory in Albuquerque NM the location of the Astronomical Lidar for Extinction (ALE) and the two instruments were operated together under varying amounts of cloud coverage. The poster will present the results obtained so far from this set of simultaneous observations.

Sebag, Jacques; Zimmer, P.; Klebe, D.; Mcgraw, J.; Krabbendam, V.

2011-03-01

137

Structures of stratiform clouds as measured by a scanning 35.5GHz cloud radar  

Microsoft Academic Search

Most cloud radars worldwide operate at vertical incidence delivering only height-time-cross-sections. Consequently the interpretation of time-dependent structures obtained by such instruments in terms of spatial characteristics assumes inherently that the structures move with a speed independent of time and space (ergodic hypothesis). However, this supposition may be a crude one since structures in clouds change continuously in space and time.

J. Grenzhäuser; J. Handwerker; K. D. Beheng

2009-01-01

138

Project Pre-Gondola II. Airborne Lidar Observations.  

National Technical Information Service (NTIS)

Lidar (laser radar) observations from an aircraft of the cloud of debris resulting from the Pre-GONDOLA 2 explosion at Fort Peck, Montana, are described. From the lidar observations the location, shape, and internal structure (in terms of variations of de...

J. Oblanas R. T. H. Collis

1968-01-01

139

Radar tracking of ion clouds. Technical report 1: Project STRESS  

Microsoft Academic Search

Project STRESS utilized a series of high-altitude releases of barium that became ionized by solar radiation. The project required that the resulting ion cloud be tracked in real time, and this was accomplished by operating the AN\\/FPS-85 radar in the incoherent-scatter mode. This report describes the data-acquisition process and the tracking algorithm, and presents a preliminary look at the most

V. H. Gonzalez

1977-01-01

140

Simultaneous Lidar and All-Sky IR Camera Observations to Measure Cloud Transmission  

NASA Astrophysics Data System (ADS)

We present initial results of combined lidar and all-sky thermal infrared camera measurements of transmission losses through clouds. Thermal IR observations in the 10 micron window have long been used at observatories to detect the presence of clouds by measuring the contrast in downwelling thermal radiation between clear and cloudy sky. The ability of these techniques to measure thin cirrus at high altitudes, the sort of clouds that typically ruin otherwise photometric conditions, has always been limited due to their low temperature and low emissivity. Lidar, on the other hand, is quite effective at measuring both the presence and optical depth of thin cirrus clouds, well below 1% transmission losses. A lidar can only operate in one direction at a time and thus is limited in its ability to measure transmission over wide fields of view. The combination of wide field thermal IR imaging plus lidar measurements of transmission hold significant promise for helping solve the time and field dependence of atmospheric transmission caused by clouds, especially sub-visual cirrus. To test this instrumental combination, the LSST all-sky infrared camera was deployed for several weeks at the UNM Campus Observatory in Albuquerque, NM, the location of the Astronomical Lidar for Extinction (ALE). The two instruments were operated together under various cloud cover conditions and when conditions permitted, narrowband photometry of bright stars was simultaneously obtained to verify the temporal and spatial variation of extinction. MAP atmospheric transmission research is supported by NIST Award 60NANB9D9121 and NSF Grant AST-1009878.

Zimmer, Peter C.; Sebag, J.; McGraw, J. T.; Zirzow, D. C.; Vorobiev, D. V.; UNM Measurement Astrophysics MAP Research Group

2011-01-01

141

Lidar observations of polar stratospheric clouds over northern Greenland in the period 1990-1997  

Microsoft Academic Search

Observations of the stratosphere were carried out at Thule (76.5°N, 68.8°W), Greenland, in the period 1990-1997 with an elastic backscatter\\/depolarization lidar. Polar stratospheric clouds (PSCs) were never detected during the winters 1991, 1992, 1993, and 1994. Small nondepolarizing PSCs could have been masked, however, by the large volcanic aerosol cloud that was in the stratosphere during 1992, 1993, and 1994.

A. di Sarra; M. Cacciani; G. Fiocco; D. Fuà; T. S. Jørgensen

2002-01-01

142

Lidar observations of polar stratospheric clouds over northern Greenland in the period 1990–1997  

Microsoft Academic Search

Observations of the stratosphere were carried out at Thule (76.5°N, 68.8°W), Greenland, in the period 1990–1997 with an elastic backscatter\\/depolarization lidar. Polar stratospheric clouds (PSCs) were never detected during the winters 1991, 1992, 1993, and 1994. Small nondepolarizing PSCs could have been masked, however, by the large volcanic aerosol cloud that was in the stratosphere during 1992, 1993, and 1994.

A. di Sarra; M. Cacciani; G. Fiocco; D. Fuà; T. S. Jørgensen

2002-01-01

143

Vegetation profiles in tropical forests from multibaseline interferometric synthetic aperture radar, field, and lidar measurements  

NASA Astrophysics Data System (ADS)

This paper addresses the estimation of vertical vegetation density profiles from multibaseline interferometric synthetic aperture radar (InSAR) data from the AirSAR aircraft at C band over primary, secondary, and abandoned-pasture stands at La Selva Biological Station, Costa Rica in 2004. Profiles were also estimated from field data taken in 2006 and lidar data taken with the LVIS, 25 m spot instrument in 2005. After motivating the study of tropical forest profiles based on their role in the global carbon cycle, ecosystem state, and biodiversity, this paper describes the InSAR, field, and lidar data acquisitions and analyses. Beyond qualitative agreement between profiles from the 3 measurement techniques, results show that InSAR and lidar profile-averaged mean height have RMS scatters about field-measured means of 3.4 m and 3.2 m, 16% and 15% of the average mean height, respectively. InSAR and lidar standard deviations of the vegetation distribution have RMS scatters about the field standard deviations of 1.9 m and 1.5 m, or 27% and 21%, respectively. Dominant errors in the profile-averaged mean height for each measurement technique were modeled. InSAR inaccuracies, dominated by ambiguities in finding the ground altitude and coherence calibration, together account for about 3 m of InSAR error in the mean height. The dominant, modeled error for the field measurements was the inaccuracy in modeling the trees as uniformly filled volumes of leaf area, inducing field errors in mean height of about 3 m. The dominant, modeled lidar error, also due to finding the ground, was 2 m.

Treuhaft, R. N.; Chapman, B. D.; Dos Santos, J. R.; GonçAlves, F. G.; Dutra, L. V.; GraçA, P. M. L. A.; Drake, J. B.

2009-12-01

144

NASA/GSFC Scanning Raman Lidar Measurements of Water Vapor and Clouds During IHOP.  

National Technical Information Service (NTIS)

The NASA/GSFC Scanning Raman Lidar (SRL) participated in the International H(sub 2)0 Project (IHOP) that occurred in May and June, 2002 in the midwestern part of the U.S. The SRL acquired measurements of water vapor, aerosols, cloud liquid and ice water, ...

D. N. Whiteman B. Demoz P. Di Girolamo J. Comer Z. Wang

2004-01-01

145

Analytical approximation for lidar signal from clouds under multiple light scattering  

NASA Astrophysics Data System (ADS)

The main purpose of this paper is to include analytically the angular backscattering dependence of phase function characteristic of rather large cloud droplets. We are doing so for two reasons, at least. First, the widely used approximation for the phase function, e.g. assuming it to be essentially constant near backscattering direction or using some its average value over the whole angular range of backscattering, can be shown to lead to overestimated or underestimated, respectively, light power recorded by a lidar. Second, the glory region bears the information on some microphysical parameters of clouds. So, the analytical description of backscattered light power would provide the simple prediction of lidar opportunities to measure, e.g., mean sizes or halfwidth of size distributions of cloud aerosols. To this purpose, the small-angle diffusion approximation of the radiative transfer theory (RTT) is used here to derive a lidar signal from intermediate optical thicknesses of clouds, where neither the asymptotic formulas of the RTT nor the single scattering approximation are working well. The analytical integration of radiative transfer with aerosol size distribution has enabled us to derive the explicit form of lidar signal power as a function of the microphysical parameters.

Barun, Vladimir V.

1996-11-01

146

Lidar observations of a stratospheric dust cloud layer in the tropics  

Microsoft Academic Search

Lidar observations revealed the presence of an unusual transparent whitish cloud veil above Hawaii during the period from October 1974 to early January 1975. The height of the layer was established at 19.5 km MSL, with a typical thickness of 800 m at half maximum. An attempt to attribute the layer to the eruption of the Fuego volcano in Guatemala

R. W. Fegley; H. T. Ellis

1975-01-01

147

Noctilucent cloud observations at mid-latitudes by lidar: mean state, variability and relation to MSE and temperature  

NASA Astrophysics Data System (ADS)

Noctilucent clouds (NLC) occur since more than 120 years in every summer between polar and about 50° latitude. NLC observations at mid-latitudes are of particular importance since NLC occurrence is expected to change strongly with only minor variations in temperature and water vapour. Therefore mid-latitude NLC strongly depend on atmospheric waves, trends, and solar cycle. At the Leibniz Institute of Atmospheric Physics at Kühlungsborn, Germany (54°N, 12°E) NLC are observed since 1997 at 532 nm wavelength. Until 2008 the NLC occurrence rate was up to 12%, while 2009 showed record-high 19% NLC occurrence. Nevertheless, NLC are sparse at our latitude. Altogether about 41 h of nighttime NLC observations are collected. We will present mean NLC parameters (altitude, backscatter coefficient) as well as data of the 2009 season showing comparatively frequent and strong NLC. We will discuss the relation to ambient temperatures and wave activity as observed simultaneously by Rayleigh and resonance lidars at our site. Only very few lidar stations are able to measure NLC independent of solar elevation. In 2009 we performed observations of NLC during full daylight. In future, NLC observations during day and night will allow to study for the first time the diurnal variation of NLC parameters at a mid-latitude site. We will present case studies of simultaneous observations of NLC and Mesospheric Summer Echoes as observed by the co-located OSWIN VHF radar.

Gerding, M.; Hoeffner, J.; Kopp, M.; Zecha, M.; Luebken, F.

2009-12-01

148

Combined CloudSat-CALIPSO-MODIS retrievals of the properties of ice clouds  

NASA Astrophysics Data System (ADS)

In this paper, data from spaceborne radar, lidar and infrared radiometers on the "A-Train" of satellites are combined in a variational algorithm to retrieve ice cloud properties. The method allows a seamless retrieval between regions where both radar and lidar are sensitive to the regions where one detects the cloud. We first implement a cloud phase identification method, including identification of supercooled water layers using the lidar signal and temperature to discriminate ice from liquid. We also include rigorous calculation of errors assigned in the variational scheme. We estimate the impact of the microphysical assumptions on the algorithm when radiances are not assimilated by evaluating the impact of the change in the area-diameter and the density-diameter relationships in the retrieval of cloud properties. We show that changes to these assumptions affect the radar-only and lidar-only retrieval more than the radar-lidar retrieval, although the lidar-only extinction retrieval is only weakly affected. We also show that making use of the molecular lidar signal beyond the cloud as a constraint on optical depth, when ice clouds are sufficiently thin to allow the lidar signal to penetrate them entirely, improves the retrieved extinction. When infrared radiances are available, they provide an extra constraint and allow the extinction-to-backscatter ratio to vary linearly with height instead of being constant, which improves the vertical distribution of retrieved cloud properties.

Delanoë, Julien; Hogan, Robin J.

2010-01-01

149

Influence of gravity waves and tides on mesospheric temperature inversion layers: simultaneous Rayleigh lidar and MF radar observations  

Microsoft Academic Search

Three nights of simultaneous Rayleigh lidar temperature measurements over Gadanki (13.5° N, 79.2° E) and medium frequency (MF) radar wind measurements over Tirunelveli (8.7° N, 77.8° E) have been analyzed to illustrate the possible effects due to tidal-gravity wave interactions on upper mesospheric inversion layers. The occurrence of tidal gravity wave interaction is investigated using MF radar wind measurements in

S. Sridharan; S. Sathishkumar; S. Gurubaran

2008-01-01

150

Depolarization ratio and attenuated backscatter for nine cloud types: analyses based on collocated CALIPSO lidar and MODIS measurements.  

PubMed

This paper reports on the relationship between lidar backscatter and the corresponding depolarization ratio for nine types of cloud systems. The data used in this study are the lidar returns measured by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard the Cloud- Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite and the collocated cloud products derived from the observations made by the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard Aqua satellite. Specifically, the operational MODIS cloud optical thickness and cloud-top pressure products are used to classify cloud types on the basis of the International Satellite Cloud Climatology Project (ISCCP) cloud classification scheme. While the CALIPSO observations provide information for up to 10 cloud layers, in the present study only the uppermost clouds are considered. The layer-averaged attenuated backscatter (gamma') and layer-averaged depolarization ratio (delta) from the CALIPSO measurements show both water- and ice-phase features for global cirrus, cirrostratus, and deep convective cloud classes. Furthermore, we screen both the MODIS and CALIPSO data to eliminate cases in which CALIPSO detected two- or multi-layered clouds. It is shown that low gamma' values corresponding to uppermost thin clouds are largely eliminated in the CALIPSO delta-gamma' relationship for single-layered clouds. For mid-latitude and polar regions corresponding, respectively, to latitude belts 30 degrees -60 degrees and 60 degrees -90 degrees in both the hemispheres, a mixture of water and ice is also observed in the case of the altostratus class. MODIS cloud phase flags are also used to screen ice clouds. The resultant water clouds flagged by the MODIS algorithm show only water phase feature in the delta-gamma' relation observed by CALIOP; however, in the case of the ice clouds flagged by the MODIS algorithm, the co-existence of ice- and water-phase clouds is still observed in the CALIPSO delta-gamma' relationship. PMID:18542490

Cho, Hyoun-Myoung; Yang, Ping; Kattawar, George W; Nasiri, Shaima L; Hu, Yongxiang; Minnis, Patrick; Trepte, Charles; Winker, David

2008-03-17

151

Automotive Radar and Lidar Systems for Next Generation Driver Assistance Functions  

NASA Astrophysics Data System (ADS)

Automotive radar and lidar sensors represent key components for next generation driver assistance functions (Jones, 2001). Today, their use is limited to comfort applications in premium segment vehicles although an evolution process towards more safety-oriented functions is taking place. Radar sensors available on the market today suffer from low angular resolution and poor target detection in medium ranges (30 to 60m) over azimuth angles larger than ±30°. In contrast, Lidar sensors show large sensitivity towards environmental influences (e.g. snow, fog, dirt). Both sensor technologies today have a rather high cost level, forbidding their wide-spread usage on mass markets. A common approach to overcome individual sensor drawbacks is the employment of data fusion techniques (Bar-Shalom, 2001). Raw data fusion requires a common, standardized data interface to easily integrate a variety of asynchronous sensor data into a fusion network. Moreover, next generation sensors should be able to dynamically adopt to new situations and should have the ability to work in cooperative sensor environments. As vehicular function development today is being shifted more and more towards virtual prototyping, mathematical sensor models should be available. These models should take into account the sensor's functional principle as well as all typical measurement errors generated by the sensor.

Rasshofer, R. H.; Gresser, K.

2005-05-01

152

mESY LIDAR - a new cost-effective, versatile and powerful lidar configuration for tropospheric aerosols, clouds and water vapor investigations  

NASA Astrophysics Data System (ADS)

In the context of remote sensing tools development for the monitoring of relevant atmospheric parameters triggering crucial processes in troposphere this work is presenting a new mini lidar system i.e mESY LIDAR. The basic configuration of this lidar is dedicated for tropospheric (100m to 12-15 Km ASL) aerosols and clouds high temporal (minutes) and spatial resolution (meters) investigation. Based on powerful Nd:YAG 30 Hz pulsed laser (35 mJ at 355 nm, 100 mJ at 532 nm, 200 mJ at 1064 nm), a 16" Newtonian telescope and a new easy up-gradable opto-mechanics the mESY LIDAR is a cost-effective and powerful equipment useful both for atmospherically researches and didactic - educational - lidar training activities also. The basic configuration (two detection channels) may be used either for depolarization studies (at 532, 355 or 1064nm) or the choice of two elastic and is ideal for continuous monitoring of planetary boundary layer dynamic i.e. PBL. The Raman Nitrogen at 387 nm and water vapor channels at 408 nm may be upgraded easily. The design of this lidar, developed within the research partnership between Switzerland and Romanian academic - private partnership institutions, is the standard lidar proposed for ROLINET (ROmanian LIdar NETwork) project with the final aim to be integrated in the EARLINET (European Aerosol Research LIdar NETwork) in 2010.

Cazacu, M. M.; Ristori, P.; Tudose, O.; Balanici, A.; Nicolae, D.; Ristici, V.; Balin, D.; Balin, I.

2009-04-01

153

A mid-latitude cirrus lidar climatology with thin cirrus clouds in the lowermost stratosphere  

NASA Astrophysics Data System (ADS)

Lidar observations (light detection and ranging) of cirrus clouds over Jülich, Western Germany, are performed and analyzed focusing on obtaining a representative cirrus climatology in terms of cirrus thickness, top and base heights, mid temperature, optical thickness and ice water content (IWC). The lidar instrument measures optical properties (i.e. backscatter signals, extinction coefficient and depolarization) of ice particles at a wavelength of 355 nm from the ground. The observed cirrus clouds are evaluated with a temporal averaged extinction profile and corrected for multiple scattering. The optical depth is used to classify radiative properties. Mean and median values of cirrus optical depth are found to be 0.28 and 0.12 (range: 0.002 - 3), respectively. 143 cirrus observations are analyzed together with additional meteorological data under macrophysical, radiative, and microphysical aspects. By comparing these cirrus properties to three other mid-latitude lidar climatologies (Sassen and Comstock, 2001; Immler and Schrems, 2002; Goldfarb et al., 2001), a rather good agreement is found and the Jülich lidar climatology is assessed to be representative. Most observed cirrus base heights are around 6 to 10.5 km and top heights around 12 km, implying a frequent cirrus generation due to synoptic weather pattern (e.g. frontal systems). Thus, the cirrus clouds are relatively thick with a vertical extent of about 2.25 km and occur mostly directly around the thermal tropopause. However, around 4 % of the cirrus clouds in the lidar climatology occurred above the tropopause. This indicates cirrus cloud occurrence in the lowermost stratosphere (LMS). The gradient in water vapor at the transition between troposphere and the LMS is strongly negative. Even small contributions of moist tropospheric air masses from the tropics due to quasi-horizontal transport into the LMS can increase the water vapor concentration significantly. This enhanced water vapor values could initiate the formation of thin cirrus clouds in the LMS up to polar latitudes. Further investigations could improve the understanding of mixing processes in the UT/LS. ECMWF data will be used to show the origin of the air masses which contain cirrus clouds above the tropopause as implied by the lidar observations. This will be done by using the static stability as marker for stratospheric and tropospheric air masses.

Rolf, Christian; Krämer, Martina

2013-04-01

154

Lidar and Triple-Wavelength Doppler Radar Measurements of the Melting Layer: A Revised Model for Dark- and Brightband Phenomena.  

NASA Astrophysics Data System (ADS)

During the recent Cirrus Regional Study of Tropical Anvils and Cirrus Layers (CRYSTAL) Florida Area Cirrus Experiment (FACE) field campaign in southern Florida, rain showers were probed by a 0.523-?m lidar and three (0.32-, 0.86-, and 10.6-cm wavelength) Doppler radars. The full repertoire of backscattering phenomena was observed in the melting region, that is, the various lidar and radar dark and bright bands. In contrast to the ubiquitous 10.6-cm (S band) radar bright band, only intermittent evidence is found at 0.86 cm (K band), and no clear examples of the radar bright band are seen at 0.32 cm (W band), because of the dominance of non-Rayleigh scattering effects. Analysis also reveals that the relatively inconspicuous W-band radar dark band is due to non-Rayleigh effects in large water-coated snowflakes that are high in the melting layer. The lidar dark band exclusively involves mixed-phase particles and is centered where the shrinking snowflakes collapse into raindrops-the point at which spherical particle backscattering mechanisms first come into prominence during snowflake melting. The traditional (S band) radar brightband peak occurs low in the melting region, just above the lidar dark-band minimum. This position is close to where the W-band reflectivities and Doppler velocities reach their plateaus but is well above the height at which the S-band Doppler velocities stop increasing. Thus, the classic radar bright band is dominated by Rayleigh dielectric scattering effects in the few largest melting snowflakes.

Sassen, Kenneth; Campbell, James R.; Zhu, Jiang; Kollias, Pavlos; Shupe, Matthew; Williams, Christopher

2005-03-01

155

Low clouds and fog observations by polarization lidar  

Microsoft Academic Search

In the paper some polarization investigations of objects and phenomena in the planetary boundary layer of the atmosphere are presented. The observations described were performed by a ground-based lidar over the region of Sofia city where various industrial enterprises exist along with a heavy transport and aerial communications. The changes in the optical characteristics of fog and snow depending on

Ivan N. Kolev; Boian I. Tatarov; Vassily N. Naboko; Atanas I. Blagov

1997-01-01

156

Raman lidar measurements of water vapor and cirrus clouds during the passage of Hurricane Bonnie  

NASA Astrophysics Data System (ADS)

The NASA GSFC Scanning Raman Lidar (SRL) was stationed on Andros Island in the Bahamas during August-September 1998 as a part of the third Convection and Moisture Experiment (CAMEX 3) which focused on hurricane development and tracking. During the period August 21-24, Hurricane Bonnie passed near Andros Island and influenced the water vapor and cirrus cloud measurements acquired by the SRL. Two drying signatures related to the hurricane were recorded by the SRL and other sensors. Cirrus cloud optical depths (at 351 nm) were also measured during this period. Optical depth values ranged from less than 0.01 to 1.5. The influence of multiple scattering on these optical depth measurements was studied. A correction technique is presented which minimizes the influences of multiple scattering and derives information about cirrus cloud optical and physical properties. The UV/IR cirrus cloud optical depth ratio was estimated on the basis of a comparison of lidar and GOES 8 measurements. Simple radiative transfer model calculations compared with GOES satellite brightness temperatures indicate that satellite radiances are significantly affected by the presence of cirrus clouds if IR optical depths are ˜0.005 or greater. Using the International Satellite Cloud Climatology Project (ISCCP) detection threshold for cirrus clouds on the GOES data presented here, a high bias of up to 40% was found in the GOES precipitable water retrieval.

Whiteman, D. N.; Evans, K. D.; Demoz, B.; Starr, D. O'c.; Eloranta, E. W.; Tobin, D.; Feltz, W.; Jedlovec, G. J.; Gutman, S. I.; Schwemmer, G. K.; Cadirola, M.; Melfi, S. H.; Schmidlin, F. J.

2001-03-01

157

Effects of Cloud on Goddard Lidar Observatory for Wind (GLOW) Performance and Analysis of Associated Errors  

NASA Astrophysics Data System (ADS)

The Goddard Lidar Observatory for Wind (GLOW), a mobile direct detection Doppler LIDAR based on molecular backscattering for measurement of wind in the troposphere and lower stratosphere region of atmosphere is operated and its errors characterized. It was operated at Howard University Beltsville Center for Climate Observation System (BCCOS) side by side with other operating instruments: the NASA/Langely Research Center Validation Lidar (VALIDAR), Leosphere WLS70, and other standard wind sensing instruments. The performance of Goddard Lidar Observatory for Wind (GLOW) is presented for various optical thicknesses of cloud conditions. It was also compared to VALIDAR under various conditions. These conditions include clear and cloudy sky regions. The performance degradation due to the presence of cirrus clouds is quantified by comparing the wind speed error to cloud thickness. The cloud thickness is quantified in terms of aerosol backscatter ratio (ASR) and cloud optical depth (COD). ASR and COD are determined from Howard University Raman Lidar (HURL) operating at the same station as GLOW. The wind speed error of GLOW was correlated with COD and aerosol backscatter ratio (ASR) which are determined from HURL data. The correlation related in a weak linear relationship. Finally, the wind speed measurements of GLOW were corrected using the quantitative relation from the correlation relations. Using ASR reduced the GLOW wind error from 19% to 8% in a thin cirrus cloud and from 58% to 28% in a relatively thick cloud. After correcting for cloud induced error, the remaining error is due to shot noise and atmospheric variability. Shot-noise error is the statistical random error of backscattered photons detected by photon multiplier tube (PMT) can only be minimized by averaging large number of data recorded. The atmospheric backscatter measured by GLOW along its line-of-sight direction is also used to analyze error due to atmospheric variability within the volume of measurement. GLOW scans in five different directions (vertical and at elevation angles of 45° in north, south, east, and west) to generate wind profiles. The non-uniformity of the atmosphere in all scanning directions is a factor contributing to the measurement error of GLOW. The atmospheric variability in the scanning region leads to difference in the intensity of backscattered signals for scanning directions. Taking the ratio of the north (east) to south (west) and comparing the statistical differences lead to a weak linear relation between atmospheric variability and line-of-sights wind speed differences. This relation was used to make correction which reduced by about 50%.

Bacha, Tulu

158

Laboratory simulations of lidar returns from clouds - Experimental and numerical results  

NASA Astrophysics Data System (ADS)

The experimental results of laboratory simulations of lidar returns from clouds are presented. Measurements were carried out on laboratory-scaled cloud models by using a picosecond laser and a streak-camera system. The turbid structures simulating clouds were suspensions of polystyrene spheres in water. The geometrical situation was similar to that of an actual lidar sounding a cloud 1000 m distant and with a thickness of 300 m. Measurements were repeated for different concentrations and different sizes of spheres. The results show how the effect of multiple scattering depends on the scattering coefficient and on the phase function of the diffusers. The depolarization introduced by multiple scattering was also investigated. The results were also compared with numerical results obtained by Monte Carlo simulations. Substantially good agreement between numerical and experimental results was found. The measurements showed the adequacy of modern electro-optical systems to study the features of multiple-scattering effects on lidar echoes from atmosphere or ocean by means of experiments on well-controlled laboratory-scaled models. This adequacy provides the possibility of studying the influence of different effects in the laboratory in well-controlled situations.

Zaccanti, Giovanni; Bruscaglioni, Piero; Gurioli, Massimo; Sansoni, Paola

1993-03-01

159

Study on the cloud layer height and properties in Hefei observed by lidar  

NASA Astrophysics Data System (ADS)

A co-axial transmission elastic-backscattered lidar aiming to detect the optical properties of the clouds is presented in this paper. The modular co-axial design can guarantee the consistency of the transmitting part and the receiving part. In practice a specific diaphragm is used to suppress the stray light of the primary mirror and background light to improve SNR of the backscattered signal in the daytime. So the near ground signal must be corrected with the appropriate overlap factor. A Licel transient recorder is used for data acquisition in analog and photon counting combined in one acquisition system. With the 15 MHz sampling rate, the spatial resolution of 10 m can be attained. The control over the transient recorder and the treatment of the data is performed on a PC. After getting the correctional backscattered signal, retrieving and analyzing the extinction coefficient profile, the cloud base, cloud peak and related optical parameters of the clouds can be confirmed. In order to testify the feasibility of our lidar, it was implemented with a Finland ceilometer Vaisala simultaneously in May in 2008 in Hefei. Results show the lidar system is stable and the data is reliable.

Chen, Zhenyi; Liu, Wenqing; Zhang, Yujun; He, Junfeng; Ruan, Jun; Li, Sheng; Cui, Yiben

2010-05-01

160

Microphysical characterization of microwave Radar reflectivity due to volcanic ash clouds  

Microsoft Academic Search

Ground-based microwave radar systems can have a valuable role in volcanic ash cloud monitoring as evidenced by available radar imagery. Their use for ash cloud detection and quantitative retrieval has been so far not fully investigated. In order to do this, a forward electromagnetic model is set up and examined taking into account various operating frequencies such as S-, C-,

Frank Silvio Marzano; Gianfranco Vulpiani; William I. Rose

2006-01-01

161

NEXRAD Weather Radar Observations of the 2006 Augustine Volcanic Eruption Clouds  

Microsoft Academic Search

The 2006 eruption of Augustine Volcano, Alaska provided an exceptional opportunity to detect and measure explosive volcanic events and to track drifting volcanic clouds using WRS-88D (NEXRAD) weather radar data. Radar data complemented the real-time seismic monitoring by providing rapid confirmation of ash generation and cloud height. The explosive phase of the eruption consisted of thirteen discrete Vulcanian explosions from

D. J. Schneider; C. Scott; J. Wood; T. Hall

2006-01-01

162

Versatile lidar for atmospheric studies, including plume dispersion, clouds, and stratospheric aerosol  

NASA Astrophysics Data System (ADS)

A transportable scanning lidar for studying clouds, plume dispersion, and stratospheric aerosol at any of three wavelengths is described. A ruby laser transmits linearly polarized light of 694.3 nm wavelength at a maximum 0.8/s pulse rate. The lidar can discriminate between parallel, orthogonal, or combined polarizations of backscatter in a multichannel receiver. A frequency-doubled Nd:YAG laser, emitting at 532.0 nm and at a maximum pulse rate of 10/s, normally performs mapping of plume structure. Range resolution, including response, is less than 7 m. The sample interval is typically 3 m for plume experiments and 15 m for stratospheric aerosol profiles. Beam divergence is less than 1.0 mrad, and the receiver's field of view is adjustable up to 6 mrad. The lidar's sensitivity can be altered over a wide dynamical range by selection of optical filters in the receiver and adjustments in the photomultiplier voltage.

Eberhard, W. L.; McNice, G. T.

1986-12-01

163

A Comparison of Simulated Cloud Radar Output from the Multiscale Modeling Framework Global Climate Model with CloudSat Cloud Radar Observations  

SciTech Connect

Over the last few years a new type of global climate model (GCM) has emerged in which a cloud-resolving model is embedded into each grid cell of a GCM. This new approach is frequently called a multiscale modeling framework (MMF) or superparameterization. In this article we present a comparison of MMF output with radar observations from the NASA CloudSat mission, which uses a near-nadir-pointing millimeter-wavelength radar to probe the vertical structure of clouds and precipitation. We account for radar detection limits by simulating the 94 GHz radar reflectivity that CloudSat would observe from the high-resolution cloud-resolving model output produced by the MMF. Overall, the MMF does a good job of reproducing the broad pattern of tropical convergence zones, subtropical belts, and midlatitude storm tracks, as well as their changes in position with the annual solar cycle. Nonetheless, the comparison also reveals a number of model shortfalls including (1) excessive hydrometeor coverage at all altitudes over many convectively active regions, (2) a lack of low-level hydrometeors over all subtropical oceanic basins, (3) excessive low-level hydrometeor coverage (principally precipitating hydrometeors) in the midlatitude storm tracks of both hemispheres during the summer season (in each hemisphere), and (4) a thin band of low-level hydrometeors in the Southern Hemisphere of the central (and at times eastern and western) Pacific in the MMF, which is not observed by CloudSat. This band resembles a second much weaker ITCZ but is restricted to low levels.

Marchand, Roger T.; Haynes, J. M.; Mace, Gerald G.; Ackerman, Thomas P.; Stephens, Graeme L.

2009-01-13

164

Off-beam lidar: an emerging technique in cloud remote sensing based on radiative green-function theory in the diffusion domain  

Microsoft Academic Search

Atmospheric lidars do not penetrate directly most boundary-layer clouds due to their large optical density. However, the lidar's photons are not absorbed but scattered out of the beam. Typically, about half are actually transmitted through the cloud and the other half escape the cloud by reflection in extended diffuse patterns that evolve in time. For all practical purposes, these are

A. B. Davisl; R. F. Cahalan; D. Spinehirne; M. J. McGill; S. Love

1999-01-01

165

Lidar investigation of tropical nocturnal boundary layer aerosols and cloud macrophysics  

NASA Astrophysics Data System (ADS)

Observational evidence of two-way association between nocturnal boundary layer aerosols and cloud macrophysical properties over a tropical urban site is reported in this paper. The study has been conducted during 2008–09 employing a high space–time resolution polarimetric micro-pulse lidar over a tropical urban station in India. Firstly, the study highlights the crucial role of boundary layer aerosols and background meteorology on the formation and structure of low-level stratiform clouds in the backdrop of different atmospheric stability conditions. Turbulent mixing induced by the wind shear at the station, which is associated with a complex terrain, is found to play a pivotal role in the formation and structural evolution of nocturnal boundary layer clouds. Secondly, it is shown that the trapping of energy in the form of outgoing terrestrial radiation by the overlying low-level clouds can enhance the aerosol mixing height associated with the nocturnal boundary layer. To substantiate this, the long-wave heating associated with cloud capping has been quantitatively estimated in an indirect way by employing an Advanced Research Weather Research and Forecasting (WRF-ARW) model developed by National Center for Atmospheric Research (NCAR), Colorado, USA, and supplementary data sets; and differentiated against other heating mechanisms. The present investigation as well establishes the potential of lidar remote-sensing technique in exploring some of the intriguing aspects of the cloud–environment relationship.

Manoj, M. G.; Devara, P. C. S.; Taraphdar, S.

2013-10-01

166

Retrieval of ice cloud microphysical parameters using the CloudSat millimeter-wave radar and temperature  

NASA Astrophysics Data System (ADS)

A new remote sensing retrieval of ice cloud microphysics has been developed for use with millimeter-wave radar from ground-, air-, or space-based sensors. Developed from an earlier retrieval that used measurements of radar reflectivity factor together with a priori information about the likely cloud targets, the new retrieval includes temperature information as well to assist in determining the correct region of state space, particularly for those size distribution parameters that are less constrained by the radar measurements. These algorithms have served as the ice cloud retrieval algorithms in Releases 3 and 4 of the CloudSat 2B-CWC-RO Standard Data Product. Several comparison studies have been performed on the previous and current retrieval algorithms: some involving tests of the algorithms on simulated radar data (based on actual cloud probe data or cloud resolving models) and others featuring statistical comparisons of the R04 2B-CWC-RO product (current algorithm) to ice cloud mass retrievals by other spaceborne, airborne, and ground-based instruments or alternative algorithms using the same CloudSat radar data. Comparisons involving simulated radar data based on a database of cloud probe data showed generally good performance, with ice water content (IWC) bias errors estimated to be less than 40%. Comparisons to ice water content and ice water path estimates by other instruments are mixed. When the comparison is restricted to different retrieval approaches using the same CloudSat radar measurements, CloudSat R04 results generally agree with alternative IWC retrievals for IWC < 1000 mg m-3 at altitudes below 12 km but differ at higher ice contents and altitudes, either exceeding other retrievals or falling within a spread of retrieval values. Validation and reconciliation of all these approaches will continue to be a topic for further research.

Austin, Richard T.; Heymsfield, Andrew J.; Stephens, Graeme L.

2009-04-01

167

Development of a Chaff Cloud RCS Measurement Radar at 94.5 GHz  

Microsoft Academic Search

The Radar Cross Section (RCS) signature of the chaff cloud in the millimeter wave band is useful in many research fields such\\u000a as radar countermeasure, target identification and discrimination, and so on. To obtain the RCS of the chaff cloud, practical\\u000a measurement is an effective method. This paper introduces the design and implementation of a bistatic radar which is used

Lin Zou; Xuegang Wang; Lu Qian

2010-01-01

168

A multisensor diagnostic satellite cloud property retrieval scheme  

Microsoft Academic Search

Active sensor data, in the form of lidar and radar cloud vertical boundaries, are used as a priori information to passive sensor satellite retrievals of cloud optical depth and effective particle radius. Correct placement of cloud in the vertical eliminates the need to approximate cloud height from multispectral passive techniques and is shown to improve uncertainties in nighttime retrievals of

S. D. Miller; G. L. Stephens; C. K. Drummond; A. K. Heidinger; P. T. Partain

2000-01-01

169

Validation of a radar doppler spectra simulator using measurements from the ARM cloud radars  

SciTech Connect

The use of forward models as an alternative approach to compare models with observations contains advantages and challenges. Radar Doppler spectra simulators are not new; their application in high- resolution models with bin microphysics schemes could help to compare model output with the Doppler spectra recorded from the vertically pointing cloud radars at the ARM Climate Research Facility sites. The input parameters to a Doppler spectra simulator are both microphysical (e.g., particle size, shape, phase, and number concentration) and dynamical (e.g., resolved wind components and sub-grid turbulent kinetic energy). Libraries for spherical and non-spherical particles are then used to compute the backscattering cross-section and fall velocities, while the turbulence is parameterized as a Gaussian function with a prescribed width. The Signal-to-Noise Ratio (SNR) is used to determine the amount of noise added throughout the spectrum, and the spectral smoothing due to spectral averages is included to reproduce the averaging realized by cloud radars on successive returns. Thus, realistic Doppler spectra are obtained, and several parameters that relate to the morphological characteristics of the synthetically generated spectra are computed. Here, the results are compared to the new ARM microARSCL data products in an attempt to validate the simulator. Drizzling data obtained at the SGP site by the MMCR and the AMF site at Azores using the WACR are used to ensure the liquid part and the turbulence representation part of the simulator are properly accounted in the forward model.

Remillard, J.; Luke, E.; Kollias, P.

2010-03-15

170

Determination of cloud effective particle size from the multiple-scattering effect on lidar integration-method temperature measurements  

NASA Astrophysics Data System (ADS)

A method is presented that permits the determination of the cloud effective particle size from Raman- or Rayleigh-integration temperature measurements that exploits the dependence of the multiple-scattering contributions to the lidar signals from heights above the cloud on the particle size of the cloud. Independent temperature information is needed for the determination of size. By use of Raman-integration temperatures, the technique is applied to cirrus measurements. The magnitude of the multiple-scattering effect and the above-cloud lidar signal strength limit the method's range of applicability to cirrus optical depths from 0.1 to 0.5. Our work implies that records of stratosphere temperature obtained with lidar may be affected by multiple scattering in clouds up to heights of 30 km and beyond.

Reichardt, Jens; Reichardt, Susanne

2006-04-01

171

Coordinated Imaging and Lidar measurements of Noctilucent Cloud Dynamics over Poker Flat, Alaska, August 2005.  

NASA Astrophysics Data System (ADS)

In conjunction with the 2005 Polar Aeronomy and Radio Science (PARS) Summer School coordinated observations of noctilucent clouds (NLC) were made from central Alaska during August 2005 using imaging and lidar instrumentation. The image measurements was made from a field site near Donnelly Dome (63° N, 145° W) to record NLC over the lidar facility located at Poker Flat Research Range (PFRR) approximately 160 km to the north. A combination of two low-light digital color video cameras and several digital SLR cameras were used to image the NLC field over PFRR using wide and narrow field optics. At the same time NLC observations were made using the NICT Rayleigh lidar to investigate their altitude, structure and backscatter strength. Strong NLC were imaged from Donnelly Dome on three consecutive nights (August 8-10). These events were extensive, filling the northern twilight sky and were observed for over 4 hours. In particular the display of August 9 was very bright and was observed to extend well to the south of PFRR. The lidar measurements on this night were the strongest NLC signal yet recorded at PFRR. In this talk we will present a comparison between the imaging and lidar data focusing on August 9 display which was highly dynamic and observed to split into two distinct layers separated by approximately 1 km after local midnight. The two data sets will be used to study the dynamics of this display.

Nielsen, K.; Taylor, M. J.; Jensen, P. F.; Collins, R. L.; Su, L.; Thurairajah, B.; McDonald, J. G.; Marlow, Z. J.

2005-12-01

172

Status of the ACRF Millimeter Wave Cloud Radars (MMCRs), the Path Forward for Future MMCR Upgrades, the Concept of 3D Volume Imaging Radar and the UAV Radar.  

National Technical Information Service (NTIS)

The United States (U.S.) Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) operates millimeter wavelength cloud radars (MMCRs) in several climatological regimes. The MMCRs, are the primary observing tool f...

K. B. Widener M. A. Mille P. Kollias R. T. Marchandr T. P. Ackerman

2005-01-01

173

Intercomparison of Ground-Based Radar and Satellite Cloud-Top Height Retrievals for Overcast Single-Layered Cloud Fields  

Microsoft Academic Search

The objective of this paper is to assess the accuracy of the Semi-Analytical CloUd Retrieval Algorithm (SACURA) that retrieves cloud-top heights (CTHs) using hyperspectral SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) onboard Environmental Satellite measurements for overcast single-layer cloud fields. Intercomparisons with ground-based 35-GHz millimeter wave cloud radar CTHs were performed for 14 dates during 2003-2007 at the U.S.

Alexander A. Kokhanovsky; Catherine M. Naud; Abhay Devasthale

2009-01-01

174

3D campus modeling using LiDAR point cloud data  

NASA Astrophysics Data System (ADS)

The importance of having a 3D urban city model is recognized in many applications, such as management offices of risk and disaster, the offices for city planning and developing and others. As an example of urban model, we reconstructed 3D KIT campus manually in this study, by utilizing airborne LiDAR point cloud data. The automatic extraction of building shapes was left in future work.

Kawata, Yoshiyuki; Yoshii, Satoshi; Funatsu, Yukihiro; Takemata, Kazuya

2012-10-01

175

Macrophysical properties of tropical cirrus clouds from the CALIPSO satellite and from ground-based micropulse and Raman lidars  

NASA Astrophysics Data System (ADS)

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 Infrared 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 cycle is significantly different from zero only below about 11 km; where it is of opposite sign (i.e., more clouds during the daytime). For cirrus geometrical thickness, the MPL and CALIPSO observations agree well and both data sets have significantly thinner clouds during the daytime than the RL. From the examination of hourly MPL and RL cirrus cloud thickness and through the application of 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 significant improvement the RL provides (compared to the MPL) in the ARM program's ability to observe tropical cirrus clouds and will help improve our understanding of these clouds. The RL also provides a valuable ground-based lidar data set for the evaluation of CALIPSO observations.

Thorsen, Tyler J.; Fu, Qiang; Comstock, Jennifer M.; Sivaraman, Chitra; Vaughan, Mark A.; Winker, David M.; Turner, David D.

2013-08-01

176

On the combined use of satellite multispectral and radar polarimetric measurements to infer cloud microphysics  

Microsoft Academic Search

Summary  The extensive availability of multispectral satellite observations and polarimetric ground radar measurements enhances the\\u000a remote sensing capabilities in studying structure and dynamics of cloud systems at all relevant scales. We present here a\\u000a combined approach to perform a detailed cloud vertical structure analysis, by means of MODIS VIS-NIR products and C-band polarimetric\\u000a radar data. Satellite products include estimates of cloud

M. Celano; F. Porcù; P. P. Alberoni; F. Prodi

2008-01-01

177

Smoke detection using a compact and eye-safe lidar  

Microsoft Academic Search

Cloud ceiling determination using laser radar (lidar) is a well known application of this remote sensing technique. It is no problem to measure large distances up to some kilometers, since the particles of interest (water droplets) reflect the laser radiation pretty well, even when using very tiny light sources (eye safety criterion). This detection of white scatterers (clouds) points of

Juergen Streicher; Christian Werner

1999-01-01

178

The Aerosol, Clouds and Ecosystem (ACE) Mission  

NASA Astrophysics Data System (ADS)

The Aerosol, Clouds and Ecosystem (ACE) Mission is a second tier Decadal Survey mission designed to characterize the role of aerosols in climate forcing, especially their impact on precipitation and cloud formation. ACE also includes ocean biosphere measurements (chlorophyll and dissolved organic materials) which are greatly improved by simultaneous measurements of aerosols. The nominal ACE payload includes lidar and polarimetric measurements of aerosols, radar measurements of clouds and multi-band spectrometer for the measurement of ocean ecosystems. The enhanced ACE paylosd includes ?-wave radiometer measurements of cloud ice and water outside the nadir path of the radar/lidar beams. This talk will cover ACE instrument,science options and science potential.

Schoeberl, M.; Remer, L.; Kahn, R.; Starr, D.; Hildebrand, P.; Colarco, P.; Diner, D.; Im, E.; Vanr, D.; Behrenfeld, M.; Stevens, G.; Maring, H.; Bontempi, P.; McClain, C.

2008-05-01

179

[The estimation of cirrus cloud particulate shape using combined simulation and a three-wavelength lidar measurement].  

PubMed

The global occurrence of cirrus clouds can reach as high as 30%, whose scattering properties are essential impact on the climatic model, radiative transfer, and remote sensing. Their scattering properties are determined by the ice crystal shape, size distribution, refractive index and so on. Retrieval of the backscattering color ratios of cirrus cloud using a 355, 532 and 1 064 nm three-wavelength lidar, combined with the simulation of the three backscattering color ratios of different ice crystal shape, the shape of the lidar-measured ice crystal can be estimated. The results indicate that the shape of cirrus cloud over Hefei city is mostly composed by aggregates. PMID:24059165

Tao, Zong-Ming; Liu, Dong; Wei, He-Li; Ma, Xiao-Min; Shi, Bo; Nie, Miao; Zhou, Jun; Wang, Ying-Jian

2013-07-01

180

Model interpretation of cloud observations by the LIDAR on the Phoenix Mars lander  

NASA Astrophysics Data System (ADS)

Phoenix LIDAR observations [Whiteway et al. 2009] of clouds and precipitation in the planetary boundary layer (PBL) on Mars have been interpreted by a microphysical model for Mars ice clouds in combination with a coupled PBL-Aeolian dust model [Davy et al. 2009, Daerden et al. 2010]. The model simulates nighttime clouds and fall streaks within the PBL that are similar in structure to the LIDAR observations. Sizes of precipitating crystals grow to sizes of 30-50 µm effective radius, comparable to ice crystals observed in precipitation from terrestrial cirrus clouds which are formed under similar meteorological conditions. The observed regular daily pattern of water ice cloud formation and precipitation in the PBL is indicative of a diurnal process in the local water cycle in which the combination of strong daytime vertical mixing and nighttime precipitation of large ice crystals acts to confine water to the PBL [Whiteway et al. 2009]. The simulations support this interpretation. This process may contribute to the seasonal variation of atmospheric humidity. References Daerden, F., J.A. Whiteway, R. Davy, C. Verhoeven, L. Komguem, C. Dickinson, P. A. Taylor, N. Larsen (2010), Simulating Observed Boundary Layer Clouds on Mars, Geophys. Res. Lett., in press Davy, R., P. A. Taylor, W. Weng, and P.-Y. Li (2009), A model of dust in the Martian lower atmosphere, J. Geophys. Res., 114, D04108, doi:10.1029/2008JD010481 Whiteway, J.A., L. Komguem, C. Dickinson, C. Cook, M. Illnicki, J. Seabrook, V. Popovici, T.J. Duck, R. Davy, P.A. Taylor, J. Pathak, D. Fisher, A.I. Carswell, M. Daly, V. Hipkin, L. Tamppari, N. Renno, J. Moores, M. Lemmon, F. Daerden, H. Smith (2009), Mars Water Ice Clouds and Precipitation, Science 325, 68

Daerden, Frank; Whiteway, J. A.; Davy, R.; Komguem, L.; Dickinson, C.; Taylor, P. A.

2010-05-01

181

Algorithms for computing Arctic ice thickness from space and airborne lidars and radars  

NASA Astrophysics Data System (ADS)

Air and space campaigns such as IceSAT, IceBridge, and CryoSAT have gathered data on either the elevation of the snow surface or ice surface to estimate ice thicknesses, using isostatic equilibrium, over the Arctic ice pack. A major uncertainty for airborne or spaceborne lidar elevations conversions has been lack of knowledge regarding the snow depth under the measured elevation. For spaceborne radar or the snow radar on IceBridge, the uncertainty lies in whether the radar return is truly from the snow-ice interface or instead is from some intermediate depth layer within the snow pack. We are attempting a different approach, based on direct measurements made during ice drilling campaigns conducted over several decades. From either gridded or ice line profile measurements, each data set composed of several hundred to around a thousand measurements was analyzed separately. It was found that, when averaged over lengths of several 10's to one hundred meters, that snow top elevation correlated with ice thickness with R2~ 0.80. However, individual data sets showed different linear coefficients. These coefficients have some universality, so that cutoff elevations could be chosen where different linear coefficients gave best fits to the data. These sets of equations were then applied to the data sets of elevation and a predicted ice thickness calculated was compared to the measured ice thickness. Optimum averaging distances were also determined. RMS error in predicted versus measured ice thicknesses will be presented. Similar analyses were conducted using ice freeboard as the predictor of ice thickness as a simulation of the accuracy of CryoSAT ice thicknesses. Both methods are compared to presently used algorithms which use isostasy with assumed constant densities and snow depths to compute estimated ice thickness.

Williams, S.; Ackley, S. F.; Xie, H.; Holt, B.

2011-12-01

182

Airborne CO(2) coherent lidar for measurements of atmospheric aerosol and cloud backscatter.  

PubMed

An airborne CO(2) coherent lidar has been developed and flown on over 30 flights of the NASA DC-8 research aircraft to obtain aerosol and cloud backscatter and extinction data at a wavelength near 9µm. Designed to operate in either zenith- or nadir-directed modes, the lidar can be used to measure vertical profiles of backscatter throughout the vertical extent of the troposphere and the lower stratosphere. Backscatter measurements in absolute units are obtained through a hard-target calibration methodology. The use of coherent detection results in high sensitivity and narrow field of view, the latter property greatly reducing multiple-scattering effects. Aerosol backscatter profile intercomparisons with other airborne and ground-based CO(2) lidars were conducted during instrument checkout flights over the NASA Ames Research Center before extended depolyment over the Pacific Ocean. Selected results from data taken during the flights over the Pacific Ocean are presented, emphasizing intercom arisons with backscatter profile data obtained at 1.06 µm with a NASA Goddard Space Flight Center Nd:YAG lidar on the same flights. PMID:20935971

Menzies, R T; Tratt, D M

1994-08-20

183

Corona-producing cirrus cloud properties derived from polarization lidar and photographic analyses.  

PubMed

Polarization lidar data are used to demonstrate that clouds composed of hexagonal ice crystals can generate multiple-ringed colored coronas. Although relatively uncommon in our mid-latitude cirrus sample (derived from Project FIRE extended time observations), the coronas are associated with unusual cloud conditions that appear to be effective in generating the displays. Invariably, the cirrus cloud tops are located at or slightly above elevated tropopauses (12.7-km MSL average height) at temperatures between -60 degrees and -70 degrees C. The cloud top region also generates relatively strong laser backscattering and unusually high 0.5-0.7 linear depolarization ratios. Color photograph analysis of corona ring angles indicates crystals with mean diameters of from 12 to 30 microm. The cirrus cloud types were mainly subvisual to thin (i.e., bluish-colored) cirrostratus, but also included fibrous cirrus. Estimated cloud optical thicknesses at the 0.694-microm laser wavelength ranged from 0.001 to 0.2, where the upper limit reflects the effects of multiple scattering and/or unfavorable changes in particle characteristics in deep cirrus clouds. PMID:20706407

Sassen, K

1991-08-20

184

Testing the Parameterizations of Cloud Base Mass-Flux for Shallow Cumulus Clouds using Cloud Radar Observations  

NASA Astrophysics Data System (ADS)

Shallow cumulus clouds have significant impact on the vertical distributions of heat and moisture and on surface energy fluxes over land through their effect on incoming shortwave radiation. The present resolutions of General Circulation Model (GCM) and Numerical weather prediction (NWP) models are not fine enough to simulate shallow clouds directly, leaving not much choice other than parameterizations evaluated using either Large Eddy Simulation (LES) and observations. The representation of these clouds in numerical models is an important and challenging issue in model development, because of its potential impacts on near-surface weather and long-term climate simulations. Recent studies through LES have shown that the mass flux is the important parameter for determining the characteristics of cumulus transports within cloud layer. Based on LES results and scaling arguments, substantial efforts have been made to parameterize the cloud base mass flux to improve the interactions between the subcloud and cloud layer. Despite these efforts, what factors control the mass flux and how the interaction between subcloud and cloud layers should be parameterized is not fully understood. From the observational perspective, studies have been done using aircraft and remote sensing platform to address the above issue; there have been insufficient observations to develop detailed composite studies under different conditions. The Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) in Southern Great Plains (SGP) offers unique long-term measurements from cloud radars (35 and 94 GHz) along with synergetic measurements to address the above problem of non-precipitating shallow cumulus clouds over the SGP region. Doppler velocities from the cloud radar are processed to remove the insect contamination using a fuzzy-logic approach before they are used for the mass-flux calculation. The present observations are used to validate the existing mass-flux relations used in parameterizations. The possible factors [such as, effect of wind shear, transition layer strength, lower tropospheric relative humidity, large-scale vertical velocity and stability (CAPE and CIN)] that affects the mass-flux in addition to the convective velocity (w*) are studied using sounding and ECMWF model dataset. Furthermore, the data are classified based on time of the day, and for various cloud fractions and composite profiles are calculated to define the differences for different regimes.

Chandra, A.; Kollias, P.; Albrecht, B. A.; Zhu, P.; Klein, S. A.; Zhang, Y.

2010-12-01

185

Structures of stratiform clouds as measured by a scanning 35.5GHz cloud radar  

NASA Astrophysics Data System (ADS)

Most cloud radars worldwide operate at vertical incidence delivering only height-time-cross-sections. Consequently the interpretation of time-dependent structures obtained by such instruments in terms of spatial characteristics assumes inherently that the structures move with a speed independent of time and space (ergodic hypothesis). However, this supposition may be a crude one since structures in clouds change continuously in space and time. To reveal such properties a cloud radar (MIRA36-S) - having a scanning capability - is applied to situations of stratiform clouds. MIRA36-S measures at 35.5 GHz (λ = 8.5 mm). It is a coherent and polarimetric cloud radar and has two symmetrical receivers for simultaneously receiving co- and cross-polarized signals. The cassegrain antenna can perform RHI- and PPI-Scans with azimuths ranging from 0-360 degrees and elevations ranging from 0-45 degrees relative to zenith. RHI-Scans are usually accomplished in direction of mean wind velocity. The wind direction is determined by applying an improved VAD-algorithm (Tabary et al., 2001) on a previous PPI-scan. The resolution of the raw data from RHI-scans is 1.23 ° in elevation and 30 m in range. Each profile is the average of four 256-points-FFTs (PRF=5 kHz). The raw data of these measurements are interpolated to Cartesian coordinates and smoothed with a Gaussian filter to reduce small scale fluctuations. Using the image-processing-algorithm of Canny (1986) edges of structures of reflectivity are detected. Measurements of the linear depolarisation ratio and the radial velocity are taken into account to improve the structure detection. The structures are then tracked on the basis of an adapted version of the tracking algorithm TREC (Rinehart and Garvey, 1978). The presentation comprises first results with regard to the detection of structures within stratiform clouds, the velocity and direction of their movement and their change in size and intensity. These investigations concentrate here on evaluations of (2D) RHI-data. Analyses of (3D) volume data are in preparation.

Grenzhäuser, J.; Handwerker, J.; Beheng, K. D.

2009-04-01

186

Multiple-scattering-based lidar retrieval: method and results of cloud probings  

NASA Astrophysics Data System (ADS)

Recent developments in the search for a practical method of exploiting the multiple-scattering contributions to lidar returns are consolidated in a robust retrieval algorithm. The theoretical basis is the small-angle diffusion approximation. This implies that the algorithm is limited to media of sufficient optical thickness to generate measurable multiple scattering and to geometries for which the receiver's footprint diameter is less than the scattering mean free path. The primary retrieval products are the range-resolved extinction coefficient and the effective particle diameter from which secondary products such as the particle volume mixing ratio and the extinction at other wavelengths can be calculated. We recall briefly earlier validation tests and present new data and analysis that demonstrate and quantify the solutions' accuracy. The results show that systematic lidar probings with the proposed multiple-scattering technique can provide valuable physical information on cloud formation and evolution. © Optical Society of America

Bissonnette, Luc R.; Roy, Gilles; Roy, Nathalie

2005-09-01

187

Characterization of sub-cloud vertical velocity distributions and precipitation-driven outflow dynamics using a ship-based, scanning Doppler lidar during VOCALS-Rex  

NASA Astrophysics Data System (ADS)

During the VOCALS Regional Experiment NOAA's High Resolution Doppler Lidar (HRDL) operated from the RV Ronald H. Brown and made continuous measurements of sub-cloud horizontal and vertical wind speed and aerosol backscatter signal strength. We will present averaged profiles of vertical velocity distributions and turbulence parameters, stratified by a range of conditions including diurnal variation, precipitation, and distance from shore. The results point to a strong diurnal dependence in the strength of turbulence with nighttime conditions exhibiting stronger subcloud variance. Skewness shows less diurnal sensitivity with a trend towards more negative skewness near cloud base. Combining HRDL’s scanning horizontal wind speed measurements with other ship based in-situ and remote sensing measurements, we investigate the dynamics of precipitation-driven outflows and their impact on surface thermodynamic and aerosol properties. Using a sample of over 150 airmass transitions over the course of the 5 week deployment, we observed that warmer outflow air is typically drier, has less aerosol scattering and tends to have higher ozone concentrations (indicating the transport of air from above the boundary layer top). Transitions to cooler air are generally moister, have more aerosol scattering and show no significant change in ozone concentration. We will present animations of combined lidar/radar/GOES imagery that were used to facilitate visualization and interpretation of the dynamics of the outflows.

Brewer, A.; Feingold, G.; Tucker, S. C.; Covert, D. S.; Hardesty, R.

2010-12-01

188

First observational results with the newly developed cloud profiling FM-CW radar at 95 GHz  

NASA Astrophysics Data System (ADS)

We developed a cloud profiling radar transmitting frequency-modulated continuous wave (FM-CW) at 95 GHz for ground-based observations. Millimeter wave at 95 GHz is used to realize high sensitivity to small cloud particles. An FM-CW type radar would realize similar sensitivity with much smaller output to a pulse type radar. Two 1m-diameter parabolic antennas separated by 1.4m each other are used for transmitting and receiving the wave. The direction of the antennas is fixed at the zenith. The radar is designed to observe clouds between 0.3 and 15 km in height with a resolution of 15 m. Using the facility, test observations and long term campaign observations have been done. Results of observations show that the system is sensitive and stable enough to observe various clouds.

Takano, Toshiaki; Suga, Yumiro; Akita, Kenichi; Kawamura, Youhei; Kumagai, Hiroshi; Takamura, Tamio; Nakanishi, Yuji; Nakajima, Teruyuki

2004-02-01

189

Global distribution of instantaneous daytime radiative effects of high thin clouds observed by the cloud profiling radar  

NASA Astrophysics Data System (ADS)

The instantaneous daytime geographical distribution and radiative effects of high thin clouds (optical thickness < 5) are investigated on the basis of the CloudSat Cloud Profiling Radar (CPR) radiative flux and cloud classification products. The regional features of the fraction and radiative effects of high thin clouds are associated with ITCZ, SPCZ and mid-latitude storm track regions. High thin clouds have positive net cloud-induced radiative effect (CRE) at the top of the atmosphere (TOA) and negative net CRE at the bottom of the atmosphere (BOA). The magnitudes of TOA and BOA CREs depend on cloud optical thickness, cloud fraction and geographical location. The magnitude of the net CRE of high thin clouds increases at both TOA and BOA as cloud optical thickness increases. Net CRE at both TOA and BOA contributes to a positive net CRE in-atmosphere and warms the atmosphere regardless of cloud fraction. The global annual mean of the net CRE multiplied by cloud fraction is 0.49 W/m2 at TOA, -0.54 W/m2 at BOA and 1.03 W/m2 in-atmosphere. The most radiatively effective cloud optical thickness of a high thin cloud is between 1-2 for the TOA and in-atmosphere CREs or 3-4 for the BOA CRE.

Lee, Yong-Keun; Greenwald, Thomas J.; Yang, Ping; Ackerman, Steve; Huang, Hung-Lung

2010-09-01

190

Cloud base height determination in rain, snow, and fog with a low-cost eye-safe lidar  

NASA Astrophysics Data System (ADS)

The main obstacles for a reliable cloud base height determination with a lidar system are hydrometeors and precipitation scattering the emitted laser light on its way into the atmosphere. In order to fulfill the requirements of airport and aviation safety, modern commercial ceilometers have to be designed in a way that especially takes care of this problem, and the fact that a great part of the light received by the lidar originates from multiple scattering. Results of measuring campaigns performed in Canada and Germany show that the new Hagenuk cloud height lidar LD-WH X 06 also gives reliable results in difficult weather situations. Additionally it offers features like easy servicability, high MTBF, extended maintensance intervals, and long lifetime of laser being of special interest for commercial applications. This presentation contains some examples of the measuring compaigns mentioned above along with a comparison of the cloud heights measured with two different ceilometers in Canada.

Muenkel, Christoph

1995-09-01

191

Fusion of airborne lidar point cloud and imagery captured from integrated sensor system  

NASA Astrophysics Data System (ADS)

By fusing with other sensory data, especially high resolution imagery, LiDAR can be a good source of information for DEM extraction and feature extraction because it provides integrated information of geometric (surface), spectral and spatial property. Nowadays airborne LiDAR system vendors such as Leica and Toposys and others are providing systems with integrated camera capturing 3D point cloud and high resolution images simultaneously, for example, Leica's ALS50II, ALS60, and Toposys' FALCON II. The full potential of an integrated system in surveying and mapping has to be explored yet. In this paper, taking example of Toposys' FALCON data, we discuss some issues of data fusion: (1) cross sensor data registration, including geometric error budget; (2) two methods of fused data generation - imagery fused with range image re-sampled from point cloud and point cloud with assigned image pixel attributes. (3) Occlusion problem and how to solve it. We also show the segmentation results by a combined segmentation algorithm carried out on the fused multiple layer data. The results demonstrate the advantages of data fusion due to rich information and cues of objects in the fused data.

Hu, Xiangyun; Ye, Lizhi; Li, Xiaokai; Zhu, Junfeng; Long, Huaping

2011-06-01

192

Identification of a debris cloud from the nuclear powered SNAPSHOT satellite with Haystack radar measurements  

Microsoft Academic Search

Data from the MIT Lincoln Laboratory MIT LL Long Range Imaging Radar known as the Haystack radar have been used in the past to examine families of objects from individual satellite breakups or families of orbiting objects that can be isolated in altitude and inclination This is possible because for some time after a breakup the debris cloud of particles

C. Stokley; E. Stansbery

2006-01-01

193

Identification of a debris cloud from the nuclear powered SNAPSHOT satellite with haystack radar measurements  

Microsoft Academic Search

Data from the Massachusetts Institute of Technology Lincoln Laboratory Long Range Imaging Radar (known as the Haystack radar) have been used in the past to examine families of objects from individual satellite breakups or families of orbiting objects that can be isolated in altitude and inclination. This is possible because, for some time after a breakup, the debris cloud of

C. L. Stokely; E. G. Stansbery

2008-01-01

194

Polarization lidar returns from aerosols and thin clouds: a framework for the analysis.  

PubMed

Relationships for the interpretation of polarization lidar observations of aerosols and thin clouds are presented. They allow for the separation of contributions to backscatter from solid and liquid phases by the use of either the classical backscatter and depolarization ratio parameters or the particulate cross-polarized backscatter cross sections. It is shown that different aerosol phases can be better separated by use of the latter coordinates. Emphasis is placed on the study of composition and phase properties of polar stratospheric aerosols. PMID:18286035

Gobbi, G P

1998-08-20

195

Simulation of Space-borne Radar Observation from High Resolution Cloud Model - for GPM Dual frequency Precipitation Radar -  

NASA Astrophysics Data System (ADS)

A comprehensive space-borne radar simulator has been developed to support active microwave sensor satellite missions. The two major objectives of this study are: 1) to develop a radar simulator optimized for the Dual-frequency Precipitation Radar (KuPR and KaPR) on the Global Precipitation Measurement Mission satellite (GPM-DPR) and 2) to generate the synthetic test datasets for DPR algorithm development. This simulator consists of two modules: a DPR scanning configuration module and a forward module that generates atmospheric and surface radar observations. To generate realistic DPR test data, the scanning configuration module specifies the technical characteristics of DPR sensor and emulates the scanning geometry of the DPR with a inner swath of about 120 km, which contains matched-beam data from both frequencies, and an outer swath from 120 to 245 km over which only Ku-band data will be acquired. The second module is a forward model used to compute radar observables (reflectivity, attenuation and polarimetric variables) from input model variables including temperature, pressure and water content (rain water, cloud water, cloud ice, snow, graupel and water vapor) over the radar resolution volume. Presently, the input data to the simulator come from the Goddard Cumulus Ensemble (GCE) and Weather Research and Forecast (WRF) models where a constant mass density is assumed for each species with a particle size distribution given by an exponential distribution with fixed intercept parameter (N0) and a slope parameter (?) determined from the equivalent water content. Although the model data do not presently contain mixed phase hydrometeors, the Yokoyama-Tanaka melting model is used along with the Bruggeman effective dielectric constant to replace rain and snow particles, where both are present, with mixed phase particles while preserving the snow/water fraction. For testing one of the DPR retrieval algorithms, the Surface Reference Technique (SRT), the simulator uses the normalized radar cross sections of the surface,?0, at each frequency and incidence angle to generate the radar return power from the surface. The simulated ?0 data are modeled as realizations from jointly Gaussian random variables with means, variances and correlations obtained from measurements of ?0 from the JPL APR2 (2nd generation Airborne Precipitation Radar) data, which operates at approximately the same frequencies as the DPR. We will discuss the general capabilities of the radar simulator, present some sample results and show how they can be used to assess the performance of the radar retrieval algorithms proposed for the Dual-Frequency GPM radar. In addition, we will report on updates to the simulator using inputs from cloud models with spectral bin microphysics.

Kim, H.; Meneghini, R.; Jones, J.; Liao, L.

2011-12-01

196

Lidar observations of sodium density depletions in the presence of polar mesospheric clouds  

NASA Astrophysics Data System (ADS)

Since 1997, sodium resonance lidar and Rayleigh lidar measurements have been conducted simultaneously at the Sondrestrom upper atmosphere research facility near Kangerlussuaq, Greenland (67.0°N, 309.1°E) for studying the arctic mesosphere. The summertime lidar observations during the typical polar mesospheric cloud (PMC) season from June through August are used to investigate changes in the mesospheric sodium layer related to the presence of PMCs. Our observations demonstrate, on average, a 20% reduction in sodium density below the sodium peak altitude when PMCs are detected by the Rayleigh lidar. Individual PMC events can produce appreciable depletions in the lower half of the sodium layer. We have observed nearly 50% reduction in sodium column abundance below 92 km in the presence of a PMC with moderate backscatter strength. The magnitude of the depletion is correlated with PMC backscatter strength. New modeling results that include the photolysis of sodium bicarbonate have suggested that the reduction in sodium density may be associated with adsorption of sodium atoms onto the surface of the ice particles. The observed sodium depletion is not as significant as the depletion in iron density observed from the South Pole during the austral PMC summer months. This difference in depletion may result from the fact that the sodium layer resides a few kilometers higher than the iron layer, and, therefore, is exposed to presumably smaller ice particles (with less surface area) and, thus, has a reduced uptake rate on ice. Our observations extend previously reported reductions in iron and potassium in the presence of PMCs to include sodium, and support the role of heterogeneous chemistry on ice particles as a new and important process for sodium chemistry near the mesopause.

Thayer, Jeffrey P.; Pan, Weilin

2006-01-01

197

Radiative effects of African dust and smoke observed from Clouds and the Earth's Radiant Energy System (CERES) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) data  

NASA Astrophysics Data System (ADS)

Cloud and aerosol effects have a significant impact on the atmospheric radiation budget in the tropical Atlantic because of the spatial and temporal extent of desert dust and smoke from biomass burning in the atmosphere. The influences of African dust and smoke aerosols on cloud radiative properties over the tropical Atlantic Ocean were analyzed for the month of July for 3 years (2006-2008) using colocated data collected by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Clouds and the Earth's Radiant Energy System (CERES) instruments on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and Aqua satellites. Aerosol layer height and type can be accurately determined using CALIOP data through directly measured parameters such as optical depth, volume depolarization ratio, attenuated backscatter, and color ratio. On average, clouds below 5 km had a daytime instantaneous shortwave (SW) radiative flux of 270.2 ± 16.9 W/m2 and thin cirrus clouds had a SW radiative flux of 208.0 ± 12.7 W/m2. When dust aerosols interacted with clouds below 5 km, as determined from CALIPSO, the SW radiative flux decreased to 205.4 ± 13.0 W/m2. Similarly, smoke aerosols decreased the SW radiative flux of low clouds to a value of 240.0 ± 16.6 W/m2. These decreases in SW radiative flux were likely attributed to the aerosol layer height and changes in cloud microphysics. CALIOP lidar observations, which more accurately identify aerosol layer height than passive instruments, appear essential for better understanding of cloud-aerosol interactions, a major uncertainty in predicting the climate system.

Yorks, John E.; McGill, Matt; Rodier, Sharon; Vaughan, Mark; Hu, Yongxiang; Hlavka, Dennis

2009-09-01

198

Lidar observations of subvisual cirrus clouds in the tropics and the midlatitudes  

NASA Astrophysics Data System (ADS)

Measurements performed with the Mobile Aerosol Raman Lidar MARL in Punta Arenas/Chile (53.12^oS, 70.88^oW), in Prestwick /Scotland (55.5^oN, 4.60^oW), and aboard the German research vessel Polarstern within the German PAZI project are reported. MARL is able to measure backscatter profiles at the wavelengths of 532~nm and 355~nm with a vertical resolution of 7.5~m and a time resolution of 140~s. Additionally, the depolarization is detected at both wavelengths. With the help of a newly developed algorithm the detection of clouds by the lidar is very sensitive and enables us to observe thin layers with an estimated optical depth down to 10-4 by making use of the backscatter and the depolarization caused by the ice particles. During the northern and the southern hemispheric campaigns which were part of the European INCA project, about 60 hours of lidar measurements were gathered, respectively. At both sites, subvisual cirrus with an optical depth (OD)<0.03 were present in about 30% of the obtained data. An analysis of the depolarization and the color index suggests differences in the microphysical properties of the cloud particles. The measurements in the tropics aboard Polarstern revealed the frequent occurrence of tropical subvisual cirrus (TSC) in the equatorial Atlantic region. The TSCs differed significantly from their midlatitude counterparts with respect to their horizontal extent and their lifetime as well as in their optical and microphysical properties. Simultaneous radiosonde soundings performed aboard Polarstern allowed the determination of the temperature and other meteorological parameters of the tropical tropopause layer.

Immler, F.; Schrems, O.

2003-04-01

199

Climatological characteristics of cloud distribution and planetary boundary layer structure in Jakarta, Indonesia revealed by lidar observation  

NASA Astrophysics Data System (ADS)

For two years we observed the vertical distribution of clouds and aerosols in Jakarta, Indonesia, with ground-based Mie scattering lidars. A histogram of the cloud base height shows a notable maximum at an altitude of approximately 5 km, especially in the wet season. The planetary boundary layer height we inferred from the upper boundary of the aerosol layer was approximately 1.5-2 km in the wet season and 2-3 km in the dry season.

Sugimoto, Nobuo; Matsui, Ichiro; Shimizu, Atsushi; Pinandito, Mego; Sugondo, Santoso

200

Impact of Gravity Wave events on the properties of Polar Stratospheric Clouds over Antarctica from spaceborne lidar observations  

Microsoft Academic Search

The formation and properties of Polar Stratospheric Clouds (PSCs) are extremely dependent on their formation temperature. Depending on the stratospheric concentrations of chemical species, various temperature thresholds define PSC composition: Nitric Acid Trihydrate (NAT) or Sulfuric Ternary Solutions (STS) particles, ice crystals, or a mixture thereof. Most notably, ice-based PSCs (Type II in lidar observation terminology) require colder temperatures than

V. Noel; H. Chepfer; A. Hertzog

2010-01-01

201

Space Shuttle Impacts on Mesospheric Clouds and Iron Layers as Observed by Lidars and Satellites in the Antarctic and Arctic  

Microsoft Academic Search

Meteoric iron layers and mesospheric clouds are two layered phenomena that have been used as tracers to study the global thermal and dynamic structures in the mesosphere and lower thermosphere. In January 2003, three days after the Columbia Space Shuttle was launched from the Kennedy Space Center, an iron (Fe) Boltzmann lidar detected strong sporadic Fe layers in the altitude

X. Chu; R. L. Collins; M. H. Stevens; J. M. Plane; R. R. Meier; M. T. Deland; M. C. Kelley; M. J. Nicolls; B. Thurairajah; R. H. Varney; K. Mizutani; Z. Yu

2009-01-01

202

Breakthrough in multichannel laser-radar technology providing thousands of high-sensitive lidar receivers on a chip  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to describe a new proved multi-channel laser-radar technology which enables several thousands of high-sensitive laser-radar or lidar receivers to be integrated on a fingernail-sized CMOS-chip for fast 3D-perception and, furthermore, to explain the huge number of resulting applications and to estimate the desirable scientific, economic and society impacts. These extraordinary capabilities rely on the revolutionary improvements introduced by a smart inherently-mixing photodiode with two controllable photo-current outputs [1]. We call it PMD (Photonic Mixer Device) because the opto-electronic mixing process is accomplished directly in the photonic state, followed by an integration process to get OE-correlation and the delay of the optical echo and the modulation signal. The PMD-principle provides an unbelievable simplification, size-reduction and improvement in Multi-Channel Light Detecting and Ranging as a MC-PMD-Lidar or 3D-PMD-camera without scanner. Thanks to the competence and merit of the PMDTechnologies GmbH in cooperation with the INV of the University of Siegen finally brought the PMD in big steps to reliability and to large pixel numbers and to products with today about 20.000 lidar receivers in a 120x160 PMD-matrix, which exhibits homogenous and exquisite specifications like very constant mean value and low standard deviation compared with conventional radar receivers. This innovation may be seen as a breakthrough in the history of camera development. The "3D-camera" of today comprises more 3D-pixels in a PMD-array than, about 1970, the first CCD-cameras contained 2D-pixel in a CCD-array. Both are of similar size aside from the modulated sender with integrated LED's or laser diodes required for a homogenous illumination of the field-of-view.

Schwarte, Rudolf M.

2004-11-01

203

Influence of gravity waves and tides on mesospheric temperature inversion layers: simultaneous Rayleigh lidar and MF radar observations  

NASA Astrophysics Data System (ADS)

Three nights of simultaneous Rayleigh lidar temperature measurements over Gadanki (13.5° N, 79.2° E) and medium frequency (MF) radar wind measurements over Tirunelveli (8.7° N, 77.8° E) have been analyzed to illustrate the possible effects due to tidal-gravity wave interactions on upper mesospheric inversion layers. The occurrence of tidal gravity wave interaction is investigated using MF radar wind measurements in the altitude region 86 90 km. Of the three nights, it is found that tidal gravity wave interaction occurred in two nights. In the third night, diurnal tidal amplitude is found to be significantly larger. As suggested in Sica et al. (2007), mesospheric temperature inversion seems to be a signature of wave saturation in the mesosphere, since the temperature inversion occurs at heights, when the lapse rate is less than half the dry adiabatic lapse rate.

Sridharan, S.; Sathishkumar, S.; Gurubaran, S.

2008-11-01

204

Development of a cloud profiling FM-CW radar at 95 GHz and its preliminary results  

NASA Astrophysics Data System (ADS)

A cloud profiling radar transmitting frequency-modulated continuous wave (FM-CW) at 95 GHz is developed for ground-based observations. Millimeter wave at 95 GHz is used to realize high sensitivity to small cloud particles. Two 1m-diameter parabolic antennas separated by 1.4m each other are used for transmitting and receiving the wave. The direction of the antennas is fixed at the zenith. The radar is designed to observe clouds between 0.3 and 15 km in height with a resolution of 15 m. The system was integrated and sensitivities and stabilities have been measured. Results of test measurements of clouds show that the system is sensitive and stable enough to observe various clouds.

Takano, Toshiaki; Suga, Yumiro; Takei, Kentaro; Kawamura, Youhei; Sakai, Kurt; Kumagai, Hiroshi; Takamura, Tamio; Nakanishi, Yuji; Nakajima, Teruyuki

2003-04-01

205

Doppler Radar Measurements of In-cloud Saturation Ratio and Implications for Drizzle Parameterization  

NASA Astrophysics Data System (ADS)

In-cloud water vapor saturation ratio controls the activation of aerosol particles into cloud droplets and turbulence-driven fluctuations in this quantity contribute to broadening of the cloud droplet spectrum and to the microphysical processes responsible for drizzle formation. The goal of the present study is to derive key microphysical properties related to cloud dynamics, supersaturation, and drizzle formation using ARM radar data sets from the AMF1. Emphasis is on using measured vertical velocity spectra to derive turbulence-induced fluctuations in saturation ratio in order to replace an empirical turbulence parameter, used in the kinetic potential model of drizzle parameterization, with one based on measurement. In the kinetic potential model, turbulence fluctuations generate Brownian-like diffusion along the coordinate of cloud droplet size. These tend to counter the tendency to mono-dispersity that usually results from diffusion-controlled growth and leads to significantly broader cloud droplet size distributions. We show that this diffusion parameter can be estimated remotely through radar-based determination of the variance of vertical velocity fluctuations and eddy breakup time. Data sets used in the present study are from the W-band (95GHz) ARM Cloud Radar, operating in the Azores from 5/2009 to 12/2010 as part of a study of marine stratus clouds.

McGraw, R. L.; Luke, E. P.; Kollias, P.

2011-12-01

206

On the linkage between tropospheric and Polar Stratospheric clouds in the Arctic as observed by space-borne lidar  

NASA Astrophysics Data System (ADS)

The type of Polar stratospheric clouds (PSCs) as well as their temporal and spatial extent are important for the occurrence of heterogeneous reactions in the polar stratosphere. The formation of PSCs depends strongly on temperature. However, the mechanisms of the formation of solid PSCs are still poorly understood. Recent satellite studies of Antarctic PSCs have shown that their formation can be associated with deep-tropospheric clouds which have the ability to cool the lower stratosphere radiatively and/or adiabatically. In the present study, lidar measurements aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite were used to investigate whether the formation of Arctic PSCs can be associated with deep-tropospheric clouds as well. Deep-tropospheric cloud systems have a vertical extent of more than 6.5 km with a cloud top height above 7 km altitude. PSCs observed by CALIPSO during the Arctic winter 2007/2008 were classified according to their type (STS, NAT, or ice) and to the kind of underlying tropospheric clouds. Our analysis reveals that 172 out of 211 observed PSCs occurred in connection with tropospheric clouds. 72% of these 172 observed PSCs occurred above deep-tropospheric clouds. We also find that the type of PSC seems to be connected to the characteristics of the underlying tropospheric cloud system. During the Arctic winter 2007/2008 PSCs consisting of ice were mainly observed in connection with deep-tropospheric cloud systems while no ice PSC was detected above cirrus. Furthermore, we find no correlation between the occurrence of PSCs and the top temperature of tropospheric clouds. Thus, our findings suggest that Arctic PSC formation is connected to adiabatice cooling, i.e. dynamic effects rather than radiative cooling.

Achtert, P.; Karlsson Andersson, M.; Khosrawi, F.; Gumbel, J.

2012-04-01

207

Characterization of Polar Stratospheric Clouds with spaceborne lidar: CALIPSO and the 2006 Antarctic season  

NASA Astrophysics Data System (ADS)

The role of polar stratospheric clouds in polar ozone loss has been well documented. The CALIPSO satellite mission offers a new opportunity to characterize PSCs on spatial and temporal scales previously impossible. A PSC detection algorithm based on a single wavelength threshold approach has been developed for CALIPSO. The method appears to accurately detect PSCs of all opacities, including tenuous clouds, with a very low rate of false positives and few missed clouds. We applied the algorithm to CALIOP data acquired during the 2006 Antarctic winter season from 13 June through 31 October. The spatial and temporal distribution of CALIPSO PSC observations is illustrated with weekly maps of PSC occurrence. The evolution of the 2006 PSC season is depicted by time series of daily PSC frequency as a function of altitude. Comparisons with "virtual" solar occultation data indicate that CALIPSO provides a different view of the PSC season than attained with previous solar occultation satellites. Measurement-based time series of PSC areal coverage and vertically-integrated PSC volume are computed from the CALIOP data. The observed area covered with PSCs is significantly smaller than would be inferred from the commonly used temperature-based proxy TNAT but is similar in magnitude to that inferred from TSTS. The potential of CALIOP measurements for investigating PSC composition is illustrated using combinations of lidar backscatter and volume depolarization for two CALIPSO PSC scenes.

Pitts, M. C.; Thomason, L. W.; Poole, L. R.; Winker, D. M.

2007-10-01

208

Characterization of Polar Stratospheric Clouds with Space-Borne Lidar: CALIPSO and the 2006 Antarctic Season  

NASA Astrophysics Data System (ADS)

The role of polar stratospheric clouds in polar ozone loss has been well documented. The CALIPSO satellite mission offers a new opportunity to characterize PSCs on spatial and temporal scales previously impossible. A PSC detection algorithm based on a single wavelength threshold approach has been developed for CALIPSO. The method appears to accurately detect PSCs of all opacities, including tenuous clouds, with a very low rate of false positives and few missed clouds. We applied the algorithm to CALIOP data acquired during the 2006 Antarctic winter season from 13 June through 31 October. The spatial and temporal distribution of CALIPSO PSC observations is illustrated with weekly maps of PSC occurrence. The evolution of the 2006 PSC season is depicted by time series of daily PSC frequency as a function of altitude. Comparisons with "virtual" solar occultation data indicate that CALIPSO provides a different view of the PSC season than attained with previous solar occultation satellites. Measurement-based time series of PSC areal coverage and vertically-integrated PSC volume are computed from the CALIOP data. The observed area covered with PSCs is significantly smaller than would be inferred from the commonly used temperature-based proxy TNAT but is similar in magnitude to that inferred from TSTS . The potential of CALIOP measurements for investigating PSC composition is illustrated using combinations of lidar backscatter and volume depolarization for two CALIPSO PSC scenes.

Pitts, M. C.; Thomason, L. W.; Poole, L. R.; Winker, D. M.

2007-06-01

209

Lidar observations of the El Chichon cloud in the stratosphere over Fukuoka  

NASA Astrophysics Data System (ADS)

A volcanic cloud in the stratosphere, originating from the March to April 1982 eruptions of El Chichon, has been observed for about 2.5 years at Fukuoka (33.5 degrees N, 130.4 degrees E) with two wavelengths of Nd-YAG lidar, 1.06 and 0.53 microns. Time and height variabilities of the cloud are described, using the 1.06 microns data, and some results of the two-wavelength measurements are presented. A sudden enormous increase in the total aerosol backscattering from the stratosphere (backscattering coefficient for 1.06 microns integrated over 13.5 to 28.5 km range) was followed by a decrease from late spring to summer with large fluctuations. The cloud initially appeared stratified into two layers: the upper one with fine structure and sharp edges in the easterly wind region and the lower dumpy one in the westerly wind region. Most of the aerosols were contained in the upper layer. The two layers merged into a broad, single-peaked layer as the easterly prevailed in the whole region in fall, when the total aerosol backscattering began to increase. The layer then decreased its peak height as it broadened. The difference in shape of both layers and the increase of total backscattering from fall can be interpreted by the difference in velocity of material transport in the easterly and the westerly wind region.

Fujiwara, M.; Shibata, T.; Hirono, M.

1985-12-01

210

Noctilucent cloud observations at mid-latitudes by lidar: mean state and relation to MSE and temperature during day and night  

NASA Astrophysics Data System (ADS)

Since more than 120 years Noctilucent clouds (NLC) are observed every summer poleward of about 50° latitude. Even if NLC are much more frequent at polar latitudes, NLC observations at mid-latitudes are of particular importance since the average temperature is near the saturation temperature. Hence, NLC occurrence is expected to change strongly with only minor variations in water vapour concentration and temperature, e.g. due to planetary, tidal and gravity waves, and solar cycle. At Leibniz Institute of Atmospheric Physics at Kühlungsborn, Germany (54° N, ° 12 E) NLC are observed since 1997 at 532 nm wavelength. Until 2008 the NLC occurrence rate was up to 12%, while 2009 showed record-high 19%. The altitude distribution centres at 82.9 km, i.e. similar to the polar NLC distribution even if the temperature structures are quite different at these heights. We will compare these mean NLC parameters from nighttime observations with data from the 2009 season, showing comparatively frequent and strong NLC. We will discuss the relation to simultaneously observed temperatures and wave activity for 2009 and previous years. We have set up a daylight capable lidar in summer 2009, measuring NLC independent of solar elevation. By this the retrieval of diurnal variation of NLC occurrence and strength will be possible at our mid-latitude site as one of very few stations in the world. Simultaneous observations of NLC and Mesospheric Summer Echoes (MSE) are limited to daytime since electron densities have to be sufficiently high. The new capabilities of the RMR lidar at Kühlungsborn together with the OSWIN VHF radar and the K lidar allow first case studies from simultaneous NLC and MSE observations at mid-latitudes.

Gerding, Michael; Höffner, Josef; Kopp, Maren; Zecha, Marius; Lübken, Franz-Josef

211

Real-Time C-Band Radar Observations of 1992 Eruption Clouds from Crater Peak, Mount Spurr Volcano, Alaska  

Microsoft Academic Search

Repeated aircraft hazards in Alaska related to volcanic clouds have resulted in the use of a mobile C-band radar devoted to volcanic-cloud monitoring. The radar is located at Kenai, in range of several vol- canoes in the Cook Inlet area. Three significant erup- tions from the Crater Peak vent of Mount Spurr vol- cano (about 80 km from Kenai) in

William I. Rose; Alexander B. Kostinski; Lee Kelley

1992-01-01

212

Towards Realtime Assimilation of Doppler Radar Observations for Cloud-Resolving Hurricane Prediction  

Microsoft Academic Search

This study explores the feasibility and impacts of on-demand, real-time assimilation of Doppler radar observations straight from the planes with an ensemble Kalman filter (EnKF) to initialize a cloud-resolving hurricane prediction model. The NOAA P3 aircrafts have being flying into tropical cyclones to gather radar observations since 1994. These observations are significant in investigating and anglicizing hurricane's intensity, eye-wall structure

Y. Weng; F. Zhang; J. F. Gamache; F. D. Marks

2008-01-01

213

Tracking nucleation, growth, and sublimation in cirrus clouds using ARM millimeter-wavelength radar observations  

Microsoft Academic Search

On the basis of a case study we outline a stochastic approach to investigate the internal structure of radiative properties of cirrus clouds and place it into the context of the state of the large-scale atmosphere. We analyze radar reflectivity eta(t) measurements obtained with the ground-based millimeter-wavelength radar of the Atmospheric Radiation Measurements (ARM) Program of the Department of Energy

K. Ivanova; T. P. Ackerman

2009-01-01

214

Tracking nucleation, growth, and sublimation in cirrus clouds using ARM millimeter-wavelength radar observations  

Microsoft Academic Search

On the basis of a case study we outline a stochastic approach to investigate the internal structure of radiative properties of cirrus clouds and place it into the context of the state of the large-scale atmosphere. We analyze radar reflectivity ?(t) measurements obtained with the ground-based millimeter-wavelength radar of the Atmospheric Radiation Measurements (ARM) Program of the Department of Energy

K. Ivanova; T. P. Ackerman

2009-01-01

215

Conceptual design of a spaceborne radar for rain and cloud sensing  

Microsoft Academic Search

A conceptual design for a mid-latitude orbiting precipitation and cloud mapping radar is discussed. In this conceptual design the radar utilizes a narrow, dual-frequency beam, electronically scanned antenna to achieve 4-km spatial resolution and 300-km cross-track swath. Vertical resolution of 500 m is achieved by short-pulse transmission. It is expected that such system can measure rain rates up to 100

Eastwood Im

1992-01-01

216

Evaporation of Rain Falling from Convective Clouds as Derived from Radar Measurements  

Microsoft Academic Search

The rainshafts of about 3000 summer afternoon convective rain cells in the semiarid region of central south Africa were tracked and measured with a volume scanning radar. The area and time integrated rain volume of each individual rain cell was obtained at the cloud base level and at a lower level, assuming a fixed radar reflectivity-rain intensity (Z-R) relationship.The ratio

Daniel Rosenfeld; Yale Mintz

1988-01-01

217

Precipitating clouds observed by 1.3-GHz boundary layer radars in equatorial Indonesia  

NASA Astrophysics Data System (ADS)

Temporal variations of precipitating clouds in equatorial Indonesia have been studied based on observations with 1357.5 MHz boundary layer radars at Serpong (6.4° S, 106.7° E) near Jakarta and Bukittinggi (0.2° S, 100.3° E) in West Sumatera. We have classified precipitating clouds into four types: stratiform, mixed stratiform-convective, deep convective, and shallow convective clouds, using the Williams et al. (1995) method. Diurnal variations of the occurrence of precipitating clouds at Serpong and Bukittinggi have showed the same characteristics, namely, that the precipitating clouds primarily occur in the afternoon and the peak of the stratiform cloud comes after the peak of the deep convective cloud. The time delay between the peaks of stratiform and deep convective clouds corresponds to the life cycle of the mesoscale convective system. The precipitating clouds which occur in the early morning at Serpong are dominated by stratiform cloud. Concerning seasonal variations of the precipitating clouds, we have found that the occurrence of the stratiform cloud is most frequent in the rainy season, while the occurrence of the deep convective cloud is predominant in the dry season.

Renggono, F.; Hashiguchi, H.; Fukao, S.; Yamanaka, M. D.; Ogino, S.-Y.; Okamoto, N.; Murata, F.; Sitorus, B. P.; Kudsy, M.; Kartasasmita, M.; Ibrahim, G.

2001-08-01

218

Simple eye-safe lidar for cloud height measurement and small forest fire detection  

NASA Astrophysics Data System (ADS)

A simple and robust eye-safe lidar was developed on the basis of a rangefinder optical scheme comprising an Er:glass laser which generates 8 mJ pulses of 1540-nm radiation with the pulse repetition rate of 0.17 Hz and a 38-mm-diameter telescope. Reliable measurements of the cloud height up to 3700 m and early forest-fire detection with a range of 3000 m were experimentally demonstrated. Theoretical estimations indicate that using an optical scheme built around a 10 Hz Er:glass lasers and 150 mm light gathering optics early forest fire detection in a range up to 6500 m can be achieved.

Lavrov, A.; Utkin, A. B.; Vilar, R.

2010-07-01

219

Coordinated Daytime LIDAR and 430 MHZ Radar Observations of Lower Stratospheric and Mesospheric Wave Phenomena at Arecibo  

NASA Astrophysics Data System (ADS)

We present the first-ever results procured with the Daytime Doppler Rayleigh lidar system at the Arecibo Observatory, Puerto Rico. The lidar system at Arecibo has been functional since 1990 but was restricted only to nighttime operation since the strong signal from the solar continuum, present during the day, overwhelmed the backscattered Rayleigh signal. One ambition of this study was to devise an instrument capable of rejecting this background signal, thereby facilitating data acquisition during the day. We achieved operational success by incorporating two pressure-scanned Fabry-Perot interferometers in tandem, preceded with a narrow bandwidth DayStar filter in the receiver signal path. Having accomplished this goal, the newly reconfigured system was utilized to obtain Doppler winds from the tropopausal and lower stratospheric regions. Analysis of the acquired data revealed the presence of orderly undulations superimposed on the wind profiles. Previous radar observations of these regions confirm the existence of these oscillations and have recently been postulated to be atmospheric gravity waves induced orographically by airflow over Puerto Rico. Coordinated observations of winds in the mesosphere and lower thermosphere were conducted using the powerful 430 MHz incoherent scatter radar at Arecibo to perceive atmospheric tidal oscillations. Besides purely academic, interest in investigating these small-scale vertical perturbations stems from their ability to affect the trajectories of missiles and spacecrafts.

Dighe, Kalpak Arvind

220

First observations of noctilucent clouds by lidar at Svalbard, 78°N  

NASA Astrophysics Data System (ADS)

In summer 2001 a potassium lidar was installed near Longyearbyen (78° N) on the north polar island of Spitsbergen which is part of the archipelago Svalbard. At the same place a series of meteorological rockets ("falling spheres", FS) were launched which gave temperatures from the lower thermosphere to the stratosphere. The potassium lidar is capable of detecting noctilucent clouds (NLCs) and of measuring temperatures in the lower thermosphere, both under daylight conditions. In this paper we give an overview on the NLC measurements (the first at this latitude) and compare the results with temperatures from meteorological rockets which have been published recently (Lübken and Mülleman, 2003) NLCs were observed from 12 June (the first day of operation) until 12 August when a period of bad weather started. When the lidar was switched on again on 26 August, no NLC was observed. The mean occurrence frequency in the period 12 June -- 12 August ("lidar NLC period") is 77%. The mean of all individual NLC peak altitudes is 83.6 km (variability: 1.1 km). The mean peak NLC altitude does not show a significant variation with season. The average top and bottom altitude of the NLC layer is 85.1 and 82.5 km, respectively, with a variability of ~1.2 km. The mean of the maximum volume backscatter coefficient bmax at our wavelength of 770 nm is 3.9 x 10-10/m/sr with a large variability of ±3.8 x 10-10/m/sr. Comparison of NLC characteristics with measurements at ALOMAR (69° N) shows that the peak altitude and the maximum volume backscatter coefficient are similar at both locations but NLCs occur more frequently at higher latitudes. Simultaneous temperature and NLC measurements are available for 3 flights and show that the NLC layer occurs in the lower part of the height range with super-saturation. The NLC peak occurs over a large range of degree of saturation (S) whereas most models predict the peak at S = 1. This demonstrates that steady-state considerations may not be applicable when relating individual NLC properties to background conditions. On the other hand, the mean variation of the NLC appearance with height and season is in agreement with the climatological variation of super-saturation derived from the FS temperature measurements.

Höffner, J.; Fricke-Begemann, C.; Lübken, F.-J.

2003-08-01

221

Global distribution of cirrus clouds from CloudSat\\/Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) measurements  

Microsoft Academic Search

The cirrus clouds of the upper troposphere are globally widespread and are important regulators of the radiative balance, and hence climate, of the Earth-atmosphere system. Despite their wide distribution, however, cirrus are difficult to study from satellite radiance measurements or from scattered ground observing sites because they can occur as part of multilayered cloud systems and are characteristically optically thin.

Kenneth Sassen; Zhien Wang; Dong Liu

2008-01-01

222

Turbulence induced fluctuations in cloud saturation ratio: Doppler radar measurements and implications for drizzle formation  

NASA Astrophysics Data System (ADS)

This paper presents a statistical examination of in-cloud updraft and downdraft velocities using Doppler cloud radar and radiosonde measurements collected by the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) climate research facility. The measurements, including moments and other statistical properties derived from them are used in conjunction with adiabatic parcel and entrainment models to derive the properties of turbulence-induced fluctuations in saturation ratio and cloud droplet size. An especially important parameter for models of cloud droplet evolution and dispersion and also for predicting conditions at the drizzle threshold is the ratio of saturation ratio fluctuation variance to correlation time [McGraw and Liu, GRL, 33, L03802 (2006)]. The goal of the present analysis is to develop methods to estimate this key turbulence parameter needed in the kinetic potential theory of drizzle formation from remote sensing methods and in particular from the Doppler radar measurements.

McGraw, R. L.; Luke, E. P.; Kollias, P.

2010-12-01

223

The evolution of radar echo in a seeded cloud  

Microsoft Academic Search

A convective cloud extending above a stratocumulus deck was seeded with droppable AgI flares at about the — 7°C level. Ten minutes after seeding, an echo was observed front the cloud at about the seeding level and downwind from the seeding location. The echo was very elongated and oriented parallel to the seeding track. Since the cloud was located only

Marianne English; John D. Marwitz

1982-01-01

224

Dynamical and Microphysical Retrievals from Doppler Radar Observations of a Deep Convective Cloud  

Microsoft Academic Search

A four-dimensional variational data assimilation system consisting of a three-dimensional time-dependent cloud model with both liquid and ice phase microphysics parameterization was used to assimilate radar data into a cloud model. Data of a severe thunderstorm observed during the Cooperative Huntsville Meteorological Experiment project were assimilated and results compared to a conventional analysis. The analysis system was able to retrieve

Bing Wu; Johannes Verlinde; Juanzhen Sun

2000-01-01

225

Application of the Cloude-Pottier decomposition to weather radar signatures  

NASA Astrophysics Data System (ADS)

In this paper we apply the Cloude-Pottier decomposition to Weather Radar Signatures. First, we present the results of a simulation carried out at the Chemnitz University of Technology and give the expected H-? values for different rain intensities. A comparison with standard radarmeteorological variables is also given. Then, first ever images of Entropy and Anisotropy are presented for clouds and precipitation. Experimental Data are from the POLDIRAD Weather Facility in Oberpfaffenhofen, Germany.

Galletti, M.; Chandra, M.; Pottier, E.; Ghorbani, A.

2005-05-01

226

Cloud-Resolving Model Simulations of KWAJEX: Model Sensitivities and Comparisons with Satellite and Radar Observations  

Microsoft Academic Search

ABSTRACT Three-dimensional cloud-resolving model,simulations,of a mesoscale,region around,Kwajalein Island during the Kwajalein Experiment,(KWAJEX) are performed. Using observed,winds along with surface and large-scale thermodynamic forcings, the model tracks the observed mean thermodynamic soundings without thermodynamic nudging during 52-day simulations spanning the whole experiment time period, 24 July–14 September 1999. Detailed comparisons of the results with cloud and precipitation observations, including radar reflectivities

Peter N. Blossey; Christopher S. Bretherton; Jasmine Cetrone; Marat Kharoutdinov

2007-01-01

227

Neural network sensor fusion: Creation of a virtual sensor for cloud-base height estimation  

Microsoft Academic Search

Sensor fusion has become a significant area of signal processing research that draws on a variety of tools. Its goals are many, however in this thesis, the creation of a virtual sensor is paramount. In particular, neural networks are used to simulate the output of a LIDAR (LASER. RADAR) that measures cloud-base height. Eye-safe LIDAR is more accurate than the

Hugh Joseph Christopher Pasika

2000-01-01

228

Neural network sensor fusion: Creation of a virtual sensor for cloud-base height estimation  

Microsoft Academic Search

Sensor fusion has become a significant area of signal processing research that draws on a variety of tools. Its goals are many, however in this thesis, the creation of a virtual sensor is paramount. In particular, neural networks are used to simulate the output of a LIDAR (LASER. RADAR) that measures cloud-base height. Eye-safe LIDAR is more accurate than the

Hugh Joseph Christopher Pasika

1999-01-01

229

On the Use of Polarimetric Radars for Studies of Cirrostratus Clouds: Numerical Simulations and S-Band Radar Observations  

NASA Astrophysics Data System (ADS)

Uncertainties in parameterizing clouds have been identified as important sources of error in climate model outputs. These problems are linked to insufficient data and the complex behaviors of clouds. Progress in reducing these uncertainties is being made as more data are collected and analyzed. In particular, polarimetric radars are capable of estimating microphysical cloud properties in addition to macrophysical properties. In this paper, a physical-based electromagnetic backscattering model, whose components are based on previous experimental work, is presented for diagnosing and linking cloud particle behavior to the scattered signals received. The scatterers in the model consist of prolate and oblate spheroids and the scattering regime is assumed to be Rayleigh. Inputs to the scattering model include mean drop diameter, equivalent spherical drop size distribution form, and liquid-water content. These parameters are converted to equivalent spheroids using mass conservation and diameter dependent axial ratios. A terminal fall velocity based on fall geometry is calculated and a background wind field is imposed. Finally, additional scaling and dyadic scattering of plane waves are applied to simulate the effective scattered signal. Simulation results will be presented along with comparisons to data from the S-band polarimetric radar (KOUN) operated by the National Severe Storms Laboratory in Norman, Oklahoma.

Le, K.; Palmer, R. D.; Torres, S.; Yu, T.; Zrnic, D.; Chen, S.

2005-05-01

230

Scale Dependence of Variability in Stratiform Clouds Based on Millimeter Wave Could Radar  

SciTech Connect

Internal variability of stratiform clouds is manifested on grid scales ranging from cloud resolving models to general circulation models, and its accurate formulation is one of the most important tasks in improvement of model predictions. Understanding cloud variability on different scales will help to develop and improve subgrid-scale cloud parameterizations. Information about variability is also crucial when dealing with retrieval of microphysical information from observations of volume averaged reflectivity parameters, since neglecting variability can lead to substantial biases in estimation of retrieved microphysical variables. The Atmospheric Radiation Measurement Program (ARM) operates millimeter wave cloud radar (MMCR) at the ARM Climate Research Facility over the Southern Great Plains (ACRF SGP) that provides a unique opportunity to obtain continuous observations in order to address issues of cloud variability. These data contain information on spatial and/or temporal short- and long-range correlations in cloudiness, enabling scale-by-scale (scaling) analyses over a range of hundreds of meters to hundreds of kilometers. The objective of this study is to conduct an analysis based on radar reflectivity observations of clouds over the ACRF SGP site with special emphasis on boundary layer clouds, and the effect of drizzle.

Kogan, Z.N.; Kogan, Y.L.; Mechem, D.B.

2005-03-18

231

Highly Supercooled Cirrus Cloud Water: Confirmation and Climatic Implications  

Microsoft Academic Search

Liquid cloud droplets supercooled to temperatures approaching -40 degrees C have been detected at the base of a cirrostratus cloud through a combination of ground-based, polarization laser radar (lidar) and in situ aircraft measurements. Solar and thermal infrared radiative budget calculations based on these observations indicate that significant changes in the atmospheric heating distribution and the surface radiative budget may

Kenneth Sassen; Kuo Nan Liou; Stefan Kinne; Michael Griffin

1985-01-01

232

Toward More Accurate Retrievals of Ice Water Content from Radar Measurements of Clouds  

Microsoft Academic Search

There has been considerable discussion concerning the accuracy of values of ice water content (IWC) in ice clouds derived from measurements of radar reflectivity (Z). In this paper, the various published relationships that are based on ice particle size spectra recorded from aircraft are analyzed, and it is shown that a relationship between ice water content and reflectivity can be

Chun-Lei Liu; Anthony J. Illingworth

2000-01-01

233

Additional development of remote sensing techniques for observing morphology, microphysics, and radiative properties of clouds and tests using a new, robust CO{sub 2} lidar. Final report  

SciTech Connect

A three-year project with a goal of advancing CO{sub 2} lidar technology and measurement techniques for cloud studies was successfully completed. An eyesafe, infrared lidar with good sensitivity and improved Doppler accuracy was designed, constructed, and demonstrated. Dual-wavelength operation was achieved. A major leap forward in robustness was demonstrated. CO{sub 2} lidars were operated as part of two Intensive Operations Periods at the Southern Great Plains CART site. The first used an older lidar and was intended primarily for measurement technique development. The second used the new lidar and was primarily a demonstration and evaluation of its performance. Progress was demonstrated in the development, evaluation, and application of measurement techniques using CO{sub 2} lidar.

Eberhard, W.L.; Brewer, W.A.; Intrieri, J.M.

1998-09-28

234

Towards 3D lidar point cloud registration improvement using optimal neighborhood knowledge  

NASA Astrophysics Data System (ADS)

Automatic 3D point cloud registration is a main issue in computer vision and remote sensing. One of the most commonly adopted solution is the well-known Iterative Closest Point (ICP) algorithm. This standard approach performs a fine registration of two overlapping point clouds by iteratively estimating the transformation parameters, assuming good a priori alignment is provided. A large body of literature has proposed many variations in order to improve each step of the process (namely selecting, matching, rejecting, weighting and minimizing). The aim of this paper is to demonstrate how the knowledge of the shape that best fits the local geometry of each 3D point neighborhood can improve the speed and the accuracy of each of these steps. First we present the geometrical features that form the basis of this work. These low-level attributes indeed describe the neighborhood shape around each 3D point. They allow to retrieve the optimal size to analyze the neighborhoods at various scales as well as the privileged local dimension (linear, planar, or volumetric). Several variations of each step of the ICP process are then proposed and analyzed by introducing these features. Such variants are compared on real datasets with the original algorithm in order to retrieve the most efficient algorithm for the whole process. Therefore, the method is successfully applied to various 3D lidar point clouds from airborne, terrestrial, and mobile mapping systems. Improvement for two ICP steps has been noted, and we conclude that our features may not be relevant for very dissimilar object samplings.

Gressin, Adrien; Mallet, Clément; Demantké, Jérôme; David, Nicolas

2013-05-01

235

Autonomous full-time lidar measurements of polar stratospheric clouds at the South Pole  

NASA Astrophysics Data System (ADS)

Polar stratospheric clouds (PSC) are an artifact of extremely low temperatures in the lower-stratosphere caused by a lack of sunlight during winter. Their presence induces increased concentrations of chlorine and bromine radicals that drive catalytic ozone destruction upon the return of sunlight in spring. An eye-safe micropulse lidar (MPL; 0.23 mum) was installed at the Scott-Amundsen South Pole Station, Antarctica in December 1999 to collect continuous long-term measurements of polar clouds. A four-year data subset for analyzing PSC is derived from measurements for austral winters 2000 and 2003--2005. A statistical algorithm based on MPL signal uncertainties is designed to retrieve PSC boundary heights, attenuated scattering ratios and demonstrate instrument performance for low signal-to-noise measurements. The MPL measurements consist mostly of Type II PSC (i.e., ice). The likelihood for Type I measurements are described for specific conditions. Seasonal PSC macrophysical properties are examined relative to thermodynamic and chemical characteristics. The potential for dehumidification and denitrification of the lower Antarctic stratosphere is examined by comparing PSC observations to theoretical predictions for cloud based on common scenarios for water vapor and nitric acid concentrations. Conceptual models for seasonal PSC occurrence, denitrification and dehumidification and ozone loss are described. A linear relationship is established between total integrated PSC scattering and ozone loss, with high correlation. Polar vortex dynamics are investigated in relation to PSC occurrence, including synoptic-scale geopotential height anomalies, isentropic airmass trajectories and local-scale gravity waves. Moisture overrunning, from quasi-adiabatic cooling and transport along isentropic boundaries, is considered a primary mechanism for PSC occurrence. Middle and late-season PSC are found to be the result of mixing of moist air from the outer edges of the vortex that coots upon reaching South Pole. Gravity waves are considered to be only a secondary influence on PSC nucleation and growth.

Campbell, James R.

236

Continuous Profiles of Cloud Microphysical Properties for the Fixed Atmospheric Radiation Measurement Sites  

SciTech Connect

The Atmospheric Radiation Measurement (ARM) Program defined a specific metric for the third quarter of Fiscal Year 2006 to produce and refine a one-year continuous time series of cloud microphysical properties based on cloud radar measurements for each of the fixed ARM sites. To accomplish this metric, we used a combination of recently developed algorithms that interpret radar reflectivity profiles, lidar backscatter profiles, and microwave brightness temperatures into the context of the underlying cloud microphysical structure.

Jensen, M; Jensen, K

2006-06-01

237

Automated Detection of Geomorphic Features in LiDAR Point Clouds of Various Spatial Density  

NASA Astrophysics Data System (ADS)

LiDAR, also referred to as laser scanning, has proved to be an important tool for topographic data acquisition. Terrestrial laser scanning allows for accurate (several millimeter) and high resolution (several centimeter) data acquisition at distances of up to some hundred meters. By contrast, airborne laser scanning allows for acquiring homogeneous data for large areas, albeit with lower accuracy (decimeter) and resolution (some ten points per square meter) compared to terrestrial laser scanning. Hence, terrestrial laser scanning is preferably used for precise data acquisition of limited areas such as landslides or steep structures, while airborne laser scanning is well suited for the acquisition of topographic data of huge areas or even country wide. Laser scanners acquire more or less homogeneously distributed point clouds. These points represent natural objects like terrain and vegetation and artificial objects like buildings, streets or power lines. Typical products derived from such data are geometric models such as digital surface models representing all natural and artificial objects and digital terrain models representing the geomorphic topography only. As the LiDAR technology evolves, the amount of data produced increases almost exponentially even in smaller projects. This means a considerable challenge for the end user of the data: the experimenter has to have enough knowledge, experience and computer capacity in order to manage the acquired dataset and to derive geomorphologically relevant information from the raw or intermediate data products. Additionally, all this information might need to be integrated with other data like orthophotos. In all theses cases, in general, interactive interpretation is necessary to determine geomorphic structures from such models to achieve effective data reduction. There is little support for the automatic determination of characteristic features and their statistical evaluation. From the lessons learnt from automated extraction and modeling of buildings (Dorninger & Pfeifer, 2008) we expected that similar generalizations for geomorphic features can be achieved. Our aim is to recognize as many features as possible from the point cloud in the same processing loop, if they can be geometrically described with appropriate accuracy (e.g., as a plane). For this, we propose to apply a segmentation process allowing determining connected, planar structures within a surface represented by a point cloud. It is based on a robust determination of local tangential planes for all points acquired (Nothegger & Dorninger, 2009). It assumes that for points, belonging to a distinct planar structure, similar tangential planes can be determined. In passing, points acquired at continuous such as vegetation can be identified and eliminated. The plane parameters are used to define a four-dimensional feature space which is used to determine seed-clusters globally for the whole are of interest. Starting from these seeds, all points defining a connected, planar region are assigned to a segment. Due to the design of the algorithm, millions of input points can be processed with acceptable processing time on standard computer systems. This allows for processing geomorphically representative areas at once. For each segment, numerous parameter are derived which can be used for further exploitation. These are, for example, location, area, aspect, slope, and roughness. To prove the applicability of our method for automated geomorphic terrain analysis, we used terrestrial and airborne laser scanning data, acquired at two locations. The data of the Doren landslide located in Vorarlberg, Austria, was acquired by a terrestrial Riegl LS-321 laser scanner in 2008, by a terrestrial Riegl LMS-Z420i laser scanner in 2009, and additionally by three airborne LiDAR measurement campaigns, organized by the Landesvermessungsamt Vorarlberg, Feldkirch, in 2003, 2006, and 2007. The measurement distance of the terrestrial measurements was considerably varying considerably because of the various base points that were neede

Dorninger, Peter; Székely, Balázs; Zámolyi, András.; Nothegger, Clemens

2010-05-01

238

Simultaneous lidar observations of a polar stratospheric cloud on the east and west sides of the Scandinavian mountains and microphysical box model simulations  

NASA Astrophysics Data System (ADS)

The importance of polar stratospheric clouds (PSC) for polar ozone depletion is well established. Lidar experiments are well suited to observe and classify polar stratospheric clouds. On 5 January 2005 a PSC was observed simultaneously on the east and west sides of the Scandinavian mountains by ground-based lidars. This cloud was composed of liquid particles with a mixture of solid particles in the upper part of the cloud. Multi-colour measurements revealed that the liquid particles had a mode radius of r?300 nm, a distribution width of ??1.04 and an altitude dependent number density of N?2-20 cm-3. Simulations with a microphysical box model show that the cloud had formed about 20 h before observation. High HNO3 concentrations in the PSC of 40-50 weight percent were simulated in the altitude regions where the liquid particles were observed, while this concentration was reduced to about 10 weight percent in that part of the cloud where a mixture between solid and liquid particles was observed by the lidar. The model simulations also revealed a very narrow particle size distribution with values similar to the lidar observations. Below and above the cloud almost no HNO3 uptake was simulated. Although the PSC shows distinct wave signatures, no gravity wave activity was observed in the temperature profiles measured by the lidars and meteorological analyses support this observation. The observed cloud must have formed in a wave field above Iceland about 20 h prior to the measurements and the cloud wave pattern was advected by the background wind to Scandinavia. In this wave field above Iceland temperatures potentially dropped below the ice formation temperature, so that ice clouds may have formed which can act as condensation nuclei for the nitric acid trihydrate (NAT) particles observed at the cloud top above Esrange.

Blum, U.; Khosrawi, F.; Baumgarten, G.; Stebel, K.; Müller, R.; Fricke, K. H.

2006-12-01

239

Development of Spaceborne Radar Simulator by NICT and JAXA using JMA Cloud-resolving Model  

NASA Astrophysics Data System (ADS)

We are developing synthetic spaceborne radar data toward a simulation of the Dual-frequency Precipitation Radar (DPR) aboard the Global Precipitation Measurement (GPM) core-satellite. Our purposes are a production of test-bed data for higher level DPR algorithm developers, in addition to a diagnosis of a cloud resolving model (CRM). To make the synthetic data, we utilize the CRM by the Japan Meteorological Agency (JMA-NHM) (Ikawa and Saito 1991, Saito et al. 2006, 2007), and the spaceborne radar simulation algorithm by the National Institute of Information and Communications Technology (NICT) and the Japan Aerospace Exploration Agency (JAXA) named as the Integrated Satellite Observation Simulator for Radar (ISOSIM-Radar). The ISOSIM-Radar simulates received power data in a field of view of the spaceborne radar with consideration to a scan angle of the radar (Oouchi et al. 2002, Kubota et al. 2009). The received power data are computed with gaseous and hydrometeor attenuations taken into account. The backscattering and extinction coefficients are calculated assuming the Mie approximation for all species. The dielectric constants for solid particles are computed by the Maxwell-Garnett model (Bohren and Battan 1982). Drop size distributions are treated in accordance with those of the JMA-NHM. We assume a spherical sea surface, a Gaussian antenna pattern, and 49 antenna beam directions for scan angles from -17 to 17 deg. in the PR. In this study, we report the diagnosis of the JMA-NHM with reference to the TRMM Precipitation Radar (PR) and CloudSat Cloud Profiling Radar (CPR) using the ISOSIM-Radar from the view of comparisons in cloud microphysics schemes of the JMA-NHM. We tested three kinds of explicit bulk microphysics schemes based on Lin et al. (1983), that is, three-ice 1-moment scheme, three-ice 2-moment scheme (Eito and Aonashi 2009), and newly developed four-ice full 2-moment scheme (Hashimoto 2008). The hydrometeor species considered here are rain, graupel, snow, cloud water, cloud ice and hail (4-ice scheme only). We examined a case of an intersection with the TRMM PR and the CloudSat CPR on 6th April 2008 over sea surface in the south of Kyushu Island of Japan. In this work, observed rainfall systems are simulated with one-way double nested domains having horizontal grid sizes of 5 km (outer) and 2 km (inner). Data used here are from the inner domain only. Results of the PR indicated better performances of 2-moment bulk schemes. It suggests that prognostic number concentrations of frozen hydrometeors are more effective in high altitudes and constant number concentrations can lead to the overestimation of the snow there. For three-ice schemes, simulated received power data overestimated above freezing levels with reference to the observed data. In contrast, the overestimation of frozen particles was heavily reduced for the four-ice scheme.

Kubota, T.; Eito, H.; Aonashi, K.; Hashimoto, A.; Iguchi, T.; Hanado, H.; Shimizu, S.; Yoshida, N.; Oki, R.

2009-12-01

240

3D cloud reconstructions: Evaluation of scanning radar scan strategy with a view to surface shortwave radiation closure  

NASA Astrophysics Data System (ADS)

ability of six scanning cloud radar scan strategies to reconstruct cumulus cloud fields for radiation study is assessed. Utilizing snapshots of clean and polluted cloud fields from large eddy simulations, an analysis is undertaken of error in both the liquid water path and monochromatic downwelling surface irradiance at 870 nm of the reconstructed cloud fields. Error introduced by radar sensitivity, choice of radar scan strategy, retrieval of liquid water content (LWC), and reconstruction scheme is explored. Given an infinitely sensitive radar and perfect LWC retrieval, domain average surface irradiance biases are typically less than 3 W m-2 µm-1, corresponding to 5-10% of the cloud radiative effect (CRE). However, when using a realistic radar sensitivity of -37.5 dBZ at 1 km, optically thin areas and edges of clouds are difficult to detect due to their low radar reflectivity; in clean conditions, overestimates are of order 10 W m-2 µm-1 (~20% of the CRE), but in polluted conditions, where the droplets are smaller, this increases to 10-26 W m-2 µm-1 (~40-100% of the CRE). Drizzle drops are also problematic; if treated as cloud droplets, reconstructions are poor, leading to large underestimates of 20-46 W m-2 µm-1 in domain average surface irradiance (~40-80% of the CRE). Nevertheless, a synergistic retrieval approach combining the detailed cloud structure obtained from scanning radar with the droplet-size information and location of cloud base gained from other instruments would potentially make accurate solar radiative transfer calculations in broken cloud possible for the first time.

Fielding, Mark D.; Chiu, J. Christine; Hogan, Robin J.; Feingold, Graham

2013-08-01

241

Application technology of micro pulse lidar  

NASA Astrophysics Data System (ADS)

With the constant exploration to the atmosphere and the attention to the air quality of the living environment, the applications of micro-pulse lidar are more and more important. Micro Pulse Lidar can be used to observe the distribution of atmospheric aerosol and analyse structure, spatial and temporal evolution of the aerosol. The paper gives the introduction about the reference of micro-pulse lidar which is researched in the laboratory. Through the precision optical design, the blind area of Micro Pulse Lidar can be less than 45m. The portable requirement in the structure is implemented. The software function of micro-pulse lidar includes: extinction coefficiency monitoring, tracking the pollution source, distinguish spherical particular (fog) from no-sphercial particular(ice or dust)? simulating the Mass concentration, scanning date integrating with GIS, and so on. The average height of the boundary layer measured by micro-pulse lidar. The relationship between the cloud height and aerosol echo signal can be seen from the data received from micro-pulse lidar and the peak is at 6KM. By acquiring corresponding visibility values from probing different heights, a conclusion can be drawn that visibility and extinction coeffcient is inversely proportionate. Take a 24 hour day as a circle and divide it into several time periods. An atmosphere evolution diagram of the backscattering of the height of atmospheric boundary layer and the atmospheric aerosol particles can be derived according to the difference in sun radiation. Information like structure and the evolution characteristics of atmospheric boundary layer, cloud height, cloud cover structure, atmospheric visibility and space particles obtained by the laser radar detection provides a basis for the establishment of the correct atmospheric model. At the same time because lidar can monitor the emissions of industrial soot and detect the law of diffusion of environmental pollutants of the sky over cities, it is of great significance to the environmental monitoring of the atmosphere and atmospheric science research.

Xu, Yan-ming; Tong, Shou-feng; Jia, Yu-guang

2013-09-01

242

Towards the improvement of cloud microphysical retrievals using simultaneous Doppler and polarimetric radar measurements  

NASA Astrophysics Data System (ADS)

Radar-based retrievals are often employed to characterize the microphysical properties of cloud hydrometeors, i.e., their phases, habits, densities as well as their respective size and orientation distributions. These techniques are based on a synergetic use of different cloud observation sensor(s) and microphysical algorithm(s) where the information extracted from both sensors and models are combined and converted into microphysical cloud properties. However, the amount of available information is often limited, which forces current microphysical retrieval techniques to base their algorithms on several microphysical assumptions which affect the retrieval accuracy. By simultaneously combining Doppler and polarimetric measurements obtained from fully Doppler polarimetric radar, it is possible to create spectral polarimetric parameters. Although these parameters are easily contaminated with unwanted echoes, this work shows that, from a correct radar signal processing based on filtering and averaging techniques, spectral polarimetric parameters can be correlated to microphysical cloud properties. In particular, preliminary results suggest that particle orientations and habits can be easily determined from the solely use of such spectral polarimetric parameters. Therefore, such additional microphysical information offers a great opportunity to improve current microphysical models by reducing their amount of microphysical assumptions.

Dufournet, Y.; Russchenberg, H. W. J.

2011-01-01

243

Towards the improvement of cloud microphysical retrievals using simultaneous Doppler and polarimetric radar measurements  

NASA Astrophysics Data System (ADS)

Radar-based retrievals are often employed to characterize the microphysical properties of cloud hydrometeors, i.e. their phases, habits, densities as well as their respective size and orientation distributions. These techniques are based on a synergetic use of different cloud observation sensor(s) and microphysical model(s) where the information extracted from both sensors and models is combined and converted into microphysical cloud properties. However, the amount of available information is often limited, which forces current microphysical retrieval techniques to base their algorithms on several microphysical assumptions which affect the retrieval accuracy. By simultaneously combining Doppler and polarimetric measurements obtained from fully Doppler polarimetric radars, it is possible to create spectral polarimetric parameters. Although these parameters are easily contaminated with unwanted echoes, this work shows that, from a correct radar signal processing based on filtering and averaging techniques, spectral polarimetric parameters can be correlated to microphysical cloud properties. In particular, preliminary results suggest that particle orientations and habits can be determined from the sole use of such spectral polarimetric parameters. Therefore, such additional spectral polarimetric information offers an opportunity to improve current microphysical retrievals by reducing the number of microphysical assumptions in them.

Dufournet, Y.; Russchenberg, H. W. J.

2011-10-01

244

Identification of a debris cloud from the nuclear powered SNAPSHOT satellite with Haystack radar measurements  

NASA Astrophysics Data System (ADS)

Data from the MIT Lincoln Laboratory MIT LL Long Range Imaging Radar known as the Haystack radar have been used in the past to examine families of objects from individual satellite breakups or families of orbiting objects that can be isolated in altitude and inclination This is possible because for some time after a breakup the debris cloud of particles can remain grouped together in similar orbit planes This cloud will be visible to the radar in fixed staring mode for a short time twice each day as the orbit plane moves through the field of view There should be a unique three-dimensional pattern in observation time range and range rate which can identify the cloud Eventually through slightly differing precession rates of the right ascension of ascending node of the debris cloud the observation time becomes distributed so that event identification becomes much more difficult Analyses of the patterns in observation time range and range rate have identified good debris candidates released from the polar orbiting SNAPSHOT satellite International Identifier 1965-027A For orbits near 90 o inclination there is essentially no precession of the orbit plane The SNAPSHOT satellite is a well known nuclear powered satellite launched in 1965 to a near circular 1300 km orbit with an inclination of 90 1 o This satellite began releasing debris in 1979 with new pieces being discovered and cataloged over the years 51 objects are still being tracked by the United States Space Surveillance Network An analysis of the Haystack data has

Stokley, C.; Stansbery, E.

245

A Motion-Stabilized W-Band Radar for Shipboard Observations of Marine Boundary-Layer Clouds  

NASA Astrophysics Data System (ADS)

Cloud radars at X, Ka and W-bands have been used in the past for ocean studies of clouds, but the lack of suitable stabilization has limited their usefulness in obtaining accurate measurements of the velocity structure of cloud particles and the heights of cloud features. A 94 GHz (W-band) radar suitable for use on shipboard studies of clouds has been developed that is small and lightweight and can maintain the radar's beam pointing in the vertical to reduce the affects of the pitch and roll of the ship. A vertical velocity sensor on the platform allows the effects of the ship's heave to be removed from the measured cloud particle motions. Results from the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-Rex) field program on the NOAA vessel Ronald H. Brown demonstrate the improvements to the cloud measurements after the ship's motion effects are removed. The compact design of the radar also makes it suitable for use in aircraft studies. The radar is being repackaged to fit in an aft bay of a NOAA P3 aircraft to observe sea-spray profiles during ocean storms.

Moran, Ken; Pezoa, Sergio; Fairall, Chris; Williams, Chris; Ayers, Tom; Brewer, Alan; de Szoeke, Simon P.; Ghate, Virendra

2012-04-01

246

NEXRAD Weather Radar Observations of the 2006 Augustine Volcanic Eruption Clouds  

NASA Astrophysics Data System (ADS)

The 2006 eruption of Augustine Volcano, Alaska provided an exceptional opportunity to detect and measure explosive volcanic events and to track drifting volcanic clouds using WRS-88D (NEXRAD) weather radar data. Radar data complemented the real-time seismic monitoring by providing rapid confirmation of ash generation and cloud height. The explosive phase of the eruption consisted of thirteen discrete Vulcanian explosions from January 11 to 28, with seismic durations that ranged from one to eleven minutes. The ash columns and drifting clouds from all of the events were observed via a NEXRAD located 185 km NE of the volcano on the Kenai Peninsula (site PAHG). The radar was operated in both precipitation and clear air modes, resulting in a temporal resolution of 4.1 to 10 minutes per complete scan, respectively. Scan elevation angles for the radar beam centroid varied slightly depending upon mode of operation, but values of 0.5, 1.5, 2.5, and 3.5 degrees were typically used, corresponding to altitudes over the volcano of 3.8, 7.2, 10.5, and 13.8 km above sea level. Estimates of eruption cloud height were made by the National Weather Service (NWS) Anchorage Forecast Office using range-height indication cross-sections and radar echo tops (the altitude of the +18.5 dBZ reflectance surface). The observed cloud heights typically ranged from 7.5 to 10.5 km above sea level, with the exception of the January 17 event which briefly had an echo top of about 14 km. Most of the eruption clouds reached their maximum height in the first scan in which they were visible, suggesting an energetic and impulsive initial event, and were at lower heights in subsequent views. These height estimates may be minimum values because very fine-grained ash at the top of eruption clouds has low radar reflectance, and thus may not be observed. Height estimates were rapidly communicated to the NWS Alaska Aviation Weather Unit and the Alaska Volcano Observatory for use in hazard statements and related cloud dispersion modeling. Base reflectivity images at four scan angles provided additional insight into the vertical ash distribution. Generally, the eruption column and associated volcanic clouds had the greatest areal coverage and highest reflectivity values (as high as +60 dBZ) at the two lowest scan elevation angles (0.5 and 1.5 degrees or heights of about 3.8 to 7.2 km above sea level). The explosions on January 13 and 17 produced volcanic clouds that propagated upwind for ten to twenty minutes before dispersing, suggesting that some of the ash was being generated by pyroclastic flows on the flanks. Drifting volcanic clouds were tracked in the data for as long as two hours after the start of the eruption, with reflectivity values as low as -4 dBZ observed. Retrospective analyses of level-3 NEXRAD data from the Kenai (PAHG) and King Salmon (PAKC) radars (200 km SW of Augustine) examined radial base velocity and spectrum width (a measure of the velocity variance within a scan volume) at four scan angles. The highest base velocities observed were for the January 17 event, which reached 33 m/s, the maximum value computed by the level-3 algorithm. This event, and similar ones on January 13, were characterized by moderately high spectrum widths (as large as 9.8 m/s), indicative of turbulence and wind shear.

Schneider, D. J.; Scott, C.; Wood, J.; Hall, T.

2006-12-01

247

Towards Realtime Assimilation of Doppler Radar Observations for Cloud-Resolving Hurricane Prediction  

NASA Astrophysics Data System (ADS)

This study explores the feasibility and impacts of on-demand, real-time assimilation of Doppler radar observations straight from the planes with an ensemble Kalman filter (EnKF) to initialize a cloud-resolving hurricane prediction model. The NOAA P3 aircrafts have being flying into tropical cyclones to gather radar observations since 1994. These observations are significant in investigating and anglicizing hurricane's intensity, eye-wall structure and intensity changes, but the radar data has never been ingested into hurricane prediction models in real-time. Likely reasons are (1) insufficient model resolution due to inadequate computing resources for ingesting convective-scale details observed by the radar, (2) inadequacy of existing data assimilation method for operational models, and (3) lack of sufficient bandwidth in transmitting huge volume radar data to the ground in realtime. This work is built on our recent case studies of predicting the rapid formation and intensification of past hurricanes in assimilating both ground-base and/or airborne radial velocity into a cloud-resolving mesoscale model with EnKF. Under the auspices of NOAA Hurricane Forecasting Improvement Project (HFIP), we have access to the NSF-sponsored high-performance computing facility TACC at University of Texas at Austin that makes realtime cloud-resolving hurricane data assimilation and forecasting possible. We alleviate the requirement of large volume data transfer from the aircraft through developing a radar radial velocity data quality and thinning procedure (namely to produce superobervations or SOs) to significantly reduce the data size before being transferred. We have first conducted near realtime testing of the cloud-resolving data assimilation and forecasting with Weather Research and Forecast (WRF) model using 40.5, 13.5, 4.5 and 1.5 km grid spacings and movable nested grids for Hurricanes Dolly and Fay (2008). As of today, we have successfully demonstrated the feasibility, data follow and effectiveness of on-demand, realtime data assimilation of airborne Doppler observations and subsequent cloud-resolving deterministic and ensemble hurricane forecasting for Hurricanes Gustav and Ike. We plan to conduct more assimilation experiments both in realtime and retrospectively to improve the efficiency and effectiveness of our data assimilation system for future on- demand cloud-resolving hurricane predictions.

Weng, Y.; Zhang, F.; Gamache, J. F.; Marks, F. D.

2008-12-01

248

Analysis of polarization radar returns from ice clouds  

Microsoft Academic Search

Using a modified T-matrix code, some polarimetric single-scattering radar parameters (Zh,v, LDRh,v, ?hv, ZDR and ?hv) from populations of ice crystals in ice phase at 94 GHz, modeled with axisymmetric prolate and oblate spheroidal shapes for a ?-size distribution with different ? parameter (?=0, 1, 2) and characteristic dimension Lm varying from 0.1 to 1.8 mm, have been computed. Some

A. Battaglia; O. Sturniolo; F. Prodi

2001-01-01

249

One Decade of Noctilucent Cloud Observations Above ALOMAR by Lidar: Persistence and Variability at Different Time Scales.  

NASA Astrophysics Data System (ADS)

Noctilucent clouds (NLC) are the visible manifestation of icy particles persistently present in the polar summer mesopause region. Their formation is a rather complicated physical process depending on atmospheric background parameters, such as temperature and water vapor, which are hardly to measure directly at the altitudes of interest. This strong dependence on the atmospheric parameters and the fact that the clouds show variabilities at different time scales from minutes to several years, make NLC an attractive tracer for dynamic processes in the atmosphere. We report on observations of NLC using the ALOMAR Rayleigh/Mie/Raman (RMR) lidar in Northern Norway at 69N from 1997 to 2006. At this latitude NLC occur regularly from the beginning of June to the middle of August. Using the primary wavelength of the lidar at 532nm we have observed NLC signatures covering all local times even during highest solar background conditions. From the vertically resolved volume backscatter coefficient of the NLC particles, cloud parameters like brightness and altitude are derived. Furthermore, NLC occurrence frequencies as function of the cloud brightness are calculated. Investigations of the local time dependencies of cloud occurrence, brightness, and altitude yield a remarkable persistence concerning diurnal and semidiurnal variations. Within our 10-years data set, the year-to-year variations of cloud occurrence and brightness show signatures which we discuss in respect of the solar cycle. Furthermore our data are analyzed regarding a time lag between NLC occurrence/brightness and solar activity, as shown by visual as well as satellite observations. We compare our measurements with results from the Leibniz Institute Middle Atmosphere model (LIMA), a 3D GCM containing the relevant physical and chemical processes, such as dynamics, radiation, chemistry, and transport, including a mesospheric ice module. Spatial and temporal variability is introduced by assimilation of ECMWF data. These capabilities make it very suitable for comparisons with our experimental NLC data at different time scales.

Fiedler, J.; Baumgarten, G.; Berger, U.; von Cossart, G.

2006-12-01

250

Using radar and lidar instrument simulators to evaluate moist processes in the Community Atmosphere Model  

Microsoft Academic Search

Global vertically-profiling active satellite observations and instrument simulator packages enable new exposure of moist processes in global climate models. We evaluate the representation of cloud and precipitation processes within two versions of NCAR's Community Atmosphere Model (CAM) that will be used for IPCC integrations (CAM3.5, CAM4). The two CAM model versions have large differences in cloud water content, cloud particle

J. E. Kay; A. Gettelman; Y. Zhang; G. L. Stephens

2009-01-01

251

An intercomparison of radar-based liquid cloud microphysics retrievals and implications for model evaluation studies  

NASA Astrophysics Data System (ADS)

This paper presents a statistical comparison of three cloud retrieval products of the Atmospheric Radiation Measurement (ARM) program at the Southern Great Plains (SGP) site from 1998 to 2006: MICROBASE, University of Utah (UU), and University of North Dakota (UND) products. The probability density functions of the various cloud liquid water content (LWC) retrievals appear to be consistent with each other. While the mean MICROBASE and UU cloud LWC retrievals agree well in the middle of cloud, the discrepancy increases to about 0.03 gm-3 at cloud top and cloud base. Alarmingly large differences are found in the droplet effective radius (re) retrievals. The mean MICROBASE re is more than 6 ?m lower than the UU re, whereas the discrepancy is reduced to within 1 ?m if columns containing raining and/or mixed-phase layers are excluded from the comparison. A suite of stratified comparisons and retrieval experiments reveal that the LWC difference stems primarily from rain contamination, partitioning of total liquid later path (LWP) into warm and supercooled liquid, and the input cloud mask and LWP. The large discrepancy among the re retrievals is mainly due to rain contamination and the presence of mixed-phase layers. Since rain or ice particles are likely to dominate radar backscattering over cloud droplets, the large discrepancy found in this paper can be thought of as a physical limitation of single-frequency radar approaches. It is therefore suggested that data users should use the retrievals with caution when rain and/or mixed-phase layers are present in the column.

Huang, D.; Zhao, C.; Dunn, M.; Dong, X.; Mace, G. G.; Jensen, M. P.; Xie, S.; Liu, Y.

2012-06-01

252

Hail embryons detection in clouds using passive and active radars in millimeter and submillimeter wave bands  

NASA Astrophysics Data System (ADS)

Two detection methods of hail embryons in a cloud are discussed in the paper: combined passive/active and purely active sensing of a convective cloud from board of air or space carrier. The first method makes it possible to determine the spectral dependence of absorption coefficient by oversized drops in convective cloud in the millimeter (MM) and submillimeter (SbMM) wavebands. With this purpose a highly sensitive 16-channel Dicke radiometer is used. In the second method a multiwave (12 wavelength) active radar is used to determine the spectral dependence of backscatter coefficient in the same wavebands. Variation of these spectral characteristics in time makes possible the detection of physical processes taking place in a cloud, such as drops drowth and evaporation, as well as transition of oversized drops into the overcooled state. The instant of water/ice phase transition in oversized drops is determined in both methods by means of active radar in SbMM waveband (in the transparency “window” of ice and atmosphere, 0.64 mm). Corresponding hardware, antennas, and wavelengths are considered for active/passive and purely active sensind of clouds. The effect of antenna beamwidth in SbMM on anomalous backscatter is discussed.

Ajvazyan, H. M.; Ajvazyan, H. H.

1993-05-01

253

Retrieval of Vertical Profiles of Cirrus Cloud Microphysical Parameters from Doppler Radar and Infrared Radiometer Measurements.  

NASA Astrophysics Data System (ADS)

This paper describes a new method to retrieve vertical profiles of the parameters of cirrus cloud microphysics that are important for the estimation of climatic feedback. These parameters are the particle characteristic size and ice mass content. The method also allows calculations of vertical profiles of particle concentrations and ice mass flux. The method uses measurements of radar reflectivities and Doppler velocities from the ground-based zenith-viewing radar combined with measurements of downwelling brightness temperatures from an infrared radiometer operating in the `window' (10 12 µm) region. The proposed method is illustrated on data obtained on 26 November 1991 during FIRE-II [First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment] in Coffeyville, Kansas. This paper also presents estimates of uncertainties of parameter retrieval due to different a priori assumptions about particle shapes, distributions, fall velocity-size relationships and due to errors in measurements. Comparisons with in situ measurements showed reasonable agreement.

Matrosov, S. Y.; Orr, B. W.; Kropfli, R. A.; Snider, J. B.

1994-05-01

254

Using Doppler spectra to separate hydrometeor populations and analyze ice precipitation in multilayered mixed-phase clouds  

SciTech Connect

Multimodality of cloud radar Doppler spectra is used to partition cloud particle phases and to separate distinct ice populations in the radar sample volume, thereby facilitating analysis of individual ice showers in multilayered mixed-phase clouds. A 35-GHz cloud radar located at Barrow, Alaska, during the Mixed-Phase Arctic Cloud Experiment collected the Doppler spectra. Data from a pair of collocated depolarization lidars confirmed the presence of two liquid cloud layers reported in this study. Surprisingly, both of these cloud layers were embedded in ice precipitation yet maintained their liquid. Our spectral separation of the ice precipitation yielded two distinct ice populations: ice initiated within the two liquid cloud layers and ice precipitation formed in higher cloud layers. Comparisons of ice fall velocity versus radar reflectivity relationships derived for distinct showers reveal that a single relationship might not properly represent the ice showers during this period.

Rambukkange, Mahlon P.; Verlinde, J.; Eloranta, E. W.; Flynn, Connor J.; Clothiaux, Eugene E.

2011-01-31

255

Cloud Characteristics by Using Doppler Radar over Kolkata  

Microsoft Academic Search

In present days radio communication scenario, three issues are considered to be the most important. These are reliability, directivity and regulation of transmitted power. All such issues can be taken care provided the characterization of our tropospheric medium is done with good degree accuracy. The radio wave propagating above 10 GHz is affected severely by rain and cloud. In case

A. Kumar; D. Pradhan; H. A. K. Singh; M. M. Gupta; A. K. de; J. Das; S. K. Sarkar

2007-01-01

256

Identification of a debris cloud from the nuclear powered SNAPSHOT satellite with haystack radar measurements  

NASA Astrophysics Data System (ADS)

Data from the Massachusetts Institute of Technology Lincoln Laboratory Long Range Imaging Radar (known as the Haystack radar) have been used in the past to examine families of objects from individual satellite breakups or families of orbiting objects that can be isolated in altitude and inclination. This is possible because, for some time after a breakup, the debris cloud of particles can remain grouped together in similar orbit planes. This cloud will be visible to the radar, in fixed staring mode, for a short time twice each day, as the orbit plane moves through the field of view. There should be a unique three-dimensional pattern in observation time, range, and range rate which can identify the cloud. Eventually, through slightly differing precession rates of the right ascension of ascending node of the debris cloud, the observation time becomes distributed so that event identification becomes much more difficult. Analyses of the patterns in observation time, range, and range rate have identified good debris candidates released from the polar orbiting SNAPSHOT satellite (International Identifier: 1965-027A). For orbits near 90° inclination, there is essentially no precession of the orbit plane. The SNAPSHOT satellite is a well known nuclear powered satellite launched in 1965 to a near circular 1300 km orbit with an inclination of 90.3°. This satellite began releasing debris in 1979, with new pieces being discovered and cataloged over the years. Fifty-one objects are still being tracked by the United States Space Surveillance Network. An analysis of the Haystack data has identified at least 60 pieces of debris separate from the 51 known tracked debris pieces, where all but 2 of the 60 pieces have a size less than 10 cm. The altitude and inclination (derived from range-rate with a circular orbit assumption) are consistent with the SNAPSHOT satellite and its tracked debris cloud.

Stokely, C. L.; Stansbery, E. G.

257

Laser remote sensing of tropospheric aerosols and clouds  

NASA Astrophysics Data System (ADS)

Aerosols and clouds have significant impact on global climate. In this work experimental results from regular lidar investigations of tropospheric aerosols and clouds are presented. Examples of calculated atmospheric backscatter coefficient profiles extracted from four years lidar dataset collected in the city of Sofia (Bulgaria) are offered and analyzed. They illustrate remote detection of aerosol fields and clouds at different altitudes including Saharan dust intrusion over the city and highly situated cirrus clouds. The mass temporal evolution and the spatial distribution of registered atmospheric layers are visualized by 2D-colormaps in height-time coordinates. The ground-based measurements are performed with a newly developed lidar in the Laser Radar Lab, Institute of Electronics, Bulgarian Academy of Sciences. The good parameters of all the laser, telescope, photo-receiving modules and software make it possible the developed lidar to be utilized for carrying out fast and accurate remote atmospheric measurements with high spatial and temporal resolution.

Deleva, Atanaska D.; Avramov, Lachezar A.; Stoyanov, Dimitar V.

2010-10-01

258

Two-wavelength lidar measurement of Cloud-aerosol optical properties  

NASA Astrophysics Data System (ADS)

Based on unstability of inversion algorithms of the lidar equation caused by molecular scattering, a new algorithm to derive both the aerosol extinction to backscatter ratio and the extinction coefficient profile is proposed in this paper. As shown in numerical experiments, in case of a ground-based lidar, the error in the aerosol optical depth solution can be less than 10%, and the error of < 6.7 in the aerosol extinction to backscatter ratio can be obtained if the error in the lidar constant is < 6%; and in the case of a spaceborne lidar, the present method can be used to de-termine the lidar constant at a short wavelength with an accuracy of being better than 1%.

Qiu, Jinhuan

1995-05-01

259

Using radar and lidar instrument simulators to evaluate moist processes in the Community Atmosphere Model  

NASA Astrophysics Data System (ADS)

Global vertically-profiling active satellite observations and instrument simulator packages enable new exposure of moist processes in global climate models. We evaluate the representation of cloud and precipitation processes within two versions of NCAR’s Community Atmosphere Model (CAM) that will be used for IPCC integrations (CAM3.5, CAM4). The two CAM model versions have large differences in cloud water content, cloud particle size, tropospheric humidity, and precipitation frequency and intensity. CloudSat and CALIOP observations and the COSP simulator package are used to produce “apple-to-apple” comparisons between observed and modeled cloud and precipitation properties. We then assess the fidelity of CAM3.5 and CAM4 cloud and precipitation fields to the CloudSat and CALIOP observations in three areas of climatological interest: the Pacific stratocumulus regions, the Tropical Pacific warm pool, and the North Pacific mid-latitude storm track. In addition to observational comparison, the climate implications of the revealed inter-model and observational differences will be discussed.

Kay, J. E.; Gettelman, A.; Zhang, Y.; Stephens, G. L.

2009-12-01

260

Toward the characterization of upper tropospheric clouds using Atmospheric Infrared Sounder and Microwave Limb Sounder observations  

Microsoft Academic Search

We estimate the accuracy of cloud top altitude (Z) retrievals from the Atmospheric Infrared Sounder (AIRS) and Advanced Microwave Sounding Unit (AMSU) observing suite (ZA) on board the Earth Observing System Aqua platform. We compare ZA with coincident measurements of Z derived from the micropulse lidar and millimeter wave cloud radar at the Atmospheric Radiation Measurement (ARM) program sites of

Brian H. Kahn; Annmarie Eldering; Amy J. Braverman; Eric J. Fetzer; Jonathan H. Jiang; Evan Fishbein; Dong L. Wu

2007-01-01

261

Radar\\/Lidar sensor fusion for car-following on highways  

Microsoft Academic Search

We present a real-time algorithm which enables an autonomous car to comfortably follow other cars at various speeds while keeping a safe distance. We focus on highway scenarios. A velocity and distance regulation approach is presented that depends on the position as well as the velocity of the followed car. Radar sensors provide reliable information on straight lanes, but fail

Daniel Gohring; Miao Wang; Michael Schnurmacher; Tinosch Ganjineh

2011-01-01

262

Characteristics of a lambda/2 Kerr cell ruby oscillator for use as an optical radar (Lidar).  

PubMed

A Q-switched ruby laser has been developed that is useful as an optical radar for clear air turbulence detection. The output is a single clean pulse of 35 MW, free of noise sources such as spontaneous emission, superradiance, and after-pulsing. A comparison is made with the standard quarter-wave mode of operation. PMID:20057633

Mocker, H W

1966-11-01

263

A comparison between CloudSat and aircraft data for mixed-phase and cirrus clouds  

Microsoft Academic Search

Nowadays, space remote sensing measurements are a very useful way to study the atmosphere on a global scale. Among the numerous scientific satellites in space, the A-Train is a constellation of 6 satellites flying together with on board complementary instruments of new generation (radiometers, radar, lidar, spectrometers...) to study all parts of the atmosphere: gas composition, clouds and aerosols distribution

G. Mioche; J.-F. Gayet; A. Minikin; A. Herber; J. Pelon

2009-01-01

264

DC-8 Scanning Lidar Characterization of Aircraft Contrails and Cirrus Clouds.  

National Technical Information Service (NTIS)

A Subsonic Assessment (SASS) element of the overall Atmospheric Effects of Aviation Project (AEAP) was initiated by NASA to assess the atmospheric impact of subsonic aircraft. A scanning mirror pod attached to the DC-8 aircraft provides for scanning lidar...

N. B. Nielsen E. E. Uthe

1996-01-01

265

Profiling snow-precipitating clouds with Doppler multi-wavelength radars  

NASA Astrophysics Data System (ADS)

Precipitation is an essential climate variable. Knowledge of precipitation and its underlying processes are required in a number of research and application disciplines directly related to the global energy and water cycle. At high latitudes precipitation typically occurs in the form of snow. All current active and passive remote sensing techniques are known to perform poorly when estimating snow-rate and even worse when trying to predict microphysical properties (e.g. snow size distribution, snow habit, coexistence of super cooled liquid water). In this paper we investigate the potential of multi-wavelength Doppler radars in overcoming this problem. Subsets of frequencies are selected from the following set: 13.8, 35.0, 94.0, 150, 220 GHz. The first three values are associated with already deployed radar systems, the last two refer to new research avenues. The notional study is based on thermodynamic and bulk-microphysical profiles extracted from cloud resolving model simulations and on a database of scattering properties for non-spherical ice crystals. This framework allows the evaluation of the combined effect of spectral differential attenuation and differential reflectivity to be investigated. Dual-wavelength systems generally improve the capabilities in sizing the snowflakes while the use of very high frequency is particularly effective for the detection of mixed phased clouds. This work has relevance for the evaluation of ground-based and space-borne millimetre wave radar performances currently under study.

Kollias, Pavlos; Battaglia, Alessandro; Kneifel, Stefan; Loenhert, Ulrich; Tanelli, Simone; Szyrmer, Wanda

2010-05-01

266

Turn-key Raman lidar for profiling atmospheric water vapor, clouds, and aerosols at the US Southern Great Plains Climate Study Site  

SciTech Connect

There are clearly identified scientific requirements for continuous profiling of atmospheric water vapor at the Department of Energy, Atmospheric Radiation Measurement program, Southern Great Plains CART (Cloud and Radiation Testbed) site in northern Oklahoma. Research conducted at several laboratories has demonstrated the suitability of Raman lidar for providing measurements that are an excellent match to those requirements. We have developed and installed a ruggedized Raman lidar system that resides permanently at the CART site, and that is computer automated to eliminate the requirements for operator interaction. In addition to the design goal of profiling water vapor through most of the troposphere during nighttime and through the boundary layer during daytime, the lidar provides quantitative characterizations of aerosols and clouds, including depolarization measurements for particle phase studies.

Goldsmith, J.E.M.; Blair, F.H.; Bisson, S.E.

1997-12-31

267

Cloud screening and quality control algorithm for star photometer data: assessment with lidar measurements and with all-sky images  

NASA Astrophysics Data System (ADS)

This paper presents the development and set up of a cloud screening and data quality control algorithm for a star photometer based on CCD camera as detector. These algorithms are necessary for passive remote sensing techniques to retrieve the columnar aerosol optical depth, ?Ae(?), and precipitable water vapor content, W, at nighttime. This cloud screening procedure consists of calculating moving averages of ?Ae(?) and W under different time-windows combined with a procedure for detecting outliers. Additionally, to avoid undesirable ?Ae(?) and W fluctuations caused by the atmospheric turbulence, the data are averaged on 30 min. The algorithm is applied to the star photometer deployed in the city of Granada (37.16° N, 3.60° W, 680 m a.s.l.; South-East of Spain) for the measurements acquired between March 2007 and September 2009. The algorithm is evaluated with correlative measurements registered by a lidar system and also with all-sky images obtained at the sunset and sunrise of the previous and following days. Promising results are obtained detecting cloud-affected data. Additionally, the cloud screening algorithm has been evaluated under different aerosol conditions including Saharan dust intrusion, biomass burning and pollution events.

Pérez-Ramírez, D.; Lyamani, H.; Olmo, F. J.; Whiteman, D. N.; Navas-Guzmán, F.; Alados-Arboledas, L.

2012-07-01

268

Cloud screening and quality control algorithm for star photometer data: assessment with lidar measurements and with all-sky-images  

NASA Astrophysics Data System (ADS)

This paper present the development and set up of a cloud screening and data quality control algorithm for a star photometer based on CCD camera as detector. This kind of algorithms is necessary for passive remote sensing techniques to retrieve the columnar aerosol optical depth, ?Ae(?), and precipitable water vapor content, W, at night-time. This cloud screening procedure consists of calculating moving averages of ?Ae(?) and W under different time-windows combined with a procedure for detecting outliers. Additionally, to avoid undesirable ?Ae(?) and W fluctuations caused by the atmospheric turbulence, the data are averaged on 30 min. The algorithm is applied to the star photometer deployed in the city of Granada (37.16° N, 3.60° W, 680 m a.s.l.; South-East of Spain) for the measurements acquired between March 2007 and September 2009. The algorithm is evaluated with correlative measurements registered by a lidar system and also with all-sky images obtained at the sunset and sunrise of the previous and following days. Promising results are obtained detecting cloud-affected data. Additionally, the cloud screening algorithm has been evaluated under different aerosol conditions including Saharan dust intrusion, biomass burning and pollution events.

Pérez-Ramírez, D.; Lyamani, H.; Olmo, F. J.; Whiteman, D. N.; Navas-Guzman, F.; Alados-Arboledas, L.

2012-02-01

269

Wide-angle imaging LIDAR (WAIL): a ground-based instrument for monitoring the thickness and density of optically thick clouds.  

SciTech Connect

Traditional lidar provides little information on dense clouds beyond the range to their base (ceilometry), due to their extreme opacity. At most optical wavelengths, however, laser photons are not absorbed but merely scattered out of the beam, and thus eventually escape the cloud via multiple scattering, producing distinctive extended space- and time-dependent patterns which are, in essence, the cloud's radiative Green functions. These Green functions, essentially 'movies' of the time evolution of the spatial distribution of escaping light, are the primary data products of a new type of lidar: Wide Angle Imaging Lidar (WAIL). WAIL data can be used to infer both optical depth and physical thickness of clouds, and hence the cloud liquid water content. The instrumental challenge is to accommodate a radiance field varying over many orders of magnitude and changing over widely varying time-scales. Our implementation uses a high-speed microchannel plate/crossed delay line imaging detector system with a 60-degree full-angle field of view, and a 532 nm doubled Nd:YAG laser. Nighttime field experiments testing various solutions to this problem show excellent agreement with diffusion theory, and retrievals yield plausible values for the optical and geometrical parameters of the observed cloud decks.

Love, Steven P.; Davis, A. B. (Anthony B.); Rohde, C. A. (Charles A.); Ho, Cheng,

2001-01-01

270

Detection of potentially hazardous convective clouds with a dual-polarized C-band radar  

NASA Astrophysics Data System (ADS)

A method for forecasting very short-term rainfall to detect potentially hazardous convective cloud that produces heavy local rainfall was developed using actual volumetric C-band polarimetric radar data. Because the rainfall estimation algorithm used in this method removed the effect of ice particles based on polarimetric measurements, it was immune to the high reflectivity associated with hail. The reliability of the algorithm was confirmed by comparing the rainfall rate estimated from the polarimetric radar measurements at the lowest elevation angle with that obtained from optical disdrometers on the ground. The rainfall rate estimated from polarimetric data agreed well with the results obtained from the disdrometers, and was much more reliable than results derived from reflectivity alone. Two small cumulus cells were analyzed, one of which developed and later produced heavy rainfall, whereas the other did not. Observations made by polarimetric radar with a volumetric scan revealed that a high vertical maximum intensity of rainfall rate and a vertical area of enhanced differential reflectivity extending above the freezing level, often termed a high ZDR column, were clearly formed about 10 min prior to the onset of heavy rainfall on the ground. The onset time of the heavy rainfall could be estimated in advance from the polarimetric data, which agreed fairly well with observations. These polarimetric characteristics were not observed for the cumulus cell that did not produce heavy rainfall. The results suggest that both the vertical maximum intensity of the rainfall rate and a high ZDR column, estimated from polarimetric measurements, can be used to identify potentially hazardous clouds. Furthermore, this study shows that polarimetric radar measurements with high spatial and temporal resolutions are invaluable for disaster reduction.

Adachi, A.; Kobayashi, T.; Yamauchi, H.; Onogi, S.

2013-10-01

271

Detection of potentially hazardous convective clouds with a dual-polarized C-band radar  

NASA Astrophysics Data System (ADS)

A method for forecasting very short-term rainfall to detect potentially hazardous convective cloud that produces heavy local rainfall was developed using actual volumetric C-band polarimetric radar data. Because the rainfall estimation algorithm used in this method removed the effect of ice particles based on polarimetric measurements, it was immune to the high reflectivity associated with hail. The reliability of the algorithm was confirmed by comparing the rainfall rate estimated from the polarimetric radar measurements at the lowest elevation angle with that obtained from an optical disdrometer on the ground. The rainfall rate estimated from polarimetric data agreed well with the results obtained from the disdrometer, and was much more reliable than results derived from reflectivity alone. Two small cumulus cells were analyzed, one of which developed and later produced heavy rainfall, whereas the other did not. Observations made by polarimetric radar with a volumetric scan revealed that a high vertical maximum intensity of rainfall rate and a vertical area of enhanced differential reflectivity extending above the freezing level, often termed a high ZDR column, were clearly formed about 10 min prior to the onset of heavy rainfall on the ground. The onset time of the heavy rainfall could be estimated in advance from the polarimetric data, which agreed fairly well with observations. These polarimetric characteristics were not observed for the cumulus cell that did not produce heavy rainfall. The results suggest that both the vertical maximum intensity of the rainfall rate and a high ZDR column, estimated from polarimetric measurements, can be used to identify potentially hazardous clouds. Furthermore, this study shows that polarimetric radar measurements with high spatial and temporal resolutions are invaluable for disaster reduction.

Adachi, A.; Kobayashi, T.; Yamauchi, H.; Onogi, S.

2013-04-01

272

Radar Analysis of Precipitation Initiation in Maritime versus Continental Clouds near the Florida Coast: Inferences Concerning the Role of CCN and Giant Nuclei  

Microsoft Academic Search

A method of analyzing radar data is developed and applied to determine whether the X-band radar reflectivity evolution of clouds observed during summertime on the northeast Florida coast during the Small Cumulus Microphysics Study (SCMS) shows distinct differences in precipitation development that can be associated with the clouds' maritime or continental characteristics. For this study, the entire National Center for

Sabine Göke; Harry T. Ochs; Robert M. Rauber

2007-01-01

273

Segmentation-based filtering and object-based feature extraction from airborne LiDAR point cloud data  

NASA Astrophysics Data System (ADS)

Three dimensional (3D) information about ground and above-ground features such as buildings and trees is important for many urban and environmental applications. Recent developments in Light Detection And Ranging (LiDAR) technology provide promising alternatives to conventional techniques for acquiring such information. The focus of this dissertation research is to effectively and efficiently filter massive airborne LiDAR point cloud data and to extract main above-ground features such as buildings and trees in the urban area. A novel segmentation algorithm for point cloud data, namely the 3D k mutual nearest neighborhood (kMNN) segmentation algorithm, was developed based on the improvement to the kMNN clustering algorithm by employing distances in 3D space to define mutual nearest neighborhoods. A set of optimization strategies, including dividing dataset into multiple blocks and small size grids, and using distance thresholds in x and y, were implemented to improve the efficiency of the segmentation algorithm. A segmentation based filtering method was then employed to filter the generated segments, which first generates segment boundaries using Voronoi polygon and dissolving operations, and then labels the segments as ground and above-ground based on their size and relative heights to the surrounding segments. An object-based feature extraction approach was also devised to extract buildings and trees from the above-ground segments based on object-level statistics derived, which were subject to a rule based classification system developed by either human experts or an inductive machine-learning algorithm. Case studies were conducted with four different LiDAR datasets to evaluate the effectiveness and efficiency of the proposed approaches. The proposed segmentation algorithm proved to be not only effective in separating ground and above-ground measurements into different segments, but also efficient in processing large datasets. The segmentation based filtering and object based feature extraction approaches have also demonstrated effectiveness in labeling the segments into ground and above-ground and in extracting buildings and trees from the above-ground segments. When incorporating spectral information from remote sensing imagery with the LiDAR data, the accuracy for feature extraction was further increased.

Chang, Jie

274

Observations of tornadoes and wall clouds with a portable FM-CW Doppler radar: 1989--1990 results  

SciTech Connect

The purpose of this paper is to report on our progress using a portable, 1 W,FM (frequency modulated)-CW (continuous wave) Doppler radar developed at the Los Alamos National Laboratory (LANL), to make measurements of the wind field in tornadoes and wall clouds along with simultaneous visual documentation. Results using a CW version of the radar in 1987--1988 are given in Bluestein and Unruh (1989). 18 refs., 2 figs., 1 tab.

Bluestein, H.B. (Oklahoma Univ., Norman, OK (USA). School of Meteorology); Unruh, W.P. (Los Alamos National Lab., NM (USA))

1990-01-01

275

Eto Lidar Studies of Cirrostratus Altocumulogenitus: Another Role for Supercooled Liquid Water in Cirrus Cloud Formation.  

National Technical Information Service (NTIS)

Cirrus clouds have traditionally been viewed as cold, wispy, or stratiform ice clouds, typically displaying optical phenomena such as haloes. A composition entirely of hexagonal ice crystals, of one habit or another could only have a transitory existence ...

K. Sassen

1990-01-01

276

Project Pre-Gondola I: Cloud Development Studies.  

National Technical Information Service (NTIS)

The clouds resulting from four 20-ton nitromethane cratering explosions in a wet clay shale medium were studied by photographic analysis and lidar (laser-radar) tracking. A technique for detecting tracers in future events in the same medium was investigat...

R. F. Rohrer W. C. Day

1967-01-01

277

Use of In Situ Data to Test a Raman Lidar-Based Cloud Condensation Nuclei Remote Sensing Method  

SciTech Connect

A method of retrieving vertical profiles of cloud condensation nuclei (CCN) concentration from surface measurements is proposed. Surface measurements of the CCN concentration are scaled by the ratio of the backscatter (or extinction) vertical profile to the backscatter (or extinction) at or near the surface. The backscatter (or extinction) profile is measured by Raman lidar, and is corrected to dry conditions using the vertical profile of relative humidity (also measured by Raman lidar) and surface measurements of the dependence of backscatter (or extinction) on relative humidity. The method assumes the surface aerosol size distribution and composition are representative of the vertical column. Aircraft measurements of aerosol size distribution are used to test the dependence of the retrieval on the uniformity of aerosol size distribution. The retrieval is found to be robust for supersaturations less than 0.02%, but breaks down at higher supersaturations if the vertical profile of aerosol size distribution differs markedly from the distribution at the surface. Such conditions can be detected from the extinction/backscatter ratio.

Ghan, Steven J.; Collins, Donald R.

2004-02-01

278

Lidar temperature measurements during the SOLVE campaign and the absence of polar stratospheric clouds from regions of very cold air  

NASA Astrophysics Data System (ADS)

NASA Goddard Space Flight Center's Airborne Raman Ozone, Temperature, and Aerosol Lidar (AROTEL) measured extremely cold temperatures during all three deployments (1-16 December 1999, 14-29 January 2000, and 27 February to 15 March 2000) of the SAGE III Ozone Loss and Validation Experiment (SOLVE). Temperatures were significantly below values observed in previous years with large regions regularly below 191 K and frequent temperature retrievals yielding values at or below 187 K. Temperatures well below the saturation point of type I polar stratospheric clouds (PSCs) were regularly encountered, but their presence was not well correlated with PSC observations made by NASA Langley Research Center's aerosol lidar colocated with AROTEL. Temperature measurements by meteorological sondes launched within areas traversed by the DC-8 showed minimum temperatures consistent in time and vertical extent with those derived from AROTEL data. Calculations to establish whether PSCs could exist at measured AROTEL temperatures and observed mixing ratios of nitric acid and water vapor showed large areas favorable to PSC formation but that were lacking PSCs. The flight on 12 December 1999 encountered large regions having temperatures up to 10 K below the NAT saturation temperature but only small, localized regions that might be identified as PSCs.

Burris, John; McGee, Thomas; Hoegy, Walt; Newman, Paul; Lait, Leslie; Twigg, Laurence; Sumnicht, Grant; Heaps, William; Hostetler, Chris; Neuber, Roland; Künzi, Klaus F.

2002-10-01

279

Behavior of decaying El Chichon cloud over Toyokawa, Japan (35 deg N) observed by 532-NM lidar  

NASA Astrophysics Data System (ADS)

The stratospheric aerosol state in 1982 and 1983 was in a violet excitation due to the eruption of Mt. El Chichon. A number of direct and indirect soundings of the stratosphere confirmed that the aftereffect of it covered almost the entire Northern Hemisphere by the end of 1982 (e.g., POLLACK et al., 1983). The lidar system constructed at Toyokawa (34.8 deg N, 137.4 deg E) have entered routine base observations since December 1982 (IWATA et al., 1983). The state of observations was 8 months after the eruption, and researchers missed monitoring the drastic variations in the stratosphere just following the event. However, the El Chichon cloud over Japan was reported to have reached the second maximum concentration in November or December 1982 according to the lidar observations at Tsukuba, Nagoya and Fukuoka, so the researchers' observations corresponded to the decaying phase of it. Presented are some characteristics of the aerosol profile over Toyokawa during a period of 20 months from December 1982 to July 1984.

Takagi, M.; Iwata, A.; Kondo, Y.

1985-12-01

280

Automated Detection of Geomorphic Features in LiDAR Point Clouds of Various Spatial Density  

Microsoft Academic Search

LiDAR, also referred to as laser scanning, has proved to be an important tool for topographic data acquisition. Terrestrial laser scanning allows for accurate (several millimeter) and high resolution (several centimeter) data acquisition at distances of up to some hundred meters. By contrast, airborne laser scanning allows for acquiring homogeneous data for large areas, albeit with lower accuracy (decimeter) and

Peter Dorninger; Balázs Székely; András. Zámolyi; Clemens Nothegger

2010-01-01

281

Documentation of cloud characteristics inferred from ground and satellite measurements within West Africa  

NASA Astrophysics Data System (ADS)

Clouds have a major impact on the redistribution of water within the atmosphere and on ground radiation budget. The occurrence of type of clouds in West Africa has only be little documented and quantified. The ARM mobile facility, including vertically pointing 94GHz Doppler radar, micropulse lidar, ceilometer and flux measurements, was implemented in April 2006 at Niamey (Niger), allowing to document for six entire months the characteristics of clouds. Independently, CloudSat and Calipso, launched in April 2006, sample clouds from above using the same instrumentation (Cloud Profiling Radar and CALIOP) passing over West Africa every day around 0200LT (night and day). A survey of cloud characteristics inferred from ground and satellite measurements is presented focusing on the seasonal evolution and the diurnal cycle of cloud occurrence. In particular, four types of clouds are distinguished: high-level clouds (cirrus or anvils), deep convective clouds, shallow convective clouds and mid-level clouds. This study highlights the frequent occurrence of these latter clouds located at the top of the Saharan Air Layer. High-level clouds are ubiquitous throughout the period whereas shallow convective clouds are mainly present during the core of the monsoon. A particular attention is given to possible instrumental bias as the same statistics may be retrieved independently from each instrument (lidar or radar) or by using the lidar-radar synergy. Combining information from ground and satellite platforms enables to tackle the question of the temporal representativeness of the latitudinal transect sampled twice a day by the satellite. On the other hand, satellite sampling provides the latitudinal variations of these characteristics and enables to place ARM local observations in a larger framework.

Couvreux, F.; Bouniol, D.; Kamsu-Tamo, P.-H.; Leplay, M.; Guichard, F.; 0'connor, E.

2009-09-01

282

An Integrated Approach toward Retrieving Physically Consistent Profiles of Temperature, Humidity, and Cloud Liquid Water  

Microsoft Academic Search

A method is presented for deriving physically consistent profiles of temperature, humidity, and cloud liquid water content. This approach combines a ground-based multichannel microwave radiometer, a cloud radar, a lidar-ceilometer, the nearest operational radiosonde measurement, and ground-level measurements of standard meteorological properties with statistics derived from results of a microphysical cloud model. All measurements are integrated within the framework of

Ulrich Löhnert; Susanne Crewell; Clemens Simmer

2004-01-01

283

Investigation of the vertical structure of clouds using coincident measurements from airborne W-band radar and C-band ground based radar during HyMex campaign in Central Italy  

NASA Astrophysics Data System (ADS)

Analysis methodologies involving simultaneous observations collected by remote sensing instruments with different acquisition characteristics, such as airborne- and ground-based weather radar measurements, offer an attractive chance of investigating the vertical structure of clouds and precipitation. During the first HyMeX Special Observing Period (SOP), running from 5 September till 6 November 2012, the ISAC-CNR Doppler polarimetric C-band radar Polar 55C located in Rome, provides volume observations of clouds and precipitation within a 120 km distance running specific scanning strategies to compare radar measurements with measurements collected by other precipitation measuring instruments located at selected sites within the Polar 55C coverage and to coincident measurements during instrumented flights. The Flacon-20 with cloud radar RASTA (multi beam W-band at 95 GHz) and microphysics sensors on board flew three times over Central Italy: on 15 October 2012 (IOP13), on 27 October 2012 (IOP16), on 31 October 2012 (IOP18). During the F20 flights, simultaneous Polar 55C radar measurements were performed: several volumes of PPI and different vertical sections (RHI scanning) intersected the F20 track. The aim of this work is to investigate microphysical characteristics of clouds analyzing combined observations from airborne W-band radar and ground C-band polarimetric Radar (5.6 GHz). The analysis of returns, recorded by the two radars from the bottom and from the top of clouds at different wavelength measurements and at different spatial resolution allows to identify some microphysical characteristics and the vertical structure of cloud systems (such as melting layer location and thickness, liquid water content, ice particle presence) in order to improve the understanding of formation and development processes of cloud systems. Furthermore, the polarimetric capability of the C-band radar allows discriminating the nature of the hydrometeors in vertical sections obtained by oversampled RHI measurements, while high resolution vertical W-band observations allow investigating the hydrometeor at top of cloud systems.

Roberto, Nicoletta; Baldini, Luca; Gorgucci, Eugenio; Adirosi, Elisa; Delanoë, Julien

2013-04-01

284

Investigation of polar stratospheric clouds in January 2008 by means of ground-based and spaceborne lidar measurements and microphysical box model simulations  

NASA Astrophysics Data System (ADS)

Polar stratospheric clouds (PSCs) play a key role in heterogeneous chemistry and ozone depletion in the lower stratosphere. The type of PSC as well as their temporal and spatial extent are important for the occurrence of heterogeneous reactions and, thus, ozone depletion. In this study a combination of ground-based and spaceborne lidar measurements were used together with microphysical box model simulations along back trajectories to investigate the formation and alteration of Arctic PSCs. The measurements were made by the Rayleigh/Mie/Raman lidar system at Esrange and by the Cloud-Aerosol Lidar with Orthogonal Polarization aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite. Between 20 and 23 January 2008 PSCs composed of liquid particles were observed by CALIPSO between Greenland and the western side of the Scandinavian Mountains. Between 21 and 23 January 2008 the Esrange lidar observed a PSC composed of distinct layers of liquid and solid particles on the eastern side of the mountain range. Microphysical box model simulations along air parcel back trajectories indicate that liquid particles had formed at least 40 h before the observation at Esrange. Furthermore, the model indicates a high HNO3 uptake into the liquid layer between 10 and 20 h before the observation. The PSC was formed when the air mass was over Greenland. On two occasions during these 20 h, CALIPSO observed PSCs when its measurement tracks crossed the air parcel back trajectory ending at the location of the Esrange lidar. Backscatter ratios calculated from the output of the box model simulation indicate good agreement with the values observed with the Esrange lidar and by CALIPSO. The box model simulations along the back trajectories from Esrange to the CALIPSO ground track and beyond provide us with the unique opportunity to relate ground-based and spaceborne lidar measurements that were not performed at the same spatial location and time. Furthermore, possible differences in the observations from ground and space can be traced to temporal and/or geographically induced changes in particle microphysics within the measured PSCs.

Achtert, P.; Khosrawi, F.; Blum, U.; Fricke, K. H.

2011-04-01

285

Evaluation of Passive Multilayer Cloud Detection Using Preliminary CloudSat and CALIPSO Cloud Profiles  

NASA Astrophysics Data System (ADS)

During the last few years, several algorithms have been developed to detect and retrieve multilayered clouds using passive satellite data. Assessing these techniques has been difficult due to the need for active sensors such as cloud radars and lidars that can "see" through different layers of clouds. Such sensors have been available only at a few surface sites and on aircraft during field programs. With the launch of the CALIPSO and CloudSat satellites on April 28, 2006, it is now possible to observe multilayered systems all over the globe using collocated cloud radar and lidar data. As part of the A- Train, these new active sensors are also matched in time ad space with passive measurements from the Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) and Advanced Microwave Scanning Radiometer - EOS (AMSR-E). The Clouds and the Earth's Radiant Energy System (CERES) has been developing and testing algorithms to detect ice-over-water overlapping cloud systems and to retrieve the cloud liquid path (LWP) and ice water path (IWP) for those systems. One technique uses a combination of the CERES cloud retrieval algorithm applied to MODIS data and a microwave retrieval method applied to AMSR-E data. The combination of a CO2-slicing cloud retireval technique with the CERES algorithms applied to MODIS data (Chang et al., 2005) is used to detect and analyze such overlapped systems that contain thin ice clouds. A third technique uses brightness temperature differences and the CERES algorithms to detect similar overlapped methods. This paper uses preliminary CloudSat and CALIPSO data to begin a global scale assessment of these different methods. The long-term goals are to assess and refine the algorithms to aid the development of an optimal combination of the techniques to better monitor ice 9and liquid water clouds in overlapped conditions.

Minnis, P.; Sun-Mack, S.; Chang, F.; Huang, J.; Nguyen, L.; Ayers, J. K.; Spangenberg, D. A.; Yi, Y.; Trepte, C. R.

2005-05-01

286

Evaluation of Passive Multilayer Cloud Detection Using Preliminary CloudSat and CALIPSO Cloud Profiles  

NASA Astrophysics Data System (ADS)

During the last few years, several algorithms have been developed to detect and retrieve multilayered clouds using passive satellite data. Assessing these techniques has been difficult due to the need for active sensors such as cloud radars and lidars that can "see" through different layers of clouds. Such sensors have been available only at a few surface sites and on aircraft during field programs. With the launch of the CALIPSO and CloudSat satellites on April 28, 2006, it is now possible to observe multilayered systems all over the globe using collocated cloud radar and lidar data. As part of the A- Train, these new active sensors are also matched in time ad space with passive measurements from the Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) and Advanced Microwave Scanning Radiometer - EOS (AMSR-E). The Clouds and the Earth's Radiant Energy System (CERES) has been developing and testing algorithms to detect ice-over-water overlapping cloud systems and to retrieve the cloud liquid path (LWP) and ice water path (IWP) for those systems. One technique uses a combination of the CERES cloud retrieval algorithm applied to MODIS data and a microwave retrieval method applied to AMSR-E data. The combination of a CO2-slicing cloud retireval technique with the CERES algorithms applied to MODIS data (Chang et al., 2005) is used to detect and analyze such overlapped systems that contain thin ice clouds. A third technique uses brightness temperature differences and the CERES algorithms to detect similar overlapped methods. This paper uses preliminary CloudSat and CALIPSO data to begin a global scale assessment of these different methods. The long-term goals are to assess and refine the algorithms to aid the development of an optimal combination of the techniques to better monitor ice 9and liquid water clouds in overlapped conditions.

Minnis, P.; Sun-Mack, S.; Chang, F.; Huang, J.; Nguyen, L.; Ayers, J. K.; Spangenberg, D. A.; Yi, Y.; Trepte, C. R.

2006-12-01

287

Using multi-frequency radar and discrete-return LiDAR measurements to estimate above-ground biomass and biomass components in a coastal temperate forest  

NASA Astrophysics Data System (ADS)

Height measurements from small-footprint discrete-return LiDAR and backscatter coefficients from C- and L-band radar were used independently and in combination to estimate above-ground component and total biomass for a coniferous temperate forest, located on Vancouver Island, British Columbia, Canada. Reference biomass data were obtained from plot-level data and used for comparison against the LiDAR and radar-based biomass models. For the LiDAR-only model, height metrics such as mean first return height and percentiles (e.g., 10th and 90th) of first returns correlated best to total above-ground and stem biomass. While percent of first returns above 2 m and percentiles (75th and 90th) of first returns height metrics correlated best to crown biomass. A comparison between above-ground components and total biomass indicate that stem biomass displayed the highest relationship with the LiDAR measurements while crown biomass showed the lowest relationship with relative root mean squared error ranging from 16% to 22%, respectively. Alternatively, the radar-only models indicated that for C-band radar, a combination of HH and VV backscatter demonstrated the most significant correlation with forest biomass compared to coherence based models with a relative root mean squared error of 53%. For L-band radar, a combination of HH and HV backscatter showed the most significant correlation compared to coherence based models with a relative root mean squared error of 44%. Exploring a mixture of C- and L-band backscatter and coherence based models revealed that a combination of C-HV and L-HV coherence magnitudes provided the best radar relationship with forest biomass with a relative root mean squared error of 35%. Also for all radar-based models, L- and C-band backscatter and coherence magnitudes were poorly correlated with individual biomass components when compared to total above-ground biomass. The addition of C- and L-band backscatter and coherence variables to the LiDAR-only biomass model was also investigated. The results showed that the integration of C-band HH backscatter to the LiDAR-only model significantly improved the relationship with forest biomass by explaining an additional 8.9% and 6.5% of the variability in total aboveground and stem biomass respectively, while C-band polarimetric entropy explained an additional 17.9% of the variability in crown biomass. Improvements in the relative root mean squared errors were also observed ranging from 7.1% to 11.7%. The study suggests that for a temperate forest dominated by coniferous stands, the addition of C-band radar variables to a best LiDAR-only linear model provides improved estimates of above-ground component and total biomass.

Tsui, Olivier W.; Coops, Nicholas C.; Wulder, Michael A.; Marshall, Peter L.; McCardle, Adrian

2012-04-01

288

Multi-wavelength Raman lidar observations of the Eyjafjallajökull volcanic cloud over Potenza, southern Italy  

NASA Astrophysics Data System (ADS)

During the eruption of Eyjafjallajökull in April-May 2010 multi-wavelength Raman lidar measurements were performed at the CNR-IMAA Atmospheric Observatory (CIAO), whenever weather conditions permitted observations. A methodology both for volcanic layer identification and accurate aerosol typing has been developed. This methodology relies on the multi-wavelength Raman lidar measurements and the support of long-term lidar measurements performed at CIAO since 2000. The aerosol mask for lidar measurements performed at CIAO during the 2010 Eyjafjallajökull eruption has been obtained. Volcanic aerosol layers were observed in different periods: 19-22 April, 27-29 April, 8-9 May, 13-14 May and 18-19 May. A maximum aerosol optical depth of about 0.12-0.13 was observed on 20 April, 22:00 UTC and 13 May, 20:30 UTC. Volcanic particles were detected at low altitudes, in the free troposphere and in the upper troposphere. Occurrences of volcanic particles within the PBL were detected on 21-22 April and 13 May. A Saharan dust event was observed on 13-14 May: dust and volcanic particles were simultaneously detected at CIAO at separated different altitudes as well as mixed within the same layer. Lidar ratios at 355 and 532 nm, the Ångström exponent at 355/532 nm, the backscatter-related Ångström exponent at 532/1064 nm and the particle linear depolarization ratio at 532 nm measured inside the detected volcanic layers are discussed. The dependence of these quantities on relative humidity has been investigated by using co-located microwave profiler measurements. The measured values of these intensive parameters indicate the presence of volcanic sulfates/continental mixed aerosol in the volcanic aerosol layers observed at CIAO. In correspondence of the maxima observed in the volcanic aerosol load on 19-20 April and 13 May, different values of intensive parameters were observed. Apart from the occurrence of sulfate aerosol, these values indicate also the presence of some ash which is affected by the aging during transport over Europe.

Mona, L.; Amodeo, A.; D'Amico, G.; Giunta, A.; Madonna, F.; Pappalardo, G.

2012-02-01

289

Ice clouds microphysical retrieval using 94-GHz Doppler radar observations: Basic relations within the retrieval framework  

NASA Astrophysics Data System (ADS)

High quality measurements of ice cloud properties from ground- and space-based sensors are key for improving our understanding of processes that affect ice cloud radiative effects and lifetime. Doppler cloud radars provide two independent measurements (reflectivity and Doppler velocity) to constrain the ice clouds microphysical retrievals. However, the retrievals are highly sensitive to the choice of the scattering forward model for non-spherical particles at millimeter-wavelengths and the selection of parameters in the mass- and velocity-size relationships, as well as to the representation of the particle size distribution (PSD). In this paper (part 1), the development of the basic relations used in the retrieval is presented. A novel approach for reducing the number of free parameters required to describe the microphysical properties of ice particles is described. The new proposed form of the mass-size relationship significantly reduces the sensitivity of the quantities of interest to the power law mass exponent, leaving only one parameter controlling mass dimensional relationship. A similar approach is adopted in the velocity calculation. In order to reduce the retrieval's dependence on the size distribution, the PSD defined for liquid-equivalent diameter is described using the concept of double moment normalization. The two normalizing quantities, mean mass-weighted diameter (Dm) and ice water content (IWC) are controlled mainly by the PSD size interval that is also an important contributor to the two Doppler observables. Both Dm and IWC are generally not very sensitive to the PSD segments of the smallest and largest particles that are considered as very uncertain.

Szyrmer, Wanda; Tatarevic, Aleksandra; Kollias, Pavlos

2012-07-01

290

Tropical cirrus clouds near cold point tropopause under ice supersaturated conditions observed by lidar and balloon-borne cryogenic frost point hygrometer  

Microsoft Academic Search

Simultaneous vertical profiles of cirrus cloud backscattering and frost point temperature were obtained for the first time in the tropopause region over Bandung, Indonesia, (6.9°S, 107.6°E). These profiles were measured by ground-based lidar and by balloon-borne Cryogenic Frost point Hygrometer (CFH) sondes. Supersaturation up to several ten percent was observed by the CFH just below the cold point tropopause at

Takashi Shibata; Holger Vömel; Saipul Hamdi; Sri Kaloka; Fumio Hasebe; Masatomo Fujiwara; Masato Shiotani

2007-01-01

291

Aerosol vertical distribution in dust outflow over the Atlantic: Comparisons between GEOS-Chem and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO)  

Microsoft Academic Search

Vertically resolved attenuated backscatter from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission and aerosol optical thickness (AOT) from the Moderate-resolution Imaging Spectroradiometer (MODIS) are used to characterize the Saharan dust outflow over the Atlantic and to evaluate results from a global chemical and transport model (GEOS-Chem). We first document two events of dust plume transport from the

Sylvia Generoso; Isabelle Bey; Mathieu Labonne; François-Marie Bréon

2008-01-01

292

Evaluation of cloud microphysics schemes in simulations of a winter storm using radar and radiometer measurements  

NASA Astrophysics Data System (ADS)

observations from a space-borne radiometer and a ground-based precipitation profiling radar, the impact of cloud microphysics schemes in the WRF model on the simulation of microwave brightness temperature (Tb), radar reflectivity, and Doppler velocity (Vdop) is studied for a winter storm in California. The unique assumptions of particles size distributions, number concentrations, shapes, and fall speeds in different microphysics schemes are implemented into a satellite simulator and customized calculations for the radar are performed to ensure consistent representation of precipitation properties between the microphysics schemes and the radiative transfer models.Simulations with four different schemes in the WRF model, including the Goddard scheme (GSFC), the WRF single-moment 6-class scheme (WSM6), the Thompson scheme (THOM), and the Morrison double-moment scheme (MORR), are compared directly with measurements from the sensors. Results show large variations in the simulated radiative properties. General biases of ~20 K or larger are found in (polarization-corrected) Tb, which is linked to an overestimate of the precipitating ice aloft. The simulated reflectivity with THOM appears to agree well with the observations, while high biases of ~5-10 dBZ are found in GSFC, WSM6 and MORR. Peak reflectivity in MORR exceeds other schemes. These biases are attributable to the snow intercept parameters or the snow number concentrations. Simulated Vdop values based on GSFC agree with the observations well, while other schemes appear to have a ~1 m s-1 high bias in the ice layer. In the rain layer, the model representations of Doppler velocity vary at different sites.

Han, Mei; Braun, Scott A.; Matsui, Toshihisa; Williams, Christopher R.

2013-02-01

293

Lidar observations of the El Chichon dust cloud at 23 deg S  

NASA Astrophysics Data System (ADS)

Lidar observations of the stratospheric aerosol scattering at Sao Josedos Campos (23 deg S, 46 deg W) show a very large increase in the stratospheric aerosol burden to have occurred in mid-1982. Peak scattering ratios greater than 5 have been observed, as compared with pre-enhancement values between 1.1 and 1.2, representing an increase by more than an order of magnitude in particulate scattering. It is concluded that the main source of the dust was the eruption of El Chichon in Mexico in late March and early April of 1982.

Clemesha, B. R.; Simonich, D. M.

1983-04-01

294

Size distribution time series of a polar stratospheric cloud observed above Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) (69°N) and analyzed from multiwavelength lidar measurements during winter 2005  

NASA Astrophysics Data System (ADS)

A case study of a polar stratospheric cloud (PSC) is described using multiwavelength (355, 532, and 1064 nm) lidar measurements performed at the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) on 6 December 2005. Rotational Raman signals at 529 and 530 nm are used to derive a temperature field within the cloud using the rotational Raman technique (RRT). The PSC size distributions are retrieved between 1500 and 2000 UTC through a combination of statistical filtering and best match approaches. Several PSC types were detected between 22 and 26 km during the measurement session. Liquid ternary aerosols are identified before about 1600 and after 1900 UTC typically; their averaged retrieved size distribution parameters and associated errors at the backscatter peak are: No ? 1-10 cm-3 (50%), rm ? 0.15 ?m (20%), and ? ? 1.2 (15%). A mode of much larger particles is detected between 1600 and 1900 UTC (No ? 0.04 cm-3 (30%), rm ? 1.50 ?m (15%), and ? ? 1.37 (10%). The different PSC types are also identified using standard semiempirical classifications, based on lidar backscatter, temperature, and depolarization. Overall, the characteristics of the retrieved size distributions are consistent with these classifications. They all suggest that these very large particles are certainly nitric acid trihydrate that could have been generated by the strong gravity wave activity visible in the temperature profiles. The results demonstrate that multiwavelength lidar data coupled to both RRT temperatures and our size distribution retrieval can provide useful additional information for identification of PSC types and for direct comparisons with microphysical model simulations.

Jumelet, Julien; Bekki, Slimane; David, Christine; Keckhut, Philippe; Baumgarten, Gerd

2009-01-01

295

Lidar calibration  

NASA Astrophysics Data System (ADS)

Owing to its inherent low gain detection of the 1064nm channel and a negligible molecular return from the atmosphere, a boundary condition for the retrieval of optical data by inversion cannot be assumed with high confidence as for the other channels in the multiwavelength Mie lidar. It is therefore necessary to evaluate the calibration constant for the 1064nm channel. Two methods of calibration are studied and compared. One method is calibration by high or low clouds. The other method is calibration by a ceilometer which is itself calibrated and co-located at the lidar site. The results are compared with the aerosol optical depth measured by a calibrated sun photometer co-located at the same site as part of the AERONET network at CCNY. In the latter method, all three instruments are located at the same site, there is no issue of atmospheric differences when comparing data but it makes calibration dependent on that of other instruments. Clouds are a natural and frequent occurrence but the lidar system may change between cloud appearances. Both methods have their merits and shortcomings.

Chaw, Shuki

296

Evaluation of cloud microphysics simulated by a meso-scale model coupled with a bin-based scheme using observation data by W-band radar  

Microsoft Academic Search

Radar reflectivity factors measured by W-band radars were directly compared with the corresponding values calculated from a three-dimensional non-hydrostatic meso-scale model coupled with a bin-based cloud microphysical scheme. Three case studies are studied: one targets a part of shipborne observation using 95 GHz Doppler radar over the Pacific Ocean near Japan in May 2001; other two aim at two short

T. Iguchi; N. Teruyuki; A. Khain; K. Saito; T. Takemura; H. Okamoto; T. Nishizawa; W. Tao

2009-01-01

297

Automatic forest canopy removal algorithm for underneath obscure target detection by airborne lidar point cloud data  

NASA Astrophysics Data System (ADS)

The thermal imaging cameras can see the heat signature of people, boats, and vehicles in total darkness as well as through smoke, haze, and light fog, but not through the forest canopy. This study develops a novel algorithm to help detecting obscure targets underneath forest canopy and mitigate the vegetation problem for those bare ground point extraction filters as well. By examining our automatically processed results with actual LiDAR data, the forest canopy is successfully removed where all obscure vehicles or buildings underneath canopy can now be easily seen. Besides, the occluded rate of forest canopy and the detailed underneath x-y point distribution can be easily obtained accordingly. This will be very useful for predicting the performance of occluded target detection with respect to various object locations.

Chang, Li-Der; Slatton, K. Clint; Anand, Vivek; Liu, Pang-Wei; Lee, Heezin; Campbell, Michael V.

2010-04-01

298

Depolarization ratio of polar stratospheric clouds in coastal Antarctica: comparison analysis between ground-based Micro Pulse Lidar and space-borne CALIOP observations  

NASA Astrophysics Data System (ADS)

Polar stratospheric clouds (PSCs) play an important role in polar ozone depletion, since they are involved in diverse ozone destruction processes (chlorine activation, denitrification). The degree of that ozone reduction is depending on the type of PSCs, and hence on their occurrence. Therefore PSC characterization, mainly focused on PSC-type discrimination, is widely demanded. The backscattering (R) and volume linear depolarization (?V) ratios are the parameters usually used in lidar measurements for PSC detection and identification. In this work, an improved version of the standard NASA/Micro Pulse Lidar (MPL-4), which includes a built-in depolarization detection module, has been used for PSC observations above the coastal Antarctic Belgrano II station (Argentina, 77.9° S 34.6° W, 256 m a.s.l.) since 2009. Examination of the MPL-4 ?V feature as a suitable index for PSC-type discrimination is based on the analysis of the two-channel data, i.e., the parallel (p-) and perpendicular (s-) polarized MPL signals. This study focuses on the comparison of coincident ?V-profiles as obtained from ground-based MPL-4 measurements during three Antarctic winters with those reported from the space-borne lidar CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) aboard the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) satellite in the same period (83 simultaneous cases are analysed for 2009-2011 austral winter times). Three different approaches are considered for the comparison analysis between both lidar profile data sets in order to test the degree of agreement: the correlation coefficient (CC), as a measure of the relationship between both PSC vertical structures; the mean differences together with their root mean square (RMS) values found between data sets; and the percentage differences (BIAS), parameter also used in profiling comparisons between CALIOP and other ground-based lidar systems. All of them are examined as a function of the CALIPSO ground-track distance from the Belgrano II station. Results represent a relatively good agreement between both ground-based MPL-4 and space-borne CALIOP profiles of the volume linear depolarization ratio ?V for PSC events, once the MPL-4 depolarization calibration parameters are applied. Discrepancies between CALIOP and MPL-4 profiles in vertical layering structure are enhanced from 20 km up, likely due to a decrease of the signal-to-noise ratio (SNR) for both lidar systems at those altitudes. Regarding the results obtained from the mean and the percentage differences found between MPL-4 and CALIOP ?V profiles, a predominance of negative values is also observed, indicating a generalized underestimation of the MPL-4 depolarization as compared to that reported by CALIOP. However, absolute differences between those ?V-profile data sets are no higher than a 10 ± 11% in average. Moreover, the degree of agreement between both lidar ?V data sets is slightly dependent on the CALIPSO ground-track overpass distance from the Belgrano II station. That is, small discrepancies are found when CALIPSO ground-track distance is as close as far from the ground-based station. These results would indicate that MPL-4 depolarization observations would reflect relatively well the PSC field that CALIOP can detect at relatively large distances from the ground-based station. As a consequence, PSC properties can be statistically similar, on average, over large volumes, and hence the present weak disagreement found between both the lidar ?V data sets can be likely dominated by small spatial PSC inhomogeneities along the CALIPSO separation from the station. This statement is based on the fact that Belgrano II is a station located well inside the stable Antarctic polar vortex, allowing determined thermodynamic conditions leading to a very low variability in the PSC field, and in their properties.

Córdoba-Jabonero, C.; Guerrero-Rascado, J. L.; Toledo, D.; Parrondo, M.; Yela, M.; Gil, M.; Ochoa, H. A.

2013-03-01

299

Observations on Stratospheric-Mesospheric-Thermospheric temperatures using Indian MST radar and co-located LIDAR during Leonid Meteor Shower (LMS)  

NASA Astrophysics Data System (ADS)

The temporal and height statistics of the occurrence of meteor trails during the Leonid meteor shower revealed the capability of the Indian MST radar to record large numbers of meteor trails. The distribution of radio meteor trails due to a Leonid meteor shower in space and time provided a unique opportunity to construct the height profiles of lower thermospheric temperatures and winds, with good time and height resolution. There was a four-fold increase in the meteor trails observed during the LMS compared to a typical non-shower day. The temperatures were found to be in excellent continuity with the temperature profiles below the radio meteor region derived from the co-located Nd-Yag LIDAR and the maximum height of the temperature profile was extended from the LIDAR to ~110 km. There are, how-ever, some significant differences between the observed profiles and the CIRA-86 model profiles. The first results on the meteor statistics and neutral temperature are presented and discussed below.

Selvamurugan, R.; Devasia, C. V.; Jain, A. R.; Raghava Reddi, C.; Rao, P. B.; Sridharan, R.

2002-11-01

300

An Evaluation of the Observational Capabilities of A Scanning 95-GHz Radar in Studying the 3D Structures of Marine Stratocumulus Clouds  

NASA Astrophysics Data System (ADS)

Marine stratocumulus clouds play a critical role in Earth's radiative balance primarily due to the role of their high albedo reflecting incoming solar radiation, causing a cooling effect, while weakly reflecting outgoing infrared radiation. Characterization of the 3-Dimensional (3D) structure of these cloud systems over scales of 20-40 km is required to accurately account for the role of cloud inhomogeneity and structure on their shortwave forcing and lifetime, which has important applications for Global Climate Models. For first time, such 3D measurements in clouds were made available from a scanning cloud radar during the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program's Clouds, Aerosol, and Precipitation in the Marine Boundary Layer (CAP-MBL) field campaign in the Azores Islands. The scanning radar observations were complemented by a suite of zenith-pointing active and passive remote sensors that were deployed to provide a detailed description of marine stratus over a long-term observation period in the ideal marine environment commonly found at the Azores. The scanning cloud radar observations present a shift from a multi-instrument, vertically pointing 'soda-straw' observation technique to a radar-only, 'radar-centric' observation technique. The scanning radar observations were gridded using a nearest-neighbor type scheme devised to take the natural variability of the observed field into account. The ability of the scheme to capture primary cloud properties (cloud fraction, cloud boundaries, drizzle detection) was assessed using measurements from the vertically pointing sensors. Despite the great sensitivity of the scanning cloud radar (-42.5 dBZ at 1 km range), the drop in sensitivity with range resulted in an artificial thinning of clouds with range from the radar. Drizzle-free cloud structures were undetectable beyond 5 km from the radar. Cloud fields containing drizzle were generally detectable to ranges exceeding 10 km from the radar. Well-defined streaking patterns in the drizzle field (reflectivity greater than -15 dBZ) at cloud base were concluded to be concomitant with the formation of boundary layer rolls. Sounding data for these well-defined (unbroken) rolls revealed a mean sub-cloud layer wind exceeding 3.9 ms -1, sub-cloud layer shear exceeding 7.5 x 10-3 s-1, and a majority of streaks oriented within 20° of the mean sub-cloud layer wind, satisfying many boundary layer roll criteria proposed in past studies. Attempts to reconstruct the 3D cloud liquid water content and 2D column liquid water path across the scanning radar domain using Z (Reflectivity) vs. LWC (Liquid Water Content) regressions trained using the zenith measurements were proved ineffective due to the overall extent of drizzle at Graciosa, and errors associated with sensitivity loss at range. Despite some difficulties, the SWACR satisfied ARM metrics for success by proving effective at detecting weak clouds for extended time periods across a 10 km plane, and drizzle across a 20 km range, at high spatial resolutions. Difficulties in resolving accurate vertical velocity patterns also suggest the need for an adaptive sampling strategy to most effectively remove horizontal wind components.

Bowley, Kevin

301

Development of retrieval algorithms for the EarthCARE lidar using the EarthCARE simulator  

NASA Astrophysics Data System (ADS)

The Earth Clouds, Aerosol and Radiation Explorer (EarthCARE) is a combined ESA/JAXA mission to be flown in 2013. EarthCARE will study the spatial distribution of clouds and aerosols and their effects on radiation by combining active (Doppler radar, HSRL lidar) and passive sensors (multispectral imager, broadband radiometer). The aims of the EarthCARE mission will be pursued exploiting various synergies from combining two or more of the instruments (lidar+radar, lidar+msi or lidar+radar+msi). In this work two algorithms for the EarthCARE lidar are described, one for retrieving the feature mask and one for the extinction and Backscatter retrieval. Both algorithms have been integrated with the EarthCARE simulator (ECSIM) for testing and validation of the retrievals with synthetic data. The use of ECSIM has greatly facilitated the development and testing these two algorithms by providing “realistic” instrument data data sets with a know “truth” to compare with. The feature mask identifies 'significant return' in the lidar signal. As the signal strength of aerosol or very optically thin ice clouds on the single shot grid can be comparable to the noise levels it was chosen to rely on image reconstruction techniques and not on signal to noise ratios and thresholds. This type of algorithm ensures the derivation of a feature mask on the single shot resolution enabling both the use of variable masks, e.g. use only those profiles which are sure to have no clouds to derive the mean aerosol signals, and calculation of feature fractions which can result in a better determination of higher order products like extinction, backscatter and depolarization. Next to the ECSIM scenes the algorithm has been tested with Calipso data. The Rayleigh signal from a High-Spectral Resolution Lidar (HSRL) can be used to estimate the extinction profile in a rather direct manner by estimating the derivative of the range-corrected logarithmic signal. However, the applicability of this method is limited due to the high SNR required. In contrast, extinction information can also be extracted from the Mie signal channel which, in general, may be viewed as less accurate (since factors such as the extinction-to-backscatter ratio must be assumed) but more precise (since the sensitivity to the SNR ratio of the input data is much lower). To optimally use both signals and SNR ratio constraints an optimal-estimation based variational approach has been developed for the retrieval of lidar extinction and backscatter from HSRL lidar data. In this presentation, the algorithms will be described with an emphasis on the role ECSIM has played in the development process.

van Zadelhoff, G.; Donovan, D. P.

2009-12-01

302

Origin of Ice in Supercooled layer clouds influenced by lower level convection: In-situ and remote sensing measurements from a case study  

Microsoft Academic Search

The UK BAe146 atmospheric research aircraft flew in the vicinity of the Chilbolton Observatory in Southern England as part of the NERC APPRAISE-Clouds project. In-situ cloud microphysics were measured onboard the BAe146 whilst cloud properties were simultaneously measured using Radar and Lidar from Chilbolton. A flight took place on the 18th February 2009 when a stationary front was located over

Keith Bower; Thomas Choularton; Jonathan Crosier

2010-01-01

303

Impact of Gravity Wave events on the properties of Polar Stratospheric Clouds over Antarctica from spaceborne lidar observations  

NASA Astrophysics Data System (ADS)

The formation and properties of Polar Stratospheric Clouds (PSCs) are extremely dependent on their formation temperature. Depending on the stratospheric concentrations of chemical species, various temperature thresholds define PSC composition: Nitric Acid Trihydrate (NAT) or Sulfuric Ternary Solutions (STS) particles, ice crystals, or a mixture thereof. Most notably, ice-based PSCs (Type II in lidar observation terminology) require colder temperatures than NAT- or STS-based PSCs (Type Ia and Ib). On the other hand, ice-based PSC form in a relatively short time, while other PSCs require temperature to stay below their formation threshold for a much longer period (days or weeks). During the Antarctic winter, stratospheric temperatures are generally in a range conducive to the formation of Type Ia and Ib PSCs, even if their dominant nucleation mechanisms are still not well understood. Type II PSCs are rarer overall, as temperatures cold enough for their formation is less frequent. This description based on temperature is generally considered sufficient to explain the spatial and temporal distribution of PSCs. A recent theory however suggests that ice-based PSCs might play a more substantial role in the formation of NAT- and STS-based PSCs. According to the mountain-wave seeding hypothesis, ice-based PSCs form quickly following intense temperature drops due to gravity wave events propagating in the mid-stratosphere ; melting ice crystals exiting the gravity wave region then act as the basis for fast NAT nucleation. NAT particles are then widely disseminated around the Antarctic continent by the strong winds of the polar vortex. We aim to study the validity of this hypothesis by evaluating the impact of gravity wave events on the population of PSCs. PSC observations will be presented from the spaceborne lidar CALIOP, which is able to identify PSC altitude and composition with high accuracy. These observations will be correlated with high-resolution mesoscale simulations over the Antarctic peninsula and extensive time periods to detect gravity wave events and evaluate their importance on PSC properties over the course of a full PSC season.

Noel, V.; Chepfer, H.; Hertzog, A.

2010-12-01

304

Comparison of CERES-MODIS and CloudSat/CALIPSO cloud properties with DOE ARM AMF measurements at Shouxian, China  

NASA Astrophysics Data System (ADS)

Cloud properties derived from both the CERES-MODIS SSF Ed-2B products and CloudSat/CALIPSO level 2B products have been compared with Department of Energy, Atmospheric Radiation Measurements Mobile Facility (DOE AMF) measurements taken at the Shouxian site (32.55N, 116.78E), China during the period Oct. 15-Dec. 15 of 2008. The AMF data, such as cloud base/top heights and liquid water path are averaged over a 1-h interval centered at the time of each satellite overpass, and the CERES-MODIS and CloudSat/CALIPSO cloud properties are averaged within a 1x1 degree grid box centered at the Shouxian site. A total of 41 satellite overpasses have been selected for this study. The preliminary results show that most of the cloud effective heights derived from CERES-MODIS agree very well with the ARM cloud radar-lidar observations. However, some discrepancies in cloud LWP exist between MODIS and ARM AMF observations. For CERES-MODIS data, the median and mean of cloud effective heights are 6.6 and 6.9 km, respectively. The median and mean of cloud-base height observed by AMF cloud radar are 4.4 and 4.1 km, they are 8.5 and 7.9 km for cloud-top height. During the ARM AMF deployment, four cloud systems have been observed by both surface and satellite and used to improve our understanding to the cloud formation, growth, and dissipation process. For the observed four cloud systems, we will investigate the effect of CCN loading on the different stage of cloud process, and/or show how the satellite observations can improve our knowledge of the evolving process of clouds. The vertical profiles of cloud properties observed by both CloudSat/CALIPSO and ARM cloud radar are also compared where the peak reflectivity heights measured by CloudSat/CALIPSO are ~ 0.5 km lower than that measured by the ARM radar/lidar for both high level clouds and low level clouds.

Qiu, Y.; Dong, X.; Xi, B.; Minnis, P.

2010-12-01

305

Depolarization ratio of Polar Stratospheric Clouds in coastal Antarctica: profiling comparison analysis between a ground-based Micro Pulse Lidar and the space-borne CALIOP  

NASA Astrophysics Data System (ADS)

Polar Stratospheric Clouds (PSCs) play an important role in polar ozone depletion. In particular ice clouds, type PSC-II, with respect to the type PSC-I (nitric acid clouds) produce the most significant effects. Therefore PSC characterization, mainly focused on PSC-II discrimination is needed. The backscattering (R) and volume linear depolarization (?V) ratios are the parameters usually used in lidar measurements for PSC detection and identification. In this work, an improved version of the standard NASA/Micro Pulse Lidar (MPL-4), which includes a built-in depolarization detection module, has been used for PSC observations above the coastal Antarctic Belgrano II station (Argentina, 77.9° S 34.6° W, 256 m a.s.l.) since 2009. Examination of the MPL-4 ?V feature as a suitable index for PSC-type discrimination is based on the analysis of the two-channel data, i.e. the parallel (p-) and perpendicular (s-) polarized MPL signals. This study focuses on the comparison of simultaneous ?V-profiles as obtained from ground-based MPL-4 measurements during three Antarctic winters with those reported from the space-borne lidar CALIOP aboard the CALIPSO satellite in the same period (48 simultaneous cases are analysed for 2009-2011 austral winter times). Two different variables are considered for the comparison analysis between both lidar datasets in order to test the degree of agreement: the correlation coefficient (CC) and the percentage difference (BIAS). Results indicate a relatively good correlation between the ?V-profiles once MPL-4 depolarization calibration parameters are applied. This correlation is based on the linear fitted height-range of the layered structure, obtaining CC values higher than 0.5 for 54% (26 cases) out of all the analysed cases (48 in total). However, less satisfactory results are found when the BIAS test is used in the comparison procedure to test the degree of agreement between the lidar datasets. A predominance of negative BIAS values are observed showing that the MPL-4 ?V values are underestimated with respect to CALIOP data; however, differences between the MPL-4 datasets are no greater than an 11% (absolute value) with respect to CALIOP values. Moreover, the agreement appears to be unexpectedly independent of the CALIPSO ground-track overpass distance from the Belgrano II station. Consequently, differences between the ?V datasets are not dominated by spatial inhomogeneity of the PSC field.

Córdoba-Jabonero, C.; Guerrero-Rascado, J. L.; Toledo, D.; Parrondo, M.; Yela, M.; Gil, M.; Ochoa, H. A.

2012-10-01

306

On the camparability of cloud fractions derived from whole sky imager and ceilometer data  

SciTech Connect

The Atmospheric Radiation Measurement (ARM) Program`s most heavily instrumented site is its central facility in Lamont, OK. With respect to cloud observations, the instrumentation included a whole sky imager, ceilometers, lidar, millimeter cloud radar, microwave profilers, and radiosondes. Data from three of these instrument--the Whole Sky Imager (WSI), Belfort Laser Ceilometer (BLC) and Micropulse Lidar (MPL)-- are used in this study primarily to investigate the utility of using ceilometers, now strategically emplaced at four additional locations along the perimeter of the site.

Rodriguez, D.

1998-01-30

307

Multi-beam radar observations of polar mesosphere summer echoes during the MIDAS/DROPPS/MiniDUSTY campaign at Andenes, Norway in July 1999  

NASA Astrophysics Data System (ADS)

The dynamical and physical parameters of polar mesosphere summer echoes (PMSE) and noctilucent clouds (NLC) have been studied using co-ordinated rocket, radar, and lidar experiments (ALWIN MST radar, ALOMAR MF radar, and ALOMAR RMR lidar) at Andenes, Norway during the MIDAS/DROPPS/Mini-DUSTY campaign. A strong, long lasting PMSE event connected with a weak NLC was present during the first salvo on July 5/6, 1999. The ALWIN MST radar (53.5 MHz) performed spaced antenna measurements and Doppler beam steering observations using nine beam directions (vertical beam and oblique beams at 7° and 14° off-zenith). For the first time radar observations were possible along rocket trajectories allowing common-volume observations on intersections at altitudes between 75 and 90 km. The observed PMSE characteristics (echo power, aspect sensitivity, spatial coherence, wind field) are discussed with particular emphasis to the times of rocket soundings.

Latteck, R.; Singer, W.

2001-01-01

308

A new method of 3D reconstruction using the point cloud and distance images of laser radar  

NASA Astrophysics Data System (ADS)

As for the characteristic of the data acquired by laser radar and the three dimentional point cloud in disorder, and by combining the abundant in three dimentional information of point cloud with the specific textural information of distance images, we raised a new algorithm on the reconstruction of laser radar based on simplified point cloud and distance images. In this article, we take advantage of the feature that Delaunay triangulation have to raise a simplified algorithm to achieve the model network. In this algorithm, at first we build up the Delaunay triangulation, then comfirm the vector by calculating the distance that every vertex in the network from the adjacency vertex, and then calculate the intersection angle that the vector with triangle around; at the same time set the angular threshold in order to generate the new Delaunay triangulation. Experimental results show that this algorithm can accomplish the simplication of triangulation without affecting the accuracy of the modeling, along with the detailed, textural and shading information, we can achieve 3D reconstruction of the target images effectively.

Lan, Jinhui; Li, Jiehui; Zheng, Liujiang; Wu, Yang; Li, Xisheng

2012-05-01

309

Radar analysis of cloud systems and their rainfall yield in Israel  

Microsoft Academic Search

Abstract This study documents,the climatological occurrence of rainfall contributed from different types of rain cloud systems over Israel and the adjacent sea. The rainy cloud types are: a. Cold front. b. Cloud systems that develop in the cold sector of the cyclones. c. Cloudiness of the cyclone center (vortex). The cloud systems within the cold sector include: a. Convection lines.

Yair Goldreich; Hanan Mozes; Daniel Rosenfeld

2004-01-01

310

A study of modulation of polar stratospheric clouds by atmospheric waves in the Southern Hemisphere using CALIPSO lidar data  

NASA Astrophysics Data System (ADS)

Polar stratospheric clouds (PSCs) are the clouds that appear in the cold lower stratosphere in polar regions and play a key role in the destruction of polar stratospheric ozone. Atmospheric waves including planetary, synoptic-scale and gravity waves modulate temperature fields and hence affect the PSC amounts as shown by previous studies. Thus, for better understanding of stratospheric ozone destruction, a comprehensive and quantitative analysis was made in this study on the relationship between atmospheric waves and PSCs. We used the PSC data from satellite lidar observations (CALIPSO), H2O and HNO3 data from a satellite microwave limb sounder (Aura MLS), reanalysis data (ERA Interim) and high-resolution dry temperature data from GPS radio occultation observations (COSMIC). The analysis was focused on the Southern Hemisphere. The frequency of PSC occurrence at each location and time, hereafter referred to as the PSC frequency, was calculated as a proxy of the PSC amount from CALIPSO data (VFM data, showing the presence of cloud at observation points). The polar-stereo map shows that the PSC frequency is not regionally uniform, and suggests influence of the atmospheric waves. It is seen in the longitude-time section that high PSC frequency regions propagate eastward, which accords well with the movement of negative temperature anomaly from the zonal mean. First the effects of planetary waves in the stratosphere and synoptic-scale waves in the upper troposphere are analyzed using potential vorticity (PV) on the isentropic surfaces of 650 K (a height of about 20 km) and 300 K (about 9 km) respectively. It is shown that low (cyclonic) PV anomaly is frequently associated with high PSC frequency at 650K, while high (anti-cyclonic) PV anomaly is sometimes accompanied with high PSC frequency. The low PV anomaly in the stratosphere generally has long vertical scales and is associated with low temperature, while the high PV anomaly in the upper troposphere has very short vertical scales and hence negative temperature anomaly is formed in the lower stratosphere. The eastward propagation of PSC frequency observed in the longitude-time section is frequently followed by these low PV anomaly in the stratosphere and occasionally by high PV anomaly in the upper troposphere. To estimate the net effect of the planetary waves on the PSC quantitatively, we compared two “PSC area” with and without planetary wave effects. The former is calculated as the area where the temperature is below the TNAT based on unfiltered H2O and HNO3 data, and the latter is calculated using temperature, H2O and HNO3 data from which the zonal wavenumber 1-3 components were extracted. It was shown that the PSC area is increased by about 10% by planetary waves on average. Similar analysis was made on the PSC area excluding synoptic-scale wave effects. However, meaningful results were not obtained. Next, to examine the gravity wave effects on the PSC, we used GPS temperature data. The gravity wave potential energy is usually higher near the Antarctic Peninsula than in the other regions in June through September. However, the PSC frequency around the Antarctic Peninsula is higher than the other regions only in June and September, while the difference is small in July and August.

Kohma, M.; Sato, K.

2010-12-01

311

27-28 October 1986 FIRE IFO Cirrus Case Study: Cloud Optical Properties Determined by High Spectral Resolution Lidar.  

National Technical Information Service (NTIS)

During the First ISCCP Region Experiment (FIRE) cirrus intensive field observation (IFO) the High Spectral Resolution Lidar was operated from a roof top site on the University of Wisconsin-Madison campus. Because the HSRL technique separately measures the...

C. J. Grund E. W. Eloranta

1996-01-01

312

10-Year Climatology of Cloud Cover and Vertical Distribution Derived from Both Surface and GOES Observations Over the DOE ARM SGP Site.  

National Technical Information Service (NTIS)

Analysis of a decade of ARM radar-lidar and GOES observations at the SGP site reveal that 0.5 and 4-hr averages of the surface cloud fraction correspond closely to 0.5deg and 2.5deg averages of GOES cloudiness, respectively. The long-term averaged surface...

B. Xi M. Khaiyer P. Minnis X. Dong

2010-01-01

313

A comparison of cloud and boundary layer variables in the ECMWF forecast model with observations at Surface Heat Budget of the Arctic Ocean (SHEBA) ice camp  

Microsoft Academic Search

Cloud and boundary layer variables from the European Centre for Medium- Range Weather Forecasts (ECMWF) forecast model were compared with measurements made from surface instruments and from upward looking 8 mm wavelength radar and lidar at the Surface Heat Budget of the Arctic Ocean (SHEBA) ice camp during November and December of 1997. The precipitation accumulation, near-surface winds, and surface

J. A. Beesley; C. S. Bretherton; C. Jakob; E. L. Andreas; J. M. Intrieri; T. A. Uttal

2000-01-01

314

A comparison of cloud and boundary layer variables in the ECMWF forecast model with observations at Surface Heat Budget of the Arctic Ocean (SHEBA) ice camp  

Microsoft Academic Search

Cloud and boundary layer variables from the European Center for Medium-Range Weather Forecasts (ECMWF) forecast model were compared with measurements made from surface instruments and from upward looking 8 mm wavelength radar and lidar at the Surface Heat Budget of the Arctic Ocean (SHEBA) ice camp during November and December of 1997. The precipitation accumulation, near-surface winds, and surface downward

J. A. Beesley; C. S. Bretherton; C. Jakob; E. L. Andreas; J. M. Intrieri; T. A. Uttal

2000-01-01

315

Alpine snow distribution from-ground based radar measurements compared with a high resolution digital elevation model from ground-based LiDAR observations  

NASA Astrophysics Data System (ADS)

Collection of snow depth and precipitation measurements is exceedingly difficult above treeline in exposed areas of alpine terrain. Variability in surface topography combined with wind can cause large variations in snow depth and snow water equivalent over tens of meters, and precipitation measurements are often unreliable where wind speeds are high. Total snow depth and water equivalent measurements are often not representative in these highly variable snowpacks, while alpine locations often contain a large percentage of the water stored as snow in many watersheds. We use two different ground-based radar systems to measure snow distribution near an alpine weather station at 3719 m (12,200 ft) in SW Colorado at the Center for Snow and Avalanche Studies' Senator Beck Basin Study Area. The spatial distribution of snow is compared with a high resolution digital elevation model derived from ground-based LiDAR observations in snow-free conditions. The length scales of variation in both subsurface topography and snow depth are investigated in the region surrounding the weather station to help place the continuous snow depth observations at the weather station in the context of the snow distribution at the slope scale across this low angle site.

Marshall, H.; Deeb, E. J.; Gleason, A.; Heilig, A.; Finnegan, D. C.; Deems, J. S.; Havens, S.; Kormos, P. R.; Landry, C.; McCreight, J. L.

2011-12-01

316

A comparison between CloudSat and aircraft data for a multilayer, mixed phase cloud system during the Canadian CloudSat-CALIPSO Validation Project  

NASA Astrophysics Data System (ADS)

Reflectivities recorded by the W-band Cloud Profiling Radar (CPR) aboard NASA's CloudSat satellite and some of CloudSat's retrieval products are compared to Ka-band radar reflectivities and in situ cloud properties gathered by instrumentation on the NRC's Convair-580 aircraft. On 20 February 2007, the Convair flew several transects along a 60 nautical mile stretch of CloudSat's afternoon ground track over southern Quebec. On one of the transects it was well within CloudSat's radar's footprint while in situ sampling a mixed phase boundary layer cloud. A cirrus cloud was also sampled before and after overpass. Air temperature and humidity profiles from ECMWF reanalyses, as employed in CloudSat's retrieval stream, agree very well with those measured by the Convair. The boundary layer cloud was clearly visible, to the eye and lidar, and dominated the region's solar radiation budget. It was, however, often below or near the Ka-band's distance-dependent minimum detectable signal. In situ samples at overpass revealed it to be composed primarily of small, supercooled droplets at the south end and increasingly intermixed with ice northward. Convair and CloudSat CPR reflectivities for the low cloud agree well, but while CloudSat properly ascribed it as overcast, mixed phase, and mostly liquid near the south end, its estimates of liquid water content LWC (and visible extinction coefficient ?) and droplet effective radii are too small and large, respectively. The cirrus consisted largely of irregular crystals with typical effective radii ˜150 ?m. While both CPR reflectivities agree nicely, CloudSat's estimates of crystal number concentrations are too large by a factor of 5. Nevertheless, distributions of ice water content and ? deduced from in situ data agree quite well with values retrieved from CloudSat algorithms.

Barker, H. W.; Korolev, A. V.; Hudak, D. R.; Strapp, J. W.; Strawbridge, K. B.; Wolde, M.

2008-04-01

317

Rain clouds tracking with radar image processing based on morphological skeleton matching  

Microsoft Academic Search

The aim of this study is to perform a short term forecasting of dynamic radar clutter evolution (shape and position). This dynamic clutter, like thunderstorms, can be tracked by means of adapted algorithms based on the matching of the morphological skeleton polygonal approximation by relaxation labeling processes. The efficiency of our methods is demonstrated on meteorological radar images. The objective

Fridiric BARBARESCO; Bernard MONNIER

2001-01-01

318

Modeling of clouds and radiation for developing parameterizations for general circulation models. Annual report, 1994  

SciTech Connect

We are using a hierarchy of numerical models of cirrus and stratus clouds and radiative transfer to improve the reliability of general circulation models. Our detailed cloud microphysical model includes all of the physical processes believed to control the lifecycle of liquid and ice clouds in the troposphere. In our one-dimensional cirrus studies, we find that the ice crystal number and size in cirrus clouds are not very sensitive to the number of condensation nuclei which are present. We have compared our three-dimensional meoscale simulations of cirrus clouds with radar, lidar satellite and other observations of water vapor and cloud fields and find that the model accurately predicts the characteristics of a cirrus cloud system. The model results reproduce several features detected by remote sensing (lidar and radar) measurements, including the appearance of the high cirrus cloud at about 15 UTC and the thickening of the cloud at 20 UTC. We have developed a new parameterizations for production of ice crystals based on the detailed one-dimensional cloud model, and are presently testing the parameterization in three-dimensional simulations of the FIRE-II November 26 case study. We have analyzed NWS radiosonde humidity data from FIRE and ARM and found errors, biases, and uncertainties in the conversion of the sensed resistance to humidity.

NONE

1994-12-31

319

The four cumulus cloud modes and their progression during rainfall events: A C-band polarimetric radar perspective  

NASA Astrophysics Data System (ADS)

There is no objective definition to separate cumulus congestus clouds from the shallow cumulus and deep clouds. This has generated misinterpretation about the role of congestus clouds to promote deep convection through the potential of moistening the middle troposphere. In this study, an objective identification for the different tropical cumulus modes is found by examining the occurrence frequency of the cloud cell top heights (CTHs) and near-ground (at 2.5 km height) rainfall properties of these cells using a three-season database of the Darwin C-band polarimetric radar. Four cumulus modes were identified, namely a shallow cumulus mode with CTH in the trade inversion layer (1-3 km), a congestus mode with tops in the highly stable middle troposphere (3-6.5 km), a deep convective mode with tops in the region of free convection (6.5-15 km), and an overshooting convection mode with tops in the tropical tropopause layer (CTH >15 km). The study also investigates the connections between these cumulus modes during heavy rainfall events. The congestus mode occurs predominantly from ~10 h prior to the peak rainfall event to ~2 h past the event. The deep cloud populations (Modes 3 and 4) have their maxima at and shortly after the time of the rainfall peak, with maximum occurrence just below the tropical tropopause layer. A comparison of the heavy rainfall events occurring in morning (oceanic) conditions against the afternoon (continental) conditions revealed a higher ratio of the shallow to the deep cloud population and a shorter transition time from the shallow to the onset of deep population in the morning-oceanic conditions than the afternoon-land conditions. It is also found through the analysis of the large-scale moisture budget data set that for both the morning and afternoon events, the moistening peaked before the peak in the congestus populations.

Kumar, Vickal V.; Jakob, Christian; Protat, Alain; May, Peter T.; Davies, Laura

2013-08-01

320

Dusty cloud properties and radiative forcing over dust source and downwind regions derived from A-Train data during the Pacific Dust Experiment  

NASA Astrophysics Data System (ADS)

Dusty cloud properties and radiative forcing over northwestern China (source region) are compared to the same quantities over the northwestern Pacific (downwind region) during the Pacific Dust Experiment (PACDEX; April 2007 to May 2007) using collocated data from three satellites in the A-Train constellation: CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations), the Clouds and Earth Radiant Energy System on Aqua, and CloudSat. Dusty clouds are defined as clouds extant in a dust plume environment (i.e., dust aerosols observed within 50 m of the cloud), while pure clouds are those in dust-free conditions. CALIPSO lidar and CloudSat radar measurements are used to discriminate between dusty and pure clouds in both study regions. It was found that dust aerosols change the microphysical characteristics of clouds, reducing the cloud optical depth, liquid and ice water path, and effective droplet size. The decreased cloud optical depths and water paths diminish the cloud cooling effect, leading to a greater warming effect. The dust aerosols cause an instantaneous net cloud cooling effect of 43.4% and 16.7% in the source and downwind regions, respectively. The dust aerosol effects appear to be greater for ice clouds than for liquid water clouds in the downwind region. These results are consistent with PACDEX aircraft observations.

Wang, Wencai; Huang, Jianping; Minnis, Patrick; Hu, Yongxiang; Li, Jiming; Huang, Zhongwei; Ayers, J. Kirk; Wang, Tianhe

2010-01-01

321

Evaluation of clouds in ACCESS using the satellite simulator package COSP: Global, seasonal, and regional cloud properties  

NASA Astrophysics Data System (ADS)

Cloud properties from the Australian Community Climate and Earth System Simulator (ACCESS1.3) are evaluated using the Cloud Feedback Model Intercomparison Project (CFMIP) Observational Simulator Package (COSP). CloudSat, CALIPSO, and International Satellite Cloud Climatology Project (ISCCP) observations are used to evaluate the modeled cloud cover, condensate properties, and cloud optical depths for two seasons. The global distribution of cloud in the model is generally well represented with maximum high cloud in the tropics and low cloud over the eastern edges of the ocean basins. The model captures the observed position of the midlatitude storm track clouds and the modeled cloud top heights compare well with the observations in the upper troposphere. However, there is a lack of modeled midlevel cloud in the tropics and midlatitudes. The average high cloud cover in the Tropical Warm Pool region shows good agreement with CALIPSO. However, the modeled radar reflectivities and lidar scattering ratios are biased toward lower values, suggesting that the ice water contents and particles sizes of these clouds in the model are too small. Over the Southern Ocean the modeled cloud cover is underestimated due to a lack of mid- and low-level cloud. The low clouds over the Southern Ocean and the California stratocumulus clouds in the model have too little condensate and optical thickness and too much rain and drizzle. A sensitivity experiment showed that reducing the ice fall speeds improves aspects of the modeled cloud properties by increasing the frequency of occurrence of high clouds with large scattering ratios and optically thick low clouds. ACCESS1.3 has a reasonable representation of cloud. However, the underestimate of ice water content and particles sizes in high clouds and the too frequent occurrence of drizzle may impact the modeled cloud feedbacks and regional precipitation associated with current and perturbed climates.

Franklin, Charmaine N.; Sun, Zhian; Bi, Daohua; Dix, Martin; Yan, Hailin; Bodas-Salcedo, Alejandro

2013-01-01

322

Validation of the version 5 Goddard Earth Observing System (GEOS-5) using Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO)  

NASA Astrophysics Data System (ADS)

This dissertation compares the Planetary Boundary Layer (PBL) height produced by the Goddard Earth Observing System-version 5 (GEOS-5) model with Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). Part of GEOS-5 is an Atmosphere Global Circulation Model (GCM). Developers are uncertain of the precision of model PBL height predictions (i.e. climatology), since there are limited direct observations of the PBL height. Validation of the PBL height serves as a diagnostic on whether the physics and dynamics packages are correct in the model. Thus, verification is needed. For the first time ever, PBL heights have been derived from CALIPSO using a new hybrid standard deviation algorithm, which in some cases is more sensitive than traditional approaches (i.e. Haar wavelet method). Observations made at the UMBC Elastic Lidar Facility (ELF) have been used to determine the validity of the satellite-derived PBL estimate. This is the first global observational study of PBL heights using CALIPSO with match-ups to the GEOS-5 MERRA model. Extensive comparisons between the model output and satellite observations in the western Hemisphere and over Africa gave model-measurement correlation coefficients between 0.47--0.73. Comparisons have been performed for regions over land and water using clouds, aerosols and mixed cloud-aerosol features to detect the PBL. The present study provides insight of PBL height variances in the GEOS-5 model. A case over the Equatorial Pacific indicates that PBL heights from the GEOS-5 model are greater than 25%, on average, than the satellite-derived PBL parameter. PBL height biases in the Equatorial Pacific may be related to the General Circulation Model (GCM) coupling scheme implemented in GEOS-5.

Jordan, Nikisa Samantha

323

Different Applications of FORTRACC: From Convective Clouds to thunderstorms and radar fields  

Microsoft Academic Search

The algorithm Forecasting and Tracking the Evolution of Cloud Clusters (ForTraCC), Vila et al. (2008), has been employed operationally in Brazil since 2005 to track and forecast the development of convective clouds. This technique depicts the main morphological features of the cloud systems and most importantly it reconstructs its entire life cycle. Based on this information, several relationships that use

C. Morales; L. A. Machado

2009-01-01

324

Hail embryons detection in clouds using passive and active radars in millimeter and submillimeter wave bands  

Microsoft Academic Search

Two detection methods of hail embryons in a cloud are discussed in the paper: combined passive\\/active and purely active sensing of a convective cloud from board of air or space carrier. The first method makes it possible to determine the spectral dependence of absorption coefficient by oversized drops in convective cloud in the millimeter (MM) and submillimeter (SbMM) wavebands. With

H. M. Ajvazyan; H. H. Ajvazyan

1993-01-01

325

Short range tracking of rainy clouds by multi-image flow processing of X-band radar data  

NASA Astrophysics Data System (ADS)

Two innovative algorithms for motion tracking and monitoring of rainy clouds from radar images are proposed. The methods are generalizations of classical optical flow techniques, including a production term (modelling formation, growth or depletion of clouds) in the model to be fit to the data. Multiple images are processed and different smoothness constraints are introduced. When applied to simulated maps (including additive noise up to 10 dB of SNR) showing formation and propagation of objects with different directions and velocities, the algorithms identified correctly the production and the flow, and were stable to noise when the number of images was sufficiently high (about 10). The average error was about 0.06 pixels (px) per sampling interval (? T) in identifying the modulus of the flow (velocities between 0.25 and 2 px/? T were simulated) and about 1° in detecting its direction (varying between 0° and 90°). An example of application to X-band radar rainfall rate images detected during a stratiform rainfall is shown. Different directions of the flow were detected when investigating short (10 min) or long time ranges (8 h), in line with the chaotic behaviour of the weather condition. The algorithms can be applied to investigate the local stability of meteorological conditions with potential future applications in nowcasting.

Mesin, Luca

2011-12-01

326

Simulating Z-LWC Relations in Natural Fogs with Radiative Transfer Calculations for Future Application to a Cloud Radar Profiler  

NASA Astrophysics Data System (ADS)

The vertical distribution of liquid water content (LWC) in natural fog and low stratus is a crucial variable in many applications, e.g. the development of satellite based retrievals of ground fog. Unfortunately, there is very little data concerning fog LWC-profiles, mainly due to the lack of suitable operational instrumentation. A novel ground-based 94 GHz FMCW cloud radar could fill this gap if radar reflectivity Z could be converted to LWC by using appropriate Z-LWC relations. However, this relation strongly depends on drop size distribution (DSD) and is hardly known for natural fog types. In this sensitivity study, the influence of the DSD on the Z-LWC relation in different types and life cycle stages of natural fogs is analyzed using a radiative transfer code (RTC) and published fog drop size distributions. It could be shown that there is a direct but nonlinear relationship between LWC and radar reflectivity. The proportionality factor of the Z-LWC equation in particular reveals specific ranges for the different life cycle stages. If a proper classification of fog life cycle in the field is possible, the results could be used to properly convert Z to LWC.

Maier, F.; Bendix, J.; Thies, B.

2012-05-01

327

SAR and LIDAR fusion: experiments and applications  

NASA Astrophysics Data System (ADS)

In recent years ARTEMIS, Inc. has developed a series of compact, versatile Synthetic Aperture Radar (SAR) systems which have been operated on a variety of small manned and unmanned aircraft. The multi-frequency-band SlimSAR has demonstrated a variety of capabilities including maritime and littoral target detection, ground moving target indication, polarimetry, interferometry, change detection, and foliage penetration. ARTEMIS also continues to build upon the radar's capabilities through fusion with other sensors, such as electro-optical and infrared camera gimbals and light detection and ranging (LIDAR) devices. In this paper we focus on experiments and applications employing SAR and LIDAR fusion. LIDAR is similar to radar in that it transmits a signal which, after being reflected or scattered by a target area, is recorded by the sensor. The differences are that a LIDAR uses a laser as a transmitter and optical sensors as a receiver, and the wavelengths used exhibit a very different scattering phenomenology than the microwaves used in radar, making SAR and LIDAR good complementary technologies. LIDAR is used in many applications including agriculture, archeology, geo-science, and surveying. Some typical data products include digital elevation maps of a target area and features and shapes extracted from the data. A set of experiments conducted to demonstrate the fusion of SAR and LIDAR data include a LIDAR DEM used in accurately processing the SAR data of a high relief area (mountainous, urban). Also, feature extraction is used in improving geolocation accuracy of the SAR and LIDAR data.

Edwards, Matthew C.; Zaugg, Evan C.; Bradley, Joshua P.; Bowden, Ryan D.

2013-05-01

328

Cloud Altitude Determination of Overshooting Tops in Severe Thunderstorms  

NASA Astrophysics Data System (ADS)

The maximum heights of deep convective clouds and overshooting tops have been analyzed and compared using a combination of space and ground-based measurement systems. Deeply convective cumulonimbus clouds are capable of reaching and penetrating the tropopause. The portions of convective clouds that extend into the stratosphere are known as overshooting tops. Instances of tornado onset have been observed to match or slightly lag the timing of maximum cloud-top altitudes. In addition, precise forecasting and measurement of convective cloud-top heights are of critical importance to the safety and efficiency of commercial aviation flight routings. This study included the use of data from three NASA A-Train satellites, 88-D and TDWR Doppler radar, NAM modeling output, and direct visual sightings. The three polar-orbiting satellites included Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), CloudSat, and Aqua. CALIPSO and CloudSat return a vertical profile of microphysical parameters as their near-nadir beams intersect clouds. CALIPSO uses a lidar instrument (CALIOP), operating at 532 and 1064 nm, that is capable of detecting aerosol and small cloud particles. CloudSat uses a radar system called Cloud Profiling Radar (CPR), operating at 94 GHz (3.2 mm), that can penetrate thicker clouds, including those with precipitation. The Moderate Resolution Imaging Spectroradiometer (MODIS) on board Aqua provided a 250m resolution map view that permitted identification of the unique texture of overshooting tops. Satellite data and ground-based Doppler radar were co-located and used to compare cloud-top and echo-top measurements and products. In addition to co-located observational data, North American Mesoscale (NAM) model output with maximum 6-hour lead time was analyzed for convective cloud top forecasts. Finally, direct sightings of cloud tops were made at the time of CALIPSO overpasses of New Jersey. Using a surveyor's transit, the angle from the observation spot to the cloud top was measured and the geographic position of the cloud was determined using MODIS images and Google Earth. After cataloging about 125 A-Train intersects of deep convection from January 1 to July 1 of 2011, the maximum convective cloud altitudes were collected from CALIPSO, CloudSat, radar, and modeling data. Our results confirm previous findings that CALIPSO consistently detects cloud tops at a higher altitude than CloudSat. It was also found that CALIPSO cloud tops were consistently higher than Doppler-radar echo tops or NAM cloud tops. However, CALIPSO altitudes were very consistent with altitudes determined by direct sighting. Doppler radar and modeling data often closely matched satellite observations, but on occasion they showed large differences. Careful analysis of the limitations and the biases of these data could improve our understanding of convective cloud-top dynamics and improve in-flight routing decisions for commercial aviation.

Goldberg, R.; Magee, N. B.

2011-12-01

329

Investigation into clouds and precipitation over an urban area using micro rain radars, satellite remote sensing and fluorescence spectrophotometry  

NASA Astrophysics Data System (ADS)

The observation and modeling of the indirect effects of aerosols on clouds remain an enormous challenge. Aerosols have a significant yet complicated impact on the precipitation processes. They can either enhance or suppress precipitation depending upon type of aerosol, seasonality, climate regime, cloud type or orographic profile of a region, particularly over populated areas. In order to observe and examine both cloud and precipitation processes, a combination of both satellite and ground-based remote sensing techniques can be employed. This paper presents the results from three years of data collection in Birmingham, United Kingdom. It describes and explains the application of a range of complimentary techniques: fluorescence spectrophotometry to examine dissolved organic carbon compounds in rainwater samples; satellite analysis tools are used to assess cloud-top microphysics; and an array of vertically-pointing micro-rain radars (MRRs) are used to assess variations in drop size distribution (DSD) for categorized events. Events are classified as microphysically 'maritime' or 'continental', showing that full development of the ice phase was reached at relatively warm temperatures for microphysically 'maritime' events, but at colder temperatures for microphysically 'continental' events. The importance of updrafts in severe thunderstorms and tornadic events is highlighted. High rainwater content of tyrosine-like substances (TYLIS) and tryptophan-like substances (TRYLIS) is found to be associated mainly with microphysically 'maritime' events, providing evidence for these substances acting as ice nuclei at relatively warm temperatures. High rainwater content of humic-like substances (HULIS) is associated with both microphysically 'maritime' and 'continental' events due to the complexity of such substances. As might be expected, continentally-sourced events had a similar structure to microphysically 'continental' events, whereas maritime-sourced events differed in their microphysical structure, indicating the local impacts on their microstructure. The DSD appears to vary between different events — for example, continentally-sourced, microphysically 'continental', convective events with low rainwater TRYLIS have a DSD containing fewer smaller droplets, whereas maritime-sourced, microphysically 'maritime', stratiform events with high TRYLIS had a DSD containing a greater number of smaller droplets. Satellite observations and vertically-pointing radars were found to be useful for analyzing clouds and precipitation since they provide a wealth of information to allow microphysical parameters to be investigated in detail.

Muller, Catherine L.; Kidd, Chris; Fairchild, Ian J.; Baker, Andy

2010-05-01

330

The Atmospheric Infrared Sounder Version 6 cloud products  

NASA Astrophysics Data System (ADS)

The Version 6 cloud products of the Atmospheric Infrared Sounder (AIRS) and Advanced Microwave Sounding Unit (AMSU) instrument suite are described. The cloud top temperature, pressure, and height and effective cloud fraction are now reported at the AIRS field of view (FOV) resolution. Significant improvements in cloud height assignment over Version 5 are shown with pixel-scale comparisons to cloud vertical structure observed by the CloudSat 94 GHz radar and the Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP). Cloud thermodynamic phase (ice, liquid, and unknown phase), ice cloud effective diameter (De), and ice cloud optical thickness (?) are derived using an optimal estimation methodology for AIRS FOVs, and global distributions for January 2007 are presented. The largest values of ? are found in the storm tracks and near convection in the Tropics, while De is largest on the equatorial side of the midlatitude storm tracks in both hemispheres, and lowest in tropical thin cirrus and the winter polar atmosphere. Over the Maritime Continent the diurnal cycle of ? is significantly larger than for the total cloud fraction, ice cloud frequency, and De, and is anchored to the island archipelago morphology. Important differences are described between northern and southern hemispheric midlatitude cyclones using storm center composites. The infrared-based cloud retrievals of AIRS provide unique, decadal-scale and global observations of clouds over the diurnal and annual cycles, and captures variability within the mesoscale and synoptic scales at all latitudes.

Kahn, B. H.; Irion, F. W.; Dang, V. T.; Manning, E. M.; Nasiri, S. L.; Naud, C. M.; Blaisdell, J. M.; Schreier, M. M.; Yue, Q.; Bowman, K. W.; Fetzer, E. J.; Hulley, G. C.; Liou, K. N.; Lubin, D.; Ou, S. C.; Susskind, J.; Takano, Y.; Tian, B.; Worden, J. R.

2013-06-01

331

A detailed view into the eruption clouds of Santiaguito volcano, Guatemala, using Doppler radar  

NASA Astrophysics Data System (ADS)

Using Doppler radar technology we are able to show that eruptions at Santiaguito volcano, Guatemala, are comprised of multiple explosive degassing pulses occurring at a frequency of 0.2 to 0.3 Hz. The Doppler radar system was installed about 2.7 km away from the active dome on the top of Santa Maria volcano. During four days of continuous measurement 157 eruptive events were recorded. The Doppler radar data reveals a vertical uplift of the dome surface of about 50 cm immediately prior to a first degassing pulse. Particle velocities range from 10 to 15 m/s (in the line of sight of the radar). In 80% of the observed eruptions a second degassing pulse emanates from the dome with significantly higher particle velocities (20-25 m/s again line of sight) and increased echo power, which implies an increase in mass flux. We carry out numerical experiments of ballistic particle transport and calculate corresponding synthetic radar signals. These calculations show that the observations are consistent with a pulsed release of material from the dome of Santiaguito volcano.

Scharff, L.; Ziemen, F.; Hort, M.; Gerst, A.; Johnson, J. B.

2012-04-01

332

A study of cloud and drizzle properties in the Azores using Doppler Radar spectra  

SciTech Connect

Understanding the onset of coalescence in warm clouds is key in our effort to improve cloud representation in numerical models. Coalescence acts at small scales, and its study requires detailed high-resolution dynamical and microphysical measurements from a comprehensive suite of instruments over a wide range of environmental conditions (e.g., aerosol loading). The first AMF is currently in its second year of a two-year deployment at Graciosa Island in the Azores, offering the opportunity to collect a long data set from a stable land-based platform in a marine stratocumulus regime. In this study, recorded WACR Doppler spectra are used to characterize the properties of Doppler spectra from warm clouds with and without drizzle, and from drizzle only, in an effort to observe the transition (onset) to precipitation in clouds. A retrieval technique that decomposes observed Doppler spectra into their cloud and/or drizzle components is applied in order to quantify drizzle growth.

Luke, E.; Remillard, J.; Kollias, P.

2010-03-15

333

Initial High Spectral Resolution Lidar Results From the Cumulus Humilis Aerosol Processing Study (CHAPS) and Cloud and Land Surface Interaction Campaign (CLASIC)  

NASA Astrophysics Data System (ADS)

The Cumulus Humilis Aerosol Processing Study (CHAPS) field campaign, sponsored by the Department of Energy Atmospheric Science Program (ASP), and the Cloud and Land Surface Interaction Campaign (CLASIC), sponsored by the DOE Atmospheric Radiation Measurement (ARM) Program, were performed during June 2007, with the respective goals of studying aerosol and cloud interactions and advancing the understanding of how land surface processes influence cumulus convection in the Oklahoma City region. The campaigns involved several coordinated air- and ground-based remote and in situ sensors, including, among others, the NASA Langley Research Center (LaRC) Airborne High Spectral Resolution Lidar (HSRL) aboard the NASA King Air B-200 aircraft, instruments located at the DOE Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) Climate Research Facility (CRF), and instruments aboard the DOE Gulfstream-1, the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter, and the DOE ARM Cessna 206 aircraft. The aircraft were flown in coordinated patterns over common ground tracks on several occasions, some of which involved passing over the SGP CRF and/or were coordinated with overpasses from satellites in the A-Train constellation. These coordinated measurements enabled coincident observations of aerosol properties near clouds, facilitating analyses of cloud and aerosol interactions and properties across changing atmospheric conditions. Over the course of the CHAPS-CLASIC mission, the NASA LaRC Airborne HSRL instrument flew 22 flights obtaining nearly 70 hours of observations. The Airborne HSRL directly measured aerosol backscatter and depolarization at wavelengths of 532 nm and 1064 nm, and aerosol extinction at 532 nm, allowing for calibrated computation of the aerosol extinction-to-backscatter ratio, wavelength dependence, and depolarization ratio profiles extending from near the surface to about 8 km above ground level. An overview of the NASA LaRC HSRL mission, as well as preliminary results from the HSRL during the CLASIC/CHAPS field campaign will be presented.

Obland, M. D.; Cook, A. L.; Ferrare, R. A.; Hair, J. W.; Harper, D. B.; Hostetler, C. A.; Rogers, R. R.

2007-12-01

334

Water Vapor and Cloud Detection Validation for Aqua Using Raman Lidars and AERI and the AWEX-G Validation Experiment  

Microsoft Academic Search

The early work in this investigation focused on the use of Raman lidar, ra- diosonde and AERI measurements for AIRS validation measurements as was reported in last year's annual report. That report revealed at times large unex- plained differences in various validation datasets being used forAIRS valida- tion. Because of this, the AIRS Water Vapor Experiment-Ground (AWEX-G) was proposed, funded

David Whiteman; Belay Demoz; Frank Schmidlin; Zhien Wang; Igor Veselovskii; Wallace McMillan; Ray Hoff; Felicita Russo; Scott Hannon; Larry Miloshevich; Barry Lesht; Gary Jedlovec; Madison WI; Martin Cadirola

335

A global view of horizontally oriented crystals in ice clouds from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO)  

Microsoft Academic Search

We analyze optical signatures in 18 months of CALIOP layer-integrated backscatter and depolarization ratio to investigate the geographical and seasonal distribution of oriented crystals in ice clouds on a global scale. Oriented crystals are found to be rare: they appear in ?6% of all ice cloud layers, and inside these layers the proportion of oriented crystals is estimated below 5%,

Vincent Noel; Helene Chepfer

2010-01-01

336

An Assessment of Cloud and Aerosol Radiative Forcing from CERES with Independent Passive (Ground Networks) and Active (Calipso Lidar) Measurements  

Microsoft Academic Search

Much of the interest in clouds and aerosols relates to the direct radiative forcing of these atmospheric constituents. Satellite data are the main tools for estimating both cloud and aerosol forcing on the global scale. What are the strengths and weaknesses of the satellite record for these forcings? Here we test the CERES Terra (March 2000 - December 2006) and

T. P. Charlock; F. G. Rose; D. A. Rutan; Z. Jin

2008-01-01

337

Preliminary comparison of CloudSAT-derived microphysical quantities with ground-based measurements for mixed-phase cloud research in the Arctic  

NASA Astrophysics Data System (ADS)

The omnipresent existence of thin, mixed-phase clouds in northern polar latitudes presents special challenges to CloudSAT as it attempts to map radiatively relevant cloudiness around the globe. In this work, retrieved cloud properties of Arctic mixed-phase clouds observed simultaneously in Eureka, Canada by ground-based cloud radar and lidar, and by the CloudSAT Cloud-Profiling Radar (CPR) are compared. Through these comparisons, we evaluate the efficacy of identification of precipitation and assignment of cloud type by the 2B-CLDCLASS product, as well as the accuracy of microphysical retrievals from the 2B-CWC-RO product. These preliminary comparisons result in the following findings with regard to the CloudSAT retrievals: (1) The cloud detection algorithm worked well, detecting all clouds observed from surface based sensors. (2) Precipitation was not well identified, and was often mislabeled as cloud. (3) Both liquid and ice particle number densities retrieved by CloudSAT are found to be 1 to 2 orders of magnitude too high when compared to surface-based retrievals and previous studies of these cloud types. (4) CloudSAT particle effective sizes are often too large, with the exception of the largest particles, which are misidentified as liquid. (5) Water contents show the best agreement between the two retrieval types, as well as with measured values from outside studies. All comparisons were completed for raw liquid and ice retrievals, as well as for "composite" retrievals that partition liquid and ice contributions to measured reflectivity through a temperature-dependent algorithm. Differences found for these limited cases imply that careful analysis is required for application of these cloud products to mixed-phase cloud research. Furthermore, these differences help highlight specific assumptions within the CloudSAT algorithms that are in need of improvement to complete mixed-phase cloud retrievals.

de Boer, Gijs; Tripoli, Gregory J.; Eloranta, Edwin W.

2008-04-01

338

A comparison between CloudSat and aircraft data for mixed-phase and cirrus clouds  

NASA Astrophysics Data System (ADS)

Nowadays, space remote sensing measurements are a very useful way to study the atmosphere on a global scale. Among the numerous scientific satellites in space, the A-Train is a constellation of 6 satellites flying together with on board complementary instruments of new generation (radiometers, radar, lidar, spectrometers…) to study all parts of the atmosphere: gas composition, clouds and aerosols distribution and properties, and radiation budget. Among these satellites, two of them where launched in 2006: CALIPSO and CloudSat, respectively with a Lidar (532 and 1064 nm channels with depolarization) and a 94 GHz radar on board. They are especially dedicated to the study of clouds and aerosols, and will allow to obtain for the first time the vertical profiles of clouds and aerosols on a global scale during 3 years. However, to determine clouds and aerosols properties from space raw data, retrieval methods need to be developed. In order to validate these retrieved techniques, and thus the clouds and aerosols properties, numerous validation plans take place around the world, included different ways as ground based measurements, in situ measurements, or airborne remote sensing instruments in collocation with the satellite tracks. In this context, the ASTAR-2007 and POLARCAT-2008 campaigns took place respectively in the Arctic region of Spitzbergen-Norway in April 2007 and in North part of Sweden in April 2008 to study mixed-phase clouds and the CIRCLE-2 campaign was carried out in Western Europe in May 2007 to sample mid-latitude cirrus clouds. The main objectives are the study of microphysical and optical properties of mixed-phase and ice clouds with particular interest on the validation of clouds products derived from CloudSat and CALIPSO data during co-located remote and in situ observations. The airborne microphysical instruments include the Polar Nephelometer probe to measure the scattering phase function and asymmetry parameter of cloud particles, the high resolution Cloud Particle Imager probe (CPI) for imaging the ice particle morphology (2.3 microns pixels size) and standard PMS probes: 2D-C, FSSP-100 and FSSP-300. This presentation focuses on the validation of the standard parameter of the Cloud Profiling Radar (CPR) of CloudSat (equivalent radar reflectivity factor Z). The different IWC(ice water content)-Z relationships determined from combined CloudSat and in situ data are then discussed. The method to derive equivalent reflectivity factor from the CPI data is first presented. According to the particle shape, a mass-diameter relationship and thus a reflectivity factor is determined for each type of ice crystal. This technique noticeably decreases the discrepancies of radar reflectivity-derived values due to the natural variability of ice crystal shapes. Comparisons of the reflectivity factor deduced from CPI and those from CloudSat for various types of clouds are then discussed. The next step to the interpretation of the CloudSat product is to derive IWC-Z relationships for assessing IWC distributions on a global scale, which is an important improvement to constrain global scale modelling. Several IWC-Z relationships are determined from in situ measurements according to the various case studies including Arctic mixed-phase clouds, Arctic and mid-latitude cirrus. The improvements on the results by using the CPI data-processing method are discussed. Acknowledgements: This work was funded by the Centre National d'Etudes Spatiales (CNES), the Agence Nationale de la Recherche (ANR BLAN06-1_137670), the Institut National des Sciences de l'Univers (INSU/CNRS), the Institut Polaire Français Paul Emile Victor (IPEV), the Alfred Wegener Institute (AWI) and the Deutsches Zentrum für Luft-und Raumfahrt (DLR). The CloudSat data are courtesy of the CloudSat Data Processing Center.

Mioche, G.; Gayet, J.-F.; Minikin, A.; Herber, A.; Pelon, J.

2009-04-01

339

Evaluation of single field-of-view cloud top height retrievals from hyperspectral infrared sounder radiances with CloudSat and CALIPSO measurements  

NASA Astrophysics Data System (ADS)

Accurate cloud top height retrievals from hyperspectral infrared (IR) sounder radiances are needed for weather and climate prediction. To account for the nonlinearity of the cloud parameters with respect to the IR radiances, a one-dimensional variational retrieval algorithm is used to derive the cloud top heights (CTHs) from the Atmospheric Infrared Sounder (AIRS) radiances on a single field-of-view basis. The CTHs are evaluated by comparison with the measurements from radar and lidar instruments onboard the Earth Observing System (EOS) CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellites. Using the retrievals from a global 3 day dataset, it is found that the variational algorithm compared with the regression algorithm could reduce the variability of the difference between the AIRS and active measurements by 1 km. And the biases of AIRS CTHs range from +1.5 to -1.4 km and from +1.6 to -3.8 km, depending on the Cloud Profiling Radar (CPR) and CALIPSO CTHs between 3 and 18 km, respectively. Globally, the AIRS CTH is overestimated (underestimated) when the CTH from active measurements is below (above) 5 km. The bias decreases from -1.9 to -0.8 km, and the variability decreases from 2.8 to about 1.6 km with the increase of the CALIPSO cloud optical thickness from 0.1 to 2.5. It also reveals that the AIRS CTHs agree better with the CPR than the CALIPSO.

Yao, Zhigang; Li, Jun; Weisz, Elisabeth; Heidinger, Andrew; Liu, Chian-Yi

2013-08-01

340

Validation of CERES-MODIS Arctic cloud properties using CloudSat/CALIPSO and ARM NSA observations  

NASA Astrophysics Data System (ADS)

The traditional passive satellite studies of cloud properties in the Arctic are often affected by the complex surface features present across the region. Nominal visual and thermal contrast exists between Arctic clouds and the snow- and ice-covered surfaces beneath them, which can lead to difficulties in satellite retrievals of cloud properties. However, the addition of active sensors to the A-Train constellation of satellites has increased the availability of validation sources for cloud properties derived from passive sensors in the data-sparse high-latitude regions. In this study, Arctic cloud fraction and cloud heights derived from the NASA CERES team (CERES-MODIS) have been compared with CloudSat/CALIPSO and DOE ARM NSA radar-lidar observations over Barrow, AK, for the two-year period from 2007 to 2008. An Arctic-wide comparison of cloud fraction and height between CERES-MODIS and CloudSat/CALIPSO was then conducted for the same time period. The CERES-MODIS cloud properties, which include cloud fraction and cloud effective heights, were retrieved using the 4-channel VISST (Visible Infrared Solar-Infrared Split-window Technique) [Minnis et al.,1995]. CloudSat/CALIPSO cloud fraction and cloud-base and -top heights were from version RelB1 data products determined by both the 94 GHz radar onboard CloudSat and the lidar on CALIPSO with a vertical resolution of 30 m below 8.2 km and 60 m above. To match the surface and satellite observations/retrievals, the ARM surface observations were averaged into 3-hour intervals centered at the time of the satellite overpass, while satellite observations were averaged within a 3°x3° grid box centered on the Barrow site. The preliminary results have shown that all observed CFs have peaks during April-May and September-October, and dips during winter months (January-February) and summer months (June-July) during the study period of 2007-2008. ARM radar-lidar and CloudSat/CALIPSO show generally good agreement in CF (0.79 vs. 0.74), while CERES-MODIS derived values are much lower (0.60). CERES-MODIS derived cloud effective height (2.7 km) falls between the CloudSat/CALIPSO derived cloud base (0.6 km) and top (6.4 km) and the ARM ceilometers and MMCR derived cloud base (0.9 km) and radar derived cloud top (5.8 km). When extended to the entire Arctic, although the CERES-MODIS and Cloudsat/CALIPSO derived annual mean CFs agree within a few percents, there are significant differences over several regions, and the maximum cloud heights derived from CloudSat/CALIPSO (13.4 km) and CERES-MODIS (10.7 km) show the largest disagreement during early spring.

Giannecchini, K.; Dong, X.; Xi, B.; Minnis, P.; Kato, S.

2011-12-01

341

Anisotropic multi-resolution analysis in 2D, application to long-range correlations in cloud mm-radar fields  

SciTech Connect

Because of Earth`s gravitational field, its atmosphere is strongly anisotropic with respect to the vertical; the effect of the Earth`s rotation on synoptic wind patterns also causes a more subtle form of anisotropy in the horizontal plane. The authors survey various approaches to statistically robust anisotropy from a wavelet perspective and present a new one adapted to strongly non-isotropic fields that are sampled on a rectangular grid with a large aspect ratio. This novel technique uses an anisotropic version of Multi-Resolution Analysis (MRA) in image analysis; the authors form a tensor product of the standard dyadic Haar basis, where the dividing ratio is {lambda}{sub z} = 2, and a nonstandard triadic counterpart, where the dividing ratio is {lambda}{sub x} = 3. The natural support of the field is therefore 2{sup n} pixels (vertically) by 3{sup n} pixels (horizontally) where n is the number of levels in the MRA. The natural triadic basis includes the French top-hat wavelet which resonates with bumps in the field whereas the Haar wavelet responds to ramps or steps. The complete 2D basis has one scaling function and five wavelets. The resulting anisotropic MRA is designed for application to the liquid water content (LWC) field in boundary-layer clouds, as the prevailing wind advects them by a vertically pointing mm-radar system. Spatial correlations are notoriously long-range in cloud structure and the authors use the wavelet coefficients from the new MRA to characterize these correlations in a multifractal analysis scheme. In the present study, the MRA is used (in synthesis mode) to generate fields that mimic cloud structure quite realistically although only a few parameters are used to control the randomness of the LWC`s wavelet coefficients.

Davis, A.B. [Los Alamos National Lab., NM (United States). Space and Remote Sensing Science Group; Clothiaux, E. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Meteorology

1999-03-01

342

Raman lidar measurements of water vapor and aerosol/clouds during the FIRE/SPECTRE field campaign.  

National Technical Information Service (NTIS)

The FIRE/SPECTRE field campaign was conducted during November- December 1991 in Coffeyville, Kansas. The main objective of FIRE (First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment) was to study the development and radiativ...

S. H. Melfi D. Whiteman R. Ferrare K. Evans J. E. M. Goldsmith

1992-01-01

343

Cloud and radiation mission with active and passive sensing from the space station  

SciTech Connect

A cloud and aerosol radiative forcing and physical process study involving active laser and radar profiling with a combination of passive radiometric sounders and imagers would use the space station as an observation platform. The objectives are to observe the full three dimensional cloud and aerosol structure and the associated physical parameters leading to a complete measurement of radiation forcing processes. The instruments would include specialized radar and lidar for cloud and aerosol profiling, visible, infrared and microwave imaging radiometers with comprehensive channels for cloud and aerosol observation and specialized sounders. The low altitude, available power and servicing capability of the space station are significant advantages for the active sensors and multiple passive instruments.

Spinhirne, James D. [Laboratory for Atmospheres, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States)

1999-01-22

344

Partitioning of cloud water and rainwater content by ground-based observations with the Advanced Microwave Radiometer for Rain Identification (ADMIRARI) in synergy with a micro rain radar  

NASA Astrophysics Data System (ADS)

Cloud and rain liquid water path and total water vapor are retrieved simultaneously from passive microwave observations with the multifrequency dual-polarized Advanced Microwave Radiometer for Rain Identification (ADMIRARI). A data set of linearly polarized brightness temperatures has been collected at 30° elevation angle together with slant radar reflectivity profiles at 24.1 GHz from a micro rain radar (MRR) pointing into the same viewing direction. The slant path integrated values are retrieved via a Bayesian inversion approach, the quality of which is evaluated by a simulation-based retrieval sensitivity study. The algorithm includes a physical constraint by taking into account the rain column structural information from the MRR observations. Measurements and derived path-integrated water component estimates from 23 August to 12 November 2008, obtained in Cabauw, Netherlands, are analyzed. During raining cloud conditions the zenith-normalized root-mean-square error for water vapor, cloud liquid water path, and rain liquid water path are, on average, estimated to 1.54 kg m-2, 144 g m-2, and 52 g m-2, respectively. On the basis of these results, long-term estimated distributions of cloud water-rainwater partitioning for midlatitude precipitating clouds are presented for the first time as obtained by a ground-based radiometer.

Saavedra, Pablo; Battaglia, Alessandro; Simmer, Clemens

2012-03-01

345

Cloud fraction at the ARM SGP site  

NASA Astrophysics Data System (ADS)

The Atmospheric Radiation Measurement (ARM) Program Southern Great Plains (SGP) site has a rich history of actively sensed cloud observations. Fourteen years (1997-2010) of observations from the Millimeter Cloud Radar (MMCR), Micropulse Lidar (MPL), and Belfort/Vaisala Ceilometers are used to understand how instrument selection and sampling impacts estimates of Cloud Fraction (CF) at this location. Although all instruments should be used in combination for the best estimates of CF, instrument downtime limits available samples and increases observational errors, demanding that users make sacrifices when calculating CF at longer intervals relevant to climate studies. Selection of MMCR or MMCR + MPL cloud masks changes very little in the overall understanding of total CF. Addition of the MPL increases the 14-year average CF by 9 %, mainly through an increase in optically thin high clouds year-round, and mid-level clouds during the summer months. Splitting the period into two equal 7-year periods reveals negligible change in MMCR + MPL CF. For the MMCR, however, CF deceases by 6.1 %. This sudden change in CF occurs around the time the radar was upgraded, suggesting that this decrease is tied to hardware sensitivity or scanning strategy changes. Users must be cognizant of this and other issues when calculating CF from the variety of observations available at the ARM SGP site.

Kennedy, Aaron D.; Dong, Xiquan; Xi, Baike

2013-03-01

346

Investigations on the physical and optical properties of cirrus clouds and their relationship with ice nuclei concentration using LIDAR at Gadanki, India (13.5°N, 79.2°E)  

NASA Astrophysics Data System (ADS)

Cirrus cloud measurements over the tropics are receiving much attention recently due to their role in the Earth's radiation budget. The interaction of water vapor and aerosols plays a major role in phase formation of cirrus clouds. Many factors control the ice supersaturation and microphysical properties in cirrus clouds and, as such, investigations on these properties of cirrus clouds are critical for proper understanding and simulating the climate. In this paper we report on the evolution, microphysical, and optical properties of cirrus clouds using the Mie LIDAR operation at the National Atmospheric Research Laboratory, Gadanki, India (13.5°N, 79.2°E), an inland tropical station. The occurrence statistics, height, optical depth, depolarization ratio of the cirrus clouds, and their relationship with ice nuclei concentration were investigated over 29 days of observation during the year 2002. Cirrus clouds with a base altitude as low as 8.4 km are observed during the month of January and clouds with a maximum top height of 17.1 km are observed during the month of May. The cirrus has a mean thickness of 2 km during the period of study. The LIDAR ratio varies from 30 to 36 sr during the summer days of observation and 25 to 31 sr during the winter days of observation. Depolarization values range from 0.1 to 0.58 during the period of observation. The ice nuclei concentration has been calculated using the De Motts equation. It is observed that during the monsoon months of June, July, and August, there appears to be an increase in the ice nuclei number concentration. From the depolarization data an attempt is made to derive the ice crystal orientation and their structure of the cirrus. Crystal structures such as thin plates, thick plates, regular hexagons, and hexagonal columns are observed in the study. From the observed crystal structure and ice nuclei concentration, the possible nucleation mechanism is suggested.

Krishnakumar, Vasudevannair; Satyanarayana, Malladi; Radhakrishnan, Soman R.; Dhaman, Reji K.; Pillai, Vellara P. Mahadevan; Raghunath, Karnam; Ratnam, Madineni Venkat; Rao, Duggirala Ramakrishna; Sudhakar, Pindlodi

2011-01-01

347

Bayesian estimation of precipitating cloud parameters from combined measurements of spaceborne microwave radiometer and radar  

Microsoft Academic Search

The objective of this paper is to evaluate the potential of a Bayesian inversion algorithm using microwave multisensor data for the retrieval of surface rainfall rate and cloud parameters. The retrieval scheme is based on the maximum a posteriori probability (MAP) method, extended for the use of both spaceborne passive and active microwave data. The MAP technique for precipitation profiling

Frank Silvio Marzano; Alberto Mugnai; Giulia Panegrossi; Nazzareno Pierdicca; Eric A. Smith; Joseph Turk

1999-01-01

348

Dynamics of Dust Particles Released from Oort Cloud Comets and Their Contribution to Radar Meteors.  

National Technical Information Service (NTIS)

The Oort Cloud Comets (OCCs), exemplified by the Great Comet of 1997 (Hale-Bopp), are occasional visitors from the heatless periphery of the solar system. Previous works hypothesized that a great majority of OCCs must physically disrupt after one or two p...

D. Janches D. Nesvorny D. Vokrouhlicky P. Pokorny

2012-01-01

349

Clouds  

NSDL National Science Digital Library

First, the Project Atmosphere Canada offers a module to educate primary and secondary students about cloud formation and characteristics (1). The website outlines key points and offers a more in-depth discussion of water vapor, cloud formation, convection, air motion, severe weather, and more. The second website, by Scholastic, supplies many pdf documents of activities and lesson plans for all types of weather phenomena including clouds (2). Students can learn about condensation, discover what makes up a cloud, and find a key identifying the cloud types. Next, USA Today offers an online tutorial of the differing characteristics of clouds (3). Users can learn about Mammatus clouds, contrails, cloud seeding, and other cloud-related topics. At the fourth website, visitors can view meteorologist Dan Satterfield's amazing cloud photographs (4). Educators may find useful materials to supplement their lectures. Next, NASA's Climate and Radiation Branch furnishes "information on the fantastic variety of cloud forms and structures, and their implications for climate" (5). While the website is still being constructed, users can find useful information about the Bounded Cascades Fractal Cloud model, animations, and definitions of inhomogeneous cloud terminology. The sixth website, created by the National Center for Atmospheric Research and the University Corporation for Atmospheric Research, addresses how clouds impact our lives, how they cause chaos, and how they form (6). The enlightening descriptions are packed with colorful images and short quizzes. Next, The Australian Government's Bureau of Meteorology describes the useful of clouds as an indicator of weather conditions (7). After learning how moist air can form clouds, individuals can view images of the ten most common cloud types. Lastly, Enchanted Learning offers a table of the cloud types with their abbreviation, appearance, composition, and altitude along with explanations of cloud formation and the atmosphere (8). Educators can find simple activities dealing with cloud types and the water cycle.

350

Inversion of radar backscatter from millimeter wave smoke  

NASA Astrophysics Data System (ADS)

This paper describes the results of an analysis of radar backscatter and attenuation data collected during field trials of the MMW Module of the XM56 Large Area Screening Generator. The trials were conducted by Edgewood Research Development and Engineering Center personnel at Dugway Proving Ground in 1989 and 1990, and at Eglin AFB in 1992. The purpose of this analysis was to use inversion techniques, similar to those developed for lidar systems, to translate the radar backscatter data from the XM56 smoke clouds into estimates of cloud concentration, and to compare the resulting concentration estimates with those produces by independent, point sampling nephelometers. Three dimensional cloud concentration profiles have been produced and were found to be consistent with the Pasquill stability category. In addition, the overall correlation between the radar-generated concentration data and those collected using the nephelometers was quite good. Examples of these results are presented for the 1989, long range trials, which allowed characterization of a large volume cloud, and the 1990 and 1992 trials, which were performed over a much shorter range, but provided more useful nephelometer data.

Perry, Benjamin; Hale, D. J.

1994-08-01

351

Influence of Humidified Aerosol on Lidar Depolarization Measurements below Ice-Precipitating Arctic Stratus  

NASA Astrophysics Data System (ADS)

Lidar measurements obtained during the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment under a mixed-phase stratus cloud that was lightly precipitating ice show a range of surprisingly low depolarization ratios (4%-23%), despite an absence of cloud droplets there. These depolarization ratios are much lower than the range of theoretical values obtained for various ice habits. The depolarization ratios correlate well with radar reflectivity, suggesting that the variation in depolarization ratios results from variations in ice water content, rather than variation in ice habits or orientation. By calculating lidar depolarization based on (i) large-eddy simulations and (ii) in situ ice size distribution measurements, it is shown that the presence of humidified aerosol particles in addition to the ice precipitation can explain the distribution and vertical profile of the observed depolarization ratios, although uncertainties related to the aerosol size distributions are substantial. These calculations show that humidified aerosol must be taken into account when interpreting lidar depolarization measurements for cloud and precipitation phase discrimination or ice habit classification, at least under conditions similar to those observed during SHEBA.

van Diedenhoven, Bastiaan; Fridlind, Ann M.; Ackerman, Andrew S.

2011-10-01

352

Lidar Report  

SciTech Connect

This report provides an overview of the LiDAR acquisition methodology employed by Woolpert on the 2009 USDA - Savannah River LiDAR Site Project. LiDAR system parameters and flight and equipment information is also included. The LiDAR data acquisition was executed in ten sessions from February 21 through final reflights on March 2, 2009; using two Leica ALS50-II 150kHz Multi-pulse enabled LiDAR Systems. Specific details about the ALS50-II systems are included in Section 4 of this report.

Wollpert.

2009-04-01

353

Performance analysis for standoff biological warfare agent detection lidar  

Microsoft Academic Search

Lidar has been identified as a promising sensor for remote detection of biological warfare agents. Elastic lidar can be used for cloud detection at long ranges and UV laser induced fluorescence can be used for discrimination of bioaerosols against naturally occurring aerosols. This paper analyzes the performance of elastic lidar such as sensitivity, range and angular coverage rate vs. atmospheric

Ove Steinvall; Per Jonsson; Fredrik Kullander

2007-01-01

354

Arctic Cloud Cover Characteristics from MODIS, CALIOP, and CloudSat  

NASA Astrophysics Data System (ADS)

Cloud cover as inferred from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), Cloud Profiling Radar (CPR) on board CloudSat, and Moderate Resolution Imaging Spectroradiometer (MODIS)is studied over the Arctic Region. For MODIS, it is well known that cloud discrimination has been a challenging problem over snow and sea-ice surface types due to the limited thermal and visible contrast between clouds and the surface and is further exacerbated with the occurrence of low-level inversion. On the other hand, active sensors, such as CPR and CALIOP utilizes the return signal from radio waves or light pulses to identify cloud cover and is generally known to perform well even on cold and highly reflective surfaces, although they have several issues that are identified. In this study, Arctic cloud fraction during the months of February and September (2007 and 2010) were estimated and statistics of collocated data were created to investigate how the data can be combined to improve our characterization of the Arctic cloud cover. CALIOP being the most sensitive sensor was chosen to be the baseline for comparison. Cloud fraction from MODIS indicates fewer clouds when compared to that of CALIOP, differing by more than 50%, over sea ice and Greenland. In open water areas, MODIS overestimates cloud cover by as much as 30% thereby exhibiting a suspiciously big change in cloud fraction between sea ice and open water at the edge of the sea ice cover. CloudSat, on the other hand, appears to consistently underestimate cloud fraction on all surface types compared to CALIOP. In general, MODIS misses 26% of the clouds in the entire Arctic and 42% of the clouds in sea ice covered regions (concentration > 90%) in winter. During the summer, the performance improves to 8.7% in the entire Arctic and 13.5% in sea ice regions. Over Greenland, MODIS misses 17.3% and 13.3% for summer and winter, respectively. Furthermore, over open water, MODIS improves dramatically being able to properly detect cloud features 98.5% and 99.65% of the time over winter and summer, respectively. Interestingly, CloudSat misses 18.7% of the clouds in winter and 23.3% during summer over the entire Arctic. Sample cases where there exists considerable disagreement were analyzed and with the derived cloud characteristics from MODIS and CALIOP, we are able to establish that cloud height and geometrical/optical thicknesses are key reasons why some of the clouds were not detected. It is apparent that the three systems when used concurrently provide a more complete representation of the Arctic cloud cover.

Chan, M. C.; Comiso, J. C.

2012-04-01

355

Corona-producing ice clouds: a case study of a cold mid-latitude cirrus layer.  

PubMed

A high (14.0-km), cold (-71.0 degrees C) cirrus cloud was studied by ground-based polarization lidar and millimeter radar and aircraft probes on the night of 19 April 1994 from the Cloud and Radiation Testbed site in northern Oklahoma. A rare cirrus cloud lunar corona was generated by this 1-2-km-deep cloud, thus providing an opportunity to measure the composition in situ, which had previously been assumed only on the basis of lidar depolarization data and simple diffraction theory for spheres. In this case, corona ring analysis indicated an effective particle diameter of ~22 mum. A variety of in situ data corroborates the approximate ice-particle size derived from the passive retrieval method, especially near the cloud top, where impacted cloud samples show simple solid crystals. The homogeneous freezing of sulfuric acid droplets of stratospheric origin is assumed to be the dominant ice-particle nucleation mode acting in corona-producing cirrus clouds. It is speculated that this process results in a previously unrecognized mode of acid-contaminated ice-particle growth and that such small-particle cold cirrus clouds are potentially a radiatively distinct type of cloud. PMID:18268738

Sassen, K; Mace, G G; Hallett, J; Poellot, M R

1998-03-20

356

Corona-producing ice clouds: A case study of a cold mid-latitude cirrus layer  

SciTech Connect

A high (14.0-km), cold ({minus}71.0thinsp{degree}C) cirrus cloud was studied by ground-based polarization lidar and millimeter radar and aircraft probes on the night of 19 April 1994 from the Cloud and Radiation Testbed site in northern Oklahoma. A rare cirrus cloud lunar corona was generated by this 1{endash}2-km-deep cloud, thus providing an opportunity to measure the composition {ital in situ}, which had previously been assumed only on the basis of lidar depolarization data and simple diffraction theory for spheres. In this case, corona ring analysis indicated an effective particle diameter of {approximately}22 {mu}m. A variety of {ital in situ} data corroborates the approximate ice-particle size derived from the passive retrieval method, especially near the cloud top, where impacted cloud samples show simple solid crystals. The homogeneous freezing of sulfuric acid droplets of stratospheric origin is assumed to be the dominant ice-particle nucleation mode acting in corona-producing cirrus clouds. It is speculated that this process results in a previously unrecognized mode of acid-contaminated ice-particle growth and that such small-particle cold cirrus clouds are potentially a radiatively distinct type of cloud. {copyright} 1998 Optical Society of America

Sassen, K.; Mace, G.G. [University of Utah, Salt Lake City, Utah 84112 (United States); Hallett, J. [Desert Research Institute, Reno, Nevada 89506 (United States); Poellot, M.R. [University of North Dakota, Grand Forks, North Dakota 58202 (United States)

1998-03-01

357

Laser radar device and method  

US Patent & Trademark Office Database

A coherent laser radar or lidar device (2;20;84;90) for measuring wind speed is described that comprises a transmitter for transmitting a beam of light to a remote probe volume (6;54), a receiver for detecting back-scattered light and an analyzer for calculating wind velocity at the remote probe volume from the Doppler shift in frequency of the detected back-scattered light. The analyzer is arranged to monitor for the presence of, and/or to ensure the calculated wind speed is corrected for, any Doppler frequency components of the detected back-scattered light that arise from back-scatter off cloud located at a range greater than the range of the remote probe volume. It is described how the lidar (2;20;84;90) may be scanned and wind velocity components calculated by fitting the scanned line of sight velocity values to a predetermined function. Furthermore, it is outlined how an initial fit may be performed to determine which points are to be used in this calculation. The incorporation of a back scatter profiling means, such as ceilometer (82), is also described. A wind turbine (902) incorporating such a device (90) is also described.

2008-06-24

358

Remote sensing of atmosphere with aircraft borne lidar systems  

NASA Astrophysics Data System (ADS)

Spatial and temporal distribution of clouds and aerosols are measured by lidar. Their optical properties are evaluated using additional assumptions. Wind velocities are mapped by backscatter Doppler lidar systems. Raman lidars are to be used for the supervision of factory emissions. It is shown that Differential Absorptions Lidar (DIAL) systems offer considerable physical advantages in measuring atmospheric constituents; experiences with an airborne device are described.

Ehret, Gerhard; Renger, Wolfgang; Roesler, Uwe; Kiemle, Christian; Simmet, Georg; Ruppersberg, Gerhard

1991-09-01

359

Application of Stochastic Techniques to Radiative Transfer Through Mixed-phase Clouds  

NASA Astrophysics Data System (ADS)

Mixed-phase clouds make up about one-third of all Arctic clouds. Despite the prevalence of mixed phase clouds at high latitudes, most climate models represent such clouds with a single phase. The microphysical composition of clouds is one of the major influences on cloud radiative characteristics and contributes to the sensitivity in many cloud-radiation parameterizations. A stochastic radiative transfer model is applied to the problem of shortwave radiation passing through a layer cloud of mixed phase (ice patches in a liquid cloud). The size and distribution of ice and liquid in the cloud has been determined from co-located radar and lidar observations taken during the SHEBA campaign. Recent research indicates that liquid and ice are not homogeneously distributed throughout the cloud suggesting that a statistical representation of cloud properties may be a more successful approach to modeling radiative transfer in these situations. Model results suggest that at large scales a linear approximation similar to cloud fraction may capture the impact of the presence of both water phases.

Veron, D. E.; Brodie, J.; Barton, N.

2006-12-01

360

The vertical cloud structure of the West African monsoon: A 4 year climatology using CloudSat and CALIPSO  

NASA Astrophysics Data System (ADS)

The West African summer monsoon (WAM) is an important driver of the global climate and locally provides most of the annual rainfall. A solid climatological knowledge of the complex vertical cloud structure is invaluable to forecasters and modelers to improve the understanding of the WAM. In this paper, 4 years of data from the CloudSat profiling radar and CALIPSO are used to create a composite zonal mean vertical cloud and precipitation structure for the WAM. For the first time, the near-coincident vertical radar and lidar profiles allow for the identification of individual cloud types from optically thin cirrus and shallow cumulus to congestus and deep convection. A clear diurnal signal in zonal mean cloud structure is observed for the WAM, with deep convective activity enhanced at night producing extensive anvil and cirrus, while daytime observations show more shallow cloud and congestus. A layer of altocumulus is frequently observed over the Sahara at night and day, extending southward to the coastline, and the majority of this cloud is shown to contain supercooled liquid in the top. The occurrence of deep convective systems and congestus in relation to the position of the African easterly jet is studied, but only the daytime cumulonimbus distribution indicates some influence of the jet position.

Stein, T. H. M.; Parker, D. J.; Delanoë, J.; Dixon, N. S.; Hogan, R. J.; Knippertz, P.; Maidment, R. I.; Marsham, J. H.

2011-11-01

361

A study of how aerosols affect low-level clouds over the Nordic Countries using MODIS, ground-based, ECMWF and weather radar data.  

NASA Astrophysics Data System (ADS)

Several types of data have been combined to investigate how aerosol particles and meteorological parameters affect microphysical, radiative and precipitation properties of low-level clouds over Sweden and Finland. The cloud data was obtained from the MODIS (Moderate Resolution Imaging Spectrometer) instrument on board the Terra and Aqua satellites. The satellite scenes were screened manually for low-level clouds in limited areas around two background aerosol measurement stations. One of the stations, Vavihill, is located in Southern Sweden (56.01° N 13.9° E) and 9 years of number size distribution data from a DMPS (Differential Mobility Particle Sizer) instrument placed there was used in this study. Hyytiälä, the other station, is situated in central Finland (61.51° N 24.17° E) and 10 years of DMPS from this station data were analysed. Furthermore, modelled meteorological parameters from the European Centre for Medium-Range Forecasts (ECMWF) as well as ground-based precipitation measurements from the SMHI (Swedish Meteorological and Hydrological Institute) and from FMI (Finish Meteorological Institute) have been used in the study. Also, to be able to estimate precipitation rates in the clouds, weather radar data obtained in the BALTEX (Baltic Sea Experiment) project were utilized. The study includes 229 cases from the Vavihill region and 313 cases from the Hyytiälä area. The results from both regions show that aerosol concentrations measured at the ground-based stations have significant negative correlations with the effective radius (re) of the low-level clouds. The correlation is stronger when the re at 3.7?m is used rather than that at 2.1?m and the highest correlations are obtained when aerosol number concentrations of particles with sizes above 180 nm are used. The correlations between cloud optical thickness (COT) and aerosol number concentrations are on the other hand are positive but lower than for the re. Also, the COT correlate better with particles at larger size than the re and the strongest correlation occur at aerosol number concentrations of particles above 500 nm. However, the relative humidity at 1000 hPa is the variable that has the strongest correlation with COT. Neither the ground-based precipitation data nor the weather radar data show any significant correlations with the aerosol number concentrations at both stations. Nevertheless, there is a significant but low positive correlation between the re and the strength of the radar reflectivity factor. Hence, the first indirect aerosol effect can be detected in this dataset but not the second indirect aerosol effect.

Sporre, M. K.; Swietlicki, E.; Glantz, P.; Kulmala, M.

2012-04-01

362

The NSA/SHEBA Cloud & Radiation Comparison Study  

SciTech Connect

Cloud and radiation data from two distinctly different Arctic areas are analyzed to study the differences between coastal Alaskan and open Arctic Ocean region clouds and their respective influence on the surface radiation budget. The cloud and radiation datasets were obtained from 1) the DOE North Slope of Alaska (NSA) facility in the coastal town of Barrow, Alaska, and 2) the SHEBA field program, which was conducted from an icebreaker frozen in, and drifting with, the sea-ice for one year in the Western Arctic Ocean. Radar, lidar, radiometer, and sounding measurements from both locations were used to produce annual cycles of cloud occurrence and height, atmospheric temperature and humidity, surface longwave and shortwave broadband fluxes, surface albedo, and cloud radiative forcing. In general, both regions revealed a similar annual trend of cloud occurrence fraction with minimum values in winter (60-75%) and maximum values during spring, summer and fall (80-90%). However, the annual average cloud occurrence fraction for SHEBA (76%) was lower than the 6-year average cloud occurrence at NSA (92%). Both Arctic areas also showed similar annual cycle trends of cloud forcing with clouds warming the surface through most of the year and a period of surface cooling during the summer, when cloud shading effects overwhelm cloud greenhouse effects. The greatest difference between the two regions was observed in the magnitude of the cloud cooling effect (i.e., shortwave cloud forcing), which was significantly stronger at NSA and lasted for a longer period of time than at SHEBA. This is predominantly due to the longer and stronger melt season at NSA (i.e., albedo values that are much lower coupled with Sun angles that are somewhat higher) than the melt season observed over the ice pack at SHEBA. Longwave cloud forcing values were comparable between the two sites indicating a general similarity in cloudiness and atmospheric temperature and humidity structure between the two regions.

Janet M. Intrieri; Matthew D. Shupe

2004-08-23

363

Investigation of the adiabatic cloud model combining SEVIRI data and ground site measurements from Leipzig  

NASA Astrophysics Data System (ADS)

The first indirect aerosol effect or Twomey effect predicts a higher cloud albedo as reponse to increased aerosol load. Satellites provide a unique global coverage with high temporal and spatial resolution to investigate the climate relevance of this effect and quantify its magnitude. Different studies show that a higher aerosol concentration does not necessarily lead to higher cloud albedo if the geometrical cloud thickness is lowered. To validate the Twomey effect accurate retrievals of both cloud droplet number concentration and geometrical extent are necessary. Satellite retrievals of these quantities require an assumption about the vertical cloud profile as it can not be inferred directly from satellites. A common assumption for Stratocumulus clouds is the adiabatic cloud model that assumes a linear increasing liquid water content and constant cloud droplet number concentration with height. Due to entrainment of dry air the vertical cloud profile may be sub-adiabatic or show even a more complex vertical behaviour. To validate the robustness of satellite estimates of cloud geometrical thickness and cloud droplet number concentration, and the resulting metrics for the Twomey effect, we address the question how closley the assumption of an adiabatic or sub-adiabatic profile represents real clouds over Europe. For this purpose we compare micro- and macro-physical properties from geostationary satellite measurements of Meteosat SEVIRI with ground measurements at the Tropos Institute (Leipzig, Germany). The site provides a detailed characterization of atmospheric state through microwave radiometer, millimeter radar and lidar instruments as well as aerosol optical thickness measurements from an AERONET station.

Merk, Daniel; Ansmann, Albert; Deneke, Hartwig; Pospichal, Bernhard; Seifert, Patric

2013-04-01

364

Boreal Forest Biomass Estimation using Radar Derived Vertical and Morphological Forest Structure Indicators  

Microsoft Academic Search

Radar and lidar remote sensing techniques have demonstrated the ability to estimate the above ground biomass within a reasonable (10%-35%) accuracy level over a wide range of forest types. The conventional local approaches are based on relationships of biomass to polarimetric radar backscatter and to vertical height profiles derived from either lidar or radar interferometry. In the framework of the

M. Neumann; S. S. Saatchi

2010-01-01

365

Overview of A-Train Satellite Cloud Measurements  

NASA Astrophysics Data System (ADS)

NASA satellites make a wide variety of cloud measurements for climate and meteorological research and prediction. The A-Train is a constellation of satellites in coordinated low earth orbits with an extensive array of sensors making a wide variety of complementary observations of the earth system. The satellite constellation provides synergistic measurements enabling data from several different satellites/sensors to be used together to obtain comprehensive information about various key components and processes of the earth system. The A-Train consists of the following satellites and sensors currently in operation: Aqua, launched 4 May 2002 carries: Atmospheric Infrared Sounder-high spectral resolution (2378 channels) grating spectrometer. Advanced Microwave Sounding Unit-15 channel microwave radiometer. Humidity Sounder for Brazil is a 4 channel microwave radiometer, which provided data until February 2003. Advanced Microwave Scanning Radiometer for EOS-12 channel, 6 frequency microwave radiometer. Moderate Resolution Imaging Spectroradiometer-36 band visible and infrared imaging spectroradiometer. Cloud's and the Earth's Radiant Energy System-3 channel scanning visible and infrared radiometers. Aura, launched 15 July 2004 carries: High Resolution Dynamics Limb Sounder-multi channel infrared radiometer. Microwave Limb Sounder-multi channel microwave radiometer. Ozone Monitoring Instrument-visible and ultra violet hyperspectral imaging spectrometers. Tropospheric Emission Spectrometer-high-resolution, infrared Fourier transform spectrometer. Polarization & Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar-launched 18 December 2004 by the French space agency Centre National d'Etudes Spatiales (CNES) and carries a polarimeter. CloudSat and CALIPSO launched together 28 April 2005. CloudSat-US/Canadian cooperative project carries a 94 GHz nadir cloud profiling radar. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations-US/French mission carrying:. Cloud-Aerosol Lidar with Orthogonal Polarization-532 (polarized)and 1064 nm backscatter lidar Wide Field Camera-single channel (620-670 nm) nadir view imager. Imaging Infrared Radiometer-3 channel, nadir viewing, imaging radiometer. Two more satellites will be joining the A-Train: Orbiting Carbon Observatory-to launch in early 2009 and will carry a single instrument comprised of 3 high-resolution infrared grating spectrometers. Glory to launch in early 2009 will carry: Aerosol Polarimetry Sensor-which will measure 9 channels from 410 to 2200 nm at angles ranging from +60° to -80° with respect to nadir. Cloud Cameras-2 high spatial resolution cameras. Total Irradiance Monitor-high accuracy and precision solar radiometer The A-Train satellites fly in formation independently in polar orbits 705 km above Earth at an inclination of 98 degrees and cross over the equator a few minutes apart at approximately 1:30 p.m. local time. A-Train cloud measurements are made primarily by visible, infrared and microwave radiometers. Retrievals using these observations provide measurements of cloud areal and vertical distributions, properties, and radiative effects. Optically thin clouds, multi-layer clouds and clouds over cold bright surfaces, polar regions, represent particular challenges for passive sensors. Recently, measurements by active sensors such as lidar and radar provide detailed vertical distributions of clouds and cloud properties, complementing the passive sensors.

Maring, H.

2007-12-01

366

Model Cloud Relationships.  

National Technical Information Service (NTIS)

Contents: Radar Reflectivity Studies; Three-Dimensional Cloud/Mesoscale Model Investigations of Potential Aircraft Icing Regions; Inclusion of Ice Processes in the One-Dimensional Cloud/Turbulence Model.

W. R. Cotton E. E. Hindman G. Tripoli R. L. McAnelly C. Chen

1983-01-01

367

Combined lidar measurements of cloud properties, stratospheric, aerosols, and ozone profiles over Geesthacht(53.4 degrees N, 10.4 degrees E)  

Microsoft Academic Search

A combined Raman and elastic-backscatter lidar for independent profiling of tropospheric aerosols, moisture, and ozone and aerosol parameters is presented. GKSS operates this advanced Raman lidar at Geesthacht, Germany. First routine ozone measurements were taken between February and April 1995, Simultaneously with the European SESAME (Second European Stratospheric Arctic and Mid-latitude Experiment) campaign. The transmitter contains two lasers, a XeCl

Marcus Serwazi; Jens Reichardt; Claus Weitkamp

1995-01-01

368

GEWEX assessment of global cloud climatologies: cloud properties and their variation  

NASA Astrophysics Data System (ADS)

and GEWEX Cloud Assessment Team Satellite observations provide a continuous survey of the state of the atmosphere over the whole globe. One GEWEX activity is to assess the quality and reliability of available global cloud data sets for climate studies (http://climserv.ipsl.polytechnique.fr/gewexca). GEWEX cloud products are provided by the International Satellite Cloud Climatology Project (ISCCP), using data from a combination of polar orbiting and geostationary imagers. There are two cloud analyses (HIRS-NOAA and TOVS Path-B) using TIROS-N Operational Vertical Sounder Operational (TOVS) observations onboard the NOAA polar orbiting satellites. The relatively high spectral resolution of these instruments provides reliable cirrus identification, day and night. Recently, the NOAA PATMOS-x project has reanalyzed the Advanced Very High Resolution Radiometer (AVHRR) data onboard the same satellites. Cloud occurrence climatologies using sun occultation measurements from the Stratospheric Aerosol and Gas Experiment (SAGE) and from surface observations also participate in the assessment, as well as analyses using the second generation instruments MODIS (Moderate Resolution Imaging Spectroradiometer), MISR (Multi-angle Imaging SpectroRadiometer) and AIRS (Atmospheric Infrared Sounder) aboard the NASA the Earth Observing System (EOS). Since summer 2006 data are available from two active instruments aboard the A-Train: the lidar of the CALIPSO mission and the CloudSat radar, giving for the first time a global insight on cloud layering. Recently, also cloud climatologies from PARASOL and ATSR (Along-Track-Scanning Radiometer) joined this project. Climatological averages of cloud properties, their regional, seasonal and diurnal variations as well as time series of these climatologies are presented. One outcome of this study was, that the different datasets compared better when high, midlevel and lowlevel cloud amount were scaled by total cloud amount. This approach might also be useful for comparisons with climate models. One should also remember that passive remote sensing gives only information on the uppermost cloud layer. About 40% of all clouds are high clouds (with a cloud pressure smaller than 440 hPa) and about 40% of all clouds are single-layer lowlevel clouds (with a cloud pressure larger than 680 hPa). Differences in relative high cloud amount (scaled by total cloud amount) can be mostly understood by different instrument sensitivities: the active lidar CALIPSO as well as limb sounding SAGE are the most sensitive instruments to very thin cirrus. The relatively high spectral resolution of IR sounders (TOVS/HIRS and AIRS) makes them the passive instruments most sensitive to cirrus. They only miss 10% and 5% of all high clouds in the tropics and midlatitudes, respectively (being subvisible cirrus). ISCCP misses further 15% and 10% of high clouds in the tropics and midlatitudes, respectively. These thin cirrus (often above lower clouds) are misidentified as midlevel clouds. The MODIS Science Team algorithm misidentifies some thin cirrus as lowlevel clouds. The seasonal cycles of the different cloud properties, however, agree very well.

Stubenrauch, Claudia

2010-05-01

369

Systematic variations of cloud top temperature and precipitation rate with aerosols over the global tropics  

NASA Astrophysics Data System (ADS)

Aerosols may modify cloud properties and precipitation via a variety of mechanisms with varying and contradicting consequences. Using a large ensemble of satellite data acquired by the Moderate Resolution Imaging Spectroradiometer onboard the Earth Observing System's Aqua platform, the CloudSat cloud profiling radar and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite over the tropical oceans, we identified two distinct correlations of clouds and precipitation with aerosol loading. Cloud-top temperatures are significantly negatively correlated with increasing aerosol index (AI) over oceans and aerosol optical depth (AOT) over land for deep mixed-phase clouds with liquid droplets near the warm bases and ice crystals near the cold tops; no significant changes were found for uniformly liquid clouds. Precipitation rates are positively correlated with the AI for mixed-phase clouds, but negatively correlated for liquid clouds. These distinct correlations might be a manifestation of two potential mechanisms: the invigoration effect (which enhances convection and precipitation) and the microphysical effect (which suppresses precipitation). We note that the highly limited information garnered from satellite products cannot unequivocally support the causal relationships between cloud-top temperature/precipitation rate and aerosol loading. But if aerosols are indeed the causes for the observed relationships, they may change the overall distribution of precipitation, leading to a more extreme and unfavorable rainfall pattern of suppressing light rains and fostering heavy rains.

Niu, Feng; Li, Zhanqing

2012-09-01

370

MATLAB tools for lidar data conversion, visualization, and processing  

NASA Astrophysics Data System (ADS)

LIDAR (LIght Detection and Ranging) [1] is an optical remote sensing technology that has gained increasing acceptance for topographic mapping. LIDAR technology has higher accuracy than RADAR and has wide applications. The relevant commercial market for LIDAR has developed greatly in the last few years. LAS format is approved to be the standard data format for interchanging LIDAR data among different software developers, manufacturers and end users. LAS data format reduces the data size compared to ASCII data format. However, LAS data file can only be visualized by some expensive commercial software. There are some free tools available, but they are not user-friendly and have less or poor visualization functionality. This makes it difficult for researchers to investigate and use LIDAR data. Therefore, there is a need to develop an efficient and low cost LIDAR data toolbox. For this purpose we have developed a free and efficient Matlab tool for LIDAR data conversion, visualization and processing.

Wang, Xiao; Zhou, Kaijing; Yang, Jie; Lu, Yilong

2011-06-01

371

Assessing the Value Added to Radar-Radiometer Cirrus Retrievals by Ice Water Path Derived From Sub-millimeter Radiometry  

NASA Astrophysics Data System (ADS)

During the CRYSTAL-FACE and TC4 campaigns, observations of several cirrus cloud events were made. Several retrieval algorithms designed for use with A-train instruments are applied to these events for the computation of ice water content and of effective particle size profiles. These retrievals are further constrained by values of cloud ice water path obtained from a sub-millimeter wavelength retrieval in order to study the efficacy of such a constraint. To these ends, data from the Cloud Radar System (CRS), the Cloud Physics Lidar (CPL), the MODIS Airborne Simulator (MAS), the MODIS/ASTER Airborne Simulator (MASTER), and from the Compact Scanning Submillimeter-wave Imaging Radiometer (CoSSIR) aboard the NASA ER-2 are used; and the results of these retrievals are compared with coordinated in situ measurements.

Schwartz, M. C.; Mace, G. G.

2008-12-01

372

Lidar studies of particles and temperatures of the atmosphere: First results from National Central University lidar  

Microsoft Academic Search

With a Rayleigh and Mie scattering lidar, installed at the Central University in Chung-Li, Taiwan (25°N, 121°E), we studied the high clouds, aerosols, and temperatures of the atmosphere in the 15-60 km region since July, 1993. High clouds located near the tropopause were observed consistently. The clouds had stable structure and persisted for hours. One of the clouds presented had

J. B. Nee; G. B. Wang; P. C. Lee; S. B. Lin

1995-01-01

373

Lidar studies of particles and temperatures of the atmosphere: First results from National Central University lidar  

Microsoft Academic Search

With a Rayleigh and Mie scattering lidar, installed rat the Central University in Chung-Li, Taiwan (25øN, 121øE), we studied the high clouds, aerosols, and temperatures of the atmosphere in the i5-60 km region since July, 1993. High clouds located near the tropopause were observed consistently. The clouds had stable structure and persisted for hours. One of the clouds presented had

J. B. Nee; G. B. Wang; P. C. Lee; S. B. Lin

1995-01-01

374

A global view of midlevel liquid-layer topped stratiform cloud distribution and phase partition from CALIPSO and CloudSat measurements  

NASA Astrophysics Data System (ADS)

The first 2 year measurements from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) lidar and CloudSat radar were analyzed to study the distribution and phase partition of midlevel liqu