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1

Cloud particle size measurements in Arctic clouds using lidar and radar data  

Microsoft Academic Search

The ratio of the lidar and radar scattering cross section is sensitive to cloud particle size. High Spectral Resolution Lidar (HSRL) provides robustly calibrated scattering cross sections without the uncertainties introduced when conventional lidar data are corrected for attenuation. This paper explores the use of HSRL data and 35 GHz radar data for measuring particle size, particle phase, number density

Edwin W. Eloranta; Taneil Uttal; Matthew Shupe

2007-01-01

2

Analysis of radar and lidar returns from clouds: Implications for the proposed Earth Radiation Mission  

E-print Network

Analysis of radar and lidar returns from clouds: Implications for the proposed Earth Radiation 1999, a near�continuous dataset of observations by cloud radar, lidar ceilometer and drop reflectiv� ity, the difference in radar and lidar measured cloud base, and the frequency of occurrence

Hogan, Robin

3

Facilitating cloud radar and lidar algorithms: the Cloudnet Instrument Synergy/Target Categorization product  

E-print Network

Facilitating cloud radar and lidar algorithms: the Cloudnet Instrument Synergy other sources such as lidar, radiometers, rain gauge and a forecast model. For cloud retrievals. Ingestion of model data: Many algorithms require tem- perature and horizontal wind speed, and unless

Hogan, Robin

4

215 GHz for monitoring ice clouds: Comparison with radar/lidar synergy  

E-print Network

215 GHz for monitoring ice clouds: Comparison with radar/lidar synergy 2.2.1 Introduction and a visible lidar; the very different scattering behaviour of the two instruments would enable aerosols, rain, and cloud of all types to be detected. In section 2.5 we will show how lidar and radar can be used to infer

Hogan, Robin

5

HIGH SPECTRAL RESOLUTION LIDAR EMULATION VIA DOPPLER CLOUD RADAR SPECTRUM PROCESSING AND ITS IMPLICATIONS FOR  

E-print Network

measurements of high spectral resolution lidar (HSRL) through processing of Doppler cloud radar spectra from the operational MPACE HSRL and reveal new structure in multilayer clouds that was undetected

6

Facilitating cloud radar and lidar algorithms: the Cloudnet Instrument Synergy/Target Categorization product  

E-print Network

Facilitating cloud radar and lidar algorithms: the Cloudnet Instrument Synergy other sources such as lidar, radiometers, rain gauge and a forecast model. For cloud retrievals. Ingestion of model data: Many algorithms require tem­ perature and horizontal wind speed, and unless

Hogan, Robin

7

Ground-Based Lidar and Radar Remote Sensing of Tropical Cirrus Clouds at Nauru Island: Cloud Statistics and Radiative Impacts  

SciTech Connect

Ground based active and passive remote sensing instrumentation are combined to derive radiative and macrophysical properties of tropical cirrus clouds. Eight months of cirrus observations at the Department of Energy Atmospheric Radiation Measurement site located on Nauru Island provide independent retrieval of cloud height and visible optical depth using lidar and radar techniques. Comparisons reveal the millimeter cloud radar does not detect 13% of cirrus clouds with a cloud base higher than 15 km that are detected by the lidar. Lidar and radar cloud heights demonstrate good agreement when the cloud lies below 15 km. Radar and lidar retrievals of visible optical depth also compare well for all but the optically thinnest clouds. Cloud occurrence at Nauru as measured by lidar, reveal clear sky conditions occur on average 40%, low clouds 16%, and high clouds 44% of the time. Analysis of observed cirrus macrophysical and radiative properties suggests that two different types of cirrus exist in the tropical western Pacific: high, thin, laminar cirrus with cloud base higher than 15 km, and lower, physically thicker, more structured cirrus clouds. Differences in cirrus types are likely linked to their formation mechanisms. Radiosonde profiles of temperature and equivalent potential temperature near the tropical tropopause show a clear transition between neutrally stable and stable air at ~15 km, which may also explain the presence of two distinct cirrus types. Radiative heating rate and cloud forcing calculations for specific cirrus cases reveal the impact of tropical cirrus clouds on the earth?s radiation budget.

Comstock, Jennifer M.; Ackerman, Thomas P.; Mace, Gerald G.

2002-12-12

8

Arctic-Winter Climatology and Radiative Effects of Clouds and Aerosols Based on Lidar and Radar Measurements at PEARL  

E-print Network

Arctic-Winter Climatology and Radiative Effects of Clouds and Aerosols Based on Lidar and Radar Atmospheric Radiative Transfer (SBDART) code. Results on the climatology and radiative effects of clouds

Eloranta, Edwin W.

9

Cloud Effects on Radiative Heating Rate Profiles over Darwin using ARM and A-train Radar/Lidar Observations  

SciTech Connect

Observations of clouds from the ground-based U.S. Department of Energy Atmospheric Radiation Measurement program (ARM) and satellite-based A-train are used to compute cloud radiative forcing profiles over the ARM Darwin, Australia site. Cloud properties are obtained from both radar (the ARM Millimeter Cloud Radar (MMCR) and the CloudSat satellite in the A-train) and lidar (the ARM Micropulse lidar (MPL) and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite in the A-train) observations. Cloud microphysical properties are taken from combined radar and lidar retrievals for ice clouds and radar only or lidar only retrievals for liquid clouds. Large, statistically significant differences of up to 1.43 K/day exist between the mean ARM and A-train net cloud radiative forcing profiles. The majority of the difference in cloud radiative forcing profiles is shown to be due to a large difference in the cloud fraction above 12 km. Above this altitude the A-train cloud fraction is significantly larger because more clouds are detected by CALIPSO than by the ground-based MPL. It is shown that the MPL is unable to observe as many high clouds as CALIPSO due to being more frequently attenuated and a poorer sensitivity even in otherwise clear-sky conditions. After accounting for cloud fraction differences and instrument sampling differences due to viewing platform we determined that differences in cloud radiative forcing due to the retrieved ice cloud properties is relatively small. This study demonstrates that A-train observations are better suited for the calculation cloud radiative forcing profiles. In addition, we find that it is necessary to supplement CloudSat with CALIPSO observations to obtain accurate cloud radiative forcing profiles since a large portion of clouds at Darwin are detected by CALIPSO only.

Thorsen, Tyler J.; Fu, Qiang; Comstock, Jennifer M.

2013-06-11

10

Cloud radiative forcing on surface shortwave fluxes: A case study based on Cloud Lidar and Radar Exploratory Test  

SciTech Connect

Shortwave downward fluxes for selected stratus, cirrus, and mixed phase cloud cases are analyzed based on cloud and surface radiation measurements from the Cloud Lidar and Radar Exploratory Test conducted in the Denver-Boulder area of Colorado during September-October, 1989. A medium resolution, discrete-ordinate shortwave radiative transfer model is used to provide clear-sky conditions and to examine the cloud shortwave radiative forcing. The model simulation indicates that for stratus clouds the effective radius increases with increasing liquid water path. For cirrus cloud simulation, the model results are within 10% agreement with the surface flux measurements. However, using the one-dimensional plane-parallel model, the model results are in poor agreement for the inhomogeneous mixed phase cloud case. Over the elevated observation site, the reduction in shortwave downward flux by clouds can be as large as 40% for a small cloud water path value of 20 g m{sup {minus}2}. The variation in observed cloud shortwave forcing is highly correlated with the integrated cloud water path. The normalized (by the clear-sky value) cloud shortwave forcing increases rapidly when the cloud water path is small. The rate of increase decreases, and the normalized cloud forcing approaches saturation when cloud water path becomes large. The magnitude of the saturation value depends on cloud optical properties. The variation in observed cloud forcing is consistent with the theoretical curve for cloudy atmospheric albedo variation. At a constant value of cloud water path, the normalized cloud forcing increases with solar zenith angle. The solar zenith angle effect is less significant for larger value of cloud water path. 44 refs., 11 figs.

Shi, L. [Univ. of California, San Diego, CA (United States)] [Univ. of California, San Diego, CA (United States)

1994-12-20

11

Evaluation of Cloud-Phase Retrieval Methods for SEVIRI on Meteosat-8 Using Ground-Based Lidar and Cloud Radar Data  

E-print Network

Evaluation of Cloud-Phase Retrieval Methods for SEVIRI on Meteosat-8 Using Ground-Based Lidar and Cloud Radar Data ERWIN L. A. WOLTERS, ROBERT A. ROEBELING, AND ARNOUT J. FEIJT Royal Netherlands 2007) ABSTRACT Three cloud-phase determination algorithms from passive satellite imagers are explored

Stoffelen, Ad

12

Cloud fraction, liquid and ice water contents derived from long-term radar, lidar, and microwave radiometer data are systematically compared to models to quantify and  

E-print Network

Cloud fraction, liquid and ice water contents derived from long-term radar, lidar, and microwave a systematic evaluation of clouds in forecast models. Clouds and their associated microphysical processes for end users of weather forecasts, who may be interested not only in cloud cover, but in other variables

Hogan, Robin

13

The CloudSat radar-lidar geometrical profile product (RL-GeoProf): Updates, improvements, and selected results  

NASA Astrophysics Data System (ADS)

by combining data from the CloudSat radar and the CALIPSO lidar, the so-called radar-lidar geometrical profile product (RL-GeoProf) allows for characterization of the vertical and spatial structure of hydrometeor layers. RL-GeoProf is one of the standard data products of the CloudSat Project. In this paper we describe updates to the RL-GeoProf algorithm. These improvements include a significant fix to the CALIPSO Vertical Feature Mask (VFM) that more accurately renders the occurrence frequencies of low-level clouds over the global oceans. Additionally, we now account for the navigational challenges associated with coordinated measurements of the two instruments by providing additional diagnostic information in the data files. We also document how the along-track averaging of the VFM influences the accuracy of RL-GeoProf. We find that the 5 km averaged VFM when merged with data from the CloudSat radar provides a global description of cloud occurrence that best matches an independently derived cloud mask from Moderate Resolution Imaging Spectroradiometer (MYD35) over daytime global oceans. Expanding on the comparison with MYD35, we demonstrate that RL-GeoProf and MYD35 closely track the monthly averaged cloud occurrence fraction during a 4 year span of measurements. A more detailed examination reveals latitudinal dependency in the comparison. Specifically, MYD35 tends to be significantly low biased relative to RL-GeoProf over the Polar Regions when cloud layers present low visible and thermal contrast with underlying surfaces. Additional analyses examine the geometrically defined hydrometeor layer occurrence climatologies over select regions of the Earth and the seasonal variations of low-based and low-topped cloud cover.

Mace, Gerald G.; Zhang, Qiuqing

2014-08-01

14

Combined remote sensing of cloud characteristics with surface-based radar, lidar, and all sky imagers over Beijing, China  

NASA Astrophysics Data System (ADS)

Clouds have been known as the key components of atmospheric processes in climate, weather, and environment related issues. Owing to its highly complicated processes relating to atmospheric dynamic, macro and microphysical characteristics reveal distinct regional and seasonal features, thus observations at various typical sites are very important to quantitatively understand cloud characteristics with their functions. In this paper, we introduce combined ground-based instruments, i.e., a Mie Lidar, a Ka-band Doppler radar, an IR and a visible all sky imagers, and an automatic weather station, to continuously observe the clouds over Beijing. Synthetic analyses are made to derive the cloud base height, vertical structure, horizontal distribution, radiative effect, etc. About 1 year observation data are used to obtain the statistics of cloud characteristics in this area. A simple introduction of the surface-based remote sensing system and some preliminary results are given.

Liu, Jinli; Lu, Daren; Bi, Yongheng; Duan, Shu; Yang, Yong; Pan, Yubin; Li, Yu

2013-05-01

15

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 Lop 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

16

Parameterizing the Difference in Cloud Fraction Defined by Area and by Volume as Observed with Radar and Lidar.  

NASA Astrophysics Data System (ADS)

Most current general circulation models (GCMs) calculate radiative fluxes through partially cloudy grid boxes by weighting clear and cloudy fluxes by the fractional area of cloud cover (Ca), but most GCM cloud schemes calculate cloud fraction as the volume of the grid box that is filled with cloud (C). In this paper, 1 yr of cloud radar and lidar observations from Chilbolton in southern England, are used to examine this discrepancy. With a vertical resolution of 300 m it is found that, on average, Ca is 20% greater than C, and with a vertical resolution of 1 km, Ca is greater than C by a factor of 2. The difference is around a factor of 2 larger for liquid water clouds than for ice clouds, and also increases with wind shear. Using Ca rather than C, calculated on an operational model grid, increases the mean total cloud cover from 53% to 63%, and so is of similar importance to the cloud overlap assumption.A simple parameterization, Ca = [1 + e(-f)(C-1 - 1)]-1, is proposed to correct for this underestimate based on the observation that the observed relationship between the mean Ca and C is symmetric about the line Ca = 1 - C. The parameter f is a simple function of the horizontal (H) and vertical (V) grid-box dimensions, where for ice clouds f = 0.0880 V0.7696 H-0.2254 and for liquid clouds f = 0.1635 V0.6694 H-0.1882.Implementing this simple parameterization, which excludes the effect of wind shear, on an independent 6-month dataset of cloud radar and lidar observations, accounts for the mean underestimate of Ca for all horizontal and vertical resolutions considered to within 3% of the observed Ca, and reduces the rms error for each individual box from typically 100% to approximately 30%. Small biases remain for both weakly and strongly sheared cases, but this is significantly reduced by incorporating a simple shear dependence in the calculation of the parameter f, which also slightly improves the overall performance of the parameterization for all of the resolutions considered.

Brooks, Malcolm E.; Hogan, Robin J.; Illingworth, Anthony J.

2005-07-01

17

Independent evaluation of the ability of spaceborne radar and lidar  

E-print Network

Chapter 1 Independent evaluation of the ability of spaceborne radar and lidar to retrieve the microphysical and radiative properties of ice clouds Summary. The combination of radar and lidar in space offers, that of correcting the lidar signal for extinction. In this chapter "blind tests" of these two algorithms are carried

Hogan, Robin

18

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

NASA Astrophysics Data System (ADS)

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 occurrence was 11.5% at 1 km. The cloud fraction, radar reflectivity factor, and lidar backscattering coefficient were simulated along the Mirai cruise track using the output from the Center for Climate System Research, University of Tokyo; National Institute for Environmental Studies; and Frontier Research Center for Global Change (CCSR/NIES/FRCGC) general circulation model (GCM). The original output showed the maximum cloud fraction at 15 km; however, after considering attenuation and the minimum sensitivity of the radar, the maximum shifted to 12 km. The model overestimated the cloud fraction above 8 km, with the simulated fraction more than twice as large as the observed fraction. The model overpredicted the frequency of deep convection reaching the upper atmosphere above 12 km. Further, it overestimated precipitation frequency. Simulated radar reflectivity was underestimated throughout the entire altitude range, whereas simulated and observed lidar backscattering were in good agreement above 12 km with subgrid-scale treatment. The ice effective radius of 40 ?m and ice water content were reasonable in thin clouds, but the radius was underestimated in other regions. The simulated liquid water content was overestimated.

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

2008-12-01

19

An Assessment of MultiAngle Imaging SpectroRadiometer (MISR) Stereo-Derived Cloud Top Heights and cloud top winds using ground-based radar, lidar, and microwave radiometers  

SciTech Connect

Clouds are of tremendous importance to climate because of their direct radiative effects and because of their role in atmospheric dynamics and the hydrological cycle. The value of satellite imagery in monitoring cloud properties on a global basis can hardly be understated. One cloud property that satellites are in an advantageous position to monitor is cloud top height. Cloud top height retrievals are especially important for MISR because the derived height field is used to co-register the measured radiances. In this presentation we show the results of an ongoing comparison between ground-based millimeter-wave cloud radar and lidar measurements of cloud top and MISR stereo-derived cloud top height. This comparison is based on data from three radar systems located in the U.S Southern Great Plains (Lamont, Oklahoma), the Tropical Western Pacific (Nauru Island) and the North Slope of Alaska (Barrow, Alaska). These radars are operated as part of the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) program. The MISR stereo height algorithm is performing largely as expected for most optically thick clouds. As with many satellite retrievals, the stereo-height retrieval has difficulty with optically thin clouds or ice clouds with little optical contrast near cloud top.

Marchand, Roger T.; Ackerman, Thomas P.; Moroney, C.

2007-03-17

20

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

21

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

22

Using Radar, Lidar and Radiometer Data from NSA and SHEBA to Quantify Cloud Property Effects on the Surface Heat Budget in the Arctic  

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 Intrieri; Mathhew Shupe

2005-01-01

23

Mapping tropical forest biomass with radar and spaceborne LiDAR in Lop 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 Lop 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

24

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; Hller, Hartmut; Schmidt, Kersten

25

The Evaluation of CloudSat and CALIPSO Ice Microphysical Products Using Ground-Based Cloud Radar and Lidar Observations  

E-print Network

by a large positive bias of 8­12 mm. A sensitivity test shows that in response to such a bias the cloud are suggested in this study. Effective radii retrievals from the standard CloudSat algorithms are characterized longwave forcing is increased from 44.6 to 46.9 W m22 (implying an error of about 5%), whereas the negative

Protat, Alain

26

Upgraded Doppler Rayleigh Lidar and Comparisonswith Stratospheric Radar: 1: Observations Following Initial System Modifications  

E-print Network

Upgraded Doppler Rayleigh Lidar and Comparisonswith Stratospheric Radar: 1: Observations Following-mail mikek@ee,comell.edu We prescnt lidar observations of density fluctuations in the presence of thin cloud. These observationsfollowedthe initial stage of a Doppler Rayleigh lidar system upgrade. These initial observations were made

Cho, John Y. N.

27

The variability of tropical ice cloud properties as a function of the large-scale context from ground-based radar-lidar observations over Darwin, Australia  

NASA Astrophysics Data System (ADS)

The high complexity of cloud parameterizations now held in models puts more pressure on observational studies to provide useful means to evaluate them. One approach to the problem put forth in the modelling community is to evaluate under what atmospheric conditions the parameterizations fail to simulate the cloud properties and under what conditions they do a good job. It is the ambition of this paper to characterize the variability of the statistical properties of tropical ice clouds in different tropical "regimes" recently identified in the literature to aid the development of better process-oriented parameterizations in models. For this purpose, the statistical properties of non-precipitating tropical ice clouds over Darwin, Australia are characterized using ground-based radar-lidar observations from the Atmospheric Radiation Measurement (ARM) Program. The ice cloud properties analysed are the frequency of ice cloud occurrence, the morphological properties (cloud top height and thickness), and the microphysical and radiative properties (ice water content, visible extinction, effective radius, and total concentration). The variability of these tropical ice cloud properties is then studied as a function of the large-scale cloud regimes derived from the International Satellite Cloud Climatology Project (ISCCP), the amplitude and phase of the Madden-Julian Oscillation (MJO), and the large-scale atmospheric regime as derived from a long-term record of radiosonde observations over Darwin. The vertical variability of ice cloud occurrence and microphysical properties is largest in all regimes (1.5 order of magnitude for ice water content and extinction, a factor 3 in effective radius, and three orders of magnitude in concentration, typically). 98 % of ice clouds in our dataset are characterized by either a small cloud fraction (smaller than 0.3) or a very large cloud fraction (larger than 0.9). In the ice part of the troposphere three distinct layers characterized by different statistically-dominant microphysical processes are identified. The variability of the ice cloud properties as a function of the large-scale atmospheric regime, cloud regime, and MJO phase is large, producing mean differences of up to a factor 8 in the frequency of ice cloud occurrence between large-scale atmospheric regimes and mean differences of a factor 2 typically in all microphysical properties. Finally, the diurnal cycle of the frequency of occurrence of ice clouds is also very different between regimes and MJO phases, with diurnal amplitudes of the vertically-integrated frequency of ice cloud occurrence ranging from as low as 0.2 (weak diurnal amplitude) to values in excess of 2.0 (very large diurnal amplitude). Modellers should now use these results to check if their model cloud parameterizations are capable of translating a given atmospheric forcing into the correct statistical ice cloud properties.

Protat, A.; Delano, J.; May, P. T.; Haynes, J.; Jakob, C.; O'Connor, E.; Pope, M.; Wheeler, M. C.

2011-08-01

28

A Radar Safety Device for Lidars Probing the Atmosphere  

NASA Technical Reports Server (NTRS)

Lasers have been used for important atmospheric research almost since their inception. Present day lidar systems continue this serious work and lasers are currently being used in increasingly sophisticated ways to expand our knowledge of atmospheric processes. Langley Research Center, for example, has been performing airborne and ground-based stratospheric volcanic-aerosol lidar measurements for the past 27 years and the University of Utah has been measuring cirrus cloud radiative properties with lidar for the past 20 years. Although the widespread use of lasers probing the atmosphere is too voluminous to cite in an extended abstract, one critical fact must be noted: atmospheric lidar measurements must increasingly be performed wherever they are needed and thus the problems associated with the operation of lidars and aircraft in the same airspace are becoming increasingly vexatious. The lidar community is quite sensitive to this issue and procedures such as the issuance of Notices to Airmen (NOTAMS), informing the FAA of lidar operations, and use of ground-based aircraft observers are already being widely utilized. Current measures, however, depend largely on pilots receiving the NOTAM and acting on it or approach control vectoring the aircraft away from the lidar site. Perhaps a better approach is to provide the lidar site with an autonomous capability to automatically interrupt laser operations while any aircraft is close-by. This abstract describes our efforts to develop and test an inexpensive radar system for use as an aircraft proximity warning and laser shut-down device during atmospheric lidar operations.

Alvarez, J. M.; Fuller, W. H., Jr.; Lawrence, R. M.

1998-01-01

29

Fast Lidar and Radar Multiple-Scattering Models. Part I: Small-Angle Scattering Using the Photon VarianceCovariance Method  

E-print Network

Fast Lidar and Radar Multiple-Scattering Models. Part I: Small-Angle Scattering Using the Photon method is described for the calculation of the intensity of multiply scattered lidar returns from clouds-based and airborne lidars because of their small footprint on the cloud. For spaceborne lidar, it must be used

Hogan, Robin

30

Parameterizing the Difference in Cloud Fraction Defined by Area and by Volume as Observed with Radar and Lidar  

E-print Network

is a simple function of the horizontal (H) and vertical (V) grid-box dimensions, where for ice clouds f 0 with the vertical dimension of the grid box. Most schemes for determining the cloud fraction yield C , which is more, are used to examine this discrepancy. With a vertical resolution of 300 m it is found that, on average, Ca

Reading, University of

31

Ground Based Lidar Characterization of Cirrus Clouds  

NASA Technical Reports Server (NTRS)

This paper presents cirrus cloud observations made with the High Spectral Resolution Lidar (HSRL) and the Volume Imaging Lidar (VIL). The HSRL was redesigned to use an iodine absorption filter in place of the Fabry-Perot etalon that was used for spectral separation of the aerosol and molecular lidar returns. These modifications, which improve both sensitivity and calibration stability, are described.

Eloranta, Edwin W.

1996-01-01

32

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

33

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

34

An Initial Application of Polarization Lidar for Orographic Cloud Seeding Operations  

Microsoft Academic Search

Ground-based polarization lidar measurements have been obtained in conjunction with a commercial cloud seeding program to evaluate the potential of pulsed laser remote sensing techniques for increasing the effectiveness of orographic cloud seeding operations. The lidar measurements, supplemented by microwave radar cloud top and rawinsonde data, are shown to aid in the determination of seeding criteria. Our real-time seed, no-seed

Kenneth Sassen

1980-01-01

35

Laser Heterodyne Radars and Lidars  

Microsoft Academic Search

\\u000a The title of this chapter is so contradictory that it needs special clarification before commencing the detailed discussion\\u000a of the chapter matter. The term RADAR emerged in 1941 as an acronym for radio detection and ranging. Thus, the two words laser\\u000a radar being put together represent first contradiction. It sounds even more curios, considering the fact that both words\\u000a are

Vladimir Protopopov

36

CLOUD FRACTION STATISTICS DERIVED FROM 2YEARS OF HIGH SPECTRAL RESOLUTION LIDAR DATA ACQUIRED AT EUREKA, CANADA.  

E-print Network

(AHSRL) and the NOAA 8.6 mm wavelength cloud radar (MMCR). Both instruments have operated nearly continuously since from the lidar. It also presents comparisons between lidar, radar, and convention is warming faster than the rest of the globe. Warming is also predicted by climate models. However

Eloranta, Edwin W.

37

THOR: Cloud Thickness from Off beam Lidar Returns  

NASA Technical Reports Server (NTRS)

Conventional wisdom is that lidar pulses do not significantly penetrate clouds having optical thickness exceeding about tau = 2, and that no returns are detectable from more than a shallow skin depth. Yet optically thicker clouds of tau much greater than 2 reflect a larger fraction of visible photons, and account for much of Earth s global average albedo. As cloud layer thickness grows, an increasing fraction of reflected photons are scattered multiple times within the cloud, and return from a diffuse concentric halo that grows around the incident pulse, increasing in horizontal area with layer physical thickness. The reflected halo is largely undetected by narrow field-of-view (FoV) receivers commonly used in lidar applications. THOR - Thickness from Off-beam Returns - is an airborne wide-angle detection system with multiple FoVs, capable of observing the diffuse halo, detecting wide-angle signal from which physical thickness of optically thick clouds can be retrieved. In this paper we describe the THOR system, demonstrate that the halo signal is stronger for thicker clouds, and validate physical thickness retrievals for clouds having z > 20, from NASA P-3B flights over the Department of Energy/Atmospheric Radiation Measurement/Southern Great Plains site, using the lidar, radar and other ancillary ground-based data.

Cahalan, Robert F.; McGill, Matthew; Kolasinski, John; Varnai, Tamas; Yetzer, Ken

2004-01-01

38

Combined Lidar-Radar Remote Sensing: Initial Results from CRYSTAL-FACE and Implications for Future Spaceflight Missions  

NASA Technical Reports Server (NTRS)

In the near future NASA plans to fly satellites carrying a multi-wavelength backscatter lidar and a 94-GHz cloud profiling radar in formation to provide complete global profiling of cloud and aerosol properties. The CRYSTAL-FACE field campaign, conducted during July 2002, provided the first high-altitude colocated measurements from lidar and cloud profiling radar to simulate these spaceborne sensors. The lidar and radar provide complementary measurements with varying degrees of measurement overlap. This paper presents initial results of the combined airborne lidar-radar measurements during CRYSTAL-FACE. The overlap of instrument sensitivity is presented, within the context of particular CRYSTAL-FACE conditions. Results are presented to quantify the portion of atmospheric profiles sensed independently by each instrument and the portion sensed simultaneously by the two instruments.

McGill, Matthew J.; Li, Li-Hua; Hart, William D.; Heymsfield, Gerald M.; Hlavka, Dennis L.; Vaughan, Mark A.; Winker, David M.

2003-01-01

39

Raman lidar observations of cloud liquid water.  

PubMed

We report the design and the performances of a Raman lidar for long-term monitoring of tropospheric aerosol backscattering and extinction coefficients, water vapor mixing ratio, and cloud liquid water. We focus on the system's capabilities of detecting Raman backscattering from cloud liquid water. After describing the system components, along with the current limitations and options for improvement, we report examples of observations in the case of low-level cumulus clouds. The measurements of the cloud liquid water content, as well as the estimations of the cloud droplet effective radii and number densities, obtained by combining the extinction coefficient and cloud water content within the clouds, are critically discussed. PMID:15617280

Rizi, Vincenzo; Iarlori, Marco; Rocci, Giuseppe; Visconti, Guido

2004-12-10

40

Automated registration of synthetic aperture radar imagery to LIDAR  

Microsoft Academic Search

The registration of synthetic aperture radar imagery to other images is difficult, especially in mountainous terrain. We introduce a new approach to this problem that registers radar images to digital elevation models derived from LIDAR. The algorithm generates a predicted image from the elevation model using the radar geometry and then registers the predicted image to the radar image with

Mark D. Pritt; Kevin J. LaTourette

2011-01-01

41

An improved model for snowfall measurement using lidar and radar Lidar Backscatter Cross Section ~ number density * Radar Backscatter Cross Section ~ number density * Radar Doppler Velocity ~ f( mass, projected area, air density)  

E-print Network

An improved model for snowfall measurement using lidar and radar Lidar Backscatter Cross Section * radar Doppler velocity = precipitation rate Integrating precip rate yields total precipitation Eureka

Eloranta, Edwin W.

42

Drizzle Droplet Size Estimation Using High Spectral Resolution LIDAR and Millimeter Radar Data  

NASA Astrophysics Data System (ADS)

High spectral resolution lidar(HSRL) provides calibrated measurement of optical extinction that can be used with millimeter wavelength radar to provide a measure of drizzle droplet size. The strengths and limitations of the this approach are examined using a combination of HSRL, KAZR radar and disdrometer data acquired during the MAGIC deployment of the DOE AMF2 mobile facility. Data was collected on a ship during multiple trips between Long Beach, CA an Honolulu, HI. Lidar-radar particle size estimations are typically based on the assumption of a mono-modal size distribution. The multi-mode particle size distributions that exist in clouds where drizzle co-exists with cloud droplets yield lidar-radar size estimates that are not characteristic of either distribution. A similar problem is encountered in the sub-cloud layer where aerosol scattering co-exists with drizzle. This paper examines the possibility of using aerosol scattering measured outside the drizzle shafts to correct for aerosol contributions and compares the lidar-radar drizzle derived particle sizes with disdrometer measurements.

Eloranta, E. W.; Bartholomew, M. J.; Bharadwaj, N.

2013-12-01

43

Lidar cloud studies for FIRE and ECLIPS  

NASA Technical Reports Server (NTRS)

Optical remote sensing measurements of cirrus cloud properties were collected by one airborne and four ground-based lidar systems over a 32 h period during this case study from the First ISCCP (International Satellite Cloud Climatology Program) Regional Experiment (FIRE) Intensive Field Observation (IFO) program. The lidar systems were variously equipped to collect linear depolarization, intrinsically calibrated backscatter, and Doppler velocity information. Data presented describe the temporal evolution and spatial distribution of cirrus clouds over an area encompassing southern and central Wisconsin. The cirrus cloud types include: dissipating subvisual and thin fibrous cirrus cloud bands, an isolated mesoscale uncinus complex (MUC), a large-scale deep cloud that developed into an organized cirrus structure within the lidar array, and a series of intensifying mesoscale cirrus cloud masses. Although the cirrus frequently developed in the vertical from particle fall-streaks emanating from generating regions at or near cloud tops, glaciating supercooled (-30 to -35 C) altocumulus clouds contributed to the production of ice mass at the base of the deep cirrus cloud, apparently even through riming, and other mechanisms involving evaporation, wave motions, and radiative effects are indicated. The generating regions ranged in scale from approximately 1.0 km cirrus uncinus cells, to organized MUC structures up to approximately 120 km across.

Sassen, Kenneth; Grund, Christian J.; Spinhirne, James D.; Hardesty, Michael; Alvarez, James

1990-01-01

44

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

45

Fast lidar and radar multiple-scattering models Part 1: Quasi-small-angle scattering using the photon variance-covariance method  

E-print Network

Fast lidar and radar multiple-scattering models Part 1: Quasi-small-angle scattering using for the calculation of the intensity of multiply scattered lidar returns from clouds. At each range gate-angle forward scattering events, which is suitable for most ground-based and airborne lidars due to their small

Reading, University of

46

Fast lidar and radar multiple-scattering models Part 2: Wide-angle scattering using the time-dependent two-stream approximation  

E-print Network

Fast lidar and radar multiple-scattering models Part 2: Wide-angle scattering using the time. Atmos. Sci., October 2007 ABSTRACT Spaceborne lidar returns from liquid water clouds contain significant a near-direct path out to and back from a single backscattering event (in the case of lidar, accounting

Reading, University of

47

Multiple scattering lidar returns from stratus clouds  

NASA Technical Reports Server (NTRS)

Multiple scattering lidar returns from stratus clouds were measured using a multi-field-of-view (MFOV) lidar operating at 1.054 microns. The detector consists of four concentric silicon photodiodes which define half-angle fields of view (FOV) of 3.8, 12.5, 25 and 38.5 mrad. The central FOV receives the conventional lidar signal, while the outer FOV's receive only multiply scattered contributions. The ratios of the signals in the outer FOV's to the signal in the central FOV is an indication of the lateral spreading of the scattered component of the laser pulse as it propagates through the cloud. MFOV lidar returns from stratus clouds measured between October 1991 and March 1992 can be divided into two distinct types, those with large multiple scattering ratios and those with small ratios. An example of each type of return is shown. Both measurements were made at an elevation angle of 45 degrees. Clouds with small multiple scattering signals probably have a high concentration of much larger particles on the order of hundreds of micrometers in size. This is a typical size range for suspended ice crystals or precipitations. Stratus clouds often have a high concentration of ice crystals even when there is no precipitation. Large ice crystals would give smaller signals in the outer FOV's because much of the scattered intensity is contained in a narrow diffraction peak with an angular width on the order of milliradians. The result is that for a given extinction, many more orders of scattering are required for the laser pulse to spread out. So far we have not been able to do simulations of MFOV lidar returns from ice crystal clouds because of uncertainties about the phase function of the crystals, particularly the magnitude of the backscatter peak at 180 degrees. On two occasions, MFOV lidar returns measured just prior to snowfall, showed a striking vertical profile. An example is shown. From 900 to 1300m, the multiply scattered signals are negligible compared to the return in the central FOV. Abruptly, at 1300m strong signals begin in the outer FOVs. These results could be explained by the presence of a cloud layer composed of water droplets at a range of 1300m (or 900m above ground) with snow precipitations forming at the bottom of the cloud. By measuring the polarization ratio of lidar signals, Pal and Carswell have observed snow precipitating from a cloud layer composed of water droplets. Based on these results, we believe that analysis of multiple scattering lidar returns can yield important information on the phase of cloud particles.

Hutt, D. L.; Bissonnette, L. R.

1992-01-01

48

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

49

Cloud properties derived from two lidars over the ARM SGP site  

NASA Astrophysics Data System (ADS)

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. 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 cloud optical thickness larger than 3. 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 and (2) to estimate the discrepancies between the two remote sensing systems (pulse energy, sampling, resolution, etc.). Our first results tend to show that the MPL, which are the primary ARM lidars, have a distinctly limited range within which all of these cloud properties are detectable, especially cloud top and cloud thickness, but this can include cloud base particularly 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 MPL-derived 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 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 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 Long et al.'s (2006) cloud fraction calculation derived from radiative flux analysis.

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

2011-04-01

50

Cloud Layer Detection by WSR-57 Radar  

Microsoft Academic Search

The ability of the WSR-57 radar to detect `cloud' layers of various types is studied from data collected during the period from late winter through mid-summer of 1960. Results indicate the best correlation between the radar echo layers and those visually observed is among the middle cloud types. Detection of the low cloud types was impeded, to some extent, by

James H. Hand

1964-01-01

51

Lidar Studies of Clouds at Toronto During the ECLIPS Program  

NASA Technical Reports Server (NTRS)

The Experimental Cloud Lidar Pilot Study (ECLIPS) measurement program involves the measurement of cloud optical and physical parameters with vertically pointing ground-based lidars simultaneously with satellites observing the same cloud system from above. Our frequency doubled Nd:YAG lidar transmits about 500 mJ of linearly polarized radiation at each wavelength (532, 1064 nm) with a prf of 20 Hz. An overview of the statistical behavior of cloud physical parameters and optical parameters is presented.

Pal, S. R.; Carswell, A. I.; Fong, A. Y.; Pribluda, I.; Steinbrecht, W.

1992-01-01

52

Improved Snowfall Measurements using High Spectral Resolution Lidar and Radar  

Microsoft Academic Search

Lidar and radar measurements can be combined to estimate the effective diameter of precipitation particles(Donovan and Lammeren, J. Geophys. Res. 106, 2001). When these size estimates are combined with radar vertical velocity measurements it is possible to estimate precipitation rates in a layer a short distance above the ground. These retrievals are made much more robust when a high spectral

E. W. Eloranta

2008-01-01

53

Air-Truth Lidar Polarization Studies of Orographic Clouds  

Microsoft Academic Search

The results of a field program of coordinated lidar and aircraft observations of orographically induced clouds are reported. An evaluation of polarization diversity lidar for cloud physics research applications on the basis of the air-truth measurements and earlier findings indicates that the remote sensing technique can monitor some kinds of cloud microphysical information currently measured only through in situ sampling

Kenneth Sassen

1978-01-01

54

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

55

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

56

A depolarisation lidar based method for the determination of liquid-cloud microphysical properties  

NASA Astrophysics Data System (ADS)

The fact that polarisation lidars measure a depolarisation signal in liquid clouds due to the occurrence of multiple-scattering is well-known. The degree of measured depolarisation depends on the lidar characteristics (e.g. wavelength and receiver field-of-view) as well as the cloud macrophysical (e.g. liquid water content) and microphysical (e.g. effective radius) properties. Efforts seeking to use depolarisation information in a quantitative manner to retrieve cloud properties have been undertaken with, arguably, limited practical success. In this work we present a retrieval procedure applicable to clouds with (quasi-)linear liquid water content (LWC) profiles and (quasi-)constant cloud droplet number density in the cloud base region. Thus limiting the applicability of the procedure allows us to reduce the cloud variables to two parameters (namely the derivative of the liquid water content with height and the extinction at a fixed distance above cloud-base). This simplification, in turn, allows us to employ a fast and robust optimal-estimation inversion using pre-computed look-up-tables produced using extensive lidar Monte-Carlo multiple-scattering simulations. In this paper, we describe the theory behind the inversion procedure and successfully apply it to simulated observations based on large-eddy simulation model output. The inversion procedure is then applied to actual depolarisation lidar data corresponding to a range of cases taken from the Cabauw measurement site in the central Netherlands. The lidar results were then used to predict the corresponding cloud-base region radar reflectivities. In non-drizzling condition, it was found that the lidar inversion results can be used to predict the observed radar reflectivities with an accuracy within the radar calibration uncertainty (2-3 dBZ). This result strongly supports the accuracy of the lidar inversion results. Results of a comparison between ground-based aerosol number concentration and lidar-derived cloud droplet number densities are also presented and discussed. The observed relationship between the two quantities is seen to be consistent with the results of previous studies based on aircraft-based in situ measurements.

Donovan, D. P.; Klein Baltink, H.; Henzing, J. S.; de Roode, S. R.; Siebesma, A. P.

2014-09-01

57

An analysis of lidar observations of polar stratospheric clouds  

Microsoft Academic Search

Lidar observations by Browell et al. (1990) are interpreted using single scattering calculations for nonspherical particles and aerosol microphysical calculations. Many of the lidar observations are consistent with particles containing 10 ppbv of condensed nitric acid vapor and an equivalent mass of water. The lidar observations of these Type 1 clouds identify two subtypes, whose properties are deduced. Type 1b

Owen B. Toon; S. Kinne; E. V. Browell; J. Jordan

1990-01-01

58

ROUTINE CLOUD-BOUNDARY ALGORITHM DEVELOPMENT FOR ARM MICROPULSE LIDAR  

E-print Network

ROUTINE CLOUD-BOUNDARY ALGORITHM DEVELOPMENT FOR ARM MICROPULSE LIDAR Chitra Sivaraman, Pacific implemented for use with the ARM micropulse lidar (MPL) systems. As part of this value-added product (VAP backscatter lidar signal to provide a corrected attenuated backscatter profile. This VAP will be the primary

59

First radar echoes from cumulus clouds  

SciTech Connect

In attempting to use centimeter-wavelength radars to investigate the early stage of precipitation formation in clouds, 'mantle echoes' are rediscovered and shown to come mostly from scattering by small-scale variations in refractive index, a Bragg kind of scattering mechanism. This limits the usefulness of single-wavelength radar for studies of hydrometeor growth, according to data on summer cumulus clouds in North Dakota, Hawaii, and Florida, to values of reflectivity factor above about 10 dBZe with 10-cm radar, 0 dBZe with 5-cm radar, and -10 dBZe with 3-cm radar. These are limits at or above which the backscattered radar signal from the kinds of clouds observed can be assumed to be almost entirely from hydrometeors or (rarely) other particulate material such as insects. Dual-wavelength radar data can provide the desired information about hydrometeors at very low reflectivity levels if assumptions can be made about the inhomogeneities responsible for the Bragg scattering. The Bragg scattering signal itself probably will be a useful way to probe inhomogeneities one-half the radar wavelength in scale for studying cloud entrainment and mixing processes. However, this use is possible only before scattering from hydrometeors dominates the radar return. 25 refs.

Knight, C.A.; Miller, L.J. (NCAR, Boulder, CO (United States))

1993-02-01

60

First radar echoes from cumulus clouds  

NASA Technical Reports Server (NTRS)

In attempting to use centimeter-wavelength radars to investigate the early stage of precipitation formation in clouds, 'mantle echoes' are rediscovered and shown to come mostly from scattering by small-scale variations in refractive index, a Bragg kind of scattering mechanism. This limits the usefulness of single-wavelength radar for studies of hydrometeor growth, according to data on summer cumulus clouds in North Dakota, Hawaii, and Florida, to values of reflectivity factor above about 10 dBZe with 10-cm radar, 0 dBZe with 5-cm radar, and -10 dBZe with 3-cm radar. These are limits at or above which the backscattered radar signal from the kinds of clouds observed can be assumed to be almost entirely from hydrometeors or (rarely) other particulate material such as insects. Dual-wavelength radar data can provide the desired information about hydrometeors at very low reflectivity levels if assumptions can be made about the inhomogeneities responsible for the Bragg scattering. The Bragg scattering signal itself probably will be a useful way to probe inhomogeneities one-half the radar wavelength in scale for studying cloud entrainment and mixing processes. However, this use is possible only before scattering from hydrometeors dominates the radar return.

Knight, Charles A.; Miller, L. J.

1993-01-01

61

Lidar methods for measuring distributions and characteristics of aerosols and clouds  

Microsoft Academic Search

Mie scattering lidar methods for measuring aerosols and clouds are described. The concepts of Mie scattering lidars, depolarization measurements, and bistatic lidar methods will be described. High-spectral-resolution lidar (HSRL) method for measuring optical characteristics of aerosols and clouds will be also described. Lidar systems and recent applications of Mie scattering lidars will be then introduced. These include development of a

Nobuo Sugimoto

2003-01-01

62

Forest Biomass Mapping From Lidar and Radar Synergies  

NASA Technical Reports Server (NTRS)

The use of lidar and radar instruments to measure forest structure attributes such as height and biomass at global scales is being considered for a future Earth Observation satellite mission, DESDynI (Deformation, Ecosystem Structure, and Dynamics of Ice). Large footprint lidar makes a direct measurement of the heights of scatterers in the illuminated footprint and can yield accurate information about the vertical profile of the canopy within lidar footprint samples. Synthetic Aperture Radar (SAR) is known to sense the canopy volume, especially at longer wavelengths and provides image data. Methods for biomass mapping by a combination of lidar sampling and radar mapping need to be developed. In this study, several issues in this respect were investigated using aircraft borne lidar and SAR data in Howland, Maine, USA. The stepwise regression selected the height indices rh50 and rh75 of the Laser Vegetation Imaging Sensor (LVIS) data for predicting field measured biomass with a R(exp 2) of 0.71 and RMSE of 31.33 Mg/ha. The above-ground biomass map generated from this regression model was considered to represent the true biomass of the area and used as a reference map since no better biomass map exists for the area. Random samples were taken from the biomass map and the correlation between the sampled biomass and co-located SAR signature was studied. The best models were used to extend the biomass from lidar samples into all forested areas in the study area, which mimics a procedure that could be used for the future DESDYnI Mission. It was found that depending on the data types used (quad-pol or dual-pol) the SAR data can predict the lidar biomass samples with R2 of 0.63-0.71, RMSE of 32.0-28.2 Mg/ha up to biomass levels of 200-250 Mg/ha. The mean biomass of the study area calculated from the biomass maps generated by lidar- SAR synergy 63 was within 10% of the reference biomass map derived from LVIS data. The results from this study are preliminary, but do show the potential of the combined use of lidar samples and radar imagery for forest biomass mapping. Various issues regarding lidar/radar data synergies for biomass mapping are discussed in the paper.

Sun, Guoqing; Ranson, K. Jon; Guo, Z.; Zhang, Z.; Montesano, P.; Kimes, D.

2011-01-01

63

First radar echoes from cumulus clouds  

Microsoft Academic Search

In attempting to use centimeter-wavelength radars to investigate the early stage of precipitation formation in clouds, 'mantle echoes' are rediscovered and shown to come mostly from scattering by small-scale variations in refractive index, a Bragg kind of scattering mechanism. This limits the usefulness of single-wavelength radar for studies of hydrometeor growth, according to data on summer cumulus clouds in North

Charles A. Knight; L. J. Miller

1993-01-01

64

Nonlinear stochastic filtering technique for radar\\/lidar inversion  

Microsoft Academic Search

Abstract: The paper addresses the joint estimation of backscatter and extinction coefficients from range\\/time noisy dataunder a nonlinear stochastic filtering setup. This problem is representativeofmany remote sensing applicationssuchasweather radar and elastic-backscatter lidar. A Bayesian perspective is adopted. Thus, in addition to theobservation mechanism, relating in a probabilistic sense the observed data with the parameters to be estimated, aprior probability density

J. Dias; E. Susana

1999-01-01

65

Nonlinear stochastic filtering technique for radar\\/lidar inversion  

Microsoft Academic Search

This paper addresses the joint estimation of backscatter and extinction coefficients from range\\/time noisy data under a nonlinear stochastic filtering setup. This problem is representative of many remote sensing applications such as weather radar and elastic-backscatter lidar. A Bayesian perspective is adopted. Thus, in addition to the observation mechanism, relating in a probabilistic sense the observed data with the parameters

Jose M. Dias; Elsa S. Fonseca

1999-01-01

66

Use of a Lidar Forward Model for Global Comparisons of Cloud Fraction between the ICESat Lidar and the ECMWF Model  

E-print Network

Use of a Lidar Forward Model for Global Comparisons of Cloud Fraction between the ICESat Lidar observations by the Geoscience Laser Altimeter System lidar on the Ice, Cloud, and Land Elevation Satellite (ICESat). To account for lidar attenuation in the comparison, model variables are used to simulate

Reading, University of

67

Use of a Lidar Forward Model for Global Comparisons of Cloud Fraction between the ICESat Lidar and the ECMWF Model  

E-print Network

Use of a Lidar Forward Model for Global Comparisons of Cloud Fraction between the ICESat Lidar Altimeter System (GLAS) lidar on the ICESat satellite. In order to account for lidar attenuation in the comparison, we use model variables to simulate the attenuated backscatter using a lidar forward model

Hogan, Robin

68

Improving combined lidar-radar snowfall retrievals with Doppler spectra (Invited)  

NASA Astrophysics Data System (ADS)

Thin mixed phase clouds are frequently observed in the Arctic. These often persist for days with nearly continuous, light precipitation. They play a key role in Arctic climate through their influence on the surface radiation balance. Models have difficulty maintaining these clouds. They are very sensitive to micro-physical assumptions; small changes affect precipitation rates and lead to large changes in predicted cloud lifetimes. Reliable measurements of the ice crystal precipitation rate are needed to improve and validate the cloud models. This paper describes describes how Doppler fall velocity spectra can be used to improve ice crystal precipitation measurements derived from High Spectral Resolution Lidar (HSRL) and millimeter wavelength cloud radar(MMCR) data. The basic measurement uses a ratio formed from HSRL and MMCR signals. This yields a particle size measurement proportional to the fourth root of the average mass-squared over the average area of the ice crystals. Ice crystals are represented by equivalent spheroids having the same volume and projected area as the crystals. The equivalent crystals have the same radar and lidar cross sections, and nearly the same fall velocities, as the actual crystals. A comparison of the fall velocity and the radar/lidar ratio and with calculated spheroid fall velocities yields the aspect ratio of the spheroids. This allows us to compute the ice water content in the precipitation. Multiplying the ice water content by the Doppler velocity generates the precipitation rate. The measured velocity is a sum of the particle fall velocity and the vertical air motion. Because these are both order 1 m/s, time averaging was necessary to suppress the air motion. However, slowly varying vertical motions,often caused by gravity waves and convection, could not be removed by while maintaining structure in the ice fall streaks. We assume that the lowest frequency contributions to the MMCR Doppler spectra are produced by particles with negligible fall velocities that trace air motion. Time average profiles of the vertical air motion show limitations of this approach. In regions of high turbulence, the Doppler spectrum is broadened by velocity variations within a single radar range bin. This produces an small apparent mean upward vertical velocity. In regions where the radar return is small the vertical velocity shows a small mean downward motion. This indicates the absence of small particle radar returns. To reduce these errors, we use a 1-hour mean vertical air motion profile to correct individual air motions. We propose future measurements with a combination of HSRL, MMCR, and Doppler lidar measurements. The high sensitivity of the Doppler lidar to small particles, including aerosols, will provide accurate vertical air velocity measurements. Furthermore, the HSRL measured backscatter cross sections can be used to calibrate the Doppler lidar as long as it operates at a wavelength where ice absorption is small, and the ice particles are large compared to the wavelength. In this case, the radar/lidar ratio can be measured as a function of fall velocity. This will remove the need for two assumptions in the current algorithm. It will not be necessary to assume a functional forms for the particle size distribution or the relationship between particle aspect ratio and particle size.

Eloranta, E.

2010-12-01

69

Lidar-Radar Measurements of Snowfall Edwin W. Eloranta--Univ. Of Wisconsin  

E-print Network

Lidar-Radar Measurements of Snowfall Edwin W. Eloranta--Univ. Of Wisconsin Aerodynamic flow around a lidar-radar based technique to measure the downward flux of snow at an altitude of ~100m. When particles the square of the mass of the average snowflake. For particles large compared to the wavelength, the lidar

Eloranta, Edwin W.

70

Comparison of meteor radar and Na Doppler lidar measurements of winds in the mesopause region  

E-print Network

Comparison of meteor radar and Na Doppler lidar measurements of winds in the mesopause region above 29 January 2005. [1] Simultaneous sodium (Na) Doppler lidar and meteor radar measurements/s at altitudes below 96 km. This is smaller than the RMS differences observed in a previous Na lidar and meteor

Chu, Xinzhao

71

Quality assessment of water cycle parameters in REMO by Radar-Lidar synergy  

NASA Astrophysics Data System (ADS)

A comparison study of water cycle parameters derived from ground-based remote-sensing instruments and from the regional model REMO is presented. Observational data sets were collected during three measuring campaigns in summer/autumn 2003 and 2004 at Richard Amann Observatory, Lindenberg, Germany. The remote sensing instruments which were used are differential absorption lidar, Doppler lidar, ceilometer, cloud radar, and micro rain radar for the derivation of humidity profiles, ABL height, water vapour flux profiles, cloud parameters, and rain rate. Additionally, surface latent and sensible heat flux and soil moisture were measured. Error ranges and representativity of the data are discussed. For comparisons the regional model REMO was run for all measuring periods with a horizontal resolution of 18 km and 33 vertical levels. Parameter output was every hour. The measured data were transformed to the vertical model grid and averaged in time in order to better fit with gridbox model values. The comparisons show that the atmospheric boundary layer is not adequately simulated, on most days it is too shallow and too moist. This is found to be caused by a wrong partitioning of energy at the surface, particularly a too large latent heat flux. The reason is obviously an overestimation of soil moisture during drying periods by the one-layer scheme in the model. The profiles of water vapour transport within the ABL appear to be realistically simulated. The comparison of cloud cover reveals an underestimation of low-level and mid-level clouds by the model, whereas the comparison of high-level clouds is hampered by the inability of the cloud radar to see cirrus clouds above 10 km. Simulated ABL clouds apparently have a too low cloud base, and the vertical extent is underestimated. The ice water content of clouds agree in model and observation whereas the liquid water content is unsufficiently derived from cloud radar reflectivity in the present study. Rain rates are similar, but the representativeness of both observations and grid box values is low.

Hennemuth, B.; Weiss, A.; Bsenberg, J.; Jacob, D.; Linn, H.; Peters, G.; Pfeifer, S.

2007-06-01

72

Quality assessment of water cycle parameters in REMO by radar-lidar synergy  

NASA Astrophysics Data System (ADS)

A comparison study of water cycle parameters derived from ground-based remote-sensing instruments and from the regional model REMO is presented. Observational data sets were collected during three measuring campaigns in summer/autumn 2003 and 2004 at Richard Amann Observatory, Lindenberg, Germany. The remote sensing instruments which were used are differential absorption lidar, Doppler lidar, ceilometer, cloud radar, and micro rain radar for the derivation of humidity profiles, ABL height, water vapour flux profiles, cloud parameters, and rain rate. Additionally, surface latent and sensible heat flux and soil moisture were measured. Error ranges and representativity of the data are discussed. For comparisons the regional model REMO was run for all measuring periods with a horizontal resolution of 18 km and 33 vertical levels. Parameter output was every hour. The measured data were transformed to the vertical model grid and averaged in time in order to better match with gridbox model values. The comparisons show that the atmospheric boundary layer is not adequately simulated, on most days it is too shallow and too moist. This is found to be caused by a wrong partitioning of energy at the surface, particularly a too large latent heat flux. The reason is obviously an overestimation of soil moisture during drying periods by the one-layer scheme in the model. The profiles of water vapour transport within the ABL appear to be realistically simulated. The comparison of cloud cover reveals an underestimation of low-level and mid-level clouds by the model, whereas the comparison of high-level clouds is hampered by the inability of the cloud radar to see cirrus clouds above 10 km. Simulated ABL clouds apparently have a too low cloud base, and the vertical extent is underestimated. The ice water content of clouds agree in model and observation whereas the liquid water content is unsufficiently derived from cloud radar reflectivity in the present study. Rain rates are similar, but the representativeness of both observations and grid box values is low.

Hennemuth, B.; Weiss, A.; Bsenberg, J.; Jacob, D.; Linn, H.; Peters, G.; Pfeifer, S.

2008-01-01

73

Potential of airborne lidar measurements for cirrus cloud studies  

NASA Astrophysics Data System (ADS)

Aerosol and water vapour measurements were performed with the lidar system WALES of Deutsches Zentrum fr Luft- und Raumfahrt (DLR) in October and November 2010 during the first mission with the new German research aircraft G55-HALO. Curtains composed of lidar profiles beneath the aircraft show the vertical and horizontal distribution and variability of water vapour mixing ratio and backscatter ratio above Germany. Two missions on 3 and 4 November 2010 were selected to derive the water vapour mixing ratio inside cirrus clouds from the lidar instrument. A good agreement was found with in situ observations performed on a second research aircraft flying below HALO. ECMWF analysis temperature data are used to derive relative humidity fields with respect to ice (RHi) inside and outside of cirrus clouds from the lidar water vapour observations. The RHi variability is dominated by small-scale fluctuations in the water vapour fields while the temperature variation has a minor impact. The most frequent in-cloud RHi value from lidar observations is 98%. The RHi variance is smaller inside the cirrus than outside of the cloud. 2-D histograms of relative humidity and backscatter ratio show significant differences for in-cloud and out-of-cloud situations for two different cirrus cloud regimes. Combined with accurate temperature measurements, the lidar observations have a great potential for detailed statistical cirrus cloud and related humidity studies.

Gro, S.; Wirth, M.; Schfler, A.; Fix, A.; Kaufmann, S.; Voigt, C.

2014-08-01

74

Potential of airborne lidar measurements for cirrus cloud studies  

NASA Astrophysics Data System (ADS)

Aerosol and water vapour measurements were performed with the lidar system WALES of Deutsches Zentrum fr Luft- und Raumfahrt (DLR) in October and November 2010 during the first mission with the new German research aircraft G55-HALO. Curtains composed of lidar profiles beneath the aircraft show the vertical and horizontal distribution and variability of water vapour mixing ratio and backscatter ratio above Germany. Two missions on 3 and 4 November 2010 were selected to derive the water vapour mixing ratio inside cirrus clouds from the lidar instrument. A good agreement was found with in-situ observations performed on a second research aircraft flying below HALO. ECMWF analysis temperature data are used to derive relative humidity fields (RHi) inside and outside of cirrus clouds from the lidar water vapour observations. The RHi variability is dominated by small scale fluctuations in the water vapour fields while the temperature variation has a minor impact. The most frequent in-cloud RHi value from lidar observations is 98%. The RHi variance is smaller inside the cirrus than outside of the cloud. 2-dimensional histograms of relative humidity and backscatter ratio show significant differences for in-cloud and out-of cloud situations for two different cirrus cloud regimes. Combined with accurate temperature measurements, the lidar observations have a great potential for detailed statistical cirrus cloud and related humidity studies.

Gro, S.; Wirth, M.; Schfler, A.; Fix, A.; Kaufmann, S.; Voigt, C.

2014-04-01

75

Observations of multi-layered clouds using K-band radar  

NASA Technical Reports Server (NTRS)

Rudimentary ground-based K-band radars were once used by the U.S. Air Force to monitor clouds over air bases. The NOAA wave Propagation Laboratory has developed a significantly advanced dual-polarization Doppler K-band system that provides remarkably detailed visualizations of the structure and kinematics of nonprecipitating and weakly precipitating clouds. Unlike lidar and infrared radiometer systems, K-band radar can penetrate liquid water cloud layers and obtain measurements through moderate rainfall and heavy snowfall to reveal intricate cloud features including multiple layers of cloud. This is accomplished at less cost than would be possible with traditional longer wavelength weather radars. The radar's capabilities have been demonstrated in several recent cloud research field projects. In combination with measurements by other remote sensors, the radar can help detect aircraft icing hazards and infer microphysical properties of clouds. An automated, unattended version of the radar could provide a continuous, detailed depiction of the cloud environment in the vicinity of airports.

Martner, Brooks E.; Kropfli, Robert A.

1993-01-01

76

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 km16 km, with thickness in the range 0.2 km5 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 Angstrmexponent 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

77

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

E-print Network

Cloud radar Doppler spectra in drizzling stratiform clouds: 2. Observations and microphysical 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

78

Cloud Thickness from Diffusion of Lidar Pulses in Clouds  

NASA Technical Reports Server (NTRS)

Measurements of the distribution of reflected light from a laser beam incident on an aqueous suspension of particles or "cloud" with known thickness and particle size distribution are reported. The distribution is referred to as the "cloud radiative Green's function", G. In the diffusion domain, G is sensitive to cloud thickness, allowing that important quantity to be retrieved. The goal of the laboratory simulation is to provide preliminary estimates of sensitivity of G to cloud thickness,for use in the optimal design of an offbeam Lidar instrument for remote sensing of cloud thickness (THOR, Thickness from Offbeam Returns). These clouds of polystyrene microspheres suspended in water are analogous to real clouds of water droplets suspended in air. The microsphere size distribution is roughly lognormal, from 0.5 microns to 25 microns, similar to real clouds. Density of suspended spheres is adjusted so mean-free-path of visible photons is about 10 cm, approximately 1000 times smaller than in real clouds. The light source is a ND:YAG laser at 530 nm. Detectors are flux and photon-counting Photomultiplier Tube (PMTS), with a glass probe for precise positioning. A Labview 5 VI controls positioning, and data acquisition, via an NI Motion Control board connected to a stepper motor driving an Edmund linear slider, and a 16-channel 16-bit NI-DAQ board. The stepper motor is accurate to 10 microns, and step size is selectable from the VI software. Far from the incident beam, the rate of exponential increase as the direction of the incident beam is approached scales as expected from diffusion theory, linearly with the cloud thickness, and inversely as the square root of the reduced optical thickness, and is independent of particle size. Near the beam the signal begins to increase faster than exponential, due to single and low-order scattering near the backward direction, and here the distribution depends on particle size. Results are being used to verify 3D Monte Carlo radiative transfer simulations, used to estimate signal-to-noise ratios for remotely sensed off beam returns, for both homogeneous and inhomogeneous clouds. Signal-to-noise estimates show that unfiltered observations are straight forward at night, while narrow band pass filters are being studied for day.

Cahalan, Robert F.; Davis, A.; McGill, Matthew

1999-01-01

79

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

80

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

81

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

82

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

83

Polarization Lidar Liquid Cloud Detection Algorithm for Winter Mountain Storms  

NASA Technical Reports Server (NTRS)

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 through a roof window equipped with a wiper system to prevent snowfall accumulation. Lidar returns were collected at a rate of one shot every 1 to 5 min during declared storm periods over the 1985 and 1987 mid-Jan. to mid-Mar. Field seasons. The mid-barrier remote sensor field site was located at 2.57 km MSL. Of chief interest to weather modification efforts are the heights of supercooled liquid water (SLW) clouds, which must be known to assess their 'seedability' (i.e., temperature and height suitability for artificially increasing snowfall). We are currently re-examining out entire dataset to determine the climatological properties of SLW clouds in winter storms using an autonomous computer algorithm.

Sassen, Kenneth; Zhao, Hongjie

1992-01-01

84

NASA DC-8 Airborne Scanning Lidar Cloud and Contrail Observations  

NASA Technical Reports Server (NTRS)

An angular scanning backscatter lidar has been developed and operated from the NASA DC-8 aircraft; the lidar viewing direction could be scanned from vertically upward to forward in the direction of aircraft travel to vertically downward. The scanning lidar was used to generate real-time video displays of clouds and contrails above, below, and ahead of the aircraft to aid in positioning the aircraft for achieving optimum cloud/contrail sampling by onboard in situ samplers. Data examples show that the lidar provides unique information for the interpretation of the other data records and that combined data analyses provides enhanced evaluations of contrail/cloud structure, dynamics, composition, and optical/radiative properties.

Uthe, Edward E.; Oseberg, Terje E.; Nielsen, Norman B.

1997-01-01

85

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

NASA Astrophysics Data System (ADS)

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 (34.85N, 136.10E, Japan). Coincident observations from the VHF (46.5 MHz) MU radar in range imaging (FII) mode revealed the presence of downward developing turbulent layers and oscillatory vertical wind perturbations (+/-0.7 m/s) near the cirrus cloud base and in the mammatus environment. Moreover, simultaneous radiosonde data showed the presence of a dry and weakly stable layer underneath the cirrus. Our analysis suggests that turbulence and mammatus were generated by convective overturns due to evaporative cooling in the subcloud region. The cooling was likely the consequence of sublimation of ice crystals below the cloud base due to either precipitation or, more likely, spontaneous mixing of the saturated air and the dry air through the cloud-base detrainment instability (CDI) mechanism at the cloud base. Clear air downdrafts measured by the MU radar were associated with the descending mammatus lobes and clear air updrafts were observed between the lobes. Consequently, in addition to a possible negative buoyancy of the cloudy air, the cloudy air might have been pushed down by the downdrafts of the "upside-down" convective instability and pushed up by the updrafts to form mammatus lobes.

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

2009-04-01

86

A Wing Pod-based Millimeter Wave Cloud Radar on HIAPER  

NASA Astrophysics Data System (ADS)

One of the attractive features of a millimeter wave radar system is its ability to detect micron-sized particles that constitute clouds with lower than 0.1 g m-3 liquid or ice water content. Scanning or vertically-pointing ground-based millimeter wavelength radars are used to study stratocumulus (Vali et al. 1998; Kollias and Albrecht 2000) and fair-weather cumulus (Kollias et al. 2001). Airborne millimeter wavelength radars have been used for atmospheric remote sensing since the early 1990s (Pazmany et al. 1995). Airborne millimeter wavelength radar systems, such as the University of Wyoming King Air Cloud Radar (WCR) and the NASA ER-2 Cloud Radar System (CRS), have added mobility to observe clouds in remote regions and over oceans. Scientific requirements of millimeter wavelength radar are mainly driven by climate and cloud initiation studies. Survey results from the cloud radar user community indicated a common preference for a narrow beam W-band radar with polarimetric and Doppler capabilities for airborne remote sensing of clouds. For detecting small amounts of liquid and ice, it is desired to have -30 dBZ sensitivity at a 10 km range. Additional desired capabilities included a second wavelength and/or dual-Doppler winds. Modern radar technology offers various options (e.g., dual-polarization and dual-wavelength). Even though a basic fixed beam Doppler radar system with a sensitivity of -30 dBZ at 10 km is capable of satisfying cloud detection requirements, the above-mentioned additional options, namely dual-wavelength, and dual-polarization, significantly extend the measurement capabilities to further reduce any uncertainty in radar-based retrievals of cloud properties. This paper describes a novel, airborne pod-based millimeter wave radar, preliminary radar measurements and corresponding derived scientific products. Since some of the primary engineering requirements of this millimeter wave radar are that it should be deployable on an airborne platform, occupy minimum cabin space and maximize scan coverage, a pod-based configuration was adopted. Currently, the radar system is capable of collecting observations between zenith and nadir in a fixed scanning mode. Measurements are corrected for aircraft attitude changes. The near-nadir and zenith pointing observations minimize the cross-track Doppler contamination in the radial velocity measurements. An extensive engineering monitoring mechanism is built into the recording system status such as temperature, pressure, various electronic components' status and receiver characteristics. Status parameters are used for real-time system stability estimates and correcting radar system parameters. The pod based radar system is mounted on a modified Gulfstream V aircraft, which is operated and maintained by the National Center for Atmospheric Research (NCAR) on behalf of the National Science Foundation (NSF). The aircraft is called the High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER) (Laursen et al., 2006). It is also instrumented with high spectral resolution lidar (HSRL) and an array of in situ and remote sensors for atmospheric research. As part of the instrument suite for HIAPER, the NSF funded the development of the HIAPER Cloud Radar (HCR). The HCR is an airborne, millimeter-wavelength, dual-polarization, Doppler radar that serves the atmospheric science community by providing cloud remote sensing capabilities for the NSF/NCAR G-V (HIAPER) aircraft. An optimal radar configuration that is capable of maximizing the accuracy of both qualitative and quantitative estimated cloud microphysical and dynamical properties is the most attractive option to the research community. The Technical specifications of cloud radar are optimized for realizing the desired scientific performance for the pod-based configuration. The radar was both ground and flight tested and preliminary measurements of Doppler and polarization measurements were collected. HCR observed sensitivity as low as -37 dBZ at 1 km range and resolved linear depolarization ratio (LDR) si

Vivekanandan, Jothiram; Tsai, Peisang; Ellis, Scott; Loew, Eric; Lee, Wen-Chau; Emmett, Joanthan

2014-05-01

87

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

1995-11-01

88

Use of a lidar forward model for global comparisons of cloud fraction  

E-print Network

555 Use of a lidar forward model for global comparisons of cloud fraction between the ICESat lidar;Comparisons of cloud fraction between the ICESat lidar and the ECMWF model Abstract The performance observations by the Geoscience Laser Altimeter System (GLAS) lidar on the ICESat satellite. In order to account

Hogan, Robin

89

Lidar multiple scattering models for use in cirrus clouds E. W. Eloranta  

E-print Network

Lidar multiple scattering models for use in cirrus clouds E. W. Eloranta University of Wisconsin: eloranta@lidar.ssec.wisc.edu ABSTRACT An approximate model for lidar multiple scattering has been extend to compute lidar returns when the cloud particle sizes are described by log-normal, gamma or exponential

Eloranta, Edwin W.

90

Lidar-Radar velocimetry using a pulse-to-pulse coherent RF-modulated Q-switched laser  

E-print Network

Lidar-Radar velocimetry using a pulse-to-pulse coherent RF- modulated Q-switched laser M. Vallet,1 of this transmitter for Lidar-Radar are demonstrated by performing Doppler velocimetry on indoor moving targets. In particular, we show experimentally and theoretically that Lidar-Radar is a promising technique that allows

Paris-Sud XI, Université de

91

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

92

Lidar validation of VAS cirrus cloud height determinations  

NASA Technical Reports Server (NTRS)

The determination of cirrus cloud pressure altitude and IR attenuation using CO2 channel radiometric data from the VISSR (Visible and Infrared Spin Scan Radiometer) Atmospheric Sounder (VAS) on board the GOES geostationary satellite is discussed. The independent ground-based determination of cirrus cloud altitude, thickness, and optical properties obtained with the High Spectral Resolution Lidar (HSRL) is described. HSRL cirrus cloud measurements are compared to VAS CO2 cloud top height retrievals generated for the First International Satellite Cloud Climatology Project Regional Experiment cirrus intensive Field Observations, held in Wisconsin in October and November of 1986.

Grund, Christian J.; Eloranta, Edwin W.; Wylie, Donald P.

1989-01-01

93

Pseudo-random noise-continuous-wave laser radar for surface and cloud measurements  

NASA Astrophysics Data System (ADS)

Laser radar (lidar) application may require an instrument with compact size, long life of the components, low consumption and eye-safety. One possibility to achieve these features is to use a continuous-wave (cw) diode laser as lidar transmitter. A practical way to perform range-resolved measurements with a cw laser diode is the pseudo-random noise (PRN) modulation. This paper presents a compact PRN-cw lidar, using a 370-mW cw diode laser and an APD as detector. Daytime measurements of cloud base and topographic surface are demonstrated with the PRN-cw lidar technique, where the range detection exceeds 2 km. The detection of the topographic surface is performed with integration time of some tens of milliseconds during daytime and some tens of microseconds during night-time.

Matthey, Renaud; Mitev, Valentin

2005-03-01

94

Cloud Optical Depth Retrievals from Solar Background "signal" of Micropulse Lidars  

NASA Technical Reports Server (NTRS)

Pulsed lidars are commonly used to retrieve vertical distributions of cloud and aerosol layers. It is widely believed that lidar cloud retrievals (other than cloud base altitude) are limited to optically thin clouds. Here we demonstrate that lidars can retrieve optical depths of thick clouds using solar background light as a signal, rather than (as now) merely a noise to be subtracted. Validations against other instruments show that retrieved cloud optical depths agree within 10-15% for overcast stratus and broken clouds. In fact, for broken cloud situations one can retrieve not only the aerosol properties in clear-sky periods using lidar signals, but also the optical depth of thick clouds in cloudy periods using solar background signals. This indicates that, in general, it may be possible to retrieve both aerosol and cloud properties using a single lidar. Thus, lidar observations have great untapped potential to study interactions between clouds and aerosols.

Chiu, J. Christine; Marshak, A.; Wiscombe, W.; Valencia, S.; Welton, E. J.

2007-01-01

95

Observations of Cloud Anisotropy Using ARM Scanning Cloud Radars  

NASA Astrophysics Data System (ADS)

For many years, vertically pointing measurements from the millimeter wavelength radars of the DOE ARM Climate Research Facility have provided information on the vertical distribution of the hydrometeors in the sampled atmospheric column (the "soda-straw" view of the atmosphere). Looking vertically maximizes the potential of synergistic observations across multiple platforms, but provides little information on the true three-dimensional cloud structure. The new Scanning ARM Cloud Radars (SACR) recently added to the observational capabilities of ARM now provide a means for observing true three-dimensional cloud structure. Every thirty minutes, the SACRs perform a series of six horizon-to-horizon RHI scans spaced 30 degrees apart in azimuth. These surveillance scans performed over a short time period (3-4 min) provide a coherent snapshot of cloud structure across a large area. In this study, we apply spectral analysis to the reflectivity fields measured by these scans to gain insight into the spatial structure of layered and broken clouds of both solid and liquid phases, and its variability in connection with wind shear, wind direction, and cloud altitude.

Luke, E. P.; Lamer, K.; Jo, I.; Huang, D.; Kollias, P.

2012-12-01

96

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 Eyjafjallajkull 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 Eyjafjallajkull 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 Eyjafjallajkull 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

97

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

E-print Network

Cloud radar Doppler spectra in drizzling stratiform clouds: 1. Forward modeling and remote sensing broadening and drizzle growth in shallow liquid clouds remain not well understood. Detailed, cloudscale. Profiling, millimeterwavelength (cloud) radars can provide such observations. In particular, the first three

98

Ice cloud microphysics retrievals from millimeter radar and visible optical depth using an estimation theory approach  

E-print Network

Ice cloud microphysics retrievals from millimeter radar and visible optical depth using method to estimate ice cloud microphysical properties from cloud radar reflectivities and visible optical microphysical properties, radar reflectivity and optical depth retrieval, estimation-theory-based retrieval

Stephens, Graeme L.

99

Lidar remote measurements of Space Shuttle ground cloud emissions  

NASA Technical Reports Server (NTRS)

The application of lidar remote sensing techniques to the measurement of spacecraft-booster-exhaust-cloud parameters is illustrated, using data obtained from the launch of STS-3. Mie-scatter measurements of plume and cloud particulates were made by a mobile unit with computer controlled elevation and azimuth coverage. Scattergraphs of typical STS-3 lidar data are presented and discussed. The potential use of DIAL techniques to measure the concentrations of HCl, N2H4, and NO2 is evaluated in terms of EPA overall-standard-deviation guidelines. It is shown that currently operational lidar systems can be modified to determine contamination or air pollution by these molecular species resulting from spacecraft launches.

Caputo, B.; Dow, R. E.; Johnson, R. L.; Leonard, D. A.

1983-01-01

100

Multiple scattering depolarization in marine stratus clouds: Lidar experiments  

NASA Technical Reports Server (NTRS)

The depolarization of ruby lidar backscattering caused by multiple scattering in marine stratus clouds was examined systematically from a field site on the southern California coast. Investigated were the effects on the linear depolarization (delta) of lidar receiver field of view (FOV), elevation angle and laser beam pointing errors. An approximately linear increase in maximum delta values was observed with increasing receiver FOV, and the importance of accurate transmitter/receiver beam alignment was demonstrated during experiments in which the laser axis was deliberately misaligned. An elevation angle dependence to the delta values was observed as a consequence of the natural vertical inhomogeneity of water cloud content above the cloud base. Time histories of the depolarization characteristics of dissipating stratus clouds revealed significant spatial and temporal variability in delta values attributed to cloud composition variations. Employing a 1 mrad transmitter FOV, maximum delta values of 0.21 nd 0.33 were observed with 1 and 3 mrad receiver FOVs, respectively, from the low stratus clouds. The fundamental causes and effects on the lidar equation of multiple scattering are also discussed.

Sassen, K.; Petrilla, R. L.

1986-01-01

101

An investigation of cirrus cloud properties using airborne lidar  

NASA Astrophysics Data System (ADS)

The impact of cirrus clouds on the Earth's radiation budget remains a key uncertainty in assessing global radiative balance and climate change. Composed of ice, and located in the cold upper troposphere, cirrus clouds can cause large warming effects because they are relatively transmissive to short-wave solar radiation, but absorptive of long wave radiation. Our ability to model radiative effects of cirrus clouds is inhibited by uncertainties in cloud optical properties. Studies of mid-latitude cirrus properties have revealed notable differences compared to tropical anvil cirrus, likely a consequence of varying dynamic formation mechanisms. Cloud-aerosol lidars provide critical information about the vertical structure of cirrus for climate studies. For this dissertation, I helped develop the Airborne Cloud-Aerosol Transport System (ACATS), a Doppler wind lidar system at NASA Goddard Space Flight Center (GSFC). ACATS is also a high spectral resolution lidar (HSRL), uniquely capable of directly resolving backscatter and extinction properties of a particle from high-altitude aircraft. The first ACATS science flights were conducted out of Wallops Island, VA in September of 2012 and included coincident measurements with the Cloud Physics Lidar (CPL) instrument. In this dissertation, I provide an overview of the ACATS method and instrument design, describe the ACATS retrieval algorithms for cloud and aerosol properties, explain the ACATS HSRL retrieval errors due to the instrument calibration, and use the coincident CPL data to validate and evaluate ACATS cloud and aerosol retrievals. Both the ACATS HSRL and standard backscatter retrievals agree well with coincident CPL retrievals. Mean ACATS and CPL extinction profiles for three case studies demonstrate similar structure and agree to within 25 percent for cirrus clouds. The new HSRL retrieval algorithms developed for ACATS have direct application to future spaceborne missions. Furthermore, extinction and particle wind velocity retrieved from ACATS can be used for science applications such as dust transport and convective anvil outflow. The relationship between cirrus cloud properties and dynamic formation mechanism is examined through statistics of CPL cirrus observations from more than 100 aircraft flights. The CPL 532 nm lidar ratios (also referred to as the extinction to backscatter ratio) for cirrus clouds formed by synoptic-scale uplift over land are lower than convectively-generated cirrus over tropical oceans. Errors in assuming a constant lidar ratio can lead to errors of 50% in cloud optical extinction derived from space-borne lidar such as CALIOP. The 1064 nm depolarization ratios for synoptically-generated cirrus over land are lower than convectively-generated cirrus, formed due to rapid upward motions of tropical convection, as a consequence of differences in cloud temperatures and ice particle size and shape. Finally, the backscatter color ratio is directly proportional to depolarization ratio for synoptically-generated cirrus, but not for any other type of cirrus. The relationships between cirrus properties and formation mechanisms determined in this study can be used as part of a larger global climatology of cirrus clouds to improve parameterizations in global climate models and satellite retrievals to improve our understanding of the impact of clouds on weather and climate.

Yorks, John Edward

102

Doppler lidar measurements of oriented planar ice crystals falling from supercooled and glaciated layer clouds  

E-print Network

The properties of planar ice crystals settling horizontally have been investigated using a vertically-pointing Doppler lidar. Strong specular reflections were observed from their oriented basal facets, identified by comparison with a second lidar pointing 4 degrees from zenith. Analysis of 17 months of continuous high-resolution observations reveal that these pristine crystals are frequently observed in ice falling from mid-level mixed-phase layer clouds (85% of the time for layers at -15C). Detailed analysis of a case study indicates that the crystals are nucleated and grow rapidly within the supercooled layer, then fall out, forming well-defined layers of specular reflection. Polarimetric radar measurements confirmed that a substantial fraction of the crystal population was well oriented. As the crystals fall into subsaturated air, specular reflection is observed to switch off as the crystal faces become rounded and lose their faceted structure. Specular reflection in ice falling from supercooled layers col...

Westbrook, CD; O'Connor, EJ; Hogan, RJ

2009-01-01

103

Comparison of millimeter-wave cloud radar measurements for the Fall 1997 Cloud IOP  

Microsoft Academic Search

One of the primary objectives of the Fall 1997 IOP was to intercompare Ka-band (350Hz) and W-band (95GHz) cloud radar observations and verify system calibrations. During September 1997, several cloud radars were deployed at the Southern Great Plains (SOP) Cloud and Radiation Testbed (CART) site, including the full time operation 35 GHz CART Millimeter-wave Cloud Radar (MMCR), the University of

S. M. Sekelsky; L. Li; J. Galloway; R. E. McIntosh; M. A. Miller; E. E. Clothiaux; S. Haimov; G. G. Mace; K. Sassen

1998-01-01

104

Enhanced aerosol backscatter adjacent to tropical trade wind clouds revealed by satellite-based lidar  

Microsoft Academic Search

sensing with lidar offers several advantages over passive instruments, including range-resolved backscattered radian- ces, better cloud detection, and essentially no 3-D radiative cloud-adjacency effects when operated at night. Two notable studies used lidar to observe how aerosol properties change near cloud edge. The first and earliest study qualitatively reported an aerosol backscatter increase near two clouds from a ground-based lidar

Jason Lucas Tackett; Larry Di Girolamo

2009-01-01

105

The interdependence of continental warm cloud properties derived from unexploited solar background signals in ground-based lidar measurements  

NASA Astrophysics Data System (ADS)

We have extensively analysed the interdependence between cloud optical depth, droplet effective radius, liquid water path (LWP) and geometric thickness for stratiform warm clouds using ground-based observations. In particular, this analysis uses cloud optical depths retrieved from untapped solar background signals that are previously unwanted and need to be removed in most lidar applications. Combining these new optical depth retrievals with radar and microwave observations at the Atmospheric Radiation Measurement (ARM) Climate Research Facility in Oklahoma during 2005-2007, we have found that LWP and geometric thickness increase and follow a power-law relationship with cloud optical depth regardless of the presence of drizzle; LWP and geometric thickness in drizzling clouds can be generally 20-40% and at least 10% higher than those in non-drizzling clouds, respectively. In contrast, droplet effective radius shows a negative correlation with optical depth in drizzling clouds and a positive correlation in non-drizzling clouds, where, for large optical depths, it asymptotes to 10 ?m. This asymptotic behaviour in non-drizzling clouds is found in both the droplet effective radius and optical depth, making it possible to use simple thresholds of optical depth, droplet size, or a combination of these two variables for drizzle delineation. This paper demonstrates a new way to enhance ground-based cloud observations and drizzle delineations using existing lidar networks.

Chiu, J. C.; Holmes, J. A.; Hogan, R. J.; O'Connor, E. J.

2014-08-01

106

Report on the Radar/PIREP Cloud Top Discrepancy Study  

NASA Technical Reports Server (NTRS)

This report documents the results of the Applied Meteorology Unit's (AMU) investigation of inconsistencies between pilot reported cloud top heights and weather radar indicated echo top heights (assumed to be cloud tops) as identified by the 45 Weather Squadron (45WS). The objective for this study is to document and understand the differences in echo top characteristics as displayed on both the WSR-88D and WSR-74C radars and cloud top heights reported by the contract weather aircraft in support of space launch operations at Cape Canaveral Air Station (CCAS), Florida. These inconsistencies are of operational concern since various Launch Commit Criteria (LCC) and Flight Rules (FR) in part describe safe and unsafe conditions as a function of cloud thickness. Some background radar information was presented. Scan strategies for the WSR-74C and WSR-88D were reviewed along with a description of normal radar beam propagation influenced by the Effective Earth Radius Model. Atmospheric conditions prior to and leading up to both launch operations were detailed. Through the analysis of rawinsonde and radar data, atmospheric refraction or bending of the radar beam was identified as the cause of the discrepancies between reported cloud top heights by the contract weather aircraft and those as identified by both radars. The atmospheric refraction caused the radar beam to be further bent toward the Earth than normal. This radar beam bending causes the radar target to be displayed erroneously, with higher cloud top heights and a very blocky or skewed appearance.

Wheeler, Mark M.

1997-01-01

107

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

108

LIDAR AND RADAR INVESTIGATION OF INERTIA GRAVITY WAVE INTRINSIC PROPERTIES AT MCMURDO, ANTARCTICA  

E-print Network

LIDAR AND RADAR INVESTIGATION OF INERTIA GRAVITY WAVE INTRINSIC PROPERTIES AT MCMURDO, ANTARCTICA lidar campaign ongoing at McMurdo (77.8° S, 166.7° E), Antarctica has provided high Antarctica are rare yet important due to its potential influence on MLT temperatures and dynamics [4

Chu, Xinzhao

109

The RAMNI airborne lidar for cloud and aerosol research  

NASA Astrophysics Data System (ADS)

We describe an airborne lidar for the characterization of atmospheric aerosol. The system has been set up in response to the need to monitor extended regions where the air traffic may be posed at risk by the presence of potentially harmful volcanic ash, and to study the characteristics of volcanic emissions both near the source region and when transported over large distances. The lidar provides backscatter and linear depolarization profiles at 532 nm, from which aerosol and cloud properties can be derived. The paper presents the characteristics and capabilities of the lidar system and gives examples of its airborne deployment. Observations from three flights, aimed at assessing the system capabilities in unperturbed atmospheric conditions, and at characterizing the emissions near a volcanic ash source (Mt. Etna) and transported far away from the source, are presented and discussed.

Cairo, F.; Di Donfrancesco, G.; Di Liberto, L.; Viterbini, M.

2012-07-01

110

Exploring Stratocumulus Cloud-Top Entrainment Processes and Parameterizations Using Doppler Cloud Radar Observations  

NASA Astrophysics Data System (ADS)

Observations from an upward-pointing Doppler cloud radar are used to examine the vertical velocity variance and energy dissipation rate at the top of continental stratocumulus clouds. These observations are used to examine terms in the turbulence kinetic energy (TKE) budget in the entrainment zone that are related to the entrainment rate. When this budget (without wind shear) is applied to the entrainment zone, the entrainment rate is proportional to a vertical transport and pressure perturbation term minus a dissipation term and inversely proportional to the strength of the inversion. The transport-pressure term is usually assumed to be proportional to the vertical velocity variance to the 3/2 power and inversely proportional to the boundary layer depth (called the variance term in this study). In this study the observations are made in a continental stratocumulus cloud observed over the Southern Great Plains (SGP) at the DOE ARM site for a 14-hour period. Clouds were solid during this entire period and had thicknesses of 300-400 meters and tops increasing from 800-1200 m. The turbulence forcing due to surface buoyancy fluxes and radiative cooling at cloud top is obtained from surface flux measurements and radiative transfer calculations based on the cloud characteristics derived from cloud radar and lidar observations. During the day surface forcing dominates as the radiative warming at cloud top by solar absorption compensates the cloud-top longwave cooling. At night the surface buoyancy fluxes are close to zero and the longwave cooling at cloud top dominates the turbulence forcing. Vertical velocity and spectrum width observations from the upward pointing millimeter cloud radar (MMCR) at the SGP site are used to examine the turbulence in the top 20% (60-80 m) of the cloud, which is define as the entrainment zone. The spectrum width is used to define energy dissipation rates directly in the entrainment zone and the vertical velocity observations are used to define vertical velocity variance for one-hour periods. These quantities are then used to examine the terms in the TKE budget in this layer. It is found for the 14 hours of observations used in this study that the variance term is strongly correlated to the dissipation rates in the entrainment zone. However, the ratio of the variance term to the dissipation rate term is 0.12 during the day and 0.06 at night. This difference indicates that the length scales involved in the turbulence and entrainment processes may depend on whether the turbulence is forced by the surface fluxes or cloud-top cooling. To further explore this possibility, the relationships among the convective velocity scales, the vertical velocity variances, and the dissipation rates are examined and compared with entrainment rates from parameterizations based on the convective velocity scale and the strength of the inversion.

Albrecht, B. A.; Fang, M.

2012-12-01

111

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

112

A new cloud and aerosol layer detection method based on micropulse lidar measurements  

E-print Network

A new cloud and aerosol layer detection method based on micropulse lidar measurements Chuanfeng algorithm to detect aerosols and clouds based on micropulse lidar measurements. A semidiscretization is then introduced. Combined with empirical threshold values, we determine if the signal waves indicate clouds

Li, Zhanqing

113

Validating Lidar Depolorization Calibration using Solar Radiation Scattered by Ice Clouds  

NASA Technical Reports Server (NTRS)

This letter proposes the use of solar background radiation scattered by ice clouds for validating space lidar depolarization calibration. The method takes advantage of the fact that the background light scattered by ice clouds is almost entirely unpolarized. The theory is examined with Cloud Physics Lidar (CPL) background light measurements.

Liu, Zhao-Yang; McGill, Matthew; Hu, Yong-Xiang; Hostetter, Chris; Winker, David; Vaughan, Mark

2004-01-01

114

UNCERTAINTIES OF RADAR-DERIVED VERTICAL VELOCITIES IN DEEP CONVECTIVE CLOUDS USING ARM PRECIPITATION RADARS  

E-print Network

PRECIPITATION RADARS Kirk North, McGill University Scott Collis, Argonne National Laboratory Scott GiangrandeUNCERTAINTIES OF RADAR-DERIVED VERTICAL VELOCITIES IN DEEP CONVECTIVE CLOUDS USING ARM of the new ARRA enhanced radar networks is to provide such measurements routinely. The retrieval approach

115

First detection of a noctilucent cloud by lidar  

Microsoft Academic Search

During the night of August 5\\/6, 1989 for the first time a noctilucent cloud (NLC) was detected and measured by a lidar instrument. The NLC developed at about 22:20 UT, reached its maximum backscatter cross-section at 23:05 UT and became unobservable at around 00:10 UT. During this period, the NLC exhibited the following properties: (1) its altitude ranged between 83.4

G. Hansen; M. Serwazi; U. von Zahn

1989-01-01

116

Cloud Physics Lidar: instrument description and initial measurement results  

Microsoft Academic Search

The new Cloud Physics Lidar (CPL) has been built for use on the NASA ER-2 high-altitude aircraft. The purpose of the CPL is to provide multiwavelength measurements of cirrus, subvisual cirrus, and aerosols with high temporal and spatial resolution. The CPL utilizes state-of-the-art technology with a high repetition rate, a low-pulse-energy laser, and photon-counting detection. The first deployment for the

Matthew McGill; Dennis Hlavka; William Hart; V. Stanley Scott; James Spinhirne; Beat Schmid

2002-01-01

117

Laboratory scaled simulation of lidar cloud sounding experiments  

NASA Technical Reports Server (NTRS)

The results of lidar measurements carried out on laboratory scale models of clouds are presented. Measurements on laboratory scale models are important since one has the knowledge of the relevant parameters of the diffusing medium, such as: scattering and absorption coefficients, phase function, homogeneity, shape, etc. Knowledge of these parameters enables one to use the results to test the reliability of theoretical and numerical investigations. To obtain a laboratory scaled model of a lidar system sounding a cloud, it is necessary to scale down all the geometrical quantities by the same factor to reduce distances of the order of kilometers to the order of meters, keeping the size and the optical depth of the diffusers unchanged. If a time resolution of the order of nanoseconds is necessary for a lidar sounding actual clouds, the corresponding time resolution for the laboratory model should be of the order of picoseconds. It is possible to obtain this resolution by using picosecond laser systems and fast electrooptical detectors like the streak camera. The results of the laboratory measurements showed that the multiple scattering effect strongly depends on the size of the diffusers, as well as on the concentration. The experimental results were compared with the numerical results of a Monte Carlo code. A generally good agreement was obtained.

Zaccanti, G.; Bruscaglioni, P.; Gurioli, M.; Sansoni, P.

1992-01-01

118

A comparison of ambipolar diffusion coefficients in meteor trains using VHF radar and UV lidar  

Microsoft Academic Search

In this paper we present the first comparative estimations of ionic diffusion rates for sporadic meteor trains near the mesopause made using VHF radar and UV Rayleigh lidar observations. In both cases we initially assumed that the meteor trains dissipate primarily through ambipolar diffusion. For the radar data, the diffusion coefficient within the meteor train was determined from the decay

Phillip B. Chilson; Peter Czechowsky; Gerhard Schmidt

1996-01-01

119

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

SciTech Connect

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, P.; Luke, E.; Rmillard, J.; Szyrmer, W.

2011-07-02

120

Raster Vs. Point Cloud LiDAR Data Classification  

NASA Astrophysics Data System (ADS)

Airborne Laser Scanning systems with light detection and ranging (LiDAR) technology is one of the fast and accurate 3D point data acquisition techniques. Generating accurate digital terrain and/or surface models (DTM/DSM) is the main application of collecting LiDAR range data. Recently, LiDAR range and intensity data have been used for land cover classification applications. Data range and Intensity, (strength of the backscattered signals measured by the LiDAR systems), are affected by the flying height, the ground elevation, scanning angle and the physical characteristics of the objects surface. These effects may lead to uneven distribution of point cloud or some gaps that may affect the classification process. Researchers have investigated the conversion of LiDAR range point data to raster image for terrain modelling. Interpolation techniques have been used to achieve the best representation of surfaces, and to fill the gaps between the LiDAR footprints. Interpolation methods are also investigated to generate LiDAR range and intensity image data for land cover classification applications. In this paper, different approach has been followed to classifying the LiDAR data (range and intensity) for land cover mapping. The methodology relies on the classification of the point cloud data based on their range and intensity and then converted the classified points into raster image. The gaps in the data are filled based on the classes of the nearest neighbour. Land cover maps are produced using two approaches using: (a) the conventional raster image data based on point interpolation; and (b) the proposed point data classification. A study area covering an urban district in Burnaby, British Colombia, Canada, is selected to compare the results of the two approaches. Five different land cover classes can be distinguished in that area: buildings, roads and parking areas, trees, low vegetation (grass), and bare soil. The results show that an improvement of around 10 % in the classification results can be achieved by using the proposed approach.

El-Ashmawy, N.; Shaker, A.

2014-09-01

121

Interpretation of the optical and morphological properties of Cirrus clouds from lidar measurements  

NASA Technical Reports Server (NTRS)

Lidar measurements can provide a great deal of information about the structure, location, and scattering properties of cirrus clouds. However, caution must be used when interpreting raw lidar backscatter profiles in terms of relative or absolute extinction distribution, internal cloud structure, and, at times, cloud location. The problem arises because the signal measured from a range by any monostatic lidar system depends on the backscatter cross section at that range and the 2-way optical thickness to the scattering volume. Simple lidar systems, however, produce only one measurement of attenuated backscatter from each range. The general FIRE research community is given aid in interpretation of lidar measurements, and the special capabilities of the High Spectral Resolution Lidar (HSRL) is explained. Some examples are given of conditions under which direct interpretation of cirrus cloud morphology from simple lidar profiles could be misleading.

Grund, Christian John; Eloranta, Edwin W.

1990-01-01

122

Radar Evaluation of Optical Cloud Constraints to Space Launch Operations  

NASA Technical Reports Server (NTRS)

Weather constraints to launching space vehicles are designed to prevent loss of the vehicle or mission due to weather hazards (See, e.g., Ref 1). Constraints include Lightning Launch Commit Criteria (LLCC) designed to avoid natural and triggered lightning. The LLCC currently in use at most American launch sites including the Eastern Range and Kennedy Space Center require the Launch Weather Officer to determine the height of cloud bases and tops, the location of cloud edges, and cloud transparency. The preferred method of making these determinations is visual observation, but when that isn't possible due to darkness or obscured vision, it is permissible to use radar. This note examines the relationship between visual and radar observations in three ways: A theoretical consideration of the relationship between radar reflectivity and optical transparency. An observational study relating radar reflectivity to cloud edge determined from in-situ measurements of cloud particle concentrations that determine the visible cloud edge. An observational study relating standard radar products to anvil cloud transparency. It is shown that these three approaches yield results consistent with each other and with the radar threshold specified in Reference 2 for LLCC evaluation.

Merceret, Francis J.; Short, David A.; Ward, Jennifer G.

2005-01-01

123

Simulations of the Observation of Clouds and Aerosols with the Experimental Lidar in Space Equipment System  

Microsoft Academic Search

We carried out a simulation study for the observation of clouds and aerosols with the Japanese Experimental Lidar in Space Equipment (ELISE), which is a two-wavelength backscatter lidar with three detection channels. The National Space Development Agency of Japan plans to launch the ELISE on the Mission Demonstrate Satellite 2 (MDS-2). In the simulations, the lidar return signals for the

Zhaoyan Liu; Peter Voelger; Nobuo Sugimoto

2000-01-01

124

A 2year climatology of clouds at Eureka, Canada prepared from High Spectral Resolution lidar data.  

E-print Network

A 2year climatology of clouds at Eureka, Canada prepared from High Spectral Resolution lidar data. Edwin W. Eloranta University of WisconsinMadison eloranta@lidar.ssec.wisc.edu Measurements show. These instruments include the University of Wisconsin Arctic High Spectral Resolution Lidar(AHSRL) and the NOAA 8

Eloranta, Edwin W.

125

Estimate of the global distribution of stratiform supercooled liquid water clouds using the LITE lidar  

E-print Network

lidar Robin J. Hogan, Mukunda D. Behera,1 Ewan J. O'Connor, and Anthony J. Illingworth Department distinguished from ice by their high lidar backscatter coefficient and sharp backscatter gradient at cloud top. In this paper, data from the Lidar In-space Technology Experiment (LITE), which flew on the space shuttle

Hogan, Robin

126

Comparison of millimeter-wave cloud radar measurements for the fall 1997 cloud iop.  

National Technical Information Service (NTIS)

One of the primary objectives of the Fall 1997 IOP was to intercompare Ka-band (35GHz) and W-band (95GHz) cloud radar observations and verify system calibrations. During September 1997, several cloud radars were deployed at the Southern Great Plains (SGP)...

Sekelsky Li Galloway McIntosh Miller Clothiaux Haimov Mace Sassen

1998-01-01

127

Doppler Cloud Radar Derived Drop Size Distributions in Liquid Water Stratus Clouds  

Microsoft Academic Search

A cloud particle size retrieval algorithm that uses radar reflectivity factor and Doppler velocity obtained by a 35-GHz Doppler radar and liquid water path estimated from microwave radiometer radiance measurements is developed to infer the size distribution of stratus cloud particles. Assuming a constant, but unknown, number concentration with height, the algorithm retrieves the number concentration and vertical profiles of

Seiji Kato; Gerald G. Mace; Eugene E. Clothiaux; James C. Liljegren; Richard T. Austin

2001-01-01

128

The polarization lidar technique for cloud research - A review and current assessment  

NASA Technical Reports Server (NTRS)

The development of the polarization lidar technique is reviewed, and the current capabilities and limitations of the technique for the cloud research are discussed. At present, polarization lidar is a key component of climate-research programs designed to characterize the properties of cirrus clouds and is an integral part of multiple remote-sensor studies of mixed-phase cloud systems such as winter mountain storms, making it possible to discriminate between cloud phases and to identify some particle types and orientations. Recent theoretical approaches involving ice crystal ray-tracing and cloud microphysical-model simulations are expected to increase the utility of the polarization lidar technique.

Sassen, Kenneth

1991-01-01

129

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

130

Comparison of meteor radar and Na Doppler lidar measurements of winds in the mesopause region above Maui, Hawaii  

Microsoft Academic Search

Simultaneous sodium (Na) Doppler lidar and meteor radar measurements of horizontal winds in the mesopause region over Maui, Hawaii, were collected in July 2002 and October\\/November 2003. The coincident measurements span 96 hours and altitudes between 80 and 100 km. Statistical comparisons are carried out on radar\\/lidar winds with 1 hour and 4 km time and height resolution, respectively. The

S. J. Franke; X. Chu; A. Z. Liu; W. K. Hocking

2005-01-01

131

Cirrus cloud characteristics derived from volume imaging lidar, high spectral resolution lidar, HIS radiometer, and satellite  

NASA Technical Reports Server (NTRS)

Preliminary measurement results are presented from the Cirrus Remote Sensing Pilot Experiment which used a unique suite of instruments to simultaneously retrieve cirrus cloud visible and IR optical properties, while addressing the disparities between satellite volume averages and local point measurements. The experiment employed a ground-based high resolution interferometer sounder (HIS) and a second Fourier transform spectrometer to measure the spectral radiance in the 4-20 micron band, a correlated high spectral resolution lidar, a volume imaging lidar, a CLASS radiosonde system, the Scripps Whole Sky Imager, and multispectral VAS, HIRS, and AVHRR satellite data from polar orbiting and geostationary satellites. Data acquired during the month long experiment included continuous daytime monitoring with the Whole Sky Imager.

Grund, Christian J.; Ackerman, Steven A.; Eloranta, Edwin W.; Knutsen, Robert O.; Revercomb, Henry E.; Smith, William L.; Wylie, Donald P.

1990-01-01

132

The Cloud Physics Lidar: Instrument Description and Initial Measurement Results  

NASA Technical Reports Server (NTRS)

The new Cloud Physics Lidar (CPL) has been built for use on the NASA ER-2 high altitude aircraft. The purpose of the CPL is to provide multi-wavelength measurements of cirrus, subvisual cirrus, and aerosols with high temporal and spatial resolution. The CPL utilizes state-of-the-art technology with a high repetition rate, a low pulse energy laser, and photon-counting detection. The first deployment for the CPL was the SAFARI-2000 field campaign during August-September 2000. We provide here an overview of the instrument and initial data results to illustrate the measurement capability of the CPL.

McGill, Matthew; Hlavka, Dennis; Hart, William; Spinhirne, James; Scott, V. Stanley; Starr, David OC. (Technical Monitor)

2001-01-01

133

Cloud Physics Lidar: Instrument Description and Initial Measurement Results  

NASA Technical Reports Server (NTRS)

The Cloud Physics Lidar (CPL) is a new custom-built instrument for the NASA ER-2 high-altitude aircraft. The CPL can provide multiwavelength measurements of cirrus, subvisual cirrus, and aerosols with high temporal and spatial resolution. Its state-of-the-art technology gives it a high repetition rate, and photon-counting detection, and includes a low-pulse-energy laser. The CPL was first deployed at the Southern African Regional Science Initiative's 2000 field campaign during August and September 2000. This paper provides an overview of the instrument and initial data results to illustrate the measurement capability of the CPL.

McGill, Matthew; Hlavka, Dennis; Hart, William; Scott, V. Stanley; Spinhirne, James; Schmid, Beat

2002-01-01

134

The Atmospheric Radiation Measurement Program Cloud Profiling Radars: Second-Generation Sampling Strategies, Processing, and Cloud Data Products  

Microsoft Academic Search

The United States Department of Energy Atmospheric Radiation Measurement program operates millimeter-wavelength cloud radars in several climatologically distinct regions. The digital signal processors for these radars were recently upgraded and allow for enhancements in the operational parameters running on them. Recent evaluations of millimeter-wavelength cloud radar signal processing performance relative to the range of cloud dynamical and microphysical conditions encountered

Pavlos Kollias; Eugene E. Clothiaux; Mark A. Miller; Edward P. Luke; Karen L. Johnson; Kenneth P. Moran; Kevin B. Widener; Bruce A. Albrecht

2007-01-01

135

Fog monitoring using a new 94 GHz FMCW cloud radar  

NASA Astrophysics Data System (ADS)

A new solid state frequency modulated continuous wave (FMCW) cloud radar and its potential for monitoring the life cycle of fog and low stratus is presented. The radar operates at a frequency of 94 GHz, which is ideal for observing clouds as it lies within a part of the spectrum which experiences relatively low absorption in the atmosphere. With a wavelength of approximately 3 mm, scattering from cloud droplets is by Rayleigh scattering. So the new 94 GHz FMCW radar provides best resolution of cloud and fog in the lower troposphere. Due to the FMCW technique, the radar can detect clouds with a minimum range of ~30 m making it ideal for monitoring fog and low stratus. A vertical resolution of 4 m from the surface to 2 km permits fine vertical cloud structures to be resolved. The high temporal resolution of 10 seconds makes it highly suitable to capture and analyze the dynamics of fog development and its evolutionary stages. Since the radar reflectivity is strongly related to the cloud liquid water content within the respective scan level, it is possible to retrieve and analyze this essential microphysical cloud parameter with a high vertical and temporal resolution. Only some studies investigated the profile of the liquid water content during fog events so far. Very few of them combined the vertical and the temporal component by investigating the variation of the liquid water content profile during different fog evolutionary stages. This is mainly due to the laborious measurement techniques using balloon-borne sensor platforms. In this context the radar offers new insights into fog development and the associated liquid water content based on continuous profile measurements. Such a continuous monitoring of fog and its vertical structure has applications for aviation as well as for climatological and meteorological research. The poster presents the vertical fog structure and its temporal dynamic for selected fog events and investigate the existence of distinct evolutionary stages as concluded from former studies.

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

2010-07-01

136

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

137

An Automated Cloud-edge Detection Algorithm Using Cloud Physics and Radar Data  

NASA Technical Reports Server (NTRS)

An automated cloud edge detection algorithm was developed and extensively tested. The algorithm uses in-situ cloud physics data measured by a research aircraft coupled with ground-based weather radar measurements to determine whether the aircraft is in or out of cloud. Cloud edges are determined when the in/out state changes, subject to a hysteresis constraint. The hysteresis constraint prevents isolated transient cloud puffs or data dropouts from being identified as cloud boundaries. The algorithm was verified by detailed manual examination of the data set in comparison to the results from application of the automated algorithm.

Ward, Jennifer G.; Merceret, Francis J.; Grainger, Cedric A.

2003-01-01

138

Separating Cloud and Drizzle Radar Moments during Precipitation Onset Using Doppler Spectra  

E-print Network

Separating Cloud and Drizzle Radar Moments during Precipitation Onset Using Doppler Spectra EDWARD, and turbulence parameters using radar Doppler spectra is challenged by the convolution of microphysical recorded radar Doppler spectra from profiling cloud radars is presented here. The technique applies

Ohta, Shigemi

139

Mixed-phase cloud phase partitioning using millimeter wavelength cloud radar Doppler velocity spectra  

NASA Astrophysics Data System (ADS)

and quantifying cloud liquid drop contributions to radar returns from mixed-phase clouds remains a challenge because the radar signal is frequently dominated by the returns from the ice particles within the radar sample volume. We present a technique that extracts the weak cloud liquid drop contributions from the total radar returns in profiling cloud radar Doppler velocity spectra. Individual spectra are first decomposed using a continuous wavelet transform, the resulting coefficients of which are used to identify the region in the spectra where cloud liquid drops contribute. By assuming that the liquid contribution to each Doppler spectrum is Gaussian shaped and centered on an appropriate peak in the wavelet coefficients, the cloud liquid drop contribution may be estimated by fitting a Gaussian distribution centered on the velocity of this peak to the original Doppler spectrum. The cloud liquid drop contribution to reflectivity, the volume mean vertical air motion, subvolume vertical velocity variance, and ice particle mean fall speed can be estimated based on the separation of the liquid contribution to the radar Doppler spectrum. The algorithm is evaluated using synthetic spectra produced from output of a state-of-the-art large eddy simulation model study of an Arctic mixed-phase cloud. The retrievals of cloud liquid drop mode reflectivities were generally consistent with the original model values with errors less than a factor of 2. The retrieved volume mean vertical air velocities reproduced the updraft and downdraft structures, but with an overall bias of approximately -0.06 m s-1. Retrievals based on Ka-band Atmospheric Radiation Measurement Program Zenith Radar observations from Barrow, Alaska, during October 2011 are also presented.

Yu, G.; Verlinde, J.; Clothiaux, E. E.; Chen, Y.-S.

2014-06-01

140

Aerosol and cloud interaction observed from high spectral resolution lidar data  

Microsoft Academic Search

Recent studies utilizing satellite retrievals have shown a strong correlation between aerosol optical depth (AOD) and cloud cover. However, these retrievals from passive sensors are subject to many limitations, including cloud adjacency (or three-dimensional) effects, possible cloud contamination, uncertainty in the AOD retrieval. Some of these limitations do not exist in High Spectral Resolution Lidar (HSRL) observations; for instance, HSRL

Wenying Su; Gregory L. Schuster; Norman G. Loeb; Raymond R. Rogers; Richard A. Ferrare; Chris A. Hostetler; Johnathan W. Hair; Michael D. Obland

2008-01-01

141

THREE-DIMENSIONAL TOMOGRAPHY OF CLOUD MICROPHYSICS BY COMBINING MICROWAVE RADAR AND RADIOMETER  

E-print Network

as microwave radiometers measure path-integrated water content while cloud radars provide range concentration to retrieve effective radius when combining microwave cloud tomography and radar measurements. WeTHREE-DIMENSIONAL TOMOGRAPHY OF CLOUD MICROPHYSICS BY COMBINING MICROWAVE RADAR AND RADIOMETER

142

VII Workshop on Lidar Measurements in Latin America Pucn, 2013 Characteristics of Cirrus Clouds in the Central Amazon region during one week in  

E-print Network

VII Workshop on Lidar Measurements in Latin America Pucón, 2013 Characteristics of Cirrus Clouds and the lidar technique is very useful for their study. In the present work, data from a lidar instrument clouds; lidar; Central Amazon Region. WLMLA Area: Lidar applications in environmental sciences

Barbosa, Henrique

143

Algorithm for detecting important changes in lidar point clouds  

NASA Astrophysics Data System (ADS)

Protection of installations in hostile environments is a very critical part of military and civilian operations that requires a significant amount of security personnel to be deployed around the clock. Any electronic change detection system for detection of threats must have high probability of detection and low false alarm rates to be useful in the presence of natural motion of trees and vegetation due to wind. We propose a 3D change detection system based on a LIDAR sensor that can reliably and robustly detect threats and intrusions in different environments including surrounding trees, vegetation, and other natural landscape features. Our LIDAR processing algorithm finds human activity and human-caused changes not only in open spaces but also in heavy vegetated areas hidden from direct observation by 2D imaging sensors. The algorithm processes a sequence of point clouds called frames. Every 3D frame is mapped into a 2D horizontal rectangular grid. Each cell of this grid is processed to calculate the distribution of the points mapped into it. The spatial differences are detected by analyzing the differences in distributions of the corresponding cells that belong to different frames. Several heuristic filters are considered to reduce false detections caused by natural changes in the environment.

Korchev, Dmitriy; Owechko, Yuri

2014-06-01

144

Coherent Doppler Lidar for Wind and Cloud Measurements on Venus from an Orbiting or Floating/Flying Platform  

NASA Astrophysics Data System (ADS)

Abstract Given the presence of clouds and haze in the upper portion of the Venus atmosphere, it is reasonable to consider a Doppler wind lidar (DWL) for making remote measurements of the 3D winds within the tops of clouds and the overlying haze layer. Assuming an orbit altitude of 250 km and cloud tops at 60km (within the upper cloud layer), an initial performance assessment of an orbiting DWL was made using a numerical instrument and atmospheres model developed for both Earth and Mars. The threshold aerosol backscatter for 2-micron was taken to be 1.0*10-6 msr-1. This backscatter value is between 1 and 2 orders of magnitude lower than that expected for clouds with optical depths greater than 2.0. Cloud composition was assumed to be mixture of dust, frozen CO2 and sulfuric acid. Based on the DWL assessment and simulation, it is reasonable to expect vertical profiles of the 3D wind speed with 1 km vertical resolution and horizontal spacing of 25 km to several 100 kms depending upon the desired integration times. These profiles would begin somewhere just below the tops of the highest clouds and extend into the overlying haze layer to some TBD height. Getting multiple layers of cloud returns is also possible with no negative impact on velocity measurement accuracy. With support from the NASA Laser Risk Reduction Program (LRRP) and Instrument Incubator Program (IIP), NASA Langley Research Center has developed a state-of-the-art compact lidar transceiver for a pulsed 2-micron coherent Doppler lidar system for wind measurement in the Earths atmosphere [1-3]. The knowledge and expertise for developing coherent Doppler wind lidar technologies and techniques for Earth related mission at NASA LaRC is being leveraged to develop an appropriate system suitable for wind measurement around Venus. We are considering a fiber laser based lidar system of high efficiency and smaller size and advancing the technology level to meet the requirements for DWL system for Venus from an orbiting or floating/flying platform. This presentation will describe the concept, simulation and technology development plan for wind and cloud measurements on Venus. References [1] M.J. Kavaya, U.N. Singh, G.J. Koch, B.C. Trieu, M. Petros, and P.J. Petzar, "Development of a Compact, Pulsed, 2-Micron, Coherent-Detection, Doppler Wind Lidar Transceiver and Plans for Flights on NASA's DC-8 and WB-57 Aircraft," Coherent Laser Radar Conference, Toulouse, France, June 2009. [2] G.J. Koch, J.Y. Beyon, B.W. Barnes, M. Petros, J. Yu, F. Amzajerdian, M.J. Kavaya, and U.N. Singh, "High-Energy 2-micron Doppler Lidar for Wind Measurements," Optical Engineering 46(11), 116201-14 (2007). [3] J.Y. Beyon and G.J. Koch, "Novel Nonlinear Adaptive Doppler Shift Estimation Technique for the Coherent Doppler Validation Lidar," Optical Engineering 46(1), 0160021-9 (2007).

Singh, Upendra; Limaye, Sanjay; Emmitt, George; Kavaya, Michael; Yu, Jirong; Petros, Mulugeta

145

G band atmospheric radars: new frontiers in cloud physics  

NASA Astrophysics Data System (ADS)

Clouds and associated precipitation are the largest source of uncertainty in current weather and future climate simulations. Observations of the microphysical, dynamical and radiative processes that act at cloud scales are needed to improve our understanding of clouds. The rapid expansion of ground-based super-sites and the availability of continuous profiling and scanning multi-frequency radar observations at 35 and 94 GHz have significantly improved our ability to probe the internal structure of clouds in high temporal-spatial resolution, and to retrieve quantitative cloud and precipitation properties. However, there are still gaps in our ability to probe clouds due to large uncertainties in the retrievals. The present work discusses the potential of G band (frequency between 110 and 300 GHz) Doppler radars in combination with lower frequencies to further improve the retrievals of microphysical properties. Our results show that, thanks to a larger dynamic range in dual-wavelength reflectivity, dual-wavelength attenuation and dual-wavelength Doppler velocity (with respect to a Rayleigh reference), the inclusion of frequencies in the G band can significantly improve current profiling capabilities in three key areas: boundary layer clouds, cirrus and mid-level ice clouds, and precipitating snow.

Battaglia, A.; Westbrook, C. D.; Kneifel, S.; Kollias, P.; Humpage, N.; Lhnert, U.; Tyynel, J.; Petty, G. W.

2014-06-01

146

High-spectral-resolution lidar measurements of aerosols, clouds, and temperature at NIES  

Microsoft Academic Search

A high spectral resolution lidar (HSRL) using a narrow-band frequency-doubled Nd:YAG laser and an iodine absorption filter has been developed and used for the observations of aerosols, clouds and temperature profiles at NIES, Tsukuba since December 1997. Examples of the measurements of the cloud and aerosol scattering parameters with this lidar are given in the paper. The results show that

Zhaoyan Liu; Ichiro Matsui; Nubuo Sugimoto

1998-01-01

147

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

Microsoft Academic Search

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

Steven P. Love; Anthony B. Davis; Charles A. Rohde; Larry Tellier; Cheng Ho

2002-01-01

148

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.; Rmillard, J.

2011-07-02

149

Geophysical Analysis of a Central Florida Karst Terrain using Light Detection and Ranging (LIDAR) and Ground Penetrating Radar (GPR) Derived Surfaces  

Microsoft Academic Search

Airborne LIDAR (Light Detecting and Ranging) is a relatively new technique that rapidly and accurately measures micro-topographic features. This study compares topography derived from LIDAR with subsurface karst structures mapped in 3-dimensions with ground penetrating radar (GPR). Over 500 km of LIDAR data were collected in 1995 by the NASA ATM instrument. The LIDAR data was processed and analyzed to

Juana Maria Montane

2001-01-01

150

Simulations of the observation of clouds and aerosols with the Experimental Lidar in Space Equipment system.  

PubMed

We carried out a simulation study for the observation of clouds and aerosols with the Japanese Experimental Lidar in Space Equipment (ELISE), which is a two-wavelength backscatter lidar with three detection channels. The National Space Development Agency of Japan plans to launch the ELISE on the Mission Demonstrate Satellite 2 (MDS-2). In the simulations, the lidar return signals for the ELISE are calculated for an artificial, two-dimensional atmospheric model including different types of clouds and aerosols. The signal detection processes are simulated realistically by inclusion of various sources of noise. The lidar signals that are generated are then used as input for simulations of data analysis with inversion algorithms to investigate retrieval of the optical properties of clouds and aerosols. The results demonstrate that the ELISE can provide global data on the structures and optical properties of clouds and aerosols. We also conducted an analysis of the effects of cloud inhomogeneity on retrievals from averaged lidar profiles. We show that the effects are significant for space lidar observations of optically thick broken clouds. PMID:18345243

Liu, Z; Voelger, P; Sugimoto, N

2000-06-20

151

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

NASA Technical Reports Server (NTRS)

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 cloud base altitude, cloud top altitude, and mid-cloud altitude. Two dimensional auto-correlation functions describing the mean shape of cirrus clouds were computed. Because cirrus clouds seldom have distinct edges, these correlation functions are derived as a function of a threshold value which defines the cloud edge.

Eloranta, E. W.; Wylie, D.; Wolf, W.

1996-01-01

152

Comparison of Meteor Radar and Na Doppler Lidar Measurements of Winds in the Mesopause Region Above Maui, HI  

Microsoft Academic Search

Abstract. Simultaneous sodium (Na) Doppler lidar and meteor radar mea- surements of horizontal winds in the mesopause region over Maui, HI were collected in July, 2002 and October\\/November 2003. The coincident mea- surements span 96 hours and altitudes between 80-100 km. Statistical com- parisons are carried out on radar\\/lidar winds with 1 h and 4 km time and height resolution,

S. J. Franke; X. Chu; A. Z. Liu; W. K. Hocking

2004-01-01

153

Using MSG-SEVIRI Cloud Physical Properties and Weather Radar Observations for the Detection of Cb/TCu Clouds  

E-print Network

Using MSG-SEVIRI Cloud Physical Properties and Weather Radar Observations for the Detection of Cb (SEVIRI) on board Meteosat Second Generation (MSG) satellites and weather radar reflectivity factors/TCu clouds for the collection of pixels that pass the CCM. In this model, MSG-SEVIRI cloud physical

Schmeits, Maurice

154

An Airborne Profiling Radar Study of the Impact of Glaciogenic Cloud Seeding on Snowfall from Winter Orographic Clouds  

E-print Network

An Airborne Profiling Radar Study of the Impact of Glaciogenic Cloud Seeding on Snowfall from millimeter-wave Doppler radar are used to study the cloud microphysical effect of glaciogenic seeding of cold can have an immediate and obvious benefit for society'' (Nature 2008). Cloud seeding probably has been

Geerts, Bart

155

A comparison of cloud top heights computed from airborne lidar and MAS radiance data using CO2 slicing  

E-print Network

A comparison of cloud top heights computed from airborne lidar and MAS radiance data using CO2]. Other studies have compared CO2- slicing cloud heights with those computed from lidar data [Smith in assessing the accuracy of the CO2-slicing cloud height algorithm. Infrared measurements of upwelling

Sheridan, Jennifer

156

Compact airborne Raman lidar for profiling aerosol, water vapor and clouds.  

PubMed

A compact airborne Raman lidar system, which can perform water vapor and aerosol measurements both during nighttime and daytime is described. The system design, setup and the data processing methods are described in the paper. The Raman lidar was tested on University of Wyoming King Air research aircraft (UWKA) during the Wyoming King Air PBL Exploratory Experiment (KAPEE) in 2010. An observation showing clouds, aerosols and a dry line is presented to illustrate the lidar detection capabilities. Comparisons of the water vapor and aerosol measurements using the Raman lidar and other in situ airborne instruments show good agreement. PMID:25321266

Liu, Bo; Wang, Zhien; Cai, Yong; Wechsler, Perry; Kuestner, William; Burkhart, Matthew; Welch, Wayne

2014-08-25

157

Analysis of cloud layer structure in Shouxian, China using RS92 radiosonde aided by 95 GHz cloud radar  

E-print Network

Analysis of cloud layer structure in Shouxian, China using RS92 radiosonde aided by 95 GHz cloud to analyze cloud vertical structure over this area by taking advantage of the first direct measurements of cloud vertical layers from the 95 GHz radar. Singlelayer, twolayer, and threelayer clouds account for 28

Li, Zhanqing

158

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

159

The Cloud-Aerosol Transport System (CATS): a New Lidar for Aerosol and Cloud Profiling from the International Space Station  

NASA Technical Reports Server (NTRS)

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, Ellsworth J.; McGill, Matthew J.; Yorks, John E.; Hlavka, Dennis L.; Hart, William D.; Palm, Stephen P.; Colarco, Peter R.

2011-01-01

160

A New Technique for Measurements of Cloud Properties Using Lidar Depolarization  

NASA Astrophysics Data System (ADS)

The radiative behaviour of clouds is dependent on cloud particle phase. Water droplets can exist in temperatures well below 0 C for extended periods. Lidar depolarization ratio measurements allow liquid and solid states to be differentiated in individual clouds at high spatial-temporal resolution. The 2012 and 2013 Canadian Arctic ACE Validation Campaigns in Eureka, Nunavut, Canada (80N, 86W) provided an opportunity to make nearly continuous depolarization measurements using the CANDAC Rayleigh-Mie-Raman Lidar (CRL) in the troposphere. Depolarization ratio measurements using two techniques are presented here. The CRL transmits linearly polarized 532 nm laser pulses. The depolarizing effect of the cloud particles on the backscattered 532 nm photons is expressed as the linear depolarization ratio. A typical lidar uses two detection channels to determine the ratio: a 'Parallel' channel and a 'Perpendicular' channel. Backscattered photons may all remain polarized parallel to the transmitted beam (depol ratio = 0), or be depolarized, up to half parallel and half perpendicular (depol ratio = 1; light unpolarized). Thus, even before taking receiver optics into account, maximum possible count rates differ by a factor of two between the channels. In the CRL, optics further suppress perpendicular photons, reducing perpendicular rates to an order of magnitude smaller than the parallel rates, making the conventional retrieval technique challenging. To use the conventional technique, perpendicular signals require considerable co-adding to meet acceptable signal-to-noise thresholds, i.e. greater than 30 minutes even in ice clouds where signal rates are highest. Clear-sky retrievals are impossible. The CRL has been experimenting with an alternate approach: using the parallel channel in conjunction with the familiar polarization-insensitive Rayleigh Elastic channel. Sufficient parallel and Rayleigh elastic photons are recorded that depolarization ratio calculations with the new technique are possible at 10-minute resolution even in clear sky, and better in clouds. The 2012 measurements were made using the parallel and Rayleigh elastic channels, and are examined in the context of local meteorological measurements including radiosonde temperature. Results from this campaign were encouraging, and an expanded investigation of the technique was carried out simultaneously with the old technique during the 2013 Canadian Arctic ACE Validation Campaign. Calibrations and analyses which are currently underway will explicitly demonstrate the validity of the alternate depolarization ratio technique, and will quantify its advantages. Our plan is to combine the improved depolarization ratio measurements from the CRL with complementary, coincident measurements at Eureka. Comparisons with both ground-based instruments (e.g. millimetre cloud radar, microwave radiometer, several spectrometers) and satellite-borne instruments with overpasses of the high Arctic (in particular the ACE experiment) are possible at Eureka, and measurements by these instruments were also made during the 2012 and 2013 ACE validation campaigns.

McCullough, E. M.; Perro, C. W.; Sica, R. J.; Duck, T.; Walker, K. A.; Drummond, J. R.

2013-12-01

161

Particle Cloud Detection Using Coherent Laser Radar Systems Step One  

NASA Astrophysics Data System (ADS)

Biological and chemical agents are spread out in the atmosphere in the form of particle clouds. Hence, a method to detect and localize such clouds remotely is desired. The authors report some initial experiments performed with a recently developed coherent laser radar (CLR) system wherein the results direct their future work. The CLR was used to detect particles in motion at a distance of about 25 m in a laboratory environment. These initial tests have revealed that particles are detectable by the use of a CLR and that their velocity distribution can be measured. In coming studies the authors are going to use particles with known size distribution and measure the concentration of the generated clouds/particle streams. The detection capability of the CLR system will then be determined as a function of distance and particle cloud characteristics. The goal will be to describe the conditions under which the CLR can perform as a detector of various types of clouds.

Kullander, F.; Carlsson, T.; Letalick, D.; Lindgren, M.

2001-11-01

162

Comparison of lidar and stereo photogrammetric point clouds for change detection  

NASA Astrophysics Data System (ADS)

The advent of Light Detection and Ranging (LiDAR) point cloud collection has significantly improved the ability to model the world in precise, fine, three dimensional detail. The objective of this research was to demonstrate accurate, foundational methods for fusing LiDAR data and photogrammetric imagery and their potential for change detection. The scope of the project was to investigate optical image-to-LiDAR registration methods, focusing on dissimilar image types including high resolution aerial frame and WorldView-1 satellite and LiDAR with varying point densities. An innovative optical image-to-LiDAR data registration process was established. Comparison of stereo imagery point cloud data to the LiDAR point cloud using a 90% confidence interval highlighted changes that included small scale (< 50cm), sensor dependent change and large scale, new home construction change.

Basgall, Paul L.; Kruse, Fred A.; Olsen, Richard C.

2014-06-01

163

First results from an iron lidar and a VHF radar at Davis, Antarctica  

NASA Astrophysics Data System (ADS)

We present temperature measurements at Davis, Antarctica (69S, 78E), and compare with simultaneous and co-located radar measurements of polar mesosphere summer echoes (PMSE). The mobile scanning iron lidar of the IAP in Kuehlungsborn was installed at Davis in December 2010. It measures iron densities, vertical winds, and temperatures in the iron layer, i. e. from approximately 80 to 100 km. It is based on probing the Doppler broadened resonance line of iron atoms at 386 nm and can operate under daylight conditions. Typical values for temperature uncertainty, altitude and time resolution are 3-5 K, 1 km, and 1 hour, respectively. The lidar also measures neutral air densities and temperatures in the stratosphere and lower mesosphere. At Davis the lidar has up to now achieved approximately 2700 hours of data which is presumably the largest nearly continuous data set in Antarctica. The mesopause altitude changes throughout the summer season by several kilometers, significantly different from the northern hemisphere summer. Depending on altitude, temperatures can be warmer or colder compared to the NH summer. Temperatures at Davis near 86 km are rather similar to the NH, but they are much colder at higher altitudes. The thermal structure around the mesopause at Davis is closely related to the general circulation in the stratosphere, namely to the transition from winter to summer conditions. Different from expectations we sometimes find the mesopause significantly higher and colder(!) compared to the NH. Furthermore, we find large thermal tides in the summer months with amplitudes of up to 6-7~K, which is much larger than expected from models. The Australien Antarctic Division operates a 55 MHz VHF radar at Davis since February 2003. We report first simultaneous measurements of PMSE and temperatures by the Fe lidar. PMSE are strong radar echoes related to ice particles and therefore require atmospheric temperatures being lower than the frost point temperature. Several hours of simultaneous lidar/radar observations are now available from the Antarctic summer seasons 2010/2011 and 2011/2012. The VHF radar frequently detected PMSE. Temperatures at PMSE altitudes are below the frost point. To our surprise PMSE were sometimes absent at altitudes where temperatures are much lower than the frost point. We note that (apart from low temperatures) more ingredients are required for PMSE, for example, background electrons and neutral air turbulence. We will discuss potential explanations for the presence and absence of PMSE.Thermal tide from the iron resonance lidar located at Davis, Antarctica (from Lbken et al., Geophys. Res. Lett., 2011).

Luebken, F.; Morris, R. J.; Hoeffner, J.; Kaifler, B.; Viehl, T.

2012-12-01

164

Characterizing Vegetation 3D structure Globally using Spaceborne Lidar and Radar  

Microsoft Academic Search

We characterized global vegetation 3D structure using ICEsat-I\\/Geoscience Laser Altimeter (GLAS) and improved spatial resolution using ALOS\\/Phased Array L-band Synthetic Aperture radar (PALSAR) data over 3 sites in the United States. GLAS is a 70m footprint lidar altimeter sampling the ground along-track every 170m with a track separation near the equator around 30km. Forest type classes were initially defined according

M. Simard; N. Pinto; S. Riddick

2008-01-01

165

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

Microsoft Academic Search

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

R. N. Treuhaft; B. D. Chapman; J. R. dos Santos; F. G. Gonalves; L. V. Dutra; P. M. L. A. Graa; J. B. Drake

2009-01-01

166

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

167

A HIGH SPECTRAL RESOLUTION LIDAR DESIGNED FOR LONG-TERM ARCTIC CLOUD AND HAZE OBSERVATIONS.  

E-print Network

A HIGH SPECTRAL RESOLUTION LIDAR DESIGNED FOR LONG-TERM ARCTIC CLOUD AND HAZE OBSERVATIONS. E. W are available. Quantitative information on the optical properties of arctic clouds and hazes is needed to verify and hazes. Unlike the current HSRL which is housed in a 46 ft semi-trailer and requires continuous attention

Eloranta, Edwin W.

168

A Compact Airborne High Spectral Resolution Lidar for Observations of Aerosol and Cloud Optical Properties  

Microsoft Academic Search

We are in the process of developing a nadir-viewing, aircraft-based high spectral resolution lidar (HSRL) at NASA Langley Research Center. The system is designed to measure backscatter and extinction of aerosols and tenuous clouds. The primary uses of the instrument will be to validate spaceborne aerosol and cloud observations, carry out regional process studies, and assess the predictions of chemical

Chris A. Hostetler; John W. Hair; Anthony L. Cook

169

The Polarization Lidar Technique for Cloud Research: A Review and Current Assessment  

Microsoft Academic Search

The development of the polarization lidar field over the past two decades is reviewed, and the current cloud-research capabilities and limitations are evaluated. Relying on fundamental scattering principles governing the interaction of polarized laser light with distinctly shaped hydrometers, this remote-sensing technique has contributed to our knowledge of the composition and structure of a variety of cloud types. For example,

Kenneth Sassen

1991-01-01

170

The CALIPSO mission: Spaceborne lidar for observation of aerosols and clouds  

Microsoft Academic Search

Current uncertainties in the effects of aerosols and clouds on the Earth radiation budget limit our understanding of the climate system and the potential for global climate change. The CALIPSO satellite will use an active lidar together with passive instruments to provide vertical profiles of aerosols and clouds and their properties which w ill help address these uncertainties. CALIPSO will

David M. Winker; Jacques Pelon; M Patrick McCormick

171

Cirrus cloud-temperature interactions over a tropical station, Gadanki from lidar and satellite observations  

NASA Astrophysics Data System (ADS)

The cirrus clouds play an important role in the radiation budget of the earth's atmospheric system and are important to characterize their vertical structure and optical properties. LIDAR measurements are obtained from the tropical station Gadanki (13.50 N, 79.20 E), India, and meteorological indicators derived from Radiosonde data. Most of the cirrus clouds are observed near to the tropopause, which substantiates the strength of the tropical convective processes. The height and temperature dependencies of cloud height, optical depth, and depolarization ratio were investigated. Cirrus observations made using CALIPSO satellite are compared with lidar data for systematic statistical study of cirrus climatology.

S, Motty G.; Satyanarayana, M.; Krishnakumar, V.; Dhaman, Reji k.

2014-10-01

172

Aerosol and Cloud Interaction Observed from High Spectral Resolution Lidar  

Microsoft Academic Search

Studies have shown that aerosol optical depth is higher in the vicinity of clouds than in the clear air between clouds. The possible causes for this increased aerosol optical depth have been attributed to cloud contamination, swelling of aerosols as humidity increases in the vicinity of clouds, scattering from clouds into adjacent cloud-free columns, increased particle production near clouds, and

W. Su; G. L. Schuster; N. G. Loeb; R. R. Rogers; R. A. Ferrare; J. W. Hair; C. A. Hostetler; M. D. Obland

2008-01-01

173

The 1973-1974 lidar observations of cirrus clouds at Kwajalein  

NASA Technical Reports Server (NTRS)

A series of surface-based lidar measurements was made in support of reentry tests at Kwajalein. The measurement periods were conducted during May to June, Aug., Dec. 1973, and Mar. to Apr. 1974. The lidar used was the SRI Mark IX, a ruby lidar installed within a van complete with its own power supplies, azimuth and elevation scanning capabilities and real time digital data recording, processing, and display systems. The digital data system was used to estimate cirrus cloud equivalent ice water content as the cloud was being observed. Other supporting equipment included an instrumented WB-57 aircraft used for sampling cirrus cloud ice crystals. An altitude time intensity modulated video display of cirrus cloud structure observed on 17 Dec. 1973 is presented.

Uthe, Edward E.

1990-01-01

174

Dual-FOV Raman and Doppler lidar studies of aerosol-cloud interactions: Simultaneous profiling of aerosols, warm-cloud properties, and vertical wind  

NASA Astrophysics Data System (ADS)

For the first time, colocated dual-field of view (dual-FOV) Raman lidar and Doppler lidar observations (case studies) of aerosol and cloud optical and microphysical properties below and within thin layered liquid water clouds are presented together with an updraft and downdraft characterization at cloud base. The goal of this work is to investigate the relationship between aerosol load close to cloud base and cloud characteristics of warm (purely liquid) clouds and the study of the influence of vertical motions and turbulent mixing on this relationship. We further use this opportunity to illustrate the applicability of the novel dual-FOV Raman lidar in this field of research. The dual-FOV lidar combines the well-established multiwavelength Raman lidar technique for aerosol retrievals and the multiple-scattering Raman lidar technique for profiling of the single-scattering extinction coefficient, effective radius, number concentration of the cloud droplets, and liquid water content. Key findings of our 3 year observations are presented in several case studies of optically thin altocumulus layers occurring in the lower free troposphere between 2.5 and 4 km height over Leipzig, Germany, during clean and polluted situations. For the clouds that we observed, the most direct link between aerosol proxy (particle extinction coefficient) and cloud proxy (cloud droplet number concentration) was found at cloud base during updraft periods. Above cloud base, additional processes resulting from turbulent mixing and entrainment of dry air make it difficult to determine the direct impact of aerosols on cloud processes.

Schmidt, Jrg; Ansmann, Albert; Bhl, Johannes; Baars, Holger; Wandinger, Ulla; Mller, Detlef; Malinka, Aleksey V.

2014-05-01

175

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

NASA Astrophysics Data System (ADS)

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 at its Southern Great Plains facility. We demonstrate that the evolution of observed non-Gaussian, time-dependent probability distribution functions of ?(t) at each of various depths into cloud relative to cloud top is governed by the Fokker-Planck equation with linear drift D1(x) and stochastic multiplicative noise D2(x). The former is tentatively identified with larger-scale forcing, and the latter is identified with in-cloud circulations and turbulence. Obtained quadratic dependence of D2(x) leads to a noise-induced drift that presents the influence of the small-scale noise on the slow, large-scale deterministic processes. Obtained larger values of the noise-induced drift for the middle 50% of cirrus versus both the upper and lower 25% is anticipated from an ice crystal growth and deposition region. We find that the probability distribution functions of the cirrus that developed above a low-pressure system exhibit behavior at larger scales, e.g., delay times of 2 h, that is consistent with the structure of cirrus based on aircraft in situ measurements and with results from ground-based Raman lidar studies of cirrus. In contrast, the tails of the probability distribution functions of the cirrus over high-pressure system do not show the structure of properties that is distinctive for the cirrus above low-pressure synoptics.

Ivanova, K.; Ackerman, T. P.

2009-03-01

176

The impact of explicit cloud boundary information on ice cloud microphysical property retrievals from infrared radiances  

E-print Network

accurate radar- based or lidar-based estimates are included. It is demonstrated that the improvements) instrument aboard the Earth Observing System (EOS) Aqua satellite and cloud radar observations from the Cloud and Structure: Cloud physics and chemistry; 3359 Meteorology and Atmospheric Dynamics: Radiative processes; 3360

Stephens, Graeme L.

177

Assessing spaceborne lidar detection and characterization of aerosols near clouds using coincident airborne lidar and other measurements  

NASA Astrophysics Data System (ADS)

The objectives are to 1) evaluate potential shortcomings in the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aerosol height detection concerning specific biomass burning smoke events informed by airborne High Spectral Resolution Lidar (HSRL) in different cloud environments and 2) study the lidar-derived atmospheric parameters in the vicinity of clouds for the cases where smoke is within or above clouds. In the case of light absorbing aerosols like biomass burning smoke, studies show that the greater the cloud cover below the aerosols, the more likely the aerosols are to heat the planet. An accurate aerosol height assumption is also crucial to a correct retrieval of aerosol chemical composition from passive space-based measurements (through the Single Scattering Albedo (SSA) and aerosol absorption coefficient, as exemplified by aerosol retrievals using the passive Ozone Monitoring Instrument (OMI)). Strong smoke events are recognized as very difficult to quantify from space using passive (MODIS, OMI etc...) or active (CALIOP) satellite sensors for different reasons. This study is performed through (i) the selection of smoke events with coincident CALIOP and airborne HSRL aerosol observations, with smoke presence determined according to the HSRL aerosol classification data, (ii) the order of such events by range of HSRL aerosol optical depth, total color ratio and depolarization ratio (the latter two informing on the size and shape of the particles) and the evaluation of CALIOP's detection, classification and retrieval performance for each event, (iii) the study of the HSRL (or CALIOP when available) atmospheric parameters (total color ratio, volume depolarization ratio, mean attenuated backscatter) in the vicinity of clouds for each smoke event.

Kacenelenbogen, M. S.; Redemann, J.; Russell, P. B.; Vaughan, M.; Omar, A. H.; Burton, S. P.; Rogers, R.; Ferrare, R. A.; Hostetler, C. A.; Hair, J. W.

2011-12-01

178

Independent measurement of extinction and backscatter profiles in cirrus clouds by using a combined Raman elastic-backscatter lidar  

Microsoft Academic Search

Height profiles of the extinction and the backscatter coefficients in cirrus clouds are determined independently from elastic- and inelastic- (Raman) backscatter signals. An extended error analysis is given. Examples covering the measured range of extinction-to-backscatter ratios (lidar ratios) in ice clouds are presented. Lidar ratios between 5 and 15 sr are usually found. A strong variation between 2 and 20

Albert Ansmann; Ulla Wandinger; Maren Riebesell; Claus Weitkamp; Walfried Michaelis

1992-01-01

179

Determining water cloud particle sizes from lidar depolarization measurements and time dependent multiple scattering coefficients  

NASA Technical Reports Server (NTRS)

We present a technique of extracting water cloud particle size information from lidar measurements in conjunction with double scattering calculations. In this presentation, we describe the technique and give examples using data taken with the Air Force Phillips Laboratory's (Geophysics Directorate) low altitude Nd:YAG, elastic backscatter lidar. In a related presentation we describe the double scattering lidar model which we developed for this work. The technique uses simultaneous measurements of two orthogonal linear polarization components of lidar returns from water clouds or other media composed of spherical particles. Any depolarization of the incident lidar radiation backscattered by such a media can only be due to multiple scattering. The amount of depolarization is dependent on the extinction coefficient and the single scatter phase matrix, both of which are functions of position in the medium. The phase matrix is dependent on the index of refraction of the particles and the particle size distribution. Our technique is a modification of a procedure presented in Reference 1. There, particle sizes of water clouds are determined from double scattering calculations together with measurements of radiation scattered from volumes outside the lidar receiver's field of view (which can only be multiply scattered radiation). The methodology of our technique is similar but our 'probe' of the scattering phase function (and thus the particle size distribution) is different.

Garner, R. C.; Koenig, G. G.

1992-01-01

180

Lidar Monitoring of Clouds and Aerosols at the Facility for Atmospheric Remote Sensing  

NASA Technical Reports Server (NTRS)

We report on findings from ongoing polarization lidar research at the University of Utah Facility for Atmospheric Remote Sensing (FARS). This facility was established in 1987, and the current total of lidar and radiometric measurements is approx. 2,900-h. Research at FARS has been applied to the climatological investigation of cirrus cloud properties for basic research and satellite measurement validation (currently in its 13th year), and studies of contrails, mixed phase clouds, and volcanic and Asian dust aerosols. Among the techniques utilized for monitoring cloud and aerosol properties are triple-wave length linear depolarization measurements, and high (1.5-m by 10-Hz) resolution scanning observations. The usefulness of extended time lidar studies for atmospheric and climate research is illustrated.

Sassen, Kenneth

2000-01-01

181

Airborne CO2 coherent lidar measurements of cloud backscatter and opacity over the ocean surface  

NASA Technical Reports Server (NTRS)

The use of an airborne CO2 lidar to obtain cloud backscatter and extinction data at a thermal infrared wavelength is described. The extinction in this spectral region is proportional to the cloud liquid water content. The use of coherent detection results in high sensitivity and narrow field of view, the latter property greatly reducing multiple-scattering effects. Backscatter measurements in absolute units are obtained through a hard target calibration methodology. For clouds of low to moderate optical thickness at the lidar wavelength, both geometric thickness and optical thickness can be measured. The sea surface reflectance signal is used to obtain estimates of the cloud optical thickness. The utility of this technique results from studies that indicate that the spatial scale of variability of the sea surface reflectance is generally large compared with that of cloud optical thickness. Selected results are presented from data taken during flights over the Pacific Ocean.

Menzies, Robert T.; Tratt, David M.; Flamant, Pierre H.

1994-01-01

182

Reducing Surface Clutter in Cloud Profiling Radar Data  

NASA Technical Reports Server (NTRS)

An algorithm has been devised to reduce ground clutter in the data products of the CloudSat Cloud Profiling Radar (CPR), which is a nadir-looking radar instrument, in orbit around the Earth, that measures power backscattered by clouds as a function of distance from the instrument. Ground clutter contaminates the CPR data in the lowest 1 km of the atmospheric profile, heretofore making it impossible to use CPR data to satisfy the scientific interest in studying clouds and light rainfall at low altitude. The algorithm is based partly on the fact that the CloudSat orbit is such that the geodetic altitude of the CPR varies continuously over a range of approximately 25 km. As the geodetic altitude changes, the radar timing parameters are changed at intervals defined by flight software in order to keep the troposphere inside a data-collection time window. However, within each interval, the surface of the Earth continuously "scans through" (that is, it moves across) a few range bins of the data time window. For each radar profile, only few samples [one for every range-bin increment ((Delta)r = 240 m)] of the surface-clutter signature are available around the range bin in which the peak of surface return is observed, but samples in consecutive radar profiles are offset slightly (by amounts much less than (Delta)r) with respect to each other according to the relative change in geodetic altitude. As a consequence, in a case in which the surface area under examination is homogenous (e.g., an ocean surface), a sequence of consecutive radar profiles of the surface in that area contains samples of the surface response with range resolution (Delta)p much finer than the range-bin increment ((Delta)p << r). Once the high-resolution surface response has thus become available, the profile of surface clutter can be accurately estimated by use of a conventional maximum-correlation scheme: A translated and scaled version of the high-resolution surface response is fitted to the observed low-resolution profile. The translation and scaling factors that optimize the fit in a maximum-correlation sense represent (1) the true position of the surface relative to the sampled surface peak and (2) the magnitude of the surface backscatter. The performance of this algorithm has been tested on CloudSat data acquired over an ocean surface. A preliminary analysis of the test data showed a surface-clutter-rejection ratio over flat surfaces of >10 dB and a reduction of the contaminated altitude over ocean from about 1 km to about 0.5 km (over the ocean). The algorithm has been embedded in CloudSat L1B processing as of Release 04 (July 2007), and the estimated flat surface clutter is removed in L2B-GEOPROF product from the observed profile of reflectivity (see CloudSat product documentation for details and performance at http://www.cloudsat.cira.colostate.edu/ dataSpecs.php?prodid=1).

Tanelli, Simone; Pak, Kyung; Durden, Stephen; Im, Eastwood

2008-01-01

183

Fast Lidar and Radar Multiple-Scattering Models. Part II: Wide-Angle Scattering Using the Time-Dependent Two-Stream Approximation  

E-print Network

Fast Lidar and Radar Multiple-Scattering Models. Part II: Wide-Angle Scattering Using the Time (Manuscript received 5 October 2007, in final form 7 April 2008) ABSTRACT Spaceborne lidar returns from liquid backscattering event (in the case of lidar, accounting for small-angle forward scatterings on the way

Hogan, Robin

184

Gravity wave momentum fluxes studies using OH imager, Na Lidar and meteor radar  

NASA Astrophysics Data System (ADS)

In this paper we have used atmospheric data, from 80 to 100 km altitude, measured by three different equipments for studying gravity wave activity. An OH CCD imager and a meteor radar located at Cachoeira Paulista (22.7 S, 45 W) were used together with a sodium lidar operating at So Jos dos Campos (23.1 S, 45.9 W). We have used two years of data from 2007 to 2008 with 28 days of simultaneous data, totalizing 148 hours of observations. In an earlier presentation we inferred mean momentum fluxes and variances by using Hockings (2005) analysis of the meteor radar data and compared the variances values with the ones derived from Na lidar temperature profiles. The main objective of the present work is a comparison between the momentum fluxes inferred by using Hockings (2005) analysis of the meteor radar data and those derived from imaging data using the Swenson and Gardner (1998) model. This is an analytical model that relates the intensity perturbation of the OH emission to the relative perturbation in the atmospheric density. And then applying the GW polarization relations it is possible to compute the vertical energy and momentum fluxes due to waves seen in the OH emission.This analysis will make possible a comprehensive study of the momentum flux and variance due to GW over this region.

Andrioli, Vania Fatima; Clemesha, Barclay; Batista, Paulo

185

On the Feasibility of Precisely Measuring the Properties of a Precipitating Cloud with a Weather Radar  

E-print Network

In this paper the results of an investigation are presented that are concerned with the feasibility of employing a weather radar to make precise measurements of the properties of a precipitating cloud. A schematic cloud is proposed as a model...

Runnels, R.C.

186

Optical and morphological properties of Cirrus clouds determined by the high spectral resolution lidar during FIRE  

NASA Technical Reports Server (NTRS)

Cirrus clouds reflect incoming solar radiation and trap outgoing terrestrial radiation; therefore, accurate estimation of the global energy balance depends upon knowledge of the optical and physical properties of these clouds. Scattering and absorption by cirrus clouds affect measurements made by many satellite-borne and ground based remote sensors. Scattering of ambient light by the cloud, and thermal emissions from the cloud can increase measurement background noise. Multiple scattering processes can adversely affect the divergence of optical beams propagating through these clouds. Determination of the optical thickness and the vertical and horizontal extent of cirrus clouds is necessary to the evaluation of all of these effects. Lidar can be an effective tool for investigating these properties. During the FIRE cirrus IFO in Oct. to Nov. 1986, the High Spectral Resolution Lidar (HSRL) was operated from a rooftop site on the campus of the University of Wisconsin at Madison, Wisconsin. Approximately 124 hours of fall season data were acquired under a variety of cloud optical thickness conditions. Since the IFO, the HSRL data set was expanded by more than 63.5 hours of additional data acquired during all seasons. Measurements are presented for the range in optical thickness and backscattering phase function of the cirrus clouds, as well as contour maps of extinction corrected backscatter cross sections indicating cloud morphology. Color enhanced images of range-time indicator (RTI) displays a variety of cirrus clouds with approximately 30 sec time resolution are presented. The importance of extinction correction on the interpretation of cloud height and structure from lidar observations of optically thick cirrus are demonstrated.

Grund, Christian John; Eloranta, Edwin W.

1990-01-01

187

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 (NRT) data capability of the ISS will enable CATS to support operational applications such as aerosol and air quality forecasting 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. Results from the NASA Goddard Earth Observing System general circulation model and data assimilation system (GEOS-5) have been used to generate the simulated data, and will be used to help process CATS data after launch.

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

2012-12-01

188

The Cloud-Aerosol Transport System (CATS): A New Lidar for Aerosol and Cloud Profiling from the International Space Station  

NASA Technical Reports Server (NTRS)

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 (NRT) data capability ofthe ISS will enable CATS to support operational applications such as aerosol and air quality forecasting 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. Input from the ICAP community is desired to help plan our NRT mission goals and interactions with ICAP forecasters.

Welton, Ellsworth J.; McGill, Mathew J.; Yorks. John E.; Hlavka, Dennis L.; Hart, William D.; Palm, Stephen P.; Colarco, Peter R.

2012-01-01

189

Cirrus cloud transmittance and backscatter in the infrared measured with a CO(2) lidar.  

PubMed

Two independent methods of measuring the transmittance of cirrus clouds are compared. Both used a CO(2) pulsed Doppler lidar at a wavelength of 10.59 microm. The first method used backscatter from the calibration target El Chichon stratospheric cloud that was present over Boulder in 1982 and 1983. The second method used conical lidar scans at different zenith angles when uniform cirrus decks were present. Extinction coefficients measured from both methods average 0.1 km(-1) for tenuous cirrus 1.0 km thick to 0.78 km(-1) for cirrus several kilometers thick. There is a wide standard deviation in extinction values. Extinction-tobackscatter ratios S vary from <1000 sr for tenuous clouds to 2600 sr for dense clouds. Mie scattering and extinction calculations for spherical ice particles of 10-50 microm in radius lead to ratios S > 2000 sr, so long as the ice absorption is entered into the calculations. The backscattering ratio for ice cylinders is 1 order of magnitude lower than for spheres. Backscatter in the IR may, therefore, be reasonably well modeled by some combination of spheres and cylinders. Cloud thickness statistics from lidar returns show that cirrus decks average ~500 m thick. Clouds thinner than 300 m were often overlooked by the unaided surface-based observer. These preliminary results are in rather close agreement with the LOWTRAN 6 cirrus cloud model predictions. PMID:20531784

Hall, F F; Cupp, R E; Troxel, S W

1988-06-15

190

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 (80N, 86W) 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

191

Analysis of airborne Doppler lidar, Doppler radar and tall tower measurements of atmospheric flows in quiescent and stormy weather  

NASA Technical Reports Server (NTRS)

The first experiment to combine airborne Doppler Lidar and ground-based dual Doppler Radar measurements of wind to detail the lower tropospheric flows in quiescent and stormy weather was conducted in central Oklahoma during four days in June-July 1981. Data from these unique remote sensing instruments, coupled with data from conventional in-situ facilities, i.e., 500-m meteorological tower, rawinsonde, and surface based sensors, were analyzed to enhance understanding of wind, waves and turbulence. The purposes of the study were to: (1) compare winds mapped by ground-based dual Doppler radars, airborne Doppler lidar, and anemometers on a tower; (2) compare measured atmospheric boundary layer flow with flows predicted by theoretical models; (3) investigate the kinematic structure of air mass boundaries that precede the development of severe storms; and (4) study the kinematic structure of thunderstorm phenomena (downdrafts, gust fronts, etc.) that produce wind shear and turbulence hazardous to aircraft operations. The report consists of three parts: Part 1, Intercomparison of Wind Data from Airborne Lidar, Ground-Based Radars and Instrumented 444 m Tower; Part 2, The Structure of the Convective Atmospheric Boundary Layer as Revealed by Lidar and Doppler Radars; and Part 3, Doppler Lidar Observations in Thunderstorm Environments.

Bluestein, H. B.; Doviak, R. J.; Eilts, M. D.; Mccaul, E. W.; Rabin, R.; Sundara-Rajan, A.; Zrnic, D. S.

1986-01-01

192

Simulation of Lidar Return Signals Associated with Water Clouds  

E-print Network

We revisited an empirical relationship between the integrated volume depolar- ization ratio, oacc, and the effective multiple scattering factor, -n, on the basis of Monte Carlo simulations of spaceborne lidar backscatter associated with homogeneous...

Lu, Jianxu

2010-01-14

193

Cloud effects from boreal forest fire smoke: evidence for ice nucleation from polarization lidar data and cloud model simulations  

NASA Astrophysics Data System (ADS)

Polarization lidar observations from the interior of Alaska have revealed unusual supercooled altocumulus cloud conditions in the presence of boreal forest fire smoke from local and regional fires. At temperatures of about -15 C, the lidar data show ice nucleation prior to liquid cloud formation (i.e. below water saturation), as well as the occasional glaciation of the liquid layer. Thus the smoke aerosol appears to act as ice nuclei that become activated in updrafts before the liquid cloud forms, as the concentrated aqueous organic solutions are diluted sufficiently to allow them to freeze heterogeneously. This haze particle freezing process is similar to the production of cirrus ice crystals homogeneously at much colder temperatures. To test this hypothesis, cloud microphysical model simulations constrained by the measurements were performed. They indicate that this heterogeneous ice nucleation scenario can be supported by the cloud model. Although ice formation in this manner may generally act in the atmosphere, the boreal smoke particles produce an unusually dramatic effect in the lidar data. We conclude that smoke-induced ice nucleation occurs at moderate supercooled temperatures either through the effects of raised soil/dust particles embedded in the smoke droplets, coated soot aerosol or through the nucleation via certain organic solutions.

Sassen, Kenneth; Khvorostyanov, Vitaly I.

2008-04-01

194

STUDY OF CLOUD LIFETIME EFFECTS USING THE SGP HETEROGENEOUS DISTRIBUTED RADAR NETWORK: PRELIMINARY CONSIDERATIONS  

E-print Network

STUDY OF CLOUD LIFETIME EFFECTS USING THE SGP HETEROGENEOUS DISTRIBUTED RADAR NETWORK: PRELIMINARY-dimensional morphology and life cycle of clouds. Detailing key cloud processes as they transit from the formation stage to precipitation onset and cloud dissipation is critical towards establishing uncertainties in climate models

195

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

196

Time and polarization dependent double scattering calculations of lidar returns from water clouds  

NASA Technical Reports Server (NTRS)

We describe and present results of a double scattering lidar model which we use to calculate lidar returns from water clouds. The model is used in conjunction with the Phillips Laboratory's (Geophysics Directorate) low altitude Nd:YAG lidar system to determine microphysical properties of water clouds. The model determines the Stokes parameters of the backscattered lidar radiation, from media composed of spherical particles, as a function of time. The Stokes parameters of the radiation of the lidar return are determined, at each time, by considering all radiation which has traveled the same path length from transmitter to receiver while making two successive single scatters. Each single scatter is considered a Mie scatter. We have also developed a Mie scattering program for use with the double scattering model. Each single scatter takes into account the polarization of the incident and scattered radiation. Inputs to the double scattering mode include the receiver area and field of view, the receiver integration time, the extinction coefficient as a function of distance into the cloud, the particle size distribution (assumed independent of position), and the complex index of refraction of the spherical particles.

Garner, R. C.

1992-01-01

197

Lidar System for Airborne Measurement of Clouds and Aerosols  

NASA Technical Reports Server (NTRS)

A lidar system for measuring optical properties of clouds and aerosols at three wavelengths is depicted. The laser transmitter is based on a Nd:YVO4 laser crystal pumped by light coupled to the crystal via optical fibers from laser diodes that are located away from the crystal to aid in dissipating the heat generated in the diodes and their drive circuits. The output of the Nd:YVO4 crystal has a wavelength of 1064 nm, and is made to pass through frequency-doubling and frequency-tripling crystals. As a result, the net laser output is a collinear superposition of beams at wavelengths of 1064, 532, and 355 nm. The laser operates at a pulse-repetition rate of 5 kHz, emitting per-pulse energies of 50 microJ at 1064 nm, 25 microJ at 532 nm and 50 microJ at 355 nm. An important feature of this system is an integrating sphere located between the laser output and the laser beam expander lenses. The integrating sphere collects light scattered from the lenses. Three energy-monitor detectors are located at ports inside the integrating sphere. Each of these detectors is equipped with filters such that the laser output energy is measured independently for each wavelength. The laser output energy is measured on each pulse to enable the most accurate calibration possible. The 1064-nm and 532-nm photodetectors are, more specifically, single photon-counting modules (SPCMs). When used at 1064 nm, these detectors have approximately 3% quantum efficiency and low thermal noise (fewer than 200 counts per second). When used at 532 nm, the SPCMs have quantum efficiency of about 60%. The photodetector for the 355-nm channel is a photon-counting photomultiplier tube having a quantum efficiency of about 20%. The use of photon-counting detectors is made feasible by the low laser pulse energy. The main advantage of photon-counting is ease of inversion of data without need for complicated calibration schemes like those necessary for analog detectors. The disadvantage of photon-counting detectors is that they inherently have narrow dynamic ranges. However, by using photon-counting detectors along with a high-repetition rate laser, it is possible to obtain wide dynamic range through accumulation of counts over many pulses.

McGill, Matthew; Scott, V. Stanley; Izquierdo, Luis Ramos; Marzouk, Joe

2008-01-01

198

The Composite Characteristics of Cirrus Clouds: Bulk Properties Revealed by One Year of Continuous Cloud Radar Data  

Microsoft Academic Search

The properties of midlatitude cirrus clouds are examined using one year of continuous vertically pointing millimeter-wave cloud radar data collected at the Atmospheric Radiation Measurement Program Southern Great Plains site in Oklahoma. The goal of this analysis is to present the cloud characteristics in a manner that will aid in the evaluation and improvement of cirrus parameterizations in large-scale models.

Gerald G. Mace; Eugene E. Clothiaux; Thomas P. Ackerman

2001-01-01

199

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

200

El Chichon eruption cloud - Comparison of lidar and optical thickness measurements for October 1982  

NASA Astrophysics Data System (ADS)

Sun photometer and lidar backscatter measurements of the El Chichon volcanic cloud were obtained during an airborne latitude survey. The observations were collected between 46 deg N and 46 deg S from Oct. 19-Nov. 7, 1982. Comparisons between these data sets have been performed. An aerosol optical model was developed for the conversion of the lidar measurements to optical thickness values using numerical aerosol size distribution data and index of refraction information collected with coordinated dustsonde balloon flights. The derived lidar optical thickness values were found to agree with the sun photometer optical thickness values within measurement uncertainties. The lidar derived values ranged from 0.16 at the equator to 0.03 at 30 deg S latitude. Peak values were concentrated between 35 deg N and 10 deg S.

Swissler, T. J.; McCormick, M. P.; Spinhirne, J. D.

1983-09-01

201

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

202

Modeling urban LIDAR point clouds with combined 2D TIN and 3D tetrahedron structure  

NASA Astrophysics Data System (ADS)

This paper presents our research on exploring the combined 2D TIN and 3D Tetrahedra structure to quickly model large-range Urban LIDAR point clouds for 3D visualization purpose. To this end, Morphological grayscale reconstruction is first implemented to segment LIDAR point clouds into terrain and non-terrain regions. After that, segmented Lidar terrain points are modeled with Constrained Delaunay Triangulation under constrain of building boundary as well as non-terrain points are modeled with Power Crust algorithm to obtain reconstructed building surface. Next, two kinds of model are combined based on shared building boundary. Finally, 3D visualization of selected urban area with presented technique clearly demonstrates higherefficiency. Valuable conclusions are given as well.

Wu, Jun; Liao, Honggang; Chen, Menmen; Peng, Zhiyong

2013-10-01

203

Arctic polar stratospheric cloud measurements by means of a four wavelength depolarization lidar  

NASA Technical Reports Server (NTRS)

A four wavelength depolarization backscattering lidar has been operated during the European Arctic Stratospheric Ozone Experiment (EASOE) in Sodankyl, in the Finnish Arctic. The lidar performed measurements during the months of December 1991, January, February and March 1992. The Finnish Meteorological Institute during the same period launched regularly three Radiosondes per day, and three Ozone sondes per week. Both Mt. Pinatubo aerosols and Polar Stratospheric Clouds were measured. The use of four wavelengths, respectively at 355 nm, 532 nm , 750 nm, and 850 nm permits an inversion of the lidar data to determine aerosol particle size. The depolarization technique permits the identification of Polar Stratospheric Clouds. Frequent correlation between Ozone minima and peaks in the Mt. Pinatubo aerosol maxima were detected. Measurements were carried out both within and outside the Polar Vortex.

Stefanutti, L.; Castagnoli, F.; Delguasta, M.; Flesia, C.; Godin, S.; Kolenda, J.; Kneipp, H.; Kyro, Esko; Matthey, R.; Morandi, M.

1994-01-01

204

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

NASA Technical Reports Server (NTRS)

An angular-scanning large-aperture (36 cm) backscatter lidar was developed and deployed on the NASA DC-8 research aircraft as part of the SUCCESS (Subsonic Aircraft: Contrail and Cloud Effects Special Study) program. The lidar viewing direction could be scanned continuously during aircraft flight from vertically upward to forward to vertically downward, or the viewing could be at fixed angles. Real-time pictorial displays generated from the lidar signatures were broadcast on the DC-8 video network and used to locate clouds and contrails above, ahead of, and below the DC-8 to depict their spatial structure and to help select DC-8 altitudes for achieving optimum sampling by onboard in situ sensors. Several lidar receiver systems and real-time data displays were evaluated to help extend in situ data into vertical dimensions and to help establish possible lidar configurations and applications on future missions. Digital lidar signatures were recorded on 8 mm Exabyte tape and generated real-time displays were recorded on 8mm video tape. The digital records were transcribed in a common format to compact disks to facilitate data analysis and delivery to SUCCESS participants. Data selected from the real-time display video recordings were processed for publication-quality displays incorporating several standard lidar data corrections. Data examples are presented that illustrate: (1) correlation with particulate, gas, and radiometric measurements made by onboard sensors, (2) discrimination and identification between contrails observed by onboard sensors, (3) high-altitude (13 km) scattering layer that exhibits greatly enhanced vertical backscatter relative to off-vertical backscatter, and (4) mapping of vertical distributions of individual precipitating ice crystals and their capture by cloud layers. An angular scan plotting program was developed that accounts for DC-8 pitch and velocity.

Uthe, Edward E.; Nielsen, Norman B.; Oseberg, Terje E.

1998-01-01

205

Retrieve Optically Thick Ice Cloud Microphysical Properties by Using Airborne Dual-Wavelength Radar Measurements.  

National Technical Information Service (NTIS)

An algorithm to retrieve optically thick ice cloud microphysical property profiles is developed by using the GSFC 9.6 GHz ER-2 Doppler Radar (EDOP) and the 94 GHz Cloud Radar System (CRS) measurements aboard the high-altitude ER-2 aircraft. In situ size d...

Z. Wang, G. M. Heymsfield, L. Li A. J. Heymsfield

2005-01-01

206

First results of combined Fe-lidar/Radar measurements at Davis, 69 S.  

NASA Astrophysics Data System (ADS)

The mobile scanning Fe-lidar of the IAP-Khlungsborn was moved to Davis, Antarctica, 69 S, 78 E during November 2010. This location was chosen because PMSE/NLC observations by MST-radar/RMR-lidar have been performed since 2003/2001 by the Australian Antarctic Division. Davis is the only station in Antarctica where comparable long-term observations to Alomar, 69 N are available. A comparison of both locations allows a detailed comparison of differences or similarities between the northern (NH) / southern hemisphere (SH) at mesopause altitudes. The Fe-lidar is a two wavelength system which measures Doppler temperature/vertical wind and iron densities by resonance scattering at 386 nm. The fundamental wavelength at 772 nm is used for aerosol measurements from the stratosphere to the mesosphere including NLC in summer or PSC in winter. Measurements are almost background free which allows year round operation independent of sunlight. At Davis the lidar was in operation 24% of the first year (2150 hours) which has not been achieved elsewhere with a mesospheric lidar. This unusual and already largest lidar data base of Antarctica shows the thermal structure of the mesopause region and the iron layer in great detail. Strong tides throughout the year have been observed and a link of the early part of the PMSE season to the stratospheric vortex has been found. More than 700 hours of temperature observation during the PMSE-season are compared with common volume PMSE/NLC observations. For the first time temperature and vertical wind measurements through PMSE and NLC have been achieved by a lidar showing that the SH in particular in December/January differs significantly from the NH in June/July. The temperature measurements near 86 km altitude show that the summer mesopause is surprisingly similar to the NH at PMSE altitudes but differs significantly at higher altitudes. Unlike the NH the southern mesopause altitude changes throughout the season by several kilometres. Depending on altitude temperatures can be warmer but also much colder than at the NH causing a change in PMSE altitude over the season.

Hffner, J.; Morris, R. J.; Kaifler, B.; Viehl, T.; Lbken, F.-J.

2012-04-01

207

COMPARISON OF AMV CLOUD TOP PRESSURE DERIVED FROM MSG WITH SPACE BASED LIDAR OBSERVATIONS (CALIPSO)  

E-print Network

COMPARISON OF AMV CLOUD TOP PRESSURE DERIVED FROM MSG WITH SPACE BASED LIDAR OBSERVATIONS (CALIPSO found between all CTHs from MSG (CLA box and AMV) and CALIOP. However, the AMV pressure allocation of the HA methods to several atmospheric parameters. Meteosat Second Generation (MSG) provides many new

Madeleine, Jean-Baptiste

208

Airborne lidar observations in the wintertime Arctic stratosphere: Polar stratospheric clouds  

Microsoft Academic Search

Polar stratospheric cloud (PSC) distributions in the wintertime Arctic stratosphere and their optical characteristics were measured with a multi-wavelength airborne lidar system as part of the 1989 Airborne Arctic Stratospheric Expedition. PSCs were observed on 10 flights between January 6 and February 2, 1989, into the polar vortex. The PSCs were found in the 14-27 km altitude range in regions

E. V. Browell; S. Ismail; A. F. Carter; N. S. Higdon; C. F. Butler; P. A. Robinette; O. B. Toon; M. R. Schoeberl; A. F. Tuck

1990-01-01

209

On an 8 km-altitude cloud and precipitation radar echo peak observed during EPIC Paquita Zuidema  

E-print Network

On an 8 km- altitude cloud and precipitation radar echo peak observed during EPIC Paquita Zuidema precipitation radar data evaluates the vertical structure of the precipitation and can provide statistics for a larger spatial area than is sampled by the cloud radar. This poster presents the cloud and precipitation

Zuidema, Paquita

210

ETO lidar studies of cirrostratus altocumulogenitus: Another role for supercooled liquid water in cirrus cloud formation  

NASA Technical Reports Server (NTRS)

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 in cirrus, since the concentrations of ice nuclei (IN) measured by various techniques (at the surface or in the lower troposphere) indicate an enormous number of IN that should be active at cirrus cloud temperatures. In light of recent instrumental aircraft and polarization lidar studies of cirrus clouds, it is clear that highly supercooled cloud droplets can sometimes be a component of cirrus clouds. It remains to be determined if supercooled liquid water (SLW) is present abundantly enough in cirrus to play a significant role in earth's radiance balance, or is merely a curious, infrequent occurrence. To help evaluate this issue, the UH polarization lidar FIRE Extended Time Observation (ETO) of cirrus clouds are being utilized to compile, among other parameters, a climatological record of SLW clouds associated with and within cirrus.

Sassen, Kenneth

1990-01-01

211

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

212

Global Monitoring of Clouds and Aerosols Using a Network of Micro-Pulse Lidar Systems  

NASA Technical Reports Server (NTRS)

Long-term global radiation programs, such as AERONET and BSRN, have shown success in monitoring column averaged cloud and aerosol optical properties. Little attention has been focused on global measurements of vertically resolved optical properties. Lidar systems are the preferred instrument for such measurements. However, global usage of lidar systems has not been achieved because of limits imposed by older systems that were large, expensive, and logistically difficult to use in the field. Small, eye-safe, and autonomous lidar systems are now currently available and overcome problems associated with older systems. The first such lidar to be developed is the Micro-pulse lidar System (MPL). The MPL has proven to be useful in the field because it can be automated, runs continuously (day and night), is eye-safe, can easily be transported and set up, and has a small field-of-view which removes multiple scattering concerns. We have developed successful protocols to operate and calibrate MPL systems. We have also developed a data analysis algorithm that produces data products such as cloud and aerosol layer heights, optical depths, extinction profiles, and the extinction-backscatter ratio. The algorithm minimizes the use of a priori assumptions and also produces error bars for all data products. Here we present an overview of our MPL protocols and data analysis techniques. We also discuss the ongoing construction of a global MPL network in conjunction with the AERONET program. Finally, we present some early results from the MPL network.

Welton, Ellsworth J.; Campbell, James R.; Spinhirne, James D.; Scott, V. Stanley

2000-01-01

213

CALIPSO: Global Aerosol and Cloud Observations from Lidar and Passive Instruments  

NASA Technical Reports Server (NTRS)

CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Spaceborne Observations) is an approved satellite mission being developed through collaboration between NASA and the French space agency CNES. The mission is scheduled for launch in 2004 and will operate for 3 years as part of a five-satellite formation called the Aqua constellation. This constellation will provide a unique data set on aerosol and cloud optical and physical properties and aerosol-cloud interactions that will substantially increase our understanding of the climate system and the potential for climate change.

Poole, L. R.; Winker, D. M.; Pelon, J. R.; McCormick, M. P.

2002-01-01

214

Inertia-gravity waves in Antarctica: A case study using simultaneous lidar and radar measurements at McMurdo/Scott  

E-print Network

Inertia-gravity waves in Antarctica: A case study using simultaneous lidar and radar measurements March 2013; published 9 April 2013. [1] This study presents the first coincident observation of inertia: Chen, C., X. Chu, A. J. McDonald, S. L. Vadas, Z. Yu, W. Fong and X. Lu (2013), Inertia-gravity waves

Vadas, Sharon

215

Analysis of surface wind and roughness length evolution with fetch using a combination of airborne lidar and radar measurements  

Microsoft Academic Search

A combination of surface wind speed (SWS) and sea state variables, derived from quasi-simultaneous airborne lidar and radar measurements, made in the framework of the Flux, tat de mer et Tldtection en Condition de fetcH variable (FETCH) experiment, is used to analyze the evolution of surface roughness length, neutral drag coefficient, and friction velocity coefficient with fetch in the first

Cyrille Flamant; Jacques Pelon; Danile Hauser; Cline Quentin; William M. Drennan; Francis Gohin; Bertrand Chapron; Jrome Gourrion

2003-01-01

216

Remote sensing of vegetation 3-D structure for biodiversity and habitat: Review and implications for lidar and radar spaceborne  

E-print Network

measurements, or at larger scales to generalizations. New lidar and radar remote sensing instruments of biodiversity is concerned with life on Earth at levels of organization from genes to species, communities on biodiversity and habitat. Multispectral passive optical sensors such as Landsat TM/ETM+ or MODIS are useful

Radeloff, Volker C.

217

Laser radar characterization of atmospheric aerosols in the troposphere and stratosphere using range dependent lidar ratio  

NASA Astrophysics Data System (ADS)

Laser radar (lidar) provides an excellent tool for characterizing the physical properties of atmospheric aerosols which play a very important role in modifying the radiative budget of the Earth's atmosphere. One of the important issues in lidar research is to derive accurate backscattering or extinction coefficient profiles required for understanding the basic mechanisms in the formation of aerosols and identifying their sources and sinks. Most of the inversion methods used for deriving the aerosol coefficients assume a range independent value for the extinction-to- backscattering ratio [lidar ratio, (LR)]. However, it is known that in a realistic atmosphere the value of LR is range dependent and varies with the physical and chemical properties of the aerosols. In this paper, we use a variant of widely applied Klett's method to obtain the range dependent LR values and derive the aerosol extinction profiles with good accuracy. We present the lidar derived aerosol extinction profiles in the upper troposphere and lower stratosphere corresponding to different seasons of the year of two distinctly different stations in the Indian subcontinent namely Trivandrum (8.33 N, 77 E), Kerala, India, a coastal station and Gadanki (13.5 N, 79.2 E), Tirupati, India an inland station. The range dependent LR is derived corresponding to different seasons of the year at the two stations. The lidar ratio, aerosol extinction coefficient (AEC), aerosol scattering ratio and aerosol optical depth show strong to medium seasonal variation at both the stations. The lidar ratio values at Trivandum vary in the range of 11-38 sr whereas the values range from 20-34 sr at Gadanki. AEC values at the Trivandum station vary from 7.9x10-6 to 6.9x10-5 m-1 and at Gadanki station the variation is from 1.27x10-5 to 6.9x10-5 m-1. It is proposed to use back-trajectory analysis to understand the sources of aerosol at the two stations.

Malladi, Satyanarayana; Soman Radha, Radhakrishnan; Mahadevan Pillai, V. P.; Sangipillai, Veerabuthiran; Bhargavan, Presennakumar; Vinjanampaty, Murty; Karnam, Reghunath

2010-01-01

218

An approach to DSM refinement with fusion of airborne lidar point cloud data and optical imagery  

NASA Astrophysics Data System (ADS)

The airborne LiDAR system, which usually integrated with optical camera, is an efficient way of acquiring 3D geographic information and enjoys widely application in building DSM. However, when the airborne LiDAR is used in urban area, where there are a large amount of tall buildings, the characteristic points of buildings are seldom measured and the measured points are frequently too sparse to create precise building models. In this paper, an approach to DSM refining DSM in urban area with fusion of airborne LiDAR point cloud data and optical imagery is put forward. Firstly, the geometric relationship between the airborne LiDAR point and the correspondent pixel on the image synchronously taken by optical camera is analyzed. The relative position and attitude parameters between the laser rangefinder and the camera are determined in the process of alignment and calibration. Secondly, the building roof edges on the optical image are extracted by edge detection. By tracing the building roof edges, the contours of building roofs in vector format are acquired and the characteristic points of buildings are further extracted. Thirdly, all the LiDAR measured points on the roof of specific building are separated from the point cloud data by judging the geometric relation between LiDAR measured points and the building outline, which is represented by a polygon, according to their plane coordinates. Finally, the DSM refinement for buildings can be implemented. All pixels representing the building roof are given heights as same as that of nearer LiDAR point inside the polygon. Ortho-photo map and virtual building models of urban area with higher quality can be reached with the refined DSM and optical images.

Hao, Xiangyang; Zhang, Weiqiang; Jiang, Lixing

2013-05-01

219

SHORELINE EXTRACTION FROM THE INTEGRATION OF LIDAR POINT CLOUD DATA AND AERIAL ORTHOPHOTOS USING MEAN SHIFT SEGMENTATION  

Microsoft Academic Search

A method for shoreline extraction from integrated LiDAR point cloud data and aerial orthophotos is presented. First, a Mean Shift Algorithm is used for LiDAR point segmentation. The horizontal position and elevation of the LiDAR point plus color information obtained from the corresponding orthophoto are used as the point features in the Mean Shift Algorithm. Due to the homogenous nature

I-Chieh Lee; Bo Wu; Ron Li

2009-01-01

220

Cloud model-based simulation of spaceborne radar observations  

NASA Technical Reports Server (NTRS)

Simulations of observations from potential spaceborne radars are made based on storm structure generated from the three-dimensional (3D) Goddard cumulus ensemble model simulation of an intense overland convective system. Five frequencies of 3, 10, 14, 35, and 95 GHz are discussed, but the Tropical Rainfall Measuring Mission precipitation radar sensor frequency (14 GHz) is the focus of this study. Radar reflectives and their attenuation in various atmospheric conditions are studied in this simulation. With the attenuation from cloud and precipitation in the estimation of reflectivity factor (dBZ), the reflectivities in the lower atmosphere in the convective cores are significantly reduced. With spatial resolution of 4 km X 4 km, attenuation at 14 GHz may cause as large as a 20-dBZ difference between the simulated measurements of the peak, Z(sub mp) and near-surface reflectivity, Z(sub ms) in the most intense convective region. The Z(sub mp) occurs at various altitudes depending on the hydrometeor concentrations and their vertical distribution. Despite the significant attenuation in the intense cores, the presence of the rain maximum is easily detected by using information of Z(sub mp). In the stratiform region, the attenuation is quite limited (usually less than 5 dBZ), and the reduction of reflectivity is mostly related to the actual vertical structure of cloud distribution. Since Z(sub ms) suffers severe attenuation and tends to underestimate surface rainfall intensity in convective regions. Z(sub mp) can be more representative for rainfall retrieval in the lower atmosphere in these regions. In the stratiform region where attenuation is negligible, however, Z(sub mp) tends to overestimate surface rainfall and Z(sub ms) is more appropriate for rainfall retrieval. A hybrid technique using a weight between the two rain intensities is tested and found potentially usefull for future applications. The estimated surface rain-rate map based on this hybrid approach captures many of the details of the cloud model rain field but still slightly underestimates the rain-rate maximum.

Yeh, H.-Y. M.; Prasad, N.; Meneghini, R.; Tao, W.-K.; Jones, J. A.; Adler, R. F.

1995-01-01

221

Ice iron/sodium film as cause for high noctilucent cloud radar reflectivity  

E-print Network

and sodium layers located immediately above the noctilucent cloud layer. The number of conduction electrons of free electrons. A noctilucent cloud dust grain could be charged negatively because of ambient electron other means. [4] Existing models proposed to explain radar echoes from noctilucent clouds are based

Bellan, Paul M.

222

Model driven reconstruction of roofs from sparse LIDAR point clouds  

NASA Astrophysics Data System (ADS)

This article presents a novel, fully automatic method for the reconstruction of three-dimensional building models with prototypical roofs (CityGML LoD2) from LIDAR data and building footprints. The proposed method derives accurate results from sparse point data sets and is suitable for large area reconstruction. Sparse LIDAR data are widely available nowadays. Robust estimation methods such as RANSAC/MSAC, are applied to derive best fitting roof models in a model-driven way. For the identification of the most probable roof model, supervised machine learning methods (Support Vector Machines) are used. In contrast to standard approaches (where the best model is selected via MDL or AIC), supervised classification is able to incorporate additional features enabling a significant improvement in model selection accuracy.

Henn, Andr; Grger, Gerhard; Stroh, Viktor; Plmer, Lutz

2013-02-01

223

The eyesafe visioceilometer - A tactical visibility and cloud height lidar  

NASA Astrophysics Data System (ADS)

A recent breakthrough in the mathematical solution to the lidar equation combined with state-of-the-art microelectronics has made it possible to produce the first portable ceiling, visibility, and rangefinding device suitable for tactical use by the U.S. Army. The signal processor of the former XE-2 (Nd:YAG) can be adapted to an eyesafe unit by making use of an erbium glass laser and a GaInAs PIN photodiode detector. It is pointed out that the XE-3 (Eyesafe Visioceilometer) provides tactical real-time data when and where the user needs it, with an accuracy superior to existing nonportable runway equipment. Attention is given to system evolution, lidar theory, the relationship of backscattering and extinction coefficients, a system description, the transient recorder, the analysis of data, and details regarding tactical applications.

Barnes, E. S.; Lentz, W. J.

224

Active probing of cloud multiple scattering, optical depth, vertical thickness, and liquid water content using wide-angle imaging lidar  

Microsoft Academic Search

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

Steven P. Love; Anthony B. Davis; Charles A. Rohde; Larry Tellier; Cheng Ho

2002-01-01

225

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

SciTech Connect

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 greater than that of liquid water from 10 to 13 ?m, whereas liquid water is more absorbing than ice from 16 to 25 ?m. MIXCRA retrievals are only valid for optically thin (?visible < 6) single-layer clouds when the precipitable water vapor is less than 1 cm. MIXCRA was applied to the Atmospheric Emitted Radiance Interferometer (AERI) data that were collected during the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment from November 1997 to May 1998, where 63% of all of the cloudy scenes above the SHEBA site met this specification. The retrieval determined that approximately 48% of these clouds were mixed phase and that a significant number of clouds (during all 7 months) contained liquid water, even for cloud temperatures as low as 240 K. The retrieved distributions of effective radii for water and ice particles in single-phase clouds are shown to be different than the effective radii in mixed-phase clouds.

Turner, David D.

2005-04-01

226

Lidar Investigation of Tropical Nocturnal Boundary Layer Aerosols and Cloud Macrophysics  

SciTech Connect

Observational evidence of two-way association between nocturnal boundary layer aerosols and cloud macrophysical properties under different meteorological conditions 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 version 2.2 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, PC S.; Taraphdar, Sourav

2013-10-01

227

Automated Extraction of 3D Trees from Mobile LiDAR Point Clouds  

NASA Astrophysics Data System (ADS)

This paper presents an automated algorithm for extracting 3D trees directly from 3D mobile light detection and ranging (LiDAR) data. To reduce both computational and spatial complexities, ground points are first filtered out from a raw 3D point cloud via blockbased elevation filtering. Off-ground points are then grouped into clusters representing individual objects through Euclidean distance clustering and voxel-based normalized cut segmentation. Finally, a model-driven method is proposed to achieve the extraction of 3D trees based on a pairwise 3D shape descriptor. The proposed algorithm is tested using a set of mobile LiDAR point clouds acquired by a RIEGL VMX-450 system. The results demonstrate the feasibility and effectiveness of the proposed algorithm.

Yu, Y.; Li, J.; Guan, H.; Zai, D.; Wang, C.

2014-06-01

228

Calibration of elastic scattering lidar at 1064-nm channel using the water-phase and cirrus clouds  

NASA Astrophysics Data System (ADS)

Lidar calibration is important for the elastic-scattering lidar at 1064-nm to quantify the aerosol backscatter profile. Because of the weak molecular scattering at 1064-nm, the conventional calibration approach normalizing the lidar return to molecular reference value has the large uncertainty at the wavelength 1064-nm. Alternatively, as the good natural targets, water cloud and cirrus cloud have been applied for lidar calibration, but the detailed comparisons of these cloud methods have not been done. In this study, we explored the calibration methods for 1064-nm channel with the water-phase and cirrus clouds based on an elastic-Raman lidar. Good consistency was illustrated by noting that the relative differences of their daily averages were smaller than 15%. Calibration constants taken using both methods showed the compatibility as evidenced by the stability (< 7 %) over a 2-month long period. We further applied the calibration result to obtain aerosol backscatter coefficient and column lidar ratio at 1064-nm by constraining lidar-integrated backscatter profile with sunphotometer-measured aerosol optical depth and showed that under prescribed conditions, this method had less uncertainty than the result based on Fernald processing.

Wu, Y.; Cordero, L.; Gan, C.; Gross, B.; Moshary, F.; Ahmed, S. A.

2010-12-01

229

High Spectral Resolution Lidar Measurements of Extinction and Particle Size in Clouds  

NASA Technical Reports Server (NTRS)

The University of Wisconsin High Spectral Resolution Lidar (HSRL) measures optical properties of the atmosphere by separating the Doppler broadened molecular backscatter return from the unbroadened aerosol return. In the past, the HSRL employed a 150 mm diameter Fabry-Perot etalon to separate the aerosol and molecular signals. The replacement of the etalon with an I2 absorption filter significantly improved the ability of the HSRL to separate weak molecular signals inside dense clouds.

Eloranta, E. W.; Piirronen, P.

1996-01-01

230

Airborne lidar observation of mountain-wave-induced polar stratospheric clouds during EASOE  

Microsoft Academic Search

The airborne backscatter lidar Leandre was flown during the EASOE campaign on board the French ARAT-Fokker 27, to provide mesoscale observations of scattering layers in the stratosphere. The use of crosspolarization channels at the 532 nm laser emitted wavelength, allowed discrimination between the quasi-spherical particles of the Pinatubo aerosol and the non-spherical frozen particles of polar stratospheric clouds. Measurements taken

S. Godin; G. Mgie; C. David; D. Haner; C. Flesia; Y. Emery

1994-01-01

231

Turnkey Raman lidar for profiling atmospheric water vapor, clouds, and aerosols  

Microsoft Academic Search

We describe an operational, self-contained, fully autonomous Raman lidar system that has been developed for unattended, around-the-clock atmospheric profiling of water vapor, aerosols, and clouds. During a 1996 three-week intensive observational period, the system operated during all periods of good weather (339 out of 504 h), including one continuous five-day period. The system is based on a dual-field-of-view design that

J. E. M. Goldsmith; Forest H. Blair; Scott E. Bisson; David D. Turner

1998-01-01

232

Extracting vertical winds from simulated clouds with ground-based coherent Doppler lidar.  

PubMed

The performance of mean velocity estimators is determined by computer simulations for solid-state coherent Doppler lidar measurements of wind fields at a cloud interface with deterministic profiles of velocity and aerosol backscatter. Performance of the velocity estimates is characterized by the standard deviation about the estimated mean and the bias referenced to the input velocity. A new class of estimators are required for cloud conditions, as traditional techniques result in biased estimates. We consider data with high signal energy that produces negligible random outliers. PMID:18301652

Lottman, B T; Frehlich, R G

1998-12-20

233

Macrophysical Properties of Tropical Cirrus Clouds from the CALIPSO Satellite and from Ground-based Micropulse and Raman Lidars  

SciTech Connect

Lidar observations of cirrus cloud macrophysical properties over the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) program Darwin, Australia site are compared from the Cloud-Aerosol Lidar and In- frared Pathfinder Satellite Observation (CALIPSO) satellite, the ground-based ARM micropulse lidar (MPL), and the ARM Raman lidar (RL). Comparisons are made using the subset of profiles where the lidar beam is not fully attenuated. Daytime measurements using the RL are shown to be relatively unaffected by the solar background and are therefore suited for checking the validity of diurnal cycles. RL and CALIPSO cloud fraction profiles show good agreement while the MPL detects significantly less cirrus, particularly during the daytime. Both MPL and CALIPSO observations show that cirrus clouds occur less frequently during the day than at night at all altitudes. In contrast, the RL diurnal cy- cle is significantly different than zero only below about 11 km; where it is the opposite sign (i.e. more clouds during the daytime). For cirrus geomet- rical thickness, the MPL and CALIPSO observations agree well and both datasets have signficantly thinner clouds during the daytime than the RL. From the examination of hourly MPL and RL cirrus cloud thickness and through the application 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 vast im- provement the RL provides (compared to the MPL) in the ARM program's ability to observe tropical cirrus clouds as well as a valuable ground-based lidar dataset for the validation of CALIPSO observations and to help im- prove our understanding of tropical cirrus clouds.

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

2013-08-27

234

Multiple Backscattering and Depolarization from Water Clouds for a Pulsed Lidar System  

Microsoft Academic Search

A computational approach for the multiple backscattering from spherical cloud droplets for a collimated pulsed radar system has been developed, based on the geometry of the system. The radiative transfer relationships include a complete set of Stokes' parameters. The depolarization ratio of the multiple backscattering from a volume of spherically symmetrical and uniformly distributed water drops is obtained.Calculations are performed

Kuo-Nan Liou; Richard M. Schotland

1971-01-01

235

CHAPTER 2: Analysis of cloud radar data 21 1000 1030 1100 1130 1200 1230 1300 1330  

E-print Network

the sensitivity of the radar is to subtract an estimate of the noise ?? N from the measured average power ? P of magnitude below the noise level. Of­ ten rain radars simply reject the data that fall below a particularCHAPTER 2: Analysis of cloud radar data 21 0 0.5 1 1.5 2 2.5 Height (km) Z 35 -40 -30 -20 -10 d

Hogan, Robin

236

Measurement of Correlation Functions and Power Spectra in Clouds Using the NRL WARLOC Radar  

Microsoft Academic Search

The Naval Research Laboratory W-band Advanced Radar for Low Observable Control (WARLOC) is a high-power 94-GHz radar, with 3-10-kW average and 80-kW peak power, now set up on the western shore of the Chesapeake Bay. It has three orders of magnitude more power and sensitivity than other W-band radar systems. This enables cloud reflectivity to be measured with high signal-to-noise

Arne W. Fliflet; Wallace M. Manheimer

2006-01-01

237

A Midlatitude Cirrus Cloud Climatology from the Facility for Atmospheric Remote Sensing. Part II: Microphysical Properties Derived from Lidar Depolarization  

Microsoft Academic Search

In Part II of this series of papers describing the results of the extended time observations of cirrus clouds from the University of Utah Facility for Atmospheric Remote Sensing (FARS), the information content of laser backscatter depolarization measurements in terms of cloud microphysical content is treated. The authors rely on scattering principles indicating that polarization lidar can be applied to

Kenneth Sassen; Sally Benson

2001-01-01

238

Nineteenth International Laser Radar Conference. Part 2  

NASA Technical Reports Server (NTRS)

This publication contains extended abstracts of papers presented at the Nineteenth International Laser Radar Conference, held at Annapolis, Maryland, July 6-10, 1998; 260 papers were presented in both oral and poster sessions. The topics of the conference sessions were Aerosol Clouds, Multiple Scattering; Tropospheric Profiling, Stratospheric/Mesospheric Profiling; Wind Profiling; New Lidar Technology and Techniques; Lidar Applications, Including Altimetry and Marine; Space and Future Lidar; and Lidar Commercialization/Eye Safety. This conference reflects the breadth of research activities being conducted in the lidar field. These abstracts address subjects from lidar-based atmospheric investigations, development of new lasers and lidar system technology, and current and future space-based lidar systems.

Singh, Upendra N. (Editor); Ismail, Syed (Editor); Schwemmer, Geary K. (Editor)

1998-01-01

239

Validation of Satellite-Based Objective Overshooting Cloud-Top Detection Methods Using CloudSat Cloud Profiling Radar Observations  

NASA Technical Reports Server (NTRS)

Two satellite infrared-based overshooting convective cloud-top (OT) detection methods have recently been described in the literature: 1) the 11-mm infrared window channel texture (IRW texture) method, which uses IRW channel brightness temperature (BT) spatial gradients and thresholds, and 2) the water vapor minus IRW BT difference (WV-IRW BTD). While both methods show good performance in published case study examples, it is important to quantitatively validate these methods relative to overshooting top events across the globe. Unfortunately, no overshooting top database currently exists that could be used in such study. This study examines National Aeronautics and Space Administration CloudSat Cloud Profiling Radar data to develop an OT detection validation database that is used to evaluate the IRW-texture and WV-IRW BTD OT detection methods. CloudSat data were manually examined over a 1.5-yr period to identify cases in which the cloud top penetrates above the tropopause height defined by a numerical weather prediction model and the surrounding cirrus anvil cloud top, producing 111 confirmed overshooting top events. When applied to Moderate Resolution Imaging Spectroradiometer (MODIS)-based Geostationary Operational Environmental Satellite-R Series (GOES-R) Advanced Baseline Imager proxy data, the IRW-texture (WV-IRW BTD) method offered a 76% (96%) probability of OT detection (POD) and 16% (81%) false-alarm ratio. Case study examples show that WV-IRW BTD.0 K identifies much of the deep convective cloud top, while the IRW-texture method focuses only on regions with a spatial scale near that of commonly observed OTs. The POD decreases by 20% when IRW-texture is applied to current geostationary imager data, highlighting the importance of imager spatial resolution for observing and detecting OT regions.

Bedka, Kristopher M.; Dworak, Richard; Brunner, Jason; Feltz, Wayne

2012-01-01

240

Assessing riparian shade for the Lemhi River, Idaho using LiDAR: A point cloud analysis  

NASA Astrophysics Data System (ADS)

Riparian vegetation plays a crucial role in shading streams by reducing the amount of incoming solar insolation that would otherwise reach the water surface, negatively affecting water temperature and photosynthetic organisms within the water column. Unlike incoming solar insolation, riparian shade can be manipulated by adding or removing riparian vegetation, making it attractive for restoration as well as thermal credit trading programs. Before riparian shade can be evaluated in such trading programs, the existing riparian vegetation needs to be quantified. Several studies have investigated the utility of LiDAR derived canopy height models for estimating riparian shade, however, few to no studies have used point cloud data as a direct model input in order to improve the riparian shade estimates. Using point cloud data increases spatial resolution and the ability to extract vegetation shape information without losses due to interpolation/rasterization. In this study, we assessed the ability of LiDAR point cloud data to estimate riparian shade for 32 km of the Lemhi River in north central Idaho. Riparian shade quantification of the point cloud and canopy height models are compared to shade values calculated using established models in practice.

Spaete, L.; Glenn, N. F.; Shrestha, R.; Shumar, M. L.; Mitchell, J.

2012-12-01

241

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

242

a Data Driven Method for Building Reconstruction from LiDAR Point Clouds  

NASA Astrophysics Data System (ADS)

Airborne laser scanning, commonly referred to as LiDAR, is a superior technology for three-dimensional data acquisition from Earth's surface with high speed and density. Building reconstruction is one of the main applications of LiDAR system which is considered in this study. For a 3D reconstruction of the buildings, the buildings points should be first separated from the other points such as; ground and vegetation. In this paper, a multi-agent strategy has been proposed for simultaneous extraction and segmentation of buildings from LiDAR point clouds. Height values, number of returned pulse, length of triangles, direction of normal vectors, and area are five criteria which have been utilized in this step. Next, the building edge points are detected using a new method named "Grid Erosion". A RANSAC based technique has been employed for edge line extraction. Regularization constraints are performed to achieve the final lines. Finally, by modelling of the roofs and walls, 3D building model is reconstructed. The results indicate that the proposed method could successfully extract the building from LiDAR data and generate the building models automatically. A qualitative and quantitative assessment of the proposed method is then provided.

Sajadian, M.; Arefi, H.

2014-10-01

243

Active probing of cloud multiple scattering, optical depth, vertical thickness, and liquid water content using wide-angle imaging lidar  

NASA Astrophysics Data System (ADS)

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-degree 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, and, from there, estimate the volume-averaged liquid water content. WAIL is notable in that it is applicable to optically thick clouds, a regime in which traditional lidar is reduced to ceilometry. Here we present recent WAIL data on various clouds and discuss the extension of WAIL to full diurnal monitoring by means of an ultra-narrow magneto-optic atomic line filter for daytime measurements.

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

2002-09-01

244

Active probing of cloud multiple scattering, optical depth, vertical thickness, and liquid water content 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-degree 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, and, from there, estimate the volume-averaged liquid water content. WAIL is notable in that it is applicable to optically thick clouds, a regime in which traditional lidar is reduced to ceilometry. Here we present recent WAIL data oti various clouds and discuss the extension of WAIL to full diurnal monitoring by means of an ultra-narrow magneto-optic atomic line filter for daytime measurements.

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

2002-01-01

245

Performance of mean-frequency estimators for Doppler radar and lidar  

NASA Technical Reports Server (NTRS)

The performance of mean-frequency estimators for Doppler radar and lidar measurements of winds is presented in terms of two basic parameters: Phi, the ratio of the average signal energy per estimate to the spectral noise level; and Omega, which is proportional to the number of independent samples per estimate. For fixed Phi and Omega, the Cramer-Rao bound (CRB) (theoretical best performance) for unbiased estimators of mean frequency (normalized by the spectral width of the signal), signal power, and spectral width are essentially independent of the number of data samples M. For large Phi, the estimators of mean frequency are unbiased and the performance is independent of M. The spectral domain estimators and covariance based estimators are bounded by the approximate period of M. The spectral domain estimators and covariance based estimators are bounded by the approximate periodogram CRB. The standard deviation of the maximum-likelihood estimator approaches the exact CRB, which can be more than a factor of 2 better than the performance of the spectral domain estimators or covariance-based estimators for typical Omega. For small Phi, the estimators are biased due to the effects of the uncorrelated noise (white noise), which results in uniformly distributed 'bad' estimates. The fraction of bad estimates is a function of Phi and M with weak dependence on the parameter Omega. Simple empirical models describe the standard deviation of the good estimates and the fraction of bad estimates. For Doppler lidar and for large Phi, better performance is obtained by using many low-energy pulses instead of one pulse with the same total energy. For small Phi, the converse is true.

Frehlich, R. G.; Yadlowsky, M. J.

1994-01-01

246

Southern Hemisphere Lidar Measurements of the Aerosol Clouds from Mt. Pinatubo and Mt. Hudson  

NASA Technical Reports Server (NTRS)

On 19 Jul., 1991, during tests to determine the ability of the newly-modified CSIRO Ns:YAG lidar to measure signals from the stratosphere before the arrival of dust from the eruption of Mt. Pinatubo, a strongly scattering layer was detected at an altitude of 2 km. That evening, the spectacular sunset and twilight were typical of volcanically disturbed conditions. Lidar measurements at 532 nm were made between 1400 and 1500 EST (0400-0500 UT) on 19 Jul. through broken cloud. Approximately 3800 laser firings were averaged in 256 shot blocks. These and subsequent data have been analyzed to produce profiles of aerosol volume backscatter function and scattering ratio. Clouds again prevented a clear view of the twilights on the next two nights, although there was some evidence for an enhanced glow. The evidence suggested that the aerosol layer had disappeared. An explanation for this disappearance and the earlier than expected arrival of the layer over Melbourne was required. Nimbus 7 TOMS data for 23 Jun. showed that the SO2 from the eruption had extended at least 11000 km to the west and that the southern boundary of the cloud had reached 15 degrees S just 8 days after the climactic eruption. It can be assumed that this cloud also contained dust and sulphuric acid aerosol. It was proposed that a section had then been broken away from the main cloud and carried south by a large scale eddy between the low latitude easterlies and the strong mid-latitude westerlies which finally carried the aerosol cloud over southern Australia. Accompanying 30 mb wind data showed a counter clockwise circulation, responsible for the transport, located in the South Atlantic Ocean.

Young, Stuart A.; Manson, Peter J.; Patterson, Graeme R.

1992-01-01

247

The Atmospheric Radiation Measurement Program Cloud Profiling Radars: Second-Generation Sampling Strategies, Processing, and Cloud Data Products  

SciTech Connect

The United States Department of Energy Atmospheric Radiation Measurement program operates millimeter-wavelength cloud radars in several climatologically distinct regions. The digital signal processors for these radars were recently upgraded and allow for enhancements in the operational parameters running on them. Recent evaluations of millimeter-wavelength cloud radar signal processing performance relative to the range of cloud dynamical and microphysical conditions encountered at the Atmospheric Radiation Measurement program sites have indicated that improvements are necessary, including significant improvement in temporal resolution (i.e., less than 1 s for dwell and 2 s for dwell and processing), wider Nyquist velocities, operational dealiasing of the recorded spectra, removal of pulse compression while sampling the boundary layer, and continuous recording of Doppler spectra. The new set of millimeter-wavelength cloud radar operational modes that incorporate these enhancements is presented. A significant change in radar sampling is the introduction of an uneven mode sequence with 50% of the sampling time dedicated to the lower atmosphere, allowing for detailed characterization of boundary layer clouds. The changes in the operational modes have a substantial impact on the post-processing algorithms that are used to extract cloud information from the radar data. New methods for post-processing of recorded Doppler spectra are presented that result in more accurate identification of radar clutter (e.g., insects) and extraction of turbulence and microphysical information. Results of recent studies on the error characteristics of derived Doppler moments are included so that uncertainty estimates are now included with the moments. A micro-scale data product based on the new temporal resolution of the millimeter-wavelength cloud radars is proposed that contains the number of local maxima in each Doppler spectrum, the Doppler moments of the primary peak, uncertainty estimates for the Doppler moments of the primary peak, Doppler moment shape parameters (e.g., skewness and kurtosis), and clear-air clutter flags. A macro-scale, or coarse temporal resolution, product is also proposed that includes summary statistics derived from the micro-scale product. These statistics characterize the microphysical and dynamical properties of clouds over time periods of 5 min and 60 min.

Kollias, Pavlos; Clothiaux, Eugene E.; Miller, Mark A.; Luke, Edward; Johnson, Karen L.; Moran, Kenneth P.; Widener, Kevin B.; Albrecht, Bruce A.

2007-07-01

248

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

PubMed

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. PMID:16161672

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

2005-09-10

249

Building a LiDAR point cloud simulator: Testing algorithms for high resolution topographic change  

NASA Astrophysics Data System (ADS)

Terrestrial laser technique (TLS) is becoming a common tool in Geosciences, with clear applications ranging from the generation of a high resolution 3D models to the monitoring of unstable slopes and the quantification of morphological changes. Nevertheless, like every measurement techniques, TLS still has some limitations that are not clearly understood and affect the accuracy of the dataset (point cloud). A challenge in LiDAR research is to understand the influence of instrumental parameters on measurement errors during LiDAR acquisition. Indeed, different critical parameters interact with the scans quality at different ranges: the existence of shadow areas, the spatial resolution (point density), and the diameter of the laser beam, the incidence angle and the single point accuracy. The objective of this study is to test the main limitations of different algorithms usually applied on point cloud data treatment, from alignment to monitoring. To this end, we built in MATLAB(c) environment a LiDAR point cloud simulator able to recreate the multiple sources of errors related to instrumental settings that we normally observe in real datasets. In a first step we characterized the error from single laser pulse by modelling the influence of range and incidence angle on single point data accuracy. In a second step, we simulated the scanning part of the system in order to analyze the shifting and angular error effects. Other parameters have been added to the point cloud simulator, such as point spacing, acquisition window, etc., in order to create point clouds of simple and/or complex geometries. We tested the influence of point density and vitiating point of view on the Iterative Closest Point (ICP) alignment and also in some deformation tracking algorithm with same point cloud geometry, in order to determine alignment and deformation detection threshold. We also generated a series of high resolution point clouds in order to model small changes on different environments (erosion, landslide monitoring, etc) and we then tested the use of filtering techniques using 3D moving windows along the space and time, which considerably reduces data scattering due to the benefits of data redundancy. In conclusion, the simulator allowed us to improve our different algorithms and to understand how instrumental error affects final results. And also, improve the methodology of scans acquisition to find the best compromise between point density, positioning and acquisition time with the best accuracy possible to characterize the topographic change.

Carrea, Dario; Abelln, Antonio; Derron, Marc-Henri; Jaboyedoff, Michel

2014-05-01

250

Lidar observations of polar mesospheric clouds at Rothera, Antarctica (67.5S, 68.0W)  

E-print Network

Lidar observations of polar mesospheric clouds at Rothera, Antarctica (67.5°°S, 68.0°°W) Xinzhao lidar at Rothera (67.5°S, 68.0°W), Antarctica in the austral summer of 2002­2003. The Rothera PMC at Rothera, Antarctica (67.5°S, 68.0°W), Geophys. Res. Lett., 31, L02114, doi:10.1029/ 2003GL018638. 1

Chu, Xinzhao

251

Global Lidar Measurements of Clouds and Aerosols from Space Using the Geoscience Laser Altimeter System (GLAS)  

NASA Technical Reports Server (NTRS)

The Geoscience Laser Altimeter System (GLAS) is scheduled for launch on the ICESat satellite as part of the NASA EOS mission in 2002. GLAS will be used to perform high resolution surface altimetry and will also provide a continuously operating atmospheric lidar to profile clouds, aerosols, and the planetary boundary layer with horizontal and vertical resolution of 175 and 76.8 m, respectively. GLAS is the first active satellite atmospheric profiler to provide global coverage. Data products include direct measurements of the heights of aerosol and cloud layers, and the optical depth of transmissive layers. In this poster we provide an overview of the GLAS atmospheric data products, present a simulated GLAS data set, and show results from the simulated data set using the GLAS data processing algorithm. Optical results from the ER-2 Cloud Physics Lidar (CPL), which uses many of the same processing algorithms as GLAS, show algorithm performance with real atmospheric conditions during the Southern African Regional Science Initiative (SAFARI 2000).

Hlavka, Dennis L.; Palm, S. P.; Welton, E. J.; Hart, W. D.; Spinhirne, J. D.; McGill, M.; Mahesh, A.; Starr, David OC. (Technical Monitor)

2001-01-01

252

The 94 GHz Cloud Radar System on a NASA ER-2 Aircraft  

NASA Technical Reports Server (NTRS)

The 94-GHz (W-band) Cloud Radar System (CRS) has been developed and flown on a NASA ER-2 high-altitude (20 km) aircraft. The CRS is a fully coherent, polarimeteric Doppler radar that is capable of detecting clouds and precipitation from the surface up to the aircraft altitude in the lower stratosphere. The radar is especially well suited for cirrus cloud studies because of its high sensitivity and fine spatial resolution. This paper describes the CRS motivation, instrument design, specifications, calibration, and preliminary data &om NASA s Cirrus Regional Study of Tropical Anvils and Cirrus Layers - Florida Area Cirrus Experiment (CRYSTAL-FACE) field campaign. The unique combination of CRS with other sensors on the ER-2 provides an unprecedented opportunity to study cloud radiative effects on the global energy budget. CRS observations are being used to improve our knowledge of atmospheric scattering and attenuation characteristics at 94 GHz, and to provide datasets for algorithm implementation and validation for the upcoming NASA CloudSat mission that will use a 94-GHz spaceborne cloud radar to provide the first direct global survey of the vertical structure of cloud systems.

Li, Lihua; Heymsfield, Gerald M.; Racette, Paul E.; Tian, Lin; Zenker, Ed

2003-01-01

253

CART Raman Lidar Aerosol and Water Vapor Measurements in the Vicinity of Clouds  

NASA Technical Reports Server (NTRS)

Aerosol and water vapor profiles acquired by the Raman lidar instrument located at the Climate Research Facility (CRF) at Southern Great Plains (SGP) provide data necessary to investigate the atmospheric variability in the vicinity of clouds near the top of the planetary boundary layer (PBL). Recent CARL upgrades and modifications to the routine processing algorithms afforded the necessarily high temporal and vertical data resolutions for these investigations. CARL measurements are used to investigate the behavior of aerosol backscattering and extinction and their correlation with water vapor and relative humidity.

Clayton, Marian B.; Ferrare, Richard A.; Turner, David; Newsom, Rob; Sivaraman, Chitra

2008-01-01

254

Cloud-Aerosol LIDAR and Infrared Pathfinder Satellite Observation (CALIPSO) Spacecraft: Independent Technical Assessment  

NASA Technical Reports Server (NTRS)

CALIPSO is a joint science mission between the CNES, LaRC and GSFC. It was selected as an Earth System Science Pathfinder satellite mission in December 1998 to address the role of clouds and aerosols in the Earth's radiation budget. The spacecraft includes a NASA light detecting and ranging (LIDAR) instrument, a NASA wide-field camera and a CNES imaging infrared radiometer. The scope of this effort was a review of the Proteus propulsion bus design and an assessment of the potential for personnel exposure to hydrazine propellant.

Gilbrech, Richard J.; McManamen, John P.; Wilson, Timmy R.; Robinson, Frank; Schoren, William R.

2004-01-01

255

ARM Millimeter Wave Cloud Radars (MMCRs) and the Active Remote Sensing of Clouds (ARSCL) Value Added Product (VAP).  

National Technical Information Service (NTIS)

The Millimeter Wave Cloud Radars (MMCRs) are designed as a remote sensing tool that can accurately detect almost all of the hydrometeors present in the atmosphere. To illustrate the difficulty of this task, the various types of hydrometeors that can occur...

E. E. Clothiaux, M. A. Miller, R. C. Perez, D. D. Turner, K. P. Moran

2001-01-01

256

Evaluation of gridded Scanning ARM Cloud Radar reflectivity observations and vertical Doppler velocity retrievals  

NASA Astrophysics Data System (ADS)

The Scanning ARM Cloud Radars (SACR's) provide continuous atmospheric observations aspiring to capture the 3-D cloud-scale structure. Sampling clouds in 3-D is challenging due to their temporal-spatial scales, the need to sample the sky at high elevations and cloud radar limitations. Thus, a common scan strategy is to repetitively slice the atmosphere from horizon to horizon as clouds advect over the radar (Cross-Wind Range Height Indicator - CWRHI). Here, the processing and gridding of the SACR CW-RHI scans are presented. First, the SACR sample observations from the ARM Oklahoma (SGP) and Cape-Cod (PVC) sites are post-processed (detection mask, velocity de-aliasing and gaseous attenuation correction). The resulting radial Doppler moment fields are then mapped to Cartesian coordinates with time as one of the dimension. The Cartesian-gridded Doppler velocity fields are next decomposed into the horizontal wind velocity contribution and the vertical Doppler velocity component. For validation purposes, all gridded and retrieved fields are compared to collocated zenith pointing ARM cloud radar measurements. We consider that the SACR sensitivity loss with range, the cloud type observed and the research purpose should be considered in determining the gridded domain size. Our results also demonstrate that the gridded SACR observations resolve the main features of low and high stratiform clouds. It is established that the CW-RHI observations complemented with processing techniques could lead to robust 3-D clouds dynamical representations up to 25-30 off zenith. The proposed gridded products are expected to advance our understanding of 3-D cloud morphology, dynamics, anisotropy and lead to more realistic 3-D radiative transfer calculations.

Lamer, K.; Tatarevic, A.; Jo, I.; Kollias, P.

2013-11-01

257

Introduction Mixed-phase clouds, such as those found in the Arctic  

E-print Network

) and NSA Millimeter Cloud Radar (MMCR) (left,top and bottom) show a cloud layer extending from ~600 m-1600 Amount: Total Sky Imager (Long) - Precipitation Rate: NSA 40m Tower Barrow Radiosonde Mea- surements from made using a combination of the AHSRL and NSA MMCR (see Lidar/Radar section, top). For these re

Eloranta, Edwin W.

258

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

259

A new method for building roof segmentation from airborne LiDAR point cloud data  

NASA Astrophysics Data System (ADS)

A new method based on the combination of two kinds of clustering algorithms for building roof segmentation from airborne LiDAR (light detection and ranging) point cloud data is proposed. The K-plane algorithm is introduced to classify the laser footprints that cannot be correctly classified by the traditional K-means algorithm. High-precision classification can be obtained by combining the two aforementioned clustering algorithms. Furthermore, to improve the performance of the new segmentation method, a new initialization method is proposed to acquire the number and coordinates of the initial cluster centers for the K-means algorithm. In the proposed initialization method, the geometrical planes of a building roof are estimated from the elevation image of the building roof by using the mathematical morphology and Hough transform techniques. By calculating the number and normal vectors of the estimated geometrical planes, the number and coordinates of the initial cluster centers for the K-means algorithm are obtained. With the aid of the proposed initialization and segmentation methods, the point cloud of the building roof can be rapidly and appropriately classified. The proposed methods are validated by using both simulated and real LiDAR data.

Kong, Deming; Xu, Lijun; Li, Xiaolu

2013-09-01

260

Off-beam (multiply-scattered) lidar returns from stratus. 1; Cloud-information content and sensitivity to noise  

NASA Technical Reports Server (NTRS)

We review the basic multiple scattering theory of off-beam lidar returns from optically thick clouds using the diffusion approximation. The shape of the temporal signal - the stretched pulse - depends primarily on the physical thickness of the cloud whereas its spatial counterpart - the diffuse spot - conveys specific information on the cloud's optical thickness, as do the absolute returns. This makes observation of the weak off-beam lidar returns an attractive prospect in remote sensing of cloud properties. By estimating the signal-to-noise ratio, we show that night-time measurements can be performed with existing technology. By the same criterion, day-time operation is a challenge that can only be met with a combination of cutting-edge techniques in filtering and in laser sources.

Davis, Anthony B.; Cahalan, Robert F.

1998-01-01

261

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

E-print Network

Radar Analysis of Precipitation Initiation in Maritime versus Continental Clouds near the Florida the evolution in X-band radar reflectivity, from the clouds' earliest detection through precipitation of analyzing radar data is developed and applied to determine whether the X-band radar reflectivity evolution

Rutledge, Steven

262

Development of a low-power high-sensitivity cloud profiling FM-CW radar at 95 GHz  

Microsoft Academic Search

We developed a low-power and high-sensitivity cloud profiling radar transmitting frequency-modulated continuous waves (FM-CW) at 95 GHz for ground-based observations. Millimeter waves at 95 GHz are used to realize high sensitivity to small cloud particles. An FM-CW type radar realizes similar sensitivity with much smaller output power than a pulse type radar. Two 1 m-diameter parabolic antennas, separated by 1.4

Toshiaki TAKANO; Ken-ichi AKITA; Hiroshi KUBO; Youhei KAWAMURA; Hiroshi KUMAGAI; Tamio TAKAMURA; Yuji NAKANISHI; Teruyuki NAKAJIMA

2004-01-01

263

Noctilucent cloud variability and mean parameters from 15 years of lidar observations at a mid-latitude site (54N, 12E)  

NASA Astrophysics Data System (ADS)

Noctilucent clouds (NLC) are an important tracer of temperature and dynamics of the summer mesopause region. Our site at Khlungsborn (Germany, 54N) is at the equatorward edge of the NLC region and therefore of special interest for the understanding of these clouds. 41 nights (63 h) of NLC are observed since 1997. They form the largest lidar data set from mid-latitudes. NLC are typically weak, with nearly 70% having a backscatter coefficient ?max,532nm < 2 ? 10-10 m-1 sr-1. The seasonal variation of NLC shows maximum occurrence around the temperature minimum (saturation maximum) but lower temperatures (higher saturation) at the beginning compared to the end of the season. Mean centroid altitude is 82.7 0.03 km, with strong NLC being typically lower and vertically thinner compared to weak clouds. NLC occurrence was lowest in the years 2000-2002 and reached a maximum in 2009 with a rate of 19%. Overall, NLC are less frequent and dimmer compared to higher latitudes. The occurrence is highly anti-correlated with solar activity. Beside NLC, we are measuring mesospheric temperatures since 2002 by lidars, complemented by microwave observations of water vapor (since October 2009) and radar observations of mesospheric winds. NLC occurrence is found anti-correlated with ambient temperatures (r = -0.85 at 84 km), while low temperatures are necessary but not sufficient for individual events. Meridional winds at 84 km are weakly anti-correlated with NLC occurrence (r = -0.58 at 84 km). Furthermore, we find some biennial variation of NLC occurrence in part of the time series. Any additional trend has not yet been detected.

Gerding, M.; HFfner, J.; Hoffmann, P.; Kopp, M.; Lbken, F.-J.

2013-01-01

264

Measurements of Backscatter Phase Function and Depolarization in Cirrus Clouds made with the University of Wisconsin High Spectral Resolution Lidar.  

E-print Network

for climate modeling. The University of Wisconsin High Spectral Resolu- tion Lidar (HSRL) measures optical depth, backscat- ter cross section and depolarization. The HSRL sep- arates the molecular backscatter of backscat- ter phase function and depolarization in cirrus clouds. 2 Observations During 1994, the HSRL

Eloranta, Edwin W.

265

LIDAR POINT CLOUD BASED FULLY AUTOMATIC 3D SINGL TREE MODELLING IN FOREST AND EVALUATIONS OF THE PROCEDURE  

Microsoft Academic Search

A whole procedure of fully automatic 3D single tree modelling based on LIDAR point cloud is introduced in the paper. The evaluation of the procedure is then delivered by verifying the modelling results with field collecting data in sample plots. With the procedure, individual trees are extracted not only from the top canopy layer but also from the sub canopy

Yunsheng Wang; Holger Weinacker; Barbara Koch

266

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

267

Constraining CloudSat-based snowfall profiles using surface observations and C-band ground radar  

NASA Astrophysics Data System (ADS)

The CloudSat Precipitation Radar, launched in 2006, provides vertical profiles of W-band (94 GHz) reflectivity and is sensitive to falling snow through all but the most intense precipitating cloud structures. Precipitation retrievals of falling snow are affected by a wide diversity of factors describing the medium, such as snow particle shape, size, and composition, which in turn are controlled by ambient factors including the environmental temperature and humidity. Because satellite-based radiometric sounders such as the Microwave Humidity Sounder (MHS) operate without the benefit of coordinated space radar observations, microphysical descriptions of the snow particle medium derived from CloudSat or other radar observations are beneficial to passive microwave (PMW) radiometer-only snowfall retrieval methods. At the coarse scale of these PMW observations, the radiative signal due to the snow is relatively weak compared to the contributions from the atmosphere and the land surface emissivity. Using the C-band (5 GHz) polarization-agile King City radar (WKR) operated by Environment Canada, we examined the vertical structure of winter precipitation events from coordinated overpasses of CloudSat and NOAA 18 (MHS). Two-dimensional video disdrometer observations are used to limit (constrain) the range of the drop-size distribution parameters that are provided through a priori databases to dual-frequency (C/W-band) radar retrieval. Bayesian retrievals using the constrained database produce water content profiles that more closely replicate the observed radar reflectivity profiles and transition smoothly between the single-frequency (CloudSat only) and dual-frequency regions.

Turk, F. Joseph; Park, Kyung-Won; Haddad, Ziad S.; Rodriguez, Peter; Hudak, David R.

2011-12-01

268

Extinction coefficients from lidar observations in ice clouds compared to in-situ measurements from the Cloud Integrating Nephelometer during CRYSTAL-FACE  

NASA Technical Reports Server (NTRS)

This paper presents a comparison of volume extinction coefficients in tropical ice clouds retrieved from two instruments : the 532-nm Cloud Physics Lidar (CPL), and the in-situ probe Cloud Integrating Nephelometer (CIN). Both instruments were mounted on airborne platforms during the CRYSTAL-FACE campaign and took measurements in ice clouds up to 17km. Coincident observations from three cloud cases are compared : one synoptically-generated cirrus cloud of low optical depth, and two ice clouds located on top of convective systems. Emphasis is put on the vertical variability of the extinction coefficient. Results show small differences on small spatial scales (approx. 100m) in retrievals from both instruments. Lidar retrievals also show higher extinction coefficients in the synoptic cirrus case, while the opposite tendency is observed in convective cloud systems. These differences are generally variations around the average profile given by the CPL though, and general trends on larger spatial scales are usually well reproduced. A good agreement exists between the two instruments, with an average difference of less than 16% on optical depth retrievals.

Noel, Vincent; Winker, D. M.; Garrett, T. J.; McGill, M.

2005-01-01

269

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

270

Vertical Mass Flux Calculations in Hawaiian Trade Cumulus Clouds from Dual-Doppler Radar.  

NASA Astrophysics Data System (ADS)

Two ground-based Doppler radars and an instrumented aircraft provided a means for computing the vertical mass flux in trade wind cumulus clouds that formed east of the island of Hawaii dining the Hawaiian Rainband Project of 1990. This study compares the mass fluxes of small isolated cells with larger groups of clouds and rainbands. Because of excellent sensitivity, the 5.5-cm wavelength radars were capable of detecting Bragg backscatter, which extended the measurements to include some precipitation-free air within and surrounding the clouds.The shape of the vertical profile of vertical mass flux within shallow cumulus clouds and cloud groups varied considerably over the cloud's life cycle but was comparatively independent of cloud size. The early stages of convection displayed a mass flux profile that resembled those produced by buoyancy sorting and entraining plume models, but the mature and later stages were considerably more affected by precipitation-driven down-drafts and included mean downward mass fluxes. The vertical mass flux profiles predicted by a three-dimensional LES model of an isolated cumulus cloud showed the same evolutionary phases as the observations.

Grinnell, Scott A.; Bretherton, Christopher S.; Fraser, Alistair M.; Stevens, David E.

1996-07-01

271

Measurements of the Vertical Structure of Aerosols and Clouds Over the Ocean Using Micro-Pulse LIDAR Systems  

NASA Technical Reports Server (NTRS)

The determination of the vertical distribution of aerosols and clouds over the ocean is needed for accurate retrievals of ocean color from satellites observations. The presence of absorbing aerosol layers, especially at altitudes above the boundary layer, has been shown to influence the calculation of ocean color. Also, satellite data must be correctly screened for the presence of clouds, particularly cirrus, in order to measure ocean color. One instrument capable of providing this information is a lidar, which uses pulses of laser light to profile the vertical distribution of aerosol and cloud layers in the atmosphere. However, lidar systems prior to the 1990s were large, expensive, and not eye-safe which made them unsuitable for cruise deployments. During the 1990s the first small, autonomous, and eye-safe lidar system became available: the micro-pulse lidar, or MPL. The MPL is a compact and eye-safe lidar system capable of determining the range of aerosols and clouds by firing a short pulse of laser light (523 nm) and measuring the time-of-flight from pulse transmission to reception of a returned signal. The returned signal is a function of time, converted into range using the speed of light, and is proportional to the amount of light backscattered by atmospheric molecules (Rayleigh scattering), aerosols, and clouds. The MPL achieves ANSI eye-safe standards by sending laser pulses at low energy (micro-J) and expanding the beam to 20.32 cm in diameter. A fast pulse-repetition-frequency (2500 Hz) is used to achieve a good signal-to-noise, despite the low output energy. The MPL has a small field-of-view (< 100 micro-rad) and signals received with the instrument do not contain multiple scattering effects. The MPL has been used successfully at a number of long-term sites and also in several field experiments around the world.

Welton, Ellsworth J.; Spinhirne, James D.; Campbell, James R.; Berkoff, Timothy A.; Bates, David; Starr, David OC. (Technical Monitor)

2001-01-01

272

Global Observations of Aerosols and Clouds from Combined Lidar and Passive Instruments to Improve Radiation Budget and Climate Studies  

NASA Technical Reports Server (NTRS)

Current uncertainties in the effects of clouds and aerosols on the Earth radiation budget limit our understanding of the climate system and the potential for global climate change. Pathfinder Instruments for Cloud and Aerosol Spaceborne Observations - Climatologie Etendue des Nuages et des Aerosols (PICASSO-CENA) is a recently approved satellite mission within NASA's Earth System Science Pathfinder (ESSP) program which will address these uncertainties with a unique suite of active and passive instruments. The Lidar In-space Technology Experiment (LITE) demonstrated the potential benefits of space lidar for studies of clouds and aerosols. PICASSO-CENA builds on this experience with a payload consisting of a two-wavelength polarization-sensitive lidar, an oxygen A-band spectrometer (ABS), an imaging infrared radiometer (IIR), and a wide field camera (WFC). Data from these instruments will be used to measure the vertical distributions of aerosols and clouds in the atmosphere, as well as optical and physical properties of aerosols and clouds which influence the Earth radiation budget. PICASSO-CENA will be flown in formation with the PM satellite of the NASA Earth Observing System (EOS) to provide a comprehensive suite of coincident measurements of atmospheric state, aerosol and cloud optical properties, and radiative fluxes. The mission will address critical uncertainties iin the direct radiative forcing of aerosols and clouds as well as aerosol influences on cloud radiative properties and cloud-climate radiation feedbacks. PICASSO-CENA is planned for a three year mission, with a launch in early 2003. PICASSO-CENA is being developed within the framework of a collaboration between NASA and CNES.

Winker, David M.

1999-01-01

273

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

Microsoft Academic Search

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

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

1994-01-01

274

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

NASA Technical Reports Server (NTRS)

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.

1985-01-01

275

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

Microsoft Academic Search

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

Steven P. Love; A. B. Davis; C. A. Rohde; Cheng Ho

2001-01-01

276

Design and development of micro pulse lidar for cloud and aerosol studies  

NASA Astrophysics Data System (ADS)

A micro pulse lidar (MPL) has been indigenously designed and developed at the National Physical Laboratory, New Delhi using a 532 nm, 500 pico second pulsed laser having average power of 50mW (at 7.5 KHz PRR). Photon counting technique has been incorporated using the conventional optics, multichannel scaler (Stanford Research Systems SR430) and high sensitive photomultiplier tube. The sensitivity, range and bin etc are computer controlled in the present system. The interfacing between MPL and computer has been achieved by serial (RS232) and parallel printer port. The necessary software and graphical user interface has been developed using visual basic. In addition to this the telescope cover status sensing circuit has been incorporated to avoid conflict between dark count and background acquisition. The micro pulse lidar will be used for the aerosol, boundary layer and the cloud studies at a bin resolution of 6 meters. In the present communication the details of the system and preliminary results will be presented.

Dubey, P. K.; Arya, B. C.; Ahammed, Y. Nazeer; Kumar, Arun; Kulkarni, P. S.; Jain, S. L.

2008-12-01

277

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 Khlungsborn, 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 Khlungsborn 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; Hffner, Josef; Kopp, Maren; Zecha, Marius; Lbken, Franz-Josef

278

Sensitivity of S- and Ka-band matched dual-wavelength radar system for detecting nonprecipitating cloud  

NASA Astrophysics Data System (ADS)

Remote detection of cloud phase in either liquid, ice or mixed form a key microphysical observation. Evolution of a cloud system and associated radiative properties depend on microphysical characteristics. Polarization radars rely on the shape of the particle to delineate the regions of liquid and ice. For specified transmitter and receiver characteristics, it is easier to detect a high concentrations of larger atmospheric particles than a low concentration of small particles. However, the radar cross-section of a given hydrometeor increases as the transmit frequency of the radar increases. Thus, in spite of a low transmit power, the sensitivity of a millimeter-wave radar might be better than high powered centimeter-wave radars. Also, ground clutter echoes and receiver system noise powers are sensitive functions of radar transmit frequency. For example, ground clutter in centimeter-wave radar sample volumes might mask non-precipitating or lightly precipitating clouds. An optimal clutter filter or signal processing technique can be used to suppress clutter masking its effects and/or enhanced weak cloud echoes that have significantly different Doppler characteristics than stationary ground targets. In practice, it is imperative to investigate the actual performance of S and Ka-band radar systems to detect small-scale, weak cloud reflectivity. This paper describes radar characteristics and the sensitivity of the new system in non-precipitating conditions. Recently, a dual-wavelength S and Ka-band radar system with matched resolution volume and sensitivity was built to remotely detect supercooled liquid droplets. The detection of liquid water content was based on the fact that the shorter of the two wavelengths is more strongly attenuated by liquid water. The radar system was deployed during the Winter Icing Storms Project 2004 (WISP04) near Boulder, Colorado to detect and estimate liquid water content. Observations by dual-wavelength radar were collected in both non-precipitating and lightly precipitating clouds.

Vivekanandan, J.; Politovich, Marcia; Rilling, Robert; Ellis, Scott; Pratte, Frank

2004-12-01

279

Observations of noctilucent clouds and temperature structure from 1 - 105 km by co-located lidars at 54N  

NASA Astrophysics Data System (ADS)

At the mid-latitude location of Kuehlungsborn (54N, 12E) a resonance lidar and a Rayleigh-Mie-Raman (RMR) lidar are operated to observe e.g. the occurrence and particle properties of Noctilucent Clouds (NLC) and to measure continuous temperature profiles from the troposphere to the lower thermosphere. For the temperature profiles the two lidars (RMR lidar and potassium lidar) and three different measurement methods (rotational Raman, Rayleigh/vib. Raman, Doppler resonance) are combined. The profiles are obtained continuously between 1 and 105 km with a temporal and vertical resolution of at least 15 min and 1 km, respectively. Temperature fluctuations due to gravity waves and tides with amplitudes of up to +/-20 K are observed. In summer during the cold phases of waves the temperature above 80 km drops occasionally below the frostpoint temperature. However, the mean temperature below 83 km is a few Kelvin above the frost point and only for about two weeks in summer the air becomes continuously supersaturated between 85 and 90 km. Therefore, the existence of NLC ice particles above our site is only allowed in the cold phases of waves. We will present lidar-observations of NLC and temperatures below and above the NLC layer showing the coupling of the NLC to supersaturated air in the mesopause region.

Gerding, M.; Hffner, J.; Rauthe, M.; Lbken, F. J.

2006-09-01

280

Synergetic use of millimeter and centimeter wavelength radars for retrievals of cloud and rainfall parameters  

NASA Astrophysics Data System (ADS)

A remote sensing approach for simultaneous retrievals of cloud and rainfall parameters in the vertical column above the US Department of Energy's (DOE) Climate Research Facility at the Tropical Western Pacific (TWP) Darwin site in Australia is described. This approach uses vertically pointing measurements from a DOE Ka-band radar and scanning measurements from a nearby C-band radar pointing toward the TWP Darwin site. Rainfall retrieval constraints are provided by data from a surface impact disdrometer. The approach is applicable to stratiform precipitating cloud systems when a separation between the liquid hydrometeor layer, which contains rainfall and liquid water clouds, and the ice hydrometeor layer is provided by the radar bright band. Absolute C-band reflectivities and Ka-band vertical reflectivity gradients in the liquid layer are used for retrievals of the mean layer rain rate and cloud liquid water path (CLWP). C-band radar reflectivities are also used to estimate ice water path (IWP) in regions above the melting layer. The retrieval uncertainties of CLWP and IWP for typical stratiform precipitation systems are about 500-800 g m-2 (for CLWP) and a factor of 2 (for IWP). The CLWP retrieval uncertainties increase with rain rate, so retrievals for higher rain rates may be impractical. The expected uncertainties of layer mean rain rate retrievals are around 20%, which, in part, is due to constraints available from the disdrometer data. The applicability of the suggested approach is illustrated for two characteristic events observed at the TWP Darwin site during the wet season of 2007. A future deployment of W-band radars at the DOE tropical Climate Research Facilities can improve CLWP estimate accuracies and provide retrievals for a wider range of stratiform precipitating cloud events.

Matrosov, S. Y.

2010-01-01

281

Synergetic use of millimeter- and centimeter-wavelength radars for retrievals of cloud and rainfall parameters  

NASA Astrophysics Data System (ADS)

A remote sensing approach for simultaneous retrievals of cloud and rainfall parameters in the vertical column above the US Department of Energy's (DOE) Climate Research Facility at the Tropical Western Pacific (TWP) Darwin site in Australia is described. This approach uses vertically pointing measurements from a DOE Ka-band radar and scanning measurements from a nearby C-band radar pointing toward the TWP Darwin site. Rainfall retrieval constraints are provided by data from a surface impact disdrometer. The approach is applicable to stratiform precipitating cloud systems when a separation between the liquid hydrometeor layer, which contains rainfall and liquid water clouds, and the ice hydrometeor layer is provided by the radar bright band. Absolute C-band reflectivities and Ka-band vertical reflectivity gradients in the liquid layer are used for retrievals of the mean layer rain rate and cloud liquid water path (CLWP). C-band radar reflectivities are also used to estimate ice water path (IWP) in regions above the melting layer. The retrieval uncertainties of CLWP and IWP for typical stratiform precipitation systems are about 500-800 g m-2 (for CLWP) and a factor of 2 (for IWP). The CLWP retrieval uncertainties increase with rain rate, so retrievals for higher rain rates may be impractical. The expected uncertainties of layer mean rain rate retrievals are around 20%, which, in part, is due to constraints available from the disdrometer data. The applicability of the suggested approach is illustrated for two characteristic events observed at the TWP Darwin site during the wet season of 2007. A future deployment of W-band radars at the DOE tropical Climate Research Facilities can improve CLWP estimation accuracies and provide retrievals for a wider range of stratiform precipitating cloud events.

Matrosov, S. Y.

2010-04-01

282

Analysis and Calibration of CRF Raman Lidar Cloud Liquid Water Measurements  

SciTech Connect

The Atmospheric Radiation Measurement (ARM) Raman lidar (RL), located at the Southern Great Plains (SGP) Climate Research Facility (CRF), is a unique state-of-the-art active remote sensor that is able to measure profiles of water vapor, aerosol, and cloud properties at high temporal and vertical resolution throughout the diurnal cycle. In October 2005, the capability of the RL was extended by the addition of a new detection channel that is sensitive to the Raman scattering of liquid water. This new channel permits the system, in theory, to measure profiles of liquid water content (LWC) by the RL. To our knowledge, the ARM RL is the only operation lidar with this capability. The liquid water Raman backscattering cross-section is a relatively weak and spectrally broad feature, relative to the water vapor Raman backscatter signal. The wide bandpass required to achieve reasonable signal-to-noise in the liquid water channel essentially eliminates the ability to measure LWC profiles during the daytime in the presence of large solar background, and thus all LWC observations are nighttime only. Additionally, the wide bandpass increases the probability that other undesirable signals, such as fluorescence from aerosols, may contaminate the observation. The liquid water Raman cross-section has a small amount of overlap with the water vapor Raman cross-section, and thus there will be a small amount of cross-talk between the two signals, with water vapor contributing a small amount of signal to the LWC observation. And finally, there is significant uncertainty in the actual strength of the liquid water Raman cross-section in the literature. The calibrated LWC profiles, together with the coincident cloud backscatter observations also made by the RL, can be used to derive profiles of cloud droplet effective radius. By combining these profiles of effective radius in the lower portion of the cloud with the aerosol extinction measurements made below the cloud by the RL, the first aerosol indirect effect can be investigated using a single instrument, thereby reducing the uncertainty associated with aligning the different sampling periods and fields of view of multiple instruments. We have applied a first principles calibration to the LWC profiles. This approach requires that the relative differences in optical efficiency between the water vapor and liquid water channels be known; this relative difference is easily computed using the efficiency values of the beam splitters and interference filters in the lidar that were provided by the vendors of these components. The first principles approach then transfers the calibration from the water vapor mixing ratio to the LWC using the difference in the optical efficiency and an interpolated value of the liquid water Raman cross section from the literature, and the better established water vapor Raman cross section. After accounting for all known error sources, the vertical integral of LWC was compared against a similar value retrieved from a co-located ground-based infrared radiometer. The RL and infrared radiometer have significantly different fields of view; thus to compare the two sensors the data were averaged to 5 min intervals where only cloudy samples were included in the average of each. While there is fair scatter in the data (r=0.47), there is also a clear indication of a positive correlation between the infrared and the RL values. The value of the slope of the regression is 0.49, which indicates a tendency of the RL measurements to underestimate the total liquid amount with respect to the infrared retrieval. Research continues to investigate the source of the bias, but the most likely candidate is the large uncertainty in the liquid water Raman cross-section as there have been no direct measurements made of this parameter at the lidars laser wavelength of 355 nm. The calibrated LWC profile was then used together with the cloud backscatter coefficient profile from the RL to derive profiles of cloud droplet effective radius and cloud droplet number density. These profiles o

Turner, D.D.

2007-10-31

283

The role of spaceborne millimeter-wave radar in the global monitoring of ice cloud  

SciTech Connect

The potential of spaceborne 94-GHz radar for measuring global vertical distribution and water content of ice clouds is assessed. Longwave (LW) fluxes for model ice clouds are calculated and used to determine minimum cloud optical depths that will change outgoing longwave radiation or flux divergence within a cloud layer greater than 10 W m{sup -2}, and in surface downward LW flux greater than 5 W m{sup -2}, compared to clear-sky value. Optical depth values are used to define radiatively significant clouds. Thresholds of radiative significance are calculated for radiation parameters and for tropical and midlatitude cirrus clouds. Observational data of ice crystal size spectra from midlatitude and tropical cirrus are used to assess radar capability to meet measurement requirements. A radar threshold of -30 dBZ should detect 99% (92%) of radiatively significant clouds in the midlatitudes. Detection efficiency may be reduced significantly for tropical clouds at very low temperatures (-80 C). LW flux calculations also establish the optical depth accuracy required to estimate LW fluxes or flux divergence. Accuracy requirements are also given in terms of ice water content (IWC) for validating cloud parameterization in general circulation models (GCMs). IWC estimates are derived using radar and additional information to define mean crystal size. IWC for samples with a horizontal scale of 1-2 km has a bias of less than 8%. For IWC larger than 0.01 g m{sup -3}, random error is from +50 to -35%; for 0.001 g m{sup -3}, random error is between +80 and -45%. This is also the best achievable accuracy for cloud optical depth estimates and meets requirements derived from LW flux calculations. Without independent particle size information, random error is from +85 to -55% for IWC greater than 0.01 g m{sup -3} and estimated bias is less than {plus_minus}15%. This accuracy is sufficient to provide useful constraints on GCM cloud parameterization schemes. 34 refs., 15 figs., 6 tabs.

Brown, P.R.A.; Illingworth, A.J. [Univ. of Reading, Reading (United Kingdom)] [Univ. of Reading, Reading (United Kingdom); Heymsfield, A.J. [National Center for Atmospheric Research, Boulder, CO (United States)] [National Center for Atmospheric Research, Boulder, CO (United States)

1995-11-01

284

Macrophysical and optical properties of midlatitude cirrus clouds from four ground-based lidars and collocated CALIOP observations  

SciTech Connect

Ground-based lidar and CALIOP datasets gathered over four mid-latitude sites, two US and two French sites, are used to evaluate the consistency of cloud macrophysical and optical property climatologies that can be derived by such datasets. The consistency in average cloud height (both base and top height) between the CALIOP and ground datasets ranges from -0.4km to +0.5km. The cloud geometrical thickness distributions vary significantly between the different datasets, due in part to the original vertical resolutions of the lidar profiles. Average cloud geometrical thicknesses vary from 1.2 to 1.9km, i.e. by more than 50%. Cloud optical thickness distributions in subvisible, semi-transparent and moderate intervals differ by more than 50% between ground and space-based datasets. The cirrus clouds with 2 optical thickness below 0.1 (not included in historical cloud climatologies) represent 30-50% of the non-opaque cirrus class. The differences in average cloud base altitude between ground and CALIOP datasets of 0.0-0.1 km, 0.0-0.2 km and 0.0-0.2 km can be attributed to irregular sampling of seasonal variations in the ground-based data, to day-night differences in detection capabilities by CALIOP, and to the restriction to situations without low-level clouds in ground-based data, respectively. The cloud geometrical thicknesses are not affected by irregular sampling of seasonal variations in the ground-based data, while up to 0.0-0.2 km and 0.1-0.3 km differences can be attributed to day-night differences in detection capabilities by CALIOP, and to the restriction to situations without lowlevel clouds in ground-based data, respectively.

Dupont, Jean-Charles; Haeffelin, M.; Morille, Y.; Noel, V.; Keckhut, P.; Winker, D.; Comstock, Jennifer M.; Chervet, P.; Roblin, A.

2010-05-27

285

Evaluation of the performance of the WRF model to reproduce the cloud cover and clouds features over the Mediterranean area using the CALIPSO lidar observations  

NASA Astrophysics Data System (ADS)

It is widely accepted that clouds play a major role on weather and climate forecast. However, the representation of clouds in models is largely uncertain due (i) to the number of processes and interactions involved in the formation and persistence of a cloud and (ii) the difficulty in obtaining accurate observations of clouds at all altitudes and locations. The evaluation of mesoscale models using recently developed parameterizations in different areas is therefore an essential step towards the improvement of clouds representation in models. The Aqua-Train offers an unprecedented set of observations for the microphysical properties of clouds that is very useful for validation of clouds features in models, especially over the sea where ground based instrumentation can not furnish observations. To avoid any inversion of the observed lidar signal that could induce errors responsible for discrepancies between observations and model, we use a model-to-satellite approach (Chepfer et al., 2008) to diagnose the lidar signal directly from model outputs. We then compare the observed space borne lidar profiles with the simulated ones. In this paper, we choose to evaluate the Thompson et al. (2004, 2008) microphysics scheme within the WRF model over the Mediterranean area. The occurrence of severe weather phenomenons, as well as the probable role of Mediterranean sea on climate change make the understanding and the representation of processes in this area a challenge for the future. A statistical study is carried out over several full months of observations. The first stage of the analysis focuses on the cloud occurrence discrepancy between observations and model for the three classes of clouds (low-level, middle and high clouds). In particular the analysis aims to evaluate how much the absence of aerosols in the simulations may be a cause of discrepancies in this area. Chepfer H., S. Bony, D. Winker, M. Chiriaco, J-L. Dufresne, G. Sze, 2008: Use of CALIPSO lidar observations to evaluate the cloudiness simulated by a climate model. Geophys. Res. Let., 35, L15704, doi:10.1029/2008GL034207. Thompson G., R. M. Rasmussen, K. Manning, 2004: Explicit forecasts of winter precipitations using an improved bulk microphysics scheme. Part I: description and sensitivity analysis. Mon. Wea. Rev., 132, 519-542. Thompson G., P. Field, R. M. Rasmussen, W. D. Hall, 2008: Explicit forecasts of winter precipitations using an improved bulk microphysics scheme. Part II: Implementation of a new snow parameterization. Mon. Wea. Rev., 136, 5095-5115.

Bastin, S.; Chepfer, H.; Chiriaco, M.; Cesana, G.

2009-12-01

286

Comparison of convective clouds observed by spaceborne W-band radar and simulated by cloud-resolving atmospheric models  

NASA Astrophysics Data System (ADS)

Deep convective clouds (DCCs) play an important role in regulating global climate through vertical mass flux, vertical water transport, and radiation. For general circulation models (GCMs) to simulate the global climate realistically, they must simulate DCCs realistically. GCMs have traditionally used cumulus parameterizations (CPs). Much recent research has shown that multiple persistent unrealistic behaviors in GCMs are related to limitations of CPs. Two alternatives to CPs exist: the global cloud-resolving model (GCRM), and the multiscale modeling framework (MMF). Both can directly simulate the coarser features of DCCs because of their multi-kilometer horizontal resolutions, and can simulate large-scale meteorological processes more realistically than GCMs. However, the question of realistic behavior of simulated DCCs remains. How closely do simulated DCCs resemble observed DCCs? In this study I examine the behavior of DCCs in the Nonhydrostatic Icosahedral Atmospheric Model (NICAM) and Superparameterized Community Atmospheric Model (SP-CAM), the latter with both single-moment and double-moment microphysics. I place particular emphasis on the relationship between cloud vertical structure and convective environment. I also emphasize the transition between shallow clouds and mature DCCs. The spatial domains used are the tropical oceans and the contiguous United States (CONUS), the latter of which produces frequent vigorous convection during the summer. CloudSat is used to observe DCCs, and A-Train and reanalysis data are used to represent the large-scale environment in which the clouds form. The CloudSat cloud mask and radar reflectivity profiles for CONUS cumuliform clouds (defined as clouds with a base within the planetary boundary layer) during boreal summer are first averaged and compared. Both NICAM and SP-CAM greatly underestimate the vertical growth of cumuliform clouds. Then they are sorted by three large-scale environmental variables: total preciptable water (TPW), surface air temperature (SAT), and 500hPa vertical velocity (W500), representing the dynamical and thermodynamical environment in which the clouds form. The sorted CloudSat profiles are then compared with NICAM and SP-CAM profiles simulated with the Quickbeam CloudSat simulator. Both models have considerable difficulty representing the relationship of SAT and clouds over CONUS. For TPW and W500, shallow clouds transition to DCCs at higher values than observed. This may be an indication of the models' inability to represent the formation of DCCs in marginal convective environments. NICAM develops tall DCCs in highly favorable environments, but SP-CAM appears to be incapable of developing tall DCCs in almost any environment. The use of double moment microphysics in SP-CAM improves the frequency of deep clouds and their relationship with TPW, but not SAT. Both models underpredict radar reflectivity in the upper cloud of mature DCCs. SP-CAM with single moment microphysics has a particularly unrealistic DCC reflectivity profile, but with double moment microphysics it improves substantially. SP-CAM with double-moment microphysics unexpectedly appears to weaken DCC updraft strength as TPW increases, but otherwise both NICAM and SP-CAM represent the environment-versus-DCC relationships fairly realistically.

Dodson, Jason B.

287

Investigating particle orientation in cirrus clouds by measuring backscattering phase matrices with lidar.  

PubMed

The relation between the orientation of particles in ice-crystal clouds and backscattering phase matrices (BSPMs) is considered. Parameters characterizing the predominant orientation of particles in the azimuthal direction and in the horizontal position are presented. The parameters are expressed through BSPM elements. A technique for measuring BSPM elements with lidar is described. Examples of some measurements are presented along with a statistical generalization of the results from more than 400 BSPM measurements. It is found that the orientation of coarse particles with large diameters in an azimuthal direction and in a horizontal position is more probable than in a random direction. However, the orientation of large particles is often masked by small particles that are not subject to the effect of orienting factors. Thus the mean parameters characterizing the state of orientation of particles in clouds as a whole correspond to weak orientation. It is supposed that the orientation of particles in the azimuthal direction is caused by wind-velocity pulsations. PMID:15646781

Kaul, Bruno V; Samokhvalov, Ignatii V; Volkov, Sergei N

2004-12-20

288

Can we estimate precipitation rate during snowfall using a scanning terrestrial LiDAR?  

NASA Astrophysics Data System (ADS)

Accurate snowfall measurements in windy areas have proven difficult. To examine a new approach, we have installed an automatic scanning terrestrial LiDAR at Mammoth Mountain, CA. With this LiDAR, we have demonstrated effective snow depth mapping over a small study area of several hundred m2. The LiDAR also produces dense point clouds by detecting falling and blowing hydrometeors during storms. Daily counts of airborne detections from the LiDAR show excellent agreement with automated and manual snow water equivalent measurements, suggesting that LiDAR observations have the potential to directly estimate precipitation rate. Thus, we suggest LiDAR scanners offer advantages over precipitation radars, which could lead to more accurate precipitation rate estimates. For instance, uncertainties in mass-diameter and mass-fall speed relationships used in precipitation radar, combined with low reflectivity of snow in the microwave spectrum, produce errors of up to 3X in snowfall rates measured by radar. Since snow has more backscatter in the near-infrared wavelengths used by LiDAR compared to the wavelengths used by radar, and the LiDAR detects individual hydrometeors, our approach has more potential for directly estimating precipitation rate. A key uncertainty is hydrometeor mass. At our study site, we have also installed a Multi Angle Snowflake Camera (MASC) to measure size, fallspeed, and mass of individual hydrometeors. By combining simultaneous MASC and LiDAR measurements, we can estimate precipitation density and rate.

LeWinter, A. L.; Bair, E. H.; Davis, R. E.; Finnegan, D. C.; Gutmann, E. D.; Dozier, J.

2012-12-01

289

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

290

Comparison between active sensor and radiosonde cloud boundaries over the ARM Southern Great Plains site  

Microsoft Academic Search

In order to test the strengths and limitations of cloud boundary retrievals from radiosonde profiles, 4 years of radar, lidar, and ceilometer data collected at the Atmospheric Radiation Measurements Southern Great Plains site from November 1996 through October 2000 are used to assess the retrievals of Wang and Rossow [1995] and Chernykh and Eskridge [1996]. The lidar and ceilometer data

Catherine M. Naud; Jan-Peter Muller; Eugene E. Clothiaux

2003-01-01

291

Space radar image of Western Pacific rain clouds  

NASA Technical Reports Server (NTRS)

This radar image shows the ocean surface in a portion of the Western Pacific Ocean. Scientists are using images like this to study the occurrence, distribution and activity of tropical rain squalls and to understand the exchange of heat between the atmosphere and ocean and the upper layer mixing in the tropical oceans, which are critical factors for understanding the driving forces which produce the El Nino phenomenon. The white, curved area at the top of the image is a portion of the Ontong Java Atoll, part of the Solomon Islands group. The yellowish green area near the bottom of the image is an intense rain cell. This image is centered near 5.5 degrees South latitude and 159.5 degrees East longitude. The area shown is 50 kilometers by 21 kilometers (31 miles by 13 miles). This image was acquired by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) aboard the space shuttle Endeavour on its 13th orbit on April 10, 1994. The colors in the image are assigned to different frequencies and polarizations of the SIR-C radar as follows: Red is C-band horizontally transmitted and received; green is L-band horizontally transmitted and vertically received and blue is L-band horizontally transmitted and received. The large rain cell is about 15 kilometers by 15 kilometers (9 miles by 9 miles) and contains two dark regions, one circular and one rectangular, inside it. Two smaller reddish cells are visible closer to the atoll. The red areas may be caused by reflection from ice particles in the colder, upper portion of the storm cell and not from the ocean surface at all. This provides direct evidence that it is raining within this storm cell, valuable information which is usually very difficult to measure over more remote regions of the ocean away from coastal-based weather systems. The dark holes in the middle of the cell are thought to be areas of very heavy rainfall which actually smooth out the ocean surface and result in lower radar returns. The surrounding ocean is blue to green plus black. Winds and currents cause the ocean surface to be rough and those variations on the surface affect how the radar signals bounce off the surface. The bright areas on the image correspond to areas where the wind speed is high. The highest winds are seen as the yellow-green region of the large rain cell. The lowest winds are seen inside the atoll as dark areas. Outside the rain cell, the winds are moderately low, which is indicated by the puff-like, blue patterns surrounding the cell and extending into the atoll. The long, thin, dark lines extending across the ocean are surface currents. Here the currents are likely accumulating natural oils caused by small marine biological organisms. The oils cause the small, wind-generated waves to be reduced in size or damped which produces a smooth, dark zone on the radar image.

1995-01-01

292

Evaluations of Three-Dimensional Building Model Reconstruction from LiDAR Point Clouds and Single-View Perspective Imagery  

NASA Astrophysics Data System (ADS)

This paper briefly presents two approaches for effective three-dimensional (3D) building model reconstruction from terrestrial laser scanning (TLS) data and single perspective view imagery and assesses their applicability to the reconstruction of 3D models of landmark or historical buildings. The collected LiDAR point clouds are registered based on conjugate points identified using a seven-parameter transformation system. Three dimensional models are generated using plan and surface fitting algorithms. The proposed single-view reconstruction (SVR) method is based on vanishing points and single-view metrology. More detailed models can also be generated according to semantic analysis of the faade images. Experimental results presented in this paper demonstrate that both TLS and SVR approaches can successfully produce accurate and detailed 3D building models from LiDAR point clouds or different types of single-view perspective images.

Tsai, F.; Chang, H.

2014-06-01

293

Layers of quasi-horizontally oriented ice crystals in cirrus clouds observed by a two-wavelength polarization lidar.  

PubMed

Layers of quasi-horizontally oriented ice crystals in cirrus clouds are observed by a two-wavelength polarization lidar. These layers of thickness of several hundred meters are identified by three attributes: the backscatter reveals a sharp ridge while the depolarization ratio and color ratio become deep minima. These attributes have been justified by theoretical calculations of these quantities within the framework of the physical-optics approximation. PMID:25322032

Borovoi, Anatoli; Balin, Yurii; Kokhanenko, Grigorii; Penner, Iogannes; Konoshonkin, Alexander; Kustova, Natalia

2014-10-01

294

Long-term measurements of Polar Stratospheric Clouds with the Esrange lidar  

NASA Astrophysics Data System (ADS)

Polar Stratospheric Clouds (PSCs) play a key role for ozone depletion in the polar stratosphere whose magnitude depends on the type of PSC and its lifetime and extent. PSCs are classified into three types (PSC Ia: nitric acid di- or trihydrate crystals, NAD or NAT; PSC Ib: supercooled liquid ternary solutions, STS; PSC II: ice) according to their particle composition and to their physical phase. This study presents long-term statistics of PSC occurrence from measurements with the lidar system at the Esrange Space Centre (68N, 21E), northern Sweden. The study gives an overview of the occurrence frequency of different PSC types in connection to the prevailing meteorological conditions for the northern hemispheric winters from 1996/97 to 2013/14. During these 18 years, most of the measurements were conducted in January. The geographical location of Esrange in the lee of the Scandinavian mountain range allows for the observation of a wide range of PSC growth conditions due to mountain-wave activity. The Esrange lidar data set contains hourly mean values of the parallel and perpendicularly polarized backscatter ratio and the linear particle depolarization ratio - all measured at 532 nm. These parameters are used for PSC classification. The lowest occurrence frequency is found for PSCs of type II (6% for the entire period). This low occurrence rate is reasonable since PSCs of type II are formed at temperatures below the ice-frost point. Such temperatures are rarely reached in the Arctic polar vortex. Most of the observations between 1997 and 2014 showed low particle depolarization ratios and low backscatter ratios according to which observed PSCs were classified as type Ib (47%) or mixtures (33%). The remaining 13% of the observation were classified as type Ia PSCs (NAT particles).

Achtert, Peggy; Tesche, Matthias; Blum, Ulrich

2014-05-01

295

VALIDATION OF A RADAR DOPPLER SPECTRA SIMULATOR USING MEASUREMENTS FROM THE ARM CLOUD RADARS  

E-print Network

to compare models with observations contains advantages and challenges. Radar Doppler spectra simulators 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

296

Polarimetric Radar Observations of Arctic Clouds: Signal Processing and First Results from the may 2013 Iop  

NASA Astrophysics Data System (ADS)

The ARM Climate Research Facility site at the North Slope of Alaska in Barrow provides polarimetric radar observations of Arctic clouds at X, Ka and W bands. During the May 2013 Scanning radar Intensive Observation Period, raw I and Q data were acquired with the X-SAPR and the Ka-W SACR for the purpose of validating existing, and testing new signal processing procedures specifically tailored for Arctic observations. The raw I and Q datasets were collected on May 3rd 2013 for the case of low-level boundary layer mixed-phase arctic clouds and on May 6th 2013 for the case of a synoptic low moving in from the west. http://www.arm.gov/campaigns/nsa2013nsasr The present paper describes the impact of signal processing procedures on the data, and establishes dual-polarization radar as a valuable tool for the microphysical characterization of ice clouds. In particular, the X-SAPR operates at STSR mode, making available differential reflectivity ZDR, copolar correlation coefficient ?hv, specific differential phase KDP and Degree of Polarization at Simultaneous Transmit DOPS. Low-level boundary layer mixed-phase Arctic clouds are characterized by layers of supercooled liquid water aloft, which present a stark polarimetric contrast with respect to the associated ice precipitation fallout. The ice particles falling from boundary layer Arctic clouds on May 2nd, 3rd and 4th 2013 (winds were very weak or absent) showed the remarkable property of being composed exclusively by large dendrites - fern-like, stellars, twelve-branched - indicating deposition as the main accretion mechanism. http://www.flickr.com/photos/michele_galletti/sets/72157633422079814/ Boundary Layer mixed-phase Arctic clouds provide an exceptional natural laboratory for the exploration of polarimetric signatures in presence of dendritic ice particles. The first-ever X-band analysis of differential reflectivity ZDR of mixed-phase Arctic clouds is presented in [1]. For the May 6th case, ice particle populations associated with frontal systems underwent more significant vertical mixing, and therefore more significant break-up and aggregation, with the overall result that ice particles possessed less geometrical symmetry, and consequently less prominent polarimetric contrast was detected by the radars. [1] Oue, Galletti, Verlinde "Observations of X-band differential reflectivity in Arctic mixed-phase clouds", submitted.

Galletti, M.; Oue, M.; Verlinde, J.

2013-12-01

297

Requirements for laser radar detection of a barium ion cloud at five earth radii.  

NASA Technical Reports Server (NTRS)

The requirements for a tuned laser radar capable of detecting and ranging a high altitude barium ion cloud release are discussed. A high energy pulsed dye laser tuned to the 455.4 nm Ba II resonance line is considered as the transmitter. Photon counting detection is employed and the resultant signal is integrated over a number of successive laser firings. The solar induced radiance of the cloud is the major background noise source. Detection and ranging may be achieved with signal-to-noise ratios of the order of unity using currently available equipment. This technique has the potential of improved resolution as compared to photographic measurements previously made.

Mumola, P. B.

1972-01-01

298

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; Szkely, Balzs; Zmolyi, Andrs.; Nothegger, Clemens

2010-05-01

299

Polar Stratospheric Clouds from ground-based lidar and CALIPSO observations and Chemistry Climate Models evaluation  

NASA Astrophysics Data System (ADS)

We evaluate the Antarctic PSC observational databases of CALIPSO and the ground-based lidars of NDACC (Network for Detection of Atmospheric Composition Changes) located in McMurdo and Dumont D'Urville stations and provide a process-oriented evaluation of PSC in a subset of CCMVAL-2 chemistry-climate models. Lidar observatories have a decadal coverage, albeit with discontinuities, spanning from 1992 to today hence offering a unique database. A clear issue is the representativeness of ground-based long-term data series of the Antarctic stratosphere conditions that may limit their value in climatological studies and model evaluation. The comparison with the CALIPSO observations with a global coverage is, hence, a key issue. In turn, models can have a biased representation of the stratospheric conditions and of the PSC microphysics leading to large discrepancies in PSC occurrence and composition. CALIPSO observations indicate a large longitudinal variability in PSC formation in the polar atmosphere and ground-based observations are hence representative of different cloud conditions. Point-to-point comparison is difficult due to sparseness of the database (or PSC appearance at the edge of the vortex) and to intrinsic differences in spatial distribution between models and observations. So the use of simple diagnostics that are independent from instrumental coverage is fundamental. Comparison between ground-based and satellite borne-lidar is overall satisfactory and differences may be attributed to differences in coverage. As expected, McMurdo site is dominated by a NAT-type regime that is a clear feature of the eastern part of polar vortex while Dumont D'Urville is largely influenced by the transition at the edge the polar vortex resulting, on average, in a much reduced PSC coverage with a partition between NAT and STS cloud types. Data from the 5 CCMs having provided PSC surface areas on daily basis have been evaluated using the same diagnostic type that may be derived CALIPSO (i.e. frequency of PSC occurrence function of lon-lat, height and temperature) showing large differences that may be explained by the interplay of model temperatures that may show a large bias (negative for 3 models over 5) and the microphysical scheme itself. Two models in fact show an excess of NAT formation relative to ice clouds while two others have an unrealistic dominance of ice. Most of them show a somewhat too efficient PSC production with temperature decrease below NAT formation temperature. Evaluation CCMs with ground-based instruments databases should be done with great care due to the large spatial differences inside the polar vortex that are not fully reproduced by the models. In turn, longer series as provided by NDACC should be used to evaluate interannual variability and trends that is difficult to identify in the shorter CALIPSO database.

Fierli, Federico; Di Liberto, Luca; Cairo, Francesco; Cagnazzo, Chiara; Snels, Marcel; Keckhut, Philippe; Jumelet, Julien; Pitts, Michael C.

2014-05-01

300

A case study of gravity wave dissipation in the polar MLT region using sodium LIDAR and radar data  

NASA Astrophysics Data System (ADS)

This paper is primarily concerned with an event observed from 16:30 to 24:30 UT on 29 October 2010 during a very geomagnetically quiet interval (Kp ≤ 1). The sodium LIDAR observations conducted at Tromsø, Norway (69.6 N, 19.2 E) captured a clearly discernible gravity wave (GW) signature. Derived vertical and horizontal wavelengths, maximum amplitude, apparent and intrinsic period, and horizontal phase velocity were about ~ 11.9 km, ~ 1.38 103 km, ~ 15 K, 4 h, ~ 7.7 h, and ~ 96 m s-1, respectively, between a height of 80 and 95 km. Of particular interest is a temporal development of the uppermost altitude that the GW reached. The GW disappeared around 95 km height between 16:30 and 21:00 UT, while after 21:00 UT the GW appeared to propagate to higher altitudes (above 100 km). We have evaluated three mechanisms (critical-level filtering, convective and dynamic instabilities) for dissipations using data obtained by the sodium LIDAR and a meteor radar. It is found that critical-level filtering did not occur, and the convective and dynamic instabilities occurred on some occasions. MF radar echo power showed significant enhancements between 18:30 and 21:00 UT, and an overturning feature of the sodium mixing ratio was observed between 18:30 and 21:20 UT above about 95 km. From these results, we have concluded that the GW was dissipated by wave breaking and instabilities before 21:00 UT. We have also investigated the difference of the background atmosphere for the two intervals and would suggest that a probable cause of the change in the GW propagation was due to the difference in the temperature gradient of the background atmosphere above 94 km.

Takahashi, T.; Nozawa, S.; Tsutsumi, M.; Hall, C.; Suzuki, S.; Tsuda, T. T.; Kawahara, T. D.; Saito, N.; Oyama, S.; Wada, S.; Kawabata, T.; Fujiwara, H.; Brekke, A.; Manson, A.; Meek, C.; Fujii, R.

2014-10-01

301

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

302

Application of Cloude's target decomposition theorem to polarimetric imaging radar data  

NASA Technical Reports Server (NTRS)

In this paper we applied Cloude's decomposition to imaging radar polarimetry. We show in detail how the decomposition results can guide the interpretation of scattering from vegetated areas. For multifrequency polarimetric radar measurements of a clear-cut area, the decomposition leads us to conclude that the vegetation is probably thin compared to even the C-band radar wavelength of 6 cm. For a frosted area, we notice an increased amount of even number of reflection scattering at P-band and L-band, probably the result of penetration through the coniferous canopy resulting in trunk-ground double reflection scattering. However, the scattering for the forested area is still dominated by scattering from randomly oriented cylinders. It is found that these cylinders are thicker than in the case of clear-cut areas, leading us to conclude that scattering from the branches probably dominates in this case.

Vanzyl, Jakob J.

1993-01-01

303

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

304

Combined infrared emission spectra and radar reflectivity studies of cirrus clouds  

Microsoft Academic Search

Thermal-infrared emission spectra from cirrus clouds taken with a unique prism spectrograph are combined with Ka-band radar reflectivity measurements to obtain mass concentration and size information on the cirrus ice crystals. A two-stream radiation transfer model utilizing Mie scattering theory was used to infer the averaged effective ice sphere diameter which, for the cirrus studied, was near 50 ?m

A. Jay Palmer; S. Y. Matrosov; B. E. Martner; T. Uttal; D. K. Lynch; M. A. Chatelain; J. A. Hackwell; R. W. Russell

1993-01-01

305

Simulation for spaceborne cloud profiling Doppler radar: EarthCARE/CPR  

NASA Astrophysics Data System (ADS)

The Cloud Profiling Radar (CPR) on EarthCARE satellite is the first spaceborne cloud profiling Doppler radar using Wband frequency in order to measure vertical velocity of clouds and rain. The EarthCARE/CPR has -35dBZ in sensitivity after 10km integration and less than 1 m/s in Doppler velocity measurement error. Because satellite velocity and beam width spread Doppler spectrum and coherency is low, the measurement error of Doppler velocity is increased. EarthCARE/CPR is the first Doppler radar, so we need to make simulation data for the algorithm development, but the simulation itself is difficult in order to take into account these effects. The current method is calculated 2-dimentional integration within illuminated area by antenna beam and hit by hit for all pulses, then it takes many computation times. We developed the new simple calculation method, which is calculated using integrated antenna pattern, then the computation time is decreased significantly. This paper is reported the comparison for, both methods.

Horie, Hiroaki; Takahashi, Nobuhiro; Ohno, Yuichi; Sato, Kenji

2012-11-01

306

Sensitivity of S- and Ka-band matched dual-wavelength radar system for detecting nonprecipitating cloud  

Microsoft Academic Search

Remote detection of cloud phase in either liquid, ice or mixed form a key microphysical observation. Evolution of a cloud system and associated radiative properties depend on microphysical characteristics. Polarization radars rely on the shape of the particle to delineate the regions of liquid and ice. For specified transmitter and receiver characteristics, it is easier to detect a high concentrations

J. Vivekanandan; Marcia Politovich; Robert Rilling; Scott Ellis; Frank Pratte

2004-01-01

307

High resolution retrieval of liquid water vertical distributions using collocated Ka-band and W-band cloud radars  

E-print Network

reflectivity. Either a long radar dwell time or an average over many range gates is needed to reduce random microphysical and cloud radiation transfer studies. In order to obtain more useful moments like the third moment clouds from both field campaign studies and satellite observations [Fox and Illingworth, 1997; Mace et al

308

Vertical Velocity Measurements in Warm Stratiform Clouds  

NASA Astrophysics Data System (ADS)

Measurements of vertical air motion in warm boundary layer clouds are key for quantitatively describing cloud-scale turbulence and for improving our understanding of cloud and drizzle microphysical processes. Recently, a new technique that produces seamless measurements of vertical air velocity in the cloud and sub-cloud layers for both drizzling and non-drizzling stratocumulus clouds has been developed. The technique combines radar Doppler spectra-based retrievals of vertical air motion in cloud and light drizzle conditions with a novel neural network analysis during heavily drizzling periods. Observations from Doppler lidars are used to characterize sub-cloud velocities and to evaluate the performance of the technique near the cloud base. The technique is applied to several cases of stratiform clouds observed by the ARM Mobile Facility during the Two-Column Aerosol Project (TCAP) campaign in Cape Cod. The observations clearly illustrate coupling of the sub-cloud and cloud layer turbulent structures.

Luke, E. P.; Kollias, P.

2013-12-01

309

Analysis of Doppler Lidar Wind Measurements.  

National Technical Information Service (NTIS)

Doppler lidar and multiple Doppler radar data were obtained in a convectively mixed planetary boundary layer. The lidar measurements were possible due to scattering from existing aerosols; radar reflecting chaff was released in the atmosphere to make it v...

R. C. ivastava

1986-01-01

310

The Use of Coincident Synthetic Aperture Radar and Visible Imagery to Aid in the Analysis of Photon-Counting Lidar Data Sets Over Complex Ice/Snow Surfaces  

NASA Astrophysics Data System (ADS)

Qualitative and quantitative analysis of multi-sensor data is becoming increasingly useful as a method of improving our understanding of complex environments, and can be an effective tool in the arsenal to help climate scientists to predict sea level rise due to change in the mass balance of large glaciers in the Arctic and Antarctic. A novel approach to remote sensing of the continuously changing polar environment involves the use of coincident RADARSAT-2 synthetic aperture radar (SAR) imagery and Landsat 7 visible/near-infrared imagery, combined with digital elevation models (DEM) developed from Multiple Altimeter Beam Experimental Lidar (MABEL) data sets. MABEL is a scaled down model of the lidar altimeter that will eventually be flown on ICESat-2, and provides dense along-track and moderate slope (cross-track) elevation data over narrow (~198 m) aircraft transects. Because glacial terrain consists of steep slopes, crevices, glacial lakes, and outflow into the sea, accurate slope information is critical to our understanding of any changes that may be happening in the ice sheets. RADARSAT-2 operates in the C-band, at a wavelength of 5.55 cm, and was chosen partly for its ability to image the Earth under all atmospheric conditions, including clouds. The SAR images not only provide spatial context for the elevation data found using the lidar, but also offer key insights into the consistency of the snow and ice making up the glacier, giving us some idea of mean temperature and surface conditions on the ice sheet. Finally, Landsat 7 images provide us with information on the extent of the glacier, and additional understanding of the state of the glacial surface. To aid in the analysis of the three data sets, proper preparation of each data set must first be performed. For the lidar data, this required the development of a new data reduction technique, based on statistical analysis, to reduce the number of received photons to those representing only the surface return. Accordingly, the raw SAR images require calibration, speckle reduction, and geocorrection, before they can be used. Landsat 7 bands are selected to provide the most contrast between rock, snow, and other surface features, and compiled into a three-band red, green, blue (RGB) image. By qualitatively analyzing images and data taken only a short time apart using multiple imaging modalities, we are able to accurately compare glacial surface features to elevation provided by MABEL, with the goal of increasing our understanding of how the glacier is changing over time. Quantitative analysis performed throughout this thesis has indicated that there is a strong correlation between top-of-the-atmosphere reflectance (Landsat 7), sigma,0-calibrated HH and HV polarized backscatter coefficients (RADARSAT-2), elevation (MABEL), and various surface features and glacial zones on the ice sheet. By comparing data from unknown or mixed surfaces to known quantities scientists can effectively estimate the type of glacial zone the area of interest occurs in. Climate scientists can then use this data, along with long-term digital elevations models, as a measure of predicting climate change.

Horan, Kimberly H.

311

Extraction of Features from High-resolution 3D LiDaR Point-cloud Data  

NASA Astrophysics Data System (ADS)

Airborne and tripod-based LiDaR scans are capable of producing new insight into geologic features by providing high-quality 3D measurements of the landscape. High-resolution LiDaR is a promising method for studying slip on faults, erosion, and other landscape-altering processes. LiDaR scans can produce up to several billion individual point returns associated with the reflection of a laser from natural and engineered surfaces; these point clouds are typically used to derive a high-resolution digital elevation model (DEM). Currently, there exist only few methods that can support the analysis of the data at full resolution and in the natural 3D perspective in which it was collected by working directly with the points. We are developing new algorithms for extracting features from LiDaR scans, and present method for determining the local curvature of a LiDaR data set, working directly with the individual point returns of a scan. Computing the curvature enables us to rapidly and automatically identify key features such as ridge-lines, stream beds, and edges of terraces. We fit polynomial surface patches via a moving least squares (MLS) approach to local point neighborhoods, determining curvature values for each point. The size of the local point neighborhood is defined by a user. Since both terrestrial and airborne LiDaR scans suffer from high noise, we apply additional pre- and post-processing smoothing steps to eliminate unwanted features. LiDaR data also captures objects like buildings and trees complicating greatly the task of extracting reliable curvature values. Hence, we use a stochastic approach to determine whether a point can be reliably used to estimate curvature or not. Additionally, we have developed a graph-based approach to establish connectivities among points that correspond to regions of high curvature. The result is an explicit description of ridge-lines, for example. We have applied our method to the raw point cloud data collected as part of the GeoEarthScope B-4 project on a section of the San Andreas Fault (Segment SA09). This section provides an excellent test site for our method as it exposes the fault clearly, contains few extraneous structures, and exhibits multiple dry stream-beds that have been off-set by motion on the fault.

Keller, P.; Kreylos, O.; Hamann, B.; Kellogg, L. H.; Cowgill, E. S.; Yikilmaz, M. B.; Hering-Bertram, M.; Hagen, H.

2008-12-01

312

Classification of Particle Shapes from Lidar Depolarization Ratios in Convective Ice Clouds Compared to in situ Observations During CRYSTAL-FACE  

NASA Technical Reports Server (NTRS)

This manuscript describes a method to class@ cirrus cloud ice particle shape using lidar depolarization measurements as a basis for segregating different particle shape regimes. Measurements from the ER-2 Cloud Physics Lidar (CPL) system during CRYSTAL-FACE provide the basis for this work. While the CPL onboard the ER-2 aircraft was providing remote sensing measurements of cirrus clouds, the Cloud Particle Imager (CPI) onboard the WB-57 aircraft was flying inside those same clouds to sample particle sizes. The results of classifying particle shapes using the CPL data are compared to the in situ measurements made using the CPI , and there is found to be good agreement between the particle shape inferred from the CPL data and that actually measured by the CPI. If proven practical, application of this technique to spaceborne observations could lead to large-scale classification of cirrus cloud particle shapes.

Noel, Vincent; Winker, David; McGill, Matthew; Lawson, Paul

2004-01-01

313

a 33GHZ and 95GHZ Cloud Profiling Radar System (cprs): Preliminary Estimates of Particle Size in Precipitation and Clouds.  

NASA Astrophysics Data System (ADS)

The Microwave Remote Sensing Laboratory (MIRSL) st the University of Massachusetts has developed a unique single antenna, dual-frequency polarimetric Cloud Profiling Radar System (CPRS). This project was funded by the Department of Energy's Atmospheric Radiation Measurement (ARM) program, and was intended to help fill the void of ground-based remote sensors capable of characterizing cloud microphysical properties. CPRS is unique in that it can simultaneously measure the complex power backscattered from clouds at 33 GHz and 95 GHz through the same aperture. Both the 33 GHz and 95 GHz channels can transmit pulse-to-pulse selectable vertical or horizontal polarization, and simultaneously record both the copolarized and crosspolarized backscatter. CPRS Doppler, polarimetric and dual-wavelength reflectivity measurements combined with in situ cloud measurements should lead to the development of empirical models that can more accurately classify cloud-particle phase and habit, and make better quantitative estimates of particle size distribution parameters. This dissertation describes the CPRS hardware, and presents colocated 33 GHz and 95 GHz measurements that illustrate the use of dual-frequency measurements to estimate particle size when Mie scattering, is observed in backscatter from rain and ice-phase clouds. Polarimetric measurements are presented as a means of discriminating cloud phase (ice-water) and estimating crystal shape in cirrus clouds. Polarimetric and dual-wavelength observations of insects are also presented with a brief discussion of their impact on the interpretation of precipitation and liquid cloud measurements. In precipitation, Diermendjian's equations for Mie backscatter (1) and the Marshal-Palmer drop-size distribution are used to develop models relating differences in the reflectivity and mean velocity at 33 GHz and 95 GHz to the microphysical parameters of rain. These models are then used to estimate mean droplet size from CPRS measurements of drizzle, which were collected in July, 1993 during the system's first field test in Lincoln, NE. The dissertation also presents cirrus cloud and other measurements collected during the DOE-sponsored Remote Cloud Sensing Intensive Operations Period (RCS-IOP) experiment in April, 1994. Zenith-pointing cirrus measurements show small differences in 33 GHz and 95 GHz reflectivity, as models have predicted (2). Depolarization was also detected in a few cases when ice crystals precipitated from the base of a cloud. On May 29, 1994 CPRS observed a convective storm that produced a cirrus anvil cloud and hail. These storms are one 'engine' producing cirrus clouds and are currently a topic of intensive research by climatologists. Both zenith-pointing and range-height data formats are presented. Measurements of depolarization above the melting/layer are compared to in situ observations of particle size and shape. The RCS-IOP experiment also provided a first opportunity to verify our calibration with aircraft in situ measurements, and to compare our cloud measurements to those collected by other remote sensors. (Abstract shortened by UMI.).

Sekelsky, Stephen Michael

314

Improving combined lidar-radar snowfall retrievals with Doppler spectra (Invited)  

Microsoft Academic Search

Thin mixed phase clouds are frequently observed in the Arctic. These often persist for days with nearly continuous, light precipitation. They play a key role in Arctic climate through their influence on the surface radiation balance. Models have difficulty maintaining these clouds. They are very sensitive to micro-physical assumptions; small changes affect precipitation rates and lead to large changes in

E. Eloranta

2010-01-01

315

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

316

Combined Microwave Radiometer and Micro Rain Radar Analysis of Cloud Liquid Water  

NASA Astrophysics Data System (ADS)

The cloud liquid water is a parameter of vital interest in both modeling and forecasting weather. In meso- scale models, the magnitude of latent heat effects corresponds to the amount of cloud liquid water, which is important in the development of a certain weather system. The purpose of this study is to obtain the combined cloud liquid water from a 21.8 and 31.4 GHz ground based microwave radiometer (MWR) and the micro rain radar (MRR), because each instrument has the limitation of observation; it is widely known that the measurements of MWR and MRR are not meaningful with and without rainfall, respectively. The cloud liquid water of the two instruments has been measured at the Cloud Physics Observation System (CPOS) site, located at 37.41 N, 128.45 E and 842 m from mean sea level. To examine the performance of instruments, the precipitable water vapor (PWV) measured by the MWR was compared with the calculated PWV of nearest radiosonde from December 2003 to July 2008, and MRR was compared with the several accumulated precipitation observed by AWS. The PWV of MWR gives good agreement with that of radiosonde: R-square = 0.82 for spring, 0.78 for summer, 0.83 for fall, but 0.25 for winter. This bad performance in the winter season seems from the heavy snow on the radome, and then the winter data of MWR has been not considered in the combining algorithm. The comparison of MRR and AWS a correlation coefficient: 30min accumulated precipitation was R-square = 0.84. To combine the MRR and MWR cloud liquid water, firstly we estimate the cloud physical thickness from the difference between the MTSAT-1R cloud top height and cloud base height of visual observation of Daegwallyeong weather station, and the cloud liquid water path of MRR is obtained by multiplying the LWC of MRR and the estimated cloud physical thickness. The trend of MWR liquid water path agrees with that of the MRR during small precipitation. We study these characteristics of MRR and MWR for small precipitation to obtain the combined cloud water content of MRR and MWR, constantly operated regardless to the rainfall.

Yang, H.; Chang, K.; Jeong, J.; Lee, S.; Jang, Y.; Lee, M.; Kim, K.

2008-12-01

317

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

318

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

319

Comparison of Airborne and Spaceborne 95-GHz Radar Reflectivities and Evaluation of Multiple Scattering Effects in Spaceborne Measurements  

E-print Network

and to the evaluation of the CloudSat­Cloud- Aerosol Lidar and Infrared Pathfinder Satellite Obser- vations (CALIPSO. To fulfill these objectives, the French Falcon 20 (F-F20) was deployed with a 95-GHz Doppler radar Society #12;(CNES) Afternoon Satellite Constellation (A-Train) track and to then document the cross-track

Protat, Alain

320

3D Observations of Marine Stratocumulus Structure and Dynamics at the Azores Using a Scanning Cloud Radar  

NASA Astrophysics Data System (ADS)

The US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility recently upgraded its infrastructure at the fixed and mobile sites by adding scanning cloud and precipitation radars of frequencies ranging from 5 to 94 GHz. The first scanning ARM 94-GHz radar was deployed for a short period of 2 months (October-November 2009) on Graciosa Island, Azores as part of the ARM Mobile Facility (AMF) deployment to support the Clouds, Aerosol, and Precipitation in the Marine Boundary Layer (CAP-MBL) field campaign (www.arm.gov/sites/amf/grw). Several scan strategies were tested during the scanning cloud radar deployment. One of these strategies is the Cross Wind Range Height Indicator (CW-RHI) scan that consist of keeping a constant azimuth oriented perpendicular to the mean wind direction at the cloud level and operating scans with changing elevations from horizon to horizon passing over the radar location for a duration of one continuous hour. This unique scan strategy allows to slice clouds entirely as they move over time above the radar. Then using the wind magnitude and direction, it is possible to convert time to along-wind length and thus reconstruct the complete 3D cloud structure. Cross wind measurements of all Doppler moments are reported in radar spherical coordinates that can be transform to Cartesian coordinate system to simplify result analysis using an adaptive gridding algorithms. The raw observed Doppler velocities are quality controlled and corrected for folding. Then, the Doppler velocities are corrected for the horizontal wind contribution and the effect of the viewing angle. The resulting information provide 3D observations of the vertical component of the Doppler velocity in 3D and can be used to describe for the first time the 3D structure of large eddies in marine stratocumulus clouds at scales ranging from 50 m to 5km across.

Lamer, K.; Jo, I.; Tatarevic, A.; Kollias, P.

2012-12-01

321

Measurement of Cirrus Cloud Optical Properties by High Spectral Resolution LIDAR  

Microsoft Academic Search

Lidar backscatter signals are generated by scattering from both molecules and particles. The spectral distribution of light scattered by molecules is Doppler-broadened by rapid, thermally induced, molecular motions. Light scattered by aerosols and cirrus particles is essentially unshifted because of the relatively slow Brownian motion of particles. Using this difference, the High Spectral Resolution Lidar (HSRL) interferometrically separates particulate from

Christian John Grund

1987-01-01

322

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

Microsoft Academic Search

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

Tulu Bacha

2011-01-01

323

Geometric and optical properties of cirrus clouds inferred from three-year ground-based lidar and CALIOP measurements over Seoul, Korea  

NASA Astrophysics Data System (ADS)

This study examines cirrus cloud top and bottom heights (CTH and CBH, respectively) and the associated optical properties revealed by ground-based lidar in Seoul (SNU-L), Korea, and space-borne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), which were obtained during a three-year measurement period between July 2006 and June 2009. From two selected cases, we determined good agreement in CTH and CBH with cirrus cloud optical depth (COD) between ground-based lidar and space-borne CALIOP. In particular, CODs at a wavelength of 532 nm calculated from the three years of SNU-L and CALIOP measurements were 0.417 0.394 and 0.425 0.479, respectively. The fraction of COD lower than 0.1 was approximately 17% and 25% of the total SNU-L and CALIOP profiles, respectively, and approximately 50% of both lidar profiles were classified as sub-visual or optically thin such that COD was < 0.3. The mean depolarization ratio was estimated to be 0.30 0.06 for SNU-L and 0.34 0.08 for CALIOP. The monthly variation of CODs from SNU-L and CALIOP measurements was not distinct, whereas cirrus altitudes from both SNU-L and CALIOP showed distinct monthly variation. CALIOP observations showed that cirrus clouds reached the tropopause level in all months, whereas the up-looking SNU-L did not detect cirrus clouds near the tropopause in summer due to signal attenuation by underlying optically thick clouds. The cloud layer thickness (CLT) and COD showed a distinct linear relationship up to approximately 2 km of the CLT; however, the COD did not increase, but remained constant when the CLT was greater than 2.0 km. The ice crystal content, lidar signal attenuation, and the presence of multi-layered cirrus clouds may have contributed to this tendency.

Kim, Yumi; Kim, Sang-Woo; Kim, Man-Hae; Yoon, Soon-Chang

2014-03-01

324

Science Goals for the ARM Recovery Act Radars  

SciTech Connect

Science Goals for the ARM Recovery Act Radars. In October 2008, an ARM workshop brought together approximately 30 climate research scientists to discuss the Atmospheric Radiation Measurement (ARM) Climate Research Facility's role in solving outstanding climate science issues. Through this discussion it was noted that one of ARM's primary contributions is to provide detailed information about cloud profiles and their impact on radiative fluxes. This work supports cloud parameterization development and improved understanding of cloud processes necessary for that development. A critical part of this work is measuring microphysical properties (cloud ice and liquid water content, cloud particle sizes, shapes, and distribution). ARM measurements and research have long included an emphasis on obtaining the best possible microphysical parameters with the available instrumentation. At the time of the workshop, this research was reaching the point where additional reduction in uncertainties in these critical parameters required new instrumentation for applications such as specifying radiative heating profiles, measuring vertical velocities, and studying the convective triggering and evolution of three-dimensional (3D) cloud fields. ARM was already operating a subset of the necessary instrumentation to make some progress on these problems; each of the ARM sites included (and still includes) a cloud radar (operating at 35 or 94 GHz), a cloud lidar, and balloon-borne temperature and humidity sensors. However, these measurements were inadequate for determining detailed microphysical properties in most cases. Additional instrumentation needed to improve retrievals of microphysical processes includes radars at two additional frequencies for a total of three at a single site (35 GHz, 94 GHz, and a precipitation radar) and a Doppler lidar. Evolving to a multi-frequency scanning radar is a medium-term goal to bridge our understanding of two-dimensional (2D) retrievals to the 3D cloud field. These additional microphysical measurements would allow detailed cloud properties to be derived even in the presence of light precipitation. It is important to couple these detailed measurements of cloud microphysics to vertical motion on the cloud scale to couple microphysics with meteorological processes. Vertically pointing Doppler radars provide the vertical motion of cloud particles but, to separate particle motion from air motion, a wind profiler is required. The American Recovery and Reinvestment Act provided the means to address these needs and implement a multi-frequency suite of radars, including scanning radars, at each of the ARM sites. In addition, Doppler lidars have been deployed at several sites. With these new measurement capabilities, ARM has the measurement capabilities to tackle the problems of improving microphysical profile descriptions and evaluating the relationship between our current narrow-field-of view, zenith perspective on clouds to a description of the full 3D cloud field and its temporal evolution.

JH Mather

2012-05-29

325

investigate the effects of cloud composition, such as ice particle shape and orientation, on  

E-print Network

use CFARR's sophisticated RADAR (Radio Detection And Ranging), LIDAR (LIght Detection And Ranging: · understand how clouds form and develop into rain or storm clouds, The Chilbolton Observatory 25m antenna contact +44 (0)1235 445627 Version 02 - Dec 11 The Science and Technology Facilities Council Space Agency

326

Observations of Kelvin-Helmholtz instability at a cloud base with the middle and upper atmosphere (MU) and weather radars  

NASA Astrophysics Data System (ADS)

Using the very high frequency (46.5 MHz) middle and upper atmosphere radar (MUR), Ka band (35 GHz) and X band (9.8 GHz) weather radars, a Kelvin-Helmholtz (KH) instability occurring at a cloud base and its impact on modulating cloud bottom altitudes are described by a case study on 8 October 2008 at the Shigaraki MU Observatory, Japan (34.85N, 136.10E). KH braids were monitored by the MUR along the slope of a cloud base gradually rising with time around an altitude of 5.0 km. The KH braids had a horizontal wavelength of about 3.6 km and maximum crest-to-trough amplitude of about 1.6 km. Nearly monochromatic and out of phase vertical air motion oscillations exceeding 3 m s-1 with a period of 3 min 20 s were measured by the MUR above and below the cloud base. The axes of the billows were at right angles of the wind and wind shear both oriented east-north-east at their altitude. The isotropy of the radar echoes and the large variance of Doppler velocity in the KH billows (including the braids) indicate the presence of strong turbulence at the Bragg (3.2 m) scale. After the passage of the cloud system, the KH waves rapidly damped and the vertical scale of the KH braids progressively decreased down to about 100 m before their disappearance. The radar observations suggest that the interface between clear air and cloud was conducive to the presence of the dynamical shear instability by reducing static stability (and then the Richardson number) near the cloud base. Downward cloudy protuberances detected by the Ka band radar had vertical and horizontal scales of about 0.6-1.1 and 3.2 km, respectively, and were clearly associated with the downward air motions. Observed oscillations of the reflectivity-weighted Doppler velocity measured by the X band radar indicate that falling ice particles underwent the vertical wind motions generated by the KH instability to form the protuberances. The protuberances at the cloud base might be either KH billow clouds or perhaps some sort of mamma. Reflectivity-weighted particle fall velocity computed from Doppler velocities measured by the X band radar and the MUR showed an average value of 1.3 ms-1 within the cloud and in the protuberance environment.

Luce, Hubert; Mega, Tomoaki; Yamamoto, Masayuki K.; Yamamoto, Mamoru; Hashiguchi, Hiroyuki; Fukao, Shoichiro; Nishi, Noriyuki; Tajiri, Takuya; Nakazato, Masahisa

2010-10-01

327

Three-dimensional surface displacements and rotations from differencing pre- and post-earthquake LiDAR point clouds  

NASA Astrophysics Data System (ADS)

The recent explosion in sub-meter resolution airborne LiDAR data raises the possibility of mapping detailed changes to Earth's topography. We present a new method that determines three-dimensional (3-D) coseismic surface displacements and rotations from differencing pre- and post-earthquake airborne LiDAR point clouds using the Iterative Closest Point (ICP) algorithm. Tested on simulated earthquake displacements added to real LiDAR data along the San Andreas Fault, the method reproduces the input deformation for a grid size of ?50 m with horizontal and vertical accuracies of ?20 cm and ?4 cm, values that mimic errors in the original spot height measurements. The technique also measures rotations directly, resolving the detailed kinematics of distributed zones of faulting where block rotations are common. By capturing near-fault deformation in 3-D, the method offers new constraints on shallow fault slip and rupture zone deformation, in turn aiding research into fault zone rheology and long-term earthquake repeatability.

Nissen, Edwin; Krishnan, Aravindhan K.; Arrowsmith, J. Ramn; Saripalli, Srikanth

2012-08-01

328

A technique for autocalibration of cloud lidar EWAN J. O'CONNOR  

E-print Network

, wavelengths of about 700 nm or less are used and, to avoid any contam- ination from aerosol returns, unless the lidar has a very narrow beam, but can be accounted for by using suitable models (e.g. Eloranta

Hogan, Robin

329

Studying Clouds and Aerosols with Lidar Depolarization Ratio and Backscatter Relationships  

E-print Network

This dissertation consists of three parts, each devoted to a particular issue of significant importance for CALIPSO lidar observation of depolarization ratio (delta) and backscatter (gamma?) to improve current understanding of the microphysical...

Cho, Hyoun-Myoung

2012-02-14

330

Intercomparison of Vertical Structure of Storms Revealed by Ground-Based (NMQ) and Spaceborne Radars (CloudSat-CPR and TRMM-PR)  

PubMed Central

Spaceborne radars provide great opportunities to investigate the vertical structure of clouds and precipitation. Two typical spaceborne radars for such a study are the W-band Cloud Profiling Radar (CPR) and Ku-band Precipitation Radar (PR), which are onboard NASA's CloudSat and TRMM satellites, respectively. Compared to S-band ground-based radars, they have distinct scattering characteristics for different hydrometeors in clouds and precipitation. The combination of spaceborne and ground-based radar observations can help in the identification of hydrometeors and improve the radar-based quantitative precipitation estimation (QPE). This study analyzes the vertical structure of the 18 January, 2009 storm using data from the CloudSat CPR, TRMM PR, and a NEXRAD-based National Mosaic and Multisensor QPE (NMQ) system. Microphysics above, within, and below the melting layer are studied through an intercomparison of multifrequency measurements. Hydrometeors' type and their radar scattering characteristics are analyzed. Additionally, the study of the vertical profile of reflectivity (VPR) reveals the brightband properties in the cold-season precipitation and its effect on the radar-based QPE. In all, the joint analysis of spaceborne and ground-based radar data increases the understanding of the vertical structure of storm systems and provides a good insight into the microphysical modeling for weather forecasts. PMID:24459424

Fall, Veronica M.; Hong, Yang

2013-01-01

331

Radar Reflectivity Simulated by a 2-D Spectra Bin Model: Sensitivity of Cloud-aerosol Interaction  

NASA Technical Reports Server (NTRS)

The Goddard Cumulus Ensemble (GCE) model with bin spectra microphysics is used to simulate mesoscale convective systems.The model uses explicit bins to represent size spectra of cloud nuclei, water drops, ice crystals, snow and graupel. Each hydrometeorite category is described by 33 mass bins. The simulations provide a unique data set of simulated raindrop size distribution in a realistic dynamic frame. Calculations of radar parameters using simulated drop size distribution serve as an evaluation of numerical model performance. In addition, the GCE bin spectra modes is a very useful tool to study uncertainties related to radar observations; all the environmental parameters are precisely known. In this presentation, we concentrate on the discussion of Z-R (ZDR-R) relation in the simulated systems. Due to computational limitations, the spectra bin model has been run in two dimensions with 31 stretched vertical layers and 1026 horizontal grid points (1 km resolution). Two different cases, one in midlatitude continent, the other in tropical ocean, have been simulated. The continental case is a strong convection which lasted for two hours. The oceanic case is a persistent system with more than 10 hours' life span. It is shown that the simulated Z-R (ZDR-R) relations generally agree with observations using radar and rain gauge data. The spatial and temporal variations of Z-R relation in different locations are also analyzed. Impact of aerosols on cloud formation and raindrop size distribution was studied. Both clean (low CCN) and dirty (high CCN) cases are simulated. The Z-R relation is shown to vary considerable in the initial CCN concentrations.

Li, Kiaowen; Tao, Wei-Kuo; Khain, Alexander; Simpson, Joanne; Johnson, Daniel

2003-01-01

332

The 27-28 October 1986 FIRE IFO cirrus case study - Cloud optical properties determined by High Spectral Resolution Lidar  

NASA Technical Reports Server (NTRS)

The High Spectral Resolution Lidar (HSRL) was operated from a roof-top site in Madison, Wisconsin. The transmitter configuration used to acquire the case study data produces about 50 mW of ouput power and achieved eye-safe, direct optical depth, and backscatter cross section measurements with 10 min averaging times. A new continuously pumped, injection seeded, frequency doubled Nd:YAG laser transmitter reduces time-averaging constraints by a factor of about 10, while improving the aerosol-molecular signal separation capabilities and wavelength stability of the instrument. The cirrus cloud backscatter-phase functions have been determined for the October 27-28, 1986 segment of the HSRL FIRE dataset. Features exhibiting backscatter cross sections ranging over four orders of magnitude have been observed within this 33 h period. During this period, cirrus clouds were observed with optical thickness ranging from 0.01 to 1.4. The altitude relationship between cloud top and bottom boundaries and the optical center of the cloud is influenced by the type of formation observed.

Grund, C. J.; Eloranta, E. W.

1990-01-01

333

Cloud Screening and Quality Control Algorithm for Star Photometer Data: Assessment with Lidar Measurements and with All-sky Images  

NASA Technical Reports Server (NTRS)

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, delta Ae(lambda), and precipitable water vapor content, W, at nighttime. This cloud screening procedure consists of calculating moving averages of delta Ae() and W under different time-windows combined with a procedure for detecting outliers. Additionally, to avoid undesirable Ae(lambda) 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 ma.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.

Ramirez, Daniel Perez; Lyamani, H.; Olmo, F. J.; Whiteman, D. N.; Navas-Guzman, F.; Alados-Arboledas, L.

2012-01-01

334

Orographic precipitation enhancement by boundary-layer turbulence: evidence from vertically pointing airborne cloud radar data  

NASA Astrophysics Data System (ADS)

The University of Wyoming King Air, with multi-antenna 3 mm Doppler radar (the Wyoming Cloud Radar, or WCR), is used to examine shallow orographic precipitation growth. The key question regards how boundary-layer turbulence affects orographic precipitation growth in cold clouds. Houze and Medina and (2005) speculate that BL turbulence is important in snow growth, mainly though riming in turbulent eddies whose updraft speed far exceeds the average ascent rate over the terrain. Flight-level cloud microphysics data and WCR data were collected in flights across the Snowy range in Wyoming. The WCR Doppler velocity transects across the mountain clearly indicate intense turbulence, not in a stable shear layer intersecting the terrain (the mechanism proposed by Houze and Medina (2005)), but rather in the boundary-layer, roughly in the lowest 1 km above the undulating ground, especially on the windier days. This turbulence enhances the hydrometeor growth rate by riming, and thus more precipitation reaching the ground before the crest. Also, ice nucleation may occur along rimed surfaces on the ground, such as trees, or by snow on the ground lofted by turbulent wind gusts. The resulting ice crystals are readily mixed by BL turbuelnce, and thus the Bergeron process too may enhance the growth rate of snow. Specifically, BL turbulence co-locates supercooled liquid water and near-surface ice crystals in updrafts, where rapid growth is likely. This work addresses both the significance of BL turbulence, surface-induced nucleation, and possible interaction between the turbulence and upper level processes. This work is based on evidence from a single mountain range. It remains unclear how common the observed conditions are

Geerts, B.; Miao, Q.

2010-09-01

335

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

336

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

NASA Astrophysics Data System (ADS)

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, Anthony B.; Rohde, Charles A.; Ho, Cheng

2001-09-01

337

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

E-print Network

, Alaska By William I. Rose, Alexander B. Kostinski, and Lee Kelley CONTENTS ABSTRACT Repeated aircraft hazards in Alaska related to volcanic clouds have resulted in the use of a mobile C-band radar devoted (Augustine, Redoubt, and Mount Spurr) have erupted in the Cook Inlet area of Alaska (fig. 1). Each

Rose, William I.

338

JP4.15 SEMI-DISCRETE WAVELET CHARACTERIZATION OF STRATUS CLOUD STRUCTURE FROM MM-RADAR AND SATELLITE DATA  

E-print Network

-RADAR AND SATELLITE DATA Anthony B. Davis #3; Space & Remote Sensing Sciences Group, Los Alamos National Laboratory where correlations can trigger 3D radiative transfer e#11;ects; and dynamical cloud modeling where complexity then grows only as N log N , where N is the number of points (pixels) in the time- series (image

Petrov, Nikola

339

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; Delano, Julien

2013-04-01

340

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

Microsoft Academic Search

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

G. van Zadelhoff; D. P. Donovan

2009-01-01

341

Airborne Doppler wind lidar to evaluate cloud and water vapor motion vectors from GIFTS  

NASA Astrophysics Data System (ADS)

Planning is in progress to launch a much improved temperature and moisture sounder called GIFTS- Geosynchronous Imaging Fourier Transform Spectrometer. The IPO of the NPOESS had developed an Airborne Sounder Test bed, NAST, to simulate GIFTS data products. The IPO has also developed an airborne Doppler wind lidar (Twin Otter Doppler Wind Lidar - TODWL) to provide accurate wind profiles over the oceans to enable evaluation of the GIFTS and other space-based wind observing systems. This presentation reports on the first in a series of TODWL under flights of the NAST flown on NASA"s ER-2.

Emmitt, G. David; Smith, William L., Sr.

2003-12-01

342

Inversion of water cloud lidar signals based on accumulated depolarization ratio.  

PubMed

The relation between the accumulated single scattering factor and the layer accumulated depolarization ratio appears to be independent of the geometry of the measurements and contains information on the optical depth and thus on the extinction coefficient. A simple equation is developed to retrieve the extinction coefficient from the total integrated signal and the integrated depolarization ratio measurements. The results compare well with Klett and Weinman lidar inversion techniques. The results from the measurements of the integrated depolarization ratio can be used to set the far end initial extinction coefficient value required for Klett and Weinman lidar inversion or can be used directly. PMID:20300160

Roy, Gilles; Cao, Xiaoying

2010-03-20

343

Multi-wavelength Airborne High Spectral Resolution Lidar Observations of Aerosol Above Clouds in California during DISCOVER-AQ  

NASA Astrophysics Data System (ADS)

Accurately representing the vertical profile of aerosols is important for determining their radiative impact, which is still one of the biggest uncertainties in climate forcing. Aerosol radiative forcing can be either positive or negative depending on aerosol absorption properties and underlying albedo. Therefore, accurately characterizing the vertical distribution of aerosols, and specifically aerosols above clouds, is vital to understanding climate change. Unlike passive sensors, airborne lidar has the capability to make vertically resolved aerosol measurements of aerosols above and between clouds. Recently, NASA Langley Research Center has built and deployed the world's first airborne multi-wavelength High Spectral Resolution Lidar, HSRL-2. The HSRL-2 instrument employs the HSRL technique to measure extinction at both 355 nm and 532 nm and also measures aerosol depolarization and backscatter at 355 nm, 532 nm and 1064 nm. Additional HSRL-2 data products include aerosol type and range-resolved aerosol microphysical parameters (e.g., effective radius, number concentration, and single scattering albedo). HSRL-2 was deployed in the San Joaquin Valley, California, from January 16 to February 6, 2013, on the DISCOVER-AQ field campaign (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality). On February 6, the observation region was mostly cloudy, and HSRL-2 saw two distinct aerosol layers above the clouds. One layer was aged boundary-layer pollution located just above cloud top at approximately 1.5 km above sea level. An aged smoke layer was also observed over land and over the ocean at altitudes 4-7 km ASL. In this study, we will show HSRL-2 products for these cases, and compare them with airborne in situ measurements of the 1.5-km layer from a coincident flight of the NASA P3B. We will also compare and contrast the HSRL-2 measurements of these two aerosol layers with each other and the clear-air boundary layer observed on other dates during DISCOVER-AQ. In addition, we will discuss scaling this measurement technique to satellite applications such as the Aerosols-Clouds-Ecosystems mission.

Hostetler, C. A.; Burton, S. P.; Ferrare, R. A.; Rogers, R. R.; Mueller, D.; Chemyakin, E.; Cook, A. L.; Harper, D. B.; Ziemba, L. D.; Beyersdorf, A. J.; Anderson, B. E.

2013-12-01

344

Evaluation of Cloud Microphysics in JMA-NHM Simulations Using Bin or Bulk Microphysical Schemes through Comparison with Cloud Radar Observations  

NASA Technical Reports Server (NTRS)

Numerical weather prediction (NWP) simulations using the Japan Meteorological Agency NonhydrostaticModel (JMA-NHM) are conducted for three precipitation events observed by shipborne or spaceborneW-band cloud radars. Spectral bin and single-moment bulk cloud microphysics schemes are employed separatelyfor an intercomparative study. A radar product simulator that is compatible with both microphysicsschemes is developed to enable a direct comparison between simulation and observation with respect to theequivalent radar reflectivity factor Ze, Doppler velocity (DV), and path-integrated attenuation (PIA). Ingeneral, the bin model simulation shows better agreement with the observed data than the bulk modelsimulation. The correction of the terminal fall velocities of snowflakes using those of hail further improves theresult of the bin model simulation. The results indicate that there are substantial uncertainties in the masssizeand sizeterminal fall velocity relations of snowflakes or in the calculation of terminal fall velocity of snowaloft. For the bulk microphysics, the overestimation of Ze is observed as a result of a significant predominanceof snow over cloud ice due to substantial deposition growth directly to snow. The DV comparison shows thata correction for the fall velocity of hydrometeors considering a change of particle size should be introducedeven in single-moment bulk cloud microphysics.

Iguchi, Takamichi; Nakajima, Teruyuki; Khain, Alexander P.; Saito, Kazuo; Takemura, Toshihiko; Okamoto, Hajime; Nishizawa, Tomoaki; Tao, Wei-Kuo

2012-01-01

345

Doppler radar signatures of developing thunderstorms and their potential to indicate the onset of cloud-to-ground lightning  

NASA Technical Reports Server (NTRS)

The capability of Doppler weather radars to short-term forecast the initiation of thunderstorms and the onset of cloud-to-ground (CG) lightning is examined. Doppler weather radar data from 28 thunderstorms were analyzed from August 1990 in the central Florida environment. These radar echoes were associated with CG lightning strike locations from the National Lightning Detection Network and two lightning detection systems operated by the U.S. Air Force in the vicinity of Kennedy Space Center. From a time history of these radar echoes it was found that a 10-dBZ echo, first detected near the freezing level, may be the first definitive echo of a future thunderstorm. This thunderstorm initiation signature is often accompanied by low-altitude convergence and divergence at the top of the radar echo. The observed lead times between this thunderstorm initiation signature and the first detected CG lightning strike ranged from 5 to 45 min with a median lead time of 15 min. All lightning-producing radar echoes were detected using the thunderstorm initiation signature; however, some echoes exceeded the 10-dBZ threshold and did not produce andy CG lightning. The charecteristics of the WSR-88D and Terminal Doppler Weather Radar systems are evaluated for their capability to detect the thunderstorm initiation signature in central Florida with sufficient temporal and spatial resolution.

Hondl, Kurt D.; Eilts, Michael D.

1994-01-01

346

DYNAMICS OF DUST PARTICLES RELEASED FROM OORT CLOUD COMETS AND THEIR CONTRIBUTION TO RADAR METEORS  

SciTech Connect

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 passages through the inner solar system, where strong thermal gradients can cause phase transitions or volatile pressure buildup. Here we study the fate of small debris particles produced by OCC disruptions to determine whether the imprints of a hypothetical population of OCC meteoroids can be found in the existing meteor radar data. We find that OCC particles with diameters D {approx}< 10 {mu}m are blown out from the solar system by radiation pressure, while those with D {approx}> 1 mm have a very low Earth-impact probability. The intermediate particle sizes, D {approx} 100 {mu}m, represent a sweet spot. About 1% of these particles orbitally evolve by Poynting-Robertson drag to reach orbits with semimajor axis a {approx} 1 AU. They are expected to produce meteors with radiants near the apex of Earth's orbital motion. We find that the model distributions of their impact speeds and orbits provide a good match to radar observations of apex meteors, except for the eccentricity distribution, which is more skewed toward e {approx} 1 in our model. Finally, we propose an explanation for the long-standing problem in meteor science related to the relative strength of apex and helion/antihelion sources. As we show in detail, the observed trend, with the apex meteors being more prominent in observations of highly sensitive radars, can be related to orbital dynamics of particles released on the long-period orbits.

Nesvorny, David; Vokrouhlicky, David; Pokorny, Petr [Department of Space Studies, Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, CO 80302 (United States); Janches, Diego [Space Weather Laboratory, Code 674, GSFC/NASA, Greenbelt, MD 20771 (United States)

2011-12-10

347

Dynamics of Dust Particles Released from Oort Cloud Comets and Their Contribution to Radar Meteors  

NASA Technical Reports Server (NTRS)

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 passages through the inner solar system, where strong thermal gradients can cause phase transitions or volatile pressure buildup. Here we study the fate of small debris particles produced by OCC disruptions to determine whether the imprints of a hypothetical population of OCC meteoroids can be found in the existing meteor radar data. We find that OCC particles with diameters D < or approx. 10 microns are blown out from the solar system by radiation pressure, while those with D > or approx. 1 mm have a very low Earth-impact probability. The intermediate particle sizes, D approx. 100 microns represent a sweet spot. About 1% of these particles orbitally evolve by Poynting-Robertson drag to reach orbits with semimajor axis a approx. 1 AU. They are expected to produce meteors with radiants near the apex of the Earth s orbital motion. We find that the model distributions of their impact speeds and orbits provide a good match to radar observations of apex meteors, except for the eccentricity distribution, which is more skewed toward e approx. 1 in our model. Finally, we propose an explanation for the long-standing problem in meteor science related to the relative strength of apex and helion/antihelion sources. As we show in detail, the observed trend, with the apex meteors being more prominent in observations of highly sensitive radars, can be related to orbital dynamics of particles released on the long-period orbits.

Nesvorny, David; Vokrouhlicky, David; Pokorny, Petr; Janches, Diego

2012-01-01

348

Measurements of the backscattering phase matrices of crystal clouds with a polarization lidar  

NASA Technical Reports Server (NTRS)

A polarization technique based on measurements of intensities of the polarized I(parallel) and crosspolarized I(perpendicular) components of scattered radiation is often used in lidar studies of aerosols. The ratio I(perp)/I(para) is related to nonsphericity of scattering particles and it is often called, though unjustified, depolarization. Correct definition of the term has previously been shown to be the value d = 1 - P, where P is the degree of polarization defined in terms of the Stokes parameters. In fact, measurements of I(para) and I(perp) enable one to determine the Stokes parameter Q = I(para) - I(perp), and under the condition U = V = 0 the depolarization is determined by the relationship d = 2 x I(perp)/(I(para) + I(perp)). In 1988 a new cycle of measuring the Stokes parameters of lidar returns from scattering media irradiated with a linearly polarized light was started. Based on the lidar data obtained during the 1988-1990 period, a classification of scattering ensembles was made which reveals five types of the scattering particle ensembles differing by a combination of the Stokes parameters. In the 1990-1991 period, a cycle of measurements of the lidar returns' Stokes parameters was carried out using sounding radiation.

Kaul, B. V.; Kuznetsov, A. L.; Polovtseva, E. R.

1992-01-01

349

Internet-Based Software Tools for Analysis and Processing of LIDAR Point Cloud Data via the OpenTopography Portal  

NASA Astrophysics Data System (ADS)

LIDAR is an excellent example of the new generation of powerful remote sensing data now available to Earth science researchers. Capable of producing digital elevation models (DEMs) more than an order of magnitude higher resolution than those currently available, LIDAR data allows earth scientists to study the processes that contribute to landscape evolution at resolutions not previously possible, yet essential for their appropriate representation. Along with these high-resolution datasets comes an increase in the volume and complexity of data that the user must efficiently manage and process in order for it to be scientifically useful. Although there are expensive commercial LIDAR software applications available, processing and analysis of these datasets are typically computationally inefficient on the conventional hardware and software that is currently available to most of the Earth science community. We have designed and implemented an Internet-based system, the OpenTopography Portal, that provides integrated access to high-resolution LIDAR data as well as web-based tools for processing of these datasets. By using remote data storage and high performance compute resources, the OpenTopography Portal attempts to simplify data access and standard LIDAR processing tasks for the Earth Science community. The OpenTopography Portal allows users to access massive amounts of raw point cloud LIDAR data as well as a suite of DEM generation tools to enable users to generate custom digital elevation models to best fit their science applications. The Cyberinfrastructure software tools for processing the data are freely available via the portal and conveniently integrated with the data selection in a single user-friendly interface. The ability to run these tools on powerful Cyberinfrastructure resources instead of their own labs provides a huge advantage in terms of performance and compute power. The system also encourages users to explore data processing methods and the variations in algorithm parameters since all of the processing is done remotely and numerous jobs can be submitted in sequence. The web-based software also eliminates the need for users to deal with the hassles and costs associated with software installation and licensing while providing adequate disk space for storage and personal job archival capability. Although currently limited to data access and DEM generation tasks, the OpenTopography system is modular in design and can be modified to accommodate new processing tools as they become available. We are currently exploring implementation of higher-level DEM analysis tasks in OpenTopography, since such processing is often computationally intensive and thus lends itself to utilization of cyberinfrastructure. Products derived from OpenTopography processing are available in a variety of formats ranging from simple Google Earth visualizations of LIDAR-derived hillshades to various GIS-compatible grid formats. To serve community users less interested in data processing, OpenTopography also hosts 1 km^2 digital elevation model tiles as well as Google Earth image overlays for a synoptic view of the data.

Nandigam, V.; Crosby, C. J.; Baru, C.; Arrowsmith, R.

2009-12-01

350

Active optical remote sensing of dense clouds with diffusing light : Early results, present implementations, and the challenges ahead  

SciTech Connect

We survey the rapid progress of 'off-beam' cloud lidar, from inception to validation via laboratory-scale simulations. Cloud observations from ground, aircraft and even space are covered. Finally, we describe future work in this instrument development effort born out of pure theory in the mid-1990s. We foresee a bright future for off-beam lidar which is, in essence, an atmospheric application of the general principles of optical diffuse-light tomography. The physical cloud-boundary information it delivers is, in principle, the same as given from ground or space (upcoming CloudSat mission) obtained by mm-radar. And mm-radar gives some information about internal variability. However, radar reflectivities quite often disagree with optical estimates of cloud base and optical thickness for well-understood reasons. So optical and microwave cloud probes are now considered as complimentary rather then competitive in our efforts to better understand cloud radiative properties in the context of climate research. We are confident that off-beam lidar will be a valuable and, ultimately, cost-effective source of information about cloud processes. In this, we include direct insight into the present issues in large-scale short-wave absorption based on unambiguous geometrical pathlength statistics, a unique capability of off-beam cloud lidar.

Davis, A. B. (Anthony B.); Cahalan, R. F. (Robert F.); Winker, D. M. (David M.)

2002-01-01

351

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

NASA Technical Reports Server (NTRS)

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.

1985-01-01

352

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; Knzi, Klaus F.

2002-10-01

353

Relationship between cloud base height retrieved from lidar and downward longwave irradiance  

NASA Astrophysics Data System (ADS)

Downward longwave radiation is a key process to understand the climate change, energy budget, and water cycle at the earth's surface. Cloud is a dominant factor to determine the intensity of longwave radiation. It is widely known that cloud cover and cloud base height (CBH) have strong effects on the downward longwave radiation, however there are not so many studies regarding the quantitative evaluation of relationship between cloud properties and downward longwave radiation. The intent of the present study is to quantify the impact of cloud property on the downward longwave irradiance (DLI). We used the data obtained with CGR-4 pyrgeometer at Tateno, Japan for the period from January 2002 to December 2011. Cloud radiative contribution fraction (CRC) is evaluated with a ratio of the difference of DLI between observation under cloudy sky without precipitation and calculation assumed clear-sky condition to the observed DLI. The difference between calculation and observation is -4.60+/-3.00 W/m2, and the calculation method reproduced to observation. Cloud is classified into three types by CBH, low (CBH<2000 m), middle (2000?CBH<5000 m), and high (CBH?5000 m). In the results, CRC is almost proportional and inverse proportional to cloud cover (CC) and CBH in the average, respectively. However, CRC for low cloud shows proportion to CBH because existence of low altitude cloud is related to large precipitable water (PW).

Yamada, Kyohei; Hayasaka, Tadahiro; Sugimoto, Nobuo

2012-11-01

354

Monitoring of the Polar Stratospheric Clouds formation and evolution in Antarctica in August 2007 during IPY with the MATCH method applied to lidar data  

NASA Astrophysics Data System (ADS)

The project ORACLE-O3 ("Ozone layer and UV RAdiation in a changing CLimate Evaluated during IPY") is one of the coordinated international proposals selected for the International Polar Year (IPY). As part of this global project, LOLITA-PSC ("Lagrangian Observations with Lidar Investigations and Trajectories in Antarctica and Arctic, of PSC") is devoted to Polar Stratospheric Clouds (PSC) studies. Indeed, understanding the formation and evolution of PSC is an important issue to quantify the impact of climate changes on their frequency of formation and, further, on chlorine activation and subsequent ozone depletion. In this framework, three lidar stations performed PSC observations in Antarctica during the 2006, 2007, and 2008 winters: Davis (68.58S, 77.97E), McMurdo (77.86S, 166.48E) and Dumont D'Urville (66.67S, 140.01E). The data are completed with the lidar data from CALIOP ("Cloud-Aerosol Lidar with Orthogonal Polarization") onboard the CALIPSO ("Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation") satellite. Lagrangian trajectory calculations are used to identify air masses with PSCs sounded by several ground-based lidar stations with the same method, called MATCH, applied for the first time in Arctic to study the ozone depletion with radiosoundings. The evolution of the optical properties of the PSCs and thus the type of PSCs formed (supercooled ternary solution, nitric acid trihydrate particles or ice particles) could thus be linked to the thermodynamical evolution of the air mass deduced from the trajectories. A modeling with the microphysical model of the Danish Meteorological Institute allows assessing our ability to predict PSCs for various environmental conditions. Indeed, from pressure and temperature evolution, the model allows retrieving the types of particles formed as well as their mean radii, their concentrations and could also simulate the lidar signals. In a first step, a case in August 2007 around 17-18 km, involving the three ground-based lidar stations and CALIOP has been selected. Trajectories with different models (gscf and ecmwf), grids and initializations have been computed to test the robustness of the MATCH. Then the DMI model has been used with these different trajectories to test its ability to reproduce the observations. For a same case, the temperature differences (~2-3 K) between the trajectories have a strong impact on the number density of the particles formed (factor 1000). This case is presented here in detail and a statistical comparison is planned with the numerous MATCH cases identified during the three winters and which involve most of the time two ground-based lidar stations with CALIOP.

Montoux, Nadege; David, Christine; Klekociuk, Andrew; Pitts, Michael; di Liberto, Luca; Snels, Marcel; Jumelet, Julien; Bekki, Slimane; Larsen, Niels

2010-05-01

355

Comparison of Cloud Properties from CALIPSO-CloudSat and Geostationary Satellite Data  

NASA Technical Reports Server (NTRS)

Cloud properties are being derived in near-real time from geostationary satellite imager data for a variety of weather and climate applications and research. Assessment of the uncertainties in each of the derived cloud parameters is essential for confident use of the products. Determination of cloud amount, cloud top height, and cloud layering is especially important for using these real -time products for applications such as aircraft icing condition diagnosis and numerical weather prediction model assimilation. Furthermore, the distribution of clouds as a function of altitude has become a central component of efforts to evaluate climate model cloud simulations. Validation of those parameters has been difficult except over limited areas where ground-based active sensors, such as cloud radars or lidars, have been available on a regular basis. Retrievals of cloud properties are sensitive to the surface background, time of day, and the clouds themselves. Thus, it is essential to assess the geostationary satellite retrievals over a variety of locations. The availability of cloud radar data from CloudSat and lidar data from CALIPSO make it possible to perform those assessments over each geostationary domain at 0130 and 1330 LT. In this paper, CloudSat and CALIPSO data are matched with contemporaneous Geostationary Operational Environmental Satellite (GOES), Multi-functional Transport Satellite (MTSAT), and Meteosat-8 data. Unlike comparisons with cloud products derived from A-Train imagers, this study considers comparisons of nadir active sensor data with off-nadir retrievals. These matched data are used to determine the uncertainties in cloud-top heights and cloud amounts derived from the geostationary satellite data using the Clouds and the Earth s Radiant Energy System (CERES) cloud retrieval algorithms. The CERES multi-layer cloud detection method is also evaluated to determine its accuracy and limitations in the off-nadir mode. The results will be useful for constraining the use of the passive retrieval data in models and for improving the accuracy of the retrievals.

Nguyen, L.; Minnis, P.; Chang, F.; Winker, D.; Sun-Mack, S.; Spangenberg, D.; Austin, R.

2007-01-01

356

Doppler Radar and Cloud-to-Ground Lightning Observations of a Severe Outbreak of Tropical Cyclone Tornadoes  

NASA Technical Reports Server (NTRS)

Data from a single WSR-88D Doppler radar and the National Lightning Detection Network are used to examine the characteristics of the convective storms that produced a severe tornado outbreak within Tropical Storm Beryl's remnants on 16 August 1994. Comparison of the radar data with reports of tornadoes suggests that only 12 cells produced the 29 tornadoes that were documented in Georgia and the Carolinas on that date. Six of these cells spawned multiple tornadoes, and the radar data confirm the presence of miniature supercells. One of the cells was identifiable on radar for 11 hours, spawning tornadoes over a time period spanning approximately 6.5 hours. Time-height analyses of the three strongest supercells are presented in order to document storm kinematic structure and evolution. These Beryl mini-supercells were comparable in radar-observed intensity but much more persistent than other tropical cyclone-spawned tornadic cells documented thus far with Doppler radars. Cloud-to-ground lightning data are also examined for all the tornadic cells in this severe swarm-type tornado outbreak. These data show many of the characteristics of previously reported heavy-precipitation supercells. Lightning rates were weak to moderate, even in the more intense supercells, and in all the storms the lightning flashes were almost entirely negative in polarity. No lightning at all was detected in some of the single-tornado storms. In the stronger cells, there is some evidence that lightning rates can decrease during tornadogenesis, as has been documented before in some midlatitude tornadic storms. A number of the storms spawned tornadoes just after producing their final cloud-to-ground lightning flashes. These findings suggest possible benefits from implementation of observing systems capable of monitoring intracloud as well as cloud-to-ground lightning activity.

McCaul, Eugene W., Jr.; Buechler, Dennis; Cammarata, Michael; Arnold, James E. (Technical Monitor)

2002-01-01

357

The relation of radar to cloud area-time integrals and implications for rain measurements from space  

NASA Technical Reports Server (NTRS)

The relationships between satellite-based and radar-measured area-time integrals (ATI) for convective storms are determined, and both are shown to depend on the climatological conditional mean rain rate and the ratio of the measured cloud area to the actual rain area of the storms. The GOES precipitation index of Arkin (1986) for convective storms, an area-time integral for satellite cloud areas, is shown to be related to the ATI for radar-observed rain areas. The quality of GPI-based rainfall estimates depends on how well the cloud area is related to the rain area and the size of the sampling domain. It is also noted that the use of a GOES cloud ATI in conjunction with the radar area-time integral will improve the accuracy of rainfall estimates and allow such estimates to be made in much smaller space-time domains than the 1-month and 5-deg boxes anticipated for the Tropical Rainfall Measuring Mission.

Atlas, David; Bell, Thomas L.

1992-01-01

358

Integrated framework for retrievals in a networked radar environment: Application to the Mid-latitude Continental Convective Clouds Experiment  

NASA Astrophysics Data System (ADS)

The Mid-Latitude Continental Convective Clouds Experiment (MC3E), was a joint DOE Atmospheric Radiation Measurement (ARM) and NASA Global Precipitation Measurements (GPM) field campaign that took place from April - June 2011 in Central Oklahoma centered at the ARM Southern Great Plains site. The experiment was a collaborative effort between the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility and the National Aeronautics and Space Administration (NASA) Global Precipitation Measurement (GPM) mission Ground Validation (GV) program. The field campaign involved a large suite of observing infrastructure currently available in the central United States, combined with an extensive sounding array, remote sensing and in situ aircraft observations, NASA GPM ground validation remote sensors, and new ARM instrumentation. The overarching goal was to provide the most complete characterization of convective cloud systems, precipitation, and the environment that has ever been obtained, providing constraints for model cumulus parameterizations and space-based rainfall retrieval algorithms over land that had never before been available. The experiment consisted of a large number of ground radars, including NASA scanning dual-polarization radar systems (NPOL) at S-band, wind profilers, and a dense network of surface disdrometers. In addition to these special MC3E instruments, there were three networked scanning X-band radar systems, four wind profilers, a C-band scanning radar, a dual-wavelength (Ka/W) scanning cloud radar. There is extensive literature on the retrieval algorithms for precipitation and cloud parameters from single frequency, dual-polarization radar systems. With the cost of instruments such as radars becoming more affordable, multiple radar deployments are becoming more common in special programs, and the MC3E is a text book example of such a deployment. Networked deployments are becoming more common popularized by the CASA program, resulting in networked retrievals which was initially used for attenuation mitigation. Since then Networked retrievals have expanded reach to include retrieval of DSDs from networked X-band or Ku-band radars. All the above retrieval methodologies were for homogeneous, single frequency systems; however the multi frequency nature of the deployment during the MC3E program is the motivation for the integrated formulation presented in this paper. This paper presents a comprehensive integrated retrieval methodology to obtain microphysical retrieval such as the drop size distribution for the complete MC3E network, for the multi frequency radar systems. References Chandrasekar, V., et al. (2010), "The CASA IP Test-bed after 5 Years Operation: Accomplishments, Breakthroughs, Challenges and Lessons Learned.", (2010) Proceedings of the Sixth European Conference on Radar Meteorology and Hydrology. Sibiu, 2012 Jensen, MP, et al.(2011), Midlatitude Continental Convective Clouds Experiment (MC3E). ARM Climate Facility: U.S. Department of Energy. Yoshikawa, Ei-ichi, V Chandrasekar, Tamoo Ushio, and Zen Kawasaki.(2012), "Bayesian Formulation of DSD Retrieval Algorithm for Dual-Polarized X-Band Weather Radar Network." Proceedings of IGARSS 2012. Munich: Proceedings of the IGARSS 2012.

Hardin, J. C.; Chandrasekar, C. V.; Yoshikawa, E.; Ushio, T.

2012-12-01

359

Spaceborne lidar observations of the ice-nucleating potential of dust, polluted dust, and smoke aerosols in mixed-phase clouds  

NASA Astrophysics Data System (ADS)

Previous laboratory studies and in situ measurements have shown that dust particles possess the ability to nucleate ice crystals, and smoke particles to some extent as well. Even with coatings of pollutants such as sulphate and nitrate on the surface of dust particles, it has been shown that polluted dust particles are still able to nucleate ice in the immersion, deposition, condensation, and contact freezing modes, albeit less efficiently than unpolluted dust. The ability of these aerosols to act as ice nuclei in the Earth's atmosphere has important implications for the Earth's radiative budget and hence global climate change. Here we determine the relationship between cloud thermodynamic phase and dust, polluted dust, and smoke aerosols individually by analyzing their vertical profiles over a 5 year period obtained by NASA's spaceborne lidar, Cloud-Aerosol Lidar with Orthogonal Polarization. We found that when comparing the effects of temperature and aerosols, temperature appears to have the dominant influence on supercooled liquid cloud fraction. Nonetheless, we found that aerosols still appear to exert a strong influence on supercooled liquid cloud fraction as suggested by the existence of negative temporal and spatial correlations between supercooled liquid cloud fraction and frequencies of dust aerosols from around the world, at the -10C, -15C, -20C, and -25C isotherms. Although smoke aerosol frequencies were also found to be negatively correlated with supercooled liquid cloud fraction, their correlations are weaker in comparison to those between dust frequencies and supercooled liquid cloud fraction. For the first time, we show this based on observations from space, which lends support to previous studies that dust and potentially smoke aerosols can globally alter supercooled liquid cloud fraction. Our results suggest that the ice-nucleating ability of these aerosols may have an indirect climatic impact that goes beyond the regional scale, by influencing cloud thermodynamic phase globally.

Tan, Ivy; Storelvmo, Trude; Choi, Yong-Sang

2014-06-01

360

Analysis of Aircraft, Radiosonde and Radar Observations in Cirrus Clouds Observed During FIRE II: The Interactions Between Environmental Structure, Turbulence and Cloud Microphysical Properties  

NASA Technical Reports Server (NTRS)

Ways to determine the turbulence intensity and the horizontal variability in cirrus clouds have been investigated using FIRE-II aircraft, radiosonde and radar data. Higher turbulence intensities were found within some, but not all, of the neutrally stratified layers. It was also demonstrated that the stability of cirrus layers with high extinction values decrease in time, possibly as a result of radiative destabilization. However, these features could not be directly related to each other in any simple manner. A simple linear relationship was observed between the amount of horizontal variability in the ice water content and its average value. This was also true for the extinction and ice crystal number concentrations. A relationship was also suggested between the variability in cloud depth and the environmental stability across the depth of the cloud layer, which requires further investigation.

Smith, Samantha A.; DelGenio, Anthony D.

1999-01-01

361

Cloud Physics Lidar Optical Measurements During the SAFARI-2000 Field Campaign  

NASA Technical Reports Server (NTRS)

In this presentation, we will show new optical data processing results from the Cloud Physics War during SAFARI-2000. Retrieved products include aerosol and cloud layer location and identification, layer optical depths, vertical extinction profiles, and extinction-to-backscatter (S) ratios for 532 and 1064 nm. The retrievals will focus on the persistent and smoky planetary boundary layer and occasional elevated aerosol layers found in southern Africa during August and September 2000.

Hlavka, Dennis L.; McGill, Matt; Hart, William D.; Spinhirne, James D.; Starr, David OC. (Technical Monitor)

2002-01-01

362

Integrated Cloud-Aerosol-Radiation Product using CERES, MODIS, CALIPSO and CloudSat Data  

NASA Technical Reports Server (NTRS)

This paper documents the development of the first integrated data set of global vertical profiles of clouds, aerosols, and radiation using the combined NASA A-Train data from the Aqua Clouds and Earth's Radiant Energy System (CERES) and Moderate Resolution Imaging Spectroradiometer (MODIS), Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), and CloudSat. As part of this effort, cloud data from the CALIPSO lidar and the CloudSat radar are merged with the integrated column cloud properties from the CERES-MODIS analyses. The active and passive datasets are compared to determine commonalities and differences in order to facilitate the development of a 3- dimensional cloud and aerosol dataset that will then be integrated into the CERES broadband radiance footprint. Preliminary results from the comparisons for April 2007 reveal that the CERES-MODIS global cloud amounts are, on average, 0.14 less and 0.15 greater than those from CALIPSO and CloudSat, respectively. These new data will provide unprecedented ability to test and improve global cloud and aerosol models, to investigate aerosol direct and indirect radiative forcing, and to validate the accuracy of global aerosol, cloud, and radiation data sets especially in polar regions and for multi-layered cloud conditions.

Sun-Mack, Sunny; Minnis, Patrick; Chen, Yan; Gibson, Sharon; Yi, Yuhong; Trepte, Qing; Wielicki, Bruce; Kato, Seiji; Winker, Dave

2007-01-01

363

Lidar Ratios for Dust Aerosols Derived From Retrievals of CALIPSO Visible Extinction Profiles Constrained by Optical Depths from MODIS-Aqua and CALIPSO/CloudSat Ocean Surface Reflectance Measurements  

NASA Technical Reports Server (NTRS)

CALIPSO's (Cloud Aerosol Lidar Infrared Pathfinder Satellite Observations) analysis algorithms generally require the use of tabulated values of the lidar ratio in order to retrieve aerosol extinction and optical depth from measured profiles of attenuated backscatter. However, for any given time or location, the lidar ratio for a given aerosol type can differ from the tabulated value. To gain some insight as to the extent of the variability, we here calculate the lidar ratio for dust aerosols using aerosol optical depth constraints from two sources. Daytime measurements are constrained using Level 2, Collection 5, 550-nm aerosol optical depth measurements made over the ocean by the MODIS (Moderate Resolution Imaging Spectroradiometer) on board the Aqua satellite, which flies in formation with CALIPSO. We also retrieve lidar ratios from night-time profiles constrained by aerosol column optical depths obtained by analysis of CALIPSO and CloudSat backscatter signals from the ocean surface.

Young, Stuart A.; Josset, Damien B.; Vaughan, Mark A.

2010-01-01

364

Installation of a Permanent Doppler Radar Monitoring System at Colima Volcano, Mexico, and its use for Eruption Cloud Modelling  

NASA Astrophysics Data System (ADS)

In February 2007 we installed a standalone Doppler radar monitoring station at Colima volcano, Mexico. During that time, a new episode of dome growth was underway with daily Vulcanian eruptive events occurring. These were continuously recorded with the Doppler radar. In December 2008 we upgraded the monitoring station with a second Doppler radar, a network video camera, and a direct WLAN connection to the 28.5km distant Colima University, which allows us to remotely reconfigure the whole system in times of volcanic crises. A custom made data logger collects and stores all data at the station before transmitting data in packages to the office. The entire system is powered by solar panels. The camera is triggered by the Doppler radar that is aimed at the vent. In case an eruption is detected, the camera switches from taking pictures at arbitrary intervals to continuous video recording until the end of the eruption. Similarly the Doppler radar switches to a high sampling rate (15Hz). In 2007 we recorded 92 events during six months with durations of 20 to 200 seconds. The velocity spectra clearly show two regimes: (a) buoyant updraft with 20 to 60 seconds of constant velocities and a maximum of 20 m/s (vertical) and (b) series of pulses of intense jetting where every pulse lasts about 20s and starts with vertical velocities up to 85 m/s (measured ~75m above vent). Our deployment at Colima volcano is the first investigation of Vulcanian eruption column dynamics using Doppler radar. The data provide particle velocities and a proxy of the particles mass ~75m above the vent, which allows us to define the activity status in near real time during an eruption. Here we focus on the dynamic processes during the early stages of eruption cloud formation. Using (1) a simple ballistic model for particle transport and (2) the active tracer high-resolution atmospheric model (ATHAM) we model the first 100 m of cloud formation in 2D (axis-symmetric) and 3D. We constrain the initial conditions for both models trying to reproduce the dynamics measured by the radars. For this comparison synthetic Doppler radar data are calculated from the numerical models by converting particle properties (size, velocity, and backscatter-efficiency) into synthetic velocity spectra. First results show that pure ballistic transport of particles in a gas jet cannot reproduce the measured spectra. Eruption clouds are a major hazard to aviation. Hence real-time tracking and forecasting of ash clouds are increasingly important tasks in volcanology. In-situ measurements of the dynamics inside the developing cloud are needed to constrain the input parameters of the Volcanic Ash Advisory Center's (VAAC) numerical ash cloud dispersion models. Our aim is to directly deduce the initial conditions for an eruption column model or ash dispersal model from the radar data in near-real time.

Scharff, L.; Hort, M. K.; Varley, N. R.; Herzog, M.

2011-12-01

365

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

366

Cloud and Aerosol Lidar Channel Design and Performance of the Geoscience Laser Altimeter System on the ICESat Mission  

NASA Technical Reports Server (NTRS)

The design of the 532 and 1064nm wavelength atmosphere lidar channels of the Geoscience Laser Altimeter System on the ICESat spacecraft is described. The lidar channel performance per on orbit measurements data will be presented.

Sun, Xiaoli; Abshire, James B.; Krainak, Michael A.; Spinhirne, James D.; Palm, Steve S.; Lancaster, Redgie S.; Allan, Graham R.

2004-01-01

367

Atmospheric Boundary Layer and Clouds wind speed profile measurements with the new compact long range wind Lidar WindCube(TM) WLS70  

NASA Astrophysics Data System (ADS)

To fully understand atmospheric dynamics, climate studies, energy transfer, and weather prediction the wind field is one of the most important atmospheric state variables. Small scales variability and low atmospheric layers are not described with sufficient resolution up to now. To answer these needs, the WLS70 long-range wind Lidar is a new generation of wind Lidars developed by LEOSPHERE, derived from the commercial WindCube Lidar widely used by the wind power industry and well-known for its great accuracy and data availability. The WLS70 retrieves the horizontal and vertical wind speed profiles as well as the wind direction at various heights simultaneously inside the boundary layer and cloud layers. The amplitude and spectral content of the backscattering signal are also available. From raw data, the embedded signal processing software performs the computation of the aerosol Doppler shift and backscattering coefficient. Higher values of normalized relative backscattering (NRB) are proportional to higher aerosol concentration. At 1540 nm, molecular scattering being negligible, it is then possible to directly retrieve the Boundary Layer height evolution observing the height at which the WindCube NRB drops drastically. In this work are presented the results of the measurements obtained during the LUAMI campaign that took place in Lindenberg, at the DWD (Deutscher WetterDienst) meteorological observatory, from November 2008 to January 2009. The WLS70 Lidar instrument was placed close together with an EZ Lidar ALS450, a rugged and compact eye safe aerosol Lidar that provides a real time measurement of backscattering and extinction coefficients, aerosol optical depth (AOD), automatic detection of the planetary boundary layer (PBL) height and clouds base and top from 100m up to more than 20km. First results put in evidence wind shear and veer phenomena as well as strong convective effects during the raise of the mixing layer or before rain periods. Wind speed profiles and atmospheric structures (PBL height, clouds top and base) are retrieved from the WLS Lidar data with outstanding time resolution (10s per profile), spatial resolution (50m) and velocity resolution (0.4m/s) for a heights range from 100m to 2km. Intercomparison results with wind profilers and cup anemometers are also available. Due to its robustness and fully transportability (95x65x55cm dimensions and 50kg weight), together with velocity resolution, range and temporal resolutions of 0.4 m/s, 50m, 10s, are potentially useful for a range of boundary layer meteorology applications where punctual measurements in the micro and mesoscale are required.

Boquet, M.; Cariou, J. P.; Sauvage, L.; Lolli, S.; Parmentier, R.; Loaec, S.

2009-04-01

368

Automatic Roof Plane Detection and Analysis in Airborne Lidar Point Clouds for Solar Potential Assessment  

PubMed Central

A relative height threshold is defined to separate potential roof points from the point cloud, followed by a segmentation of these points into homogeneous areas fulfilling the defined constraints of roof planes. The normal vector of each laser point is an excellent feature to decompose the point cloud into segments describing planar patches. An object-based error assessment is performed to determine the accuracy of the presented classification. It results in 94.4% completeness and 88.4% correctness. Once all roof planes are detected in the 3D point cloud, solar potential analysis is performed for each point. Shadowing effects of nearby objects are taken into account by calculating the horizon of each point within the point cloud. Effects of cloud cover are also considered by using data from a nearby meteorological station. As a result the annual sum of the direct and diffuse radiation for each roof plane is derived. The presented method uses the full 3D information for both feature extraction and solar potential analysis, which offers a number of new applications in fields where natural processes are influenced by the incoming solar radiation (e.g., evapotranspiration, distribution of permafrost). The presented method detected fully automatically a subset of 809 out of 1,071 roof planes where the arithmetic mean of the annual incoming solar radiation is more than 700 kWh/m2. PMID:22346695

Jochem, Andreas; Hofle, Bernhard; Rutzinger, Martin; Pfeifer, Norbert

2009-01-01

369

A Variational Method to Retrieve the Extinction Profile in Liquid Clouds Using Multiple-Field-of-View Lidar  

E-print Network

-Field-of-View Lidar NICOLA L. POUNDER AND ROBIN J. HOGAN Department of Meteorology, University of Reading, Reading, but it is difficult to retrieve their vertical profile remotely. Ordinary narrow-field-of-view (FOV) lidars receive-angle multiple-FOV lidars can isolate radiation that is scattered multiple times before returning

Hogan, Robin

370

Size distribution time series of a polar stratospheric cloud observed above Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) (69N) 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

371

Frequency of tropical precipitating clouds as observed by the Tropical Rainfall Measuring Mission Precipitation Radar and  

E-print Network

Precipitation Radar and ICESat/Geoscience Laser Altimeter System Sean P. F. Casey,1 Andrew E. Dessler,1) Precipitation Radar (PR). Fractional areal coverage (FAC) data is calculated at each of the three levels Rainfall Measuring Mission Precipitation Radar and ICESat/Geoscience Laser Altimeter System, J. Geophys

372

Modeling of apparent radar reflectivity due to convective clouds at attenuating wavelengths  

E-print Network

; published 4 January 2003. [1] Spaceborne precipitation radars are usually designed to operate at attenuating Dynamics: Precipitation (1854); KEYWORDS: rainfall, microwave radar, attenuating wavelength, radiative and airborne radar sensing and profil- ing of precipitation has been well established in the last two decades

Marzano, Frank Silvio

373

Observations of ice motion changes at the terminus of Hubbard Glacier using co-located ground-based radar interferometer and LiDAR scanning systems (Invited)  

NASA Astrophysics Data System (ADS)

The tidewater terminus of Hubbard Glacier extends into Disenchantment Bay and currently blocks most of the mouth of Russell Fjord. Recent advances of Hubbard Glacier (1986 and 2002) caused the damming of Russell Fjord, creating one of the largest glacier-dammed lakes on the continent and exposing the community of Yakutat to a host of potential hazards. Detailed observations of the terminus of Hubbard Glacier were conducted during a field campaign in May 2013. Ground-based radar interferometer (GBRI) and ground-based light detection and ranging (LiDAR) scanning systems were deployed to observe changes in ice motion in response to calving events and tidal cycles. GBRI and LiDAR units were co-located and data acquisition was synchronized to maximize data recovery and to aid inter-system comparisons. Observations from ground-based scanners were also compared to meteorological and tidal measurements and to time-lapse photography and satellite data. Both ground-based scanning systems capture ice motion at very high resolution, but each offer specific technical and logistical advantages. The combination of these ground-based remote sensing techniques allows us to quantify high-frequency changes in the velocity and surface deformation at the terminus of Hubbard Glacier and to develop a better understanding of the mechanisms associated with advancing tidewater termini.

Wolken, G. J.; Finnegan, D. C.; Sharp, M. J.; LeWinter, A.; Fahnestock, M. A.; Stevens, R.

2013-12-01

374

Lidar observations of polar stratospheric clouds at the South Pole: 2. Stratospheric perturbed conditions, 1992 and 1993  

NASA Astrophysics Data System (ADS)

Observations of polar stratospheric clouds (PSCs), carried out at the Amundsen Scott South Pole Station by lidar from May 1992 through October 1993, are reported and compared with previously obtained results. At that time the Antarctic stratosphere was loaded with sulfuric acid aerosol due to the eruptions of Mount Pinatubo, primarily, and of Mount Hudson. The seasonal evolution of the backscatter profiles has been investigated in relation to the presence of the volcanic aerosol and to the processes of PSC formation, particle sedimentation, and dehydration. During the first winter after the eruptions the PSC activity was more intense than in the following year, particularly above 12.5 km, where the amount of volcanic aerosol was larger in 1992 than in 1993. At lower altitudes the volcanic aerosol loading as well as the PSC phenomenon were comparable during the 2 years. No substantial changes in the signal due to the volcanic aerosol has been observed comparing the backscattering profiles before and after the PSC periods (June-September), except for a downward shift, attributed to the subsidence of the air inside the polar vortex. It is concluded that only a small fraction of the aerosol particles, probably those with the largest radii, were involved in the nucleation of PSC particles.

Cacciani, Marco; Colagrande, Paola; di Sarra, Alcide; Fu, Daniele; di Girolamo, Paolo; Fiocco, Giorgio

1997-06-01

375

Energetics of persistent turbulent layers underneath mid-level clouds estimated from concurrent radar and radiosonde data  

NASA Astrophysics Data System (ADS)

Two Japanese-French field campaigns devoted to studying small-scale turbulence and instabilities in the lower atmosphere were conducted in September 2011 and November 2012 at the Shigaraki Middle and Upper atmosphere (MU) Observatory (34.85N, 136.15E; Japan). The Very High Frequency Middle and Upper atmosphere radar (MUR) was operated with a time resolution of the order of 10 s in range imaging mode allowing echo power measurements at fine range-resolutions (typically, a few tens of meters). In addition, balloons instrumented with RS92G Vaisala radiosondes were launched from the observatory during the radar operations. From the raw data of temperature, pressure and humidity, temperature turbulent layers can be identified from the detection of overturns by using the Thorpe (1977) method. During the two campaigns, both radar and balloon data revealed turbulent layers of about 1.0 km in depth, underneath mid-level clouds and meteorological frontal zones. They persisted for about 10 h in the radar data. The balloon data collected were undoubtedly representative of the conditions met by the radar. Turbulence parameters associated with stably stratified flows were tentatively estimated by using different methods involving both radar and balloon observations for 4 balloon flights. These parameters included the Thorpe, buoyancy, and Ozmidov scales LT, LB and LO, potential and kinetic turbulent energies TPE and TKE, potential kinetic energy dissipation rates ?P and ?K and turbulent diffusivities K?. The turbulence scales were found to be consistent between each other within a factor of about 2. Energy dissipation rates of 0.6 mW/kg were found for 3 cases and 0.06 mW/kg for one case.

Wilson, R.; Luce, H.; Hashiguchi, H.; Nishi, N.; Yabuki, Y.

2014-10-01