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1

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 near­continuous dataset of observations by cloud radar, lidar ceilometer and drop to the proposed ESA Earth Radiation Mission, and in this study we examine the frequency distribution of radar

Hogan, Robin

2

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 recognition of the usefulness of cloud radar for evaluating numerous aspects of the representation of clouds.j.hogan@reading.ac.uk. 1http://www.met.rdg.ac.uk/radar/cloudnet/ 2http://www.arm.gov/ are regular 6-hourly radiosonde

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 recognition of the usefulness of cloud radar for evaluating numerous aspects of the representation of clouds, UK. E­mail: r.j.hogan@reading.ac.uk. 1 http://www.met.rdg.ac.uk/radar/cloudnet/ 2 http

Hogan, Robin

4

Combined vertical-velocity observations with Doppler lidar, cloud radar and wind profiler  

NASA Astrophysics Data System (ADS)

Case studies of combined vertical-velocity measurements of Doppler lidar, cloud radar and wind profiler are presented. The measurements were taken at the Meteorological Observatory Lindenberg, Germany. Synergistic products are presented that are derived from the vertical-velocity measurements of the three instruments: A comprehensive classification mask of vertically moving atmospheric targets and the terminal fall velocity of water droplets and ice crystals corrected for vertical air motion. It is shown that the measurements of the Doppler lidar can extent the view of the cloud radar and the wind profiler, especially when observing clouds.

Bhl, J.; Leinweber, R.; Grsdorf, U.; Radenz, M.; Ansmann, A.; Lehmann, V.

2015-01-01

5

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

E-print Network

- erties such as cloud particle size, cloud temperature, cloud phase, water vapor and aerosol abundanceEvaluation of Cloud-Phase Retrieval Methods for SEVIRI on Meteosat-8 Using Ground-Based Lidar-phase retrievals obtained from cloud radar and lidar observations at Cabauw, Netherlands. Three aspects

Stoffelen, Ad

6

A variational scheme for retrieving ice cloud properties from combined radar, lidar, and infrared radiometer  

NASA Astrophysics Data System (ADS)

A variational method is described for retrieving profiles of visible extinction coefficient, ice water content and effective radius in ice clouds using the combination of ground-based or spaceborne radar, lidar and infrared radiometer. The forward model includes effects such as non-Rayleigh scattering by the radar and molecular and multiple scattering by the lidar. By rigorous treatment of errors and a careful choice of state variables and associated a priori estimates, a seamless retrieval is possible between regions of the cloud detected by both radar and lidar and regions detected by just one of these two instruments. Thus, when the lidar signal is unavailable (for reasons such as strong attenuation), the retrieval tends toward an empirical relationship using radar reflectivity factor and temperature, and when the radar signal is unavailable (such as in optically thin cirrus), accurate retrievals are still possible from the combination of lidar and radiometer. The method is tested first on simulated profiles from aircraft data and then on real observations taken in West Africa. It would be straightforward to expand the approach to include other measurements simply by including a forward model for them.

Delano, Julien; Hogan, Robin J.

2008-04-01

7

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

8

Comparison of cloud boundaries measured with 8.6 mm radar and 10.6 micrometer lidar  

NASA Technical Reports Server (NTRS)

One of the most basic cloud properties is location; the height of cloud base and the height of cloud top. The glossary of meteorology defines cloud base (top) as follows: 'For a given cloud or cloud layer, that lowest (highest) level in the atmosphere at which the air contains a perceptible quantity of cloud particles.' Our studies show that for a 8.66 mm radar, and a 10.6 micrometer lidar, the level at which cloud hydrometers become 'perceptible' can vary significantly as a function of the different wavelengths, powers, beamwidths and sampling rates of the two remote sensors.

Uttal, Taneil; Intrieri, Janet M.

1993-01-01

9

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

10

Cirrus Clouds Optical, Microphysical and Radiative Properties Observed During Crystal-Face Experiment: I. A Radar-Lidar Retrieval System  

NASA Technical Reports Server (NTRS)

A method of retrieving cloud microphysical properties using combined observations from both cloud radar and lidar is introduced. This retrieval makes use of an improvement to the traditional optimal estimation retrieval method, whereby a series of corrections are applied to the state vector during the search for an iterative solution. This allows faster convergence to a solution and is less processor intensive. The method is first applied to a synthetic cloud t o demonstrate its validity, and it is shown that the retrieval reliably reproduces vertical profiles of ice water content. The retrieval method is then applied to radar and lidar observations from the CRYSTAL-FACE experiment, and vertical profiles of ice crystal diameter, number concentration, and ice water content are retrieved for a cirrus cloud layers observed one day of that experiment. The validity of the relationship between visible extinction coefficient and radar reflectivity was examined. While synthetic tests showed such a functional relationship, the measured data only partially supported such a conclusion. This is due to errors in the forward model (as explained above) as well as errors in the data sets, including possible mismatch between lidar and radar profiles or errors in the optical depth. Empirical relationships between number concentrations and mean particle diameter were also examined. The results indicate that a distinct and robust relationship exists between these retrieved quantities and it is argued that such a relationship is more than an artifact of the retrieval process offering insight into the nature of the microphysical processes taking place in cirrus.

Mitrescu, C.; Haynes, J. M.; Stephens, G. L.; Heymsfield, G. M.; McGill, M. J.

2004-01-01

11

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

12

Vertical Cloud Climatology During TC4 Derived from High-Altitude Aircraft Merged Lidar and Radar Profiles  

NASA Technical Reports Server (NTRS)

Aircraft lidar works by shooting laser pulses toward the earth and recording the return time and intensity of any of the light returning to the aircraft after scattering off atmospheric particles and/or the Earth s surface. The scattered light signatures can be analyzed to tell the exact location of cloud and aerosol layers and, with the aid of a few optical assumptions, can be analyzed to retrieve estimates of optical properties such as atmospheric transparency. Radar works in a similar fashion except it sends pulses toward earth at a much larger wavelength than lidar. Radar records the return time and intensity of cloud or rain reflection returning to the aircraft. Lidar can measure scatter from optically thin cirrus and aerosol layers whose particles are too small for the radar to detect. Radar can provide reflection profiles through thick cloud layers of larger particles that lidar cannot penetrate. Only after merging the two instrument products can accurate measurements of the locations of all layers in the full atmospheric column be achieved. Accurate knowledge of the vertical distribution of clouds is important information for understanding the Earth/atmosphere radiative balance and for improving weather/climate forecast models. This paper describes one such merged data set developed from the Tropical Composition, Cloud and Climate Coupling (TC4) experiment based in Costa Rica in July-August 2007 using the nadir viewing Cloud Physics Lidar (CPL) and the Cloud Radar System (CRS) on board the NASA ER-2 aircraft. Statistics were developed concerning cloud probability through the atmospheric column and frequency of the number of cloud layers. These statistics were calculated for the full study area, four sub-regions, and over land compared to over ocean across all available flights. The results are valid for the TC4 experiment only, as preferred cloud patterns took priority during mission planning. The TC4 Study Area was a very cloudy region, with cloudy profiles occurring 94 percent of the time during the ER-2 flights. One to three cloud layers were common, with the average calculated at 2.03 layers per profile. The upper troposphere had a cloud frequency generally over 30%, reaching 42 percent near 13 km during the study. There were regional differences. The Caribbean was much clearer than the Pacific regions. Land had a much higher frequency of high clouds than ocean areas. One region just south and west of Panama had a high probability of clouds below 15 km altitude with the frequency never dropping below 25% and reaching a maximum of 60% at 11-13 km altitude. These cloud statistics will help characterize the cloud volume for TC4 scientists as they try to understand the complexities of the tropical atmosphere.

Hlavka, Dennis; Tian, Lin; Hart, William; Li, Lihua; McGill, Matthew; Heymsfield, Gerald

2009-01-01

13

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

NASA Astrophysics Data System (ADS)

The CloudSat satellite supports a W-band (94 GHz) cloud profiling radar. At this 3.2 mm wavelength, ground-based measurements of rainfall associated with melting snowflakes do not show the radar reflectivity peak that is characteristic of bright band measurements at longer (Rayleigh scattering-dominated) wavelengths. Nonetheless, examination of downward-looking CloudSat returns in precipitation often indicate an obvious signal peak in the melting region. Through melting layer microphysical and scattering model simulations, we demonstrate that this downward-viewing radar feature is analogous to the lidar bright band observed from the ground in that it owes its existence to strong attenuation. In the upward-looking lidar case, the strong attenuation comes from large low-density snowflakes. In the downward-looking 94 GHz radar case, it is due to the effects of the greater refractive index of water particles compared to ice: it is comparable to an upside-down lidar bright band. A W-band radar dark band, which contributes to the visibility of the bright band, is shown to be due to attenuation in the snowfall. For comparison, the bright and dark bands for an upward viewing lidar are also modeled: the latter is simulated by a reduction in light backscattering efficiency of ice-containing raindrops.

Sassen, Kenneth; Matrosov, Sergey; Campbell, James

2007-08-01

14

Comparison of Airborne In Situ, Airborne RadarLidar, and Spaceborne RadarLidar Retrievals of Polar Ice Cloud Properties Sampled during the POLARCAT Campaign  

E-print Network

of Polar Ice Cloud Properties Sampled during the POLARCAT Campaign JULIEN DELANOE¨ ,* ALAIN PROTAT,1 OLIVIER JOURDAN,# JACQUES PELON,@ MATHIEU PAPAZZONI,@ RE´ GIS DUPUY,# JEAN-FRANCOIS GAYET,# AND CAROLINE, for studying cloud processes and evaluating satellite products when satellite overpasses are available

Protat, Alain

15

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

E-print Network

, the statistical relationship used to produce ice water content from extinction and air temperature obtained ice clouds, but that the temperature dependence of the statistical relationship used should) ABSTRACT In this paper, the statistical properties of tropical ice clouds (ice water content, visible

Protat, Alain

16

The Cloud Radar System  

NASA Technical Reports Server (NTRS)

Improvement in our understanding of the radiative impact of clouds on the climate system requires a comprehensive view of clouds including their physical dimensions, dynamical generation processes, and detailed microphysical properties. To this end, millimeter vave radar is a powerful tool by which clouds can be remotely sensed. The NASA Goddard Space Flight Center has developed the Cloud Radar System (CRS). CRS is a highly sensitive 94 GHz (W-band) pulsed-Doppler polarimetric radar that is designed to fly on board the NASA high-altitude ER-2 aircraft. The instrument is currently the only millimeter wave radar capable of cloud and precipitation measurements from above most all clouds. Because it operates from high-altitude, the CRS provides a unique measurement perspective for cirrus cloud studies. The CRS emulates a satellite view of clouds and precipitation systems thus providing valuable measurements for the implementation and algorithm validation for the upcoming NASA CloudSat mission that is designed to measure ice cloud distributions on the global scale using a spaceborne 94 GHz radar. This paper describes the CRS instrument and preliminary data from the recent Cirrus Regional Study of Tropical Anvils and Cirrus Layers - Florida Area Cirrus Experiment (CRYSTAL-FACE). The radar design is discussed. Characteristics of the radar are given. A block diagram illustrating functional components of the radar is shown. The performance of the CRS during the CRYSTAL-FACE campaign is discussed.

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

2003-01-01

17

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. Introduction Lidar and radar have been used extensively from the ground to study clouds (Ackerman and Stokes in combined radar­lidar retrievals of ice clouds from space, the retrieved optical depth

Hogan, Robin

18

Vertical Motion Long-Term Lidar and Radar Observations of Arctic Stratus at Two Locations  

E-print Network

Vertical Motion Long-Term Lidar and Radar Observations of Arctic Stratus at Two Locations Gijs de.D.Shupe ( NOAA Earth System Research Laboratory ) P 2.20 Mixed-Phase Arctic Stratus Long-Term Stratus Properties-located with a NOAA Millimeter Cloud Radar (MMCR). Mixed phase stratus has been readily de- tected at both locations

Eloranta, Edwin W.

19

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 of the cloud. A similar effect occurs for spaceborne millimeter-wave radar observations of deep convective well in comparison to Monte Carlo calculations (for both radar and lidar) but is much more efficient

Hogan, Robin

20

Raman LIDAR Detection of Cloud Base  

NASA Technical Reports Server (NTRS)

Advantages introduced by Raman lidar systems for cloud base determination during precipitating periods are explored using two case studies of light rain and virga conditions. A combination of the Raman lidar derived profiles of water vapor mixing ratio and aerosol scattering ratio, together with the Raman scattered signals from liquid drops, can minimize or even eliminate some of the problems associated with cloud boundary detection using elastic backscatter lidars.

Demoz, Belay; Starr, David; Whiteman, David; Evans, Keith; Hlavka, Dennis; Peravali, Ravindra

1999-01-01

21

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

22

Lidar  

NASA Technical Reports Server (NTRS)

Lidar is an optical radar technique employing laser energy. Variations in signal intensity as a function of range provide information on atmospheric constituents, even when these are too tenuous to be normally visible. The theoretical and technical basis of the technique is described and typical values of the atmospheric optical parameters given. The significance of these parameters to atmospheric and meteorological problems is discussed. While the basic technique can provide valuable information about clouds and other material in the atmosphere, it is not possible to determine particle size and number concentrations precisely. There are also inherent difficulties in evaluating lidar observations. Nevertheless, lidar can provide much useful information as is shown by illustrations. These include lidar observations of: cirrus cloud, showing mountain wave motions; stratification in clear air due to the thermal profile near the ground; determinations of low cloud and visibility along an air-field approach path; and finally the motion and internal structure of clouds of tracer materials (insecticide spray and explosion-caused dust) which demonstrate the use of lidar for studying transport and diffusion processes.

Collis, R. T. H.

1969-01-01

23

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

SciTech Connect

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

Lo, C; Comstock, JM; Flynn, C

2006-10-01

24

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

25

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

NASA Technical Reports Server (NTRS)

While liquid clouds playa very important role in the global radiation budget, it's been very difficult to remotely determine their internal cloud structure. Ordinary lidar instruments (similar to radars but using visible light pulses) receive strong signals from such clouds, but the information is limited to a thin layer near the cloud boundary. Multiple field-of-view (FOV) lidars offer some new hope as they are able to isolate photons that were scattered many times by cloud droplets and penetrated deep into a cloud before returning to the instrument. Their data contains new information on cloud structure, although the lack of fast simulation methods made it challenging to interpret the observations. This paper describes a fast new technique that can simulate multiple-FOV lidar signals and can even estimate the way the signals would change in response to changes in cloud properties-an ability that allows quick refinements in our initial guesses of cloud structure. Results for a hypothetical airborne three-FOV lidar suggest that this approach can help determine cloud structure for a deeper layer in clouds, and can reliably determine the optical thickness of even fairly thick liquid clouds. The algorithm is also applied to stratocumulus observations by the 8-FOV airborne "THOR" lidar. These tests demonstrate that the new method can determine the depth to which a lidar provides useful information on vertical cloud structure. This work opens the way to exploit data from spaceborne lidar and radar more rigorously than has been possible up to now.

Pounder, Nicola L.; Hogan, Robin J.; Varnai, Tamas; Battaglia, Alessandro; Cahalan, Robert F.

2011-01-01

26

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

27

Micropulse Lidar Cloud Mask Value-Added Product Technical Report  

SciTech Connect

Lidar backscattered signal is a useful tool for identifying vertical cloud structure in the atmosphere in optically thin clouds. Cloud boundaries derived from lidar signals are a necessary input for popular ARM data products, such as the Active Remote Sensing of Clouds (ARSCL) product. An operational cloud boundary algorithm (Wang and Sassen 2001) has been implemented for use with the ARM Micropulse Lidar (MPL) systems. In addition to retrieving cloud boundaries above 500 m, the value-added product (VAP) named Micropulse Lidar Cloud Mask (MPLCMASK) applies lidar-specific corrections (i.e., range-square, background, deadtime, and overlap) as described in Campbell et al. (2002) to the measured backscattered lidar. Depolarization ratio is computed using the methodology developed by Flynn et al. (2007) for polarization-capable MPL systems. The cloud boundaries output from MPLCMASK will be the primary lidar cloud mask for input to the ARSCL product and will be applied to all MPL systems, including historical data sets.

Sivaraman, C; Comstock, J

2011-07-25

28

LIDAR, Point Clouds, and their Archaeological Applications  

SciTech Connect

It is common in contemporary archaeological literature, in papers at archaeological conferences, and in grant proposals to see heritage professionals use the term LIDAR to refer to high spatial resolution digital elevation models and the technology used to produce them. The goal of this chapter is to break that association and introduce archaeologists to the world of point clouds, in which LIDAR is only one member of a larger family of techniques to obtain, visualize, and analyze three-dimensional measurements of archaeological features. After describing how point clouds are constructed, there is a brief discussion on the currently available software and analytical techniques designed to make sense of them.

White, Devin A [ORNL

2013-01-01

29

Using Lidar and Radar measurements to constrain predictions of forest2 ecosystem structure and function3  

E-print Network

#12;1 1 Using Lidar and Radar measurements to constrain predictions of forest2 ecosystem structure in their spatial extent. Lidar and Synthetic Aperture Radar are promising remote47 sensing-based techniques investigate how Lidar-derived forest heights and49 Radar-derived above-ground biomass can be used to constrain

Moorcroft, Paul R.

30

Scanning ARM Cloud Radar Handbook  

SciTech Connect

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

Widener, K; Bharadwaj, N; Johnson, K

2012-06-18

31

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. cloud-base altitude) and microphysical (e.g. effective radius, liquid water content) 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 (MC) 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 (LES) 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.

2015-01-01

32

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

33

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

34

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

35

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

36

Lidar observations of cirrus cloud near the tropical tropopause: temporal variations and association with tropospheric turbulence  

NASA Astrophysics Data System (ADS)

Cirrus clouds forming just below the tropical tropopause and associated atmospheric turbulence are studied using a monostatic lidar and Mesosphere-Stratosphere-Troposphere (MST) radar. Lidar data show that the vertical extent of these clouds is confined to the region 14-16 km. Based on their visible optical depth, they can be classified as sub-visual (SVC), thin (TC) and dense cirrus (DC). Physical and optical properties of the cirrus clouds show significant temporal and spatial variability. While on some days, the clouds are strong and persistent throughout the night, they are weak and intermittent on some other days. Lidar backscattered signal from the clouds shows significant depolarisation indicating presence of non-spherical particles in abundance. The mean altitude of the cloud increases with decrease in tropopause temperature. The MST radar observations of vertical wind revealed that the region where these clouds are observed is highly turbulent. The vertical gradient of eddy diffusion coefficient shows a sharp discontinuity in the altitude region where the cirrus is strong and persistent, indicating that a region of divergence followed by a convergence above is conducive for cirrus formation.

Parameswaran, K.; SunilKumar, S. V.; Krishna Murthy, B. V.; Satheesan, K.; Bhavani Kumar, Y.; Krishnaiah, M.; Nair, Prabha R.

2003-10-01

37

An Automated Cloud Mask Algorithm for the Micropulse Lidar  

Microsoft Academic Search

To perform cloud base analysis, an automated technique fo r sky signal using the standard lidar equation (Spinhirn e determination of cloud base height from the raw lidar return s 1993) and midlatitude standard atmospheres. Afte r is needed. Previously, a straightforwar d signal thresholdin g normalization, the observations form a swarm of points about algorithm was used to determine

G. G. Mace

38

Lidar simulation. [measurement of atmospheric water vapor via optical radar  

NASA Technical Reports Server (NTRS)

The feasibility of measuring atmospheric water vapor via orbital lidar is estimated. The calculation starts with laser radar equations representing backscatter with and without molecular line absorption; the magnitudes of off-line backscatter are demonstrated. Extensive prior data on water line strengths are summarized to indicate the available sensitivity to water vapor concentration. Several lidar situations are considered starting with uniform and perturbed atmospheres at 0, 3, 10 and 20 kM (stratosphere) altitudes. These simulations are indicative of results to be obtained in ground truth measurements (ground-based and airborne). An approximate treatment of polar observations is also given. Vertical atmospheric soundings from orbit and from ground stations are calculated. Errors are discussed as regards their propagation through the lidar equation to render the measured water vapor concentration imprecise; conclusions are given as to required laser energy and feasible altitude resolution.

1976-01-01

39

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

40

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

41

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

42

Feature enhancing aerial lidar point cloud refinement  

NASA Astrophysics Data System (ADS)

Raw aerial LiDAR point clouds often suffer from noise and under-sampling, which can be alleviated by feature preserving refinement. However, existing approaches are limited to only preserving normal discontinuous features (ridges, ravines and crest lines) while position discontinuous features (boundaries) are also universal in urban scenes. We present a new refinement approach to accommodate unique properties of aerial LiDAR building points. By extending recent developments in geometry refinement to explicitly regularize boundary points, both normal and position discontinuous features are preserved and enhanced. The refinement includes two steps: i) the smoothing step applies a two-stage feature preserving bilateral filtering, which first filters normals and then updates positions under the guidance of the filtered normals. In a separate similar process, boundary points are smoothed directed by tangent directions of underlying lines, and ii) the up-sampling step interpolates new points to fill gaps/holes for both interior surfaces and boundary lines, through a local gap detector and a feature-aware bilateral projector. Features can be further enhanced by limiting the up-sampling near discontinuities. The refinement operates directly on points with diverse density, shape and complexity. It is memory-efficient, easy to implement, and easily extensible.

Gao, Zhenzhen; Neumann, Ulrich

2014-03-01

43

Lidar depolarization from multiple scattering in marine stratus clouds  

Microsoft Academic Search

The generation of ruby lidar depolarization from multiple scattering in marine stratus clouds has been examined systematically from a field site on the southern California coast. Investigated were the effects on the linear depolarization ratio delta of lidar receiver field of view (FOV), elevation angle, and laser alignment error. An approximately linear increase in maximum delta values was observed with

Kenneth Sassen; R. L. Petrilla

1986-01-01

44

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

45

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

46

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. Profiling, millimeterwavelength (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

47

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

NASA Technical Reports Server (NTRS)

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 distribution and total water content data from the CRYSTAL-FACE field campaign are used for the algorithm development. To reduce uncertainty in calculated radar reflectivity factors (Ze) at these wavelengths, coincident radar measurements and size distribution data are used to guide the selection of mass-length relationships and to deal with the density and non-spherical effects of ice crystals on the Ze calculations. The algorithm is able to retrieve microphysical property profiles of optically thick ice clouds, such as, deep convective and anvil clouds, which are very challenging for single frequency radar and lidar. Examples of retrieved microphysical properties for a deep convective clouds are presented, which show that EDOP and CRS measurements provide rich information to study cloud structure and evolution. Good agreement between IWPs derived from an independent submillimeter-wave radiometer, CoSSIR, and dual-wavelength radar measurements indicates accuracy of the IWC retrieved from the two-frequency radar algorithm.

Wang, Zhien; Heymsfield, Gerald M.; Li, Lihua; Heymsfield, Andrew J.

2005-01-01

48

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

49

Liquid Water Cloud Measurements Using the Raman Lidar Technique: Current Understanding and Future Research Needs  

NASA Technical Reports Server (NTRS)

This paper describes recent work in the Raman lidar liquid water cloud measurement technique. The range-resolved spectral measurements at the National Aeronautics and Space Administration Goddard Space Flight Center indicate that the Raman backscattering spectra measured in and below low clouds agree well with theoretical spectra for vapor and liquid water. The calibration coefficients of the liquid water measurement for the Raman lidar at the Atmospheric Radiation Measurement Program Southern Great Plains site of the U.S. Department of Energy were determined by comparison with the liquid water path (LWP) obtained with Atmospheric Emitted Radiance Interferometer (AERI) and the liquid water content (LWC) obtained with the millimeter wavelength cloud radar and water vapor radiometer (MMCR-WVR) together. These comparisons were used to estimate the Raman liquid water cross-sectional value. The results indicate a bias consistent with an effective liquid water Raman cross-sectional value that is 28%-46% lower than published, which may be explained by the fact that the difference in the detectors' sensitivity has not been accounted for. The LWP of a thin altostratus cloud showed good qualitative agreement between lidar retrievals and AERI. However, the overall ensemble of comparisons of LWP showed considerable scatter, possibly because of the different fields of view of the instruments, the 350-m distance between the instruments, and the horizontal inhomogeneity of the clouds. The LWC profiles for a thick stratus cloud showed agreement between lidar retrievals andMMCR-WVR between the cloud base and 150m above that where the optical depth was less than 3. Areas requiring further research in this technique are discussed.

Tetsu, Sakai; Whiteman, David N.; Russo, Felicita; Turner, David D.; Veselovskii, Igor; Melfi, S. Harvey; Nagai, Tomohiro; Mano, Yuzo

2013-01-01

50

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

51

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

52

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

E-print Network

VALIDATION OF A RADAR DOPPLER SPECTRA SIMULATOR USING MEASUREMENTS FROM THE ARM CLOUD RADARS to compare models with observations contains advantages and challenges. Radar Doppler spectra simulators model output with the Doppler spectra recorded from the vertically pointing cloud radars at the ARM

53

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

54

Simultaneous PMC and PMSE observations with a ground-based lidar and SuperDARN HF radar at Syowa Station, Antarctica  

NASA Astrophysics Data System (ADS)

A Rayleigh-Raman lidar system was installed in January 2011 at Syowa Station, Antarctica (69.0 S, 39.6 E). Polar mesospheric clouds (PMCs) were detected by lidar at around 22:30 UTC (LT -3 h) on 4 February 2011, which was the first day of observation. This was the first detection of PMCs over Syowa Station by lidar. On the same day, a Super Dual Auroral Radar Network (SuperDARN) HF radar with oblique-incidence beams detected polar mesospheric summer echoes (PMSE) between 21:30 and 23:00 UTC. This event is regarded as the last PMC activity around Syowa Station during the austral summer season (2010-2011), since no other PMC signals were detected by lidar in February 2011. This is consistent with results of PMC and mesopause temperature observations by satellite-born instruments of AIM (Aeronomy of Ice in the Mesosphere)/CIPS (Cloud Imaging and Particle Size) and AURA/MLS (Microwave Limb Sounder) and horizontal wind measurements taken by a separate MF radar. Doppler velocity of PMSE observed by the HF radar showed motion toward Syowa Station (westward). This westward motion is consistent with the wind velocities obtained by the MF radar. However, the PMSE region showed horizontal motion from a north-to-south direction during the PMC event. This event indicates that the apparent horizontal motion of the PMSE region can deviate from neutral wind directions and observed Doppler velocities.

Suzuki, H.; Nakamura, T.; Ejiri, M. K.; Ogawa, T.; Tsutsumi, M.; Abo, M.; Kawahara, T. D.; Tomikawa, Y.; Yukimatu, A. S.; Sato, N.

2013-10-01

55

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

56

First flight of the Cloud Detection Lidar Instrument Package  

SciTech Connect

The Cloud Detection Lidar Instrument Package is composed of three instruments: the Cloud Detection Lidar (CDL) and two Wide Field of View (WFOV) cameras. The CDL can be rotated to operate in either a nadir-looking or zenith-looking mode. The WFOV cameras provide imagery to complement the CDL measurements. One camera is fixed at nadir looking and the other at zenith looking. Only one camera may be operational at a time. All instruments were successfully flown in September--November 1995.

Henderson, J.R.; Ledebuhr, A.G.; Cameron, G.; Carter, P.; Hugenberger, R.E.; Kordas, J.F.; Nielsen, D.P.; Stratton, P.; Taylor, B. [Lawrence Livermore National Lab., CA (United States)

1996-03-01

57

SCANNING CLOUD RADAR OBSERVATIONS AT AZORES: PRELIMINARY 3D CLOUD PRODUCTS  

E-print Network

SCANNING CLOUD RADAR OBSERVATIONS AT AZORES: PRELIMINARY 3D CLOUD PRODUCTS P. Kollias, I. Jo, A, NY www.bnl.gov ABSTRACT The deployment of the Scanning W-Band ARM Cloud Radar (SWACR) during the AMF campaign at Azores signals the first deployment of an ARM Facility-owned scanning cloud radar and offers

58

Distinguishing cirrus cloud presence in autonomous lidar measurements  

NASA Astrophysics Data System (ADS)

2012 Level-2 Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite-based cloud data sets are investigated for thresholds that distinguish the presence of cirrus clouds in autonomous lidar measurements, based on temperatures, heights, optical depth and phase. A thermal threshold, proposed by Sassen and Campbell (2001) for cloud top temperature Ttop ? -37 C, is evaluated versus CALIOP algorithms that identify ice-phase cloud layers using polarized backscatter measurements. Derived global mean cloud top heights (11.15 vs. 10.07 km above mean sea level; a.m.s.l.), base heights (8.76 km a.m.s.l. vs. 7.95 km a.m.s.l.), temperatures (-58.48 C vs. -52.18 C and -42.40 C vs. -38.13 C, respectively, for tops and bases) and optical depths (1.18 vs. 1.23) reflect the sensitivity to this constraint. Over 99 % of all Ttop ? -37 C clouds are classified as ice by CALIOP Level-2 algorithms. Over 81 % of all ice clouds correspond with Ttop ? -37 C. For instruments lacking polarized measurements, and thus practical estimates of phase, Ttop ? -37 C provides sufficient justification for distinguishing cirrus, as opposed to the risks of glaciated liquid-water cloud contamination occurring in a given sample from clouds identified at relatively "warm" (Ttop > -37 C) temperatures. Although accounting for uncertainties in temperatures collocated with lidar data (i.e., model reanalyses/sondes) may justifiably relax the threshold to include warmer cases, the ambiguity of "warm" ice clouds cannot be fully reconciled with available measurements, conspicuously including phase. Cloud top heights and optical depths are investigated, and global distributions and frequencies derived, as functions of CALIOP-retrieved phase. These data provide little additional information, compared with temperature alone, and may exacerbate classification uncertainties overall.

Campbell, J. R.; Vaughan, M. A.; Oo, M.; Holz, R. E.; Lewis, J. R.; Welton, E. J.

2015-01-01

59

An analysis of lidar observations of polar stratospheric clouds  

SciTech Connect

The authors interpret lidar observations by Browell et al. (1990) 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 the authors deduce. Type 1b particles are spherical, or nearly spherical, and typically have radii near 0.5 {mu}m; Type 1a particles are not spherical, and have a spherical volume equivalent radius exceeding 1.0 {mu}m. Several factors may cause variations in the size of the particles. The most significant factors are the cooling rate and the degree to which the air parcels cool below the condensation point. Specific examples in which cooling rate and cooling point may have led to variations in particle size are found in the Browell et al. (1990) data set. Condensation of 1 ppmm of water or less is quantitatively sufficient to account for the magnitude of the lidar backscatter observed from water ice clouds. The ice particles are not spherical in shape. The sizes of particles in water ice clouds cannot be determined because they are much larger than the wavelength of the lidar.

Toon, O.B.; Kinne, S. (NASA Ames Research Center, Moffett Field, CA (USA)); Browell, E.V. (NASA Langley Research Center, Hampton, VA (USA)); Jordan, J. (Sterling Inc., Palo Alto, CA (USA))

1990-03-01

60

An analysis of lidar observations of polar stratospheric clouds  

NASA Technical Reports Server (NTRS)

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 particles are spherical, or nearly spherical, and typically have radii near 0.5 micron; Type 1a particles are not spherical, and have a spherical volume equivalent radius exceeding 1.0 micron. Several factors may cause variations in the size of the particles. The most significant factors are the cooling rate and the degree to which the air parcels cool below the condensation point. Specific examples in which cooling rate and cooling point may have led to variations in particle size are found in the Browell et al. (1990) data set. Condensation of 1 ppmm of water or less is quantitatively sufficient to account for the magnitude of the lidar backscatter observed from water ice clouds. The ice particles are not spherical in shape. The sizes of particles in water ice clouds cannot be determined because they are much larger than the wavelength of the lidar.

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

1990-01-01

61

24th International Laser Radar Conference BACKSCATTER NEPHELOM.ETER TO CALIBRATE SCANNING LIDAR  

E-print Network

;(h) is the power of the backscatter signal measured at the height h for elevation angle 24th International Laser Radar Conference BACKSCATTER NEPHELOM.ETER TO CALIBRATE SCANNING LIDAR-grade instrument, which operates at the wavelength 355 nm, will be co-located with a scanning-lidar at measurement

62

Affordable lidar for atmospheric aerosol and cloud studies  

NASA Astrophysics Data System (ADS)

The Vaisala ceilometer LD-40 'Tropopauser' is a compact eye-safe lidar measuring continuously under all possible climatic conditions and scanning the atmosphere up to a height of 13000 m. It uses laser diodes with 855 nm wavelength that are pulsed at an average frequency of 4000 Hz. The distance of the system's range bins is 7.5 m. Its main purpose is reporting cloud base heights and vertical visibility for aviation safety purposes. This paper focuses on the additional parameters this affordable lidar is able to report due to its advanced technical properties. These parameters include kind of precipitation detected, presence and distance of cirrus, extinction coefficients within clouds, vertical profiles of planetary boundary layer backscatter power, and a comparison of cloud coverage detected by a ceilometer with values obtained with a total cloud coverage scanner. Comparison instruments include regular radiosonde soundings performed at the Meteorological Observatory Lindenberg of the German Weather Service.

Muenkel, Christoph; Leiterer, Ulrich; Dier, Horst-D.

2002-01-01

63

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

SciTech Connect

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 Massachusetts (UMass) single antenna 33GHz/95 GHz Cloud Profiling Radar System (CPRS), the 95 GHz Wyoming Cloud Radar (WCR) flown on the University of Wyoming King Air, the University of Utah 95 GHz radar and the dual-antenna Pennsylvania State University 94 GHz radar. In this paper the authors discuss several issues relevant to comparison of ground-based radars, including the detection and filtering of insect returns. Preliminary comparisons of ground-based Ka-band radar reflectivity data and comparisons with airborne radar reflectivity measurements are also presented.

Sekelsky, S.M.; Li, L.; Galloway, J.; McIntosh, R.E. [Univ. of Massachusetts, Amherst, MA (United States); Miller, M.A. [Brookhaven National Lab., Upton, NY (United States); Clothiaux, E.E. [Pennsylvania State Univ., University Park, PA (United States); Haimov, S. [Univ. of Wyoming, Laramie, WY (United States); Mace, G.; Sassen, K. [Univ. of Utah, Salt Lake City, UT (United States)

1998-05-01

64

Lidar multiple scattering as a tool for cloud microphysical parameters  

NASA Astrophysics Data System (ADS)

Lidar was applied to identify atmospheric inhomogeneities by different scattering behavior of the aerosol particles. Aerosol is a general term, it includes also the aggregation to clouds. In the stratosphere there exist droplets of sulfuric acid (from volcanic eruptions), nitric acids and water vapor in mixed phases. In the polar region polar stratospheric (aerosol) clouds form during winter at temperatures around 195K. Usually the nucleation of nitric acid trihydrate (NAT) and nitric acids dihydrate (NAD) happens in a complicated mechanism. A lidar can identify the result of the nucleation process, not the gas phases. It can distinguish between droplets (as Mie particles) and crystal (frozen droplets of NAT and NAD) by polarization. Because the aerosols are driven with the wind and have a tendency to sediment, the orientation of the lidar to the aerosol particles is an important factor. Improvement of lidar measurements to distinguish between stratospheric aerosols and polar stratospheric clouds (i.e. by the given definition the frozen aggregation) was focused: 1) on the use of multiple wavelength lidar with a polarization channel, 2) on a theoretical study on the possibility to use multiple scattering as an additional discriminant and, 3) on scanning. Points 2 and 3 require a better detection and signal processing system. Statistical problems arise for the comparison of measurements, for example if one compares ground-based and airborne measurements of the same cloud. Airborne measurements can contribute to the problem because one can reduce the distance to the object and therefore the 1/R2-dependency leads to larger signals. Averaging with respect to ensemble statistics are covered in this report. It is accepted that ground-based lidar systems especially with a Raman channel measure with a high pulse repetition rate over a few minutes to get a signal which can be processed.

Werner, Christian; Oppel, Ulrich G.

1995-09-01

65

Threshold radar reflectivity for drizzling clouds Yangang Liu,1  

E-print Network

Threshold radar reflectivity for drizzling clouds Yangang Liu,1 Bart Geerts,2 Mark Miller,2 Peter; published 7 February 2008. [1] Empirical studies have suggested the existence of a threshold radar cloud to rain when the radar reflectivity exceeds some value (threshold reflectivity) but also reveals

66

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

67

Cirrus cloud optical, microphysical, and radiative properties observed during the CRYSTAL-FACE  

E-print Network

through cloud and water vapor feedbacks [Stephens, 2005; Held and Soden, 2000]. Understanding-FACE experiment: A lidar-radar retrieval system C. Mitrescu,1 J. M. Haynes,2 G. L. Stephens,2 S. D. Miller,1 G. M from both cloud radar and lidar is introduced. The description of the lidar-radar model accounts

Stephens, Graeme L.

68

Seasonal and optical characterisation of cirrus clouds over Indian sub-continent using LIDAR  

NASA Astrophysics Data System (ADS)

Light Detection and Ranging (LIDAR) is an important remote sensing technique to study about the cirrus clouds. The subject of cirrus clouds and related climate is challenging one. The received scattered signal from Lidar contains information on the physical and optical properties of cirrus clouds. The Lidar profile of the cirrus cloud provides information on the optical characteristics like depolarisation ratio, lidar ratio and optical depth, which give knowledge about possible phase, structure and orientation of cloud particle that affect the radiative budgeting of cirrus clouds. The findings from the study are subjected to generate inputs for better climatic modelling.

Jayeshlal, G. S.; Satyanarayana, Malladi; Dhaman, Reji K.; Motty, G. S.

2014-10-01

69

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

70

Investigation on cirrus clouds by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation data  

NASA Astrophysics Data System (ADS)

Understanding and describing the role of clouds in the climate system need intensive and extensive research on cloud properties. The albedo and greenhouse effects of clouds and their relations with the physical properties of clouds are analyzed. Cloud-top height and ice water content are key factors in impacting the longwave and shortwave radiation, respectively. Lidar and infrared radiometer measurement technologies are introduced. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) level 1 Lidar profile, level 2 cloud layer, and level 2 Lidar/IIR track products are briefly reviewed. The algorithms for identification of cirrus clouds, Linear Depolarization Ratio (LDR), and effective diameter are presented. An average LDR profile is calculated by using the sum of total attenuated backscattering profiles and the sum of perpendicular attenuated backscattering profiles. A weight-average method is applied to calculate the average LDR. A split-window method is applied to estimate the effective diameters of clouds. A set of bulk ice crystal models and a radiative transfer model are applied to produce a look-up table that includes the radiative transfer simulation results. The macro-physical properties of cirrus clouds are analyzed. The frequency of occurrence of cirrus clouds varies with latitude, and strongly relates to the atmospheric circulation. Cirrus clouds are few in high-pressure zones and abundant where seasonal monsoonal circulation occurs. Cloud-top height decreases with increasing latitude. Cloud-top temperature is lower in the tropical regions than in the midlatutude and the polar regions. The measured cloud thickness shows a great diurnal variation.

Zhu, Jiang

2011-12-01

71

Surface Roughness Impact on the Sea Ice Thickness Measurements Based on LIDAR/Radar Altimetry  

NASA Astrophysics Data System (ADS)

The Radar and/or LIDAR measurements of sea ice freeboard provide an indirect approach to infer sea ice thickness via isostasy. The underlying assumption is that the LIDAR signal returns at the air/snow interface and radar signal at the snow/ice interface. Thus the surface roughness at the air, snow and ice interface has a significant impact on the LIDAR/Radar returns, which can lead to very significant errors in the ice thickness retrievals. Recent Cryosat-2 validation results suggest that its altimetry-based technique is very effective in mapping hemispheric sea ice thickness. However, in some cases significant bias exists in the Cryosat-2 data product. To understand the performance of those data depends on our skills in quantifying the impacts of the secondary parameters, such as surface roughness of snow and ice surfaces and the penetration depth of the snow/ice by the radar. To this end, we analyze airborne radar and lidar altimeter data collected during a Cryosat-2 under-flight by the NRL and the NASA IceBridge missions, as well as the in-situ data from the coordinated CRREL/NRL field campaign. In this presentation we will show some surface roughness data from airborne LIDAR for leveled and deformed first year ice, and ice pressure ridges. Their impacts on radar returns and sea ice thickness retrieval will be presented.

Li, L.; Truesdale, D.; Posey, P.; Allard, R.; Gardner, J. M.; Brozena, J. M.; Richter-Menge, J.

2013-12-01

72

The interdependence of continental warm cloud properties derived from unexploited solar background signal 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 signal that is previously unwanted and needs 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, while it increases with optical depth and reaches an asymptote of 10 ?m in non-drizzling clouds. This asymptotic behaviour in non-drizzling clouds is found in both 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.

2014-04-01

73

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

74

Lidar Studies on The Optical Characteristics of High Altitude Cirrus Clouds at A Low Latitiude Station, Gadanki (13.5N , 79.2E ) India  

NASA Astrophysics Data System (ADS)

Light Detection and Ranging (LIDAR) which is analogous to Radio Detection And Ranging (RADAR), has become an important and unique technology for atmospheric research and applications. The technology is widely used for the remote sensing of the Earth's atmosphere, oceans, vegetation and the characteristics of Earth's topography. Remote sensing of atmosphere, for its structure, composition and dynamics, is one of the proven applications of the lidar systems. More importantly the lidar technique is applied for the study of clouds, aerosols and minor constituents in the atmosphere. It provides the information on the above with good spatial and temporal resolutions and accuracy. The high altitude cirrus clouds which play an important role in the Earth's radiative budget and global climate can be studied by using the LIDAR system. These clouds absorb long-wave outgoing radiation from Earth's surface while reflecting part of the incoming short-wave solar radiation. Lidar measurements are useful in deriving the altitude, top height, bottom height and the optical properties of cirrus clouds, which are essential in understanding the cloud-radiation effects. The optical depth, the effective lidar ratio and the depolarization of the clouds are also derived by inverting the lidar signals from the cirrus clouds. In this paper we present the results on the lidar derived optical and microphysical properties of the cirrus clouds at a tropical station Gadanki (13.5N, 79.2E) India during two year period from 2009 to210. The seasonal variations of the cloud properties during the observation period are presented and discussed with reference to earlier period.

Jayeshlal, G. S.; Satyanarayana, M.; Motty, G. S.; Dhaman, R. K.; Krishnakumar, V.; Mahadevan Pillai, V. P.; Ramakrishnarao, D.; Sudhakar, P.; Kalavathi, P.

2014-11-01

75

Cloud Coverage and Height Distribution from the GLAS Polar Orbiting Lidar: Comparison to Passive Cloud Retrievals  

NASA Technical Reports Server (NTRS)

The Geoscience Laser Altimeter System (GLAS) began full on orbit operations in September 2003. A main application of the two-wavelength GLAS lidar is highly accurate detection and profiling of global cloud cover. Initial analysis indicates that cloud and aerosol layers are consistently detected on a global basis to cross-sections down to 10(exp -6) per meter. Images of the lidar data dramatically and accurately show the vertical structure of cloud and aerosol to the limit of signal attenuation. The GLAS lidar has made the most accurate measurement of global cloud coverage and height to date. In addition to the calibrated lidar signal, GLAS data products include multi level boundaries and optical depth of all transmissive layers. Processing includes a multi-variable separation of cloud and aerosol layers. An initial application of the data results is to compare monthly cloud means from several months of GLAS observations in 2003 to existing cloud climatologies from other satellite measurement. In some cases direct comparison to passive cloud retrievals is possible. A limitation of the lidar measurements is nadir only sampling. However monthly means exhibit reasonably good global statistics and coverage results, at other than polar regions, compare well with other measurements but show significant differences in height distribution. For polar regions where passive cloud retrievals are problematic and where orbit track density is greatest, the GLAS results are particularly an advance in cloud cover information. Direct comparison to MODIS retrievals show a better than 90% agreement in cloud detection for daytime, but less than 60% at night. Height retrievals are in much less agreement. GLAS is a part of the NASA EOS project and data products are thus openly available to the science community (see http://glo.gsfc.nasa.gov).

Spinhime, J. D.; Palm, S. P.; Hlavka, D. L.; Hart, W. D.; Mahesh, A.

2004-01-01

76

Lidar-Derived Cloud Optical Properties Obtained during the ECLIPS Program.  

NASA Astrophysics Data System (ADS)

This paper presents the Statistical properties of lidar-derived values of cloud extinction coefficients and optical depths . The data were collected at Toronto during two measurement phases (phase 1: September October 1989; phase 2: June July 1991) or the Experimental Cloud Lidar Pilot Study. Although the small dataset limits general application of the statistical trends observed, the measurements demonstrate the valuable potential of lidar data for improving cloud parameterization in general circulation models. The measurements show the frequent occurrence of optically thin clouds (0.2 km1 and 0.2), demonstrating the ability of lidars to detect these dilute clouds and the importance of including them in radiative transfer models.

Pal, S. R.; Carswell, A. I.; Gordon, I.; Fong, A.

1995-11-01

77

Dust-cloud density estimation using a single wavelength lidar  

NASA Astrophysics Data System (ADS)

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

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

1994-09-01

78

Using Lidar and Radar measurements to constrain predictions of forest ecosystem structure and function.  

PubMed

Insights into vegetation and aboveground biomass dynamics within terrestrial ecosystems have come almost exclusively from ground-based forest inventories that are limited in their spatial extent. Lidar and synthetic-aperture Radar are promising remote-sensing-based techniques for obtaining comprehensive measurements of forest structure at regional to global scales. In this study we investigate how Lidar-derived forest heights and Radar-derived aboveground biomass can be used to constrain the dynamics of the ED2 terrestrial biosphere model. Four-year simulations initialized with Lidar and Radar structure variables were compared against simulations initialized from forest-inventory data and output from a long-term potential-vegtation simulation. Both height and biomass initializations from Lidar and Radar measurements significantly improved the representation of forest structure within the model, eliminating the bias of too many large trees that arose in the potential-vegtation-initialized simulation. The Lidar and Radar initializations decreased the proportion of larger trees estimated by the potential vegetation by approximately 20-30%, matching the forest inventory. This resulted in improved predictions of ecosystem-scale carbon fluxes and structural dynamics compared to predictions from the potential-vegtation simulation. The Radar initialization produced biomass values that were 75% closer to the forest inventory, with Lidar initializations producing canopy height values closest to the forest inventory. Net primary production values for the Radar and Lidar initializations were around 6-8% closer to the forest inventory. Correcting the Lidar and Radar initializations for forest composition resulted in improved biomass and basal-area dynamics as well as leaf-area index. Correcting the Lidar and Radar initializations for forest composition and fine-scale structure by combining the remote-sensing measurements with ground-based inventory data further improved predictions, suggesting that further improvements of structural and carbon-flux metrics will also depend on obtaining reliable estimates of forest composition and accurate representation of the fine-scale vertical and horizontal structure of plant canopies. PMID:21774418

Antonarakis, Alexander S; Saatchi, Sassan S; Chazdon, Robin L; Moorcroft, Paul R

2011-06-01

79

Comparison of SEVIRI Cloud Product with both the POLDER and the GLAS Space Lidar one  

E-print Network

Radiation Budget, water vapor and clouds" line (hereafter "ERB & clouds") applied to POLDER dataComparison of SEVIRI Cloud Product with both the POLDER and the GLAS Space Lidar one G. Sèze(1) , F of the Earth's Reflectances) on board the ADEOS2 platform and (4) measurements from the space lidar GLAS

Madeleine, Jean-Baptiste

80

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

81

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

82

Lidar Observations of the Optical Properties and 3-Dimensional Structure of Cirrus Clouds  

NASA Technical Reports Server (NTRS)

The scientific research conducted under this grant have been reported in a series of journal articles, dissertations, and conference proceedings. This report consists of a compilation of these publications in the following areas: development and operation of a High Spectral Resolution Lidar, cloud physics and cloud formation, mesoscale observations of cloud phenomena, ground-based and satellite cloud cover observations, impact of volcanic aerosols on cloud formation, visible and infrared radiative relationships as measured by satellites and lidar, and scattering cross sections.

Eloranta, E. W.

1996-01-01

83

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

84

Balloonborne lidar for cloud physics studies  

NASA Astrophysics Data System (ADS)

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

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

2006-08-01

85

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

86

W-band ARM Cloud Radar (WACR) Handbook  

SciTech Connect

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

Widener, KB; Johnson, K

2005-01-05

87

Sampling Error Characteristics Of Cloud Observations From LiDAR  

NASA Astrophysics Data System (ADS)

Height profiles of cloud fraction is an important parameter that is not well represented in GCMs and in smaller scale models. Improvements should come from new and existing remote sensing technologies that will increasingly provide the science community with direct observations of such profiles. However, an inherent error or uncertainty is associated with any cloud fraction estimate from remote sensing data due to instrument and atmospheric noise, sensor resolution and the sampling scheme. While all sources of uncertainties need to be investigated further, this project focuses on the characteristics of the errors originating from the sampling scheme. Space-borne LiDAR data from the 1994 NASA LITE campaign is used to study and quantify the characteristics of such sampling errors in cloud fraction estimates from along transect measurements. This is done within a general model for sampling along a transect, which has been developed based on an approach from queuing theory, without making prior assumptions on the type of cloud distribution (Astin and Di Girolamo, 1999). Results will be presented giving estimates of the cloud fraction and its distributions over a range of altitudes as evaluated from cloudy and clear interval lengths as observed along the transects of the LITE observations. The estimates themselves are refined to account for missing data due to attenuation of the LiDAR signal by dense cloud. Further, the distribution of cloud cover fraction over the earth is also presented, which allows for climatological interpretation of the results. In this, estimates of the mean cloud cover fraction and distributions and confidence intervals are provided for pressure levels from the boundary layer to the tropopause. Estimates are also inferred from transects over the whole globe, but separated into climatological regions based on mean precipitation-evapotranspiration, as well as separated by surface type such as clouds over land versus those above sea. The above results allow examination of the error characteristics of the cover fraction estimates in relation with the underlying process and the LiDAR sampling scheme.

van de Poll, M.

2001-12-01

88

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

E-print Network

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

89

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

Microsoft Academic Search

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

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

1998-01-01

90

The first observed cloud echoes and microphysical parameter retrievals by China's 94-GHz cloud radar  

NASA Astrophysics Data System (ADS)

By using the cloud echoes first successfully observed by China's indigenous 94-GHz SKY cloud radar, the macrostructure and microphysical properties of drizzling stratocumulus clouds in Anhui Province on 8 June 2013 are analyzed, and the detection capability of this cloud radar is discussed. The results are as follows. (1) The cloud radar is able to observe the time-varying macroscopic and microphysical parameters of clouds, and it can reveal the microscopic structure and small-scale changes of clouds. (2) The velocity spectral width of cloud droplets is small, but the spectral width of the cloud containing both cloud droplets and drizzle is large. When the spectral width is more than 0.4 m s-1, the radar reflectivity factor is larger (over -10 dBZ). (3) The radar's sensitivity is comparatively higher because the minimum radar reflectivity factor is about -35 dBZ in this experiment, which exceeds the threshold for detecting the linear depolarized ratio (LDR) of stratocumulus (commonly -11 to -14 dBZ; decreases with increasing turbulence). (4) After distinguishing of cloud droplets from drizzle, cloud liquid water content and particle effective radius are retrieved. The liquid water content of drizzle is lower than that of cloud droplets at the same radar reflectivity factor.

Wu, Juxiu; Wei, Ming; Hang, Xin; Zhou, Jie; Zhang, Peichang; Li, Nan

2014-06-01

91

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

92

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

E-print Network

) [Clothiaux et al., 1995], or from temperature and water vapor profiles [Zhang et al., 2013]. The micropulseA 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

Li, Zhanqing

93

Uncertainty in Cloud Aerosol Transport System (CATS) Doppler Lidar Products and Measurements  

Microsoft Academic Search

The Cloud Aerosol Transport System (CATS) is both a high spectral resolution lidar and Doppler lidar currently being developed at NASA Goddard Space Flight Center for use as a demonstrator instrument for NASA's Aerosol Cloud Ecosystem (ACE) Mission. CATS is intended to fly on NASA's high-altitude ER-2 aircraft. CATS will be capable of measuring both aerosol properties and horizontal wind

P. A. Selmer

2010-01-01

94

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

NASA Astrophysics Data System (ADS)

The retrieval of cloud water content using dual-frequency radar attenuation is very sensitive to error in radar reflectivity. Either a long radar dwell time or an average over many range gates is needed to reduce random noise in radar data and thus to obtain accurate retrievals - but at the cost of poorer temporal and spatial resolution. In this letter we have shown that, by using advanced mathematical inversion techniques like total variation regularization, vertically resolved liquid water content can be retrieved at an accuracy of about 0.15 gm-3 at 40 m resolution. This is demonstrated using the co-located Ka-band and W-band cloud radars operated by the Atmospheric Radiation Measurement program. The liquid water path calculated from the radars agrees closely with that from a microwave radiometer, with a mean difference of 70 gm-2. Comparison with lidar observations reveals that the dual-frequency retrieval also reasonably captures the cloud base height of drizzling clouds - something that is very difficult to determine from radar reflectivity alone.

Huang, Dong; Johnson, Karen; Liu, Yangang; Wiscombe, Warren

2009-12-01

95

ARRA-funded Cloud Radar Development for the Department of Energy's ARM Climate Research Facility  

E-print Network

ARRA-funded Cloud Radar Development for the Department of Energy's ARM Climate Research Facility six dual frequency cloud radar systems. These radars will be used by the Atmospheric Radiation on the effects of clouds and precipitation on the climate. Four cloud radar systems will be permanently installed

96

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 gauges and the horizontal transport of windblown snow along the surface produce errors in snowfall in the high Arctic where snowfall amount are very low and blowing snow is frequent. This paper describes

Eloranta, Edwin W.

97

Polarization-diversity radar and lidar technology in meteorological research: A review of theory and measurements  

Microsoft Academic Search

Research in polarization-diversity radar and lidar technology as applied to meteorology is reviewed. Review of theory includes development of models for computing hydrometeor backscatter in main and orthogonal channels and development of techniques for interpreting measured parameters. Measurement programs have generally been undertaken with a particular operational objective, such as the identification of hail in severe storms or the measurement

J. I. Metcalf; S. P. Brookshire; T. P. Morton

1977-01-01

98

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

99

Scanning ARM Cloud Radars Part I: Operational Sampling Strategies  

SciTech Connect

Probing clouds in three-dimensions has never been done with scanning millimeter-wavelength (cloud) radars in a continuous operating environment. The acquisition of scanning cloud radars by the Atmospheric Radiation Measurement (ARM) program and research institutions around the world generate the need for developing operational scan strategies for cloud radars. Here, the first generation of sampling strategies for the Scanning ARM Cloud Radars (SACRs) is discussed. These scan strategies are designed to address the scientific objectives of the ARM program, however, they introduce an initial framework for operational scanning cloud radars. While the weather community uses scan strategies that are based on a sequence of scans at constant elevations, the SACRs scan strategies are based on a sequence of scans at constant azimuth. This is attributed to the cloud properties that are vastly different for rain and snow shafts that are the primary target of precipitation radars. A cloud surveillance scan strategy is introduced (HS-RHI) based on a sequence of horizon-to-horizon Range Height Indicator (RHI) scans that sample the hemispherical sky (HS). The HS-RHI scan strategy is repeated every 30 min to provide a static view of the cloud conditions around the SACR location. Between HS-RHI scan strategies other scan strategies are introduced depending on the cloud conditions. The SACRs are pointing vertically in the case of measurable precipitation at the ground. The radar reflectivities are corrected for water vapor attenuation and non-meteorological detection are removed. A hydrometeor detection mask is introduced based on the difference of cloud and noise statistics is discussed.

Kollias, Pavlos; Bharadwaj, Nitin; Widener, Kevin B.; Jo, Ieng; Johnson, Karen

2014-03-01

100

On Integrating Cloud-Radar-Derived Arctic Ice Cloud Properties into the Radiative Transfer Model "Streamer" 1.Introduction  

E-print Network

On Integrating Cloud-Radar-Derived Arctic Ice Cloud Properties into the Radiative Transfer Model "Streamer" 1.Introduction Millimeter-wavelength cloud radars can potentially provide a vast dataset on ice cloud optical properties.The problem arises, however,of how best to integrate the radar-retrieved ice

Zuidema, Paquita

101

Lidar measurements of boundary layers, aerosol scattering and clouds during project FIFE  

NASA Technical Reports Server (NTRS)

A detailed account of progress achieved under this grant funding is contained in five journal papers. The titles of these papers are: The calculation of area-averaged vertical profiles of the horizontal wind velocity using volume imaging lidar data; Volume imaging lidar observation of the convective structure surrounding the flight path of an instrumented aircraft; Convective boundary layer mean depths, cloud base altitudes, cloud top altitudes, cloud coverages, and cloud shadows obtained from Volume Imaging Lidar data; An accuracy analysis of the wind profiles calculated from Volume Imaging Lidar data; and Calculation of divergence and vertical motion from volume-imaging lidar data. Copies of these papers form the body of this report.

Eloranta, Edwin W. (Principal Investigator)

1995-01-01

102

Improved retrievals of the optical properties of cirrus clouds by a combination of lidar methods.  

PubMed

We focus on improvement of the retrieval of optical properties of cirrus clouds by combining two lidar methods. We retrieve the cloud's optical depth by using independently the molecular backscattering profile below and above the cloud [molecular integration (MI) method] and the backscattering profile inside the cloud with an a priori effective lidar ratio [particle integration (PI) method]. When the MI method is reliable, the combined MI-PI method allows us to retrieve the optimal effective lidar ratio. We compare these results with Raman lidar retrievals. We then use the derived optimal effective lidar ratio for retrieval with the PI method for situations in which the MI method cannot be applied. PMID:15818860

Cadet, Bertrand; Giraud, Vincent; Haeffelin, Martial; Keckhut, Philippe; Rechou, Anne; Baldy, Serge

2005-03-20

103

COMPARISON OF MILLIMETER-WAVE CLOUD RADAR MEASUREMENTS FOR THE FALL 1997 CLOUD IOP  

SciTech Connect

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) Cloud and Radiation Testbed (CART) site, including the full time operation 35 GHz CART Millimeter-wave Cloud Radar (MMCR), (Moran, 1997), the University of Massachusetts (UMass) single antenna 33GHz/95 GHz Cloud Profiling Radar System (CPRS), (Sekelsky, 1996), the 95 GHz Wyoming Cloud Radar (WCR) flown on the University of Wyoming King Air (Galloway, 1996), the University of Utah 95 GHz radar and the dual-antenna Pennsylvania State University 94 GHz radar (Clothiaux, 1995). In this paper the authors discuss several issues relevant to comparison of ground-based radars, including the detection and filtering of insect returns. Preliminary comparisons of ground-based Ka-band radar reflectivity data and comparisons with airborne radar reflectivity measurements are also presented.

SEKELSKY,S.M.; LI,L.; GALLOWAY,J.; MCINTOSH,R.E.; MILLER,M.A.; CLOTHIAUX,E.E.; HAIMOV,S.; MACE,G.; SASSEN,K.

1998-03-23

104

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

NASA Astrophysics Data System (ADS)

A number of proposed lidar systems, such as ESAs AEOLUS (formerly ADM) and DIAL missions (e.g. WALES) are to make use of lidar returns in clear air. However, on average, two-thirds of the globe is covered in cloud. Hence, there is a strong likelihood that data from these instruments may be contaminated by cloud. Similarly, optically thick cloud may not be penetrated by a lidar pulse, resulting in unobservable regions that are overshadowed by the cloud. To address this, it is suggested, for example, in AEOLUS, that a number of consecutive short sections of lidar data (between 1 and 3.5 km in length) be tested for cloud contamination or for overshadowing and only those that are unaffected by cloud be used to derive atmospheric profiles. The prob-ability of obtaining profiles to near ground level using this technique is investigated both analytically and using UV air-borne lidar data recorded during the CLARE98 campaign. These data were measured in the presence of broken cloud on a number of flights over southern England over a four-day period and were chosen because the lidar used has the same wavelength, footprint and could match the along-track spacing of the proposed AEOLUS lidar.

Astin, I.; Kiemle, C.

2003-03-01

105

Reconstruction of 3-D cloud geometry using a scanning cloud radar  

NASA Astrophysics Data System (ADS)

Clouds are one of the main reasons of uncertainties in the forecasts of weather and climate. In part, this is due to limitations of remote sensing of cloud microphysics. Present approaches often use passive spectral measurements for the remote sensing of cloud microphysical parameters. Large uncertainties are introduced by three dimensional (3-D) radiative transfer effects and cloud inhomogeneities. Such effects are largely caused by unknown orientation of cloud sides or by shadowed areas on the cloud. Passive ground based remote sensing of cloud properties at high spatial resolution could be improved crucially with this kind of additional knowledge of cloud geometry. To this end, a method for the accurate reconstruction of 3-D cloud geometry from cloud radar measurements is developed in this work. Using a radar simulator and simulated passive measurements of static LES model clouds, the effects of different radar scan resolutions and varying interpolation methods are evaluated. In reality a trade-off between scan resolution and scan duration has to be found as clouds are changing quickly. A reasonable choice is a scan resolution of 1 to 2. The most suitable interpolation procedure identified is the barycentric interpolation method. The 3-D reconstruction method is demonstrated using radar scans of convective cloud cases with the Munich miraMACS, a 35 GHz scanning cloud radar. As a successful proof of concept, camera imagery collected at the radar location is reproduced for the observed cloud cases via 3-D volume reconstruction and 3-D radiative transfer simulation. Data sets provided by the presented reconstruction method will aid passive spectral ground-based measurements of cloud sides to retrieve microphysical parameters.

Ewald, F.; Winkler, C.; Zinner, T.

2014-11-01

106

Space-Based Lidar Systems  

NASA Technical Reports Server (NTRS)

An overview of space-based lidar systems is presented. from the first laser altimeter on APOLLO 15 mission in 1971 to the Mercury Laser Altimeter on MESSENGER mission currently in orbit, and those currently under development. Lidar, which stands for Light Detection And Ranging, is a powerful tool in remote sensing from space. Compared to radars, lidars operate at a much shorter wavelength with a much narrower beam and much smaller transmitter and receiver. Compared to passive remote sensing instruments. lidars carry their own light sources and can continue measuring day and night. and over polar regions. There are mainly two types of lidars depending on the types of measurements. lidars that are designed to measure the distance and properties of hard targets are often called laser rangers or laser altimeters. They are used to obtain the surface elevation and global shape of a planet from the laser pulse time-of-night and the spacecraft orbit position. lidars that are designed to measure the backscattering and absorption of a volume scatter, such as clouds and aerosols, are often just called lidars and categorized by their measurements. such as cloud and aerosol lidar, wind lidar, CO2 lidar, and so on. The advantages of space-based lidar systems over ground based lidars are the abilities of global coverage and continuous measurements.

Sun, Xiaoli

2012-01-01

107

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

108

High altitude Balloon Borne Lidar experiment for the study of aerosols and clouds  

Microsoft Academic Search

Ground based light detection and ranging (LIDAR) instruments are routinely used for the study of aerosols and clouds using remote sensing technique. Such measurements can only give local\\/regional scale data. Space based system can provide data on global scale and the same can be used for climate modeling and weather forecasting applications. Development of a Balloon Borne Lidar (BBL) system

RK Manchanda; S. Ramaratnam; AR Krishnan; B. Presenna Kumar; J. Jeswin Vetha Jeyasingh; S. Sreekumar; Sherly Joy; S. Thirupathirajan; Y. Bhavanikumar; Anand Devarajan

2010-01-01

109

Modeling Residential Urban Areas from Dense Aerial LiDAR Point Clouds  

E-print Network

Modeling Residential Urban Areas from Dense Aerial LiDAR Point Clouds Qian-Yi Zhou and Ulrich) Aerial imagery is shown as a reference. 1 Introduction Urban modeling from aerial LiDAR scans has been; building reconstruction is be- lieved to be the core of urban modeling, which has attracted much attention

Shahabi, Cyrus

110

Evaluation of MM5 Optically Thin Clouds over Europe in Fall Using ICESat Lidar Spaceborne Observations  

Microsoft Academic Search

The description of clouds in mesoscale models has progressed significantly during recent years by im- proving microphysical schemes with more physical parameterizations deduced from observations. Recently, the first lidar in space, the Ice, Cloud, and Land Elevation Satellite (ICESat)\\/Geosciences Laser Altimeter System, has collected a valuable dataset that improves the knowledge of occurrence and macrophysical properties of clouds, and particularly

H. Chepfer; M. Chiriaco; R. Vautard; J. Spinhirne

2007-01-01

111

The structure of the convective atmospheric boundary layer as revealed by lidar and Doppler radars  

NASA Technical Reports Server (NTRS)

Results on the structure of the convective atmospheric boundary layer based on the analyses of data from the instrumented NSSL-KTVY tower, airborne Doppler lidar, and ground-based Doppler radars are presented. The vertically averaged wind over the boundary layer was found to be insensitive to baroclinicity, supporting the hypothesis of Arya and Wyngaard (1975). The computed momentum flux profiles were affected by baroclinicity. Horizontal wind spectra from lidar, radar, and tower data compared well with each other both in shape and magnitude. A consistent peak found near 4 km in all the computed spectra might have been caused by horizontally symmetric cells with horizontal wavelength 4 times the boundary-layer height as shown in Kuettner (1971) for the case of weak wind shear.

Eilts, M. D.; Sundara-Rajan, A.; Doviak, R. J.

1985-01-01

112

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

113

Polar Cirrus Cloud Properties Through Long-Term Lidar and Radiometer Observations  

NASA Technical Reports Server (NTRS)

In comparison to mid latitude cloud cover, knowledge of polar cirrus and other cloud cover is limited. The interpretations of satellite-based cloud imaging and retrievals in polar regions have major problems due to factors such as darkness and extreme low temperatures. Beginning in 2002 a NASA orbiting lidar instrument, GLAS, (Geoscience Laser Altimeter System) will unambiguously define cloud type and fraction with good coverage of polar regions. Active laser sensing gives the spatial and temporal distribution of clouds and diamond dust. In preparation for, and supplementing the GLAS measurements are ground based MP (micro pulse) lidar experiments providing continuous profiling. MP lidar installations have been operating at the South Pole since December 1999 and at the Atmospheric Radiation Measurement (ARM) program arctic site since 1996. Both at the ARM Barrow, Alaska site and at the South Pole station, Fourier-transform interferometers also observe clouds in the wavelength intervals between approximately 5 and 18 microns. Spectral instruments can yield cloud microphysical properties with additional information from lidar about the vertical extent of clouds being modeled. We examine the simultaneous lidar and spectral data from both Barrow and South Pole, to obtain cloud properties (optical depth, particle size) by the use of both instruments. The results have applications to interpretation of current satellite data, and GLAS measurements when available.

Spinhirne, James; Campbell, James; Mahesh, Ashwin; Welton, Judd; Starr, David OC. (Technical Monitor)

2001-01-01

114

Aircraft-protection radar for use with atmospheric lidars Thomas J. Duck, Bernard Firanski, Frank D. Lind, and Dwight Sipler  

E-print Network

must be taken to avoid illuminating aircraft with these lasers owing to eye- safety concerns.8Aircraft-protection radar for use with atmospheric lidars Thomas J. Duck, Bernard Firanski, Frank D. Lind, and Dwight Sipler A modified X-band radar system designed to detect aircraft during atmospheric

Duck, Thomas J.

115

Simulated polarization diversity lidar returns from water and precipitating mixed phase clouds.  

PubMed

The dependence of polarization lidar returns on basic microphysical and thermodynamic variables is assessed by using a cloud model to simulate the growth of water and mixed (water and ice) phase clouds. Cloud contents that evolve with height in updrafts are converted, by using Mie theory, into cloud droplet single and double backscattering and attenuation coefficients. The lidar equation includes forward multiple scattering attenuation corrections based on diffraction theory for droplets and ice crystals, whose relative scattering contributions are treated empirically. Lidar depolarization is computed from droplet and crystal single scattering and an analytical treatment of droplet double scattering. Water cloud results reveal the expected increases in linear depolarization ratios (delta) with increasing lidar field of view and distance to cloud but also show that depolarization is a function of cloud liquid water content, which depends primarily on temperature. Ice crystals modulate mixed phase cloud liquid water contents through water vapor competition effects, thereby affecting multiple scattering delta values as functions of updraft velocity, temperature, and crystal size and concentration. Although the minimum delta at cloud base increases with increasing ice content, the peak measurable delta in the cloud decreases. Comparison with field data demonstrate that this modeling approach is a valuable supplement to cloud measurements. PMID:20725225

Sassen, K; Zhao, H; Dodd, G C

1992-05-20

116

Simulated polarization diversity lidar returns from water and precipitating mixed phase clouds  

SciTech Connect

The dependence of polarization lidar returns on basic microphysical and thermodynamic variables is assessed by using a cloud model to simulate the growth of water and mixed (water and ice) phase clouds. Cloud contents that evolve with height in updrafts are converted, by using Mie theory, into cloud droplet single and double backscattering and attenuation coefficients. The lidar equation includes forward multiple scattering attenuation corrections based on diffraction theory for droplets and ice crystals, whose relative scattering contributions are treated empirically. Lidar depolarization is computed from droplet and crystal single scattering and an analytical treatment of droplet double scattering. Water cloud results reveal the expected increases in linear depolarization ratios ({delta}) with increasing lidar field of view and distance to cloud but also show that depolarization is a function of cloud liquid water content, which depends primarily on temperature. Ice crystals modulate mixed phase cloud liquid water contents through water vapor competition effects, thereby affecting multiple scattering {delta} values as functions of updraft velocity, temperature, and crystal size and concentration. Although the minimum {delta} at cloud base increases with increasing ice content, the peak measurable {delta} in the cloud decreases. Comparison with field data demonstrate that this modeling approach is a valuable supplement to cloud measurements.

Sassen, K.; Zhao, H.; Dodd, G.C. (Department of Meteorology, University of Utah, Salt Lake City, Utah 84112 (United States))

1992-05-20

117

Use of probability distribution functions for discriminating between cloud and aerosol in lidar backscatter data  

Microsoft Academic Search

In this paper, we describe the algorithm that will be used during the upcoming Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission for discriminating between clouds and aerosols detected in two-wavelength backscatter lidar profiles. We first analyze single-test and multiple-test classification approaches based on one-dimensional (1-D) and multidimensional probability distribution functions (PDFs) in the context of a two-class feature

Zhaoyan Liu; Mark A. Vaughan; David M. Winker; Chris A. Hostetler; Lamont R. Poole; Dennis Hlavka; William Hart; Matthew McGill

2004-01-01

118

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

PubMed

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

Reichardt, J

2000-11-20

119

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

120

cloud albedo effect -1.8 --0.3 W m-2 (IPCC 2007) cloud lifetime effect comparable  

E-print Network

Tuesday, December 18, 2012 #12;SouthEast Pacific free tropo as dry as Arctic above-cloud water vapor paths Lidar (cloud base) millimeter-wave radiometer (lwp) broadband visible radiometer (cloud optical depth) distance analyzed here ~ 3,500 km from 150 lon by 100 lat area radar, lidar, radiometer aerosol cloud drop

Zuidema, Paquita

121

Scanning Cloud Radar Observations at the ARM sites  

NASA Astrophysics Data System (ADS)

Recently, the DOE Atmospheric Radiation Measurement (ARM) program upgraded its fixed and mobile facilities with the acquisition of state-of-the-art scanning, dual-wavelength, polarimetric, Doppler cloud radars. The scanning ARM cloud radars (SACR's) are the most expensive and significant radar systems at all ARM sites and eight SACR systems will be operational at ARM sites by the end of 2013. The SACR's are the primary instruments for the detection of 3D cloud properties (boundaries, volume cloud fractional coverage, liquid water content, dynamics, etc.) beyond the soda-straw (profiling) limited view. Having scanning capabilities with two frequencies and polarization allows more accurate probing of a variety of cloud systems (e.g., drizzle and shallow, warm rain), better correction for attenuation, use of attenuation for liquid water content retrievals, and polarimetric and dual-wavelength ratio characterization of non-spherical particles for improved ice crystal habit identification. Examples of SACR observations from four ARM sites are presented here: the fixed sites at Southern Great Plains (SGP) and North Slope of Alaska (NSA), and the mobile facility deployments at Graciosa Island, Azores and Cape Cod, Massachusetts. The 3D cloud structure is investigated both at the macro-scale (20-50 km) and cloud-scale (100-500 m). Doppler velocity measurements are corrected for velocity folding and are used either to describe the in-cloud horizontal wind profile or the 3D vertical air motions.

Kollias, P.; Clothiaux, E. E.; Shupe, M.; Widener, K.; Bharadwaj, N.; Miller, M. A.; Verlinde, H.; Luke, E. P.; Johnson, K. L.; Jo, I.; Tatarevic, A.; Lamer, K.

2012-12-01

122

Monitoring of tropospheric clouds and precipitation with a dual-polarization scanning lidar  

NASA Astrophysics Data System (ADS)

Currently, the commercial use of atmospheric lidar is limited to the measurement of cloud ceiling. However, very pertinent meteorological information (such as the structure and phase of clouds and precipitation) can be obtained by recording both polarization components of the returns while operating the lidar at a fixed repetition rate and scanning its axis at a constant angular elevation speed. We present results obtained with our dual-polarization scanning lidar system during two measurement campaigns: MWISP (Mount Washington Icing Sensors Project) in April 1999, and AIRS (Alliance Icing Research Study) in the 1999-2000 winter

Roy, Gilles; Bissonnette, Luc R.; Vallee, Gilles; Cantin, Sylvain

2000-12-01

123

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

124

Coordinated radar/lidar observations of troposphere and middle atmosphere at Shigaraki MU observatory, Japan  

NASA Astrophysics Data System (ADS)

The MU (middle and upper atmosphere) radar in Shigaraki, Japan (35N, 136E) is an MST (mesosphere- stratosphere- troposphere) radar, as well as an IS (incoherent scatter) radar, operated at 46.5 MHz with 1 MW transmission power. Although the atmospheres between 2 - 500 km can be observed, the heights between 25 and 60 km cannot be observed due to the lack of scatterers. In order to fill the gap height above, a Rayleigh/Raman lidar system with SHG-YAG laser (532nm, 30W) and a Cassegrain telescope (82 cm diameter) was installed in the MU observatory in 2000, and further improvement has realized the increase of sensitivity as well as capability of measuring rotational temperature from pure rotational Raman signals. Currently, it is capable of measuring temperature in the troposphere and middle atmosphere, as well as humidity and daytime temperature in the troposphere. The combined observation of the radar and the lidar has enabled to capture vertical propagation of gravity waves in detail, as well as comprehensive observation of temperature, wind and humidity in the troposphere.

Nakamura, T.; Behrendt, A.; Onishi, M.; Sawai, Y.; Tsuda, T.

125

The structure and phase of cloud tops as observed by polarization lidar  

NASA Technical Reports Server (NTRS)

High-resolution observations of the structure of cloud tops have been obtained with polarization lidar operated from a high altitude aircraft. Case studies of measurements acquired from cumuliform cloud systems are presented, two from September 1979 observations in the area of Florida and adjacent waters and a third during the May 1981 CCOPE experiment in southeast Montana. Accurate cloud top height structure and relative density of hydrometers are obtained from the lidar return signal intensity. Correlation between the signal return intensity and active updrafts was noted. Thin cirrus overlying developing turrets was observed in some cases. Typical values of the observed backscatter cross section were 0.1-5 (km/sr) for cumulonimbus tops. The depolarization ratio of the lidar signals was a function of the thermodynamic phase of cloud top areas. An increase of the cloud top depolarization with decreasing temperature was found for temperatures above and below -40 C.

Spinhirne, J. D.; Hansen, M. Z.; Simpson, J.

1983-01-01

126

Role of updrafts in aerosol-cloud interactions: lidar observations of layered warm clouds over central Europe  

NASA Astrophysics Data System (ADS)

Twenty nine cases of layered liquid-water cloud systems were observed with dual-field-of-view (dual-FOV) Raman lidar over the polluted central European site of Leipzig, Germany, between September 2010 and September 2012. For the first time, a detailed lidar-based study of aerosol-cloud-dynamics relationship was conducted. A collocated Doppler lidar provided information on vertical velocity and thus on updraft and downdraft occurrence. The novel dual-FOV lidar permits the retrieval of the particle extinction coefficient (used as aerosol proxy just below cloud base) and cloud properties such as droplet effective radius and cloud droplet number concentration in the lower part of optically thin cloud layers. Here, we present the key results of our statistical analysis of the 2010-2012 observations. Besides a clear aerosol effect on cloud droplet number concentration in the lower part of the convectively weak cloud layers during updraft periods, meteorological effects (turbulent mixing, entrainment of dry air) were found to diminish the observable aerosol effect higher up in the clouds. The corresponding aerosol-cloud interaction (ACI) parameter based on changes in cloud droplet number concentration with aerosol loading was found to be close to 0.8 at 30-70 m above cloud base during updraft periods which points to values around 1 at cloud base (0-30 m above cloud base). Our findings are extensively compared with literature values and agree well with airborne observations. As a conclusion, ACI studies over continental sites should include vertical wind observations to avoid a~bias (too low values) in the obtained ACI results.

Schmidt, J.; Ansmann, A.; Bhl, J.; Wandinger, U.

2014-12-01

127

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

128

Use of a cloud-sensing radar and a microwave radiometer as a stratus cloud profiler  

SciTech Connect

Remote sensors such as radar offer an alternate approach to the study of could and drizzle properties. Combining stratus cloud measurements from a K{sub {alpha}}-band radar and microwave radiometer can give profiles of liquid water and droplet distribution. In addition, in drizzle, the radar measurements can be used to estimate drizzle parameters such as number concentration, liquid water, and droplet distribution.

Frisch, A.S.; Fairall, C.W.; Snider, J.B. [NOAA Environmental Technology Lab., Boulder, CO (United States)

1994-12-31

129

Cloud Distribution Statistics from LITE  

NASA Technical Reports Server (NTRS)

The Lidar In-Space Technology Experiment (LITE) mission has demonstrated the utility of spaceborne lidar in observing multilayer clouds and has provided a dataset showing the distribution of tropospheric clouds and aerosols. These unambiguous observations of the vertical distribution of clouds will allow improved verification of current cloud climatologies and GCM cloud parameterizations. Although there is now great interest in cloud profiling radar, operating in the mm-wave region, for the spacebased observation of cloud heights the results of the LITE mission have shown that satellite lidars can also make significant contributions in this area.

Winker, David M.

1998-01-01

130

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

131

Aerosol and Cloud Interaction Observed From High Spectral Resolution Lidar Data  

NASA Technical Reports Server (NTRS)

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 3D) 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 observations are not a ected by cloud adjacency effects, are less prone to cloud contamination, and offer accurate aerosol property measurements (backscatter coefficient, extinction coefficient, lidar ratio, backscatter Angstrom exponent,and aerosol optical depth) at a neospatial resolution (less than 100 m) in the vicinity of clouds. Hence, the HSRL provides an important dataset for studying aerosol and cloud interaction. In this study, we statistically analyze aircraft-based HSRL profiles according to their distance from the nearest cloud, assuring that all profile comparisons are subject to the same large-scale meteorological conditions. Our results indicate that AODs from HSRL are about 17% higher in the proximity of clouds (approximately 100 m) than far away from clouds (4.5 km), which is much smaller than the reported cloud 3D effect on AOD retrievals. The backscatter and extinction coefficients also systematically increase in the vicinity of clouds, which can be explained by aerosol swelling in the high relative humidity (RH) environment and/or aerosol growth through in cloud processing (albeit not conclusively). On the other hand, we do not observe a systematic trend in lidar ratio; we hypothesize that this is caused by the opposite effects of aerosol swelling and aerosol in-cloud processing on the lidar ratio. Finally, the observed backscatter Angstrom exponent (BAE) does not show a consistent trend because of the complicated relationship between BAE and RH. We demonstrate that BAE should not be used as a surrogate for Angstrom exponent, especially at high RH.

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

2008-01-01

132

Analysis of lidar observations of Arctic polar stratospheric clouds during January 1989  

Microsoft Academic Search

We present analyses of lidar backscatter and depolarization ratios for polar stratospheric clouds (PSCs) observed during the 1989 Airborne Arctic Stratospheric Experiment. The backscatter and depolarization ratios are available at one visible and one infrared wavelength. Water ice PSCs were identified at low ambient temperatures based upon their relatively large backscattering and depolarization ratios. The remaining clouds fall into four

Owen B. Toon; Azadeh Tabazadeh; Edward V. Browell; Joseph Jordan

2000-01-01

133

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

NASA Astrophysics Data System (ADS)

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

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

2009-11-01

134

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

NASA Astrophysics Data System (ADS)

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

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

2009-07-01

135

Cloud radar deployment for Indian Monsoon observations: Preliminary Results  

NASA Astrophysics Data System (ADS)

Indian Institute of Tropical Meteorology (IITM)'s acquired Ka-band radar for the Study of the interaction between Cloud and Environment for formation of Precipitation. Main objective of it is to make simultaneous high resolution measurements on dynamical, cloud microphysical and precipitation parameters pertain to monsoon system probably at diverse locations. The goal is to understand the interplay between cloud processes and environment that not only allow understanding the fundamental cloud-environment interactions but also precipitation formation mechanisms and further to estimate cloud contribution to the re-distribution of energy and water in climate system. For this, Polarimetric weather Doppler Radar at higher frequencies (9.5 and 35 GHz) can be a potential tool to gain knowledge on this scientific as well as societal application oriented programme. IITM's Polarimetric scanning Ka-band (cloud) radar operations started recently during May 2013. Mobile Ka-band Scanning Polarimetric Doppler Radar (KaSPR) is a cloud radar operating at wavelength of 8.5 mm with average powers of 110 W. KaSPR incorporates a conduction cooled Extended Interaction Klystron Amplifier. It is having four foot diameter Ka-band cassegrain antenna. Liquid cooled air-sealed RF unit provides excellent temperature stability. Antenna on the top of RF unit is mounted on the Elevation over azimuth pedestal which is designed to rotate continuously in the azimuth axis and a full 180 degrees in the elevation axis (horizon to horizon) with a maximum velocity of 200/sec and maximum acceleration of 120/s2. KaSPR uses dual channel 16-bit digital receiver having dynamic range of more than 80 dB with bandwidths 10 MHz. Arbitrary waveform generator capable of generating any user-defined waveform of up to 16K samples in length. It is having sensitivity of the order -45 dBZ at 5 km. KaSPR has been providing high sensitivity versatile measurements of cloud and precipitation at tropical site (Manderdev, 18.04290 N, 73.86890 E, 1.35 km AMSL) from a scanning mobile platform since May, 2013. The initial results of the above cloud radar observations on Indian monsoon will be discussed.

Chakravarty, K.; Kalapureddy, M.; Pa, M.; Deshpandy, S.; Das, S.; Pandithurai, G.; Prabhakaran, T.; Chandrasekar, C. V.; Goswami, B.

2013-12-01

136

Micropulse Lidar (MPL) Handbook  

SciTech Connect

The micropulse lidar (MPL) is a ground-based optical remote sensing system designed primarily to determine the altitude of clouds overhead. The physical principle is the same as for radar. Pulses of energy are transmitted into the atmosphere; the energy scattered back to the transceiver is collected and measured as a time-resolved signal. From the time delay between each outgoing transmitted pulse and the backscattered signal, the distance to the scatterer is infered. Besides real-time detection of clouds, post-processing of the lidar return can also characterize the extent and properties of aerosol or other particle-laden regions.

Mendoza, A; Flynn, C

2006-05-01

137

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

138

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

SciTech Connect

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

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

2002-01-01

139

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

140

Macrophysical and optical properties of midlatitude high-altitude clouds from 4 ground-based lidars and collocated CALIOP observations  

NASA Astrophysics Data System (ADS)

Cirrus clouds not only play a major role in the energy budget of the Earth-Atmosphere system, but are also important in the hydrological cycle [Stephens et al., 1990; Webster, 1994]. According to satellite passive remote sensing, high-altitude clouds cover as much as 40% of the earth's surface on average (Liou 1986; Stubenrauch et al., 2006) and can reach 70% of cloud cover over the Tropics (Wang et al., 1996; Nazaryan et al., 2008). Hence, given their very large cloud cover, they have a major role in the climate system (Lynch et al. 2001). Cirrus clouds can be classified into three distinct families according to their optical thickness, namely subvisible clouds (OD<0.03), semi-transparent clouds (0.03clouds (0.3Lidar measurements however show that subvisible and semi-transparent clouds represent 50% or more of cirrus cloud population. The radiative effects of cirrus clouds are found to be significant by many studies both at the top of the atmosphere and surface. The contribution of the subvisible and semi-transparent classes is strongly affected by levels of other scatterers in the atmosphere (gases, aerosols). This makes them quite an important topic of study at the global scale. In the present work, we applied the cloud structure analysis algorithm STRAT to long time series of lidar backscatter profiles from multiple locations around the world. Our goal was to establish a Mid-Latitude climatology of cirrus clouds macrophysical properties based on active remote sensing: ground-based lidars at four mid-latitude observatories and the spaceborne instrument CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization). Lidar sampling, macrophysical (cloud base height, cloud top height, cloud thickness) and optical (cloud optical thickness) properties statistics are then evaluated and compared between the four observatories ground-based lidar measurements and quasi-simultaneously CALIOP overpasses. We note an overall good consistency in the macrophysical properties statistics derived from ground- based Lidar and CALIOP. For high altitude clouds, using consistent transmission-based retrieval methods, discrepancies are found in COT retrievals between ground Lidars and CALIOP. Ground-based Lidar retrievals contain less thick cirrus clouds than CALIOP. Overall, the results show that cirrus clouds with COD<0.1 (not included in historical cloud climatologies) represent 30-50% of the non-opaque cirrus class (COD<3, Pressure<440mb from ISCCP). Finally, we analyze the statistic consistencies between each dataset and investigate the possible bias due to lidar sampling and instrument/algorithm differences between ground-based lidar and CALIOP.

Dupont, J. C.; Haeffelin, M.; Morille, Y.; Noel, V.; Keckhut, P.; Comstock, J.; Winker, D.; Chervet, P.; Roblin, A.

2009-04-01

141

GPGPU-based parallel processing of massive LiDAR point cloud  

Microsoft Academic Search

Processing the massive LiDAR point cloud is a time consuming process due to the magnitude of the data involved and the highly computational iterative nature of the algorithms. In particular, many current and future applications of LiDAR require real- or near-real-time processing capabilities. Relevant examples include environmental studies, military applications, tracking and monitoring of hazards. Recent advances in Graphics Processing

Xun Zeng; Wei He

2009-01-01

142

Autonomous, Full-Time Cloud Profiling at Arm Sites with Micro Pulse Lidar  

NASA Technical Reports Server (NTRS)

Since the early 1990's technology advances permit ground based lidar to operate full time and profile all significant aerosol and cloud structure of the atmosphere up to the limit of signal attenuation. These systems are known as Micro Pulse Lidars (MPL), as referenced by Spinhirne (1993), and were first in operation at DOE Atmospheric Radiation Measurement (ARM) sites. The objective of the ARM program is to improve the predictability of climate change, particularly as it relates to cloud-climate feedback. The fundamental application of the MPL systems is towards the detection of all significant hydrometeor layers, to the limit of signal attenuation. The heating and cooling of the atmosphere are effected by the distribution and characteristics of clouds and aerosol concentration. Aerosol and cloud retrievals in several important areas can only be adequately obtained with active remote sensing by lidar. For cloud cover, the height and related emissivity of thin clouds and the distribution of base height for all clouds are basic parameters for the surface radiation budget, and lidar is essetial for accurate measurements. The ARM MPL observing network represents the first long-term, global lidar study known within the community. MPL systems are now operational at four ARM sites. A six year data set has been obtained at the original Oklahoma site, and there are several years of observations at tropical and artic sites. Observational results include cloud base height distributions and aerosol profiles. These expanding data sets offer a significant new resource for cloud, aerosol and atmospheric radiation analysis. The nature of the data sets, data processing algorithms, derived parameters and application results are presented.

Spinhirne, James D.; Campbell, James R.; Hlavka, Dennis L.; Scott, V. Stanley; Flynn, Connor J.

2000-01-01

143

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

Microsoft Academic Search

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

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

2009-01-01

144

GPGPU-based parallel processing of massive LiDAR point cloud  

NASA Astrophysics Data System (ADS)

Processing the massive LiDAR point cloud is a time consuming process due to the magnitude of the data involved and the highly computational iterative nature of the algorithms. In particular, many current and future applications of LiDAR require real- or near-real-time processing capabilities. Relevant examples include environmental studies, military applications, tracking and monitoring of hazards. Recent advances in Graphics Processing Units (GPUs) open a new era of General-Purpose Processing on Graphics Processing Units (GPGPU). In this paper, we seek to harness the computing power available on contemporary Graphic Processing Units (GPUs), to accelerate the processing of massive LiDAR point cloud. We propose a CUDA-based method capable of accelerating processing of massive LiDAR point cloud on the CUDA-enabled GPU. Our experimental results showed that we are able to significantly reduce processing time of constructing TIN from LiDAR point cloud with GPGPU based parallel processing implementation, in comparison with the current state-of-the-art CPU-based algorithms.

Zeng, Xun; He, Wei

2009-10-01

145

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

146

Retrieval of atmospheric attenuation using combined ground-based and airborne 95-GHz cloud radar measurements  

NASA Technical Reports Server (NTRS)

This paper discusses cloud radar calibration and intercomparison of airborne and ground-based radar measurements and presents a unique algorithm for attenuation retrieval. This algorithm is based on dual 95-GHz radar measurements of the same cloud and precipitation volumes collected from opposing viewing angles.

Li, L.; Sekelsky, S.; Reising, S.; Swift, C.; Durden, S.; Sadowy, G.; Dinardo, S.; Li, F.; Huffman, A.; Stephens, G.; Babb, D.; Rosenberger, H.

2001-01-01

147

Aerosols and cirrus clouds over Hanoi, Vietnam: comparison between satellite products and results derived from ground-based lidar measurements  

NASA Astrophysics Data System (ADS)

In this paper, we present examples of aerosol and Cirrus cloud altitude profiles over Hanoi, Vietnam, measured with the ground LIDAR setup of the Institute of Physics. Comparisons are made to LIDAR data collected by the Calipso satellite of the NASA A-Train during its orbits over the Hanoi area. The height distributions for both surface aerosols and Cirrus clouds derived from ground and satellite observations are generally consistent, with distributions between 2km-3km, and 8km-15km respectively for aerosols and Cirrus clouds. Cirrus cloud locations inferred from an analysis of limb spectral radiances obtained by the SCIAMACHY satellite are also consistent with the LIDAR data.

Dothe, H.; Dinh, Trung van; Bui, Hai van; Gruninger, J. H.

2014-11-01

148

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

149

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, pulsed operation is required because the maximum range is proportional to the square of the retro on i) external amplitude modulation [2], ii) phase-locked dual-seed pulsed laser [7], iii) cw dual

Paris-Sud XI, Université de

150

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: Chen, C., X. Chu, A. J. McDonald, S. L. Vadas, Z. Yu, W. Fong and X. Lu (2013), Inertia-gravity waves [Fritts and Alexander, 2003]. Unfortunately, the gravity wave parameterizations used in global models

Vadas, Sharon

151

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

152

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

153

Aerosol and Cloud Observations and Data Products by the GLAS Polar Orbiting Lidar Instrument  

NASA Technical Reports Server (NTRS)

The Geoscience Laser Altimeter System (GLAS) launched in 2003 is the first polar orbiting satellite lidar. The instrument was designed for high performance observations of the distribution and optical scattering cross sections of clouds and aerosol. The backscatter lidar operates at two wavelengths, 532 and 1064 nm. Both receiver channels meet and exceed their design goals, and beginning with a two month period through October and November 2003, an excellent global lidar data set now exists. The data products for atmospheric observations include the calibrated, attenuated backscatter cross section for cloud and aerosol; height detection for multiple cloud layers; planetary boundary layer height; cirrus and aerosol optical depth and the height distribution of aerosol and cloud scattering cross section profiles. The data sets are now in open release through the NASA data distribution system. The initial results on global statistics for cloud and aerosol distribution has been produced and in some cases compared to other satellite observations. The sensitivity of the cloud measurements is such that the 70% global cloud coverage result should be the most accurate to date. Results on the global distribution of aerosol are the first that produce the true height distribution for model inter-comparison.

Spinhirne, J. D.; Palm, S. P.; Hlavka, D. L.; Hart, W. D.; Mahesh, A.; Welton, E. J.

2005-01-01

154

High altitude Balloon Borne Lidar experiment for the study of aerosols and clouds  

NASA Astrophysics Data System (ADS)

Ground based light detection and ranging (LIDAR) instruments are routinely used for the study of aerosols and clouds using remote sensing technique. Such measurements can only give local/regional scale data. Space based system can provide data on global scale and the same can be used for climate modeling and weather forecasting applications. Development of a Balloon Borne Lidar (BBL) system was taken up as a precursor to the development of Space Borne Lidar system by Indian Space Research Organization (ISRO). A downward looking low power, high PRF laser based lidar system (Micro Pulse Lidar) operating at 532nm having 150mm Cassegrain type small telescope and a photomultiplier tube based photon counting data acquisition system was developed for the measurement of backscattered signal from aerosols and clouds. The BBL instrument was flown successfully in a high altitude balloon platform from National Balloon Facility in Hyderabad. The balloon reached a ceiling altitude of 35 km and scientific data on aerosol and clouds were collected for duration of 5 hours. This paper describes the design challenges and the technical complexity associated with the laser based active payload in a balloon platform. Preliminary results of the experiment will also be presented.

Manchanda, R. K.; Ramaratnam, S.; Krishnan, A. R.; Presenna Kumar, Bharghavan; Jeswin Vetha Jeyasingh, J.; Sreekumar, S.; Joy, Sherly; Thirupathirajan, S.; Bhavanikumar, Y.; Devarajan, Anand

155

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

156

ARM Raman Lidar Measurements of High Ice Supersaturation in Cirrus Clouds  

SciTech Connect

Water vapor amounts in the upper troposphere are crucial to understanding the radiative feedback of cirrus clouds on the Earth's climate. We use a unique, year-long dataset of water vapor mixing ratio inferred from ground-based Raman lidar measurements to study the role of ice supersaturation in ice nucleation processes. We find that ice supersaturation occurs 31% of the time in over 300,000 data points. We also examine the distribution of ice supersaturation with height and find that in the uppermost portion of a cloud layer, the air is ice supersaturated 43% of the time. These measurements show that large ice supersaturation is common in cirrus clouds, which supports the theory of ice forming homogeneously. Given the continuous nature of these Raman lidar measurements, our results have important implications for studying ice nucleation processes using cloud microphysical models.

Comstock, Jennifer M.; Ackerman, Thomas P.; Turner, David D.

2004-09-01

157

Cloud liquid water, mean droplet radius, and number density measurements using a Raman lidar  

SciTech Connect

A new technique for measuring cloud liquid water, mean droplet radius, and droplet number density is outlined. The technique is based on simultaneously measuring Raman and Mie scattering from cloud liquid droplets using a Raman lidar. Laboratory experiments on liquid microspheres have shown that the intensity of Raman scattering is proportional to the amount of liquid present in the spheres. This fact is used as a constraint on calculated Mie intensity assuming a gamma function particle size distribution. The resulting retrieval technique is shown to give stable solutions with no false minima. It is tested using Raman lidar data where the liquid water signal was seen as an enhancement to the water vapor signal. The general relationship of retrieved average radius and number density is consistent with traditional cloud physics models. Sensitivity to the assumed maximum cloud liquid water amount and the water vapor mixing ratio calibration are tested. Improvements to the technique are suggested. (c) 1999 American Geophysical Union.

Whiteman, David N. [Laser Remote Sensing Branch, NASA Goddard Space Flight Center, Greenbelt, Maryland (United States)] [Laser Remote Sensing Branch, NASA Goddard Space Flight Center, Greenbelt, Maryland (United States); Melfi, S. Harvey [Department of Physics, University of Maryland, Baltimore County, Baltimore (United States)] [Department of Physics, University of Maryland, Baltimore County, Baltimore (United States)

1999-12-27

158

Evidence of High Ice Supersaturation in Cirrus Clouds Using ARM Raman Lidar Measurements  

SciTech Connect

Water vapor amounts in the upper troposphere are crucial to understanding the radiative feedback of cirrus clouds on the Earths climate. We use a unique, year-long dataset of water vapor mixing ratio inferred from ground-based Raman lidar measurements to study the role of ice supersaturation in ice nucleation processes. We find that ice supersaturation occurs 31% of the time in over 300,000 data points. We also examine the distribution of ice supersaturation with height and find that in the uppermost portion of a cloud layer, the air is ice supersaturated 43% of the time. These measurements show that large ice supersaturation is common in cirrus clouds, which supports the theory of ice forming homogeneously. Given the continuous nature of these Raman lidar measurements, our results have important implications for studying ice nucleation processes using cloud microphysical models.

Comstock, Jennifer M.; Ackerman, Thomas P.; Turner, David D.

2004-06-05

159

High-precision DEM reconstruction based on airborne LiDAR point clouds  

NASA Astrophysics Data System (ADS)

Airborne LiDAR point clouds have become important data sources for DEM generation recently; however the problem of low precision and low efficiency in DEM production still exists. This paper proposes a new technical scheme for high-precision DEM production based on airborne LiDAR point clouds systematically. Firstly, an elevation and density analysis method is applied to filter out outliers. Secondly, ground points are detected by an improved filter algorithm based on the hierarchical smoothing method. Finally, feature lines are extracted by the planar surface fitting and intersecting method, and a simple data structure of feature lines preserved DEM is proposed to achieve reconstructing high accuracy DEM, combing feature lines with ground points. Experimental results show that the proposed scheme is able to compensate for deficiencies of existing DEM reconstruction techniques and can meet the needs of high precision DEM production based on LiDAR data.

Xu, Jingzhong; Kou, Yuan; Wang, Jun

2014-05-01

160

Backscattered signal modulation and emitting module design for a cloud lidar  

NASA Astrophysics Data System (ADS)

The cloud lidar, with the character of high precision and good stability, is an effective way to detect the cloud height. Pulse diode laser (PLD), as an essential part of the lidar system, needs the triggering pulse. In this paper, the emitting part of the lidar is studied - including the simulation of the backscatter SNR, the choose of the PLD and the design of trigging circuit to drive the 905nm PLD with the consideration of the optical system. A circuit for trigging the laser pulse with adjustable power and pulse width is contrived. Then the software Systemview is used to emulate the design and finally the making of PCB is finished. The results show whatever the parameters of the pulse, namely trigging pulse width, the rising edge, dithering , all these can be qualified to be in use in the practice and enjoys the merits of the low cost and convenience. The emitting module operates well.

Shu, Xiaowen; Chen, Zhenyi; Lian, Xu; Jin, Hui; Zhang, Xiaofu

2014-02-01

161

Electric Field Magnitude and Radar Reflectivity as a Function of Distance from Cloud Edge  

NASA Technical Reports Server (NTRS)

The results of analyses of data collected during a field investigation of thunderstorm anvil and debris clouds are reported. Statistics of the magnitude of the electric field are determined as a function of distance from cloud edge. Statistics of radar reflectivity near cloud edge are also determined. Both analyses use in-situ airborne field mill and cloud physics data coupled with ground-based radar measurements obtained in east-central Florida during the summer convective season. Electric fields outside of anvil and debris clouds averaged less than 3 kV/m. The average radar reflectivity at the cloud edge ranged between 0 and 5 dBZ.

Ward, Jennifer G.; Merceret, Francis J.

2004-01-01

162

DC-8 scanning lidar characterization of aircraft contrails and cirrus clouds  

NASA Technical Reports Server (NTRS)

A Subsonic Assessment (SASS) element of the overall Atmospheric Effects of Aviation Project (AEAP) was initiated by NASA to assess the atmospheric impact of subsonic aircraft. SRI was awarded a project to develop and test a scanning backscatter lidar for installation on the NASA DC-8 (year 1), participate in the Subsonic Aircraft: Contrail and Cloud Effects Special Study (SUCCESS) field program (year 2), and conduct a comprehensive analysis of field data (year 3). A scanning mirror pod attached to the DC-8 aircraft provides for scanning lidar observations ahead of the DC-8 and fixed-angle upward or downward observations. The lidar system installed within the DC-8 transmits 275 MJ at 1.06 gm wavelength or about 130 mJ at 1.06 and 0.53 gm simultaneously. Range-resolved aerosol backscatter is displayed in real time in terms of cloud/contrail spatial distributions. The objectives of the project are to map contrail/cloud vertical distributions ahead of DC-8; provide DC-8 guidance into enhanced scattering layers; document DC-8 flight path intersection of contrail and cloud geometries (in-situ measurement positions relative to cloud/contrail shape and an extension of in-situ measurements into the vertical -- integrated contrail/cloud properties); analyze contrail/cloud radiative properties with LIRAD (combined lidar and radiometry) technique; evaluate mean particle sizes of aircraft emissions from two-wavelength observations; study contrail/cloud interactions, diffusion, and mass decay/growth; and make observations in the near-field of aircraft engine emissions. The scanning mirror pod may also provide a scanning capability for other remote sensing instruments.

Nielsen, Norman B.; Uthe, Edward E. (Principal Investigator)

1996-01-01

163

Comparison of winds, waves, and turbulence as observed by airborne lidar, ground-based radars, and instrumented tower  

NASA Technical Reports Server (NTRS)

On June 29, 1981, two ground-based Doppler radars, an airborne Doppler optical radar (lidar), an instrumented tower, and a rawinsonde were employed to collect wind data in the planetary boundary layer (PBL) in central Oklahoma. The main objectives of this experiment were related to a comparison of wind estimates and the visualization of the three-dimensional eddy structure in the convective atmospheric boundary layer. Discrepancies in the mean wind and wind profile detected by the different sensing systems were explained as being caused by a Schuler resonance of the aircraft's inertial navigation system, which caused an erroneous component of the aircraft's ground-relative velocity vector to be subtracted from the lidar-measured radial velocities. It is concluded that NASA's airborne Doppler optical radar system is capable of measuring wind fields in clear air on a smaller scale than was previously available with fixed remote sensors.

Eilts, M. D.; Doviak, R. J.; Sundara-Rajan, A.

1984-01-01

164

Lidar studies of interannual, seasonal, and diurnal variations of polar mesospheric clouds at the South Pole  

E-print Network

water vapor and temper- atures, and possibly as an indicator of long-term global climate change [Thomas water vapor concentration possibly caused by the rising level of mesospheric CO2 and CH4, respectivelyLidar studies of interannual, seasonal, and diurnal variations of polar mesospheric clouds

Chu, Xinzhao

165

A method of deriving features of building from LIDAR point clouds in urban area  

Microsoft Academic Search

This research paper aims at extracting features, especially the plane feature, of building from Light Detection And Ranging (LiDAR) point clouds in Urban Area, and with these features and information to build the model of object. Unlike modeling object in other fields, such as reverse engineering, surfaces of building usually consist of abundant big and plane surfaces which are significant

Weian Wang; Bo Zheng; Jue Lu; Jiao Lu; Yi Liu

2009-01-01

166

ER-2 lidar measurements of stratocumulus cloud top structure on July 14, 1987  

NASA Technical Reports Server (NTRS)

On July 14, 1987 NASA's ER-2 high altitude aircraft flew a mission to measure the structure of stratocumulus clouds off the coast of California. A flight pattern was executed so that the two-dimensional variability of the clouds could be detected. The technique of analysis of the lidar data to measure cloud tops follows. First each signal is searched for its maximum in return strength. This maximum is caused by scattering of the laser light off cloud particles or from the ocean surface. Next the variance of the signal return above the level of maximum backscatter is determined. Cloud top is assigned to a level (above the level of maximum backscatter) where the backscatter exceeds the average variance. This two-step process is necessary because the level of maximum backscatter does not correspond to the cloud top. Ocean surface returns are easily separated from cloud returns in this process, described in detail by Boers, Spinhirne, and Hart (1988). Analysis of the data so far has shown that there were very few breaks in the clouds. Furthermore the layer top was very flat with local oscillations not exceeding 30 m. Such small cloud top variations are still well within the range of detectability, because the precision of this technique of cloud top detection has previously been established to be 13 to 15 m. Data are presently being analyzed to compute cloud top distributions and fractional cloudiness. The aim of this research is to relate the fractional cloudiness to the mean thermodynamic structure of the boundary layer. Researchers plan to compute spectral scales of the cloud top variability in two dimensions to determine the orientation of the clouds with respect to the mean wind. Furthermore the lidar derived cloud top distribution will be used in the computation of the thermodynamic and radiation budget of the boundary layer.

Boers, Reinout; Spinhirne, James D.

1990-01-01

167

Scanning Cloud Radar Observations at Azores: Preliminary 3D Cloud Products  

SciTech Connect

The deployment of the Scanning W-Band ARM Cloud Radar (SWACR) during the AMF campaign at Azores signals the first deployment of an ARM Facility-owned scanning cloud radar and offers a prelude for the type of 3D cloud observations that ARM will have the capability to provide at all the ARM Climate Research Facility sites by the end of 2010. The primary objective of the deployment of Scanning ARM Cloud Radars (SACRs) at the ARM Facility sites is to map continuously (operationally) the 3D structure of clouds and shallow precipitation and to provide 3D microphysical and dynamical retrievals for cloud life cycle and cloud-scale process studies. This is a challenging task, never attempted before, and requires significant research and development efforts in order to understand the radar's capabilities and limitations. At the same time, we need to look beyond the radar meteorology aspects of the challenge and ensure that the hardware and software capabilities of the new systems are utilized for the development of 3D data products that address the scientific needs of the new Atmospheric System Research (ASR) program. The SWACR observations at Azores provide a first look at such observations and the challenges associated with their analysis and interpretation. The set of scan strategies applied during the SWACR deployment and their merit is discussed. The scan strategies were adjusted for the detection of marine stratocumulus and shallow cumulus that were frequently observed at the Azores deployment. Quality control procedures for the radar reflectivity and Doppler products are presented. Finally, preliminary 3D-Active Remote Sensing of Cloud Locations (3D-ARSCL) products on a regular grid will be presented, and the challenges associated with their development discussed. In addition to data from the Azores deployment, limited data from the follow-up deployment of the SWACR at the ARM SGP site will be presented. This effort provides a blueprint for the effort required for the development of 3D cloud products from all new SACRs that the program will deploy at all fixed and mobile sites by the end of 2010.

Kollias, P.; Johnson, K.; Jo, I.; Tatarevic, A.; Giangrande, S.; Widener, K.; Bharadwaj, N.; Mead, J.

2010-03-15

168

Use of Probability Distribution Functions for Discriminating Between Cloud and Aerosol in Lidar Backscatter Data  

NASA Technical Reports Server (NTRS)

In this paper we describe the algorithm hat will be used during the upcoming Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission for discriminating between clouds and aerosols detected in two wavelength backscatter lidar profiles. We first analyze single-test and multiple-test classification approaches based on one-dimensional and multiple-dimensional probability density functions (PDFs) in the context of a two-class feature identification scheme. From these studies we derive an operational algorithm based on a set of 3-dimensional probability distribution functions characteristic of clouds and aerosols. A dataset acquired by the Cloud Physics Lidar (CPL) is used to test the algorithm. Comparisons are conducted between the CALIPSO algorithm results and the CPL data product. The results obtained show generally good agreement between the two methods. However, of a total of 228,264 layers analyzed, approximately 5.7% are classified as different types by the CALIPSO and CPL algorithm. This disparity is shown to be due largely to the misclassification of clouds as aerosols by the CPL algorithm. The use of 3-dimensional PDFs in the CALIPSO algorithm is found to significantly reduce this type of error. Dust presents a special case. Because the intrinsic scattering properties of dust layers can be very similar to those of clouds, additional algorithm testing was performed using an optically dense layer of Saharan dust measured during the Lidar In-space Technology Experiment (LITE). In general, the method is shown to distinguish reliably between dust layers and clouds. The relatively few erroneous classifications occurred most often in the LITE data, in those regions of the Saharan dust layer where the optical thickness was the highest.

Liu, Zhaoyan; Vaughan, Mark A.; Winker, Davd M.; Hostetler, Chris A.; Poole, Lamont R.; Hlavka, Dennis; Hart, William; McGill, Mathew

2004-01-01

169

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

170

Advances in Raman Lidar Measurements of Water Vapor, Cirrus Clouds and Carbon Dioxide  

NASA Technical Reports Server (NTRS)

Narrow-band interference filters with improved transmission in the ultraviolet have been developed under NASA-funded research and used in the Raman Airborne Spectroscopic Lidar (RASL) in ground- based, upward-looking tests. RASL is an airborne Raman Lidar system designed to measure water vapor mixing ratio, and aerosol backscatter/extinction/depolarization. It also possesses the capability to make experimental measurements of cloud liquid water and carbon dioxide. It is being prepared for first flight tests during the summer of 2006. With the newly developed filters installed in RASL, measurements were made of atmospheric water vapor, cirrus cloud optical properties and carbon dioxide that improve upon any previously demonstrated using Raman lidar. Daytime boundary layer profiling of water vapor mixing ratio is performed with less than 5% random error using temporal and spatial resolution of 2-minutes and 60 - 210, respectively. Daytime cirrus cloud optical depth and extinction- to-backscatter ratio measurements are made using 1-minute average. Sufficient signal strength is demonstrated to permit the simultaneous profiling of carbon dioxide and water vapor mixing ratio into the free troposphere during the nighttime. Downward-looking from an airborne RASL should possess the same measurement statistics with approximately a factor of 5 - 10 decrease in averaging time. A description of the technology improvements are provided followed by examples of the improved Raman lidar measurements.

Whiteman, David N.; Potter, John R.; Tola, Rebecca; Rush, Kurt; Veselovskii, Igor; Cadirola, Martin; Comer, Joseph

2006-01-01

171

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

NASA Technical Reports Server (NTRS)

The NASA/GSFC Scanning Raman Lidar (SRL) participated in the International H2O Project (IHOP) that occurred in May and June, 2002 in the midwestern part of the U.S. The SRL acquired measurements of water vapor, aerosols, cloud liquid and ice water, and temperature for more than 200 hours during IHOP. Here we report on the SRL water vapor and cirrus cloud measurements with particular emphasis being given to the measurements of June 19-20, 2002, which are motivating cirrus cloud model comparison studies.

Whiteman, David N.; Demoz, Belay; DiGirolamo, Paolo; Comer, Joe; Wang, Zhien; Lin, Rei-Fong; Evans, Keith; Veselovskii, Igor

2004-01-01

172

Automatic large-volume object region segmentation in LiDAR point clouds  

NASA Astrophysics Data System (ADS)

LiDAR is a remote sensing method which produces precise point clouds consisting of millions of geo-spatially located 3D data points. Because of the nature of LiDAR point clouds, it can often be difficult for analysts to accurately and efficiently recognize and categorize objects. The goal of this paper is automatic large-volume object region segmentation in LiDAR point clouds. This efficient segmentation technique is intended to be a pre- processing step for the eventual classification of objects within the point cloud. The data is initially segmented into local histogram bins. This local histogram bin representation allows for the efficient consolidation of the point cloud data into voxels without the loss of location information. Additionally, by binning the points, important feature information can be extracted, such as the distribution of points, the density of points and a local ground. From these local histograms, a 3D automatic seeded region growing technique is applied. This technique performs seed selection based on two criteria, similarity and Euclidean distance to nearest neighbors. The neighbors of selected seeds are then examined and assigned labels based on location and Euclidean distance to a region mean. After the initial segmentation step, region integration is performed to rejoin over-segmented regions. The large amount of points in LiDAR data can make other segmentation techniques extremely time consuming. In addition to producing accurate object segmentation results, the proposed local histogram binning process allows for efficient segmentation, covering a point cloud of over 9,000 points in 10 seconds.

Varney, Nina M.; Asari, Vijayan K.

2014-10-01

173

GROUND BASED LIDAR OBSERVATIONS OF AEROSOL AND CIRRUS CLOUDS OPTICAL PROPERTIES IN CENTRAL AMAZON DURING THE DRY SEASON  

E-print Network

to perform continuous measurements of aerosols and water vapor and aiming to study and monitor the atmosphereGROUND BASED LIDAR OBSERVATIONS OF AEROSOL AND CIRRUS CLOUDS OPTICAL PROPERTIES IN CENTRAL AMAZON Paulo, São Paulo, S.P., Brazil E-mail: hbarbosa@if.usp.br A permanent UV Raman Lidar station, designed

Barbosa, Henrique

174

Can we measure the aerosol and cloud liquid characteristics by using Mie and liquid-water Raman lidar?  

Microsoft Academic Search

Liquid water Raman signal was measured and normalized by Mie and water vapor Raman signals. In simple theoretical point of view, these normalized cloud liquid water lidar signals have information about the aerosol hydroscopic characteristics and cloud size information. We obtained the qualitative information for these parameters at the cloud and normal atmospheric aerosol. Here we have discussed the possibility

Dukhyeon Kim; Sunho Park; Hai-Du Cheong; Wonseok Choi; Yong-Gi Kim; Moonsang Yun; Imkang Song

2011-01-01

175

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

NASA Astrophysics Data System (ADS)

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, polarization lidar is a key component of current climate-research programs 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. Although unambiguous cloud-phase discrimination and the identification of some ice particle types and orientations are demonstrated capabilities, recent theoretical approaches involving ice crystal ray-tracing and cloud microphysical model simulations are, promising to increase the utility of the technique. New results simulating the single and multiple scattering properties of precipitating mixed-phase clouds are given for illustration of such methods.

Sassen, Kenneth

1991-12-01

176

The 27-28 October 1986 FIRE IFO cirrus case study - A five lidar overview of cloud structure and evolution  

NASA Technical Reports Server (NTRS)

During the case study from the First ISCCP (International Satellite Cloud Climatology Program) Regional Experiment (FIRE) Intensive Field Observation (IFO), one airborne lidar system and four ground-based systems collected 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. Cirrus cloud types include dissipating subvisual and thin fibrous cirrus cloud bands, an isolated mesoscale uncinus complex, 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. It is noted that the cirrus frequently developed in the vertical from particle fallstreaks emanating from generating regions at or near cloud tops; however, glaciating supercooled altocumulus clouds contributed to the production of ice mass at the base of the deep cirrus cloud.

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

1990-01-01

177

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

SciTech Connect

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

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

2010-03-15

178

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

NASA Astrophysics Data System (ADS)

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

Bacha, Tulu

179

Bistatic imaging lidar measurements of aerosols, fogs, and clouds in the lower atmosphere  

NASA Astrophysics Data System (ADS)

We have been developing a bistatic imaging lidar using a high sensitive CCD camera with an image intensifier as a high speed shutter for measuring spatial distributions of aerosols, fogs and clouds in the lower atmosphere at daytime as well as at nighttime. The bistatic imaging lidar was applied to two field observation campaigns. One was made cooperatively with a wind profiler and a radiosonde at Moriya (36 km north of Tokyo) for five days from May 26 to 30, 1997 and another cooperatively with a monostatic lidar at Hakuba alpine ski area of Nagano for 10 days from February 7 to 16, 1998 during the period of the 18th Winter Olympic Games in Japan. We report the results obtained at both campaigns and discuss the ability of this system in measuring the meteorological features of the local lower atmosphere under different conditions.

Lin, Jinming; Mishima, Hidetsugu; Kawahara, Takuya D.; Saito, Yasunori; Nomura, Akio; Yamaguchi, Kenji; Morikawa, Kimio

1998-08-01

180

Raman Lidar Measurements of Water Vapor and Cirrus Clouds During the Passage of Hurricane Bonnie  

NASA Technical Reports Server (NTRS)

The NASA/GSFC Scanning Raman Lidar (SRL) was stationed on Andros Island in the Bahamas during August - September, 1998 as a part of the third Convection and Moisture Experiment (CAMEX-3) which focussed on hurricane development and tracking. During the period August 21 - 24, hurricane Bonnie passed near Andros Island and influenced the water vapor and cirrus cloud measurements acquired by the SRL. Two drying signatures related to the hurricane were recorded by the SRL (Scanning Raman Lidar) and other sensors. Cirrus cloud optical depths (at 351 nm) were also measured during this period. Optical depth values ranged from approximately 0.01 to 1.4. The influence of multiple scattering on these optical depth measurements was studied with the conclusion that the measured values of optical depth are less than the actual value by up to 20% . The UV/IR cirrus cloud optical depth ratio was estimated based on a comparison of lidar and GOES measurements. Simple radiative transfer model calculations compared with GOES satellite brightness temperatures indicate that satellite radiances are significantly affected by the presence of cirrus clouds if IR optical depths are approximately 0.02 or greater. This has implications for satellite cirrus detection requirements.

Whiteman, D. N.; Evans, K. D.; Demoz, B.; Starr, D. OC; Tobin, D.; Feltz, W.; Jedlovec, G. J.; Gutman, S. I.; Schwemmer, G. K.; Cardirola, M.; Melfi, S. H.; Schmidlin, F. J.

2000-01-01

181

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

182

Second annual progress report of the Millimeter Wave Cloud Profiling Radar System (CPRS)  

SciTech Connect

The Cloud Profiling Radar System (CPRS) is a single antenna, two frequency (33 GHz and 95 GHz) polarimetric radar which is currently under the development at the University of Massachusetts (UMASS). This system will be capable of making four dimensional Doppler and polarimetric measurements of clouds. This report gives details about the status of the various subsystems under development and discusses current research activities.

Pazmany, A.L.; Sekelsky, S.M.; McIntosh, R.E.

1992-06-07

183

Precipitating Snow Retrievals from Combined Airborne Cloud Radar and Millimeter-Wave Radiometer Observations  

Microsoft Academic Search

An algorithm for retrieving snow over oceans from combined cloud radar and millimeter-wave radiom- eter observations is developed. The algorithm involves the use of physical models to simulate cloud radar and millimeter-wave radiometer observations from basic atmospheric variables such as hydrometeor con- tent, temperature, and relative humidity profiles and is based on an optimal estimation technique to retrieve these variables

Mircea Grecu; William S. Olson

2008-01-01

184

Microphysical characterization of microwave Radar reflectivity due to volcanic ash clouds  

Microsoft Academic Search

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

Frank Silvio Marzano; Gianfranco Vulpiani; William I. Rose

2006-01-01

185

Aircraft Microphysical and Surface-Based Radar Observations of Summertime Arctic Clouds  

E-print Network

Aircraft Microphysical and Surface-Based Radar Observations of Summertime Arctic Clouds R. PAUL Updated analyses of in situ microphysical properties of three Arctic cloud systems sampled by aircraft to the North Pole. Radar­aircraft agreement in reflectivity and derived microphysical parameters was reasonably

Zuidema, Paquita

186

Retrieval of Polar Stratospheric Cloud Microphysical Properties from Lidar Measurements: Dependence on Particle Shape Assumptions  

NASA Technical Reports Server (NTRS)

A retrieval algorithm has been developed for the microphysical analysis of polar stratospheric cloud (PSC) optical data obtained using lidar instrumentation. The parameterization scheme of the PSC microphysical properties allows for coexistence of up to three different particle types with size-dependent shapes. The finite difference time domain (FDTD) method has been used to calculate optical properties of particles with maximum dimensions equal to or less than 2 mu m and with shapes that can be considered more representative of PSCs on the scale of individual crystals than the commonly assumed spheroids. Specifically. these are irregular and hexagonal crystals. Selection of the optical parameters that are input to the inversion algorithm is based on a potential data set such as that gathered by two of the lidars on board the NASA DC-8 during the Stratospheric Aerosol and Gas Experiment 0 p (SAGE) Ozone Loss Validation experiment (SOLVE) campaign in winter 1999/2000: the Airborne Raman Ozone and Temperature Lidar (AROTEL) and the NASA Langley Differential Absorption Lidar (DIAL). The 0 microphysical retrieval algorithm has been applied to study how particle shape assumptions affect the inversion of lidar data measured in leewave PSCs. The model simulations show that under the assumption of spheroidal particle shapes, PSC surface and volume density are systematically smaller than the FDTD-based values by, respectively, approximately 10-30% and approximately 5-23%.

Reichardt, J.; Reichardt, S.; Yang, P.; McGee, T. J.; Bhartia, P. K. (Technical Monitor)

2001-01-01

187

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

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

188

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

189

Raman Lidar Measurements of Water Vapor and Cirrus Clouds During The Passage of Hurricane Bonnie  

NASA Technical Reports Server (NTRS)

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

Whiteman, D. N.; Evans, K. D.; Demoz, B.; Starr, D OC.; Eloranta, E. W.; Tobin, D.; Feltz, W.; Jedlovec, G. J.; Gutman, S. I.; Schwemmer, G. K.; Smith, David E. (Technical Monitor)

2000-01-01

190

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

191

Cloud and Aerosol Measurements from the GLAS Polar Orbiting Lidar: First Year Results  

NASA Technical Reports Server (NTRS)

The Geoscience Laser Altimeter System (GLAS) launched in 2003 is the first polar orbiting satellite lidar. The instrument was designed for high performance observations of the distribution and optical scattering cross sections of clouds and aerosol. GLAS is approaching six months of on orbit data operation. These data from thousands of orbits illustrate the ability of space lidar to accurately and dramatically measure the height distribution of global cloud and aerosol to an unprecedented degree. There were many intended science applications of the GLAS data and significant results have already been realized. One application is the accurate height distribution and coverage of global cloud cover with one goal of defining the limitation and inaccuracies of passive retrievals. Comparison to MODIS cloud retrievals shows notable discrepancies. Initial comparisons to NOAA 14&15 satellite cloud retrievals show basic similarity in overall cloud coverage, but important differences in height distribution. Because of the especially poor performance of passive cloud retrievals in polar regions, and partly because of high orbit track densities, the GLAS measurements are by far the most accurate measurement of Arctic and Antarctica cloud cover from space to date. Global aerosol height profiling is a fundamentally new measurement from space with multiple applications. A most important aerosol application is providing input to global aerosol generation and transport models. Another is improved measurement of aerosol optical depth. Oceanic surface energy flux derivation from PBL and LCL height measurements is another application of GLAS data that is being pursued. A special area of work for GLAS data is the correction and application of multiple scattering effects. Stretching of surface return pulses in excess of 40 m from cloud propagation effects and other interesting multiple scattering phenomena have been observed. As an EOS project instrument, GLAS data products are openly available to the science community. First year results from GLAS are summarized.

Spinhirne, J. D.; Palm, S. P.; Hlavka, D. L.; Hart, W. D.; Mahesh, A.; Welton, E. J.

2004-01-01

192

Range determination for generating point clouds from airborne small footprint LiDAR waveforms.  

PubMed

This paper presents a range determination approach for generating point clouds from small footprint LiDAR waveforms. Waveform deformation over complex terrain area is simulated using convolution. Drift of the peak center position is analyzed to identify the first echo returned by the illuminated objects in the LiDAR footprint. An approximate start point of peak in the waveform is estimated and adopted as the indicator of range calculation; range correction method is proposed to correct pulse widening over complex terrain surface. The experiment was carried out on small footprint LiDAR waveform data acquired by RIEGL LMS-Q560. The results suggest that the proposed approach generates more points than standard commercial products; based on field measurements, a comparative analysis between the point clouds generated by the proposed approach and the commercial software GeocodeWF indicates that: 1). the proposed approach obtained more accurate tree heights; 2). smooth surface can be achieved with low standard deviation. In summary, the proposed approach provides a satisfactory solution for range determination in estimating 3D coordinate values of point clouds, especially for correcting range information of waveforms containing deformed peaks. PMID:23187409

Qin, Yuchu; Vu, Tuong Thuy; Ban, Yifang; Niu, Zheng

2012-11-01

193

Airborne Doppler radar observations of convective plumes and radar `fine-lines' ERAD02-A-00007  

E-print Network

data suggest that these plumes are buoyant and that they contain more water vapor. The detectability measured directly. Ground-based radar and lidar systems have been used to profile the BL Cloud Radar (WCR, http://www.atmos.uwyo.edu/wcr/projects/ihop02/) taken during the International Water

Geerts, Bart

194

Orbiting lidar simulations. I - Aerosol and cloud measurements by an independent-wavelength technique  

NASA Technical Reports Server (NTRS)

Aerosol and cloud measurements have been simulated for a Space Shuttle lidar. Expected errors - in signal, transmission, density, and calibration - are calculated algebraically and checked by simulating measurements and retrievals using random-number generators. By day, vertical structure is retrieved for tenuous clouds, Saharan aerosols, and boundary layer aerosols (at 0.53 and 1.06 micron) as well as strong volcanic stratospheric aerosols (at 0.53 micron). By night, all these constituents are retrieved plus upper tropospheric and stratospheric aerosols (at 1.06 micron), mesospheric aerosols (at 0.53 micron), and noctilucent clouds (at 1.06 and 0.53 micron). The vertical resolution was 0.1-0.5 km in the troposphere, 0.5-2.0 km above, except 0.25-1.0 km in the mesospheric cloud and aerosol layers; horizontal resolution was 100-2000 km.

Russell, P. B.; Morley, B. M.; Livingston, J. M.; Grams, G. W.; Patterson, E. M.

1982-01-01

195

Operational processing and cloud boundary detection from micro pulse lidar data  

NASA Technical Reports Server (NTRS)

Micro Pulse Lidar (MPL) was developed at NASA Goddard Space Flight Center (GSFC) as the result of research on space-borne lidar techniques. It was designed to provide continuous, unattended observations of all significant atmospheric cloud and aerosol structure with a rugged, compact system design and the benefit of eye safety (Spinhirne 1993). The significant eye safety feature is achieved by using low pulse energies and high pulse repetition rates compared to standard lidar systems. MPL systems use a diode pumped 10 microj, 2500 Hz doubled Nd:YLF laser. In addition, a solid state Geiger mode avalanche photo diode (GAPD) photon counting detector is used allowing for quantum efficiencies approaching 70%. Other design features have previously been noted by Spinhirne (1995). Though a commercially available instrument, with nearly 20 systems operating around the world, the most extensive MPL work has come from those operated by the Atmospheric Radiation Measurement (ARM) (Stokes and Schwartz 1994) program. The diverse ability of the instrument relating to the measurement of basic cloud macrophysical structure and both cloud and aerosol radiative properties well suits the ARM research philosophy. MPL data can be used to yield many parameters including cloud boundary heights to the limit of signal attenuation, cloud scattering cross sections and optical thicknesses, planetary boundary layer heights and aerosol scattering profiles, including those into the stratosphere in nighttime cases (Hlavka et al 1996). System vertical resolution ranges from 30 m to 300 m (i.e. high and low resolution respectively) depending on system design. The lidar research group at GSFC plays an advisory role in the operation, calibration and maintenance of NASA and ARM owned MPL systems. Over the past three years, processing software and system correction techniques have been developed in anticipation of the increasing population of systems amongst the community. Datasets produced by three ARM-owned systems have served as the basis for this development. With two operating at the southern Great Plains Cloud and Radiation Testbed Site (SGP CART) since December 1993 and another at the Manus Island Atmospheric Radiation and Cloud Station (TWP ARCS) location in the tropical western Pacific since February 1997, the ARM archive contains over 4 years of observations. In addition, high resolution systems planning to come on-line at the North Slope, AK CART shortly with another scheduled to follow at the TWP ARCS-II will diversify this archive with more extensive observations.

Campbell, James R.; Hlavka, Dennis L.; Spinhirne, James D.; Scott, V. Stanley., III; Turner, David D.

1998-01-01

196

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

197

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

PubMed

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

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

2013-07-01

198

Multidimensional Cloud Images Retrieval From Dual-Frequency Millimeter-Wave Radar  

E-print Network

meteorological and climate prediction models [1, 5, 6, 9]. In this work, stratus clouds are studied using dual- frequency radar. Liquid stratus clouds are found in the lower part of the atmosphere and have a profound extinction rate. In this work, we retrieve stratus cloud properties in two dimensions using a dual

Cruz-Pol, Sandra L.

199

Dust-cloud density estimation using a single wavelength lidar  

Microsoft Academic Search

The passage of commercial and military aircraft through invisible fresh volcanic ash clouds has caused damage to many airplanes. On December 15, 1989 all four engines of a KLM Boeing 747 were temporarily extinguished in a flight over Alaska resulting in $DOL80 million for repair. Similar aircraft damage to control systems, FLIR\\/EO windows, wind screens, radomes, aircraft leading edges, and

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

1994-01-01

200

Estimation of Microphysical and Radiative Parameters of Precipitating Cloud Systems Using mm-Wavelength Radars  

NASA Astrophysics Data System (ADS)

A remote sensing approach is described to retrieve cloud and rainfall parameters within the same precipitating system. This approach is based on mm-wavelength radar signal attenuation effects which are observed in a layer of liquid precipitation containing clouds and rainfall. The parameters of ice clouds in the upper part of startiform precipitating systems are then retrieved using the absolute measurements of radar reflectivity. In case of the ground-based radar location, these measurements are corrected for attenuation in the intervening layer of liquid hydrometers.

Matrosov, Sergey Y.

2009-03-01

201

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

202

Retrieval of Cirrus Cloud Radiative and Backscattering Properties Using Combined Lidar and Infrared Radiometer (LIRAD) Measurements  

SciTech Connect

A method for retrieval of cirrus macrophysical and radiative properties using combined ruby lidar and infrared radiometer measurements is explained in detail. The retrieval algorithm includes estimation of a variable backscatter-to-extinction ratio for each lidar profile, which accounts for changes in cloud microphysical properties with time. The technique also utilizes a correlated K distribution radiative transfer model,where absorption coefficients K have been tabulated specifically for the bandwidth and filter function of the infrared radiometer. The radiative transfer model allows for estimation of infrared emission due to atmospheric water vapor,ozone,and carbon dioxide, which is essential for deriving cirrus radiative properties. Also described is an improved technique for estimation of upwelling IR radiation that is emitted by the surface of the earth and reflected by the cloud into the radiometer field-of-view. Derived cirrus cloud properties include base and top height and temperature, visible optical depth, emittance, backscatter-to-extinction ratio, and extinction-to-absorption ratio. The purpose of this algorithm is to facilitate the analysis of the extensive high-cloud dataset obtained at the University of Utah, Facility for Atmospheric Remote Sensing in Salt Lake City, UT. To illustrate the method, a cirrus case study is presented.

Comstock, Jennifer M.; Sassen, Kenneth

2001-10-01

203

Performance of the Lidar Design and Data Algorithms for the GLAS Global Cloud and Aerosol Measurements  

NASA Technical Reports Server (NTRS)

The Geoscience Laser Altimeter System (GLAS) launched in early 2003 is the first polar orbiting satellite lidar. The instrument design includes high performance observations of the distribution and optical scattering cross sections of atmospheric clouds and aerosol. The backscatter lidar operates at two wavelengths, 532 and 1064 nm. For the atmospheric cloud and aerosol measurements, the 532 nm channel was designed for ultra high efficiency with solid state photon counting detectors and etalon filtering. Data processing algorithms were developed to calibrate and normalize the signals and produce global scale data products of the height distribution of cloud and aerosol layers and their optical depths and particulate scattering cross sections up to the limit of optical attenuation. The paper will concentrate on the effectiveness and limitations of the lidar channel design and data product algorithms. Both atmospheric receiver channels meet and exceed their design goals. Geiger Mode Avalanche Photodiode modules are used for the 532 nm signal. The operational experience is that some signal artifacts and non-linearity require correction in data processing. As with all photon counting detectors, a pulse-pile-up calibration is an important aspect of the measurement. Additional signal corrections were found to be necessary relating to correction of a saturation signal-run-on effect and also for daytime data, a small range dependent variation in the responsivity. It was possible to correct for these signal errors in data processing and achieve the requirement to accurately profile aerosol and cloud cross section down to 10-7 llm-sr. The analysis procedure employs a precise calibration against molecular scattering in the mid-stratosphere. The 1064 nm channel detection employs a high-speed analog APD for surface and atmospheric measurements where the detection sensitivity is limited by detector noise and is over an order of magnitude less than at 532 nm. A unique feature of the GLAS is a full acquisition of the surface return pulse, which has important application to the atmospheric transmission retrieval.

Spinhirne, James D.; Palm, Stephen P.; Hlavka, Dennis L.; Hart, William D.

2007-01-01

204

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

205

Turn-key Raman lidar for profiling atmospheric water vapor, clouds, and aerosols.  

PubMed

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 provides excellent daytime capability without sacrificing nighttime performance. It is fully computer automated and runs unattended following a simple, brief (~5-min) start-up period. We discuss the theory and design of the system and present detailed analyses of the derivation of water-vapor profiles from the lidar measurements. PMID:18285967

Goldsmith, J E; Blair, F H; Bisson, S E; Turner, D D

1998-07-20

206

Turn-key Raman lidar for profiling atmospheric water vapor, clouds, and aerosols  

SciTech Connect

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 provides excellent daytime capability without sacrificing nighttime performance. It is fully computer automated and runs unattended following a simple, brief ({approximately}5-min) start-up period. We discuss the theory and design of the system and present detailed analysis of the derivation of water-vapor profiles from the lidar measurements. {copyright} 1998 Optical Society of America

Goldsmith, J.E.M.; Blair, Forest H.; Bisson, Scott E. [Sandia National Laboratories, P. O. Box 969, MS 9409, Livermore, California 94551-0969 (United States)] Turner, David D. [Pacific Northwest National Laboratory, P. O. Box 999, Richland, Washington 99352 (United States)

1998-07-01

207

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

E-print Network

to hemispherical differences in the mesopause temperatures, water vapor concentrations, and winds. SatelliteLidar 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

Chu, Xinzhao

208

Vertical velocities within a Cirrus cloud from Doppler lidar and aircraft measurements during FIRE: Implications for particle growth  

NASA Technical Reports Server (NTRS)

A large and comprehensive data set taken by the NOAA CO2 Doppler lidar, the NCAR King Air, and rawinsondes on 31 October 1986 during the FIRE (First ISCCP Regional Experiment) field program which took place in Wisconsin are presented. Vertical velocities are determined from the Doppler lidar data, and are compared with velocities derived from the aircraft microphysical data. The data are used for discussion of particle growth and dynamical processes operative within the cloud.

Gultepe, Ismail; Heymsfield, Andrew J.

1990-01-01

209

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

210

Snowfall Retrievals Using Millimeter-Wavelength Cloud Radars SERGEY Y. MATROSOV, MATTHEW D. SHUPE, AND IRINA V. DJALALOVA  

E-print Network

Snowfall Retrievals Using Millimeter-Wavelength Cloud Radars SERGEY Y. MATROSOV, MATTHEW D. SHUPE primarily for cloud studies can be also used effectively for snowfall retrievals. Radar reflectivity­liquid equivalent snowfall rate (Ze­S) rela- tions specifically tuned for Ka- and W-band radar frequencies

Shupe, Matthew

211

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

212

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

213

Profiling Cloud Ice Mass and Particle Characteristic Size from Doppler Radar Measurements  

Microsoft Academic Search

A remote sensing method is proposed for the retrievals of vertical profiles of ice cloud microphysical parameters from ground-based measurements of radar reflectivity and Doppler velocity with a vertically pointed cloud radar. This method relates time-averaged Doppler velocities (which are used as a proxy for the reflectivity-weighted particle fall velocities) to particle characteristic sizes such as median or mean. With

SERGEY Y. M ATROSOV; ALEXEI V. K OROLEV; ANDREW J. HEYMSFIELD

2002-01-01

214

A compact millimeter wave radar for airborne studies of clouds and precipitation  

Microsoft Academic Search

We present a compact 95 GHz radar designed for cloud and precipitation research. This instrument is suitable for deployment on a wide variety of aircraft including an unmanned aerospace vehicle (UAV). The radar was designed and is being built at the University of Massachusetts to fly with a suite of instruments in the Atmospheric Radiation Measurement-Unmanned Aerospace Vehicle (ARM-UAV) program.

Ray P. Bambha; James R. Carswell; James B. Mead; Robert E. McIntosh

1998-01-01

215

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

216

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

217

Vertical distribution of clouds over Hampton, Virginia observed by lidar under the ECLIPS and FIRE ETO programs  

NASA Technical Reports Server (NTRS)

Intensive cloud lidar observations have been made by NASA Langley Research Center during the two observation phases of the ECLIPS project. Less intensive but longer term observations have been conducted as part of the FIRE extended time observation (ETO) program since 1987. We present a preliminary analysis of the vertical distribution of clouds based on these observations. A mean cirrus thickness of just under 1 km has been observed with a mean altitude of about 80 percent of the tropopause height. Based on the lidar data, cirrus coverage was estimated to be just under 20 percent, representing roughly 50 percent of all clouds studied. Cirrus was observed to have less seasonal variation than lower clouds. Mid-level clouds are found to occur primarily in association with frontal activity.

Vaughan, M. A.; Winker, D. M.

1994-01-01

218

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

NASA Astrophysics Data System (ADS)

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

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

2010-09-01

219

Observations of atmospheric water vapor, aerosol, and cloud with a Raman lidar  

NASA Astrophysics Data System (ADS)

To realize the improvement of signal-to-noise ratio and rejection rate for elastic Mie-Rayleigh signals, a set of dichroic mirrors and narrow-band interference filters with high efficiency was proposed to constitute a new spectroscopy for atmospheric water vapor, aerosol, and cloud studies. Based on the curves of signal-to-noise ratio at three different channels, the actual rejection rates of elastic Mie-Rayleigh signals at the Raman channels were found to be higher than eight orders of magnitude with the cloudy conditions. Continuous nighttime observations showed that the statistical error of the water vapor mixing ratio was <10% at a height of 2.3 km with an aerosol backscatter ratio of 17. Temporal variations of water vapor and aerosols were obtained under the conditions of cloud and cloud-free, the change relevance between aerosol and water vapor was analyzed, and the growth characteristics of water vapor and aerosols showed a good agreement within the cloud layers. Obtained results indicate achievement of the continuous detection of water vapor, aerosol, and cloud with a high efficiency and stability by Raman lidar.

Yufeng, Wang; Fei, Gao; Chengxuan, Zhu; Qing, Yan; Dengxin, Hua

2014-11-01

220

TOWARDS A CHARACTERIZATION OF ARCTIC MIXED-PHASE CLOUDS CIRES/NOAA/ETL  

E-print Network

sensors including radar, lidar, and temperature soundings, have been utilized in an automated cloud type of these parameters from year-to-year at the NSA site, and in comparison with similar observations from the SHEBA

221

20 Years Lidar Observations of Clouds at the Edge of Space  

NASA Astrophysics Data System (ADS)

The highest clouds in the Earth atmosphere are located around 83 km altitude. They were first documented in 1885 and are called noctilucent clouds (NLC) because of the impressive bluish-white displays they form against the dark night sky. NLC occur during the summer months from mid to high latitudes and are a visible sign of the extreme conditions in the mesopause region. They consist of nano-sized ice particles (mean value 481 nm) which are subject to the variability of the ambient atmosphere. Ice formation and growth at these high altitudes is very sensitive to temperature and water vapor content which are hardly to measure directly with high accuracy. Thus NLC can act as tracers for short-term variations and are thought to document long-term atmospheric changes as well. We will report about our NLC time series obtained by laser optical remote sensing at the research station ALOMAR in Northern Norway (69N, 16E). The data archive obtained with the Rayleigh/Mie/Raman-lidar covers now 20 summer seasons and is the largest NLC data set acquired by lidar. It shows variabilities of basic cloud parameters like occurrence, altitude and brightness on time scales ranging from minutes to years. Using the capability of all three emitted laser wavelengths we are able to determine ice particle properties like mean and width of the size distribution and number density. This allows investigation of the cloud water content and its variability. Comparing our ground-based measurements on a fixed location to data sets obtained from sun-synchronous satellites shows certain differences. They could at least partly be attributed to the observation conditions like measurement volume, local time, scattering angles etc. We found atmospheric tides to have a significant influence on the NLC properties. Additionally microphysical processes limit the duration within the ice particles can be considered as passive tracers. Long-term data sets are subject to varying instrument sensitivities, caused by atmospheric transmission as well as system performance. We have investigated the temporal development of the lower lidar detection limit and its impact on the retrieved cloud properties. It is important to take these effects into account as they can change the tendency of long time series.

Fiedler, J.; Baumgarten, G.; Luebken, F.

2013-12-01

222

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

NASA Astrophysics Data System (ADS)

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

Thayer, Jeffrey P.; Pan, Weilin

2006-01-01

223

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

E-print Network

Ice iron/sodium film as cause for high noctilucent cloud radar reflectivity P. M. Bellan1 Received that such a film exists and is caused by the deposition of iron and sodium atoms on the ice grain from iron observations indicating that noctilucent clouds are the dominant sink for the summer-time iron and sodium

Bellan, Paul M.

224

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

E-print Network

as surface heating over the continents; by definition, these clouds precipitate at some stageFrequency of tropical precipitating clouds as observed by the Tropical Rainfall Measuring Mission Precipitation Radar and ICESat/Geoscience Laser Altimeter System Sean P. F. Casey,1 Andrew E. Dessler,1

225

Water Vapor, Cloud Liquid Water Paths, and Rain Rates over the Northern High Latitude Open Seas  

E-print Network

Water Vapor, Cloud Liquid Water Paths, and Rain Rates over the Northern High Latitude Open Seas-based Instrumentation: May 1-8 time series 35 GHz cloud radar ice cloud properties depolarization lidar-determined liquid cloud base Microwave radiometer-derived liquid water paths Near-surface T ~ -30 C, inversion

Zuidema, Paquita

226

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

227

Lidar investigations on the optical and dynamical properties of cirrus clouds in the upper troposphere and lower stratosphere regions at a tropical station, Gadanki, India (13.5N, 79.2E)  

NASA Astrophysics Data System (ADS)

High altitude cirrus clouds are composed mainly of ice crystals with a variety of sizes and shapes. They have a large influence on Earth's energy balance and global climate. Recent studies indicate that the formation, dissipation, life time, optical, and micro-physical properties are influenced by the dynamical conditions of the surrounding atmosphere like background aerosol, turbulence, etc. In this work, an attempt has been made to quantify some of these characteristics by using lidar and mesosphere-stratosphere-troposphere (MST) radar. Mie lidar and 53 MHz MST radar measurements made over 41 nights during the period 2009 to 2010 from the tropical station, Gadanki, India (13.5N, 79.2E). The optical and microphysical properties along with the structure and dynamics of the cirrus are presented as observed under different atmospheric conditions. The study reveals the manifestation of different forms of cirrus with a preferred altitude of formation in the 13 to 14 km altitude. There are considerable differences in the properties obtained among 2009 and 2010 showing significant anomalous behavior in 2010. The clouds observed during 2010 show relatively high asymmetry and large multiple scattering effects. The anomalies found during 2010 may be attributed to the turbulence noticed in the surrounding atmosphere. The results show a clear correlation between the crystal morphology in the clouds and the dynamical conditions of the prevailing atmosphere during the observational period.

Krishnakumar, Vasudevannair; Satyanarayana, Malladi; Radhakrishnan, Soman R.; Dhaman, Reji K.; Jayeshlal, Glory Selvan; Motty, Gopinathan Nair S.; Pillai, Vellara P. Mahadevan; Raghunath, Karnam; Ratnam, Madineni Venkat; Rao, Duggirala Ramakrishna; Sudhakar, Pindlodi

2014-01-01

228

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

229

A joint study of the lower ionosphere by radar, lidar, and spectrometer  

NASA Astrophysics Data System (ADS)

The dynamics and associated phenomena occurring in the lower ionospheric-E region, especially the mesopause region between 80 km to 110 km at low latitude, are studied. In particular, incoherent scatter radar (ISR), sodium lidar and airglow spectrometry are used to study the ionospheric structure and neutral sodium structure. The simultaneous study of the ionospheric plasma and neutral atomic sodium is unprecedented in scope and detail. The joint study of the mesopause region reveals that plasma, neutral densities and temperature are interconnected through the same atmospheric dynamics. The theme of the thesis is to explain the formation of the controversial sporadic sodium layer (SSL) events. Strong correlation is established between the average total ion and sodium concentrations, and between sporadic-E and SSL events. The mechanism proposed in the thesis, which invokes temperature fluctuations induced by tides and gravity waves, finds good agreement with observations. Tides and gravity waves can converge ions into thin layers through the windshear mechanisms and can influence the concentration of atomic sodium through temperature fluctuations. Sodium abundance is shown to augment rapidly when the temperature is increased. Gravity wave theory states that the ion convergence node coincides with a temperature maximum for a westward propagating gravity wave, and coincides with a temperature minimum for an eastward propagating wave. Because tidal winds propagate westward, the ion layer coincides with the temperature maximum which consequently induces higher sodium concentration. This can account for the general correlation between sodium and total ion concentration and is supported by the O2(0-1) rotational temperature. Gravity waves and their interaction with tidal winds are believed to be responsible for the close association between sudden sodium layers and sporadic-E layers. It is hypothesized that there may exist a sodium dust layer with peak amplitude around the mesopause height. When this dust layer is pushed up or down, sodium may be released from the dust to cause the structural change in the sodium layer. An effective and fast ISR interference detection and correction scheme is presented. The O2(0-1) and OH(6-2) rotational densities and temperatures of the airglow have been derived and studied.

Zhou, Qihou

1991-05-01

230

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

231

Coordinated radar\\/lidar observations of troposphere and middle atmosphere at Shigaraki MU observatory, Japan  

Microsoft Academic Search

The MU (middle and upper atmosphere) radar in Shigaraki, Japan (35N, 136E) is an MST (mesosphere- stratosphere- troposphere) radar, as well as an IS (incoherent scatter) radar, operated at 46.5 MHz with 1 MW transmission power. Although the atmospheres between 2 - 500 km can be observed, the heights between 25 and 60 km cannot be observed due to the

T. Nakamura; A. Behrendt; M. Onishi; Y. Sawai; T. Tsuda

2002-01-01

232

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.

233

Polar Mesospheric Clouds and Rocket Exhaust in the Arctic Middle Atmosphere: Lidar Observations and Analysis  

NASA Astrophysics Data System (ADS)

We report observations of polar mesospheric clouds (PMC) and rocket exhaust by ground-based lidar at Poker Flat Research Range (PFRR), Chatanika, Alaska (65N, 147W). The PMC observations have been made in late summer over several years in years when space shuttle launches both did and did not occur. The rocket exhaust observations have been made in late winter and spring on three nights when Black Brandt XII (two) and X (one) rockets were launched at PFRR. The PMCs are observed at altitudes between 80 and 86 km during visual displays. The rocket exhaust is observed at altitudes between 66 and 82 km, with the strongest echoes from the cloud at the higher altitudes. The aerosol backscatter ratios of the clouds and exhaust have magnitudes from 0.1 to 100. We consider the areal extent, seasonal evolution, and environmental conditions of the PMCs as observed by satellites (i.e., EOS-Aura/OMI, NOAA/SBUV, and EOS-Aura/MLS). We analyze the structure of the PMCs in different years in terms of current microphysical models and analyze the characteristics of the clouds in terms of the influence of space shuttle exhaust. We consider the formation of the rocket exhaust in terms of the combustion products of the rocket fuel and the environmental conditions measured by satellites (i.e., UARS/MLS). We compare and contrast the structure of the PMCs and rocket exhaust and discuss them as indicators of atmospheric conditions.

Collins, R. L.; Deland, M. T.; Lieberman, R. S.; Walker, G. W.

2010-12-01

234

3-D earthquake surface displacements from differencing pre- and post-event LiDAR point clouds  

NASA Astrophysics Data System (ADS)

The explosion in aerial LiDAR surveying along active faults across the western United States and elsewhere provides a high-resolution topographic baseline against which to compare repeat LiDAR datasets collected after future earthquakes. We present a new method for determining 3-D coseismic surface displacements and rotations by differencing pre- and post-earthquake LiDAR point clouds using an adaptation of the Iterative Closest Point (ICP) algorithm, a point set registration technique widely used in medical imaging, computer vision and graphics. There is no need for any gridding or smoothing of the LiDAR data and the method works well even with large mismatches in the density of the two point clouds. To explore the method's performance, we simulate pre- and post-event point clouds using real ("B4") LiDAR data on the southern San Andreas Fault perturbed with displacements of known magnitude. For input point clouds with ~2 points per square meter, we are able to reproduce displacements with a 50 m grid spacing and with horizontal and vertical accuracies of ~20 cm and ~4 cm. In the future, finer grids and improved precisions should be possible with higher shot densities and better survey geo-referencing. By capturing near-fault deformation in 3-D, LiDAR differencing with ICP will complement satellite-based techniques such as InSAR which map only certain components of the surface deformation and which often break down close to surface faulting or in areas of dense vegetation. It will be especially useful for mapping shallow fault slip and rupture zone deformation, helping inform paleoseismic studies and better constrain fault zone rheology. Because ICP can image rotations directly, the technique will also help resolve the detailed kinematics of distributed zones of faulting where block rotations may be common.

Krishnan, A. K.; Nissen, E.; Arrowsmith, R.; Saripalli, S.

2012-12-01

235

Retrieval of ice cloud microphysics by synergy use of CloudSat and CALIPSO data  

Microsoft Academic Search

We examined the global distribution of ice cloud microphysics from CloudSat and CALIPSO in October 2006. We first developed the synergy cloud mask scheme to specify cloud pixels. Radar-only mask was the same as in 2B-GEOPROF for CloudSat but the lidar mask was developed and was different from the CALIPSO Vertical Feature Mask (VFM) in order to remove the contamination

Hajime Okamoto; Kaori Sato; Yuichiro Hagihara

2009-01-01

236

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

NASA Technical Reports Server (NTRS)

During the First ISCCP Region Experiment (FIRE) cirrus intensive field observation (IFO) the High Spectral Resolution Lidar was operated from a roof top site on the University of Wisconsin-Madison campus. Because the HSRL technique separately measures the molecular and cloud particle backscatter components of the lidar return, the optical thickness is determined independent of particle backscatter. This is accomplished by comparing the known molecular density distribution to the observed decrease in molecular backscatter signal with altitude. The particle to molecular backscatter ratio yields calibrated measurements of backscatter cross sections that can be plotted ro reveal cloud morphology without distortion due to attenuation. Changes in cloud particle size, shape, and phase affect the backscatter to extinction ratio (backscatter-phase function). The HSRL independently measures cloud particle backscatter phase function. This paper presents a quantitative analysis of the HSRL cirrus cloud data acquired over an approximate 33 hour period of continuous near zenith observations. Correlations between small scale wind structure and cirrus cloud morphology have been observed. These correlations can bias the range averaging inherent in wind profiling lidars of modest vertical resolution, leading to increased measurement errors at cirrus altitudes. Extended periods of low intensity backscatter were noted between more strongly organized cirrus cloud activity. Optical thicknesses ranging from 0.01-1.4, backscatter phase functions between 0.02-0.065 sr (exp -1) and backscatter cross sections spanning 4 orders of magnitude were observed. the altitude relationship between cloud top and bottom boundaries and the cloud optical center altitude was dependent on the type of formation observed Cirrus features were observed with characteristic wind drift estimated horizontal sizes of 5-400 km. The clouds frequently exhibited cellular structure with vertical to horizontal dimension ratios of 1:5-1:1.

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

1996-01-01

237

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

238

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

239

The VAMOS Ocean Cloud AtmosphereThe VAMOS Ocean-Cloud-Atmosphere-R b t W d U i it f W hi tRobert Wood, University of Washington  

E-print Network

, cloud microphysics, turbulence microphysics, radiative measurementsRemote sensing and cloud imaging remote sensing, microphysics,Chemistry and microphysics, turbulence Aerosols, cloud i h i y aerosols Chemistry and aerosols, cloud microphysics, turbulence, radar/lidar remote sensing NERC Dornier 228 UK

Wood, Robert

240

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

241

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

242

Rule-based segmentation of LIDAR point cloud for automatic extraction of building roof planes  

NASA Astrophysics Data System (ADS)

This paper presents a new segmentation technique for LIDAR point cloud data for automatic extraction of building roof planes. Using the ground height from a DEM (Digital Elevation Model), the raw LIDAR points are separated into two groups: ground and nonground points. The ground points are used to generate a "building mask" in which the black areas represent the ground where there are no laser returns below a certain height. The non-ground points are segmented to extract the planar roof segments. First, the building mask is divided into small grid cells. The cells containing the black pixels are clustered such that each cluster represents an individual building or tree. Second, the non-ground points within a cluster are segmented based on their coplanarity and neighbourhood relations. Third, the planar segments are refined using a rule-based procedure that assigns the common points among the planar segments to the appropriate segments. Finally, another rule-based procedure is applied to remove tree planes which are small in size and randomly oriented. Experimental results on the Vaihingen data set show that the proposed method offers high building detection and roof plane extraction rates.

Awrangjeb, M.; Fraser, C. S.

2013-10-01

243

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

244

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

245

Application of the CloudSat and NEXRAD Radars Toward Improvements in High Resolution Operational Forecasts  

NASA Technical Reports Server (NTRS)

As computational power increases, operational forecast models are performing simulations with higher spatial resolution allowing for the transition from sub-grid scale cloud parameterizations to an explicit forecast of cloud characteristics and precipitation through the use of single- or multi-moment bulk water microphysics schemes. investments in space-borne and terrestrial remote sensing have developed the NASA CloudSat Cloud Profiling Radar and the NOAA National Weather Service NEXRAD system, each providing observations related to the bulk properties of clouds and precipitation through measurements of reflectivity. CloudSat and NEXRAD system radars observed light to moderate snowfall in association with a cold-season, midlatitude cyclone traversing the Central United States in February 2007. These systems are responsible for widespread cloud cover and various types of precipitation, are of economic consequence, and pose a challenge to operational forecasters. This event is simulated with the Weather Research and Forecast (WRF) Model, utilizing the NASA Goddard Cumulus Ensemble microphysics scheme. Comparisons are made between WRF-simulated and observed reflectivity available from the CloudSat and NEXRAD systems. The application of CloudSat reflectivity is made possible through the QuickBeam radiative transfer model, with cautious application applied in light of single scattering characteristics and spherical target assumptions. Significant differences are noted within modeled and observed cloud profiles, based upon simulated reflectivity, and modifications to the single-moment scheme are tested through a supplemental WRF forecast that incorporates a temperature dependent snow crystal size distribution.

Molthan, A. L.; Haynes, J. A.; Case, J. L.; Jedlovec, G. L.; Lapenta, W. M.

2008-01-01

246

Comparison of lightning location data and polarisation radar observations of clouds  

NASA Technical Reports Server (NTRS)

Simultaneous observations of both the precipitation and the lightning associated with thunderstorms show that the lightning is within 3 km of the maximum precipitation echo. The intensity and type of the precipitation is observed with 500 m spatial accuracy using an S-band polarization radar and the position of the lightning is inferred from a low frequency magnetic direction finding location system. Empirical adjustment to the angles using the redundancy of the lightning data reduce this error. Radar echoes above 45dBZ may be caused by soft hail or hailstones, but similarly intense echoes may result from melting snow. The data show that a new polarization radar parameter, the linear depolarization ratio, can distinguish between soft hail and melting snow, and that the intense radar echoes associated with melting snow pose no threat of lightning. A lightning risk only exists when the radar indicates that the clouds contain soft hail or hailstones.

Illingworth, A. J.; Lees, M. I.

1991-01-01

247

A composite study of Florida thunderstorms, using radar, cloud-to-ground lightning, and surface winds  

NASA Technical Reports Server (NTRS)

Two thunderstorms occurring in Florida during the summer of 1987 are studied in order to determine the location of cloud-to-ground (CG) lightning in terms of surface winds and radar reflectivity. Composites of radar, CG lightning locations, and surface winds during the development, mature, and dissipation stages of the storms are presented and analyzed. The relationship between lightning and radar reflectivity is examined. It is noted that the main CG lightning activity region is on the upshear side of the storm in the reflectivity gradient where upward motion is between the convergent gust front and reflectivity center, and lightning avoids areas of maximum reflectivity.

Watson, Andrew I.; Lopez, Raul E.; Daugherty, John R.; Ortiz, Robert; Holle, Ronald L.

1989-01-01

248

Estimation of cirrus cloud particle fallspeeds from vertically pointing Doppler radar  

NASA Technical Reports Server (NTRS)

The First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment 2 (FIRE 2) was conducted in Coffeyville, Kansas in late 1991 to study the microphysical and radiative properties of cirrus clouds. A variety of active and passive remote sensors were employed, including an 8-mm-wavelength cloud-sensing Doppler radar developed at the Wave Propagation Laboratory (WPL). The radar, having excellent sensitivity to cloud particles (-30 dBZ at 10 km), good spatial resolution (37 m), and velocity precision (.05 ms -1), is an excellent tool for observing cirrus clouds. Having this radar directed toward the zenith for long periods of time during FIRE 2 permitted the reflectivity-weighted particle fallspeed to be related to reflectivity which allowed a separation of ice particle fallspeeds from vertical air motions. Additionally, such relationships proved useful in other multi-sensor techniques for determining vertical profiles of ice particle characteristic size and ice water content in cirrus clouds. The analysis method and the results of applying it to cirrus cloud reflectivity and velocity data collected during FIRE 2 are discussed.

Orr, Brad W.; Kropfli, Robert A.

1993-01-01

249

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

250

Cloud Radar Observations made during the Rains of EPIC-2001 P.Zuidema,C.Fairall,T.Uttal,I.Djalalova,S.Matrosov  

E-print Network

Cloud Radar Observations made during the Rains of EPIC-2001 P-31, the ship remained located at roughly 10N,95 W. A cloud radar (Ka-band,8.66 mm wavelength) was present on the RHB during this time. Although cloud radars are not normally applied within heavily-raining regions

Zuidema, Paquita

251

Microphysical and Radar Observations of Seeded and Nonseeded Continental Cumulus Clouds.  

NASA Astrophysics Data System (ADS)

Controlled cloud seeding experiments were conducted near Bethlehem, South Africa during the summer of 1984-85. The experimental unit was the semi-isolated cumulus congestus cloud. Microphysical measurements were obtained by three instrumented aircraft flying in stacked formation. Radar observations were made by a 5-cm wavelength radar performing volume scans at 5-min intervals. A three-way balanced randomization scheme was used to seed the clouds near the 8C level with either dry ice pellets, silver iodide pyrotechnics, or a placebo (no-seed) treatment. Strict cloud selection criteria, based on the measurements made during an initial inspection penetration, assured the treatment of clouds in their developing stages as their tops row up through the 10C level. A total of 60 clouds were chosen and treated.Using ice crystal measurements, mostly above the seeding level, it was conclusively demonstrated that some cumulus clouds were modified by the injection of either dry ice or silver iodide. High ice concentrations were produced and the evolution of the ice particle size distribution is consistent with a rain enhancement hypothesis involving an artificially induced ice embryo process. However, the liquid water contents decayed rapidly, primarily due to entrainment, and in the majority of the seeded cases precipitation particles formed due to low-density accretion onto aggregates resulting in little or no precipitation at the ground. The dry ice and silver iodide seeded clouds that echoed had significantly higher maximum 1-km average ice concentrations than the placebo clouds, as measured by the research aircraft during the clouds' developing stages.Approximately 67% of the dry ice-treated clouds, 63% of the silver iodide-treated clouds and 45% of the placebo clouds produced radar echoes >10 dBZ. The dry ice-seeded clouds that echoed had significantly higher maximum cell heights than the placebo cells and the silver iodide-seeded cells. When the test cloud data were stratified according to cloud diameter, a positive association existed between seeding and the number of clouds that echoed. Wider clouds responded more favorably to seeding, presumably because they were affected less by entrainment.

Krauss, T. W.; Bruintjes, R. T.; Verlinde, J.

1987-05-01

252

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

253

Continuous Lidar Monitoring of Polar Stratospheric Clouds at the South Pole  

NASA Technical Reports Server (NTRS)

Polar stratospheric clouds (PSC) play a primary role in the formation of annual ozone holes over Antarctica during the austral sunrise. Meridional temperature gradients in the lower stratosphere and upper troposphere, caused by strong radiative cooling, induce a broad dynamic vortex centered near the South Pole that decouples and insulates the winter polar airmass. PSC nucleate and grow as vortex temperatures gradually fall below equilibrium saturation and frost points for ambient sulfate, nitrate, and water vapor concentrations (generally below 197 K). Cloud surfaces promote heterogeneous reactions that convert stable chlorine and bromine-based molecules into photochemically active ones. As spring nears, and the sun reappears and rises, photolysis decomposes these partitioned compounds into individual halogen atoms that react with and catalytically destroy thousands of ozone molecules before they are stochastically neutralized. Despite a generic understanding of the ozone hole paradigm, many key components of the system, such as cloud occurrence, phase, and composition; particle growth mechanisms; and denitrification of the lower stratosphere have yet to be fully resolved. Satellite-based observations have dramatically improved the ability to detect PSC and quantify seasonal polar chemical partitioning. However, coverage directly over the Antarctic plateau is limited by polar-orbiting tracks that rarely exceed 80 degrees S. In December 1999, a NASA Micropulse Lidar Network instrument (MPLNET) was first deployed to the NOAA Earth Systems Research Laboratory (ESRL) Atmospheric Research Observatory at the Amundsen-Scott South Pole Station for continuous cloud and aerosol profiling. MPLNET instruments are eye-safe, capable of full-time autonomous operation, and suitably rugged and compact to withstand long-term remote deployment. With only brief interruptions during the winters of 2001 and 2002, a nearly continuous data archive exists to the present.

Campbell, James R.; Welton, Ellsworth J.; Spinhirne, James D

2009-01-01

254

Coupling high resolution 3D point clouds from terrestrial LiDAR with high precision displacement time series from GB-InSAR to understand landslide kinematic: example of the La Perraire instability, Swiss Alps.  

NASA Astrophysics Data System (ADS)

Terrestrial Laser Scanning and Ground-Based Radar Interferometry have changed our perception and interpretation of slope activities for the last 20 years and are now routinely used for monitoring and even early warning purposes. Terrestrial LiDAR allows indeed to model topography with very high point density, even in steep slopes, and to extract 3D displacements of rock masses by comparing successive datasets. GB-InSAR techniques are able to detect mm displacements over large areas. Nevertheless, both techniques suffer of some limitations. The precision of LiDAR devices actually limits its ability to monitor very slow-moving landslides, as well as by the dam resolution and the particular geometry (in azimuth/range) of GB-InSAR data may complicate their interpretations. To overcome those limitations, tools were produced to truly combine strong advantages of both techniques, by coupling high resolution geometrical data from terrestrial LiDAR or photogrammetry with high precision displacement time series from GB-InSAR. We thus developed a new exportation module into the processing chain of LiSAmobile (GB-InSAR) devices in order to wrap radar results from their particular geometry on high resolution 3D point clouds with cm mean point spacing. Furthermore, we also added new importation and visualization functionalities into Coltop3D (software for geological interpretations of laser scanning data) to display those results in 3D and even analyzing displacement time series. This new method has also been optimized to create as few and small files as possible and for time processing. Advantages of coupling terrestrial LiDAR and GB-InSAR data will be illustrated on the La Perraire instability, an active large rockslide involving frequent rockfalls and threatening inhabitant within the Val de Bagnes in the Swiss Alps. This rock mass, monitored by LiDAR and GPS since 2006, is huge enough and long-term movements are big (up to 1.6 m in 6 years) and complex enough to make difficult point cloud comparisons and LiDAR interpretations. Two monitoring campaigns with GB-InSAR devices were later performed and caught mm daily displacements (up to 8 mm in 15 days in September 2011). By coupling both datasets, we were able to clearly identify back scarps, as well as the most active masses within the whole instability, and thus to map limits of the instability and stable parts of the slope. Here the integration and the coupling of ground-based monitoring techniques were necessary to understand the whole landslide kinematic.

Michoud, Clment; Baillifard, Franois; Harald Blikra, Lars; Derron, Marc-Henri; Jaboyedoff, Michel; Kristensen, Lene; Leva, Davide; Metzger, Richard; Rivolta, Carlo

2014-05-01

255

Constructing a Merged Cloud-Precipitation Radar Dataset for Tropical Convective Clouds during the DYNAMO/AMIE Experiment at Addu Atoll  

SciTech Connect

To improve understanding of the convective processes key to the Madden-Julian-Oscillation (MJO) initiation, the Dynamics of the MJO (DYNAMO) and Atmospheric Radiation Measurement MJO Investigation Experiment (AMIE) collected four months of observations from three radars, the S-band Polarization Radar (S-Pol), the C-band Shared Mobile Atmospheric Research & Teaching Radar (SMART-R), and Ka-band Zenith Radar (KAZR) on Addu Atoll in the tropical Indian Ocean. This study compares the measurements from the S-Pol and SMART-R to those from the more sensitive KAZR in order to characterize the hydrometeor detection capabilities of the two scanning precipitation radars. Frequency comparisons for precipitating convective clouds and non-precipitating high clouds agree much better than non-precipitating low clouds for both scanning radars due to issues in ground clutter. On average, SMART-R underestimates convective and high cloud tops by 0.3 to 1.1 km, while S-Pol underestimates cloud tops by less than 0.4 km for these cloud types. S-Pol shows excellent dynamic range in detecting various types of clouds and therefore its data are well suited for characterizing the evolution of the 3D cloud structures, complementing the profiling KAZR measurements. For detecting non-precipitating low clouds and thin cirrus clouds, KAZR remains the most reliable instrument. However, KAZR is attenuated in heavy precipitation and underestimates cloud top height due to rainfall attenuation 4.3% of the time during DYNAMO/AMIE. An empirical method to correct the KAZR cloud top heights is described, and a merged radar dataset is produced to provide improved cloud boundary estimates, microphysics and radiative heating retrievals.

Feng, Zhe; McFarlane, Sally A.; Schumacher, Courtney; Ellis, Scott; Comstock, Jennifer M.; Bharadwaj, Nitin

2014-05-16

256

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

257

NASA/GSFC Scanning Raman Lidar Measurements of Water Vapor and Cirrus Clouds during WVIOP2000 and AFWEX  

NASA Technical Reports Server (NTRS)

The NASA/GSFC Scanning Raman Lidar (SRL) was deployed to the Southern Great Plains CART site from September - December, 2000 and participated in two field campaigns devoted to comparisons of various water vapor measurement technologies and calibrations. These campaigns were the Water Vapor Intensive Operations Period 2000 (WVIOP2000) and the ARM FIRE Water Vapor Experiment (AFWEX). WVIOP2000 was devoted to validating water vapor measurements in the lower atmosphere while AFWEX had similar goals but for measurements in the upper troposphere. The SRL was significantly upgraded both optically and electronically prior to these field campaigns. These upgrades enabled the SRL to demonstrate the highest resolution lidar measurements of water vapor ever acquired during the nighttime and the highest S/N Raman lidar measurements of water vapor in the daytime; more than a factor of 2 increase in S/N versus the DOE CARL Raman Lidar. Examples of these new measurement capabilities along with comparisons of SRL and CARL, LASE, MPI-DIAL, in-situ sensors, radiosonde, and others will be presented. The profile comparisons of the SRL and CARL have revealed what appears to be an overlap correction or countrate correction problem in CARL. This may be involved in an overall dry bias in the precipitable water calibration of CARL with respect to the MWR of approx. 4%. Preliminary analysis indicates that the application of a temperature dependent correction to the narrowband Raman lidar measurements of water vapor improves the lidar/Vaisala radiosonde comparisons of upper tropospheric water vapor. Other results including the comparison of the first-ever simultaneous measurements from four water vapor lidar systems, a bore-wave event captured at high resolution by the SRL and cirrus cloud optical depth studies using the SRL and CARL will be presented at the meeting.

Whiteman, D. N.; Evans, K. D.; DiGirolamo, P.; Demoz, B. B.; Turner, D.; Comstock, J.; Ismail, S.; Ferrare, R. A.; Browell, E. V.; Goldsmith, J. E. M.; Abshire, James B. (Technical Monitor)

2002-01-01

258

Simulations of multiply scattered polarized returns of a spaceborne lidar from a model atmosphere consisting of a mixture of molecules, aerosols, and water clouds  

NASA Astrophysics Data System (ADS)

In lidar remote sensing the classical lidar equation is normally used for the retrieval of environmental parameters from the return signal. One of the most important reasons for this is the simplicity of this equation which describes the contribution of single scattering to the return signal only. But it is well known that multiple scattering occurs in lidar sensing of dense clouds and remote cirrus clouds. Therefore a more precise description of lidar returns is needed. We use a general stochastic model for the description of the transport of light through the atmosphere. This model is a 'corpuscular stochastic multiple scattering process including polarization, and random change of type of scatterers (for fixed wavelength)' which is (under mild conditions) equivalent to a corresponding general radiative transfer equation. From this exact multiple scattering lidar equation a hierarchy of lidar equations including the classical lidar equation may be derived by introducing simplifying assumptions step by step. Of course, more information about the scattering behavior of the scattering particles or molecules of the atmosphere is needed for such an exact multiple scattering equation, but the more input is necessary the more output is possible. Indeed, it is possible to obtain simultaneously quite different environmental parameters (e.g. extinction and size distribution) from one multiply scattered return signal. We show examples of simulations of multiply scattered returns of a spaceborne lidar from an atmosphere consisting of a mixture of molecules, cirrus, water clouds, and haze with a height dependent extinction coefficient for each component.

Oppel, Ulrich G.

2001-04-01

259

Height Distribution Between Cloud and Aerosol Layers from the GLAS Spaceborne Lidar in the Indian Ocean Region  

NASA Technical Reports Server (NTRS)

The Geoscience Laser Altimeter System (GLAS), a nadir pointing lidar on the Ice Cloud and land Elevation Satellite (ICESat) launched in 2003, now provides important new global measurements of the relationship between the height distribution of cloud and aerosol layers. GLAS data have the capability to detect, locate, and distinguish between cloud and aerosol layers in the atmosphere up to 40 km altitude. The data product algorithm tests the product of the maximum attenuated backscatter coefficient b'(r) and the vertical gradient of b'(r) within a layer against a predetermined threshold. An initial case result for the critical Indian Ocean region is presented. From the results the relative height distribution between collocated aerosol and cloud shows extensive regions where cloud formation is well within dense aerosol scattering layers at the surface. Citation: Hart, W. D., J. D. Spinhime, S. P. Palm, and D. L. Hlavka (2005), Height distribution between cloud and aerosol layers from the GLAS spaceborne lidar in the Indian Ocean region,

Hart, William D.; Spinhirne, James D.; Palm, Steven P.; Hlavka, Dennis L.

2005-01-01

260

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

261

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

262

Multifractals, universality classes and satellite and radar measurements of cloud and rain fields  

Microsoft Academic Search

The extreme variability of cloud and rain fields poses serious problems in quantitative use of remotely sensed satellite and radar data. We show how to characterize this variability using scale invariant (sensor resolution independent) codimension functions which are exponents characterizing the probability distributions. These codimension functions in turn form a three parameter universality class. We review the properties of these

Shaun Lovejoy; Daniel Schertzer

1990-01-01

263

Applications of the NCAR Electra Doppler radar for the study of physical parameters of clouds  

NASA Astrophysics Data System (ADS)

An airborne Doppler X-band radar to be mounted in the tail of a Lockheed Electra (ELDORA) is presented. The ELDORA is designed with a primary emphasis on the study of storm and mesoscale weather phenomena. However, the radar will also be very useful for the study of cloud physical parameters. Because the aircraft can be positioned close to the area of interest, reasonably fine scale data can be taken in a very short length of time. Since these types of measurements are not available, there is much to be learned even with the moderately course resolution of the ELDORA. The use of a larger, vertically pointing antenna will further enhance the ability of the ELDORA to measure these properties. Once this effort is completed, the information obtained will greatly enhance the cloud physics community's ability to determine what specific properties of airborne radar are necessary to measure their phenomena of interest.

Walther, Craig; Frush, Charles; Hildebrand, Peter

264

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

265

Uncertainties in Ice-Sheet Altimetry from a Spaceborne 1064-nm Single-Channel Lidar Due to Undetected Thin Clouds  

NASA Technical Reports Server (NTRS)

In support of the Ice, Cloud, and land Elevation Satellite (ICESat)-II mission, this paper studies the bias in surface-elevation measurements caused by undetected thin clouds. The ICESat-II satellite may only have a 1064-nm single-channel lidar onboard. Less sensitive to clouds than the 532-nm channel, the 1064-nm channel tends to miss thin clouds. Previous studies have demonstrated that scattering by cloud particles increases the photon-path length, thus resulting in biases in ice-sheet-elevation measurements from spaceborne lidars. This effect is referred to as atmospheric path delay. This paper complements previous studies in the following ways: First, atmospheric path delay is estimated over the ice sheets based on cloud statistics from the Geoscience Laser Altimeter System onboard ICESat and the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Terra and Aqua. Second, the effect of cloud particle size and shape is studied with the state-of-the-art phase functions developed for MODIS cirrus- cloud microphysical model. Third, the contribution of various orders of scattering events to the path delay is studied, and an analytical model of the first-order scattering contribution is developed. This paper focuses on the path delay as a function of telescope field of view (FOV). The results show that reducing telescope FOV can significantly reduce the expected path delay. As an example, the average path delays for FOV = 167 microrad (a 100-m-diameter circle on the surface) caused by thin undetected clouds by the 1064-nm channel over Greenland and East Antarctica are illustrated.

Yang, Yuekui; Marshak, Alexander; Varnai, Tamas; Wiscombe, Warren; Yang, Ping

2010-01-01

266

Augmented reality system using lidar point cloud data for displaying dimensional information of objects on mobile phones  

NASA Astrophysics Data System (ADS)

Mobile augmented reality system is the next generation technology to visualise 3D real world intelligently. The technology is expanding at a fast pace to upgrade the status of a smart phone to an intelligent device. The research problem identified and presented in the current work is to view actual dimensions of various objects that are captured by a smart phone in real time. The methodology proposed first establishes correspondence between LiDAR point cloud, that are stored in a server, and the image t hat is captured by a mobile. This correspondence is established using the exterior and interior orientation parameters of the mobile camera and the coordinates of LiDAR data points which lie in the viewshed of the mobile camera. A pseudo intensity image is generated using LiDAR points and their intensity. Mobile image and pseudo intensity image are then registered using image registration method SIFT thereby generating a pipeline to locate a point in point cloud corresponding to a point (pixel) on the mobile image. The second part of the method uses point cloud data for computing dimensional information corresponding to the pairs of points selected on mobile image and fetch the dimensions on top of the image. This paper describes all steps of the proposed method. The paper uses an experimental setup to mimic the mobile phone and server system and presents some initial but encouraging results

Gupta, S.; Lohani, B.

2014-05-01

267

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

268

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

269

Island based radar and microwave radiometer measurements of stratus cloud parameters during the Atlantic Stratocumulus Transition Experiment (ASTEX)  

SciTech Connect

During the Atlantic Stratocumulus Transition Experiment (ASTEX) in June 1992, simultaneous measurements were made with a vertically pointing cloud sensing radar and a microwave radiometer. The radar measurements are used to estimate stratus cloud drizzle and turbulence parameters. In addition, with the microwave radiometer measurements of reflectivity, we estimated the profiles of cloud liquid water and effective radius. We used radar data for computation of vertical profiles of various drizzle parameters such as droplet concentration, modal radius, and spread. A sample of these results is shown in Figure 1. In addition, in non-drizzle clouds, with the radar and radiometer we can estimate the verticle profiles of stratus cloud parameters such as liquid water concentration and effective radius. This is accomplished by assuming a droplet distribution with droplet number concentration and width constant with height.

Frisch, A.S. [Colorado State Univ., Fort Collins, CO (United States); Fairall, C.W.; Snider, J.B. [NOAA Environmental Technology Lab., Boulder, CO (United States); Lenshow, D.H.; Mayer, S.D. [National Center for Atmospheric Research, Boulder, CO (United States)

1996-04-01

270

P2A.4 On the vertical profile of stratus liquid water flux using a millimeter cloud radar Shelby Frisch  

E-print Network

P2A.4 On the vertical profile of stratus liquid water flux using a millimeter cloud radar Shelby components of the vertical flux of liquid wa- ter in stratus clouds, one component is due to the mean fall microphysical retrievals can be used to estimate the stratus cloud droplet liquid water flux. Earlier retrievals

Zuidema, Paquita

271

On the vertical profile of stratus liquid water flux using a millimeter cloud radar Shelby Frisch Paquita Zuidema Chris Fairall  

E-print Network

On the vertical profile of stratus liquid water flux using a millimeter cloud radar Shelby Frisch estimating liquid water contents and droplet sizes within all-liquid,non-drizzling stratus clouds velocity of the cloud droplets can also be estimated for non-drizzling stratus. Previous work has shown

Zuidema, Paquita

272

Precipitating Snow Retrievals from Combined Airborne Cloud Radar and Millimeter-Wave Radiometer Observations  

NASA Technical Reports Server (NTRS)

An algorithm for retrieving snow over oceans from combined cloud radar and millimeter-wave radiometer observations is developed. The algorithm involves the use of physical models to simulate cloud radar and millimeter-wave radiometer observations from basic atmospheric variables such as hydrometeor content, temperature, and relative humidity profiles and is based on an optimal estimation technique to retrieve these variables from actual observations. A high-resolution simulation of a lake-effect snowstorm by a cloud-resolving model is used to test the algorithm. That is, synthetic observations are generated from the output of the cloud numerical model, and the retrieval algorithm is applied to the synthetic data. The algorithm performance is assessed by comparing the retrievals with the reference variables used in synthesizing the observations. The synthetic observation experiment indicates good performance of the retrieval algorithm. The algorithm is also applied to real observations from the Wakasa Bay field experiment that took place over the Sea of Japan in January and February 2003. The application of the retrieval algorithm to data from the field experiment yields snow estimates that are consistent with both the cloud radar and radiometer observations.

Grecu, Mircea; Olson, William S.

2008-01-01

273

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

274

Lidar Measurements of Wind, and Cloud & Aerosol Structures using HARLIE at the WVIOP, Sept/Oct 2000  

NASA Technical Reports Server (NTRS)

The holographic scanning lidar HARLIE made continuous measurements of aerosol and cloud one-micron backscatter and derived the horizontal wind speed and direction at cloud height over the ARM (SGP) site during the water vapor campaign WVIOP, September 17 - October 6, 2000. Whenever possible, these measurements were compared with Loran-C winds as measured by the routine launches of Vaisala radiosonde balloons scheduled by the ARM project. Taken overall, the agreement between these two types of observation is excellent, which could be taken merely as a validation of the relatively new HARLIE technique. However, the detailed comparison for a given sonde launch clearly requires that, out of the HARLIE data which are taken all the time at all altitudes, one must select those segments that match the altitude-time trajectory of the sonde. Moreover, the conical HARLIE scan at a 45 deg. elevation angle covers a wide area that is more representative of the average wind conditions above the site than the isolated track of the sonde's ascent. We suggest that the HARLIE instrument offers a more general and improved representation of the horizontal wind profile whenever there is sufficient backscatter by clouds and aerosols for lidar operation. HARLIE is a rugged and compact lidar that operates from aircraft as well as from the ground and has been used in several meteorological campaigns. As a "direct detection" lidar, HARLIE does not require the complexity of a coherent detection system. The data reduction algorithms facilitate the rapid and accurate determination of wind speed and direction at all altitudes. Wind measurements and HARLIE performance data from WVIOP 2000 and other campaigns will be presented.

Schwemmer, Geary; Miller, D.; Wilkerson, T.; Andrus, I.; Einaudi, Franco (Technical Monitor)

2001-01-01

275

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

NASA Astrophysics Data System (ADS)

Meteoric iron layers and mesospheric clouds are two layered phenomena that have been used as tracers to study the global thermal and dynamic structures in the mesosphere and lower thermosphere. In January 2003, three days after the Columbia Space Shuttle was launched from the Kennedy Space Center, an iron (Fe) Boltzmann lidar detected strong sporadic Fe layers in the altitude range from 105 to 115 km at Rothera (67.5 S, 68.0 W), Antarctica. Located ~20 km above the peak of meteoric iron layers (near 90 km), these sporadic Fe layers were believed to be from the relocated shuttle exhaust plume and produced by the normal ablation of main engine components during the shuttle launch. This hypothesis was supported by Lyman-alpha observations from the Global Ultraviolet Imager on NASAs TIMED satellite, showing a major portion of the shuttle plume transported to Antarctica. Enhanced polar mesospheric cloud (PMC) occurrence was observed by the same lidar at Rothera after the shuttle launch, and confirmed by the SBUV data. Such an enhancement of PMC occurrence has been attributed to the large amount of water vapor injected by the shuttles main engines near 110 km altitude. Similar phenomena were observed in the Arctic by a resonance Fe lidar and a Rayleigh lidar at Chatanika, Alaska (65 N, 147 W) after the launch of Space Shuttle Endeavor in August 2007. An intense sporadic E layer was co-located with the atom layer indicating a steady state in which iron atoms and ions are in some type of equilibrium. Initial analysis indicates the water vapor plays an important role in the chemistry. In this paper through detailed study of these examples, we demonstrate the impacts of Space Shuttle traffic on the ice mass of mesospheric clouds and on the mesosphere environment.

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

2009-12-01

276

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

277

VII Workshop on Lidar Measurements in Latin America Pucn, 2013 Characterization of cirrus clouds in central Amazon (2.89 S 59.97 W): Firsts results from  

E-print Network

and top heights, and cloud thickness. The slope method was used to derive the cirrus optical depthVII Workshop on Lidar Measurements in Latin America Pucón, 2013 Characterization of cirrus clouds using a 95 mJ Nd-Yag laser at 355 nm. Receiving optics consists of a cassegrain telescope with 400 mm

Barbosa, Henrique

278

Airborne LIDAR Measurements of Water Vapor, Ozone, Clouds, and Aerosols in the Tropics Near Central America During the TC4 Experiment  

NASA Technical Reports Server (NTRS)

Large scale distributions of ozone, water vapor, aerosols, and clouds were measured throughout the troposphere by two NASA Langley lidar systems on board the NASA DC-8 aircraft as part of the Tropical Composition, Cloud, and Climate Coupling Experiment (TC4) over Central and South America and adjacent oceans in the summer of 2007. Special emphasis was placed on the sampling of convective outflow and transport, sub-visible cirrus clouds, boundary layer aerosols, Saharan dust, volcanic emissions, and urban and biomass burning plumes. This paper presents preliminary results from this campaign, and demonstrates the value of coordinated measurements by the two lidar systems.

Kooi, Susan; Fenn, Marta; Ismail, Syed; Ferrare, Richard; Hair, John; Browell, Edward; Notari, Anthony; Butler, Carolyn; Burton, Sharon; Simpson, Steven

2008-01-01

279

Fast Occlusion and Shadow Detection for High Resolution Remote Sensing Image Combined with LIDAR Point Cloud  

NASA Astrophysics Data System (ADS)

The orthophoto is an important component of GIS database and has been applied in many fields. But occlusion and shadow causes the loss of feature information which has a great effect on the quality of images. One of the critical steps in true orthophoto generation is the detection of occlusion and shadow. Nowadays LiDAR can obtain the digital surface model (DSM) directly. Combined with this technology, image occlusion and shadow can be detected automatically. In this paper, the Z-Buffer is applied for occlusion detection. The shadow detection can be regarded as a same problem with occlusion detection considering the angle between the sun and the camera. However, the Z-Buffer algorithm is computationally expensive. And the volume of scanned data and remote sensing images is very large. Efficient algorithm is another challenge. Modern graphics processing unit (GPU) is much more powerful than central processing unit (CPU). We introduce this technology to speed up the Z-Buffer algorithm and get 7 times increase in speed compared with CPU. The results of experiments demonstrate that Z-Buffer algorithm plays well in occlusion and shadow detection combined with high density of point cloud and GPU can speed up the computation significantly.

Hu, X.; Li, X.

2012-08-01

280

Combined satellite and radar retrievals of drop concentration and CCN at convective cloud base  

NASA Astrophysics Data System (ADS)

number of activated cloud condensation nuclei (CCN) into cloud drops at the base of convective clouds (Na) is retrieved based on the high-resolution (375 m) satellite retrievals of vertical profiles of convective cloud drop effective radius (re). The maximum cloud base supersaturation (S) is calculated when Na is combined with radar-measured updraft and yields CCN(S), which was validated well against ground-based CCN measurements during the conditions of well-mixed boundary layer over the U.S. Department of Energy's Atmospheric System Research Southern Great Plains site. Satellite retrieving Na is a new capability, which is one essential component of simultaneous measurements of cloud microstructure and CCN from space by using clouds as natural CCN chambers. This has to be complemented by a methodology for satellite estimates of cloud base updraft, which is yet to be developed and demonstrated. In the mean time, the retrieved Na can be used for the assimilation of the combined CCN and updraft effects on clouds in models.

Rosenfeld, Daniel; Fischman, Baruch; Zheng, Youtong; Goren, Tom; Giguzin, David

2014-05-01

281

An Assessment of the Parameterization of Subgrid-Scale Cloud Effects on Radiative Transfer. Part II: Horizontal Inhomogeneity  

E-print Network

in downwelling radiative fluxes at the surface induced by changes in cloud cover and water vapor distributions. 1 is used to evaluate the characteristics of inhomogeneous cloud fields observed by radar and lidar over liquid water path and cloud droplet effective radius led to errors of up to 10 W m 2 in the net top

Stephens, Graeme L.

282

Raman lidar measurements of water vapor and aerosol/clouds during the FIRE/SPECTRE field campaign  

SciTech Connect

The FIRE/SPECTRE field campaign was conducted during November- December 1991 in Coffeyville, Kansas. The main objective of FIRE (First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment) was to study the development and radiative characteristics of cirrus clouds. The SPECTRE (Spectral Radiation Experiment) project was designed to acquire the necessary atmospheric observations to compare radiative measurements with radiative transfer theory, with special emphasis on understanding the water vapor spectral continuum. A complete understanding of water vapor, its distribution with height, and its temporal variation was important for both experiments. A ground-based Raman Lidar was deployed at Coffeyville, Kansas from November 12 until December 7, 1991. During the campaign, the lidar operated during 14 observation periods. The periods ranged in length from 3.5 hours to 12 hours for a total operating time of approximately 119 hours. During each of the operational periods the lidar obtained vertical profiles of water vapor mixing ratio and aerosol scattering ratio once every minute with vertical resolution of 75 meters from near the earth's surface to an altitude of 9--10 km for water vapor and higher for aerosols. Several balloon-sondes were launched during each operational period providing an independent measurement of humidity with altitude. For each operational period, the 1-minute profiles of water vapor mixing ratio and aerosol scattering ratio are composited to give a color- coded time-height display of water vapor and aerosol scattering, respectively.

Melfi, S.H.; Whiteman, D. (National Aeronautics and Space Administration, Greenbelt, MD (United States). Goddard Space Flight Center); Ferrare, R. (Universities Space Research Associates, Columbia, MD (United States)); Evans, K. (Hughes-STX, Lanham, MD (United States)); Goldsmith, J.E.M.; Lapp, M.; Bisson, S.E. (Sandia National Labs., Livermore, CA (United States))

1992-01-01

283

Raman lidar measurements of water vapor and aerosol/clouds during the FIRE/SPECTRE field campaign  

SciTech Connect

The FIRE/SPECTRE field campaign was conducted during November- December 1991 in Coffeyville, Kansas. The main objective of FIRE [First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment] was to study the development and radiative characteristics of cirrus clouds. The SPECTRE [Spectral Radiation Experiment] project was designed to acquire the necessary atmospheric observations to compare radiative measurements with radiative transfer theory, with special emphasis on understanding the water vapor spectral continuum. A complete understanding of water vapor, its distribution with height, and its temporal variation was important for both experiments. A ground-based Raman Lidar was deployed at Coffeyville, Kansas from November 12 until December 7, 1991. During the campaign, the lidar operated during 14 observation periods. The periods ranged in length from 3.5 hours to 12 hours for a total operating time of approximately 119 hours. During each of the operational periods the lidar obtained vertical profiles of water vapor mixing ratio and aerosol scattering ratio once every minute with vertical resolution of 75 meters from near the earth`s surface to an altitude of 9--10 km for water vapor and higher for aerosols. Several balloon-sondes were launched during each operational period providing an independent measurement of humidity with altitude. For each operational period, the 1-minute profiles of water vapor mixing ratio and aerosol scattering ratio are composited to give a color- coded time-height display of water vapor and aerosol scattering, respectively.

Melfi, S.H.; Whiteman, D. [National Aeronautics and Space Administration, Greenbelt, MD (United States). Goddard Space Flight Center; Ferrare, R. [Universities Space Research Associates, Columbia, MD (United States); Evans, K. [Hughes-STX, Lanham, MD (United States); Goldsmith, J.E.M.; Lapp, M.; Bisson, S.E. [Sandia National Labs., Livermore, CA (United States)

1992-07-01

284

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.

285

Evaluation of Ice Water Content Retrievals from Cloud Radar Reflectivity and Temperature Using a Large Airborne In Situ Microphysical Database  

E-print Network

Evaluation of Ice Water Content Retrievals from Cloud Radar Reflectivity and Temperature Using the performances of the proposed ice water content (IWC)­radar reflectivity Z and IWC­Z­temperature T relationships larger IWCs) different sets of relationships would have to be used for midlatitude and tropical ice

Protat, Alain

286

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

287

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

288

BOREAS AFM-6 NOAA/ETL 35 GHz Cloud/Turbulence Radar GIF Images  

NASA Technical Reports Server (NTRS)

The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-6 team from the National Oceanic and Atmospheric Administration/Environment Technology Laboratory (NOAA/ETL) operated a 35-GHz cloud-sensing radar in the Northern Study Area (NSA) near the Old Jack Pine (OJP) tower from 16 Jul 1994 to 08 Aug 1994. This data set contains a time series of GIF images that show the structure of the lower atmosphere. The NOAA/ETL 35-GHz cloud/turbulence radar GIF images are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

Martner, Brooks E.; Newcomer, Jeffrey A. (Editor); Hall, Forrest G.; Smith, David E. (Technical Monitor)

2000-01-01

289

Active remote sensing of cloud microphysics  

NASA Astrophysics Data System (ADS)

We discuss recent progress in analyses of retrieved cloud properties by active sensors. We have developed several types of algorithms that can be applied to data obtained by cloud profiling radar (CPR) and lidar to retrieve cloud macroscale and microphysical properties. The retrieved properties include cloud occurrence, cloud particle phase, orientation and microphysics. Combined use of CPR and lidar has been recognized to be a powerful tool for the retrieval of cloud microphysics. Single scattering property of ice particles is one of the key elements in the analyses. It has been necessary to develop appropriate scattering theories and inversion methods that can take into account the particle shape and its orientation for the analyses of CPR and lidar data. We have been analyzing the data obtained by the ground based, ship-borne and space-borne active sensors. Space-borne active sensors CloudSat and CALIPSO successfully started global observations of cloud and aerosols in June 2006. The theoretical basis of the analysis of these active sensors is given. Global analysis of cloud macro-scale and microphysical properties has been performed. After these space missions, JAXA and ESA are planning a new space mission, EarthCARE which will carry four sensors including 95 GHz Doppler radar and high spectral resolution lidar. It will be launched in 2015 and is expected to provide information of cloud microphysics as well as vertical air motion. The retrieval algorithms for EarthCARE have been developed by using the existing radar and lidar data including CloudSat and CALIPSO.

Okamoto, Hajime

2013-05-01

290

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

291

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

292

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

293

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

294

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

Microsoft Academic Search

The United States (U.S.) Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) operates millimeter wavelength cloud radars (MMCRs) in several climatological regimes. The MMCRs, are the primary observing tool for quantifying the properties of nearly all radiatively important clouds over the ACRF sites. The first MMCR was installed at the ACRF Southern Great Plains (SGP) site

P. Kollias; MA Miller; KB Widener; RT Marchand; TP Ackerman

2005-01-01

295

HIGH-RESOLUTION RETRIEVAL OF CLOUD LIQUID WATER PROFILES USING THE COLLOCATED ARM Ka-AND W-BAND RADARS  

E-print Network

HIGH-RESOLUTION RETRIEVAL OF CLOUD LIQUID WATER PROFILES USING THE COLLOCATED ARM Ka- AND W-BAND RADARS D. Huang, K. Johnson, Y. Liu, and W. Wiscombe For presentation at the First Science Team Meeting. The validity of this dual-frequency approach is demonstrated using the co-located Ka-band and W-band cloud

296

Characteristics of Convective Clouds Observed by a Doppler Radar at Naqu on Tibetan Plateau during the GAME-Tibet IOP  

Microsoft Academic Search

In order to reveal the characteristics of convective clouds over the Tibetan Plateau, we carried out Doppler radar observations of the clouds in the suburbs of Naqu city (4500 m ASL), which is located in the central part of the Tibetan Plateau, from 27 May to 19 September 1998, during the intensive observation period of the GEWEX Asian Monsoon Experiment

Hiroshi Uyeda; Hiroyuki Yamada; Junichi Horikomi; Ryuichi Shirooka; Shuji Shimizu; Liu Liping; Kenichi Ueno; Hideyuki Fujii; Toshio Koike

2001-01-01

297

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

298

Scanning ARM Cloud Radars Part II: Data Quality Control and Processing  

SciTech Connect

The Scanning ARM Cloud Radars (SACRs) are the primary instruments for documenting the four-dimensional structure and evolution of clouds within a 20-30 km radius from the ARM fixed and mobile sites. Here, the post-processing of the calibrated SACR measurements is discussed. First, a feature mask algorithm that objectively determines the presence of significant radar returns is described. The feature mask algorithm is based on the statistical properties of radar receiver noise. It accounts for atmospheric emission and is applicable even for SACR profiles with few or no signal-free range gates. Using the nearest-in-time atmospheric sounding, the SACR radar reflectivities are corrected for gaseous attenuation (water vapor and oxygen) using a line-by-line absorption model. Despite having a high pulse repetition frequency, the SACR has a narrow Nyquist velocity limit and thus Doppler velocity folding is commonly observed. An unfolding algorithm that makes use of a first guess for the true Doppler velocity using horizontal wind measurements from the nearest sounding is described. The retrieval of the horizontal wind profile from the Hemispherical Sky Range Height Indicator SACR scan observations and/or nearest sounding is described. The retrieved horizontal wind profile can be used to adaptively configure SACR scan strategies that depend on wind direction. Several remaining challenges are discussed, including the removal of insect and second-trip echoes. The described algorithms significantly enhance SACR data quality and constitute an important step towards the utilization of SACR measurements for cloud research.

Kollias, Pavlos; Jo, Ieng; Borque, Paloma; Tatarevic, Aleksandra; Lamer, Katia; Bharadwaj, Nitin; Widener, Kevin B.; Johnson, Karen; Clothiaux, Eugene E.

2014-03-01

299

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

300

Synergistic use of very high-frequency radar and discrete-return lidar for estimating biomass in temperate hardwood and mixed forests  

Microsoft Academic Search

Introduction\\u000a Accurate estimation of aboveground biomass is essential to better understand the carbon cycle in forest ecosystems.\\u000a \\u000a \\u000a \\u000a Methods\\u000a The objective of this study was to determine whether biomass in temperate hardwood forests is better estimated using very\\u000a high-frequency radar data (from BioSAR) alone or in combination with small-footprint discrete-return lidar data (both profiling\\u000a and scanning). The study area

Asim Banskota; Randolph H. Wynne; Patrick Johnson; Bomono Emessiene

2011-01-01

301

CRYSTAL-FACE Polarization Lidar Research  

NASA Technical Reports Server (NTRS)

The University of Alaska Fairbanks (UAF) Polarization Diversity Lidar (PDL, Sassen 1994) participated in the July 2002 CRYSTAL-FACE field campaign, shortly after the PI moved from the University of Utah to UAF. The truck-mounted PDL is an advanced dual wavelength (1.06 and 0.532 micron), high resolution (0.1-s by 1.5-m), scanning lidar system designed as a testbed for evaluating laser backscatter depolarization techniques for the study of clouds and aerosols in the atmosphere. The main goals identified in our proposal for the CRYSTAL-FACE experiment were, i) the characterization of Florida thunderstorm anvil macrophysical and microphysical properties from lidar backscattering and depolarization, ii) the study of thin to subvisual tropopause-topped subtropical cirrus, iii) the search for indirect cloud effects of trans- Atlantic advected Saharan dust storm aerosols on clouds, and iv) the investigation of melting layer effects on lidar and multi-wavelength Doppler radar measurements in precipitation. Although we experienced adversity in the field during the campaign, sufficient data was collected to begin addressing these topics, and several conference presentations, three journal articles, and one book chapter have resulted from the data analysis effort supported by this grant. (PDL operations were delayed by FAA concerns over the initial sighting at the Kendall-Tamiami Airport, and a brief but major laser breakdown was experienced during the re- setup at the remote Ochopee Everglades site that also supported the N-POL radar.) All lidar data collected by the PDL system were processed and quality checked, and submitted to the CRYSTAL-FACE data archive in a timely manner.

Sassen, Kenneth

2005-01-01

302

The influence of rain and clouds on a satellite dual frequency radar altimeter system operating at 13 and 35 GHz  

NASA Technical Reports Server (NTRS)

The effects of inhomogeneous spatial attenuation resulting from clouds and rain on the altimeter estimate of the range to mean sea level are modelled. It is demonstrated that typical cloud and rain attenuation variability at commonly expected spatial scales can significantly degrade altimeter range precision. Rain cell and cloud scale sizes and attenuations are considered as factors. The model simulation of altimeter signature distortion is described, and the distortion of individual radar pulse waveforms by different spatial scales of attenuation is considered. Examples of range errors found for models of a single cloud, a rain cell, and cloud streets are discussed.

Walsh, E. J.; Monaldo, F. M.; Goldhirsh, J.

1983-01-01

303

Multiwavelength observations of a devleoping cloud system: The FIRE II 26 November 1991 case study  

SciTech Connect

Simultaneous multiwavelength measurements of a developing cloud system were obtained by NOAA Doppler lidar, Doppler radar, Fourier transform infrared interferometer, and microwave and infrared radiometers on 26 November 1991. The evolution of the cloud system is described in terms of lidar backscatter, radar reflectivity and velocity, interferometer atmospheric spectra, and radiometer brightness temperature, integrated liquid water, and water vapor paths. Utilizing the difference in wavelength between the radar and lidar, and therefore their independent sensitivity to different regions of the same cloud, the cloud top, base, depth, and multiple layer heights can be determined with better accuracy than with either instrument alone. Combining the radar, lidar, and radiometer measurements using two different techniques allows an estimation of the vertical profile of cloud microphysical properties such as particle sizes. Enhancement of lidar backscatter near zenith revealed when highly oriented ice crystals were present. The authors demonstrate that no single instrument is sufficient to accurately describe cirrus clouds and that measurements in combination can provide important details on their geometric, radiative, and microphysical properties.

Intrieri, J.M.; Eberhard, W.L.; Uttal, T. [NOAA/ERL/Environmental Technology Lab., Boulder, CO (United States)] [and others] [NOAA/ERL/Environmental Technology Lab., Boulder, CO (United States); and others

1995-12-01

304

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

305

Remote sensing of three-dimensional cirrus clouds from satellites: application to continuous-wave laser  

E-print Network

- geneous high-level clouds, in which scattering and ab- sorption associated with aerosols, water vapor, and Jeffrey Cetola A satellite remote sensing methodology has been developed to retrieve 3D ice water content derived from the ground-based lidar and cloud radar returns1­3 have shown significant vertical variability

Takano, Yoshihide

306

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

1995-11-01

307

Breaking Kelvin-Helmholtz waves and cloud-top entrainment as revealed by K-band Doppler radar  

NASA Technical Reports Server (NTRS)

Radars have occasionally detected breaking Kelvin-Helmholtz (KH) waves under clear-air conditions in the atmospheric boundary layer and in the free troposphere. However, very few direct measurements of such waves within clouds have previously been reported and those have not clearly documented wave breaking. In this article, we present some of the most detailed and striking radar observations to date of breaking KH waves within clouds and at cloud top and discuss their relevance to the issue of cloud-top entrainment, which is believed to be important in convective and stratiform clouds. Aircraft observations reported by Stith suggest that vortex-like circulations near cloud top are an entrainment mechanism in cumuliform clouds. Laboratory and modeling studies have examined possibility that KH instability may be responsible for mixing at cloud top, but direct observations have not yet been presented. Preliminary analyses shown here may help fill this gap. The data presented in this paper were obtained during two field projects in 1991 that included observations from the NOAA Wave Propagation Laboratory's K-band Doppler radar (wavelength = 8.7 mm) and special rawinsonde ascents. The sensitivity (-30 dBZ at 10 km range), fine spatial resolution (375-m pulse length and 0.5 degrees beamwidth), velocity measurement precision (5-10 cm s-1), scanning capability, and relative immunity to ground clutter make it sensitive to non-precipitating and weakly precipitating clouds, and make it an excellent instrument to study gravity waves in clouds. In particular, the narrow beam width and short pulse length create scattering volumes that are cylinders 37.5 m long and 45 m (90 m) in diameter at 5 km (10 km) range. These characteristics allow the radar to resolve the detailed structure in breaking KH waves such as have been seen in photographic cloud images.

Martner, Brooks E.; Ralph, F. Martin

1993-01-01

308

Smoke detection using a compact and eye-safe lidar  

NASA Astrophysics Data System (ADS)

Cloud ceiling determination using laser radar (lidar) is a well known application of this remote sensing technique. It is no problem to measure large distances up to some kilometers, since the particles of interest (water droplets) reflect the laser radiation pretty well, even when using very tiny light sources (eye safety criterion). This detection of white scatterers (clouds) points of course to the question whether it will be possible to measure dark particles for example smoke as well. The possible measurement range of the remote sensing smoke detectors cover medium scale observations, like corridor sensors, as well as large scale systems, like replacing fire alarm sensors in a tunnel by one single lidar system. It will be reported on the double impact using the laser radar technique: the range resolved measurement of black smoke as well as using the transmission path of the laser light as a control device.

Streicher, Juergen; Werner, Christian

1999-05-01

309

Gravity Waves and Mesospheric Clouds in the Summer Middle Atmosphere: A Comparison of Lidar Measurements and Ray Modeling of Gravity Waves Over Sondrestrom, Greenland  

NASA Technical Reports Server (NTRS)

We conducted gravity wave ray-tracing experiments within an atmospheric region centered near the ARCLITE lidar system at Sondrestrom, Greenland (67N, 310 deg E), in efforts to understand lidar observations of both upper stratospheric gravity wave activity and mesospheric clouds during August 1996 and the summer of 2001. The ray model was used to trace gravity waves through realistic three-dimensional daily-varying background atmospheres in the region, based on forecasts and analyses in the troposphere and stratosphere and climatologies higher up. Reverse ray tracing based on upper stratospheric lidar observations at Sondrestrom was also used to try to objectively identify wave source regions in the troposphere. A source spectrum specified by reverse ray tracing experiments in early August 1996 (when atmospheric flow patterns produced enhanced transmission of waves into the upper stratosphere) yielded model results throughout the remainder of August 1996 that agreed best with the lidar observations. The model also simulated increased vertical group propagation of waves between 40 km and 80 km due to intensifying mean easterlies, which allowed many of the gravity waves observed at 40 km over Sondrestrom to propagate quasi-vertically from 40-80 km and then interact with any mesospheric clouds at 80 km near Sondrestrom, supporting earlier experimentally-inferred correlations between upper stratospheric gravity wave activity and mesospheric cloud backscatter from Sondrestrom lidar observations. A pilot experiment of real-time runs with the model in 2001 using weather forecast data as a low-level background produced less agreement with lidar observations. We believe this is due to limitations in our specified tropospheric source spectrum, the use of climatological winds and temperatures in the upper stratosphere and mesosphere, and missing lidar data from important time periods.

Gerrard, Andrew J.; Kane, Timothy J.; Eckermann, Stephen D.; Thayer, Jeffrey P.

2004-01-01

310

Automatic reconstruction of 3D urban landscape by computing connected regions and assigning them an average altitude from LiDAR point cloud image  

NASA Astrophysics Data System (ADS)

The demand of 3D city modeling has been increasing in many applications such as urban planing, computer gaming with realistic city environment, car navigation system with showing 3D city map, virtual city tourism inviting future visitors to a virtual city walkthrough and others. We proposed a simple method for reconstructing a 3D urban landscape from airborne LiDAR point cloud data. The automatic reconstruction method of a 3D urban landscape was implemented by the integration of all connected regions, which were extracted and extruded from the altitude mask images. These mask images were generated from the gray scale LiDAR image by the altitude threshold ranges. In this study we demonstrated successfully in the case of Kanazawa city center scene by applying the proposed method to the airborne LiDAR point cloud data.

Kawata, Yoshiyuki; Koizumi, Kohei

2014-10-01

311

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

312

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

313

NASA/GSFC Scanning Raman Lidar Measurements of Water Vapor and Clouds during the International H2O Project (IHOP) Field Campaign  

NASA Technical Reports Server (NTRS)

The NASA/GSFC Scanning Raman Lidar (SFL) acquired approximately 200 hours of water vapor, aerosol and cloud measurements during the IHOP field campaign. The detailed water vapor structure of events such as a dryline passage and internal bores were revealed. We discuss the error characteristics of the instrument as well as the water vapor and cirrus cloud structure during the 19-20 June bore event.

Whiteman, David; Demoz, Belay; DiGirolamo, Paolo; Wang, Zhi-En; Evans, Keith; Lin, Ruei-Fong

2003-01-01

314

Retrievals of vertical profiles of stratus cloud properties from combined oxygen A-band and radar observations  

NASA Astrophysics Data System (ADS)

A synergetic algorithm of retrieving vertical distribution of cloud drop effective radius (Re), liquid water content (LWC), and optical depth has been developed by combining oxygen A-band spectral measurements with radar reflectivity. The underlying physics is to utilize the photon path length information from oxygen A-band measurements to constrain the retrievals of cloud microphysical properties from radar reflectivity. Through a radiation closure of the rotating shadowband spectrometer (RSS) diffuse-horizontal irradiances in the oxygen A-band (which is sensitive to vertical distribution of the 2nd moment of particle size distribution), vertical distributions of cloud microphysical property (the 3rd moment of particle size distribution) are optimized and retrieved from Millimeter Wave Cloud Radar (MMCR) reflectivity (the 6th moment of particle size distribution). The critical issues in the synergetic cloud retrievals of combining passive and active instruments are discussed and carefully taken into account. Evaluation and validation through case studies show that the retrieved column mean values of cloud optical depth, effective radius, and liquid water path agree well with independent measurements from the microwave radiometer (MWR) and independent retrievals from a combined algorithm of multifilter rotating shadowband radiometer (MFRSR) and MWR and the column physical characterization (CPC) of MMCR. These studies demonstrate that this active-passive synergetic retrieval algorithm is feasible and accurate for retrievals of vertical distribution of cloud Re and LWC for stratus clouds.

Li, Siwei; Min, Qilong

2013-01-01

315

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

316

A one year comparison of 482 MHz radar wind profiler, RS92-SGP Radiosonde and 1.5 ?m Doppler Lidar wind measurements  

NASA Astrophysics Data System (ADS)

We present the results of a one-year quasi-operational testing of the 1.5 ?m StreamLine Doppler lidar developed by Halo Photonics from 2 October 2012 to 2 October 2013. The system was configured to continuously perform a velocity-azimuth display (VAD) scan pattern using 24 azimuthal directions with a constant beam elevation angle of 75. Radial wind estimates were selected using a rather conservative signal-to-noise ratio (SNR) based threshold of -18.2 dB (0.015). A 30 min average wind vector was calculated based on the assumption of a horizontally homogeneous wind field through a singular-value decomposed Moore-Penrose pseudoinverse of the overdetermined linear system. A strategy for a quality control of the retrieved wind vector components is outlined which is used to ensure consistency between the retrieved winds and the assumptions inherent to the employed wind vector retrieval. Finally, the lidar measurements are compared with operational data from a collocated 482 MHz radar wind profiler running in a four-beam Doppler beam swinging (DBS) mode and winds from operational radiosonde measurements. The intercomparisons show that the Doppler lidar is a reliable system for operational wind measurements in the atmospheric boundary layer (ABL).

Pschke, E.; Leinweber, R.; Lehmann, V.

2014-11-01

317

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

SciTech Connect

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

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

2001-01-01

318

Radar detectability studies of slow and small Zodiacal Cloud Dust Particles  

NASA Astrophysics Data System (ADS)

The total amount of meteoric input in the upper atmosphere is a hotly debated quantity, which estimates vary by 2 orders of magnitude, depending on measuring techniques. The majority of the input is in the form of microgram size particles, which, in most cases, completely ablate injecting metals in the mesosphere. These metals are the primordial material for most of the layered phenomena (LP) occurring in the mesospause region (MR). Accurate knowledge of this quantity is crucial for the study of LPMR and in many cases it can contribute to the improvement of Whole Atmosphere Models (WAM) by constraining parameters such as vertical transport in the middle atmosphere. In an effort that ultimately aims to estimate this quantity, we utilize a new Zodiacal Dust Cloud (ZDC) model that follows the dynamical evolution of dust particles after ejection utilizing the orbital properties of comets and asteroids. One of the main results of this model is that it predicts that 85 - 95% of the dust in the inner solar system comes from Jupiter family comets (JFCs), with the remainder from the asteroid belt and Oort Cloud comets (OCCs). Furthermore, the modeled results show that most of the dust, which drifts down towards the inner solar system under the influence of Poynting-Robertson drag, has a mass in the range 1 - 10 ?g at a near-prograde orbit with a mean speed of about 14 km/s, producing a global meteoric mass input around 41 t/d. The low average speed and the absence of significant orbital eccentricities, also a result of the model, do not accord with various types of meteor radar observations, which record average speeds closer to 30 km/s. One of the key problems with this model is that it is currently quantitatively only constrained by Infrared Astronomical Satellite (IRAS) observations of the ZDC and only qualitatively constrained with terrestrial observations using radars. Furthermore, the radars utilized do not have the sensitivity to observe the particle masses dominant in the ZDC model when they travel at low speed (i.e. low ionization production). In this paper we discuss a methodology to better constrain the ZDC physical model utilizing ground-based meteor radar observations of head echoes and modelling. For this, we integrate and employ existing comprehensive models of meteoroid ablation, ionization and radar detection and thus enable accurate interpretation of radar observations. This will address potential biases that could, in principle, prevent them to detect the large population of small slow particles predicted by the ZDC model.

Janches, D.; Plane, J. M.; FENG, W.; Carillo Sanchez, J.; Nesvorny, D.; Nicolls, M. J.; Marsh, D. R.

2013-12-01

319

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

Microsoft Academic Search

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

H. B. Bluestein; W. P. Unruh

1990-01-01

320

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

SciTech Connect

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

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

1990-01-01

321

Multi-wavelength Raman lidar observations of the Eyjafjallajkull volcanic cloud over Potenza, Southern Italy  

NASA Astrophysics Data System (ADS)

Multi-wavelength Raman lidar measurements were performed at CNR-IMAA Atmospheric Observatory (CIAO) during the entire Eyjafjallajkull explosive eruptive period in April-May 2010, whenever weather conditions permitted. A methodology for volcanic layer identification and accurate aerosol typing has been developed on the basis both of the multi-wavelength Raman lidar measurements and EARLINET measurements performed at CIAO since 2000. The aerosol mask for lidar measurements performed at CIAO during the 2010 Eyjafjallajkull eruption has been obtained. Volcanic aerosol layers have been observed in different periods: 19-22 April, 27-29 April, 8-9 May, 13-14 May and 18-19 May. A maximum aerosol optical depth of about 0.12-0.13 was observed on 20 April, 22:00 UTC and 13 May, 20:30 UTC. Volcanic particles have been detected both at low altitudes, in the free troposphere and in the upper troposphere. Intrusions into the PBL have been revealed on 21-22 April and 13 May. In the April-May period Saharan dust intrusions typically occur in Southern Italy. For the period under investigations, a Saharan dust intrusion was observed on 13-14 May: dust and volcanic particles have been simultaneously observed at CIAO both at separated different levels and mixed within the same layer. Lidar ratios at 355 and 532 nm, ngstrm exponent at 355/532 nm, backscatter related ngstrm exponent at 532/1064 nm and particle linear depolarization ratio at 532 nm measured inside the detected volcanic layers have been discussed. The dependence of these quantities on relative humidity (RH) has been investigated by using co-located microwave profiler measurements. The particle linear depolarization ratio increasing with RH, lidar ratio values at 355 nm around 80 sr, and values of the ratio of lidar ratios greater than 1 suggest the presence of sulfates mixed with continental aerosol. Lower lidar ratio values (around 40 sr) increasing with RH and values of the ratio of lidar ratios lower than 1 indicate the presence of some aged ash inside these sulfate layers.

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

2011-04-01

322

Evaporation of rain falling from convective clouds as derived from radar measurements  

NASA Technical Reports Server (NTRS)

A computerized method developed by Rosenfeld (1987) is used to track the three-dimensional structure of the rainshafts of about 3000 summer afternoon convective rain cells in the semiarid region of central South Africa. By assuming a fixed relationship between the radar reflectivity factor and the rain intensity, time- and area-integrated rain volumes of each individual rainshaft are obtained at the cloudbase level and at a lower level. These results are used to obtain the cumulative fractional evaporation of the falling rain. This permits the cumulative evaporation of the falling rain to be obtained in a quantitative way as a function of the fall distance from the cloud base level and the rain intensity at the cloud base.

Rosenfeld, Daniel; Mintz, Yale

1988-01-01

323

Characterization of rockslide dynamics by the joint analysis of airborne LiDAR and stereo-photogrammetric point clouds.  

NASA Astrophysics Data System (ADS)

The catchment of Sanires is located on the South-facing slope of the Barcelonnette basin (South French Alps). This region is known to be highly prone to gravitational processes including large landslides and debris-flows. In early August 2013, a large rockslide event occurred in the lower part of the catchment. During several days, a large amount of debris have been mobilised along a 300m length cliff. Deposits have reached and filled the torrential channel downslope. Several field observations carried out in the following weeks have shown the progressive opening of fissures along the main scarp. Today, large volumes of unstable debris are still available on the slope. Local stakeholders are now expecting the formation of a debris-dam in the channel which could lead to a debris flow in case of failure. Since the rockslide cannot be stabilized, it is necessary to monitor the site in order to track the evolution of the sliding processes for hazard assessment purposes. This work is focused on the use of remote sensing techniques (terrestrial photogrammetry, LiDAR) to detect and quantify spatial and temporal distribution of materials on the slope. Dataset includes ground-based and aerial optical images acquired through several field surveys together with an airborne LiDAR points clouds. The Structure From Motion (SFM) technique is used to generate multi-date high-resolution digital elevation models (HRDEMs) in order to quantify volumes changes. Images correlation technique is used to estimate displacements at the surface from images acquired continuously by a fixed camera mounted on the opposite slope and facing the rockslide. The analysis of the terrestrial point clouds indicates two types of dynamics: (i) surficial transport of debris (boulders, tree trunks) which can be identified on daily observations, and (ii) a global deformation of the rockslope along several slip surfaces. The progressive development of the main scarp with velocity of a few cm.month-1 is also monitored. The analysis of an airborne LiDAR point cloud allows to characterize the main discontinuities and the possibility of movement of the global deformation. Finally, an indicator of activity of the slope is proposed from the time serie analysis. The possibility of extension of the rockslide is discussed.

Mathieu, Alexandre; Malet, Jean-Philippe; Stumpf, Andr

2014-05-01

324

Ice Concentration Retrieval in Stratiform Mixed-phase Clouds Using Cloud Radar Reflectivity Measurements and 1D Ice Growth Model Simulations  

SciTech Connect

Measurement of ice number concentration in clouds is important but still challenging. Stratiform mixed-phase clouds (SMCs) provide a simple scenario for retrieving ice number concentration from remote sensing measurements. The simple ice generation and growth pattern in SMCs offers opportunities to use cloud radar reflectivity (Ze) measurements and other cloud properties to infer ice number concentration quantitatively. To understand the strong temperature dependency of ice habit and growth rate quantitatively, we develop a 1-D ice growth model to calculate the ice diffusional growth along its falling trajectory in SMCs. The radar reflectivity and fall velocity profiles of ice crystals calculated from the 1-D ice growth model are evaluated with the Atmospheric Radiation Measurements (ARM) Climate Research Facility (ACRF) ground-based high vertical resolution radar measurements. Combining Ze measurements and 1-D ice growth model simulations, we develop a method to retrieve the ice number concentrations in SMCs at given cloud top temperature (CTT) and liquid water path (LWP). The retrieved ice concentrations in SMCs are evaluated with in situ measurements and with a three-dimensional cloud-resolving model simulation with a bin microphysical scheme. These comparisons show that the retrieved ice number concentrations are within an uncertainty of a factor of 2, statistically.

Zhang, Damao; Wang, Zhien; Heymsfield, Andrew J.; Fan, Jiwen; Luo, Tao

2014-10-01

325

Studying Clouds and Aerosols with Lidar Depolarization Ratio and Backscatter Relationships  

E-print Network

properties of clouds and aerosols. The relationships between depolarization ratio and backscatter allow us to retrieve particle thermodynamic phase and shape and/or orientation of aerosols and clouds. The first part is devoted to the investigation...

Cho, Hyoun-Myoung

2012-02-14

326

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

NASA Technical Reports Server (NTRS)

We apply Cloude's decomposition to imaging radar polarimetry. We derive the general expressions for the eigenvalues and eigenvectors for the case of terrain with reflection symmetry, and show in detail how the decomposition results can guide the interpretation of scattering from vegetated areas. For multi-frequency 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 forested 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. The scattering for the forested area is still dominated by scattering from randomly oriented cylinders, however. 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 dominate in this case.

Vanzyl, Jakob J.

1993-01-01

327

A Cloud and Precipitation Radar System Concept for the ACE Mission  

NASA Technical Reports Server (NTRS)

One of the instruments recommended for deployment on the Aerosol/Cloud/Ecosystems (ACE) mission is a new advanced cloud profiling radar. In this paper, we describe such a radar design, called ACERAD, which has 35- and 94-GHz channels, each having Doppler and dual-polarization capabilities. ACERAD will scan at Ka-band and will be nadir-looking at W-band. To get a swath of 25-30 km, considered the minimum useful for Ka-band, ACERAD needs to scan at least 2 degrees off nadir; this is at least 20 beamwidths, which is quite large for a typical parabolic reflector. This problem is being solved with a Dragonian design; a scaled prototype of the antenna is being fabricated and will be tested on an antenna range. ACERAD also uses a quasi-optical transmission line at W-band to connect the transmitter to the antenna and antenna to the receiver. A design for this has been completed and is being laboratory tested. This paper describes the current ACERAD design and status.

Durden, S. L.; Tanelli, S.; Epp, L.; Jamnejad, V.; Perez, R.; Prata, A.; Samoska, L.; Long, E; Fang, H.; Esteban-Fernandez, D.; Lee, C.

2011-01-01

328

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

329

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

330

Stratus cloud measurements with a K{sub {alpha}}-band Doppler radar and a microwave radiometer  

SciTech Connect

The goal of the Atlantic Stratocumulus Transition Experiment (ASTEX) held in the North Atlantic during June 1992 was to determine the physical reasons for the transition from stratocumulus to broken clouds. Some possible reasons for this transition were such things as cloud top entrainment instability and the decoupling effects of drizzle. As part of this experiment, the Environmental Technology Laboratory`s cloud sensing Doppler radar and three-channel microwave radiometer were deployed in the island of Porto Santo in the Madeira Islands of Portugal along with a carbon dioxide Doppler lider. Drizzle properties in stratus were examined using a log-normal droplet distribution model that related the model`s three parameters to the first three Doppler spectral moments of the cloud radar. With these moments, we are then able to compute the drizzle droplet concentration, modal radius, liquid water, and liquid water flux as a function of height.

Frisch, A.S.; Fairall, C.W.; Snider, J.B. [National Oceanic and Atmospheric Administration, Boulder, CO (United States); Lenschow, D.H. [National Center for Atmospheric Research, Boulder, CO (United States)

1995-04-01

331

Lidar observations of Arctic polar stratospheric clouds, 1988 - Signature of small, solid particles above the frost point  

NASA Technical Reports Server (NTRS)

The paper presents recent (January 1988) Arctic airborne lidar data which suggest that Type I polar stratospheric clouds (PSCs) are composed of small solid particles with radii on the order of 0.5 micron. PSCs were observed remotely in the 21-24 km altitude range north of Greenland during a round-trip flight from Andenes, Norway on January 29, 1988, aboard the NASA Wallops Flight Facility P-3 Orion aircraft. Synoptic analyses at the 30-mb level show local temperatures of 191-193 K, which are well above the estimated frost point temperature of 185 K; this suggests that the PSCs were probably of the binary HNO3-H2O (Type I) class.

Poole, L. R.; Osborn, M. T.; Hunt, W. H.

1988-01-01

332

Lidar Remote Sensing  

NASA Technical Reports Server (NTRS)

The laser radar, or lidar (for light detection and ranging) is an important tool for atmospheric studies. Lidar provides a unique and powerful method for unobtrusively profiling aerosols, wind, water vapor, temperature, and other atmospheric parameters. This brief overview of lidar remote sensing is focused on atmospheric applications involving pulsed lasers. The level of technical detail is aimed at the educated non-lidar expert and references are provided for further investigation of specific topics. The article is divided into three main sections. The first describes atmospheric scattering processes and the physics behind laser-atmosphere interactions. The second section highlights some of the primary lidar applications, with brief descriptions of each measurement capability. The third section describes the practical aspects of lidar operation, including the governing equation and operational considerations.

McGill, Matthew J.; Starr, David OC. (Technical Monitor)

2002-01-01

333

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

334

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

335

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

336

Infrared, microwave, and spaceborne radar simulations of a deep convective system using a 3-D cloud ensemble method  

NASA Technical Reports Server (NTRS)

A 3D cloud model is used to simulate the storm structure, and the results are linked to microwave and infrared radiative transfer models for simulation of aircraft observations. Spaceborne radar data are also simulated along the aircraft flight track. The cloud and radiative model simulations are studied and compared with aircraft observations. The initial results indicate that the 3D cloud model is capable of simulating the major features of observed storm systems when given a representative atmospheric sounding to initialize the convective systems. The simulations of infrared and microwave radiances provide reasonably good comparisons with the observations.

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

1992-01-01

337

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

338

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

SciTech Connect

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, K.D.; Eilts, M.D. [National Severe Storms Lab., Norman, OK (United States)] [National Severe Storms Lab., Norman, OK (United States)

1994-08-01

339

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

340

Fast, Space Qualified 3000 V Modulator for a Cloud Profiling Radar  

NASA Technical Reports Server (NTRS)

Cloudsat's Cloud Profiling Radar (CPR) delivers a 2 kW of RF pulse using an extended Interaction Klystron (EIK). 'To drive such an EIK, it was necessary to develop a -16.3 kV High Voltage Power Supply (HVPS) and a Focus Electrode Modulator (FEM), floating at Cathode potential to turn the EIK's Beam on and off -45V to -3kV with respect to the Cathode. This paper describes the design approach for the FEM and its performance at EM and Flight Configuration. In author's opinion it a simple but universal approach which allow designer to achieve greater flexibility and freedom in designing high swinging space qualifiable FEM.

Haque, Inam U.; Harvey, Wayne; Duong, Johnny; Packard, Roy; Ispirian, Julie

2005-01-01

341

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

SciTech Connect

The United States (U.S.) Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) operates millimeter wavelength cloud radars (MMCRs) in several climatological regimes. The MMCRs, are the primary observing tool for quantifying the properties of nearly all radiatively important clouds over the ACRF sites. The first MMCR was installed at the ACRF Southern Great Plains (SGP) site nine years ago and its original design can be traced to the early 90s. Since then, several MMCRs have been deployed at the ACRF sites, while no significant hardware upgrades have been performed. Recently, a two-stage upgrade (first C-40 Digital Signal Processors [DSP]-based, and later the PC-Integrated Radar AcQuisition System [PIRAQ-III] digital receiver) of the MMCR signal-processing units was completed. Our future MMCR related goals are: 1) to have a cloud radar system that continues to have high reliability and uptime and 2) to suggest potential improvements that will address increased sensitivity needs, superior sampling and low cost maintenance of the MMCRs. The Traveling Wave Tube (TWT) technology, the frequency (35-GHz), the radio frequency (RF) layout, antenna, the calibration and radar control procedure and the environmental enclosure of the MMCR remain assets for our ability to detect the profile of hydrometeors at all heights in the troposphere at the ACRF sites.

P Kollias; MA Miller; KB Widener; RT Marchand; TP Ackerman

2005-12-30

342

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

343

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

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

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

346

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

347

RAMSES: German Meteorological Service autonomous Raman lidar for water vapor, temperature, aerosol, and cloud measurements.  

PubMed

The Raman lidar for atmospheric moisture sensing (RAMSES) for unattended, continuous multiparameter atmospheric profiling is presented. A seeded frequency-tripled Nd:YAG laser serves as the light source. A nine-channel polychromator, nonfiber coupled to the main telescope (790mm diameter), is used for far-range measurements. Near-range observations are performed with a three-channel polychromator, fiber coupled to a secondary telescope (200mm diameter). Measurement parameters are water-vapor mixing ratio (MR), temperature, and the optical particle parameters, which are extinction coefficient, backscatter coefficient, lidar ratio, and depolarization ratio at 355nm. Profiles of water-vapor MR are measured from close to the surface up to 14km at night and 5km during the day under favorable atmospheric conditions in 20min. Temperature profiles of the troposphere and lower stratosphere are determined with the rotational-Raman technique. For the detection of the rotational Raman signals, a new beamsplitter/interference-filter experimental setup is implemented that is compact, robust, and easy to align. Furthermore, the polychromator design allows two independent methods for calibrating measurements of depolarization ratio. RAMSES optical design concept and experimental setup are detailed, and a description of the operational near-real-time data evaluation software is given. A multiday observation is discussed to illustrate the measurement capabilities of RAMSES. PMID:23207381

Reichardt, Jens; Wandinger, Ulla; Klein, Volker; Mattis, Ina; Hilber, Bernhard; Begbie, Robert

2012-12-01

348

Area-wide roof plane segmentation in airborne LiDAR point clouds  

Microsoft Academic Search

Most algorithms performing segmentation of 3D point cloud data acquired by, e.g. Airborne Laser Scanning (ALS) systems are not suitable for large study areas because the huge amount of point cloud data cannot be processed in the computers main memory. In this study a new workflow for seamless automated roof plane detection from ALS data is presented and applied to

Andreas Jochem; Bernhard Hfle; Volker Wichmann; Martin Rutzinger; Alexander Zipf

349

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

350

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

351

Numerical Simulation of the Dynamics, Cloud Microphysics and Radar Echo Structures of Tropical and Mid-Latitude Convection.  

NASA Astrophysics Data System (ADS)

Tropical convective cells have radar echo patterns that are distinctly different from many mid-latitude convective cells. Also, tropical convection develops associated regions of rain falling from thick anvil clouds. This anvil rain is stratiform and its radar reflectivity pattern contrasts sharply with the radar echoes of the cells. The goal of this study is to use numerical modeling to achieve a better understanding of the dynamical-microphysical interactions that result in the radar echo patterns of tropical and mid-latitude convective cells and of tropical anvil precipitation. A parameterized cloud microphysical scheme with ice-phase processes is coupled first with a one-dimensional time-dependent convective cloud model to simulate tropical and mid-latitude convective cells. Then the microphysical scheme is coupled with a set of prescribed mesoscale anvil cloud vertical motions to simulate the radar reflectivity in anvil precipitation. The simulated tropical convective cells are generally consistent with vertical velocities, and water contents observed by aircraft, although the model vertical velocities may be somewhat higher than those observed. Inclusion of the ice-phase microphysics and in-cloud perturbation pressure are both important in obtaining reasonable cloud dynamics. Tropical clouds of various maximum heights can be produced by varying the cell radius (which is prescribed parameter), cloud base conditions and the environment sounding. With a few exceptions, it was necessary to destabilize the input sounding (by lifting it on an adiabatic chart) prior to using it as input to the model, in order to generate tropical cells greater than 9 km in maximum height. This result indicates the importance of mesoscale forcing prior to the outbreak of deep convection. Warm-rain microphysics are found to account for 40-100% of the rain that falls from the simulated tropical cells. A portion of the rain in deep cells, however, is accounted for by graupel, which forms at high levels but melts well before reaching the surface. When a mid-latitude hailstorm sounding (also lifted) is used as input to the convective model, the radar reflectivity occurs aloft and is associated with hail. The stronger updraft of the hailstorm cell allows raindrops to accumulate aloft. Since the drops are suspended high enough and for a sufficiently long time above the 0(DEGREES)C level the raindrops are converted to hail. This result confirms quantitatively the hypothesis of Zipser and Le Mone that the strong vertical velocity in the hailstorm accounts for its different radar echo structure compared to tropical cells. The model further reveals the microphysical-dynamical chain of events involved, especially the effectiveness of the ice-phase processes in the hailstorm case and its relative ineffectiveness in the tropical cells. When the microphysical equations are coupled with tropical anvil cloud air motions, a stratiform radar echo is produced and the precipitation particle growth, melting and evaporation in the model confirm anvil-cloud processes inferred and hypothesized by Leary and Houze. Output from model runs for tropical cells of different sizes are used to estimate mass and heat fluxes by an ensemble of tropical convective cells. The model cells cannot by themselves match the heat flux profiles derived from large -scale heat-budget studies, unless mesoscale anvil vertical motions are invoked to supplement the convective motions.

Cheng, Chee Pong

352

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

353

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

NASA Astrophysics Data System (ADS)

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

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

2010-04-01

354

Implementation of Raman lidar for profiling of atmospheric water vapor and aerosols at the Southern Great Plains Cloud and Radiation Testbed Site  

SciTech Connect

There are clearly identified scientific requirements for continuous profiling of atmospheric water vapor at the Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) site. Research conducted at several laboratories, including our own collaboration in a previous Instrument Development Project for the Atmospheric Radiation Measurement (ARM) Program, has demonstrated the suitability of Raman lidar for providing measurements that are an excellent match to those requirements. We are currently building a rugged Raman lidar system that will reside permanently at the CART site and that is computer-automated to reduce 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 is intended to provide quantitative characterizations of aerosols and clouds, including depolarization measurements for particle phase studies. Raman lidar systems detect selected species by monitoring the wavelength-shifted molecular return produced by Raman scattering from the chosen molecule or molecules. For water-vapor measurements, the nitrogen Raman signal is observed simultaneously with the water-vapor Raman signal; proper ratioing of the signals yields the water-vapor mixing ratio. Similarly, when the backscatter signal at the laser wavelength (which contains contributions from both Rayleigh and aerosol scattering) is also recorded simultaneously, the ratio of the backscatter signal to the nitrogen Raman signal yields a quantitative measurement of the aerosol scattering ratio. A variety of aerosol and cloud parameters can be derived from this measurement. In aerosol-free regions of the atmosphere, temperature profiles can be derived from the density measurements obtained from the nitrogen Raman signal.

Goldsmith, J.E.M.; Bisson, S.E.; Blair, F.H. [Sandia National Labs., Livermore, CA (United States); Whiteman, D.N.; Melfi, S.H. [NASA/Goddard Space Flight Facility, Greenbelt, MD (United States); Ferrare, R.A. [Hughes STX Corp., Lanham, MD (United States)

1995-04-01

355

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

356

Cloud Properties and Radiative Heating Rates for TWP  

SciTech Connect

A cloud properties and radiative heating rates dataset is presented where cloud properties retrieved using lidar and radar observations are input into a radiative transfer model to compute radiative fluxes and heating rates at three ARM sites located in the Tropical Western Pacific (TWP) region. The cloud properties retrieval is a conditional retrieval that applies various retrieval techniques depending on the available data, that is if lidar, radar or both instruments detect cloud. This Combined Remote Sensor Retrieval Algorithm (CombRet) produces vertical profiles of liquid or ice water content (LWC or IWC), droplet effective radius (re), ice crystal generalized effective size (Dge), cloud phase, and cloud boundaries. The algorithm was compared with 3 other independent algorithms to help estimate the uncertainty in the cloud properties, fluxes, and heating rates (Comstock et al. 2013). The dataset is provided at 2 min temporal and 90 m vertical resolution. The current dataset is applied to time periods when the MMCR (Millimeter Cloud Radar) version of the ARSCL (Active Remotely-Sensed Cloud Locations) Value Added Product (VAP) is available. The MERGESONDE VAP is utilized where temperature and humidity profiles are required. Future additions to this dataset will utilize the new KAZR instrument and its associated VAPs.

Comstock, Jennifer

2013-11-07

357

Cloud Properties and Radiative Heating Rates for TWP  

DOE Data Explorer

A cloud properties and radiative heating rates dataset is presented where cloud properties retrieved using lidar and radar observations are input into a radiative transfer model to compute radiative fluxes and heating rates at three ARM sites located in the Tropical Western Pacific (TWP) region. The cloud properties retrieval is a conditional retrieval that applies various retrieval techniques depending on the available data, that is if lidar, radar or both instruments detect cloud. This Combined Remote Sensor Retrieval Algorithm (CombRet) produces vertical profiles of liquid or ice water content (LWC or IWC), droplet effective radius (re), ice crystal generalized effective size (Dge), cloud phase, and cloud boundaries. The algorithm was compared with 3 other independent algorithms to help estimate the uncertainty in the cloud properties, fluxes, and heating rates (Comstock et al. 2013). The dataset is provided at 2 min temporal and 90 m vertical resolution. The current dataset is applied to time periods when the MMCR (Millimeter Cloud Radar) version of the ARSCL (Active Remotely-Sensed Cloud Locations) Value Added Product (VAP) is available. The MERGESONDE VAP is utilized where temperature and humidity profiles are required. Future additions to this dataset will utilize the new KAZR instrument and its associated VAPs.

Comstock, Jennifer

358

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

E-print Network

, but ECMWF accepts no liability for error, omission and for loss or damage arising from its use. #12 orbits of Earth, or roughly 9 million km) of data. The model is assessed by cloud fraction statistics, surface temperature forecasts, visibility, aircraft icing forecasts and their role in the formation

Hogan, Robin

359

A Method for the Automatic Detection of Insect Clutter in Doppler-Radar Returns.  

SciTech Connect

The accurate detection and removal of insect clutter from millimeter wavelength cloud radar (MMCR) returns is of high importance to boundary layer cloud research (e.g., Geerts et al., 2005). When only radar Doppler moments are available, it is difficult to produce a reliable screening of insect clutter from cloud returns because their distributions overlap. Hence, screening of MMCR insect clutter has historically involved a laborious manual process of cross-referencing radar moments against measurements from other collocated instruments, such as lidar. Our study looks beyond traditional radar moments to ask whether analysis of recorded Doppler spectra can serve as the basis for reliable, automatic insect clutter screening. We focus on the MMCR operated by the Department of Energy's (DOE) Atmospheric Radiation Measurement (ARM) program at its Southern Great Plains (SGP) facility in Oklahoma. Here, archiving of full Doppler spectra began in September 2003, and during the warmer months, a pronounced insect presence regularly introduces clutter into boundary layer returns.

Luke,E.; Kollias, P.; Johnson, K.

2006-06-12

360

Remote sensing of cirrus cloud vertical size profile using MODIS data Xingjuan Wang,1  

E-print Network

at the 0.645 mm band, above-cloud water vapor absorption, and 3.75 mm thermal emission. The algorithmic coefficients derived from lidar and radar returns [Sassen, 1991; Spinhirne and Hart, 1990; Mace et al., 2002 water content (IWC), and are strongly sensitive to vertical temper- ature distribution [Ou and Liou

Liou, K. N.

361

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

362

Integrated cloud-aerosol-radiation product using CERES, MODIS, CALIPSO, and CloudSat data  

NASA Astrophysics Data System (ADS)

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; Stephens, Graeme; Partain, Philip

2007-10-01

363

Water Measurements using a Raman Lidar  

NASA Technical Reports Server (NTRS)

The research record for the usefulness of Raman Lidar in addressing a broad range of important atmospheric research topics is well established. Raman lidar technology has been used to measure tropospheric aerosols, stratospheric aerosols and cirrus clouds. Arguably the most important measurements offered by Raman lidar for both dynamic and radiative studies, however, is that of water vapor. We will describe large improvements in Raman lidar measurements of water vapor made possible through recent technology upgrades. Furthermore, we will present the use of Raman lidar to study liquid water in the atmosphere and describe current research into the use of Raman lidar measurements to estimate ice water content of cirrus clouds.

Whiteman, D. N.; Demoz, B.; Wang, Z.; Veselovskii, I.; Evans, K.; DiGirolamo, P.

2002-01-01

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

Study of atmospheric parameters measurements using MM-wave radar in synergy with LITE-2  

NASA Technical Reports Server (NTRS)

The Lidar In-Space Technology Experiment, (LITE), has been developed, designed, and built by NASA Langley Research Center, to be flown on the space shuttle 'Discovery' on September 9, 1994. Lidar, which stands for light detecting and ranging, is a radar system that uses short pulses of laser light instead of radio waves in the case of the common radar. This space-based lidar offers atmospheric measurements of stratospheric and tropospheric aerosols, the planetary boundary layer, cloud top heights, and atmospheric temperature and density in the 10-40 km altitude range. A study is being done on the use, advantages, and limitations of a millimeterwave radar to be utilized in synergy with the Lidar system, for the LITE-2 experiment to be flown on a future space shuttle mission. The lower atmospheric attenuation, compared to infrared and optical frequencies, permits the millimeter-wave signals to penetrate through the clouds and measure multi-layered clouds, cloud thickness, and cloud-base height. These measurements would provide a useful input to radiation computations used in the operational numerical weather prediction models, and for forecasting. High power levels, optimum modulation, data processing, and high antenna gain are used to increase the operating range, while space environment, radar tradeoffs, and power availability are considered. Preliminary, numerical calculations are made, using the specifications of an experimental system constructed at Georgia Tech. The noncoherent 94 GHz millimeter-wave radar system has a pulsed output with peak value of 1 kW. The backscatter cross section of the particles to be measured, that are present in the volume covered by the beam footprint, is also studied.

Andrawis, Madeleine Y.

1994-01-01

366

Optical Properties of Aerosols - Clouds - Contrails and Water Vapor Mixing Ratio By Lidar From The Jungfraujoch Research Station (3580 M Asl)  

NASA Astrophysics Data System (ADS)

The direct (as suspended particles) and indirect (by induced clouds/contrails) effects of the aerosols on the Sun - Earth system radiation budget is still remaining an important climate topic [IPCC, Report 2001]. The indirect effect is very complex (difficult to be quantified) is influencing also the hydrological cycle (evaporation/precipitation rates) [Ramamathan et al.,Science, Dec 2001]. Thus more space-time resolved measure- ments in order to retrieve optical, chemical and microphysical properties of aerosols are still needed. In this context the implementation of a new multi-wavelength (Ra- man) lidar system at the Jungfraujoch station (3580m ASL, January 2000) allows the retrieval of aerosols backscatter and extinction coefficients at 355nm, 532nm and 1064nm with a vertical resolution around 100 to 200m in the upper troposphere and lower stratosphere (UTLS). Depolarization studies (e.g. clouds) are also performed detecting parallel and cross polarization signals at 532nm. The water vapor mixing ratio retrieval is based on the spontaneous Raman shifts (387nm for N2 and 408nm for H2O) of the 355nm. This work will focus mainly on the results obtained using a 20cm diameter Newtonian configuration telescope. The Jungfraujoch lidar is part of the EARLINET European lidar network for aerosols measurements and is operating since May 2000. Furthermore these range resolved lidar measurements are bringing new insights in some of the column density measurements performed by FTIR or Sun photometry, or the passive microwave measurements, and are also linked to the direct "in situ" aerosols measurements.

Larchevque, G.; Balin, I.; Quaglia, P.; Nessler, R.; Simeonov, V.; van den Bergh, H.; Calpini, B.

367

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

E-print Network

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 D1 um have a very low Earth-impact probability. The intermediate particle sizes, D=100 um, represent a sweet spot. About 1% of these particles orbitally evolve by Poynting-Robertson drag to reach orbits with semimajor axis a=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 o...

Nesvorny, David; Pokorny, Petr; Janches, Diego

2011-01-01

368

Millimeter wave scattering from ice crystals and their aggregates: Comparing cloud model simulations with X- and Ka-band radar measurements  

NASA Astrophysics Data System (ADS)

Arctic clouds are often mixed-phase, such that the radiative properties of the clouds are a strong function of the relative amounts of cloud liquid and ice. Modeling studies have shown that the poorly understood ice phase processes are the regulators of the liquid water fraction. However, evaluating the fidelity of the model ice parameterizations has proven to be a difficult task. This study evaluates results of different ice microphysics representations in a cloud resolving model (CRM) using cloud radar measurements. An algorithm is presented to generate realistic ice crystals and their aggregates from which radar backscattering cross sections may be calculated using a generalized solution for a cluster of spheres. The aggregate is composed of a collection of ice crystals, each of which is constructed from a cluster of tiny ice spheres. Each aggregate satisfies the constraints set by the component crystal type and the mass-dimensional relationship used in the cloud resolving model, but is free to adjust its aspect ratio. This model for calculating radar backscattering is compared to two spherical and two spheroidal (bulk model) representations for ice hydrometeors. It was found that a refined model for representing the ice hydrometeors, both pristine crystals and their aggregates, is required in order to obtain good comparisons between the CRM calculations and the radar measurements. The addition of the radar-CRM comparisons to CRM-in situ measurements comparisons allowed conclusions about the appropriateness of different CRM ice microphysics parameterizations.

Botta, Giovanni; Aydin, Kultegin; Verlinde, Johannes; Avramov, Alexander E.; Ackerman, Andrew S.; Fridlind, Ann M.; McFarquhar, Greg M.; Wolde, Mengistu

2011-01-01

369

Inter-seasonal surface deformations of an active rock glacier imaged with radar and lidar remote sensing; Turtmann valley, Switzerland  

NASA Astrophysics Data System (ADS)

Inter-seasonal changes in surface deformation were imaged using a portable radar interferometer and terrestrial laser scanner during a series of three campaigns that took place in autumn 2011, summer 2012 and autumn 2012 on a rock glacier located in the Turtmann valley, Switzerland. Satellite radar interferometry (ERS 1 & 2, CosmoSkymed) indicate that accelerated downslope movement of the rock glacier commenced during the 1990s. Due to signal decorrelation associated with the satellite repeat pass time interval, continuous ground-based radar interferometry measurements were undertaken. Results show that the rock glacier accelerated significantly in Summer (Vmax = 6.0cm/25hrs), probably in response to the condition of the subsurface hydrology (e.g. post-peak spring snow melt and/or infiltration of rainfall). In autumn, the displacement velocity was reduced (Vmax = 2.0cm/25hrs). A one year surface difference of the glacier topography, derived from terrestrial laser scanning, provided insight into the rock glacier kinematics. Ongoing research is aimed at integrating surface displacement results with an extensive borehole monitoring system consisting of inclinometers and temperature sensors.

Kos, Andrew; Buchli, Thomas; Strozzi, Tazio; Springman, Sarah

2013-04-01

370

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

NASA Technical Reports Server (NTRS)

A cloud frequency of occurrence matrix is generated using merged cloud vertical profile derived from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Cloud Profiling Radar (CPR). The matrix contains vertical profiles of cloud occurrence frequency as a function of the uppermost cloud top. It is shown that the cloud fraction and uppermost cloud top vertical pro les can be related by a set of equations when the correlation distance of cloud occurrence, which is interpreted as an effective cloud thickness, is introduced. The underlying assumption in establishing the above relation is that cloud overlap approaches the random overlap with increasing distance separating cloud layers and that the probability of deviating from the random overlap decreases exponentially with distance. One month of CALIPSO and CloudSat data support these assumptions. However, the correlation distance sometimes becomes large, which might be an indication of precipitation. The cloud correlation distance is equivalent to the de-correlation distance introduced by Hogan and Illingworth [2000] when cloud fractions of both layers in a two-cloud layer system are the same.

Kato, Seiji; Sun-Mack, Sunny; Miller, Walter F.; Rose, Fred G.; Chen, Yan; Minnis, Patrick; Wielicki, Bruce A.

2009-01-01

371

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

Microsoft Academic Search

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

Edward Luke; Pavlos Kollias