A53A-01 INVITED
Airborne High Spectral Resolution Lidar Measurements of Atmospheric Aerosols
NASA Langley Research Center (LaRC) recently developed an airborne High Spectral Resolution Lidar (HSRL) to measure aerosol distributions and optical properties. The HSRL technique takes advantage of the spectral distribution of the lidar return signal to discriminate aerosol and molecular signals and thereby measure aerosol extinction and backscatter independently. The LaRC instrument employs the HSRL technique to measure aerosol backscatter and extinction profiles at 532 nm and the standard backscatter lidar technique to measure aerosol backscatter profiles at 1064 nm. Depolarization profiles are measured at both wavelengths. Since March 2006, the airborne HSRL has acquired over 215 flight hours of data deployed on the NASA King Air B200 aircraft during several field experiments. Most of the flights were conducted during two major field experiments. The first major experiment was the joint Megacity Initiative: Local and Global Research Observations (MILAGRO) /Megacity Aerosol Experiment in Mexico City (MAX-MEX)/Intercontinental Chemical Transport Experiment-B (INTEX B) experiment that was conducted during March 2006 to investigate the evolution and transport of pollution from Mexico City. The second major experiment was the Texas Air Quality Study (TEXAQS)/Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS) that was conducted during August and September 2006 to investigate climate and air quality in the Houston/Gulf of Mexico region. Several flights were also conducted to help validate the Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) lidar on board the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite (CALIPSO) satellite. In February 2007, several flights were carried out as part of an Environmental Protection Agency (EPA) experiment to assess air quality in central California. Airborne HSRL data acquired during these missions were used to quantify aerosol extinction and optical thickness contributed by various aerosol types. Several B200 flights conducted during MILAGRO were coordinated with flights carried out by the Department of Energy G-1 aircraft, the National Center for Atmospheric Research (NCAR) C-130 aircraft, and/or the Sky Research J-31 aircraft. In situ measurements of aerosol microphysical properties acquired on G-1 and C-130 are being used to investigate the ability to discern various aerosol types using the HSRL data. Aerosol extinction profiles derived from the in situ measurements and from the NASA Ames Airborne Tracking Sun Photometer on board the J-31 are being used to assess the HSRL aerosol extinction profiles. Additional applications of airborne HSRL data to be discussed include: 1) characterization of the spatial and vertical distributions of aerosols, 2) investigation of aerosol variability near clouds, 3) evaluation of model simulations of aerosol transport, and 4) assessments of aerosol optical properties derived from a combination of surface, airborne, and satellite measurements.
A53A-02 INVITED
High Resolution Doppler Lidar Measurements of Boundary Layer Dynamics Made From Multiple Platforms.
NOAA's Earth System Research Laboratory (ESRL) has developed and deploys two coherent Doppler lidars to
study boundary layer dynamics. These systems, which operate at 2 and 9 microns, use high pulse rates and
motion-compensated hemispheric scanning to provide profiles of horizontal wind speed and direction,
backscatter intensity, vertical velocity, and velocity variances from a variety of stationary and moving platforms: land
based as well as ship and aircraft based. Operating the systems with low elevation angle vertical and horizontal
sector scans permits study of evolving low-level horizontal wind fields, such as nocturnal low-level jets, flow in
complex terrain, and coherent wind features generated from air/sea interactions with extremely high temporal and
vertical spatial resolution. The ability to operate from moving platforms has provided a unique opportunity to
study boundary layer dynamics over the ocean and over much larger horizontal scales accessible from aircraft.
http:www.esrl.noaa.gov
A53A-03
Ground based and ultralight-borne lidar to highlight multilayered aerosol in the frame of AMMA
The lidar system EZ LIDAR/textregister/LAUVA was operated both onboard an ultrahigh aircraft (ULA) and at the ground level (Niamey international airport, Niger, 13°31'N-2°07'E) within the framework of the first intensive field phase of the African Monsoon Multidisciplinary Analysis (AMMA; http:amma.mediasfrance.org/) which took place in the West African Sahel during the dry season in January-February 2006. This phase of AMMA was dedicated to the study of tropospheric aerosols from biomass burning and Aeolian erosion which are known to be the major aerosol sources in the West African Sahel (10-18°N) in winter. The overall objective of the campaign was to characterize the aerosol mixing between biomass burning and dust aerosols. Our system offered the only opportunity to deploy an airborne lidar during the campaign, which in turn offered a unique opportunity to document the vertical profile of the aerosol backscatter to extinction ration in a complex environment. Different aerosol layers have been observed against the altitude from both the ULA and the ground level. The lower layers were mainly composed of dust aerosol coming from the Saharan region. Significant variability has been observed in these layers due to frontal activity during the night. The upper layers were mainly associated to biomass burning aerosols coming from the Nigeria and Benin. Biomass burning aerosols were observed in the free troposphere between 2 and 5 km above the mean sea level. The presence of the biomass burning aerosols at such an altitude is likely due to the air mass ascendance associated to the monsoon flux. The existence of a complex multilayer aerosol structures against the altitude could significantly influence the radiative budget in the Sahelian area. Different aerosol vertical structures observed from lidar will be presented and their radiative impact in terms of heating rate will be discussed.
A53A-04
LASE Measurements of Water Vapor, Aerosol, and Cloud Distributions in Regions of African Easterly Waves and Saharan Dust Layers
LASE (Lidar Atmospheric Sensing Experiment) measured high resolution profiles of water vapor and aerosols, and cloud distributions in 14 flights over the eastern Atlantic region during the NAMMA (NASA African Monsoon Multidisciplinary Analyses) field experiment which was conducted from August 15 to September 12, 2006. Measurements were made in conjunction with African Easterly Waves (AEW), Tropical Disturbances (TDs), and Saharan Aerosol Layers (SALs); and in clear air and convective regions. Interactions of Saharan dust layers with tropical air during early stages of the development of TDs were observed. LASE measurements were used to profile the dust layers and guide in situ aircraft sampling. The dust layers over the ocean and the continent were found to range in altitude from near surface to 6 km. Aerosol scattering ratios at 817 nm ranged from 0 to >20, and their optical thickness ranged from 0 to >1. Highly attenuating (cloud) regions with high (~100%) RH were occasionally observed within the dust layers. Dust layers were situated generally north of the TDs, however, dust layers were also observed in and around the TDs. A wide range of water vapor concentrations were observed in and around the TDs, and in general, the dust layers were anti-correlated with the water vapor distributions. LASE water vapor, aerosol, cloud measurements during NAMMA provided an opportunity to compare with in situ aircraft, dropsonde, and radiosonde measurements; and satellite observations. Examples of LASE measurements along with their relationship with the AEWs, at various stages of their development, will be presented in this paper.
A53A-05
The Influence of Lidar based Water Vapor Assimilation on a Regional Forecast over the Mid- Atlantic
Forecasting subtle, small-scale convective cases in both winter and summer time is an ongoing challenge within our field. Recent studies have shown that better structure of moisture within the boundary layer is crucial for improved forecasting skills. Lidars, which take high temporal observations, are therefore able to capture moisture structures very well in the boundary layer. Therefore, this study investigates the impact of assimilating water vapor mixing ratio from the Howard University Beltsville Lidar and Goddard's Scanning Raman Lidar for one case during the Water Vapor Validation Experiment- Satellite and Sondes (WAVES) field campaign located in Beltsville, Md. Specifically, we use lidar based water vapor observations to drive the Weather Research and Forecasting (WRF) regional model over a 5 km grid resolution. The timing, location, strength and spatial coverage of convection are studied and analyzed.
A53A-06
Applications of GLAS Satellite Lidar Cloud, Aerosol and PBL Measurements at High Spatial Resolution
The Geoscience Laser Altimeter System, GLAS, beginning in 2003, provides space borne lidar observations of
global clouds and aerosol from polar orbit. The measurements in fall 2003 and spring 2004 include highly
sensitive aerosol detection and profiling by photon counting detection at 532 nm wavelength to backscatter cross
section below 10-7 1/m-sr. Data products from the measurements include aerosol optical depth of layers and
the profile of extinction cross section. An analog channel at 1064 nm also gives aerosol profiles, and
measurements include the precise pulse reflectance from the surface. A special data product is the height of the
planetary boundary layer, PBL, from analysis of the signal structure. Over the ocean, we have shown that the
pulse reflectance is a function of wind speed. The satellite lidar data is uniquely accurate for the global height
distributions of scattering layers. However due to the height and speed of the platform, the measurement cannot
be applied to as high a resolution as aircraft or ground based measurements. For GLAS data products, limiting
horizontal resolution can be as low as 176m for cloud heights and as large as 28 km for aerosol optical
thickness. Surface signals over the ocean will allow higher resolution analysis of some parameters. An
application of the GLAS data has been comparison to model cloud or aerosol distribution with the goal of
improving cloud and aerosol parameterizations in GCM's and aerosol transport models. Initial comparisons are
completed. A full description of the GLAS data products and their resolution factors will be presented. Examples
of how the data may be applied to model comparisons, such as ECMWF clouds, PBL height aerosol transport,
and polar blowing snow will be described.
http:glo.gsfc.nasa.gov
A53A-07
Polar Stratospheric Clouds Observed by Lidar in Antarctica and the Effect of Polar Vortex
The University of Illinois Fe (iron) Boltzmann temperature lidar was operated at the South Pole (90°S) from November 1999 to October 2001, and afterward at the Rothera Station (67.5°S, 68.0°W) from December 2002 to March 2005. This lidar operates at two UV wavelengths, 372 and 374 nm. By combining the Boltzmann and Rayleigh lidar techniques, it is capable of measuring the middle and upper atmosphere temperature, Fe density, polar mesospheric clouds (PMCs), and polar stratospheric clouds (PSCs). The observations of PSCs at Rothera are the first ground-based lidar observations there and also the first in West Antarctica. Overall PSCs were observed in the range of 12-28 km during the seasons from May/June to September/October. The derived PSC mean peak backscattering ratio, centroid altitude and RMS width are comparable at both locations. However, from May to October PSCs occurred much less frequently (~24.8%) and in shorter periods (June 16th to October 5th) at Rothera comparing with the South Pole (~65.4% and May 28th to October 8th) by our observations, which is reasonable given the longer persistence of the lower temperature favorable for PSC formation at the South Pole. And the PSC occurrence is strongly correlated with local temperature. We calculated the Ertel's potential vorticity of southern hemisphere on 450K isentropic surface in 2003 and 2004 from NCEP temperature and wind data, and derived the relative distance between Rothera and the calculated polar vortex edge when the vortex is stable (from June to September). The relative distance correlates well with the local temperature (at 50 mbar level) and the PSC occurrence. When the vortex edge approaches Rothera closer (< 5 degree latitude difference) or crosses it further from the south, temperature drops and PSC occurs when the temperature is below 194K. An unusual case occurred on August 18th 2003. With 190K temperature and 2.5 degree inside the vortex, no PSC was detected. This may be caused by the vortex edge acting as a barrier to tracer gas transport preventing type I PSC formation.
A53A-08
Tropospheric Planetary Wave Influence on Polar Stratospheric Clouds Over Davis, Antarctica
Observations of Polar Stratospheric Clouds (PSC) were obtained with a Rayleigh lidar at Davis Station, Antarctica (78.0°~E, 68.6°~S), during the winter of 2006. Davis is located near the nominal edge of the Antartic polar vortex. A strong influence of planetary waves (PW) on the occurrence of PSC was seen, as has been observed for this site in previous seasons. We also saw an apparent correlation between the occurrence of tropopausal cirrus and moderately strong PSC, as has been seen elsewhere by other authors. Examination of the data showed that PW--induced vertical motion was present from low in the troposphere through to at least the mid--stratosphere, resulting in adiabatic cooling (from uplift) and heating (downward motion). The cooling either contributed to the formation of PSC, or allowed previously existing PSC to remain, and possibly intensify. The PW may have a similar influence on the occurrence of tropopausal cirrus. Co--incidental location of cirrus and PSC has been seen previously by others, but in those cases the cause appeared to be uplift resulting from synoptic-- scale disturbances in the upper troposphere, whereas we find that at Davis, during mid--winter, the vertical movement appears to have a planetary--scale origin.