An attempt is made here to evaluate the skill of forecast during boreal summer monsoon regime over the Indian region using the Observation Simulation System Experiment (OSSE) with Doppler Wind LIDAR (DWL) onboard International Space Station (ISS), assimilated in the initial condition. Through various techniques such as pattern correlation, root mean square error etc, we found that there is some positive impact of assimilating the DWL data on the forecast particularly at the lower tropospheric level. Impact on lowering the RMSE is seen for wind fields in the 850 and 500 hPa over Indian domain but not much impact is seen over larger domain. The moisture field and cloud also show marginal impact due to assimilation of DWL. This indicates that possibly due to lower spatial resolution of DWL data and more data gap over Indian and surrounding oceanic region, the impact on forecast is less. However, it shows the promise that monsoon being a convectively coupled system; increase in spatial data by DWL may better resolve the low level wind and subsequently the low level shear which is important for convection trigger in boundary layer.
Doppler lidar continues to advance as a useful method for remote sensing of atmospheric winds. Applications from
mobile and ship-based platforms have demonstrated the impact of coherent lidar observations for studying the structure
of the stable and marine boundary layers. Airborne deployments enable observations over extended areas, and were used
to measure water vapor transport over the US Great Plains. Recently, smaller coherent lidars operating at 1.6 μm have
become commercially available. A new direct detection lidar currently will enable airborne observations in aerosol-sparse
atmospheric regions. Efforts to extend Doppler lidar to space are underway in Europe, with a Doppler lidar winds
mission planned for late 2010.
Global measurement of tropospheric winds is a key
measurement for understanding atmospheric
dynamics and improving numerical weather
prediction. Global wind profiles remain a high
priority for the operational weather community and
also for a variety of research applications including
studies of the global hydrologic cycle and transport
studies of aerosols and trace species. In addition to
space based winds, high altitude airborne Doppler
lidar systems flown on research aircraft, UAV's or
other advanced sub-orbital platforms would be of
great scientific benefit for studying mesoscale
dynamics and storm systems such as hurricanes. The
Tropospheric Wind Lidar Technology Experiment
(TWiLiTE) is a three year program to advance the
technology readiness level of the key technologies and
subsystems of a molecular direct detection wind lidar
system by validating them, at the system level, in an
integrated airborne lidar system. The TWiLiTE
Doppler lidar system is designed for autonomous
operation on the WB57, a high altitude aircraft
operated by NASA Johnson. The WB57 is capable of
flying well above the mid-latitude tropopause so the
downward looking lidar will measure complete
profiles of the horizontal wind field through the
lower stratosphere and the entire troposphere. The
completed system will have the capability to profile
winds in clear air from the aircraft altitude of 18 km
to the surface with 250 m vertical resolution and < 3
m/s velocity accuracy. Progress in technology
development and status of the instrument design will
be presented.
At NOAA's Earth System Research Laboratory, lidar systems have been developed and applied to environmental probing for more than three decades. Progressing from early investigations of atmospheric turbidity and winds employing ruby and CO2 lasers, current work is focused on the application of sensors to measure atmospheric properties important for improving air quality understanding and forecasting, and quantifying important climate forcing mechanisms. Additionally, lidar systems are being used for probing the ocean to observe fish schools and marine mammals for research on estuarine health. Here we briefly describe development and applications of lidar systems for characterizing winds and turbulence in the atmosphere, distribution and transport of ozone and aerosol concentrations in urban areas, and inventory of fish stocks in coastal water.
A field campaign featuring three collocated Doppler wind lidars was conducted over ten days during September 2000 at the GroundWinds Observatory in New Hampshire. The lidars were dissimilar in wavelength and Doppler detection method. The GroundWinds lidar operated at 532 nm and used fringe-imaging direct detection, while the Goddard Lidar Observatory for Winds (GLOW) ran at 355 nm and employed double-edge filter direct detection, and the NOAA mini-MOPA operated at 10 microns and used heterodyne detection. The objectives of the campaign were (1) to demonstrate the capability of the GroundWinds lidar to measure winds while employing several novel components, and (2) to compare directly the radial wind velocities measured by the three lidars for as wide a variety of conditions as possible. Baseline wind profiles and ancillary meteorological data (temperature and humidity profiles) were obtained by launching GPS radiosondes from the observatory as frequently as every 90 minutes. During the final week of the campaign the lidars collected data along common lines-of-sight for several extended periods. The wind speed varied from light to jet stream values, and sky conditions ranged from clear to thick clouds. Intercomparisons of overlapping lidar and radiosonde observations show that all three lidars were able to measure wind given sufficient backscatter. At ranged volumes containing thicker clouds, and those beyond, the wind sensing capability of the direct detection lidars was adversely affected.
The Multicenter Airborne Coherent Atmospheric Wind Sensor instrument is an airborne coherent Doppler laser radar (Lidar) capable of measuring atmospheric wind fields and aerosol structure. Since the first demonstration flights onboard the NASA DC-8 research aircraft in September 1995, two additional science flights have been completed. Several system upgrades have also bee implemented. In this paper we discuss the system upgrades and present several case studies which demonstrate the various capabilities of the system.
A transportable ground-based differential absorption lidar specifically designed for ozone and aerosol profiling in the lower troposphere was developed at the National Oceanic and Atmospheric Administration/Environmental Technology Laboratory (NOAA/ETL). The NOAA/ETL ozone lidar has the unique capability of measuring vertical profiles of ozone concentration from near the surface up to 3 km, and measuring vertical profiles of aerosol from the surface to about 10 km. The innovative hardware design and improved signal processing techniques make the system efficient, compact, and easily transportable. A recently implemented 2D scanning system provides the capability of measuring ozone concentrations and aerosol in a vertical plane. The lidar has been deployed in seven field experiments in California, Illinois, and Boulder, Colorado since summer 1993. Lidar observations of vertical profiles of ozone concentrations and ozone advection fluxes in Southern California during high ozone season revealed interesting structures of ozone distributions in the Los Angeles urban area, and near the Cajon Pass which is a major corridor of ozone transport from Los Angeles to the Mojave Desert.
The first Multi center Airborne Coherent Atmospheric Wind Sensor (MACAWS) field experiment demonstrated an airborne high energy TEA CO2 Doppler lidar system for measurement of atmospheric wind fields and aerosol structure. The system was deployed on the NASA DC-8 during September 1995 in a series of checkout flights to observe several important atmospheric phenomena, including upper level winds in a Pacific hurricane, marine boundary layer winds, cirrus cloud properties, and land-sea breeze structure. The instrument, with its capability to measure 3D winds and backscatter fields, promises to be a valuable tool for climate and global change, severe weather, and air quality research. In this paper, we describe the airborne instrument, assess its performance, discuss future improvements, and show some preliminary results from the September experiments.
A very compact, transportable differential absorption lidar (DIAL) for ozone and aerosol profiling in the lower troposphere (from near surface to about 3 km) has been developed at the National Oceanic and Atmospheric Administration's Environmental Technology Laboratory. The ozone lidar has been employed in two field experiments in California. the first was in intercomparison experiment of the lidar and an airborne ozone analyzer carried out in the Sacramento valley of northern California during July 1993. The second field experiment involving the ozone lidar was the Free Radical Study, carried out in the Los Angeles basin during September 1993, where the highest ozone episode of the year was observed during the experiment. The system will be described and examples of ozone profiles during the high- ozone episode in inland Los Angeles will be shown.
It is very difficult for both detectors and data acquisition systems to cope with the enormous signal dynamic range of incoherent lidar systems. The high power of the near-range atmosphere-backscattered radiation may cause serious problems to detectors. If the detector can endure the high power, the dynamic range of the output electric signal still remains a problem. To solve the problems, this paper suggests using a multibeam transmitter instead of a single-beam transmitter. With a multibeam transmitter a significant reduction of the signal dynamic range can always be achieved simultaneously with good near-range coverage even under different atmospheric conditions. Numerical simulations for a differential absorption lidar (DIAL) system measuring ozone in the lower troposphere below 3 km show the advantage of using a three-beam transmitter rather than a single-beam transmitter.
System considerations and the design of infrared coherent lidars utilizing tropospheric backscatter are discussed. Requirements regarding power measurement, Doppler measurement, antenna and laser energy considerations are addressed. A design for an improved CO2 laser source is proposed that meets these requirements and is compact and capable of unattended operation.
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