James G. Yoe

LIDAR-MEASURED WIND PROFILES The Missing Link in the Global Observing System

The three-dimensional global wind field is the most important remaining measurement needed to accurately assess the dynamics of the atmosphere. Wind information in the tropics, high latitudes, and stratosphere is particularly deficient. Furthermore, only a small fraction of the atmosphere is sampled in terms of wind profiles. This limits our ability to optimally specify initial conditions for numerical weather prediction (NWP) models and our understanding of several key climate change issues. Because of its extensive wind measurement heritage (since 1968) and especially the rapid recent technology advances, Doppler lidar has reached a level of maturity required for a space-based mission. The European Space Agency (ESA)s Atmospheric Dynamics Mission Aeolus (ADM-Aeolus) Doppler wind lidar (DWL), now scheduled for launch in 2015, will be a major milestone. This paper reviews the expected impact of DWL measurements on NWP and climate research, measurement concepts, and the recent advances in technology that ...

The Validation of AIRS Retrievals of Integrated Precipitable Water Vapor Using Measurements from a Network of Ground-Based GPS Receivers over the Contiguous United States

A robust and easily implemented verification procedure based on the column-integrated precipitable water (IPW) vapor estimates derived from a network of ground-based global positioning system (GPS) receivers has been used to assess the quality of the Atmospheric Infrared Sounder (AIRS) IPW retrievals over the contiguous United States. For a period of six months from April to October 2004, excellent agreement has been realized between GPS-derived IPW estimates and those determined from AIRS, showing small monthly bias values ranging from 0.5 to 1.5 mm and root-mean-square (rms) differences of 4 mm or less. When the spatial (latitude–longitude) window for the GPS and AIRS matchup observations is reduced from the initial 1U2 °b y1U2 °t o1U4 °b y1U4°, the rms differences are reduced. Analysis revealed that the observed IPW biases between the instruments are strongly correlated to the reported surface pressure differences between the GPS and AIRS observational points. Adjusting the AIRS IPW values to account for the surface pressure discrepancies resulted in significant reductions of the bias between GPS and AIRS. A similar reduction can be obtained by comparing only (GPS–AIRS) match-up pairs for which the corresponding surface pressure differences are 0.5 mb or less. The comparisons also revealed that the AIRS IPW tends to be relatively dry in moist atmospheres (when IPW values 40 mm) but wetter in dry cases (when IPW values 10 mm). This is consistent with the documented bias of satellite measurements toward the first guess used in retrieval algorithms. However, additional study is needed to verify whether the AIRS water vapor retrieval process is the source of the discrepancies. It is shown that the IPW bias and rms differences have a seasonal dependency, with a maximum in summer (bias 1.2 mm, rms 4.14 mm) and minimum in winter (bias 0.5 mm, rms 3 mm).

The joint center for satellite data assimilation

Abstract The Joint Center for Satellite Data Assimilation (JCSDA) was established by NASA and NOAA in 2001, with Department of Defense (DoD) agencies becoming partners in 2002. The goal of JCSDA is to accelerate the use of observations from Earth-orbiting satellites in operational environmental analysis and prediction models for the purpose of improving weather, ocean, climate, and air quality forecasts and the accuracy of climate datasets. Advanced instruments of current and planned satellite missions do and will increasingly provide large volumes of data related to the atmospheric, oceanic, and land surface state. During this decade, this will result in a five order of magnitude increase in the volume of data available for use by the operational and research weather, ocean, and climate communities. These data will exhibit accuracies and spatial, spectral, and temporal resolutions never before achieved. JCSDA will help ensure that the maximum benefit from investment in the space-based global observation ...

GroundWinds 2000 field campaign: demonstration of new Doppler lidar technology and wind lidar data intercomparison

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 Joint Center for Satellite Data Assimilation: formation and achievements

The Joint Center for Satellite Data Assimilation (JCSDA) was established by NASA and NOAA in 2001, with the DoD becoming a partner in 2002. The goal of the JCSDA is to accelerate the use of observations from earth-orbiting satellites in operational numerical analysis and prediction models for the purpose of improving weather forecasts, improving seasonal to interannual climate forecasts, and increasing the accuracy of climate data sets. Advanced instruments of the current and planned satellite missions, do and will increasingly provide large volumes of data related to atmospheric, oceanic, and land surface state. These data will exhibit accuracies and spatial, spectral and temporal resolutions never before achieved. The JCSDA will ensure that the maximum benefit from investment in space is realised from the advanced global observing system. It will also help accelerate the use of satellite data from both operational and experimental spacecraft for weather and climate related activities. To this end the advancement of data assimilation science by JCSDA has included the establishment of the JCSDA Community Radiative Transfer Model (CRTM) and continual upgrades including, the incorporation of AIRS and snow and ice emissivity models for improving the use of microwave sounding data over high latitudes, preparation for use of METOP IASI/AMSU/HSB, DMSP SSMIS and CHAMP GPS data, real-time delivery of EOS-Aqua AMSR-E to NWP centers, and improved physically based SST analyses. Eighteen other research projects are also being supported by the JCSDA (e.g. use of cloudy radiances from advanced satellite instruments) to develop a state of-the-art satellite data assimilation system. The work undertaken by the JCSDA represents a key component of GEOSS. In particular data assimilation, data impact studies, OSSEs, THORPEX and network design studies are key activities of GEOSS.

Intercomparison of Doppler Wind Lidar Velocity Measurements

Three collocated Doppler Wind Lidars (DWLs) were used to measure winds during a demonstration campaign in New Hampshire September 2000. Corresponding line-of-sight (LOS) velocities determined by pairs of DWLs realized good agreement under clear sky conditions with random differences that increase as a function of decreasing signal strength. The radiosonde wind component projected along the DWL LOS typically showed good agreement. Clouds caused sharp attenuation of the signal and adversely affected LOS retrievals at cloud levels and beyond. Implications of the results for improving the instruments and organizing future Doppler wind lidar field campaigns are discussed.