Cao C.,STAR |
Xiong J.,NASA |
Blonski S.,University of Maryland University College |
Liu Q.,University of Maryland University College |
And 4 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2013
The successful launch of the Suomi National Polar-orbiting Partnership Satellite on 28 October 2011 with the key instrument Visible Infrared Imaging Radiometer Suite signifies a new era of moderate-resolution imaging capabilities following the legacy of AVHRR and Moderate-Resolution Imaging Spectroradiometer (MODIS). After a year and half of calibration and validation, the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument is performing very well. By early 2013, the sensor data records have achieved provisional maturity status and have been used in the routine production of more than 20 environmental data records by users worldwide. Based on comparisons with MODIS, the VIIRS reflective solar band radiometric uncertainties are now comparable in reflectance to that of MODIS Collection 6 equivalent bands (within 2%) although radiance differences could be larger for several bands, while an agreement on the order of 0.1 K has also been achieved for the thermal emissive bands, except for bands with significant spectral differences or certain bands at extreme temperatures (below 200 K or above 343 K). The degradation in the VIIRS rotating telescope assembly mirrors is gradually leveling off after reaching ~30% and thus far has limited impact on instrument performance and products. Environmental data record users are generally satisfied with the VIIRS data quality which meets the product requirements. While the specific technical details are documented in other papers in this special issue and in Cao et al. (2013a), this paper focuses on the major findings of VIIRS calibration and validation since launch, radiometric performance validation, and uncertainties, as well as lessons learned. Key Points Suomi NPP VIIRS is performing well based on extensive verification validation VIIRS radiometric accuracy comparable to that of MODIS for RSB and TEB bands The impact of RTA mirror degradation mitigated and most other issues resolved ©2013. American Geophysical Union. All Rights Reserved.
Smith D.A.,National Oceanic and Atmospheric Administration |
Holmes S.A.,SGT Inc. |
Li X.,ERT Inc. |
Guillaume S.,ETH Zurich |
And 4 more authors.
Journal of Geodesy | Year: 2013
A terrestrial survey, called the Geoid Slope Validation Survey of 2011 (GSVS11), encompassing leveling, GPS, astrogeodetic deflections of the vertical (DOV) and surface gravity was performed in the United States. The general purpose of that survey was to evaluate the current accuracy of gravimetric geoid models, and also to determine the impact of introducing new airborne gravity data from the 'Gravity for the Redefinition of the American Vertical Datum' (GRAV-D) project. More specifically, the GSVS11 survey was performed to determine whether or not the GRAV-D airborne gravimetry, flown at 11 km altitude, can reduce differential geoid error to below 1 cm in a low, flat gravimetrically uncomplicated region. GSVS11 comprises a 325 km traverse from Austin to Rockport in Southern Texas, and includes 218 GPS stations (σΔ h = 0.4 cm over any distance from 0.4 to 325 km) co-located with first-order spirit leveled orthometric heights (σ Δ H = 1.3 cm end-to-end), including new surface gravimetry, and 216 astronomically determined vertical deflections (σ DOV= 0.1′). The terrestrial survey data were compared in various ways to specific geoid models, including analysis of RMS residuals between all pairs of points on the line, direct comparison of DOVs to geoid slopes, and a harmonic analysis of the differences between the terrestrial data and various geoid models. These comparisons of the terrestrial survey data with specific geoid models showed conclusively that, in this type of region (low, flat) the geoid models computed using existing terrestrial gravity, combined with digital elevation models (DEMs) and GRACE and GOCE data, differential geoid accuracy of 1 to 3 cm (1 σ) over distances from 0.4 to 325 km were currently being achieved. However, the addition of a contemporaneous airborne gravity data set, flown at 11 km altitude, brought the estimated differential geoid accuracy down to 1 cm over nearly all distances from 0.4 to 325 km. © 2013 © Springer-Verlag (outside the USA).
Stone A.A.,State University of New York at Stony Brook |
Stone A.A.,ERT Inc. |
Schneider S.,State University of New York at Stony Brook |
Broderick J.E.,State University of New York at Stony Brook |
Schwartz J.E.,State University of New York at Stony Brook
Clinical Journal of Pain | Year: 2014
INTRODUCTION:: Pain diaries are important tools for clinical trials and optimal assay sensitivity of outcomes derived from these diaries is a worthwhile goal. Jensen and colleagues recently reported results suggesting that single-day diary-based outcomes could possibly be as psychometrically sound as outcomes based on taking the average of many diaries. MATERIALS AND METHODS:: In this paper, we attempted to replicate those results with several diary data sets. RESULTS AND DISCUSSION:: We come to a different conclusion than that advanced by Jensen and colleagues and conclude that their results were unusual in that very high test-retest reliability among days was found. With our 4 diary data sets we find that aggregating multiple diaries yields more reliable outcomes and improved sensitivity. We suggest that using single-day diaries will often lead to underpowered studies and that pretesting is advised before adopting single-day diaries. We also suggest that other researchers replicate these findings within their diary-based clinical trials. © 2013 by Lippincott Williams & Wilkins.
Kunkel K.E.,North Carolina State University |
Kunkel K.E.,National Oceanic and Atmospheric Administration |
Karl T.R.,National Oceanic and Atmospheric Administration |
Easterling D.R.,National Oceanic and Atmospheric Administration |
And 5 more authors.
Geophysical Research Letters | Year: 2013
Probable maximum precipitation (PMP) is the greatest accumulation of precipitation for a given duration meteorologically possible for an area. Climate change effects on PMP are analyzed, in particular, maximization of moisture and persistent upward motion, using both climate model simulations and conceptual models of relevant meteorological systems. Climate model simulations indicate a substantial future increase in mean and maximum water vapor concentrations. For the RCP8.5 scenario, the changes in maximum values for the continental United States are approximately 20%-30% by 2071-2100. The magnitudes of the maximum water vapor changes follow temperature changes with an approximate Clausius-Clapeyron relationship. Model-simulated changes in maximum vertical and horizontal winds are too small to offset water vapor changes. Thus, our conclusion is that the most scientifically sound projection is that PMP values will increase in the future due to higher levels of atmospheric moisture content and consequent higher levels of moisture transport into storms. Key Points Maximum atmospheric water vapor will increase in the future Estimates of Probable Maximum Precipitation will increase commensurately Dams and other similar structures are vulnerable to future climate change ©2013. American Geophysical Union. All Rights Reserved.
Wang Y.M.,National Geodetic Survey |
Saleh J.,ERT Inc. |
Li X.,ERT Inc. |
Roman D.R.,National Geodetic Survey
Journal of Geodesy | Year: 2012
A new gravimetric geoid model, USGG2009 (see Abbreviations), has been developed for the United States and its territories including the Conterminous US (CONUS), Alaska, Hawaii, Guam, the Commonwealth of the Northern Mariana Islands, American Samoa, Puerto Rico and the US Virgin Islands. USGG2009 is based on a 1′ × 1′ gravity grid derived from the NGS surface gravity data and the DNSC08 altimetry-derived anomalies, the SRTM-DTED1 3′′ DEM for its topographic reductions, and the global geopotential model EGM08 as a reference model. USGG2009 geoid heights are compared with control values determined at 18,398 Bench Marks over CONUS, where both the ellipsoidal height above NAD 83 and the Helmert orthometric height above NAVD 88 are known. Correcting for the ellipsoidal datum difference, this permits a comparison of the geoid heights to independent data. The standard deviation of the differences is 6. 3 cm in contrast to 8. 4 cm for its immediate predecessor- USGG2003. To minimize the effect of long-wavelength errors that are known to exist in NAVD88, these comparisons were made on a state-by-state basis. The standard deviations of the differences range from 3-5 cm in eastern states to about 6-9 cm in the more mountainous western states. If the GPS/Bench Marks-derived geoid heights are corrected by removing a GRACE-derived estimate of the long-wavelength NAVD88 errors before the comparison, the standard deviation of their differences from USGG2009 drops to 4. 3 cm nationally and 2-4 cm in eastern states and 4-8 in states with a maximum error of 26. 4 cm in California and minimum of -32. 1 cm in Washington. USGG2009 is also compared with geoid heights derived from 40 tide-gauges and a physical dynamic ocean topography model in the Gulf of Mexico; the mean of the differences is 3. 3 cm and their standard deviation is 5. 0 cm. When USGG2009-derived deflections of the vertical are compared with 3,415 observed surface astro-geodetic deflections, the standard deviation of the differences in the N-S and E-W components are 0. 87′′ and 0. 94′′, respectively. © 2011 Springer-Verlag.
Stein A.F.,ERT Inc. |
Saylor R.D.,National Oceanic and Atmospheric Administration
Atmospheric Chemistry and Physics | Year: 2012
The processes of aerosol sulfate formation are vital components in the scientific understanding of perturbations of earth's radiative balance via aerosol direct and indirect effects. In this work, an analysis of the influence of changes in oxidant levels and sulfur dioxide oxidation pathways was performed to study the underlying pathways for sulfate formation. Sensitivities of this constituent were calculated from a series of photochemical model simulations with varying rates of NOx and VOC emissions to produce variations in oxidant abundances using a photochemical model (CMAQ) that covers the eastern US for part of the ICARTT 2004 campaign. Three different chemical mechanisms (CBIV, CB05, and SAPRC99) were used to test model responses to changes in NOx and VOC concentrations. Comparison of modeled results and measurements demonstrates that the simulations with all three chemical mechanisms capture the levels of sulfate reasonably well. However, the three mechanisms are shown to have significantly different responses in sulfate formation when the emissions of NOx and/or VOC are altered, reflecting different photochemical regimes under which the formation of sulfate occurs. Also, an analysis of the oxidation pathways that contribute to sulfur dioxide conversion to sulfate reveals substantial differences in the importance of the various pathways among the three chemical mechanisms. These findings suggest that estimations of the influence that future changes in primary emissions or other changes which perturb SO2 oxidants have on sulfate abundances, and on its direct and indirect radiative forcing effects, may be dependent on the chemical mechanism employed in the model analysis. © 2012 Author(s).
Yu F.,ERT Inc. |
Wu X.,National Oceanic and Atmospheric Administration
IEEE Transactions on Geoscience and Remote Sensing | Year: 2013
During the Geostationary Operational Environmental Satellite (GOES)-14 and -15 post-launch test (PLT) for science periods, an up to ∼2 K mean brightness temperature (Tb) bias with respect to collocated Atmospheric Infrared Sounder (AIRS) and Infrared Atmospheric Sounding Interferometer (IASI) observations was observed in the absorptive IR channels of the GOES-14/15 Imagers. These large scene-dependent biases were believed to be caused mainly by spectral characterization errors. In this paper, we refined the spectral response function (SRF) shift algorithm which was developed during the GOES-13 PLT period to improve the GOES-14/15 Imager IR radiometric calibration accuracy by accurately calculating the impact of blackbody on the calibrated scene radiance. The uncertainty of the SRF shift algorithm was estimated and used to guide the final selection of the total amount of central wave-number shift. This refined algorithm was first verified with GOES-13 Imager Ch6 data and then used to evaluate and further revise the audited GOES-14/15 SRFs provided by the instrument vendor. Based on this algorithm, the optimal SRF shifts were -1.98cm-1 for GOES-13 Ch6, -8.25cm-1 for GOES-14 Ch3, -0.25cm-1 for GOES-14 Ch6, -6.25cm-1 for GOES-15 Ch3 and +0.50cm-1 for GOES-15 Ch6. The newly shifted SRFs were operationally implemented into the GOES-14/15 Imager IR calibrations in the August of 2011 and successfully reduced the mean all-sky Tb bias with respect to the reference instrument to less than 0.15 K. The scene-dependent bias, which can be nonlinear at large erroneous SRF, was also greatly reduced. The same method was applied to correct the GOES-12 Imager Ch6 SRF which has a changing SRF error during its mission life. A strong linear relationship between the optimal SRF shifts and the mean Tb bias with respect to the AIRS data was observed at this channel. This strong linear relationship can be used to revise the GOES-12 Ch6 SRF for a better radiance simulation. The method described in this paper is particularly important to evaluate and revise the erroneous SRF, if it exists, after satellite launch yet before it becomes fully operational. © 2012 IEEE.
Kruk M.C.,ERT Inc. |
Hilburn K.,Helios Remote Sensing Systems, Inc. |
Marra J.J.,National Oceanic and Atmospheric Administration
Monthly Weather Review | Year: 2015
This study analyzes 25 years of Special Sensor Microwave Imager (SSM/I) retrievals of rain rate and wind speed to assess changes in storminess over the open water of the Pacific Ocean. Changes in storminess are characterized by combining trends in both the statistically derived 95th percentile exceedance frequencies of rain rate and wind speed (i.e., extremes). Storminess is computed annually and seasonally, with further partitioning done by phase of the El Niño-Southern Oscillation (ENSO) index and the Pacific decadal oscillation (PDO) index. Overall, rain-rate exceedance frequencies of 6-8 mm h-1 cover most of the western and central tropical Pacific, with higher values present around the Philippines, Japan, Mexico, and the northwest coast of Australia. Wind speed exceedance frequencies are a strong function of latitude, with values less (greater) than 12 m s-1 equatorward (poleward) of 30°N/S. Statistically significant increasing trends in rain rate were found in the western tropical Pacific near the Caroline Islands and the Solomon Islands, and in the extratropics from the Aleutian Islands down the coast along British Columbia and Washington State. Statistically significant increasing trends in wind speed are present in the equatorial central Pacific near Kiribati and the Republic of the Marshall Islands (RMI), and in the extratropics along the west coast of the United States and Canada. Thus, while extreme rain and winds are both increasing across large areas of the Pacific, these areas are modulated according to the phase of ENSO and the PDO, and their intersection takes aim at specific locations.
Ngan F.,National Oceanic and Atmospheric Administration |
Ngan F.,University of Maryland College Park |
Stein A.,National Oceanic and Atmospheric Administration |
Stein A.,ERT Inc. |
Draxler R.,National Oceanic and Atmospheric Administration
Journal of Applied Meteorology and Climatology | Year: 2015
The Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT), a Lagrangian dispersion model, has been coupled (inline) to the the Weather Research and Forecasting (WRF) Model meteorological model in such a way that the HYSPLIT calculation is run as part of the WRF-ARW prediction calculation. This inline version of HYSPLIT takes advantage of the higher temporal frequency of WRF-ARW variables relative to what would be available for the offline approach. Furthermore, the dispersion calculation uses the same vertical coordinate system as WRF-ARW, resulting in a more consistent depiction of the state of the atmosphere and the dispersion simulation. Both inline and the offline HYSPLIT simulations were conducted for two tracer experiments at quite different model spatial resolutions: the Cross Appalachian Tracer Experiment (CAPTEX) in regional scale (at 9-km grid spacing) and the Atmospheric Studies in Complex Terrain (ASCOT) in finescale (at 333.3-m grid spacing). A comparison of the model with the measured values showed that the results of the two approaches were very similar for all six releases in CAPTEX. For the ASCOT experiments, the cumulative statistical score of the inline simulations was better than or equal to offline runs in four of five releases. Although the use of the inline approach did not provide any advantage over the offline method for the regional spatial scale and medium-range temporal scale represented by the CAPTEX experiment, the inline HYSPLIT was able to improve the simulation of the dispersion when compared with the offline version for the fine spatial and temporal resolutions over the complex-terrain area represented by ASCOT. The improvement of the inline over the offline calculation is attributed to the elimination of temporal and vertical interpolation of the meteorological data as compared with the offline version. © 2015 American Meteorological Society.
Yu F.,ERT Inc. |
Wu X.,College Park
IEEE Transactions on Geoscience and Remote Sensing | Year: 2013
Quality infrared (IR) radiances and their derived products from the Geostationary Environmental Operational Satellite (GOES) Sounder are very important data sources to weather prediction and nowcasting applications for the continental United States and adjacent ocean regions. With demanding requirements for more accurate weather nowcasting models and climate change studies, it is necessary to assess and improve the radiometric calibration accuracy of the GOES Sounder data. The objective of this paper is to examine the GOES Sounder IR radiometric calibration accuracy, and the diurnal calibration variation using intercalibration with two well-calibrated hyperspectral radiometers onboard low earth orbit satellites, the Atmospheric Infrared Sounder (AIRS) on the Aqua satellite and the Infrared Atmospheric Sounding Interferometer (IASI) on the Metop-A satellite. The results show that most sounder IR channels of GOES-11 through GOES-15 are well calibrated outside of the satellite midnight effect time period, with a less than 0.5 K of mean bias of brightness temperature with respect to IASI. Yet, the impact of the satellite midnight effect on the radiance quality varies greatly at different IR channels among different satellites. Further research is needed to understand the changes of instrument environmental flux on the GOES IR radiance around satellite midnight. © 2012 IEEE.