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Steven L. Mullen and Bruce B. Smith

Abstract

A study of sea-level cyclone errors which occurred in 24- and 48-h forecasts of the National Meteorological Center's nested grid model (NGM) is performed for the 1987–88 winter season (1 December 1987–31 March 1988). All available 0000 UTC and 1200 UTC forecast cycles are analyzed for North America and adjacent ocean regions. Errors in forecasted central pressure and position are computed.

NGM forecasts of cyclone central pressure average 0.6 mb too deep at 24 hours and 0.3 mb too deep at 48 hours. The root-mean-square (RMS) errors for central pressure are 5.7 mb at 24 hours and 7.9 mb at 48 hours. The mean systematic displacement errors are 29 km at 24 hours and 51 km at 48 hours, and are directed towards the west at both times. The mean absolute displacement errors are much larger, 268 km at 24 hours and 393 km at 48 hours. Cyclone movement is forecasted too slow more frequently than too fast. Large variability in the skill of successive runs characterizes NGM cyclone forecasts though, with ∼70%–∼75% of the temporal variance being associated with fluctuations having periods shorter than seven days.

The results for the 1987–88 NGM are compared to those for the limited-area fine-mesh model (LFM) for the 1978–79 winter season. The size of the systematic pressure error decreased 50%–75% over the past decade. The absolute displacement error only decreased 10%–15%. Forecast variability, as measured by the RMS error of central pressure, is ∼15% smaller at 48 hours but remains essentially the same at 24 hours.

The comparison of the NGM and LFM results suggests that the nature of the short-range forecast problem for wintertime extratropical cyclones has changed somewhat over the past decade. It now appears that the problem is no longer one of primarily reducing the systematic error but also involves minimizing the impact of variability among individual forecasts.

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Bruce B. Smith and Steven L. Mullen

Abstract

Sea level cyclone errors are computed for the National Meteorological Center's Nested-Grid Model (NGM) and the Aviation Run of the Global Spectral Model (AVN). The study is performed for the 1987/88 and 1989/90 cool seasons. All available 24- and 48-h forecast cycles are analyzed for North America and adjacent ocean regions. Forecast errors in the central pressure, position, and 1000-500-mb thickness of the cyclone center are computed.

Aggregate errors can be summarized as follows: NGM forecasts of central pressure are too low (forecast pressure lower than analyzed) by 0.72 mb at 24 h and 0.66 mb at 48 h, while AVN forecasts are too high by 2.06 mb at 24 h and 2.50 mb at 48 h. Variance statistics for the pressure error indicate that AVN forecasts possess less variability than those of the NGM. Both mean absolute displacement errors and mean vector displacement errors are smaller for the AVN. The NGM moves surface cyclones too slowly and places them too far poleward into the cold air; the AVN possesses a smaller, slow bias only. Both models contain a weak cold bias as judged from the 1000-500-mb thickness over the cyclone center.

The aforementioned aggregate error characteristics exhibit significant variability when the data are stratified by geographical region, observed central pressure, and observed 12-h pressure change, however. For most regional, central pressure, and pressure change categories, the AVN performs better than the NGM in terms of smaller mean pressure errors, reduced pressure error variances, and shorter displacement errors. One noteworthy exception is deepening systems where the NGM's systematic pressure errors are generally 2–3 mb smaller than the AVN's errors.

The impact that ensemble averaging of individual NGM and AVN cyclone forecasts has on skill is examined. An equally weighted average of the NGM and AVN increasingly becomes the best forecast (more skillful than both the AVN and NGM individually) as the difference between the two models increases. This finding suggests that ensemble averaging offers increased skill during situations when the NGM and AVN forecasts diverge widely.

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Steven L. Mullen and Bruce B. Smith

Abstract

Sea level cyclone errors for two contrasting planetary-scale flow regimes, a long-wave trough verses a long-wave ridge over western North America, are computed for the National Meteorological Center's Nested Grid Model (NGM) and “Aviation Run” of the Global Spectral Model (AVN). The study is performed for the 1987/88 and 1989/90 cool seasons (1 December–31 March). All available 24- and 48-h forecast cycles are analyzed for North America and adjacent ocean regions. Errors in the central pressure and position of the cyclone are computed.

Statistically significant differences in forecast skill are found between the two flow patterns. This finding suggests that the utility of cyclone forecasts can be improved if model performance is documented for other recurrent, persistent flow regimes.

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Bruce A. Wielicki, Bruce R. Barkstrom, Edwin F. Harrison, Robert B. Lee III, G. Louis Smith, and John E. Cooper

Clouds and the Earth's Radiant Energy System (CERES) is an investigation to examine the role of cloud/radiation feedback in the Earth's climate system. The CERES broadband scanning radiometers are an improved version of the Earth Radiation Budget Experiment (ERBE) radiometers. The CERES instruments will fly on several National Aeronautics and Space Administration Earth Observing System (EOS) satellites starting in 1998 and extending over at least 15 years. The CERES science investigations will provide data to extend the ERBE climate record of top-of-atmosphere shortwave (SW) and longwave (LW) radiative fluxes. CERES will also combine simultaneous cloud property data derived using EOS narrowband imagers to provide a consistent set of cloud/radiation data, including SW and LW radiative fluxes at the surface and at several selected levels within the atmosphere. CERES data are expected to provide top-of-atmosphere radiative fluxes with a factor of 2 to 3 less error than the ERBE data. Estimates of radiative fluxes at the surface and especially within the atmosphere will be a much greater challenge but should also show significant improvements over current capabilities.

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G. Louis Smith, D. K. Pandey, Robert B. Lee III, Bruce R. Barkstrom, and Kory J. Priestley

Abstract

The Clouds and Earth Radiant Energy System (CERES) scanning radiometer was designed to provide high accuracy measurements of the radiances from the earth. Calibration testing of the instruments showed the presence of an undesired slow transient in the measurements of all channels at 1% to 2% of the signal. Analysis of the data showed that the transient consists of a single linear mode. The characteristic time of this mode is 0.3 to 0.4 s and is much greater than that the 8–10-ms response time of the detector, so that it is well separated from the detector response. A numerical filter was designed for the removal of this transient from the measurements. Results show no trace remaining of the transient after application of the numerical filter. The characterization of the slow mode on the basis of ground calibration data is discussed and flight results are shown for the CERES instruments aboard the Tropical Rainfall Measurement Mission and Terra spacecraft. The primary influence of the slow mode is in the calibration of the instrument and the in-flight validation of the calibration. This method may be applicable to other radiometers that are striving for high accuracy and encounter a slow spurious mode, regardless of the underlying physics.

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Takmeng Wong, Bruce A. Wielicki, Robert B. Lee III, G. Louis Smith, Kathryn A. Bush, and Joshua K. Willis

Abstract

This paper gives an update on the observed decadal variability of the earth radiation budget (ERB) using the latest altitude-corrected Earth Radiation Budget Experiment (ERBE)/Earth Radiation Budget Satellite (ERBS) Nonscanner Wide Field of View (WFOV) instrument Edition3 dataset. The effects of the altitude correction are to modify the original reported decadal changes in tropical mean (20°N to 20°S) longwave (LW), shortwave (SW), and net radiation between the 1980s and the 1990s from 3.1, −2.4, and −0.7 to 1.6, −3.0, and 1.4 W m−2, respectively. In addition, a small SW instrument drift over the 15-yr period was discovered during the validation of the WFOV Edition3 dataset. A correction was developed and applied to the Edition3 dataset at the data user level to produce the WFOV Edition3_Rev1 dataset. With this final correction, the ERBS Nonscanner-observed decadal changes in tropical mean LW, SW, and net radiation between the 1980s and the 1990s now stand at 0.7, −2.1, and 1.4 W m−2, respectively, which are similar to the observed decadal changes in the High-Resolution Infrared Radiometer Sounder (HIRS) Pathfinder OLR and the International Satellite Cloud Climatology Project (ISCCP) version FD record but disagree with the Advanced Very High Resolution Radiometer (AVHRR) Pathfinder ERB record. Furthermore, the observed interannual variability of near-global ERBS WFOV Edition3_Rev1 net radiation is found to be remarkably consistent with the latest ocean heat storage record for the overlapping time period of 1993 to 1999. Both datasets show variations of roughly 1.5 W m−2 in planetary net heat balance during the 1990s.

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Robert B. Lee III, Bruce R. Barkstrom, G. Louis Smith, John E. Cooper, Leonard P. Kopia, R. Wes Lawrence, Susan Thomas, Dhirendra K. Pandey, and Dominique A. H. Crommelynck

Abstract

The Clouds and the Earth's Radiant Energy System (CERES) spacecraft sensors are designed to measure broadband earth-reflected solar shortwave (0.3–5 µm) and earth-emitted longwave (5– > 100 µm) radiances at the top of the atmosphere as part of the Mission to Planet Earth program. The scanning thermistor bolometer sensors respond to radiances in the broadband shortwave (0.3–5 µm) and total-wave (0.3– > 100 µm) spectral regions, as well as to radiances in the narrowband water vapor window (8–12 µm) region. The sensors are designed to operate for a minimum of 5 years aboard the NASA Tropical Rainfall Measuring Mission and Earth Observing System AM-I spacecraft platforms that are scheduled for launches in 1997 and 1998, respectively. The flight sensors and the in-flight calibration systems will he calibrated in a vacuum ground facility using reference radiance sources, tied to the international temperature scale of 1990. The calibrations will be used to derive sensor gains, offsets, spectral responses, and point spread functions within and outside of the field of view. The shortwave, total-wave, and window ground calibration accuracy requirements (1 sigma) are ±0.8, ±0.6, and ±0.3 W m−2 sr−1, respectively, while the corresponding measurement precisions are ±0.5% and ±1.0% for the broadband longwave and shortwave radiances, respectively. The CERES sensors, in-flight calibration systems, and ground calibration instrumentation are described along with outlines of the preflight and in-flight calibration approaches.

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Howard B. Bluestein, Robert M. Rauber, Donald W. Burgess, Bruce Albrecht, Scott M. Ellis, Yvette P. Richardson, David P. Jorgensen, Stephen J. Frasier, Phillip Chilson, Robert D. Palmer, Sandra E. Yuter, Wen-Chau Lee, David C. Dowell, Paul L. Smith, Paul M. Markowski, Katja Friedrich, and Tammy M. Weckwerth

To assist the National Science Foundation in meeting the needs of the community of scientists by providing them with the instrumentation and platforms necessary to conduct their research successfully, a meeting was held in late November 2012 with the purpose of defining the problems of the next generation that will require radar technologies and determining the suite of radars best suited to help solve these problems. This paper summarizes the outcome of the meeting: (i) Radars currently in use in the atmospheric sciences and in related research are reviewed. (ii) New and emerging radar technologies are described. (iii) Future needs and opportunities for radar support of high-priority research are discussed. The current radar technologies considered critical to answering the key and emerging scientific questions are examined. The emerging radar technologies that will be most helpful in answering the key scientific questions are identified. Finally, gaps in existing radar observing technologies are listed.

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Britton B. Stephens, Matthew C. Long, Ralph F. Keeling, Eric A. Kort, Colm Sweeney, Eric C. Apel, Elliot L. Atlas, Stuart Beaton, Jonathan D. Bent, Nicola J. Blake, James F. Bresch, Joanna Casey, Bruce C. Daube, Minghui Diao, Ernesto Diaz, Heidi Dierssen, Valeria Donets, Bo-Cai Gao, Michelle Gierach, Robert Green, Justin Haag, Matthew Hayman, Alan J. Hills, Martín S. Hoecker-Martínez, Shawn B. Honomichl, Rebecca S. Hornbrook, Jorgen B. Jensen, Rong-Rong Li, Ian McCubbin, Kathryn McKain, Eric J. Morgan, Scott Nolte, Jordan G. Powers, Bryan Rainwater, Kaylan Randolph, Mike Reeves, Sue M. Schauffler, Katherine Smith, Mackenzie Smith, Jeff Stith, Gregory Stossmeister, Darin W. Toohey, and Andrew S. Watt

Abstract

The Southern Ocean plays a critical role in the global climate system by mediating atmosphere–ocean partitioning of heat and carbon dioxide. However, Earth system models are demonstrably deficient in the Southern Ocean, leading to large uncertainties in future air–sea CO2 flux projections under climate warming and incomplete interpretations of natural variability on interannual to geologic time scales. Here, we describe a recent aircraft observational campaign, the O2/N2 Ratio and CO2 Airborne Southern Ocean (ORCAS) study, which collected measurements over the Southern Ocean during January and February 2016. The primary research objective of the ORCAS campaign was to improve observational constraints on the seasonal exchange of atmospheric carbon dioxide and oxygen with the Southern Ocean. The campaign also included measurements of anthropogenic and marine biogenic reactive gases; high-resolution, hyperspectral ocean color imaging of the ocean surface; and microphysical data relevant for understanding and modeling cloud processes. In each of these components of the ORCAS project, the campaign has significantly expanded the amount of observational data available for this remote region. Ongoing research based on these observations will contribute to advancing our understanding of this climatically important system across a range of topics including carbon cycling, atmospheric chemistry and transport, and cloud physics. This article presents an overview of the scientific and methodological aspects of the ORCAS project and highlights early findings.

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Greg M. McFarquhar, Elizabeth Smith, Elizabeth A. Pillar-Little, Keith Brewster, Phillip B. Chilson, Temple R. Lee, Sean Waugh, Nusrat Yussouf, Xuguang Wang, Ming Xue, Gijs de Boer, Jeremy A. Gibbs, Chris Fiebrich, Bruce Baker, Jerry Brotzge, Frederick Carr, Hui Christophersen, Martin Fengler, Philip Hall, Terry Hock, Adam Houston, Robert Huck, Jamey Jacob, Robert Palmer, Patricia K. Quinn, Melissa Wagner, Yan (Rockee) Zhang, and Darren Hawk
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