Engineering topics

Baker, W. E.

Publications and source records attributed to Baker, W. E..

At least 37 records · Page 2

NASA NTRS1984

Large-scale analysis and forecast experiments with wind data from the Seasat A scatterometer

A series of data assimilation experiments is performed to assess the impact of Seasat A satellite scatterometer (SASS) wind data on Goddard Laboratory for Atmospheric Sciences (GLAS) model forecasts. The SASS data are dealiased as part of an objective analysis system utilizing a three-pass procedure. The impact of the SASS data is evaluated with and without temperature soundings from the NOAA 4 Vertical Temperature Profile Radiometer (VTPR) instrument in order to study possible redundancy between surface wind data and upper air temperature data. In the northern hemisphere the SASS data are generally found to have a negligible effect on the forecasts. In the southern hemisphere the forecast impact from SASS data is somewhat larger and primarily beneficial in the absence of VTPR data. However, the inclusion of VTPR data effectively eliminates the positive impact over Australia and South America. This indicates that SASS data can be beneficial for numerical weather prediction in regions with large data gaps, but in the presence of satellite soundings the usefulness of SASS data is significantly reduced.

Baker, W. E.↗

NASA NTRS1984

The impact of scatterometer wind data on global weather forecasting

The impact of SEASAT-A scatterometer (SASS) winds on coarse resolution atmospheric model forecasts was assessed. The scatterometer provides high resolution winds, but each wind can have up to four possible directions. One wind direction is correct; the remainder are ambiguous or "aliases'. In general, the effect of objectively dealiased-SASS data was found to be negligible in the Northern Hemisphere. In the Southern Hemisphere, the impact was larger and primarily beneficial when vertical temperature profile radiometer (VTPR) data was excluded. However, the inclusion of VTPR data eliminates the positive impact, indicating some redundancy between the two data sets.

Atlas, D.↗

NASA NTRS1984

Simulation studies of proposed observing systems and their impact on numerical weather prediction

A series of realistic simulation studies is being conducted as a cooperative effort between the European Centre for Medium Range Weather Forecasts (ECMWF), the National Meteorological Center (NMC), and the Goddard Laboratory for Atmospheric Sciences (GLAS) to provide a quantitative assessment of the potential impact of proposed observation systems on large scale numerical weather prediction. A special objective of this project is to avoid the unrealistic character of earlier simulation studies.

Atlas, R.↗

NASA NTRS1984

FGGE data impact studies in the Southern Hemisphere

The purpose of this paper is to quantify the impact of the FGGE SOS on the GLAS analyses and forecasts in the Southern Hemisphere, and to evaluate the relative importance of its components, and in particular, the impact of the loss of surface buoys. This discussion is limited to the forecast impact of the FGGE system upon a region between 28 deg S and 56 deg S, 50 deg W-80 W which includes essentially the southern cone of South America. Although forecast skill is verified against the NMC analysis, which used only VTPR but no TIROS-N data in the Southern Hemisphere, enough conventional data exists over this region to avoid biased verifications.

Kalnay, E.↗

NASA NTRS1984

SASS wind forecast impact studies using the GLAS and NEPRF systems: Preliminary conclusions

For this project, a version of the GLAS Analysis/Forecast System was developed that includes an objective dealiasing scheme as an integral part of the analysis cycle. With this system the (100 sq km) binned SASS wind data generated by S. Peteherych of AER, Canada corresponding of the period 0000 GMT 7 September 1978 to 1200 GMT 13 September 1978 was objectively dealiased. The dealiased wind fields have been requested and received by JPL, NMC and the British Meteorological Office. The first 3.5 days of objectively dealiased fields were subjectively enhanced on the McIDAS system. Approximately 20% of the wind directions were modified, and of these, about 70% were changed by less than 90 deg. Two SASS forecast impact studies, were performed using the dealiased fields, with the GLAS and the NEPRF (Navy Environmental Prediction Research Facility) analysis/forecast systems.

Kalnay, E.↗

NASA NTRS1984

Simulation studies of the impact of advanced observing systems on numerical weather prediction

To study the potential impact of advanced passive sounders and lidar temperature, pressure, humidity, and wind observing systems on large-scale numerical weather prediction, a series of realistic simulation studies between the European Center for medium-range weather forecasts, the National Meteorological Center, and the Goddard Laboratory for Atmospheric Sciences is conducted. The project attempts to avoid the unrealistic character of earlier simulation studies. The previous simulation studies and real-data impact tests are reviewed and the design of the current simulation system is described. Consideration is given to the simulation of observations of space-based sounding systems.

Atlas, R.↗

NASA NTRS1984

Multivariate optimum interpolation of surface pressure and surface wind over oceans

The present multivariate analysis method for surface pressure and winds incorporates ship wind observations into the analysis of surface pressure. For the specific case of 0000 GMT, on February 3, 1979, the additional data resulted in a global rms difference of 0.6 mb; individual maxima as larse as 5 mb occurred over the North Atlantic and East Pacific Oceans. These differences are noted to be smaller than the analysis increments to the first-guess fields.

Bloom, S. C.↗

NASA NTRS1983

The influence of the tropics on the prediction of ultralong waves. I - Tropical wind field

The effects of tropical wind data from the FGGE and tropical latent heating on numerical modeling of ultralong waves are considered in a two-part study. The model studied is the global fourth-order GLAS general circulation model, an energy-conserving format with horizontal differences calculated with fourth-order accuracy. Data assimilation experiments were performed with and without the wind data, with account taken of eastward and northward wind components, the geopotential height, and the relative humidity, all over pressure surfaces. The initial conditions were used to generate six pairs of forecasts, and the tropical wind error decreased after two days of prediction when the initial conditions contained the wind data. The deviations from the measured planetary wave data were attributed to differences in the initial rotational wind field, which varied on a three-day basis. The latent heat initial data had a five-day period and extended its influence beyond the tropical zone. The tropical heat sources sustained the tropical westerlies in the GLAS model, and removal of the tropical heat sources reversed the wind to easterlies.

Baker, W. E.↗

NASA NTRS1983

Objective analysis and assimilation of observational data from FGGE

An objective analysis scheme is presented for the assimilation of meteorological data in which wind, geopotential height, and relative humidity are analyzed on mandatory pressure levels, and surface pressure and temperature are reduced to sea level for analysis. The present analysis/forecast system demonstrates a reasonable degree of forecast skill over the Northern Hemisphere for an ensemble of five-day integrations during the First Special Observing Period of the First GARP Global Experiment (FGGE) The vertical motion field shows outstanding agreement with the large scale synoptic pattern for the sample analysis presented, and the mean meridional circulation portrayed in the FGGE analysis is in close agreement with observational estimates.

Baker, W. E.↗

NASA NTRS1983

A case study of the sensitivity of forecast skill to data and data analysis techniques

A series of experiments have been conducted to examine the sensitivity of forecast skill to various data and data analysis techniques for the 0000 GMT case of January 21, 1979. These include the individual components of the FGGE observing system, the temperatures obtained with different satellite retrieval methods, and the method of vertical interpolation between the mandatory pressure analysis levels and the model sigma levels. It is found that NESS TIROS-N infrared retrievals seriously degrade a rawinsonde-only analysis over land, resulting in a poorer forecast over North America. Less degradation in the 72-hr forecast skill at sea level and some improvement at 500 mb is noted, relative to the control with TIROS-N retrievals produced with a physical inversion method which utilizes a 6-hr forecast first guess. NESS VTPR oceanic retrievals lead to an improved forecast over North America when added to the control.

Baker, W. E.↗

NASA NTRS1983

The impact of Seasat-A scatterometer data on GLAS model forecasts

The effect of SASS (Seasat-A Satellite Scatterometer) data on the GLAS analysis and forecast system is assessed. After discussing the objective analysis and assimilation of SASS winds, consideration is given to a scheme developed to objectively dealias the SASS data. Results are then presented from analysis and forecast experiments. The evaluation finds a negligible effect of the SASS data in the Northern Hemisphere. In the Southern Hemisphere, the impact is larger and for the most part beneficial when the VTPR (vertical temperature profile radiometer) is excluded. However, the inclusion of VTPR data effectively eliminates this positive impact, suggesting some redundancy between the two data sets.

Atlas, R.↗

NASA NTRS1983

The influence of the tropics upon the prediction of the Southern Hemisphere circulation within the GLAS GCM

An examination is undertaken of the sensitivity of short term Southern Hemisphere circulation prediction to tropical wind data and tropical latent heat release. The data assimilation experiments employ the Goddard Laboratory for Atmospheric Sciences' fourth-order general circulation model. Two of the experiments are identical, but for the fact that one uses tropical wind data while the other does not. A third experiment contains the identical initial conditions of forecasts with tropical winds, while suppressing tropical latent heat release.

Baker, W. E.↗

NASA NTRS1982

Global-scale weekly and monthly energetics during January and February 1979

Time averages of the latitudinal distribution of kinetic energy and terms of the kinetic energy equation are presented as depicted by analyses of the First GARP Global Experiment during the First Special Observing Period. It is found that the monthly averages exhibit peaks in the stationary wave energy at 30 degrees N and in the tropics, while global decompositions of the streamfunction and velocity potential in spherical harmonics are truncated at the fourth degree. The kinetic energy distribution of the associated wind field displays peaks in the tropics and northern mid-latitudes in January, but only a tropical peak in February. These analyses support the Eliassen-Palm relationship for latitudinal momentum and geopotential wave transport, particularly in the mid-latitudes. However, in the deep tropics, latitudinal convergence of the fully resolved stationary wave momentum transport accompanies latitudinal convergence of stationary wave geopotential flux in westerly flow.

Paegle, J.↗

NASA NTRS1982

Planetary-scale characteristics of the atmospheric circulation during January and February 1979

The global scale mass and wind fields observed during FGGE special observing period (SOP) are studied, with attention given to the time variation and vertical structure of the ultralong waves. A spherical harmonic representation is developed for the global fields. The tropical circulation is found to imprint more amplitude on the lower-order components than the midlatitude circulation does. High amplitude oscillations are determined to be present in the divergent fields on all time scales, i.e., diurnal to monthly. The global scale wind was found to change on scales approaching a week. Good agreement with teleconnection predictions was demonstrated for the cross-equatorial divergent and zonal rotational flow changes. The global scale was concluded to resemble force modes of linear tidal theory, with important contributions from longitudinal heating gradients.

Paegle, J.↗

NASA NTRS1982

An assessment of the FGGE satellite observing system during SOP-1

The sensitivity of a Goddard Laboratory for Atmospheric Sciences global objective analysis cycle to the addition of FGGE level II-b data is assessed. The GOAS system comprises a predictive continuity provided by a model first-guess forecast integrated from a previous forecast and updated by data gathered in the interim. FGGE data originated in the Jan.-Mar. 1979 period and were acquired by rawinsondes, pilot balloons, surface stations, satellites, ships, and drifting buoys deployed during SOP-1. Focussing on 2-5 and 8-day forecasts, comparisons were made of the 6 hr forecast error at the 300 mb height in three experiments using all, no-satellite (NOSAT), and without rawinsondes or pilot balloons modes. Larger errors occurred in the case of NOSAT, while significant corrections to the GOAS predictions were noted using all the FGGE data. It was concluded that all forecasts were improved by inclusion of full FGGE data sets, including forecasting beyond one week.

Halem, M.↗

NASA NTRS1981

The effects of tropical wind data on the prediction of ultralong waves

The influence of tropical wind data on the prediction of planetary waves were studied. Two assimilation experiments were performed, one with and one without FGGE tropical winds. The planetary wave error was then analyzed in 72 h forecasts from the initial conditions provided by the two assimilations.

Baker, W. E.↗

NASA NTRS1981

The state of the atmosphere as inferred from the FGGE satellite observing systems during SOP-1

Data assimilation experiments were performed to test the influence of different elements of the satellite observing systems. Results from some of the experiments are presented. These findings show that the FGGE satellite systems are able to infer the three-dimensional motion field and improve the representation of the large-scale state of the atmosphere. Preliminary results of the forecast impact of the FGGE data sets are also presented.

Halem, M.↗

NASA NTRS1981

Numerical prediction of the large scale tropical flow

The mean error characteristics of two series of forecasts of the tropical flow were studied. By using as initial conditions analyses made with and without the FGGE special observing system, the impact that initial data has on the accuracy of the forecasts is estimated.

Kalnay, E.↗