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Y. C. Sud and W. E. Smith

Abstract

Twelve July integrations were made with the GLAS (Goddard Laboratory for Atmospheres) GCM (General Circulation Model) to investigate the influence of changes in the land-surface fluxes over the Indian subcontinent on the monsoon circulation and rainfall. The runs consist of an ensemble of three integrations for each of four separate cases: i) a control, ii) an experiment with increased land-surface albodo, iii) an experiment with increased land-surface albedo and reduced land-surface roughness, and iv) an experiment with increased land-surface albedo, reduced surface roughness and no evapotranspiration. All the prescribed land-surface anomalies were limited to the Indian region.

An intercomparison of the ensemble means of monthly fields produced by the experiments with those of the control showed that the Indian Monsoon was significantly weakened by both the increase of surface albedo and by the reduction in surface roughness. Higher surface albedo reduced the monsoon rainfall in conformity with Charney's hypothesis; the low surface roughness made the horizontal transport of moisture in the PBL (planetary boundary layer) more westerly, which reduced the cross-isobaric moisture convergence and hence the rainfall over northwestern India while correspondingly increasing it over China. The curl of surface stress divided by the Coriolis parameter (k· ∇ × τs)/f represents the boundary layer convergence. There is a remarkable correspondence between changes of this field and rainfall for all the experiments. Since the magnitude of prescribed changes in surface albedo and surface roughness could plausibly be produced by deforestation, the results suggest that major changes in the tall natural vegetation over the Indian subcontinent would have a significant influence on its July rainfall.

The last experiment delineated the role of evapotranspiration over India. It was found that the rainfall was essentially unaltered by the absence of evapotranspiration, because the increased moisture convergence produced by the enhanced sensible heating of the PBL largely compensated for the reduction in evapotranspiration.

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William W. Vaughan and Orvel E. Smith

Some of the accomplishments made during the past decade toward the solution of atmospheric problems associated with aerospace vehicle design and operations are reviewed. Improved measurement systems, atmospheric models and data applications, and some current aerospace related atmospheric problems are discussed. A summary of the planned Space Shuttle and some of the atmospheric properties which will be of concern in the design and operation are given.

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Norman L. Canfield, Orvel E. Smith, and William W. Vaughan

Abstract

Climatological upper wind records have been found to be inadequate for certain statistical analyses such as the computation of interlevel correlation coefficients, time series analysis and persistence analysis. This article presents a comparison of upper wind data as observed and made available for climatological purposes with that of upper wind records that have been made serially complete. During the winter months at Kennedy Space Center the mean wind speed, as derived from the serially completed wind records, can be as much as 10 meters per second greater than the mean wind speed derived from the observed wind data.

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W. L. Smith, H. M. Woolf, and H. E. Fleming

Abstract

The method of real-time retrieval of atmospheric temperature profiles from Nimbus IV Satellite Infrared Spectrometer observations currently used in dynamical weather analysis-forecast operation is described. Each vertical temperature profile is determined by its deviation from a “guess” profile. The deviation is expressed as a linear combination of differences between the measured radiances and those computed from the guess profile. The coefficients are estimated, by matrix inversion, from the weighting functions (i.e., derivatives of atmospheric transmittance functions), which are regularized by the ratio of the expected variance of the measurement errors to the expected variance of the errors in the guess profile. The deviations are iterated until the variance of the radiance residuals is less than the expected variance of the measurement errors.

For weather analysis-forecast operation the dynamical forecast is used as the first guess; therefore, the calculated profiles should differ from the forecast profiles only when the measurable error in the forecast exceeds the instrumental noise level. The retrieved profiles are those which deviate least from the forecast in order to satisfy all the radiance observations. This property is well suited to dynamical forecasting in that it does not tend to produce erroneous atmospheric waves.

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William W. Vaughan, James R. Scoggins, and Orvel E. Smith

This paper discusses the role of applied meteorology in the solution of large space vehicle development problems. A general outline of the role of the applied meteorologist is given, followed by a discussion of the data requirements for vehicle design and test evaluation, analytical procedures for data presentation, and areas of influence on space vehicle development. Examples of the influence of atmospheric conditions in the design are presented illustrating the utility of applied meteorology.

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J. K. Angell, W. P. Elliott, and M. E. Smith

Abstract

As a preliminary step in evaluating the feasibility of determining meaningful tropospheric humidity trends on a hemispheric or global scale using a sparse radiosonde network, radiosonde data at the earth's surface and at 850, 700 and 500 mb mandatory pressure surfaces, and significant levels between, have been examined for the interval 1958-80 at Brownsville, Texas and Great Falls, Montana. Adjustments had to be applied to the data prior to 1966 because at this earlier time dry observations (“motorboating”) were not reported. In general, the relative humidity at these two stations decreased or remained constant between 1958 and about 1970, and increased between about 1970 and 1980, but over the full record, it decreased at Brownsville and increased at Great Falls. Mixing ratio and precipitable water decreased during the earlier interval and increased during the later interval, similar to the variation in Northern Hemisphere temperature, although this may well be coincidence. On the seasonal and yearly time scale the relative humidity has tended to vary inversely with station temperature, and mixing ratio directly with this temperature, but these two stations do not define the relation among long-term trends in temperature, relative humidity and mixing ratio. It is concluded that to establish hemispheric or global trends in humidity will require use of a fairly extensive radiosonde network, as well as knowledge of instrumental changes and changes in measurement technique at individual stations within this network.

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Y. C. Sud, G. K. Walker, and W. E. Smith

Abstract

An ensemble of three sets of simulations is produced with the GLA (Goddard Laboratory for Atmospheres) GCM to assess the effect of the El Niño event of 1982–83 on winter climate. The three sets of runs are started from the analyzed initial states of the atmosphere for the 14, 15, and 16 December 1982, respectively, and are integrated through the end of February 1983. Each set consists of a control run, which was forced with climatological SSTs, and a corresponding anomaly run, which was forced with the observed SSTs. The ensemble mean of the model-simulated atmospheric circulation and rainfall anomalies is compared with the corresponding analyses of observations.

Most of the observed circulation anomaly features in the tropics are simulated rather well by the model. The tropical sea level pressure anomalies show a typical ENSO pattern: 850 mb wind anomalies show westerly winds over the equatorial Pacific Ocean; 200 mb anomalous winds show anticyclonic vortices straddling the equator; and the 200 mb height anomalies agree well with the corresponding observations. The regions of statistically significant anomaly patterns in the tropics are also in good agreement with observations. The model simulated rainfall anomalies also compare well with the rainfall analysis based on satellite-derived water vapor in the atmosphere from 37 GHz SMMR data. The model's OLR anomaly patterns show close correspondence with the anomalies in satellite observations of OLR. However, there is about a 5–10 degree eastward shift in the major simulated anomalies. This shift is also evident directly over the warm water of the equatorial eastern Pacific, with an even larger shift in the associated patterns in the extratropics. This discrepancy in the simulations leads to some very poor anomaly correlations in the extratropics.

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W. L. Smith Sr, Qi Zhang, M. Shao, and E. Weisz

Abstract

It is shown here that improvements in numerical weather prediction (NWP) model forecasts of hazardous weather can be obtained by assimilating profile retrievals obtained in real time from combined direct broadcast system (DBS) polar satellite hyperspectral and geostationary satellite multispectral radiance data. Results of NWP model forecasts are shown for two recent tornado outbreak cases: 1) the 3 March 2019 tornado outbreak over the southeast United States and 2) the tornado outbreak that occurred across Illinois, Indiana, and Ohio during the night of 27 May and the morning of 28 May 2019, and 3) the 4 March 2019 severe precipitation event that occurred in southeast China. Improvements in both quantitative precipitation forecasts (QPFs) and predictions of the location of tornado occurrence are obtained. It is also shown that geostationary satellite hyperspectral soundings [i.e., Fengyun-4A (FY-4A) Geosynchronous Interferometric Infrared Sounder (GIIRS)] further improve hazardous precipitation forecasts when used, in addition to the combined polar hyperspectral and geostationary multispectral satellite profile data, to initialize the numerical forecast model. The lowest false alarm rate (FAR) and the highest probability of detection (POD) and critical success index (CSI) scores are achieved when assimilating atmospheric profile retrievals obtained by combining all the available satellite high-vertical-resolution hyperspectral radiance measurements with geostationary satellite high-spatial-resolution and high-temporal-resolution multispectral radiance measurements.

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D. E. Patterson, R. B. Husar, W. E. Wilson, and L. F. Smith

Abstract

The daily distribution of sulfate concentration over the eastern United States during August 1977 is simulated by a Monte Carlo model using quantized emissions, positioned in accordance with the 1973 EPA SO2 emission inventory. Horizontal advection within a single well-mixed vertical layer is driven by observed surface winds, speeded by a factor of 2.5 and veered 20°. Direct simulation of regional diffusion is implemented by random perturbation of each quantum's trajectory over each 3 h time step, corresponding to K = 105m2 s−1. First order kinetics of SO2 to SO4 transformation and deposition of SO2 and SO4 are simulated by probabilistic choice among the chemical and physical pathways over each step. The simulated spatial distributions are compared on a daily basis to measured sulfate concentration from the Sulfate Regional Experiment (SURE) and midday visual range observations, indicating the primary role of airmass residence time over the eastern United States in producing regional pollution. The light extinction coefficient, b ext and SURE SO4 show remarkable spatial and temporal agreement throughout the month. The correlations of daily average SO4 concentration and b ext over the SURE region with the Monte Carlo simulation are 0.63 and 0.67, respectively. The correlation between daily average b ext and measured SO4 is 0.84.

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E. A. Smith, X. Xiang, A. Mugnai, R. E. Hood, and R. W. Spencer

Abstract

A microwave-based, profile-type precipitation retrieval algorithm has been used to analyze high-resolution passive microwave measurements over an ocean background, obtained by the Advanced Microwave Precipitation Radiometer(AMPR) flown on ANASA ER-2 aircraft. The analysis is designed to first determine the improvements that can be gained by adding brightness temperature information from the AMPR low-frequency channel (10.7 GHz) to a multispectral retrieval algorithm nominally run with satellite information at 19, 37, and 85 GHZ. The impact of spatial resolution degradation of the high-resolution brightness temperature information on the retrieved rain/cloud liquid water contents and ice water contents is then quantified in order to assess the possible biases inherent to satellite-bawd retrieval. The tests are conducted on a dataset obtained during a preliminary flight experiment that took place on 18 October 1990 over a Gulf of Mexico squall line that developed south of the Florida Panhandle. Careful inspection of the high-resolution aircraft dataset reveals five distinctive brightness temperature features associated with cloud structure and scattering effects that are not generally detectable in current passive microwave satellite measurements. Recovery of such high-resolution information by satellites would generally be expected to improve precipitation retrieval, but these improvements have never been quantified and thus are addressed in this study. Results suggest that the inclusion of 10.7-GHz information overcomes two basic problems associated with three-channel retrieval. First, unresolved rainfall gradients in the lower cloud layers due to 19-GHz blackbody saturation effects are recovered when the 10.7-GHz channel data are included. Second, unrealistic oscillations in the retrieved rain liquid water contents that arise from the highly variable scattering signatures at 19, 37, and 85 GHz are eliminated by virtue of the 10.7-GHz Rayleigh frequency probing into the lower cloud containing the bulk of the liquid water. Intercomparisons of retrievals carried out at high-resolution and then averaged to a characteristic satellite spatial scale to the corresponding retrievals in which the brightness temperatures are first convolved down to the satellite scale suggest that with the addition of the 10.7-GHz channel, the rain liquid water contents will not be negatively impacted by special resolution degradation. That is not the case with the ice water contents as they appear to be quite sensitive to the imposed scale, the implication being that as spatial resolution is reduced, ice water contents will become increasingly underestimated. The overall implications of this study in the context of the upcoming United States–Japan Tropical Rainfall Measuring Mission are that the inclusion of a 10.7-GHz frequency on the passive microwave radiometer and the relatively higher spatial resolution of the low and intermediate frequencies at 10.7, 19, and 35 GHz resulting from the relatively low orbit (− 350 km) will lead to significantly improved microwave-based rainfall measurements over what are currently available today.

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