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  • 11
    Electronic Resource
    Electronic Resource
    Rain rates based on SSM/I, OLR and raingauge data sets (1992)
    Springer
    Meteorology and atmospheric physics 50 (1992), S. 165-174 
    Details
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary In this paper we present a methodology for evaluating rain rates from a mix of satellite and surface based observations. The component data sets include the outgoing longwave radiation (OLR), microwave radiometric data from the special sensor microwave imager (SSM/I) and surface raingauge data from the World Weather Watch. We have noted some deficiencies in the SSM/I algorithm-based rain rate over land areas; the OLR-based rain rates exhibit a larger lateral spread and lower intensities than the observed rainfall structures. The proposed combined method assimilates these three data sets to provide improved fields of global tropical rainfall.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01026014
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  • 12
    Electronic Resource
    Electronic Resource
    Recurvature dynamics of a typhoon (1992)
    Springer
    Meteorology and atmospheric physics 50 (1992), S. 105-126 
    Details
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary In this paper we present some recent work on typhoon prediction with a high resolution global model. The emphasis of this paper is on typhoon recurvature. Here we include examples of successful typhoon recurvature track forecasts made from a very high resolution global spectral model. The main objective of this study however is to go beyond the forecasts, i.e. to interrogate the history tapes and to diagnose residue-free budgets of the divergence and vorticity. The premise of this paper is that the recurvature of the typhoons depends on both the usual advection of vorticity by the layer mean winds and the advection of divergence in the outflow layers of the storm. The region immediately outside the heavy rain area of the storm experiences large values of divergent outflows which contribute a significant advection of divergence. Through the Dine's compensation this region must, in consort, experience an enhancement of low level convergence and of deep convection, thus contributing to the storm motion. We distinguish two facets of storm motion and recurvature, one based on the conventional steering that invokes the advection of vorticity by a vertical integrated flow, the other is the generation mechanism proposed here. During recurvature the storm appears to move in a direction which is influenced by the rotational and the divergent flow dynamics. Increased vertical resolution in the outflow layer is shown to resolve stronger amplitudes in the outflow layer divergence and thus to contribute to improved forecasts of recurvature. A number of processes seem to simultaneously evolve, these include the strong advection of divergence part of the wind, enhancement of cumulus convection over this region, an enhancement of lower tropospheric convergence, generation of vorticity of the lower troposphere and the attendant recurvature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01025508
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  • 13
    Electronic Resource
    Electronic Resource
    An improvement in cumulus parameterization by invoking outgoing longwave radiation (1992)
    Springer
    Meteorology and atmospheric physics 50 (1992), S. 175-187 
    Details
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary The Kuo-type cumulus parameterization and rainfall rate scheme is extended by including the outgoing longwave radiation (OLR), the local time rate of change of OLR, and the horizontal Laplacian of OLR to include the additional source of mesoscale moisture supply. The extended scheme remains simple and efficient. A series of 5-day forecasts of the 1979 monsoon for the tropical belt between the Arabian Sea and the western Pacific Ocean show improvement in the 3-day forecast in the daily accumulated precipitation in both the amount and location. Further RMS error analyses indicate that using OLR and the Laplacian of OLR also produces a significant improvement in a 3-day forecast. Additional tests of the extended scheme for the 1987 and 1988 monsoons produced consistent and characteristic areal rainfall rates in the tropics. The improvement in the “OLR model” forecasts is attributed to the improved skill of OLR forecast in the forecast model as the RMS errors for 5 consecutive days in the 6 experimental forecasts are smaller than those of the 3 control forecasts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01026015
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  • 14
    Electronic Resource
    Electronic Resource
    Improving Precipitation Forecasts over the Global Tropical Belt (1999)
    Springer
    Meteorology and atmospheric physics 70 (1999), S. 1-14 
    Details
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary  This study explores the nowcasting and short-range forecasting (up to 3 days) skills of rainfall over the tropics using a high resolution global model. Since the model-predicted rainfall is very sensitive to model parameters, four key model parameters were first selected. They are the Asselin filter coefficient, the fourth order horizontal diffusion coefficient, the surface moisture flux coefficient, and the vertical diffusion coefficient. The optimal values were defined as those which contributed to the best one day rainfall forecasts in the present study. In order to demonstrate and improve the precipitation forecast skill, several numerical experiments were designed using the 14-level Florida State University Global Spectral Model (FSUGSM) at a resolution of T106. Comparisons were also made of the short-range forecasts obtained from a control experiment subjected to normal mode initialization (NMI) versus experiments based on physical initialization (PI). The latter experiments were integrated using the original FSUGSM and a modified version. This modified FSUGSM was developed here by applying a reverse cumulus parameterization alorithm to the regular forecast model, which restructures the vertical humidity distribution and constrains the large-scale model’s moisture error growth during the model integration. An improved short-range rainfall prediction skill was achieved from the modified FSUGSM in this study. The results showed a better agreement between model-based and observed rainfall intensity and pattern.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007030050021
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  • 15
    Electronic Resource
    Electronic Resource
    The summer monsoon of 1988 (1990)
    Springer
    Meteorology and atmospheric physics 42 (1990), S. 19-37 
    Details
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary Time averaged, monthly mean fields of a number of climate parameters such as sea surface temperature anomalies, outgoing longwave radiation anomalies, 200 mb velocity potential field, streamfunction anomaly at the lower and the upper troposphere and percentage rainfall amounts are presented, for the summer of 1988 over the regions of Asian summer monsoon. Above normal rainfall occurred over most of the Indian subcontinent, southeast Asia and eastern China during 1988. In comparison, 1987 was a drought year. This paper presents a comparison of some of the salient aforementioned parameters. The evolution of the planetary scale divergent motions and the streamfunction anomaly exhibit prominent differences during the life cycle of the monsoon in these two years. The velocity potential field exhibits a pronounced planetary scale geometry with the divergent outflows emanating from the monsoon region during 1988. The descending branches of these time averaged circulations are found over the Atlantic ocean to the west and over the eastern Pacific and North America to the east. The immense size of this circulation is indicative of an above normal monsoon activity. During 1987, the outflow center was located much further to the southeast over the western Pacific ocean. The longitudinal extent of the monsoonal divergent circulations were much smaller in 1987. The positive sea surface temperature anomaly of the El Nino year 1987 is seen to move westwards to the western Pacific in 1988, a warm anomaly also appears over the eastern equatorial Indian ocean and the Bay of Bengal at this time. The latter contributes to the supply of moisutre during the active monsoon season of 1988. The outgoing long wave radiation anomalies evolve with a westward propagation of strong positive anomalies from the central Pacific ocean consistent with the evolution of divergent circulation. The streamfunction anomalies basically show westerly zonal wind anomalies being replaced by easterly anomalies during 1988 over the upper troposphere of the monsoon region. The lower tropospheric streamfunction anomaly during the drought year 1987 showed a pronounced counter monsoon circulation. That feature was absent in 1988.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01030576
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  • 16
    Electronic Resource
    Electronic Resource
    Predictability of low frequency modes (1990)
    Springer
    Meteorology and atmospheric physics 44 (1990), S. 63-83 
    Details
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary In this paper we propose a procedure for the extended integration of low frequency modes of the time scale of 30 to 50 days. A major limitation of the extended integrations arise from a contamination of low frequency modes as a result of energy exchanges from the higher frequency modes. In this study we show an example on the prediction of low frequency mode to almost a month which is roughly 3 weeks beyond the conventional predictability. This was accomplished by filtering the higher frequency modes from the initial state. The initial state included a time mean state and a low frequency mode. The sea surface temperature anomalies on this time scale and the annual cycle were also prescribed. The specific experiment relates to the occurrence of a dry and a wet spell in the monsoon region. The meridional passage of an anticyclonic circulation anomaly over the lower troposphere and the eastward passage of a negative velocity potential anomaly over the upper levels of the Indian monsoon, on this time scale, are reasonably predicted. The aforementioned experiment was carried out with the 1979 data sets of the global experiment. A second example during an anomalous southward propagation of the low frequency waves over the Indian monsoon region during 1984 was also reasonably predicted by this model. Suggestions for further experimentation on the predictability of low frequency modes are proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01026811
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  • 17
    Electronic Resource
    Electronic Resource
    Introductory comment — Special issue on the impact of satellite products on numerical analysis and prediction (1996)
    Springer
    Meteorology and atmospheric physics 60 (1996), S. 1-1 
    Details
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01029781
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  • 18
    Electronic Resource
    Electronic Resource
    A brief review of physical initialization (1996)
    Springer
    Meteorology and atmospheric physics 60 (1996), S. 137-142 
    Details
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary This review presents a short summary of studies on physical initialization carried out at Florida State University. This summarizes the findings in several areas such as: the formulation of physical initialization, impact (and skill) on the nowcasting and short range prediction of rainfall, medium range prediction of typhoons, mesoscale structures implied by physical initialization, impact on the spread of an ensemble of typhoon forecasts and the improvements of hydrological budget during flooding events. References are provided in each section where further details for each of these areas are presented. A brief summary of the ongoing work on Physical Initialization at Florida State University is presented here. This summary includes the following areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01029790
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  • 19
    Electronic Resource
    Electronic Resource
    Influence of soil moisture on the Sahelian climate prediction I (1993)
    Springer
    Meteorology and atmospheric physics 52 (1993), S. 183-203 
    Details
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary An energy balance based statistical parameterization of the soil moisture availability has been developed and implemented in the Florida State University Global Spectral Model to test its performance in long range prediction. Specifically, a soil moisture parameter based on a moisture budget analysis has been introduced to estimate the Bowen ratio. It is expressed as an evolutive function of the model predicted rainfall and surface temperature and takes into account some of the ground characteristics through its dependence on albedo and surface elevation. This scheme is used in conjunction with a prognostic equation for surface temperature to estimate the different energy fluxes at the surface. A 42 waves triangular truncation global spectral model with 12 vertical levels has been used to perform parallel simulations, one of which includes the new planetary boundary layer parameterization. Seasonal simulations covering the onset and active phase of the West African monsoon have been carried out for the period between May and August 1979. A comprehensive comparison of the components of the surface energy balance between the two experiments has been carried out for different climatic regimes over the North African continent during the northern summer. The new scheme appears to capture the essence of the surface layer physics in a simple formulation of the processes and has introduced an interesting description of the surface fluxes. Significant modulation of the surface temperature and its diurnal cycle amplitude were obtained. This was particularly evident over arid zones where extremely high surface temperatures were predicted by a simpler scheme. An important and coherent interaction between the principal physical processes parameterized in the model has resulted from the introduction of the new scheme and has led to a better representation of the surface flux balance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01031877
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  • 20
    Electronic Resource
    Electronic Resource
    Influence of soil moisture on the Sahelian climate prediction II (1993)
    Springer
    Meteorology and atmospheric physics 52 (1993), S. 205-224 
    Details
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary The sensitivity of short-term climate to soil moisture parameterization has been investigated using the Florida State University Global Spectral Model. This is done through the implementation of a simple and realistic soil moisture availability in a prognostic equation for the surface temperature. The results from two seasonal simulations between 11 May and 31 August 1979 are discussed with an emphasis on the Sahelian regions. These experiments indicated that most of the significant changes that resulted from the new parameterization occurred at and near the surface. Above the surface, land surface effects were strongly diffused and for most of the cases were not conclusively discernible. At the surface, however, soil moisture appeared to be a parameter of large influence. Important modulations in the surface temperature were obtained. The time dependence of the soil moisture availability has led to an evolution of the surface heat sources in the model resulting in an apparent northward propagation of the centers of maximum temperature as the rainfall season progressed over the north African continent from May to August. This has had an important effect on the distribution of the primary variables and showed significant departures from the control. The interaction introduced by the new scheme between the physical processes parameterized in the model, has resulted in a differential modification of the rainfall distribution, and the changes in the hydrological cycle have remarkably affected the summer Sahelian rainfall.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01031878
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