Search Results
(and other modules, such as radiation and boundary layer processes) on the cumulus parameterization, which is called “forcing.” Fig . 16-1. (a) A schematic diagram showing the two-way interaction between the dynamics core and cumulus parameterization. (b) A schematic diagram showing the logical structure of the analysis performed by Yanai et al. (1973) . As pointed out by Arakawa (2004) , the procedure followed by Yanai et al. (1973) reverses the lower half of the loop, as shown in Fig. 16-1b
(and other modules, such as radiation and boundary layer processes) on the cumulus parameterization, which is called “forcing.” Fig . 16-1. (a) A schematic diagram showing the two-way interaction between the dynamics core and cumulus parameterization. (b) A schematic diagram showing the logical structure of the analysis performed by Yanai et al. (1973) . As pointed out by Arakawa (2004) , the procedure followed by Yanai et al. (1973) reverses the lower half of the loop, as shown in Fig. 16-1b
entire global ocean at one time with useful resolution. Instead, the World Ocean Circulation Experiment (WOCE) divided the ocean into control volumes and, over the period 1990–98, measured them in sequence with intervolume transports deduced primarily from hydrography ( Siedler et al. 2001 ). WOCE global hydrographic observations were supplemented mainly with surface drifters, moored arrays across major boundary currents and circulation chokepoints, and the first midlevel profiling floats; the in
entire global ocean at one time with useful resolution. Instead, the World Ocean Circulation Experiment (WOCE) divided the ocean into control volumes and, over the period 1990–98, measured them in sequence with intervolume transports deduced primarily from hydrography ( Siedler et al. 2001 ). WOCE global hydrographic observations were supplemented mainly with surface drifters, moored arrays across major boundary currents and circulation chokepoints, and the first midlevel profiling floats; the in
isolating the meridional derivative of the Coriolis acceleration as the essential element in producing western boundary currents like the Gulf Stream in the North Atlantic—a prototype of GFD reductionism. 7 Closely following on the Sverdrup/Stommel papers were those of Munk (1950) , who effectively combined the Sverdrup and Stommel solutions, Munk and Carrier (1950) , Charney (1955) , Morgan (1956) , and a host of others. 8 Following the lead of Munk and Carrier (1950) the Gulf Stream was
isolating the meridional derivative of the Coriolis acceleration as the essential element in producing western boundary currents like the Gulf Stream in the North Atlantic—a prototype of GFD reductionism. 7 Closely following on the Sverdrup/Stommel papers were those of Munk (1950) , who effectively combined the Sverdrup and Stommel solutions, Munk and Carrier (1950) , Charney (1955) , Morgan (1956) , and a host of others. 8 Following the lead of Munk and Carrier (1950) the Gulf Stream was
Abstract
The nature of the different types of surface boundaries that appear in the southern plains of the United States during the convectively active season is reviewed. The following boundaries are discussed: fronts, the dryline, troughs, and outflow boundaries, The boundaries are related to their environment and to local topography. The role these boundaries might play in the initiation of convective storms is emphasized. The various types of boundary-related vertical circulations and their dynamics are discussed. In particular, quasigeostrophic and semigeostrophic dynamics, and the dynamics of solenoidal circulations, density currents, boundary layers, and gravity waves are considered.
Miscellaneous topics pertinent to convective storms and their relationship to surface boundaries such as along-the-boundary variability, boundary collisions, and the role of vertical shear are also discussed. Although some cases of storm initiation along surface boundaries have been well documented using research datasets collected during comprehensive field experiments, much of what we know is based only on empirical forecasting and nowcasting experience. It is suggested that many problems relating to convective-storm formation need to be explored in detail using real datasets with new observing systems and techniques, in conjunction with numerical simulation studies, and through climatological studies.
Abstract
The nature of the different types of surface boundaries that appear in the southern plains of the United States during the convectively active season is reviewed. The following boundaries are discussed: fronts, the dryline, troughs, and outflow boundaries, The boundaries are related to their environment and to local topography. The role these boundaries might play in the initiation of convective storms is emphasized. The various types of boundary-related vertical circulations and their dynamics are discussed. In particular, quasigeostrophic and semigeostrophic dynamics, and the dynamics of solenoidal circulations, density currents, boundary layers, and gravity waves are considered.
Miscellaneous topics pertinent to convective storms and their relationship to surface boundaries such as along-the-boundary variability, boundary collisions, and the role of vertical shear are also discussed. Although some cases of storm initiation along surface boundaries have been well documented using research datasets collected during comprehensive field experiments, much of what we know is based only on empirical forecasting and nowcasting experience. It is suggested that many problems relating to convective-storm formation need to be explored in detail using real datasets with new observing systems and techniques, in conjunction with numerical simulation studies, and through climatological studies.
Abstract
Assimilation of radar data is one of the key scientific challenges for numerical weather prediction of convective systems. Considerable progress has been made in recent years including retrieval of boundary layer winds from single-Doppler observations, assimilation of radar observations into convective-scale numerical models for explicit thunderstorm prediction, and assimilation of radar estimates of rainfall and wind into mesoscale models. However, the assimilation of radar data for weather prediction remains an important scientific area that demands further investigation. In this paper, the techniques that are currently being used and have demonstrated potential in radar data assimilation are presented. The progress on the research and applications is described and the future directions and challenges are outlined.
Abstract
Assimilation of radar data is one of the key scientific challenges for numerical weather prediction of convective systems. Considerable progress has been made in recent years including retrieval of boundary layer winds from single-Doppler observations, assimilation of radar observations into convective-scale numerical models for explicit thunderstorm prediction, and assimilation of radar estimates of rainfall and wind into mesoscale models. However, the assimilation of radar data for weather prediction remains an important scientific area that demands further investigation. In this paper, the techniques that are currently being used and have demonstrated potential in radar data assimilation are presented. The progress on the research and applications is described and the future directions and challenges are outlined.
developing observational, analytical, and numerical modeling techniques largely determine the speed of progress. 2. Responses to oceanic boundaries While the existence of warm currents along the western boundaries of oceans and cool currents along the eastern boundaries has been known since well before the twentieth century, it was not until the advent of infrared (IR) imagery from polar-orbiting satellites that their mesoscale structure gained widespread appreciation. The existence of a sharp sea
developing observational, analytical, and numerical modeling techniques largely determine the speed of progress. 2. Responses to oceanic boundaries While the existence of warm currents along the western boundaries of oceans and cool currents along the eastern boundaries has been known since well before the twentieth century, it was not until the advent of infrared (IR) imagery from polar-orbiting satellites that their mesoscale structure gained widespread appreciation. The existence of a sharp sea
primary examples of model innovation, parameterization development, and evaluation at ECMWF that were directly motivated and facilitated by the ARM Program: the development of an innovative boundary layer parameterization, the operational implementation of new accurate and efficient radiation parameterizations, and a process-oriented model evaluation with ARM observations to guide development of cloud and radiation parameterizations. All three areas have contributed to the ongoing drive for
primary examples of model innovation, parameterization development, and evaluation at ECMWF that were directly motivated and facilitated by the ARM Program: the development of an innovative boundary layer parameterization, the operational implementation of new accurate and efficient radiation parameterizations, and a process-oriented model evaluation with ARM observations to guide development of cloud and radiation parameterizations. All three areas have contributed to the ongoing drive for
Heaven, there are two matters on which I hope to be enlightened. One is quantum electrodynamics, and the other is turbulence. About the former, I am really rather optimistic” ( Goldstein 1969 ). The first analytical treatment of boundary layer flow in the geophysical context is attributed to Vagn Ekman (1905) , a Swedish oceanographer, who employed momentum balance equations for viscous fluid to explain Fritjof Nansen’s observation during the Fram expedition ( Mohn 1905 ) that the surface current
Heaven, there are two matters on which I hope to be enlightened. One is quantum electrodynamics, and the other is turbulence. About the former, I am really rather optimistic” ( Goldstein 1969 ). The first analytical treatment of boundary layer flow in the geophysical context is attributed to Vagn Ekman (1905) , a Swedish oceanographer, who employed momentum balance equations for viscous fluid to explain Fritjof Nansen’s observation during the Fram expedition ( Mohn 1905 ) that the surface current
. At the start of the ARM Program, Stokes and Schwartz (1994) listed three different projects that were related to land surface processes: point–area relationships for global climate modeling led by Chris Doran; area-representative estimates of surface heat flux led by Richard Coulter; and remote sensing of surface fluxes important for cloud development led by Fairley Barnes. Two additional projects related to boundary layer clouds were led by Steve Ghan and the team of Ronald Stull (of which the
. At the start of the ARM Program, Stokes and Schwartz (1994) listed three different projects that were related to land surface processes: point–area relationships for global climate modeling led by Chris Doran; area-representative estimates of surface heat flux led by Richard Coulter; and remote sensing of surface fluxes important for cloud development led by Fairley Barnes. Two additional projects related to boundary layer clouds were led by Steve Ghan and the team of Ronald Stull (of which the
this effort in the past two decades. Earlier versions of space observations were combined with oceanic in situ data to produce global fields with enhanced resolution (e.g., Rio et al. 2011 ; Maximenko et al. 2009 ). However, the result of Knudsen was obtained solely from space observations. It reveals a high degree of details: not only the midlatitude gyres and boundary currents, but also the structure of the high-latitude circulation. b. Basin-scale variability It has been known from the
this effort in the past two decades. Earlier versions of space observations were combined with oceanic in situ data to produce global fields with enhanced resolution (e.g., Rio et al. 2011 ; Maximenko et al. 2009 ). However, the result of Knudsen was obtained solely from space observations. It reveals a high degree of details: not only the midlatitude gyres and boundary currents, but also the structure of the high-latitude circulation. b. Basin-scale variability It has been known from the
