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Weather


Page Menu

  1. Selected Weather Web Sites

  2. Atmosphere-Surface Prediction (ASP) weather forecast model


Selected Weather web sites

After years of looking at I don't know how many weather related web pages, I have put a few of my favorites here.

  • For an optimal combination of download speed, simplicity, quality of graphics, and quantity of data, UNISYS Weather is still the North American Authority
  • For the best composite US weather radar image (with frozen precipitation well depicted) Intellicast has the market cornered...
  • It takes a bit of digging, but for quick real-time Sounding data downloads for the western hemisphere north of about the equator (ASCII format!) The NOAA Air Resources Lab is quite good...(one can download all of North America or Canada as a single text file)
  • Again for sounding data, the Univ. of Wyoming is also good for single site downloads, and the map is quite handy for locating some of the more obscure station identifiers!
  • The most comprehensive and easy to navigate Hurricane page (for the Atalantic and ajoining basins) is the NOAA Hurricane Page
  • For those seeking information on meteorological models and an overview of their inner-workings, a great place to start is UCAR's Operational Models Matrix site
  • For text data (forecast discussions, zone forecasts, public information (like snowfall totals by city, etc...) The NWS has a good site, and the example for Kentucky is given here.
  • For basic forecast info over France and detailed info on all-important ski and beach conditions, of course I must recommend the Meteo-France site.
  • Radar images in almost-real time (plus about 2 hours worth of animation!) over France from Meteox, with links to satellite images over Europe
  • A site which includes a comprehensive set of operational NWP outputs over Europe (and elsewhere) from Meteo-France (ARPEGE), UKMetOffice, Canada (GLB), NCEP (GFS) and somewhat limited data from ECMWF (their unfortunate policy) public, and a great site for France is the UQAM site. Also, the site is rich in observations: the (near) real time surface analysis maps over all of Europe and France.
  • The most comprehensive collection of meteorological condtions, web links, model outputs...can be found at Meteo-Ciel, including real time WRF runs over France.
  • Short range forecast data from the Meteo-France operational high resolution mesoscale NWP model (centered over France) AROME



ASP Weather Forecast Model

I have developed the ASP (Atmosphere-Surface forecast Prediction) model over the last few years in my free time. The model is under continuous development and it must be noted that it is simpler and uses slightly more coarse vertical and horizontal resolutions than operational hydrostatic models (although it is comparable to some such models)... but it has baseline physics and a solid dynamical core and thus can produce reasonable forecasts. I have developed all the code and scripts using free sotware and literature from the web under the Linux operating system on my home PC.

ASP is a hybrid-mass coordinate primitive equation hydrostatic model with equations expressed in flux form. The model baseline physics consist in: bulk microphysics, broadband longwave and two-stream shortwave radiation models with clouds, a mass-flux convection scheme, vertical diffusion/turbulence with non-local diffusivities (K) and an EDMF scheme within the PBL and a Louis-type local K above the PBL with a fully implicit coupling between the atmosphere and three sub-grid surface tiles (continental surface, liquid water surfaces and sea ice). The four prognostic dynamic (atmospheric) variables consist in the u and v wind components, the air temperature, and the surface pressure. There are 5 microphysical variables: the specific humidity, cloud liquid water content, cloud ice content, and 2 precipitation variables (rainfall and snowfall). There are 6 prognostic variables for the land surface; the soil temperature, moisture and ice content for N-layers (the current default is 5), snow density, SWE and albedo (currently a 2 layer snow scheme). The frozen water tile uses a single prognostic variables for ice temperature (2 layers). Finally, the surface water scheme (lakes and oceans/seas), uses a cool-skin prognostic temperature (with a relaxation to SSTs provided from an external source). Heat transfer uses diffusion, while soil moisture transfer is modeled using Richard's equation. The time integration schemes use linearized fluxes and are implicit (soil, water and water-ice temperatures are implicitly coupled with the atmospheric temperature profiles).

The numerical schemes are fairly standard compared to research and operational models. The vertical resolution is variable and is greatest near the surface: terrain following pressure (mass) coordinates are used in the lower atmosphere, while constant pressure surfaces are used in the upper atmosphere. The vertical discretization uses a Lorenz staggered grid, and horizontal discreization is on an Arakawa C-grid. The model has options for Lambert and Mercator map projections for limited area applications, and now a Plate Carree projection over the globe has been developed (on the C-grid). Fourier filtering of certain variables is used above a critical latitude for this application to optimize the balnce between model time step and CPUs. The model has options for high order diffusion, divergence damping, and advection finite differences (including a 5th order WENO scheme). The numerical integration includes 3 time steps (from largest to smallest): i) large/physics time step, ii) Runge-Kutta (RK) time integration methods for advection and coriolis terms, and iii) foward-backward time splitting for gavity wave terms. Note that there is implicit vertical advection of temperature within the RK loop, and fully implicit vertical turbulence-coupling with surface (on large/physics model time step). Finally, radiation and the convection schemes are generally called at a lower frequency than the large time step (depending on size of large time step).

The model is initialized either using a "cold-start" (NWP analysis interpolated to the ASP grid, followed by a digital filter using short forward and backward dry-adiabtic integrations), or a simple data assimilation scheme in which a previous forecast is nudged to the NWP provided initial state. Finally, a "big-brother" option exists in which certain variables can be nudged using large scale variables (from an NWP model which is also providing the time varying lateral boundary conditions) during the early part of the forecast to potentially improve the trajectory (a simple economical way to benefit from a NWP models likely better early forecast period owing to a more elaborate data assimilation scheme).

For a more detailed description of ASP (physics, dynamics, numerics...), go to the ASP Documentation Page. For real-timee forecast plots for domains over Western Europe and North America, go to the LAM Real Time Forecast Page. For real-timee forecast plots for different selected domains over the globe, go to the Global Real Time Forecast Page.

Disclaimer

Please note that this page has nothing to do with my employer, CNRS, or where I am employed, at the National Center for Meteorological Research (Centre National de Recherches Meteorologiques: CNRM) at Meteo-France. The opinions expressed herein are my own, and are not a reflection of those where I work or of my employer.