Meteorology 5540
Mini-Lecture 3: Climatology and Observational Systems

I. Climatology

  • Averages and extrema
  • Synoptic and Mesoscale patterns and associated weather
  • Mesoscale weather variability and relation to synoptic scale flow
  • Local effects II. Observational systems
      A. Your own two eyes and other senses!
    • Rarely lie
    • Perception of weather is extremely important

      B. Conventional surface and upper-air observations

    • Hourly surface observations of wind, pressure, temp, dewpoint, etc...
    • 12-h upper-air observations
    • Remain backbone of our observing system
    • Upper-air observations offer limited resolution in time and space
    • ASOS stations lack important information (e.g., upper-level cloud cover)

      C. Mesonets

    • Higher spatial and temporal resolution than conventional obs
    • Resolution can be better than 10 km spatially and 15 min temporally
    • Helpful for identifying frontal structure and position, outflow boundaries, and local structure of features such as downslope winds, etc...
    • Particularly insightful when integrated with NEXRAD imagery
    • Communication and maintenance costs can be expensive, particularly in areas of complex terrain

      D. Wind Profilers and acoustic sounders

    • High temporal resolution compared to conventional upper-level data.
    • Some wind profilers can remotely sense winds through entire troposphere.
    • Wind profilers detect small variations in density. Returned signals are digitaly filtered and are frequently averaged over a 1-h period. Like NEXRAD radar, derived winds are subject to problems (e.g., migrating birds).
    • Acoustic sounders (RASS) provide vertical profiles of density (and hence virtual temperature).

      E. NEXRAD Radar

    • Information on precipitation and winds, identification of wind shear, microbursts, mesocyclones, hail, etc...
    • Automated algorithms to alert forecasters to severe weather
    • Accumulated precipitation estimates and information on precipitaiton type
    • Algorithms not site specific and in some cases are not particularly useful in the complex terrain of the west.
    • Velocity data is helpful for identifying frontal position and structure in the western United States.
    • Case by case diagnosis is greatly enhanced if surface mesonet data is integrated with NEXRAD imagery.

      F. Satelite Imagery

    • GOES-8,9, and 10 are major geostationary weather satelites.
    • Scan in five spectral bands (vis, shortwave IR, WV, IR, and split window IR)
    • Visible: Clouds, snow cover, haze and pollution
    • Shortwave IR: fog/stratus, ice vs. water clouds during the day, clouds over snow
    • Water Vapor: upper-level winds, mesoscale features of upper-level flow
    • IR: Cloud top temperature, surface temps
    • Split window IR: Low-level moisture when used with longwave IR.
    • Multiple IR band sounders also retrieve vertical profiles of moisture and temperature that are used for forecasting and model initialization.
    • The SSMI (Special Sensor Microwave Imager) from a polar orbiting satelite provides precipitation and wind information over water and precipitation information over land.

      G. Data Assimilation Systems

    • Attempt to integrate all this information into a single, four-dimensional gridded data set.
    • Include a prognostic component (i.e. a numerical forecast model)
    • RUC and LAPS represent current systems
    • Expect major advances in this area over the next decade

    III. References and on-line links
    Updated May 1, 1997