The Hanscom AFB mesonetwork was established to examine the potential forecasting benefits to be derived from automated mesoscale observations. Experiments were set up to evaluate three objective procedures for prediction short-period (15 to 60 min) fluctuations in sensor equivalent visibility against a specialized conditional climatology model. The procedures evaluated were: a translation technique based on vectors determined by tracking mesoscale disturbances objectively, an advection technique which utilized forecast wind fields from a limited-area fine-mesh model, and a simple area-averaged trend technique. Data from 24 episodes of reduced visibility gathered during the 1972-74 period of mesonetwork operations were used to evaluate the techniques. The translation and area-averaged trend technique yielded positive skill relative to the conditional climatology model, while the advection technique did not. Although there were episodes in which the spatial selectivity of the translation technique yielded significant improvements, the trend technique was an overall better forecast indicator, especially when one considers its relative simplicity. (Author).

The Hanscom AFB mesonetwork was established to examine the potential forecasting benefits to be derived from automated mesoscale observations. Experiments were set up to evaluate three objective procedures for prediction short-period (15 to 60 min) fluctuations in sensor equivalent visibility against a specialized conditional climatology model. The procedures evaluated were: a translation technique based on vectors determined by tracking mesoscale disturbances objectively, an advection technique which utilized forecast wind fields from a limited-area fine-mesh model, and a simple area-averaged trend technique. Data from 24 episodes of reduced visibility gathered during the 1972-74 period of mesonetwork operations were used to evaluate the techniques. The translation and area-averaged trend technique yielded positive skill relative to the conditional climatology model, while the advection technique did not. Although there were episodes in which the spatial selectivity of the translation technique yielded significant improvements, the trend technique was an overall better forecast indicator, especially when one considers its relative simplicity. (Author)

A microprocessor-based automated airfield weather observing and forecasting system called MAWS (Modular Automated Weather System) was developed to demonstrate the feasibility of modernizing many of the observing and forecasting functions performed in operational base weather stations. Scott Air Force Base, Illinois, was chosen as the demonstration site and operations were conducted from January 1977 through January 1979. Weather sensors at five observation sites around the airfields were polled several times each minute, the data transmitted over commercial, voice-grade telephone lines to a central supervisory microprocessor where the data were suitably collated, averaged and formatted for display on alpha-numeric display devices at key locations and for magnetic tape archiving for post analysis. The demonstration confirmed that modernized weather support can be largely achieved with state-of-the-art, commercially available hardware/software. Such a system would be compatible with other automation efforts in civilian weather services and other C-cubed efforts in the DOD. The advantage of spatially and temporally detailed weather information in marginal and adverse situations was documented. Sensor siting considerations were addressed in relation to specific weather elements and observational requirements. The contributions of automated met watch procedures and short-range guidance forecasts of RVR landing minima were demonstrated. Feedback on system performance and acceptability was obtained from cognizant AWS offices.

Field experiments were conducted with the AFGL Mesonet and FPS-77 digital radar during snowstorms for evaluation of the use of radar to observe and predict snow. Simultaneous measurements of optical extinction coefficient, radar reflectivity, and snow depth were made, together with determinations of visual range. The measurements verify both the calibration of the visibility instruments and the relationship between visual range and extinction coefficient. A relationship found between extinction coefficient and snowfall rate compares well with relationships found by other investigators. Radar reflectivity is found to be related to extinction coefficient, with the correlation being improved by time averaging and by allowance for velocity of snowflakes from the radar beam to the ground. However, the specification errors are of the order of + or - 42 percent to + or - 65 percent, and with the small spatial and temporal variability of extinction coefficient in snow, the radar is of marginal use where observations are available from the airways network. (Author).