Wind Profilers - Weather Forecast
Author : Dr. Srinivasa Rao Vanukuru
Abstract :
Wind profilers are an important source of meteorological data for numerical weather prediction. Wind profilers are Doppler radars that most often operate in the VHF (30-300 MHz) or UHF (300-1000 MHz) frequency bands. A wind profiler is a type of weather observing equipment that uses radar or sound waves (SODAR) to detect the wind speed and direction at various elevations above the ground. Readings are made at each kilometer above sea level, up to the extent of the troposphere.
In meteorology, wind profilers play an increasingly important role. They can provide upper-wind measurements with an accuracy comparable to radiosonde data, but with a significantly higher temporal resolution. Height coverage and vertical resolution depend on the operating frequency, which, depending on the application, is usually chosen to be around 50, 400 or 1000 MHz. Information from nearby profilers can help the individual meteorologist to optimize local short-term weather forecasts.
Wind profiler Observations at Pune (18º32N, 73º51E) reveal the potential in identifying the various phases associated with monsoon such as onset, active and weak and/or break phases, and withdrawal rather solely. For this, all three wind vectors (zonal, meridional and vertical), wind speed and wind direction for years 2004 and 2005 has been examined. The monsoon winds are westerly i.e., dominance of zonal wind, average wind speeds are around 15 m/sec with westerly in direction. Daily average zonal wind speed shows above 20 m/sec with westerly wind direction around 270°, identified as active monsoon spell. During break monsoon spell it has noticed wind speeds are meager with change in wind direction from existing westerly to easterly. This criterion has been checked with IMD reported monsoon active and break spells for the years 2004 and 2005 and found good correlation as well. It is also interesting to see the change in seasonal wind from prevailing easterlies during pre-monsoon season to westerlies around the middle of May and is similar but opposite change is noticed around at the end of monsoon season near the end of September.
Keywords :
Wind Profilers, Weather Forecast, Indian Summer Monsoon, Low-Level Jet (LLJ), Doppler radar.
