There are many kinds of meteorological phenomena, which may cause serious trouble to aircraft operations. Among them, atmospheric turbulences sometimes bring significant aircraft accidents because it is difficult to detect them by visual observation or weather radar. At present, PIlot weather REPort (PIREP) is a major method for observation of atmospheric turbulences, however, PIREP is not suitable for monitoring them at all times at a specific point or altitude. Therefore the development of new observation instruments, which can always catch them at any altitudes, is expected.

Wind Profiler is one of the observation instruments that can frequently measure the vertical profiles of wind speed and direction using radio waves. It has been installed at airport and used for aviation weather observation such as monitoring low-level wind shear as well as for synoptic and mesoscale weather observations. Wind profiler can obtain additional atmospheric information called as spectral width which broadens owing to atmospheric turbulence. Spectral width also grows wider in accordance with other factors. However it is possible to evaluate the strength of atmospheric turbulence from the spectral width by adding the appropriate correction to it. So it was reported that there is good agreement between eddy (energy) dissipation rate derived from the spectral width of wind profiler data and low-level turbulence in the vicinity of the airport (Chan and Chan, 2004).

Japan Meteorological Agency (JMA) has been operating a network consisting of thirty-one 1.3GHz-band wind profilers throughout the Japanese islands from 2001. This system makes it possible to observe the wind speed and direction up to 9 km altitude at the maximum, or up to 5 km altitude on the average through a year. In addition JMA has been sharing PIREP data with the airlines for ten years. From the comparison of these data sets, it is found that there is good correspondence between the spectral width retrieved from wind profilers and the intensity of turbulence in PIREP data. With spectral width we can catch not only clear air turbulences caused in the areas with strong vertical wind shear but also other turbulences which may not be related to the vertical wind shear. It is concluded that wind profiler has the potential to become an effective means of monitoring atmospheric turbulences on the airways. On the other hand, because of weaker signal from dry air (especially in high altitude), it cannot often obtain the data even if turbulences occur frequently in the atmosphere. So the current performance of the wind profilers for JMA network is not sufficient for monitoring high-altitude turbulences.

In July 2011, Kyoto University, National Institute of Information and Communications Technology and Meteorological Research Institute of JMA launched the project team to make up for this disadvantage. The 1.3GHz-band wind profiler has advantages of smaller antenna size as well as lower cost of installation, operation and maintenance ,compared to other frequency band's one. The objectives of this team are to develop a next generation wind profiler which can observe continuously from near the ground up to cruising altitude of the aircraft by combining increase of the transmission power and advanced signal processing, and to establish the turbulence detection techniques from this new wind profiler by 2014. In addition, various forecasting techniques for turbulence have been developed based on PIREP data. Therefore there is still big room for improvement of the atmospheric turbulence forecast. In this regard, using the data from the next generation wind profiler as the validation data, we will develop new forecasting technique for atmospheric turbulence.

Acknowledgments: The present study was supported by the Program for Promoting Fundamental Transport Technology Research from the Japan Railway Construction, Transport and Technology Agency (JRTT).