5:15 PM - 6:45 PM
[AAS08-P04] Characteristics of Meso-γ-Scale Precipitation Distribution in Hitoyoshi/Kuma Area of Kumamoto
Keywords:radar analysis rainfall, meso-γ-scale precipitation distribution
_The Japan Meteorological Agency provides the radar analysis rainfall, which is the areal precipitation estimated by transforming the echo intensity of the meteorological radar with the observed precipitation at observatories. This study diagnoses the characteristics of meso-γ-scale precipitation distribution in the Hitoyoshi/Kuma area of Kumamoto, using this radar analysis rainfall and observed station precipitation. In particular, we estimated the error of the radar analysis rainfall in this area and diagnosed the topographic effects for precipitation in this area.
_First of all, correlation coefficients and root mean square errors (RMSE) were estimated between precipitation data at all combinations of observatories located by the Japan Meteorological Agency, Kumamoto Prefecture, and the Ministry of Land, Infrastructure, Transport and Tourism. We confirmed that the correlation coefficient (RMSE) became larger (smaller) as the distance between the two observatories became smaller.
_Next, we estimated based on the correlation coefficient of 0.8 that the meso-γ-scale precipitation distribution in this area was an ellipse with the short radius of about 5 km and with the long one of about 10 km, resulting in an area of 628 km2 and an eccentricity of about 0.9, where the long radius directed from west-southwest to east-northeast. Within this ellipse, the RMSE was estimated about 2 mm/h.
_Finally, we confirmed that the correlation coefficients between the observed precipitation at observatories and the radar analysis rainfall just above the points were greater than 0.95 at most points. However, we found that the radar analysis rainfall tends to vary more largely in the range of larger values than the observatory precipitation. The correlation coefficients and RMSE between radar analysis rainfall and observed precipitation at JMA’s stations at Hitoyoshi and Itsuki were also examined specifically. The distribution based on the correlation coefficient of 0.8 was again an ellipse with an area of 810 km2 and an eccentricity of about 0.9, and its long radius directed from west-southwest to east-northeast. The direction was inferred that in the Hitoyoshi/Kuma area, the low-level convergence of water vapor tend to be distributed in the west-southwest-northeast direction. When the precipitation distribution was examined with more stringent criteria, i.e., correlation coefficients of 0.9 or higher and RMSE of 1.5 mm/h or lower, these areas become smaller, and the shape seemed to be broken.
_First of all, correlation coefficients and root mean square errors (RMSE) were estimated between precipitation data at all combinations of observatories located by the Japan Meteorological Agency, Kumamoto Prefecture, and the Ministry of Land, Infrastructure, Transport and Tourism. We confirmed that the correlation coefficient (RMSE) became larger (smaller) as the distance between the two observatories became smaller.
_Next, we estimated based on the correlation coefficient of 0.8 that the meso-γ-scale precipitation distribution in this area was an ellipse with the short radius of about 5 km and with the long one of about 10 km, resulting in an area of 628 km2 and an eccentricity of about 0.9, where the long radius directed from west-southwest to east-northeast. Within this ellipse, the RMSE was estimated about 2 mm/h.
_Finally, we confirmed that the correlation coefficients between the observed precipitation at observatories and the radar analysis rainfall just above the points were greater than 0.95 at most points. However, we found that the radar analysis rainfall tends to vary more largely in the range of larger values than the observatory precipitation. The correlation coefficients and RMSE between radar analysis rainfall and observed precipitation at JMA’s stations at Hitoyoshi and Itsuki were also examined specifically. The distribution based on the correlation coefficient of 0.8 was again an ellipse with an area of 810 km2 and an eccentricity of about 0.9, and its long radius directed from west-southwest to east-northeast. The direction was inferred that in the Hitoyoshi/Kuma area, the low-level convergence of water vapor tend to be distributed in the west-southwest-northeast direction. When the precipitation distribution was examined with more stringent criteria, i.e., correlation coefficients of 0.9 or higher and RMSE of 1.5 mm/h or lower, these areas become smaller, and the shape seemed to be broken.