HR: 0800h
AN: A21C-0633    [Abstracts]
TI: Intensity and Development Forecasts of Tropical Cyclones by the JMA High-Resolution Global NWP Model: Impacts of Resolution Enhancement
AU: * Komori, T
EM: komori@met.kishou.go.jp
AF: Japan Meteorological Agency (JMA), 1-3-4 Otemachi Chiyoda-ku, Tokyo, 100-8122, Japan
AU: Kitagawa, H
EM: hiroto@naps.kishou.go.jp
AF: Japan Meteorological Agency (JMA), 1-3-4 Otemachi Chiyoda-ku, Tokyo, 100-8122, Japan
AB: It is widely considered that a spatial resolution of numerical weather prediction (NWP) model plays an important role for forecasting severe weather events such as tropical cyclones (TCs) and heavy rainfall. Under the KAKUSHIN project (funded by the Japanese Ministry of Education, Culture, Sports, Science and Technology), the Japan Meteorological Agency (JMA) has developed a new Global Spectral Model (GSM) with a high horizontal resolution of about 20km and 60 vertical layers (hereafter called g20km GSMh), which is utilized to evaluate severe weather events in future climate. The 20km GSM will be operational in November 2007 replacing the current GSM with a horizontal resolution of about 60km and 40 vertical layers (hereafter called g60km GSMh). In the present study, we investigate how a model resolution impacts on TC forecasts because this resolution enhancement aims to improve the modelfs ability to forecast severe weather. Due to the more realistic model topography in higher horizontal resolution, the 20km GSM can give more accurate forecasts of orographic precipitation than the 60km GSM, especially over the area range of heavy precipitation. According to the statistically verified results, the enhancement of horizontal and vertical resolution appears to fairly improve the accuracy of TC intensity forecasts. However, for TC track forecasts, it may be more important to accurately represent large-scale environmental contexts surrounding the TC than to resolve the TC structure itself. In order to clarify resolution impacts on the TC intensity prediction, we categorize the TC intensity forecasts into three stages (development stage, maturation stage and dissipation stage). The results show that the effectiveness of the resolution enhancement is bigger in the development stage and relatively small in the maturation and dissipation stages. For the maturation and dissipation stages, improvement of physical processes seems to be more important than the resolution enhancement to provide better accuracy of TC intensity forecasts by the 20km GSM. For very strong TCs in the development stage, however, it may be hard to provide enough accuracy in the intensity forecasts even by the 20km GSM. It is also suggested in the study that initial analyzed fields and model physics are more essential rather than the resolution enhancement for TC genesis forecasting.
DE: 3337 Global climate models (1626, 4928)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting