Cut off and Weakening Processes of an Upper Cold Low
スポンサーリンク
概要
- 論文の詳細を見る
Near the tropopause over the North Pacific in summer an isolated low pressure system (Upper Cold Low, UCL) is often generated by the deepening and cutting off of a trough in the mid-latitude westerlies. The tracks and structures of these UCLs have been investigated in previous studies, but understanding of the cut off and weakening processes remains poor. In this paper, the tracks of UCLs generated in the 1999 summer are analyzed using ECMWF data. The physical processes occurring in one of these systems are investigated in detail using the ECMWF data, and the meso-scale model MM5. We focus particularly on cut off and weakening processes, and on the structure of the vertical velocity in the UCL. The summer of 1999 was hot over Japan, and part of the Tibetan high pressure, around 200hPa, was shifted northward. This allowed some UCLs to approach Japan in July and August. A UCL on August 19th is selected for detailed analysis, and was generated in the following process. Positive vorticity in a westerly wave at 200hPa was extended by a northeast wind in the upper layer only. The positive vorticity was cut off by non-liner effects and upper level divergence, associated with convective clouds, generating the isolated UCL. The structure of the cyclonic circulation and the warm and cold cores were similar to those in previous studies. The structure of the vertical motion of the moving UCL was explained by dry dynamics and there was upward motion on the front side of the UCL, in the direction of movement. Upper level clouds in the UCL strengthened this upward motion. Convective clouds were seen in the system. The latent heat of these convective clouds played an important role in weakening the cold core of the UCL.
- 社団法人日本気象学会の論文
- 2005-10-25
著者
-
TAKAHASHI Masaaki
Center for Climate System Research, University of Tokyo
-
Sakamoto Kei
Center For Climate System Research University Of Tokyo
-
Takahashi Masaaki
Center For Climate System Res. Univ. Of Tokyo
-
Takahashi Masaaki
Center For Climate System Research University Of Tokyo:frontier Research Center For Global Change
関連論文
- Simulation of the Martian Atmosphere Using a CCSR/NIES AGCM
- Connection between the Asian Summer Monsoon and Stratosphere-Troposphere Circulation over the Asian Region
- Long-term Variations of the Baiu Frontal Zone and Midsummer Weather in Japan
- Cut off and Weakening Processes of an Upper Cold Low
- Low-N_2O Air Masses after the Breakdown of the Arctic Polar Vortex in 1997 Simulated by the CCSR/NIES Nudging CTM
- On Forcing the Winter Polar Warmings in the Martian Middle Atmosphere during Dust Storms
- Simulation of the Baiu Front in a High Resolution AGCM
- Observations of Deep Convective Updrafts in Tropical Convection and their Role in the Generation of Gravity Waves
- A Gravity wave generation in the lower stratosphere due to passage of the typhoon 9426 (Orchid) observed by the MU radar at Shigaraki (34.85^0N, 136.10^0E)
- Simulations of superrotation using a GCM for Venus' middle atmosphere
- Gravity Waves Observed in a High-Resolution GCM Simulation(Pattern Formation and Singularity in Wave Phenomena)
- Analysis of the East Asian Subtropical Westerly Jet Simulated by CCSR/NIES/FRCGC Coupled Climate System Model