ASYMMETRICAL STRUCTURES OF THE TEMPERATURE AND HUMIDITY OF TROPICAL CYCLONES

Abstract:

Based on NCEP/CFSR 0.5° reanalysis data and the best track data from the Japan Tokyo Typhoon Center, composite and comparative analyses demonstrate the asymmetrical structures of the temperature and humidity in tropical cyclones over the Western North Pacific and the South China Sea from 1979 to 2010. The results are shown as follows. (1) With intensifying tropical cyclones, the flow field tends to become gradually more axisymmetric; however, the asymmetry of the specific humidity in the outer regions is more obvious. (2) In general, tropical cyclones have a non-uniform, vertical, “double warm-core” structure. The “warm-cores” in the lower level of weak tropical cyclones and in the higher level of strong tropical cyclones are the stronger of the two. (3) The distribution area of a “warm-core” is enhanced with cyclone intensification and tends to become more axisymmetric. At 200 hPa, the “warm-core” of a weak cyclone has a weak anticyclone in the center, whereas that of a strong cyclone has a weak cyclone in the center. (4) The “wet-core” of a tropical cyclone is primarily located in the lower level (700–C850 hPa). With the cyclone’s intensification, the intensity of the “wet-core” increases and the scope of the 0.8 g?kg?1 specific humidity anomaly tends to expand to higher levels. (5) With the cyclone’s deepening, the pseudo-equivalent potential temperature at different levels in different regions increases. In addition, the largest warming rates at each intensity level in the different regions occur in the core area, followed in turn by the envelope and outer areas.