| Abstract: | The distribution of precipitation field from the typhoon Haitang (2005)
during its landing on Fujian province shows obvious asymmetric feature. Based on
the NCEP/NCAR FNL (Final Analysis) data, this study reveals the contributions of
atmospheric factor to the asymmetrical distribution characteristics of
precipitation associated with the typhoon, through the analysis of water vapor
condition, vertical ascending motion condition, the calculation of the dry Q
vector and its decomposition, and adiabatic heating in the air column of 1000hPa
-600hPa (lower atmosphere) and 500hPa-100hPa (upper atmosphere). The results are
as follows: (1) In the lower atmosphere, the humidity on both sides of typhoon
path can be equivalent, while it is more wet on the right side than left in the
upper atmosphere, which obviously presents asymmetric distribution
characteristics. (2) Both range and intensity of the vertical motion on the right
side are wider and stronger than counterparts on the left side no matter in the
lower or upper atmosphere. (3) In the upper atmosphere, forcing role of
atmosphere in vertical upward motion on the right side of typhoon path is the
same as that on the left, while it is significantly different in the lower
atmosphere, which is significantly broader in scope and stronger in the
intensity, along with obvious asymmetric distribution characteristics. In
addition, the further analysis of the Q vector decomposition indicates that the
forcing effect of mesoscale weather systems on vertical upward motion is stronger
than that of large scale weather systems in the lower atmosphere. (4) The
adiabatic heating always exists on both lower and upper atmosphere, and the range
and intensity of the adiabatic heating forcing showed asymmetric distribution on
both lower and upper atmosphere. (5) In a summary, the upper atmosphere humidity
conditions, the forcing role of lower atmosphere in vertical upward motion,
especially, to mesoscale weather system, and adiabatic heating in the lower
atmosphere, all show similar asymmetric distribution characteristics to that of
precipitation field from the typhoon Haitang (2005), that is to say, the
atmospheric factors as mentioned above are all contributed to genesis of the
asymmetric distribution characteristics of precipitation. |
