利用探空资料建立北京地区水汽廓线的参数化方案

利用 2008年探空资料分析了北京地区水汽廓线的分布特征, 提出不同边界层状况下水汽廓线的参数化方案。 在稳定边界层或浅对流边界层条件下, 水汽廓线的参数化方案可以用q=q₀e^z/2624(q₀为地面水汽比湿)表示。在对流边界层条件下, 水汽垂直分布受大气边界层影响非常显著, 参数化方案可以采用: 1) 对流边界层内(0≤z0; 2) 对流边界层高度附近(|z-PBL|<200), q=q₀(A-B(z-PBL)); 3) 对流边界层高度之上(PBL+200≤z), q=Cq₀(z-5000-PBL) (z和PBL分别为距地面高度和对流边界层高度, 单位均为m)。参数分别为A=0.72, B=1.4×10^-3m^-1, C＝-9.17×10^?5m^-1。在对流边界层下, 水汽廓线的参数化方案如果仅采用e指数分布会低估10%的水汽总量, 而新提出的参数化方案能更好地给出水汽的垂直分布。

A Parameterization Scheme of Water Vapor Profiles over Beijing Based on Radiosonde Data

Radiosonde (RS) data over Beijing in 2008 was employed to analyze vertical distributions of water vapor in this area. A parameterization scheme of water vapor profiles is proposed according to different conditions of Planetary Boundary Layer (PBL). In the condition of Stable Boundary Layer (SBL) or shallow boundary layer, the parameterization scheme of water vapor profiles can be formulated by q=q₀e^z/2624, here q₀ is specific humidity at surface. In the condition of Convective Boundary Layer (CBL), the vertical distribution of water vapor is significantly influenced by CBL. The parameterization scheme of water vapor profiles can be expressed as 1) within the CBL (0≤ z0; 2) near the top of CBL (|z-PBL|<200), q=q₀(A-B(z-PBL)); 3) above the CBL (PBL+200≤z), q=Cq₀(z-5000-PBL), here z is height (unit is metre), PBL is the height of PBL (unit is metre). A=0.72, B=1.4×10^-3m^-1, C=?9.17×10^?5m^-1. For CBL, the IWV would be underestimated by 10% using the exponential distribution. A better estimation is achieved with this parameterization scheme proposed.