数值天气预报模式的行星边界层方案热力预报变量选择
On the choice of prognostic thermal variable in planetary boundary layer schemes for numerical weather prediction models
赵怡雪 1周博闻1
作者信息
- 1. 中尺度灾害性天气教育部重点实验室,南京大学大气科学学院,南京,210023
- 折叠
摘要
在数值天气预报模式中,大气边界层湍流混合由行星边界层方案承担.传统的边界层方案多采用位温作为热力学预报变量,计算感热通量并获得位温的湍流倾向,多数边界层方案设计之初,也往往只考虑干边界层中的位温湍流混合.事实上,驱动边界层热对流的是浮力而非热力,前者还包含了水汽的作用,由虚位温表征.基于湍流可分辨的大涡模拟来评估传统边界层方案所参数化的感热通量在湿边界层中的适用性,重点关注方案中涉及逆梯度修正项的关键系数,同时也考察浮力通量的参数化评估结果显示浮力通量在干湿边界层中具备一致性,其模式系数不随水汽条件变化,因此,推荐以虚位温替代位温作为行星边界层方案热力预报变量.
Abstract
In numerical weather prediction models,atmospheric boundary layer turbulence is parameterized via planetary boundary layer(PBL)schemes.Traditional PBL schemes often adopt potential temperature θ as the prognostic thermal variable,compute sensible heat flux and the corresponding θ-tendency.As such,most PBL schemes are designed by considering turbulent mixing of θ in a dry boundary layer.In fact,boundary layer convection is driven by buoyancy rather than sensible heat.The former accounts for moisture effects,and is represented by the virtual potential temperature θv.Based on turbulence-resolving large-eddy simulations,this study evaluates the applicability of sensible heat flux-based turbulence parameterizations in the moist boundary layer,focusing on counter-gradient correction related model coefficients.The performance of buoyancy flux-based parameterization is also investigated.It is found that buoyancy fluxes are consistent for the dry and moist boundary layers,with identical model coefficients for both cases.This study therefore recommends the use of θv instead of θ as the prognostic thermal variable for PBL schemes.
关键词
行星边界层方案/对流边界层/虚位温/浮力通量/感热通量Key words
planetary boundary layer scheme/convective boundary layer/virtual potential temperature/buoyancy flux/sensible heat flux引用本文复制引用
出版年
2024
国家科技期刊平台
NSTL
万方数据