Page 278 - 《高原气象》2022年第6期

6 期 田高山等：混合截断尺度Blending方案及其在西南区域模式中的应用 1641

Blending Scheme with Mixed Truncation Scale and Its

Application in Southwest Regional Model

TIAN Gaoshan ，CHEN Yaodeng ，GAO Qingjiu ，ZANG Zengliang 2
1
1
1
（1. Key Laboratory of Meteorological Disaster of Ministry of Education/Collaborative Innovation Center on Forecast and Evaluation of
Meteorological Disasters，Nanjing University of Information Science and Technology，Nanjing 210044，Jiangsu，China；
2. College of Meteorology and Oceanography，National University of Defence Technology，Nanjing 211101，Jiangsu，China）

Abstract：The complex and diverse topography of the southwest region generates disastrous weather systems
with multi-scale characteristics，and fluctuation information of each scale affects the occurrence and develop‐
ment of the weather systems. In order to introduce the information from the background field of the global model
in a timely and appropriate approach during the update cycle assimilation process，and to correct the bias of the
regional model in the analysis and forecasting of large-scale waveform information，this paper takes the south‐
west region as the research background，setting the truncation scale of wind field and the truncation scale of tem‐
perature & humidity variables differently according to the length scale characteristics of different types of model
variables. A blending scheme with mixed truncation scale is proposed，and a one-week continuous batch update
cycle assimilation experiments and diagnostics of one case are carried out based on the southwest regional update
cycle assimilation system. The results show that both the unified and mixed truncation scale blending schemes
can reduce the analysis and forecast bias in the process of update cycle assimilation，while the mixed-truncation-
scale blending scheme can further reduce the bias of regional background field by adopting different truncation
scales for the dynamic，temperature，and humidity field，and introduce the global background field information
that is more consistent with the scale characteristics of the dynamic，temperature，and humidity field，respective‐
ly. The continuous update cycle assimilation analysis and the accuracy of meteorological element forecasting are
improved. In the analysis of precipitation case，the model shows significant precipitation misreporting and falling
area bias in the steep topography area. The mixed truncation scale blending scheme can further reduce the false
report rate of heavy precipitation，improve the forecast skill of precipitation magnitude and falling area，and in‐
crease the accuracy of precipitation forecast.
Key words：Southwest region；update cycle assimilation；blending scheme；truncation scale；precipitation fore‐
cast