Characteristics of Spatio-temporal Inhomogeneities in the Growth of Ensemble Forecast Perturbations in East Asian Monsoon Region
WU Xiaowen
CHEN Jing
WANG Jingzhuo
MA Yanan
LIU Xin
CHEN Fajing
Abstract：This study aims to gain a deeper understanding of the spatio-temporal evolution characteristics of the growth of ensemble perturbations so as to better improve the structure of ensemble forecast perturbations in the East Asian monsoon region.Using the China Meteorological Administration-Regional Ensemble Prediction System(CMA-REPS)and ensemble forecast results from January to December 2021,we analyzed and compared the spatio-temporal characteristics of perturbation growth in wind and temperature fields at different latitudes.Evaluation indexes such as perturbation energy,ensemble spread,and ensemble consistency were employed.Moreover,the growth characteristics of ensemble forecast perturbations during a typical precipitation event were examined.The results show that:(1)The spatio-temporal distribution of ensemble spread in the process of ensemble forecast perturbations growth showed latitude zone difference and seasonal characteristics.The value of the ensemble spread showed a decreasing trend from north to south.In the 45-60 °N and 30-45 °N regions,the maximum value of ensemble spread usually occurred in spring,which was related to seasonal transitions in atmospheric circulation and the convergence of cold and warm air masses.This demonstrated a clear flow-dependence in the evolution of ensemble spread.However,the maximum value of ensemble spread in the 15-30 °N low-latitude region usually appeared in summer,which was related to typhoon activities.Notably,the Qinghai-Tibet Plateau exhibited a region of high ensemble spread,likely due to the influence of its topography on perturbation growth.(2)The spatio-temporal distribution of ensemble consistency during the perturbation growth process was highly consistent with the spread.The ensemble consistency was closer to 1 in the spring in the 30-45 °N and 45-60 °N mid-to high-latitude regions,and the ensemble consistency was closer to 1 in the summer in the low-latitude region of 15-30 °N.By contrast,the consistency in all seasons was significantly smaller.(3)The vertical distribution of ensemble forecast perturbation energy and its growth rate also exhibited significant latitudinal and seasonal differences.In the 30-45 °N and 45-60 °N mid-to high-latitude regions,perturbation energy showed high values in both upper and lower levels,with the maximum occurring in spring;in the low-latitude region of 15-30 °N,the total perturbation energy was small and did not change significantly with height,and the growth rate of the perturbation energy in all seasons was relatively small,indicating the need for the development of specific ensemble forecast perturbation methods for low-latitude regions.The observed seasonal,flow-dependent,and regional variations in ensemble perturbation growth highlight the necessity of conducting separate studies for different latitudes and seasons in the East Asian monsoon region,particularly with regard to adjusting the ensemble perturbation structure in low-latitude regions.
Keywords：ensemble forecastgrowth characteristicsseasonal characteristicslatitudinal zone differences
Publication Date：2025-04-30
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：18( 270-287 )