A Frequent-Updating Analysis System Based on Radar, Surface, and Mesoscale Model Data for the Beijing 2008 Forecast Demonstration Project

Abstract

The Variational Doppler Radar Analysis System (VDRAS) was implemented in Beijing, China, and contributed to the Beijing 2008 Forecast Demonstration Project (B08FDP) in support of the Beijing Summer Olympics. VDRAS is a four-dimensional variational data assimilation system that produces frequently updated analyses using Doppler radar radial velocities and reflectivities, surface observations, and mesoscale model data. The system was tested in real time during the B08FDP pretrials in the summers of 2006 and 2007 and run during the Olympics to assist the 0-6-h convective weather nowcasting. This paper provides a description of the upgraded system and its Beijing implementation, an evaluation of the system performance using data collected during the pretrials, and its utility on convective weather nowcasting through two case studies. Verification of VDRAS wind against a wind profiler shows that the analyzed wind is reasonably accurate with a smaller RMS difference for 2006 than for 2007 due to better radar data coverage in 2006. The analyzed cold pools in three convective episodes are compared with surface observations at selected stations. The result shows good agreement between the analysis and the observations. The two case studies demonstrate the role that VDRAS could play in nowcasting convective initiation.

An observational analysis of warm‐sector rainfall characteristics associated with the 21 July 2012 Beijing extreme rainfall event

“…Sun et al . [] examined errors of the retrieved wind fields using the upgraded version of the 4DVAR analysis system and the Doppler radar data at Beijing radar station and its adjacent (Tianjin) radar station. Their sensitivity study with and without the Tianjin data showed that the inclusion of the data did not make much difference to the assimilation analysis.…”

“…Following Sun et al . [], the single‐radar velocity azimuthal display (VAD) profile at Beijing radar station is interpolated onto the 4DVAR grids. The initial horizontal wind fields are calculated from a radar VAD analysis, and the initial vertical velocity is assumed zero.…”

An Application of the Immersed Boundary Method for Recovering the Three-Dimensional Wind Fields over Complex Terrain Using Multiple-Doppler Radar Data

“…It is shown that the prevailing wind moves from the oceans to the southwestern part of Taiwan. It should be pointed out that although the wind profile at LD is obtained by relying on single-Doppler data, the error is still comparable to that in other relevant studies, such as Sun et al (2010) or Tai et al (2011). The solid triangle, circle, square, and diamond represent that this particular layer is covered by zero, one, two, and three radars, respectively.…”

Impact of radar data assimilation for the simulation of a heavy rainfall case in central Italy using WRF–3DVAR

“…A so-called 3.5-dimensional variational radar data assimilation based on the navy's COAMPS (Coupled Ocean/Atmosphere Mesoscale Prediction System) was developed and verified through a number of studies (Zhao et al, 2006;Xu et al, 2010). These variational systems showed great potential in the use of radar observations for initializing high-resolution numerical models through several case studies and real-time demonstrations (Sun et al, 2010;Xue et al, 2010).…”