Evaluation Of Chinese AMDAR Weather Reports And Applied Research

To facilitate worldwide cooperation in the establishment of networks of meteorological observations and other geophysical observations related to meteorology, the World Meteorological Organization (WMO) put forward a plan called the World Weather Watch (WWW) in 1963. Aircraft Meteorological Data Relay (AMDAR) plan joined the WWW since’90s and started to promote around the world by WMO. Chinese AMDAR started at the beginning of 21st century; compare with the developed regions such as Europe and the United States, nowadays Chinese AMDAR observations are not well applied in weather monitoring and numerical weather prediction (NWP), which is mainly due to the lack of relevant studies about data quality and applied research. In order to increase the application value of Chinese AMDAR observations, this article will focus on the following issues:1. Knowing how the instruments collect meteorological data is the basic work before any observation is put into use. This article has discussed the observation principles and inversion methods of AMDAR. The main instruments of AMDAR are "Pitot system" and "Total Temperature Sensor". The original meteorological observations are sampled during the high speed flight, thus, the true temperature and wind states of atmosphere are calculated by meteorological observations and flight information. These results are very important for how to use the AMDAR observations.2. The AMDAR observations are not widely applied in China because of a lack of quality evaluation works. This article has discussed the distribution characteristics of Chinese AMDAR observations, and also a comparison of temperature and wind observations has been formed between Chinese AMDAR observations and nearby rawinsonde data during 2004-2010, in order to evaluate the accuracy of Chinese AMDAR observations. Results shows that AMDAR observations mainly locate on central and east China, temporal distribution mainly concentrates in 2300 UTC-1500 UTC period. Temperature and wind speed differences of Chinese AMDAR and rawinsonde observations satisfy normal distribution, when wind direction shows less bias; and the standard deviation is 1.3℃/3 m s-1/27 deg respectively; these two results indicate the Chinese AMDAR observations have reliable quality. The differences between AMDAR and rawinsonde observations mainly arise from instrument measurement and reporting errors, spatial and temporal representativeness, flight phases and environmental factors. The results above increase the credibility of Chinese AMDAR observations, and provide the objective and quantitative reference to the data assimilation system.3. Any observational data should be evaluated by Observation System Experiments (OSEs) before using them in NWP. This article has employed OSEs to evaluate the impacts that Chinese AMDAR observations bring through data assimilation on the NWP for China region. The evaluation results show that either in summer or in winter, AMDAR observations assimilation always improve the numerical simulation results, and high-frequency rapid updated cycling (RUC) experiment shows larger improvements. The improvements bring by AMDAR assimilation appear at any model level, but most significant improvements appear above 400 hPa. These improvements are closely related to the spatial and temporal distribution of Chinese AMDAR observations which indicate that Chinese AMDAR observations are essential to operational NWP in future.4. AMDAR observations are widely used in weather monitoring and disaster warning on the international, but in China, relevant works are still very few. This article has studied a case of extreme wind event called "Southeast Gale" which occurred in Urumchi, and analyzed the positive effects that AMDAR observations bring to both event monitoring and numerical simulation. During the whole process, AMDAR observations provide the wind and temperature profiles near Urumchi continually, which can be used as a reference for numerical simulation results, and also will help monitor the similar events in future. Through AMDAR observations simulation, positive impacts are also found on the simulated element fields. From these results, it can be expected that Chinese AMDAR will play a greater role in weather monitoring and disaster warning in future.