Approved for Public Release, AEDC PA 2014-292 Distribution is Unlimited. A LIDAR DATA ASSIMILATION SYSTEM FOR THE UPPER TROPOSPHERE AND STRATOSPHERE George Modica*, Thomas Nehrkorn 1 , Mark Leidner 1 , John Henderson 1 , and David Johnson 2 1 Atmospheric and Environmental Research, Inc., Lexington, Massachusetts 2 Michigan Aerospace Corp., Ann Arbor, Michigan Corresponding author address: George D. Modica, AER, Inc., 131 Hartwell Ave., Lexington, MA, 02421- 3126; email: gmodica@aer.com 1. INTRODUCTION This paper presents the results of an effort to develop a data assimilation capability for measurements of environmental parameters at altitudes up to the mesopause (~80 km). Some background information is provided in Sections 1.1 and 1.2; descriptions of the data assimilation system and the data are presented in Sections 2 and 3, respectively; Results are provided in Section 4. 1.1. The High Speed Systems Test Program The High Speed Systems Test (HSST) area of the Department of Defense Test Resource Management Center (TRMC) Test/Evaluation and Science/Technology (T&E/S&T) program has articulated a requirement for real-time meteorological assessment in support of flight testing hypersonic vehicles, particularly, “detailed atmospheric assessments for a given volume along the flight path close to the real-time location of the vehicle” (U.S. Army BAA 2008). Furthermore, “…prediction of atmospheric flight conditions on the flight paths of high speed, hypersonic vehicles is highly desired to better assess flight test variables and also to better understand flight vehicle performance as it accomplishes its mission.” The altitudes of interest are from the surface to 80 km. Situational awareness of the meteorological conditions will result in a reduction in the vehicle performance uncertainty that is a large contributor to the costs of flight testing as well as providing numerous other benefits. Michigan Aerospace Corporation, Inc. (MAC) is leading the development of a LIDAR instrument that will acquire meteorological conditions at the altitudes of interest. In a parallel effort, Atmospheric and Environmental Research, Inc. (AER) is providing a data assimilation system (DAS) intended to combine the LIDAR measurements with other conventional sources of data as a means of producing useful 3- and 4- dimensional datasets of state variables, thereby directly addressing the requirements described above. 1.2. The High-Altitude LIDAR Atmospheric Sensing The effort to acquire a high-altitude atmospheric sensing capability for the HSST program is being led by Michigan Aerospace Corporation (MAC). They have developed the High-Altitude LIDAR Atmospheric Sensing System capable of providing measurements of density, temperature, and wind speed and direction within the troposphere and stratosphere, up to approximately 80 km. The LIDAR is based on the principle of ultraviolet-based direct detection of constituent gases and is combined with a Raman channel to measure nitrogen and oxygen concentration. Results from a demonstration and test phase were provided for use in the DAS acquired as part of this project. 2. DATA ASSISMILATION SYSTEM The purpose of the DAS is to optimally combine meteorological information distributed irregularly in space and time with a background, thereby creating a new, dynamically consistent dataset having better quality and more information content than what would otherwise be provided by either source alone. Like most DAS, the one described here for HALAS can utilize data originating from a wide variety of atmospheric observational platforms and backgrounds; however, it is also well-suited to non-conventional sources of data such as the high-altitude observations from HALAS. The HALAS DAS utilizes the ensemble method. The main components of that system are the Community Earth System Model (CESM) and an algorithm provided by the Data Assimilation Research Testbed (DART). The specific details of the DAS configuration adopted for the HALAS project are similar to that described in Raeder et al. (2012) and Pedatella et al. (2013) and are detailed in the next sections. 2.1. CESM CESM is the Community Earth System Model designed and created by the National Center for Atmospheric Research (NCAR) as a community tool capable of representing many hydrodynamic physical processes over a wide range of time and space scales by coupling atmospheric, land, ocean, and other components (Figure 1). For the HALAS project the DAS was run as single-component assimilation for the atmosphere only; we assume the physical processes relevant to the time and space scales of the stratosphere and lower mesosphere (SLM) that are P741