Multi-Doppler Radar Observations of Boundary Layer Winds in Support of the Second Texas Air Quality Field Study (TexAQS II)

The Second Texas Air Quality Study (TexAQS II) is a comprehensive research initiative to better understand the causes of air pollution and ultimately to improve regulatory analysis and prediction tools for developing ozone and regional haze State Implementation Plans. Air pollution events are the consequence of complex processes involving both atmospheric chemistry and meteorology on local to regional scales. An important component of this research initiative is to provide enhanced meteorological measurements during an 18-month period (May 2005 – October 2006) over eastern Texas, including the urban environments of Houston and Dallas-Fort Worth. A key objective of the enhanced meteorological monitoring is to quantify the transport into, within, and out of Texas so that the formation and accumulation of ozone and regional haze can be better predicted. As part of this objective, the Texas Commission on Environmental Quality (TCEQ) and the Texas Environmental Research Consortium (TERC) have sponsored the participation of the Shared Mobile Atmospheric Research and Teaching (SMART) radars (two, C-band, Doppler) in TexAQS II to measure clear-air winds in the boundary layer for the purpose of quantifying mesoscale transport in and around urban environments. A SMART radar will be deployed to both the Houston and Dallas-Fort Worth areas in a 25-35 km baseline from the corresponding WSR-88D (KHGX and KFWS respectively) where they will run nearly continuously from June-September 2005 and again from May-September 2006. The size and orientation of the dual-Doppler lobes have been designed to sample both ozone hotspots and pollution precursor sources. These dual-Doppler radar data will be quality controlled and synthesized into maps of low-level horizontal winds over both the Houston and Dallas-Fort Worth areas. On occasion, the mobile capability of the SMART radars will be utilized to measure single-Doppler wind profiles near selected ozone precursor point sources in coordination with research aircraft over eastern Texas. Both single-Doppler (e.g., VAD/VVP wind profiles) and dual-Doppler wind products will be used to validate, constrain and improve the numerical models used to predict the buildup of ozone and transport of regional haze. For selected cases over Houston, we will explore assimilation of SMART radar observations with an Ensemble-Kalman Filter (EnKF) for the modeling of air pollution meteorology and compare the results to traditional dual-Doppler synthesis and other assimilation techniques such as nudging. The purpose of this paper is to present an overview of the experimental design, including radar deployment and scanning strategies, data communications, quality control, and processing. We will also present preliminary radar observations and dual-Doppler analyses from the summer 2005 field campaign.