The National Aeronautics and Space Administration’s (NASA) Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA-2) has used data from Earth Observing System satellites to enhance precipitation and water vapor climatology since 1979. The Federal Highway Administration (FHWA) and the American Association of State Highway and Transportation Officials (AASHTO) have adopted MERRA-2, integrating its variables into civil engineering applications, particularly pavement design. FHWA’s Long Term Pavement Performance (LTPP) Climate Tool provides access to the MERRA-2 database and generates site-specific climate data in compatible formats for AASHTO Pavement Mechanistic-Empirical (Pavement ME) Design.
MERRA-2 data provides opportunities for enhancements to the climatic parameters and climatic module calculations for pavement design using Pavement ME. It provides improved climatology, higher frequency outputs including hourly data updates, and additional locations beyond the United States. Additionally, studies have shown the impediments in aligning parameters from the Enhanced Integrated Climatic Model with field observations and pavement performance, as well as variations in climatic attribute measurements reported by Operating Weather Stations. Research was needed to develop climate-related models based on identified parameter enhancements that could be implemented into state agencies’ asset and pavement management systems.
Under NCHRP Project 20-50(21)A, “Enhancements of Climatic Inputs and Related Models for Pavement ME Using LTPP Climate Tool (MERRA-2),” Applied Research Associates, Inc. was asked to evaluate the impact of using NASA’s MERRA-2 to improve the climatic inputs and related models for Pavement ME that can be implemented by transportation agencies. The research included a synopsis for an implementation plan of the research findings in collaboration with AASHTO/AASHTOWare.
The conduct of research report will be published as NCHRP Research Report 1151: Mechanistic-Empirical Pavement Design Model: Enhancements of Climatic Inputs available on the TRB website at trb.org by searching for NCHRP Research Report 1151.
