BACKGROUND

The National Aeronautics and Space Administration’s (NASA) Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA-2 ) utilized data from the Earth Observing System satellites to improve precipitation and water vapor climatology beginning in 1979. The Federal Highway Administration (FHWA) and the American Association of State Highway Transportation Officials (AASHTO) have adopted its use and translated the variables into civil engineering applications, specifically 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 ME Design (Pavement ME). AASHTO will soon use MERRA-2 climatic data for AASHTOWare applications. MERRA-2 data sets include accurate hourly solar radiation values based on measured cloud covered fractions which can significantly improve the accuracy of predicted pavement temperatures.

Studies reveal challenges in matching the predictions from the Enhanced Integrated Climatic Model (EICM) with field observations and pavement performance. Variations in measurement of climatic attributes have also been reported to Operating Weather Stations (OWS). 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. Available data categories include: temperature, precipitation, surface pressure, cloud cover, humidity, wind speed, and solar radiation.

OBJECTIVES

The objectives of this project are to (1) evaluate the impact of using NASA’s Modern-Era Retrospective Analysis for Research and Application, version 2 (MERRA-2) through the FHWA LTPP Climate Tool to improve the climatic inputs and related models for Pavement ME; (2) enhance and simplify climate input parameters for Pavement ME that can be implemented by transportation agencies; and (3) develop climate-related models based on identified parameter enhancements.

RESEARCH PLAN

The NCHRP is seeking the insights of proposers on how best to achieve the research objective. Proposers are expected to describe research plans that can realistically be accomplished within the constraints of available funds and contract time. Proposals must present the proposers' current thinking in sufficient detail to demonstrate their understanding of the issues and the soundness of their approach to meeting the research objective.

The research plan should: (1) include a kick-off teleconference with the research team and NCHRP convened within 1 month of the contract’s execution; (2) address the manner in which the proposer intends to satisfy the project objectives; (3) be divided logically into detailed tasks that are necessary to fulfill the research objectives and include appropriate milestones and interim deliverables; and (4) incorporate opportunities for the project panel to review, comment and approve milestone deliverables.

At a minimum, the research plan shall include the following tasks: 

PHASE I – (Completed)

Research conducted for Phase I was completed under NCHRP Project 20-50(21).

PHASE II

Task 1. Improve and simplify the climate input parameters for Pavement ME that can be implemented by transportation agencies.

Task 2. Develop enhancements of climatic inputs and related models for future incorporation in the Pavement ME including developing appropriate functional requirements and software engineering-related criteria.

Task 3. Develop enhancements to improve EICM functionality and maintenance.

Task 4. Validate any new or enhanced model(s) developed in Task 2 and 3.

Task 5. Arrange coordination and provide opportunities for review and approval of enhancements by NCHRP and AASHTO.

Task 6. Submit the draft final deliverables including (1) a final research report documenting the entire research effort and findings; (2) a stand-alone deliverable that includes the enhanced climatic models and related input parameters; (3) the AASHTO Deliverable; (4) prioritized recommendations for future research; (5) presentation material and resources; and (6) technical memorandum on implementation.