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Objective

This Product Brief describes 

the Long-Term Pavement 

Performance (LTPP) Climate 

Tool (intended for use by infrastructure engineers) that provides convenient access to the 

National Aeronautics and Space 

Administration (NASA) ModernEra Retrospective Analysis 

for Research and Applications 

(MERRA) climatic data.(1)

Introduction

The LTPP Climate Tool is an 

online tool hosted on LTPP 

InfoPaveTM that provides users 

with access to processed versions of MERRA data using 

different visual features and 

interfaces.(1,3) MERRA is a global 

climate data reanalysis repository that combines computed 

model fields with the basic climatic data attributes.(4,5) The data 

have been collected globally from 

1979 to the present at an hourly 

temporal resolution and a 

horizontal spatial resolution 

of 0.5 degrees latitude by 

0.67 degrees longitude 

(approximately 50 by 65 km at 

mid-latitudes). Further details 

regarding the MERRA data can 

be found in the Federal Highway 

Administration (FHWA) publication Evaluation of LTPP Climatic 

Data for Use in MechanisticEmpirical Pavement Design 

Guide (MEPDG) Calibration and 

Other Pavement Analysis.(6)

The LTPP Climate Tool offers 

users convenient access to 

climate data derived from the 

MERRA database in an intuitive and easy-to-use format.(1)

The MERRA Climate Data for 

Mechanistic-Empirical Pavement 

Design Guide (MEPDG) Inputs 

button under the tools menu 

of the LTPP InfoPaveTM Web 

site allows users to extract the 

MERRA data in a format that is 

compatible with the American 

Association of State Highway 

and Transportation Officials 

AASHTOWare® Pavement ME 

Design software.(3,7,8)

Available Data

The climatic attributes available 

through the LTPP Climate Tool 

include temperature, precipitation, humidity, wind, and solar 

data.(1) The data elements available for each climatic attribute 

include the following: 

• Temperature: This element 

provides access to temperature, soil temperature 

layers 1–6, soil temperature 

unsaturated zone, and soil 

temperature saturated zone.

• Precipitation: This element 

provides access to precipitation, evaporation, infiltration, 

overland runoff, snow mass, 

snow melt,snow-covered area 

fraction, and snowfall.

Publication No. FHWA-HRTM 2444, Pub 17-011

FHWA Contact: Larry Wiser, HRDI-30, (202) 493-3079, larry.wiser@dot.gov

This document provides an overview of the Long-Term Pavement Performance (LTPP) Climate Tool

functionality.(1) Details are provided in the LTPP Climate Tool User Guide (FHWA-HRT-17-012).(2)

PRODUCTBRIEF

LTPP Climate Tool

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• Humidity: This element 

provides access to specific 

humidity, relative humidity, 

and air pressure.

• Wind: This element 

provides access to north 

wind, east wind, wind 

velocity, and air density.

• Solar: This element 

provides access to 

shortwave surface, 

shortwave top of 

atmosphere, cloud 

cover, percent sunshine, 

emissivity, and albedo.

The data are available in 

hourly, daily, monthly, and 

annual temporal resolutions. 

Data summaries, including 

average, maximum, minimum, standard deviation, and 

count, are provided for various elements. 

LTPP Climate Tool 

Interface

The LTPP Climate Tool is 

composed of three modules: 

Location, Country, and Map.(1)

These modules are used 

to select and download the 

desired data. The location 

module allows the user to 

select the desired data geographically, while the country 

module allows the user to 

select data based on country 

and State/Province for any 

country in the world. 

The map module provides 

geographic information 

service (GIS)-based files for 

all of the MERRA data cells 

for a selected year. 

Location Module

The location module offers 

users multiple options for 

selecting geographic data. 

The single-point selection 

tool allows the user to select 

a single location on the map, 

and the corresponding data 

cell will be highlighted. The 

area selection tool allows the 

user to select an area consisting of multiple locations for 

which the climatic data can 

be extracted. The Climate Tool 

graphical interface is shown 

in figure 1.(1)

The search location bar allows 

the user to search for and 

access the required data for 

the geographic location by 

name. The user can also highlight one or more LTPP test 

sections by applying the filters 

on the left-hand side of the 

window and then using the 

single-point or area selection 

tool to highlight the data cell 

encompassing the LTPP test 

section(s).

Country Module

The country module allows 

users to select and extract data 

based on country and State/

Province for any country in the 

world as shown in figure 2.

Map Module

The map module allows users 

to download GIS-based data 

files for all of the MERRA data 

cells for a selected data attribute and time frame. Files can 

be downloaded either in ESRI 

Shape File (*.shp) or Keyhole 

Markup Language (*.kml) 

format.

Data Extraction

The MERRA data selected 

using the location or country 

options can be downloaded 

for a specific time range, 

climatic attribute (temperature, precipitation, humidity, 

wind, or solar), and frequency 

(annual, monthly, daily, or 

hourly). These data can be 

obtained in a Microsoft® 

Excel (.xlsx) format file, a 

Microsoft® Access database 

(.mdb) format, or a Microsoft® 

SQL database (.bak) format. 

A complete user guide is 

available in FHWA publication 

number FHWA-HRT-17-012.(2)
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Figure 1. LTPP Climate Tool—select data by location.(1)

Figure 2. LTPP Climate Tool—select data by country.(1)
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Contact Information

For questions about the LTPP 

Climate Tool, contact LTPP 

Customer Support Service 

Center at ltppinfo@dot.gov or 

submit questions using the 

customer support feature under 

the help tab of the menu bar of 

LTPP InfoPaveTM.(1,3)

References

1. FHWA. LTPP Climate 

Tool, Federal Highway 

Administration, Washington, 

DC, obtained from: https://

infopave.fhwa.dot.gov/data/

climatetool, last accessed 

December 21, 2016.

2. FHWA. (2016). LTPP Climate 

Tool User Guide, Report 

No. HRT-17-012, Federal 

Highway Administration, 

Washington, DC.

3. Federal Highway 

Administration. LTPP 

InfoPaveTM, Federal Highway 

Administration, Washington, 

DC, obtained from: https://

infopave.fhwa.dot.gov/, last 

accessed August 8, 2016.

4. Rienecker, M.M., Suarez, 

M.J., Gelaro, R., Todling, 

R., Bacmeister, J., Liu, E., 

Bosilovich, M.G., Schubert, 

S.D., Takacs, L., Kim, G., 

Bloom, S., Chen, J., Collins, 

D., Conaty, A., Da Silva, A., 

Gu, W., Joiner, J., Koster, 

R.D., Lucchesi, A M., Owens, 

T., Pawson, S., Pegion, P., 

Redder, C.R., Reichle, R., 

Robertson, F.R., Ruddick, 

A.G., Sienkiewicz, M., and 

Woollen, J. (2011). “MERRA: 

NASA’s Modern-Era 

Retrospective Analysis for 

Research and Applications,” 

Journal of Climate, 24(14), 

pp. 3624–3648.

5. NASA. (2012). MERRA: 

Modern-Era Retrospective 

Analysis for Research and 

Applications, Goddard 

Space Flight Center, Global 

Modeling and Assimilation 

Office, Greenbelt, MD, 

obtained from: http://gmao.

gsfc.nasa.gov/merra, last 

accessed March 9, 2015.

6. Schwartz, C.H., Elkins, 

G.E., Li, R., Visintine, B.A., 

Forman, B., Rada, G.R., 

and Groeger, J.L. (2015). 

Evaluation of LTPP Climatic 

Data for Use in MechanisticEmpirical Pavement Design 

Guide (MEPDG) Calibration 

and Other Pavement 

Analysis, Report No. 

FHWA-HRT-15-019, Federal 

Highway Administration, 

Washington, DC.

7. AASHTO. (2015). 

Mechanistic-Empirical 

Pavement Design Guide: 

A Manual of Practice, 

Second Edition, American 

Association of State 

Highway and Transportation 

Officials, Washington, DC. 

8. AASHTO. (2015). 

AASHTOWare® Pavement 

ME Design Software, 2.2 

Build 2.2.4, American 

Association of State and 

Highway Transportation 

Officials, Washington, DC.

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Research, Development, and Technology Turner-Fairbank Highway Research Center

6300 Georgetown Pike • McLean, VA 22101 Visit us on the Web at www.tfhrc.gov

JANUARY 2017 FHWA-HRT-17-011

HRDI-30/01-17(1,000)E

Additional 

Information

Researchers—This study was performed 

by iENGINEERING Corporation.

Distribution—This Product Brief is being 

distributed according to a standard distribution. Direct distribution is being made 

to the FHWA Divisions and Resource 

Center.

Availability—The LTPP Climate Tool can 

be accessed via the LTPP InfoPaveTM 

Web site at https://infopave.fhwa.dot.gov/ 

under the data tab. 

Key Words—MERRA, MEPDG, pavement 

performance, climate data, pavement 

design.

Notice—This document is disseminated under the sponsorship of the U.S. 

Department of Transportation in the interest of information exchange. The U.S. 

Government assumes no liability for the 

use of the information contained in this 

document. The U.S. Government does 

not endorse products or manufacturers. 

Trademarks or manufacturers’ names appear in this report only because they are 

considered essential to the objective of 

the document.

Quality Assurance Statement—

The Federal Highway Administration 

(FHWA) provides high-quality information 

to serve Government, industry, and the 

public in a manner that promotes public 

understanding. Standards and policies 

are used to ensure and maximize the 

quality, objectivity, utility, and integrity 

of its information. FHWA periodically 

reviews quality issues and adjusts its 

programs and processes to ensure 

continuous quality improvement.