MERRA: NASA’s Modern-Era Retrospective Analysis for Research and Applications

Abstract

The Modern-Era Retrospective Analysis for Research and Applications (MERRA) was undertaken by NASA’s Global Modeling and Assimilation Office with two primary objectives: to place observations from NASA’s Earth Observing System satellites into a climate context and to improve upon the hydrologic cycle represented in earlier generations of reanalyses. Focusing on the satellite era, from 1979 to the present, MERRA has achieved its goals with significant improvements in precipitation and water vapor climatology. Here, a brief overview of the system and some aspects of its performance, including quality assessment diagnostics from innovation and residual statistics, is given. By comparing MERRA with other updated reanalyses [the interim version of the next ECMWF Re-Analysis (ERA-Interim) and the Climate Forecast System Reanalysis (CFSR)], advances made in this new generation of reanalyses, as well as remaining deficiencies, are identified. Although there is little difference between the new reanalyses in many aspects of climate variability, substantial differences remain in poorly constrained quantities such as precipitation and surface fluxes. These differences, due to variations both in the models and in the analysis techniques, are an important measure of the uncertainty in reanalysis products. It is also found that all reanalyses are still quite sensitive to observing system changes. Dealing with this sensitivity remains the most pressing challenge for the next generation of reanalyses. Production has now caught up to the current period and MERRA is being continued as a near-real-time climate analysis. The output is available online through the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC).

Simulation study for measurement of horizontal wind profiles in the polar stratosphere and mesosphere using ground-based observations of ozone and carbon monoxide lines in the 230–250 GHz region

“…For the reasons outlined above, global models such as the semi-empirical Horizontal Wind Model (HWM) (Drob et al, 2008 and reanalysis datasets such as the European Centre for Medium-Range Weather Forecasts (ECMWF) operational analyses (Dee et al, 2011) and NASAs ModernEra Retrospective Analysis for Research and Applications (MERRA) (Rienecker et al, 2011) contain sparse information based on observations above 20 km, in contrast to the widespread operational data for the lower atmosphere. Systematic comparisons between co-located ground-based wind radiometer, lidar, and infrasound observations and reanalysis data found both temperature and horizontal wind speeds deviate increasingly above 40 km as the assimilated observations became sparser (Le Pichon et al, 2015).…”

The poleward migration of the location of tropical cyclone maximum intensity

“…This period also encompasses a recent satellite-based global tropical cyclone intensity reanalysis 3 , and represents the most reliable period of the atmospheric reanalysis products [12][13][14] that provide information on the environmental changes that affect tropical cyclones.…”

“…Decreased PI in the deep tropics and/or increased PI at higher latitudes could be expected to result in a similar migration. Here we explore these environmental factors using three different atmospheric reanalysis products, NCEP/NCAR 12 , ERA-Interim 13 , and MERRA 14 . All three products exhibit broad regions of increased shear in the deep tropics and decreased shear in the subtropics (Fig.…”

Disagreements in Low-Level Moisture between (Re)Analyses over Summertime West Africa

“…The (re)analysis products used in this study are 1) the National Centers for Environmental Prediction (NCEP)-National Center for Atmospheric Research (NCAR) 40-Year Reanalysis (NCEP-NCAR hereafter; Kalnay et al 1996;Kistler et al 2001), 2) the NCEP-Department of Energy (DOE) Reanalysis 2 (NCEP-DOE hereafter; Kanamitsu et al 2002), 3) the NCEP Climate Forecast System Reanalysis (CFSR; Saha et al 2010), 4) the National Aeronautics and Space Administration's (NASA) Modern-Era Retrospective Analysis for Research and Applications (MERRA; Rienecker et al 2008, Rienecker et al 2011, 5) the ECMWF ERA-Interim (ERA-Int hereafter; Dee et al 2011), 6) the ECMWF operational analysis (ECMWF-op hereafter), and 7) the NCEP Final (FNL) operational Global Forecast System (GFS) analysis. Details of all these products can be found in Table 1.…”