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Agenda Topic: NCEP North American Land Data Assimilation Systems, NLDAS (“Off Line Land Modeling”)

Presented By: Mike Ek and Helin Wei (NWS/NCEP/EMC)Contributors: NCEP/EMC land team and others

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NLDAS Attribute(s)

System Name Acronym Areal Coverage Horz Res Cycle Freq

Fcst Length (hr)

North American Land Data Assimilation System

NLDAS CONUS 0.125-deg Daily Analysis

System Attributes

NLDAS Four-land model ensemble uncoupled (“offline”) analysis.

Land models: NCEP/Noah, NASA/Mosaic, NWC/SAC, Princeton & Univ.Wash/VIC.

Forcing: atmospheric

Regional Climate Data Assimilation System (R-CDAS; 32-km), realtime extension of North American Regional Reanalysis (NARR).

Forcing: precipitation

CPC gauge-based, radar disaggregated (temporally) precipitation.

Output Surface fluxes, land states (soil moisture & temp, snow), streamflow.

Use Ensemble fields and anomalies in fluxes, states, streamflow compared to 30+ year land reanalyses (using NARR) from 4 land models.

System Data Assimilation or Initialization Technique

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Why NLDAS is Operational

Primary stakeholders and requirement drivers• NCEP/CPC monthly drought briefings/outlooks, US Drought Monitor

(USDM), National Integrated Drought Information System (NIDIS), others.

What products are the models contributing to?• Drought and water resources community needs, i.e. fluxes, states and

anomalies compared to long-term climatologies; also land initialization.

What product aspects are you trying to improve with your development plans?• Higher spatial/temporal resolution output: land surface fluxes, land states

(e.g. soil moisture, snow), streamflow, near-realtime, large domain.

Top 3 System Performance Strengths• State-of-the-art land models.• Broad community participation in NLDAS.• Brings together atmospheric and hydrology communities.

Top 3 System Performance Challenges • Atmospheric forcing/downscaling for land model, especially precipitation.• Land model spin-up procedures.• Surface energy partition and surface-layer turbulence parameterizations.

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NLDAS Evolution Over the Next 5 Years

Major forcing factors• Need for even higher-resolution near-realtime land products for drought &

water resources communities; initial land states for atmospheric models.

Science and development priorities• Atmospheric forcing (especially precipitation), land data sets (in situ and

remotely-sensed), downscaling (especially precipitation), land data assimilation, improved land physics (especially surface energy partition & surface-layer turbulence), freshwater lakes, ecosystems/biogeochemical cycles (e.g. carbon), land-hydrology validation data, e.g. soil moisture.

What are you top challenges to evolving NLDAS to meet stakeholder requirements?• Sufficient and sustained resources, i.e. staffing, computational.

Potential opportunities for simplification going forward• Merge operational NLDAS with operational GLDAS (from CFS) into one

high-res. global system to provide initial land states to all NCEP models.• Coordinate closely with NWC on their higher-resolution hydrological

modeling (i.e. WRF-Hydro) to be part of a fully-coupled earth system model in order to complete the water cycle while properly modeling the energy budget, and accounting for ecosystems/biogeochemical cycles.

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Top 3 Things You Need From the UMAC

Advocate for:

1. Strong cross-NOAA coordination, i.e. all research activities should map into the NOAA mission such that all activities in the “R2O2R funnel” are properly connected. No stovepipes. No exceptions.

2. Sufficient and sustained resources to allow NCEP, and especially EMC to properly fit into that R2O2R funnel plus have a strong voice in those activities.

3. Strong interagency (including state and local agencies) coordination on research activities, and strong links with academia and international projects and programs.