NDLAS LSWG README - CICS

README for the NLDAS data prepared for the GPM Land Surface Characterization Working
Group, Emissivity comparison study.
Contents
Output from NLDAS forcing and one land-surface model
Format
ASCII
Temporal resolution 1-hourly
Temporal coverage July 1, 2006 – June 30, 2007
Forcing data and
FORCING, NLDAS/FORCING “a” files (1/8 th degree)
Land surface model MOSAIC, NLDAS/MOSAIC LSM output (1/8 th degree)
Target areas
C3VP (44N, 80W)
(valid NLDAS land points) Desert-2 (34N, 117W)
SGP (35N, 97W)
SE US (HMT-E) (34N, 81W)
Inland Water (48N, 87W) – FORCING only
The exact latitudes/longitudes of the above points are on the corners of NLDAS grid boxes.
Therefore, the values listed in these ASCII files for this study are the average of the 4
surrounding 1/8 th degree NLDAS native grid boxes around these points – making them an
average over a 1/4 th degree box centered at the lat/lon locations.
The time series were extracted from NLDAS-2 products that span hourly from 1979 to present.
The forcing data set combines multiple data sets throughout the simulation period. The nonprecipitation
land surface forcing fields for NLDAS-2 are derived from the analysis fields of the
NCEP North American Regional Reanalysis (NARR). NARR analysis fields are 32-km spatial
resolution and 3-hourly temporal frequency. Those NARR fields that are utilized to generate
NLDAS-2 forcing fields are spatially interpolated to the finer resolution of the NLDAS 1/8thdegree
grid and then temporally disaggregated to the NLDAS hourly frequency. Additionally,
the fields of surface pressure, surface downward longwave radiation, near-surface air
temperature and near-surface specific humidity are adjusted vertically to account for the vertical
difference between the NARR and NLDAS fields of terrain height. This vertical adjustment
applies the traditional vertical lapse rate of 6.5 K/km for air temperature. The details of the
spatial interpolation, temporal disaggregation and vertical adjustment are those employed in
NLDAS-1, as presented by Cosgrove et al. (2003, JGR, Vol. 108). The surface downward
shortwave radiation field is a bias-corrected field wherein a bias-correction algorithm was
applied to the NARR surface downward shortwave radiation. This bias correction utilizes five
years (1996-2000) of the hourly 1/8th-degree GOES-based surface downward shortwave
radiation fields derived by Pinker et al. (2003). The precipitation field is not the NARR
precipitation forcing, but is rather a product of a temporal disaggregation of a gauge-only CPC
analysis of daily precipitation, performed directly on the NLDAS grid and including an
orographic adjustment based on the widely-applied PRISM climatology. The total precipitation
field is derived from CPC daily CONUS gauge data (with the PRISM topographical adjustment),
CPC daily North American gauge data, hourly Stage 2 precipitation data, half-hourly CMORPH
data, and 3-hourly NARR precipitation data. Reflecting the strengths of each data set, NLDAS
precipitation is derived by using the hourly Doppler radar and half-hourly CMORPH products to
temporally disaggregate the daily gauge products. This process capitalizes on the accuracy of

the daily gauge product, and on the temporal and spatial resolutions of the Doppler radar and
CMORPH products. CPC PRISM-adjusted daily gauge analyses serve as the backbone of the
NLDAS hourly precipitation forcing. Outside of the CONUS, where this dataset is unavailable,
CPC's 1 degree (0.25 degree after 2001) North American daily gauge product is used instead. In
NLDAS, these gauge-only daily precipitation analyses are first processed to fill in any missing
values, and then are temporally disaggregated into hourly fields. This is accomplished by
deriving hourly disaggregation weights from NWS real-time, 4 km Stage II and 8km CMORPH
hourly precipitation analyses. Stage II data is available from 1996 to the present, while
CMORPH data is available from 2002 to the present. The Stage II product consists of WSR-88D
Doppler radar-based precipitation estimates that have been bias corrected using hourly multiagency
gauge data (Fulton et al., 1998), and mosaicked into a national product over the
Continental United States (CONUS) by NCEP/EMC (Baldwin and Mitchell, 1997). This
CONUS mosaic of the Stage II product is interpolated to 1/8th degree and any gaps in radar
coverage (which total on average 13% of the area of the CONUS and are due to lack of radar
coverage or equipment maintenance) are filled in with nearest neighbor Stage II data from within
a 2-degree radius. If no Stage II data are available, then CMORPH data are used instead.
CMORPH data is also used over the Mexican portion of the NLDAS domain which is outside of
the Stage II's region of coverage. When CMORPH data is unavailable, NARR data is used
instead. The hourly patched Stage II and CMORPH fields are then divided by fields of patched
Stage II and CMORPH daily precipitation totals to create hourly temporal disaggregation
weights representing the proportion of the 24 hour total precipitation which fell in each hour. If
the daily Stage II or CMORPH total is zero in an area of non-zero CPC precipitation, hourly
weights are set to 1/24 to spread the precipitation evenly over the entire day. These hourly
weights are then multiplied by the daily gauge-only CPC precipitation analysis to arrive at
temporally disaggregated, hourly NLDAS fields. Since the Stage II and CMORPH data is only
used to derive the hourly disaggregation weights, a daily summation of these NLDAS
precipitation fields will exactly reproduce the original CPC daily precipitation analysis. Since
daily gauge and hourly precipitation data is sparse over Canada, NARR precipitation is used over
all Canadian regions within the NLDAS domain. Rather than have an abrupt cutoff at the United
States border, a one degree wide blending area is used. In this region, precipitation forcing
consists of a weighted combination of the precipitation datasets discussed above. More
information on NLDAS-2 forcing data can be found here:
http://ldas.gsfc.nasa.gov/LDAS8th/forcing/forcing_narr.shtml
File naming convention
_nldas_.txt
Data contents
Each text file contains header and lat/lon information in the first row, followed by a row listing
the soil and vegetation type index at the point. The soil/vegetation index values are listed here:
Soil Index:
0 W Water
1 S Sand
2 LS Loamy sand
3 SL Sandy loam

4 SIL Silt loam
5 SI Silt
6 L Loam
7 SCL Sandy clay loam
8 SICL Silty clay loam
9 CL Clay loam
10 SC Sandy clay
11 SIC Silty clay
12 C Clay
13 OM Organic materials
Vegetation Index:
0 Water
1 Evergreen Needleleaf Forest
2 Evergreen Broadleaf Forest
3 Deciduous Needleleaf Forest
4 Deciduous Broadleaf Forest
5 Mixed Cover
6 Woodland
7 Wooded Grassland
8 Closed Shrubland
9 Open Shrubland
10 Grassland
11 Cropland
12 Bare Ground
13 Urban and Built-Up
The third row lists is a header listing the variable name for each column below, starting with:
YEAR MON DAY GMT var1 var2 var3 ….. varN.
The FORTRAN write statements for the ASCII data are:
FORCING format(4(1X,I4),11(1X,F9.2))
MOSAIC
format(4(1X,I4),37(1X,F12.2))
FORCING variables:
APCPsfc Precipitation hourly total [kg/m^2]
CAPE180 180-0 mb aboveground Convective Available Potential Energy [J/kg]
CONVfrac Fraction of total precipitation that is convective [unitless]
DLWRFsfc LW radiation flux downwards (surface) [W/m^2]
DSWRFsfc SW radiation flux downwards (surface) [W/m^2]
PEVAPsfc Potential evaporation [kg/m^2]
PRESsfc Surface pressure [Pa]
SPFH2m 2-m above ground Specific humidity [kg/kg]
TMP2m 2-m above ground Temperature [K]
UGRD10m 10-m above ground Zonal wind speed [m/s]
VGRD10m 10-m above ground Meridional wind speed [m/s]

MOSAIC variables:
ACONDsfc Aerodynamic conductance [m/s]
ALBDOsfc Albedo [%]
ARAINsfc Liquid precipitation (rainfall) [kg/m^2]
ASNOWsfc Frozen precipitation (e.g. snowfall) [kg/m^2]
AVSFTsfc Average surface skin temperature [K]
BGRUNsfc Subsurface runoff (baseflow) [kg/m^2]
CCONDsfc Canopy conductance [m/s]
CNWATsfc Plant canopy surface water [kg/m^2]
DLWRFsfc LW radiation flux downwards (surface) [W/m^2]
DSWRFsfc SW radiation flux downwards (surface) [W/m^2]
EVBSsfc Direct evaporation from bare soil [W/m^2]
EVCWsfc Canopy water evaporation [W/m^2]
EVPsfc Evaporation [kg/m^2]
GFLUXsfc Ground heat flux [W/m^2]
LAIsfc
Leaf area index (0-9) [non-dim]
LHTFLsfc Latent heat flux [W/m^2]
MSTAV0_40cm 0-40 cm underground Moisture availability [%]
MSTAV0_200cm 0-200 cm underground Moisture availability [%]
NLWRSsfc LW radiation flux net (surface) [W/m^2]
NSWRSsfc SW radiation flux net (surface) [W/m^2]
SBSNOsfc Sublimation (evaporation from snow) [W/m^2]
SHTFLsfc Sensible heat flux [W/m^2]
SNODsfc Snow depth [m]
SNOHFsfc Snow phase-change heat flux [W/m^2]
SNOMsfc Snow melt [kg/m^2]
SNOWCsfc Snow cover [%]
SOILM0_10cm 0-10 cm underground Soil moisture content [kg/m^2]
SOILM0_40cm 0-40 cm underground Soil moisture content [kg/m^2]
SOILM0_100cm 0-100 cm underground Soil moisture content [kg/m^2]
SOILM0_200cm 0-200 cm underground Soil moisture content [kg/m^2]
SOILM10_40cm 10-40 cm underground Soil moisture content [kg/m^2]
SOILM40_200cm 40-200 cm underground Soil moisture content [kg/m^2]
SSRUNsfc Surface runoff (non-infiltrating) [kg/m^2]
TRANSsfc Transpiration [W/m^2]
TSOIL0_0cm 0-0 cm underground Soil temperature [K]
VEGsfc Vegetation [%]
WEASDsfc Accumulated snow water-equivalent [kg/m^2]
Questions or problems
Please contact David Mocko (David.Mocko@nasa.gov).