(Notice: This release notice covers the data range of March, 2000 forward.
For the data range of June, 1997 to September, 1999 click here.)
Data Stream Names
(raw input file)
nacmoltsedasclass1X1.00
(netcdf output files)
sgpmoltsedassndclass1X1.a1
sgpmoltsedassfcclass1X1.a1
nsamoltsedassndclass1X1.a1
nsamoltsedassfcclass1X1.a1
1. OVERVIEW
The Model Output Location
Time Series (MOLTS) data are provided by the National Centers for
Environmental Prediction
(NCEP). Currently
there are over 500 MOLTS stations across the United
States (including Alaska
and Hawaii) and southern Canada. The locations of the MOLTS stations
are based on requests
from the scientific community.
The Eta 4-D Data Assimilation System (EDAS) is an integral part of NCEP's mesoscale numerical weather prediction (NWP) model known as the Early Eta Model. The name "Eta" derives from the model's vertical coordinate known as the "eta" or "step-mountain" coordinate. The Eta forecast model generates forecast fields out to 36 hours from initial states at 00Z and 12Z, whereas the EDAS generates eight 3-hourly initial states or analyses during each 24-hour period, utilizing a vast set of observed data.
Both the Early Eta Model
data and the Eta Data Assimilation System (EDAS) data are
available for the MOLTS
network of stations on an hourly basis. Two subsets are
extracted from the total
set of stations; one in the SGP
CART site area and
the other in Alaska.
All the Alaskan stations north of 60 deg N latitude are retrieved.
The
XDC began retrieving the MOLTS Eta and EDAS data files on June 1, 1997
in bufr format.
2. STATIONS AND CLASSES
The MOLTS output stations
are located near meteorological or research stations, which we will call
input stations. The MOLTS
output station locations are the latitude and longitude of the Eta grid
point which is nearest
the meteorological station of the same earth surface type (ie., land, sea).
There are two possible
classes assigned to each station, Class 0 (basic) and Class 1 (enhanced).
The
classes differ in the
number of surface parameters and sounding parameters reported. After
November 1999
only Class 1 data are
provided but with many more stations than previously.
3. DATA FILES
(1) Parameters
Below is an example of
Class 1 parameters for a single station:
Sounding levels vary
by station; maximum is between 40 and 50 levels.
CONTENTS OF A CLASS
1 MOLTS STATION AT WASHINGTON/DULLES, VA:
HEADER INFORMATION:
Station
ID number
= 72403
Cycle
= 97040112
Forecast
time
= 86400 sec
Station
latitude
= 39.12 deg
Station
longitude
= -77.69 deg
Station
elevation
= 186. m
Number
of surface parameters
= 58
Number
of sounding parameters
= 14
Number
of sounding levels
= 34
SURFACE PARAMETERS:
Pressure
at mean sea level
= 0.1029E+06 Pa
Surface
pressure
= 0.1005E+06 Pa
Skin temperature
= 0.2722E+03 K
1-hr min
temperature at lowest model lvl
= 0.2702E+03 K
1-hr max
temperature at lowest model lvl
= 0.2706E+03 K
Soil moisture
availability
= 0.6200E+02 %
1-hr accumulated
total precip
= 0.0000E+00 kg/m**2
1-hr accumulated
convective precip
= 0.0000E+00 kg/m**2
1-hr average
flux of latent heat
= -0.1060E+02 w/m**2 (+:downward)
1-hr avg
potential flux of latent heat
= -0.3040E+02 w/m**2 (+:downward)
1-hr average
flux of sensible heat
= 0.2410E+02 w/m**2 (+:downward)
1-hr average
flux of sub-surface heat
= 0.2350E+02 w/m**2 (+:downward)
1-hr avg
flux of snow phase change heat
= 0.0000E+00 w/m**2 (+:downward)
1-hr average
shortwave downward flux
= 0.1260E+03 w/m**2 (+:downward)
1-hr average
shortwave upward flux
= -0.7250E+02 w/m**2 (+:downward)
1-hr average
longwave downward flux
= 0.2103E+03 w/m**2 (+:downward)
1-hr average
net longwave flux at top
= -0.2387E+03 w/m**2 (+:downward)
1-hr average
net shortwave flux at top
= 0.7090E+02 w/m**2 (+:downward)
1-hr accumulated
snow fall
= 0.0000E+00 kg/m**2
Total
soil moisture
= 0.6646E+03 kg/m**2
Snow water
equivalent
= 0.0000E+00 kg/m**2
1-hr accumulated
snow melt
= 0.0000E+00 kg/m**2
1-hr accumulated
surface runoff
= 0.0000E+00 kg/m**2
1-hr accumu
baseflow-groundwater runoff
= 0.1000E-01 kg/m**2
Bottom
soil temperature
= 0.2801E+03 K
Roughness
length
= 0.1200E+00 m
U-component
at 10 m
= 0.4300E+01 m/s
V_component
at 10 m
= -0.3500E+01 m/s
Potential
temperature at 10 m
= 0.2702E+03 K
Specific
humidity at 10 m
= 0.2510E-02 kg/kg
2-meter
temperature
= 0.2704E+03 K
2-meter
specific humidity
= 0.2530E-02 kg/kg
Surface
exchange coefficient
= 0.2300E-01 m/s
Green
vegetation cover
= 0.5000E+02 %
Canopy
water
= 0.0000E+00 kg/m**2
Layer-1
volumetric soil moisture
= 0.3080E+00 None
Layer-1
soil temperature
= 0.2711E+03 K
Layer-2
volumetric soil moisture
= 0.3340E+00 None
Layer-2
soil temperature
= 0.2812E+03 K
Station
land/sea mask
= 0.0000E+00 0 (land) or 1 (sea)
Amount
of low cloud
= 0.0000E+00 %
Amount
of middle cloud
= 0.0000E+00 %
Amount
of high cloud
= 0.0000E+00 %
Snow ratio
from explicit cloud sch
= 0.0000E+00
Ice pellet?
(0 - no, 1 - yes)
= 0.0000E+00
Freezing
rain? (0 - no, 1 - yes)
= 0.0000E+00
Rain precip?
(0 - no, 1 - yes)
= 0.0000E+00
U-component
of storm motion
= -0.1400E+01 m/s
V_component
of storm motion
= -0.1740E+02 m/s
Storm
relative helicity
= 0.5240E+02 m**2/s**2
Pressure at the base of cloud
=
Pa
Horizontal visibility
=
m
SOUNDING ON LEVEL 1:
Pressure
0.9996E+05 Pa
Temperature
0.2706E+03 K
U wind
0.3000E+01 m/s
V wind
-0.6600E+01 m/s
Specific
humidity
0.2520E-02 kg/kg
Omega
0.0000E+00 Pa/s
Cloud
water mixing ratio
0.0000E+00 kg/kg
Convective
latent heating rate
0.0000E+00 K/s
Stable
latent heating rate
0.0000E+00 K/s
Short-wave
heating rate
0.6900E-05 K/s
Long-wave
heating rate
-0.8000E-06 K/s
Cloud
fraction in a layer
0.0000E+00 %
Turbulent
kin energy in a layer
0.7900E+00 m**2/s**2
Ice mixing
ratio
kg/kg
SOUNDING ON LEVEL 2:
.
.
SOUNDING ON LEVEL 34 (TOP LEVEL):
.
.
.
(2) Station Inventory
Below is a table
of the number of stations for the total MOLTS stations, the SGP area, and
Alaska
stations.
(See corresponding maps discussed in the Overview Section to view the station
locations.)
Table of Station Counts*
__________________________________________________________________________
domain+ Class
1
__________________________________________________________________________
Stations
sgp
103
nsa
39
__________________________________________________________________________
*sample station counts based on MOLTS files from July 15, 1997
+ defined as follows:
sgp:
lat = 31.941 : 41.00; lon = -103.541 : -91.585 (corresponding to the box)
nsa:
lat > 60.0; lon = -140 : -175
(3) Grid-cell Averaging Consideration
The Eta model generates
averages across a grid cell for any particular variable, for example, terrain
elevation.
If a meteorological input station is near rugged terrain, but is located
in a valley, the
modeled elevation
for that station will be higher than reality. Temperature, in turn, may
be modeled cooler
than reality.
NCEP suggests that if the modeled elevation is more than 30 meters from
the actual elevation
that adjustments
be made for the temperature variable (although Yarosh et al, 1997 have
found this
to rarely be the
case). The actual elevation can be checked by looking at the list
of input
stations .
(4) Forecast vs. Instantaeous Parameter Data
The Eta output
files contain profiles at t0, t0+1hr, t0+2hr,... t0+48hr (t0 is the starting
time of the free
forecast).
Each EDAS output file contains four hourly profiles, for example, class1.bufr.tm09
contains
output at t0-9hr,
t0-8hr, t0-7hr, and t0-6hr. These output hours can be called hour0,
hour1, hour2, and
hour3. In
each case, the hour0 output should not be used for the surface parameters
that are values
accumulated over
a period of time (for example, surface fluxes, maximum temperature over
an hour), since
hour0 is output
after integration over just one time step, and the values are not true
accumulations.
However, parameters
that are instantaneous values (for example, skin temperature) are still
good at hour0.
Since 12Z 3 Nov
1998, the parameters that are cumulative or averaged are given a value
of -9999 at hour0.
For more information about obtaining the MOLTS data please contact:
Joyce Tichler
tichler@bnl.gov
phone: (631)344-3801
or Alice Cialella
cialella@bnl.gov
phone (631)344-3286
REFERENCES:
Rogers, E., D.
G. Deaven and G. J. DiMego, 1995. The Regional Analysis System
for the
Operational "Early"
Eta Model: Original 80-km Configuration and Recent Changes, Weather and
Forecasting, 10:810-825
Yarosh, Ropelewski,
Mitchell, 1996. Comparisons of humidity observations and Eta model
analyses
and forecasts
for water balance studies. Journal of Geophysical Research, 101(18):23,289-23,298.
http://sgi62.wwb.noaa.gov:8080/BUFR_TAF/index.html
http://www.emc.ncep.noaa.gov/mmb/gcp/overview.html
http://www.emc.ncep.noaa.gov/mmb/gcp/molts.html
