Transcript WRF-LIS at SPoRT/MSFC

Evaluation of WRF Using High-Resolution Soil Initial
Conditions from the NASA Land Information System
University of Maryland WRF Workshop, 14 September 2007
Presented by: Jonathan L. Case
• Project overview / Hypothesis
• Experiment design
• Results
– Land Information System vs. Eta comparison
– Impacts on short-term numerical forecasts
• Summary / Future Work
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Project Overview
• Hypothesis: Can short-term mesoscale numerical forecasts
of sensible weather elements be improved by using
optimally-tuned, high-resolution soil fields?
• Project Goals: Investigate and evaluate the potential
benefits of using high-resolution land surface data derived
from NASA systems and tools on regional short-term
numerical guidance (024 hours)
– Use LIS software to initialize soil temperature and moisture
in the WRF model
– Examine one month period with relatively benign weather
• Isolate influence of land-atmosphere interactions
• May 2004 over Florida peninsula
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Experiment Design
• LIS offline simulation using Noah LSM
– Nested 9-km/3-km grid domain over SE U.S.
– Simulation from 1 May 2002 to 1 June 2004
– Output every 12 hours during May 2004
to initialize WRF runs
– Atmospheric forcing datasets
• North American Land Data Assimilation System (NLDAS; hourly, ~14 km)
• Global Data Assimilation System (GDAS; 6-hourly, ~52 km)
• GDAS used where NLDAS forcing is missing
• Compare regional WRF simulations with high-resolution
LIS soil data to WRF runs with Eta model soil data
– Calculate verification statistics at 80 surface stations
– Plot fields to compare phenomenology differences
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Control WRF and LIS/WRF Configuration
9-km
• Common characteristics
– Nested grids: 9-km and 3-km spacing
– Noah LSM
– Daily 24-hour forecasts during May 2004
initialized at 0000 UTC and 1200 UTC
– Atmospheric initial & boundary conditions
from NCEP Eta model on 40-km grid
3-km
• Differences
– Control WRF: Initial soil data from Eta model
– LIS/WRF experiment: Initial soil data from 2+ year
LIS run on exact WRF grids
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Daily 0-10 cm initial soil moisture (%)
(0000 UTC values during May 2004)
Eta soil moisture
LIS soil moisture
Difference (LIS – Eta)
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Daily 0-10 cm initial soil moisture (%)
(0000 UTC values during May 2004)
Eta soil moisture
• Much more detail in
LIS (as expected)
• LIS drier, especially
over N. FL & S. GA
• LIS slightly more moist
over Everglades
LIS soil moisture
Difference (LIS – Eta)
LIS Substantially
Drier
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Daily 0-10 cm initial soil temperature (°C)
(0000 UTC values during May 2004)
Eta soil temperature
LIS soil temperature
• LIS systematically
cooler over most of
domain
Difference (LIS – Eta)
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0-10 cm initial soil moisture (%)
(1200 UTC 6 May 2004)
Eta soil moisture
LIS soil moisture
Difference (LIS – Eta)
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Sample Sea Breeze Evolution Differences
(9-hour forecast valid 2100 UTC 6 May)
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Sample Sea Breeze Evolution Differences
(10-hour forecast valid 2200 UTC 6 May)
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Sample Sea Breeze Evolution Differences
(11-hour forecast valid 2300 UTC 6 May)
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Sample Sea Breeze Evolution Differences
(12-hour forecast valid 0000 UTC 7 May)
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Sample Sea Breeze Evolution Differences
(Meteogram plots at 40J and CTY)
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Verification Stats: 0000 UTC Cycle
(29 forecasts @ 80 surface stations)
2-m Temperature Errors (°C): 0000 UTC Cycle
• LIS/WRF runs reduced RMS errors
by a few tenths of a degree over
most forecast hours
3
1
0
Bias-CON
RMSE-CON
Bias-LIS
RMSE-LIS
-1
-2
• Nocturnal warm bias and daytime
cold bias both improved
-3
0
3
6
9
12
15
18
21
24
Forecast Hour
2-m Dewpoint Errors (°C): 0000 UTC Cycle
3
• Not much change in dewpoint
verification stats
• LIS/WRF daytime dewpoints about
0.5°C lower than control WRF
• Wind Speed (not shown): LIS/WRF
improved nocturnal high bias
2
Error (°C)
Error (°C)
2
1
0
-1
-2
-3
0
3
6
9
12
15
18
21
Forecast Hour
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Summary / Preliminary Conclusions
• Configured and tested LIS/WRF on Florida case
– Initial soil fields generated on exact WRF grids
– LIS generated soil fields cooler and drier than Eta model
• Simulated atmosphere sensitive to changes in soil
characteristics provided by LIS
– Demonstrated positive improvement in sea-breeze prediction
on 6 May
– Improvements in diurnal prediction of 2-m temperatures during whole
month (both 0000 and 1200 UTC forecast cycles)
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Backup Slides
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Proposed Future Activities with LIS/WRF
• Merge MODIS sea-surface temperatures with LIS soil data
• Study impacts of LIS soil data on convective initiation
– Different regional domains & cases
– Varying weather regimes (e.g. supercells vs. air-mass storms)
• New case study period over Tennessee Valley
– Very warm March followed by killing freeze in early April 2007
– Use real-time MODIS greenness fraction products in LIS/WRF system
• Regional modeling ensembles
– Summertime forecast sensitivity to soil initial condition perturbations
– Run different LSMs within LIS/WRF for ensemble members
• Pathway to operational regional LIS/WRF runs
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Alabama Freeze Case: April 2007
N Alabama / SE Tennessee
Apr 5, 2007 (Before freeze)
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Alabama Freeze Case: April 2007
N Alabama / SE Tennessee
April 8, 2007 (After Freeze)
Proposal:
• Use real greenness fraction data in LIS/WRF simulations,
derived from MODIS vegetation index composite products
• Measure impact on WRF forecasts compared to climo datasets
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Soil Moisture: Grid-Wide Stats; Land Points
0-10 cm Soil Moisture: Mean & SD
• LIS is a few % drier than Eta model
in volumetric soil moisture
Control Mean
Control SD
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LISWRF Mean
LISWRF SD
• Variation about mean is very
similar to Eta model soil moisture
15
10
5
0
40-100 cm Soil Moisture: Mean & SD
1
6
11
16
21
26
31
25
Day (May 2004)
Volumetric Water (%)
Volumetric Water (%)
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20
15
10
5
0
1
6
11
16
21
26
31
Day (May 2004)
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Soil Temp: Grid-Wide Stats; Land Points
0-10 cm Soil Temp: Mean & SD
• LIS 0-10 cm soil temperatures
typically cooler than Eta at 00z
35
25
• LIS 0-10 cm soil temperatures
about the same or slightly warmer
at 12z
20
15
Control Mean
Control SD
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LISWRF Mean
LISWRF SD
5
40-100 cm Soil Temp: Mean & SD
0
1
6
11
16
21
26
31
30
Day (May 2004)
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• LIS deeper soil temperatures
consistently colder than Eta
Temperature (°C)
Temperature (°C)
30
20
15
10
5
0
1
6
11
16
21
26
31
Day (May 2004)
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Sample Sea Breeze Evolution Differences
(Forecasts from 1200 UTC 6 May Simulations)
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Verification Stats: 1200 UTC Cycle
(Surface station 40J)
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Verification Stats: 1200 UTC Cycle
(Surface station CTY)
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