The Eta Regional Climate Model: Model Development and Its Sensitivity in NAMAP Experiments to Gulf of California Sea Surface Temperature Treatment

1
The Eta Regional Climate Model Model Development
and Its Sensitivity in NAMAP Experiments to Gulf
of California Sea Surface Temperature Treatment
Rongqian Yang and Kenneth Mitchell
Environmental Modeling Center
National Centers for Environmental Prediction
2
The Eta Regional Climate Model Development at NCEP

• Developed uses very recent version of Eta
  Model physics
• As implemented in operational NCEP Eta on 24 Jul
  01
• Virtually exact match to Eta model in Regional
  Reanalysis (R/R)
• R/R domain and grid (32-km, 45-levels, large R/R
  domain)
• R/R Eta model physics, e.g. NOAH Version 2.3
  with R/R 4 soil layers
• NCEP will provide as a community workstation
  Eta RCM

3
Model Simulations

• Executions summer seasonal simulations (32-km)
• Summers 1990 (NAME choice, with and without
  Baja) and 1991
• Temporal lateral boundary conditions
• Used NCEP/NCAR Global Reanalysis II (6-hourly)
• Daily updates of several surface boundary
  fields
• Daily observed 1-deg weekly Reynolds/Stokes SST
  (NCEP)
• Satellite NDVI-based 0.15-degree monthly
  greenness (NESDIS)
• Seasonal 1.0-deg snow-free albedo climatology
  (NASA)
• Initial land states of soil moisture and soil
  temperature
• Soil moist/temp from Global Reanalysis II ---
  plan to repeat with Regional Reanalysis land
  states
• Snow depth USAF operational 47-km daily global
  snow depth

4
(No Transcript)
5
GoC SST Treatment

• 1x1 degree Reynolds/NCEP SST treatment does not
  capture observed summer warming of GOC
• Correction method developed by David Stensrud for
  use with the Penn State/NCAR mesoscale model,
  modified for Eta model by Tom Black
• 1. Alter SSTs in the Gulf of California
  to a areal mean value,
• valid near Guaymas, Mexico
• 2. This treatment defines mean GoC SST
  values valid at the
• beginning of each month. Then
  performs temporal interpolation
• to get SST at any date

6
GoC Land Sea Mask and SST Treatment
7
(No Transcript)
8
(No Transcript)
9
(No Transcript)
10
(No Transcript)
11
(No Transcript)
12
(No Transcript)
13
(No Transcript)
14
(No Transcript)
15
(No Transcript)
16
(No Transcript)
17
(No Transcript)
18
(No Transcript)
19
Discussions

• The GoC is only a small area relative to the
  model domain. Both treatments in the GoC SST can
  make a difference in the local circulation and
  precipitation patterns in the GoC region,
  demonstrating that the model can capture the
  difference arising from using both treatments
  although the model has great inherent internal
  variability
• The results suggest that SST (resolution and
  quality) play an important role in regional
  climate modeling.
• Need to test the impact of domain size on model
  results

20
Conclusions

• The GoC SST treatment has important impact to
  local low-level circulations and precipitation
  pattern in the GoC region
• The GoC SST treatment has relatively small impact
  on large scale and upper level circulations
• The results suggest that the GoC SST must be
  taken into account in order to model North
  American Monsoon correctly