# Presentation: 367800

## Physical Initialization  for the Regional Spectral Model

*Ana Nunes, John Roads and Masao Kanamitsu*
*Scripps Experimental Climate Prediction Center  (ECPC)**La Jolla, California, USA*
**anunes@ucsd.edu**

## Although atmospheric analyses and reanalyses are now providing physical realistic fields for many variables, precipitation remains problematic. Physical initialization (PI) has been proposed as a methodology for improving precipitation and related hydroclimatological simulation skill. For this reason, the Scripps Experimental Climate Prediction Center (ECPC) is now implementing a PI procedure in the Regional Spectral Model (RSM). 

- Although atmospheric analyses and reanalyses are now providing physical realistic fields for many variables, precipitation remains problematic. Physical initialization (PI) has been proposed as a methodology for improving precipitation and related hydroclimatological simulation skill. For this reason, the Scripps Experimental Climate Prediction Center (ECPC) is now implementing a PI procedure in the Regional Spectral Model (RSM).
- We summarize here some of the improvements obtained for  climate simulations over two distinct domains: (1) U. S. and Mexico during a Southwest-Mexico monsoon season; and (2) South America during the rainfall season of the Amazon region and increased activity of the South Atlantic Convergence Zone.

## The Scripps ECPC RSM, described previously by Juang and Kanamitsu (1994); Anderson et al.  (2001); and Roads (2003), used for these experiments had 60-km resolution and 28 levels in the vertical. A Mercator projection was used for the projection of the regional grid.  The RSM is a primitive equation model, with similar physics as the driving NCEP-DOE reanalysis II (R-2) Global Spectral Model as reported in Kanamitsu et al. (2002). 

- The Scripps ECPC RSM, described previously by Juang and Kanamitsu (1994); Anderson et al.  (2001); and Roads (2003), used for these experiments had 60-km resolution and 28 levels in the vertical. A Mercator projection was used for the projection of the regional grid.  The RSM is a primitive equation model, with similar physics as the driving NCEP-DOE reanalysis II (R-2) Global Spectral Model as reported in Kanamitsu et al. (2002).

## RSM initial and boundary conditions were obtained from the coarser-scale R-2 reanalysis (1.875° resolution) and 28 vertical levels.

- Daily rain rates were provided by the Climate Prediction Center (CPC) precipitation analysis (see Higgins et al., 2001) over the U. S. domain.  R-2 precipitation fields were used for the rest of the model domain, including Mexico. The CPC precipitation was provided on a regular grid of 0.25o.
- SSM/I-OLR precipitation estimates were used in the simulations over South America.  The SSM/I-OLR estimate was provided on a Gaussian grid of 0.7o. The NOAA/NESDIS SSM/I algorithm (Ferraro and Marks, 1995) was used to estimate the rain rates.
- All rainfall fields were bi-linearly interpolated to the regional model’s grid.
- SST (1 degree resolution) was taken from the PIRCS data set.

## PI-ANALYSIS 

**“****OBSERVED” **
**RAIN RATES**
**TIME STEP ASSIMILATED**

**DAY  -1**
**ANALYSIS**

**DAY  0**
**ANALYSIS**

**PHYSICAL INITIALIZATION**
**SCHEME**

- PI-ANALYSIS** **

- FORECAST** **

- Fig. 1 -  General overview of  the  PI procedure considering  a  continuous data assimilation system.

- This scheme basically adjusts the humidity profile using the difference between the “observed” and predicted rain rates as factor of this adjustment.  In order to provide consistent temperature profiles, the cumulus and large-scale precipitation parameterizations are then immediately called.  This methodology differs from the used by the FSU Nested Regional Spectral Model (Nunes and Cocke, 2003), where a modified Kuo parameterization is the convection scheme, however the general PI procedure follows the same structure as shown in Fig. 1.

## The experiments were performed during the summertime.

- U. S. and Mexico: -
- July-August-September, starting at July 1st, 1999 at 0 UTC.
- South America: -
- January, starting at January 1st, 1999 at 0 UTC.
- The control simulations were not initialized. In the PI simulations, the rain rates were updated every 24 hours, and the moisture adjustment took place every time-step which was 3 min. The boundary conditions were updated every 6 hours.

## U. S. and MexicoMonthly Accumulated Precipitation (mm)July 1999

- SAS

- Verification

- RAS

## U. S. and MexicoMonthly Accumulated Precipitation (mm)August 1999

- SAS

- Verification

- RAS

## U. S. and MexicoMonthly Accumulated Precipitation (mm)September 1999

- SAS

- Verification

- RAS

## South AmericaMonthly Accumulated Precipitation (mm)January 1999

- SAS

- Verification

- RAS

## A preliminary evaluation of the PI scheme results was based on spatial correlation coefficient (r) and bias given by:

- The variables x and y represent the predicted and observed precipitations, and the subscript i, the grid point on the Mercator projection.

- PHYSICAL INITIALIZATION FOR THE REGIONAL SPECTRAL MODEL

## U. S. and MexicoSpatial Correlation CoefficientJuly 1999

## U. S. and MexicoSpatial Correlation CoefficientAugust 1999

## U. S. and MexicoSpatial Correlation CoefficientSeptember 1999

## U. S. and MexicoBias: July 1999

- SAS

- RAS

## U. S. and MexicoBias: August 1999

- SAS

- RAS

## U. S. and MexicoBias: September 1999

- SAS

- RAS

## South AmericaSpatial Correlation CoefficientJanuary 1999

## South AmericaBias: January 1999

- SAS

- RAS

## U. S. and Mexico850 hPa Temperature (K)July 1999

- SAS

- R-2

- RAS

## U. S. and Mexico500 hPa Temperature (K)July 1999

- SAS

- R-2

- RAS

## U. S. and Mexico300 hPa Temperature (K)July 1999

- SAS

- R-2

- RAS

## U. S. and Mexico850 hPa Temperature (K)August 1999

- SAS

- R-2

- RAS

## U. S. and Mexico500 hPa Temperature (K)August 1999

- SAS

- R-2

- RAS

## U. S. and Mexico300 hPa Temperature (K)August 1999

- SAS

- R-2

- RAS

## U. S. and Mexico850 hPa Temperature (K)September 1999

- SAS

- R-2

- RAS

## U. S. and Mexico500 hPa Temperature (K)September 1999

- SAS

- R-2

- RAS

## U. S. and Mexico300 hPa Temperature (K)September 1999

- SAS

- R-2

- RAS

## South America850 hPa Temperature (K)January 1999

- SAS

- R-2

- RAS

## South America500 hPa Temperature (K)January 1999

- SAS

- R-2

- RAS

## South America300 hPa Temperature (K)January 1999

- SAS

- R-2

- RAS

## U. S. and MexicoJuly 1999

| Monthly
Accumulated
Precipitation | Corr. Coeff. | RMSE (mm) |
| --- | --- | --- |
| PI 
SAS/RAS | 0.97/0.97 | 38.7/23.9 |
| Control SAS/RAS | 0.65/0.66 | 79.6/77.5 |

## U. S. and MexicoAugust 1999

| Monthly 
Accumulated
Precipitation | Corr. Coeff. | RMSE (mm) |
| --- | --- | --- |
| PI 
SAS/RAS | 0.96/0.98 | 40.5/22.8 |
| Control SAS/RAS | 0.52/0.58 | 90.9/85.3 |

## U. S. and MexicoSeptember 1999

| Monthly
Accumulated
Precipitation | Corr. Coeff. | RMSE (mm) |
| --- | --- | --- |
| PI 
SAS/RAS | 0.97/0.98 | 46.8/24.1 |
| Control SAS/RAS | 0.74/0.76 | 89.9/86.3 |

## South AmericaJanuary 1999

| Monthly
Accumulated
Precipitation | Corr. Coeff. | RMSE (mm) |
| --- | --- | --- |
| PI 
SAS/RAS | 0.98/0.98 | 50.2/26.9 |
| Control SAS/RAS | 0.37/0.31 | 196.0/189.8 |

## Preliminary evaluations of the PI implementations indicate that the RSM was able to successfully assimilate the merged precipitation analysis and SSM/I estimates as well.

- The correlation coefficients exceeded 0.9 and the spin-up problem was noticeably reduced during the continuous assimilation period.
- The temperature fields are not degraded by using a rainfall nudging and they are well correlated with the R-2 fields.
- We are now attempting to implement a physically initialized analyses as part of our effort to develop useful downscaled reanalysis fields