# Presentation: 437392

## --Bob Kistler has rerun analyses and forecasts for this summer using the old T254 system.

***--This study compares the two systems for 24 days in July.***

**Last 31 days:**
**NH 5 day ac    EC .821       GFS .793        MO   .759**
**SH 5 day ac    EC .852       MO   .807        GFS .790**
**Concern about GFS hurricane forecasts**

## GFS error grows faster than other centers first 24 hours, then slower day 1 to day3.

**GFS error grows faster than other centers first 24 hours, then slower day 1 to day3.**

## July 9-31 2005 1 day forecasts rms height error

**--gbl:        T254 9.80   gfs    9.81**
**--20-80N: T254 9.30   gfs    9.31**
**--20-80S:  T254 *****14.68***** gfs  14.15**

**July 11-31 2005 3 day forecasts rms height error**
**--gbl:        T254 *****21.76*****   gfs    21.41**
**--20-80N: T254 *****19.88*****   gfs    19.38**
**--20-80S:  T254 *****37.82*****  gfs    36.71**

***New model better in SH***

***New model better***

## Old-New

- Old GFS (T254) had less 1 day error in northern subtropics and over Antarctica.

*Old-New*

## Old GFS had more error in 3-day forecasts in stratosphere, higher latitude

## T254-gfs

- New model has less time-mean error at higher latitudes, reflecting changes in both analyses and forecasts (next slide)

## Slide 7

## Old gfs has less error over south Asia, Caribbean and Antarctica

## Old gfs has slightly less systematic error over south Asia, Caribbean and Antarctica

## Near Antarctica analysis differences larger than forecast differences

## Slide 11

## Areas of greater rms error reflect greater time-mean errors.

## New ice model warms up lower layers, model more consistent with analysis, effect restricted to boundary layer

## Old-New

***Old-New***

## 2 meter Temperatures at 1200 GMT are higher near and over Antarctica in the GFS than in ECMWF.  The largest differences are found over the continent, indicating differences in the treatment of land ice as well as sea ice.

## New system has shallower boundary layer—what does that mean?

## Increased gwd except over Antarctica, where increased error is seen in new model.

## --Old model has less 1-day rms height error west of Himalayas, over Caribbean and over Antarctica, reflecting mainly less systematic error.

***--By day 3 new model clearly superior to old model, but still has large growth of error in first 24 hours.***
***--New model much warmer over sea ice, but effect seems limited to low levels of atmosphere.***

## Old-New

***Better***

***Worse***

***Old-New***

## Slide 20

## Slide 21

## RMS error over Caribbean, Mexico develop largely in first 6 hours—analysis problem or inconsistency between analysis and model??

- RMS error over Asia slower to develop
- 1 day GFS forecast wants to weaken upper level Asian monsoon anticyclone

## Slide 23

## --GFS has large 1-day rms errors associated with systematic errors—west of Himalayas (weakening of Asian monsoon circulation), over Mexico, Caribbean, Antarctica (less gwd than before)

- --lower analysed heights in tropical eastern Pacific than other centers, perhaps a result of more low-level clouds; differences from EC suggest differences in shallow convection, clouds
- --new land model has increased surface temperatures and decreased surface moisture, increasing sensible heat and decreasing latent heat
- --new ice model has less ice, warmer low-level temperatures, greater fluxes, but effect mostly in lower levels
- --enhanced orography may not have same effect in summer as in winter; mountains have different effects in summer than in winter

## New model has slightly more wind error

## Slide 26

## Slide 27

## Slide 28

## Old model had much more low cloud over Arctic, higher clouds near Antarctica

## Operational vs pry (GSI) July-August 2005

***Operational vs pry (GSI) July-August 2005***

## CDAS 2m temperatures are generally 1-3K cooler over the land

- surfaces than is observed; regions where CDAS is up to
- 1K warmer than the obs. are generally in areas with high terrain.
- In contrast, GDAS 2m temps. are 1-3K warmer than CDAS over
- the majority of the continental regions.

- John Janowiak

## Pry colder near orography

## Slide 33

## Slide 34

## An error in our land-sea mask??