# Presentation: 670177

## Effects of Increasing Vertical Resolution on Precipitation in AMIP Runs

- Glenn.White@noaa.gov

## An Evaluation of  Monthly Means From Suru Saha’s AMIP Runs With Observed SST 
1979-83 PWAT, PRX
PWAT versus PRX
PWAT:  Increased Evaporation of Convective Rain
1979-2001 PRX
28 versus 64 levels
Validation 
NCEP Reanalyses 
CDAS, NCEP2
CMAP Precipitation 1979-2001

- 1979-83 PWAT, PRX
***PWAT versus PRX***
- PWAT:  Increased Evaporation of Convective Rain
- 1979-2001 PRX
***28 versus 64 levels***
**Validation***** ***
- NCEP Reanalyses
- CDAS, NCEP2
- CMAP Precipitation 1979-2001

## In the eastern equatorial Pacific, monthly anomalies from the PWAT AMIP runs correlate the best with CMAP, even better than the reanalyses.

**Notes:**
Epacac

## Mean precipitation 1979-1983

**CMAP**

## Pwat 28 levels

- X 28 levels

## PW28 – CMAP

- X28-CMAP

## PW 64 levels

- X 64 levels

## PWAT64-CMAP

- X64-CMAP

## 28X-PWAT

- 64X-PWAT

## 28 levels

- Dec.-Feb. 1979-83 Mean Precip

- CMAP

- PWAT

- PRX

## 28 levels

- PW-CMAP

- X-CMAP

- X-PW

## DJF79-83 Mean Precip

- 64 levels

- CMAP

- PWAT

- PRX

## 64 levels

- PWAT-CMAP

- X-CMAP

- X-PWAT

## The precipitable water change has not been tested in the medium range forecasts.

We may need to examine its impact on US precipitation in summer.

With 64 levels PWAT does not improve time-mean precip over Indonesia.

- The precipitable water change has not been tested in the medium range forecasts.
- We may need to examine its impact on US precipitation in summer.
- With 64 levels PWAT does not improve time-mean precip over Indonesia.

## 28 levels AMIP with CMAP

**28 levels AMIP with CMAP**

**64 levels AMIP with CMAP**

## CDAS with CMAP

- NCEP2 with CMAP

## Difference

- In correlation
- 28 levels minus NCEP2

- 64 levels
- Minus
- NCEP2
- 1979-2001

## Standard deviation of monthly means

**Standard deviation of monthly means**

**Zonal mean**
**1979-2001**

## Time-mean 1979-2001

**Time-mean 1979-2001**

**CMAP**

## 28 levels

**28 levels**

**64 levels**

## 28-CMAP

**28-CMAP**

**64-CMAP**

## 64-28 levels

***1979-2001***

**64-28 levels**

## 20S-20N

- A quantitative measure of systematic error (or difference)

- 30-60N

## 64 level’s time-mean precip agrees significantly better in the tropics with CMAP than 28 levels, but does not agree as well in the northern mid-latitudes.
AMIP anomalies correlate as highly with CMAP over the eastern equatorial pacific as the reanalyses and display some agreement with CMAP over the equatorial Atlantic, but display no significant correlation with CMAP elsewhere.

- AMIP anomalies correlate as highly with CMAP over the eastern equatorial pacific as the reanalyses and display some agreement with CMAP over the equatorial Atlantic, but display no significant correlation with CMAP elsewhere.

## DJF 1979-2001

**DJF 1979-2001**

**CMAP**

**28**

**64**

## 28-CMAP

**28-CMAP**

**64-CMAP**

**64-28**

**DJF 1979-2001**

## OPI

**OPI**

**Operational GFS 0-6hr**

## CDAS

**CDAS**

**NCEP2**

## 0-24hr minus 0-6hr

**0-24hr minus 0-6hr**

**336-360hr minus 0-6 hr**

## 28-CMAP

**28-CMAP**

**64-CMAP**

## Model gives too much precipitation in mid-latitudes

- CMAP, OPI questionable in higher latitudes
- Satellite estimates generally developed for tropics, not higher latitudes oceans
- Over land, frozen precip may be under-measured.
- OPI more precip in midlatitudes than CMAP.
- Operational analysis cycle gives better precip pattern than reanalyses.

## JJA1979-2001

**JJA1979-2001**

**CMAP**

**28**

**64**

## JJA1979-2001

**28-CMAP**

**64-CMAP**

**64-28**

**JJA1979-2001**

## Observed SST plays leading role in determining precip only over equatorial Atl., e. Pac.

**64 levels produces better  tropical precip than 28 levels**
**NCEP reanalysis precip deficient in tropics, bias problem elsewhere.  **
**New reanalysis with current GFS would produce better precipitation.  **
**Need more accurate independent estimates of precipitation.**