# Presentation: 471076

## Spatial and Temporal Variability of GPCP 

**Spatial and Temporal Variability of GPCP **
**Precipitation Estimates**

- By C. F. Ropelewski
- Summarized from the generous input
- Provided by
- G. Huffman, R. Adler, S. Curtis,
**P. Arkin**, X. Yin
- J.Janowiak, P. Xie
- R. Ferraro
- P. Bauer
- C.Beck, J.Grieser, B.Rudolf
- M. Bell, B. Blumenthal, B. Lyon
- F. R. Robertson
- T. Smith

- Presented at the 30th Climate Diagnostics
- and Prediction WS, 24-28 Oct 2005
- State College, PA

- Go LIONS

## Characteristics of the GPCP Data Set

-  Global Complete Monthly Precipitation Analysis
- January 1979 to Present
- 2.5o latitude by 2.5o longitude
-  Input data
-  Satellite Infrared (geostationary0
-  Microwave (from mid-1987)
-  Gauge data (Global Precipitation Climatology
-   Center (GPCC) operated by the DWD
-  Output Data
- Satellite only
- Merged gauge and satellite
-  Monthly, pentad, daily

## “Real-time” monthly gauge data from the GTS

- “Real-time” monthly gauge data from the GTS

## Major GPCP contributions

**P **estimated a 2.61 mm/day
- Yearly Standard Deviation 0.03mm/day

- Estimated mean global rainfall rates

- Estimates of the global
- Precipitation patterns

## Figure 1a.  Zonal mean precipitation, land versus ocean, 1979-2003, after Adler et al, (2003) Courtesy of Scott Curtis

## Figure 1b.  Zonal mean precipitation, land versus ocean, 1979-86 versus 1988-2003

- After Adler et al, (2003) Courtesy of Scott Curtis

## Fig 2.  Mean GPCP precipitation 1979-2002 (mm/day)

- Courtesy John Janowiak

## Mean Annual Cycle

## Standard deviations of Annual mean GPCP Precipitation 

- Standard deviations of Annual mean GPCP Precipitation
- Courtesy Michael Bell

## Slide 10

## Fig 5b. Mean annual cycle (mm/day) Global (white), Northern Hemisphere (green), Southern Hemisphere (yellow). 

- Fig 5b. Mean annual cycle (mm/day) Global (white), Northern Hemisphere (green), Southern Hemisphere (yellow).

## Fig 5c. Mean annual cycle of precipitation. Oceans (green),  Global (white), Land (yellow).   Courtesy P. Arkin

## Fig. 6a Annual cycle of zonal mean GPCP Precipitation (mm/day) and 

- Fig. 6a Annual cycle of zonal mean GPCP Precipitation (mm/day) and
- b) the difference between total period zonal mean 1979 – 2002
- and 1979-86/87. Courtesy J. Janowiak

## Fig 3 (top) Mean GPCP Precipitation

- P1-1979-86 (left)
- P2 -1988-95 (middle)
- P3- 1996-2003 (right)
- Courtesy P. Arkin

- Fig 4 Mean Differences
-  P1 minus P2 left-middle
-  P2minus P3 rt-middle
-  P1 minus P3 bottom
- Courtesy P. Arkin

**Notes:**
This is candidate Fig 3 for the paper

## Fig. 3a, Mean precipitation for P1 (1979-86) – Includes a Major ENSO 

- Fig. 3a, Mean precipitation for P1 (1979-86) – Includes a Major ENSO
- Warm episode but no microwave estimates.   (Courtesy P. Arkin)

## Fig. 3b, Mean precipitation for P2 (1988-95) – no major ENSO warm

- Episodes, includes microwave estimates. (Courtesy P. Arkin)

## Fig 4a P1 minus P2 8 year mean GPCP precipitation.  (Courtesy P. Arkin)

**Notes:**
Candidate Fig 4a for the paper.  Areas in the orange through pink tones are those for which precipitation was greater in the 79-86 period and regions in the yellow through greens are  regions where the precipitation was larger in the later period. In general, the largest differences occur in the tropics. Elsewhere the differences tend to be less than 0.5 mm/day. The West Coast of the United States is a notable exception.

## Fig. 3c, Mean precipitation for P3 (1996-2003) –  Major ENSO warm

- Episode, includes microwave estimates.  (Courtesy P. Arkin)

## Fig. 4b  P2 minus P3 eight year periods. Highlights ENSO-No ENSO 

- Fig. 4b  P2 minus P3 eight year periods. Highlights ENSO-No ENSO

**Notes:**
Candidate figure 4b for the paper.  Again the bulk of the differences in the precipitation patterns are consistent with existence of a strong ENSO episode in one 8-year period, 1996 – 2003 in this instance.  The larger magnitudes in the differences in the tropics compared to the differences between the first and second 8-year period may reflect the relative strength of the 1997/98 ENSO relative to the 1982/83 episode. High latitude differences in precipitation are generally larger in magnitude than in the comparisons between the first two 8-year periods. Since both of these later periods include the same satellite data inputs these differences likely reflect climate variability in addition to ENSO. 

## Fig 4c  P1 minus P3. Shows the differences in strengths between the  1982/83 and 

- Fig 4c  P1 minus P3. Shows the differences in strengths between the  1982/83 and
- 1997/98 ENSOs and due to the addition of microwave estimates. (Courtesy P. Arkin)

**Notes:**
Candidate Fig 4c if we decide to use it.  I don’t think it that much to the discussion but we could include it just for completeness.  Alternatively we could include this figure (now or later) and refer to any detailed differences in the context of differences between ENSO in the both periods.  We could also use it in comparison to the trends in Beck et al but I wouldn’t recommend it...unless that’s the point we want to make wrt to trend analyses with these data.

## Fig.7 Seasonal mean precipitation (mm/day) for a) DJF, b) MAM, c) JJA and

- d) SON.  Courtesy P. Arkin

## Fig. 8 Standard deviations

## P estimated at 2.61 mm/day

**P **estimated at 2.61 mm/day
- Yearly Standard Deviation 0.03mm/day

- Time series of GPCP annual mean global precipitation 1979-2003

- See Allen, M.R. and W. J. Ingram, 2002: Constraints on future changes in climate and the Hydrologic cycle. *Nature*, **419**, 224-232

## Figure 9.  (a) Global averages of monthly precipitation (mm day-1)

- Figure 9.  (a) Global averages of monthly precipitation (mm day-1)
-  for ocean, total, and land . From Adler et al. 2003.

## Fig. 9b) Tropical (30oN-30oS) averages of monthly precipitation 

- Fig. 9b) Tropical (30oN-30oS) averages of monthly precipitation
- anomalies (mm day-1) for (top) total, (middle) ocean, and (bottom) land.
- Vertical dashed lines indicate the months of significant volcanic
- eruptions. The thin black curves indicate the Niño-3.4 SST index (oC).
- After Adler et al 2003.

## Fig. 11. Time series of zonal mean precipitation anomaly. Vertical arrow 

- Fig. 11. Time series of zonal mean precipitation anomaly. Vertical arrow
- shows the approximate introduction of microwave data Courtesy P. Arkin

## Fig 10 Alternate. Zonal means for tropics only. 

- Fig 10 Alternate. Zonal means for tropics only.

## Fig 10.  Time series of zonally averaged GPCP estimates over land (left hand panels) and over the ocean (right hand panels).  Zonal averages are for 50N to 90N (a,e); 25N to 50N (b,f); 25S to 25N (c,g) and 50S to 25S (d,h). The introduction of microwave data in 1987 is evident for the data over land.

- a

- b

- c

- d

- e

- f

- g

- h

**Notes:**
Fig 10.  Time series of zonally averaged GPCP estimates over land (left hand panels) and over the ocean (right hand panels).  Zonal averages are for 50N to 90N (a,e); 25N to 50N (b,f); 25S to 25N (c,g) and 50S to 25S (d,h). The introduction of microwave data in 1987 is evident for the data over land.

## Fig 10a Linear trends in the zonally averaged GPCP estimated 

- _Zonal averages_ of 25-
- year linear trend show
- quite different trends in
- different lat. bands –
- again, note _regional _
- _coherence_.
- 25°S-25°N
- ~ .08  / 3.1 = ~ 2.5%
- 25°-50°N
- ~ -.12 / 2.4 = ~ -5.4%
- Land and Ocean are not
- uniformly related.

- Fig 10a Linear trends in the zonally averaged GPCP estimated
- precipitation. Huffman et al.

## Slide 30

**Notes:**
Fig. 11 Trends for various bands (Huffman et al.)

## Figure 12.  Map of linear changes in GPCP precipitation anomalies 

- Figure 12.  Map of linear changes in GPCP precipitation anomalies
- from January 1979 to December 2003.  The thin black contour outlines
- the local 1% significance level.  Courtesy Huffman, Curtis and Adler

## Fig 12 Spatial correlations between global trend maps computed for the 

- Fig 12 Spatial correlations between global trend maps computed for the
- 1979 to 2004 period and trends computed from successively fewer years.
- E.g., the spatial correlation at “lag” 1 is for the 1980 to 2004 period and
- so on. (from Smith et al., 2005).

## Fourth Rotated EOF of the GPCP Annual data for the period 1979 - 2004. This REOF accounts for 6% of the total variance.

- (**From Smith et al. 2005**)

## Summary:

-  The GPCP Data provide (relatively) consistent and complete
-    global precipitation estimates from (1979) 1988 to the present.
-  These data identify (illuminate) features of the large-scale
-    precipitation fields not (well) known before. E.g, oceanic
-    precipitation patterns, storm tracks, individual ENSO patterns.
-   Global precipitation shows no significant trends over the
-     period of record...however regional “trends” are evident
-     in the tropics.  These aren’t easily untangled from instrumental
-     differences and differences in ENSO in the 17 (25) yr record.
-  These are research data.  For real-time monitoring go to CAMS-OPI or other “operational” estimates (eventually go to CMORPH).