CPC Unified Gauge – Satellite Merged CPC Unified Gauge – Satellite Merged Precipitation Analysis Precipitation Analysis

for Improved Monitoring and Assessments for Improved Monitoring and Assessments of Global Climate of Global Climate

Pingping Xie, Pingping Xie, Soo-Hyun Yoo, Robert Joyce, and Yelena YaroshSoo-Hyun Yoo, Robert Joyce, and Yelena Yarosh

2009.10.29.2009.10.29.

CPC’s Unified Precipitation ProjectCPC’s Unified Precipitation Project

• Multiple precipitation analyses generated at CPC over the past ~20 years to satisfy various requirements

• Inconsistencies due to different input data and analysis procedures used

• A project is underway at CPC• To create a single suite of unified precipitation

products for global / regional applications;• To increase the accuracy, reliability and quantitative

consistency of the new products.

Components of the Unified ProductsComponents of the Unified Products

• Station reports

• Unified, quality controlled

• Satellite estimates

• Multiple satellites / multiple instruments / integrated

• Analyses

• Gauge-based; gauge-satellite merged

• Global / Regional ;

Gauge Analysis of Global Daily PrecipitationGauge Analysis of Global Daily Precipitation

• Interpolation of gauge reports from ~30K stations• Optimal Interpolation (OI) with orographic correction (Xie et al. 2007)• Interpolated on 0.125olat/lon, then averaged on 0.5olat/lon grid over

global land for release

• Global fields from1979 to present updated daily on a real-time basis• CONUS analysis

from 1948 on 0.25olat/lon

• Example for July 1, 2003

High-Resolution Satellite EstimatesHigh-Resolution Satellite Estimates

CMORPH : CPC Morphing technique (Joyce et al. 2004) Combined use of satellite PMW and IR data 8kmx8km / 60oS-60oN; 30-min interval / from September 2000 / Real-time Project on the way to back-extend the CMORPH to 1998 Sample for August 18, 2003

Merging Gauge and Satellite Data [ 1 ]Merging Gauge and Satellite Data [ 1 ]

• Combining the strength of gauge and satellite data to produce a merged analysis with improved quality

• Gauge: accurate point measurements but sparse distribution

• Satellite: complete coverage but with bias and random error

• Bias-corrected Satellite Estimates over the Globe

– Correcting the bias and discontinuities in the CMORPH estimates

• over land – through matching the PDF of CMORPH against that of the gauge-

based analysis• Over ocean

– Adjusting the CMORPH to a long-term data set (pentad GPCP) to facilitate the definition of anomaly

Merging Gauge and Satellite Data [ 2 ]Merging Gauge and Satellite Data [ 2 ]

• Sample bias-corrected Satellite Estimates

Merging Gauge and satellite data [3]Merging Gauge and satellite data [3]

Comparison of satellite estimates with gauge data for Apr. – Sep., 2009

Bias is corrected almost completely over the global land;

Correlation for daily precipitation over 0.25olat/lon grid boxes is improved by ~0.05

Daily Gauge

CMORPH

Gauge-Adjusted CMORPH

Merging Gauge and Satellite Data [ 4 ]Merging Gauge and Satellite Data [ 4 ]

• July 2005 Monthly Mean Precip at T382

Merging Gauge and Satellite Data [ 5 ]Merging Gauge and Satellite Data [ 5 ]• July 2005 Diurnal Standard Deviation of Hourly Precip.

Merging Gauge and Satellite Data [6]Merging Gauge and Satellite Data [6]

• Combining Bias-corrected Satellite Estimates with Daily gauge over the Several Regions

– This is only possible for several regions due to different daily ending time in the gauge reports

• Africa (06Z)• CONUS/MEX (12Z)• S. America (12Z)• Australia (00Z)• China (00Z)

– Combining the bias-corrected CMORPH with gauge observations through the Optimal Interpolation (OI) over selected regions where gauge observations have the same daily ending time

• in which the CMORPH and gauge data are used as the first guess and observations, respectively

Merging Gauge and Satellite Data [ 7 ] Merging Gauge and Satellite Data [ 7 ] Example over ChinaExample over China

Merging Gauge with Satellite Data [ 8 ] Merging Gauge with Satellite Data [ 8 ] Example over CONUSExample over CONUS

Merging Gauge with Satellite Data [ 89] Merging Gauge with Satellite Data [ 89] Example over AfricaExample over Africa

SummarySummary• Prototype algorithm is developed and test products are constructed for the gauge-satellite merged global precipitation analyses

• Two sets of gauge-satellite precipitation analyses • Bias-corrected Satellite Estimates

•Global •8kmx8km; 30-min •1998 to the present

• Gauge-satellite combined analyses •Regional •0.25olat/lon; daily •1998 to the present

• Unified gauge – satellite precipitation analyses useful for climate monitoring, model verifications, hydrological studies, et al.