Abstract
The new Version 2.3 of the GPCP Monthly analysis is described in terms of changes made to improve the homogeneity of the product, especially after 2002. These changes include corrections to cross calibration of satellite data inputs and updates to the gauge analysis. Over ocean, changes starting in 2003 result in an overall precipitation increase of 1.8% after 2009. Updating the gauge analysis to its final, high quality version increases the global land total by 1.8% for the post-2002 period. These changes correct a small, incorrect dip in the estimated global precipitation over the last decade in the earlier Version 2.2. The GPCP analysis is also used to describe global precipitation for 2017. The general La Nina pattern for 2017 is noted and the evolution from the early 2016 El Nino pattern is described. The 2017 global value is one of the highest for the 19792017 period, exceeded only by 2016 and 1998 (both El Nino years) and reinforces the small positive trend. Results for 2017 also reinforce significant trends in precipitation intensity (on a monthly scale) in the tropics. These results for 2017 indicate the value of the GPCP analysis for climate monitoring in addition to research.
Highlights
The Global Precipitation Climatology Project (GPCP) has been in existence for over twenty years as part of the Global Energy and Water Cycle Exchanges (GEWEX) activity under the World ClimateResearch Program (WCRP)
The GPCP Monthly product is widely used in the scientific community for analysis of regional and global precipitation climatologies and climate-scale variations and trends during the satellite era
The objective of this paper is to describe the improvements that have been made in the new Version 2.3 of the GPCP Monthly product and the impact of these changes compared to the previous version (Version 2.2)
Summary
The Global Precipitation Climatology Project (GPCP) has been in existence for over twenty years as part of the Global Energy and Water Cycle Exchanges (GEWEX) activity under the World Climate. The false decrease in global precipitation in V2.2 noted after ~2005 (Figure 1a) essentially disappears in V2.3 after the improvements and new data sets are incorporated All these changes in magnitude are well within the bias error estimates for the GPCP climatology [15]. These variations are related to changes made in the weighting in the transition from SSMI/SSMIS-based estimates to AIRS-based estimates as a function of latitude above 40◦ latitude. V2.3 is given in [16], along with a summary of the comparisons with the recent precipitation estimates from the Tropical Rainfall Measuring Mission (TRMM) and CloudSat
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