29 February 2008 | Mingyue Chen, Wei Shi, Pingping Xie, Viviane B. S. Silva, Vernon E. Kousky, R. Wayne Higgins, and John E. Janowiak
This study evaluates three objective techniques for generating gauge-based daily precipitation analyses over global land areas: inverse-distance weighting algorithms of Cressman (1959) and Shepard (1968), and the optimal interpolation (OI) method of Gandin (1965). The analyses are based on quality-controlled daily precipitation reports from approximately 16,000 stations worldwide, collected from various data sources including the Global Telecommunication System (GTS) and the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center (CPC) unified daily gauge data sets. The study compares the performance of these techniques across different regions and network densities.
The OI method consistently performs the best among the three techniques, showing the highest correlation and close agreement with independent gauge observations in most situations. The Shepard method performs reasonably well compared to the OI, while the Cressman method tends to generate smoother precipitation fields with broader areas of precipitation relative to station observations. The quality of the gauge-based analyses degrades as the station network becomes sparser, although the OI technique exhibits relatively stable performance statistics over regions with fewer gauges.
The study concludes that the OI technique is the most reliable for generating daily precipitation analyses from gauge networks of various densities. It provides better correlation and smaller biases compared to the other two techniques, especially in regions with sparse gauge networks. The OI method is recommended for use in creating unified analyses of daily precipitation over global land areas, with applications in weather/climate monitoring, climate variability studies, and model verification. The analysis is created on a 0.5° lat/lon grid to represent area-averaged daily precipitation values over grid boxes. The study also highlights the importance of quality control in precipitation data and the need for further research to improve the accuracy of gauge-based analyses.This study evaluates three objective techniques for generating gauge-based daily precipitation analyses over global land areas: inverse-distance weighting algorithms of Cressman (1959) and Shepard (1968), and the optimal interpolation (OI) method of Gandin (1965). The analyses are based on quality-controlled daily precipitation reports from approximately 16,000 stations worldwide, collected from various data sources including the Global Telecommunication System (GTS) and the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center (CPC) unified daily gauge data sets. The study compares the performance of these techniques across different regions and network densities.
The OI method consistently performs the best among the three techniques, showing the highest correlation and close agreement with independent gauge observations in most situations. The Shepard method performs reasonably well compared to the OI, while the Cressman method tends to generate smoother precipitation fields with broader areas of precipitation relative to station observations. The quality of the gauge-based analyses degrades as the station network becomes sparser, although the OI technique exhibits relatively stable performance statistics over regions with fewer gauges.
The study concludes that the OI technique is the most reliable for generating daily precipitation analyses from gauge networks of various densities. It provides better correlation and smaller biases compared to the other two techniques, especially in regions with sparse gauge networks. The OI method is recommended for use in creating unified analyses of daily precipitation over global land areas, with applications in weather/climate monitoring, climate variability studies, and model verification. The analysis is created on a 0.5° lat/lon grid to represent area-averaged daily precipitation values over grid boxes. The study also highlights the importance of quality control in precipitation data and the need for further research to improve the accuracy of gauge-based analyses.