Scientific Objectives

  • Develop long-term daily grid precipitation datasets from rain-gauge observation records over Asia.
  • Refine algorithms in collaboration with climate modelers and data users so that our products are useful to various environmental sciences.
  • Improve the quantification of orographic precipitation by combining rain-gauge data, remotely sensed data, and geographic information.
  • Add a rain/snow flag to the APHRODITE precipitation product.
  • Develop a daily temperature dataset from in-situ observation records over Asia.
  • Validate precipitation and its characteristics (e.g., extreme events) simulated using APHRODITE.
  • Assess statistics of the APHRODITE datasets and interpolation methods.

Our Achievements

  • We developed and released daily precipitation data on a 0.25/0.5-degree grid for Asia (APHRO_MA/ME/RU_V1003R1) for the period 1951?2007. They are the only long-term continental-scale daily grid precipitation data for Asia and include data from many rain-gauge stations. ⇒ Advantage of the APHRODITE product
  • We developed and released daily precipitation data on a 0.05-degree grid for Japan (APHRO_JP_V1003R1) for the period 1901?2008. A version that uses constant input data was also released, and this “Japan analysis” is used to study the long-term change of extreme events.
  • We wrote five peer-reviewed papers that presented the algorithm of our products, and 12 other peer-reviewed papers on application studies.
  • We give feedback to data providers by providing a 0.05-degree version of the dataset of each country/domain and we held a training seminar. We have received feedback from users through our website and an international session of the Japan Geophysical Union meeting held in May 2010.
  • Advantage of the APHRODITE product and application studies
    APHRODITE’s daily gridded precipitation is the only long-term (1951 onward) continental-scale daily product that contains a dense network of daily rain-gauge data for Asia including the Himalayas, South and Southeast Asia and mountainous areas in the Middle East. Our number of valid stations was between 5000 and 12,000, representing 2.3 to 4.5 times the data available through the Global Telecommunication System network, which were used for most daily grid precipitation products. The product contributes to studies such as the diagnosis of climate changes, evaluation of Asian water resources, statistical downscaling, forecast improvements, and verification of numerical model simulation and satellite precipitation estimates. The data are available free of charge and are easy for GrADS and netCDF users to handle. We attach information of the density of station data on each grid for each day with the daily precipitation product, so that users know whether a grid box is close to an observation point or has an interpolated value. Therefore, APHRODITE precipitation data can be used as a benchmark for various estimations of gridded precipitation.

Background and History

The quantitative estimation of precipitation and thus the development of a gridded precipitation product are crucial for many scientific studies. Thus, many methods of interpolating station data have been developed in the last century, and considerable efforts have been made to derive precipitation information from satellites over the last two decades.

However, precipitation datasets that were available in the early 2000s do not meet the demands for validating high-resolution climate model outputs and those for statistical downscaling since rain-gauge-based products have a monthly time interval and satellite-derived products have a short time series. Lack of a rain-gauge-based daily product was a bottleneck for many studies on the impact of climate change on local environments.

Hence, to drive hydrologic models over the Yellow River basins and assess natural as well as human-induced impacts on the runoff of the Yellow River, a rain-gauge-based daily precipitation dataset (Xie et al., 2007; EA_V0409) was constructed. Since this kind of rain-gauge-based product was found to be beneficial in validating super-high-resolution climate model simulations (Yatagai et al., 2005) and since a similar product for the East Mediterranean was expected, a feasibility study (FS) “Development of daily grid precipitation dataset for assessing the impact of global warming on the hydrological resources over arid regions” supported by the Ministry of the Environment in Japan was carried out at RIHN from May 2005 to March 2006.

A proposal to carry out work similar to that in FS for the whole of Asia (for three years at a cost of 40,000,000 yen/year) was approved in February 2006. This work is the APHRODITE project. From the start of the APHRODITE project (May 2006), experts in climate models and analyses of MRI/JMA collaborated with climatologists/hydrologists at RIHN. Therefore, our algorithm was basically constructed for hydrological application over land areas, and our first main task was to collect as many rain-gauge observation data as possible.

Meanwhile, the Fourth Assessment Report of the IPCC (2007) stated that the assessment of “extreme events” in relation to climate change is an increasing concern. Hence, we refined the algorithm and tremendous efforts were made to check the quality of the original data. As the results of our first three years of work, we released APHRO_PR_V0804 and APHRO_PR_V0902. These products have been used to validate and modify satellite products and hydrological studies as well as climatological studies.

The APHRODITE project was highly regarded in an interim evaluation in 2007 and 2008 and received the go-ahead for a two-year continuation (second term of the project) for April 2009 to March 2011. During the second term, we enhanced communication with data users and international organizations/projects and addressed new objectives. To contribute to satellite retrievals and the hydrological analysis of cold regions and, we will create a temperature grid product and add a rain/snow flag to the precipitation product.

Project Schedule

  • Feasibility Study: May 2005?March 2006
  • APHRODITE first term: May 2006?March 2009
  • APHRODITE second term: April 2009?March 2011