Asian Monsoon

Gridded Precipitation Data of the Asian Region

Integration and Analysis: Outline of the Gridded precipitation data of the Asian region

This is a gridded precipitation data set of the Asian region, for the period 1997 - 2002, based on the daily values of precipitation observed by ground-based raingauges.

Gridded data sets of precipitation of the world have been already produced at institutions in Europe and in America. But, since their main data sources of ground-based raingauge observations are archives of telecommunications between national meteorological agencies, failure of data communication from Asia to Europe and America often result in inferior quality of their products with respect to Asian region, in spite of regular observations conducted by Asian countries.

In the present product, observational data provided by operational meteorological and hydrological agencies of Asian countries "GAME" (GEWEX Asian Monsoon Experiment) are utilized. Those data were provided in the framework of an international scientific research initiative in which our members participated. Accordingly this product represents geographical distribution of precipitation better than previously available global products.

Note, however, that the method used for producing gridded data is two-dimensional spatial interpolation from the locations of observing stations to the grid points. Effects of topography are represented just as far as the stations represent them, and precipitation at high mountains is not well represented. Also it is known that observations by raingauges have systematic errors, in particular, that they tend to undercatch snowfall, but we have not incorporate corrections to compensate for the biases.

In our product, we take those grid boxes over the oceans and those grid boxes which are far from any observing stations to be void of data.

The production of this data set is also a part of MAHASRI (Monsoon Asian Hydro-Atmosphere Scientific Research and Prediction Initiative) which has evolved from the legacy of GAME.

Products

Gridded precipitation data of the Asian region

This is a gridded data set of precipitation made from station precipitation included in the GAME Phase 2 Collected Data, by first summing up for each month at each station and then interpolating spatially.

As the algorithm for interpolation, "Spheremap" of Willmott et al. (1985) is used. This is originally the two-dimensional spatial interpolation algorithm by Shepard (1968) which is a kind of weighted average method, but modified to work with the spherical coordinates. The algorithm is also used by Global Precipitation Data Centre (located in the German Weather Bureau) in production of their gridded data set of precipitation.

Precipitation interpolated from stations

Seasonal Cycle of Precipitation in Continental
Southeast Asia

We have not taken account of topographical effects, nor systematic errors of raingauges.

In our product, we take those grid boxes over the oceans and those grid boxes which are far from any observing stations to be void of data. (The threshold distance is predetermined by subjective decision of the analyst.)

The current Version 1.1 has basically the same specification as the Version 1 which was released previously, but it has incorporated a few modifications in the details of the production algorithm.

In the next step (version 2), we are going to include available data sets other than GAME Phase 2 as well, and make a gridded data set by similar interpolation.

Name of data set Gridded data of precipitation in Asia (version 1)
Data format ASCII, gridpoint
Organization of data one file for one month
Coordinates longitude and latitude
Spatial extent 60 - 145 deg. E, 5 deg. S - 50 deg. N.
Grid boxes of land only.
Spatial resolution 1 degree longitude and latitude. (A value exists for a box surrounded by lines of integer values of longitude and latitude.)
Time period January 1997 to December 2002
Time resolution 1 month
Size of data approximately 10 MB

References of the algorithm for interpolation

  • Shepard, D. 1968. A two-dimensional interpolation function for irregularly-spaced data. Proceedings, 1968 ACM National Conference, 517 - 524.
  • Willmott, C.J., Rowe, C.M. and Philpot, W.D. 1985. Small-scale climate maps: a sensitivity analysis of some common assumptions associated with grid-point interpolation and contouring. The American Cartographer, 12, 5-16.

Reference web sites

Source dataset

GAME Phase 2 Collected Data

GAME (GEWEX Asian Monsoon Experiment) was an international collaborative research project conducted from Japanese Fiscal Years 1996 to 2004 as a part of GEWEX (Global Energy and Water Cycle Experiment) of WCRP (World Climate Research Program).

As an item of the Phase 2 (JFY 2002 - 2004) of GAME, meteorological data for the 6-year period from 1997 to 2002 was collected through collaboration of operational meteorological agencies of Asian countries (including Japan Meteorological Agency). This collection of data includes daily values of precipitation observed by raingauges at approximately 1000 stations.
 
Name of data set GAME Phase 2 Collected Data (part of precipitation)
Data format ASCII
Organization of data Each file contains a record of a station in a year. Such files are gathered in archive files with respect to agencies that provided the data.
Coordinate system latitude and longitude of stations
Spatial extent Countries in East, Southeast and South Asia
(Bangladesh, Cambodia, China (mainland, Taiwan), Japan, Korea (south), Laos, Malaysia, Myanmar, Nepal, Philippines, Singapore, Thailand, Vietnam)
Number of stations approximately 1000 stations
Time period 1 January 1997 to 31 December 2002
Time resolution 1 day
Size of data approximately 17 MB as archive files
 

Reference web sites