README document for APHRO_V1101 (Last updated 27 December, 2012) 1. Introduction A suite of precipitation products is being constructed by the Asian Precipitation -- Highly-Resolved Observational Data Integration Towards Evaluation of the Water Resources (APHRODITE's water resources) project in collaboration with the Research Institute for Humanity and Nature and the Meteorological Research Institute of the Japan Meteorological Agency. After releasing our last product, APHRO_V1003R1, in July 2010, we have made continuous efforts to collect more data and improve quality control and analysis method. We now release APHRO_V1101, which includes more rain-gauge data and data region is changed for the Middle East product according to the distribution of input gauge data. This README interprets the structure of APHRO_V1101 data files (sections 2-5), explains changes from the previous versions (section 6), and gives relevant references (section 7). 2. General Information 2.1 Products The products we release are 0.5x0.5-degree and 0.25x0.25-degree gridded data over Monsoon Asia (APHRO_MA_V1101), the Middle East (APHRO_ME_V1101), and Russia/Northern Eurasia (APHRO_RU_V1101). The gridded fields of daily precipitation are defined by interpolating rain-gauge observations obtained from meteorological and hydrological stations throughout the region. We use new daily precipitation climatology and interpolate the ratio of the daily precipitation to the climatology at a resolution of 0.05 degrees, then multiplied each gridded ratio by each gridded climatology value day-by-day. We then re-gridded the 0.05-degree analysis to both 0.5-degree and 0.25-degree grids. Details are given in a paper by Yatagai et al. (2009, 2012) and other related papers listed in section 7. An indicator is introduced to represent the reliability of the interpolated daily precipitation fields. This indicator, named RSTN, was calculated for each re-gridded 0.50-degree (0.25-degree) cell, by calculating the proportion of 0.05-degree cell(s) containing station(s). The number of input data differs from year to year. Users, interested in long-term changes should consider this variable. 2.2 Spatial and Temporal Coverage Spatial coverage : (MA) 60.0E - 150.0E, 15.0S - 55.0N : (ME) 20.0E - 65.0E, 15.0N - 45.0N : (RU) 15.0E - 165.0W, 34.0N - 84.0N Spatial resolution : 0.5 degree and 0.25 degree latitude/longitude Temporal coverage : January 1, 1951 - December 31, 2007 (57 years) Temporal resolution : Daily 2.3 Units Precipitation : mm/day Ratio of 0.05 grid box containing station(s) : % 2.4 Missing Code Precipitation : -99.9 Ratio of 0.05 grid box containing station(s) : -99.9 3. Data Files and Their Structure The product is stored in one file per year. 3.1 Denotation APHRO_XX_YYYdeg_V1101.ZZZZ XX : Region (MA/ME/RU for Monsoon Asia/Middle East/Russia) YYY : Resolution (050/025 for 0.5/0.25-degree grid) ZZZZ : The year in 4 digits (e.g. 1951, 1952, ..., 2007) For the file in NetCDF format, filename ends with the suffix ".nc." 3.2 Structure of Data Files Each file contains daily fields for 365 (366 for leap years) days. These daily fields are arranged according to the Julian calendar. Daily fields (data arrays) contain information on the precipitation amount and ratio of 0.05-degree cells containing a rain gauge. In the case of a 0.5-degree grid file, each field consists of a data array with longitude by latitude dimensions of 180 x 140 elements for APHRO_MA, 90 x 60 elements for APHRO_ME, 360 x 100 elements for APHRO_RU. In the case of the 0.5-degree APHRO_MA product, the first element is a cell at the southwest corner centered at [60.25E, 14.75S], the second is a cell at [60.75E, 14.75S], ..., the 180th is a cell at [149.75E, 14.75S], and the 181st is a cell at [60.25E, 14.25S]. [Note for plain binary format] The data files are written in PLAIN DIRECT ACCESS BINARY. In each daily field, the array for precipitation comes first, followed by information on the rain gauge. Each element (both precipitation and rain gauge information) is written as a 4-byte floating-point number in little endian byte order. Users should swap the byte order to big endian if necessary. There are no 'space', 'end of record', or 'end of file' marks in between. In the case of the 0.5-degree APHRO_MA product, the size of a file (0.5-degree grid) is 4 bytes x 180 x 140 x 2 fields x 365 days = 73,584,000 bytes for a non-leap year, or 73,785,600 bytes for a leap year. 4. How to handle the dataset 4.1 Sample of GrADS Control Files Each data file needs a *.ctl file to be handled by the GrADS software (http://www.iges.org/grads/). Control files for APHRO_V1101 are available in the same directory as for the corresponding gridded data. After saving the control file in the same location as the downloaded data, open this file after the "ga" prompt (e.g., ga-> open APHRO_MA_050deg_V1101.ctl). 4.2 Sample Fortran 90 Program A sample program written in Fortran 90 (read_aphro_v1101.f90) is available in the directory /V1101. Note that the little-endian byte order is assumed in this program. 4.3 NetCDF files We provide NetCDF files for each year. They are stored in /V1101/nc with suffix ".nc". Matlab, ArcGIS and many applications can handle NetCDF. 5. Differences with Previous Products 5.1 Basic Algorithm of APHRO_V1101 The APHRO_V1101 product uses an algorithm similar to that presented by Yatagai et al. (2009, 2012), on the basis of V1003R1. The interpolation algorithm is based on a modified version of the distance-weighting interpolation method (Shepard, 1968) in which the sphericity and orography are considered using Spheremap (Willmott et al., 1985) and the Mountain Mapper method (Schaake et al., 2004). The algorithm is improved in that the weighting function considers the local topography between the rain-gauge and interpolated point. In the current version (V1101), we develop our daily climatology with 1) A series of monthly and daily rain-gauge data that have a period of 5 years or more, and 2) WorldClim (Hijmans et al., 2005; http://www.worldclim.org/). 5.2 Differences between APHRO_V1101 and APHRO_V1003R1 We improved our quality control method. In addition, V1101 has the following advantages. 1. Changed areas in ME that cover Saudi Arabia and reduce African region, 2. More input data or updates of off-line data recorded in Belarus, Bhutan, Saudi Arabia, Taiwan, and Thailand. 5.3 Differences between APHRO_V1101 and APHRO_V0804 and EA_V0409 We used the same algorithm/scheme for the three domains (MA, ME and RU), when developing V0902, V1003R1 and V1101. Hence, although the following advantages may extend to the previous versions, the latter versions are better in terms of the inclusion of number of input data. Optimum interpolation is applied for daily analysis. Station data with valid reports (more than 90% for 1978-2003) are used, since the product is designed for assessing the interannual variation of hydrological resources in China (e.g., Yellow River run-off). Daily climatology (EA_clim) is obtained by Parameter-Elevation Regressions on Independent Slopes Model (PRISM) for China and Mongolia to correct the bias due to orographic effects. The daily climatology adopted in EA_V0409 is also used in APHRO_MA_V0804. Compared with EA_V0409, APHRO_MA_V0804 uses more data outside China. Among the daily and sub-daily precipitation data for the former USSR (NCDC 9813 dataset), we use data with homogenized wetting bias and rain-gauge changes employing the technique developed by Groisman and Rankova (2001). The following table summarizes the coverage and major characteristics of each version. The reference number in the table corresponds to that listed in section 7. For reference, we list APHRO_JP, which was also developed as a part of APHRODITE's activity and only covers Japan. Details of APHRO_JP were described by Kamiguchi et al. (2010, 2011) and the product's README. ----------------------------------------------------------------------------- Name | Domain | Period |Reference| Characteristics ----------------------------------------------------------------------------- EA_0409 EA | 65-155E, 5-60N | 1978-2003 | 1 | PRISM climatology,constant input ----------------------------------------------------------------------------- APHRO_V0804 EA | 65-155E, 5-60N | 1980-2002 |2,3| PRISM climatology ME | 25-60E, 25-45N | 1979-2001 | 4 | RU | 20-160E, 40-75N | 1980-2002 | 5 | Groisman and Rankova (2001) data ----------------------------------------------------------------------------- APHRO_V0902 MA | 60-150E, 0-55N | 1961-2004 | 6 | A consistent algorithm described ME | 15-65E, 25-45N | 1961-2004 | 6 | in Yatagai et al.(2009) is used RU | 15E-165W,34-84N | 1961-2004 | 6 | for the three domains. ----------------------------------------------------------------------------- APHRO_V1003R1 MA | 60-150E,15S-55N | 1951-2007 | * | Covers Indonesia, QC improved ME | 15-65E, 25-45N | 1951-2007 | * | QC improved RU | 15E-165W,34-84N | 1951-2007 | * | More inputs, QC improved ----------------------------------------------------------------------------- APHRO_V1101 MA | 60-150E,15S-55N | 1951-2007 |8,9| More inputs, QC improved ME | 20-65E, 15-45N | 1951-2007 |8,9| Covers Saudi Arabia, QC improved RU | 15E-165W,34-84N | 1951-2007 |8,9| More inputs, QC improved ----------------------------------------------------------------------------- APHRO_JP_V1207 |123-146E, 24-46N | 1900-2011 |7,10| 0.05deg./long-term over Japan ------------------------------------------------------------------------------- * see below (section 7.1) 6. References 6.1 How to cite APHRO_V1101 Should you refer to our product in your paper/presentation, please cite Yatagai et al. (2012). Yatagai, A., K. Kamiguchi, O. Arakawa, A. Hamada, N. Yasutomi and A. Kitoh, 2012: APHRODITE: constracting a long-term daukt gridded precipitation dataset for Asia based on a dense network of rain gauges, BAMS, doi:10.1175/BAMS-D-11-00122.1 Details on quality control method of our product is described in Hamada et al.(2011) Hamada, A., O. Arakawa and A. Yatagai, 2011: An automated quality control method for daily rain-gauge data. Global Environmental Research, V15N2, pp183-192. When you write/publish papers, please access the "Research Activities" page of our website (http://www.chikyu.ac.jp/precip/research/index.html) to obtain the latest information on our reference papers that present our algorithms and products. 6.2 Reference for the previous and related products As explained in section 6.2, there is no advantage in using V1003R1. However, as explained in section 6.3, APHRO_V0804 (MA, RU) or EA_V0409 may still be useful depending on the users' purposes. The following are references of the previous/related versions. 1. Xie, P., A. Yatagai, M. Chen, T. Hayasaka, Y. Fukushima, C. Liu, and S. Yang, 2007: A Gauge-Based Analysis of Daily Precipitation over East Asia, J. Hydrometeor., 8, 607-627. 2. Yatagai, A., P. Xie, P, 2006: Utilization of a rain-gauge-based daily precipitation dataset over Asia for validation of precipitation derived from TRMM/PR and JRA-25. SPIE 0604-53, doi:10.1117/12.723829. 3. Yatagai, A., P. Xie, and A. Kitoh, 2005: Utilization of a new gauge-based daily precipitation dataset over monsoon Asia for validation of the daily precipitation climatology simulated by the MRI/JMA 20-km-mesh AGCM, SOLA, 1, 193-196, DOI:10.2151/sola.2005-050. 4. Yatagai, A., P. Xie and P. Alpert, 2008: Development of a daily gridded precipitation data set for the Middle East, Adv. in Geosci., 12, 165-170. 5. Takashima, H., A. Yatagai, H. Kawamoto, O. Arakawa, and K. Kamiguchi, 2009: Hydrological balance over northern Eurasia from gauge-based high-resolution daily precipitation data, M. Taniguchi (eds), From Headwaters to the Ocean: Hydrological Change and Watershed Management, Talor & Francis, 137-141. 6. Yatagai, A., O. Arakawa, K. Kamiguchi, H. Kawamoto, M. I. Nodzu, and A. Hamada, 2009: A 44-year daily gridded precipitation dataset for Asia based on a dense network of rain gauges, SOLA, 5, 137-140, doi:10.2151/sola.2009-035. 7. Kamiguchi, K., O. Arakawa, A. Kitoh, A. Yatagai, A. Hamada, and N. Yasutomi, 2010: Development of APHRO_JP, the first Japanese high-resolution daily precipitation product for more than 100 years, Hydrological Research Letters, 4, 60-64. 8. Yatagai, A., K. Kamiguchi, O. Arakawa, A. Hamada, N. Yasutomi and A. Kitoh, 2012: APHRODITE: constracting a long-term daukt gridded precipitation dataset for Asia based on a dense network of rain gauges, BAMS, doi:10.1175/BAMS-D-11-00122.1 9. Hamada, A., O. Arakawa and A. Yatagai, 2011: An automated quality control method for daily rain-gauge data. Global Environmental Research, V15N2, pp183-192. 10. Kamiguchi, K., O. Arakawa, and A. Kitoh, 2011: Long-term Changes in Japanese Extreme Precipitation Analyzed with APHRO_JP_EX, Global Environmental Research, V15N2, 91-99. 8. Contacts Please contact APHRODITE project (led by Dr. Akiyo Yatagai of RIHN) for further questions regarding this product. APHRODITE's Water Resources project aphrodite.precinfo@gmail.com http://www.chikyu.ac.jp/precip/index.html Research Institute for Humanity and Nature 457-4 Kamigamo-Motoyama, Kita-ku, Kyoto 603-8047, Japan Dr. Akiyo Yatagai (present affiliation) Research Institute for Sustainable Humanosphere (RISH) Kyoto University