README document for the APHRO_V1003 (Last updated 29 July, 2010) 1. Introduction A suite of precipitation products are being constructed by the Asian Precipitation - Highly-Resolved Observational Data Integration Towards Evaluation of the Water Resources (APHRODITE's water resources) project in collaboration of Research Institute for Humanity and Nature and Meteorological Research Institute of Japan Meteorological Agency. Since we released last product, APHRO_V0902 in May 2009, we have made continuous efforts to collect data and to improve quality control and the analysis method. Now we release a new version "APHRO_V1003", which includes more rain-gauge data and covers longer period: 1951-2007. This README interprets the structure of APHRO_V1003 data files (section 2-5), explains the differences from the previous versions (section 6), and designates relevant references (section 7). 2. General Information 2.1 The Products The products we release are 0.5x0.5 and 0.25x0.25 degree gridded data over Monsoon Asia (APHRO_MA_V1003), Middle East (APHRO_ME_V1003), and Russia (APHRO_RU_V1003). The gridded fields of daily precipitation are defined by interpolating rain-gauge observations obtained from meteorological and hydrological stations over the region. We used new daily precipitation climatology and interpolated the ratio of the daily precipitation to the climatology in 0.05 degree grid resolution, then multiply each gridded ratio by each gridded climatology value day by day. After that, we re-grid the 0.05 degree analysis to both 0.5 degree and 0.25 degree grids. Details are shown Yatagai et al.(2009) 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 at each re-gridded 0.50(0.25) degree grid box, by calculating the ratio of 0.05 degree grid(s) containing station(s) to 25(100) grids of 0.05 degree in that box. The number of input data differs from year to year. Users who are interested in the long-term change should be careful about this variable. 2.2 Spatial and Temporal Coverage Spatial coverage : (MA) 60.0E - 150.0E, 15.0S - 55.0N : (ME) 15.0E - 65.0E, 25.0N - 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_V1003.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 Every file contains daily fields for 365 (366 for leap years) days. These daily fields are arranged according to Julian calendar. Daily fields (data arrays) hold information on precipitation amount and ratio of 0.05 degree grid box containing rain gauge. In the case of 0.5 degree grid file, each field consists of a data array of 180 x 140 for APHRO_MA; 100 x 40 for APHRO_ME; 360 x 100 for APHRO_RU; elements in longitude and latitude. In the case of 0.5-degree of APHRO_MA, the first element is for a grid box at the southwest corner centered at [60.25E, 14.75S], the second at [60.75E, 14.75S], ..., the 180th at [149.75E, 14.75S], and the 181th 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 the information on rain gauge. Each element (both precipitation and rain gauge information) is written in 4-byte floating-point number in 'LITTLE ENDIAN' byte order. You should swap the byte order to big endian if necessary. There is no 'space', 'end of record', or 'end of file' marks in between. In the case of 0.5-degree of APHRO_MA, The size of a file (0.5-degree grid) is: 4 byte x 180 x 140 x 2 fields x 365 days = 73,584,000 bytes for a non-leap year, and 73,785,600 bytes for a leap year. 4. Sample of GrADS Control Files Each data file needs *.ctl file to handle with the GrADS software (http://www.iges.org/grads/). Control files for APHRO_V1003 are available at the same directory for the corresponding gridded data. After saving the control file at the same location as downloaded data, open this file after the "ga" prompt (e.g., ga-> open APHRO_MA_050deg_V1003.ctl). 5. Sample of Fortran 90 Program A sample program written in Fortran 90 (read_aphro_v1003.f90) is also available at the same directory for the corresponding gridded data. Note that the LITTLE-ENDIAN byte order is assumed in this program. 6. Difference from the previous products 6.1 Basic Algorithm of APHRO_V1003 The APHRO_V1003 took the similar algorithm defined in Yatagai et al. (2009). The interpolation algorithm is based on a modified version of distance- weighting interpolation method (Shepard,1968) in which the sphericity and orography are considered using Spheremap (Willmott et al., 1985) and Mountain Mapper method (Schaake et al., 2004). The algorithm for the new version (V1003) is further improved where the weighting function is revised by considering the local topography between the rain-gauge and interpolated point. In the current version (V1003), we developed our daily climatology with 1) monthly and daily rain-gauge data that have data for 5 years or more and 2) WorldClim (Hijmans et al., 2005; http://www.worldclim.org/). 6.2 Difference between APHRO_V1003 and APHRO_V0902 We fixed known bugs in V0902 and improved our QC method. Hence, replacement of V0902 with V1003 is highly recommended. In addition, V1003 has the following advantages. 1. longer period; 2. extended areas in MA that covers Indonesia; and 3. more input data or update of off-line data in the following countries (Bangladesh, Bhutan, Brunei, Cambodia, China, Indonesia, Israel, Kazakhstan, Malaysia, Nepal, Pakistan, Philippines, Thailand and Vietnam). 6.3 Difference of APHRO_V1003 from APHRO_V0804 and EA_V0409 We took a strategy to use the same algorithm/scheme for the three domains (MA, ME and RU), when we developed V0902 and V1003. Hence, the following advantages may remain in the previous versions, although the latter ones (V1003 and V0902) are better in terms of the number of input data. Optimum interpolation is applied for daily analysis. Station data of constantly reported(more than 90% for 1978-2003) are used, since it is designed for assessing the interannual variation of hydrological resources in China (e.g. Yellow River run-off). To make a daily climatology (EA_clim), it adopts the Parameter-Elevation Regressions on Independent Slopes Model (PRISM) for China and Mongolia to correct the bias caused by orographic effects. A daily climatology adopted in EA_V0409 is also used in APHRO_MA_V0804. Compared with EA_V0409, APHRO_MA_V0804 used more data outside China. Among the Daily and sub-daily precipitation for the former USSR (NCDC 9813 dataset), we used data homogenized wetting bias and rain-gauge changes by the technique developed by Groisman and Rankova (2001). The following table summarize the coverage and major characteristics of each version. The reference number in the table corresponds to that listed in section 7. For the reference, we list APHRO_JP in the table. It is also developed as a part of APHRODITE's activity, which only covers over Japan. Details of APHRO_JP is described in Kamiguchi et al. (2010) and its "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_V1003 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_JP_V1005 |123-146E, 24-46N | 1900-2009 | 7 | 0.05deg./long-term over Japan ------------------------------------------------------------------------------- * see below (section 7.1) 7. References 7.1 How to refer APHRO_V1003 At the moment, we have not published a reviewed paper which exactly shows our algorithm for APHRO_V1003. So far, when you refer our product in your paper/presentation, please refer the following paper (Yatagai et al.2009) which describes the previous version V0902. 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. The following is an example statement. We used APHRO_MA_V1003 which was fixed several bugs, applied advanced quality control (QC) and incorporated more data from APHRO_MA_V0902 (Yatagai et al., 2009). When you write/publish papers, please access the "Research Activities" page of our website (http://www.chikyu.ac.jp/precip/research/index.html), in order to know the latest information on our reference papers which show our algorithms and products. We will update the information when we submit a reference paper of version APHRO_V1003. 7.2 Reference for the previous and related products As explained in 6.2, there is no advantage in V0902. However, as explained in 6.3, APHRO_V0804 (MA, RU) or EA_V0409 may be still useful depending on the 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. Contacts Please contact APHRODITE project (led by Dr. Akiyo Yatagai of RIHN) for further questions regarding this product. APHRODITE's Water Resources project precinfo@chikyu.ac.jp http://www.chikyu.ac.jp/precip/index.html Dr. Akiyo Yatagai Research Institute for Humanity and Nature 457-4 Kamigamo-Motoyama, Kita-ku, Kyoto 603-8047, Japan Tel : +81-75-707-2204 (direct) Fax : +81-75-707-2506