README document for AphroTemp_V1204R1 (Last updated 26 February, 2013) 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. In addition to precipitation product, daily temperature product are released on June 2012. Our new temperature product (AphroTemp_V1204R1) is developed by the APHRODITE project utilizing the collection of observed temperature data. This README interprets the structure of AphroTemp_V1204R1 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 daily mean temperature data over Monsoon Asia (APHRO_TAVE_MA_V1204R1). The gridded fields of daily mean temperature are defined by interpolating gauge observations obtained from meteorological stations throughout the region. The algorithm for the new product is made with a few modification on that of APHRO_V1101. We interpolate the subtraction of the daily mean temperature from the climatology at a resolution of 0.05 degrees, then add each gridded subtraction to 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 Yasutomi et al. (2011) and other related papers listed in section 7. An indicator is introduced to represent the reliability of the interpolated daily temperature 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. Please note that we found serious mistake in calculation of former version AphroTemp_V1204. Users please don't forget to replace V1204 with V1204R1. 2.2 Spatial and Temporal Coverage Spatial coverage : (MA) 60.0E - 150.0E, 15.0S - 55.0N Spatial resolution : 0.5 degree and 0.25 degree latitude/longitude Temporal coverage : January 1, 1961 - December 31, 2007 (47 years) Temporal resolution : Daily 2.3 Units Daily mean temperature : degC Ratio of 0.05 grid box containing station(s) : % 2.4 Missing Code Daily mean temperature : -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_MA_TAVE_YYYdeg_V1204R1.ZZZZ YYY : Resolution (050/025 for 0.5/0.25-degree grid) ZZZZ : The year in 4 digits (e.g. 1961, 1962, ..., 2007) 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 monsoon Asia. In the case of the 0.5-degree APHRO_MA_TAVE 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_TAVE_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. 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 AphroTemp_V1204R1 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_TAVE_MA_050deg_V1204R1.ctl). 5. Sample Fortran 90 Program A sample program written in Fortran 90 (read_aphro_v1204.f90) is available in the same directory as for the corresponding gridded data. Note that the little-endian byte order is assumed in this program. 6. References 6.1 How to cite AphroTemp_V1204R1 We have published a paper that presents our algorithm for AphroTemp_V1204R1. Should you refer to our product in your paper/presentation, please cite Yasutomi et al. (2011). Yasutomi, N., A. Hamada and A. Yatagai (2011): Development of a long-term daily gridded temperature dataset and its application to rain/snow descrimination of daily precipitation, Global Environmental Research, V15N2, 165-172. 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 related products The following are references of the related versions. 1) Yatagai, A., K. Kamiguchi, O. Arakawa, A. Hamada, N. Yasutomi and A. Kitoh (2012): APHRODITE: Constructing a Long-term Daily Gridded Precipitation Dataset for Asia based on a Dense Network of Rain Gauges, Bulletin of American Meteorological Society, doi:10.1175/BAMS-D-11-00122.1. 2) Yasutomi, N., A. Hamada and A. Yatagai (2011): Development of a long-term daily gridded temperature dataset and its application to rain/snow descrimination of daily precipitation, Global Environmental Research, V15N2, 165-172. 3) Hamada, A., O. Arakawa and A. Yatagai, 2011: An automated quality control method for daily rain-gauge data. Global Environmental Research, V15N2, pp183-192. 7. Points of concern 1) Seasonal variation of observations Total Number of observations is smaller in wintertime. That is because some stations under severe climate are closed in winter. Users should take care when they analyze data in mountaineous regions, for example. Users can check the distribution of valid station observation for each day by referring to the indicator RSTN. 2) Lack of observation data (in India, Indonesia and Papua New Guinea) APHRODITE project has not collected temperature data in India while many precipitation data has been collected. Input of daily temperature observation in India is dependent on GTS data. Therefore, most grid data of Indian subcontinent are missing until 1972. Input of daily observations over Indonesia and Papua New Guinea are also lacked. A considerable number of temperature grids over New Guinea Island are missing until 1980's. Distribution of valid station observation is provided (RSTN) for each day. Users please pay attention to the density of observations. 3) Homogenization of observation We do not homogenize the observed time series of temperature data. Changes in gauges, location of the stations, and many other factors might cause discontinuity of observation data. 4) Improvement in calculation after Yasutomi et al.(2011) Anomaly interpolation method is introduced after publish of Yasutomi et al. (2011). Climatological mean temperature is based on WorldClim (Hijmans et al., 2005; http://www.worldclim.org/). First, we derive anomaly from climatology, next, anomalies are interpolated into 0.05 degree grid. Then summed up to climatology and regridded into 0.25 degree and 0.50 degree grid. 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 (Contact) Dr. Natsuko Yasutomi Research Institute for Humanity and Nature 457-4 Kamigamo-Motoyama, Kita-ku, Kyoto 603-8047, Japan Tel : +81-75-707-2412 (direct) Fax : +81-75-707-2506 Principal Investigator Dr. Akiyo Yatagai Kyoto University (present affiliation)