IOWA SOIL MOISTURE DATA Soil Moisture Observations, 1972-94 Alan Robock Department of Environmental Sciences Rutgers, The State University of New Jersey Jared Entin Hydrological Sciences Branch, NASA-GSFC Konstantin Vinnikov Department of Meteorology, University of Maryland Larry Kramer Mike Burkart USDA-ARS-National Soil Tilth Laboratory 1. DESCRIPTION OF THE DATA SET The Iowa data set for the period 1972-1994, consists of soil moisture observations from two different catchments (W2 & W3), located at 41.2°N, 95.6°W in the southwestern part of the state. The data set is described in detail by Entin (1998), and were used by Entin et al. (1999a) to evaluate the Global Soil Wetness Project soil moisture model calculations and by Entin et al. (1999b) to study the scales of soil moisture variations. Each catchment has three sites where soil moisture observations were taken. Observations are available for 12 soil layers extending to a depth of 2.6 m. Details of each layer along with the technique used, are given in Table 1. For the first catchment the top four layers were measured using the gravimetric technique, and a neutron probe was used for the layers beneath 45.7 cm. For the second catchment, the gravimetric method was used for the top five layers and a neutron probe for the lower layers. Soil moisture was recorded in percent wetness by weight. Soil density observations are only available for those layers that were monitored gravimetrically. For the other layers soil density was estimated from observations from similar layer depths using other columns in the region. The record of observations begins in 1972 and continues until 1994, giving 23 years of record. For the most part, observations were made only between April and October, on average twice a month. Although observations were not taken at any fixed day of a month, they were always taken on the same day at all the six sites. Time series data corresponding to each individual layer are available for downloading in both GrADS and ASCII formats. 2. DATA SETS IN ASCII FORMAT These data are archived in files Iowa.*.dat, where * is W2 or W3 corresponding to the two catchments. The numbers (1, 3, 4, 11, 14 and 16) together with W2 or W3 refer to observation points in the respective catchments. Following the header information, the data for the 12 levels (in inches) are written according to FORTRAN format format(i4,x,i2,x,i2,x,i3,x,i5,6x,i2,12(x,f5.1)). (Year, month, day, day of year, day of record, site code, data) A Fortran program reader.f, to read the data is also included in the directory containing the ASCII data. 3. GrADS FILES GrADS control and binary files consisting time series for Iowa can be also downloaded for visualization. These files are iowa.ctl and iowa.bdat and contain time-series for three stations in each of the two catchments. The variable names tr21, tr23, tr24, tr311, tr314, and tr316 correspond to the different catchments and locations. The z levels are the twelve soil layers for which the data are available. The layer thicknesses are in inches as in the ASCII data files and the soil moisture values are in percent weight. These files can be downloaded through anonymous ftp as follows: ftp climate.envsci.rutgers.edu login as: anonymous password: your e-mail address cd pub/soil_moisture/IOWA/Grads/ bin prompt mget * bye or directly from ftp://climate.envsci.rutgers.edu/pub/soil_moisture/IOWA/Grads/ 4. REFERENCES Entin, J.K., 1998: Temporal and spatial scales of soil moisture variations. Ph.D. dissertation, Department of Meteorology, University of Maryland, College Park, 143 pp. Entin, Jared, Alan Robock, Konstantin Y. Vinnikov, Shuang Qiu, Vladimir Zabelin, Suxia Liu, A. Namkhai, and Ts. Adyasuren, 1999a: Evaluation of Global Soil Wetness Project soil moisture simulations. J. Meteorol. Soc. Japan, in press. Entin, Jared K., Alan Robock, Konstantin Y. Vinnikov, Steven E. Hollinger, Suxia Liu, and A. Namkhai, 1999b: Temporal and spatial scales of observed soil moisture variations in the extratropics. Submitted to J. Geophys. Res. Table 1. Soil layers observed and technique used at the two catchments in Iowa. (1 inch = 2.54 cm) ------------------------------------------------------------------------------ Layer Layer Boundaries Thickness of Catchment W-2 Catchment W-3 # (in inches) Layer (inches) ------------------------------------------------------------------------------ 1 0 - 3 3.0 Gravimetric Gravimetric 2 3 - 6 3.0 Gravimetric Gravimetric 3 6 - 12 6.0 Gravimetric Gravimetric 4 12 - 18 6.0 Gravimetric Gravimetric 5 18 - 27 9.0 Neutron Probe Gravimetric 6 27 - 33 6.0 Neutron Probe Neutron Probe 7 33 - 42 9.0 Neutron Probe Neutron Probe 8 42 - 54 12.0 Neutron Probe Neutron Probe 9 54 - 66 12.0 Neutron Probe Neutron Probe 10 66 - 78 12.0 Neutron Probe Neutron Probe 11 78 - 90 12.0 Neutron Probe Neutron Probe 12 90 -102 12.0 Neutron Probe Neutron Probe ------------------------------------------------------------------------------- If you have any problems or questions you can contact us for assistance: Dr. Konstantin Ya. Vinnikov OR Prof. Alan Robock Department of Meteorology Department of Environmental Sciences University of Maryland Rutgers, The State University of New Jersey College Park, Maryland 20742 USA New Brunswick, New Jersey 08901 USA Phone: (301) 405-5382 Phone: (732) 932-9478 Fax: (301) 314-9482 Fax: (732) 932-8644 E-mail: kostya@atmos.umd.edu E-mail: robock@envsci.rutgers.edu OR Dr. Jared Entin Hydrological Sciences Branch NASA-GSFC, Building #33, Mail Code 974 Greenbelt MD 20771 Phone: (301)-614-5825 Fax: (301)-614-5808 E-mail: Jared.Entin@gsfc.nasa.gov Prepared by Alan Robock (robock@envsci.rutgers.edu) and Govindarajalu Srinivasan (srini@envsci.rutgers.edu) Last updated on May 11, 1999