Notice to Data Users: The documentation for this data set was provided solely by the Principal Investigator(s) and was not further developed, thoroughly reviewed, or edited by NSIDC. Thus, support for this data set may be limited. This data set contains data from in situ meteorological measurements collected during the Soil Moisture Experiment 2004 (SMEX04) in Arizona, USA. The data parameters ... and sensors include the following: relative humidity and temperature from the temperature and relative humidity probe; wind speed, wind vector, wind direction and standard deviation of wind direction from the 3-cup anemometer and wind vane; barometric pressure from the barometric pressure sensor; solar radiation from the pyranometer; Photosynthetically Active Radiation (PAR) incoming and PAR reflected from the Quantum Sensor; soil heat flux from the soil heat flux plate; soil temperature from the Type T thermocouple wire; net radiation from the net radiometer; and soil moisture from the Theta Probe. Temporal coverage for the data spans 01 June 2004 to 30 September 2004. The total volume of this data set is approximately two megabytes in four ASCII text files. The data are available via FTP. These data were collected as part of a validation study for the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E). AMSR-E is a mission instrument launched aboard NASA's Aqua Satellite on 04 May 2002. AMSR-E validation studies linked to SMEX are designed to evaluate the accuracy of AMSR-E soil moisture data. Specific validation objectives include assessing and refining soil moisture algorithm performance; verifying soil moisture estimation accuracy; investigating the effects of vegetation, surface temperature, topography, and soil texture on soil moisture accuracy; and determining the regions that are useful for AMSR-E soil moisture measurements.