Which meteorological data were produced by AgMERRA?

Based on the NASA Modern Era Retrospective Analysis for Research and Applications (MERRA) outputs (Rienecker et al., 2011), the AgMERRA global gridded climate dataset (0.25*0.25) horizontal resolution; ~25 km) provided daily, high-resolution and continuous meteorological datasets for the period 1980-2010 and was advocated to be useful for agricultural and meteorological projects (Ruane et al., 2015). These data are including: Mean, maximum and minimum temperatures (C), Relative Humidity (%), Precipitation (mm), wind (m/s), Solar Radiation (MJ/m2/day). If you want read time series from .nc4 files you can use Netcdf Extractor.

AgMERRA's incorporation of the MERRA-Land product provides substantial improvements in the resolution of the daily precipitation distribution and precipitation extremes over other climate forcing datasets, and both AgCFSR and AgMERRA utilize the NASA/GEWEX Solar Radiation Budget data for improved solar radiation values (see Ruane et al., 2015). In addition, AgMERRA and AgCFSR provide relative humidity at the time of maximum daily temperature in order to better gauge maximum evapotranspiration in agricultural applications.

For downloading the data of Agmerra you can visit Rienecker et al., 2011, as you see in the download page, you can easily understand theat which data refer to your desirable variable. For example, consider "AgMERRA_1980_prate.nc4"(or "AgMERRA_1980_prate.hdf"), it refers to precipitation data of 1980. Other variables are rhstmax, srad, tavg, tmax, tmin, and wndspd which they present Maximum relative humidity, Solar Radiation, Mean Temperature, Maximum Temperature, Minimum Temperature, and Wind Speed, respectively. The data are presented from 1980 to 2010, in daily scale.

During past few decades few database sources of gridded daily datasets have been developed. These can be classified into three categories: gauge-based such as APHRODITE (Asian Precipitation-Highly-Resolved Observational Data Integration Towards Evaluation) (Yatagai et al., 2009 and 2012), satellite-based like PERSIANN (Rainfall Estimation from Remotely Sensed Information using Artificial Neural Networks) (Hong et al.,2004) and TRMM (Tropical Rainfall Measuring Mission) (Huffman et al., 2007), and merged satellite-gauge products such as AgMERRA (The Modern-Era Retrospective analysis for Research and Applications).