IMERG Early Run

This algorithm is intended to intercalibrate, merge, and interpolate “all” satellite microwave precipitation estimates, together with microwave-calibrated infrared (IR) satellite estimates, precipitation gauge analyses, and potentially other precipitation estimators at fine time and space scales for the TRMM and GPM eras over the entire globe. The system is run several times for each observation time, first giving a quick estimate (IMERG Early Run) and successively providing better estimates as more data arrive (IMERG Late Run). The final step uses monthly gauge data to create research-level products (IMERG Final Run).

The main difference between the IMERG Early and Late Run is that Early only has forward propagation (which basically amounts to extrapolation) due to the short latency, while the Late has both forward and backward propagation (allowing interpolation).

Notes:

• The PPS has completed reprocessing GPM IMERG data for IMERG V06B. The IMERG dataset now includes TRMM-era data going back to June 2000.
• As of IMERG V05B, full coverage is provided for the latitudes of 60°N-60°S, while the remaining upper and lower latitudes extending to 90° are considered "partial coverage".