Himawari-8 rainfall estimation from infrared channels based on machine learning methods

Accuracy Assessment of a Satellite-Based Rain Estimation Algorithm Using a Network of Meteorological Stations over Epirus Region, Greece

“…The rain rate is estimated by the satellite algorithm every 15 min. The selection of the specific five SEVIRI channels (Table 2) was made because their band combinations can be used during day/night (channels in the InfraRed region) to delineate cloud convection and in general cloud patterns with potential to produce heavy rainfall [36][37][38][39].…”

“…More specifically, if for a specific pixel: (i) the Brightness Temperature (BT) in channel 9 centered at 10.8 µm (BT 10.8µm ) is lower than 265 K, i.e., if BT 10.8µm < 265 K, (ii) the Brightness Temperature Difference (BTD) between the channels 5 and 6, centered at 6.2 µm and 7.3 µm, respectively (BTD 6.2µm-7.3µm ) is larger than −20 K, i.e., if BTD 6.2µm-7.3µm > −20 K, and (iii) the Brightness Temperature Difference (BTD) between the channels 9 and 10, centered at 10.8 µm and 12.0 µm respectively (BTD 10.8µm-12.0µm ) is smaller than 3 K, i.e., if BTD 10.8µm-12.0µm < 3 K, then the pixel is considered as rainy, while if the three thresholds are not met the pixel is considered as not rainy. As abovementioned, the utilized set of criteria can delineate satisfactorily humid atmospheric areas in the middle to upper troposphere and greater areas of cloud convective cells, which are major source of heavy rainfall [36][37][38][39][40][41][42].…”

“…The next step is these values being linked with representative RR values and creating five different pairs of data which are used to calculate the least square equations for the six different parameters. The RR values are standard [43] and are based on the general theoretical concept that lower BT (and BTD) are linked with higher RR values as the cold/opaque cloud tops depict convective cloud patterns where heavy rainfall usually occur [39][40][41][42]. More specifically, for every different timeslot, the value of P 5% for each parameter is linked with the RR = 1 mm/h, the value of P 25% for each parameter is linked with the RR = 5 mm/h, the value of P 50% for each parameter is linked with the RR = 10 mm/h, the value of P 75% for each parameter is linked with the RR = 20 mm/h and the value of P 95% for each parameter is linked with the RR = 30 mm/h.…”