MERRA-2 Air temperature data extraction and cleaning

I would like to extract daily averaged air temperature data from the M2I3NPASM v5.12.4 3 hourly data set from 01-01-1998 to 31-12-2018 for both the 1000ha and 975ha vertical slices. I would like this done for the following longitude and latitude regions [-12,50,2,61]. I would like to compare the air temperature at both vertical slices and aggregate the number of days each year where there is an air temperature at 975ha that's greater than at 1000ha. On the days the air temperature is greater I would like to record how much greater it is each day this occurs.