Return Value maps based on Generalized Extreme Value (GEV) Distribution


Return value (with N year return level) is defined as a value which is expected to be equaled or exceeded on average once every N years. Therefore, conceptual basis on the calculation of return value is inverting the probability distribution function of a sample of extremes. Calculation details including GEV distribution fitting is available at GEV and RV calculation. In this work, return values were calculated for 2-, 5-, 10-, and 20-yr return period, for the four extreme value-related quantities in each season. From the return value maps, we can find out the anticipated return values for the amount of heavy rainfall, the number of heavy rainfall days, the number of rainy days, and maximum consecutive dry days for a given return period. Please be advised that the return values for the maximum daily precipitation tend to be overestimated by CFSR, while they are underestimated by MERRA, compared with return values calculated from gridded observation (NCEP/CPC). We suggest that overestimation by CFSR might be associated with longer tail of the PDF curves that were shown in section 3.1. Please also note that the datasets used for return value calculation are gridded ones that were averaged over a grid box. Therefore, return values calculated here could be lower than return values calculated from local station data.
 
Return Value maps based on Generalized Extreme Value distribution
MAM JJA SON DJF
daily maximum precipitation MERRA
CFSR
CPC-US,MX
CPC-SA
CDC-SA
MERRA
CFSR
CPC-US,MX
CPC-SA
CDC-SA
MERRA
CFSR
CPC-US,MX
CPC-SA
CDC-SA
MERRA
CFSR
CPC-US,MX
CPC-SA
CDC-SA
the number of heavy rain days (>10mm/day) MERRA
CFSR
CPC-US,MX
CPC-SA
CDC-SA
MERRA
CFSR
CPC-US,MX
CPC-SA
CDC-SA
MERRA
CFSR
CPC-US,MX
CPC-SA
CDC-SA
MERRA
CFSR
CPC-US,MX
CPC-SA
CDC-SA
the number of rainy days (>1mm/day) MERRA
CFSR
CPC-US,MX
CPC-SA
CDC-SA
MERRA
CFSR
CPC-US,MX
CPC-SA
CDC-SA
MERRA
CFSR
CPC-US,MX
CPC-SA
CDC-SA
MERRA
CFSR
CPC-US,MX
CPC-SA
CDC-SA
maximum consecutive dry days MERRA
CFSR
CPC-US,MX
CPC-SA
CDC-SA
MERRA
CFSR
CPC-US,MX
CPC-SA
CDC-SA
MERRA
CFSR
CPC-US,MX
CPC-SA
CDC-SA
MERRA
CFSR
CPC-US,MX
CPC-SA
CDC-SA