Global Precipitation and Thunderstorm Frequency Data Set, 1975-1997 mean

The 3 netCDF files in this dir contain the main data products
(seasonal mean only) created by Dai (2001, J. Climate, part I, 
p.1092 and part II, p.1112). The user should read these papers 
for details about procedures used to create these data. Spatial 
interpolation and smoothing were applied in creating the maps 
(for phase this was done using its x and y components). Sampling 
is limited for the diurnal analysis over many oceans in the tropics 
and southern hemisphere (see Fig. 2 of Dai (2001, J. Climate, 
p.1097)), especially for the odd hours (03, 09, 15 and 21Z). This 
makes the estimates of the semidiurnal harmonic generally unreliable
over the oceans and thus the semidiurnal results are not included
in these files. The diurnal harmonic results over most of the 
southern ocean and many tropical oceans have large sampling errors 
(especially for thunderstorms) and thus should be interpreted with 
caution.  

---Aiguo Dai, NCAR (adai@ucar.edu), March 28, 2003.  


precip-freq.r2x2-land+ocn-4sea-75-97mean.nc  :
  Long-term (1975-1997) mean precipitation and thunderstorm frequency
  and wet-day probability.

precip-3hrlyFreqAnom.r2x2-land+ocn-75-97mean.nc  :  
 3 hourly diurnal anomaly (relative to daily mean) of precip. frequency.

precip-s1.r2x2-land+ocn-4sea-75-97mean.nc  :
  Phase (LST of the peak) and amplitude (mean-to-peak) of the diurnal 
  harmonic of the long-term mean precipitation frequency. 
   
2/13/2004:

Tstorm-freq.r5x4-land+ocn-4sea-75-99.nc  :
  Time series of seasonal (DJF, MAM, JJA, SON) thunderstorm frequency (in %) 
  from 1975 to 1999.