Research on the Collocation Criteria in the Statistical Comparisons of GPS Radio Occultation and Radiosonde Observations

When verifying the precision of atmospheric parameter profiles obtained with GPS radio occultation (RO) technology with radiosonde observations,the collocation criterion should reasonable. The impacts of different collocation criterias on the statistical comparisons of GPS RO and radiosonde observations were studied. The time difference between the two types of observations are set to be 1 h,2 h,and 3 h. The distance differences are set to be 100 km,200 km,and 300 km,respectively. Different combinations of time differences and distance differences lead to 9 collocation criteria in total. Collocated GPS RO and radiosonde refractivity profiles are got and statistically compared with the 9 different collocation criterias,respectively. The results show that the variation of time differences and distance differences have little impact on the total refractivity mean relative deviation.