Table 1. Statistics of Perturbations in the Stratosphere at 10 mb That Reach the Surface Under Solar Maximum and Minimum Conditions During 1948-2004				
	Maxima	Minima		
Signal strength	1.0sigma	1.5sigma	1.0sigma	1.5sigma
10 mb	35	22	39	26
1000 mb	16	11	5	3
Ratio	0.46	0.50	0.13	0.12
ratio for west QBO	0.53	0.64	0.0	0.0
ratio for east QBO	0.39	0.36	0.31	0.27