Global morphology of convection indices observed using COSMIC GPS RO satellite measurements

In the present study we report the global morphology of atmospheric stability indices using COSMIC GPS RO data obtained from April 2006 to December 2011. An initial validation study has been made by comparing all these indices with ground based GPS radiosonde observations collected from Gadanki (13.5 degrees N, 79.2 degrees E) with special focus on the uncertainty in estimating these indices using GPS RO data. A mean correlation of 0.65 is found between the two. Using COSMIC GPS RO measurements high CAPE values are observed in the tropics during the summer in the Northern and Southern hemispheres, where the convective activity is predominant. The seasonal shift of CAPE is also reproduced well with respect to season along with the motion of the Inter Tropical Convergence Zone (ITCZ). A strong diurnal variation in CAPE and other thermodynamic parameters are noticed. In this study it is shown that the diurnal variation obtained from satellite measurements while integrated over a season does not represent the true diurnal variation as observed by radiosonde collected within a day. Caution is also advised in using GPS RO data that are not available down to the surface. It is found that about 40% error may occur if the data in the profiles are not available down to 1 km. (C) 2013 Elsevier B.V. All rights reserved.