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Zenith Total Delay Study of A Mesoscale Convective System: GPS Observations and FINE-SCALE Modeling


Zenith Total Delay (ZTD) observations and model calculations are used to analyze a mesoscale convective system which yielded a large amount of precipitation over a short period of time in the north-western Mediterranean. ZTD observations are derived from the GPS signal delay whereas the ZTD model results are calculated by means of the MM5 mesoscale model. Large values of the root-mean-square (rms) differences between the ZTD derived from the observations and the modeling are found for the maximum activity of the mesoscale convective system. It appears that the average bias between observations and modeling results is slightly affected (20%) by the passage of the storm system which is associated to the water vapor variability of the atmosphere. We have analyzed the ZTD differences in terms of the two components: the Zenith Hydrostatic Delay (ZHD) and the Zenith Wet Delay (ZWD). The hydrostatic error is mainly caused by the differences between the elevation of the GPS stations and the model topography and is reduced when using a more accurate topography data set. We propose a correction for this error assuming hydrostatic equilibrium. The remaining average ZTD difference is associated to the ZWD and is mainly generated by inaccuracies of the mesoscale model to predict the water vapor content during the rainfall event.

Article / Publication Data
Available Metadata
Fiscal Year
Publication Name
Tellus A
Published On
March 01, 2002
Final Online Publication On
March 01, 2002
Publisher Name
John Wiley & Sons, Ltd.
Print Volume
Print Number
Page Range
Submitted On
October 02, 2000


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