Analysis of daily precipitation based on weather radar information in México City

Abstract

In México, there is a network of 12 meteorological radars to monitor intense convective systems. Data from Cerro de la Catedral Doppler radar, 40 km northwest of México City, have been used to obtain precipitation rates estimates during intense precipitation events. Results show that although estimates are close to the observed precipitation in surface stations, a new configuration of the radar system is necessary to better capture the characteristics of intense storms, particularly at the foothills of the western mountains. The comparison between the estimate from the radar and a dense network of rain gauges shows that such deficiency may be related to systematic errors due to blockage (radar), but also to sampling problems (radar and rain gauge). The calibration by itself may not be enough since there is significant blockage with the radar at the peak of a high elevation but relatively distant mountain. Such location limits the scan capacity from making a good vertical coverage. The present characteristics of the elevation of the radar beam prevent the radar from estimating the amount of precipitation in the lowest part of the clouds, near the cloud base. A new configuration of the radar system for México City is proposed taking into account spatial coverage and propagation effects upon a standard atmosphere in a horizontally constant reflectivity field.