Methods of Filtering Parsivel2 Data For Different Rain Regimes

Poster PDF

Description

The ARM Facility has long-term data sets of the rainfall drop size distribution collected by OTT Parsivel2 disdrometers deployed during MAGIC, AWARE, and GoAmazon and from ARM’s permanent ENA site in the Azores. The Parsivel2 disdrometers have proven to be very robust, exhibiting very few data interruptions. While the Parsivel2 version showed much improvement over its predecessor, fall velocity observations remain problematic for drops greater than 1mm (Tokay et al., 2014). It became standard practice to filter out drops from the observations when the associated fall velocities for those drops did not fall within a +- 50% envelope of Gunn and Kinzer expected fall velocity behavior (Gunn and Kinzer, 1949). For GoAmazon, a more restrictive additional filtering method was developed that was based upon fall velocity and maximum drop size. This filtering resulted in excellent agreement between the rain rate from filtered Parsivel2 drop size distributions and that from a co-located tipping bucket rain gauge (correlation coefficient of 0.92). The equivalent radar reflectivity calculated from the filtered observations also agreed with radar wind profiler observations of droplet reflectivity. This poster explores how well this filtering method performs for data collected from various rain regimes. Gunn, R, and GD Kinzer. 1949. "The terminal velocity of fall for water droplets in stagnant air." Journal of Meteorology 6: 243-248. Tokay, A, DB Wolff, and WA Petersen. 2014. "Evaluation of the new version of the laser-optical disdrometer, OTT Parsivel2." Journal of Atmospheric and Oceanic Technology 31: 1276-1288, doi:10.1175/JTECH-D-13-00174.1.