A Gaussian Mixture Model to Separate Birds and Insects in Single-Polarization Weather Radar Data

Raphaël Nussbaumer,Silke Bauer,Felix Liechti,Baptiste Schmid

doi:10.3390/rs13101989

Abstract

Recent and archived data from weather radar networks are extensively used for the quantification of continent-wide bird migration patterns. While the process of discriminating birds from weather signals is well established, insect contamination is still a problem. We present a simple method combining two Doppler radar products within a Gaussian mixture model to estimate the proportions of birds and insects within a single measurement volume, as well as the density and speed of birds and insects. This method can be applied to any existing archives of vertical bird profiles, such as the European Network for the Radar surveillance of Animal Movement repository, with no need to recalculate the huge amount of original polar volume data, which often are not available.

Highlights

Weather radar data are increasingly being used for quantifying the flow of nocturnal bird migration [1,2,3]
The weather radar data publicly available in Europe to ecologists consist only of vertical profiles of bird migration intensities derived from single-polarization weather radar data
The bird reflectivity resulting from this threshold approach is similar to the proportion approach during the bird migration period (March–May, and mid-Sept–midOct), showing that the known threshold from the literature is well calibrated to the airspeed data

Summary

Introduction

Weather radar data are increasingly being used for quantifying the flow of nocturnal bird migration [1,2,3]. The reflectivity from birds in the air and mean radial velocity has been used to quantify bird biomass [4] before algorithms were developed to extract bird data automatically [5,6,7,8]. These algorithms distinguish between bio-scatterers and precipitation but perform less well in distinguishing between the two main bioscatterers, birds and insects. The weather radar data publicly available in Europe to ecologists consist only of vertical profiles of bird migration intensities derived from single-polarization weather radar data

Methods

Results

Conclusion