My fraternal organization Alpha Phi Alpha is convening in Las Vegas for its General Convention so I am seeing a lot posts from the city. The WNBA All-Star game is also being played there. It is on my television as I write this article. However, the Vegas strip and surrounding areas have been visited by another group, grasshoppers. If you were looking at the National Weather Service - Las Vegas weather radar this week (graphic below), you probably thought that it was showing rain. Nope, the radar was actually "seeing" biological targets and mostly grasshoppers. Why are there so many grasshoppers in Vegas right now, and how can a weather radar see them?
NWS Las Vegas weather radar detecting grasshoppers
NWS
Before I answer that question, it is instructive to review a Tweet by the National Weather Service - Las Vegas last evening:
Some of you have been asking about the widespread radar returns the past few nights in #Vegas. Radar analysis suggests most of these echoes are biological targets. This typically includes birds, bats, and bugs, and most likely in our case--> Grasshoppers.
Many news outlets were also reporting about swarms of grasshoppers in and around Las Vegas, Nevada. While many thoughts might run through the minds of residents and visitors, there is a simple weather-related explanation, but you will have to keep reading for the explanation.
950PM: Outflow winds from earlier storms over Nye County have just entered NW Las Vegas. Wind gusts between 30-40 mph will be likely as these winds move through the valley. Watch for areas of blowing dust and grasshoppers which may limit visibility. #vegasweather #nvwx
Satellite image of storms in and around Nevada
NWS
How does the radar "see" the grasshoppers. Radar is actually an acronym for "RAdio Detection And Ranging." A radar sends out a pulse of microwave energy. Yep, it is the same part of the
electromagnetic spectrum that many of us also use to cook food. Some portion of the pulse is scatters (or "bounces") back to the radar from things like a population of raindrops, a plane or a swarm of insects. Doppler radar even allows for detection of the motion of the "target" towards or away from the radar.
Radars operate at different wavelengths. The most common wavelengths for weather radars are 5 cm and 10 cm. At these wavelengths, a swarm of grasshoppers can appear as a "bio-target" to the radar. While insect returns are often consider "noise" to meteorologists, a recent project called BioDar is leveraging weather radar detection to study insect diversity and abundance.
According to an article in Phys.Org:
The information they (Biodar) collect will support the conservation of insects that are vital to ecosystems such as bees and other pollinators, and will help protect against crop pests. The new project will initially aim to monitor insect populations in the UK, followed by Rwanda, Mali, and South Africa.
How weather radar works
Hong Kong Observatory Website
This project, funded by Natural Environment Research Council, is a collaboration between the University of Leeds, University of Exeter, and the National Center for Atmospheric Research (NCAR). The project will use sophisticated computer algorithms called machine learning to identify and count insect diversity.
Why are there so many grasshoppers around Las Vegas right now? Blame the weather. Las Vegas has received quite a bit of rainfall in recent months. It averages just under 5 inches per year. In about 6 months, the area has surpassed that amount (graphic below). Jeff Laughlin, an entomologist with the Nevada Department of Agriculture, told Lukas Mikelionis in an article on the Fox News website:
It appears through history that when we have a wet winter or spring, these things build up often down below Laughlin and even into Arizona....We'll have flights about this time of the year, migrations, and they'll move northward
Percent of normal rainfall over the past 6 months in the United States.
NOAA
#News | https://sciencespies.com/news/why-grasshoppers-are-invading-las-vegas-and-how-weather-radar-sees-them/
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