Frequently Asked Questions: Instruments
Over the years, CSWR employees have been asked a lot of great questions by people who approach us in the field. Many of these questions pertain to the instruments we use. Here are some answers to the most frequently-asked questions:
Who designed the PODs, who builds them, and how many of them are there?
The PODs came from a discussion about how to put instruments into the path of a hurricane or tornado, while at the same time trying to minimize the risk to the instruments. Sketched out by Joshua Wurman and built by CSWR, the number of PODs utilized in the field has grown over the years. There are currently 16 PODs which are deployed during hurricane and tornado projects. During the longer projects, participating scientists and crew routinely examine/check the PODs for leaks, bad data loggers, structural integrity, etc., just to ensure that everything is working as expected.
How do the PODs get transported during scientific missions?
Usually, the PODs are placed in the back of the mesonet "probe" vehicles, with three PODs going in each vehicle.
How do you use the PODs in field campaigns?
When given the word, passengers (and sometimes the driver) in the mesonet probe vehicles exit their vehicles, and pull the PODs out of the back, placing the POD on the ground. Since the PODs are heavy (about 120 pounds, on average), they require two people to deploy them. Once the POD is on the ground, pictures are taken and the GPS position of the POD is recorded to ensure that we know exactly where the data is being obtained. (This is also useful in case the PODs get hit by debris and/or moved out of position - we can have both "before" and "after" comparisons!)
How long does it take to set out a POD?
Ideally, we like to do POD deployments as quickly as we can (since we're usually dealing with weather features such as tornadoes, it's important that we get in and get out of the region quickly). A typical deployment is around 50 seconds, including jumping out of the vehicle, pulling the instrument out, setting it down on the ground, recording its location/orientation and then getting back into the vehicle.
How are the PODs powered?
Currently, every POD has a marine battery affixed to its base, allowing for 18 continuous hours of data recording.
How long can the video cameras record?
Right now, the battery life for the camera is approximately eight hours. Of course, this will depend on what is actually being recorded (for example, if it's night-time, the battery life is longer, since there's not much to "see", but during bright sunlight the batteries are used up much faster.)
How often do your check that your PODs are working?
Depending on the field campaign or scientific mission, the PODs are hooked up to a laptop computer at least once a day, to check that the recorded data are good, their clocks match UTC time, etc. All of this ensures that the data we're recording is accurate. At the end of every mission day, the data are pulled off the PODs - if we didn't, and left the PODs recording all night, all of our data would be over-written!
Why don't the PODs get sucked up by a tornado or hurricane?
If you look at a picture of a POD, one of the first things you'll notice is that the base of it is very wide, and the rest of it is rather narrow. This leaves a minimal amount of surface area actually exposed to the high winds of the stormy environments we place them in. This, combined with their hefty weight, gives the PODs a pretty good amount of stability.
What are the biggest dangers that the PODs face, then?
Actually, during tornado deployments, the biggest risk to these instruments is debris which can become airborne in high winds. As might be expected, during hurricane deployments, the biggest risk to these instruments is becoming water-logged.
What's it like to drive a mesonet?
Excluding the DOWs, driving a CSWR mesonet vehicle is not unlike driving a pickup truck. The only real difference is that the instruments are attached to the top of a very high mast (about 13 feet), and so drivers have to be especially careful of this when they're driving under awnings, low bridge clearances, wires, etc.
How are the mesonet instruments powered?
Unlike the PODs, which have batteries attached to their bases, the mesonet instruments are powered directly from the vehicle battery.