Per Sean Waugh:
In response to the issue of outfitting chaser vehicles with Mobile Mesonet type instruments racks, the idea does have some merit. If it were possible to do, the data that was collected could provide sometimes dense, high spatial and temporal observations in real time to forecasters, which could prove to be very helpful. The data could also be used to research projects that need that type of data, assuming that the quality is good. That being said, I have a few comments.
First off, my experience with Mobile Mesonets is probably higher than most. I built all of the Mobile Mesonets for the VORTEX 2 project and helped significantly with the construction and wiring of the instrumented racks. I have done a number of research projects examining the validity of the measurements and am currently redesigning a few instruments. Ok, enough of my references to my credibility.
The main point for most people will be cost. The Mobile Mesonet racks that the National Severe Storms Lab (NSSL) uses cost approximately $10,000 (which for some people is probably more than their chase car is worth). This cost represents the instruments, the shields, the wiring, the logger, the aluminum pipe that the rack in constructed out of, everything. The racks measure Temperature, RH, Wind Speed, Wind Direction, and Pressure. In order to get a worthwhile picture of the storm, you really need to have all of those instruments on there. From those you can derive almost anything you need. So this will not be able to be done cheaply. The RM Young Wind Monitors are approx. $1000 and a viable data logger (Campbell Sci. has a few) is about the same in cost.
The second issue is standardization. One of the most important aspects of taking measurements is that each measurement be made in the exact same manner to ensure comparison. For example, all wind speed/direction measurements on ALL of the NSSL vehicles are taken at 11 ft. This would require that each vehicle had the instrument in the same position. The problem here is that each car has a unique flow field over it, making each type of car different with respect to mixing of ambient air, wind speed, wind direction, etc. Just FYI, in order to be completely out of the slip stream of a vehicle, you must go 3X the height of the car. Reflectance and re-radiance off car roofs would affect temperature data if the instruments were located too close to the roof. This would make it very difficult and time consuming to have two different vehicles have measurements that are taken in the same way. Essentially, each type of vehicle would have to be compared to a previously established MM to ensure similarity. Wear on the instruments would also be a problem. They break, they need replaced b/c they are worn out, etc. = more cost.
Driving habits would be a slight concern, though to be honest the derived wind speed and direction actually does a pretty good job at keeping up with fast accelerations and turns. The programming for this system is complex to say the least, but obviously doable and able to run on almost any system.
So I think the idea has merit, but it is going to be VERY difficult to put together. There are many more things to consider that most people don’t think about. I’m trying to limit the length of my initial post on this, but I’ll post answers to more questions/comments as I see them. Feel free to message/email me, I will have an active account in a few days.
