May 28, 2004
Some examples of my MCS work
I have completed the basic form of a program that loops through all 11 June 2000 MCS lightning data, as measured by the LMA, and compares these data to a simple convective/stratiform partitioning of the KGLD NEXRAD radar data. The purpose is to understand gross differences between lightning occurring in the convective and stratiform regions of the MCS. The CS partitioning algorithm is still under refinement, but it basically looks for 30 dBZ echo at 6 km MSL (-10 C). This does a pretty good job of picking out the convective line vs. the stratiform region, as conventional algorithms get fooled by the intense stratiform echo in this storm. However, the algorithm currently lumps in weak/decaying convection with stratiform. What might be ideal is to get 3 categories working - stratiform, convective, and transitional - that would be consistent with the 3 basic zones of an MCS.
The first plot is a simple histogram of VHF source altitudes in convective and stratiform regions, from 10 minutes of data starting at 2140 UTC (early part of storm). Note how stratiform sources are distributed lower in altitude than convective sources.
The next plot shows density of convective, stratiform, and unclassified (i.e., no radar data in same location) sources in the horizontal, for the same time period. This is more a sanity check than anything, to make sure the algorithm is working as wished. Note that I require a 5-km radius to no convective pixels before I will classify an LMA source as stratiform or unclassified (red is convective, yellow is stratiform, white unclassified).
Here is a plot of the mean initiation locations of convective-, stratiform-, and unclassified-initiated flashes. If 50%+ of a flash's first 10 points or first 10% of points (whichever is smaller) fall within convective (stratiform) echo, then the flash is called convective(stratiform)-initiated. If this threshold is not reached, it is an unclassified-initiated flash. The location is determined from the mean of the first 10 points or first 10% of points, so sometimes the initiation location may appear in what appears to be the wrong echo, if the initial points skirt the boundary between the two types of echo. Note how within the convective region there are definite "hot spots" of flash initiation. It will be interesting to examine kinematic and microphysical data from the radar network in the context of these "hot spots."
This plot shows a simple time series of the number of LMA sources per category. Note how convective sources dominate the overall number, as expected, and there is a distinct peak after 2200 UTC, as well as a late-lifetime recovery. Interestingly, the stratiform source numbers are volatile but with a fairly flat long-term trend, despite the fact that stratiform echo grew significantly with time in this storm. Finally, the third panel, which is unclassified points, shows a 2300-0000 UTC spike caused by the MCS passing over the KGLD radar.
This last plot shows 2140 UTC data again. Now we are looking at just the propagation characteristics of convectively initiated flashes with significant stratiform components. The idea is to see how such a flash behaves vertically as it propagates into the stratiform region (represented by horizontal distance from flash initiation point). For example, is there downward sloping as might be expected by theorized charge structures? This plot is similar to many other times from this storm, and shows that downward sloping does occur, but by no means is universal.
(Edit: Fixed last figure due to problems with original algorithm.)
Posted by Timothy at 01:51 PM
May 26, 2004
Template Finished!
OK, the major updates to the website template are done. Minor ones may occur in the future, however. Now I can get on with posting my research!
Posted by Timothy at 02:34 PM
May 25, 2004
Testing an image
Here's an example figure from my STEPS research, showing a plot of lightning relative to convective and stratiform areas of an MCS.
Here is the figure, from 2150 UTC on 11 June 2000:
Posted by Timothy at 06:59 PM
Test Post
Checking how things look with multiple entries.
Testing extended entry
Posted by Timothy at 05:54 PM
Welcome!
Welcome to my new research weblog! Expect numerous updates as I configure this site the way I want. Links that were on the former home page can be found on the right sidebar.
Posted by Timothy at 11:36 AM