Introduction
Recently, I've been looking for ways to start going through the enormous amount of literature on severe storms and data assimilation that has been produced over the years, and I'd like to keep working on my writing skills, as well. To those ends, I came up with the idea of doing a blog series, kind of like what +Patrick Marsh did in 2010 with his "image a day" series, to which I now cannot find a link.My original idea was to do one paper per day, as in Patrick's series, but I'm six days behind already. This, combined with the need to focus on other things on certain days, like my wedding in September, means I won't be writing an entry every day, but some days will have multiple entries. If I keep it up, by 31 December 2014, there should be 365 papers reviewed on here.
I've always been a fan of the idea that if you can't explain a topic to someone who knows nothing about it in terms they can understand, then you don't truly understand it. As such, I will attempt to read the paper and interpret it for the layperson who doesn't know anything about severe storms or data assimilation. I'll start off with some seminal papers to get some background for the reader (and myself).
Review
Today, I figured I'd start off with a seminal paper in the field of severe storms research: Keith Browning's 1964 supercell paper. The purpose of the paper is to unify a bunch of already-existing concepts related to what Browning called "Severe Right-moving" (SR) storms. The term "supercell" had not been coined yet, but they are the same concept that has been developed throughout the years.By 1964, it had been observed that most thunderstorms move with the wind averaged over the depth of the cloud. However, it had also been observed that some of the most intense storms deviated from the mean wind in a right-hand direction. Furthermore, many of these storms occur on days when the winds turn clockwise and strengthen as one ascends in the atmosphere. An example of such a profile is given in the image below (Figure 1 from Browning, 1964), where "L" represents the wind at low levels (approximately surface to 5000 ft), "M" represents the wind at middle levels (10,000-20,000 ft), and "H" represents the wind at high levels (30,000 ft and above).
One of Browning's points is to identify the structure and air circulations inside these storms. Based on earlier work by Ted Fujita, he concludes that the predominant circulations must be in the counter-clockwise direction. Additionally, he concludes from previous research that the main updraft (a region of air moving upwards) must originate in the low levels, and the main downdraft (a region of air moving downwards) must originate in the mid levels. Also, Browning cites previous research identifying several features of the supercell commonly known today. These are the hook echo as seen from a radar, the vault, which is a region of precipitation-free air in the updraft, and the "overhang" of radar echoes above the vault.
Another of Browning's major points is to map out the general paths that raindrops and hailstones follow through storms. The precipitation particles (i.e. raindrops and hailstones) are generated in the updraft and are then thrown out to other parts of the storm (see the image below, which is Figure 5 from Browning, 1964). The size of particle determines how far it can be thrown: smaller raindrops can be thrown farther than larger raindrops, and smaller hailstones can be thrown farther than larger hailstones (this concept is known as "size sorting"). The lightly stippled area in Figure 5 is where light precipitation is usually found, and the denser the stippling in Figure 5, the heavier the precipitation. The most intense updraft is found to be co-located with the vault, and is the reason for the lack of precipitation there.
