Drizzle

Drizzle is a light liquid precipitation consisting of liquid water drops smaller than those of rain – generally smaller than 0.5 mm (0.02 in) in diameter. Drizzle is normally produced by low stratiform clouds and stratocumulus clouds. Precipitation rates from drizzle are on the order of a millimetre per day or less at the ground. Owing to the small size of drizzle drops, under many circumstances drizzle largely evaporates before reaching the surface and so may be undetected by observers on the ground. The METAR code for drizzle is DZ.

Effects

While most drizzle has only a minor immediate impact upon humans, freezing drizzle can lead to treacherous conditions. Freezing drizzle occurs when supercooled drizzle drops land on a surface whose temperature is below freezing. These drops immediately freeze upon impact, leading to the buildup of sheet ice (sometimes called black ice) on the surface of roads.

Occurrence

Drizzle (database server)

Drizzle is a free software/open source relational database management system (DBMS) that was forked from the now-defunct 6.0 development branch of the MySQL DBMS.

Like MySQL, Drizzle has a client/server architecture and uses SQL as its primary command language. Drizzle is distributed under version 2 and 3 of the GNU General Public License (GPL) with portions, including the protocol drivers and replication messaging under the BSD license.

Early work on the fork was done mid-2008 by Brian Aker. Ongoing development is handled by a team of contributors that includes staff members from Canonical Ltd., Google, Six Apart, Sun Microsystems, Rackspace, Data Differential, Blue Gecko, Intel, Percona, Hewlett-Packard, Red Hat, and others. Drizzle source code, along with instructions on compiling it, are available via the project's Launchpad website.

In October 2010, Drizzle had 13,478 total contributions, 96 total contributors, and 37 active contributors. It was also announced that Drizzle had entered Beta,. The first GA version was released in March 2011. Drizzle has actively participated in the Google Summer of Code Project since 2010.

Drizzle (image processing)

Drizzle (or DRIZZLE) is a digital image processing method for the linear reconstruction of undersampled images. It is normally used for the combination of astronomical images and was originally developed for the Hubble Deep Field observations made by the Hubble Space Telescope. The algorithm, known as Variable-Pixel Linear Reconstruction, or informally as "Drizzle," preserves photometry and resolution, can weight input images according to the statistical significance of each pixel, and removes the effects of geometric distortion on both image shape and photometry. In addition, it is possible to use drizzling to combine dithered images in the presence of cosmic rays.

According to astrophotographer David Ratledge, "Results using the DRIZZLE command can be spectacular with amateur instruments."

Overview

Camera optics generally introduce geometric distortion of images. Undersampled images are, for example, common in astronomy because instrument designers are frequently forced to choose between properly sampling a small field of view and undersampling a larger field. This is a particular problem for the Hubble Space Telescope (HST), where the corrected optics may provide superb resolution, but the detectors are only able to take full advantage of the full resolving power of the telescope over a limited field of view. Fortunately, much of the information lost to undersampling can be restored. The most commonly used of these techniques are shift-and-add and interlacing.