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For over sixty years, the peer-reviewed Glossary of Meteorology has been the authoritative source for definitions of meteorological terms. A living document, containing over 12,000 terms, individual Glossary terms are periodically updated as our fields evolve.

Translation Project

In January 2024 AMS launched a pilot project to translate our authoritative, peer-reviewed Glossary of Meteorology into Spanish. You can view the translated entries here.

Following a request for proposal process in summer 2023, AMS identified four translation vendors to participate in the Glossary translation pilot. A request for volunteer help was sent out to the AMS Committee for Hispanic and Latinx Advancement (CHALA) and the Scientific and Technological Activities Commission (STAC) and a group of more than a dozen volunteers was selected to evaluate the vendor translations of the top 50, most-visited, Glossary terms. Each volunteer was assigned 6 or 7 terms and definitions from the list and asked to review each vendor’s translation of those terms. Each term was evaluated by at least two volunteers. A translation evaluation rubric was used to score each of the four translation vendors on the following aspects: meaning, functional and textual adequacy, target language mechanics, and style, register and idiomaticity. Each dimension could be rated as excellent, acceptable, deficient, or unacceptable. The volunteers were also asked to provide an overall recommendation.

Ultimately, AMS selected Lilt as our translation partner. In addition to the volunteers’ positive assessment of Lilt’s translation, the National Weather Service (NWS) has already partnered with Lilt, a machine learning company specializing in large language models focused on multilingual customer experiences. This allows AMS to benefit from the work already done by NWS forecasters, who have been training artificial intelligence (AI) software for weather, water and climate terminology in Spanish.

Although the pilot was able to be funded with available funds, translation of the full Glossary is contingent on AMS securing adequate funding.

Preface to the Second Edition

The first edition of the Glossary of Meteorology was published by the American Meteorological Society (AMS) in 1959. In the four decades between its publication and this second edition, entire discipline areas of the field of meteorology have been born and flourished. Despite this, the first edition has sold over 10,000 copies through five printings. It is a tribute to the editors of the first edition that it has withstood the tests of time and continued to be among the leading reference sources in meteorology and related sciences for four decades.

The beginning of the process to publish a second edition can be traced to two documents, "How Can We Do Another Glossary of Meteorology: A Discussion Paper," and "Preparatory Document for Meeting on Glossary of Meteorology," authored by AMS past-president Werner A. Baum in the early 1990s. These papers were discussed and reviewed in 1993 by the ad hoc Committee on the New Glossary of Meteorology, formed by the Council of the AMS. Over a two-day period, this committee laid the foundation for what would become the second edition. In addition to developing the overall philosophy of the second edition, the ad hoc committee developed an outline for the management structure of the enormous task that lay ahead.

In 1994, AMS submitted a proposal to the National Science Foundation (NSF) for a grant supporting the publication of an update of the Glossary. Later that year, the NSF awarded a grant to the AMS, with funding from five U.S. government agencies. In addition, the AMS committed to its own matching funds, the source of which included interest generated from funds on reserve. Central to the project, as in the first edition, would be drawing upon the volunteer efforts of many individuals from every facet of the Society.

The effort began in the fall of 1994 with the appointment of the Glossary of Meteorology Advisory Board. The immediate task of the board, under the chairmanship of Ronald Taylor, was to take as its starting point the output of the ad hoc committee and develop a detailed plan for the implementation of the project. During the early planning for the second edition, lengthy discussions were held on the intended coverage of the volume. As the AMS serves many related disciplines, how should the Glossary cover these? Does it make more sense to produce several independent glossaries, each for a subarea of meteorology? Should it have a different title such as the Glossary of Atmospheric Sciences? While the field would be covered fully, terms from related sciences would be included if they directly impacted meteorology. This would require prudent addition of terms from areas such as physical oceanography and hydrology, fields in themselves that would not be covered in their entirety. Overall guidance was that if terms were likely to appear in AMS journals or other literature, they should be included. With meteorology becoming more integrated with other sciences, it was determined that the volume would be most useful if it were not divided into several subject areas. It was finally agreed that this second edition, as its name implies, is intended to be a glossary of the science of meteorology, as defined in the first edition:

The study dealing with the phenomena of the atmosphere. This includes not only the physics, chemistry, and dynamics of the atmosphere, but is extended to include many of the direct effects of the atmosphere upon the earth's surface, the oceans, and life in general.

Since the publication of the first edition in 1959, the science of meteorology has evolved considerably. A number of new specialty areas have developed, and others have undergone radical changes since then (e.g. atmospheric chemistry, satellite meteorology, numerical weather prediction). The substantial growth in the number of terms for the second edition reflects these changes, rather than a change of scope or philosophy of the book.

Much of the success of the first edition has been ascribed to the fact that the science of meteorology is thoroughly covered and that terms from associated fields are also included. Yet, to ensure the focus of the book, these terms from associated fields were carefully screened prior to inclusion. The second edition encompasses the same philosophy: Terms from hydrology, oceanography, etc., are included if their inclusion is important to the understanding of meteorology as broadly defined above. The second edition follows the wise philosophy of the editor of the first edition, as stated in its preface:

The Glossary of Meteorology purports to define every important meteorological term likely to be found in the literature today. It attempts to present definitions that are understandable to the generalist and yet palatable to the specialist; and it intends to be a reference book that satisfies its user in a minimum of his time. Finally the Glossary provides an excellent opportunity to collect and define terms that are either obscure or very local in nature.

The second edition maintains, in many respects, the format of the first edition. in most cases, the first sentence of the definition has "stand-alone" properties; the remainder of the definition is elaboration. Defining by pure mathematics is not permitted. A worded, physical definition must be given; it may then be elaborated by one or more equations or mathematical terms to follow-up the word-based definition. References are used sparingly within a definition, and only if they clarify the user and practice of a term. In addition, references provided should be readily accessible to most individuals. Popular slang and folk terms are included in the Glossary. They are colorful and add value. In addition, many are regional in nature, but show up in the literature and may be unfamiliar to those from other regions. Acronyms are included if they are part of the "scientific vocabulary." Mathematical and statistical terms are included that are widely used in the science of meteorology. As a general rule, if a mathematical or statistical term is utilized as part of another definition in the Glossary, it will itself be included. The Glossary of Meteorology consistently uses the International System of Units (Le Système International d'Unités, SI) except in special circumstances where the preponderance of uses of a term requires otherwise. Abbreviations are included as terms to be defined if the abbreviations are popularly used in the science of meteorology. They may be used as part of the definition of a term, as long as they are not a critical part of the definition, and more clarity would be provided by spelling the abbreviated word in its entirety. Abbreviations so used conform to the standards published in the Authors' Guide (Bulletin of the American Meteorological Society, Vol. 76, No. 8, August 1995). Some terms from the first edition that were of a historical nature, or deemed to be very obscure or obsolete, have been omitted from the second edition upon the recommendation of our editors. Readers are encouraged to consult the first edition to gain a historical perspective on these terms.

Terms in this volume have been alphabetized such that those beginning with numerals or Greek letters are inserted as if they were spelled out in Roman letters. Alphabetization of compound and hyphenated words, and other style rules follow the guidance of the Chicago Manual of Style and the AMS Authors' Guide. Terms displayed in bold type (in the print edition) and hyperlinks (in the electronic edition) refer to the other terms that are themselves defined in the Glossary. We have attempted to be as comprehensive as possible, through some versions of terms (plurals, modified terms, unusual combinations etc.) may not be so linked, nor are some common words that are not used in the scientific manner as they are defined in the Glossary.

As of the date of its first printing, the print edition of the Glossary is as current as our esteemed subject area editors' work permitted. Recognizing that both the science of meteorology and publishing technology is changing rapidly, the Glossary of Meteorology is now a "living document." It is being simultaneously published in electronic form and will be updated on a regular basis to ensure that its contents remain current.

The Council of the AMS, upon recommendation of the Glossary Advisory Board and concurrence of the Managing Editor, voted unanimously to dedicate this second edition to two individuals: Charles F. Talman, whose exhaustive work as librarian of the U.S. Weather Bureau compiling terms served as a basis for the U.S. Department of Commerce Weather Glossary (1946), and by extension, the AMS Glossary of Meteorology (1959); and to Werner A. Baum, whose leadership helped shape this project from its inception through its final stages of preparation.

Todd S. Glickman Cambridge, Massachusetts June, 2000

1. The study of the physics, chemistry, and dynamics of the earth's atmosphere, including the related effects at the air–earth boundary over both land and the oceans. Fundamental topics include the composition, structure, and motion of the atmosphere. The goals ascribed to meteorology are the complete understanding and accurate prediction of atmospheric phenomena.

Any function of time f(t) is periodic with period t if f(t) = f(t + τ) for all times t, where τ is the smallest number for which this equality holds.

A law or regulation that governs behavior, actions, or operations.