This list addresses changes/corrections that are frequently requested by authors at proof stage for American Meteorological Society (AMS) journals and explains some points of AMS style. All references to the Chicago Manual of Style (Chicago) below refer to sections in the 17th edition.

Please note: edits contrary to AMS style will not be incorporated into the final version.

1. Why were commas and periods set inside quotation marks? We follow the Chicago Manual of Style (6.9) on this point: “Periods and commas precede closing quotation marks, whether double or single. This is a traditional style, in use in the United States well before the first edition of this manual (1906).”
2. Why was the capitalization of some words and phrases changed? Please see the AMS Acronym List, the AMS Style for Geography and Oceanography Terms, and the AMS Glossary of Meteorology for the correct capitalization of common terms. AMS also follows the Merriam-Webster Unabridged Dictionary and Merriam-Webster Geographical Dictionary for geographical names. Note that AMS style does not allow capitals within a syllable, such as are sometimes used to indicate the origin of an acronym.
3. Why have the times been changed to 4-digit time? Why were colons deleted from the 4-digit times provided? See Units, Time, and Date for an explanation. Note that AMS style reserves colons to separate seconds from the four-digit UTC or local times.
4. Why were hyphens added to or removed from number–unit pairs? It is AMS style to hyphenate number–unit pairs when they are used to modify a noun but not when they are the nouns themselves. See Units, Time, and Date for examples and further explanation.
5. Why were some hyphens changed to longer dashes [en dash (–) or em dash(—)]? 
   1. An en dash (–) is used to connect a numerical range (such as dates, times, and page numbers) and, less often, words (except when the first term is preceded by “from” or “between”). See Chicago 6.78.
   2. Per Chicago 6.80, “The en dash can be used in place of a hyphen in a compound adjective when one of its elements consists of an open compound or when both elements consist of hyphenated compounds.” For example, terms like “cross–Gulf Stream” and “climate change–related” use en dashes because “Gulf Stream” and “climate change” are open compounds.
   3. Per Chicago 6.85, em dashes (—) can function as an alternative to parentheses, commas, or a colon. There should be no spaces around em dashes. Chicago notes that in British usage (and some non-British usage), spaced en dashes are used in place of em dashes. If an author uses spaced en dashes, AMS will change them to closed em dashes. Hyphens should never be used in place of em dashes.
6. Why were hyphens deleted from some compound terms (e.g., midlevel, subtropical)? AMS follows the Merriam-Webster Unabridged Dictionary and the Chicago Manual of Style as our primary guides for when to hyphenate compound terms. Compounds with prefixes are generally closed, with some exceptions. This means that most words beginning with prefixes like non-, sub-, pre-, post-, over-, under-, etc. will be closed up (i.e., not use a hyphen). See Chicago’s Hyphenation Guide (7.89) for a more detailed explanation.
7. Why were author names replaced by long dashes (2 em dashes) in the references? Chicago style is to use a 3-em dash for repeated author names in references; AMS uses a 2-em dash. Authors should not use 2- or 3-em dashes for repeated names in their manuscripts; this change is applied during editing. Additionally, authors should not try to replace the 2-em dashes with the author names at proof stage; this change will not be allowed.
8. Why is the link for the supplemental material not working? The hyperlink for the supplemental material will appear in the proof, but it will not be activated until the paper is published.
9. Why were sentences edited so they no longer start with a variable/symbol/numeral? Per AMS style, symbols and variables should not begin a sentence. Words such as “The,” “Parameter,” “Term,” and “Variable” or the definition of the symbol/variable may be inserted at the beginning of the sentence. If a sentence begins with a number, the number may be written out (e.g., “Thirteen” instead of “13”) or the sentence restructured so that it no longer begins with a number.
10. Why were the parentheses or brackets changed? For both text and equations/mathematics, AMS uses a standard hierarchy to indicate levels of fencing: ({[()]}). Authors can define a special usage exception (for a function, set, matrix/vector expansion, etc.).
11. Why does it appear that “Figure” and “Fig.” are used inconsistently? AMS uses “Figure(s)” at the start of a sentence and “Fig(s).” internally within text, except for caption labels, which use “Fig.”
12. Why is the word “section” (e.g., “as described in section 3”) lowercase? When referencing numbered sections in text, the leading S is lowercased: “The data were processed using the method that is outlined in section 2a.”
13. Why have units (e.g., km, %) been deleted in some places but retained (or added) in others? When two or more numbers that carry the same unit are listed consecutively, the unit is placed after the last item (1 and 2 km; 1, 3, and 4 m). The exception to this is for percent and degree symbols, which are used after every number in a series (3%, 10%, and 30%; 2° and 4°C).
14. Why are there spaces in the middle of a number or value? To avoid any possible confusion with the European convention of using commas for decimal points and vice versa, AMS follows the AIP Style Manual and the Chicago Manual of Style (9.56) in its treatment of scientific numbers and page numbers that have five or more digits to the right or left of a decimal point. Commas are dropped, and groups of three digits are formed moving outward from the decimal point, separated by thin spaces. Also, four-digit numbers are not separated by a comma after the first digit. Examples of AMS style are 2178, 0.2178, 25 000, 1 500 000, 0.034 46, and 0.034 467 1.
15. Why is the end year in year ranges sometimes only the last two digits and sometimes the full year? Per Chicago 9.64, year ranges do not include the century in the second year unless a transition of centuries is spanned (e.g., 1988–92 but 1887–1901).
16. Why is a/an used instead of an/a before an abbreviation? Per Chicago 7.33 and 10.9, the choice of the article a or an is determined by the way the abbreviation would be read aloud. AMS style generally “reads” abbreviations as the letters of the abbreviation versus as the full term. For example, the text “SS” for “skill score” would be read as “an SS” as opposed to “a skill score.”
17. Why are there square brackets around the equation numbers in the text? If an equation is referred to parenthetically in the text, the equation number is enclosed in brackets. Examples: "This prevents the algorithm from optimizing the objective function [Eq. (4)]"; "This prevents the algorithm from optimizing the objective function [(4)]."