Journal topic

# Manuscript preparation guidelines for authors

The following sections provide guidelines on how to prepare and compose your manuscript. Please follow these standards to ensure a smooth peer-review and production process. When preparing your manuscript, please also refer to the manuscript-type-specific guidelines.

If you or your institute plans a press release or some other promotional work on your paper, please inform Media and Communications at Copernicus (media@copernicus.org) and at EGU (Terri Cook, media@egu.eu) before. We may be able to assist you and help distribute your work further.

## Physical dimensions and units

1. Make sure that all quantities are dimensionally correct and that relationships thereof, expressed in equations, are dimensionally consistent. In hydrology it is paramount to distinguish between stocks and fluxes. Stocks (storages) are expressed in a volume (L3) or a depth (L) if the stock is per unit area. Fluxes, such as precipitation, evaporation, infiltration, percolation, or runoff, are always expressed as a flux, expressed in L3 T–1 or L T–1 if the flux is per unit area. Even if fluxes are accumulated over a period of time, the period of integration needs to be reflected in the denominator (e.g. mm/year). Accumulated rainfall over a year does not make it a stock. It remains a flux. Although storage (S) is a stock (L3 or L), storage variation in time t, dS/dt, is a flux (so that dS/dt = PEQ is correct, whereas ΔS = PEQ is not).
2. The use of SI units or SI-derived units is mandatory.
3. Use s, min, h, d (or day) and a (or yr) for second, minute, hour, day and year, respectively. Do not abbreviate week or month.
4. Multiplication of units should be indicated by a space (e.g. N m) and division by negative exponents (e.g. m s–2). Units should be displayed using exponential formatting.
5. Prefixes of units such as M (mega = 106) and μ (micro = 10–6) have no space between (e.g. μs, MW). Note that, according to SI, any power to a unit applies also to the prefix. Note also that the prefix kilo is lower-case k (e.g. km, not Km – the upper-case K is the symbol of kelvin).
6. For areas and volumes use m2 and m3, multiplied by a power of 10, using multiples of 3 for the power (e.g. 106 m3). Alternatively use prefixed units where appropriate (e.g. km2 for 106 m2 or km3 for 109 m3). Note that a million cubic metres can be written as 106 m3 but not as 1 Mm3. In addition, hectare (ha) and litre (L) are also allowed in SI.
7. All units should be typeset using upright (roman) fonts, not italic or bold.
8. Numerals should also be typeset using upright fonts. The symbol for the decimal marker is the dot. To facilitate reading, numbers may be divided in groups of three using a thin space (e.g. 12 345.6), starting with the ten-thousand digit. Neither dots nor commas are permitted as group separators.

## Symbols and equations

1. Equations should be numbered sequentially with Arabic numerals in parentheses on the right-hand side, e.g. (1), (2), etc. If too long, split them accordingly. If there are chemical formulae included (i.e. reactions), please number them (R1), (R2), etc. When using Word, the equation editor and not the graphic mode should be used under all circumstances.
2. Multi-letter variables should be avoided. Instead use single-letter variables with subscript (e.g. ERMS instead of RMSE, or ET instead of ET). Single-letter variables or parameters and  user-defined function symbols should be italic (e.g. x, Y, β, f(x)). Multi-letter variables, if they cannot  be avoided, should be roman.
3. Common, explicitly defined, functions should not be italic, whether their symbols are single-letter (e.g. Γ(x) for the gamma function, B(y, z) for the beta function) or multi-letter (e.g. ln x, exp(x + y)).
4. Textual subscripts or superscripts should not be italic (e.g. xmax, Tmin where "max" and "min" stand for maximum and minimum, respectively).
5. Mathematical constants should not be italic (e.g. e = 2.718…, π = 3.141…, i2 = −1). Also, mathematical operators should not be italic (e.g. dx in integrals and derivatives, Δγ for the difference operator on γ).
6. Vectors and vector functions should be bold and italic (for single-letter variables). In particular, vectors are usually denoted with lower-case letters (e.g. x, ω as vectors; f(x) as a vector function of a vector variable). Matrices should be identified in bold with upper-case letters (e.g. A as matrix; AB as the product of matrices A and B, AT as the transpose of A, and A as the determinant of a square matrix A).
7. To distinguish between random variables and their realizations, use upper-case symbols for the former and lower-case ones for the latter (e.g. P{X = x}).
8. Do not use the hyphen (-) as a minus or subtraction sign; use the en dash (–) instead. Also do not use the letter x or the symbol * as a multiplication sign; either use the symbol × or middle dot (·) between numerals, or use a thin space (or even no space) between variables.
9. For simple expressions in the body of the text, use slash (/) to denote division (e.g. (x + y)/2η) rather than a fraction with a horizontal division line.

## Date and time

25 July 2007 (dd month yyyy), 15:17:02 (hh:mm:ss). Often it is necessary to specify the time if referring to local time or universal time coordinated. This can be done by adding "LT" or "UTC", respectively.