1. Qc computations

For the computation of Qs usually the radiation in clear sky is computed first and with this data the net short-wave radiation is computed including the effect of clouds. The clear sky short-wave radiation (Qc) has been computed by several authors:

Hastenrath (1968) and Hastenrath and Lamb (1978) takes data from Bernhard and Phillips (1958) maps.

Etter (1983) and Etter et al. (1987) used a combination of results from Bunker (1976) and Hastenrath and Lamb (1978).

Bunker (1976) based its computations on Budyko (1963).

Adem et al. (1993) used data from Budyko (1974).

This work uses Seckel and Beaudry formula: Qc = A0 + A1 cos ɸ + B1 sin ɸ + A2 cos 2ɸ + B2 sin 2ɸ, from Reed (1977) and Reed (1983) for the coefficients values.

2. Qs estimations

Hastenrath (1968) takes data from Bernhard and Phillips maps (1958). He used A = 6%.

Etter (1983), and Etter et al. (1987) used a combination of results from Bunker (1976) computed with the formula of Budyko and Hastenrath and Lamb (1978) data.

Adem et al. (1993) used the formula given by Budyko (1974), 1 I = (Q + q)0(1-(a + bC)C)(1-A), where (Q + q)0 is the total radiation received by the surface with clear sky with a = 0.35, b = 0.38, (parameters recommended for 25°N), C is the cloud cover in tenths, and A = 6% the albedo at the sea surface.

In this work we follow Reed (1977) using the formula Qs = Qc(1 - 0.62C + 0.0019)(1- A).

3. Qb computations

Hastenrath (1968) used Qb = Qb0(1 0.60C), where Qb0 is the long-wave radiation for clear skies, and C the fraction of sky covered by clouds (in tenths). He follow Kuhn (1962) for the computation of Qb0.

Etter (1983) and Etter et al. (1987) used Hastenrath and Lamb (1978) results.

Adem et al. (1993) used Qb = -δσTa4[0.254 - 0.0066Ues(Ta)](1 - AC) - 4δσTa3(T - Ta); from Budyko (1974), where δ = 0.96 is the emissivity of the sea surface, A is the cloud cover coefficient (= 0.65 in their computation), U is the relative humidity and es the saturation vapor pressure.

In this work we use Qb = σ∈Ta4(0.254 - 0.00495ea)(1- 0.7C) following Reed (1983).

9.4. Qe, Qh, CE and CH computations

All works use the formulae: Qe = ρaCEwL(qs — qa) and Qh = paCpCHw(Ts — Ta), or an equivalent set using different unit system, but with different turbulent coefficients.

Hastenrath (1968) used CE = CH = 1.4 x 10–3.

Etter (1983) and Etter et al. (1987) computed Qe as an average of the results of the work of Budyko (1974), which uses CE = CH = 2.1 x 10–3, and Bunker (1976) with turbulent coefficients computed as a function of the wind speed and the difference of temperature between the air and the sea surface (CE and CH get values from 0.071 x 10–3 to 2.52 x 10–3).

Adem et al. (1993, 1994) used an equivalent formula, with CE = CH = 1.6 x 10–3.

In this work CE = CH = 1.4 x 10–3, a value slightly higher than those suggested in recent papers (Geernaert, 1990).