Cloudiness is the fraction of sky covered with clouds and varies from 0.0 to 0.9. Cloudiness is a required parameter for both calculated solar radiation and down welling long wave radiation.
An increase in cloudiness leads to a decrease in computed solar radiation and an increase in computed down welling long wave radiation.
A rough guideline for cloudiness is shown in Table 3.2.
Table 3.2 – Guideline for Cloudiness

The Meteorological Dataset Editor (Figure 3.29) provides three data source options for entering cloudiness (as a fraction, 0.0 to 1.0): Constant Value, DSS and Compute from ObsSW and Lat-Long (Table 3.1). Refer to Section 3.5.1 for instructions on entering cloudiness using the Constant Value (Figure 3.24) or DSS (Figure 3.25) data source option.

Compute from ObsSW and Lat-Long

Unique to the cloudiness variable, select Compute from ObsSW and Lat-Long (Figure 3.35) to have HEC-ResSim compute the cloudiness based on the met station latitude and longitude (set from the Watershed Setup module, from the Station Editor as described in Section 2.2.3) and the observed water temperature (refer to Chapter 7).

Figure 3.35 – Compute from ObsSW and Lat-Long Data Source – Available for Cloudiness
Enter a description (optional, but recommended) from the Description (Figure 3.35) box. Click Apply (Figure 3.23) to save the entered value before navigating to a different data source, met variable, met station, or met dataset. Click OK (Figure 3.23), to save the entered data and close the Meteorological Dataset Editor (Figure 3.29).