Besides the dependence on the geographic location of a transmitter and a receiver, HF propagation conditions of an ionospheric transmission path between two points on the earth vary with daytime, season, and the solar cycle. Therefore it is important to find and predict the parameters for optimum operational frequencies and other radio propagation applications.
We distinguish between long term (on a monthly basis) and short term (on daily basis) HF propagation predictions. In the frame of long-term HF prediction the IAP develops and provides a software package (RPPx) to the users to calculate worldwide radio propagation predictions in the shortwave radio band 2-30 MHz. The RPPx software, primary implemented by Damboldt/Süßmann (2000-2007), calculates monthly mean values of HF propagation related parameters according to the various user specific inputs. The integrated prediction model is based on an ITU (International Telecommunication Union) recommended method. The short-term version is related to the prediction of the current regional state of the ionosphere and the geomagnetic activity. Based on ionosonde measurements it calculates the daily deviation/correction of actually propagation conditions in comparison to the monthly mean values as supplement to the long term prediction. At the same time additional selected space weather conditions are noted.
J. Mielich und J. Bremer, A modified index for the description of the ionospheric short- and long-term activity, Ann. Geophys., 28, 2227-2236, doi:10.5194/angeo-28-2227-2010, 2010