| 690 | | Describes r6614. The calculation of wind storm damage can be activated by setting '''ok_windthrow''' to y in the orchidee.def. This module calculates the critical wind speed of a stand taking stand and soil properties into account. If the stand is managed, the damaged trees are salvaged logged. If the stand is unmanaged the damaged trees are left on-site to decompose. The default setting for ok_windthrow is n. The damaged fractions of the stands are replanted and moved to the first age class (if more than 1 age class is used). |
| | 690 | Describes r6614. The calculation of wind storm damage can be activated by setting '''ok_windthrow''' to y in the orchidee.def. This module recognizes storms and calculates the critical wind speed of a stand taking stand and soil properties into account. If the stand is managed, the damaged trees are salvaged logged. If the stand is unmanaged the damaged trees are left on-site to decompose. The default setting for ok_windthrow is n. The damaged fractions (if this fraction is more than the replace_threshold of the total biomass per PFT) of the stands are replanted and moved to the first age class (if more than 1 age class is used). |
| | 691 | |
| | 692 | |
| | 693 | Winthrow damage calculation can be divided into two parts: storm recognition and damage calculation. |
| | 694 | |
| | 695 | Storm recognition is sensitive to 3 parameters |
| | 696 | |
| | 697 | || '''wind _ratio_threshold''' || The ratio of the current wind speed to the 5-year-mean wind speed will be summed if the ratio is above this threshold. A lower threshold causes more frequent storms. \\ Note that excessively low values can cause continuous storms in the coastal areas. || |
| | 698 | || '''wind_sum_threshold''' || The first condition to identify a storm. If the total sum of that ratio exceeds this threshold, then it is considered a storm. A lower threshold will result in the storm affecting a larger area. || |
| | 699 | || '''wind_speed_storm_thr''' || The second condition to identify a storm. Maximum wind speed of 3 days (legacy_years_wind) should be over this threshold. Lower threshold causes more frequent storm. || |
| | 700 | |
| | 701 | Calculation for windthrow damage is sensitive to 2 parameters |
| | 702 | |
| | 703 | || '''daily _max_tune''' || This represents wind gustiness. ORCHIDEE uses interpolated 6-hourly wind speed data, which means that it cannot capture wind gusts that occur at finer spatial and temporal scales. A higher value leads to greater damage. || |
| | 704 | || '''factor_closer''' and '''sfactor_further''' (PFT-level parameters) || This parameter alters the shape of the sigmoid function which represents the damage probability within a pixel. A low value makes the function stepwise, which causes near-zero damage when the wind speed is lower than the critical wind speed, and near the maximum damage when the wind speed is higher than the critical wind speed. A high value smoothes the function, which allows for small gaps from wind damage and damage in a broader area. || |
| | 705 | |
| | 706 | |
| | 707 | One setting that needs caution is '''use_fluxnet'''. This flag was created for the case in which the model utilizes fluxnet forcing but it can also be applied to coupled simulations. If use_fluxnet is set to y, 1) the wind speed is not retrieved (Check stomate.f90). Because loaded wind speeds from 6-hourly forcing become lower before interpolcation to translocate the wind (10m -> 2m above zhd) it was retrieved before storm recognition. 2) Gustiness is not considered. |
| | 708 | |
| | 709 | |
