I have computed the evapotranspiration in MATLAB using the FAO PM method and found negative values especially in January month. The study site was in Sicily, Italy ( very rare for snow and uncommon the temperature less than 0 degree temperature) Could yo suggest me why the value is negative, please?
Dear Tagele,
Negative values of evapotranspiration are not physically meaningful and suggest that there may be a problem with your calculation or input data. There are several possible reasons why you may be getting negative values, including:
1: Incorrect input data: Check that you have entered the correct values for temperature, humidity, wind speed, solar radiation, and other inputs. Make sure that the units are consistent and appropriate for the FAO PM method.
2: Errors in the code: Check your MATLAB code to ensure that there are no errors or typos in the equations or formulas. Check that you have used the correct constants and parameters for the FAO PM method.
3: Physical limitations: Negative values of evapotranspiration are not physically meaningful, as it represents a loss of water from the system. It may be that the FAO PM method is not appropriate for the conditions at your study site, or that there are physical limitations to the system that are not captured by the model.
4: Data quality: Check the quality of your input data to ensure that it is accurate and representative of the conditions at your study site. If your data is incomplete or unreliable, it may lead to negative values of evapotranspiration.
It is also worth noting that the FAO PM method may not be appropriate for all conditions and locations, and there may be other models or methods that are better suited for your study site. You may want to consider consulting with an expert in the field or seeking additional guidance from the literature to ensure that your evapotranspiration calculations are accurate and meaningful.
Thank you for your supportive comments. The problem was from the code. Now, it works perfectly!
I’m glad that it worked! Let me know of you need any other help. And if you need your research to ne proofread, let me know and I can assist with that! All the best.
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