Dear colleagues,
Does anyone know if there is any rainfall threshold (mm/year, month or day, etc.) for a city to be considered "rainy" or "very rainy"? Or the rainfall intensity thresholds (weak, moderate, heavy, etc.)? Are there any international standards, for example from ISO or another institution? If there is a reference to support it, it will help better.
Ditto for wind speed thresholds (m/s or kt) for a place to be considered "windy". Does anyone know any references?
Thank you in advance for your attention.
Dear Christiano, distant friend,
as I know, there is a system of distinguish rainfall intensity in many countries.
In East Asia, in meteorology, precipitation is used to distinguish the intensity of precipitation. Divided into: light rain, moderate rain, heavy rain, heavy rain, heavy rain, heavy rain, heavy rain, light snow, moderate snow, snow and blizzard.
For example, Heavy rain: all rainfall processes with more than 50mm of precipitation within 24 hours are collectively referred to as heavy rain. According to the intensity of heavy rain can be divided into: heavy rain, heavy rain, heavy rain three. Rainstorm: rainfall process with 30 ~ 70mm of precipitation within 12 hours or 50 ~ 100mm of precipitation within 24 hours. Heavy rain: the precipitation process of 70 ~ 140 mm in 12 hours or 100 ~ 250mm in 24 hours. Heavy rain: a process with precipitation greater than 140 mm in 12 hours or 250mm in 24 hours.
Actually, meteorological observations have been early standardized in the world.
Hope the above information useful for your question.
Best wishes,
Hao
As for rainfall threshold, we do not use the term rainy, but we use the rainy season terminology above 100mm/day is considered, and this is based on the meteorological agency. Not so sure about wind threshold, but storm has a threshold tropical cyclone is at 20km/hr.
Dear Cristiano,
This depends on the local topographic conditions (near the water, next to the mountains, etc.).
For rain - Bergen in Norway. It has near 300 days of rain per year.
For wind - Shetland. It had 29 days of gales ( exceeding force 8 on Beaufort Scale) in January one year.
I would reckon that climatic classification must affect people’s perception though of what is windy and what is rainy
Regards
George
Dear Christiano,
The concept of Precipitation Concentration is crucial to understand the spatial and temporal patterns of precipitations. Many authors define thresholds which mostly converge: the most common (you can find in the following open access article) are :
Wet day: >= 1mm/day
Heavy wet day: >= 10mm/day
Extreme wet day: >= 50mm/day
Best regards,
Reference: https://www.researchgate.net/publication/331411976_Rainfall_distribution_and_trends_of_the_daily_precipitation_concentration_index_in_northern_Morocco_a_need_for_an_adaptive_environmental_policy