Agroclimatological report August 2023:
This Agroclimatological Report has two objectives:
1.- Analyze the agroclimatic conditions of August, with special emphasis on storms.
2.- Project agroclimatic scenarios to September 2023.
Rain front and atmospheric river.
Figure 1. Red indicates heavy rain. Yellow indicates moderate rain. Blue indicates light rain (image corresponds to Monday, August 21, the day with the most rain in 24 hours).
Between August 18 and 22, at least three frontal systems affected the Maule region. The first three (days 19, 20 and 21) were associated with atmospheric rivers, which left amounts of 51.0, 20.6 and 110.0 millimeters respectively. In the case of Licantén, on August 21, 139.5 millimeters of rain fell in 24 hours. The image shows, in red, the distribution of intense rainfall from the mountain range (with 600.0 millimeters) passing through Curicó Hualañé, Licantén and culminating in Pichilemu, during the day of August 21.
These intense precipitations, in the short term, do not constitute the so-called “effective rains”, Those that by definition are slower and more extensive in duration, without causing serious damage to agriculture. On the other hand, when they are intense, in a short time, they only cause damage to urban areas, roads and rural areas. According to climate change models, this could be the beginning of frontal systems, associated with tropical atmospheric rivers, that could be more recurrent in the coming winters. If there were two this year, it is likely that in the coming winters there will be three. It is one of the threats to which regional agriculture must adapt to reduce its vulnerability.
It is recommended to design strategies that are more resistant to this type of intense rainfall; protect irrigation canals, floodgates, irrigation systems and watershed management to minimize future impacts that these rains could bring in the coming winters. One of the characteristics of climate change is that meteorological extremes, such as extreme temperatures, intense rainfall or long periods of drought, will be the essential characteristic in central Chile. Any additional protection can minimize damage.
Agroclimatic projections for September 2023
Probabilistic models, both statistical and dynamic, estimate that the September rain cycle will be influenced by the development of the El Niño event, which began in June and will culminate in the fall of 2024.
1.- There is a chance of rain on August 28 (4 millimeters) and from September 2 to 5 a frontal system could leave rain between 20 and 40 millimeters. The days with the highest risk of rainfall would be the 2nd and 3rd (probably the 4th) of the month. Pay attention to the conditions and evolution of this frontal system.
2.- Between September 7 and 9 we will be under the influence of cold air masses. Be aware of frosts that could occur in geographically low areas of the orchards.
3.- For the month of September, in which it is still winter until the 22nd, the greatest recommendations are due to the occurrence of late rains followed by probable frosts. For this reason, it is necessary to pay attention to the meteorological evolution. September is a month of transition from winter to spring, which is why it tends to behave in a very anomalous way; even more so with the current presence of the warm event El Niño (associated with rains with heat and hail in spring). Do not be careless in a year that has been extremely complex for agriculture.
Summary
Winter frontal systems associated with extreme atmospheric rivers may constitute a permanent risk in future winters. Prevention strategies must be developed, which are different depending on the location of crops and fruit trees. Climatic extremes are part of the changes that the climate is undergoing, a product of global warming. With the arrival of the El Niño event, which is an additional warming of the ocean and the atmosphere, September may result in both late rains and the subsequent arrival of frosts. It is advisable to be aware of the meteorological conditions in each sector: foothills, central valley and coastal dryland; in each of them it is possible that the probable rains and frosts will be mitigated or amplified.
