By: Patricio Gonzalez Colville
M.Sc. (University of Chile)
Dip. Agroclimatology, University of Israel.
AGRO-OCLIMATOLOGICAL REPORT 28 SEPTEMBER 2023.
This Agroclimatological Report has two objectives:
1.- Analyze the current and future development of the El Niño 2023-2024 event.
2.- The probable impacts and risks for fruit trees.
Projection and development of the El Niño event 2023-2024.
Figure 1 shows, in red, the rise in sea surface temperature off the coast of Peru and projecting towards the interior of the equatorial zone. The temperature ranges between 28.3° C and 29.0° C, which indicates a “strong” category event on the intensity scale. According to forecast models, this event would extend until April-May 2024. However, the highest sea temperatures would occur between December 2023 and February 2024. Some of the current consequences of this event are the rainfall that occurred during September, which in Curicó totaled 90.0 millimeters, with the normal amount for the entire month being 46.2 millimeters. The surplus is 90%.
There is a 100% probability that the heat intensity of El Niño will last through December, January, and February, and a 97% probability that it will extend into fall 2024. The model does not record any chance of a La Niña event occurring during this period, which is typically associated with warmer air temperatures and the absence of spring rains.
Effects on fruit trees.
Chart 1. Probable development of the El Niño event and the probable associated monthly rainfall.
The graph shows, in yellow bars, that late rainfall is likely to occur from October to December, in amounts ranging from 20 to 10 millimetres (in blue bars, what has already been recorded). The red line indicates the evolution of sea temperatures in the central equatorial Pacific Ocean.
These rains, although minor and sporadic, can cause cracking in cherries. After the rains, temperatures will probably rise above 25 to 30°C inclusive. For fruit trees, the combination of humidity and heat is not beneficial. The appearance of stormy clouds during some afternoons in October and/or November cannot be ruled out, which can generate risks of intense showers, including hail in specific places.
Summary.
The development of a strong El Niño event would alter the thermal and rainfall patterns of spring: special care should be taken in the months of October and the first half of November, when there could be a chance of short showers associated with heat in the following days. It is advisable to take precautions and be vigilant about the evolution of the weather during these months.
Compared to summer, December, January and February, the probability of rain is much lower. Special care must be taken with heat waves, which are when the maximum temperature of the day exceeds 33°C for three consecutive days or more. This increases evapotranspiration rates to values that could be 70 to 80 cubic meters per hectare.
