Questions posed in the last paragraph in the first part of this piece were; what are the NiMet 2020 predictions? How reliable are these predictions? Before then, what were the performances of 2019 SRP across the nation?
The rainfalls of 2019 were spectacularly different in several parts of the country as the rainfalls were heavy and the wet season lasted beyond the normal period. Was NiMet able to foresee the changes? Were Nigerians fully informed of and prepared for the changes?
National Agricultural Extension and Research Liaison Services (NAERLS) in conjunction with twenty-one important stakeholders including NiMet conducted Agricultural Performance Survey (APS).
APS is a research conducted to assess the performance of a farming season. The 2019 APS evaluated the wet (cropping) season in the month of August/September of the same year. The result of the APS on rainfall situation validated NiMet predictions in several areas and showed variations in a few areas.
Rainfall situation across the nation was a major finding of 2019 APS. Rainfall is an important and critical input to crops production during the wet season.
In fact, rainfall availability, occurrence, frequency and spatial and temporal distribution determine success or failure of a cropping season. APS Report indicates more rainfall in amount and frequency in 2019 compared to that of 2018 “most states recorded an increase in rainfall in the Northeast and Northwest in 2019”, quoted from the report.
This accounted for the greater harvest forecasts for the year; unfortunately, too, the heavy downpours and high numbers of rainy days led to nationwide floods and destruction of farmlands with the worst hit in 15 states as at August 2019.
Furthermore, the report indicated “The heavy downpours and high numbers of rainy days led to nationwide floods and destruction of farmlands across the states”. The report added.
“The flooding incidence affected all the 36 states with different degree of severity. About 70% of states in the Northwest and Southeast geopolitical regions were severely affected by the collapse of several houses in both urban and rural areas.
“As at September 2019, incidences of floods reportedly destroyed three major crops; Maize, Rice Yam and Groundnut in Nasarawa, Kogi and Plateau states. Other towns affected were Doma, Lafia, Wamba, Ibaji LG, Lokoja, Idah, Jos, Pankshin, Kanke, Shendam, Qua’anpan, Langtang N.S, Mangu, Miang and Bassa.
“Several Crops and Farmlands, Poultry, Houses and Livestock were destroyed in many towns of Borno state such as Bayo, Konduga, Maiduguri, Jere and Mafa. Similarly, crops and residential areas were affected by flood in several towns of Bauchi state covering Dass, Bogoro Tafawa, Balewa, Alkaleri, Kirfi, Toro, Warji, Jamaare Zaki, Ganjuwa, Katagum, Damban and Misau.
“In the same vein, several Poultry farms, Aquaculture and crops area were destroyed in Lagos state that included Ibeju-Lekki, Ikorodu, Badagry and Agege towns. The multifaceted impacts of flooding on the larger economy are mainly on health, creative technology, transportation education, trade and investment, business and finance”.
The 2019 APS report revealed that on the average, the flood incidences affected not less than 25 per cent of the crops grown, livestock and other properties in the aforementioned towns and villages across the nation.
The report could not quantify in monetary term the worthiness of the destroyed properties by flood in 2019. Billions of Naira worth of properties were certainly lost due to flood during the 2019 season.
While APS report presented the actual field experiences on rainfall across the nation, NiMet prediction provided expected rainfall amount, onset, length and end of the rainy season. Now, what was the performance of NiMet 2019 Seasonal Rainfall Prediction? NiMet reported the overall average performance of 81 per cent.
This result accounts for the four areas of prediction; onset of the rainy season (specific date), length (days), end of the rainy season (date) and the annual amount of rainfall (quantity).
The aggregated averages of 2019 predictions performances across the 774 LGAs were 83, 85, 83 and 74 per cent for the onset of the rainy season, the length, end of the season and amount of rainfall, respectively.
The performances were evaluated by comparison between the actual and predicted amounts. The variance was negative for under-prediction when the actual amount received is higher than the predicted one.
On the other hand, the variance is positive for over-prediction when the actual amount received is lower than the predicted one. NiMet presented the performances in map of Nigeria with shaded areas for under and over predictions.
There were four maps; each representing one area of prediction – the onset of rain, length of the rainy season, end/cessation of the rainy season and rainfall amount.
Interestingly, more than 70 per cent of the maps indicated under-prediction. Example for the onset, with the exception of few border towns in Sokoto, Ondo and Cross River states, all other areas across Nigeria received rainfall slightly earlier than dates NiMet predicted for the onsets.
A similar trend was observed for the rainfall cessation, with exception of few towns in Borno, Yobe and the northern Jigawa States, all other areas across the nation continued to receive rainfalls beyond the NiMet predicted the end of the rainy season. What are the implications of the variances between the predicted and actual onset and end of the rainy season?
Before answering this question, it is important to reflect the NiMet Prediction performances of 2018 SRP. In my 3-series article of 1st to 15th February 2019 with a similar title with this article, presentation of NiMet 2018 SRP was made.
Part of the presentation was the precision of prediction for rainfall cessation, I wrote “On the rainfall cessation dates for the 2018 rainy season, most towns in the northwest like Katsina, Sokoto and areas surrounding the towns were predicted to experience early cessation of rainfall around 28th September 2018.
Southern coastal cities were predicted to receive their last rain of the year in December 2018. However, cessation of the growing season for the majority of the towns in Nigeria was predicted to be normal with exception of Jos, Ubi, Uyo and Lagos that experienced early cession.
NiMet achieved 91% and 89% precision in the predictions of rainfall and growing seasons cessation, respectively”. The performances of the 2018 predictions (91% and 89%) are slightly higher than the 2019 predictions of 83% and 85%. Again On the 2018 annual rainfall amount, I stated, “NiMet achieved an average of 65% precision making the overall achievement of 2018 SRP to be 84%”.
This is also higher than the overall 2019-prediction performance of 81%. These results reflect the 2019 predictions made in the month of February 2019 during the SRP public presentation.
However, in the month of August 2019, NiMet concertedly adjusted or updated her predictions of rainfall amount and early cessation of rainfall that “the rain will be above normal and the season will extend beyond the predicted dates of rainfall cessation”.
This information was little too late and several stakeholders were not aware of the update. In spite of the challenges of 2019 wet season caused by incidences of flood, the agricultural productivity was found to increase in 2019 compared to 2018 wet season as presented in the 2019 APS report.
Now back to the implications of the variances between the predicted and actual onset and end of the rainy season. The implications are diverse with devastating effects on farming. Many cereal crops farmers in the affected areas experienced heavy post-harvest losses as a result of continuous rainfall after the crops were ripe and harvested.
Crops growth and maturity are basically time-dependent processes. Rainfall like other important farm inputs does not prolong the age of crops but healthy growth and high yield. It is therefore imperative that NiMet has to strive hard to achieve higher prediction precision within the range from 95 to 100 per cent.
To achieve this feat, NiMet may be facing two major challenges. First, the ability of NiMet to acquire (finance) and operate (capacity/skill) high sensitive and precision equipment to enable good weather prediction with high certainty across the country.
Second, climate change is making the business of weather prediction arduous because of high volatility spatially and temporarily across the globe.
Well, in spite of relatively low performance of 2019 predictions compared 2018, several stakeholders scored NiMet performance outstandingly high and thus, reinforced their confidence. NiMet has to work hard to improve her predictions to achieve 100% precision. Now, what is the content of 2020 SRP? To be continued next week.
Professor Othman is the Executive Director of National Agricultural Extension and Research Liaison Services (NAERLS), ABU Zaria.