Expanding Knowledge of the Monsoon

To improve climate forecasts such as those I discussed in my first post, scientists study the complex interactions and mechanisms within the climate system, such as the ways in which the Pacific and Atlantic Oceans may interact to produce unique rainfall years for the Sahel. But to better guide this research in ways that will ultimately be useful, scientists need to hear from potential users of climate information, such as farmers, and thus gain a better understanding of how people may use such information in their decision-making.

One of the ways in which scientists learn about farmers’ information needs is through workshops. Last June, with the 2015 seasonal forecast in hand, workers from Senegal’s Agence Nationale de l’Aviation Civile et de la Météorologie (ANACIM) began their field visits to share the forecast with farmers in a series of workshops. Dr. Ousmane Ndiaye, a climate scientist at ANACIM, has taught me to think of these workshops as an integral part in developing an early warning system in which climate information, including the seasonal forecast, is passed along to experts, decision makers, and the local communities in order to prepare for the climate conditions brought on by Mother Nature. The workshops allow scientists, the local working group and community members to come together to meet and foster partnerships for the success of this important system.


Setting up for a climate services workshop in Niakhar, Senegal. Photo credit: Catherine Pomposi

Now in its fifth year of running such workshops, ANACIM has scaled up to include visits to both the northern and southern regions of Senegal. After the initial visits to local communities, information continues to be distributed and exchanged between the providers and users of climate information through rural radio broadcasts and text messaging.

Throughout my time in Senegal, I’ve had the privilege of participating in several such “climate services” workshops in Niakhar and Kaffrine. The workshops typically last one to two days and include elements common of most meetings: welcoming remarks from leaders, introductions of special guests and an overview of why they are in the villages. Scientists from ANACIM then discuss the natural climate variability of the region with community members and frame the use of climate information for agricultural purposes. They explain the science behind the seasonal forecasts by talking about the oceans as the “memory” of the climate system due to how slowly they evolve compared to the rapidly-changing atmosphere.


Farmers in Niakhar listen and watch as the scientific seasonal forecast is disseminated. Photo credit: Catherine Pomposi

In addition to providing the forecast with probabilities for a  wetter- or drier-than-normal season, workshop participants discuss the timing of the rains for that particular year. From a farmer’s perspective, this is one of the most important aspects of the seasonal forecast because it influences when they should begin planting and what seed types to place in the ground (some varieties favor a longer growing season over a shorter one, for example). From a scientific perspective, the timing of monsoon rains is an even tougher question to pin down than whether or not the season will be anomalously wet or dry.

Another goal of the workshops is to build partnerships among the scientists, workshop leaders and local community members.  At a workshop in Fatick , an agricultural extension worker gave farmers rain gauges so that they could measure and record the amount of rainfall each day. The local community members then report their findings back to the meteorological agency, who can use the data in scientific research. This is one way in which the exchange between scientists and the local communities truly benefits both groups, making the partnerships more likely to last.

Participants next break into smaller groups to document both the region’s historic climate patterns and the kinds of information that would be most helpful for the scientists to provide as the exchanges continue.

What kinds of climate information could a farmer in Senegal find useful?

“Will the season be long or short?”

“When will the rains begin?”

“What is the middle of the rainy season?”

These are some of the questions farmers raised during a workshop I attended in June 2014 in Niakhar. From a scientific perspective, most of the research to date on West African monsoon variability has been to improve prediction of total rainfall for a particular year or season in terms of more or less than its average, as well as understand why. I’ve noticed time and time again though, that from a farmer’s perspective, information about the length and timing of the rainy season is more important than an estimate of total rainfall.


Farmers break into small working groups during the workshop. Photo credit: Catherine Pomposi

Based on my experiences in Senegal, I’ve expanded my own research interests to seek answers to some of the questions highlighted above. Much of the variability in West African monsoon rainfall comes from the global oceans. Prior to visiting Senegal, my research focused on how the global oceans forced drought patterns in the Sahel on long (e.g. decadal) timescales, such as during the very dry 1970s-1980s. Having now spent time with people in the area, I have a greater appreciation for the shorter-term variability and the potential for applications of research at this timescale. I am now trying to understand how the global oceans interact with one another to change precipitation patterns within a season, such as the number of times a rain event happens, the length of a season and the intensity of rain events.

These research goals fall nicely into a category of climate variability that is gaining more and more attention, known as sub-seasonal to seasonal (S2S) variability. A new S2S project sponsored by the World Meteorological Organization (WMO) and World Climate Research Programme (WCRP) aims to bridge the gap in understanding between the weather timescale (up to two weeks) and the climate timescale (anything beyond two weeks). Research stemming from this project could lead to better answers for the questions listed above. These questions are not unique to farmers in Senegal – they are asked by farmers throughout many tropical countries.

Farmers Traditional Knowledge of the Monsoon

Continuing to motivate research based on needs of end-users of climate information can increase climate resilience and lead to better food security and economic livelihoods worldwide. But scientists aren’t the only ones intimately familiar with the climate. One of my favorite parts of the climate services workshops is hearing about farmers’ traditional knowledge of the monsoon system. For many more years than scientific climate forecasts have been available, farmers throughout the region have made decisions relying on their own understanding of climate patterns passed down through generations. Indeed, scientists have shown that in some parts of the world (e.g. South America), endemic knowledge of climate patterns provides meaningful and scientifically-based information that aids local inhabitants in decision making. Now, with the establishment of partnerships among local farmers, communities and meteorological agencies such as ANACIM, scientific and traditional knowledge of rainfall patterns can be shared across the two groups.

The traditional indicators discussed at the workshops in Senegal can be broadly identified as belonging to one of three categories: scientific, coincidental or mystical.  Mystical indicators include information provided by village elders who believe that a season might be more robust or weaker and communicate this information to others. Another indicator that came up often in discussion had to do with the moon, either its phasing or shape. For example, one farmer told us that a crescent moon means that there should be a weaker rainy season than normal—small moon, small rains. Another said that when the moon is approximately 10 days into a new cycle, it’s the best period to begin planting because rains could be expected shortly after. While farmers may be using such information to guide their decisions, from a climate science perspective we would consider such indicators to be coincidental: we do not expect a direct linkage between the moon and precipitation over land.

Finally, there are traditional indicators that could have a scientific basis, though proving a direct relationships is more challenging (but could result in a really interesting research paper!). The science-based indicators include things like the behavior of plants and animals in the region, or wind patterns. When the monsoon invades the region, winds switch from coming from the north and east to coming from the south and west. It is through these changing wind patterns that moist air from the ocean is brought over land, driving the monsoon. The resulting changes in humidity and temperature over land are felt by plants and animals, which will then respond. Many of the indicators that fall into this category include changes to certain trees in the region, such as the mighty baobab and tamarind trees. Some farmers note that when the fruit of the baobab becomes about the size of a human hand, the rains should start soon. Others note the behavior of animals. One farmer said that when lizards begin to move around more, particularly up the roofs of houses or trees, rainfall should begin soon. It is likely that some of these behaviors observed for centuries by local inhabitants are grounded in the changing humidity and temperature patterns of a monsoon climate.

Members of ANACIM work to robustly document the traditional monsoon indicators and compare them against seasonal forecasting information to gain a more quantitative assessment of their use. Some years have found the scientific and traditional forecasts to be in agreement with one another, while during other years they have suggested opposing monsoon characteristics. Hearing of these indicators has been one of the most interesting and unique aspects of visiting with farmers and shows a blending of the kinds of information, scientifically-based and not, driving decision making.


The workshop ends and the school yard (site of the workshop) becomes quiet once more. Photo credit: Catherine Pomposi