This week’s post is an adjustment on our previous post on rainfall analysis in The Gambia. This post utilizes daily rainfall data collected from 11 weather station between 1st January 1973 to 25th August 2019 in The Gambia and this data was obtained from National Oceanic and Atmospheric Administration (NOAA) website. The number of weather stations in this post differs from our previous post on rainfall because of the unavailability of daily data for three of the weather stations. This post gives analysis on daily rainfall across years and records of daily rainfall by weather stations in The Gambia. The rainfall data is recorded in inches and an inch is equivalent to 25.4mm. A day is defined as a rainy day if it records a total of 1mm or more, which is equivalent to 0.04 inches.
Figure 1: Average daily rainfall across years
Figure 1 shows the average daily rainfall across years. We learned from figure 1 that on average the years 1973 to 1983 recorded the highest number of days that rained, and this is seconded by 2004 to 2013. It is also seen that the years 1984 to 1993 recorded the lowest number of days that rained as compared to the other sets of years. The figure shows that the upper 25% of the number of days that rained between 1973 to 1983 recorded up to 0.2 inches.
Figure 2: Total rainfall across years
Figure 2 is a dot graph which shows the total rainfall across years. It is seen from the graph that the years 2004 to 2013 recorded the highest total rainfall of more than 800 inches. The years 2014 to 2019 recorded little above 700 inches and this is the second highest amount of rainfall recorded. We learned from the graph that, 1984 to 1993 recorded the lowest amount of rainfall and this amount is not far from the amount of rainfall in inches recorded by the years between 1973 to 1983. The results in figure 1 and that of figure 2 shows that in the 1970’s to the 1990’s the number of days that rained were more, however the total quantity of rainfall recorded is higher in the 2000’s.
Figure 3: Proportion of days that rained in a year
Figure 3 is a line graph overlaid with a trend line between rainfall and year. The graph shows the fluctuations in the amount of rainfall across years. It is seen that around 1986 and 2003 the lowest amounts of rainfall were recorded. In 2000 and 2008 the graph shows the highest amounts of rainfall and this was after years of low records in rainfall. The graph indicates that in 2000 and 2008 more than 15% of the days rained.
The table shows the total amount of rainfall recorded by weather stations across years. Yundum weather station recorded the highest amount of rainfall as compared to other weather stations. The amount recorded for Yundum is far greater than the other stations and this could probably be due to the number of areas that are covered by Yundum weather station. The lowest amount of rainfall was experienced in Kuntaur and that too for only 1994 to 2003. This might be due to the closure of the weather station in 2008. Analyzing as per weather stations too, the years between 2004 to 2013 experienced the highest amount of rainfall. The dots in the table represents data unavailability.
Table 1: Total rainfall by weather stations across years
|Weather Stations||1973 – 1983||1984 – 1993||1994 – 2003||2004 – 2013||2014 – 2019||Total|