Ireland Rainfall for January 25 Stations

Introduction

A rainfall map of Ireland demonstrates data from 25 weather stations across the country, highlighting the median rainfall levels during the month of January from 1850 to 2014. As one of Ireland’s winter months, January is characterized by cool, wet and windy with average temperature of 5.5 degree celcius, rainfall and frost (O’Hara,.2024). This project aims to visualize the distribution of rainfall across Ireland, showcasing the median January rainfall levels recorded at these weather stations.

Data

The datasets used for the map are rainfall data for 25 weather stations in Ireland illustrating year, month, rainfall and station comprising data records from January 1850- December 2014. The other dataset used was weather stations data consisting of station name, coordinates and county name etc. These datasets were accessed on Maynooth University Moodle under analysing spatial and temporal data using R module.

Codes

# Load libraries
library(dplyr)

Attaching package: 'dplyr'

The following objects are masked from 'package:stats':

    filter, lag

The following objects are masked from 'package:base':

    intersect, setdiff, setequal, union

library(ggplot2)
library(sf)

Linking to GEOS 3.12.2, GDAL 3.9.3, PROJ 9.4.1; sf_use_s2() is TRUE

# Load data
load("rainfall.RData")
counties <- st_read("counties.geojson")

Reading layer `counties' from data source 
  `C:\Users\mauch\OneDrive\Documents\Msc Climate Change\R2 Assignment\Class Materials-20241107\counties.geojson' 
  using driver `GeoJSON'
Simple feature collection with 40 features and 2 fields
Geometry type: MULTIPOLYGON
Dimension:     XY
Bounding box:  xmin: 17528.59 ymin: 19537.25 xmax: 366403.6 ymax: 466923.2
Projected CRS: TM65 / Irish Grid

weather_stations <- st_read("weather_stations.geojson")

Reading layer `weather_stations' from data source 
  `C:\Users\mauch\OneDrive\Documents\Msc Climate Change\R2 Assignment\Class Materials-20241107\weather_stations.geojson' 
  using driver `GeoJSON'
Simple feature collection with 49500 features and 11 fields
Geometry type: POINT
Dimension:     XY
Bounding box:  xmin: 46633.44 ymin: 59756.08 xmax: 330201.3 ymax: 457227.9
Projected CRS: TM65 / Irish Grid

# Filter rainfall for January and calculate median rainfall
rainfall_summary <- rain %>%
  filter(Month == "Jan") %>%
  group_by(Station) %>%
  summarise(median_rainfall_jan = median(Rainfall, na.rm = TRUE))

# join median rainfall data with station data
stations <- stations %>%
  left_join(rainfall_summary, by = "Station")

# Plot map
ggplot() +
  geom_sf(data = counties, fill = "white", color = "gray") +
  geom_point(data = stations, 
             aes(x = Easting, y = Northing, color = median_rainfall_jan), 
             size = 3) +
  scale_color_gradient(low = "orange", high = "green", name = "Median Rainfall\n(January)") +
  labs(title = "Median Rainfall in January for 25 Weather Stations in Ireland",
       caption = "Source: Assignment Data") +
  theme_minimal()

print(plot)

function (x, y, ...) 
UseMethod("plot")
<bytecode: 0x00000161b5f80f20>
<environment: namespace:base>

Discussion

The map illustrates the median rainfall in January across 25 weather stations in Ireland showing variations in rainfall. The rainfall levels are color-coded with green and orange showing median rainfall amount ranging from 90mm to 150mm. Green representing higher median rainfall over 150mm and orange representing lower median rainfall around 90mm.

Regions along the western and southern coasts shows higher median rainfall suggesting the influence of Atlantic weather systems and prevailing westerly winds. Equally, eastern and midland areas experience lower rainfall as a result of rain shadow effect from Ireland mountain ranges.

The map gives a clear representation of rainfall trends which are essential in understanding hydrological patterns and raising awareness on flood and drought risks. This information can help policy makers in planning for agricultural and other areas such as disaster risk reduction and preparedness (Knustol et.al.2017).

Conclusion

It has been observed that regions along the western and sourthen coasts had higher median rainfall in January for the period 1850-2014 compared to eastern and midland areas due to the influence of Atlantic weather systems and prevailing westerly winds.

References

Knutson, T., Kossin, J.P., Mears, C., Perlwitz, J., Wehner, M.F., Wuebbles, D.J., Fahey, D.W., Hibbard, K.A., Dokken, D.J., Stewart, B.C., Maycock, T.K., 2017. Ch. 3: Detection and Attribution of Climate Change. Climate Science Special Report: Fourth National Climate Assessment, Volume I. U.S. Global Change Research Program. https://doi.org/10.7930/J01834ND

O’Hara,K.,2024. Ireland weather by Month. A guide to the seasons and climate in Ireland.https://www.theirishroadtrip.com/the-weather-in-ireland-by-month/