In this assignment we will explore the weather in Athens over a period of more than 50 years.
We will work with data covering the period from 1955 to 2020. The data will be obtained from two sources:
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Data downloaded from the National Oceanic and Atmospheric Administration's National Centers for Environmental Information (https://www.ncdc.noaa.gov/cdo-web/) and in particular https://www.ncdc.noaa.gov/cdo-web/search.
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As we are focusing on Athens, we will use the data from the Hellinikon weather station and we will concentrate on the average daily temperature and precipitation.
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Explore the completeness of the data.
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To fill in any missing data we will use an alternative dataset available from https://data.hellenicdataservice.gr/dataset/66e1c19a-7b0e-456f-b465-b301a1130e3f; this dataset covers only the period from 2010-2019.
The Hellenic National Meteorological Service has published a report on extreme weather events for 2020. The report is available at http://www.hnms.gr/emy/en/pdf/2020_GRsignificantEVENT_en.pdf. In page 7 of the report there is a graph showing the mean summer temperature deviation from a baseline of 1971-2000.
We will create our own version of the graph, using a baseline of 1974-1999. The line that runs through the graph is the 10 years rolling avarege of the deviation from the mean.
We will get the average temperate for each year for the full period from 1955 to 2020. We will then create a plot showing the daily temperature for each year. The line corresponding to each year will be smoothed by using a 30 days rolling average. The lines are colored from light orange to dark orange, progressing through the years in ascending order.
On that plot we will overlay a line showing the average daily temperature for the baseline period of 1974-1999 (that is the black line). The line will also be smoothed usng a 30 years rolling average.
Another mesure used by climatologists is the number of extreme events. Extreme events are defined as those beyond 5% or 10% from the expected value. We will deal with extreme heat events going 10% above the baseline.
We will count the number of extreme temperature events per year, compared to the baseline of 1974-1999. We will produce a graph. The vertical axis is the percentage of extreme heat events calculated over the number of observations for each year. The gray line in the middle is the average percentage of extreme tempearture events of the baseline. The colour blue is used for those years where the percentage is below the baseline; otherwise the colour is orange.
Continuing the thread on extreme events, another consideration is rainfall. The weather may or may not be drying up. We are, however, interested in whether precipication becomes more intense over time.
To see that, we will count the overall rainfall over the year and the number of rainy days in each year. Then, by dividing the rainfall by the number of rainy days we will get an indication of whether we are getting rain in more concentrated bursts. We will then create a plot showing the ratio of rainfall over rainy days over the years. On the plot we will overlay the 10 years rolling average.