Heatwave calculation based on maximum temperature in R

问题

A heatwave is defined if the maximum temperature at a meteorological station is 3 °C or more than the normal temperature consecutively for 3 days or more (Adopted from India Meteorological Department, Pune). I have calculated the daily average (daily normal) from multiple-year daily maximum temperature data like

df <- data.frame("date"= seq(from = as.Date("1970-1-1"), to = as.Date("2000-12-31"), by = "day"),
                        "MaxT" = runif(length(seq.Date(as.Date("1970-1-1"), as.Date("2000-12-31"), "days")), 20, 40))

df$day <- format(df$date, format='%m-%d')

daily_mean <- aggregate(MaxT ~ day, data=df, FUN=mean)

Now it has to be matched with every year's daily maximum temperature and identify the dates when the maximum temperature is 3 °C or more than the normal daily temperature consecutively for 3 days or more. Those events will be considered as heatwaves. My question is how to implement it in R?

回答1:

Here is a way using dplyr and zoo's rollapplyr.

library(dplyr)

df_out <- df %>%
           left_join(daily_mean %>% rename(mean_temp = MaxT), by = 'day') %>% 
            mutate(is_heatwave = zoo::rollapplyr(MaxT > (mean_temp + 3), 
              3, all,fill = NA))

some instances of heatwave :

df_out[31:50, ]

#         date     MaxT   day mean_temp is_heatwave
#31 1970-01-31 26.31675 01-31  28.31451       FALSE
#32 1970-02-01 22.05946 02-01  29.83059       FALSE
#33 1970-02-02 34.22469 02-02  29.84562       FALSE
#34 1970-02-03 33.03264 02-03  29.87919       FALSE
#35 1970-02-04 36.62357 02-04  31.50603        TRUE
#36 1970-02-05 29.82134 02-05  30.22581       FALSE
#37 1970-02-06 28.13625 02-06  29.64073       FALSE
#38 1970-02-07 29.95754 02-07  29.54277       FALSE
#39 1970-02-08 21.40026 02-08  30.96619       FALSE
#40 1970-02-09 33.10983 02-09  28.16146       FALSE
#41 1970-02-10 30.87346 02-10  29.37693       FALSE
#42 1970-02-11 31.08721 02-11  28.89930       FALSE
#43 1970-02-12 27.34925 02-12  29.27882       FALSE
#44 1970-02-13 31.88582 02-13  29.35825       FALSE
#45 1970-02-14 30.05155 02-14  28.24995       FALSE
#46 1970-02-15 35.07049 02-15  29.02716       FALSE
#47 1970-02-16 39.49029 02-16  32.75644       FALSE
#48 1970-02-17 37.41917 02-17  31.44022        TRUE
#49 1970-02-18 36.03564 02-18  29.56212        TRUE
#50 1970-02-19 36.48052 02-19  30.18766        TRUE

TRUE values are where heatwave was present. As we can see in row 33, 34 and 35 we had 3 consecutive days when MaxT was greater than mean_temp by more than 3 degrees. Similarly, we can verify for other days.

To get yearly heatwave occurrences, we can do :

df_year <- df_out %>%
             group_by(year = format(date, "%Y")) %>%
             summarise(total_heat = with(rle(is_heatwave), 
                                         sum(values, na.rm = TRUE)))

and sum(df_year$total_heat) would give overall count.

来源：https://stackoverflow.com/questions/61183109/heatwave-calculation-based-on-maximum-temperature-in-r

标签

dplyr

tidyverse