Heat Wave Metrics - SoCal 2006-2021

Load data with daily max and min temps for SoCal zip codes (gridMET 2006-2021)

load("~/UCSD-Scripps/R Files 2022/Heat Metrics/socal_heat.RData")
socal_heat$tmmx_C <- socal_heat$tmmx - 273.15
socal_heat$tmmn_C <- socal_heat$tmmn - 273.15

library(dplyr);

socal_heat <- socal_heat %>% select(-one_of('tmmx', 'tmmn')) # remove columns with temp in Kelvin

summary(socal_heat)

      date                 zip            tmmx_C           tmmn_C       
 Min.   :2006-01-01   Min.   :90001   Min.   :-8.142   Min.   :-20.850  
 1st Qu.:2010-01-01   1st Qu.:91205   1st Qu.:19.702   1st Qu.:  8.204  
 Median :2013-12-29   Median :92114   Median :24.024   Median : 11.994  
 Mean   :2013-12-30   Mean   :91908   Mean   :24.504   Mean   : 11.911  
 3rd Qu.:2017-12-30   3rd Qu.:92630   3rd Qu.:29.032   3rd Qu.: 15.985  
 Max.   :2021-12-31   Max.   :93591   Max.   :50.987   Max.   : 37.250  

socal_heat$year <- format(socal_heat$date, "%Y")

Find the 95th percentiles for max temp for each zip code and year

temp95 <- socal_heat %>%
    group_by(zip) %>%
    mutate(max95 = quantile(tmmx_C, probs = .95)) 

summary(temp95)

      date                 zip            tmmx_C           tmmn_C            year               max95      
 Min.   :2006-01-01   Min.   :90001   Min.   :-8.142   Min.   :-20.850   Length:4392384     Min.   :24.85  
 1st Qu.:2010-01-01   1st Qu.:91205   1st Qu.:19.702   1st Qu.:  8.204   Class :character   1st Qu.:30.56  
 Median :2013-12-29   Median :92114   Median :24.024   Median : 11.994   Mode  :character   Median :34.20  
 Mean   :2013-12-30   Mean   :91908   Mean   :24.504   Mean   : 11.911                      Mean   :34.04  
 3rd Qu.:2017-12-30   3rd Qu.:92630   3rd Qu.:29.032   3rd Qu.: 15.985                      3rd Qu.:37.12  
 Max.   :2021-12-31   Max.   :93591   Max.   :50.987   Max.   : 37.250                      Max.   :45.72  

temp95$heat95 <- ifelse(temp95$tmmx_C >= temp95$max95, 1, NA ) # assign "1" when max temp >= 95th

Create index of events where max temp > = 95th max temp (for 1st and 2nd heat waves, only)

heatwave <- temp95 %>%
  group_by(zip, year, heat95) %>%
  arrange(date) %>%
  mutate(Seq = ifelse(!is.na(heat95), 1:n(), NA))

heatwave$hw_event <- ifelse(heatwave$Seq == 1 | heatwave$Seq == 2, heatwave$Seq, NA )

summary(heatwave)

      date                 zip            tmmx_C           tmmn_C            year               max95      
 Min.   :2006-01-01   Min.   :90001   Min.   :-8.142   Min.   :-20.850   Length:4392384     Min.   :24.85  
 1st Qu.:2010-01-01   1st Qu.:91205   1st Qu.:19.702   1st Qu.:  8.204   Class :character   1st Qu.:30.56  
 Median :2013-12-29   Median :92114   Median :24.024   Median : 11.994   Mode  :character   Median :34.20  
 Mean   :2013-12-30   Mean   :91908   Mean   :24.504   Mean   : 11.911                      Mean   :34.04  
 3rd Qu.:2017-12-30   3rd Qu.:92630   3rd Qu.:29.032   3rd Qu.: 15.985                      3rd Qu.:37.12  
 Max.   :2021-12-31   Max.   :93591   Max.   :50.987   Max.   : 37.250                      Max.   :45.72  
                                                                                                           
     heat95             Seq             hw_event      
 Min.   :1         Min.   : 1        Min.   :1        
 1st Qu.:1         1st Qu.: 5        1st Qu.:1        
 Median :1         Median :11        Median :1        
 Mean   :1         Mean   :13        Mean   :1        
 3rd Qu.:1         3rd Qu.:18        3rd Qu.:2        
 Max.   :1         Max.   :78        Max.   :2        
 NA's   :4171714   NA's   :4171714   NA's   :4369215  

Plot a ZIP code

lajolla <- heatwave[heatwave$zip == 92037 & heatwave$date >= "2017-01-01", ]  # one zip code, last 5 years
unique(lajolla$max95)

[1] 27.1006

library(ggplot2)

ggplot(data = lajolla, aes(x = date, y = hw_event)) + 
    geom_bar(stat = "identity", fill = "red", width = 5) + 
    geom_text(aes(label=round(tmmx_C, 1)), vjust=1.6, hjust = 1, color="black", size=3.5)+
    scale_x_date(date_breaks = "3 month") +
    theme(axis.text.x = element_text(angle = 45, hjust = 1)) +
    labs(x = "", y = "N Heatwave", title = "La Jolla 92037 (2017-2021) \nHeatwave Event (max temp >= 95th)")