Chapter 3 Data Transformation
The (HURDAT2) data has a comma-delimited, text format with six-hourly information on the location, maximum winds, central pressure, and (beginning in 2004) size of all known tropical cyclones and subtropical cyclones. The dataset is a combination of serveral subsets. Each subset is used for a storm track record which includes header information and values. please refer to this file for detail information.
Firstly, we extract storm id, name, and subtext length from each subtext header, then read in data according to each subtext length, and merge data subset by indexing it with storm id, name. In the original text, you will find that the name is non-unique. Currently, there are six lists that are used in rotation and re-cycled every six years, i.e., the 2013 list is used again in 2019. For more information, please see tropical cyclone names. To avoid the future confusion, we create storm-id variable by combining name and year together (e.g., Sandy-2012). In the original file, there are storms labeled with NAMEs but others labelled with UNNAME. Here, we use name_id variable to indicate whether a storm has a name or not.
Secondly, we estimate category variable from wind speed based on Saffir-Simpson storm category, calculate the diameter of the area experiencing hurricane strength winds (64 knots or above), _ts_diameter_ from extent of 34 kt wind radii maximum extent in northeastern quadrant (in nautical miles, extent_34_NE), 34 kt wind radii maximum extent in southeastern quadrant (in nautical miles, extent_34_SW), 34 kt wind radii maximum extent in northeastern quadrant (in nautical miles, extent_34_NW), and 34 kt wind radii maximum extent in southeastern quadrant (in nautical miles, extent_34_SE), _hu_diameter_ from extent of 64 kt wind radii maximum extent in northeastern quadrant - extent_64_NE, southeastern quadrant - extent_34_SW, northeastern quadrant, extent_64_NW), and southeastern quadrant - extent_64_SE.
Thirdly, we estimate the storm duration tc_dur_track to those with maximum sustained surface winds of at least 35 knot and defined storms and define tc_dur_type for type of the duration. Here, S indicates storms with duration of 2.0 days or less and will be mentioned in the following text as short-lived storms, and L represnts storms with duration of more than 2.0 days and will be referred as “medium-to-long lived” storms.
Finally, the ocean surface temperature is .nc formate, we use ncdf4 to read in data. Note that there is there is an “ET” typo in Status of system in the HURDAT2, which has been corrected to EX in the output data\clean\hurricanes.csv file.
Meaning for each variables
_id_
Storm id, which is unique. An id is a combination of 8 characters,
for example, ‘AL092011’,
AL (Spaces 1 and 2) – Basin – Atlantic
09 (Spaces 3 and 4) – ATCF cyclone number for that year
2011 (Spaces 5-8, before first comma) – Year
for detail information, please see dataformat
_name_
Storm Name, which is non-unique. There are six lists that are used in rotation and re-cycled every six years, i.e., the 2013 list is used again in 2019. For more information, please see tropical cyclone names.
_storm_id_
Storm name and id combined, i.e., Sandy-2012
_unname_label_
Storms have name or not (“yes”, “no”)
_datetime, year, month, day, hour_
Date of report (in Universal Time Coordinate)
_record_identifier_
C – Closest approach to a coast, not followed by a landfall
G – Genesis
I – An intensity peak in terms of both pressure and wind
L – Landfall (center of system crossing a coastline)
P – Minimum in central pressure
R – Provides additional detail on the intensity of the cyclone when rapid changes are underway
S – Change of status of the system
T – Provides additional detail on the track (position) of the cyclone
W – Maximum sustained wind speed
_latitude,longitude_
Location of storm center
_status_
Storm classification (Tropical Depression, Tropical Storm, or Hurricane)
TD – Tropical cyclone of tropical depression intensity (< 34 knots)
TS – Tropical cyclone of tropical storm intensity (34-63 knots)
HU – Tropical cyclone of hurricane intensity (> 64 knots)
EX – Extratropical cyclone (of any intensity)
SD – Subtropical cyclone of subtropical depression intensity (< 34 knots)
SS – Subtropical cyclone of subtropical storm intensity (> 34 knots)
LO – A low that is neither a tropical cyclone, a subtropical cyclone, nor an extratropical cyclone (of any intensity)
WV – Tropical Wave (of any intensity)
DB – Disturbance (of any intensity)
_category_
Saffir-Simpson storm category (estimated from wind speed. -1 = Tropical Depression, 0 = Tropical Storm)
_max_wind_
storm’s maximum sustained wind speed (in knots)
_min_pressure_
Air pressure at the storm’s center (in millibars)
_ts_diameter_
Diameter of the area experiencing tropical storm strength winds (34 knots or above)
_hu_diameter_
Diameter of the area experiencing hurricane strength winds (64 knots or above)
_max_category_
Maximum category of each storm track
_max_status_label_
Label (“TRUE”, “FALSE”) to indicate whether the measurement is for the maximum status of each track
_max_max_wind_
The maximum value of the max_wind for each track
_min_min_pressure_
The minimum value of the min_pressure for each track
_max_ts_diameter_
The maximum value of the ts_diameter for each track
_max_hu_diamter_
The maximum value of the hu_diameter for each track
!–test–>