Consecutive Dry Days
The number of consecutive dry days (CDD) is the largest number of consecutive days with daily precipitation amount less than 1 mm (or depending on the rain days criteria of the country), within a certain time. Usually the process counts the number of days in the past 90 days to measure the drought level.
How it works
Calculate the number of rain days based on the threshold and calculate the count of the most recent days since a rain day or the most recent consecutive string of days that meet the threshold criteria is summed.
Option for rain day's threshold: 1, 2.5, 5, 10 or 20 milimeters of rainfall per day
IF previousCDD == null THEN previousCDD == 0
ELSEIF todayRAIN > 1 AND previousCDD == 0 THEN previousCDD + 1
CDD derived from IMERG data
About the data
| Characteristic | Description |
|---|---|
| Function | Display daily CDD |
| Variable | CDD |
| Geographic coverage | Global 60N-60S, 180W-180E |
| Spatial resolution | 0.1 degree ~ 11.1 km at equator |
| Temporal resolution | Daily |
| Format | GeoTIFF |
| Unit | Number of day |
Symbology
The threshold and the symbology for the CDD can follow below color codes and image.
| Class | Threshold | Hex | RGB |
|---|---|---|---|
| No Drought | 0 | #cccccc |
rgb(204, 204, 204) |
| Very Short | 1 - 5 | #ffe5d9 |
rgb(255, 229, 217) |
| Short | 6 - 10 | #fcbba2 |
rgb(252, 187, 162) |
| Moderate | 11 - 20 | #fc9272 |
rgb(252, 146, 114) |
| Long | 21 - 30 | #fa6948 |
rgb(250, 105, 72) |
| Very Long | 31 - 60 | #de2c26 |
rgb(222, 44, 38) |
| Extreme Drought | +60 | #a60f14 |
rgb(166, 15, 20) |
Data access
Global CDD data available at DEC S3: s3://wbgdecinternal-ntl/climate/products/cdd-imerg