easyclimate.field.monsoon.index_npwi

Objective globally unified summer monsoon onset or retreat dates

Functions

calc_index_NPWI(→ xarray.DataArray)

Calculate the normalized precipitable water index (NPWI).

find_PW_monsoon_region(→ xarray.DataArray)

The refined monsoon regions.

calc_NPWI_monsoon_onset(→ xarray.DataArray)

Calculate the summer monsoon onset date.

calc_NPWI_monsoon_retreat(→ xarray.DataArray)

Calculate the summer monsoon retreat date.

Module Contents

easyclimate.field.monsoon.index_npwi.calc_index_NPWI(precipitable_water_daily_data: xarray.DataArray, time_dim: str = 'time') → xarray.DataArray

Calculate the normalized precipitable water index (NPWI).

\[\mathrm{NPWI} = \frac{\mathrm{PW} - \mathrm{PW_{min}}}{\mathrm{PW_{max}} - \mathrm{PW_{min}}}\]

Parameters

precipitable_water_daily_data: xarray.DataArray.

Daily precipitable water data.

time_dim: str.

The time coordinate dimension name.

Returns

Normalized precipitable water index (NPWI).

Reference

easyclimate.field.monsoon.index_npwi.find_PW_monsoon_region(precipitable_water_daily_data: xarray.DataArray, time_dim: str = 'time') → xarray.DataArray

The refined monsoon regions.

Note

To refine the definition of monsoon regions on a grid- cell-by-cell basis, we first compute the 10-yr-averaged monthly PW over each cell. Then we obtain the maximum monthly PW during the three summer months [e.g., June–August in the Northern Hemisphere (NH), denoted as PWw], and the maximum monthly PW during the three winter months (e.g., December–February for the NH, denoted as PWc). The refined monsoon regions are simply defined as grid cells that are within the monsoon regions given in the above studies and have a difference between PWw and PWc greater than 12 mm. Initially we have also tried to use the annual maximum and minimum monthly PW values.

Parameters

precipitable_water_daily_data: xarray.DataArray.

Daily precipitable water data.

time_dim: str.

The time coordinate dimension name.

Reference

Example(s) related to the function

Onset and Retreat of Monsoon

Onset and Retreat of Monsoon
easyclimate.field.monsoon.index_npwi.calc_NPWI_monsoon_onset(NPWI: xarray.DataArray, thresh: float = 0.618, consecutive_days: int = 3, n: int = 7, lon_dim: str = 'lon', lat_dim: str = 'lat', time_dim: str = 'time') → xarray.DataArray

Calculate the summer monsoon onset date.

The summer monsoon onset date for grid cell G is defined as the first day (\(d\)) when NWPI is greater than the Golden Ratio (0.618) for three consecutive days in seven of the nine cells centered at cell G in day \(d\) or (\(d \pm 1\)).

Note

If one or more of the nine grids are undefined, for example, at the edge of monsoon regions, the required number of seven is correspondingly reduced. For instance, if only seven grid cells are defined, the required number is five.

Parameters

NPWI: xarray.DataArray.

Normalized precipitable water index (NPWI).

Attention

It must include three dimensions: time, longitude, and latitude.

thresh: float, default: 0.618.

Golden Ratio value for the threshold value.

consecutive_days: int, default: 3.

Consecutive days values.

n: int, default: 7.

\(n\) of the nine cells centered at cell G in day \(d\) or (\(d \pm 1\)).

lat_dim: str, default: lat.

Latitude coordinate dimension name. By default extracting is applied over the lat dimension.

lon_dim: str, default: lon.

Longitude coordinate dimension name. By default extracting is applied over the lon dimension.

time_dim: str, default: time.

The time coordinate dimension name.

Returns

Summer monsoon onset date.

Reference

Example(s) related to the function

Onset and Retreat of Monsoon

Onset and Retreat of Monsoon
easyclimate.field.monsoon.index_npwi.calc_NPWI_monsoon_retreat(NPWI: xarray.DataArray, monsoon_onset_date: xarray.DataArray, thresh: float = 0.618, consecutive_days: int = 3, n: int = 7, lon_dim: str = 'lon', lat_dim: str = 'lat', time_dim: str = 'time') → xarray.DataArray

Calculate the summer monsoon retreat date.

The summer monsoon retreat date for grid cell G is defined as the first day (\(d\)) when NWPI is less than the Golden Ratio (0.618) for three consecutive days in seven of the nine cells centered at cell G in day \(d\) or (\(d \pm 1\)).

Note

If one or more of the nine grids are undefined, for example, at the edge of monsoon regions, the required number of seven is correspondingly reduced. For instance, if only seven grid cells are defined, the required number is five.

Parameters

NPWI: xarray.DataArray.

Normalized precipitable water index (NPWI).

Attention

It must include three dimensions: time, longitude, and latitude.

monsoon_onset_date: xarray.DataArray.

Summer monsoon onset date. The results is generated by easyclimate.index.calc_NPWI_monsoon_onset.

thresh: float, default: 0.618.

Golden Ratio value for the threshold value.

consecutive_days: int, default: 3.

Consecutive days values.

n: int, default: 7.

\(n\) of the nine cells centered at cell G in day \(d\) or (\(d \pm 1\)).

lat_dim: str, default: lat.

Latitude coordinate dimension name. By default extracting is applied over the lat dimension.

lon_dim: str, default: lon.

Longitude coordinate dimension name. By default extracting is applied over the lon dimension.

time_dim: str, default: time.

The time coordinate dimension name.

Returns

Summer monsoon retreat date.

Reference

Example(s) related to the function

Onset and Retreat of Monsoon

Onset and Retreat of Monsoon